Enhanced electrochemical performance of Li3PO4 modified Li[Ni0.8Co0.1Mn0.1]O2 cathode material via lithium-reactive coating
Enhanced electrochemical performance of Li3PO4 modified Li[Ni0.8Co0.1Mn0.1]O2 cathode material via lithium-reactive coating
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DOI：
10.1016/j.jallcom.2018.09.237
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发表时间：
2019-01
影响因子：
6.2
通讯作者：
Jie Zhu;Yun-jiao Li;Longlong Xue;Yongxiang Chen;Tongxing Lei;Shiyi Deng;Guolin Cao
中科院分区：
文献类型：
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作者：
Jie Zhu;Yun-jiao Li;Longlong Xue;Yongxiang Chen;Tongxing Lei;Shiyi Deng;Guolin Cao
残余锂被认为是影响LiNiO2基正极材料电化学性能的关键因素之一。本文采用湿法包覆和热处理的方法制备了Li3PO4改性的LiNi0.8Co0.1Mn0.1O2（NCM811）正极材料。结果，表面残留锂的含量显著降低，如通过中和滴定所证实的，这可以归因于通过表面残留锂与（NH4）2HPO4之间的反应形成Li3PO4涂层。研究了Li3PO4包覆对LiNi0.8Co0.1Mn0.1O2（NCM811）正极材料表面状态、晶体结构和电化学性能的影响。在100次循环后，Li3PO4涂层的NCM811在25 °C和1C下的容量保持率为92.6%，而裸NCM811仅为86.1%。此外，Li3PO4涂层的NCM811在8C下的倍率性能为159.4 mAh·g− 1，比NCM811的144.4 mAh·g− 1更好。Li3PO4包覆层的形成有助于去除表面残余锂，促进锂离子扩散，降低电解液中HF和H2O的含量，抑制电解液与活性物质之间的有害副反应，从而显著改善了电解液的电化学性能。
Residue lithium is recognized as one of the critical factors affecting the electrochemical performances of LiNiO2-based cathode materials. In this paper, Li3PO4-modified LiNi0.8Co0.1Mn0.1O2(NCM811) cathode material is successfully synthesized via a wet coating followed by a heat treatment. As a consequence, the contents of surface residual lithium are significantly reduced as confirmed by neutralization titration, which can be ascribed to the formation of a Li3PO4coating layer by the reaction between surface residual lithium and (NH4)2HPO4. The effects of Li3PO4coating on the surface states, crystal structure and electrochemical performances of LiNi0.8Co0.1Mn0.1O2(NCM811) cathode material are studied in detail. After 100 cycles, the capacity retention of Li3PO4-coated NCM811 is 92.6% at 25 °C at 1C, whereas the bare NCM811 is only 86.1%. Besides, the Li3PO4-coated NCM811 delivers a better rate property of 159.4 mAh·g−1at 8C compared with 144.4 mAh·g−1for NCM811. The prominent improvements in electrochemical performances are attribute to the fact that the formation of Li3PO4coating layers help to remove the surface residual lithium, facilitate lithium ion diffusion, lower the level of HF and H2O in the electrolyte and suppress the deleterious side reactions between the electrolyte and active materials.