摘要
超高镍LiNi_(0.92)Co_(0.04)Mn_(0.04)O_(2)单晶(SC)被视为一种非常有前途的高能量密度正极材料,但其单晶材料存在首圈库伦效率低、充放电比容量较低以及锂离子扩散速度慢等一系列问题。稀土离子La^(3+)掺杂可以改善单晶材料循环性能,然而单晶颗粒的生长往往受到抑制,需要提高烧结温度。本文通过LiOH–La(NO_(3))_(3)–LiF形成微量熔盐体系,提高局部反应温度来促进La^(3+)和F-掺杂与晶粒生长,研究了La(NO_(3))_(3)、LiF用量对SC层状结构、晶体形貌和电化学性能的影响。实验结果表明,LiOH–La(NO_(3))_(3)–LiF微量熔盐法掺杂改性对SC的内部结构、颗粒形貌、首次充放电容量、倍率特性、循环性能具有明显的改善作用;适量的La^(3+)和F^(–)掺杂能够增强单晶材料的晶体结构,降低Li^(+)脱嵌过程中的迁移能垒,也提高了Li^(+)的脱嵌速度;同时缓解了单晶材料在循环过程中内部应力累积,提高了单晶材料的锂离子扩散速率与长循环稳定性。该种局部熔盐辅助掺杂的方法为开发高性能超高单晶正极材料提供了良好的借鉴。
Ultra-high nickel LiNi_(0.92)Co_(0.04)Mn_(0.04)O_(2)(SC)is regarded as a promising positive electrode material with a high energy density,while its single crystal material shows a series of obvious problems such as low first loop coulomb efficiency,low charge-to-discharge specific capacity,and low diffusion rate of lithium ion.Its cyclic performance can be improved by doping the rare earth ion La^(3+),but the growth of single crystal particles is often inhibited and the sintering temperature needs to be increased.In the present study,a trace molten salt system of LiOH-La(NO_(3))_(3)-LiF has been formed,and the doping of La^(3+)and F^(-)with grain growth are promoted with a higher local reaction temperature.The influences of the dosage of La(NO_(3))_(3) and LiF on layer structure,crystal morphology and electrochemical properties of SC are studied.The experiment results indicate that the doping modification of LiOH-La(NO_(3))_(3)-LiF trace molten salt shows an obvious improvement on the internal structure,particle morphology,initial charge-discharge capacity,rate characteristics and cyclic performance of SC.And the crystal structure of the single-crystal materials is improved with co-doping appropriate amount of La^(3+)and F^(-),which reduces the energy transfer barrier in the Li+intercalation process,increasing the Li+deintercalation rate.At the same time,the internal stress accumulation of monocrystalline materials during the cycle is alleviated,which increases the ion diffusion rate of single-crystal materials during cycling,and improves the long-term cycle stability of single-crystal materials.This local molten salt-assisted doping method provides a good reference for the development of high-performance ultrahigh single crystal positive electrode materials.
作者
张珏
曹堂哲
雷英
王洪辉
ZHANG Jue;CAO Tangzhe;LEI Ying;WANG Honghui(School of Chemical Engineering,Sichuan University of Science&Engineering,Zigong 643000,China)
出处
《四川轻化工大学学报（自然科学版）》
CAS
2023年第2期1-10,共10页
Journal of Sichuan University of Science & Engineering(Natural Science Edition)
基金
四川省自然科学基金项目(2022NSFSC1971,2022NSFSC0182)。
关键词
锂离子电池
超高镍
单晶材料
元素掺杂
微量熔盐法
lithium-ion battery
ultra-high nickel
single crystal materials
element co-doping
trace molten salt method
