Bi掺杂O3型NaNi0.5Mn0.5O2钠离子电池层状正极材料的制备与储钠性能

O3型NaNi_0.5Mn_0.5O₂拥有高理论比容量且易于制备,是商业钠离子(Na⁺)电池的首选正极材料之一,但其循环稳定性仍面临挑战。利用Bi对NaNi_0.5Mn_0.5O₂进行改性。研究发现,Bi的引入可以在晶粒生长过程中通过调节表面能实现晶粒细化,并且Bi的掺杂增加了层状正极材料的晶胞参数,为Na⁺提供了宽的扩散通道,提高了Na⁺的扩散能力,优化了Na⁺在脱嵌过程中的可逆性。改性后的NaNi_0.495Mn_0.5Bi_0.005O₂实现了在2.0～4.0 V的电势区间内0.2 C倍率下的可逆容量为138.1 mAh/g,在5 C倍率下循环100圈后容量保持率可以达到97%。

Preparation and performance of Bi doped O3 type NaNi0.5Mn0.5O2 layered cathode materials for sodium ion batteries

O3-type NaNi_0.5Mn_0.5O₂ is a preferred cathode materials for commercial sodium-ion(Na⁺) batteries due to its high theoretical specific capacity and ease of fabrication. However, its cycling stability still faces challenges. In this study, bismuth metal (Bi) is used to modify the NaNi_0.5Mn_0.5O₂. It is found that the introduction of Bi allows for grain refinement by regulating surface energy during the grain growth process. Additionally, Bi doping increases the cell parameters of the layered cathode material, providing wider diffusion channels for Na⁺, enhancing Na⁺ diffusion ability, and optimizing the reversibility of Na⁺ in the insertion/extraction process. The modified NaNi_0.495Mn_0.5Bi_0.005O₂ sample achieves a reversible capacity of 138.1 mAh/g at the rate of 0.2 C within the potential range of 2.0-4.0 V. Furthermore, it demonstrates a capacity retention of 97% after 100 cycles at the rate of 5 C. The modified NaNi_0.495Mn_0.5Bi_0.005O₂ can also be used as a high-current anode material.