Amabhethri e-lithium-ion amabhethri esibili akhula ngokushesha ngemva kwamabhethri e-nickel-cadmium kanye ne-nickel-hydrogen. Izakhiwo zayo ezinamandla amakhulu zenza ikusasa layo libukeke liqhakazile. Kodwa-ke, amabhethri e-lithium-ion awaphelele, futhi inkinga yawo enkulu ukuzinza kwemijikelezo yawo yokushaja. Leli phepha lifingqa futhi lihlaziye izizathu ezingase zibe khona zokufiphala kwamandla amabhethri e-Li-ion, okuhlanganisa ukushajwa ngokweqile, ukubola kwe-electrolyte kanye nokuzikhulula.

Amabhethri e-lithium-ion anamandla ahlukene okuxhumana lapho ukusabela kokuhlangana kwenzeka phakathi kwama-electrode amabili, futhi ukuze kutholwe ukusebenza kahle kakhulu kwebhethri, isilinganiso somthamo wama-electrode abamba amabili kufanele agcine inani elilinganiselwe.

Kumabhethri e-lithium-ion, ibhalansi yamandla ivezwa njengesilinganiso sobuningi be-electrode eyakhayo ku-electrode engemihle,

Okungukuthi: γ=m+/m-=ΔxC-/ΔyC+

Kufomula engenhla, u-C ubhekisela kumthamo we-coulombic we-theoretical we-electrode, futhi u-Δx no-Δy babhekisela kunombolo ye-stoichiometric yama-ion e-lithium ashumekwe ku-electrode engalungile kanye ne-electrode ephozithivu, ngokulandelana. Kungabonakala kufomula engenhla ukuthi isilinganiso sesisindo esidingekayo sezigxobo ezimbili sincike kumthamo we-Coulomb ohambisanayo wezigxobo ezimbili kanye nenani lama-ion e-lithium ahlehliswayo.

isithombe

Generally speaking, a smaller mass ratio leads to incomplete utilization of the negative electrode material; a larger mass ratio may cause a safety hazard due to the overcharge of the negative electrode. In short, at the optimized mass ratio, the battery performance is the best.

Ukuze kube nesistimu yebhethri ye-Li-ion ekahle, ibhalansi yamandla ayishintshi phakathi nomjikelezo wayo, futhi umthamo wokuqala kumjikelezo ngamunye uyinani elithile, kodwa isimo sangempela siyinkimbinkimbi kakhulu. Noma yikuphi ukusabela okuseceleni okungadala noma kudle ama-ion e-lithium noma ama-electron kungase kuholele ekushintsheni kwebhalansi yamandla ebhethri. Uma isimo sebhalansi yebhethri sishintsha, lolu shintsho aluhlehliseki futhi lunganqwabelana ngemijikelezo eminingi, okuholela ekusebenzeni kwebhethri. Umthelela omkhulu. Emabhethri e-lithium-ion, ngaphezu kokusabela kwe-redox okwenzeka lapho i-lithium ion ihlukaniswa, kukhona nenani elikhulu lokusabela okusemaceleni, njengokubola kwe-electrolyte, ukuchithwa kwezinto ezisebenzayo, kanye ne-metallic lithium deposition.

Isizathu 1: Ukushaja ngokweqile

1. Ukusabela kwe-overcharge ye-graphite negative electrode:

Uma ibhethri lishajwe ngokweqile, ama-ion e-lithium ancishiswa kalula futhi afakwe phezu kwe-electrode engemihle:

isithombe

I-lithium efakiwe ivala indawo ye-electrode engalungile, ivimbela ukuxhumana kwe-lithium. Lokhu kubangela ukunciphisa ukusebenza kahle kokukhishwa kanye nokulahlekelwa amandla ngenxa:

①Yehlisa inani le-lithium ekwazi ukugaywa kabusha;

②I-lithium yensimbi efakiwe ihlangana ne-solvent noma i-electrolyte esekelayo yakhe i-Li2CO3, i-LiF noma eminye imikhiqizo;

③ I-metal lithium ivame ukwakhiwa phakathi kwe-electrode engalungile kanye nesihlukanisi, esingase sivimbe ama-pores esihlukanisi futhi sikhulise ukumelana kwangaphakathi kwebhethri;

④ Ngenxa yemvelo esebenzayo ye-lithium, kulula ukusabela nge-electrolyte futhi idle i-electrolyte, okuholela ekunciphiseni kokusebenza kahle kokukhishwa kanye nokulahlekelwa amandla.

Ukushaja okusheshayo, ukuminyana kwamanje kukhulu kakhulu, i-electrode engalungile ihlukaniswa kakhulu, futhi ukubekwa kwe-lithium kuzoba sobala kakhulu. Lokhu kungenzeka uma into esebenzayo ye-electrode idlulele uma kuqhathaniswa nezinto ezisebenzayo ze-electrode negative. Kodwa-ke, esimweni sokushaja okuphezulu, ukubekwa kwe-metallic lithium kungenzeka noma ngabe isilinganiso sezinto ezisebenzayo ezinhle nezingezinhle sijwayelekile.

2. Positive electrode overcharge reaction

Uma isilinganiso se-electrode esebenzayo esebenzayo ne-electrode eyi-negative esebenzayo siphansi kakhulu, kungenzeka ukukhokhiswa kwe-electrode ephozithivu.

Ukulahleka komthamo okubangelwa ukushajwa ngokweqile kwe-electrode ephozithivu kubangelwa ikakhulukazi ukukhiqizwa kwezinto ezingasebenzi nge-electrochemically (njenge-Co3O4, Mn2O3, njll.), ezicekela phansi ibhalansi yamandla phakathi kwama-electrode, futhi ukulahlekelwa amandla akunakuhlehliswa.

(1) LiyCoO2

LiyCoO2→(1-y)/3[Co3O4＋O2(g)]＋yLiCoO2 y<0.4

Ngesikhathi esifanayo, umoya-mpilo okhiqizwa ukubola kwezinto ezibonakalayo ze-electrode ebhethri ye-lithium-ion evaliwe iqoqa ngesikhathi esifanayo ngenxa yokuthi akukho ukusabela kokuhlanganiswa kabusha (njengokukhiqizwa kwe-H2O) kanye negesi evuthayo ekhiqizwa ukubola. ye-electrolyte, futhi imiphumela izoba yinto engacabangeki.

(2) λ-MnO2

Ukusabela kwe-lithium-manganese kwenzeka lapho i-lithium-manganese oxide incithakalo ngokuphelele: λ-MnO2→Mn2O3+O2(g)

3. I-electrolyte i-oxidized uma ishajwe ngokweqile

When the pressure is higher than 4.5V, the electrolyte will be oxidized to generate insolubles (such as Li2Co3) and gases. These insolubles will block the micropores of the electrode and hinder the migration of lithium ions, resulting in capacity loss during cycling.

Izinto ezithinta izinga le-oxidation:

Indawo engaphezulu yezinto ezibonakalayo ze-electrode

Izinto zamanje zokuqoqa

I-agent conductive eyengeziwe (i-carbon black, njll.)

Uhlobo nendawo yekhabhoni emnyama

Phakathi kwama-electrolyte asetshenziswa kakhulu, i-EC/DMC ithathwa njengokumelana okuphezulu kwe-oxidation. Inqubo yesisombululo se-electrochemical oxidation ngokuvamile ivezwa njengokuthi: isixazululo→umkhiqizo wokukhipha i-oxidation (igesi, isixazululo nodaba oluqinile)+ne-

I-oxidation yanoma iyiphi i-solvent izokwandisa ukugxila kwe-electrolyte, yehlise ukuzinza kwe-electrolyte, futhi ekugcineni kuthinte umthamo webhethri. Uma sicabanga ukuthi inani elincane le-electrolyte liyasetshenziswa isikhathi ngasinye lapho lishajwa, kudingeka i-electrolyte eyengeziwe ngesikhathi sokuhlanganiswa kwebhethri. Ngesitsha esihlala njalo, lokhu kusho ukuthi inani elincane lezinto ezisebenzayo liyalayishwa, okuholela ekunciphiseni komthamo wokuqala. Ukwengeza, uma umkhiqizo oqinile ukhiqizwa, ifilimu ye-passivation izokwakhiwa ebusweni be-electrode, okuzokwandisa i-polarization yebhethri futhi kunciphise amandla okukhipha ibhethri.

Isizathu 2: Ukuwohloka kwe-Electrolyte (ukunciphisa)

Ngibola ku-electrode

1. I-electrolyte ibolile ku-electrode eyakhayo:

I-electrolyte iqukethe i-solvent kanye ne-electrolyte esekelayo. Ngemva kokubola kwe-cathode, imikhiqizo engancibiliki njenge-Li2Co3 ne-LiF ivame ukwakhiwa, okunciphisa umthamo webhethri ngokuvimbela ama-pores we-electrode. Ukusabela kokunciphisa i-electrolyte kuzoba nomthelela omubi kumthamo nempilo yomjikelezo webhethri. Igesi ekhiqizwa ukunciphisa ingakhuphula ukucindezela kwangaphakathi kwebhethri, okungaholela ezinkingeni zokuphepha.

I-voltage yokubola ye-electrode enhle ivamise ukuba nkulu kuno-4.5V (vs. Li/Li+), ngakho-ke awaboli kalula ku-electrode ephozithivu. Ngokuphambene nalokho, i-electrolyte ibola kalula ku-electrode engalungile.

2. I-electrolyte ibolile ku-electrode engeyinhle:

I-electrolyte ayizinzile ku-graphite nakwamanye ama-anode e-lithium efakwe i-carbon, futhi kulula ukusabela ukukhiqiza umthamo ongabuyiseleki emuva. Ngesikhathi sokushaja kokuqala nokukhishwa, ukubola kwe-electrolyte kuzokwakha ifilimu ye-passivation ebusweni be-electrode, futhi ifilimu ye-passivation ingahlukanisa i-electrolyte ku-carbon negative electrode ukuvimbela ukubola okuqhubekayo kwe-electrolyte. Ngakho, ukuzinza kwesakhiwo se-carbon anode kugcinwa. Ngaphansi kwezimo ezikahle, ukuncishiswa kwe-electrolyte kunqunyelwe esigabeni sokubunjwa kwefilimu ye-passivation, futhi le nqubo ayenzeki lapho umjikelezo uzinzile.

Ukwakhiwa kwefilimu ye-passivation

Ukunciphisa usawoti we-electrolyte kubamba iqhaza ekwakhiweni kwefilimu ye-passivation, enenzuzo ekuqiniseni ifilimu ye-passivation, kodwa

(1) Indaba engancibilikiyo ekhiqizwa ukuncishiswa izoba nomthelela omubi kumkhiqizo wokunciphisa i-solvent;

(2) The concentration of the electrolyte decreases when the electrolyte salt is reduced, which eventually leads to the loss of battery capacity (LiPF6 is reduced to form LiF, LixPF5-x, PF3O and PF3);

(3) The formation of the passivation film consumes lithium ions, which will cause the capacity imbalance between the two electrodes to reduce the specific capacity of the entire battery.

(4) If there are cracks on the passivation film, solvent molecules can penetrate and thicken the passivation film, which not only consumes more lithium, but also may block the micropores on the carbon surface, resulting in the inability of lithium to be inserted and extracted. , resulting in irreversible capacity loss. Adding some inorganic additives to the electrolyte, such as CO2, N2O, CO, SO2, etc., can accelerate the formation of the passivation film and inhibit the co-insertion and decomposition of the solvent. The addition of crown ether organic additives also has the same effect. 12 crowns and 4 ethers are the best.

Izinto zokulahlekelwa umthamo wefilimu:

(1) The type of carbon used in the process;

(2) Ukwakheka kwe-Electrolyte;

(3) Izithasiselo kuma-electrode noma ama-electrolyte.

U-Blyr ukholelwa ukuthi ukusabela kokushintshaniswa kwe-ion kuya phambili ukusuka ebusweni bezinhlayiya ezisebenzayo kuya emnyombweni wayo, isigaba esisha esakhiwe singcwaba izinto ezisebenzayo zokuqala, futhi ifilimu engenzi lutho ene-ionic ephansi kanye ne-electronic conductivity yakheka phezu kwezinhlayiya, i-spinel ngemva kwesitoreji I-polarization enkulu kunangaphambi kokugcinwa.

U-Zhang uthole ukuthi ukumelana kongqimba lwe-surface passivation kwanda futhi amandla okuxhumana ancipha ngokunyuka kwenani lemijikelezo. Kubonisa ukuthi ukushuba kwesendlalelo sokudlula kukhuphuka ngenani lemijikelezo. Ukuhlakazwa kwe-manganese kanye nokubola kwe-electrolyte kuholela ekwakhekeni kwamafilimu e-passivation, futhi izimo zokushisa eziphezulu zivumela kakhulu ukuqhubeka kwalokhu kusabela. Lokhu kuzokwandisa ukumelana nokuxhumana phakathi kwezinhlayiya zezinto ezisebenzayo kanye nokumelana nokufuduka kwe-Li +, ngaleyo ndlela kwandise i-polarization yebhethri, ukushaja okungaphelele nokukhipha, kanye nomthamo oncishisiwe.

II Indlela Yokunciphisa Ye-Electrolyte

The electrolyte often contains oxygen, water, carbon dioxide and other impurities, and redox reactions occur during the charging and discharging process of the battery.

The reduction mechanism of the electrolyte includes three aspects: solvent reduction, electrolyte reduction and impurity reduction:

1. Solvent reduction

Ukwehliswa kwe-PC ne-EC kuhlanganisa ukusabela kwe-electron eyodwa kanye nenqubo yokusabela kwama-electron amabili, kanye namafomu okusabela ama-electron amabili i-Li2CO3:

Fong et al. wayekholelwa ukuthi phakathi nenqubo yokuqala yokukhishwa, lapho amandla e-electrode eseduze ne-0.8V (vs. Li/Li +), ukusabela kwe-electrochemical kwe-PC/EC kwenzeka ku-graphite ukukhiqiza i-CH=CHCH3(g)/CH2=CH2(g) kanye ne-LiCO3(ama), okuholela ekulahlekelweni kwamandla okungahlehliseki kuma-graphite electrode.

U-Aurbach et al. yenza ucwaningo olunzulu ngendlela yokunciphisa kanye nemikhiqizo yama-electrolyte ahlukahlukene kuma-electrode ensimbi ye-lithium nama-electrode asekelwe ku-carbon, futhi yathola ukuthi indlela yokusabela ye-electron eyodwa ye-PC ikhiqiza i-ROCO2Li ne-propylene. I-ROCO2Li izwela kakhulu ekulandeleni amanzi. Imikhiqizo eyinhloko yi-Li2CO3 ne-propylene phambi kwamanzi okulandelela, kodwa ayikho i-Li2CO3 ekhiqizwa ngaphansi kwezimo ezomile.

Ukubuyiselwa kwe-DEC:

Ein-Eli Y reported that the electrolyte mixed with diethyl carbonate (DEC) and dimethyl carbonate (DMC) will undergo an exchange reaction in the battery to generate ethyl methyl carbonate (EMC), which is responsible for the loss of capacity. certain influence.

2. Ukuncishiswa kwe-Electrolyte

The reduction reaction of the electrolyte is generally considered to be involved in the formation of the carbon electrode surface film, so its type and concentration will affect the performance of the carbon electrode. In some cases, the reduction of the electrolyte contributes to the stabilization of the carbon surface, which can form the desired passivation layer.

Ngokuvamile kukholakala ukuthi i-electrolyte esekelayo kulula ukunciphisa kune-solvent, futhi umkhiqizo wokunciphisa uxutshwa kufilimu ye-electrode engalungile futhi ithinta ukubola kwamandla ebhethri. Ukusabela okuningana okungenzeka kokunciphisa ama-electrolyte asekelayo kungokulandelayo:

3. Ukunciphisa ukungcola

(1) If the water content in the electrolyte is too high, LiOH(s) and Li2O deposits will be formed, which is not conducive to the insertion of lithium ions, resulting in irreversible capacity loss:

H2O＋e→OH-＋1/2H2

OH-＋Li+→LiOH(ama)

LiOH+Li++e-→Li2O(s)+1/2H2

I-LiOH(ama) ekhiqiziwe ifakwa endaweni ye-electrode, yakhe ifilimu engaphezulu enokumelana okuphezulu, okuvimbela ukuxhumana kwe-Li+ ku-electrode yegraphite, okuholela ekulahlekelweni kwamandla okungahlehliseki. Inani elincane lamanzi (100-300 × 10-6) ku-solvent alinawo umthelela ekusebenzeni kwe-graphite electrode.

(2) The CO2 in the solvent can be reduced on the negative electrode to form CO and LiCO3(s):

2CO2+2e-+2Li+→Li2CO3+CO

I-CO izonyusa umfutho wangaphakathi webhethri, futhi i-Li2CO3(ama) izokhuphula ukumelana kwangaphakathi kwebhethri futhi ithinte ukusebenza kwebhethri.

(3) Ukuba khona komoyampilo ku-solvent nakho kuzokwakha i-Li2O

1/2O2+2e-+2Li+→Li2O

Ngenxa yokuthi umehluko ongaba khona phakathi kwe-metallic lithium ne-carbon intercalated ngokugcwele mncane, ukuncishiswa kwe-electrolyte ku-carbon kufana nokwehliswa kwe-lithium.

Isizathu 3: Ukuzikhulula

Ukuzikhipha ngokwakho kusho isenzeko sokuthi ibhethri ilahlekelwa amandla ayo ngokwemvelo uma ingasetshenziswa. Ukuzikhipha kwebhethri ye-Li-ion kuholela ekulahlekelweni kwamandla ezimweni ezimbili:

Enye ukulahlekelwa amandla okubuyiseleka emuva;

Okwesibili ukulahlekelwa amandla angenakuhlehliswa.

Reversible capacity loss means that the lost capacity can be recovered during charging, while irreversible capacity loss is the opposite. The positive and negative electrodes may act as a microbattery with the electrolyte in the charged state, resulting in lithium ion intercalation and deintercalation, and intercalation and deintercalation of positive and negative electrodes. The embedded lithium ions are only related to the lithium ions of the electrolyte, so the capacity of the positive and negative electrodes is unbalanced, and this part of the capacity loss cannot be recovered during charging. Such as:

I-lithium manganese oxide positive electrode kanye ne-solvent izodala umphumela webhethri elincane futhi lizikhiphe ngokwalo, okuholela ekulahlekelweni kwamandla okungenakulungiseka:

LiyMn2O4+xLi++xe-→Liy+xMn2O4

Ama-athomu (afana ne-PC) afakwa i-oxidized phezu kwe-condutive material carbon black noma isiqoqi samanje njenge-anode ye-microbattery:

xPC→xPC-radical+xe-

Ngokufanayo, izinto ezisebenzayo ezingezinhle zingase zihlanganyele ne-electrolyte ukuze kubangele ukuzikhipha futhi kubangele ukulahleka kwamandla okungahlehliseki, futhi i-electrolyte (efana ne-LiPF6) incishisiwe ku-conductive material:

PF5+xe-→PF5-x

I-lithium carbide esesimweni sokushajwa ifakwa i-oxid ngokukhipha ama-ion e-lithium njenge-electrode engeyinhle yebhethri elincane:

LiyC6→Liy-xC6+xLi+++xe-

Factors affecting self-discharge: the manufacturing process of the positive electrode material, the manufacturing process of the battery, the properties of the electrolyte, temperature, and time.