Dab tsi yog qhov electrolyte hauv lithium roj teeb?
electrolyte
Cov electrolyte hauv lithium{0}}ion roj teeb yog cov cab kuj ntawm ions hauv lub roj teeb. Nws yog feem ntau muaj lithium ntsev, organic solvents, thiab additives, raws li qhia nyob rau hauv daim duab 7-4. Cov electrolyte ua lub luag haujlwm tseem ceeb hauv kev ua ions ntawm qhov zoo thiab qhov tsis zoo electrodes ntawm lithium - ion roj teeb, ua kom nws cov txiaj ntsig zoo xws li hluav taws xob siab thiab lub zog tshwj xeeb. Electrolytes feem ntau yog npaj nyob rau hauv tej yam kev mob thiab nyob rau hauv tshwj xeeb proportions los ntawm siab -purity organic solvents, lithium ntsev, thiab tsim nyog additives. Thaum cov khoom siv hluav taws xob txiav txim siab lub roj teeb lub zog ceev, cov electrolyte hauv paus txiav txim siab nws lub neej voj voog, kev ua haujlwm siab thiab tsis kub, thiab kev nyab xeeb. Lub hauv paus muaj pes tsawg leeg ntawm cov electrolyte tseem tsis hloov pauv; innovation feem ntau yog nyob rau hauv txoj kev loj hlob ntawm tshiab lithium ntsev thiab additives, raws li zoo raws li kev nkag siab tob ntawm lub interfacial chemical txheej txheem thiab mechanisms koom nyob rau hauv lithium-ion roj teeb.
Muaj ntau hom roj lithium ntsev, raws li pom hauv daim duab 7-5, tab sis tsawg heev tau siv nyob rau hauv cov khoom lag luam muaj lithium-ion roj teeb. Ib qho zoo tagnrho lithium ntsev yuav tsum muaj cov khoom nram qab no:
1) Tsis tshua muaj kev sib koom tes, yooj yim soluble hauv cov kuab tshuaj organic, kom ntseeg tau siab ionic conductivity ntawm electrolyte.
2) Anions nrog antioxidant thiab txo tsis kam; Cov khoom txo qis pab txhawb kev tsim cov khoom ruaj khov, qis -kuj SEI zaj duab xis.
3) Kev ruaj ntseg tshuaj zoo, tsis ua rau muaj kev phom sij nrog cov khoom siv hluav taws xob, electrolytes, lossis cov khoom sib cais.
4) Cov txheej txheem kev npaj yooj yim, tus nqi qis, tsis yog - lom thiab muaj kuab paug - dawb.
LiPF6 yog lithium ntsev ntau tshaj plaws. Txawm hais tias nws cov khoom ntiag tug tsis yog nws qhov zoo tshaj plaws, nws nthuav tawm qhov kev ua tau zoo tag nrho hauv carbonate sib xyaw cov kuab tshuaj electrolytes. LiPF6 muaj cov txiaj ntsig tseem ceeb hauv qab no:
1) Tsim nyog solubility thiab siab ionic conductivity nyob rau hauv uas tsis yog - cov kuab tshuaj aqueous.
2) Nws tuaj yeem tsim cov zaj duab xis passivation ruaj khov nyob rau saum npoo ntawm txhuas ntawv ci tam sim no cov khoom siv.
3) Nws synergistically tsim ib tug ruaj khov SEI zaj duab xis ntawm graphite electrode nto nrog carbonate solvents.
Txawm li cas los xij, LiPF6 muaj qhov tsis zoo thermal stability thiab nws yooj yim rau decomposition tshuaj. Byproducts tuaj yeem ua rau SEI zaj duab xis rau ntawm qhov chaw electrode, yaj cov khoom siv hluav taws xob zoo, thiab ua rau muaj peev xwm lwj thaum caij tsheb kauj vab.
LiBF kuj yog ib qho kev siv lithium ntsev ntxiv. Piv rau LiPF6, LiBF muaj qhov dav dav ntawm kev ua haujlwm kub, zoo dua - qhov kub thiab txias, thiab qis dua - qhov kub thiab txias. LiBF muaj cov khoom siv hluav taws xob zoo, lub qhov rai electrochemical dav dav, thiab zoo thermal stability. Nws qhov txiaj ntsig zoo tshaj plaws nyob hauv nws cov yeeb yaj kiab- tsim cov khoom, raws li nws tuaj yeem koom ncaj qha rau hauv kev tsim cov yeeb yaj kiab SEI.
Raws li kev tsim qauv, LiDFOB yog tsim los ntawm ib nrab- cov molecules ntawm LiBOB thiab LiBF, sib txuas qhov zoo ntawm cov yeeb yaj kiab zoo- tsim cov khoom ntawm LiBOB thiab qhov zoo qis - qhov kub thiab txias ntawm LiBF4. Piv nrog LiBOB, LiDFOB muaj ntau dua solubility nyob rau hauv linear carbonate solvents thiab ntau dua electrolyte conductivity. Nws qhov siab -kub thiab qis- qhov kub thiab txias ua haujlwm tau zoo dua li LiPF4, thiab nws muaj kev sib raug zoo nrog lub roj teeb cathode, tsim cov zaj duab xis passivation ntawm aluminium foil nto thiab inhibiting electrolyte oxidation.
Cov pab pawg CF₃SO₂ hauv LiTFSI qauv muaj cov khoom siv hluav taws xob muaj zog- rho tawm, uas ua rau muaj kev cuam tshuam ntau ntxiv ntawm cov nqi tsis zoo thiab txo cov ion koom nrog kev sib koom ua ke, ua rau muaj kev solubility siab ntawm cov ntsev. Tsis tas li ntawd, LiTFSI muaj hluav taws xob conductivity siab, siab thermal decomposition kub, thiab tsis yooj yim hydrolyzed; Txawm li cas los xij, nws yuav hnyav corrode txhuas cov khoom tam sim no ntawm qhov hluav taws xob siab tshaj 3.7V.
Cov fluorine atoms nyob rau hauv LiFSI molecule muaj zog electron - rho tawm zog, uas delocalize tus nqi tsis zoo ntawm N, ua rau tsis muaj zog ion koom haum thiab yooj yim dissociation ntawm Li +, yog li ua rau siab conductivity.
LiPO2F2 nthuav tawm qhov ua tau zoo qis- qhov kub thiab txias thiab tseem txhim kho qhov siab - qhov kub thiab txias ntawm electrolyte. Raws li ib tug additive, nws muaj peev xwm tsim ib tug SEI zaj duab xis nplua nuj nyob rau hauv LixPOyFz thiab LiF ntawm qhov tsis zoo electrode nto, uas yuav pab txo tau roj teeb interfacial impedance thiab txhim kho lub roj teeb voj voog kev ua tau zoo. Txawm li cas los xij, LiPO2F2 kuj raug kev txom nyem los ntawm kev solubility tsawg.
Qhov tseem ceeb ntawm covkua electrolyteyog cov organic hnyav, uas dissolves lithium ntsev thiab muab cov cab kuj rau lithium ions. Cov kuab tshuaj organic zoo tagnrho rau lithium- ion roj teeb electrolyte yuav tsum tau ua raws li cov hauv qab no:
1) High dielectric tas li thiab muaj zog dissolving muaj peev xwm rau lithium ntsev.
2) Tsawg melting point thiab kub kub taw tes, tswj cov kua hauv lub xeev ntawm qhov kub thiab txias.
3) Tsawg viscosity, yooj yim rau lithium-ion thauj.
4) Kev ruaj ntseg tshuaj zoo, tsis ua rau cov qauv zoo thiab tsis zoo electrode lossis yaj cov khoom zoo thiab tsis zoo electrode.
5) Lub teeb nyem siab, kev nyab xeeb zoo, tus nqi qis, tsis yog - lom thiab tsis yog - paug.
Cov kuab tshuaj organic feem ntau siv hauv lithium-ion roj teeb electrolytes feem ntau muab faib ua cov kuab tshuaj carbonate thiab cov kuab tshuaj organic ether, raws li qhia hauv daim duab 7-6. Txhawm rau kom tau txais cov qib siab -kev ua tau zoo lithium-ion roj teeb electrolyte, cov kuab tshuaj sib xyaw uas muaj ob lossis ntau dua cov kuab tshuaj organic feem ntau yog siv, tso cai rau lawv sib xyaw ua ke thiab ua tiav kev ua tau zoo tag nrho. Lub cev muaj zog ntawm cov kuab tshuaj carbonate uas muaj nyob rau hauv Table 7-1.
Table 7-1 Lub cev muaj zog ntawm Common Carbonate Solvents
| Organic Solvent | Tus txheeb ze Dielectric Constant | Melting Point / degree | Boiling Point / degree | Viscosity Coefficient |
|---|---|---|---|---|
| Ethylene Carbonate (EC) | 89.6 | 37 | 243 | 1.86 |
| Propylene Carbonate (PC) | 64.4 | -55 | 240 | 2.53 |
| Dimethyl Carbonate (DMC) | 0.59 | 2 | 91 | 0.59 |
| Diethyl Carbonate (DEC) | 2.8 | -43 | 126 | 0.75 |
| Ethyl Methyl Carbonate (EMC) | 3.0 | -53 | 108 | 0.65 |
Cov kuab tshuaj ether feem ntau suav nrog cov saw ethers xws li 1,2-dimethoxypropane (DMP), dimethoxymethane (DMM), thiab ethylene glycol dimethyl ether (DME), thiab cyclic ethers xws li tetrahydrofuran (THF) thiab 2-methyltetrahydrofuran (2-Me-THF). Rau cov saw hlau ether cov kuab tshuaj, qhov ntev ntawm cov saw hlau, qhov zoo dua cov tshuaj ruaj khov, tab sis qhov siab dua qhov viscosity thiab qis dua lithium-ion tsiv teb tsaws tus nqi. Ethylene glycol dimethyl ether tuaj yeem tsim cov chelate ruaj khov (LiPF6·DME) nrog lithium hexafluorophosphate, nthuav tawm lub zog muaj zog rau cov ntsev lithium ntsev thiab ua rau muaj hluav taws xob zoo. Txawm li cas los xij, DME muaj cov tshuaj lom neeg tsis zoo thiab tsis tuaj yeem tsim cov zaj duab xis passivation ruaj khov rau ntawm cov khoom tsis zoo electrode.
Carbonate solvents muaj xws li cyclic carbonates xws li propylene carbonate (PC) thiab ethylene carbonate (EC), thiab chain carbonates xws li dimethyl carbonate (DMC), diethyl carbonate (DEC), thiab methyl ethyl carbonate (EMC). Cyclic carbonates muaj lub siab dielectric tas li, ua lithium ntsev ntau dua soluble, tab sis lawv kuj muaj viscosity siab, ua rau qis lithium - ion tsiv teb tsaws tus nqi. Chain carbonates muaj cov dielectric tsis tu ncua thiab tsis muaj zog lithium ntsev solubility, tab sis tsis tshua muaj viscosity thiab zoo flowability, yooj yim rau lithium - ion tsiv teb tsaws.
Hom nplaim hluav taws-cov khoom ntxiv rau lithium- ion electrolytes tau pom hauv daim duab 7-7. Cov khoom siv ntxiv, siv me me, muaj cov txiaj ntsig tseem ceeb thiab yog ib txoj hauv kev zoo thiab siv tau los txhim kho kev ua haujlwm ntawm lithium - ion roj teeb. Los ntawm kev ntxiv me me ntawm cov tshuaj ntxiv rau cov electrolyte ntawm lithium-ion roj teeb, qee yam roj teeb kev ua tau zoo tuaj yeem txhim kho tshwj xeeb, xws li thim rov qab muaj peev xwm, electrode / electrolyte compatibility, kev ua haujlwm ntawm lub voj voog, kev ua haujlwm zoo, thiab kev nyab xeeb kev ua haujlwm, ua lub luag haujlwm tseem ceeb hauv lithium - ion roj teeb. Ib qho zoo tagnrho lithium-ion roj teeb electrolyte additive yuav tsum muaj plaub yam nram qab no:
1) Siab solubility hauv cov kuab tshuaj organic.
2) Ib qho me me tuaj yeem txhim kho ib lossis ntau qhov kev ua tau zoo.
3) Tsis muaj kev cuam tshuam sab nraud nrog lwm cov khoom siv roj teeb uas cuam tshuam rau kev ua haujlwm ntawm roj teeb.
4) Tus nqi qis, tsis yog - lom lossis tsis muaj tshuaj lom.
Raws li lawv txoj haujlwm, cov khoom ntxiv tuaj yeem muab faib ua cov khoom siv hluav taws xob, cov khoom siv tiv thaiv overcharge, nplaim hluav taws xob ntxiv, SEI zaj duab xis- tsim cov khoom siv ntxiv, cov khoom tiv thaiv cathode, LiPF6 stabilizers, thiab lwm yam khoom siv ntxiv.
Conductive additives txhim kho tus nqi ntawm lithium{0}}ion roj teeb los ntawm kev sib koom tes nrog electrolyte ions, txhawb nqa lithium ntsev dissolution, thiab nce electrolyte conductivity. Vim tias cov khoom siv hluav taws xob ua haujlwm los ntawm kev sib koom ua ke, lawv tseem hu ua ligand additives, thiab muab faib ua anionic ligands, cationic ligands, thiab nruab nrab ligands raws li kev sib cuam tshuam ion.
Overcharge tiv thaiv additives muab kev tiv thaiv overcharge los yog txhim kho overcharge kam rau ua. Lawv ua haujlwm tau muab faib ua redox additives thiab monomer additives. Tam sim no, redox additives feem ntau yog anisol series, uas muaj peev xwm redox siab thiab zoo solubility. Monomer additives undergo polymerization tshwm sim nyob rau hauv high voltage, tso gases, thiab lub polymer coats lub cathode cov ntaub ntawv nto, cuam tshuam kev them nyiaj. Monomer additives feem ntau suav nrog cov tshuaj tsw qab xws li xylene thiab phenylcyclohexane.
Nplaim retardant additives muaj nuj nqi los ntawm tsa lub ignition point ntawm lub electrolyte los yog txiav tawm cov dawb radical saw cov tshuaj tiv thaiv uas inhibits combustion. Lawv hom muaj nyob rau hauv daim duab 7-8. Ntxiv cov nplaim hluav taws kub hnyiab yog ib txoj hauv kev tseem ceeb los txo cov nplaim hluav taws xob ntawm cov hluav taws xob, nthuav dav cov kev khiav hauj lwm kub ntawm lithium-ion roj teeb, thiab txhim kho lawv cov kev ua tau zoo. Cov txheej txheem ntawm kev ua ntawm nplaim retardant additives feem ntau yog ob npaug:
1) Los ntawm kev tsim ib txheej insulating ntawm cov roj theem thiab lub condensed theem, lawv tiv thaiv combustion nyob rau hauv ob qho tib si condensed thiab roj theem.
2) Lawv ntes cov dawb radicals thaum lub sij hawm combustion txheej txheem, txiav tawm cov dawb radical saw cov tshuaj tiv thaiv uas inhibits combustion tshwm sim ntawm cov roj theem.
