Lub Tshuab Khoom Tseem Ceeb Thiab Kev Txiav Txim Ntawm Lithium Ion Roj Teeb Tsis Zoo Electrode Attenuation

Tshawb nrhiav kev nce qib ntawm qhov tsis zoo electrode attenuation mechanism:

Cov khoom siv carbon, tshwj xeeb tshaj yog cov khoom siv graphite, yog cov khoom siv anode feem ntau siv hauv cov roj teeb lithium-ion. Txawm hais tias lwm cov ntaub ntawv tsis zoo electrode, xws li cov ntaub ntawv alloy, cov khoom siv roj carbon nyuaj, thiab lwm yam, tseem tab tom kawm ntau yam, kev tshawb fawb tsom feem ntau ntawm morphology tswj thiab kev txhim kho ntawm cov ntaub ntawv nquag, thiab muaj kev soj ntsuam me ntsis ntawm cov mechanism ntawm nws lub peev xwm lwj. Yog li no, feem ntau ntawm cov kev tshawb fawb ntawm attenuation mechanism ntawm qhov hluav taws xob tsis zoo yog hais txog attenuation mechanism ntawm graphite cov ntaub ntawv. Lub attenuation ntawm roj teeb muaj peev xwm suav nrog attenuation thaum lub sij hawm cia thiab siv. Attenuation thaum lub sij hawm cia feem ntau muaj feem xyuam rau kev hloov pauv hauv electrochemical kev ua haujlwm tsis haum (impedance, thiab lwm yam). Ntxiv nrog rau kev hloov pauv hauv kev siv hluav taws xob, nws kuj tseem nrog cov kev hloov pauv hauv kev ntxhov siab xws li kev teeb tsa thiab lithium evolution. Thiab lwm yam tshwm sim.

1.1 Hloov pauv ntawm tsis zoo electrode / electrolyte interface

Rau lithium-ion roj teeb, qhov hloov ntawm qhov hluav taws xob / electrolyte interface tau lees paub tias yog ib qho laj thawj tseem ceeb rau kev saib xyuas qhov hluav taws xob tsis zoo. Thaum lub sijhawm thawj zaug them ntawm lithium roj teeb, lub tshuab hluav taws xob tau txo rau ntawm cov nplaim hluav taws xob tsis zoo los ua cov txheej txheem tiv thaiv ruaj khov zaj duab xis (SEI zaj duab xis kom luv). Thaum lub sijhawm tom qab cia thiab siv cov roj teeb lithium-ion, qhov tsis zoo electrode / electrolyte interface yuav hloov, ua rau muaj kev cuam tshuam ntawm nws qhov kev ua tau zoo.

1.1.1 Thickening ntawm SEI zaj duab xis / kev hloov pauv ntawm kev muaj pes tsawg leeg

Lub tsheb qeeb qeeb ntawm lub zog ua haujlwm ntawm lub roj teeb thaum siv yog feem ntau cuam tshuam rau qhov nce ntawm electrode impedance. Qhov nce ntawm electrode impedance feem ntau yog los ntawm cov tuab ntawm SEI zaj duab xis thiab cov kev hloov pauv hauv cov lus qhia thiab kev teeb tsa.

Vim tias qhov sib txawv thiab cov kev txwv hauv tus cwj pwm ntawm tus qauv thiab cov ntawv xeem, cov txiaj ntsig ntawm cov chaw tshawb fawb sib txawv tsis zoo ib yam, yog li nws nyuaj rau kev txiav txim siab tshwj xeeb ntawm SEI zaj duab xis. Raws li cov ntaub ntawv dhau los, cov ua ke ntawm SEI zaj duab xis feem ntau suav nrog kev tiv thaiv (Li2CO3, LiF) thiab cov organic [(CH2OCO2Li) 2, ROCO2Li, ROLi] ob hom sib txuas. Thaum lub sijhawm siv los yog ntim khoom, cov muaj pes tsawg leeg thiab tuab ntawm SEI zaj duab xis tsis zoo li qub.

Txij li cov SEI membrane tsis muaj cov kev ua haujlwm ntawm cov khoom siv hluav taws xob tiag, solvated lithium ions tseem tuaj yeem hloov mus los ntawm cov SEI membrane los ntawm lwm cov ntawv sau, anions, impurities, thiab electrolyte solvents. Yog li ntawd, nyob rau lub sijhawm tom qab ntawm kev rov mus ncig ntev lossis chaw cia khoom, lub tshuab hluav taws xob tseem tseem yuav ua kom xaim thiab ua rau lub ntsej muag ntawm cov hluav taws xob tsis zoo, ua rau SEI zaj duab xis tuab. Nyob rau tib lub sijhawm, vim hais tias cov hluav taws xob tsis zoo tau nyob rau hauv lub xeev ntawm kev nthuav dav thiab kev sib cog lus thaum lub voj voog, sab saum toj SEI zaj duab xis yuav tawg, tsim kom muaj qhov tshiab interface, thiab cov interface tshiab yuav txuas ntxiv nrog cov pa roj carbon monoxide thiab cov lithium ions rau. tsim ib zaj duab xis SEI. Nrog kev nce qib ntawm cov tshuaj tiv thaiv saum npoo av, ib qho hluav taws xob electrochemically inert deg tau tsim rau saum npoo ntawm qhov tsis zoo electrode, yog li ntawd ib feem ntawm cov khoom tsis zoo electrode raug cais thiab txiav tawm ntawm tag nrho cov electrode. Ua rau muaj peev xwm ploj. Raws li pom hauv daim duab 1, tom qab kev caij tsheb mus ntev ntev, SEI zaj duab xis nyob rau saum npoo ntawm cov hluav taws xob tsis zoo yog qhov hnyav dua.

Daim duab 1. Txheeb hluav taws xob hluav taws xob micrograph ntawm qhov tsis zoo electrode tom qab kev mus ncig ntev

Cov lus sib xyaw ntawm SEI zaj duab xis yog thermodynamically tsis khov, thiab kev hloov pauv ntawm kev rhuav tshem thiab rov tsim dua yuav tshwm sim tsis tu ncua hauv cov roj teeb system. SEI zaj duab xis yuav ua kom nrawm nrawm ntawm kev rhuav tshem thiab kev tsim rov qab ntawm cov zaj duab xis nyob hauv qee yam kev mob (kev kub, HF, hlau tsis muaj zog hauv zaj duab xis, thiab lwm yam), ua rau poob peev roj teeb. Tshwj xeeb nyob rau hauv kev kub muaj peev txheej, cov organic xyaw (lithium alkyl carbonate, thiab lwm yam) hauv SEI zaj duab xis hloov mus rau hauv cov khoom ua kom muaj zog ntau yam (Li2CO3, LiF), ua rau muaj qhov txo qis ntawm cov ionic conductivity ntawm SEI zaj duab xis. Cov hlau ions eluted los ntawm qhov zoo electrode diffuse mus rau qhov tsis zoo electrode los ntawm qhov hluav taws xob, thiab raug txo thiab tso rau saum nplaim hluav taws xob tsis zoo. Theem hlau tso tawm catalyze lub decomposition ntawm qhov electrolyte, uas nws nce qhov ua hauj ntawm cov tsis zoo electrode thiab thaum kawg ua rau lub attenuation ntawm roj teeb muaj peev xwm. Los ntawm kev ntxiv cov tshuaj tiv thaiv kub siab los yog cov kua roj lithium tshiab los txhim kho kev ruaj ntseg ntawm SEI zaj duab xis, kev pab cuam lub neej ntawm cov khoom tsis zoo electrode tuaj yeem rub tau ntev, thiab kev ua tau zoo tuaj yeem hloov kho.

Cov kev tshawb fawb pom tias cov khoom siv graphite sib txawv muaj cov kev cia sib txawv, thiab kev cia khoom ntawm graphite cuav nyob rau qhov kub siab zoo dua li cov graphite ntuj. Nrog rau qhov nce ntawm cia lub sijhawm. Cov ntawv lithium nyob hauv graphite dag yog qhov pib ruaj khov, tab sis cov ntsiab lus ntawm lithium hauv ntuj graphite qhia tawm tsis poob. Los ntawm kev txheeb xyuas cov khoom siv hluav taws xob me me (SEM) thiab Fourier hloov pauv infrared spectroscopy (FTIR) kev tshuaj ntsuam xyuas kev soj ntsuam, thaum lub sijhawm ntsuas kub ntau, cov ntsiab lus ntawm Li2CO3 thiab LiOCOOR nyob rau saum npoo ntawm ntuj graphite nce ntau nrog kev ncua sijhawm cia. Qhov nce ntawm cov tuab ntawm SEI zaj duab xis yog vim li cas los ntawm cov tshuaj tiv thaiv sab ntawm electrolyte nyob rau saum npoo ntawm qhov tsis zoo electrode. Cov txheej txheem saum npoo ntawm cov khoom cua graphite thiab cov zaj lus ntawm zaj duab xis SEI yeej tsis hloov pauv.

Tsis tas li ntawd, thaum tag nrho them thiab khaws cia rau qee lub sijhawm hauv cov xwm txheej qis dua 40 ℃, txawm hais tias cov khoom siv hluav taws xob tsis zoo nrog cov nplaim hluav taws xob muaj qhov ntsuas tus kheej ntau dua, qhov kev loj hlob ntawm SEI zaj duab xis ib chav thaj chaw ntawm cov sib txawv ntawm cov hluav taws xob tsis zoo electrode zoo sib xws. Cov zaub lwj ua qauv zoo sib xws. Txawm li cas los xij, nyob rau hauv qhov kub siab tshaj (60 ° C), lub thickening ntawm ntuj graphite SEI zaj duab xis nrog zoo ib yam li thaj tsam thaj chaw yog ho siab tshaj qhov ntawm graphite dag.

1.1.2 Kev Cuam Tshuam thiab rho tawm hluav taws xob

Kev ntsuas hluav taws xob suav nrog kev txo kuab txo qis, txo qis electrolyte, thiab txo kev ua qias tuaj. Kev ua kom tsis zoo nyob rau hauv cov roj ntsha feem ntau muaj cov pa oxygen, dej thiab carbon dioxide. Thaum lub sijhawm them thiab tawm ntawm cov roj teeb, cov roj electrolyte decomposes nyob rau sab saum toj ntawm cov hluav taws xob tsis zoo, thiab nws cov khoom tseem ceeb muaj xws li lithium carbonate thiab fluoride. Raws li tus naj npawb ntawm cov voj voog nce, cov khoom decomposition maj mam nce. Cov khoom no npog cov nplaim hluav taws xob tsis zoo thiab cuam tshuam qhov deintercalation ntawm lithium ions, uas ua rau muaj qhov cuam tshuam ntawm qhov tsis zoo ntawm cov electrode tsis zoo.

1.1.3 Kev tsom xam Lithium

Txij li thaum lub sij hawm sib cuam tshuam muaj peev xwm ntawm graphite cov ntaub ntawv nyob ze rau ntawm lub peev xwm lithium, ib zaug tso ntawm cov xim hlau lithium lossis kev loj hlob ntawm lithium dendrites tshwm sim thaum lub sijhawm them nyiaj, cov tshuaj tiv thaiv tom qab ntawm lithium nrog cov electrolyte yuav ua kom nrawm ntawm cov roj teeb ua haujlwm, thiab qhov loj ntawm thaj chaw lithium yuav ua rau sab hauv luv luv ntawm lub roj teeb thiab tshwm sim ntawm thermal khiav tawm. Kev ntsuas hluav taws xob tsawg tsawg, tsis tshua muaj qhov tsis zoo ntawm cov hluav taws xob tsis zoo ntawm lub roj teeb sib piv rau cov zoo electrode, tsis sib xws ntawm cov electrode loj (qhov ntug ntawm qhov zoo electrode npog qhov tsis zoo electrode), thiab muaj peev xwm cuam tshuam (txawv hauv zos polarization degree, electrode thickness thiab porosity effect) ) txhua qhov kev pheej hmoo ntawm kev pheej hmoo ntawm lithium.

Cov qib tsis sib haum nyob rau hauv cov khoom siv graphite thiab qhov tsis sib xws ntawm kev faib tawm tam sim no yuav cuam tshuam cov roj ntsha lithium kev hloov pauv nyob rau sab ntawm cov hluav taws xob tsis zoo. Hauv qib thib peb thiab theem thib plaub ntawm graphite lithium kev tso tawm, qhov cuam tshuam ntawm cov khoom ua rau cov khoom tsis sib xws ntawm kev them nyiaj hauv cov khoom siv electrode, uas ua rau kev tsim cov khoom lag luam dendritic tso nyiaj. Txoj kev loj hlob ntawm kev tso nyiaj nruab nrab ntawm qhov sib cais thiab cov hluav taws xob tsis zoo muaj feem cuam tshuam nrog qhov ntsuas kub thiab tam sim no. Raws li qhov ntsuas kub nce, tus nqi tsub ntxiv thiab qhov hloov pauv nce, thiab cov hlau hluav taws xob tso rau saum nplaim hluav taws xob tsis zoo. Qhov siab tsis tshua muaj siab nyob rau hauv lub roj teeb tawm ntawm txoj kab nkhaus thiab qhov txo qis dua Coulomb efficiency tuaj yeem siv los txiav txim siab seb lub roj teeb muaj lithium evolution.

Cov kev tshawb nrhiav tam sim no feem ntau yog txhawm rau txhim kho kev ua haujlwm ntawm cov hluav taws xob tsis zoo los ntawm kev sib tham ntawm kev txhim kho tsis zoo ntawm cov kab hluav taws xob tsis zoo thiab ua kom zoo dua qhov system electrolyte uas muaj cov tshuaj ntxiv rau inhibit lithium evolution hauv qhov tsis zoo electrode. Txheej Sn thiab cov pa roj carbon graphite nto txhim kho cov hluav taws xob ua hluav taws xob ua kom zoo ntawm kev ua haujlwm tsis zoo. Sn ntawm daim duab graphite nto tuaj yeem txo qhov kev tiv thaiv sab hauv ntawm SEI zaj duab xis thiab cov tshuab hluav taws xob electrode ntawm qhov kub tsawg. Tsis tas li ntawd, qhov kev ua tau zoo tuaj yeem txhim kho tau los ntawm kev txhim kho cov nplaim hluav taws xob tsis zoo. Oxidizing graphite hauv huab cua tuaj yeem ua kom thaj chaw thiab ntug qhov chaw nquag, nce lub qhov hws thiab txo qhov loj me, thiaj li txo qhov tshwm sim ntawm lithium evolution tshwm sim los ntawm kev faib tawm tsis ncaj. AsF6 tuaj yeem txhim kho kev ruaj khov ntawm cov hluav taws xob tsis zoo ntawm qhov kub thiab txias, txwv tsis pub cov khoom lag luam ntawm cov xim hlau thiab cov kua paug ntawm LiPF6. Tsis tas li ntawd, cov neeg kho tshuab dov nyob rau hauv kev npaj theem ntawm tus ncej tsis zoo yuav tuaj yeem txo qhov pore loj, txo qhov tsis sib xws ntawm kev faib nqi, thiab nce lub peev xwm thim rov qab ntawm lub roj teeb.

1.2 Hloov pauv tsis zoo hauv cov khoom siv electrode

Nyob rau hauv cov txheej txheem ntawm kev maj mam ua tsis tau zoo ntawm kev ua haujlwm roj teeb, cov txheej txheem xaj ntawm graphite yog maj mam rhuav tshem. Lithium roj teeb yog cycled ntawm tus nqi siab. Vim tias qhov gradient ntawm lithium ion concentration, lub tshuab kev ntxhov siab hauv thaj chaw yog tsim hauv sab hauv cov khoom, uas hloov qhov tsis zoo electrode lub lattice, thiab thawj daim qauv ntawm cov tsis zoo electrode maj mam ua tsis taus. Cov kev hloov pauv tsis yog vim li cas lub teeb meem tsis zoo ntawm lub roj teeb ua haujlwm. Deterioration tuaj yeem raug nthuav tawm raws li kev hloov pauv ntawm lithium evolution lossis SEI zaj duab xis, tab sis thaum lub sijhawm no, cov particle loj thiab lub lattice tas li ntawm qhov tsis zoo electrode yuav tsis hloov pauv.

Lub peev xwm thim rov qab ntawm graphite hais ntsig txog lawv cov kev taw qhia thiab hom. Piv txwv li, cov tshuaj tiv thaiv lithium ion / electrolyte tuaj yeem tshwm sim vim tias muaj qhov kev sib txuam tshiab ntawm kev tsis sib haum, cov teeb meem ntawm cov roj ntsha lithium yog qhov nyuaj dua, thiab lub peev xwm thim rov qab ntawm tsis sib haum graphite hais qis dua. Piv nrog kheej kheej kheej, flake graphite muaj qhov muaj peev xwm tshwj xeeb dua nyob ntawm qib siab tawg. Txawm hais tias tus qauv ntawm qhov tsis zoo electrode tsis hloov thaum lub sijhawm ua kom lwj, qhov sib piv ntawm cov qauv rhomboid / hexagonal yuav hloov pauv. Qhov nce ntawm hexagonal tus qauv yuav txo Faraday efficiency ntawm thawj thiab theem thib peb ntawm cov roj ntsha lithium ion ntxig, yog li txo qhov peev xwm thim rov qab ntawm cov tsis zoo electrode. Yog li ntawd, qhov peev xwm thim rov qab tuaj yeem raug nce los ntawm nce qhov sib piv ntawm cov qauv rhombic / hexagonal qauv.

1.3 Hloov ntawm cov hluav taws xob tsis zoo

Lub particle loj ntawm cov khoom graphite muaj ntau dua cuam tshuam rau kev ua tiav ntawm qhov tsis zoo electrode. Cov ntaub ntawv me me tuaj yeem ua kom luv luv ntawm txoj kev sib txawv ntawm cov ntaub ntawv graphite, uas yog qhov muaj txiaj ntsig zoo rau tus nqi siab thiab tawm. Txawm li cas los xij, cov khoom siv cov khoom tawg me me muaj qhov tshwj xeeb loj dua thaj chaw, thiab yuav haus cov roj lithium ntau dua thaum muaj qhov kub siab, uas ua rau muaj peev xwm tsis muaj qhov hloov pauv ntawm qhov tsis zoo electrode. Yog li no, lub thermal stability ntawm graphite anode yog feem ntau cuam tshuam nrog cov particle loj ntawm cov khoom graphite.

Qhov porosity ntawm graphite ncej daim muaj ib qho kev sib raug zoo nrog qhov muaj peev xwm thim rov qab ntawm qhov tsis zoo electrode. Raws li qhov porosity nce, qhov chaw sib tiv tauj ntawm graphite thiab electrolyte nce ntxiv, thiab cov tshuaj tiv thaiv interface nce ntxiv, uas ua rau muaj peev xwm thim rov qab qhov peev xwm. Thaum lub sijhawm siv sijhawm ntev thiab tso tawm lub roj teeb, lub zog hluav taws xob ntawm cov kab hluav taws xob graphite cuam tshuam txog kev puas tsuaj ntawm lub roj teeb ua haujlwm. Kev kub siab ua kom tiav tau tuaj yeem txo qhov porosity ntawm electrode, txo thaj tsam sib tiv tauj ntawm graphite thiab electrolyte, thiab tom qab ntawd nce lub peev xwm thim rov qab. Ntxiv mus, ntawm qhov kub siab tshaj 120 ° C, vim yog lub cua sov ua kom tsis taus ntawm SEI zaj duab xis los tsim cov pa roj, cov khoom siv tsis zoo electrode yuav ua kom muaj cua sov ntau dua.

nyob rau hauv xaus:

Qhov tsis zoo electrode lwj ntawm lithium ion roj teeb suav nrog ntau qhov kev ua rau tsis muaj zog. Ntawm lawv, lithium yog lub hauv paus tseem ceeb uas ua rau muaj kev cuam tshuam sai ntawm lub roj teeb lub neej. Kev txiav txim siab ntawm cov roj electrolyte thiab cov zaj duab xis tom qab tsim nyob rau saum npoo ntawm qhov tsis zoo electrode ua rau muaj qhov nce ntawm sab hauv lub roj teeb thiab txo qis cov roj uas rov ua dua tshiab. Cov txheej txheem saum toj no tau cuam tshuam me me rau cov qauv siv lead ua ntawm qhov tsis zoo electrode. Kev ntsuas xws li ua kom zoo dua ntawm qhov system electrolyte, ntxiv cov stabilizers thiab ntsuas kub kho tuaj yeem txo qhov tshwm sim ntawm cov tshuaj tiv thaiv no thiab txhim kho kev ua haujlwm ntawm cov khoom tsis zoo electrode.