摘要/Abstract

本工作以聚甲基丙烯酸甲酯(PMMA)微球组装成的胶晶模板作为铸模, 溶胶-凝胶法辅助获得大孔LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811)正极材料. 结果表明, 利用PMMA作为造孔剂, 形成了由100 nm的颗粒堆积而成的大孔结构, 这种结构有效地提高了材料的倍率性能和循环稳定性. 大孔NCM811在0.1C的首次放电比容量为190.3 mAh∙g^-1. 2C倍率下NCM811纳米颗粒的放电比容量仅为129.3 mAh∙g^-1, 而大孔NCM811的放电比容量为149.8 mAh∙g^-1. 0.5C倍率下循环400次后大孔NCM811的容量保持率为83.02%, 明显高于纳米颗粒材料的38.59%.
关键词: 锂离子电池, 正极材料, 胶晶模板, 大孔, LiNi_0.8Co_0.1Mn_0.1O₂
High-performance rechargeable lithium-ion batteries (LIBs) have been widely applied in electrochemical energy storage fields. In recent years, Ni-rich ternary cathode materials have received considerable attention due to their low cost and high theoretical specific capacity, and they are regarded as promising candidates for the next-generation lithium-ion batteries. In this paper, macroporous Ni-rich LiNi_0.8Co_0.1Mn_0.1O₂(NCM811) cathode material has been successfully prepared by using a poly(methyl methacrylate) (PMMA) colloidal crystal template and sol-gel method. The typical experimental procedure for the synthesis of macroporous LiNi_0.8Co_0.1Mn_0.1O₂ is as follows: Firstly, a stoichiometric mixture of LiNO₃, (CH₃COO)₂Mn∙4H₂O, (CH₃COO)₂Co∙4H₂O, and (CH₃COO)₂Ni∙4H₂O were dissolved together in ethanol for 1 h. Acetylacetone was then drop by drop into the prepared solution under continuous stirring for 1.5 h (a molar ratio of acetylacetone to transition metal ions was 1∶1). Then, the LiNi_0.8Co_0.1Mn_0.1O₂sol was infiltrated completely into PMMA template under vacuum. After that, the as-prepared product was filtrated and dried at 50 ℃, followed by a heat treatment at 450 ℃ for 2 h for removing the PMMA template, and then calcined at 700 ℃ under a flowing oxygen atmosphere. These results suggest that the macroporous architecture stacked by the 100 nm particles is obtained by using the pore-forming agent PMMA, and this structure is beneficial to improve the rate capability and cycling stability of the Ni-rich cathode materials. Specifically, macroporous NCM811 delivers an initial discharge capacity of 190.3 mAh∙g^-1 between 2.7 V and 4.3 V at 0.1C rate. The discharge specific capacity of the nanoparticle NCM811 is only 129.3 mAh∙g^-1 at 2C rate, whereas the macroporous NCM811 is 149.8 mAh∙g^-1 at the same rate. In addition, macroporous NCM811 can still delivers a high discharge specific capacity of 111.7 mAh∙g^-1 at 10C rate. Macroporous NCM811 also exhibits superior capacity retention of 83.02% after 400 cycles at 0.5C rate, surpassing the 38.59% of nanoparticle NCM811 obviously. The macroporous architecture is conducive to shorten the transport distance of lithium ions and electrons, suppress the phase transition and structural deterioration resulting from the frequent Li⁺ insertion/deinsertion, reduce polarization, and thus improving the electrochemical performances, which provides new insights for the development of high-energy-density lithium-ion batteries.
Key words: lithium-ion batteries, cathode material, colloidal crystal template, macroporous, LiNi_0.8Co_0.1Mn_0.1O₂


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