Ni-La双掺LiMn_(2)O_(4)截角八面体正极材料的制备及电化学性能

Preparation and Electrochemical Performance of Ni-La Double-doped LiMn_(2)O_(4) Truncated Octahedral Cathode Material

采用溶液燃烧法合成了一种具有{111}和{100}晶面的截角八面体LiNi_(0.05)La_(0.04)Mn_(1.91)O_(4)正极材料。结果表明,Ni-La复合掺杂促进了尖晶石型LiMn_(2)O_(4)晶体的{111}及{100}晶面择优生长,形成了亚微米级截角八面体晶粒形貌的正极材料。在1C下,其首次放电比容量为128.5 mA·h/g,1000次循环后保持率为65.48%;10C倍率下,放电比容量为108.2 mA·h/g,1500次循环后容量保持率为75.8%;在更高倍率15C和20C下,经2000次长循环后保持率分别为74.76%和76.16%,说明LiNi_(0.05)La_(0.04)Mn_(1.91)O_(4)材料充放电倍率越高,容量保持率越优。该材料具有较大的锂离子扩散系数与较小的表观活化能。Ni-La共掺杂与截角八面体形貌联合调控策略可有效抑制Jahn-Teller畸变,减少Mn溶解及增加Li^(+)迁移通道数量,稳定晶体结构,提升尖晶石型LiMn_(2)O_(4)正极材料的倍率性能和循环寿命。

The truncated octahedral LiNi_(0.05)La_(0.04)Mn_(1.91) O_(4) cathode material with{111}and{100}crystal planes was prepared by a solution combustion method.The results show that the Ni-La co-doping promoted the preferential growth of{111}and{100}planes of spinel LiMn_(2)O_(4) crystals,forming a cathode material with sub-micron truncated octahedral grain morphology.At 1C,the first discharge specific capacity was 128.5 mA·h/g,and the retention rate after 1000 cycles was 65.48%;at 10C rate,the discharge specific capacity was 108.2 mA·h/g,and the capacity retention rate after 1500 cycles was 75.8%;at higher rates of 15C and 20C,the retention rates after 2000 long cycles were 74.76%and 76.16%,respectively,indicating that the higher the charge-discharge rate of LiNi_(0.05)La_(0.04)Mn_(1.91)O_(4) material,the better the capacity retention rate.The material has a larger lithium-ion diffusion coefficient and a smaller apparent activation energy.The combined control strategy of Ni-La co-doping and truncated octahedral morphology can effectively suppress Jahn-Teller distortion,reduce Mn dissolution,and increase the number of Li+migration channels,stabilize the crystal structure,and increase the rate performance and cycle life of spinel LiMn_(2)O_(4) cathode material.