CN117317190A - 一种钽酸锂包覆的磷酸锰铁锂正极材料及其制备方法 - Google Patents
一种钽酸锂包覆的磷酸锰铁锂正极材料及其制备方法 Download PDFInfo
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- CN117317190A CN117317190A CN202311443205.2A CN202311443205A CN117317190A CN 117317190 A CN117317190 A CN 117317190A CN 202311443205 A CN202311443205 A CN 202311443205A CN 117317190 A CN117317190 A CN 117317190A
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- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 title claims abstract description 85
- WSMQKESQZFQMFW-UHFFFAOYSA-N 5-methyl-pyrazole-3-carboxylic acid Chemical compound CC1=CC(C(O)=O)=NN1 WSMQKESQZFQMFW-UHFFFAOYSA-N 0.000 title claims abstract description 68
- 239000007774 positive electrode material Substances 0.000 title claims abstract description 26
- 238000002360 preparation method Methods 0.000 title abstract description 10
- 239000000463 material Substances 0.000 claims abstract description 39
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 24
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 17
- 239000011572 manganese Substances 0.000 claims abstract description 15
- 238000000034 method Methods 0.000 claims abstract description 13
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 9
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910000616 Ferromanganese Inorganic materials 0.000 claims abstract description 5
- 238000005336 cracking Methods 0.000 claims abstract description 5
- DALUDRGQOYMVLD-UHFFFAOYSA-N iron manganese Chemical compound [Mn].[Fe] DALUDRGQOYMVLD-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910019142 PO4 Inorganic materials 0.000 claims abstract description 4
- 239000010452 phosphate Substances 0.000 claims abstract description 4
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims abstract description 4
- 238000000498 ball milling Methods 0.000 claims description 32
- 238000005245 sintering Methods 0.000 claims description 23
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 19
- 239000000203 mixture Substances 0.000 claims description 19
- 239000002243 precursor Substances 0.000 claims description 14
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 10
- 229910052748 manganese Inorganic materials 0.000 claims description 10
- 229910052742 iron Inorganic materials 0.000 claims description 9
- 238000001354 calcination Methods 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 8
- 238000007792 addition Methods 0.000 claims description 7
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 claims description 7
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 claims description 7
- 229940062993 ferrous oxalate Drugs 0.000 claims description 7
- 238000000227 grinding Methods 0.000 claims description 7
- OWZIYWAUNZMLRT-UHFFFAOYSA-L iron(2+);oxalate Chemical compound [Fe+2].[O-]C(=O)C([O-])=O OWZIYWAUNZMLRT-UHFFFAOYSA-L 0.000 claims description 7
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 7
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 7
- 235000006748 manganese carbonate Nutrition 0.000 claims description 7
- 239000011656 manganese carbonate Substances 0.000 claims description 7
- 229940093474 manganese carbonate Drugs 0.000 claims description 7
- 229910000016 manganese(II) carbonate Inorganic materials 0.000 claims description 7
- XMWCXZJXESXBBY-UHFFFAOYSA-L manganese(ii) carbonate Chemical compound [Mn+2].[O-]C([O-])=O XMWCXZJXESXBBY-UHFFFAOYSA-L 0.000 claims description 7
- 235000019837 monoammonium phosphate Nutrition 0.000 claims description 7
- 239000006012 monoammonium phosphate Substances 0.000 claims description 7
- 238000012216 screening Methods 0.000 claims description 7
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 6
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 claims description 5
- 229930006000 Sucrose Natural products 0.000 claims description 5
- 239000005720 sucrose Substances 0.000 claims description 5
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 4
- 239000010405 anode material Substances 0.000 claims description 4
- 239000011261 inert gas Substances 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 4
- 229910052698 phosphorus Inorganic materials 0.000 claims description 4
- 239000011574 phosphorus Substances 0.000 claims description 4
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 claims description 3
- 239000008103 glucose Substances 0.000 claims description 3
- 239000005696 Diammonium phosphate Substances 0.000 claims description 2
- 239000004277 Ferrous carbonate Substances 0.000 claims description 2
- MCDLETWIOVSGJT-UHFFFAOYSA-N acetic acid;iron Chemical compound [Fe].CC(O)=O.CC(O)=O MCDLETWIOVSGJT-UHFFFAOYSA-N 0.000 claims description 2
- WQZGKKKJIJFFOK-VFUOTHLCSA-N beta-D-glucose Chemical compound OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-VFUOTHLCSA-N 0.000 claims description 2
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 claims description 2
- 229910000388 diammonium phosphate Inorganic materials 0.000 claims description 2
- 235000019838 diammonium phosphate Nutrition 0.000 claims description 2
- 235000019268 ferrous carbonate Nutrition 0.000 claims description 2
- RAQDACVRFCEPDA-UHFFFAOYSA-L ferrous carbonate Chemical compound [Fe+2].[O-]C([O-])=O RAQDACVRFCEPDA-UHFFFAOYSA-L 0.000 claims description 2
- 229960004652 ferrous carbonate Drugs 0.000 claims description 2
- 229910000015 iron(II) carbonate Inorganic materials 0.000 claims description 2
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 claims description 2
- 229940099596 manganese sulfate Drugs 0.000 claims description 2
- 235000007079 manganese sulphate Nutrition 0.000 claims description 2
- 239000011702 manganese sulphate Substances 0.000 claims description 2
- RGVLTEMOWXGQOS-UHFFFAOYSA-L manganese(2+);oxalate Chemical compound [Mn+2].[O-]C(=O)C([O-])=O RGVLTEMOWXGQOS-UHFFFAOYSA-L 0.000 claims description 2
- SQQMAOCOWKFBNP-UHFFFAOYSA-L manganese(II) sulfate Chemical compound [Mn+2].[O-]S([O-])(=O)=O SQQMAOCOWKFBNP-UHFFFAOYSA-L 0.000 claims description 2
- 239000011248 coating agent Substances 0.000 abstract description 14
- 238000000576 coating method Methods 0.000 abstract description 14
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 9
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 9
- 238000009792 diffusion process Methods 0.000 abstract description 5
- 150000002500 ions Chemical class 0.000 abstract description 5
- 238000009831 deintercalation Methods 0.000 abstract description 4
- 230000000052 comparative effect Effects 0.000 description 25
- 239000008367 deionised water Substances 0.000 description 5
- 229910021641 deionized water Inorganic materials 0.000 description 5
- 235000019441 ethanol Nutrition 0.000 description 5
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 239000013078 crystal Substances 0.000 description 4
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 230000014759 maintenance of location Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000004146 energy storage Methods 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 239000010416 ion conductor Substances 0.000 description 2
- YQNQTEBHHUSESQ-UHFFFAOYSA-N lithium aluminate Chemical compound [Li+].[O-][Al]=O YQNQTEBHHUSESQ-UHFFFAOYSA-N 0.000 description 2
- MNKMDLVKGZBOEW-UHFFFAOYSA-M lithium;3,4,5-trihydroxybenzoate Chemical compound [Li+].OC1=CC(C([O-])=O)=CC(O)=C1O MNKMDLVKGZBOEW-UHFFFAOYSA-M 0.000 description 2
- 239000010450 olivine Substances 0.000 description 2
- 229910052609 olivine Inorganic materials 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 230000005536 Jahn Teller effect Effects 0.000 description 1
- 229910010710 LiFePO Inorganic materials 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000012983 electrochemical energy storage Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000037427 ion transport Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000010534 mechanism of action Effects 0.000 description 1
- 238000007709 nanocrystallization Methods 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000012798 spherical particle Substances 0.000 description 1
- 239000011232 storage material Substances 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
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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
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/45—Phosphates containing plural metal, or metal and ammonium
-
- 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
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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Abstract
本发明公开了一种钽酸锂包覆的磷酸锰铁锂正极材料及其制备方法,钽酸锂包覆的磷酸锰铁锂材料的结构式为LixMnyFe1‑yPO4·zLiTaO3/C,其中0.95≤x≤1.05,0≤y≤0.8,0<z≤0.1,C为包覆在磷酸锰铁锂表面的裂解碳。本发明通过在磷酸锰铁锂外层包覆钽酸锂,为锂离子的脱嵌提供快速通道,提高材料的锂离子扩散速率。该方法能够提高正极材料的离子电导率,改善磷酸锰铁锂的克容量、倍率性能以及循环性能。
Description
技术领域
本发明属于电池技术领域,涉及磷酸锰铁锂正极材料,尤其涉及一种钽酸锂包覆的磷酸锰铁锂正极材料及其制备方法。
背景技术
在过去几十年里,锂离子电池实现了电子设备的便携化,奠定了消费电子、电化学储能和新能源汽车产业的基础。其中磷酸铁锂(LiFePO4)因价格低、安全性高、循环稳定性好而备受关注,但其较低的能量密度限制了在储能、新能源电动车上的应用。通过向磷酸铁锂材料掺入适量的锰,合成磷酸锰铁锂(LiMnxFe1-xPO4)固溶体材料,能够有效提高材料的能量密度,使磷酸锰铁锂成为兼顾高能量密度和高安全性的优异储能材料。
然而,磷酸锰铁锂的Jahn-Teller效应会导致晶体产生形变,电子传输的阻力增大,所以其电子电导率相较于磷酸铁锂更低(约10-13S/cm),此外磷酸锰铁锂晶格内部较大的阻力使得其离子电导率极低(约10-13S/cm,比磷酸铁锂低3-4个数量级)。为了解决上述问题,行业内主要采取纳米化、表面包覆和离子掺杂这几项举措。
其中,表面碳包覆是成本最低、效果最明显的改进方法。碳包覆能通过构建导电网络有效提升材料导电性能和循环性能,还可以有效阻止磷酸锰铁锂颗粒进一步长大以及阻止电解液中HF对其侵蚀作用。但是该方法仍存在离子导电性较差的问题,导致材料充放电循环动力学差。因此,需要开发出一种磷酸锰铁锂与高离子电导率导体复合的方法来解决上述问题。
发明内容
为了解决上述问题,本发明提供了一种钽酸锂包覆的磷酸锰铁锂正极材料及其制备方法,本发明以钽酸锂材料作为离子导体,当钽酸锂包覆在磷酸锰铁锂表面时,钽酸锂为磷酸锰铁锂提供了Li+快速脱嵌的通道,可以显著改善磷酸锰铁锂的充放电倍率性能。
为了实现上述目的,本发明采用以下技术方案:
一种钽酸锂包覆的磷酸锰铁锂正极材料,所述钽酸锂包覆的磷酸锰铁锂材料的结构式为LixMnyFe1-yPO4·zLiTaO3/C,其中0.95≤x≤1.05,0≤y≤0.8,0<z≤0.1,C为包覆在磷酸锰铁锂表面的裂解碳。
作为本发明的一种优选方案,所述裂解碳占钽酸锂包覆的磷酸锰铁锂材料质量的1-15%。
本发明还提供了上述的钽酸锂包覆的磷酸锰铁锂正极材料的制备方法,所述制备方法包括以下步骤:
1)根据材料结构式中Li:Mn:Fe:P=x:y:1-y:1的摩尔比将锂源、锰源、铁源、磷源进行球磨混合均匀,得到第一混合物;
2)将步骤1)得到的第一混合物烘干,烘干后在惰性气体氛围中煅烧,烧结后得到磷酸锰铁锂烧结前驱体;
3)向步骤2)得到的磷酸锰铁锂烧结前驱体加入碳源,根据P:Ta=1:z的摩尔比加入钽酸锂,继续球磨混合均匀,得到第二混合物;
4)将步骤3)得到的第二混合物烘干,烘干后在惰性气体氛围中煅烧,烧结后,经过碾磨筛分后得到钽酸锂包覆的磷酸锰铁锂正极材料。
作为本发明的一种优选方案,步骤1)中,0.95≤x≤1.05,0≤y≤0.8。
作为本发明的一种优选方案,步骤1)中,锂源包括碳酸锂、醋酸锂或氢氧化锂中的一种或多种;锰源包括碳酸锰、草酸锰或硫酸锰中的一种或多种;铁源包括草酸亚铁、醋酸亚铁或碳酸亚铁中的一种或多种、磷源包括磷酸二氢铵或磷酸氢二铵中的一种或多种。
作为本发明的一种优选方案,步骤1)中,球磨是在无水乙醇的球磨罐中进行,球磨时间为2-10h。
作为本发明的一种优选方案,步骤2)中,煅烧温度为200-500℃,烧结时间为2-6h。
作为本发明的一种优选方案,步骤3)中,0<z≤0.1;球磨是在无水乙醇的球磨罐中进行,球磨时间为2-10h。
作为本发明的一种优选方案,碳源的加入量为钽酸锂包覆的磷酸锰铁锂正极材料总质量的5-30%;碳源包括葡萄糖、蔗糖或柠檬酸中的一种或多种。
作为本发明的一种优选方案,步骤4)中,煅烧温度为650-800℃,烧结时间为4-15h。
与现有技术相比,本发明具有以下有益效果:
1)本发明中选择的钽酸锂离子电导率为2×10-8S/cm,远优于磷酸锰铁锂。与铝酸锂、镓酸锂相比,钽酸锂拥有更高的锂离子扩散速率,接近铌酸锂。但是铌酸锂的极化比钽酸锂更大,因此选择钽酸锂为包覆材料。
2)本发明通过包覆少量的钽酸锂可以弥补磷酸锰铁锂离子电导率低的缺陷。同时,从XRD以及SEM图中可看出包覆少量的钽酸锂,不会对磷酸锰铁锂的橄榄石晶体结构和形貌产生影响。
3)本发明通过在磷酸锰铁锂外层包覆钽酸锂,为锂离子的脱嵌提供快速通道,提高材料的锂离子扩散速率。该方法能够提高正极材料的离子电导率,改善磷酸锰铁锂的克容量、倍率性能以及循环性能。
附图说明
附图1磷酸锰铁锂材料包覆示意图。
附图2钽酸锂包覆的作用机理。
附图3实施例1-3以及对比例1-2磷酸锰铁锂材料的XRD图。
附图4实施例1-3以及对比例1-2磷酸锰铁锂材料的SEM图。
附图5实施例1和对比例1磷酸锰铁锂材料扣电的0.2C充放电曲线。
附图6实施例1和对比例1磷酸锰铁锂材料扣电的倍率性能。
附图7实施例1和对比例1磷酸锰铁锂材料扣电的0.5C循环性能。
具体实施方式
为了使本发明实现的技术手段、创作特征、达成目的与功效易于理解,下面结合具体实施例,进一步阐述本发明,但下述实施例仅仅为本发明的优选实施例,并非全部。基于实施方式中的实施例,本领域技术人员在没有做出创造性劳动的前提下所获得其它实施例,都属于本发明的保护范围。下述实施例中的实验方法,如无特殊说明,均为常规方法,下述实施例中所用的材料、试剂等,如无特殊说明,均可从商业途径得到。
钽酸锂在25℃下的离子电导率达到2×10-8S/cm(The Journal of PhysicalChemistry C,2013,117(39):20260-20267),而离子电导率比磷酸锰铁锂更好的磷酸铁锂也仅有10-17-10-12S/cm。与铝酸锂、镓酸锂相比,钽酸锂拥有更高的锂离子扩散速率,接近铌酸锂。但是铌酸锂的极化比钽酸锂更大。
为了改善磷酸锰铁锂的离子电导率,本发明以钽酸锂材料作为离子导体,提供了一种钽酸锂包覆的磷酸锰铁锂正极材料的制备方法。如图1所示,碳材料与钽酸锂共同包覆在磷酸锰铁锂的表面。图2是钽酸锂的作用机理示意图,当钽酸锂包覆在磷酸锰铁锂表面时,钽酸锂为磷酸锰铁锂提供了Li+快速脱嵌的通道,可以显著改善磷酸锰铁锂的充放电倍率性能。
实施例1
本实施例提供了钽酸锂包覆的磷酸锰铁锂正极材料的制备方法,包括:
首先,向球磨罐中分别加入2.9544g碳酸锂、5.5176g碳酸锰、5.7556g草酸亚铁、9.2024g磷酸二氢铵,22mL乙醇,球磨6h混合均匀,接着将混合物放入管式炉中,400℃预烧结4h,得到磷酸锰铁锂烧结前驱体。再将磷酸锰铁锂前驱体和0.3775g钽酸锂、3.2802g蔗糖加入到装有22mL去离子水的球磨罐中,球磨6h混合均匀。最后将混合物放入管式炉中,680℃烧结10h,经过碾磨筛分后得到钽酸锂包覆的磷酸锰铁锂材料。其中锰和铁的摩尔比为6:4。
实施例2(改变碳源)
本实施例提供了钽酸锂包覆的磷酸锰铁锂正极材料的制备方法,包括:
首先,向球磨罐中分别加入2.9544g碳酸锂、5.5176g碳酸锰、5.7556g草酸亚铁、9.2024g磷酸二氢铵,22mL乙醇,球磨6h混合均匀,接着将混合物放入管式炉中,400℃预烧结4h,得到磷酸锰铁锂烧结前驱体。再将磷酸锰铁锂前驱体和0.3775g钽酸锂、3.2802g葡萄糖加入到装有22mL去离子水的球磨罐中,球磨6h混合均匀。最后将混合物放入管式炉中,680℃烧结10h,经过碾磨筛分后得到钽酸锂包覆的磷酸锰铁锂材料。其中锰和铁的摩尔比为6:4。
实施例3(改变锰铁比和烧结参数)
本实施例提供了钽酸锂包覆的磷酸锰铁锂正极材料的制备方法,包括:
首先,向球磨罐中分别加入2.9544g碳酸锂、4.5980g碳酸锰、7.1945g草酸亚铁、9.2024g磷酸二氢铵,22mL乙醇,球磨6h混合均匀,接着将混合物放入管式炉中,300℃预烧结6h,得到磷酸锰铁锂烧结前驱体。再将磷酸锰铁锂前驱体和0.3775g钽酸锂、3.2802g蔗糖加入到装有22mL去离子水的球磨罐中,球磨6h混合均匀。最后将混合物放入管式炉中,720℃烧结8h,经过碾磨筛分后得到钽酸锂包覆的磷酸锰铁锂材料。其中锰和铁的摩尔比为5:5。
对比例1(不加入钽酸锂)
首先,向球磨罐中分别加入2.9544g碳酸锂、5.5176g碳酸锰、5.7556g草酸亚铁、9.2024g磷酸二氢铵,22mL乙醇,球磨6h混合均匀,接着将混合物放入管式炉中,400℃预烧结4h,得到磷酸锰铁锂烧结前驱体。再将磷酸锰铁锂前驱体和3.2802g蔗糖加入到装有22mL去离子水的球磨罐中,球磨6h混合均匀。最后将混合物放入管式炉中,680℃烧结10h,经过碾磨筛分后得到钽酸锂包覆的磷酸锰铁锂材料。其中锰和铁的摩尔比为6:4。
对比例2(不加入钽酸锂和碳源)
首先,向球磨罐中分别加入2.9544g碳酸锂、5.5176g碳酸锰、5.7556g草酸亚铁、9.2024g磷酸二氢铵,22mL乙醇,球磨6h混合均匀,接着将混合物放入管式炉中,400℃预烧结4h,得到磷酸锰铁锂烧结前驱体。再将磷酸锰铁锂前驱体加入到装有22mL去离子水的球磨罐中,球磨6h混合均匀。最后将混合物放入管式炉中,680℃烧结10h,经过碾磨筛分后得到钽酸锂包覆的磷酸锰铁锂材料。其中锰和铁的摩尔比为6:4。
首先对实施例1-3和对比例1-2合成的磷酸锰铁锂材料进行X射线衍射(XRD)表征。测试结果如图3所示,可以发现添加钽酸锂的实施例1-3材料特征峰与对比例1-2未添加钽酸锂的材料特征峰一致,没有出现杂质峰,表明添加少量的钽酸锂不会对磷酸锰铁锂的橄榄石结构产生影响。
接着对实施例1-3和对比例1-2合成的材料进行扫描电镜(SEM)测试,观察磷酸锰铁锂晶体颗粒大小和形貌。结果如图4所示,实施例1-3与对比例1的磷酸锰铁锂材料均为粒径8μm左右球形颗粒,表明加入钽酸锂进行包覆不会对磷酸锰铁锂晶体大小和形貌产生明显影响。而对比例2材料并未加入碳源以限制晶粒生长,所以粒径偏大,在12μm左右。
随后,将实施例1-3和对比例1-2的磷酸锰铁锂材料与SP炭黑、PVDF按照8∶1∶1的质量比加入到NMP中。再用球磨机将浆料球磨至合适的粘度和细度,并均匀涂覆在铝箔上,放入烘箱真空烘干,以获得正极极片。最后将正极极片、金属锂负极极片、隔膜、电解液组装成纽扣电池,进行电化学性能测试。其在不同倍率下的放电比容量结果如表1所示。
表1实施例1-3和对比例1-2扣电比容量
0.2C比容量(mAh/g) | 1C比容量(mAh/g) | |
实施例1 | 152.1 | 136.3 |
实施例2 | 151.9 | 136.4 |
实施例3 | 151.6 | 135.9 |
对比例1 | 144.3 | 125.5 |
对比例2 | 103.6 | 84.5 |
从表1可以看出,采用钽酸锂包覆后,实施例1-3的不同倍率比容量均明显优于对比例1-2。对比例2因未加入碳源,故其电子电导率比对比例1更低,因此比容量出现明显下降。实施例1与对比例1的0.2C充放电曲线如图5所示,可以看出实施例1比容量高于对比例1,拥有更高的放电容量。上述结果表明通过包覆钽酸锂来提供锂离子传输通道,能显著提高材料的锂离子扩散速率,从而改善磷酸锰铁锂的离子导电性。从图6倍率性能测试中可以看出,包覆钽酸锂的实施例1材料在不同倍率下的放电比容量均优于对比例1材料,倍率性能更好。实施例1和对比例1两组材料的扣电0.5C室温循环测试结果如图7所示,可以看出随着循环次数的增加,对比例1扣电容量保持率下降趋势加快。在400周时,实施例1保持率为94.7%,而对比例1保持率仅为89.6%,说明钽酸锂包覆能够有效提升磷酸锰铁锂材料的循环性能。
以上所述,仅为本发明的较佳实施例,并非对本发明任何形式上和实质上的限制,应当指出,对于本技术领域的普通技术人员,在不脱离本发明方法的前提下,还将可以做出若干改进和补充,这些改进和补充也应视为本发明的保护范围。凡熟悉本专业的技术人员,在不脱离本发明的精神和范围的情况下,当可利用以上所揭示的技术内容而做出的些许更动、修饰与演变的等同变化,均为本发明的等效实施例;同时,凡依据本发明的实质技术对上述实施例所作的任何等同变化的更动、修饰与演变,均仍属于本发明的技术方案的范围内。
Claims (10)
1.一种钽酸锂包覆的磷酸锰铁锂正极材料,其特征在于,所述钽酸锂包覆的磷酸锰铁锂材料的结构式为LixMnyFe1-yPO4·zLiTaO3/C,其中0.95≤x≤1.05,0≤y≤0.8,0<z≤0.1,C为包覆在磷酸锰铁锂表面的裂解碳。
2.根据权利要求1所述的一种钽酸锂包覆的磷酸锰铁锂正极材料,其特征在于,所述裂解碳占钽酸锂包覆的磷酸锰铁锂材料质量的1-15%。
3.一种如权利要求1所述的钽酸锂包覆的磷酸锰铁锂正极材料的制备方法,其特征在于,所述制备方法包括以下步骤:
1)根据材料结构式中Li:Mn:Fe:P=x:y:1-y:1的摩尔比将锂源、锰源、铁源、磷源进行球磨混合均匀,得到第一混合物;
2)将步骤1)得到的第一混合物烘干,烘干后在惰性气体氛围中煅烧,烧结后得到磷酸锰铁锂烧结前驱体;
3)向步骤2)得到的磷酸锰铁锂烧结前驱体加入碳源,根据P:Ta=1:z的摩尔比加入钽酸锂,继续球磨混合均匀,得到第二混合物;
4)将步骤3)得到的第二混合物烘干,烘干后在惰性气体氛围中煅烧,烧结后,经过碾磨筛分后得到钽酸锂包覆的磷酸锰铁锂正极材料。
4.根据权利要求3所述的钽酸锂包覆的磷酸锰铁锂正极材料的制备方法,其特征在于,步骤1)中,0.95≤x≤1.05,0≤y≤0.8。
5.根据权利要求3所述的钽酸锂包覆的磷酸锰铁锂正极材料的制备方法,其特征在于,步骤1)中,锂源包括碳酸锂、醋酸锂或氢氧化锂中的一种或多种;锰源包括碳酸锰、草酸锰或硫酸锰中的一种或多种;铁源包括草酸亚铁、醋酸亚铁或碳酸亚铁中的一种或多种、磷源包括磷酸二氢铵或磷酸氢二铵中的一种或多种。
6.根据权利要求3所述的钽酸锂包覆的磷酸锰铁锂正极材料的制备方法,其特征在于,步骤1)中,球磨是在无水乙醇的球磨罐中进行,球磨时间为2-10h。
7.根据权利要求3所述的钽酸锂包覆的磷酸锰铁锂正极材料的制备方法,其特征在于,步骤2)中,煅烧温度为200-500℃,烧结时间为2-6h。
8.根据权利要求3所述的钽酸锂包覆的磷酸锰铁锂正极材料的制备方法,其特征在于,步骤3)中,0<z≤0.1;球磨是在无水乙醇的球磨罐中进行,球磨时间为2-10h。
9.根据权利要求3所述的钽酸锂包覆的磷酸锰铁锂正极材料的制备方法,其特征在于,碳源的加入量为钽酸锂包覆的磷酸锰铁锂正极材料总质量的5-30%;碳源包括葡萄糖、蔗糖或柠檬酸中的一种或多种。
10.根据权利要求3所述的钽酸锂包覆的磷酸锰铁锂正极材料的制备方法,其特征在于,步骤4)中,煅烧温度为650-800℃,烧结时间为4-15h。
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