CN105118969B - 一种提高磷酸铁锂正极材料倍率性能的制备方法 - Google Patents
一种提高磷酸铁锂正极材料倍率性能的制备方法 Download PDFInfo
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 10
- 239000000463 material Substances 0.000 title claims abstract description 10
- 238000002360 preparation method Methods 0.000 title claims abstract description 10
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 20
- 239000010703 silicon Substances 0.000 claims abstract description 20
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 14
- PAZHGORSDKKUPI-UHFFFAOYSA-N lithium metasilicate Chemical compound [Li+].[Li+].[O-][Si]([O-])=O PAZHGORSDKKUPI-UHFFFAOYSA-N 0.000 claims abstract description 13
- 229910052912 lithium silicate Inorganic materials 0.000 claims abstract description 13
- 239000011159 matrix material Substances 0.000 claims abstract description 13
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 12
- 239000012298 atmosphere Substances 0.000 claims abstract description 9
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 8
- 230000001681 protective effect Effects 0.000 claims abstract description 8
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 7
- 238000000498 ball milling Methods 0.000 claims abstract description 7
- 229910052742 iron Inorganic materials 0.000 claims abstract description 7
- 239000002270 dispersing agent Substances 0.000 claims abstract description 6
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 6
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 5
- 150000002505 iron Chemical class 0.000 claims abstract description 5
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 5
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 5
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims abstract description 5
- 239000010452 phosphate Substances 0.000 claims abstract description 5
- 239000011574 phosphorus Substances 0.000 claims abstract description 5
- 239000008367 deionised water Substances 0.000 claims abstract description 4
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 4
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical class [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims abstract description 4
- 239000000843 powder Substances 0.000 claims abstract description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 4
- 238000001354 calcination Methods 0.000 claims abstract description 3
- 238000001035 drying Methods 0.000 claims abstract description 3
- 229910001386 lithium phosphate Inorganic materials 0.000 claims abstract description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 10
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 9
- 239000007789 gas Substances 0.000 claims description 7
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 6
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid group Chemical group C(CC(O)(C(=O)O)CC(=O)O)(=O)O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 5
- 229910052786 argon Inorganic materials 0.000 claims description 5
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 4
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 claims description 4
- 239000011248 coating agent Substances 0.000 claims description 4
- 238000000576 coating method Methods 0.000 claims description 4
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 4
- 229920002472 Starch Polymers 0.000 claims description 3
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical group CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 3
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical group [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 claims description 3
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 claims description 3
- 238000005253 cladding Methods 0.000 claims description 3
- 229940062993 ferrous oxalate Drugs 0.000 claims description 3
- OWZIYWAUNZMLRT-UHFFFAOYSA-L iron(2+);oxalate Chemical group [Fe+2].[O-]C(=O)C([O-])=O OWZIYWAUNZMLRT-UHFFFAOYSA-L 0.000 claims description 3
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 3
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 3
- 235000019837 monoammonium phosphate Nutrition 0.000 claims description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 3
- 239000008107 starch Substances 0.000 claims description 3
- 235000019698 starch Nutrition 0.000 claims description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical group CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 2
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims description 2
- 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 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 2
- 229910007536 Li2Si2 Inorganic materials 0.000 claims description 2
- 229910001556 Li2Si2O5 Inorganic materials 0.000 claims description 2
- 229910010846 Li6Si2O7 Inorganic materials 0.000 claims description 2
- 229910009771 Li8SiO6 Inorganic materials 0.000 claims description 2
- 229910002651 NO3 Inorganic materials 0.000 claims description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 2
- 229910019142 PO4 Inorganic materials 0.000 claims description 2
- 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 2
- 229930006000 Sucrose Natural products 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
- YNQRWVCLAIUHHI-UHFFFAOYSA-L dilithium;oxalate Chemical compound [Li+].[Li+].[O-]C(=O)C([O-])=O YNQRWVCLAIUHHI-UHFFFAOYSA-L 0.000 claims description 2
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 2
- 239000011790 ferrous sulphate Substances 0.000 claims description 2
- 239000008103 glucose Substances 0.000 claims description 2
- 239000001257 hydrogen Substances 0.000 claims description 2
- 229910052739 hydrogen Inorganic materials 0.000 claims description 2
- 229910052909 inorganic silicate Inorganic materials 0.000 claims description 2
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 2
- 229910000359 iron(II) sulfate 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
- 230000004048 modification Effects 0.000 claims description 2
- 238000012986 modification Methods 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims description 2
- 235000012239 silicon dioxide Nutrition 0.000 claims description 2
- 239000000377 silicon dioxide Substances 0.000 claims description 2
- 238000003756 stirring Methods 0.000 claims description 2
- 239000005720 sucrose Substances 0.000 claims description 2
- 229910000398 iron phosphate Inorganic materials 0.000 claims 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims 1
- 238000000227 grinding Methods 0.000 abstract description 4
- 239000000126 substance Substances 0.000 abstract description 4
- 238000009776 industrial production Methods 0.000 abstract description 3
- 239000000047 product Substances 0.000 description 10
- 229910052493 LiFePO4 Inorganic materials 0.000 description 9
- 230000006641 stabilisation Effects 0.000 description 5
- 238000011105 stabilization Methods 0.000 description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 229910032387 LiCoO2 Inorganic materials 0.000 description 2
- 229910010710 LiFePO Inorganic materials 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 238000010532 solid phase synthesis reaction Methods 0.000 description 2
- 238000003836 solid-state method Methods 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 238000010792 warming Methods 0.000 description 2
- 229910012820 LiCoO Inorganic materials 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 125000002091 cationic group Chemical group 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000001027 hydrothermal synthesis Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 239000003595 mist Substances 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- YTZVWGRNMGHDJE-UHFFFAOYSA-N tetralithium;silicate Chemical class [Li+].[Li+].[Li+].[Li+].[O-][Si]([O-])([O-])[O-] YTZVWGRNMGHDJE-UHFFFAOYSA-N 0.000 description 1
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Abstract
一种提高磷酸铁锂正极材料倍率性能的制备方法，其包括以下步骤：按铁、锂、磷和硅元素的摩尔比为1:0.95～1.05:0.90～0.99:0.01～0.10，将二价铁盐、锂盐、磷酸盐和硅源混合，加入分散剂，以转速200～500rpm球磨4～16小时，将球磨产物干燥后，在保护气氛下300～500℃烧结6～12小时，随炉冷却至室温，研磨，得到预烧产物，即硅掺杂的基体；将预烧产物、碳源和硅酸锂混合，加入去离子水中，搅拌0.5～4小时，干燥后在保护气氛下600～900℃恒温焙烧6～12小时，随炉冷却至室温，研磨，即制得改性的磷酸铁锂粉末。其不但能广泛应用于工业生产，而且电化学性能提升明显。
Description
技术领域
本发明涉及磷酸铁锂正极材料的制备方法，属于锂离子电池领域。
背景技术
1997年，Goodenough的课题组首次报道锂离子正极材料LiFePO4，其理论比容量为170mAh/g，大于已商品化的LiCoO2的实际放电比容量。而且LiFePO4具有良好的循环性能，在3.45V附近有稳定的放电平台。LiFePO4是目前动力电池中主要使用的电极材料，其主要优点有电压平台稳定，原料廉价丰富，环境友好，低毒性且由于良好的高温稳定性使其具有较高的安全性。
LiFePO4为斜方晶系橄榄石型结构，属于Pmnb空间群，其晶格常数为 LiFePO4的晶体结构在400℃时仍能保持稳定，但是LiCoO2在250℃就开始分解，使其循环性能和安全性大大提高。锂离子在LiFePO4晶格中沿一维通道迁移，大大限制了其扩散速率，而且一维通道很容易由于杂质缺陷的出现而阻塞，使其离子电导率进一步降低。由于O原子与Fe和P的结合键非常强，使得LiFePO4结构与LiCoO2等层状结构相比，有很好的高温稳定性，然而，强的P-O键也会导致离子扩散速率（10-13～10-16cm- 2s-1)和电子电导率(～10-9cm·s-1)降低。
目前合成磷酸铁锂的方法有：高温固相法，溶胶-凝胶法，水热法，碳热还原法，喷雾热解法等，但只有高温固相法广泛应用于工业生产。
LiFePO4较低的离子电导率和电子电导率，使其实际放电容量降低，极化现象严重，倍率性能也很不理想。人们对其进行了广泛而深入的研究，通过降低粒径可以改善其电化学性能；在其表面包覆一层导电的无定型碳网，不仅能提高电子电导率而且还能抑制晶粒的长大，进而有效提高离子电导率；人们还通过对Li位或Fe位进行高价阳离子掺杂形成p-型半导体来提高其电导率。这些改性方式对其离子电导率和电子电导率都产生了很大的影响，从而提高了其放电容量，循环寿命以及倍率性能。
发明内容
本发明的目的是提供一种提高磷酸铁锂正极材料倍率性能的制备方法，该制备方法不但能广泛应用于工业生产，而且电化学性能提升明显。
研究发现，当电子电导率达到10-2cm·s-1左右时，离子电导率对LiFePO4电化学性能将起主要作用。通过包覆无定型碳网，电子电导率可达到10-3-10-2cm·s-1，通过Si掺杂可进一步提升电子电导率，再通过包覆硅酸锂固态电解质，就能大大提高其离子电导率。在此基础上，本发明采用工业上广泛使用的固相法制备LiFePO4正极材料，通过简单有效的方式进行改性，同时提高其电子电导率和离子电导率，从而使电化学性能明显提升。本发明的创新性在于采用一种廉价丰富的Si元素，通过内掺和外包覆的措施，解决了电子电导和锂离子扩散速率两方面的问题。
本发明的具体技术方案为：
一种提高磷酸铁锂正极材料倍率性能的制备方法，其包括以下步骤：
制备硅掺杂的基体：按铁、锂、磷和硅元素的摩尔比为1:0.95～1.05:0.90～0.99:0.01～0.10，将二价铁盐、锂盐、磷酸盐和硅源混合，加入分散剂，以转速200～500rpm球磨4～16小时，将球磨产物干燥后，在保护气氛下300～500℃烧结6～12小时，随炉冷却至室温，研磨，得到预烧产物，即硅掺杂的基体；以及
包覆无定型碳和纳米硅酸锂：将预烧产物、碳源和硅酸锂混合，加入去离子水中，搅拌0.5～4小时，干燥后在保护气氛下600～900℃恒温焙烧6～12小时，随炉冷却至室温，研磨，即制得改性的磷酸铁锂粉末。
根据本发明，在一些实施例中，制备硅掺杂的基体时，铁、锂、磷和硅元素的摩尔比采用下述比例中的一种：1:1:0.91:0.09，1:1:0.92:0.08，1:1:0.93:0.07，1:1:0.94:0.06，1:1:0.95:0.05，1:1:0.96:0.04，1:1:0.97:0.03，1:1:0.98:0.02，1:0.97:0.91:0.09，1:0.97:0.92:0.08，1:0.97:0.93:0.07，1:0.97:0.94:0.06，1:0.97:0.95:0.05，1:0.97:0.96:0.04，1:0.97:0.97:0.03，1:0.97:0.98:0.02，1:1.03:0.91:0.09，1:1.03:0.92:0.08，1:1.03:0.93:0.07，1:1.03:0.94:0.06，1:1.03:0.95:0.05，1:1.03:0.96:0.04，1:1.03:0.97:0.03，1:1.03:0.98:0.02。但本发明并不限于上述这些比例，以铁元素为基数(1摩尔)，锂元素可以是0.95～1.05摩尔之间的任何值，磷元素可以是0.90～0.99摩尔之间的任何值，硅元素可以是0.01～0.10摩尔之间的任何值，但磷元素和硅元素的摩尔数之和应等于1。
优选地，包覆在基体表面的无定型碳的质量分数为2～10％，例如2％、2.5％、3％、3.5％、4％、4.5％、5％、5.5％、6％、6.5％、7％、7.5％、8％、8.5％、9％、9.5％。包覆在基体表面的硅酸锂盐的质量分数为0.5～5％，例如0.5％、1％、1.5％、2％、2.5％、3％、3.5％、4％、4.5％、5％。
优选地，所述二价铁盐为草酸亚铁、氯化亚铁、硫酸亚铁或硝酸亚铁。
优选地，所述锂盐为碳酸锂、氢氧化锂、草酸锂、硝酸锂或醋酸锂。
优选地，所述磷酸盐为磷酸二氢铵或磷酸氢二铵。
优选地，所述硅源为正硅酸乙酯、硅酸或二氧化硅。
优选地，所述分散剂为无水乙醇、丙酮、乙二醇、异丙醇或正丁醇。
优选地，所述碳源为柠檬酸、蔗糖、葡萄糖或淀粉。
优选地，所述硅酸锂为Li8SiO6、Li4SiO4、Li6Si2O7、Li2Si2O5和Li2Si2O11中的一种或几种。
优选地，所述保护气氛为氮气、氩气或氩气与氢气的混合气体。
本发明具有以下有益效果：
本发明采用工业上广泛使用的固相法制备磷酸铁锂正极材料，工艺成熟，同时利用硅掺杂以及无定型碳和纳米硅酸锂包覆对其进行改性，获得的磷酸铁锂晶粒尺寸大小均匀、比容量高、循环性能极佳、具有稳定的充放电平台，在大倍率充放电情况下能保持较高的库伦效率。
附图说明
图1为实施例1制得的产物的X射线衍射图谱；
图2为实施例1制得的产物的扫描电镜图；
图3为实施例1制得的产物的循环性能曲线。
具体实施方式
实施例1：
首先将草酸亚铁、碳酸锂、磷酸二氢铵和正硅酸乙酯按照铁、锂、磷和硅元素的摩尔比为：1:1:0.97:0.03混合，加入适量丙酮作为分散剂，以350rpm的转速球磨12小时，干燥后将所得产物在氩气保护气氛下450℃(升温速率为5℃/min)烧结10小时，随炉冷却至室温，将得到的产物在玛瑙研钵中研磨，得到预烧产物，即硅掺杂的基体。
然后包覆无定型碳和纳米硅酸锂：将预烧产物与马铃薯淀粉和硅酸锂在去离子水中混合，磁力搅拌作用下充分混合，升温至50℃使淀粉糊化，保温30min后升温至70℃蒸干，将产物在氩气气氛的管式炉中700℃(升温速率为5℃/min)下保温10小时，随炉冷却至室温，研磨后过300目标准筛，得到所需正极材料，即改性的磷酸铁锂粉末。其中，包覆在基体表面的无定型碳的质量分数为5.8％，包覆在基体表面的硅酸锂的质量分数为1.5％。
图1示出了制得的正极材料的X射线衍射图谱。
图2示出了制得的正极材料的扫描电镜图。可以看出，该正极材料晶粒尺寸大小均匀。
图3示出了制得的正极材料在5C、25℃、2.5-4.2V的循环性能曲线。可以看出，该正极材料比容量高、循环性能极佳、具有稳定的充放电平台，在大倍率充放电情况下能保持较高的库伦效率。
Claims (2)
1.一种提高磷酸铁锂正极材料倍率性能的制备方法，其特征在于，该制备方法包括以下步骤：
制备硅掺杂的基体：按铁、锂、磷和硅元素的摩尔比为1:0.95～1.05:0.90～0.99:0.01～0.10，将二价铁盐、锂盐、磷酸盐和硅源混合，加入分散剂，以转速200～500rpm球磨4～16小时，将球磨产物干燥后，在保护气氛下300～500℃烧结6～12小时，随炉冷却至室温，研磨，得到预烧产物，即硅掺杂的基体；以及
包覆无定型碳和纳米硅酸锂，其中，包覆在基体表面的无定型碳的质量分数为2～10％，包覆在基体表面的硅酸锂的质量分数为0.5～5％：将预烧产物、碳源和硅酸锂混合，加入去离子水中，搅拌0.5～4小时，干燥后在保护气氛下600～900℃恒温焙烧6～12小时，随炉冷却至室温，研磨，即制得包覆改性的磷酸铁锂粉末；
所述二价铁盐为草酸亚铁、氯化亚铁、硫酸亚铁或硝酸亚铁；
所述锂盐为碳酸锂、氢氧化锂、草酸锂、硝酸锂或醋酸锂；
所述磷酸盐为磷酸二氢铵或磷酸氢二铵；
所述硅源为正硅酸乙酯、硅酸或二氧化硅；
所述分散剂为无水乙醇、丙酮、乙二醇、异丙醇或正丁醇；
所述碳源为柠檬酸、蔗糖、葡萄糖或淀粉；
所述硅酸锂为Li8SiO6、Li4SiO4、Li6Si2O7、Li2Si2O5和Li2Si2O11中的一种或几种。
2.根据权利要求1所述的提高磷酸铁锂正极材料倍率性能的制备方法，其特征在于：所述保护气氛为氮气、氩气或氩气与氢气的混合气体。
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