Dɛn ne battery reaction mechanism?- Polinovel .

Dɛn ne battery reaction mechanism?

Mprempren, ntease a edi mu na ɛkɔ so daa wɔ electrochemical reaction mechanism of lifepo4 ho wɔ adwumayɛ mu. Anion a wɔabom ayɛ no (PO4)3⁻ a wɔde di dwuma no ma dade-a egyina nneɛma a wɔde afrafra so yɛ ade a ɛfata a wɔde yɛ lithium-ion battery cathodes. Nanso, lifepo4 ahwehwɛ nhyehyɛe no to ne conductivity ne lithium-ion diffusion adwumayɛ ano hye, na ɛde ade no electrochemical adwumayɛ so tew ba. Nea ɛnte sɛ nneɛma a wɔayɛ no ntoatoaso no, charge-discharge curve of limpo4 no taa wɔ asasetaw a ɛyɛ tratraa yiye, a ɛyɛ su titiriw a ɛyɛ abien-phase reactions, a ɛkyerɛ sɛ phase nsakrae nhyehyɛe a ɛda Limpo4 ne MPO a ɛba bere a lithium-oion intercalation/deintercalation di dwuma no.

LifePo4 no fa two-phase reaction mechanism mu bere a worebɔ charge na woreyiyi wɔ battery mu no, kyerɛ sɛ .

Reaction mechanism model

Bere a wɔrebɔ charge no, li⁺ tu fi FEO1 layer no mu, ɛfa electrolyte no mu, na ɛkɔ electrode a enye no mu. Fe2⁄0 no yɛ oxidized kɔ Fe3⁺, bere a electrons tu kwan fi abɔnten circuit no mu kɔ negative electrode no so denam contacting conductive agent ne current collector no so. Nneɛma a wɔde fi mu no yɛ nea ɛne no bɔ abira.

Sɛ yɛbɛkyerɛkyerɛ saa mmienu-phase suban yi mu a, Padhi ne Goodenough ne ne mfɛfoɔ. Wodii kan de "core-shell model," a ɛkyerɛ sɛ lithium-ion intercalation/deintercalation nhyehyɛe no ba wɔ lifepo4/fepo₄ abien-fase ntam, sɛnea wɔada no adi wɔ Mfonini 4-3A mu no ho nyansahyɛ mae.

Wɔ charge mu no, lifepo4/fepo1 interface no kɔ so fi soro kɔ mfinimfini, na ɛpia kɔ core no so. Li⁺ kɔ so tu kɔ abɔnten, na lifepo a ɛwɔ akyi no kɔ so dannan ne ho kɔ Fepo4 mu. Lithium ions ne electron kɔ so fa two a wɔayɛ no foforo-phase interface no mu na ama akɔ so ayɛ adwuma a etu mpɔn, nanso lithium-ion diffusion rate no yɛ nea ɛkɔ so daa wɔ tebea horow bi mu. Bere a nkitahodi a ɛda afã abien no ntam no so retew no, awiei koraa no, lithium ions no trɛw no rentumi nkɔ so nkura current a etu mpɔn mu. Lifepo4 a ɛwɔ particle core no mu no remfa nni dwuma koraa, na ɛde tumi a ɛbɛyera aba. Sɛ wɔbɔ charge wie a, lifepo4 a wɔmfa nni dwuma no bɛkɔ so atra abɔde no mfinimfini.

Sɛ yesusuw sɛ lithium ions betumi ayɛ intercalate na deintercalate wɔ mmeae pii bere koro mu a, Andersson ne ne mfɛfo. de mosaic model no too dwa sɛ ɛbɛkyerɛkyerɛ tumi a ɛyera mfitiaseɛ no mu, sɛdeɛ wɔakyerɛ wɔ Mfonini 4-3B mu no. Mosaic model no kyerɛ sɛ ɛwom sɛ lithium ion intercalation ne deintercalation nhyehyɛe no wɔ lifepo4/fepo4 abien-phase interface no so de, nanso adeyɛ no betumi aba wɔ beae biara wɔ abɔde no mu. Wɔ charge mu no, FEPO4 mantam no yɛ kɛse wɔ mmeae ahorow wɔ abɔde nketenkete no so, na saa mpɔtam yi anoano yɛ cross-contact, na ɛma mmeae pii a awu a wontumi nyɛ ho hwee ba, na ɛnam so ma tumi yera. Wɔ discharging mu no, reverse reaction no ba, a lithium ions no di nkitaho kɔ FEPO4 phase no mu. Ɔfã no wɔ core a lithium ions nyɛ intercalated no de tumi a ɛyera ba.

Figure 4-3 Lithium-ion intercalation/deintercalation model of lithium iron phosphate battery

Wɔyɛɛ nsusuwii nhwɛso abien bere koro mu, nanso nhwehwɛmu no mu ade titiriw no yɛ nea nhwehwɛmufo gye tom kɛse, ɛwom sɛ nneɛma pɔtee a ɛwɔ shell ne core no mu no da so ara yɛ akyinnyegye de. Yebetumi agyina saa nhwɛso abien yi so aka sɛ diffusion kinetics a ɛwɔ lithium ions ne charge mu no ne nneɛma a ɛkyerɛ sɛnea wɔde electrode ade no nyinaa di dwuma ankasa. Wɔ lithium iron phosphate cathode nneɛma a wɔyɛ mu no, wɔbɔ mmɔden sɛ wobenya nneɛma nketenkete a ne kɛse yɛ nketenkete na ɛyɛ pɛ (nanoscale anaa microporous), de carbon coating (nanocarbon film) ne ion doping di dwuma ma conductivity ne lithium ion diffusion tu mpɔn.

Esiane sɛ ntease a emu dɔ wɔ Limpo nneɛma ho nti, wohui sɛ saa nhwɛso abien yi bu ani gu lithium ion a wɔde fa limpo nneɛma so no anisotropic su horow a ɛyɛ anisotropic kɛse no so. Laffont de "New Core-shell model" ho nyansahyɛ mae sɛ wɔmfa nsiesie "core-akorade nhwɛso no sintɔ ahorow." Ɛnam eyi so no, Delmas suaa Lifepo abɔde nketenkete wɔ tebea horow a asɛe mu na ɔhyɛɛ nyansa sɛ wɔnyɛ "Domino-Cascade Model," a ɛkyerɛkyerɛ sɛnea nanoscale abɔde nketenkete no ahoɔden ne ne nsu a ɛkɔ ntɛmntɛm no adwumayɛ mu yiye, sɛnea wɔada no adi wɔ Mfonini 4-4 no mu no.

Ɛmfa ho nsonsonoe titiriw a ɛda nhwɛso ahorow a yɛadi kan aka ho asɛm no ntam no, asɛm titiriw no gyina nkɔmhyɛ ne su a ɛwɔ abien-phase interface no so. Esiane sɛ lithium a wɔde hyɛ mu/ayiyi ne phase nsakrae no nnyigyei gyina nneɛma nketenkete no kɛse, ne nsɛso, ne ne nipadua mu nnuru so kɛse nti, atifi hɔ nkɔmmɔbɔ (a ntawntawdi ahorow a ɛda nhwɛso ahorow ntam ka ho) no betumi afi sɔhwɛ tebea a ɛnnɔɔso.

Sɛ wɔyɛ microscopy ne spectroscopy a, wɔahu ano aduru a ɛyɛ den ne mfinimfini fã ahorow na wɔahu wɔ LIMPO4 nneɛma no mu nsakrae no mu, a ɛkyerɛ sɛ ebia fase nsakrae kwan foforo bi wɔ LiMPO4 nneɛma mu. Wɔ typical solid solution reactions mu no, cell parameters ne cell volume no da nsakrae a ɛkɔ so wɔ phase transitions mu adi. Ɛnam sɔhwɛ tebea horow bi a ɛyɛ hu ne akwan a wɔfa so kyerɛ ade so, te sɛ ultra-nneɛma nketenkete (nanoscale) ne-rate charge-discharge (atifi 10c), solid solution reactions ne intermediate phases a ɛwɔ hɔ no, wɔahu wɔ LIMPO4 mu.

Phase nsakrae bere a charge-gyae nhyehyɛe ahorow wɔ dan mu hyew. Lithium-ion battery da reversibility pa adi wɔ charge-discharge cycles mu, a ɛfa structure nsɛsoɔ a ɛwɔ phase states ntam wɔ lithium-ion deintercalation/intercalation akyi. Wɔ charge-discharge processes mu no, tumi a ɛporɔw a ɛwɔ battery no mu no ne phase transition kinetics no wɔ abusuabɔ kɛse. Sɛnea LifePo4 nhyehyɛe kyerɛ no, [100]PMNB akwankyerɛ no yɛ papa kɛse ma lithium-ion tu, na nkitahodi a ɛda fa abien no ntam no fa C-axis no so bere a charge-discharge nhyehyɛe ahorow no.

(1) Lifepo4/Fepo3 .The ratio of LiFePO₄/FePO₄ changes continuously with the battery charge-discharge reaction (the value of x in LiₓFePO₄ changes continuously). As lithium ions are extracted, the intensity of the diffraction peak produced by LiFePO₄ gradually decreases. When δ>0.2, diffraction peak a LI1 ΔFEPO4 no fi ase yera, na diffraction peak a FEPO3 de ba no mu den no kɔ soro nkakrankakra. Nea ɛne no bɔ abira no, bere a wɔde lithium ions hyɛ mu no, diffraction peak a FEPO4 de ba no mu den no so tew nkakrankakra, na diffraction peak no mu ahoɔden a Li11ΔFepo4 de ba no kɔ soro nkakrankakra.

(2) li1 10.LiₓFepo4 wɔ dan mu hyew mu yɛ Fe3-/Fe2⁄0 a wɔadi afra a wɔadi afra-Valence Mesophase Li1Fepo_/Li₁₋ Fepo4. na egyina hɔ ma carrier density ne hopping probability bere a charge ne discharging, sɛnea ɛte biara. Powder neutron diffraction daa no adi sɛ nea eye sen biara no yɛ 0.05 ne 0.11, sɛnea ɛte biara. Nneɛma te sɛ ion doping, temperature, transition metal, particle size, ne non-equilibrium tebea horow wɔ overpotential nyinaa nya values a ɛwɔ ne . Nkɔanim a ɛkɔ soro na ɛbɛma kinetic adwumayɛ a ɛwɔ electrode reaction bere a charge ne discharging wɔ dan mu hyew mu no atu mpɔn.

Wɔ 450℃, liₓfepo4 aduru a ɛyɛ den wɔ hɔ, bere a wɔ dan mu hyew mu no, metastable phases abien wɔ hɔ: li2.1 fepo4 ne li2.1 fepo4. Nea ɛboro 500℃, li1 no fi ase porɔw kɔ non-olivine nnuru mu; Nneɛma a ɛwɔ saa phosphates anaa phosphides yi mu ne nea ɛwom no gyina bo a x wɔ so. Wɔ 400 ne 500℃ntam no, liₓfepo4 ano aduru a ɛyɛ den nkutoo na ɛwɔ hɔ.

Nsakrae a ɛba bere a ɛreyɛ nwini no yɛ nea ɛyɛ den sen nea ɛwɔ ɔhyew bere mu no. Nneɛma a wɔde afrafra no bere a ɛreyɛ nwini no gyina x bo ne ɔhyew kwan no so. Sɛ ɛyɛ nwini a, li1 no di kan porɔw kɔ afrafra a ɛyɛ abien a ɛnyɛ{2}}olivine phases, a ne nsusuwii gyina ɔhyew ne x bo a edi kan no so. Sɛ ɔhyew no ba fam (140±20℃), abien-phase nhyehyɛe no bɛyɛ nhyehyɛe a ɛyɛ den kɛse, a lifepo4 ne fepo4 ne olivine foforo abien-Type compounds, liₓ1 Mpanyinyɛ a wɔde afrafra yi wɔ dan mu hyew mu no ma anan-phase nhyehyɛe no dan nkakrankakra ma ɛbɛyɛ abien-phase nhyehyɛe a ɛwɔ lifepo4 ne fepo4.

Battery reaction mechanism

FEPO4 wɔ hɔ wɔ nhyehyɛe ahorow pii mu: 1 Bere a wɔayɛ lifepo4 a ɛyɛ mmerɛw koraa akyi no, wɔhyehyɛ orthorhombic FEPO3; . 3 Monoclinic ne orthorhombic FEPO4 betumi asiesie afi wɔn mu biara hydrates mu. Saa ahwehwɛ a ɛyɛ ahwehwɛ yi nyinaa, ne fepo a ɛnyɛ amorphous, a ɛyɛ amorphous no nyinaa, betumi adan ayɛ triclinic fepo3 bere a wɔayɛ no hyew no.

Nsakrae a efi lifepo4 mu kɔ Fepo4 mu no yɛ brɛoo na enni mũ, nanso edi mũ bere a ɔhyew no boro digrii 500 no . Wɔ battery adwumayɛ tebea mu no, cathode ade no yɛ kinetically stable. Wɔ bere a wɔreyɛ lifepo4 no, ɛho hia sɛ wɔhwɛ hu sɛ FEPO3 nni hɔ. Sɛ ɛwɔ hɔ a, triclinic fepo4 bɛba bere a ɛyɛ hyew no, na ɛde non-electrochemically active glassy phase wɔ nneɛma no ani wɔ ɔhyew a ɛkɔ soro mu aba.

Ion doping betumi ama nneɛma a ɛkɔ so no atu mpɔn. P-Type semiconductor conductive nneɛma a conductivity du 10⁻2 s/cm no nam ion doping so nya. Doping yɛ adeyɛ a ɛyɛ den yiye: ɔkwan biako so no, density functional theory (DFT) akontaabu a ɛfa electronic structure of lifepo4 ho wɔ local density approximation (LDA) ase ne generalized gradient approximation (GGA) kyerɛ sɛ ɛsɛ sɛ ade no da su ahorow a ɛwɔ metallic anaa semiconductor ade bi mu adi, a conduction band no trɛw bɛyɛ 0.3 ev a ɛne no hyia. Ɔkwan foforo so no, sɛ yesusuw nkitahodi a ɛda ɛlɛtrɔnik orbitals ne Coulomb nkitahodi akyi wɔ ion doping akyi a, valence band nhyehyɛe a ɛkɔ anim no yɛ nea wobetumi ayɛ wɔ nsusuwii mu.

DFT akontabuo a ɛfa Mg- anaa Cr-doped lifepo4 ho no kyerɛ sɛ ɛlɛtrɔnik tebea a ɛwɔ hɔ no dodoɔ a ɛwɔ hɔ no bɛn Fermi level, a ɛkyerɛkyerɛ dadeɛ a ɛkɔ nsuo mu a ɛwɔ aduru a wɔde ayɛ aduru no mu. Nsakrae a ɛba wɔ conductivity mu a ion doping de ba no betumi ayɛ nea ɛfa nneɛma a edidi so yi ho:

1) Wɔde metall na ɛyɛ charge carrier regions no anoano.

2) Ion doping no ma valence band ne conduction band no tɛtrɛtɛ yɛ teateaa.

3) Sɛ ɛboro concentration a ɛho hia bi so a, ɛlɛtrɔnik wavefunction a ɛwɔ dopant ions no mu no ma ɛba conduction band.

4) Dopant ions no su, ne dodow, ne ne kyekyɛ.

5) Wɔ m{1}}o dadeɛ oxides pii mu no, dadeɛ a wɔde fa nsuo mu band bi pue berɛ a M{2}}M bond kwan no nnu 3 × 10⁻10 m.

6) Wɔ synthesis mu no, organic carbon a wɔde ka ho no ma carbon coating yɛ ade no, na ɛma conduction kwan a etu mpɔn ba.

7) Fe2p. Bere a wɔreyɛ no, carbon a ɛboro so a wɔde ka ho no ma phosphate no so tew.

Ion doping and conductivity

8) FE3⁺/Fe27 redox mmienu no yɛ adwuma sɛ ade a ɛma nkwa a ɛso tew 4.

Lifepo4 da reactivity adi ne electrolytes a wɔtaa de di dwuma. Nneɛma no mu electrochemical suban ne ne soro chemistry a ɛwɔ electrolyte no mu no wɔ abusuabɔ kɛse. Mpɛn pii no, passivation film ba wɔ ade no ani. Saa sini yi ma lithium-ion diffusion yɛ mmerɛw, esiw nneɛma a ɛyɛ adwuma a ɛyera no ano, na ɛsɛ sɛ egyina volume ne surface nsakrae ano wɔ lithium-ion insertion/extraction mu. Carbon-a wɔakata so lifepo4 no, nneɛma a ɛwɔ soro te sɛ LIF, Lipf1, Li1Fᵧ4, ne Li1

Mpɛn pii no, alkyl carbonates ne lithium nkyene wɔ electrolytes a ɛtaa ba no mu. Cathode ade no fa nneyɛe pii a ebetumi aba wɔ electrolyte no mu. Sɛ nhwɛso no, wɔ Lipf1 ano aduru mu no, acid{2}}base reaction a ɛda lifepo4 ne HF kakraa bi ntam no yɛ nea wontumi nkwati. HF a ɛwɔ electrolyte no mu no wɔ nkɛntɛnso abien a ɛsɛe ade: nea edi kan no, ade a wɔde si dade ions ne proton ntam a wɔde si ananmu; ne nea ɛto so abien no, li ions ne f ions a ɛwɔ abɔde nketenkete no ani no yɛ wɔn ade ma ɛyɛ LIF, a esiw Li⁺ diffusion kwan.

Dade ions no hohoro wɔ electrolytes mu. Nsɔhwɛ ahorow a wɔyɛe wɔ dade ion a ɛpaapae a ɛwɔ lifepo4 mu wɔ electrolytes ahorow mu no daa nea edidi so yi adi:

1) Wɔ electrolytes a acidic efĩ nni mu, wɔ ɔhyew a ɛkɔ soro mpo mu no, dade ions a ɛpaapae ne nea efi mu ba no a ɛyera wɔ ade a ɛyɛ adwuma no mu no yɛ nea wontumi mmu ani ngu so.

2) Solution acidity a ɛkorɔn no ma ɛyɛ mmerɛw sɛ iron ion dissolution.

3) Ɔhyew a ɛkɔ soro no ma ɛyɛ mmerɛw sɛ dade ion no bɛpaapae.

4) Carbon a ɛkɔ soro wɔ ade no mu no ma nneɛma a ɛyɛ den kɛse ba.

Beae a ɛda nneɛma a ɛyɛ adwuma no ne binder ntam no yɛ nea ɛyɛ mmerɛw kɛse sɛ ɛbɛsɛe. Wobetumi akwati saa nsɛe yi denam alkaline mesophase a wɔde bedi dwuma anaasɛ wɔde acid a wɔde twitwa nneɛma a wɔde ka ho a wɔde di dwuma so. Wɔ lithium-ion battery a wɔde lifepo4 di dwuma sɛ cathode ade, non{3}}acidic electrolytes anaasɛ carbon a wɔde ka ho anaasɛ coating of lifepo4 no betumi adi dwuma de asiw mass loss ano.

Wɔnnya nte kinetic su a ɛwɔ lifepo4 cathode nneɛma mu no ase yie. Wɔgye di mpɛn pii sɛ abɔdeɛ nketenkete kɛseɛ ne ne kyekyɛ, conductivity, ion diffusion, kinetics wɔ phase transitions (charge-discharge process), ne carbon coating/doping nyinaa nya battery no adwumayɛ so nkɛntɛnsoɔ wɔ charge-discharge rates soronko so. Carbon doping a ɛyɛ pɛ kyerɛ sɛ wobetumi de lithium ions ne electron ahyɛ mu na wɔayi afi beae koro wɔ ade a ɛyɛ adwuma no mu, na ɛtew electrode polarization so.

(1) Nkɛntɛnso a conductivity nya wɔ tumi so Nkɛntɛnso a ɛba fam a ɛwɔ pure lifepo4 mu no ma battery no tumi a ɛkɔ soro-rate no so tew tẽẽ. Lifepo a ɛho tew no conductivity bɛyɛ 10⁻⁹ S/cm, na tumi a ɛma nsu fi mu ba no so tew kɛse fi 148 mA·H/G wɔ 0.2C a ɛma nsu fi mu ba kosi 85 mA·H/G wɔ 5C nsu a wɔde gu mu. Ɛnkɔ soro-rate discharge tumi a cathode ade no kɔ soro bere nyinaa bere a conductivity kɔ soro no. Wɔ conductivity a ɛba fam mu no, conductivity a ɛkɔ soro no ma electrochemical kinetics a ɛwɔ ade no mu no tu mpɔn. Sɛ adeɛ no conductivity boro boɔ a ɛho hia bi so a, conductivity nyɛ adeɛ a ɛkyerɛ adeɛ no rate tumi bio. Nkwa ₀.₉ni₀.₁po₄ (1.0 × 10⁻⁷ S/cm), a ne conductivity a ɛba fam no, da no adi sɛ ɛkorɔn-rate discharge tumi sen lifepo₄ (4.0 × 10⁶ s/cm, , g ne wigities 10C a wɔde fi mu ba. Eyi kyerɛ sɛ ebia lithium-ion diffusion no besii conductivity ananmu sɛ ade titiriw wɔ electrochemical su ahorow a ɛwɔ lithium-ion batere mu.

(2) Lithium-ion diffusion lithium-ion diffusion no gyina nneɛma a ɛwɔ mu ne akyi nyinaa so. Nneɛma a ɛwɔ akyi no bi ne nneɛma nketenkete no kɛse, ne kyekyɛ, ne ne nsɛso. Nneɛma a ɛwɔ mu no titiriw na ɛkyerɛ lithium-ion diffusion coefficient. Lithium-ion diffusion coefficient no yɛ botae a ɛkɔ so daa; Lithium ions a ɛtrɛw no so tew bere a nneɛma nketenkete no kɛse kɔ soro no efisɛ lithium ions a ɛtrɛw wɔ abɔde nketenkete no mu no kɔ soro. Lithium ions no trɛw tumi no ne abɔde nketenkete no kɛse ahinanan no hyia wɔ ɔkwan a ɛnteɛ so na ɛne lithium-ion diffusion coefficient no hyia tẽẽ. Nneɛma nketenkete no kɛse wɔ nkɛntɛnso kɛse wɔ lithium-ion diffusion so sen diffusion coefficient. Ɛsɛ sɛ wɔde akontabuo akontabuo a ɛfa lithium-ion diffusion coefficient ho no ka susudua akwan pɔtee ne nsusuiɛ nhwɛsoɔ ho. Akwan titiriw a wɔfa so susuw nneɛma ne galvanostatic titration (GITT) ne electrochemical impedance spectroscopy (EIS anaa AC impedance).

(3) Mmienu-dimensional scale electrodes: Thin-Film electrodes ma electrode dwumadi nya nkɔso denam soro a ɛkɔ soro no so. Wɔ thin-Film electrodes mu no, electrons hyɛn current collector no mu bere a lithium ions hyɛn electrolyte no mu fi ɔkwan a ɛne no bɔ abira no so. Bere a FEPO4 layer no hyehyɛ no, ɛlɛtrɔnik kankyee a ɛko tia no so tew, bere a lithium-ion kankyee a ɛko tia no kɔ soro. FEPO4 di kan yɛ nucleates wɔ crystal sintɔ ahorow mu na afei enyin wɔ akwan nyinaa so, na esiw lithium-ion diffusion ano kosi sɛ lithium ions rentumi nkwati wɔ [100] kwan no so.