稀土掺杂P2型层状钠离子电池正极材料及其电化学性能研究

A Study of the Performance of Rare Earth Element Doped P2-type Layered Oxide Cathode Material for Sodium Ion Battery

由于锂资源的匮乏,钠离子电池因其丰富的钠资源储量、低廉的价格受到了人们的广泛关注.其中,P2型层状氧化物被认为是一种非常有前途的正极材料.但Mn^(3+)的Jahn-Teller效应会导致相变和结构坍塌,使得电池寿命下降.本研究采用稀土元素对三元锰铁系层状正极材料进行结构调控,采用快速微波辅助法设计Sm掺杂取代Mn的Na_(0.67)Mn_(0.58)Cu_(0.1)Fe_(0.3)Sm_(0.02)O_(2),加速钠离子在电化学反应过程中的扩散,提高材料的倍率性能.在1.0 A/g的高电流密度下,Na_(0.67)Mn_(0.58)Cu_(0.1)Fe_(0.3)Sm_(0.02)O_(2)的放电容量大幅提高.此外,Sm和Cu取代有效缓解了材料在循环过程中的Jahn-Teller效应,提高了材料的循环稳定性.Na_(0.67)Mn_(0.58)Cu_(0.1)Fe_(0.3)Sm_(0.02)O_(2)在200 mA/g条件下,经过100圈循环后容量保持率高达69.8%.稀土元素的加入成功改善了P2型层状氧化物电极的电化学性能.

Due to the shortage of lithium resources,sodium-ion batteries have been brought to an increasing attention of people because of their abundant reserves of sodium resources and low price.Among them,P2 type layer oxide is considered to be a promising cathode material.However,the Jahn-Teller effect of Mn^(3+)in P2-Na_(0.67)MnO_(2)causes phase transitions and structural collapse,resulting in reduced battery life.Therefore,in this study,we used the rare earth elements to make a structure regulation on the ternary ferromanganese layered cathode material by fast microwave assisted method,and get the Sm doped Na_(0.67)Mn_(0.58)Cu_(0.1)Fe_(0.3)Sm_(0.02)O_(2).The doped ions expand the sodium ion transfer channel,accelerate the diffusion of sodium ions in the electro-chemical reaction process,and improved the rate performance of the material.Under high current density of 1.0 A/g,discharge capacity of Na_(0.67)Mn_(0.58)Cu_(0.1)Fe_(0.3)Sm_(0.02)O_(2)was much higher than that of the pristine samples.In addition,due to the substitution of Sm and Cu,the Jahn-Teller effect of the material was effectively alleviated during the cycle process,and the cyclic stability of the material was improved.A high capacity retention rate of about 69.8%was obtained under current density of 200 mA/g after 100 cycles.It is proved that the addition of rare earth elements successfully improves the electro-chemical performance of P2-type layered oxide electrode.