Ni-Zn共掺LiMn_(2)O_(4)正极材料的制备及电化学性能

Preparation and electrochemical properties of Ni-Zn co-doped LiMn_(2)O_(4) cathode materials

利用固相燃烧法制备了Ni-Zn共掺的LiNi_(0.03)Zn_(0.02)Mn_(1.95)O_(4)正极材料。采用X射线衍射仪、扫描电子显微镜、透射电子显微镜和X射线光电子能谱仪等对材料的结构、形貌和元素价态进行分析,并且通过一系列电化学测试对材料的电化学性能进行分析。结果表明:合成的LiNi_(0.03)Zn_(0.02)Mn_(1.95)O_(4)正极材料具有较好的电化学性能,在25℃、1 C条件下首次放电比容量为125.5 mAh/g,1000次循环后的容量保持率为73.6%;在10 C和20 C下,1000次循环后的容量保持率分别为58.0%和42.7%;在55℃、1 C条件下循环200次后的容量保持率为73.2%;LiNi_(0.03)Zn_(0.02)Mn_(1.95)O_(4)材料有较大的锂离子扩散系数(3.42×10^(−8) cm^(2)/s)和较小的活化能(17.25 kJ/mol),Ni-Zn共掺稳定了尖晶石的晶体结构,有效抑制了Jahn-Teller畸变,改善了材料的循环稳定性和倍率性能。

Ni-Zn co-doped LiNi_(0.03)Zn_(0.02)Mn_(1.95)O_(4) cathode material was prepared by a solid-phase combustion method.The structure,morphology and element valence of the materials were analyzed by X-ray diffractometer,scanning electron microscope,transmission electron microscope and X-ray photoelectron spectrometer,and the electrochemical performance of the materials was analyzed through a series of electrochemical tests.The results show that the LiNi_(0.03)Zn_(0.02)Mn_(1.95)O_(4) cathode material has good electrochemical performance.The initial discharge specific capacity is 125.5 mAh/g at 25℃and 1 C,and after 1000 long cycles,the capacity retention is 73.6%.At the high current rate of 10 C and 20 C,the capacity retention are 58.0%and 42.7%after 1000 cycles.At 1 C and 55℃,the capacity retention is 73.2%after 200 cycles.The LiNi_(0.03)Zn_(0.02)Mn_(1.95)O_(4) sample has a large lithium-ion diffusion coefficient of 3.42×10^(−8) cm^(2)/s and a smaller activation energy of 17.25 kJ/mol.Ni-Zn co-doping stabilizes the crystal structure of spinel,effectively suppresses the Jahn-Teller effect,and improves the cycle stability and rate performance of the material.