Ceramic-Rich Composite Separators for High-Voltage Solid-State Batteries

Academic Edi o : Hao Liu Recei ed: 19 Decembe 2024 Re ised: 14 Janua y 2025 Accep ed: 16 Janua y 2025 Published: 21 Janua y 2025 Ci a ion: Va appa a, K.; Fins e busch, M.; Fa akho a-Rohl ing, D.; U dampille a, I.; K asha, A. Ce amic-Rich Composi e Sepa a o s o High-Vol age Solid-S a e Ba e ies. Ba e ies 2025,11, 42. h ps://doi.o g/ 10.3390/ba e ies11020042 Copy igh : © 2025 by he au ho s. Licensee MDPI, Basel, Swi ze land. This a icle is an open access a icle dis ibu ed unde he e ms and condi ions o he C ea i e Commons A ibu ion (CC BY) license (h ps://c ea i ecommons.o g/ licenses/by/4.0/). A icle Ce amic-Rich Composi e Sepa a o s o High-Vol age Solid-S a e Ba e ies Ke in Va appa a 1,2,3 , Ma in Fins e busch 4, Dina Fa akho a-Rohl ing 2,3,4 , Idoia U dampille a 1 and And iy K asha 1,2,* 1CIDETEC, Basque Resea ch and Technology Alliance (BRTA), P. Mi amón 196, 20014 Donos ia-San Sebas ián, Spain; [email p o ec ed] (K.V.); [email p o ec ed] (I.U.) 2ALISTORE-Eu opean Resea ch Ins i u e, FR CNRS 3104, Hub de I’Ene gie, 15 Rue Baudelocque, 80039 Amiens, F ance; [email p o ec ed] 3 Facul y o Enginee ing and Cen e o Nanoin eg a ion Duisbu g-Essen CENIDE, Uni e si ä Duisbu g-Essen, Lo ha s aße 1, 47057 Duisbu g, Ge many 4Ins i u e o Ene gy Ma e ials and De ices (IMD-2): Ma e ials Syn hesis and P ocessing, Fo schungszen um Jülich GmbH, Wilhelm-Johnen-S aße, 52428 Jülich, Ge many; [email p o ec ed] *Co espondence: [email p o ec ed] Abs ac : Composi e solid elec oly es a e gaining in e es ega ding hei use in Li-me al solid-s a e ba e ies. Al hough high ce amic con en imp o es he elec ochemical s a- bili y o ce amic- ich composi e sepa a o s (C-SCE), he polyme ic ma ix also plays a i al ole. In he i s gene a ion o C-SCE sepa a o s wi h a PEO-based ma ix, he ad- di ion o 90–95 w % o Li 6.45 Al 0.05 La 3 Z 1.6 Ta 0.4 O 12 (LLZO) does no make C-SCE s able o cell cycling wi h high- ol age (HV) ca hodes. Fo he nex i e a ion, he objec i e was o ind an HV-s able polyme ic ma ix o C-SCEs. He ein, we epo esul s on op imizing C-SCE sepa a o s wi h di e en ce amics and polyme s which can c a he sys em owa ds be e s abili y wi h NMC622-based composi e ca hodes. Bo h LLZO and Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) we e u ilized as ce amic componen s in C-SCE sepa a o s. Poly(diallyldime hylammonium) bis( i luo ome hanesul onyl)imide (PDDA-TFSI) and poly ( inylidene luo ide-co-hexa luo op opylene) (PVDF-HFP) we e used as polyme s in he “polyme /LiTFSI/plas icize ”-based ma ix. The ini ial phase o he selec ion c i e ia o he sepa a o ma ix in ol ed assessing mechanical s abili y and ionic conduc i i y. Two op imized sepa a o o mula ions we e hen es ed o hei elec ochemical s abili y wi h bo h Li me al and HV composi e ca hodes. The esul s showed ha Li/NMC622 cells wi h LP70_PVDF_HFP and LZ70_PDDA-TFSI sepa a o s exhibi ed mo e s able cycling pe o mance compa ed o hose wi h LZ90_PEO300k-based sepa a o s. Keywo ds: solid-s a e elec oly e; solid-s a e ba e y; ce amic- ich composi e sepa a o ; high ol age; composi e elec oly e 1. In oduc ion Wi h he comme cializa ion o li hium-ion ba e ies (LIB) aking place in 1990s by SONY Co po a ion, LIBs ha e been seen as he u u e o ene gy s o age [ 1 , 2 ]. The inc eased in e es and awa eness o mo e en i onmen - iendly ene gy p oduc ion and s o age and he boom in elec ic ehicles and sma g ids has led o de elopmen o nex -gene a ion ba e ies [ 2 , 3 ]. Simila o o he ields, concu en esea ch is ongoing on u u e echnologies such as de elopmen o solid-s a e ba e ies (SSB) [ 4 , 5 ], di e en cell designs such as anode- ee ba e ies [6,7], o he conduc ing-ion sys ems such as sodium ion [8], e c. Ba e ies 2025,11, 42 h ps://doi.o g/10.3390/ba e ies11020042 Ba e ies 2025,11, 42 2 o 24 Among upcoming echnologies, SSB ha e ga ne ed he mos in e es ecen ly [ 9 ] and a e being in ensi ely esea ched o ad ance echnology in he ene gy s o age ield. SSB looks a e ising LIB cell echnology in e ms o sa e y, accessible g a ime ic and olume ic ene gy densi y, assembly p ocedu es, ope a ional condi ions such as p essu e, e c. [ 10 ]. I also changes he en i e o ma o cells wi h espec o he elec oly e compo- nen s, ansi ioning om LIBs, which consis o wo componen s—po ous sepa a o and liquid elec oly e (LE)— o SSBs, which consis o a single componen —a solid elec oly e (SE). Liquid elec oly es ha e se e al ad an ages, bu hey a e o ganic liquids wi h high lammabili y. The e o e, he eplacemen o LE wi h he mally s able SEs con ibu es o an inc ease in o e all sa e y in SSB [ 11 , 12 ]. SSB has also been en isioned o enable he use o li hium (Li) me al as an anode o access highe he heo e ical capaci y in Li me al (Q h o 3860 mAh/g) compa ed o ha o g aphi e (Q h o 372 mAh/g) o g aphi e/SiO x blends (Q h up o 700 mAh/g) usually used in he con en ional LIBs. SE a e he co ne s one o making SSBs a comme cial success. Some o he equi e- men s o make hem an a ac i e op ion a e as ollows: (i) high ionic conduc i i y, (ii) mechanical s abili y o esis Li dend i es g ow h, (iii) cos -e ec i e p ecu so s, (i ) acile p epa a ion, and ( ) wide elec ochemical s abili y window (ESW) [ 13 ]. The e o e, i is e y impo an o e ec i ely and sa ely design SEs o achie e he expec ed pe o - mances o SSBs in e ms o sa e y, longe cycle li e, e c. The classi ica ion o SEs is based on he majo ma e ial class o hei indi idual cons i uen s. SEs can be classi ied in o wo majo g oups: (a) solid polyme elec oly e (SPE) and (b) solid ino ganic elec oly e (SIE). SPEs a e cha ac e ized by o ganic componen s such as polyme s, Li sal s, ionic liquids, e c., o ming he ma ix. On he o he hand, SIE, as he name sugges s, consis s o Li ion conduc i e ino ganics, di e en ce amics wi h unique c ys al s uc u es such as ga ne - ype Li 7 La 3 Z 2 O 12 (LLZO) [ 14 ], NASICON- ype Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) [ 15 ], and sul ides such as a gy odi e Li 6 PS 5 Cl [ 16 ] and Li 6 PSCl 5 (LPSCl) [ 17 ]. Bo h classi ica ions o SEs di e on all abo e-men ioned p ope ies. SIE and SPE ha e di e en ionic conduc ion mechanisms [ 18 , 19 ]. In e ms o he oxida i e elec ochemical s abili y limi o SEs [ 20 , 21 ], SIEs such LLZO [ 22 ] and LATP [ 23 ] epo ed o ha e s abili y up o 6 V s. Li/Li + and SPE sys ems based on polyme s such as poly( inylidene luo ide-co-hexa luo op opylene) PVDF-HFP o <5.2 V s. Li/Li + [ 24 ], poly( ε -cap olac one) PCL o 4.6 V s. Li/Li + [ 25 ], and poly(diallyldime hylammonium) PDDA-based o >5 V s. Li/Li + [ 26 ]. Bo h classes o SEs also di e in hei p epa a ion me hodology and scalabili y, wi h each o hem being on he opposi e ends o he di icul y scale o p epa a ion. In he las wo decades, solid composi e elec oly es (SCE) as a class o solid elec- oly es a e gaining ac ion in he esea ch communi y. The mo i a ion behind his class o elec oly es is o combine so and lexible polyme ic ma ix om SPE and Li conduc- i e ce amics om SIE in a singula ma ix o u ilize he ad an ages o bo h g oups o solid elec oly es. Di e en ypes o SCEs a e classi ied based on he composi ions o indi idual componen s mixed in he ma ix o SEs. Two popula classi ica ions o SCE epo ed in he li e a u e a e quasi-solid SCE [ 27 ] and polyme -ce amic SCE [ 28 ]. The class o polyme -ce amic-based SCEs can be u he ca ego ized based on he weigh ac ion o indi idual componen s: (a) polyme - ich and (b) ce amic- ich (C-SCE). Ou o he wo ca ego ies, polyme - ich sys ems a e mo e p e alen in he SSB communi y due o hei ease o handling, adap abili y o polyme ic p ope ies, and o ma ion o be - e in e aces wi h elec odes [ 29 , 30 ]. Recen ly, he e has been an inc eased ocus on explo ing he segmen o composi e elec oly es wi h ce amic dominan ma ices [ 31 ]. Fo he sake o cla i y, om his poin in he a icle, we e e o elec oly es as “sepa a- o s”. Fo he pu poses o his s udy in ou HV solid-s a e composi e ca hode, we ha e conside ed LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NMC622) as ca hode ma e ial. Since he majo i y o Ba e ies 2025,11, 42 3 o 24 s udies on C-SCEs epo he gal anos a ic cha ge–discha ge (GCD) cycling in cells wi h LiFePO4-based ca hodes. In ou p e ious s udy [ 32 ], we in es iga ed a model composi e sepa a o sys em comp ising o 90 and 95 w % LLZO in a PEO-LiTFSI ma ix. The LLZO-PEO-LiTFSI-based model composi e sepa a o s we e assessed o high- ol age (HV) s abili y in Li me al and NMC622-based solid-s a e cells a 60 ◦ C. Howe e , he in es iga ed Li/NMC622 cells exhibi ed apid discha ge capaci y ading e en wi h a high con en o LLZO in he PEO- LiTFSI ma ix. The esul was o p io i ize high oxida i e elec ochemical s abili y o he polyme ic ma ix o he sepa a o o wa an mo e s able capaci y e en ion du ing long- e m cycling. Thus, he mo i a ion o his wo k was o imp o e he o mula ion o he polyme ic ma ix, which is essen ial o s able cyclabili y in solid-s a e li hium me al cells wi h high- ol age ca hodes. Figu e 1depic s he s a egy u ilized o he selec ion o di e en composi ions. Ba e ies 2025, 11, x FOR PEER REVIEW 3 o 24 (NMC622) as ca hode ma e ial. Since he majo i y o s udies on C-SCEs epo he gal- anos a ic cha ge–discha ge (GCD) cycling in cells wi h LiFePO4-based ca hodes. In ou p e ious s udy [32], we in es iga ed a model composi e sepa a o sys em com- p ising o 90 and 95 w % LLZO in a PEO-LiTFSI ma ix. The LLZO-PEO-LiTFSI-based model composi e sepa a o s we e assessed o high- ol age (HV) s abili y in Li me al and NMC622-based solid-s a e cells a 60 °C. Howe e , he in es iga ed Li/NMC622 cells ex- hibi ed apid discha ge capaci y ading e en wi h a high con en o LLZO in he PEO- LiTFSI ma ix. The esul was o p io i ize high oxida i e elec ochemical s abili y o he polyme ic ma ix o he sepa a o o wa an mo e s able capaci y e en ion du ing long- e m cycling. Thus, he mo i a ion o his wo k was o imp o e he o mula ion o he polyme ic ma ix, which is essen ial o s able cyclabili y in solid-s a e li hium me al cells wi h high- ol age ca hodes. Figu e 1 depic s he s a egy u ilized o he selec ion o di - e en composi ions. Figu e 1. Schema ic desc ip ion o s a egy employed o de elopmen o high- ol age s able ce- amic- ich solid sepa a o s. No e: abb e ia ions used in he scheme: LLZO— Li6.45Al0.05La3Z 1.6Ta0.4O12, LATP—Li1.3Al0.3Ti1.7(PO4)3, PVDF-HFP—poly ( inylidene luo ide-co-hex- a luo op opylene), PDDA-TFSI—poly(diallyldime hylammonium)bis( i luo ome hanesul- onyl)imide, PBA—poly (1,4-bu ylene adipa e), LiTFSI—li hium bis( i luo ome hanesul onyl)im- ide, PYR14TFSI—1-bu yl-1-me hylpy olidinium bis( i luo ome hanesul onyl)imide, and SCN— succinoni ile. He ein, we epo he in luence o change in o mula ion om he e e ence LLZO- PEO-LiTFSI sepa a o on physical–chemical and elec ochemical p ope ies including ionic conduc i i y and long- e m cycling pe o mance in Li/NMC622 cell o C-SCE sepa- a o s. C-SCE sepa a o s wi h diffe en weigh ac ions o ino ganic (70, 80, and 90 w %) and o ganic componen s (30, 20, and 10 w %) we e p epa ed and es ed. LLZO and LATP we e selec ed as he Li-ion conduc i e ino ganic ce amics due o hei con ibu ions o high mechanical ionic conduc i i y and elec ochemical s abili y as ille s. In he o ganic ma ix, h ee epo ed HV-s able polyme s, poly ( inylidene luo ide-co-hexa luo op o- pylene), poly(diallyldime hylammonium)bis( i luo ome hanesul onyl)imide and poly Figu e 1. Schema ic desc ip ion o s a egy employed o de elopmen o high- ol age s able ce amic- ich solid sepa a o s. No e: abb e ia ions used in he scheme: LLZO—Li 6.45 Al 0.05 La 3 Z 1.6 Ta 0.4 O 12 , LATP—Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 , PVDF-HFP—poly ( inylidene luo ide-co-hexa luo op opylene), PDDA-TFSI—poly(diallyldime hylammonium)bis( i luo ome hanesul onyl)imide, PBA—poly (1,4-bu ylene adipa e), LiTFSI—li hium bis( i luo ome hanesul onyl)imide, PYR 14 TFSI—1-bu yl-1- me hylpy olidinium bis( i luo ome hanesul onyl)imide, and SCN—succinoni ile. He ein, we epo he in luence o change in o mula ion om he e e ence LLZO- PEO-LiTFSI sepa a o on physical–chemical and elec ochemical p ope ies including ionic conduc i i y and long- e m cycling pe o mance in Li/NMC622 cell o C-SCE sepa a o s. C-SCE sepa a o s wi h di e en weigh ac ions o ino ganic (70, 80, and 90 w %) and o ganic componen s (30, 20, and 10 w %) we e p epa ed and es ed. LLZO and LATP we e selec ed as he Li-ion conduc i e ino ganic ce amics due o hei con ibu ions o high mechanical ionic conduc i i y and elec ochemical s abili y as ille s. In he o ganic ma ix, h ee epo ed HV-s able polyme s, poly ( inylidene luo ide-co-hexa luo op opylene), poly(diallyldime hylammonium)bis( i luo ome hanesul onyl)imide and poly (1,4-bu ylene adipa e), we e e alua ed as binding agen s in he ma ix. In polyme ic ma ix, he in lu- ence o plas icize s such as ionic liquid and plas ic c ys als we e also e alua ed. Li hium Ba e ies 2025,11, 42 4 o 24 bis( i luo ome hanesul onyl)imide sal was commonly added in all sepa a o composi- ions. In his s udy, HV beha io o all op imized sepa a o s was es ed in solid-s a e coin cells wi h Li me al anodes and NMC622-based solid-s a e composi e ca hodes. Thei e alua ion also included he o ma ion o mechanically s able ilms, ionic conduc i i y, and s abili y wi h Li me al. The pe o mance o p epa ed sepa a o s was compa ed wi h GEN 1 e e ence sepa a o s con aining 90 and 95 w % o LLZO in he PEO-LiTFSI ma ix in es iga ed in ou ea lie wo k [ 32 ]. This assessmen o e s insigh in o change in he Li/NMC622 cells cycling s abili y wi h he eplacemen o PEO o mo e elec ochemically s able polyme s. 2. Ma e ials and Me hods 2.1. Ma e ials Li 6.45 Al 0.05 La 3 Z 1.6 Ta 0.4 O 12 (abb e ia ed as LLZO) and Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (abb e i- a ed as LATP) we e syn hesized in-house ia SSR and SASSR ou es, espec i ely. LLZO powde s we e syn hesized using a modi ied solid-s a e eac ion (SSR) me hod, wi h s oichio- me ic mixing o p ecu so ma e ials and li hium excess. The p ocess in ol ed calcina ion a 850 ◦ C and 1000 ◦ C, ollowed by sin e ing a 1175 ◦ C. A e milling and sie ing, he esul ing powde s we e p epa ed o C-SCE sepa a o applica ions. LATP powde s we e syn hesized using a solu ion-assis ed solid-s a e eac ion (SASSR) me hod. The p ocess in ol ed mixing and d ying p ecu so s, ollowed by calcina ion a 600 ◦ C and sin e ing a 900 ◦ C. The esul ing powde s we e milled, sie ed, and p epa ed o use in C-SCE sepa- a o s. The de ails o bo h syn hesis me hods wi h he ma e ials used in espec i e hei syn hesis ha e been discussed in he Suppo ing In o ma ion. The syn hesized ce amic powde s we e sie ed wi h 25 µ m sie e (CISA Sie ing Technologies, Ba celona, Spain) o educe he pa icle size dis ibu ion be o e addi ion o C-SCE p epa a ion p ocedu e. D50 pa icle sizes o LLZO and LATP used o p epa a ion we e 2 µ m and 5.1 µ m, espec- i ely; mo e pa icle size de ails a e added in Figu e S1e, . Poly ( inylidene luo ide-co-hexa luo op opylene), abb e ia ed as PVDF-HFP, wi h a molecula weigh o 400 kg/mol, was pu chased om Sigma-Ald ich (Bu ling on, NJ, USA) and used as ecei ed. Poly(diallyldime hylammonium)bis( i luo ome hanesul onyl)imide, abb e ia ed as PDDA-TFSI, wi h a molecula weigh o 300 kg/mol, was pu chased om Sol ionic (F ance) and used as ecei ed. Poly (1,4-bu ylene adipa e), abb e ia ed as PBA, wi h a molecula weigh o 12 kg/mol, was pu chased om Sigma Ald ich (Bu ling on, NJ, USA) and used as ecei ed. Poly (e hylene oxide) abb e ia ed as PEO300k, wi h a molecula weigh o 300 kg/mol, was pu chased om Sigma Ald ich (Bu ling on, NJ, USA) and used a e d ying a 55 ◦C unde acuum o 16 h. Li hium bis( i luo ome hanesul onyl)imide (LiTFSI, 99.9%) was pu chased om Sol ionic (F ance) and used as ecei ed. 1-Bu yl-1-me hylpy olidinium bis ( i luo ome hanesul onyl)imide (PYR 14 TFSI, 99.9%) was pu chased om Sol ionic (Toulouse, F ance) and used as ecei ed. Succinoni ile (SN, 99%) was pu chased om Sigma Ald ich (Bu ling on, NJ, USA) and used as ecei ed. Anhyd ous ace oni ile (ACN, 99.8%), used o he p epa a ion o PDDA-TFSI-based sepa a o and ca hode slu y, was pu chased om Sigma Ald ich. Ex a-d y ace one (99.8%), used o p epa a ion o PVDF- HFP-based sepa a o slu y, was pu chased om Fishe Scien i ic (Wal ham, MA, USA). Ex a-d y dime hyl ca bona e (DMC, 99%), used o p epa a ion o PBA-based sepa a o slu y, was pu chased om The mo Scien i ic Chemicals (Wal ham, MA, USA). Single-c ys al NMC622 (comme cial g ade), pu chased om Ta g ay (Ki kland, QC, Canada), was used as ca hode ac i e ma e ial. Polye hylene oxide wi h molecula weigh o 400 kg/mol (PEO400k) was pu chased om Sigma Ald ich (Bu ling on, NJ, USA). Ba e ies 2025,11, 42 5 o 24 Conduc i e ca bon black C-ENERGY Supe C45 was pu chased om IMERYS Ca bon & G aphi e (Bi onico, Swi ze land) and s o ed a 110 ◦C. 2.2. Sepa a o P epa a ion P ocedu e C-SCEs in his wo k we e en i ely ab ica ed in a d y oom wi h a dew poin lowe han − 45 ◦ C). The p epa a ion o ce amic- ich solid composi e sepa a o s ollows he de ailed p ocedu e al eady epo ed in a p e ious s udy [32]. In he i s s ep o p epa a ion o all sepa a o s, he componen s o o ganic ma ix we e weighed and mixed wi h espec i e sol en solu ions. The sol en s used o PVDF-HFP, PBA and PDDA-TFSI-based ma ix we e selec ed as ace one, DMC, and ACN, espec i ely. All polyme dissolu ions we e mixed o e nigh a 250 pm wi h mechanical mixe (Eu os a 60 digi al, IKA. S au en, Ge many). A e ob aining homogenous solu ion om o e nigh mixing, ce amic powde s (LLZO and LATP) we e added o he polyme dissolu ion. The syn hesis p ocedu e o LLZO and LATP is desc ibed in Suppo ing In o ma ion. The sepa a o slu y was hen mixed o 2 h a 1100 pm. The o mula ions o all sepa a o s p epa ed in his wo k a e lis ed in Table 1. To e alua e he in luence o change o com- ponen s in he ma ix, e e ence sepa a o s wi h a PEO-based ma ix we e also p epa ed. LZ90_PEO300k and LZ90_PEO300k wi h 90 and 95 w % o ce amic in he PEO-LiTFSI ma ix we e p epa ed using he me hod al eady epo ed in Va appa a e al. [32]. Table 1. Lis o all C-SCEs e alua ed in his s udy wi h physical a ibu es a e pos -p ocessing. C-SCE Sample Name Gene - a ion o Sepa a o s Ce amic O ganic Pos - P ocessing Pa ame e s Physical Obse a ions Ce amic Type Con en (w %) Polyme Type Polyme Con en (w %) LiTFSI Con en (w %) Plas icize Con en (w %) Sol en Used LZ90_PEO300k * GEN 1 LLZO 90 PEO Mw-300 kg/mol 7.5 2.5 0.0 ACN 60 ◦C, 100 ba , 1 min Smoo h su ace wi h less po es LZ95_PEO300k * LLZO 95 PEO Mw-300 kg/mol 3.8 1.2 ACN 60 ◦C, 100 ba , 1 min Smoo h su ace wi h less po es LZ70_PDDA-TFSI GEN 2 LLZO 70 PDDA-TFSI Mw-300 kg/mol 12 7.5 10.5 ACN 80 ◦C, 10 ba , 30 s Smoo h su ace wi h less po es LZ80_PDDA-TFSI LLZO 80 PDDA-TFSI Mw-300 kg/mol 8 5 7 ACN 80 ◦C, 10 ba , 30 s Rough su ace wi h less po es LZ90_PDDA-TFSI LLZO 90 PDDA-TFSI Mw-300 kg/mol 4 2.5 3.5 ACN 80 ◦C, 10 ba , 30 s Rough su ace wi h lo o po es LP70_PVDF-HFP LATP 70 PVDF-HFP Mw-400 kg/mol 6.9 4.8 18.3 Ace one 80 ◦C, 10 ba , 30 s Smoo h su ace wi h less po es LP70_PVDF-HFP wi hou SCN LATP 70 PVDF-HFP Mw-400 kg/mol 9 7.5 13.5 Ace one 80 ◦C, 10 ba , 30 s Smoo h su ace wi h less po es LZ70_PBA LLZO 70 PBA Mw-12 kg/mol 24.9 5.1 0.0 DMC 60 ◦C, 10 ba , 30 s Su ace c acking a e pos -p ocessing LZ80_PBA LLZO 80 PBA Mw-12 kg/mol 16.6 3.4 0.0 DMC 60 ◦C, 10 ba , 30 s Su ace c acking a e pos -p ocessing No e: * The sepa a o s ha e been s udied in de ail in ou p e ious s udy [32]. Slu y cas ing was ca ied ou on a Te lon shee ixed on a glass subs a e o PDDA- TFSI and PBA-based sepa a o s, and di ec ly on glass subs a es o PVDF-HFP-based sepa a o s. The slu y was cas using a doc o -blade- ype applica o o achie e he equi ed hickness using quad angula applica o (Nue ek, 60 mm wid h, Eiba , Spain). A e cas ing, ilms we e le o d y a oom empe a u e in he d y oom and inally acuum d ied unde ~10 mba a 60 ◦ C o 40 h o emo e aces o sol en s om sepa a o s. Ba e ies 2025,11, 42 6 o 24 A e wa ds, d ied sepa a o s we e subjec ed o pos -p ocessing s eps be o e ca ying ou a ious cha ac e iza ions. Fo he i s s ep in pos -p ocessing, sepa a o s we e cu in disks by Ø18.92 mm dies. Then, he sepa a o discs we e ho -p essed (Polys a 200T, Wus e ma k, Ge many) a he pa ame e s lis ed in Table 1. A e he ho p essing, he sepa a o s we e cu in o he inal equi ed diame e o 18.2 mm o be assembled in o 2025 coin cells o ca ying ou a ious elec ochemical cha ac e iza ions wi h he coin cell p epa a ion p ocedu e epo ed ea lie [32]. 2.3. Ca hode P epa a ion P ocedu e A solid-s a e composi e ca hode was p epa ed wi h e e ence o mula ion o compa a- i e es ing o he p epa ed C-SCEs. The ca hode slu y was p epa ed using a DISPERMAT LC30 mechanical mixe in he labo a o y a oom empe a u e. The ca hode o mula ion consis s o NMC622 as a ca hode ac i e ma e ial (CAM), “PEO400k/PYR14TFSI/LiTFSI” as a binding ca holy e, and C-ENERGY Supe C45 ca bon black as a ca bon addi i e (CA). The composi e ca hode wi h ca holy e was p epa ed o imp o e he Li ion conduc ion h ough he ac i e laye , o enhance plas ici y, and educe in e acial esis ance be ween ca hode and sepa a o . The p epa a ion o composi e ca hode also ollows he de ailed p ocedu e al eady epo ed ea lie [ 32 ]. The i s s ep in ca hode p epa a ion was he mechanical dissolu ion o PEO400k (10)-LiTFSI (1)/PYR 14 TFSI ca holy e mix u e (25 w %) o e nigh in ACN sol en a 250 pm. Nex , CA (5 w %) was added wi h small amoun s o ACN sol en o ackle slu y iscosi y change. In he inal s ep, NMC622 CAM (70 w %) powde was added in mul iple se s wi h in e mi en addi ion o ACN sol en o ackle slu y iscosi y change. The solid- o-sol en a io used in ca hode p epa a ion was 1:1.7. Slu y empe a u e was main ained o be cons an du ing he en i e p epa a ion p ocess. A e mixing, slu y was cas ed on o a 22 µ m hick ca bon coa ed aluminum cu en collec o s (Gelon, Round Rock, TX, USA) and using doc o -blade d ied in ambien a mosphe e a 55 ◦ C o 3 h. The ca hode shee s we e hen d ied a 55 ◦ C o 16 h unde acuum (Memme VO400, <10 mba ). A e d ying, cas shee s we e calende ed in hyd aulic calende machine ( om DPM Solu ions, Hebb ille, Canada) unde 400 psi a oom empe a u e. A e calende ing, he ca hode shee was punched in o Ø16.6 mm discs using high-p ecision dies (El-Cell, Hambu g, Ge many). The inal d ying o he ca hodes we e ca ied ou a 60 ◦ C o 40 h in a acuum o en (Memme VO400, <10 mba ) in he d y oom o p epa e o 2025 coin cell assembly. The a eal loading and densi y o he ca hodes we e calcula ed o be 1.0 ±0.1 mAh/cm2and 2.6 ±0.1 g/cm3, espec i ely. 2.4. Cha ac e iza ion 2.4.1. Physical–Chemical P ope ies X-Ray di ac ion (XRD) measu emen s o LLZO and LATP powde s we e ca ied ou using B uke D4 Endea ou wi h Cu-K α adia ion and da a was eco ded in he 2 θ ange o 10–80 deg ees wi h a scan a e o 0.02 deg ee/min. XRD measu emen s o p epa ed C-SCEs we e ca ied ou using B uke AXS D8 Ad ance wi h Cu K α adia ion and da a was eco ded in he 2 θ ange o 10–80 deg ees wi h a scan a e o 0.01 deg ee/min. Su ace and c oss-sec ional mo phologies o p epa ed C-SCEs we e analyzed using a Scanning Elec on Mic oscope (SEM)—JEOL JSM-5500LV. Sample p epa a ion o SEM imaging included moun ing o sepa a o agmen s using ca bon ape on Al pin-moun s and Au spu e - coa ing (60 mA, 50 s, 1 mba ). Fo c oss-sec ional imaging, pos -p ocessed sepa a o s we e imme sed in liquid N 2 and agmen ed o e eal c oss-sec ion o sepa a o s. The pa icle size dis ibu ion (PSD) o LLZO powde (a e syn hesis and a e sie ing) was ca ied ou using a lase -di ac ion-based Mas e size 3000 om Mal e n Ins umen s L d. Ba e ies 2025,11, 42 7 o 24 (Wo ces e shi e, UK) wi h a Hyd o-EV we powde dispe sion a achmen . The PSD a di e en olume dis ibu ions was calcula ed using Mas e size 3000 so wa e ( 3.40) om he acqui ed ligh sca e ing pa e n using Mie and F aunho e heo y. The pa icle sizes we e epo ed a 10% (D 10), 50% (D 50), and 90% (D 90) o he powde olume. The measu emen s o each powde we e ca ied ou in quin uplica e. TGA measu emen s we e eco ded unde ai a mosphe e om 40 ◦C o 600 ◦C a a hea ing a e o 10 ◦C/min. 2.4.2. Elec ochemical P ope ies Ionic conduc i i y ( σ ) o ab ica ed sepa a o s was measu ed in symme ic cells wi h s ainless s eel (SS) elec odes. Elec ochemical Impedance Spec oscopy (EIS) measu e- men s we e pe o med using a 1455 FRA in e ace coupled wi h 1470E po en ios a (So- la on Analy ical, UK). A sinusoidal signal wi h an ampli ude o 10 mV was applied in a 1 MHz–0.1 Hz equency ange. The coin cell was ini ially hea ed up o 80 ◦ C and held a he empe a u e o 2 h o comple ely emo e he mal o p ocessing his o y o he sample. EIS measu emen s we e ca ied ou while cooling om 80 ◦ C o 30 ◦ C a a 10 ◦ C in e al, wi h cells s abilized a each empe a u e o 90 min. The ZView so wa e 3.5e (Sc ibne , Sou he n Pines, NC, USA) was used o i ob ained impedance spec a o equi alen ci cui model (ECM). All Li/Li and Li/NMC cells we e cycled a 60 ◦ C using BaSyTec cell es ing sys em (Ge many). Symme ic Li/Li cells we e also assembled and es ed o de e mining c i - ical cu en densi y (CCD) alues and s udying long- e m cycling beha io o C-SCE sepa a o s. Fo CCD measu emen s, Li/Li symme ic cells wi h C-SCE sepa a o s we e cycled wi h 1 h s ep a di e en cu en densi y alues: 0.01, 0.02, 0.05, 0.10, 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 mA/cm 2 . Long- e m cycling o Li/Li symme ic cells we e assessed a cu en densi y o 0.1 mA/cm2. An elec ochemical loa ing es o “Li/sepa a o /NMC622” coin cells was pe o med a 60 ◦ C o assess he elec ochemical s abili y o he Li/NMC622 sys em assembled wi h in es iga ed sepa a o s. The “Li/sepa a o /NMC622” cells we e ini ially cha ged o 4.2 V a 0.05C. They we e p og ammed o be in cons an ol age (CV) mode om 4.2 V o 5.0 V, a inc emen s o 0.1 V, and main ained a each ol age alue o 1 h wi h he cu en being moni o ed. Gal anos a ic cha ge–discha ge cycling o assess discha ge C- a e pe o mance and long- e m cycling s abili y o he Li/NMC622 cells wi h in es iga ed sepa a o s was ca ied ou . The discha ge C- a e pe o mance es was ca ied ou a di e en discha ge C- a es o 0.1C, 0.2C, 0.33C, 0.5C, 1C, and 2C. Howe e , he cha ging C- a e was kep cons an a 0.05C. A e each a e es , cells unde go a eco e y cycle wi h a C- a e o 0.05C/0.1C. Long- e m cycling p o ocol o Li/NMC622-based solid-s a e coin cells was selec ed as 0.05C o cha ge and 0.1C o discha ge wi hin he ol age ange o 3.0–4.3 V. No ewo hy, as pa o es ing condi ions, no addi ional p essu e o he han coin cell sp ing was applied du ing es ing o SS/SS, Li/Li and Li/NMC622 cells. 3. Resul s and Discussion The o mula ion o ce amic- ich composi e sepa a o s plays an impo an ole in de e mining he o e all pe o mance o SSB sys em. Di e en ac o s need o be consid- e ed while selec ing componen s and composi ions o sepa a o s o SSBs. Some o he ac o s men ioned abo e include mechanical s abili y, chemical s abili y be ween sepa a o componen s, high oxida i e s abili y e sus high- ol age ca hode ma e ials, abili y o o m s able in e ace wi h elec odes, e c. P e iously, we epo ed [ 32 ] ha ce amic- ich sepa- a o s o med mechanically s able ilm and had s able in e ace wi h Li me al; howe e , he small con en o PEO in he ma ix con ibu ed o uns able long- e m cycling. The ob- se ed lack o s abili y was due o a apid dec ease in discha ge capaci y du ing cycling a Ba e ies 2025,11, 42 8 o 24 60 ◦ C. Consequen ly, he selec ion o polyme ic hos s o unc ion as ma ix o C-SCEs was pe o med based on hei elec ochemical s abili y du ing cycling in cells wi h high cha ge cu -o ol ages. 3.1. Op imiza ion o Composi e Sepa a o Fo mula ion The pu pose o his wo k is o add ess he high- ol age s abili y issues o LLZO-PEO- LiTFSI-based GEN-1 C-SCEs [ 32 ]. To imp o e he elec ochemical pe o mance, he ini ial a emp s made we e o eplace he PEO-based ma ix wi h a PVDF-HFP-based ma ix, main aining he same con en o LLZO in he sys em. Howe e , i was obse ed ha he p epa ed C-SCE would be discolo ed. I has been epo ed ha mixing LLZO wi h PVDF-HFP causes discolo a ion o he sepa a o ma ix due o dehyd o luo ina ion o PVDF-HFP which could a ec he long- e m cycling pe o mance in cells [33]. In his wo k, we elabo a ed on he ab ica ion and e alua ion o C-SCEs combining di e en ypes o Li-ion conduc i e ce amic powde s and polyme ic ma ices. The il e ing and op imiza ion p ocess o a ious sepa a o composi ions was ca ied ou based on hei physical s abili y, mic os uc u e, and ionic conduc i i y. Fo op imizing he composi ion o C-SCEs, a ious ials we e ca ied ou wi h di e en polyme -based o ganic ma ices which a e lis ed in Table 1. The p epa a ion me hodology o all C-SCE composi ions was kep analogous, as desc ibed in Sec ion 2.2. Howe e , one o he key di e ences in he p epa a ion p ocedu e be ween he ab ica ed C-SCEs is he usage o di e en empe a u es while ca ying ou pos -p ocessing s eps. 3.1.1. Mic os uc u al Analysis The homogenized C-SCE slu ies consis ing o ce amic powde s and componen s o polyme ic ma ix a e mechanical mixing we e cas on di e en subs a es, including o PVDF-HFP-based sys ems and Te lon shee s o PDDA-TFSI and PBA-based sys ems. The sepa a o memb anes we e d ied a 60 ◦ C in a acuum o en o emo e any em- nan s o sol en s. A e d ying, sepa a o memb anes in he o m o disks we e subjec ed o pos -p ocessing condi ions, as ma ked in Table 1, o ob ain lexible and mechanically s able sepa a o s. The ho p ess s ep, as pa o pos -p ocessing o all sepa a o s, has been epo ed [ 32 , 34 , 35 ] o imp o e su ace mo phology, ela i e densi y, and he ionic conduc i i y o SEs. Se e al ials we e ca ied ou o inalize he ho -p essing pa ame- e s o he GEN 2 sepa a o s. The pa icle size con ol o bo h LLZO and LATP plays an impo an ole in he o e all quali y o he sepa a o s. The sie ing o ce amic pow- de s be o e hei addi ion o he sepa a o slu y plays an impo an ole du ing cas ing o memb anes wi h homogenous mic os uc u e. Bo h LLZO and LATP powde s had D90 alues o <25 µ m (de ails on size and dis ibu ion a e a ailable in Suppo ing In o ma- ion as Figu e S3). The op imiza ion p ocess o sepa a o o mula ion o GEN 2 o C-SCEs consis ed o a selec ion o polyme -based ma ix and sui able ce amic powde s o he ma ix. The op imiza ion o he polyme ic ma ix included he selec ion o binding polyme , compa ible plas icize s, and li hium sal . Wi h PVDF-HFP as he hos , wo di e en polyme ic ma ices we e e alua ed. The i s combina ion o PVDF-HFP-based sepa a o ma ix consis ed o PYR 14 TFSI and SCN as plas icize s and LiTFSI as Li sal . PYR 14 TFSI [ 36 , 37 ] and SCN [ 38 , 39 ] we e chosen due o hei epo ed con ibu ions o imp o ing ionic conduc i i y, ion mobili y, and elec ochemical pe o mance in solid polyme elec oly e sys ems. The second combina ion consis ed o only PYR 14 TFSI as plas icizing agen and LiTFSI as he Li sal . The wo ma ix combina ions we e e alua ed o unde s and he in luence o SCN on he o e all pe o mance o PVDF-HFP-based C-SCEs. PDDA-TFSI-based sepa a o ma ix consis ed o PYR 14 TFSI as plas icize along wi h LiTFSI as Li sal . The PBA-based sepa a o Ba e ies 2025,11, 42 9 o 24 ma ix consis s o LiTFSI as Li sal , wi hou any plas icize s, due o he low molecula weigh o PBA compa ed o ha o PVDF-HFP and PDDA-TFSI. The second pa o he ma e ial selec ion p ocess was he choice o ce amic powde s in C-SCEs, depending on hei p ocessing iabili y o o m s able and sel -s anding ilms. Fo PVDF-HFP-based C-SCEs as esul o he dehyd o luo ina ion eac ion, LLZO was eplaced by LATP. Sepa a o s p epa ed wi h 80 and 90 w % o LATP we e obse ed o ha e p oblems in o ming sel -s anding sepa a o s due a lack o binding in LATP pa icles which leads o deg ada ion o con ac wi h elec odes and inc eases in e acial esis ance du ing cycling. In he PDDA-TFSI-based ma ix, he selec ion o LLZO con en was mo e lexible wi h 70 w % (LZ70_PDDA-TFSI), 80 w % (LZ80_PDDA-TFSI), and 90 w % (LZ90_PDDA-TFSI) o LLZO powde s. Simila ly o PBA-based ma ix, LLZO was selec ed as he ce amic componen wi h con en o 70 w % (LZ70_PBA) and 80 w % (LZ80_PBA). Sel -s anding and mechanically s able sepa a o s we e ab ica ed wi h hickness be- ween 100–250 µ m wi h bo h LLZO and LATP as ce amic ille s and di e en polyme -based ma ices. The di e en ma e ial conside a ions du ing he op imiza ion p ocess we e use ul in p epa ing GEN 2 sepa a o s wi h PVDF-HFP-based, PDDA-TFSI-based, and PBA-based ma ices. The p epa ed C-SCE sepa a o s we e labeled in Table 1acco ding o he ce amic con en and polyme used in he ma ix, e.g., sample LP70_PVDF-HFP con ains 70 w % sie ed LATP powde and PVDF-HFP as he polyme in he ma ix. The mechanical s abili y o he sepa a o s was highly dependen on he o mula ions and he indi idual componen s in he ma ix. Fo example, du ing ials o p epa ing PDDA-TFSI-based sepa a o s, i was obse ed ha he addi ion o SCN o sepa a o ma ix had nega i e e ec on he s abili y o sepa a o ilm. Howe e , he applica ions o addi ional s uc u al s abiliza ion echniques such c oss-linking [ 40 , 41 ] and in-si u polyme iza ion [ 42 , 43 ] o he polyme ic ma ix was ou o scope in his wo k. A scanning elec on mic oscope (SEM) was used o e alua e he mic os uc u e o he p epa ed sepa a o s. Figu es 2and S3 show he c oss-sec ional and su ace SEM mi- c og aphs o all C-SCE sepa a o s. Mic og aphs o he c oss-sec ion (Figu e 2a,b) and su ace (Figu e S3a,b) o PEO-based sepa a o s [ 32 ] we e compa ed wi h he mic os uc u e and mo phology o all o he C-SCE sepa a o s. The mic os uc u e o bo h PVDF-HFP- and PDDA-TFSI-based sepa a o s wi h 70 w % o ce amic powde s (LP70_PVDF-HFP, LP70_PVDF-HFP wi hou SCN and LZ70_PDDA-TFSI) a e shown in Figu e 2c, ,g, espec- i ely. Upon compa ison wi h e e ence sepa a o s, LZ70_PDDA-TFSI in Figu e 2g is seen o ha e a simila mic os uc u e o ha o LZ90_PEO300k sepa a o . The inc ease o polyme ic con en in he LZ70_PDDA-TFSI ma ix helped he imp o ed coa ing o LLZO pa icles along wi h educ ion o isible po es in he mic os uc u e. On he o he hand, bo h LP70_PVDF-HFP and LP70_PVDF-HFP wi hou SCN a e obse ed o ha e mic os uc u es like LZ95_PEO300k. This could be a ibu ed o hei inc eased olume ac ion o ce amic pa icles compa ed o ha o LLZO-based LZ70_PDDA-TFSI sepa a- o . None heless, all h ee sepa a o s we e seen o ha e dense mic os uc u e wi h no isible po es. Ba e ies 2025,11, 42 16 o 24 189.1 mAh/g, and LZ70_PDDA-TFSI—145.2 mAh/g, espec i ely. The capaci y ade o cells wi h LZ90_PEO300k is e y as as epo ed ea lie [ 32 ], and as seen in he ol age e sus capaci y plo in Figu e 7d. In he case o Li/NMC622 cells wi h GEN 2 sepa a o s, we obse ed a much slowe capaci y ade compa ed o ha o cells wi h LZ90_PEO300k. LP70_PVDF-HFP-based Li/NMC622 cells exhibi ed he highes alues in bo h discha ge capaci y and coulombic e iciencies wi h LZ90_PEO300k-based cells ollowing closely be- hind. The cells wi h LZ70_PDDA-TFSI showed lowe ini ial discha ge capaci y, bu o e nex ew cycles he discha ge capaci y and he Coulombic e iciency alues inc eased o he maximum alues o 155.3 mAh/g in he 3 d cycle. The slow inc ease in he discha ge capaci y o cells wi h LZ70_PDDA-TFSI could be a ibu ed o he need o ac i a ion o he “Li/sepa a o /NMC622” s ack. Ba e ies 2025, 11, x FOR PEER REVIEW 16 o 24 Figu e 7. (a) Discha ge capaci y and (b) coulombic efficiency e sus cycle numbe o Li/NMC622 cells wi h all in es iga ed sepa a o s. (c) A e age ol age o bo h cha ge and discha ge s ep o Li/NMC622 cells wi h diffe en sepa a o s. Vol age e sus capaci y cu es o Li/NMC622 cells wi h GEN 1 and GEN 2 sepa a o s a e long- e m gal anos a ic cycling (d) LZ90_PEO300k o 35 cycles, (e) LZ70_PDDA-TFSI o 50 cycles and ( ) LP70_PVDF-HFP o 50 cycles. dQ/dV e sus ol age cu es o he 1s and 10 h cycles o Li/NMC622 cells wi h (g) LZ90_PEO300k, (h) LZ70_PDDA- TFSI, and (i) LP70_PVDF-HFP sepa a o s ( ed ci cle ma king a peak wi h inc eased in ensi y). Compa ing he cyclabili y o Li/NMC622 cells wi h GEN 2 sepa a o s as shown in Table 2, in cells wi h LP70_PVDF-HFP, he discha ge capaci ies we e highe compa ed o cells assembled wi h PDDA-TFSI-based sepa a o . On he o he hand, he capaci y e en- ion o e he cycling pe iod was obse ed o be be e in he LZ70_PDDA-TFSI-based cell, which was seen in Figu e 7a and he ol age e sus capaci y p o iles in Figu e 7e. How- e e , in Li/NMC622 cells wi h LP70_PVDF-HFP, by he 22nd cycle ( ol age e sus capac- i y p o iles in Figu e 7 ), he e we e p oblems wi h excessi e cha ge capaci y (>220 mAh/g), obse ed due o so sho -ci cui s du ing cha ging. Wi h he s a o so sho ci cui s, bo h discha ge capaci y and coulombic efficiency alues dec eased apidly. The capaci y ade in he cells is mo e se e e as he numbe o cycles inc eases. By he 30 h cycle, he capaci ies ha e declined below ha o cell wi h LZ70_PDDA-TFSI. This diffe - ence in he s abili y o he wo GEN 2 sepa a o s could be a ibu ed o he polyme s hem- sel es and possible dehyd o luo ina ion o PVDF-HFP polyme in con ac wi h Li me al [55,56]. This can be obse ed in cycling p o iles o symme ic Li/Li cells (Figu e 4b), whe e he pola iza ion s ayed s able in he case o he LZ70_PDDA-TFSI-based cell, bu i was seen o be inc easing in he case o he PVDF-HFP-based cell. The slow capaci y ade in Figu e 7. (a) Discha ge capaci y and (b) coulombic e iciency e sus cycle numbe o Li/NMC622 cells wi h all in es iga ed sepa a o s. (c) A e age ol age o bo h cha ge and discha ge s ep o Li/NMC622 cells wi h di e en sepa a o s. Vol age e sus capaci y cu es o Li/NMC622 cells wi h GEN 1 and GEN 2 sepa a o s a e long- e m gal anos a ic cycling (d) LZ90_PEO300k o 35 cycles, (e) LZ70_PDDA-TFSI o 50 cycles and ( ) LP70_PVDF-HFP o 50 cycles. dQ/dV e sus ol age cu es o he 1s and 10 h cycles o Li/NMC622 cells wi h (g) LZ90_PEO300k, (h) LZ70_PDDA-TFSI, and (i) LP70_PVDF-HFP sepa a o s ( ed ci cle ma king a peak wi h inc eased in ensi y). Compa ing he cyclabili y o Li/NMC622 cells wi h GEN 2 sepa a o s as shown in Table 2, in cells wi h LP70_PVDF-HFP, he discha ge capaci ies we e highe compa ed o cells assembled wi h PDDA-TFSI-based sepa a o . On he o he hand, he capaci y e en ion o e he cycling pe iod was obse ed o be be e in he LZ70_PDDA-TFSI-based cell, which was seen in Figu e 7a and he ol age e sus capaci y p o iles in Figu e 7e. Ba e ies 2025,11, 42 17 o 24 Howe e , in Li/NMC622 cells wi h LP70_PVDF-HFP, by he 22nd cycle ( ol age e - sus capaci y p o iles in Figu e 7 ), he e we e p oblems wi h excessi e cha ge capaci y (>220 mAh/g), obse ed due o so sho -ci cui s du ing cha ging. Wi h he s a o so sho ci cui s, bo h discha ge capaci y and coulombic e iciency alues dec eased apidly. The capaci y ade in he cells is mo e se e e as he numbe o cycles inc eases. By he 30 h cycle, he capaci ies ha e declined below ha o cell wi h LZ70_PDDA-TFSI. This di e ence in he s abili y o he wo GEN 2 sepa a o s could be a ibu ed o he polyme s hemsel es and possible dehyd o luo ina ion o PVDF-HFP polyme in con ac wi h Li me al [ 55 , 56 ]. This can be obse ed in cycling p o iles o symme ic Li/Li cells (Figu e 4b), whe e he pola iza ion s ayed s able in he case o he LZ70_PDDA-TFSI-based cell, bu i was seen o be inc easing in he case o he PVDF-HFP-based cell. The slow capaci y ade in cells wi h LZ70_PDDA-TFSI and LP70_PVDF-HFP could be also seen as he e ec o PEO-based ca holy e in he composi e ca hode. Table 2. Elec ochemical pe o mance indica o s o es ed Li/NMC622 cells wi h C-SCE sepa a o s a key cycle numbe s. C-SCE Sample Name Cycle Numbe Discha ge Capaci y, mAh/g Capaci y Re en ion, % Coulombic E iciency, % A e age Vol age, V S a e o Cells Cha ge Discha ge Li/LZ90_PEO300k/NMC622 GEN 1 1 172.69 - 88.09 3.88 3.71 S a 10 111.79 64 96.64 3.94 3.51 Mid 35 6.6 3.8 106.82 ** 4.27 3.17 S op Li/LZ70_PDDA-TFSI/NMC622 GEN 2 1 145.15 - 74.94 3.94 3.46 S a 10 147.07 94 97.31 3.94 3.51 Mid 50 101.87 61 97.18 4.0 3.48 S op Li/LP70_PVDF-HFP/NMC622 GEN 2 1 189.07 - 91.59 3.87 3.75 S a 10 170.42 90 98.73 3.89 3.68 Mid 22 151.74 80 79.13 3.93 3.55 50 51.45 27 70.0 4.23 3.35 S op ** Coulombic e iciency (CE) was mo e han 100% in 35 h cycle due o cha ge (6.2 mAh/g) and discha ge (6.6 mAh/g) capaci ies measu ed we e e y small because o inc ease in cell esis ance du ing long- e m cycling. This inc eased CE alues has mino e ec on he cell because he o al summa ion o capaci ies shows ha he discha ge capaci y is less han ha o cha ged capaci y. The a e age ol ages o he Li/NMC622 cells wi h all h ee sepa a o s we e analyzed using PROTEO™ Da a Analy ics V1 (CIDETEC) and shown in Figu e 7c. In he g aph, he e a e indica ions owa ds deg ada ion in he Li/NMC622 cells wi h LZ90_PEO300k and LP70_PVDF-HFP due o he inc easing di e ence be ween he a e age ol ages o cha ge and discha ge. Howe e , in he Li/NMC622 cells wi h LZ70_PDDA-TFSI, i was obse ed ha he di e ence be ween a e age ol age alues was la ge compa ed o o he sys ems, which could be due o he highe esis ance o he “Li/sepa a o /NMC622” s ack and may co obo a e he be e s abili y o cells du ing long- e m cycling. Addi ionally, o unde s and he in luence o a ious ma ix componen s, PVDF-HFP- based sepa a o s we e es ed in Li/NMC622 cells, including he LP70_PVDF-HFP sepa a o wi hou SCN. Figu e S7 compa es he cycling pe o mance o Li/NMC622 cells wi h bo h GEN 2 PVDF-HFP-based C-SCEs. The Li/NMC622 cells wi h bo h sepa a o s demons a e ele an ini ial discha ge capaci ies. Figu e S7d,e illus a e apid capaci y decay in he ol age e sus ime plo s o Li/NMC622 cells wi h bo h sepa a o s. Howe e , i was obse ed ha om he 2nd cycle onwa ds ha he discha ge capaci y o Li/NMC622 cells wi h LP70_PVDF-HFP wi hou SCN dec eased e y apidly o less han 50% o he ini ial discha ge capaci y. One o he p obable easons o de ia ion in he cycling pe o mance could be ela ed o he abili y o SCN (p esen ed in LP70_PVDF-HFP ma ix) o sepa a e Ba e ies 2025,11, 42 18 o 24 cha ges in he elec oly e and he o a ional mo ion o SCN molecules. Bo h o which would aid in he be e anspo o ions du ing cycling [46]. Figu e 7g–i depic he inc emen al capaci y cu es (dQ/dV) o Li/NMC622 cells wi h LZ90_PEO300k, LP70_PVDF-HFP, and LZ70_PDDA-TFSI sepa a o s, espec i ely. The dQ/dV analysis has been ca ied ou on he 1s (a—cha ge and b—discha ge) and 10 h (a’—cha ge and b’—discha ge) cycle o Li/NMC622 cells. Compa ing all dQ/dV cu es in he cha ging p ocess, in he 1s cycle o Li/NMC622 cell wi h LP70_PVDF-HFP, a mo e p onounced peak (ma ked in ed ci cle) wi h inc eased in ensi y was obse ed. I has been epo ed by S. Zhang and R. Jung e al. [ 57 , 58 ] ha he i s peak is usually ela ed o hexagonal (H1) o monoclinic (M) ans o ma ion, which could be spli in some cases, whe e i s peak ep esen s Ni 3+ /Ni 4+ oxida ion and second peak is a ibu ed o Co 3+ /Co 4+ oxida ion. The spli ing o H1 o M peak is obse ed in all Li/NMC622-based sys ems; howe e , in Li/NMC622 cells wi h LZ90_PEO300k and LZ70_PDDA-TFSI sepa a o s, he i s pa o he spli peak has e y low in ensi y. The inc eased in ensi y seen o he p onounced i s peak (ma ked wi h ed ci cle in Figu e 7i) co esponds o he highe capaci ies obse ed du ing cha ge in Li/NMC622 cell wi h LP70_PVDF-HFP and could be a ibu ed o dec easing “sepa a o /ca hode” in e ace esis ance. On compa ing cha ging p ocess peaks o cells wi h LLZO-based sepa a o s, he educ ion in he peak in ensi ies o e bo h cycles is mo e p ominen in he case o cells wi h LZ90_PEO300k. This a iance in he peak in ensi ies o he 10 h cycle be ween he wo sepa a o s demons a es he la ge capaci y ade in Li/NMC622 cell wi h LZ90_PEO300k, which co obo a es he di e ences in discha ge capaci ies as seen in Table 2. No u he phase ansi ion peaks we e obse ed in NMC622 ma e ial due o he cha ging ol age no eaching 4.6 V [ 57 ]. The b oadening and shi o discha ge p ocess peaks du ing he cycling could be seen due o an inc ease in o e all cell esis ance [59]. 3.3. Compa i i e Analysis The wo k ca ied ou he e is pa o an ini ial a emp a op imiza ion o ce amic- ich sepa a o s aimed a being used in li hium me al-based high- ol age solid-s a e ba e ies. F om ou p e ious wo k [ 32 ], he key message abou PEO-based ce amic- ich sepa a o s was abou he equi emen o modi ying he polyme hos in he ma ix o pai ing wi h high- ol age ca hode ma e ials. Howe e , i has been obse ed ha he change in he o mula ion o a polyme -based ma ix is no o simply eplace PEO wi h an HV-s able polyme such as PDDA-TFSI o PVDF-HFP. The e o e, in his wo k, we we e ocused on op imizing he ma ix in GEN 2 ce amic- ich composi e sepa a o s (C-SCEs) o imp o e hei applicabili y in HV solid-s a e ba e ies wi h Li me al anode. The op imiza ion o he sepa a o ma ix was done in wo pa s, wi h he i s pa conce ning ma e ial selec ion and p epa a ion and he second pa conce ning he es ing o he sepa a o s. All GEN 2 sepa a o s we e compa ed wi h LLZO-PEO-LiTFSI-based e e ence sepa a o s du ing he op imiza ion ials. The i s pa o he op imiza ion p ocess consis ed o selec ing he componen s o each ma ix and hei success ul ab ica ion a e modi ying he pos -p ocessing pa ame e s. The in es iga ed sepa a o s we e es ed o hei ilm- o ming abili y, su ace mo phology, c oss-sec ional mic os uc u e, and ionic conduc i i y a di e en empe a u es. All GEN 2 sepa a o s ha e been p epa ed ia a acile p ocess which can be easily scaled up o la ge ba ch sizes. I is impo an o u ilize high-ene gy mixing solu ions o compensa e o p oblems wi h agglome a ion o ce amic pa icles. The p ocessing o di e en sepa a o s was highly dependen on he molecula weigh o he used polyme s, which was seen om he lack o ilm o ma ion o LZ70_PBA and LZ80_PBA. An impo an pa ame e o be moni o ed is he iscosi y o sepa a o slu y, which helps in achie ing desi ed Ba e ies 2025,11, 42 19 o 24 hicknesses and p e en sedimen a ion o ce amic pa icles. The selec ion o sepa a o s o he second pa has been done based on physical–chemical p ope y e alua ions and ionic conduc i i y measu emen s. In he second pa , selec ed GEN 2 sepa a o s ha e been e alua ed o hei s a- bili y agains li hium me al and in high- ol age Li/NMC622 cells. In Li/Li cells wi h LZ70_PDDA-TFSI and LP70_PVDF-HFP, bo h GEN 2 sepa a o s we e only able o endu e CCD o 0.1 mA/cm 2 compa ed o ha o 0.25 mA/cm 2 [ 32 ] in LLZO-PEO-based GEN 1 sepa a o s. Du ing long- e m cycling o Li/Li cells wi h GEN 2 sepa a o s, ela i ely poo cyclabili y has been demons a ed, wi h “Li/LZ70_PDDA-TFSI/Li” being s able up o 300 h and “Li/LP70_PVDF-HFP/Li” being s able up o 350 h. Bo h GEN 2 sepa a o s exhibi ed ela i ely poo s abili y wi h li hium me al compa ed o LZ90_PEO300k, which emained s able, cycling o mo e han 800 h wi h a s able pola iza ion. Li/Li cells wi h LZ70_PDDA-TFSI demons a ed s able and symme ic pola iza ion compa ed o uns able and asymme ic pola iza ion in Li/Li cells wi h LP70_PVDF-HFP du ing long- e m cycling. Howe e , when Li/NMC622 cells wi h GEN 2 sepa a o s we e e alua ed, i was seen ha he oles we e e e sed, wi h Li/NMC622 cells wi h GEN 2 sepa a o s p o ing o be mo e s able compa ed o hose o Li/NMC622 cells wi h LZ90_PEO300k du ing long- e m gal anos a ic cycling. Compa ing he pe o mance o he selec ed GEN 2 sepa a o s, i was seen ha LP70_PVDF-HFP demons a ed good discha ge C- a e pe o mance wi h ele an discha ge capaci ies up o 0.5C compa ed o ha o 0.1C o LZ70_PDDA-TFSI. On he o he hand, LZ70_PDDA-TFSI based cells exhibi ed s able cyclabili y wi h be e capaci y e en ion o he wo GEN 2 sepa a o s o e 50 cycles. Fu he ad anced cha ac e iza ion equi ed o shed ligh on he po en ial deg ada ion mechanisms o each o he sepa a o sys ems will be pe o med as pa o u u e wo k. Figu e 8summa ies he esul s om a ious indica o s e alua ed du ing his s udy. I could be obse ed ha he PEO-based GEN 1 sepa a o shows good pe o mances in ac o s which we e di ec ly a ec ed by con ac wi h Li me al, ha ing a good li hophilic beha io . On he o he hand, GEN 2 sepa a o s exhibi be e pe o mance in indica o s which di ec ly deal wi h high- ol age solid-s a e ba e ies. Thus, designing and op imizing ce amic- ich composi e sepa a o s is no s aigh - o wa d and equi es mo e inpu s o imp o e he pe o mance, especially o he s abili y wi h li hium me al and a high- ol age s able ca hode. Ba e ies 2025, 11, x FOR PEER REVIEW 19 o 24 s able, cycling o mo e han 800 h wi h a s able pola iza ion. Li/Li cells wi h LZ70_PDDA- TFSI demons a ed s able and symme ic pola iza ion compa ed o uns able and asym- me ic pola iza ion in Li/Li cells wi h LP70_PVDF-HFP du ing long- e m cycling. Howe e , when Li/NMC622 cells wi h GEN 2 sepa a o s we e e alua ed, i was seen ha he oles we e e e sed, wi h Li/NMC622 cells wi h GEN 2 sepa a o s p o ing o be mo e s able compa ed o hose o Li/NMC622 cells wi h LZ90_PEO300k du ing long- e m gal anos a ic cycling. Compa ing he pe o mance o he selec ed GEN 2 sepa a o s, i was seen ha LP70_PVDF-HFP demons a ed good discha ge C- a e pe o mance wi h ele an discha ge capaci ies up o 0.5C compa ed o ha o 0.1C o LZ70_PDDA-TFSI. On he o he hand, LZ70_PDDA-TFSI based cells exhibi ed s able cyclabili y wi h be e capaci y e en ion o he wo GEN 2 sepa a o s o e 50 cycles. Fu he ad anced cha ac- e iza ion equi ed o shed ligh on he po en ial deg ada ion mechanisms o each o he sepa a o sys ems will be pe o med as pa o u u e wo k. Figu e 8 summa ies he esul s om a ious indica o s e alua ed du ing his s udy. I could be obse ed ha he PEO-based GEN 1 sepa a o shows good pe o mances in ac o s which we e di ec ly affec ed by con ac wi h Li me al, ha ing a good li hophilic beha io . On he o he hand, GEN 2 sepa a o s exhibi be e pe o mance in indica o s which di ec ly deal wi h high- ol age solid-s a e ba e ies. Thus, designing and op imiz- ing ce amic- ich composi e sepa a o s is no s aigh - o wa d and equi es mo e inpu s o imp o e he pe o mance, especially o he s abili y wi h li hium me al and a high- ol - age s able ca hode. Figu e 8. Compa a i e diag am o essen ial p ope ies o GEN 1 and GEN 2 ce amic- ich composi e elec oly es. 4. Conclusions To summa ize, his wo k is ocused on he op imiza ion and ab ica ion o ce amic- ich composi e sepa a o s (GEN 2) o add ess high- ol age ins abili y o a polyme ic ma- ix demons a ed by PEO-based composi e sepa a o s. The composi e sepa a o s we e p epa ed using acile solu ion-cas ing me hod o s udy he in luence o diffe en ma ix componen s and composi ions on he elec ochemical s abili y o Li/NMC622 cells wi h ce amic- ich composi e sepa a o s. The in es iga ed GEN 2 composi e sepa a o s wi h diffe en ce amic con en s and polyme ma ices (PVDF-HFP, PDDA-TFSI, and PBA) ha e been explo ed in his s udy o assess hei effec on he mechanical s abili y, mic os uc u e, and high- ol age s abili y Figu e 8. Compa a i e diag am o essen ial p ope ies o GEN 1 and GEN 2 ce amic- ich composi e elec oly es. Ba e ies 2025,11, 42 20 o 24 4. Conclusions To summa ize, his wo k is ocused on he op imiza ion and ab ica ion o ce amic- ich composi e sepa a o s (GEN 2) o add ess high- ol age ins abili y o a polyme ic ma ix demons a ed by PEO-based composi e sepa a o s. The composi e sepa a o s we e p epa ed using acile solu ion-cas ing me hod o s udy he in luence o di e en ma ix componen s and composi ions on he elec ochemical s abili y o Li/NMC622 cells wi h ce amic- ich composi e sepa a o s. The in es iga ed GEN 2 composi e sepa a o s wi h di e en ce amic con en s and polyme ma ices (PVDF-HFP, PDDA-TFSI, and PBA) ha e been explo ed in his s udy o assess hei e ec on he mechanical s abili y, mic os uc u e, and high- ol age s abili y o he sepa a o s. PBA-based ce amic- ich composi e sepa a o s ha e been disca ded a an ea ly s age due o poo mechanical p ope ies and low ionic conduc i i y. O he sepa a o s based on 80 w % and 90 w % LLZO in PDDA-TFSI-based ma ix ha e been also ejec ed due o low ionic conduc i i y and poo mechanical p ope ies. The e o e, sepa a o s wi h 70 w % o he ce amic con en in PVDF, and PDDA-TFSI polyme -based ma ices we e op imized and e alua ed u he . The LP70_PVDF-HFP sepa- a o was seen o ha e he highes ionic conduc i i y a 60 ◦ C, ollowed by he LZ70_PDDA- TFSI and LZ90_PEO300k sepa a o s. Bo h LP70_PVDF-HFP and LZ70_PDDA-TFSI sepa a- o s wi h dense mic os uc u e we e e alua ed o hei s abili y agains li hium me al and high- ol age Li/NMC622 cells. The di e ences be ween he PEO-based GEN 1 and PDDA-TFSI and PVDF-HFP-based GEN 2 sepa a o s a e e y no iceable du ing he elec ochemical cha ac e iza ions in bo h Li/Li and Li/NMC622 cells. In Li/Li cells es ing he s abili y agains Li me al, cells wi h PEO-based GEN 1 sepa a o s had supe io pe o mance compa ed o cells wi h bo h GEN 2 sepa a o s. The supe io pe o mance o Li/Li cells wi h GEN 1 sepa a o s was ue in bo h cases o c i ical cu en densi y and long- e m cycling es s. Con a y o he pe o mance o Li/Li cells, Li/NMC622 cells wi h bo h GEN 2 sepa a o s showcased be e pe o mance du ing long- e m cycling compa ed o he PEO-based GEN 1 sepa a o . Li/NMC622 cells wi h LP70_PVDF-HFP and LZ70_PDDA-TFSI ha e been obse ed o ha e highe discha ge capaci y e en ion, as well as highe coulombic e iciency, signi ying imp o ed elec ochemical s abili y o he high- ol age s able polyme s and mo e e e sible sys ems du ing cycling. Li/NMC622 cells wi h LP70_PVDF-HFP and LZ70_PDDA-TFSI exhibi ed be e pe - o mances in discha ge C- a e pe o mance and long- e m cycling, espec i ely. The e o e, i was seen ha when changing om a li hophilic polyme such as PEO in he ma ix, some sac i ices need o be made o imp o e pe o mance a high ol age cycling condi ions o he solid-s a e ba e ies. Ne e heless, despi e imp o emen in high- ol age s abili y du ing cycling a e changing he polyme ype in he ma ix, he deg ada ion obse ed is signi ican and needs o be u he cha ac e ized o be e unde s anding. As pa o u u e wo k, i is ecommended ha he GEN 2 sepa a o s be es ed in cells wi h a composi e ca hode ha ing a high- ol age s able ca holy e o compa e he changes in cyclabili y and capaci y e en ion wi h he eplacemen o he PEO-based ca holy e. GEN 2 sepa a o s in combina ion wi h high- ol age s able ca hodes would also be e alua ed o cycling pe o mance a a lowe ope a ing empe a u e o 25 ◦C. Supplemen a y Ma e ials: The ollowing suppo ing in o ma ion can be downloaded a : www. mdpi.com/xxx/s1, Figu e S1 Scheme o LATP syn hesis p ocess ia solu ion assis ed solid-s a e eac ion ou e; Figu e S2 XRD di ac og ams o (a) cubic—LLZO and (b) hombohed al LATP powde wi h ( Ba e ies 2025, 11, x FOR PEER REVIEW 20 o 24 o he sepa a o s. PBA-based ce amic- ich composi e sepa a o s ha e been disca ded a an ea ly s age due o poo mechanical p ope ies and low ionic conduc i i y. O he sepa- a o s based on 80 w % and 90 w % LLZO in PDDA-TFSI-based ma ix ha e been also ejec ed due o low ionic conduc i i y and poo mechanical p ope ies. The e o e, sepa a o s wi h 70 w % o he ce amic con en in PVDF, and PDDA-TFSI polyme -based ma ices we e op imized and e alua ed u he . The LP70_PVDF-HFP sepa a o was seen o ha e he highes ionic conduc i i y a 60 °C, ollowed by he LZ70_PDDA-TFSI and LZ90_PEO300k sepa a o s. Bo h LP70_PVDF-HFP and LZ70_PDDA-TFSI sepa a o s wi h dense mic os uc u e we e e alua ed o hei s abili y agains li hium me al and high- ol age Li/NMC622 cells. The diffe ences be ween he PEO-based GEN 1 and PDDA-TFSI and PVDF-HFP- based GEN 2 sepa a o s a e e y no iceable du ing he elec ochemical cha ac e iza ions in bo h Li/Li and Li/NMC622 cells. In Li/Li cells es ing he s abili y agains Li me al, cells wi h PEO-based GEN 1 sepa a o s had supe io pe o mance compa ed o cells wi h bo h GEN 2 sepa a o s. The supe io pe o mance o Li/Li cells wi h GEN 1 sepa a o s was ue in bo h cases o c i ical cu en densi y and long- e m cycling es s. Con a y o he pe - o mance o Li/Li cells, Li/NMC622 cells wi h bo h GEN 2 sepa a o s showcased be e pe o mance du ing long- e m cycling compa ed o he PEO-based GEN 1 sepa a o . Li/NMC622 cells wi h LP70_PVDF-HFP and LZ70_PDDA-TFSI ha e been obse ed o ha e highe discha ge capaci y e en ion, as well as highe coulombic efficiency, signi y- ing imp o ed elec ochemical s abili y o he high- ol age s able polyme s and mo e e- e sible sys ems du ing cycling. Li/NMC622 cells wi h LP70_PVDF-HFP and LZ70_PDDA-TFSI exhibi ed be e pe - o mances in discha ge C- a e pe o mance and long- e m cycling, espec i ely. The e- o e, i was seen ha when changing om a li hophilic polyme such as PEO in he ma ix, some sac i ices need o be made o imp o e pe o mance a high ol age cycling condi- ions o he solid-s a e ba e ies. Ne e heless, despi e imp o emen in high- ol age s a- bili y du ing cycling a e changing he polyme ype in he ma ix, he deg ada ion ob- se ed is signi ican and needs o be u he cha ac e ized o be e unde s anding. As pa o u u e wo k, i is ecommended ha he GEN 2 sepa a o s be es ed in cells wi h a composi e ca hode ha ing a high- ol age s able ca holy e o compa e he changes in cyclabili y and capaci y e en ion wi h he eplacemen o he PEO-based ca holy e. GEN 2 sepa a o s in combina ion wi h high- ol age s able ca hodes would also be e alu- a ed o cycling pe o mance a a lowe ope a ing empe a u e o 25 °C. Supplemen a y Ma e ials: The ollowing suppo ing in o ma ion can be downloaded a : www.mdpi.com/xxx/s1, Figu e S1 Scheme o LATP syn hesis p ocess ia solu ion assis ed solid- s a e eac ion ou e; Figu e S2 XRD diff ac og ams o (a) cubic—LLZO and (b) hombohed al LATP powde wi h ( ) ma king addi ional o ho hombic phase and ( ) ma king addi ional ma king ad- di ional LiTiPO5 phase; SEM mic og aphs o (c) LLZO powde pa icles and (d) LATP powde pa - icles. Powde pa icle size dis ibu ion g aph o (e) LLZO and ( ) LATP; Figu e S3 C oss-sec ional SEM images o ab ica ed C-SCEs compa ing mic os uc u es o diffe en polyme ic ma ix g oups, s a ing om PEO-ma ix-based sepa a o s [2]: (a) LZ90_PEO300k- and (b) LZ95_PEO300k-, PVDF- HFP-ma ix-based sepa a o s (c) LP70_PVDF-HFP and ( ) LP70_PVDF-HFP wi hou SN, PBA-ma- ix-based sepa a o s (d) LZ70_PBA and (e) LZ80_PBA- and PDDA-TFSI-ma ix-based sepa a o s (g) LZ70_PDDA-TFSI (h) LZ80_PDDA-TFSI and (i) LZ90_PDDA-TFSI; Figu e S4 TGA he mo- g aphs o (a) LZ70_PDDA-TFSI and (b) LP70_PVDF-HFP; Figu e S5 O iginal and i ed EIS spec a o (a) Li/LZ70_PDDA-TFSI/Li and (d) Li/ LP70_PVDF-HFP /Li cell be o e and a e pola iza ion; Inse - Ch onoampe ome y p o ile (I s. ime) o (b) Li/LZ70_PDDA-TFSI/Li and (e) Li/ LP70_PVDF- HFP /Li symme ic cell; (c) and ( ) Equi alen ci cui used o i he (be o e and a e pola iza ion) impedance p o iles o ans e ence numbe .; Figu e S6 Vol age e sus ime p o iles o long- e m ) ma king addi ional o ho hombic phase and ( Ba e ies 2025, 11, x FOR PEER REVIEW 20 o 24 o he sepa a o s. PBA-based ce amic- ich composi e sepa a o s ha e been disca ded a an ea ly s age due o poo mechanical p ope ies and low ionic conduc i i y. O he sepa- a o s based on 80 w % and 90 w % LLZO in PDDA-TFSI-based ma ix ha e been also ejec ed due o low ionic conduc i i y and poo mechanical p ope ies. The e o e, sepa a o s wi h 70 w % o he ce amic con en in PVDF, and PDDA-TFSI polyme -based ma ices we e op imized and e alua ed u he . The LP70_PVDF-HFP sepa a o was seen o ha e he highes ionic conduc i i y a 60 °C, ollowed by he LZ70_PDDA-TFSI and LZ90_PEO300k sepa a o s. Bo h LP70_PVDF-HFP and LZ70_PDDA-TFSI sepa a o s wi h dense mic os uc u e we e e alua ed o hei s abili y agains li hium me al and high- ol age Li/NMC622 cells. The diffe ences be ween he PEO-based GEN 1 and PDDA-TFSI and PVDF-HFP- based GEN 2 sepa a o s a e e y no iceable du ing he elec ochemical cha ac e iza ions in bo h Li/Li and Li/NMC622 cells. In Li/Li cells es ing he s abili y agains Li me al, cells wi h PEO-based GEN 1 sepa a o s had supe io pe o mance compa ed o cells wi h bo h GEN 2 sepa a o s. The supe io pe o mance o Li/Li cells wi h GEN 1 sepa a o s was ue in bo h cases o c i ical cu en densi y and long- e m cycling es s. Con a y o he pe - o mance o Li/Li cells, Li/NMC622 cells wi h bo h GEN 2 sepa a o s showcased be e pe o mance du ing long- e m cycling compa ed o he PEO-based GEN 1 sepa a o . Li/NMC622 cells wi h LP70_PVDF-HFP and LZ70_PDDA-TFSI ha e been obse ed o ha e highe discha ge capaci y e en ion, as well as highe coulombic efficiency, signi y- ing imp o ed elec ochemical s abili y o he high- ol age s able polyme s and mo e e- e sible sys ems du ing cycling. Li/NMC622 cells wi h LP70_PVDF-HFP and LZ70_PDDA-TFSI exhibi ed be e pe - o mances in discha ge C- a e pe o mance and long- e m cycling, espec i ely. The e- o e, i was seen ha when changing om a li hophilic polyme such as PEO in he ma ix, some sac i ices need o be made o imp o e pe o mance a high ol age cycling condi- ions o he solid-s a e ba e ies. Ne e heless, despi e imp o emen in high- ol age s a- bili y du ing cycling a e changing he polyme ype in he ma ix, he deg ada ion ob- se ed is signi ican and needs o be u he cha ac e ized o be e unde s anding. As pa o u u e wo k, i is ecommended ha he GEN 2 sepa a o s be es ed in cells wi h a composi e ca hode ha ing a high- ol age s able ca holy e o compa e he changes in cyclabili y and capaci y e en ion wi h he eplacemen o he PEO-based ca holy e. GEN 2 sepa a o s in combina ion wi h high- ol age s able ca hodes would also be e alu- a ed o cycling pe o mance a a lowe ope a ing empe a u e o 25 °C. Supplemen a y Ma e ials: The ollowing suppo ing in o ma ion can be downloaded a : www.mdpi.com/xxx/s1, Figu e S1 Scheme o LATP syn hesis p ocess ia solu ion assis ed solid- s a e eac ion ou e; Figu e S2 XRD diff ac og ams o (a) cubic—LLZO and (b) hombohed al LATP powde wi h ( ) ma king addi ional o ho hombic phase and ( ) ma king addi ional ma king ad- di ional LiTiPO5 phase; SEM mic og aphs o (c) LLZO powde pa icles and (d) LATP powde pa - icles. Powde pa icle size dis ibu ion g aph o (e) LLZO and ( ) LATP; Figu e S3 C oss-sec ional SEM images o ab ica ed C-SCEs compa ing mic os uc u es o diffe en polyme ic ma ix g oups, s a ing om PEO-ma ix-based sepa a o s [2]: (a) LZ90_PEO300k- and (b) LZ95_PEO300k-, PVDF- HFP-ma ix-based sepa a o s (c) LP70_PVDF-HFP and ( ) LP70_PVDF-HFP wi hou SN, PBA-ma- ix-based sepa a o s (d) LZ70_PBA and (e) LZ80_PBA- and PDDA-TFSI-ma ix-based sepa a o s (g) LZ70_PDDA-TFSI (h) LZ80_PDDA-TFSI and (i) LZ90_PDDA-TFSI; Figu e S4 TGA he mo- g aphs o (a) LZ70_PDDA-TFSI and (b) LP70_PVDF-HFP; Figu e S5 O iginal and i ed EIS spec a o (a) Li/LZ70_PDDA-TFSI/Li and (d) Li/ LP70_PVDF-HFP /Li cell be o e and a e pola iza ion; Inse - Ch onoampe ome y p o ile (I s. ime) o (b) Li/LZ70_PDDA-TFSI/Li and (e) Li/ LP70_PVDF- HFP /Li symme ic cell; (c) and ( ) Equi alen ci cui used o i he (be o e and a e pola iza ion) impedance p o iles o ans e ence numbe .; Figu e S6 Vol age e sus ime p o iles o long- e m ) ma king addi ional ma king ad- di ional LiTiPO 5 phase; SEM mic og aphs o (c) LLZO powde pa icles and (d) LATP powde Ba e ies 2025,11, 42 21 o 24 pa icles. Powde pa icle size dis ibu ion g aph o (e) LLZO and ( ) LATP; Figu e S3 C oss- sec ional SEM images o ab ica ed C-SCEs compa ing mic os uc u es o di e en polyme ic ma ix g oups, s a ing om PEO-ma ix-based sepa a o s [ 2 ]: (a) LZ90_PEO300k- and (b) LZ95_PEO300k-, PVDF-HFP-ma ix-based sepa a o s (c) LP70_PVDF-HFP and ( ) LP70_PVDF-HFP wi hou SN, PBA- ma ix-based sepa a o s (d) LZ70_PBA and (e) LZ80_PBA- and PDDA-TFSI-ma ix-based sepa a o s (g) LZ70_PDDA-TFSI (h) LZ80_PDDA-TFSI and (i) LZ90_PDDA-TFSI; Figu e S4 TGA he mog aphs o (a) LZ70_PDDA-TFSI and (b) LP70_PVDF-HFP; Figu e S5 O iginal and i ed EIS spec a o (a) Li/LZ70_PDDA-TFSI/Li and (d) Li/ LP70_PVDF-HFP /Li cell be o e and a e pola iza ion; Inse - Ch onoampe ome y p o ile (I s. ime) o (b) Li/LZ70_PDDA-TFSI/Li and (e) Li/ LP70_PVDF- HFP /Li symme ic cell; (c) and ( ) Equi alen ci cui used o i he (be o e and a e pola iza ion) impedance p o iles o ans e ence numbe .; Figu e S6 Vol age e sus ime p o iles o long- e m gal anos a ic cycling o Li/Li cells wi h LP70_PVDF-HFP. Cycling condi ions: cu en densi y 0.1 mA/cm 2 , hal cycle s ep o 1 h, 60 ◦ C.; Figu e S7 Discha ge capaci y and (b) coulombic e icien- cies e iciency and (c) a e age ol age o bo h cha ge and discha ge s ep o Li/NMC622 cells wi h LP70_PVDF-HFP and LP70_PVDF-HFP wi hou SCN. Vol age e sus capaci y cu es o Li/NMC622 cells wi h GEN 2 sepa a o s a e long- e m cycling (d) LP70_PVDF-HFP wi hou SCN and (e) LP70_PVDF-HFP. All compa isons we e made a e cycling o 20 cycles. dQ/dV e sus ol age cu es o he 1s and 10 h cycles o Li/NMC622 cells wi h (g) LP70_PVDF-HFP wi hou SCN, (h) LP70_PVDF-HFP; Table S1 T ans e ence numbe o GEN 2 sepa a o s [14,32,60–63]. Au ho Con ibu ions: Concep ualiza ion, K.V., D.F.-R. and A.K.; me hodology, K.V., M.F., D.F.-R. and A.K.; alida ion, K.V. and A.K.; o mal analysis, K.V. and A.K.; in es iga ion, K.V.; esou ces, M.F., D.F.-R., I.U. and A.K.; da a cu a ion, K.V. and A.K.; w i ing—o iginal d a p epa a ion, K.V.; w i ing— e iew and edi ing, K.V., M.F., D.F.-R., I.U. and A.K.; isualiza ion, D.F.-R. and A.K.; supe ision, D.F.-R. and A.K.; p ojec adminis a ion, D.F.-R. and A.K.; unding acquisi ion, D.F.-R., I.U. and A.K. All au ho s ha e ead and ag eed o he published e sion o he manusc ip . Funding: Funding om Fundación CIDETEC, DESTINY COFUND PhD P og amme unde Ma ie Sklodowska-Cu ie g an (G.A. No 945357), and Ge man “Fede al Minis y o Educa ion and Resea ch” (BMBF) unde g an numbe s 13XP0434A (Fes Ba 2—Oxid) and 13XP0428A (Fes Ba 2—Hyb ide). Da a A ailabili y S a emen : The da a ha suppo he indings o his s udy a e a ailable om he co esponding au ho upon easonable eques . Acknowledgmen s: K.V. acknowledges he unding om he DESTINY COFUND PhD P og amme which has ecei ed unding om he Eu opean Union’s Ho izon 2020 esea ch and inno a ion p o- g amme unde he Ma ie Sklodowska-Cu ie (g an ag eemen No 945357) and Fundación CIDETEC. Financial suppo om he Ge man “Fede al Minis y o Educa ion and Resea ch” (BMBF) unde g an numbe s 13XP0434A (Fes Ba 2—Oxid) and 13XP0428A (Fes Ba 2—Hyb ide) is g a e ully acknowledged. The au ho s also g a e ully acknowledge G i Häuschen and Philipp Hecke om Fo schungszen um Jülich GmbH o help wi h he syn hesis o LLZO and LATP powde s used in his wo k. Con lic s o In e es : The au ho s decla e no con lic s o in e es . Re e ences 1. Ozawa, K. Li hium-ion echa geable ba e ies wi h LiCoO 2 and ca bon elec odes: The LiCoO 2 /C sys em. Solid. S a e Ion. 1994, 69, 212–221. [C ossRe ] 2. E ekha i, A. Li hium Ba e ies o Elec ic Vehicles: F om Economy o Resea ch S a egy. ACS Sus ain. Chem. Eng. 2019, 7, 5602–5613. [C ossRe ] 3. 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