CN114335480A - Core-shell carbon-coated doped lithium iron phosphate, and preparation method and application thereof - Google Patents
Core-shell carbon-coated doped lithium iron phosphate, and preparation method and application thereof Download PDFInfo
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- CN114335480A CN114335480A CN202111679940.4A CN202111679940A CN114335480A CN 114335480 A CN114335480 A CN 114335480A CN 202111679940 A CN202111679940 A CN 202111679940A CN 114335480 A CN114335480 A CN 114335480A
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- iron phosphate
- transition metal
- lithium iron
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 108
- 239000011258 core-shell material Substances 0.000 title claims abstract description 58
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 58
- 150000001875 compounds Chemical class 0.000 claims abstract description 48
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 45
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 44
- 238000000034 method Methods 0.000 claims abstract description 43
- TUSDEZXZIZRFGC-UHFFFAOYSA-N 1-O-galloyl-3,6-(R)-HHDP-beta-D-glucose Natural products OC1C(O2)COC(=O)C3=CC(O)=C(O)C(O)=C3C3=C(O)C(O)=C(O)C=C3C(=O)OC1C(O)C2OC(=O)C1=CC(O)=C(O)C(O)=C1 TUSDEZXZIZRFGC-UHFFFAOYSA-N 0.000 claims abstract description 37
- 239000001263 FEMA 3042 Substances 0.000 claims abstract description 37
- LRBQNJMCXXYXIU-PPKXGCFTSA-N Penta-digallate-beta-D-glucose Natural products OC1=C(O)C(O)=CC(C(=O)OC=2C(=C(O)C=C(C=2)C(=O)OC[C@@H]2[C@H]([C@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)O2)OC(=O)C=2C=C(OC(=O)C=3C=C(O)C(O)=C(O)C=3)C(O)=C(O)C=2)O)=C1 LRBQNJMCXXYXIU-PPKXGCFTSA-N 0.000 claims abstract description 37
- 238000006243 chemical reaction Methods 0.000 claims abstract description 37
- LRBQNJMCXXYXIU-NRMVVENXSA-N tannic acid Chemical compound OC1=C(O)C(O)=CC(C(=O)OC=2C(=C(O)C=C(C=2)C(=O)OC[C@@H]2[C@H]([C@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)O2)OC(=O)C=2C=C(OC(=O)C=3C=C(O)C(O)=C(O)C=3)C(O)=C(O)C=2)O)=C1 LRBQNJMCXXYXIU-NRMVVENXSA-N 0.000 claims abstract description 37
- 229940033123 tannic acid Drugs 0.000 claims abstract description 37
- 235000015523 tannic acid Nutrition 0.000 claims abstract description 37
- 229920002258 tannic acid Polymers 0.000 claims abstract description 37
- 229910052742 iron Inorganic materials 0.000 claims abstract description 35
- 229910001428 transition metal ion Inorganic materials 0.000 claims abstract description 33
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 29
- 238000005245 sintering Methods 0.000 claims abstract description 25
- 230000008569 process Effects 0.000 claims abstract description 24
- 150000003623 transition metal compounds Chemical class 0.000 claims abstract description 21
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 17
- 230000009920 chelation Effects 0.000 claims abstract description 17
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 17
- 239000002243 precursor Substances 0.000 claims abstract description 14
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 13
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 13
- 239000011574 phosphorus Substances 0.000 claims abstract description 13
- 239000013522 chelant Substances 0.000 claims abstract description 11
- 229910052723 transition metal Inorganic materials 0.000 claims abstract description 8
- 239000002904 solvent Substances 0.000 claims abstract description 7
- 229920001864 tannin Polymers 0.000 claims abstract description 7
- 235000018553 tannin Nutrition 0.000 claims abstract description 7
- 239000001648 tannin Substances 0.000 claims abstract description 7
- 150000003624 transition metals Chemical class 0.000 claims abstract description 7
- 229910001416 lithium ion Inorganic materials 0.000 claims description 26
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 23
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 19
- 239000000463 material Substances 0.000 claims description 18
- -1 iron ions Chemical class 0.000 claims description 13
- 239000007774 positive electrode material Substances 0.000 claims description 12
- 229910021578 Iron(III) chloride Inorganic materials 0.000 claims description 9
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 claims description 9
- 230000035484 reaction time Effects 0.000 claims description 9
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 8
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 claims description 6
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 6
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims description 5
- 229910002651 NO3 Inorganic materials 0.000 claims description 4
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 4
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 4
- CDVAIHNNWWJFJW-UHFFFAOYSA-N 3,5-diethoxycarbonyl-1,4-dihydrocollidine Chemical compound CCOC(=O)C1=C(C)NC(C)=C(C(=O)OCC)C1C CDVAIHNNWWJFJW-UHFFFAOYSA-N 0.000 claims description 3
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims description 3
- 239000005955 Ferric phosphate Substances 0.000 claims description 3
- 229910011902 LiFe1-xMxPO4 Inorganic materials 0.000 claims description 3
- 229910010595 LiFe1−xMxPO4 Inorganic materials 0.000 claims description 3
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 claims description 3
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 claims description 3
- 238000001816 cooling Methods 0.000 claims description 3
- YNQRWVCLAIUHHI-UHFFFAOYSA-L dilithium;oxalate Chemical compound [Li+].[Li+].[O-]C(=O)C([O-])=O YNQRWVCLAIUHHI-UHFFFAOYSA-L 0.000 claims description 3
- 229940032958 ferric phosphate Drugs 0.000 claims description 3
- KTWOOEGAPBSYNW-UHFFFAOYSA-N ferrocene Chemical compound [Fe+2].C=1C=C[CH-]C=1.C=1C=C[CH-]C=1 KTWOOEGAPBSYNW-UHFFFAOYSA-N 0.000 claims description 3
- 229960002089 ferrous chloride Drugs 0.000 claims description 3
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 3
- 239000011790 ferrous sulphate Substances 0.000 claims description 3
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 claims description 3
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 3
- RUTXIHLAWFEWGM-UHFFFAOYSA-H iron(3+) sulfate Chemical compound [Fe+3].[Fe+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O RUTXIHLAWFEWGM-UHFFFAOYSA-H 0.000 claims description 3
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 3
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims description 3
- 229910000360 iron(III) sulfate Inorganic materials 0.000 claims description 3
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 claims description 3
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 3
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 3
- INHCSSUBVCNVSK-UHFFFAOYSA-L lithium sulfate Inorganic materials [Li+].[Li+].[O-]S([O-])(=O)=O INHCSSUBVCNVSK-UHFFFAOYSA-L 0.000 claims description 3
- SNKMVYBWZDHJHE-UHFFFAOYSA-M lithium;dihydrogen phosphate Chemical compound [Li+].OP(O)([O-])=O SNKMVYBWZDHJHE-UHFFFAOYSA-M 0.000 claims description 3
- MCVFFRWZNYZUIJ-UHFFFAOYSA-M lithium;trifluoromethanesulfonate Chemical compound [Li+].[O-]S(=O)(=O)C(F)(F)F MCVFFRWZNYZUIJ-UHFFFAOYSA-M 0.000 claims description 3
- 235000019837 monoammonium phosphate Nutrition 0.000 claims description 3
- 238000004321 preservation Methods 0.000 claims description 3
- 150000003839 salts Chemical class 0.000 claims description 3
- RBTVSNLYYIMMKS-UHFFFAOYSA-N tert-butyl 3-aminoazetidine-1-carboxylate;hydrochloride Chemical compound Cl.CC(C)(C)OC(=O)N1CC(N)C1 RBTVSNLYYIMMKS-UHFFFAOYSA-N 0.000 claims description 3
- ITMCEJHCFYSIIV-UHFFFAOYSA-M triflate Chemical compound [O-]S(=O)(=O)C(F)(F)F ITMCEJHCFYSIIV-UHFFFAOYSA-M 0.000 claims description 3
- QSNQXZYQEIKDPU-UHFFFAOYSA-N [Li].[Fe] Chemical compound [Li].[Fe] QSNQXZYQEIKDPU-UHFFFAOYSA-N 0.000 claims description 2
- 238000010438 heat treatment Methods 0.000 claims description 2
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 claims 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims 1
- 239000010405 anode material Substances 0.000 abstract description 24
- 239000011248 coating agent Substances 0.000 abstract description 9
- 238000000576 coating method Methods 0.000 abstract description 9
- 239000013078 crystal Substances 0.000 description 24
- 229910019142 PO4 Inorganic materials 0.000 description 20
- 239000010936 titanium Substances 0.000 description 16
- 150000002500 ions Chemical class 0.000 description 15
- 238000009792 diffusion process Methods 0.000 description 11
- 239000010406 cathode material Substances 0.000 description 9
- 229910017677 NH4H2 Inorganic materials 0.000 description 7
- 229910003074 TiCl4 Inorganic materials 0.000 description 7
- 238000007600 charging Methods 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- 239000007772 electrode material Substances 0.000 description 7
- 239000002105 nanoparticle Substances 0.000 description 7
- 239000011247 coating layer Substances 0.000 description 6
- 238000007599 discharging Methods 0.000 description 6
- 239000010410 layer Substances 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 239000012071 phase Substances 0.000 description 5
- LCKIEQZJEYYRIY-UHFFFAOYSA-N Titanium ion Chemical compound [Ti+4] LCKIEQZJEYYRIY-UHFFFAOYSA-N 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 4
- 238000004146 energy storage Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 229910052493 LiFePO4 Inorganic materials 0.000 description 3
- 238000005054 agglomeration Methods 0.000 description 3
- 230000002776 aggregation Effects 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 238000003760 magnetic stirring Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 239000011163 secondary particle Substances 0.000 description 3
- 239000002356 single layer Substances 0.000 description 3
- 238000006467 substitution reaction Methods 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 150000001242 acetic acid derivatives Chemical class 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 238000010000 carbonizing Methods 0.000 description 2
- 150000001805 chlorine compounds Chemical class 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229910000398 iron phosphate Inorganic materials 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 150000002823 nitrates Chemical class 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 230000029219 regulation of pH Effects 0.000 description 2
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 2
- 229910032387 LiCoO2 Inorganic materials 0.000 description 1
- 229910011893 LiFe0.9Ti0.1PO4 Inorganic materials 0.000 description 1
- 229910010710 LiFePO Inorganic materials 0.000 description 1
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- 229910002097 Lithium manganese(III,IV) oxide Inorganic materials 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 238000003917 TEM image Methods 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 229960005070 ascorbic acid Drugs 0.000 description 1
- 235000010323 ascorbic acid Nutrition 0.000 description 1
- 239000011668 ascorbic acid Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- OJIJEKBXJYRIBZ-UHFFFAOYSA-N cadmium nickel Chemical compound [Ni].[Cd] OJIJEKBXJYRIBZ-UHFFFAOYSA-N 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 238000010277 constant-current charging Methods 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000011066 ex-situ storage Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000005562 fading Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 229910001386 lithium phosphate Inorganic materials 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 238000002715 modification method Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 125000002467 phosphate group Chemical group [H]OP(=O)(O[H])O[*] 0.000 description 1
- 229920001690 polydopamine Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000003746 solid phase reaction Methods 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 239000011232 storage material Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 description 1
- 238000001132 ultrasonic dispersion Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides core-shell carbon-coated doped lithium iron phosphate, and a preparation method and application thereof. The preparation method comprises the following steps: in the presence of a first solvent, carrying out a chelation reaction on an iron source compound, a transition metal compound and tannic acid to obtain a product system containing a chelate, wherein the valence state of transition metal ions in the transition metal compound is more than or equal to 4; carrying out hydrothermal synthesis reaction on a phosphorus source compound, a lithium source compound and a chelate to obtain a tannin-coated transition metal ion-doped lithium iron phosphate precursor; and sintering the precursor of the transition metal ion doped lithium iron phosphate coated with tannic acid in an inert atmosphere to obtain the core-shell type carbon-coated doped lithium iron phosphate. The core-shell carbon-coated doped lithium iron phosphate prepared by the method has the advantages of low cost, good uniformity and compactness of the carbon coating, small grain size and the like, so that the prepared anode material can obtain better rate performance and dynamic performance in the application process.
Description
Technical Field
The invention relates to the manufacture of a lithium iron phosphate type lithium ion battery, in particular to core-shell type carbon-coated doped lithium iron phosphate, a preparation method and application thereof.
Background
Compared with commercial rechargeable secondary batteries such as nickel-cadmium batteries, lead-acid batteries and the like, lithium ion batteries have the advantages of high energy density, high power density, long service life, no memory effect and the like, are widely applied to various portable electronic devices, and are gradually applied to energy storage systems of new energy vehicles. The existing lithium ion power battery can not meet the energy storage requirement of people, and the development of a lithium ion battery energy storage material with higher performance is urgently needed, wherein the development of a lithium ion power battery anode material is very critical. At present, the research on the anode material of the lithium ion battery mainly focuses on layered lithium cobaltate LiCoO2Material (LCO), spinel lithium manganate LiMn2O4Material (LMO), olivine lithium iron phosphate LiFePO4(LFP) and layered ternary material systems, and the like. As positive electrode materials, they each have advantages that cobalt in the raw material of lithium cobaltate is expensive and also toxic; the high-temperature performance and the long cycle performance of the lithium manganate are obviously insufficient, and further optimization is still needed; layered ternary systems, particularly high nickel systems, while providing high energy densities, are inherently moisture sensitive and poorly thermally stable. The lithium iron phosphate has rich resources, low cost, environment friendliness, stable crystal structure, good safety performance and higher theoretical capacity (170 mAh.g)-1) And the like, and has wide application value in lithium ion power batteries. However, based on LiFePO4As can be seen from the crystal structure, FeO6Octahedron and PO4Common angle connection of tetrahedrons and FeO6Is PO of octahedron4Tetrahedral separation during charging and discharging, Li+The migration path is limited to one-dimensional channel diffusion, resulting in LiFePO4Exhibits low electronic conductivity and ion diffusion coefficient at room temperature, thereby exhibiting poor rate performance and long cycle in practical applicationsMedium capacity severe fading.
For the LiFePO described above4The disadvantages of the materials' low electronic conductivity and ion diffusion rate, researchers have proposed many modification methods, mainly classified into the following categories: 1. the particles are nano-sized, the particle size of the lithium iron phosphate is reduced, and Li can be effectively shortened+The diffusion path of the light source can improve the diffusion rate and the rate performance of the light source; 2. after ion doping and ion doping with different grain diameters, one of the ions can produce lattice defects, widen ion diffusion channels and reduce Li+A second diffusion energy barrier which can reduce the width of an energy gap to a certain extent and improve the electronic conductivity of the body material; 3. the shape control, the special shape structure can make the material fully contact with the electrolyte, increase the electrochemical active sites of the material, and control the direction of crystal growth to Li+The crystal face of the diffusion channel carries out preferred orientation to ensure Li+Rapid insertion and efficient conduction of electrons; 4. the conductive carbon is compounded/coated, the electronic conductivity of the material can be obviously improved by adding the coated carbon, the charge and discharge performance of the battery under high multiplying power is improved, the coated carbon can limit the growth of crystal grains to a certain extent, effective electron and ion transmission channels are provided, the porous structure coated with the carbon can absorb electrolyte, the contact area of the electrolyte is increased, more electrochemical active sites can be realized, and thus excellent and stable electrochemical performance can be continuously output.
The prior art of carbon-coated lithium iron phosphate materials is as follows:
the existing literature provides a preparation method of carbon-coated lithium iron phosphate with a hierarchical structure, the method obtains lithium iron phosphate with the hierarchical structure by a one-step hydrothermal synthesis method, and the synthesized lithium iron phosphate is fully mixed with a carbon source in a subsequent sintering process to prepare the carbon-coated lithium iron phosphate with the hierarchical structure, and the carbon-coated lithium iron phosphate has high specific capacity and good cycle performance. However, the disadvantages of this method are: the selection of the organic carbon source for coating the lithium iron phosphate is limited, and part of the organic carbon source is expensive, such as ascorbic acid, polydopamine and the like.
Another prior document provides a hydrothermal preparation method of nano lithium iron phosphate, in which an organic compound having a phosphate end group is added to synthesize a lithium iron phosphate material having a small particle size (100 nm) and good uniformity, and the material is mixed with an organic carbon source in a subsequent high-temperature sintering process to prepare carbon-coated nano lithium iron phosphate, but the additive-containing wastewater is difficult to treat in the preparation process. However, the disadvantages of this method are: the coated amorphous carbon is not uniform in thickness and the coating layer may not be dense.
Another prior document provides a method for preparing lithium iron phosphate, which includes mixing phosphoric acid, an iron source and a PH buffer, performing a hydrothermal reaction to prepare an iron phosphate precursor, mixing and sintering the iron phosphate precursor, the lithium source and a carbon source to obtain lithium iron phosphate, and finally obtaining a single-phase lithium iron phosphate. However, the disadvantages of this method are: in the long-time high-temperature carbonization process, the ex-situ carbon-coated nanoscale lithium iron phosphate can be agglomerated into large secondary particles of lithium iron phosphate cathode material, and the lithium ion diffusion kinetics is slow.
In view of the above problems, it is necessary to provide a novel method for preparing lithium iron phosphate.
Disclosure of Invention
The invention mainly aims to provide core-shell type carbon-coated doped lithium iron phosphate, a preparation method and application thereof, and aims to solve the problems that the conventional lithium iron phosphate anode material is high in cost, uneven in carbon layer coating, not dense, easy to agglomerate crystal grains and the like.
In order to achieve the above object, the present invention provides a method for preparing core-shell type carbon-coated doped lithium iron phosphate, wherein the method for preparing core-shell type carbon-coated doped lithium iron phosphate comprises: in the presence of a first solvent, carrying out a chelation reaction on an iron source compound, a transition metal compound and tannic acid to obtain a product system containing a chelate, wherein the valence state of transition metal ions in the transition metal compound is more than or equal to 4; carrying out hydrothermal synthesis reaction on a phosphorus source compound, a lithium source compound and a chelate to obtain a tannin-coated transition metal ion-doped lithium iron phosphate precursor; and sintering the precursor of the transition metal ion doped lithium iron phosphate coated with tannic acid in an inert atmosphere to obtain the core-shell type carbon-coated doped lithium iron phosphate.
Further, the transition metal ion is selected from Ti4+、W6+、Ta5+、Nb5+、Zr4+、Mo6+And V5+One or more of the group, preferably Ti4+(ii) a The transition metal compound is one or more of the group consisting of chlorides, sulfates, nitrates, acetates and organic salts of transition metal ions.
Further, in the chelation reaction, the molar ratio of the tannic acid, the iron ion in the iron source compound, and the transition metal ion is (0.1 to 3): 1: (0.001-0.02).
Further, the ratio of the number of moles of transition metal ions and phosphorus source compounds in the lithium source compound, iron source compound and transition metal compound is (1 to 4): (0.9-1.5): (0.001-0.02): (0.6-1.5).
Furthermore, the temperature of the hydrothermal synthesis reaction is 120-240 ℃, the reaction time is 5-48 h, and the pH value is 5-8.
Further, the sintering temperature in the sintering process is 350-900 ℃, and the heat preservation time is 3-12 h;
the heating rate in the sintering process is 2-10 ℃ per minute-1Preferably 5 ℃ min-1And the cooling rate after sintering is 2-15 ℃ min-1Preferably 10 ℃ min-1。
Further, the iron source compound is selected from one or more of the group consisting of ferrous chloride, ferrous sulfate, ferrous nitrate, ferric chloride, ferric sulfate, ferric nitrate, ferric phosphate, ferric acetylacetonate, ferric trifluoromethanesulfonate, and ferrocene; the phosphorus source compound is selected from one or more of phosphoric acid, ammonium dihydrogen phosphate and lithium dihydrogen phosphate; and the lithium source compound is selected from one or more of the group consisting of lithium carbonate, lithium hydroxide, lithium sulfate, lithium acetate, lithium nitrate, lithium trifluoromethanesulfonate and lithium oxalate.
The second aspect of the application also provides a core-shell type carbon-coated doped phosphorus-like materialThe lithium iron phosphate is prepared by the preparation method provided by the application, and preferably, the core-shell type carbon-coated doped lithium iron phosphate can be LiFe1-xMxPO4@ C denotes where x is 0.001 to 0.02 and M is a transition metal ion having a valence of 4 or more.
A third aspect of the present application also provides a lithium ion battery comprising a positive electrode material comprising the core-shell carbon-coated doped lithium iron phosphate-like according to claim 8.
A fourth aspect of the present application also provides an electric drive device comprising the lithium ion battery of claim 9.
By applying the technical scheme of the invention, the risk that transition metal ions cannot enter lithium iron phosphate crystal lattices due to loss in the treatment processes of washing and the like can be effectively inhibited through a chelation reaction, and the precipitation of iron ions in subsequent pH regulation can be effectively reduced, so that the distribution uniformity of each component is improved. Through the hydrothermal synthesis reaction and the sintering process, the tannic acid can be carbonized on the surface of the lithium iron phosphate into a single-layer or multi-layer carbon coating layer with uniform thickness after being carbonized, so that the electronic conductivity of the cathode material is favorably and remarkably improved, and the dynamic performance of the electrode material is optimized; meanwhile, the growth of crystal grains is limited in the process of carbonizing the tannic acid, and the secondary particle agglomeration is inhibited, so that the grain size is refined, and the Li is shortened+Increase Li+The transport rate is increased, thereby greatly improving the rate capability of the electrode material. In addition, tannic acid is used as an organic carbon source, and the raw material is wide in source and low in cost, so that the production cost of the lithium iron phosphate anode material can be greatly reduced. On the basis, the core-shell carbon-coated doped lithium iron phosphate prepared by the method has the advantages of low cost, good uniformity and compactness of the carbon coating, small grain size and the like, so that the prepared anode material can obtain better rate performance and dynamic performance in the application process.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
fig. 1 is an XRD pattern of the core-shell carbon-coated nano-sized titanium-doped lithium iron phosphate cathode material prepared in example 1;
fig. 2 is an SEM image of the core-shell carbon-coated nano-sized titanium-doped lithium iron phosphate positive electrode material prepared in example 1;
fig. 3 is a TEM image of the core-shell carbon-coated nano-sized titanium-doped lithium iron phosphate cathode material prepared in example 1;
fig. 4 is a charge-discharge curve of the core-shell carbon-coated nano-sized titanium-doped lithium iron phosphate cathode material prepared in example 1.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
As described in the background art, the conventional lithium iron phosphate positive electrode material has the problems of high cost, uneven coating of a carbon layer, no density, easy agglomeration of crystal grains and the like. In order to solve the technical problems, the application provides a preparation method of core-shell type carbon-coated doped lithium iron phosphate, and the preparation method of the core-shell type carbon-coated doped lithium iron phosphate comprises the following steps: in the presence of a first solvent, carrying out a chelation reaction on an iron source compound, a transition metal compound and tannic acid to obtain a product system containing a chelate, wherein the valence state of transition metal ions in the transition metal compound is more than or equal to 4; carrying out hydrothermal synthesis reaction on a phosphorus source compound, a lithium source compound and a chelate to obtain a tannin-coated transition metal ion-doped lithium iron phosphate precursor; and sintering the precursor of the transition metal ion doped lithium iron phosphate coated with tannic acid in an inert atmosphere to obtain the core-shell type carbon-coated doped lithium iron phosphate.
Before the hydrothermal synthesis stage, the tannic acid is subjected to chelation reaction preferentially with iron ions in the iron source compound and high-valence transition metal ions in the transition metal compound to form a cyclic chelate; then in the hydrothermal synthesis process, the cyclic chelate reacts with a lithium source compound and a phosphorus source compound to generate a high valence transition metal doped lithium iron phosphate crystal nucleus, and tannic acid uniformly grows on the outer surface of the crystal nucleus to form a core-shell type nanoscale lithium iron phosphate structure (precursor). In the high-temperature solid-phase reaction process (sintering process), the tannic acid is carbonized on the surface of the lithium iron phosphate into a single-layer or multi-layer carbon coating layer with uniform thickness, so that the required core-shell type carbon-coated doped lithium iron phosphate is obtained.
The risk that transition metal ions cannot enter lithium iron phosphate crystal lattices due to loss in the washing and other treatment processes can be effectively inhibited through the chelation reaction, and the precipitation of iron ions in subsequent pH regulation can be effectively reduced, so that the distribution uniformity of each component is improved. Through the hydrothermal synthesis reaction and the sintering process, the tannic acid can be carbonized on the surface of the lithium iron phosphate into a single-layer or multi-layer carbon coating layer with uniform thickness after being carbonized, so that the electronic conductivity of the cathode material is favorably and remarkably improved, and the dynamic performance of the electrode material is optimized; meanwhile, the growth of crystal grains is limited in the process of carbonizing the tannic acid, and the secondary particle agglomeration is inhibited, so that the grain size is refined, and the Li is shortened+Increase Li+The transport rate is increased, thereby greatly improving the rate capability of the electrode material. In addition, tannic acid is used as an organic carbon source, and the raw material is wide in source and low in cost, so that the production cost of the lithium iron phosphate anode material can be greatly reduced. On the basis, the core-shell carbon-coated doped lithium iron phosphate prepared by the method has the advantages of low cost, good uniformity and compactness of the carbon coating, small grain size and the like, so that the prepared anode material can obtain better rate performance and dynamic performance in the application process.
Since tannic acid is solid, in the chelation reaction, tannic acid needs to be dissolved in a first solvent (such as water) before the chelation reaction occurs, and thus a solution a is formed. Preferably, the above dissolution process may be performed under magnetic stirring in order to increase the dissolution rate thereof. Meanwhile, in order to improve the chelating effect of the solution a with other components (iron source compound and transition metal compound), an ultrasonic device may be used for dispersion, and whether magnetic stirring is performed or not may be selected as appropriate. In another embodiment, after solution a is formulated, the iron source compound and the transition metal compound are mixed with a second solvent (such as water) to form solution B. Then, the solution A and the solution B are mixed to perform a chelation reaction.
It should be noted that the "inert atmosphere" refers to a gas which does not react with the reaction raw materials, such as nitrogen, an inert gas, and the like.
In the hydrothermal synthesis stage, transition metal ions can enter lithium iron phosphate crystal lattices to produce lattice defects, widen ion diffusion channels and reduce Li+The diffusion barrier has an effect of improving the electron conductivity of the positive electrode material. In a preferred embodiment, the transition metal ion includes, but is not limited to, Ti4+、W6+、Ta5+、Nb5+、Zr4+、Mo6+And V5+One or more of the group, preferably Ti4+(ii) a The transition metal compound is one or more of the group consisting of chlorides, sulfates, nitrates, acetates and organic salts of transition metal ions. Compared with other high-valence transition metal ions, the transition metal ions, iron ions and tannic acid have better binding performance, so that the utilization rate of the transition metal ions is further improved, the distribution uniformity of components in the anode material is improved, and the electrical properties of the anode material are more uniform. More preferably, in the chelation reaction, the molar ratio of the tannic acid, the iron ion in the iron source compound, and the transition metal ion is (0.1 to 3): 1: (0.001-0.02).
In a preferred embodiment, the ratio of the number of moles of the transition metal ion in the lithium source compound, the iron source compound, and the transition metal compound to the number of moles of the phosphorus source compound (1 to 4): (0.9-1.5): (0.001-0.02): (0.6-1.5). The mole ratio of the lithium source compound, the iron source compound, the transition metal compound and the phosphorus source compound includes but is not limited to the above range, and the limitation of the mole ratio in the above range is favorable for reducing the generation of impurity phases, better controlling the growth of crystal grains and improving the energy density and the specific discharge capacity of the lithium iron phosphate material in the application process.
The precursor material of the lithium iron phosphate can be obtained through a hydrothermal synthesis reaction. In a preferred embodiment, the temperature of the hydrothermal synthesis reaction is 120-240 ℃, the reaction time is 5-48 h, and the pH is 5-8. The temperature, the reaction time and the pH of the hydrothermal synthesis reaction are not limited to the ranges, and the limitation of the temperature, the reaction time and the pH to the ranges is favorable for further reducing the generation of a heterogeneous phase, improving the crystallinity and refining crystal grains, so that the electrochemical performance of the lithium iron phosphate material prepared subsequently is further improved.
In a preferred embodiment, the sintering temperature in the sintering process is 350-900 ℃, and the heat preservation time is 3-12 h. The temperature and holding time of the sintering process include, but are not limited to, the above ranges, and the limitation of the temperature and holding time within the above ranges is beneficial to further increase the compacted density and thus the electrochemical comprehensive performance. In order to further improve the electrochemical comprehensive performance, more preferably, the temperature rise rate in the sintering process is 2-10 ℃ per minute-1Preferably 5 ℃ min-1(ii) a The cooling rate after sintering is 2-15 ℃ min-1Preferably 10 ℃ min-1。
The iron source compound, phosphorus source compound and lithium source compound used herein may be those commonly used in the art. In a preferred embodiment, the iron source compound includes, but is not limited to, one or more of the group consisting of ferrous chloride, ferrous sulfate, ferrous nitrate, ferric chloride, ferric sulfate, ferric nitrate, ferric phosphate, ferric acetylacetonate, ferric trifluoromethanesulfonate, ferrocene; the phosphorus source compound includes, but is not limited to, one or more of the group consisting of phosphoric acid, ammonium dihydrogen phosphate, lithium dihydrogen phosphate; and lithium source compounds include, but are not limited to, one or more of the group consisting of lithium carbonate, lithium hydroxide, lithium sulfate, lithium acetate, lithium nitrate, lithium trifluoromethanesulfonate, and lithium oxalate.
The second aspect of the application also provides core-shell carbon-coated doped lithium iron phosphate, which is prepared by adopting the preparation method provided by the application. The core-shell carbon-coated doped lithium iron phosphate prepared by the method has the advantages of low cost, good uniformity and compactness of the carbon coating, small grain size and the like. To enter intoThe comprehensive performance is improved, and preferably, the core-shell type carbon-coated doped lithium iron phosphate can adopt LiFe1-xMxPO4@ C denotes where x is 0.001 to 0.02 and M is a transition metal ion having a valence of 4 or more.
Preferably, the first charge gram capacity of the lithium ion battery cathode material is 164 mAh.g at the current density of 0.1C-1And the coulomb efficiency of the first circle can reach 98%. At a current density of 1C, the capacity retention was 97% after 3000 cycles. Has higher electrochemical capacity and excellent cycling stability.
The third aspect provided by the present application further provides a lithium ion battery, which includes a positive electrode material, where the positive electrode material includes the core-shell carbon-coated doped lithium iron phosphate provided by the present application. The core-shell carbon-coated doped lithium iron phosphate prepared by the method has the advantages of low cost, good uniformity and compactness of the carbon coating layer, small grain size and the like, so that the rate capability and the dynamic performance of the prepared anode material as an anode of a lithium ion battery can be greatly improved.
The fourth aspect provided by the present application also provides an electric drive device, which includes the lithium ion battery provided by the present application. The lithium ion battery containing the core-shell carbon-coated doped lithium iron phosphate can be used as an energy module of an electric driving device, and the advantages of the lithium ion battery in the aspects of energy storage, cruising ability and environmental protection can be greatly improved.
The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.
Example 1
The preparation method of the core-shell carbon-coated nano-scale titanium-doped lithium iron phosphate cathode material of the embodiment specifically comprises the following steps:
tannic Acid (TA) was mixed with deionized water to form solution a, wherein the amount of TA in solution a was 2.5 wt.%.
FeCl is added3And TiCl4Adding the mixture into the solution A, performing ultrasonic dispersion for 1h, performing magnetic stirring at room temperature for 2-6 h, and allowing sufficient time for the tanninThe acid is complexed with transition metal iron ions and titanium ions to form a ring-shaped chelate.
Reacting LiOH with NH4H2PO4After mixing with deionized water, solution B was obtained. According to tannic acid, LiOH, FeCl3、TiCl4And NH4H2PO4The molar ratio of the solution A to the solution B is 1.5:1.4:1.0:0.005:1.3, the solution A and the solution B are uniformly stirred and then transferred to a hydrothermal reaction kettle, the pH value of the solution is adjusted to be 6.5-7.5, and the hydrothermal synthesis reaction is carried out at 180 ℃ for 18 hours. And then washing, filtering and drying to obtain the tannin-coated lithium iron phosphate precursor.
Placing the tannic acid coated lithium iron phosphate precursor into a tube furnace, and reacting in N2Or Ar and other protective atmosphere, wherein the sintering temperature is 850 ℃, the sintering time is 10h, and the required LiFe is obtained0.99Ti0.01PO4@ C. The XRD pattern, SEM pattern, and TEM pattern of the core-shell carbon-coated nano-sized titanium-doped lithium iron phosphate cathode material prepared in example 1 are sequentially shown in fig. 1, 2, and 3.
Example 2
The differences from example 1 are: the TA content in solution a was 0.5 wt.%, and the other steps were the same as in example 1.
Example 3
The differences from example 1 are: the TA content in solution a was 1.5 wt.%, and the other steps were the same as in example 1.
Example 4
The differences from example 1 are: the TA content in solution a was 5 wt.%, and the other steps were the same as in example 1.
Example 5
The differences from example 1 are: the temperature of the hydrothermal synthesis reaction was 200 ℃ and the other steps were the same as in example 1.
Example 6
The differences from example 1 are: the temperature of the hydrothermal synthesis reaction was 220 ℃ and the other steps were the same as in example 1.
Example 7
The differences from example 1 are: the hydrothermal synthesis reaction time was 6 hours, and the other steps were the same as in example 1.
Example 8
The differences from example 1 are: the hydrothermal synthesis reaction time was 12 hours, and the other steps were the same as in example 1.
Example 9
The differences from example 1 are: substitution of transition metal compound with equimolar amount of V5+The other steps are the same as in example 1. The core-shell carbon-coated nano vanadium-doped lithium iron phosphate anode material is LiFe0.99V0.01PO4@C。
Example 10
The differences from example 1 are: substitution of transition metal compound with equimolar amount of Nb5+The other steps are the same as in example 1. The core-shell carbon-coated nano-grade niobium-doped lithium iron phosphate anode material is LiFe0.99Nb.01PO4@C。
Example 11
The differences from example 1 are: substitution of transition metal compound with equimolar amount of Ta5+The other steps are the same as in example 1. The core-shell carbon-coated nano-scale tantalum-doped lithium iron phosphate anode material is LiFe0.99Ta0.01PO4@C。
Example 12
The differences from example 1 are: the differences from example 1 are: the temperature of the hydrothermal synthesis reaction was 120 ℃ and the time was 48 hours, and the other steps were the same as in example 1. The core-shell carbon-coated nano-scale titanium-doped lithium iron phosphate anode material is LiFe0.99Ti0.01PO4@C。
Example 13
The differences from example 1 are: the hydrothermal synthesis reaction was carried out at 240 ℃ for 5 hours, and the other steps were the same as in example 1.
Example 14
The differences from example 1 are: the temperature of the hydrothermal synthesis reaction was 140 ℃ and the other steps were the same as in example 1.
Example 15
The differences from example 1 are: the temperature of the hydrothermal synthesis reaction was 160 ℃ and the other steps were the same as in example 1.
Example 16
The differences from example 1 are: the temperature of the hydrothermal synthesis reaction was 100 ℃ and the other steps were the same as in example 1.
Example 17
The differences from example 1 are: LiOH and FeCl3、TiCl4And NH4H2PO4Was 1.4:1.0:0.001:1.3, and the other steps were the same as in example 1. The core-shell carbon-coated nano-scale titanium-doped lithium iron phosphate anode material is LiFe0.999Ti0.001PO4@C。
Example 18
The differences from example 1 are: LiOH and FeCl3、TiCl4And NH4H2PO4Was 1.4:1.0:0.01:1.3, and the other steps were the same as in example 1. The core-shell carbon-coated nano-scale titanium-doped lithium iron phosphate anode material is LiFe0.99Ti0.01PO4@C。
Example 19
The differences from example 1 are: LiOH and FeCl3、TiCl4And NH4H2PO4Was 1.4:1.0:0.015:1.3, and the other steps were the same as in example 1. The core-shell carbon-coated nano-scale titanium-doped lithium iron phosphate anode material is LiFe0.985Ti0.015PO4@C。
Example 20
The differences from example 1 are: LiOH and FeCl3、TiCl4And NH4H2PO4Was 1.4:1.0:0.02:1.3, and the other steps were the same as in example 1. The core-shell carbon-coated nano-scale titanium-doped lithium iron phosphate anode material is LiFe0.98Ti0.02PO4@C。
Example 21
The differences from example 1 are: LiOH and FeCl3、TiCl4And NH4H2PO4Was 1.4:1.0:0.04:1.3, and the other steps were the same as in example 1. Core-shell type carbonThe coating nano-scale titanium-doped lithium iron phosphate anode material is LiFe0.96Ti0.04PO4@C。
Example 22
The differences from example 1 are: in the chelation reaction, the molar ratio of iron ions in tannic acid and the iron source compound to transition metal ions was 0.1:1:0.02, and the other steps were the same as in example 1. The core-shell carbon-coated nano-scale titanium-doped lithium iron phosphate anode material is LiFe0.98Ti0.02PO4@C。
Example 23
The differences from example 1 are: the chelation reaction was carried out in the same manner as in example 1 except that the molar ratio of iron ions in tannic acid and the iron source compound to transition metal ions was 3:1: 0.001. The core-shell carbon-coated nano-scale titanium-doped lithium iron phosphate anode material is LiFe0.999Ti0.001PO4@C。
Example 24
The differences from example 1 are: in the chelation reaction, the molar ratio of iron ions in tannic acid and the iron source compound to transition metal ions was 0.5:1:0.1, and the other steps were the same as in example 1. The core-shell carbon-coated nano-scale titanium-doped lithium iron phosphate anode material is LiFe0.9Ti0.1PO4@C。
Comparative example 1
The comparative example uses a transition metal ion-doped lithium iron phosphate material that has not undergone any coating treatment.
And (3) performance testing:
the materials prepared in examples 1 to 24 and comparative example 1 were tested for electrochemical performance using a CR2032 button cell, wherein one electrode was a mixture of the prepared core-shell carbon-coated nanoscale lithium iron phosphate positive electrode material, acetylene black, and polyvinylidene fluoride (weight ratio 97:1.5:1.5), the other electrode was a metallic lithium sheet, and the electrolyte was 1mol/L LiPF6Dissolved in a solvent of EC/DMC/EMC (volume ratio 1:1: 1). The constant-current charging and discharging voltage range is 2.0-3.7V.
1) Testing the first discharge capacity and the first coulombic efficiency:
after the button cell is assembled, charging: charging to 3.7V at a constant current of 0.1C, and recording the charging specific capacity as Q1; discharging: discharging to 2V at a constant current of 0.1C, and recording the discharge specific capacity as Q2; the first coulombic efficiency is abbreviated ICE, ICE Q2/Q1.
2) And (3) testing the cycle performance:
charging: charging to 3.7V at constant current at 1C, and keeping the interval of 10 min; discharging: constant current at 1C is increased to 2V, and the interval is 10 min; thirdly, repeating the first step and the second step for 3000 circles; the capacity retention rate is abbreviated as CR.
3) And (3) rate performance test:
charging to 3.7V at a constant current of 0.1C, and discharging to 2V at a constant current of 0.1C after 10min intervals; ② repeating 'first' for 10 circles; thirdly, the current density in the 'first, second' is increased to 1C, 3C and 10C, wherein the discharge capacities corresponding to 1C, 3C and 10C are Q3, Q4, Q5 and Q6 respectively. The test results are shown in Table 1. Fig. 4 is a charge-discharge curve of the core-shell carbon-coated nano-sized titanium-doped lithium iron phosphate positive electrode material prepared in example 1 and the positive electrode material in comparative example 1.
TABLE 1
From the data in table 1, when the content of tannic acid is increased properly, the first charge capacity, the cycle performance and the rate of the sample are improved significantly; when the content of the tannic acid is excessively increased, the cycle performance and the rate capability of the tannin are reduced to a certain degree. Because the content of tannic acid in the solution is increased, a carbon coating layer on the surface of the lithium iron phosphate crystal grain is thickened, a thicker carbon layer can obstruct the transmission of lithium ions, and the integral specific capacity of the material can be reduced.
From examples 1, 5, 6, 12 to 16, increasing the hydrothermal temperature leads to a certain reduction in the cycle performance and rate capability of the electrode material, mainly because the increase in the hydrothermal temperature increases the collision probability of the crystal in the crystal nucleation period, and thus the crystal is easily grown into large particles. Too low a hydrothermal temperature may result in the presence of part of the lithium phosphate hetero-phase in the product which may deteriorate the electrochemical performance of the electrode material. In addition, from examples 12 and 13, it is important to select an appropriate hydrothermal reaction temperature, and it is not compensated for by lengthening or shortening the hydrothermal reaction time.
From examples 1, 7 and 8, the electrochemical performance was greatly affected by the shorter hydrothermal time, which can be attributed to incomplete crystal formation due to the excessively short reaction time.
From examples 1, 9, 10 and 11, the electrochemical performance of the lithium iron phosphate electrode material doped with different metal ions with the valence of +5 is obviously inferior to that of Ti+4The electrochemical performance of the ion-doped lithium iron phosphate anode material shows that although the defect of the lithium iron phosphate crystal lattice can be increased by selecting the doping ions with higher valence state or larger ionic radius, and the electrochemical performance of the lithium iron phosphate crystal lattice can be optimized, the doping ions with higher valence state or larger ionic radius can cause the doped ions to be difficult to enter the crystal lattice of the lithium iron phosphate, so that the ion doping effect is not achieved, and therefore, the effect of optimizing the doping ions with higher valence state or larger ionic radius to improve the electrochemical performance of the lithium iron phosphate anode needs to be explored with proper ion doping content.
In examples 1, 17 to 21, Ti4+The choice of the amount of ion doping also has an effect on the electrochemical performance of the product. The titanium ion doping content is too low, but the effect of titanium ion doping cannot be achieved; slightly excessive titanium ion doping amount has no obvious effect on improving electrochemical performance; higher titanium ion doping levels, in turn, result in a small amount of impurity phases in the product.
From examples 1, 22 to 24, it is considered that limiting the molar ratio of iron ions to transition metal ions in tannic acid and the iron source compound in the chelation reaction to the preferable range in the present application is advantageous for improving the electrochemical performance of the core-shell type carbon-coated doped lithium iron phosphate.
It is noted that the terms first, second and the like in the description and in the claims of the present application are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those described or illustrated herein.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A preparation method of core-shell type carbon-coated doped lithium iron phosphate is characterized by comprising the following steps:
in the presence of a first solvent, carrying out a chelation reaction on an iron source compound, a transition metal compound and tannic acid to obtain a product system containing a chelate, wherein the valence state of transition metal ions in the transition metal compound is more than or equal to 4;
carrying out hydrothermal synthesis reaction on a phosphorus source compound, a lithium source compound and the chelate to obtain a tannin-coated transition metal ion-doped lithium iron phosphate precursor;
and sintering the tannin-coated transition metal ion-doped lithium iron phosphate precursor in an inert atmosphere to obtain the core-shell carbon-coated doped lithium iron phosphate.
2. The method of claim 1, wherein the transition metal ion is selected from Ti4+、W6+、Ta5+、Nb5+、Zr4+、Mo6+And V5+One or more of the group, preferably Ti4+(ii) a The transition metal compound is one or more of the group consisting of chloride, sulfate, nitrate, acetate and organic salt of the transition metal ion.
3. The method for preparing the core-shell carbon-coated doped lithium iron phosphate according to claim 1, wherein in the chelation reaction, the molar ratio of the tannic acid, the iron ions in the iron source compound and the transition metal ions is (0.1-3): 1: (0.001-0.02).
4. The method for preparing the core-shell carbon-coated doped lithium iron phosphate according to claim 1 or 2, wherein the molar ratio of the transition metal ions in the lithium source compound, the iron source compound and the transition metal compound to the phosphorus source compound is (1-4): (0.9-1.5): (0.001-0.02): (0.6-1.5).
5. The method for preparing the core-shell carbon-coated doped lithium iron phosphate according to any one of claims 1 to 4, wherein the hydrothermal synthesis reaction is performed at a temperature of 120-240 ℃, for a reaction time of 5-48 h, and at a pH of 5-8.
6. The preparation method of the core-shell carbon-coated doped lithium iron phosphate according to claim 1 or 5, wherein the sintering temperature in the sintering process is 350-900 ℃, and the heat preservation time is 3-12 h;
the heating rate in the sintering process is 2-10 ℃ min-1Preferably 5 ℃ min-1And the cooling rate after sintering is 2-15 ℃ min-1Preferably 10 ℃ min-1。
7. The method for preparing the core-shell carbon-coated doped lithium iron phosphate according to claim 6, wherein the iron source compound is selected from one or more of the group consisting of ferrous chloride, ferrous sulfate, ferrous nitrate, ferric chloride, ferric sulfate, ferric nitrate, ferric phosphate, ferric acetylacetonate, ferric trifluoromethanesulfonate and ferrocene;
the phosphorus source compound is selected from one or more of phosphoric acid, ammonium dihydrogen phosphate and lithium dihydrogen phosphate; and
the lithium source compound is selected from one or more of the group consisting of lithium carbonate, lithium hydroxide, lithium sulfate, lithium acetate, lithium nitrate, lithium trifluoromethanesulfonate, and lithium oxalate.
8. A core-shell carbon-coated doped lithium iron phosphate, characterized in that the core-shell carbon-coated doped lithium iron phosphate is prepared by the preparation method of any one of claims 1 to 7, preferably, the core-shell carbon-coated doped lithium iron phosphate can be LiFe1-xMxPO4@ C denotes where x is 0.001 to 0.02 and M is a transition metal ion having a valence of 4 or more.
9. A lithium ion battery comprising a positive electrode material, wherein the positive electrode material comprises the core-shell carbon-coated doped lithium iron phosphate-like material of claim 8.
10. An electric drive device characterized in that it comprises the lithium ion battery of claim 9.
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