Cov roj teeb lithium yuav ntsib ntau qhov chaw thaum lawv siv. Nyob rau lub caij ntuj no, qhov kub nyob rau sab qaum teb Tuam Tshoj feem ntau qis dua 0 ℃ lossis txawm -10 ℃. Thaum lub sij hawm them nyiaj thiab tso tawm qhov kub ntawm lub roj teeb qis dua 0 ℃, lub peev xwm them thiab tso tawm thiab qhov hluav taws xob ntawm lithium roj teeb yuav txo qis. Qhov no yog vim hais tias kev txav ntawm lithium ions hauv electrolyte, SEI thiab graphite hais tau txo qis ntawm qhov kub thiab txias. Xws li qhov kub thiab txias ib puag ncig yuav inevitably ua rau nag lossis daus ntawm lithium hlau nrog siab tshwj xeeb thaj chaw.

Lithium nag lossis daus nrog thaj chaw tshwj xeeb yog ib qho tseem ceeb tshaj plaws rau kev ua haujlwm tsis ua haujlwm ntawm lithium roj teeb, thiab tseem yog ib qho teeb meem tseem ceeb rau kev nyab xeeb roj teeb. Qhov no yog vim hais tias nws muaj thaj tsam loj heev, lithium hlau yog heev nquag thiab flammable, siab deg cheeb tsam dendrite lithium yog me ntsis ntub cua yuav hlawv.

Nrog rau kev txhim kho cov roj teeb muaj peev xwm, ntau yam thiab kev lag luam sib koom ntawm cov tsheb hluav taws xob, kev nyab xeeb ntawm cov tsheb hluav taws xob tau dhau los ua nruj dua. Dab tsi yog qhov kev hloov pauv ntawm kev ua haujlwm ntawm cov roj teeb fais fab ntawm qhov kub thiab txias? Dab tsi yog kev ruaj ntseg yam tsim nyog sau cia?

1.18650 cryogenic voj voog kev sim thiab kev ntsuam xyuas roj teeb disassembly

Lub 18650 roj teeb (2.2A, NCM523 / graphite system) tau simulated ntawm qhov kub ntawm 0 ℃ nyob rau hauv ib qho kev them nqi-tso mechanism. The charging and discharge mechanism is: CC-CV charging, charging rate is 1C, charging cut-off voltage is 4.2V, them cut-off tam sim no yog 0.05c, ces CC tawm mus rau 2.75V. Raws li lub roj teeb SOH ntawm 70% -80% feem ntau txhais tau tias yog lub xeev txiav (EOL) ntawm lub roj teeb. Yog li ntawd, hauv qhov kev sim no, lub roj teeb raug txiav tawm thaum SOH ntawm lub roj teeb yog 70%. Lub voj voog voj voog ntawm lub roj teeb nyob rau hauv cov xwm txheej saum toj no yog qhia hauv daim duab 1 (a). Li MAS NMR tsom xam tau ua tiav ntawm cov ncej thiab cov diaphragms ntawm cov roj teeb uas tsis siv thiab tsis siv, thiab cov txiaj ntsig tshuaj hloov pauv tau pom hauv daim duab 1 (b).

Daim duab 1. Cell voj voog nkhaus thiab Li MAS NMR tsom xam

Lub peev xwm ntawm lub voj voog cryogenic tau nce hauv thawj ob peb lub voj voog, ua raws li kev poob qis, thiab SOH poob qis dua 70% hauv tsawg dua 50 lub voj voog. Tom qab disassembling lub roj teeb, nws tau pom tias muaj ib txheej ntawm nyiaj-grey cov ntaub ntawv nyob rau saum npoo ntawm lub anode, uas yog xam tau tias yog lithium hlau tso rau saum npoo ntawm lub circulating anode khoom. Li MAS NMR tsom xam tau ua rau ntawm cov roj teeb ntawm ob pawg kev sim sib piv, thiab cov txiaj ntsig tau lees paub ntxiv hauv daim duab B.

Muaj lub ncov dav ntawm 0ppm, qhia tias lithium muaj nyob hauv THE SEI lub sijhawm no. Tom qab lub voj voog, lub ncov thib ob tshwm sim ntawm 255 PPM, uas tuaj yeem tsim los ntawm nag lossis daus ntawm lithium hlau rau saum npoo ntawm cov khoom siv anode. Txhawm rau kom paub meej ntxiv seb lithium dendrites tiag tiag tshwm sim, SEM morphology tau pom, thiab cov txiaj ntsig tau pom hauv daim duab 2.

Daim duab

Daim duab 2. SEM tsom xam cov txiaj ntsig

Los ntawm kev sib piv cov duab A thiab B, nws tuaj yeem pom tias txheej tuab ntawm cov khoom tau tsim hauv daim duab B, tab sis txheej txheej no tsis tau npog tag nrho cov graphite hais. SEM magnification tau nthuav dav ntxiv thiab cov koob zoo li cov khoom tau pom nyob rau hauv daim duab D, uas tej zaum yuav yog lithium nrog qhov tshwj xeeb ntawm thaj chaw siab (tseem hu ua dendrite lithium). Tsis tas li ntawd, cov lithium hlau deposition loj hlob mus rau lub diaphragm, thiab nws cov thickness tuaj yeem pom los ntawm kev sib piv nrog cov thickness ntawm graphite txheej.

Daim ntawv tso nyiaj lithium nyob ntawm ntau yam. Xws li qhov teeb meem ntawm qhov chaw, qhov ceev tam sim no, kev them nqi, qhov kub thiab txias, electrolyte additives, electrolyte muaj pes tsawg leeg, thov voltage thiab lwm yam. Ntawm lawv, qhov kub thiab txias tsis tshua muaj siab tam sim no yog qhov yooj yim tshaj plaws los tsim cov lithium hlau ntom ntom uas muaj qhov tshwj xeeb ntawm thaj chaw.

2. Thermal stability tsom xam ntawm roj teeb electrode

TGA tau siv los txheeb xyuas cov roj teeb uas tsis muaj hluav taws xob thiab tom qab siv hluav taws xob, raws li pom hauv daim duab 3.

Daim duab

Daim duab 3. TGA tsom xam ntawm qhov tsis zoo thiab qhov zoo electrodes (A. Negative electrode B. Positive electrode)

Raws li tuaj yeem pom los ntawm daim duab saum toj no, cov khoom siv hluav taws xob tsis siv tau muaj peb lub ncov tseem ceeb ntawm T≈260 ℃, 450 ℃ thiab 725 ℃ raws li qhov qhia tau tias muaj kev kub ntxhov decomposition, evaporation lossis sublimation tshwm sim ntawm cov chaw no. Txawm li cas los xij, qhov poob ntawm cov electrode tau pom tseeb ntawm 33 ℃ thiab 200 ℃. Cov tshuaj tiv thaiv decomposition ntawm qhov kub thiab txias yog tshwm sim los ntawm decomposition ntawm SEI membrane, ntawm chav kawm, kuj muaj feem xyuam rau electrolyte muaj pes tsawg leeg thiab lwm yam. Cov nag lossis daus ntawm lithium hlau nrog qhov siab tshwj xeeb ntawm thaj chaw ua rau muaj ntau ntawm SEI cov yeeb yaj kiab nyob rau saum npoo ntawm lithium hlau, uas tseem yog ib qho laj thawj rau cov roj teeb poob qis hauv lub voj voog qis.

SEM tsis tuaj yeem pom muaj kev hloov pauv hauv morphology ntawm cov khoom siv cathode tom qab kev sim cyclic, thiab TGA tsom xam pom tias muaj qhov poob zoo thaum qhov kub siab tshaj 400 ℃. Qhov kev poob loj no tuaj yeem tshwm sim los ntawm kev txo qis ntawm lithium hauv cov khoom siv cathode. Raws li pom hauv daim duab 3 (b), nrog kev laus ntawm lub roj teeb, cov ntsiab lus ntawm Li hauv qhov zoo electrode ntawm NCM maj mam txo qis. Qhov loj poob ntawm SOH100% zoo electrode yog 4.2%, thiab ntawm SOH70% zoo electrode yog 5.9%. Hauv ib lo lus, qhov poob loj ntawm ob qho tib si zoo thiab tsis zoo electrodes nce tom qab lub voj voog cryogenic.

3. Electrochemical aging tsom xam ntawm electrolyte

Qhov cuam tshuam ntawm qhov kub thiab txias ntawm cov roj teeb electrolyte tau soj ntsuam los ntawm GC / MS. Cov qauv hluav taws xob tau muab coj los ntawm cov roj teeb uas tsis muaj hnub nyoog thiab hnub nyoog raws li, thiab GC / MS cov txiaj ntsig tau pom nyob rau hauv daim duab 4.

Daim duab

Daim duab 4.GC/MS thiab FD-MS xeem

Cov electrolyte ntawm cov roj teeb uas tsis yog-cryogenic muaj DMC, EC, PC, thiab FEC, PS, thiab SN raws li cov khoom siv los txhim kho cov roj teeb. Tus nqi ntawm DMC, EC thiab PC nyob rau hauv lub cell tsis circulating thiab circulating cell yog zoo ib yam, thiab cov additive SN nyob rau hauv lub electrolyte tom qab kev ncig (uas inhibits lub decomposition ntawm zoo electrode electrolytic kua oxygen nyob rau hauv high voltage) yog txo. , yog li vim li cas yog qhov zoo electrode yog ib nrab overcharged nyob rau hauv qis kub voj voog. BS thiab FEC yog SEI zaj duab xis tsim additives, uas txhawb kev tsim cov yeeb yaj kiab SEI ruaj khov. Tsis tas li ntawd, FEC tuaj yeem txhim kho lub voj voog ruaj khov thiab Coulomb efficiency ntawm cov roj teeb. PS tuaj yeem txhim kho thermal stability ntawm anode SEI. Raws li tuaj yeem pom los ntawm daim duab, tus nqi ntawm PS tsis txo qis nrog kev laus ntawm lub roj teeb. Muaj qhov txo qis ntawm FEC, thiab thaum SOH yog 70%, FEC tseem tsis tuaj yeem pom. Kev ploj ntawm FEC yog tshwm sim los ntawm kev rov tsim kho tas li ntawm SEI, thiab kev rov ua dua tshiab ntawm SEI yog tshwm sim los ntawm kev nag lossis daus ntawm Li ntawm lub cathode graphite nto.

Cov khoom tseem ceeb ntawm electrolyte tom qab lub voj voog roj teeb yog DMDOHC, uas nws cov synthesis yog raws li kev tsim ntawm SEI. Yog li ntawd, ntau tus DMDOHC hauv FIG. 4A qhia txog kev tsim cov cheeb tsam SEI loj.

4. Thermal stability tsom xam ntawm cov roj teeb uas tsis yog-cryogenic

ARC (Accelerated calorimeter) kev ntsuam xyuas tau ua nyob rau ntawm lub voj voog uas tsis yog-cryogenic thiab cov roj teeb lub voj voog cryogenic nyob rau hauv cov xwm txheej quasi-adiabatic thiab HWS hom. Arc-hws cov txiaj ntsig tau pom tias cov tshuaj tiv thaiv exothermic yog tshwm sim los ntawm sab hauv ntawm lub roj teeb, tsis muaj kev ywj pheej ntawm sab nraud ambient kub. Cov tshuaj tiv thaiv hauv lub roj teeb tuaj yeem muab faib ua peb theem, raws li qhia hauv Table 1.

Daim duab

Kev nqus cua sov ib nrab tshwm sim thaum lub sij hawm diaphragm thermalization thiab roj teeb tawg, tab sis diaphragm thermalization yog negligible rau tag nrho SHR. Thawj qhov exothermic cov tshuaj tiv thaiv yog los ntawm decomposition ntawm SEI, ua raws li thermal induction induce lub deembedding ntawm lithium ions, tuaj txog ntawm electrons mus rau lub graphite nto, thiab txo cov electrons los tsim kom muaj SEI membrane. Cov txiaj ntsig kev ntsuas thermal stability tau pom hauv daim duab 5.

Daim duab

Daim duab

Daim duab 5. Arc-hws cov txiaj ntsig (a) 0%SOC; (b) 50 feem pua ​​SOC; (c) 100 feem pua ​​SOC; Cov kab dashed yog thawj zaug exothermic cov tshuaj tiv thaiv kub, thawj thermal runaway kub thiab thermal runaway kub

Daim duab

Daim duab 6. Arc-hws result interpretation a. Thermal runaway kub, B.ID startup, C. Thawj qhov kub ntawm thermal runaway d. Thawj qhov kub ntawm cov tshuaj tiv thaiv exothermic

Thawj cov tshuaj tiv thaiv exothermic (OER) ntawm lub roj teeb uas tsis muaj lub voj voog cryogenic pib nyob ib ncig ntawm 90 ℃ thiab nce linearly mus rau 125 ℃, nrog kev txo qis ntawm SOC, qhia tias OER tsis tshua muaj nyob ntawm lub xeev lithium ion hauv anode. Rau cov roj teeb hauv cov txheej txheem tawm, qhov siab tshaj plaws SHR (tus kheej cua sov tus nqi) hauv cov tshuaj tiv thaiv decomposition yog tsim los ntawm 160 ℃, thiab SHR yuav txo qis ntawm qhov kub siab, yog li kev noj ntawm intercalated lithium ions txiav txim siab ntawm qhov tsis zoo electrode. .

Tsuav yog muaj lithium ions txaus nyob rau hauv qhov tsis zoo electrode, nws yog guaranteed tias SEI puas tuaj yeem rov tsim dua. Lub thermal decomposition ntawm cov khoom cathode yuav tso tawm oxygen, uas yuav oxidize nrog cov electrolyte, nws thiaj li ua rau tus cwj pwm ntawm thermal runaway ntawm lub roj teeb. Raws li SOC siab, cov khoom siv cathode yog nyob rau hauv lub xeev siab heev, thiab cov qauv ntawm cov khoom siv cathode kuj yog qhov tsis ruaj khov tshaj plaws. Dab tsi tshwm sim yog qhov thermal stability ntawm lub xov tooj ntawm tes txo qis, cov pa oxygen tso tawm nce, thiab cov tshuaj tiv thaiv ntawm cov electrode zoo thiab cov electrolyte yuav siv sij hawm nyob rau hauv qhov kub thiab txias.

4. Lub zog tso tawm thaum lub sij hawm tsim roj

Los ntawm kev soj ntsuam ntawm lub roj teeb tom qab lub voj voog, nws tuaj yeem pom tias SHR pib loj hlob hauv txoj kab ncaj nraim ntawm 32 ℃. Kev tso tawm ntawm lub zog nyob rau hauv cov txheej txheem ntawm kev tsim roj yog feem ntau tshwm sim los ntawm cov tshuaj tiv thaiv decomposition, uas feem ntau xav tias yog thermal decomposition ntawm electrolyte.

Lithium hlau nrog qhov tshwj xeeb saum npoo av precipitates rau saum npoo ntawm cov khoom siv anode, uas tuaj yeem qhia tau los ntawm kev sib npaug hauv qab no.

Daim duab

Hauv kev tshaj tawm, Cp yog lub peev xwm tshwj xeeb thaum tshav kub kub, thiab △T sawv cev rau qhov sib npaug ntawm qhov kub ntawm tus kheej qhov kub ntawm lub roj teeb uas tshwm sim los ntawm cov tshuaj tiv thaiv decomposition hauv ARC xeem.

Qhov tshwj xeeb kub muaj peev xwm ntawm cov hlwb tsis muaj zog ntawm 30 ℃ thiab 120 ℃ tau sim hauv ARC kev sim. Cov tshuaj tiv thaiv exothermic tshwm sim ntawm 125 ℃, thiab lub roj teeb nyob hauv lub xeev tawm, thiab tsis muaj lwm cov tshuaj tiv thaiv exothermic cuam tshuam nrog nws. Hauv qhov kev sim no, CP muaj kev sib raug zoo nrog qhov kub thiab txias, raws li qhia hauv kab zauv hauv qab no.

Daim duab

Tag nrho cov nqi ntawm lub zog tso tawm nyob rau hauv tag nrho cov tshuaj tiv thaiv tuaj yeem tau los ntawm kev sib koom ua ke ntawm qhov tshwj xeeb kub muaj peev xwm, uas yog 3.3Kj ib lub xov tooj ntawm kev laus ntawm qhov kub thiab txias. Tus nqi ntawm lub zog tso tawm thaum lub sij hawm thermal runaway tsis tuaj yeem xam.

5. Kev sim acupuncture

Txhawm rau kom paub meej tias lub zog ntawm cov roj teeb kev laus ntawm lub roj teeb luv luv kev sim, kev sim koob tau ua tiav. Cov txiaj ntsig kev sim tau pom hauv daim duab hauv qab no:

Daim duab

Raws li qhov tshwm sim ntawm acupuncture, A yog lub roj teeb saum npoo kub thaum lub sijhawm acupuncture txheej txheem, thiab B yog qhov kub siab tshaj plaws uas tuaj yeem ua tiav.

Nws tuaj yeem pom los ntawm daim duab uas tsuas muaj qhov sib txawv me ntsis ntawm 10-20 ℃ ntawm cov roj teeb laus tom qab tso tawm thiab cov roj teeb tshiab (SOC 0%) los ntawm kev sim needling. Rau cov hnub nyoog cell, qhov kub siab tshaj plaws mus txog T≈35 ℃ nyob rau hauv adiabatic mob, uas yog raws li SHR≈0.04K / min.

Lub roj teeb uas tsis muaj roj mus txog qhov kub siab tshaj plaws ntawm 120 ℃ tom qab 30 vib nas this thaum SOC yog 50%. Lub joule cua sov tso tawm tsis txaus kom ncav cuag qhov kub thiab txias, thiab SHR tshaj qhov kub diffusion. Thaum SOC yog 50%, lub roj teeb kev laus muaj qee yam cuam tshuam rau lub thermal khiav, thiab qhov kub thiab txias nce mus rau 135 ℃ thaum lub koob txhaj rau hauv lub roj teeb. Tshaj li 135 ℃, qhov nce ntawm SHR ua rau thermal runaway ntawm lub roj teeb, thiab qhov kub ntawm lub roj teeb nce mus txog 400 ℃.

Ib qho tshwm sim sib txawv tau pom thaum lub roj teeb tshiab tau them nrog rab koob prick. Qee lub hlwb ncaj qha poob thermal tswj, thaum lwm tus tsis poob thermal tswj thaum qhov kub thiab txias tau khaws cia qis dua 125 ℃. Ib qho ntawm cov kev tswj xyuas hluav taws xob ncaj qha ntawm lub roj teeb tom qab rab koob rau hauv lub roj teeb, qhov kub ntawm qhov chaw mus txog 700 ℃, ua rau cov ntawv ci txhuas yaj, tom qab ob peb feeb, tus ncej tau yaj thiab sib cais ntawm lub roj teeb, thiab tom qab ntawd ignited lub ejection. roj, thiab thaum kawg ua rau tag nrho lub plhaub liab. Ob pawg ntawm cov xwm txheej sib txawv tuaj yeem suav tias yog cov diaphragm melts ntawm 135 ℃. Thaum qhov kub siab tshaj 135 ℃, lub diaphragm melts thiab nyob rau hauv luv luv Circuit Court tshwm sim, generating ntau cua sov thiab nws thiaj li ua rau thermal runaway. Txhawm rau txheeb xyuas qhov no, lub roj teeb uas tsis muaj cua sov tau raug tshem tawm thiab lub diaphragm tau sim AFM. Cov txiaj ntsig tau pom tias thawj lub xeev ntawm daim nyias nyias tau tshwm sim ntawm ob sab ntawm daim nyias nyias, tab sis cov qauv ntxeem tau tseem tshwm sim ntawm qhov tsis zoo, tab sis tsis nyob rau sab zoo.