长循环高电压钠离子电池正极材料P2-Na2/3Mn1/3Bi1/3Ni1/3O2的合成及性能

镍基层状氧化物NaNiO₂钠离子电池材料具有高电压和高容量的特性,且制备方法较为简单,但姜-泰勒(Jahn-Teller)效应使其在高倍率循环下容量较低以及在高电压(4.5 V)下无法稳定循环。通过调节溶胶-凝胶工艺的条件,设计、合成了Na_2/3Mn_1/3Bi_1/3Ni_1/3O₂片层状金属氧化物,并将其作为正极活性材料,在空气环境中组装成钠离子电池,进行电化学测试,考察Bi、Mn掺入量对电池电化学影响。研究结果表明:当金属Mn和Bi共掺时,在1.2~4.5 V宽电压范围内,电池在循环50周后容量为90.39 mAh·g^-1。在2.0~4.0 V电压范围内1.0C (115 mA·g^-1)倍率下恒流充放电50周后的容量保持率为96.96%,循环850周后的保持率为80.15%,具有良好的循环稳定性和安全性。

Synthesis and properties of P2-Na2/3Mn1/3Bi1/3Ni1/3O2 as long-life and high voltage sodium-ion battery cathode

Layered nickel-based cathode materials are of great interest due to their high voltage and specific capacities for sodium ion batteries. However, the Jahn-Teller effect is detrimental for achieving considerable cycling stability at high voltage (4.5 V) and rate capability. Herein, a P2-type Na_2/3Mn_1/3Bi_1/3Ni_1/3O₂ cathode material was synthesized by adjusting the process conditions of sol-gel, and used as positive active materials to assemble sodium ion battery in air environment. The improved cycling and rate performance under high voltage can be achieved by Mnsubstitution and Bi-substitution. In a wide voltage range of 1.2 to 4.5 V, the material maintained a specific discharge capacity of 90.39 mAh·g^-1 after 50 cycles. The cathode obtained a remarkable capacity retention of 96.96% after 50 cycles at 1C (115 mA·g^-1) and 80.15% capacity retention up to 850 cycles from 2.0 to 4.0 V. The above data indicate that the cathode materials own an extremely long cycling life and better rate capability.