Optimization mechanism of Li_2ZrO_3-modified lithium-rich cathode material Li[Li_(0.2)Ni_(0.2)Mn_(0.6)]O_2 for lithium-ion batteries

摘要

To achieve lithium-ion batteries with high energy and power density, it is necessary to develop alternative high-capacity cathode materials for traditional LiCoO_2 or LiFePO_4, such as lithium-rich manganese-based cathode materials. However, there are still some practical problems that Li-rich materials need to be further improved, such as structure transformation issue and poor rate capability. Here, the modification of Li[Li_(0.2)Ni_(0.2)Mn_(0.6)]O_2 cathode material by lithium-ion conductor (Li_2ZrO_3) has been achieved by a sol-gel method, and the optimization mechanism is preliminarily explored. The first charge/discharge specific capacities of the modified material coated with 1 wt.% Li_2ZrO_3 can reach 272.1 and 196.1 mAh g~(-1) at 0.5 C, which are obviously higher than those of the pristine material. The rate capability has also been improved at 2 C and 5 C. As a fast lithium-ion conductor with good chemical stability, Li_2ZrO_3 material can form a continuous and uniform coating layer on the surface of active particles, which can inhibit the side reaction between the electrolyte and the electrode material, effectively prevent the corrosion of cathode material by HF attack, and reduce electrode polarization at high rates, leading to the improvement of the specific capacity and the structure stability of Li-rich material.