CN116856058A - Single crystal lithium-rich material, preparation method thereof and energy storage device - Google Patents
Single crystal lithium-rich material, preparation method thereof and energy storage device Download PDFInfo
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- CN116856058A CN116856058A CN202310815969.3A CN202310815969A CN116856058A CN 116856058 A CN116856058 A CN 116856058A CN 202310815969 A CN202310815969 A CN 202310815969A CN 116856058 A CN116856058 A CN 116856058A
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- lithium
- single crystal
- rich
- rich material
- temperature
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 384
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 377
- 239000000463 material Substances 0.000 title claims abstract description 318
- 239000013078 crystal Substances 0.000 title claims abstract description 240
- 238000002360 preparation method Methods 0.000 title claims abstract description 83
- 238000004146 energy storage Methods 0.000 title claims abstract description 17
- 229910052596 spinel Inorganic materials 0.000 claims abstract description 117
- 239000011029 spinel Substances 0.000 claims abstract description 117
- 239000002245 particle Substances 0.000 claims abstract description 100
- 150000001875 compounds Chemical class 0.000 claims abstract description 87
- 239000000126 substance Substances 0.000 claims abstract description 37
- 239000012298 atmosphere Substances 0.000 claims abstract description 36
- 238000002156 mixing Methods 0.000 claims abstract description 31
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 26
- 239000000203 mixture Substances 0.000 claims abstract description 24
- 238000001354 calcination Methods 0.000 claims abstract description 17
- 229910052727 yttrium Inorganic materials 0.000 claims abstract description 16
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 13
- 238000003837 high-temperature calcination Methods 0.000 claims abstract description 12
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 12
- 238000004321 preservation Methods 0.000 claims abstract description 12
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 12
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 11
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 11
- 230000001590 oxidative effect Effects 0.000 claims abstract description 10
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 9
- 238000000034 method Methods 0.000 claims description 104
- 238000010438 heat treatment Methods 0.000 claims description 91
- 239000012071 phase Substances 0.000 claims description 91
- 239000002243 precursor Substances 0.000 claims description 88
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 75
- 239000000243 solution Substances 0.000 claims description 50
- 238000006243 chemical reaction Methods 0.000 claims description 49
- 239000007774 positive electrode material Substances 0.000 claims description 49
- 229910052751 metal Inorganic materials 0.000 claims description 43
- 230000008569 process Effects 0.000 claims description 41
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 36
- 239000002184 metal Substances 0.000 claims description 36
- 238000005245 sintering Methods 0.000 claims description 32
- 229910015645 LiMn Inorganic materials 0.000 claims description 30
- 239000011247 coating layer Substances 0.000 claims description 29
- 238000000975 co-precipitation Methods 0.000 claims description 24
- -1 ammonia compound Chemical class 0.000 claims description 23
- 238000000576 coating method Methods 0.000 claims description 21
- 235000002639 sodium chloride Nutrition 0.000 claims description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 20
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 18
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 18
- 239000012266 salt solution Substances 0.000 claims description 18
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 16
- 239000010406 cathode material Substances 0.000 claims description 16
- 239000008367 deionised water Substances 0.000 claims description 16
- 229910021641 deionized water Inorganic materials 0.000 claims description 16
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 14
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 14
- 238000000498 ball milling Methods 0.000 claims description 13
- 239000002738 chelating agent Substances 0.000 claims description 13
- 239000008139 complexing agent Substances 0.000 claims description 13
- 238000011065 in-situ storage Methods 0.000 claims description 13
- 238000003756 stirring Methods 0.000 claims description 13
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 12
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 claims description 12
- 150000002736 metal compounds Chemical class 0.000 claims description 12
- 150000003839 salts Chemical class 0.000 claims description 12
- 238000010306 acid treatment Methods 0.000 claims description 11
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 10
- 239000011248 coating agent Substances 0.000 claims description 10
- 238000003980 solgel method Methods 0.000 claims description 10
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 9
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 9
- 229940039748 oxalate Drugs 0.000 claims description 9
- 239000007790 solid phase Substances 0.000 claims description 9
- 238000005979 thermal decomposition reaction Methods 0.000 claims description 9
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 8
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 8
- 239000012445 acidic reagent Substances 0.000 claims description 8
- 239000003795 chemical substances by application Substances 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 8
- 239000010410 layer Substances 0.000 claims description 8
- 239000011780 sodium chloride Substances 0.000 claims description 8
- 239000007787 solid Substances 0.000 claims description 8
- 230000032683 aging Effects 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 7
- 150000002642 lithium compounds Chemical class 0.000 claims description 7
- 230000001502 supplementing effect Effects 0.000 claims description 7
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 6
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 6
- MZRVEZGGRBJDDB-UHFFFAOYSA-N N-Butyllithium Chemical compound [Li]CCCC MZRVEZGGRBJDDB-UHFFFAOYSA-N 0.000 claims description 6
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 6
- 239000002253 acid Substances 0.000 claims description 6
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 6
- 150000001768 cations Chemical class 0.000 claims description 6
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 claims description 6
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 6
- ZCSHNCUQKCANBX-UHFFFAOYSA-N lithium diisopropylamide Chemical compound [Li+].CC(C)[N-]C(C)C ZCSHNCUQKCANBX-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
- 239000012716 precipitator Substances 0.000 claims description 6
- YGSDEFSMJLZEOE-UHFFFAOYSA-N salicylic acid Chemical compound OC(=O)C1=CC=CC=C1O YGSDEFSMJLZEOE-UHFFFAOYSA-N 0.000 claims description 6
- 238000005406 washing Methods 0.000 claims description 6
- 229910002651 NO3 Inorganic materials 0.000 claims description 5
- 239000007864 aqueous solution Substances 0.000 claims description 5
- 238000000227 grinding Methods 0.000 claims description 5
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 5
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 5
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 5
- 235000017550 sodium carbonate Nutrition 0.000 claims description 5
- 238000005507 spraying Methods 0.000 claims description 5
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 claims description 4
- FEWJPZIEWOKRBE-JCYAYHJZSA-N Dextrotartaric acid Chemical compound OC(=O)[C@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-JCYAYHJZSA-N 0.000 claims description 4
- DHMQDGOQFOQNFH-UHFFFAOYSA-N Glycine Chemical compound NCC(O)=O DHMQDGOQFOQNFH-UHFFFAOYSA-N 0.000 claims description 4
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 4
- 229910052782 aluminium Inorganic materials 0.000 claims description 4
- 239000001099 ammonium carbonate Substances 0.000 claims description 4
- WXHLLJAMBQLULT-UHFFFAOYSA-N 2-[[6-[4-(2-hydroxyethyl)piperazin-1-yl]-2-methylpyrimidin-4-yl]amino]-n-(2-methyl-6-sulfanylphenyl)-1,3-thiazole-5-carboxamide;hydrate Chemical compound O.C=1C(N2CCN(CCO)CC2)=NC(C)=NC=1NC(S1)=NC=C1C(=O)NC1=C(C)C=CC=C1S WXHLLJAMBQLULT-UHFFFAOYSA-N 0.000 claims description 3
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 claims description 3
- KXDHJXZQYSOELW-UHFFFAOYSA-N Carbamic acid Chemical compound NC(O)=O KXDHJXZQYSOELW-UHFFFAOYSA-N 0.000 claims description 3
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 claims description 3
- 229910015118 LiMO Inorganic materials 0.000 claims description 3
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 3
- 229910019142 PO4 Inorganic materials 0.000 claims description 3
- UIIMBOGNXHQVGW-DEQYMQKBSA-M Sodium bicarbonate-14C Chemical compound [Na+].O[14C]([O-])=O UIIMBOGNXHQVGW-DEQYMQKBSA-M 0.000 claims description 3
- KDYFGRWQOYBRFD-UHFFFAOYSA-N Succinic acid Natural products OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 claims description 3
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 claims description 3
- ZMZDMBWJUHKJPS-UHFFFAOYSA-M Thiocyanate anion Chemical compound [S-]C#N ZMZDMBWJUHKJPS-UHFFFAOYSA-M 0.000 claims description 3
- 235000011054 acetic acid Nutrition 0.000 claims description 3
- 150000008043 acidic salts Chemical class 0.000 claims description 3
- 125000000217 alkyl group Chemical group 0.000 claims description 3
- 229910021529 ammonia Inorganic materials 0.000 claims description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 3
- 235000012501 ammonium carbonate Nutrition 0.000 claims description 3
- 150000003863 ammonium salts Chemical class 0.000 claims description 3
- KDYFGRWQOYBRFD-NUQCWPJISA-N butanedioic acid Chemical compound O[14C](=O)CC[14C](O)=O KDYFGRWQOYBRFD-NUQCWPJISA-N 0.000 claims description 3
- 235000014113 dietary fatty acids Nutrition 0.000 claims description 3
- 238000007598 dipping method Methods 0.000 claims description 3
- 239000002270 dispersing agent Substances 0.000 claims description 3
- 239000000194 fatty acid Substances 0.000 claims description 3
- 229930195729 fatty acid Natural products 0.000 claims description 3
- 150000004665 fatty acids Chemical class 0.000 claims description 3
- ZMZDMBWJUHKJPS-UHFFFAOYSA-N hydrogen thiocyanate Natural products SC#N ZMZDMBWJUHKJPS-UHFFFAOYSA-N 0.000 claims description 3
- 239000004310 lactic acid Substances 0.000 claims description 3
- 235000014655 lactic acid Nutrition 0.000 claims description 3
- YNESATAKKCNGOF-UHFFFAOYSA-N lithium bis(trimethylsilyl)amide Chemical compound [Li+].C[Si](C)(C)[N-][Si](C)(C)C YNESATAKKCNGOF-UHFFFAOYSA-N 0.000 claims description 3
- FUJCRWPEOMXPAD-UHFFFAOYSA-N lithium oxide Chemical compound [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 claims description 3
- 229910001947 lithium oxide Inorganic materials 0.000 claims description 3
- 229910001386 lithium phosphate Inorganic materials 0.000 claims description 3
- LZWQNOHZMQIFBX-UHFFFAOYSA-N lithium;2-methylpropan-2-olate Chemical compound [Li+].CC(C)(C)[O-] LZWQNOHZMQIFBX-UHFFFAOYSA-N 0.000 claims description 3
- 229910017604 nitric acid Inorganic materials 0.000 claims description 3
- 235000006408 oxalic acid Nutrition 0.000 claims description 3
- FJKROLUGYXJWQN-UHFFFAOYSA-N papa-hydroxy-benzoic acid Natural products OC(=O)C1=CC=C(O)C=C1 FJKROLUGYXJWQN-UHFFFAOYSA-N 0.000 claims description 3
- NHKJPPKXDNZFBJ-UHFFFAOYSA-N phenyllithium Chemical compound [Li]C1=CC=CC=C1 NHKJPPKXDNZFBJ-UHFFFAOYSA-N 0.000 claims description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 3
- 239000010452 phosphate Substances 0.000 claims description 3
- ZNNZYHKDIALBAK-UHFFFAOYSA-M potassium thiocyanate Chemical compound [K+].[S-]C#N ZNNZYHKDIALBAK-UHFFFAOYSA-M 0.000 claims description 3
- 229940116357 potassium thiocyanate Drugs 0.000 claims description 3
- 238000005086 pumping Methods 0.000 claims description 3
- 150000005837 radical ions Chemical class 0.000 claims description 3
- 229960004889 salicylic acid Drugs 0.000 claims description 3
- ZNCPFRVNHGOPAG-UHFFFAOYSA-L sodium oxalate Chemical compound [Na+].[Na+].[O-]C(=O)C([O-])=O ZNCPFRVNHGOPAG-UHFFFAOYSA-L 0.000 claims description 3
- 229940039790 sodium oxalate Drugs 0.000 claims description 3
- 239000011975 tartaric acid Substances 0.000 claims description 3
- 235000002906 tartaric acid Nutrition 0.000 claims description 3
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 claims description 3
- 239000011572 manganese Substances 0.000 description 67
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 40
- 239000001301 oxygen Substances 0.000 description 39
- 229910052760 oxygen Inorganic materials 0.000 description 39
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 36
- 230000014759 maintenance of location Effects 0.000 description 29
- 238000001816 cooling Methods 0.000 description 21
- 229910017052 cobalt Inorganic materials 0.000 description 19
- 239000010941 cobalt Substances 0.000 description 19
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 19
- 238000012360 testing method Methods 0.000 description 19
- 239000007789 gas Substances 0.000 description 17
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 16
- 239000010405 anode material Substances 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 16
- 229910001416 lithium ion Inorganic materials 0.000 description 14
- 239000003792 electrolyte Substances 0.000 description 13
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- 238000007086 side reaction Methods 0.000 description 13
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- 230000006872 improvement Effects 0.000 description 10
- 230000002829 reductive effect Effects 0.000 description 10
- 239000000047 product Substances 0.000 description 8
- 229910008555 Li1.2Mn0.6Ni0.2O2 Inorganic materials 0.000 description 7
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- 230000002427 irreversible effect Effects 0.000 description 7
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- 229910052723 transition metal Inorganic materials 0.000 description 6
- 150000003624 transition metals Chemical class 0.000 description 6
- 238000001994 activation Methods 0.000 description 5
- 229910052786 argon Inorganic materials 0.000 description 5
- 230000001276 controlling effect Effects 0.000 description 5
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
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- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- 229910008514 Li1.2Mn0.54Ni0.13Co0.13O2 Inorganic materials 0.000 description 2
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- 229910016396 Mn0.75Ni0.25(OH)2 Inorganic materials 0.000 description 2
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- OMOVVBIIQSXZSZ-UHFFFAOYSA-N [6-(4-acetyloxy-5,9a-dimethyl-2,7-dioxo-4,5a,6,9-tetrahydro-3h-pyrano[3,4-b]oxepin-5-yl)-5-formyloxy-3-(furan-3-yl)-3a-methyl-7-methylidene-1a,2,3,4,5,6-hexahydroindeno[1,7a-b]oxiren-4-yl] 2-hydroxy-3-methylpentanoate Chemical compound CC12C(OC(=O)C(O)C(C)CC)C(OC=O)C(C3(C)C(CC(=O)OC4(C)COC(=O)CC43)OC(C)=O)C(=C)C32OC3CC1C=1C=COC=1 OMOVVBIIQSXZSZ-UHFFFAOYSA-N 0.000 description 2
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- MEYVLGVRTYSQHI-UHFFFAOYSA-L cobalt(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Co+2].[O-]S([O-])(=O)=O MEYVLGVRTYSQHI-UHFFFAOYSA-L 0.000 description 2
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- IKDUDTNKRLTJSI-UHFFFAOYSA-N hydrazine monohydrate Substances O.NN IKDUDTNKRLTJSI-UHFFFAOYSA-N 0.000 description 2
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- ISPYRSDWRDQNSW-UHFFFAOYSA-L manganese(II) sulfate monohydrate Chemical compound O.[Mn+2].[O-]S([O-])(=O)=O ISPYRSDWRDQNSW-UHFFFAOYSA-L 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- RRIWRJBSCGCBID-UHFFFAOYSA-L nickel sulfate hexahydrate Chemical compound O.O.O.O.O.O.[Ni+2].[O-]S([O-])(=O)=O RRIWRJBSCGCBID-UHFFFAOYSA-L 0.000 description 2
- 229940116202 nickel sulfate hexahydrate Drugs 0.000 description 2
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- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/16—Oxides
- C30B29/22—Complex oxides
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B35/00—Apparatus not otherwise provided for, specially adapted for the growth, production or after-treatment of single crystals or of a homogeneous polycrystalline material with defined structure
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- 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
Abstract
The embodiment of the invention relates to a preparation method of a monocrystal lithium-rich material and an energy storage device, wherein the chemical general formula of the monocrystal lithium-rich material is Li 1+x Mn y M 1‑x‑y O 2‑f T f X is more than 0 and less than or equal to 0.5, y is more than 0 and less than or equal to 1-x, and f is more than 0 and less than 2; m includes one or more of Mn, ni, co, al, fe, ru, nb, cr, ti, ir, V, ca, sc, cu, zn, sr, Y, zr, ta, la, ce, pr, nd, W, mo; t includes one or more of F, S, P, N; the preparation method comprises the following steps: preparing a spinel phase compound; mixing spinel phase compound with lithium-containing compound to obtainA mixture; then placing the mixture in an oxidizing atmosphere for high-temperature calcination to obtain single crystal lithium-rich material particles with {111} or {111} and {001} crystal faces exposed; wherein the molar ratio of lithium in the lithium-containing compound to the spinel phase compound is 0.2:1-3:1, the high-temperature calcination temperature range is 300-1000 ℃, and the calcination heat preservation time is 6-24h.
Description
Technical Field
The invention relates to the technical field of new energy, in particular to a monocrystal lithium-rich material, a preparation method thereof and an energy storage device.
Background
The lithium ion battery has the advantages of high energy density, power density, long cycle life, no memory effect and the like, and is widely applied to the fields of consumer electronics, electric automobiles, large-scale energy storage and the like. Compared with other energy storage sources, the lithium ion battery has obvious advantages in small and medium energy storage systems, and is expected to have better application prospects in large-scale energy storage systems in the future.
With the rapid development of various industries and the dependence on energy sources, lithium ion batteries with high energy density have become urgent demands. Currently, the improvement of the energy density of lithium ion batteries is largely limited by the performance of the cathode material. Compared with the traditional positive electrode materials such as layered lithium cobaltate, layered ternary materials, olivine-type lithium iron phosphate and spinel-type lithium manganate, the lithium-rich manganese-based positive electrode material is considered to be the positive electrode material most expected to realize a high-energy-density battery by virtue of high capacity (more than 250 mAh/g), high voltage (4.8V), low cost and the like.
However, since the lithium-rich material is represented on the nano-scale as two layered structures or solid solution forms, wherein Li 2 MnO 3 When the charging voltage reaches above 4.5V, oxidation-reduction reaction of oxygen can occur, oxygen activation can cause oxygen frame change and cation migration in a crystal structure, and meanwhile, oxygen release induces irreversible transition of a surface structure, so that the lithium-rich manganese-based positive electrode material has the problems of low initial cycle coulomb efficiency, low rate performance, obvious capacity and voltage attenuation and the like. This severely restricts the commercialization process of lithium-rich manganese-based cathode materials. At present, the surface coating, bulk doping, particle nanocrystallization and other technologies are widely applied to the performance improvement of lithium-rich manganese-based materials, the modification technologies can improve the stability or the multiplying power performance to a certain extent, but the improvement degree is limited, and in addition, the content of inactive substances in the positive electrode structure is inevitably increased Or reduced compacted density, which also results in a decrease in mass and volumetric energy density of the material when applied to a lithium battery cell.
Research shows that the positive electrode material with the single crystal structure can intrinsically improve the cycle stability, the mechanical strength and the compaction density of the positive electrode material, so that the excellent cycle stability and the high energy density can be combined. In the prior art, as disclosed in CN109778301A and CN113497227A, a monocrystal-like lithium-rich layered oxide positive electrode material and a preparation method are disclosed, wherein conventional metal solutions containing manganese salt, nickel salt and cobalt salt are respectively adopted as precursor materials, then a lithium-rich layered oxide precursor is obtained through a coprecipitation method, and a monocrystal-like lithium-rich layered oxide positive electrode material is further obtained through a molten salt sintering method. The monocrystal structure of the lithium-rich layered oxide obtained in the above patent does not show a specific crystal structure and has irregular morphology, so that the monocrystal particles can be contacted with electrolyte in the electrochemical reaction process to cause more interface side reactions, thereby leading to lower first week coulomb efficiency of the material, and the two preparation processes need post-treatment, and a large amount of industrial wastewater can be generated. CN114875471a discloses a preparation method of monocrystal lithium-rich manganese anode material, which adopts a solution spray granulation method to prepare the particle size D 50 The single crystal lithium-rich material with the particle size of 3.5 μm has poor dispersibility and irregular morphology, and has a first charge-discharge coulombic efficiency of 91.2% in a voltage range of 3-4.45V and a first discharge capacity of 158.2mAh/g at a 0.1C rate. The material has higher initial cycle coulomb efficiency, because the upper limit of the charging voltage is lower than 4.5V, thereby avoiding side reactions when the charging voltage is higher than 4.5V. However, the discharge capacity is low due to the reduction of the upper limit of the charge voltage, so that the energy density is low, and the use requirement is difficult to meet. Currently, lithium-rich materials generally have lower coulombic efficiencies when the upper limit of the charging voltage is raised above 4.5V, which is caused by irreversible loss of oxygen and side reactions between the positive electrode and the electrolyte that occur above 4.5V.
CN109537054A discloses a preparation method of a lithium-rich manganese-based positive electrode material single crystal, which comprises dissolving a manganese solution, an M solution, a precipitant solution and a complexing agentAdding the solution into a reaction kettle, adding an auxiliary agent A (for example, a hydrazine hydrate solution) to regulate the potential value of the reaction solution to-1V to-0.001V, stirring and reacting for a certain time under the conditions of nitrogen atmosphere, 20-100 ℃ and pH value of 7.0-14.0 to obtain a manganese-based coprecipitate, adding a certain amount of auxiliary agent B (for example, bromine water) into the coprecipitate, thereby obtaining a manganese-based composite metal precursor, and calcining the precursor to obtain the micro nano monocrystal lithium-rich manganese-based anode material. As shown in a test 1, the lithium-rich manganese-based positive electrode material monocrystal obtained by the method is composed of 0.1um-10um polyhedral monocrystal, and the positive electrode material has a general formula: 0.5Li 2 MnO 3 ·0.5LiMn 0.4 Co 0.2 Ni 0.4 O 2 The lithium-rich manganese-based positive electrode material monocrystal obtained by the method has the initial charge-discharge coulomb efficiency of more than 88 percent at the temperature of 25 ℃ and the cut-off voltage of 2.5-4.6V, the initial discharge capacity of more than 270mAh/g at the rate of 0.1C (1.0C=250 mA/g), and the discharge capacity of still 180mAh/g at the rate of 5.0C; the capacity retention rate of the positive electrode material after 200 weeks of circulation under the multiplying power of 1.0C reaches more than 90 percent. However, the synthesis method has complicated process steps, needs to strictly control the conditions of potential, temperature, pH value and the like of the reaction, needs to introduce a large amount of auxiliary agents in the preparation process, and is difficult to apply on a large scale. As can be seen from fig. 1 of the patent, the monocrystalline particles synthesized by the method comprise hexahedron, tetrahedron, octahedron and other polyhedrons, the crystal forms are mixed together, no specific monocrystalline morphology feature is formed, namely, the monocrystalline particles of the material are not mainly provided with a certain polyhedron structure, and although a small amount of crystal faces are exposed, the monocrystalline particles of the material do not show specific rules and do not form specific crystal face exposure. In addition, the single crystal particles have serious agglomeration phenomenon, poor dispersivity and charging cut-off voltage of only 4.6V, and the charging voltage can avoid excessive side reactions, such as irreversible oxidation-reduction reaction for reducing oxygen and interfacial side reaction between an electrode and electrolyte, improve the first coulomb efficiency, and further relieve irreversible phase change in long cycle, but the oxidation-reduction activity of oxygen cannot be completely activated in the first few weeks of electrochemical cycle due to the fact that the charging cut-off voltage is lower than the upper limit working voltage of 4.8V of lithium, so that the first week is poor Specific discharge capacity. It is therefore desirable to widen the upper limit of lithium-rich operating voltage to 4.8V while maintaining good cycle performance. And when the lithium-rich material is charged to 4.8V, excessive lithium removal is caused, so that the structure of the material is unstable, and therefore, the lithium-rich material has higher specific charge capacity although having more lithium removal amount in 2-4.8V charge and discharge, but the initial coulomb efficiency is lower, and meanwhile, more lithium removal occurs in the cycle process, so that the structure of the material is subjected to severe phase change, and the electrochemical performance is rapidly attenuated. In addition, the lithium-rich material contains cobalt element, and the introduction of cobalt element can improve the rate capability of the material in terms of electrochemical performance, but also can reduce the cycle performance. More importantly, from the commercialization perspective, cobalt is expensive and has high cost, and is difficult to realize in large scale in the fields of electric automobiles, energy storage systems and the like. Therefore, the reduction of the cobalt element content and even no cobalt conversion are extremely high in practical value.
Therefore, for the single crystal lithium-rich layered material prepared by the prior art, the problems of low initial coulomb efficiency, poor multiplying power performance, poor cycle performance and the like at high charging voltage still exist, and the single crystal lithium-rich positive electrode with high phase purity, good electrochemical performance and expandability is difficult to produce due to the limitation of factors such as lithium salt evaporation, lattice defects, particle agglomeration and the like, particles of the synthesized single crystal lithium-rich layered material have no specific morphology, irregular single crystal morphology, and the serious problems of poor single crystal particle dispersibility and the like exist. This causes problems of low initial coulombic efficiency, poor rate capability, poor cycle performance, rapid capacity and voltage decay, etc. of the lithium-rich cathode material under high voltage, and thus it is difficult to realize large-scale commercialization.
In summary, the single crystal lithium-rich cathode material in the prior art has the characteristics of high first coulombic efficiency, excellent multiplying power performance, cycle performance, stable structure and the like on the basis of high energy density, and the existing preparation method has complex process and is difficult to realize large-scale production. Further considering the high cost of cobalt element, the development of cobalt-free lithium-rich single crystal positive electrode materials has important commercialization prospect.
Disclosure of Invention
The invention aims to provide a monocrystal lithium-rich material, a preparation method thereof and an energy storage device, and solves the problems of poor dispersibility, irregular morphology, defects in a preparation process, poor electrochemical performance and the like of a monocrystal lithium-rich positive electrode material in the prior art. According to the preparation method, monocrystal particles with regular morphology and good dispersibility can be obtained through improvement of the preparation process, so that the effects of high first coulomb efficiency, poor excellent rate performance, good cycle performance, low capacity, voltage attenuation and the like of the monocrystal lithium-rich material under high voltage can be achieved, namely, the first coulomb efficiency is improved, and the rate performance, the cycle performance and the like are improved on the basis of the high-energy-density lithium-rich positive electrode material.
To this end, in a first aspect, an embodiment of the present invention provides a method for preparing a single crystal lithium-rich material, where the single crystal lithium-rich material has a chemical formula of Li 1+x Mn y M 1-x-y O 2-f T f Wherein x is more than 0 and less than or equal to 0.5, y is more than 0 and less than or equal to 1-x, and f is more than 0 and less than or equal to 2; m includes one or more of Mn, ni, co, al, fe, ru, nb, cr, ti, ir, V, ca, sc, cu, zn, sr, Y, zr, ta, la, ce, pr, nd, W, mo; t includes one or more of F, S, P, N; the crystallographic morphology of the single crystal lithium-rich material comprises one or more of octahedra and tetratetrahedra; the preparation method of the monocrystal lithium-rich material comprises the following steps:
preparing a spinel phase compound; the chemical general formula of the spinel phase compound is LiMn 2-a M a O 4-b T b ，0≤a＜2，0≤b＜4；
Mixing the spinel phase compound with a lithium-containing compound to obtain a mixture, and then placing the mixture in an oxidizing atmosphere for high-temperature calcination to obtain single crystal lithium-rich material particles with {111} or {111} and {001} crystal faces exposed; wherein the molar ratio of lithium in the lithium-containing compound to the spinel phase compound is 0.2:1-3:1, the high-temperature calcination temperature range is 300-1000 ℃, and the calcination heat preservation time is 6-24h.
Preferably, the monocrystalline lithium-rich material has a monocrystalline particle size of 0.3-5 μm; optionally, the crystallographic morphology of the single-crystal lithium-rich material further comprises one or more of tetrahedra and hexahedron.
Preferably, the method further comprises: the monocrystalline particles of the monocrystalline lithium-rich material are surface-modified to produce spinel and/or disordered rock salt coatings, preferably by gas-solid treatment or acid treatment to produce spinel coatings on the surfaces of the monocrystalline particles. Preferably, the generating the spinel coating layer on the surface of the single crystal particle by a gas-solid treatment method comprises: placing a single crystal lithium-rich material and a first substance which generates reducing gas through thermal decomposition in a closed container, heating to a temperature higher than the thermal decomposition temperature of the first substance under inert atmosphere to obtain the single crystal lithium-rich material with a spinel coating layer constructed on the surface of the material in situ, wherein the first substance preferably comprises one or more compounds of an ammonia compound, an oxalate compound and a carbonic acid compound;
the generation of the spinel coating layer on the surface of the single crystal particle by adopting an acid treatment method comprises the following steps: treating the monocrystal lithium-rich material by using an acidic reagent to obtain the monocrystal lithium-rich material with the spinel coating constructed on the surface of the material in situ; preferably, the acidic reagent comprises one or more of sulfuric acid, hydrochloric acid, hydrofluoric acid, nitric acid, phosphoric acid, fatty acid and acidic salt solution, and the specific method of the acid treatment process comprises one or more of a dipping process, a spraying process and a coating process; particularly preferred, the method further comprises: and calcining the monocrystalline lithium-rich material with the spinel coating layer constructed on the surface of the obtained material for 3-10h at 300-600 ℃.
Preferably, the preparing spinel phase compound specifically includes:
preparing a precursor material, wherein the precursor material comprises a lithium source and a metal source, and the molar ratio of lithium element in the lithium source to metal element in the metal source is (0-1): 1, preferably (0.3-0.6): 1, a step of; the metal source comprises a Mn source or comprises a Mn source and an M source;
sintering the precursor material in an oxidizing atmosphere to obtain the spinel phase compound; wherein the sintering temperature is 300-1000 ℃ and the heat preservation time is 3-48h; preferably, the sintering is specifically: raising the temperature from room temperature to 300-600 ℃ at a heating rate of 3-10 ℃/min, keeping the temperature for 3-10 hours, raising the temperature to 700-1000 ℃ at a heating rate of 3-10 ℃/min, and keeping the temperature for 10-38 hours;
preferably, the precursor material is prepared by a coprecipitation method, a solid phase ball milling method or a sol-gel method;
the coprecipitation method specifically comprises the following steps: according to the chemical formula Mn 1-c M c Preparing a metal mixed salt solution of Mn and M with the stoichiometric ratio of Q of 0.1-4mol/L, and simultaneously preparing a precipitator solution and a complexing agent solution with the stoichiometric ratio of Q of 0.2-6mol/L respectively; the Mn of 1- c M c In Q, c is more than or equal to 0 and less than 1, and Q is one or more of acid radical ions or hydroxyl radicals; pumping the metal mixed salt solution into a reaction container, and simultaneously adding the precipitant solution and the complexing agent solution to obtain mixed particles; aging, washing and drying the obtained mixed particles to obtain a coprecipitated compound, and then mixing a lithium-containing compound with the coprecipitated compound according to a molar ratio of lithium to metal elements of (0-1): 1, preferably (0.3-0.6): 1, uniformly mixing to obtain a precursor material; preferably, the precipitants in the precipitant solution include one or more of carbonate, bicarbonate, hydroxide, thiocyanide, ammonium salt, oxalate; more preferably, one or more of sodium carbonate, sodium bicarbonate, ammonium carbonate, lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium oxalate, potassium thiocyanate; preferably, the complexing agent in the complexing agent solution comprises one or more of ammonia water, acetic acid, oxalic acid, succinic acid, ethylenediamine tetraacetic acid, lactic acid, citric acid, salicylic acid, sulfosalicylic acid, tartaric acid and glycine; preferably, the particle size of the mixed particles is controlled by the reaction temperature, the feeding speed, the pH value in the reaction vessel and the rotating speed; preferably, the feeding speed is 30-150ml/h, the reaction temperature is 40-60 ℃, the pH is 7-12, the rotating speed is 300-600r/min, and the aging time is 12-24h. Preferably, the particle size of the particles is 0.3-15 μm; particularly preferably, the particle size of the particles is from 0.3 to 5. Mu.m;
the solid-phase ball milling method specifically comprises the following steps: according to the general chemical formula LiMn d-e M e O 4-b T b The stoichiometric ratio of Li, mn and M metal compounds are uniformly mixed by a high-energy ball mill to obtain a precursor material, the LiMn d-e M e O 4-b T b Wherein e is more than or equal to 0 and less than d, b is more than or equal to 0 and less than 4, and 0 is more than or equal to 1/d is less than 1;
the sol-gel method specifically comprises the following steps: according to the general chemical formula LiMn d-e M e O 4-b T b Dissolving metal salts containing Li, mn and M in deionized water, then dropwise adding a mixed aqueous solution containing a chelating agent and a dispersing agent, continuously stirring, then dropwise adding a pH regulator to adjust the pH to be 6-8, keeping the constant temperature of 80-120 ℃ after the pH is stable, continuously stirring until transparent gel is generated, and drying and grinding to obtain a precursor material; the LiMn d-e M e O 4-b T b Wherein e is more than or equal to 0 and less than d, b is more than or equal to 0 and less than 4, and 0 is more than or equal to 1/d is less than 1; the chelating agent comprises one or more of inorganic chelating agent and organic chelating agent, preferably comprises one or more of phosphate, aminocarboxylic acid, organic phosphoric acid type, carboxyl carboxylic acid and amine compound;
the lithium source comprises one or more of an inorganic lithium compound and an organic lithium compound, preferably comprises one or more of lithium oxide, lithium chloride, lithium fluoride, lithium carbonate, lithium hydroxide, lithium nitrate, lithium phosphate, lithium supplementing agent, butyl lithium, phenyl lithium, lithium tert-butoxide, lithium diisopropylamide, and lithium hexamethyldisilazide;
The metal source comprises one or more of an inorganic metal compound and an organic metal compound, preferably comprises one or more of an oxide, a carbonate, a nitrate, an oxalate, a sulfate, an alkyl-based organic metal compound.
Preferably, the molar ratio of lithium in the lithium-containing compound to spinel phase compound is (1.5-2.8): 1;
the high-temperature calcination is stepwise calcination, and specifically comprises the following steps: raising the temperature from room temperature to 300-600 ℃ at a heating rate of 3-10 ℃/min, keeping the temperature for 3-10 hours, raising the temperature to 700-1000 ℃ at a heating rate of 3-10 ℃/min, and keeping the temperature for 10-20 hours.
In a second aspect, an embodiment of the present invention provides a single crystal lithium-rich material obtained by the preparation method described in the first aspect, where the single crystal lithium-rich material has a chemical formula of Li 1+x Mn y M 1-x-y O 2-f T f Wherein x is more than 0 and less than or equal to 0.5, y is more than 0 and less than or equal to 1-x, and f is more than 0 and less than or equal to 2; m includes one or more of Mn, ni, co, al, fe, ru, nb, cr, ti, ir, V, ca, sc, cu, zn, sr, Y, zr, ta, la, ce, pr, nd, W, mo; t includes one or more of F, S, P, N; the crystallographic morphology of the single crystal lithium-rich material comprises one or more of octahedra and tetratetrahedra; optionally, the crystallographic morphology of the single-crystal lithium-rich material further comprises one or more of tetrahedra and hexahedron.
Preferably, the diffraction peaks of the crystal structure of the single crystal lithium-rich material include: layered alpha-NaFeO with R-3m space group 2 Hexagonal LiMO of structure 2 Phase, monoclinic Li with C2/m space group 2 MnO 3 A phase; TMO with lithium-rich layered oxide as crystal structure 2 The presence of part of LiMn in the layer 6 Cation arrangement; preferably, the surface of the single crystal lithium-rich material is provided with a spinel and/or disordered rock salt phase coating layer; more preferably, the spinel in-situ coating layer has a thickness of 1-500nm.
Preferably, the grain size of the monocrystalline lithium-rich material monocrystalline particles is 0.3-5 μm, preferably, the monocrystalline lithium-rich material is cobalt-free monocrystalline lithium-rich positive electrode material Li 1+x Mn m Ni q M1 1-x-m-q O 2-f T f Wherein x is more than 0 and less than or equal to 0.5, m is more than 0 and less than or equal to 1-x, q is more than or equal to 0 and less than or equal to 1-x, and f is more than or equal to 0 and less than or equal to 2; preferably, 0.1 < x.ltoreq.0.3, 0 < m.ltoreq.0.8, where M1 is one or more of Al, fe, nb, cr, ti, V, ca, sc, cu, zn, sr, Y, Y, zr, ta, la, W, mo.
In a third aspect, an embodiment of the present invention provides an energy storage device, where the energy storage device includes a lithium battery, a lithium battery pack, or a lithium battery module, and the energy storage device includes a positive electrode material, where the positive electrode material includes the single crystal lithium-rich material obtained by the preparation method in the first aspect, or the single crystal lithium-rich material in the second aspect.
According to the preparation method of the monocrystalline lithium-rich material, provided by the embodiment of the invention, the special morphological characteristics and dynamics characteristics of the spinel phase are utilized to control and synthesize the monocrystalline lithium-rich material with a specific crystal structure, and the characteristic that the spinel phase has lower formation energy and therefore the spinel oxide growth dynamics is faster than that of the layered oxide is utilized, so that the monocrystalline lithium-rich material with proper monocrystalline granularity and a specific crystal structure can be prepared under the condition that a morphology control agent and/or a fused salt cosolvent are not used, namely, the compound of the spinel phase is used as a template, and the monocrystalline lithium-rich material with one or more of an octahedron structure and a tetradecanoid structure is obtained through a lithium supplementing technology. By adopting the preparation process provided by the invention, crystal particles with good dispersibility can be obtained, and the dispersibility of the single crystal particles is improved, so that the wettability of the material and electrolyte can be effectively improved, and especially the electrochemical performance of the material in the first-week charge-discharge process can be effectively improved. Therefore, the single crystal lithium-rich cathode material prepared by the preparation method can greatly improve the first-week discharge specific capacity, thereby having high first coulomb efficiency. In addition, the improvement of the wettability of the material with the electrolyte can also improve the stability of the material during circulation. The single crystal lithium-rich material can realize charge and discharge under higher voltage, and even if the charge voltage is as high as 4.8V, the single crystal lithium-rich positive electrode material has high specific capacity and excellent cycling stability, and the capacity retention rate is still close to 100% after 200 weeks of cycling.
According to the invention, the lithium supplementing amount of the spinel phase compound is controlled, so that the reaction thermodynamics in the chemical reaction process can be effectively changed, namely, the effective conversion of the spinel phase compound to the monocrystal lithium-rich positive electrode structure is controlled, and the morphology of the finally synthesized monocrystal lithium-rich positive electrode material is effectively controlled, so that the octahedral monocrystal lithium-rich material with {111} crystal face exposure surfaces or the fourteen-plane monocrystal lithium-rich material with {111} and {001} crystal face exposure surfaces is obtained. For the layered positive electrode material, the {001} crystal face is an inert surface for lithium ion transportation, so that the charge-discharge cycle performance of the positive electrode material can be improved by exposing the {001} crystal face, and the conduction of lithium ions along a two-dimensional plane can be promoted by exposing other surfaces such as a {010} crystal face group and a {111} crystal face group, thereby improving the rate capability of the material. The applicant finds that the dynamics characteristics of spinel phase and layered oxide formation have certain difference, namely the spinel phase has lower formation energy, so that the dynamics of spinel phase growth with lower formation energy is obviously faster than that of layered oxide, therefore, the growth characteristics and dynamics of the material are utilized, the precursor of the monocrystal lithium-rich layered oxide is firstly synthesized into an intermediate with the spinel phase, then the intermediate of the spinel phase is taken as a template, and the monocrystal lithium-rich layered material with {111} or {111} and {001} crystal face exposure faces can be obtained through high-temperature calcination after lithium supplementation, so that the monocrystal lithium-rich material can still realize excellent multiplying power performance even on the basis of no cobalt element. Therefore, the cobalt-free monocrystal lithium-rich material can not only greatly reduce the material cost, but also realize excellent multiplying power performance and cycle performance.
The preparation method is simple in preparation process, does not need to additionally use morphology control agents and molten salt cosolvent, does not generate a large amount of industrial wastewater, is more green and environment-friendly, and is suitable for large-scale production. The cobalt-free monocrystal lithium-rich material has good morphology consistency, uniform grain size distribution of monocrystal grains, can effectively overcome the problems of low first coulomb efficiency, poor multiplying power performance, poor structural stability, quick capacity attenuation and the like of the existing lithium-rich cathode material under high voltage, and can obviously improve the first coulomb efficiency, the multiplying power performance and the circulation stability so as to obtain excellent capacity retention rate.
Drawings
FIGS. 1a-1c are schematic illustrations of SEM images of single crystal lithium-rich materials synthesized in example 1;
FIG. 2 is a graph showing the particle size distribution calculation of the single crystal lithium-rich material synthesized in example 1;
FIG. 3 is an XRD pattern for the spinel phase intermediate and single crystal lithium-rich material synthesized in example 1;
FIG. 4 is a plot of the first cycle charge and discharge for the single crystal lithium-rich material synthesized in example 1;
FIG. 5 is a graph of the cycling performance of the single crystal lithium-rich material synthesized in example 1;
FIG. 6 is a graph of the rate capability of the single crystal lithium-rich material synthesized in example 1;
FIG. 7 is an SEM image of a single crystal lithium-rich material synthesized in example 2;
FIG. 8 is a graph of the first cycle charge and discharge curves of the single crystal lithium-rich materials synthesized in examples 1, 2, 9, and 10;
FIG. 9 is a graph of the cycling performance of the single crystal lithium-rich material synthesized in example 2;
FIG. 10 is an SEM image of a polycrystalline lithium-rich material synthesized according to comparative example 1;
FIG. 11 is an SEM image of a single crystal lithium-rich material synthesized in comparative example 2;
FIG. 12 is an XRD contrast pattern for the synthetic single crystal lithium-rich material of example 1, comparative example 2;
FIG. 13 is a first cycle charge-discharge plot of a single crystal lithium-rich material synthesized in comparative example 2;
fig. 14 is an SEM image of a single crystal lithium-rich material obtained in patent CN109537054a serving as a comparative example of the present invention.
Detailed Description
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
The embodiment of the invention provides a monocrystal lithium-rich material and a preparation method thereof. The preparation method is described first, and then the structure and properties of the single crystal lithium-rich material of the present invention are described.
The preparation method of the monocrystal lithium-rich material mainly comprises the following two steps:
1. preparing a spinel phase compound;
2. the spinel phase compound is mixed with the lithium-containing compound to obtain a mixture, and then the mixture is subjected to high-temperature calcination in an oxidizing atmosphere to obtain single crystal lithium-rich material particles with {111} or {111} and {001} crystal faces exposed.
Aiming at the step 1:
the chemical general formula of the spinel phase compound is LiMn 2-a M a O 4-b T b 0.ltoreq.a < 2, 0.ltoreq.b < 4, where M includes one or more of Mn, ni, co, al, fe, ru, nb, cr, ti, ir, V, ca, sc, cu, zn, sr, Y, zr, ta, la, ce, pr, nd, W, mo and T includes one or more of F, S, P, N.
The spinel phase compound may be prepared by directly obtaining the spinel phase compound by market purchase, or may be synthesized by the following method.
First, a precursor material is prepared, the precursor material including a lithium source and a metal source, a molar ratio of lithium element in the lithium source to metal element in the metal source being (0-1): 1, preferably (0.3-0.6): 1. wherein the lithium source comprises one or more of an inorganic lithium compound and an organic lithium compound, and preferably comprises one or more of lithium oxide, lithium chloride, lithium fluoride, lithium carbonate, lithium hydroxide, lithium nitrate, lithium phosphate, lithium supplementing agent, butyl lithium, phenyl lithium, lithium tert-butoxide, lithium diisopropylamide and lithium hexamethyldisilazide; the metal source comprises a Mn source, or comprises a Mn source and an M source, specifically comprises one or more of an inorganic metal compound and an organic metal compound of Mn, M, preferably comprises one or more of an oxide, carbonate, nitrate, oxalate, sulfate, alkyl-based organic metal compound.
Then, placing the precursor material in an oxidizing atmosphere for sintering to obtain a spinel phase compound; wherein the sintering temperature is 300-1000 ℃ and the heat preservation time is 3-48h; preferably, the gas of the oxidizing atmosphere comprises one or more selected from the group consisting of: oxygen, air, oxygen-containing non-air type gases. The oxygen-containing non-air type gas may be a mixed gas of oxygen and other gases, such as a mixture of oxidation and nitrogen in an arbitrary ratio.
The precursor of the invention can also contain a certain proportion of lithium, the precursor is subjected to pre-lithium supplementation, and the morphology of the spinel compound can be effectively controlled by controlling the thermodynamic stability of different crystal faces, so that the finally synthesized monocrystal lithium-rich anode material can keep regular polyhedral morphology, further realize the exposure and regulation of different crystal faces, and improve the electrochemical properties of the anode material such as first coulomb efficiency, multiplying power performance, cycle performance and the like.
The sintering temperature of the precursor ranges from 300 ℃ to 1000 ℃ and the heat preservation time ranges from 3 hours to 48 hours; the sintering temperature and holding time may be any values within the above ranges, such as 300 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, etc., 3 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, 48 hours, etc., but are not limited to the recited values, and other non-recited values within the range are equally applicable.
The sintering can be one-step sintering or step sintering; the step sintering may be two-stage sintering, three-stage sintering or multi-stage sintering, and the sintering temperature and the heat-preserving time may be within the above ranges, for example, the step sintering may be performed by heating to a higher temperature for a certain time after heat preservation at a low temperature for a certain time. Preferably, the sintering is specifically: raising the temperature from room temperature to 300-600 ℃ at a heating rate of 3-10 ℃/min, keeping the temperature for 3-10 hours, raising the temperature to 700-1000 ℃ at a heating rate of 3-10 ℃/min, and keeping the temperature for 10-38 hours. By setting the sintering temperature in sections, the effective control of morphology can be realized, particles with good small particle size dispersibility can be obtained by preserving heat for a certain time at a lower temperature, and then the crystallinity of the particles can be further improved by preserving heat for a certain time at a higher temperature, so that more regular crystal faces are exposed.
The precursor material is prepared by a coprecipitation method, a solid phase ball milling method or a sol-gel method. The precursor material has simple synthesis process, is suitable for large-scale production, and is beneficial to commercialization process. For the coprecipitation method, metals except lithium are formed into a compound by a coprecipitation technology, and then the compound is uniformly mixed with the lithium-containing compound according to the proportion requirement to obtain a precursor, and it is required that in the process of generating the precursor by the coprecipitation method, if oxygen anions are substituted, the oxygen anions can be mixed with the supplemental anion compound, then the substitution of anions is realized in the calcination process, namely, the lithium-containing compound is doped with corresponding lithium salt, for example, the anions are fluorine, and the oxygen anions can be substituted in the process of generating the precursor Part of the lithium-containing compound is replaced with a fluorine-containing compound such as LiF in the precursor according to the doping amount. If the anions are sulfur doped, the precursor can be prepared by replacing part of the lithium-containing compound with a sulfur-containing compound such as Li 2 SO 4 The method is not limited to the above, and the method and process known in the art may be used for the anionic doping element. For the solid-phase ball milling method, according to the chemical general formula, lithium compounds and compounds of other metals are fully and uniformly mixed through a high-energy ball mill according to the proportion to obtain a precursor. For the sol-gel method, according to the chemical general formula, lithium salt and other metal salts are dissolved in deionized water in proportion, and an auxiliary agent is added to finally form gel, so that a precursor is obtained.
The three methods are described in detail below.
The coprecipitation method specifically comprises: according to the chemical formula Mn 1-c M c The stoichiometric ratio of Q prepares 0.1-4mol/L of Mn and M metal mixed salt solution, and simultaneously prepares 0.2-6mol/L of precipitant solution and complexing agent solution respectively. Mn (Mn) 1-c M c In Q, c is more than or equal to 0 and less than 1, M comprises one or more of Mn, ni, co, al, fe, ru, nb, cr, ti, ir, V, ca, sc, cu, zn, sr, Y, zr, ta, la, ce, pr, nd, W, mo, and Q is one or more of acid radical ions or hydroxyl radicals; preferred Q is one or more of hydroxide ion, carbonate ion, acetate ion, oxalate ion, nitrate ion, sulfate ion. Pumping a metal mixed salt solution into a reaction container, and simultaneously adding the precipitant solution and the complexing agent solution to obtain mixed particles; aging, washing and drying the obtained mixed particles to obtain a coprecipitated compound, and then mixing a lithium-containing compound with the coprecipitated compound according to a molar ratio of lithium to metal elements of (0-1): 1, preferably (0.3-0.6): 1, uniformly mixing to obtain a precursor material; the molar ratio of lithium to metal element in the precursor is (0-1): 1, can be any number within the above range, such as 0, 0.1: 1. 0.2: 1. 0.3: 1. 0.4: 1. 0.5: 1. 0.6: 1. 0.7: 1. 0.8: 1. 0.9: 1. 1:1, etc., but are not limited to the recited values, and other non-recited values within the range of values are equally applicable. When the ratio of the two is 0 I.e., it means that the precursor does not contain lithium; when the ratio of the precursor and the precursor is not 0, the precursor of the material contains a certain ratio of lithium, namely, part of lithium elements are introduced into the precursor in advance, and the morphology of the spinel compound can be effectively controlled by a pre-lithiation technology of the precursor, so that the finally synthesized monocrystal lithium-rich positive electrode material can keep regular polyhedral morphology, and the monocrystal material has higher first coulombic efficiency, excellent multiplying power performance and cycle performance when being used as a battery positive electrode material.
Preferably, the precipitants in the precipitant solution include one or more of carbonate, bicarbonate, hydroxide, thiocyanide, ammonium salt, oxalate; more preferably, one or more of sodium carbonate, sodium bicarbonate, ammonium carbonate, lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium oxalate, potassium thiocyanate; preferably, the complexing agent in the complexing agent solution comprises one or more of ammonia water, acetic acid, oxalic acid, succinic acid, ethylenediamine tetraacetic acid, lactic acid, citric acid, salicylic acid, sulfosalicylic acid, tartaric acid and glycine. The complexing agent plays a role in complexing metal ions in coprecipitation, so that the metal ions with fast precipitation are slow, the metal ions are simultaneously precipitated, and the precipitate is subjected to atomic-level mixing under the action of the precipitant.
The particle size of the mixed particles can be controlled by the reaction temperature, the feed rate, the pH in the reaction vessel and the rotational speed. By controlling the technological parameter conditions such as the feeding speed, the reaction temperature, the pH value, the rotating speed, the aging time and the like of the precipitation reaction, the synthesis uniformity of the precursor can be ensured, and the uniformity of the particle size distribution of the precursor can be ensured, so that the particle size distribution of monocrystalline particles is uniform. Preferably, the feeding speed is 30-150ml/h, the reaction temperature is 40-60 ℃, the pH is 7-12, the rotating speed is 300-600r/min, and the aging time is 12-24h. Preferably, the particle size of the particles is 0.3-15 μm; particularly preferably, the particle size is from 0.3 to 5. Mu.m.
The solid-phase ball milling method specifically comprises the following steps: according to the general chemical formula LiMn d-e M e O 4-b T b The stoichiometric ratio of Li, mn and M metal compound is passed through high-energy ball millUniformly mixing to obtain a precursor material, liMn d-e M e O 4-b T b Wherein e is greater than or equal to 0 and less than d, b is greater than or equal to 0 and less than 4,0 and less than 1/d is less than 1, M comprises one or more of Mn, ni, co, al, fe, ru, nb, cr, ti, ir, V, ca, sc, cu, zn, sr, Y, zr, ta, la, ce, pr, nd, W, mo, and T comprises one or more of F, S, P, N.
The sol-gel method specifically comprises: according to the general chemical formula LiMn d-e M e O 4-b T b Dissolving metal salts containing Li, mn and M in deionized water, then dropwise adding a mixed aqueous solution containing a chelating agent and a dispersing agent, continuously stirring, then dropwise adding a pH regulator to adjust the pH to be 6-8, keeping the constant temperature of 80-120 ℃ after the pH is stable, continuously stirring until transparent gel is generated, and drying and grinding to obtain a precursor material; liMn d-e M e O 4-b T b Wherein e is more than or equal to 0 and less than d, b is more than or equal to 0 and less than 4,0 and less than 1/d is less than 1, M comprises one or more of Mn, ni, co, al, fe, ru, nb, cr, ti, ir, V, ca, sc, cu, zn, sr, Y, zr, ta, la, ce, pr, nd, W, mo, and T comprises one or more of F, S, P, N; the chelating agent comprises one or more of inorganic chelating agent and organic chelating agent, preferably comprises one or more of phosphate, aminocarboxylic acid, organic phosphoric acid type, carboxyl carboxylic acid and amine compound. Preferably one of citric acid and acetic alcohol. The chelating agent may be a reagent conventionally used in the art for complexing with molten salts of metal salts, the purpose of which is to provide a coordinating atom for a metal atom or ion to form a complex having a cyclic structure, forming a sol with the metal salt solution.
Aiming at the step 2:
The molar ratio of lithium in the lithium-containing compound to the spinel phase compound in the invention is 0.2:1-3:1, the high-temperature calcination temperature range is 300-1000 ℃, and the calcination heat preservation time is 6-24h. In the step, the spinel phase compound is used as a template of the monocrystal lithium-rich material, and the spinel phase compound is used as a raw material for lithium supplementation, namely, after being mixed and calcined with the lithium-containing compound, the final morphology of the monocrystal lithium-rich material can be effectively controlled.
The gas of the oxidizing atmosphere comprises one or more selected from the following gases: oxygen, air, oxygen-containing non-air type gases. The oxygen-containing non-air type gas may be a mixed gas of oxygen and other gases, such as a mixture of oxidation and nitrogen in an arbitrary ratio.
The molar ratio is 0.2:1-3:1, can be any number within the above range, such as 0.2:1, 0.3:1, 0.4: 1. 0.5:1, 0.6:1, 0.7:1, 0.8: 1. 0.9:1, 1.1: 1. 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, 2.1:1, 2.5:1, 2.7:1, 3:1, etc., but are not limited to the recited values, and other non-recited values within the range of values are equally applicable. The molar ratio of lithium to the spinel-phase intermediate in the above range is satisfied, so that the reaction thermodynamics in the chemical reaction process can be effectively changed, namely, the effective conversion of the spinel-phase compound to the monocrystal lithium-rich positive electrode structure is controlled, and the crystal morphology of the {111} or {111} and {001} crystal faces exposed surfaces is ensured. Preferably, the molar ratio of lithium in the lithium-containing compound to the spinel phase compound is (1.5-2.8): 1.
The calcination temperature of the mixture ranges from 300 ℃ to 1000 ℃ and the heat preservation time ranges from 6 hours to 24 hours; the sintering temperature and holding time may be any values within the above ranges, such as 300 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, etc., 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, etc., but are not limited to the recited values, and other non-recited values within the range are equally applicable. The sintering can be one-step sintering or step sintering; the step sintering can be two-stage sintering, three-stage sintering or multi-stage sintering, and the sintering temperature and the heat preservation time can be applied within the above ranges. For example, the method can be to heat up to a higher temperature after heat preservation for a certain time at a low temperature, and the specific calcination process is to heat up to 300-600 ℃ from room temperature at a heating rate of 3-10 ℃/min, heat up to 700-1000 ℃ at a constant temperature rate of 3-10 ℃/min for 3-10h, and heat up for 10-20h. Particle size, morphology and dispersibility of the lithium-rich single crystal positive electrode material can be effectively regulated and controlled by controlling the calcination temperature, so that the electrochemical performance of the lithium-rich single crystal positive electrode material is improved. Through setting the calcination temperature in sections, the shape can be effectively controlled, for example, the lithium-rich material with low crystallization and proper particle size is obtained at first after the calcination temperature is kept at a lower temperature for a certain time, so that the lithium-rich material is ensured to have better multiplying power performance, and then the calcination temperature is kept at a higher temperature for a certain time, so that the positive electrode particles with regular polyhedral shape are obtained, and the material is ensured to have more excellent cycle performance
After the monocrystalline lithium-rich material is prepared through the steps 1 and 2, the method can further continue to execute the step 3: monocrystalline particles of the monocrystalline lithium-rich material are surface modified to produce spinel and/or disordered rock salt coatings.
Since the particle diameter of the single crystal particle of the present invention is 0.3 to 5. Mu.m, the submicron/micron order single crystal lithium-rich surface area is very small, and thus surface modification can be performed better. It may be provided with spinel and/or disordered rock salt phase coatings by surface modification.
The coating can be realized by adopting a conventional coating method, for example, the compound is uniformly dispersed on the lithium-rich surface of the monocrystal by a solid-phase ball milling method, a sol-gel method or a coprecipitation method, and then the coating of the disordered rock salt layer is realized by a high-temperature calcination method. In a preferred embodiment, the spinel coating may be produced on the surface of the monocrystalline particles by a gas-solid treatment or an acid treatment. For example, the surface modification can be performed by utilizing a reducing atmosphere generated by the thermal decomposition reaction of a solid phase substance, namely, reducing gas is generated by thermal decomposition at high temperature, transition metal reduction is induced to realize in-situ phase transition, and a thin and compact spinel coating layer is generated on the surface; or weak acid treatment is performed to induce the phase change of the surface lamellar spinel, and a thin and compact spinel coating layer is generated on the surface, so that the single crystal lithium-rich surface has a special spinel phase structure, and the in-situ coating layer is synchronously realized. Therefore, the single crystal lithium-rich material can realize the consistency and/or compatibility of the structures of the internal coating layer and the surface coating layer, thereby ensuring that the coating layer has excellent mechanical, chemical and electrochemical stability in the long-cycle process.
Generating spinel coating layers on the surfaces of the single crystal particles by adopting a gas-solid treatment method comprises the following steps: and placing the single crystal lithium-rich material and a first substance which generates reducing gas through thermal decomposition in a closed container, heating to a temperature higher than the thermal decomposition temperature of the first substance under inert atmosphere to obtain the single crystal lithium-rich material with the spinel coating layer constructed on the surface of the material in situ, wherein the first substance preferably comprises one or more compounds of an ammonia compound, an oxalate compound and a carbonic acid compound. The thermal decomposition temperature may be 150-600 ℃. In a specific example, the nitrogen-containing compound may be urea, the oxalate-type compound may be iron oxalate, the carbonic acid-type compound may be ammonium bicarbonate, and the above-mentioned compounds are thermally decomposed at high temperature to generate reducing gas, induce transition metal to reduce to realize in-situ phase transition, and generate a thin and compact spinel coating on the surface.
The generation of the spinel coating layer on the surface of the single crystal particle by adopting an acid treatment method comprises the following steps: treating the monocrystal lithium-rich material by using an acidic reagent to obtain the monocrystal lithium-rich material with the spinel coating constructed on the surface of the material in situ; preferably, the acidic reagent comprises one or more of sulfuric acid, hydrochloric acid, hydrofluoric acid, nitric acid, phosphoric acid, fatty acid, acidic salt solution, and the specific method of the acid treatment process comprises one or more of dipping process, spraying process and coating process.
Specifically, the impregnation method is to soak the monocrystal lithium-rich material in acid solution, and the lithium on the surface of the lithium-rich material will be mixed with H in the liquid phase of the acid reagent in the liquid phase system + Occurrence of Li + /H + Exchange to realize Li on surface part of monocrystal lithium-rich material + And the lithium is separated from the solution and dissolved in the solution, so that the construction of a surface lithium-deficient phase is realized. The spraying method is to react with the acid solution for a period of time and then realize solid-liquid separation by a spraying method, thereby realizing the lithium-deficient phase material and the Li dissolved in the liquid phase + A separation process; the coating method is to build a layer of H-containing layer on the surface of the monocrystal lithium-rich surface + Is a weak acid polymer coating layer for realizing interfacial Li + /H + And the construction of a surface lithium-deficient phase is realized through exchange. Particularly preferably, after the acidic reagent treatment, the single crystal lithium-rich material with the spinel coating layer constructed in situ on the surface of the obtained material is calcined at 300-600 ℃ for 3-10 hours to obtain an excellent coating layer.
In addition, the single crystal lithium-rich particles of the invention can be improved by adopting processes of doping, compounding and coating, for example, a compound with active conductive ions or conductive electrons is coated by a liquid phase method or a sol-gel method, thereby realizing further improvement of electrochemical performance; or forms a composite positive electrode material with other ion-conducting or electron-conducting compounds.
The prepared product has good shape consistency and uniform particle size distribution of monocrystalline particles. The preparation process can obtain the material with high compaction density, and the energy density of the material can be further improved. Therefore, the invention can improve the first coulombic efficiency, the cycle performance and the like on the basis of realizing the high-energy density lithium-rich anode material. In addition, the preparation process is simple, does not need to additionally use a morphology control agent and a molten salt cosolvent, does not generate a large amount of industrial wastewater, is more green and environment-friendly, and is suitable for large-scale production. The precursor preparation is generally applicable to any one of a solid phase method, a coprecipitation method and a sol-gel method, is suitable for large-scale production, and has wide commercial application prospect.
The single crystal lithium-rich material of the present invention obtained by the above method has the chemical formula of Li 1+x Mn y M 1-x-y O 2-f T f Wherein x is more than 0 and less than or equal to 0.5, y is more than 0 and less than or equal to 1-x, and f is more than 0 and less than or equal to 2; m includes one or more of Mn, ni, co, al, fe, ru, nb, cr, ti, ir, V, ca, sc, cu, zn, sr, Y, zr, ta, la, ce, pr, nd, W, mo; t includes one or more of F, S, P, N.
The grain size of the monocrystal lithium-rich material prepared by the invention is 0.3-5 mu m. Most current research on lithium enrichment focuses on lithium rich materials with high specific surface area, i.e. nanoparticles with primary particles of 100nm or less, whereas the use of nanoparticles is not suitable for industrial production, since the particle size limits the achievable electrode density (≡2.5 gcm) -3 ) Thus resulting in a lower actual volumetric energy density (2400 WhL) -1 ). In addition, the nano-sized lithium-rich material may generate problems related to oxygen when the actual battery system is used due to a high specific surface area: for example, due to the manufacture of electrodesThe cracking of the particles accelerates the irreversible reaction of the lattice oxygen and thus the electrolyte decomposition. Therefore, the invention considers the lithium-rich material with high specific surface area ratio and lacks material competitiveness and practical feasibility, and the reduction of the specific surface area ratio is a direct method for solving the practical application of the lithium-rich material, namely, the submicron/micron single crystal is prepared. The submicron/micron-sized single crystal particles, in particular micron-sized particles, are obtained through technological improvement, and have good dispersivity, so that the single crystal lithium-rich material has higher mechanical strength, side reactions of the positive electrode material in the charge and discharge processes are reduced, and the cycle performance of the lithium-rich material is improved.
The crystallographic morphology of the single crystal lithium-rich material comprises one or more of octahedra and tetratetrahedra, and can also comprise one or more of tetrahedra and hexahedra. Diffraction peaks for the crystal structure of single crystal lithium-rich materials include: layered alpha-NaFeO with R-3m space group 2 Hexagonal LiMO of structure 2 Phase, monoclinic Li with C2/m space group 2 MnO 3 A phase; TMO with lithium-rich layered oxide as crystal structure 2 The presence of part of LiMn in the layer 6 And (3) cation arrangement.
Preferably, the surface of the monocrystalline lithium-rich material is provided with a spinel and/or disordered rock salt phase coating layer; more preferably, the spinel in-situ coating layer has a thickness of 1-500nm. The thickness of the coating layer may be any value within the above range, such as 1nm, 2nm, 4nm, 6nm, 8nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 100nm, 110nm, 150nm, 200nm, 300nm, 400nm, 450nm, 500nm, etc., but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.
Preferably, the monocrystal lithium-rich material is cobalt-free monocrystal lithium-rich positive electrode material Li 1+x Mn m Ni q M1 1-x-m-q O 2-f T f Wherein x is more than 0 and less than or equal to 0.5, m is more than 0 and less than or equal to 1-x, q is more than or equal to 0 and less than or equal to 1-x, and f is more than or equal to 0 and less than or equal to 2; preferably, 0.1 < x.ltoreq.0.3, 0 < m.ltoreq.0.8, 0.ltoreq.q.ltoreq.0.8, where M1 is Al, fe, nb, cr, ti, VOne or more of Ca, sc, cu, zn, sr, Y, Y, zr, ta, la, W, mo.
The monocrystalline lithium-rich material provided by the invention has uniform particle size distribution of monocrystalline particles and good product morphology consistency.
The single crystal lithium-rich material of the invention may contain cobalt or may not contain cobalt element. The cost of the anode material can be reduced after the cobalt element is removed because the cobalt element is expensive. The monocrystal lithium-rich cathode material without cobalt provided by the invention has the advantages that the crystal structure is mainly an octahedral monocrystal lithium-rich material with {111} crystal faces exposed and a fourteen-plane monocrystal lithium-rich material with {111} and {001} crystal faces exposed, so that the monocrystal lithium-rich material can still realize excellent cycle performance and rate capability even on the basis of no cobalt element. Therefore, the material of the invention has more commercial application value. In addition, the monocrystal lithium-rich material has great amount of exposed specific crystal face, raised interface stability under high voltage, less surface oxygen release and side reaction with electrolyte, and excellent cyclic performance even in high voltage of 4.8V charge and discharge. The monocrystal lithium-rich material obtained by the invention has a large number of crystal face exposure and presents specific morphological characteristics, so compared with the existing monocrystal lithium-rich material, the monocrystal lithium-rich material has excellent cycle stability, rate capability and first coulombic efficiency. The diffraction peak of the crystal structure of the material also shows the layered structure of the finally synthesized single crystal lithium-rich material, and the superlattice diffraction peak between 20 degrees and 25 degrees exists, so the diffraction peak is the characteristic diffraction peak of the lithium-rich material, and shows the TMO of the lithium-rich layered oxide 2 The presence of part of LiMn in the layer 6 And (3) cation arrangement. The single crystal lithium-rich material obtained by the invention has stable layered structure, can keep the integrity of the layered structure in the Li+ extraction and intercalation processes, and has good cycle stability and is not easy to generate irreversible phase change due to excellent structural stability.
The monocrystalline lithium-rich material provided by the invention has the advantages of high energy density, high initial coulombic efficiency, excellent multiplying power performance and excellent cycle performance, and can be applied to lithium batteries, lithium battery packs or lithium battery modules. When the method is applied to terminal products, the method has excellent characteristics, can be widely applied to the fields of consumer electronics, electric automobiles, large-scale energy storage and the like, and has good application prospects in large-scale energy storage systems.
In order to better explain the technical scheme of the invention, the invention is further described below by combining specific embodiments. It is to be understood that these examples are provided for the purpose of further understanding of the present invention and are not limited to the preferred embodiments described herein, but are not intended to limit the scope of the invention, any product that is the same or similar to the present invention, given the teaching of the present invention or the combination of the features of the prior art, falls within the scope of the present invention.
The following examples and comparative examples were all obtained from the company Mitsu New Material Co., ltd, from the company Suzhou Duoduo chemical technologies Co., ltd, from the company Beijing Wei Lan Xin energy technologies Co., ltd, from the company Tianjin Medium energy lithium Co., ltd, from the company Beijing Yinuoka technologies Co., ltd, from the other modified materials without specific description.
The specific experimental procedures or conditions are not noted in the examples and may be performed in accordance with the operations or conditions of conventional experimental procedures described in the literature in this field. The reagents or apparatus used were conventional reagent products obtained commercially, without the manufacturer's attention.
Example 1
Single crystal lithium-rich material Li 1.2 Mn 0.6 Ni 0.2 O 2 The preparation process of (2) is as follows:
step 1. Preparation of precursor
MnSO is carried out 4 ·H 2 0、NiSO 4 ·H 2 0 is dissolved in deionized water to prepare 2mol/L mixed salt solution, wherein Mn in the mixed solution is as follows: the molar ratio of Ni is 3:1, 4mol/L sodium hydroxide solution is taken as a precipitator, 4mol/L ammonia water solution is taken as a buffering agent, the mixed salt solution, the sodium hydroxide solution and the ammonia water solution are pumped into a reaction kettle through a constant flow pump in sequence, and high-purity argon is introduced into the reaction kettle at the same timeControlling the feeding speed to be 75ml/h, controlling the rotating speed of a reaction kettle to be 600r/min, controlling the reaction temperature to be 55 ℃ and the pH value to be 10.5, washing the obtained solid product with deionized water after the coprecipitation is finished, filtering and drying to obtain a coprecipitation compound Mn 0.75 Ni 0.25 (OH) 2 And (5) standby. And uniformly mixing lithium hydroxide with the coprecipitation compound according to the molar ratio of the lithium to all metal elements of the coprecipitation compound being 0.5:1, so as to obtain a hydroxide precursor of the mixed lithium hydroxide.
Step 2. Preparation of spinel phase intermediate
Placing the precursor obtained in the step 1 in an oxygen atmosphere, then heating from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 3 hours, heating to 750 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 12 hours, and naturally cooling to room temperature to obtain a spinel-phase compound material LiMn 1.5 Ni 0.5 O 4 。
Step 3. Preparation of the Material
Uniformly mixing lithium hydroxide and the spinel compound obtained in the step 2 according to the molar ratio of 2:1, placing the mixture in an oxygen atmosphere, heating from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 3 hours, heating to 850 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 20 hours, and naturally cooling to room temperature to obtain the monocrystal lithium-rich anode material Li 1.2 Mn 0.6 Ni 0.2 O 2 。
Structural characterization:
and (3) adopting a scanning electron microscope to characterize the morphology of the monocrystal lithium-rich material. As shown in FIGS. 1a to 1c, the single crystal lithium-rich cathode material obtained in example 1 has a uniform grain size distribution, and further test using a particle size distribution calculation NanoMeasurer reveals that the grain size distribution is concentrated to about 1.03. Mu.m, as shown in FIG. 2. It can be seen from fig. 1 that the single crystal lithium-rich material has better dispersibility, no obvious agglomeration phenomenon occurs between particles, and from the figure, a large number of fourteen-sided and octahedral are present in the crystal structure of the crystal grains, which indicates that example 1 yields a single crystal lithium-rich material having mainly two crystal structures of the octahedral type with specific {111} crystal face exposure and the tetradecic type with {111} and {001} crystal face exposure. As can be seen from FIG. 1 (c), the crystal form of the single crystal particle synthesized by the method is complete in structure, crystal faces are smooth, and a large amount of {111} crystal faces and {001} crystal faces are exposed, so that the single crystal lithium-rich particle in the embodiment 1 presents a single crystal lithium-rich material with a specific crystal face exposed face and good monodispersity, and the synthesized crystal form is high in structural integrity, and the single crystal particle presents good crystallinity, thereby being beneficial to realizing uniform deintercalation of lithium ions.
And (3) analyzing the spinel compound obtained in the step (2) and the crystal structure of the monocrystal lithium-rich material obtained in the step (3) by adopting a powder X-ray diffractometer. Fig. 3 shows XRD diffraction peaks of the spinel-phase compound obtained in step 2 and the single crystal lithium-rich material obtained in step 3, and it is understood from the crystal structure spectrum that both materials correspond to the respective characteristic spectra. From the contrast spectrum, it can be found that the occurrence of weak diffraction peaks in the range of 20℃to 25℃corresponds to monoclinic symmetry Li 2 MnO 3 (space group: C2/m) crystal domains, indicating cation ordering between Li and Transition Metal (TM) in the TM layer, which is a typical feature of lithium-rich materials. It is further possible to see from the comparison that the single peak of spinel is converted into the lithium-rich (006)/(012) and (018)/(110) split peaks, which confirm that all positive electrode materials have the same layered structure, with a space group of R3 - m. It can be seen from a combination of these characteristics that it achieves a transition from spinel to lithium rich phase. In addition, no other diffraction peak appears in both materials, which indicates that the crystallinity of the materials is good and no impurity phase exists. Therefore, it is known from the analysis of the X-ray diffraction peak position that the material synthesized in example 1 is a typical lithium-rich layered material, and the single crystal has good crystallinity and high purity.
Button cell assembly and electrochemical performance test:
mixing the monocrystalline lithium-rich cathode material prepared in the example 1, acetylene black and polyvinylidene fluoride binder into slurry according to the mass ratio of 8:1:1, uniformly coating the slurry on an aluminum foil current collector to obtain a cathode sheet, taking a metal lithium sheet as a cathode, taking a polypropylene microporous membrane as a diaphragm, and 1mol/LLiPF 6 (the solvent is a mixed solution of Ethylene Carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 3:7) as an electrolyte, and the button cell is assembled in a glove box filled with argon.
Performing multiplying power charge and discharge test on the assembled button cell on a blue electric test system, wherein the voltage range is 2.0-4.8V, the test temperature is 30 ℃, and fig. 4 is a first charge and discharge curve of the positive electrode material under the multiplying power of 0.1C (1 C=250 mA/g); FIG. 5 is a graph of the charge-discharge cycle performance of the positive electrode material, wherein the first 2 weeks are activation of charge-discharge cycles at 0.1C rate, and cycle performance testing is performed at 1C rate from week 3; fig. 6 shows the charge and discharge performance of the positive electrode material at different rates, in which the battery system is sequentially cycled 5 times at 0.1C, 0.5C, 1C, 3C, 5C, 10C, 0.1C, i.e., 1 st to 5 th cycles at 0.1C rate, 6 th to 10 th cycles at 0.5C rate, and so on. The electrochemical performance data of the positive electrode material are shown in tables 1-2.
TABLE 1
TABLE 2
Wherein, the 1 st discharge specific capacity refers to the first week discharge specific capacity under the multiplying power; the 5 th discharge specific capacity refers to the 5 th week discharge specific capacity at that magnification; coulombic efficiency refers to the ratio of the specific discharge capacity to the specific charge capacity; the coulombic efficiency of the 1 st cycle refers to the ratio of the 1 st discharge specific capacity to the 1 st charge specific capacity; the 5-cycle discharge capacity retention rate is the ratio of the 5 th discharge specific capacity to the 1 st discharge specific capacity at that rate.
The single crystal lithium-rich material of example 1 is a single crystal cobalt-free lithium-rich material, and as shown in fig. 4 and table 1, the button cell (half cell) assembled from the single crystal lithium-rich material obtained in example 1 is subjected to charge-discharge cycle between 2.0 and 4.8V at 0.1C multiplying power, and it can be seen that the single crystal cobalt-free lithium-rich material has a first charge specific capacity of 327mAh/g, a discharge specific capacity of 262mAh/g and a first coulomb efficiency of 80%, which indicates that the material has excellent first charge-discharge performance, which also indicates that the cobalt-free material can realize better electrochemical reversibility, and that the single crystal particles of the invention have better dispersibility and smaller specific surface area, which substantially reduces side reactions of the electrode and electrolyte. In addition, due to the unique micron-sized monocrystal appearance design (the prior literature shows that the first-week discharge specific capacity of the micron-sized cobalt-free monocrystal material is lower than 240mAh/g or even lower), the cobalt-free monocrystal lithium-rich realizes higher and ideal discharge specific capacity, namely 262mAh/g, and compared with the prior art, the method has a great improvement.
The charge-discharge cycle process shown in fig. 5, the voltage range is 2.0-4.8V, the first two weeks cycle is an activation process at 0.1C rate, the 3 rd week is started to be a charge-discharge cycle process at 1C rate, as shown in fig. 5 and table 1, the battery system is subjected to charge-discharge cycle at 1C rate, the first charge specific capacity 239mAh/g of the single crystal lithium-rich material can reach 219mAh/g, the first coulomb efficiency is 91.63%, and when the cycle is completed to the 4 th week, the coulomb efficiency is close to 100%, which indicates that the positive electrode material can perform almost completely reversible charge-discharge process, and after 200 charge-discharge cycles, the specific discharge capacity is 222mAh/g, and the capacity retention rate is 101.37%, which are all calculated based on the first discharge specific capacity at the rate after activation. The capacity retention rate of the single crystal lithium-rich material exceeds 100% after 200 times of circulation, and the single crystal lithium-rich material is mainly characterized by comprising the following components: 1) The monocrystal particles have better crystallinity, so that lithium ions are uniformly deintercalated; 2) The presence of partially not fully activated Li in the early crystal domain at the beginning of the cycle 2 MnO 3 These components are gradually activated in the cycle, and activated Li 2 MnO 3 The oxidation-reduction reaction of the medium oxygen keeps excellent reversibility; 3) The material with specific morphology well inhibits the generation of side reaction and delays the generation of phase transition. Therefore, the positive electrode material has excellent capacity retention rate, no capacity attenuation after 200 times of circulation, and is rich in Li due to the rich Li + The discharge capacity of the lithium ion battery is improved to a certain extent when the lithium ion battery participates in the charge-discharge cycle process. Because the monocrystalline particles of the invention have better monodispersity, no generation occursThe phenomenon that the inter-crystal cracks aggravate side reactions is caused, and the fact that single crystal particles with the inert exposed surface of the {111} crystal face group have fewer interface side reactions is also shown, so that the dissolution of transition metal ions is inhibited, and the excellent cycling stability of the single crystal particles is ensured.
As shown in fig. 6 and table 2, the battery system was sequentially subjected to 5 charge and discharge cycles at 0.1C, 0.5C, 1C, 3C, 5C, 10C, and 0.1C rates. The specific capacity of the battery system at the 1 st discharge is 259.69mAh/g and the specific capacity of the battery system at the 5 th discharge is 263.51mAh/g under the 0.1C multiplying power, and the structural area of the positive electrode material is stable, and the lithium-rich material is rich in abundant Li + Takes part in the charge-discharge reaction, so that the 5 th discharge specific capacity exceeds the 1 st discharge specific capacity, thereby having excellent capacity exertion; the charge-discharge charge cycle at week 6 increases the rate to 0.5C, the specific discharge capacity at time 1 at this rate is 247mAh/g, the specific discharge capacity at time 5 is 246.03mAh/g, and the specific discharge capacity is reduced to some extent compared with the charge-discharge cycle at 0.1C rate, but the capacity retention rate at this rate is 99.60%, and the capacity retention rate is very high; the charge-discharge charge cycle at 11 weeks increases the multiplying power to 1C, the specific capacity of the 1 st discharge at the multiplying power is 223.12mAh/g, the specific capacity of the 5 th discharge is 221.73mAh/g, the retention rate of the specific capacity of the 5 th discharge is 99.38%, and the capacity retention rate is very high; the 16 th week charge-discharge charge cycle increases the multiplying power to 3C, the 1 st discharge specific capacity is 200.14mAh/g under the multiplying power, the 5 th discharge specific capacity is 198.05mAh/g, the discharging specific capacity is lower than 0.1C, 0.5C and 1C multiplying power, the discharging specific capacity shows a slow descending trend in the 1 st to 5 th charge-discharge cycle under the multiplying power, but the retention rate of the 5 th discharge specific capacity is still up to 98.96%, which indicates that the high multiplying power of 3C still has excellent capacity retention rate; the charge-discharge charge cycle at 21 weeks increases the multiplying power to 5C, the specific discharge capacity at 1 st time under the multiplying power is 178.2mAh/g, the specific discharge capacity at 5 th time is 176.31mAh/g, the specific discharge capacities under the multiplying power of 0.1C, 0.5C, 1C and 3C are lower, the specific discharge capacity shows a slow descending trend in the process of the charge-discharge cycle at 1-5 times, but the retention rate of the specific discharge capacity at 5 th time is 98.94%, and the high multiplying power at 5C also has excellent capacity retention rate; the charge-discharge charge cycle at week 26 increases the rate to 10C, which The specific discharge capacity at the 1 st time under multiplying power is 152.46mAh/g, the specific discharge capacity at the 5 th time is 149.96mAh/g, and is lower than the specific discharge capacities at the multiplying power of 0.1C, 0.5C, 1C, 3C and 5C, the specific discharge capacity shows a slow descending trend in the 1 st-5 th charge-discharge cycle process, but the retention rate of the specific discharge capacity at the 5 th time is 98.36%, which indicates that the battery has excellent capacity retention rate at the ultra-high multiplying power of 10C; the charge-discharge cycle at 31 weeks reduces the rate to 0.1C, the specific discharge capacity at 1 st time at the rate is 260.24mAh/g, and the specific discharge capacity at 5 th time is 263.75mAh/g, and it can be seen that the single crystal lithium-rich material of the present invention has excellent reversibility of electrochemical reaction, and thus the specific discharge capacity at 5 th time exceeds the specific discharge capacity at 1 st time, thereby having excellent capacity exertion. The specific discharge capacity of the battery system after the 35 th cycle is finished is 263.75mAh/g, and compared with the specific discharge capacity of 259.69mAh/g at the 1 st week in the whole cycle process, the capacity retention rate is up to 101.56%. The cobalt-free single crystal lithium-rich material in this example 1 has excellent capacity retention even when subjected to charge-discharge cycles at 2 to 4.8V.
Further, it can be seen that although the battery system underwent a charge-discharge cycle at a high rate of 25 weeks gradually increasing between the two 0.1C rate charge-discharge cycles, when the rate of the battery was restored to the initial rate state, the specific discharge capacity was also completely restored, indicating that the single crystal lithium-rich material obtained in example 1 had excellent structural stability, and almost no irreversible phase change occurred even at the high rate.
As can be seen from fig. 6, by sequentially performing charge-discharge cycles under 0.1C, 0.5C, 1C, 3C, 5C, 10C, and 0.1C of the battery system, the specific discharge capacity was reduced with increasing magnification, but the reduction was not significant, and it was found that the specific discharge capacity was reduced by only about 37mAh/g from 0.1C magnification to 1C magnification, and the specific discharge capacity was reduced by only 71mAh/g from 1C magnification to 10C magnification, and was slightly higher than the initial capacity even after the battery system was restored to 0.1C magnification.
Therefore, the cobalt-free lithium-rich monocrystal with the specific morphology has lower polarization, so that the cobalt-free lithium-rich monocrystal has excellent electrochemical reaction kinetics, can realize high-rate quick charge, has excellent rate performance, reduces the side reaction between an electrode and an electrolyte interface under high voltage due to the existence of an inert surface, inhibits the dissolution of transition metal, improves the structural stability of a material, and has excellent cycle stability.
Example 2
Single crystal lithium-rich material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 The preparation process of (2) is as follows:
step 1. Preparation of precursor
MnSO is carried out 4 ·H 2 0、NiSO 4 ·H 2 0、CoSO 4 ·7H 2 0 is dissolved in deionized water to prepare 2mol/L mixed salt solution, wherein Mn in the mixed solution is as follows: ni: co (molar ratio) is 0.68:0.16:0.16, 4mol/L sodium hydroxide solution is used as a precipitator, 4mol/L ammonia water solution is used as a buffering agent, the mixed salt solution, the sodium hydroxide solution and the ammonia water solution are pumped into a reaction kettle sequentially through a constant flow pump, high-purity argon is introduced into the reaction kettle, the feeding speed is controlled to be 100ml/h, the rotating speed of the reaction kettle is 600r/min, the reaction temperature is 55 ℃ and the pH value is 10.5, and after the coprecipitation is finished, the obtained solid product is washed, filtered and dried by deionized water to obtain a substance A (Mn 0.68 Ni 0.16 Co 0.16 (OH) 2 ) And (5) standby. And uniformly mixing lithium hydroxide with the substance A according to the molar ratio of the lithium to all metal elements of the substance A of 0.5:1 to obtain a hydroxide precursor of the mixed lithium hydroxide.
Step 2. Preparation of spinel phase intermediate
Placing the precursor obtained in the step 1 in an oxygen atmosphere, then heating from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 3 hours, heating to 800 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 10 hours, and naturally cooling to room temperature to obtain a spinel-phase intermediate material LiMn 1.35 Ni 0.325 Co 0.325 O 4 。
Step 3. Preparation of the Material
Uniformly mixing lithium hydroxide with the spinel intermediate obtained in the step 2 according to the molar ratio of 2:1, and placing the mixture in an oxygen atmosphere at the heating rate of 3 ℃/minRaising the temperature to 500 ℃ at room temperature for 3 hours, raising the temperature to 850 ℃ at the speed of 8 ℃/min, and naturally cooling to the room temperature after keeping the temperature for 15 hours, thus obtaining the monocrystal lithium-rich anode material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 。
As shown in fig. 7, the single crystal lithium-rich cathode material obtained in example 2 had a uniform distribution of crystal grains, and a large number of fourteen planes were present in the crystal structure of the crystal grains, which suggests that the single crystal particles of example 2 had a fourteen-plane type crystal structure with specific {111} and {001} crystal planes exposed. As can also be seen from fig. 7, the single crystal grain has a complete crystal structure with smooth crystal faces, is a regular and perfect fourteen-face body, and has a large exposure of {111} and {001} crystal faces, so that the single crystal lithium-rich grain in example 2 exhibits a single crystal lithium-rich material with a specific crystal face exposed face, and the synthesized crystal form has a very high structural integrity, and the single crystal grain exhibits excellent crystallinity, and the dispersibility of the single crystal grain is very good.
Structural characterization, button cell assembly and electrochemical performance testing were performed in the same manner as in example 1. The voltage range is 2.0-4.8V, the test temperature is 30 ℃, and FIG. 8 is the first charge-discharge curve of the positive electrode material under the 0.1C multiplying power; fig. 9 is a graph of the charge-discharge cycle performance of the positive electrode material, wherein the first 2 weeks are activation of charge-discharge cycles at 0.1C rate, and cycle performance test is performed at 1C rate from week 3. The first-turn charge-discharge curve data of the positive electrode material of example 2 is shown in FIG. 8, the specific charge capacity is 341.05mAh/g, the specific discharge capacity is 284.27mAh/g, the first coulomb efficiency is 83.35%, and the specific discharge capacity and the first coulomb efficiency are both increased compared with those of the cobalt-free system, because cobalt element is present in the positive electrode material system, partial reversible specific capacity can be provided due to the fact that cobalt participates in the redox reaction in the system, and the trivalent cobalt can participate in Li 2 MnO 3 The structure changes the local structure of lattice oxygen, fully activates oxygen activity, improves the contribution of oxidation reduction of oxygen to battery capacity, and in addition, cobalt element can greatly reduce the polarization of the monocrystal lithium-rich material, improve the ionic and electronic conductivity and improve the electrochemical performance of the monocrystal lithium-rich material. As shown in FIG. 9, the positive electrode material of example 2 was circulated at 2.0 to 4.8V The capacity retention rate of 200 turns is 99.14% higher than that of the existing cobalt-containing cathode material, which is mainly beneficial to the specific morphology of the single crystal lithium-rich particles of example 2, and can improve the structural stability of the material and specifically inhibit the adverse phase transition process of the material, thereby having excellent improved cycle stability even at high voltage.
Example 3
Single crystal lithium-rich material Li 1.2 Mn 0.6 Ni 0.18 Al 0.02 O 1.94 F 0.06 The preparation process of (2) is as follows:
step 1. Preparation of precursor
LiMn according to spinel precursor chemistry 1.5 Ni 0.45 Al 0.05 O 4 Li is mixed with 2 CO 3 、MnO、Ni0、Al 2 O 3 Weighing the materials according to the molar ratio of 0.5:1.5:0.47:0.03, putting the materials into a ball milling tank, and fully and uniformly mixing the materials through a high-energy ball mill according to the mass ratio of 1:2.
Step 2. Preparation of spinel phase intermediate
Placing the precursor obtained in the step 1 in an oxygen atmosphere, then heating from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 5 hours, heating to 750 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 15 hours, and naturally cooling to room temperature to obtain a spinel-phase intermediate material LiMn 1.5 Ni 0.45 Al 0.05 O 4 。
Step 3. Preparation of the Material
Uniformly mixing lithium hydroxide and lithium fluoride (molar ratio of lithium hydroxide: lithium fluoride=37:3) with the spinel intermediate obtained in the step 2 according to a molar ratio of 2:1, placing the mixture in an oxygen atmosphere, heating from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 3 hours, heating to 850 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 20 hours, and naturally cooling to room temperature to obtain the monocrystal lithium-rich cathode material Li 1.2 Mn 0.6 Ni 0.18 Al 0.02 O 1.94 F 0.06 。
Structural characterization, button cell assembly and electrochemical performance testing were performed in the same manner as in example 1.
Example 4
Single crystal lithium-rich material Li 1.2 Mn 0.54 Ni 0.16 Co 0.095 Nb 0.005 O 1.98 F 0.02 The preparation process of (2) is as follows:
step 1. Preparation of precursor
LiMn according to spinel precursor chemistry 1.35 Ni 0.4 Co 0.24 Nb 0.01 O 3.95 F 0.05 LiO, liF, mnO, ni0, co 2 O 3 、Nb 2 O 5 Weighing the materials according to the molar ratio of 0.95:0.05:1.35:0.4:0.12:0.005, then placing the materials into a ball milling tank, and fully and uniformly mixing the materials through a high-energy ball mill according to the mass ratio of 1:2.
Step 2. Preparation of spinel phase intermediate
Placing the precursor obtained in the step 1 in an oxygen atmosphere, then heating from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 5 hours, heating to 750 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 15 hours, and naturally cooling to room temperature to obtain spinel-phase intermediate material LiMn 1.35 Ni 0.4 Co 0.24 Nb 0.01 O 3.95 F 0.05 。
Step 3. Preparation of the Material
Uniformly mixing lithium hydroxide and the spinel intermediate obtained in the step 2 according to the molar ratio of 2:1, placing the mixture in an oxygen atmosphere, heating from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 3 hours, heating to 850 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 20 hours, and naturally cooling to room temperature to obtain the monocrystal lithium-rich anode material Li 1.2 Mn 0.54 Ni 0.16 Co 0.095 Nb 0.005 O 1.98 F 0.02 。
Structural characterization, button cell assembly and electrochemical performance testing were performed in the same manner as in example 1.
Example 5
Single crystal lithium-rich material Li 1.2 Mn 0.592 Ni 0.16 Co 0.04 Ru 0.008 O 2 The preparation process of (2) is as follows:
step 1. Preparation of precursor
LiMn according to spinel precursor chemistry 1.48 Ni 0.4 Co 0.1 Ru 0.02 O 4 Li is mixed with 2 CO 3 、MnO、Ni0、Co 2 O 3 The RuO is weighed according to the mole ratio of 0.5:1.48:0.4:0.05:0.02, then is put into a ball milling tank, and is fully and uniformly mixed through a high-energy ball mill according to the mass ratio of 1:2 to obtain the precursor material.
Step 2. Preparation of spinel phase intermediate
Placing the precursor obtained in the step 1 in an air atmosphere, then raising the temperature from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 5 hours, raising the temperature to 750 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 15 hours, and naturally cooling to room temperature to obtain spinel-phase intermediate material LiMn 1.48 Ni 0.4 Co 0.1 Ru 0.02 O 4 。
Step 3. Preparation of the Material
Uniformly mixing lithium hydroxide and the spinel intermediate obtained in the step 2 according to the molar ratio of 2:1, placing the mixture in an oxygen atmosphere, heating from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 3 hours, heating to 850 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 20 hours, and naturally cooling to room temperature to obtain the monocrystal lithium-rich anode material Li 1.2 Mn 0.592 Ni 0.16 Co 0.04 Ru 0.008 O 2 。
Structural characterization, button cell assembly and electrochemical performance testing were performed in the same manner as in example 1.
Example 6
Single crystal lithium-rich material Li 1.15 Mn 0.6 Ni 0.25 O 2 The preparation process of (2) is as follows:
Step 1. Preparation of precursor
LiMn according to spinel precursor chemistry 24/17 Ni 10/17 O 4 Li is mixed with 2 CO 3 Weighing MnO and Ni0 according to the mole ratio of 0.5:24/17:10/17, putting into a ball milling tank, and fully and uniformly mixing by a high-energy ball mill according to the mass ratio of 1:2 to obtain the precursor material.
Step 2. Preparation of spinel phase intermediate
Placing the precursor obtained in the step 1 in an air atmosphere, then raising the temperature from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 5 hours, raising the temperature to 750 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 15 hours, and naturally cooling to room temperature to obtain spinel-phase intermediate material LiMn 24/17 Ni 10/17 O 4 。
Step 3. Preparation of the Material
Uniformly mixing lithium hydroxide and the spinel intermediate obtained in the step 2 according to the molar ratio of 1.7:1, placing the mixture in an oxygen atmosphere, heating from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 3 hours, heating to 800 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 15 hours, and naturally cooling to room temperature to obtain the monocrystal lithium-rich anode material Li 1.15 Mn 0.6 Ni 0.25 O 2 。
Structural characterization, button cell assembly and electrochemical performance testing were performed in the same manner as in example 1.
Example 7
Single crystal lithium-rich material Li 1.2 Mn 0.6 Ni 0.16 Fe 0.04 O 2 The preparation process of (2) is as follows:
step 1. Preparation of precursor
LiMn according to spinel precursor chemistry 1.5 Ni 0.4 Fe 0.1 O 4 LiNO is to be carried out 3 、Mn(NO 3 ) 2 ·4H 2 O、Ni(NO 3 ) 2 ·6H 2 O、Fe(NO 3 ) 3 ·9H 2 O is sequentially dissolved in deionized water solution according to the mol ratio of 1:1.5:0.4:0.1, then aqueous solution containing 6mol/L citric acid is dropwise added, continuous stirring is carried out in the dropwise adding process, meanwhile, concentrated ammonia water with mass fraction of 25-28% is dropwise added to adjust the pH value to 7, after the pH value of the mixed solution is stable, a container of the mixed solution is placed in a water bath kettle to keep the temperature at 80 ℃, continuous stirring is carried out until transparent gel is generated, the obtained gel is dried in a baking oven at 120 ℃ for 24 hours, and the precursor material is obtained through grinding.
Step 2. Preparation of spinel phase intermediate
Placing the precursor obtained in the step 1Under the air atmosphere, the temperature is increased to 450 ℃ from room temperature at a heating rate of 5 ℃/min, the nitrate and the organic matters are decomposed after the temperature is kept constant for 6 hours, then the temperature is increased to 750 ℃ at a heating rate of 5 ℃/min, and the spinel phase intermediate material LiMn is obtained after the temperature is kept constant for 12 hours and then naturally cooled to the room temperature 1.5 Ni 0.4 Fe 0.1 O 4 。
Step 3. Preparation of the Material
Uniformly mixing lithium hydroxide and the spinel intermediate obtained in the step 2 according to the molar ratio of 2:1, placing the mixture in an air atmosphere, heating from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 3 hours, heating to 850 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 20 hours, and naturally cooling to room temperature to obtain the monocrystal lithium-rich anode material Li 1.2 Mn 0.6 Ni 0.16 Fe 0.04 O 2 。
Structural characterization, button cell assembly and electrochemical performance testing were performed in the same manner as in example 1.
Example 8
Single crystal lithium-rich material Li 1.3 Mn 0.6 Ni 0.1 O 2 The preparation process of (2) is as follows:
step 1. Preparation of precursor
LiMn according to spinel precursor chemistry 12/7 Ni 2/7 O 4 LiNO is to be carried out 3 、Mn(NO 3 ) 2 ·4H 2 O、Ni(NO 3 ) 2 ·6H 2 O is sequentially dissolved in deionized water solution according to the mol ratio of 1:12/7:2/7, then aqueous solution containing 6mol/L citric acid is dropwise added, continuous stirring is carried out in the dropwise adding process, meanwhile, concentrated ammonia water with mass fraction of 25-28% is dropwise added to adjust the pH value to 7, after the pH value of the mixed solution is stable, a container of the mixed solution is placed in a water bath kettle to keep the temperature at 80 ℃, continuous stirring is carried out until transparent gel is generated, the obtained gel is dried in an oven at 120 ℃ for 24 hours, and the precursor material is obtained through grinding.
Step 2. Preparation of spinel phase intermediate
Placing the precursor obtained in the step 1 in an air atmosphere, then heating the precursor from room temperature to 450 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 6 hours until nitrate and organic matters are decomposed, and then heating the precursor at 5 ℃/miThe n rate is increased to 750 ℃, the temperature is kept for 12 hours, and then the mixture is naturally cooled to room temperature, thus obtaining spinel phase intermediate material LiMn 12/7 Ni 2/7 O 4 。
Step 3. Preparation of the Material
Uniformly mixing lithium hydroxide and the spinel intermediate obtained in the step 2 according to the molar ratio of 2.7:1, placing the mixture in an air atmosphere, heating from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 3 hours, heating to 900 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 12 hours, and naturally cooling to room temperature to obtain the monocrystal lithium-rich anode material Li 1.3 Mn 0.6 Ni 0.1 O 2 。
Structural characterization, button cell assembly and electrochemical performance testing were performed in the same manner as in example 1.
Example 9
Single crystal lithium-rich material Li 1.2 Mn 0.6 Ni 0.2 O 2 The preparation process of (2) is as follows:
step 1. Direct use of commercially available spinel LiMn 1.5 Ni 0.5 O 4 The product being an intermediate
Step 2, preparing materials:
uniformly mixing lithium hydroxide with the commercial spinel purchased in the step 1 as an intermediate according to the molar ratio of 2:1, placing the mixture in an air atmosphere, heating from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 5 hours, heating to 900 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 20 hours, and naturally cooling to room temperature to obtain the monocrystal lithium-rich anode material Li 1.2 Mn 0.6 Ni 0.2 O 2
Structural characterization, button cell assembly and electrochemical performance testing were performed in the same manner as in example 1.
As shown in fig. 8, the button cell (half cell) assembled from the single crystal lithium-rich material obtained in example 9 is subjected to charge-discharge cycle at 0.1C rate, and it can be seen that the single crystal lithium-rich material has a specific capacity for initial charge of 327.59mAh/g, a specific capacity for discharge of 260.7mAh/g, and a first coulomb efficiency of 79.58%, which indicates that the preparation of single crystal lithium-rich can be achieved by using a commercial spinel precursor as the precursor material, and electrochemical performance similar to that of the stoichiometric chemical ratio example 1 is achieved, which also indicates that the preparation method has a better practical advantage.
Example 10
For the single crystal lithium-rich material Li of example 1 1.2 Mn 0.6 Ni 0.2 O 2 The gas-solid modification process comprises the following steps:
will be 5gLi 1.2 Mn 0.6 Ni 0.2 O 2 Mixing the powder directly with 250mg fine ammonium hydrogen phosphate powder, further wet milling in ethanol for more than 30 min, heat treating at 180deg.C in Ar gas atmosphere for 2 hr, heating and cooling at 2deg.C for min -1 And obtaining the monocrystalline lithium-rich material with the spinel coating layer.
Structural characterization, button cell assembly and electrochemical performance testing were performed in the same manner as in example 1. As shown in fig. 8, the button cell (half cell) assembled by the single crystal lithium-rich material obtained in example 10 is subjected to charge-discharge cycle under the 0.1C multiplying power, and it can be seen that the first charge specific capacity of the single crystal lithium-rich material is 321.27mAh/g, the discharge specific capacity can reach 276.15mAh/g, and the first coulomb efficiency is 85.96%, which indicates that the first discharge performance of the material is further improved by gas-solid modification, because the spinel coated on the surface has a three-dimensional diffusion channel, rapid lithium ion transmission is ensured, the lithium ion transmission barrier is finally reduced, and the spinel coating layer with lithium deficiency can isolate the electrolyte from directly contacting with the electrode to reduce interface side reaction, and can also back-embed and contain more additional lithium ions, thereby greatly improving the first coulomb efficiency. Such single crystal lithium-rich with a specific morphology and a certain particle size is expected to be advantageous in expanding its electrochemical performance by further modification, increasing its prospect of commercial application.
Example 11
For the single crystal lithium-rich material Li of example 1 1.2 Mn 0.6 Ni 0.2 O 2 The acid treatment modification process comprises the following steps:
will be 1gLi 1.2 Mn 0.6 Ni 0.2 O 2 The powder was dissolved in 100ml,1mol/L tartaric acid solutionIn the solution, stirring for about 2h, filtering and washing the product with deionized water for three times, vacuum drying at 120deg.C for 12h, heat treating at 450deg.C in oxidizing atmosphere for 5 hr, and heating and cooling at 5deg.C for 5 min -1 And obtaining the monocrystalline lithium-rich material with the spinel coating layer.
Structural characterization, button cell assembly and electrochemical performance testing were performed in the same manner as in example 1. The single crystal lithium-rich material obtained in example 10 was assembled into a button cell (half cell), and subjected to charge-discharge cycle at 0.1C rate, the single crystal lithium-rich material had a specific charge capacity of 321.65mAh/g for the first time, a specific discharge capacity of 272.70mAh/g, and a first coulomb efficiency of 84.78%, indicating passing Li + /H + The modification of the exchange also improved the first discharge performance of the material, achieving a modification effect more similar to that of example 10. The monocrystal lithium-rich particles with specific morphology and certain particle size are expected to be suitable for the current polycrystalline modification process, and can also realize excellent electrochemical performance, so that the monocrystal lithium-rich particles have certain commercialized application prospects.
Comparative example 1
Polycrystalline lithium-rich material Li 1.2 Mn 0.6 Ni 0.2 O 2 The preparation process of (2) is as follows:
step 1. Preparation of precursor
MnSO is carried out 4 ·H 2 0、NiSO 4 ·H 2 0 is dissolved in deionized water to prepare a mixed salt solution with the concentration of 2mol/L, wherein Mn in the mixed solution is as follows: ni (molar ratio) is 3:1, 2mol/L sodium carbonate solution is taken as a precipitator, 0.2mol/L ammonia water solution is taken as a buffer, the mixed salt solution, the sodium carbonate solution and the ammonia water solution are pumped into a reaction kettle sequentially through a constant flow pump, high-purity argon is introduced into the reaction kettle, the feeding speed is controlled to be 75ml/h, the rotating speed of the reaction kettle is 600r/min, the reaction temperature is 55 ℃, the pH value is 7.8, the reaction time is 20h, after the coprecipitation is finished, the obtained solid product is washed, filtered and dried by deionized water to obtain a preparation substance B, and then lithium carbonate and the substance B are uniformly mixed according to the molar ratio of lithium to metal elements in the precursor of 1.5:1, so as to obtain a carbonate precursor of the mixed lithium carbonate。
Step 2. Preparation of the Material
And (3) placing the precursor obtained in the step (1) in an air atmosphere, heating from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 5 hours, heating to 850 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 12 hours, and naturally cooling to the room temperature to obtain the lithium-rich layered oxide anode material with the polycrystalline morphology.
And (3) adopting a scanning electron microscope to characterize the morphology of the monocrystal lithium-rich material. The polycrystalline lithium-rich cathode material obtained in comparative example 1, which has no specific crystal structure and is severely agglomerated, has a spherical secondary particle morphology, as shown in fig. 10. The polycrystalline secondary pellet of comparative example 1 had an adverse effect of increasing the inter-granular cracking during long cycles, resulting in poor cycle performance.
The structural characterization, button cell assembly and electrochemical performance test were performed in the same manner as in example 1, and the results are shown in table 3.
TABLE 3 Table 3
As shown in Table 3, the lithium-rich material of comparative example 1 is a polycrystalline cobalt-free lithium-rich material, and charge and discharge cycles are performed between 2.0 and 4.8V at a rate of 0.1C, and it can be seen that the lithium-rich material has a specific first charge capacity of 340.3mAh/g, a specific discharge capacity of 266.74mAh/g, and a first coulomb efficiency of 78.35%, which indicates that the material has poor first charge and discharge properties, and is lower than the single crystal lithium-rich material Li of example 1 of the present invention 1.2 Mn 0.6 Ni 0.2 O 2 The first coulombic efficiency of (2) is 94.83% after 5 cycles, and the specific discharge capacity is obviously reduced after only 5 charge-discharge cycles, while the single crystal lithium-rich material Li of the embodiment 1 of the invention 1.2 Mn 0.6 Ni 0.2 O 2 The discharge capacity retention rate after 5 cycles is 98.55%, and the cycle performance of the single crystal material is obviously better than that of comparative example 1.
The battery system is 1C formed by the polycrystalline cobalt-free lithium-rich material of the comparative example 1The charge-discharge cycle is carried out under the multiplying power, the first charge specific capacity of the lithium-rich material is 221.29mAh/g, the discharge specific capacity is 200.64Ah/g, the first coulomb efficiency is 90.67%, which is lower than that of the single crystal lithium-rich material Li of the embodiment 1 of the invention 1.2 Mn 0.6 Ni 0.2 O 2 While the capacity retention rate was only 83% after 100 cycles of charge and discharge, the specific discharge capacity was greatly reduced, whereas the capacity retention rate of the single crystal lithium-rich material of example 1 of the present invention was 101.37% after 200 cycles, and it can be seen that the capacity retention rate of comparative example 1 was much lower than that of example 1 of the present invention. The material of the invention has excellent cycle performance.
Comparative example 2
Single crystal lithium-rich material Li 1.2 Mn 0.6 Ni 0.2 O 2 The preparation process of (2) is as follows:
step 1. Preparation of precursor
MnSO is carried out 4 ·H 2 0、NiSO 4 ·H 2 0 is dissolved in deionized water to prepare 2mol/L mixed salt solution, wherein Mn in the mixed solution is as follows: ni is in a molar ratio of 3:1, 4mol/L sodium hydroxide solution is taken as a precipitator, 4mol/L ammonia water solution is taken as a buffering agent, the mixed salt solution, the sodium hydroxide solution and the ammonia water solution are pumped into a reaction kettle through a constant flow pump in sequence, high-purity argon is introduced into the reaction kettle, the feeding speed is controlled to be 30-150ml/h, the rotating speed of the reaction kettle is 600r/min, the reaction temperature is 55 ℃ and the pH value is 10.5, and after the coprecipitation is finished, the obtained solid product is washed, filtered and dried by deionized water to obtain a coprecipitation compound Mn 0.75 Ni 0.25 (OH) 2 And (5) standby. And uniformly mixing lithium hydroxide with the coprecipitation compound according to the molar ratio of the lithium to all metal elements of the coprecipitation compound being 0.5:1, so as to obtain a hydroxide precursor of the mixed lithium hydroxide.
Step 2. Preparation of spinel phase intermediate
Placing the precursor obtained in the step 1 in an oxygen atmosphere, then heating from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 3 hours, heating to 750 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 12 hours, and naturally cooling to room temperature to obtain a spinel-phase compound materialMaterial LiMn 1.5 Ni 0.5 O 4 。
Step 3. Preparation of the Material
Uniformly mixing lithium hydroxide and the spinel compound obtained in the step 2 according to the molar ratio of 3.5:1, placing the mixture in an oxygen atmosphere, heating from room temperature to 500 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 3 hours, heating to 850 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 20 hours, and naturally cooling to room temperature to obtain the monocrystal lithium-rich anode material Li 1.2 Mn 0.6 Ni 0.2 O 2 。
And (3) adopting a scanning electron microscope to characterize the morphology of the monocrystal lithium-rich material. As shown in FIG. 11, it can be seen that the particles were similar to example 1 in that they had a regular polyhedral morphology with a particle size of about 1.5 μm, but the surface of the crystal grains was not smooth, a part of the crystal grain structure was severely deformed, and a large amount of impurities were present between the crystal grains.
And analyzing the crystal structure of the single crystal lithium-rich material by adopting a powder X-ray diffractometer. As shown in fig. 12, it can be seen that the diffraction peaks of the lithium-rich single crystal material obtained by the lithium-spinel structure in the molar ratio of 3.5:1 at 18.9 °, 36.7 °, 38.3 °, 44.5 °, 48.8 °, 58.9 ° and high angle positions overlap with the XRD pattern of the lithium-rich single crystal in example 1, which indicates that the main phase is still a layered lithium-rich structure. However, distinct abnormal diffraction peaks can be seen at the 15.9 °, 32.3 ° and 39.8 ° positions, which may be due to second phase products resulting from phase separation caused by excessive lithium incorporation. The above results demonstrate that the lithium dosing amount is increased from 2:1 to 3.5 compared to example 1: 1, although the morphology of the single crystal particles is not affected, the phase of the single crystal particles deviates from the crystal structure of the lithium-rich material in example 1, obvious hetero peaks appear, and the hetero peaks are caused by the fact that the lithium content is too high, so that the lithium diffusion is uneven in the sintering process, and local lithium-poor and lithium-rich areas appear, namely phase separation occurs.
Button cell assembly and electrochemical performance testing were performed in the same manner as in example 1. The results are shown in FIG. 13. The single crystal cobalt-free lithium-rich material of comparative example 2 has a specific capacity for initial charge of only 55.96mAh/g and a specific capacity for discharge of only 14.19mAh/g under a test voltage of 2.0-4.8V, which is far smaller than that of the material obtained by the embodiment of the invention. This further demonstrates that the phenomenon of phase separation caused by excessive lithium incorporation deteriorates electrochemical performance and greatly reduces specific charge and discharge capacity compared to pure-phase lithium-rich materials.
Comparative example 3
Patent CN109537054a discloses a preparation method of a monocrystal lithium-rich manganese-based positive electrode material, which comprises the following specific steps: according to stoichiometric ratio Li 1.2 Mn 0.56 Ni 0.16 Co 0.08 O 2 237 g of manganese sulfate monohydrate, 56.2 g of cobalt sulfate heptahydrate and 105.2 g of nickel sulfate hexahydrate are weighed and added into 1.0 liter of water to prepare a mixed solution; the method comprises the steps of carrying out a first treatment on the surface of the 160 g of sodium hydroxide is added into 1.0 liter of water to obtain a sodium hydroxide mixed solution, then a metal mixed solution, the sodium hydroxide mixed solution and an ammonia water buffer solution with the concentration of 6% (mass fraction) are simultaneously added into a reaction kettle by a constant flow pump, hydrazine hydrate is added to regulate the potential value of the reaction solution to-0.01V, nitrogen is introduced into the reaction kettle for protection, stirring and reacting for 12 hours under the condition that the temperature is 40 ℃ and the pH value is 11.0, then the reaction kettle is filtered, washed and dried for 12 hours at the temperature of 100 ℃ to obtain the manganese-based coprecipitate. And then mixing the obtained manganese-based coprecipitate with ammonium nitrate, ball-milling for 6 hours, washing with deionized water, filtering, and drying for 12 hours at 300 ℃ under the condition of introducing oxygen-containing gas to obtain the composite metal precursor. Finally, weighing lithium hydroxide according to 1.5 times of the sum of the amounts of manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate in the first step, uniformly mixing the lithium hydroxide with the composite metal precursor obtained in the second step to obtain a mixture, heating the mixture to 500 ℃ at a heating rate of 5 ℃/min under an oxygen-containing atmosphere, and preserving heat for 12 hours; and then heating to 900 ℃ at a heating rate of 5 ℃/min, calcining for 24 hours, and naturally cooling to obtain the lithium-rich manganese-based positive electrode material monocrystal.
The morphology of the scanning electron microscope disclosed in CN109537054A is shown in FIG. 14, and it can be seen that the single crystal lithium-rich material prepared by the method is mainly an irregular polyhedron of 0.1-10 μm. Compared with the lithium-rich single crystal material prepared in the embodiment 1 of the application, the lithium-rich single crystal material prepared in the patent CN109537054A based on the coprecipitation method has the characteristics of obvious uneven size distribution and poor dispersibility. In addition, the appearance of the regular octahedron is an irregular polyhedron with poor crystallinity, which is quite different from the regular octahedron and the tetradecedron obtained by the method.
The electrochemical test result of the lithium-rich single crystal material in the patent CN109537054A shows that the first-week discharge capacity is 270mAh/g, and the 200-week circulation capacity retention rate is about 90% at the 1C multiplying power. The lithium-rich single crystal material obtained in the embodiment 2 of the application has a first-week discharge capacity of 284.27mAh/g, and a 200-week cycle capacity retention rate of 99.14% at a 1C rate (as shown in FIG. 9).
In summary, the preparation method provided by the application has obvious advantages, and the obtained lithium-rich single crystal positive electrode material is a regular polyhedron with uniform size distribution and good dispersibility, and has excellent capacity retention rate of the first-week discharge capacity.
Therefore, the preparation method of the monocrystalline lithium-rich material provided by the embodiment of the invention utilizes the unique morphological characteristics and dynamics characteristics of the spinel phase to control and synthesize the monocrystalline lithium-rich material with a specific crystal structure, and utilizes the characteristic that the spinel phase has lower formation energy and therefore the growth dynamics of the spinel oxide is faster than that of the layered oxide, so that the monocrystalline lithium-rich material with proper monocrystalline granularity and a specific crystal structure can be prepared under the condition of not using a morphology control agent and/or a fused salt cosolvent, namely, the invention adopts the compound of the spinel phase as a template, and obtains the monocrystalline lithium-rich material with one or more of octahedron and fourteen-sided structures by a lithium supplementing technology. By adopting the preparation process provided by the invention, crystal particles with good dispersibility can be obtained, and the dispersibility of the single crystal particles is improved, so that the wettability of the material and electrolyte can be effectively improved, and especially the electrochemical performance of the material in the first-week charge-discharge process can be effectively improved. Therefore, the single crystal lithium-rich cathode material prepared by the preparation method can greatly improve the first-week discharge specific capacity, thereby having high first coulomb efficiency. In addition, the improvement of the wettability of the material with the electrolyte can also improve the stability of the material during circulation. The single crystal lithium-rich material can realize charge and discharge under higher voltage, and even if the charge voltage is as high as 4.8V, the single crystal lithium-rich positive electrode material has high specific capacity and excellent cycling stability, and the capacity retention rate is still close to 100% after 200 weeks of cycling.
According to the invention, the lithium supplementing amount of the spinel phase compound is controlled, so that the reaction thermodynamics in the chemical reaction process can be effectively changed, namely, the effective conversion of the spinel phase compound to the monocrystal lithium-rich positive electrode structure is controlled, and the morphology of the finally synthesized monocrystal lithium-rich positive electrode material is effectively controlled, so that the octahedral monocrystal lithium-rich material with {111} crystal face exposure surfaces or the fourteen-plane monocrystal lithium-rich material with {111} and {001} crystal face exposure surfaces is obtained. Therefore, the single crystal lithium-rich material can still realize excellent rate performance even on the basis of no cobalt element. Therefore, the cobalt-free monocrystal lithium-rich material can not only greatly reduce the material cost, but also realize excellent multiplying power performance and cycle performance.
The preparation method is simple in preparation process, does not need to additionally use morphology control agents and molten salt cosolvent, does not generate a large amount of industrial wastewater, is more green and environment-friendly, and is suitable for large-scale production. The cobalt-free monocrystal lithium-rich material has good morphology consistency, uniform grain size distribution of monocrystal grains, can effectively overcome the problems of low first coulomb efficiency, poor multiplying power performance, poor structural stability, quick capacity attenuation and the like of the existing lithium-rich cathode material under high voltage, and can obviously improve the first coulomb efficiency, the multiplying power performance and the circulation stability so as to obtain excellent capacity retention rate.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the invention, and is not meant to limit the scope of the invention, but to limit the invention to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (10)
1. A preparation method of a monocrystal lithium-rich material is characterized in that the chemical general formula of the monocrystal lithium-rich material is Li 1+ x Mn y M 1-x-y O 2-f T f Wherein x is more than 0 and less than or equal to 0.5, y is more than 0 and less than or equal to 1-x, and f is more than 0 and less than or equal to 2; m includes one or more of Mn, ni, co, al, fe, ru, nb, cr, ti, ir, V, ca, sc, cu, zn, sr, Y, zr, ta, la, ce, pr, nd, W, mo; t includes one or more of F, S, P, N; the crystallographic morphology of the single crystal lithium-rich material comprises one or more of octahedra and tetratetrahedra; the preparation method of the monocrystal lithium-rich material comprises the following steps:
preparing a spinel phase compound; the chemical general formula of the spinel phase compound is LiMn 2-a M a O 4-b T b ，0≤a＜2，0≤b＜4；
Mixing the spinel phase compound with a lithium-containing compound to obtain a mixture, and then placing the mixture in an oxidizing atmosphere for high-temperature calcination to obtain single crystal lithium-rich material particles with {111} or {111} and {001} crystal faces exposed; wherein the molar ratio of lithium in the lithium-containing compound to the spinel phase compound is 0.2:1-3:1, the high-temperature calcination temperature range is 300-1000 ℃, and the calcination heat preservation time is 6-24h.
2. The method of claim 1, wherein the single crystal lithium-rich material has a single crystal grain size of 0.3-5 μm; optionally, the crystallographic morphology of the single-crystal lithium-rich material further comprises one or more of tetrahedra and hexahedron.
3. The method of any one of claims 1-2, wherein the method further comprises: the monocrystalline particles of the monocrystalline lithium-rich material are surface-modified to produce spinel and/or disordered rock salt coatings, preferably by gas-solid treatment or acid treatment to produce spinel coatings on the surfaces of the monocrystalline particles.
4. A process according to claim 3, wherein,
generating spinel coating layers on the surfaces of the single crystal particles by adopting a gas-solid treatment method comprises the following steps: placing a single crystal lithium-rich material and a first substance which generates reducing gas through thermal decomposition in a closed container, heating to a temperature higher than the thermal decomposition temperature of the first substance under inert atmosphere to obtain the single crystal lithium-rich material with a spinel coating layer constructed on the surface of the material in situ, wherein the first substance preferably comprises one or more compounds of an ammonia compound, an oxalate compound and a carbonic acid compound;
The generation of the spinel coating layer on the surface of the single crystal particle by adopting an acid treatment method comprises the following steps: treating the monocrystal lithium-rich material by using an acidic reagent to obtain the monocrystal lithium-rich material with the spinel coating constructed on the surface of the material in situ; preferably, the acidic reagent comprises one or more of sulfuric acid, hydrochloric acid, hydrofluoric acid, nitric acid, phosphoric acid, fatty acid and acidic salt solution, and the specific method of the acid treatment process comprises one or more of a dipping process, a spraying process and a coating process; particularly preferred, the method further comprises: and calcining the monocrystalline lithium-rich material with the spinel coating layer constructed on the surface of the obtained material for 3-10h at 300-600 ℃.
5. The method according to any one of claims 1 to 4, wherein preparing the spinel phase compound comprises:
preparing a precursor material, wherein the precursor material comprises a lithium source and a metal source, and the molar ratio of lithium element in the lithium source to metal element in the metal source is (0-1): 1, preferably (0.3-0.6): 1, a step of; the metal source comprises a Mn source or comprises a Mn source and an M source;
sintering the precursor material in an oxidizing atmosphere to obtain the spinel phase compound; wherein the sintering temperature is 300-1000 ℃ and the heat preservation time is 3-48h; preferably, the sintering is specifically: raising the temperature from room temperature to 300-600 ℃ at a heating rate of 3-10 ℃/min, keeping the temperature for 3-10 hours, raising the temperature to 700-1000 ℃ at a heating rate of 3-10 ℃/min, and keeping the temperature for 10-38 hours;
Preferably, the precursor material is prepared by a coprecipitation method, a solid phase ball milling method or a sol-gel method;
the coprecipitation method concrete packageThe method comprises the following steps: according to the chemical formula Mn 1-c M c Preparing a metal mixed salt solution of Mn and M with the stoichiometric ratio of Q of 0.1-4mol/L, and simultaneously preparing a precipitator solution and a complexing agent solution with the stoichiometric ratio of Q of 0.2-6mol/L respectively; the Mn of 1-c M c In Q, c is more than or equal to 0 and less than 1, and Q is one or more of acid radical ions or hydroxyl radicals; pumping the metal mixed salt solution into a reaction container, and simultaneously adding the precipitant solution and the complexing agent solution to obtain mixed particles; aging, washing and drying the obtained mixed particles to obtain a coprecipitated compound, and then mixing a lithium-containing compound with the coprecipitated compound according to a molar ratio of lithium to metal elements of (0-1): 1, preferably (0.3-0.6): 1, uniformly mixing to obtain a precursor material; preferably, the precipitants in the precipitant solution include one or more of carbonate, bicarbonate, hydroxide, thiocyanide, ammonium salt, oxalate; more preferably, one or more of sodium carbonate, sodium bicarbonate, ammonium carbonate, lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium oxalate, potassium thiocyanate; preferably, the complexing agent in the complexing agent solution comprises one or more of ammonia water, acetic acid, oxalic acid, succinic acid, ethylenediamine tetraacetic acid, lactic acid, citric acid, salicylic acid, sulfosalicylic acid, tartaric acid and glycine; preferably, the particle size of the mixed particles is controlled by the reaction temperature, the feeding speed, the pH value in the reaction vessel and the rotating speed; preferably, the feeding speed is 30-150ml/h, the reaction temperature is 40-60 ℃, the pH is 7-12, the rotating speed is 300-600r/min, and the aging time is 12-24h. Preferably, the particle size of the particles is 0.3-15 μm; particularly preferably, the particle size of the particles is from 0.3 to 5. Mu.m;
The solid-phase ball milling method specifically comprises the following steps: according to the general chemical formula LiMn d-e M e O 4-b T b The stoichiometric ratio of Li, mn and M metal compounds are uniformly mixed by a high-energy ball mill to obtain a precursor material, the LiMn d-e M e O 4-b T b Wherein e is more than or equal to 0 and less than d, b is more than or equal to 0 and less than 4, and 0 is more than or equal to 1/d is less than 1;
the sol-gel method specifically comprises the following steps: according to the general chemical formula LiMn d-e M e O 4-b T b Dissolving metal salts containing Li, mn and M in deionized water, then dropwise adding a mixed aqueous solution containing a chelating agent and a dispersing agent, continuously stirring, then dropwise adding a pH regulator to adjust the pH to be 6-8, keeping the constant temperature of 80-120 ℃ after the pH is stable, continuously stirring until transparent gel is generated, and drying and grinding to obtain a precursor material; the LiMn d-e M e O 4-b T b Wherein e is more than or equal to 0 and less than d, b is more than or equal to 0 and less than 4, and 0 is more than or equal to 1/d is less than 1; the chelating agent comprises one or more of inorganic chelating agent and organic chelating agent, preferably comprises one or more of phosphate, aminocarboxylic acid, organic phosphoric acid type, carboxyl carboxylic acid and amine compound;
the lithium source comprises one or more of an inorganic lithium compound and an organic lithium compound, preferably comprises one or more of lithium oxide, lithium chloride, lithium fluoride, lithium carbonate, lithium hydroxide, lithium nitrate, lithium phosphate, lithium supplementing agent, butyl lithium, phenyl lithium, lithium tert-butoxide, lithium diisopropylamide, and lithium hexamethyldisilazide;
The metal source comprises one or more of an inorganic metal compound and an organic metal compound, preferably comprises one or more of an oxide, a carbonate, a nitrate, an oxalate, a sulfate, an alkyl-based organic metal compound.
6. The method according to any one of claims 1 to 5, wherein the molar ratio of lithium in the lithium-containing compound to spinel phase compound is (1.5 to 2.8): 1;
the high-temperature calcination is stepwise calcination, and specifically comprises the following steps: raising the temperature from room temperature to 300-600 ℃ at a heating rate of 3-10 ℃/min, keeping the temperature for 3-10 hours, raising the temperature to 700-1000 ℃ at a heating rate of 3-10 ℃/min, and keeping the temperature for 10-20 hours.
7. A single crystal lithium-rich material obtained by the preparation method according to any one of claims 1 to 6, wherein the single crystal lithium-rich material has a chemical formula of Li 1+x Mn y M 1-x-y O 2-f T f Wherein x is more than 0 and less than or equal to 0.5, and y is more than 0 and less than or equal to 01-x, f is more than or equal to 0 and less than 2; m includes one or more of Mn, ni, co, al, fe, ru, nb, cr, ti, ir, V, ca, sc, cu, zn, sr, Y, zr, ta, la, ce, pr, nd, W, mo; t includes one or more of F, S, P, N; the crystallographic morphology of the single crystal lithium-rich material comprises one or more of octahedra and tetratetrahedra; optionally, the crystallographic morphology of the single-crystal lithium-rich material further comprises one or more of tetrahedra and hexahedron.
8. The single crystal lithium-rich material of claim 7, wherein a diffraction peak of a crystal structure of the single crystal lithium-rich material comprises: layered alpha-NaFeO with R-3m space group 2 Hexagonal LiMO of structure 2 Phase, monoclinic Li with C2/m space group 2 MnO 3 A phase; TMO with lithium-rich layered oxide as crystal structure 2 The presence of part of LiMn in the layer 6 Cation arrangement; preferably, the surface of the single crystal lithium-rich material is provided with a spinel and/or disordered rock salt phase coating layer; more preferably, the spinel in-situ coating layer has a thickness of 1-500nm.
9. The single crystal lithium-rich material according to any one of claims 7-8, wherein the single crystal particles of the single crystal lithium-rich material have a particle size of 0.3-5 μm, preferably the single crystal lithium-rich material is a cobalt-free single crystal lithium-rich cathode material Li 1+ x Mn m Ni q M1 1-x-m-q O 2-f T f Wherein x is more than 0 and less than or equal to 0.5, m is more than 0 and less than or equal to 1-x, q is more than or equal to 0 and less than or equal to 1-x, and f is more than or equal to 0 and less than or equal to 2; preferably, 0.1 < x.ltoreq.0.3, 0 < m.ltoreq.0.8, 0.ltoreq.q.ltoreq.0.8, where M1 is one or more of Al, fe, nb, cr, ti, V, ca, sc, cu, zn, sr, Y, Y, zr, ta, la, W, mo.
10. An energy storage device, comprising a lithium battery, a lithium battery pack or a lithium battery module, wherein the energy storage device comprises a positive electrode material comprising the single crystal lithium-rich material obtained by the preparation method according to any one of claims 1 to 6 or the single crystal lithium-rich material according to any one of claims 7 to 9.
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