摘要/Abstract

采用溶胶-凝胶法合成Al掺杂富锂锰基Li_1.2Mn_0.54-xAl_xNi_0.13Co_0.13O₂（x=0、0.03）锂离子电池正极材料，之后采用一步液相法制备Li₂WO₄包覆层，系统地研究了Al掺杂和Li₂WO₄包覆双效改性对富锂锰基正极材料电化学性能的影响.结果表明，Al掺杂后明显提升富锂锰基正极材料的循环稳定性，包覆层Li₂WO₄明显改善其倍率性能和放电平台电压衰减问题.Li₂WO₄包覆量为5% Li_1.2Mn_0.51Al_0.03Ni_0.13Co_0.13O₂正极材料在2.0~4.8 V充放电电压区间及1000 mA·g^-1电流密度下比容量仍高达110 mAh·g^-1左右，同时在100 mA·g^-1的电流密度下循环300次容量保持率为78%，而且循环过程中放电平台电压衰减也明显减缓.该工作为解决锂离子电池富锂锰基正极材料循环稳定性和平台电压衰减提供了新的思路.
关键词: 锂离子电池, 溶胶-凝胶法, 富锂锰基正极材料, Li₂WO₄, Al掺杂
The layered lithium-rich manganese-based cathode material has been widely concerned because of it's advantages such as a specific discharge capacity greater than 250 mAh·g^-1 and a high discharge platform, and is expected to become the next-generation lithium ion battery cathode material. However, lithium-rich manganese-based cathode materials have poor cycle stability, low coulombic efficiency for the first charge and discharge, and low rate performance. The most important thing is that the problem of faster voltage decays on the discharge platform has not been effectively solved, The current it is mainly to improve the performance by element doping modification and surface coating, so it is very important to find suitable doping elements and coating materials. The common coating material is mainly to prevent direct contact between the electrolyte and the positive electrode material to improve the cycle stability, and it is difficult to slow down the attenuation of the discharge voltage platform. Al-doping lithium-rich manganese-based Li_1.2Mn_0.54-xAl_xNi_0.13Co_0.13O₂ (x=0, 0.03) cathode material was prepared by sol-gel method and Li₂WO₄ surface coating by one-step liquid phase method. The required materials were confirmed by X-ray diffractometer (XRD), energy disperse spectroscopy (EDS) and scanning electron microscope (SEM) tests, and then the effects of Al-doping and Li₂WO₄ coated double-effect modification on the electrochemical performance of lithium-rich manganese-based cathode materials were studied by electrochemical test system. The results show that Al doping significantly improves the cycling stability of lithium-rich manganese-based cathode materials, and the coating Li₂WO₄ significantly improves its rate performance and discharge platform voltage attenuation. In 5% Li₂WO₄ coated Li_1.2Mn_0.51Al_0.03Ni_0.13Co_0.13O₂ cathode material in charge and discharge voltage 2.0~4.8 V, and under the current density 1000 mA·g^-1, the specific capacity is still as high as about 110 mAh·g^-1. At the same time, the specific capacity retention rate was 78% after 300 cycles at the current density of 100 mA·g^-1, and the voltage decay of the discharge platform significantly slowed down during the cycle.
Key words: lithium ion battery, sol-gel, lithium-rich manganese-based cathode material, Li₂WO₄, Al-doping


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