In this work,we present a new design for a surface protective layer formed by a facile aqueous solution process in which a nano-amhitectured layer of LiFePO4 is grown on a Li-rich cathode material,Li1.2Mn0.54Ni0.13Co0.13O2.The coated samples are then calcined at 400 or 500 ℃ for 5 h.The sample after calcination at 400 ℃ demonstrates a high initial columbic efficiency of 91.9％,a large reversible capacity of 295.0 mAh·g-1 at 0.1C (1C =300 mA·g-1),and excellent cyclability with a capacity of 206.7 mAh·g-1after 100 cycles at 1C.Meanwhile,voltage fading of the coated sample is effectively suppressed by protection offered by a LiFePO4 coating layer.These superior electrochemical performances are attributed to the coating layer,which not only protects the Li-dch cathode material from side reaction with the electrolyte and maintains the stability of the interface structure,but also provides excess reversible capacity.%采用简单水溶液法制备LiFePO4包覆的Li1.2Mn0.54Ni0.13Co0.13O2富锂正极材料,包覆后的材料分别经过400℃ 或500℃ 煅烧处理5h.测试结果显示,400℃煅烧处理的包覆样品在0.1C (1C=300 mA·g-1)电流密度下充放电时,首次库仑效率可以高达91.9％,同时,首次放电比容量可达到295.0 mAh·g-1.此外,该包覆样品还具有良好的循环性能,在1C电流密度下循环100次放电比容量仍可保持在206.7mAh·g-1.进一步的研究发现LiFePO4的包覆不仅可以提高Li1.2Mn0.54Ni0.13Co0.13O2富锂材料的首次库仑效率和循环稳定性能,而且还能够有效抑制材料在充放电过程中的电压衰减.上述电化学性能的有效提升主要归因于LiFePO4包覆层可以阻碍Li1.2Mn0.54N0.13Co0.13O2富锂材料与电解液之间的直接接触,减少副反应的发生,增强材料表面的结构稳定性,同时还可以为富锂材料提供额外的可逆容量.
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