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Low-Tempe a u e Py ome allu gical Recycling P e-T ea men o Li hium-Ion
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Ba e ies: Unde s anding o The mal Decomposi ion and Su ace Changes
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Anna P ažano á a), Jan Kočí a), b), Jonáš Uřičář a, c), Dominik Pilnaj a), Daniel-Ioan S oe d), and
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Vacla Knap a)
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a) Depa men o Elec o echnology, Facul y o Elec ical Enginee ing, Czech
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Technical Uni e si y in P ague, P ague, Czech Republic
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b) Depa men o Glass and Ce amics, Uni e si y o Chemis y and Technology
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P ague, Technická 5, 166 28 P ague, Czechia
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c) Depa men o Polyme s, Uni e si y o Chemis y and Technology P ague, P ague,
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Czech Republic
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d) Depa men o Ene gy, Aalbo g Uni e si y, Aalbo g, Denma k
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* Co esponding au ho . E-mail add ess: anna.p azano a@c u .cz (A. P ažano á).
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Abs ac
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Escala ing global li hium-ion ba e y demand necessi a es e icien end-o -li e managemen .
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Py ome allu gical ecycling o e s a p omising ou e o me al eco e y and en i onmen al
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impac minimiza ion. Howe e , op imizing low- empe a u e p e- ea men o comple e
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o ganic emo al while p ese ing ac i e ma e ial in eg i y emains challenging. This s udy
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in es iga ed he mal decomposi ion and su ace changes o key ba e y componen s (NMC622
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ca hode, g aphi e anode, polyme ic sepa a o ) om 100 o 800 °C, ocusing on he 400-650 °C
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indus ial in e al. Ma e ial esponses we e cha ac e ized using TGA-MS, iso he mal mass loss,
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and SEM-EDS. A 500 °C ea men was iden i ied as op imal, enabling comple e o ganic
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ca bon emo al wi hin one hou wi hou comp omising NMC spinel s uc u e o cu en
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collec o deg ada ion. This p ecise con ol educes ene gy consump ion and mi iga es
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haza dous gas elease, enhancing en i onmen al sus ainabili y. Findings de ine pa ame e s o
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e icien elec oac i e ma e ial sepa a ion, p o iding a p ac ical, scalable, and cos -e ec i e
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s a egy o imp o ing ba e y ecycling. This wo k ad ances low- empe a u e
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py ome allu gical p ocessing unde s anding, suppo ing a ci cula economy o c i ical
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ma e ials.
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Keywo ds: li hium-ion ba e y, ecycling, py ome allu gy, high- empe a u e ea men ,
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he mal decomposi ion, su ace changes
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1. In oduc ion
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The escala ing global demand o li hium-ion ba e ies (LIBs), especially in elec ic
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ehicles (EVs), necessi a es e icien and sus ainable end-o -li e managemen s a egies [1], [2].
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In pa allel, g owing en i onmen al conce ns and he limi ed a ailabili y o c i ical aw ma e ials
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such as li hium, cobal , and nickel unde sco e he impo ance o de eloping ci cula economy
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solu ions ha suppo esou ce secu i y and indus ial esilience [3], [4].
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Con en ional py ome allu gical ecycling o LIBs ypically in ol es a wo-s ep p ocess:
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a low- empe a u e s age (up o ~800 °C) o decompose o ganics and sepa a e cell componen s,
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ollowed by high- empe a u e smel ing (be ween 1500 and 1800 °C) o me al eco e y [5], [6].
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The i s s age condi ions he in e nal elec ode–sepa a o assembly and mi iga es sa e y
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haza ds om esidual elec oly es and lammable ma e ials [7]. This s ep is o en decoupled
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om me allu gical eco e y o con ol o ganic deg ada ion be e , p ese e ac i e ma e ials’
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in eg i y, and acili a e delamina ion o downs eam eco e y. Howe e , decomposi ion
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in ol es o e lapping eac ions wi h speci ic onse empe a u es, equi ing p ecise p ocess
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con ol. Among a ious chemis ies, li hium nickel manganese cobal oxide (NMC) is widely
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s udied due o i s p e alence in high-ene gy cells and complex he mochemical beha iou [8].
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Indus ially, ex e nal casings (polyme -lamina ed aluminium o nickel) a e emo ed be o e
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he mal ea men , so esea ch ocuses on he in e nal s ack: ca hode, anode, and sepa a o [7],
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[9].
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NMC ca hodes a e gene ally he mally s able ela i e o o ganic compounds, bu hei
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beha iou depends on deli hia ion and esidual binde s o sal s [10]. While he spinel s uc u e
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may pe sis up o 800 °C [11], side eac ions in ol ing li hium sal s (e.g., li hium
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hexa luo ophospha e, LiPF6; li hium luo ide, LiF; li hium ca bona e, Li2CO3) can lead o
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he elease o ca bon dioxide (CO2) o hyd ogen luo ide (HF) and phospho us-con aining
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gases [12], [13]. Fu he mo e, he aluminium (Al) cu en collec o , wi h a mel ing poin o
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~660 °C, may mel and encapsula e ac i e ma e ial i empe a u es exceed his h eshold [14],
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[15], comp omising downs eam sepa a ion and ma e ial quali y [6], [16], [17]. The e o e,
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p ecise empe a u e con ol is c i ical o emo e o ganic compounds while p ese ing ca hode
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in eg i y [18].
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G aphi e anodes exhibi high he mal s abili y unde ine a mosphe es bu oxidise in ai
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abo e ~500 °C, esul ing in signi ican CO2 elease and mass loss [19]. Comple e combus ion
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ypically occu s be ween 600 and 700 °C, depending on oxygen con en in he a mosphe e,
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hea ing a e, and su ace a ea [19]–[21]. Residual su ace compounds, such as li hium alkyl
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ca bona es o Li2CO3, o igina ing om solid elec oly e in e phase (SEI) laye deg ada ion,
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may also a ec he oxida ion pa hway and ini ia e ea lie decomposi ion [22].
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Polyme ic sepa a o s, ypically made o polye hylene (PE) o polyp opylene (PP), begin
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o deg ade below 200 °C. This in ol es ini ial mel ing ollowed by decomposi ion in o
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hyd oca bon species [23]–[25]. Poly inylidene luo ide (PVDF), commonly used as a binde ,
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decomposes be ween 350 and 500 °C, eleasing HF, wa e , and low-molecula -weigh
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agmen s [26]. Abo e 500 °C, emaining esidues a e mos ly con e ed in o s able ino ganic
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phases; o example, alumina-coa ed sepa a o s may yield aluminium oxide (Al2O3) a e
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ea men [25].
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Gi en he complexi y o mul i-componen ba e y a chi ec u es, mos s udies on low-
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empe a u e py ome allu gical p e- ea men ha e ocused on achie ing e icien o ganic
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emo al while p ese ing aluable ma e ials, as bo h a e essen ial o scalable LIB
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ecycling [27]–[30]. The mal exposu e be ween 500 and 600 °C is widely ega ded as a c i ical
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s ep o decomposing polyme ic binde s and e apo a ing elec oly e esidues, he eby
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imp o ing he e iciency o mechanical comminu ion and downs eam me al eco e y [29].
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Howe e , empe a u es abo e 600 °C can lead o he emb i lemen o mel ing o Al oils,
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complica ing hei sepa a ion. In pa allel, ele a ed empe a u es also p omo e he ca bo he mic
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educ ion o ac i e ma e ials, such as LiCoO2, which begins decomposing a ound 700 °C and
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a ec s bo h mass loss and li hium eco e y yields. Al hough e iews o p e- ea men s a egies
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con i m ha calcina ion be ween 150 and 650 °C e icien ly emo es conduc i e ca bon and
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o ganic compounds, educing binde adhesion and enhancing sepa abili y, hey also emphasise
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challenges ela ed o high ene gy demands and he elease o haza dous gases, including oxic
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luo ina ed species [27], [29]. Despi e hese ad ances, a de ailed, componen -speci ic
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unde s anding o he mal deg ada ion, pa icula ly how con olled hea ing in luences he
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s uc u e, su ace chemis y, and sepa abili y o indi idual ac i e ma e ials and polyme ic
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sepa a o s, emains limi ed. Such insigh s a e c ucial o he de elopmen o ene gy-e icien ,
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scalable ecycling p ocesses ha no only ensu e e ec i e o ganic emo al bu also minimise
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unwan ed side eac ions and p ese e ma e ial unc ionali y [30], [31].
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Thus, his wo k sys ema ically in es iga es he he mal deg ada ion and su ace
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e olu ion o he NMC622 ca hode, g aphi e anode, and polyme ic sepa a o ac oss a b oad
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empe a u e ange o 100 o 800 °C, pa icula ly emphasizing he 400 o 650 °C in e al
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commonly u ilised in indus ial p e- ea men . De ailed insigh s in o ma e ial esponses we e
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p o ided by employing dynamic he mog a ime ic analysis coupled wi h mass
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spec ome y (TGA-MS), iso he mal mass loss e alua ion, and high- esolu ion scanning
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elec on mic oscopy (SEM) wi h ene gy-dispe si e X- ay spec oscopy (EDS). The esul s
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indica ed ea men a 500 °C o allow comple e emo al o o ganic cons i uen s wi hin one
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hou , c i ically p ese ing he s uc u al and unc ional in eg i y o elec ochemically ac i e
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ma e ials and cu en collec o s. This iden i ied op imal empe a u e o e s a c ucial balance
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be ween e iciency and ma e ial p ese a ion, he eby p o iding p ac ical guidance o
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designing ene gy-e icien and scalable ecycling p ocesses ha suppo he b oade
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implemen a ion o ci cula economy p inciples o c i ical aw ma e ials.
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2. Ma e ials and Me hods
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2.1 Ma e ial
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The LIB pouch cells used in his s udy possess a nominal ol age o 3.65 V and a a ed
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capaci y o 78 Ah. These cells we e p e iously cha ac e ised in ou p e ious wo k by
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P ažano á e al. [32]. Each cell comp ises 36 s acked laye s comp ising NMC622 ca hode
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ma e ials, whe e he numbe s indica e he mola a io o Ni:Mn:Co, a polyme sepa a o , and
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g aphi e-based anode laye s. The elec oly e consis s o LiPF6 in an o ganic sol en , and he
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en i e assembly is encapsula ed in a lexible polyme –aluminium lamina ed pouch.
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Ini ially used in a ully elec ic ehicle, he ba e y module had a nominal ol age
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o 29.36 V and a o al ene gy capaci y o 6.85 kWh. Be o e disassembly, he module was deeply
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discha ged ( ol age le el app oxima ely 0 V). The module’s casing was ca e ully milled open
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o access he in e nal cells, and he adhesi e bonding was weakened by applying alcohol o
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acili a e hei sepa a ion. Subsequen ly, he cells we e manually ex ac ed om he opened
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module. The open s uc u e o he module, indi idual ba e y cells, p ocedu e o hei opening,
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and specimen p epa a ion and cha ac e isa ion a e shown in Figu e 1.
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Figu e 1: O e iew o he expe imen al wo k low: opening o he ba e y module, ex ac ion
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and disassembly o pouch cells, p epa a ion o specimens o ba e y ma e ials, and subsequen
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mo phological and elemen al analyses (scanning elec on mic oscopy, SEM; ene gy-dispe si e
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X- ay spec oscopy, EDS) ollowed by he mal analyses ( he mog a ime ic analysis, TGA;
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he mog a ime ic analysis coupled wi h mass spec ome y, TGA-MS).
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2.2 Me hods
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2.2.1 Specimen P epa a ion
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A se o samples was p epa ed o analysis o moni o changes in mo phology and
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su ace composi ion induced by he mal ea men . The ba e y cell was ca e ully disassembled
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using a ce amic kni e, and indi idual componen s, speci ically he ca hode enclosed wi hin
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he sepa a o pouch and he anode, we e isola ed. All p ocedu es we e conduc ed inside
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a labo a o y ume hood.
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Following disassembly, as desc ibed in Figu e 1, in ac elec odes and he sepa a o
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laye s we e p e-d ied a ambien empe a u e o e apo a e he ca bona es. The p e-d ied laye s
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we e subsequen ly sec ioned in o 25 × 25 mm squa e samples using a p ecision pape cu e .
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A e wa ds, he sec ions we e d ied a 60 °C un il no u he dec eases in mass we e obse ed
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(app oxima ely one week). The inal samples we e weighed in po celain c ucibles using an
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analy ical balance.
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The specimens we e classi ied in o h ee g oups acco ding o hei unc ional ole wi hin
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he cell: ca hode, anode, and sepa a o . In addi ion, a ou h e e ence g oup was p epa ed,
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consis ing o he ca hode laye co e ed by a sepa a o on bo h sides, o con ol po en ial
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in e acial e ec s. This con igu a ion de ia es om he s anda d a chi ec u e, in which
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sepa a o s on bo h sides ypically enclose he ca hode. Fi e independen eplica es we e
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measu ed o each sample ca ego y o ensu e s a is ical alidi y.
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Fo he he mal deg ada ion analyses, ci cula samples wi h a diame e o 5 mm we e
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punched om an unopened ba e y cell using a manual punche . These specimens comp ised
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he en i e c oss-sec ion o he ba e y cell, including spinel, sepa a o , and g aphi e laye s, and
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a e he eina e e e ed o as “c oss-sec ion samples.” In addi ion o he ull c oss-sec ion
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samples, a sepa a e specimen o ca hode, anode, and he ca hode wi h a wo-sided sepa a o
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was explici ly p epa ed o TGA-MS measu emen s.
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2.2.2 Ma e ial Cha ac e isa ion Me hods
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The mog a ime ic Analysis
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The mal deg ada ion in dynamic mode was assessed using a he mog a ime ic analyse
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(Disco e y TGA550 Au o Ad anced, TA Ins umen s, USA). A c oss-sec ion specimen,
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including all elec ochemically ac i e laye s wi h a weigh o app oxima ely 25 mg, was
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subjec ed o hea ing om oom empe a u e (24 °C) o 1000 °C a a cons an hea ing a e
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o 10 °C∙min-1 in an ai a mosphe e wi h a low a e o 65 mL∙min-1.
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The mog a ime ic Analysis – Mass Spec ome y
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The chemical composi ion o deg ada ion p oduc s was in es iga ed using coupled
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TGA-MS. The ollowing sample ypes we e analysed: c oss-sec ion, anode, ca hode, and
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ca hode wi h one-sided sepa a o . Measu emen s we e pe o med on a TG-DTA Se sys
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E olu ion sys em (Se a am, F ance) coupled o an OmniS a TM quad upole mass spec ome e
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(P ei e Vacuum, Ge many).
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Be o e he mal ea men , all samples we e s abilised a 30 °C o 30 minu es.
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Subsequen ly, he samples we e hea ed in an ai a mosphe e a a cons an hea ing a e
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o 10 °C∙min-1. A e he hea ing and he mog a ime ic da a acquisi ion we e comple ed, he
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samples we e allowed o cool unde ambien condi ions, while mass spec ome ic da a
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acquisi ion con inued o an addi ional 50 minu es. Mass spec a we e eco ded up o 150 m/z
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(mass- o-cha ge a io) wi h a esolu ion o 1 m/z; each spec um was acqui ed o e 8 seconds,
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co esponding o a dwell ime o 53 milliseconds pe m/z uni . The da a ob ained om TGA
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and MS we e synch onously aligned, p ocessed, anno a ed, and isualised using O iginP o
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so wa e. Rep esen a i e ions co esponding o speci ic compounds o chemical g oups we e
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selec ed based on he NIST17 lib a y o elec on ionisa ion spec a.
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S a ic The mal Mass Loss Analysis
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Samples we e placed in a CLASIC labo a o y u nace wi h a on -opening design o
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s a ic he mog a ime ic measu emen s. Hea ing was pe o med a 5 °C·min-1 o a ge
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empe a u es o 100, 200, 300, 400, 500, 600, 700, and 800 °C, each ollowed by a one-hou
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iso he mal hold, hen cooled o oom empe a u e by na u al con ec ion o e nigh . The
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ela i ely high hea ing a e and sho exposu e ime we e chosen o educe he equi ed ime o
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e ec i ely ob ain he s udied ma e ials, which co esponds o he s udy's objec i es and he
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economic demands o indus ial use. This app oach is ele an o py ome allu gical
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p e ea men in ba e y ecycling, whe e ene gy e iciency and ime op imisa ion a e c i ical.
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Tempe a u es we e selec ed o iden i y he minimum e ec i e ecycling h eshold unde
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economic cons ain s, ocusing in de ail on he 400 o 650 °C ange, wi h measu emen s a 400,
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450, 500, 550, 600, and 650 °C.
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A e cooling o ambien empe a u e unde na u al condi ions, g a ime ic
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measu emen s we e pe o med using a calib a ed KERN analy ical balance o e alua e mass
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loss esul ing om he mal exposu e. Each sample ype was measu ed in i e independen
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eplica es, and he mass was eco ded o ou decimal places o ensu e high p ecision.
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This me hodology enabled a comp ehensi e assessmen o he mally induced mass changes,
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enhancing unde s anding o ma e ial decomposi ion beha iou ac oss a ious empe a u e
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condi ions.
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Scanning Elec on Mic oscopy
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Following he mal exposu e, he samples we e subjec ed o s uc u al and composi ional
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analyses o assess changes induced by hea ea men . SEM was employed o examine
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modi ica ions in su ace mo phology using a TESCAN VEGA 3 LMU scanning elec on
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mic oscope. Imaging was conduc ed a an accele a ing ol age o 20 kV, a wo king dis ance o
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15 mm, and a beam in ensi y o 15 nA, u ilising bo h seconda y and backsca e ed elec ons a
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a magni ica ion o 2000×.
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To complemen he mo phological in es iga ion, EDS was pe o med o de e mine
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al e a ions in elemen al composi ion. Measu emen s we e conduc ed using an OXFORD
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collec o in NMC ca hodes. This deg ada ion was ound o educe ma e ial eco e y e iciency
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and comp omise he quali y o eco e ed ac ions.
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3.3 Mo phological and Elemen al Composi ion Changes Analysis
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Building upon he insigh s om he mal mass loss analysis, u he in es iga ion was
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conduc ed in o he s uc u al and composi ional s abili y o he ca hode ma e ials. In line wi h
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he ecycling objec i es ha p io i ise he eco e y o aluable me als ound p ima ily in ba e y
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ca hodes [30], [40], he mally exposed ca hode samples we e analysed o examine hei
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mo phological and s uc u al changes using SEM and EDS. Figu e 4 illus a es he
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ep esen a i e ini ial condi ion o he d ied ca hode be o e he mal ea men , along wi h
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elemen al maps depic ing bo h he baseline s a e and he s a e a e exposu e o he highes
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empe a u e achie ed (800 °C). This app oach was employed o e alua e he su ace
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composi ion o he ca hode and o ack he composi ional changes esul ing om hea ea men
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ac oss a empe a u e ange o 100 o 800 °C, wi h inc emen s o 100 °C. The comp ehensi e
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esul s o all exposed ca hode samples a e p o ided in Figu e 5.
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Figu e 4: Illus a ion o (a) SEM measu emen s o he un ea ed ca hode sample using
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seconda y elec ons imaging - le , backsca e ed elec ons imaging - igh ; (b) EDS mapping
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o he un ea ed ca hode sample (T0) compa ed o he he mally ea ed ca hode sample a
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800 °C (T800). 'T' deno es he speci ic empe a u e a which he analysis was pe o med.
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The indings indica e ha he in es iga ed NMC laye possesses excep ional he mal
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s abili y, such ha exposu e o empe a u es o 800 °C does no signi ican ly al e he p ope ies
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o his c ys alline spinel s uc u e. Howe e , a c i ical obse a ion was he onse o mel ing o
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he Al cu en collec o a 700 °C. This mel ing e en signi ican ly comp omises he in eg i y
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o he su ounding elec oac i e ma e ial by causing delamina ion and po en ial encapsula ion,
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he eby diminishing he quali y o he eco e ed NMC spinel and inc easing he complexi y o
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subsequen pu i ica ion. The ul ima e objec i e o he he mal ea men p ocess is o achie e a
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empe a u e egime ha main ains he o iginal p ope ies o he aluable elec oac i e ma e ials
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while e ec i ely emo ing all o ganic componen s and acili a ing hei subsequen sepa a ion
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om cu en collec o s, suppo ing high- alue ma e ial eco e y.
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Figu e 5: Illus a ion o (a) SEM measu emen s o he ca hode sample ac oss a empe a u e
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ange o 100-800 °C, wi h inc emen s o 100 °C, using seconda y elec ons imaging - le ,
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backsca e ed elec ons imaging - igh . 'T' deno es he speci ic empe a u e a which he
361
analysis was pe o med.
362
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Complemen ing he mo phological obse a ions, de ailed elemen al analysis o he
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he mally ea ed ca hode su aces was pe o med using EDS. The s udy p ima ily ocused on
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key elec oac i e elemen s (Ni, Mn, Co) and acking changes in ca bon and luo ine esidues,
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as p esen ed in Figu e 6. Beyond hese p ima y a ge s, a ious o he elemen s we e iden i ied,
367
indica i e o esidues o igina ing om auxilia y ba e y ma e ials, including Al ( om Al2O3,
368
a sepa a o esidue [25]), P ( om he decomposi ion o LiPF6 [12], [13]), W ( aces o WO3,
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a s abilise in NMC spinel [41], [42]), and O (common o all oxide species [43]). Thei
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iden i ica ion p o ided insigh s in o po en ial con amina ion sou ces and he comple eness o
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o ganic emo al ollowing he mal ea men . I 's impo an o no e ha me allic Al and Cu
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om cu en collec o s canno be e alua ed by su ace analysis o elec odes using EDS.
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Figu e 6: EDS analysis o ca hode su ace composi ion a e he mal exposu e a selec ed
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empe a u es: (a) ull ange om 0 o 800 °C in 100 °C inc emen s; (b) de ailed ange om 400
376
o 650 °C in 50 °C inc emen s. ‘T’ indica es he speci ic empe a u e a which each sample was
377
analysed.
378
A c i ical composi ional shi was obse ed a app oxima ely 400 °C, mani es ing as
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a subs an ial educ ion in o ganic ca bon and luo ine con en . These changes led o a ela i e
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inc ease in NMC me al con en (Ni, Mn, Co) due o he elimina ion o o ganic componen s, as
381
e iden om he g aphs showing a signi ican inc ease in he ela i e yield o a ge elemen s
382
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om 400 °C. No ably, a 500 °C, he ca bon signal was absen , con i ming comple e emo al
383
o he o ganic ma ix wi hou obse able deg ada ion o he NMC phase. Fu he in es iga ion
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in o na owe empe a u e in e als e ealed ha esidual ca bon was ully combus ed e en a
385
450 °C wi h one hou o exposu e. Howe e , comple e luo ine emo al was only achie ed a
386
highe empe a u es, app oxima ely 700 °C, indica ing he p esence o mo e he mally s able
387
luo ine-con aining compounds a 500 °C. The pe sis ence o hese luo ides a 500 °C
388
is a c i ical conside a ion, as hey can complica e subsequen hyd ome allu gical leaching and
389
may con ibu e o equipmen co osion o lowe inal p oduc pu i y. Rega ding o he elemen s,
390
esidual P om he elec oly e emained unchanged, while oxygen showed an opposi e end,
391
g owing a he highes empe a u es due o high- empe a u e oxida ion. Among he iden i ied
392
con aminan s, only e ac o y Al2O3 and WO3 pe sis ed h oughou he en i e hea ea men .
393
Despi e he incomple e luo ine emo al a 500 °C, his empe a u e was ea i med as op imal
394
o py ome allu gical p e- ea men , as i e ec i ely combines ex ensi e o ganic pu i ica ion
395
(especially ca bon emo al) wi h excellen p ese a ion o he elec oac i e ma e ial s uc u e
396
be o e signi ican cu en collec o deg ada ion.
397
The sys ema ic analysis o elec ode ma e ials subjec ed o high- empe a u e exposu e
398
o one hou ac oss a ange o empe a u es om 100 o 800 °C, explici ly ocusing on NMC
399
ca hodes, g aphi e anodes, and polyme ic sepa a o s, has yielded aluable insigh s in o hei
400
he mal beha iou . The mos signi ican changes in mass and composi ion we e consis en ly
401
obse ed be ween 400 and 650 °C. This comp ehensi e in es iga ion unde sco es he sui abili y
402
o high- empe a u e py ome allu gical app oaches o eco e ing and ecycling elec oac i e
403
ma e ials om spen ba e ies.
404
A 100 °C, elec ode ma e ials unde go ho ough d ying o a cons an mass. Subsequen
405
hea ing o 200 °C ini ia es he oxida ion and b owning o PE wi hin he sepa a o , alongside he
406
decomposi ion o PVDF binde . A 300 °C, he oxida ion o he sepa a o polyme p og esses,
407
22
accompanied by he libe a ion o luo ine compounds. The i s signi ican changes in ela i e
408
composi ion a e obse ed a 400 °C, p ima ily ma ked by he onse o ca bon combus ion. By
409
500 °C, all o ganic ca bon is elimina ed; howe e , his empe a u e also ini ia es he oxida ion
410
o he anodic g aphi e. The mos p onounced oxida ion o g aphi e on he anode occu s a
411
600 °C, while ca hodic laye s emain s able. Concu en ly, he sepa a o polyme dec eases in
412
mass linea ly wi h inc easing empe a u e, and he elec oac i e ma e ial de aches sligh ly om
413
he cu en collec o . A 700 °C, almos all g aphi e on he anode is oxidised, bu impo an ly,
414
he Al cu en collec o on he ca hode begins o mel , po en ially educing he quali y o he
415
NMC spinel. E en a 800 °C, whe e he coppe cu en collec o o he anode oxidises and
416
samples disin eg a e in o powde , i was demons a ed ha he NMC spinel c ys als la gely
417
e ain hei cha ac e is ic s uc u e.
418
Based on hese indings, a empe a u e o 500 °C has been iden i ied as op imal o he
419
py ome allu gical sepa a ion o elec oac i e elec ode ma e ials. This empe a u e e ec i ely
420
emo es he binde and acili a es s aigh o wa d sepa a ion o elec oac i e ma e ials om
421
hei cu en collec o s, which emain la gely undeg aded a e jus one hou o exposu e.
422
A lowe empe a u es, he pe sis ence o o ganic compounds om he elec oly e and binde
423
polyme s signi ican ly impedes he sepa a ion o elec oac i e ma e ials and he polyme ic
424
sepa a o . Con e sely, highe empe a u es lead o de imen al oxida i e deg ada ion o anodic
425
g aphi e and me allic cu en collec o s (Al and Cu). While he NMC spinel om he ca hode
426
su ace emains s able up o 800 °C, i s pu i y and hus he e iciency o sepa a ion a e
427
comp omised a ele a ed empe a u es. Al hough g aphi e oxida ion a highe empe a u es
428
could po en ially be mi iga ed by hea ea men in a specialised u nace unde an ine
429
a mosphe e, such a p ocess would subs an ially inc ease he cos o p oduc eco e y, and
430
esiduum om o ganic ca bon compounds migh pe sis . Fu he mo e, Al, P, and W
431
con amina ing compounds om he o iginal p oduc pe sis in he eco e ed elec oac i e
432
23
ma e ials a e hea ea men , sugges ing a po en ial need o subsequen hyd ome allu gical
433
pu i ica ion o achie e a high-pu i y inal p oduc .
434
5. Conclusion
435
The he mal beha iou o key LIB componen s (NMC ca hodes, g aphi e anodes, and
436
polyme ic sepa a o s) was sys ema ically examined ac oss a comp ehensi e empe a u e ange
437
o 100 o 800 °C, wi h a speci ic ocus on he indus ially ele an window o 400 o 650 °C.
438
Unlike p io agmen ed s udies, an in eg a ed expe imen al app oach was u ilised, e ealing
439
c i ical in e -componen in e ac ions and hei impac on ma e ial in eg i y du ing low-
440
empe a u e py ome allu gical p e- ea men . The esul s show ha a ea men empe a u e o
441
500 °C o e s he bes balance o py ome allu gical p e- ea men , allowing comple e emo al
442
o o ganic binde s and elec oly e esidues wi hin one hou . A his empe a u e, elec oac i e
443
ma e ials can be e ec i ely sepa a ed om cu en collec o s, which emain mos ly in ac .
444
Lowe empe a u es did no elimina e o ganic ca bon compounds, complica ing sepa a ion,
445
while highe empe a u es led o oxida ion o g aphi e and mechanical deg ada ion o collec o s.
446
Despi e he he mal s abili y o NMC ca hodes up o 800 °C, hei pu i y dec eases a highe
447
empe a u es due o in e ac ions wi h mol en cu en collec o s. The indings con i m ha
448
ea men wi hin his speci ic empe a u e ange is a ou able o p ese ing ac i e ma e ials
449
while enabling e icien emo al o o ganics, he eby p o iding p ac ical insigh o he
450
de elopmen o ene gy-e icien , sus ainable, and cos -e ec i e LIB ecycling p ocesses.
451
This s udy, he e o e, con ibu es o he basis o he design o he mally d i en p e-
452
ea men s a egies o EOL LIBs. By clea ly de ining 500 °C as a sui able ope a ional
453
pa ame e , he wo k suppo s he de elopmen o ene gy-e icien , scalable p ocesses ha
454
minimize collec o deg ada ion and p ese e he elec ochemical in eg i y o ac i e ma e ials.
455
The e en ion o he NMC spinel s uc u e a his empe a u e no only acili a es he eco e y
456
o high-pu i y ca hode ma e ial bu also opens possibili ies o di ec e-use o simpli ied
457
24
downs eam e ining. These indings ad ance he unde s anding o low- empe a u e
458
py ome allu gical p ocessing and o e p ac ical guidance o i s implemen a ion in indus ial
459
ecycling amewo ks. As such, his app oach suppo s he b oade shi owa d ci cula
460
economy p ac ices in he ield o c i ical aw ma e ials managemen .
461
462
CRediT au ho ship con ibu ion s a emen
463
Anna P ažano á: Resou ces, Me hodology, Concep ualisa ion, W i ing – O iginal d a ,
464
P ojec adminis a ion.
465
Jan Kočí: Fo mal analysis, Da a cu a ion, Visualisa ion, In es iga ion, W i ing – O iginal
466
d a , W i ing – Re iew & Edi ing.
467
Jonáš Uřičář: Da a cu a ion, In es iga ion, Visualisa ion, W i ing – Re iew & Edi ing
468
Dominik Pilnaj: Da a cu a ion, In es iga ion.
469
Daniel-Ioan S oe: Supe ision, W i ing – Re iew & Edi ing.
470
Vacla Knap: Supe ision, W i ing – Re iew & Edi ing, Funding acquisi ion, P ojec
471
adminis a ion.
472
473
Decla a ion o compe ing in e es
474
All au ho s decla e ha hey ha e no con lic s o in e es .
475
476
Da a a ailabili y
477
Da a will be made a ailable on eques .
478
479
Acknowledgemen
480
This wo k was inancially suppo ed by he G an Agency o he CTU in P ague, g an No. No.
481
SGS24/136/OHK3/3T/13. Addi ionally, he in as uc u e used was made a ailable h ough he
482
25
p ojec "The Ene gy Con e sion and S o age", unded as p ojec No.
483
CZ.02.01.01/00/22_008/0004617 by P og amme Johannes Amos Comenius, call Excellen
484
Resea ch.
485
486
Re e ences
487
488
[1] Y. Wang, H. Yin, L. An, Y. Wang, H. Yin, and L. An, “An Upcoming Global
489
Challenge: E icien Recycling o End-o -Li e Li hium-Ion Ba e ies,” Glob.
490
Challenges, ol. 6, no. 12, p. 2200184, Dec. 2022, doi: 10.1002/GCH2.202200184.
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[2] U. Saleem, B. Joshi, and S. Bandyopadhyay, “Hyd ome allu gical Rou es o Close he
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Loop o Elec ic Vehicle (EV) Li hium-Ion Ba e ies (LIBs) Value Chain: A Re iew,”
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J. Sus ain. Me all., ol. 9, no. 3, pp. 950–971, Sep. 2023, doi: 10.1007/S40831-023-
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[3] G. Ha pe e al., “Recycling li hium-ion ba e ies om elec ic ehicles,” Na . 2019
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con en ional oas ing o syne gis ic py olysis wi h o ganic was es,” J. Ene gy Chem.,
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