He Yueyue, Wang Shuo, Zhang Haiyan, Chen Xin, Li Jin, Xu Huiyuan, Zhang Yanhui, Hu KangHui, Lv Genpin, Meng Yan, Xiang Wei
College of Materials and Chemistry & Chemical Engineering, Chengdu University of Technology, Chengdu 610059, PR China.
Sichuan Tobacco Quality Supervision and Testing Station, Chengdu 610041, PR China.
J Colloid Interface Sci. 2022 Feb;607(Pt 2):1333-1342. doi: 10.1016/j.jcis.2021.09.101. Epub 2021 Sep 21.
Li-rich disordered rock-salt cathode (DRX) materials with advantage of low cost, long cycle life, nature abundant resource and high power and energy density attracted a great deal of scholarly attention. However, the poor cycle stability and the unclear realization of cation and anion redox activity in low-cost element system have severely hindered the construction of high-performance DRX. Herein, a promising class of Ti-Mn based cathode materials LiMnNbTiO and LiMnTiOF were designed and successfully synthesized to construct high energy density DRX and investigate the effect of fluorination on cation and anion redox activity. The results show that both fluoridized and unfluoridized DRX possess a similar structure (Fm-3 m), but distinctly different charge/discharge profiles. The fluoridized cathode shows high initial charge/discharge capacity of 317.3/283.9 mAh g, specific energy density of 1370.4/735.5 Wh kg and stable capacity retention with a discharge capacity of 202.6 mAh g after 20 cycles at 20 mA g. Combining relevant spectroscopic results and HRTEM images, we revealed that the excellent cyclability of LiMnTiOF is rooted in the weakened adverse effects of moderated oxygen redox and the reduced Jahn-Teller distortion effect resulting from Mn, endowing the fluoridized DRX with better structural stability and larger Mn/Mn reservoir. The strategy of constructing low cost oxyfluoride and the understanding of the mechanism of fluorination induced cation and anion redox activity would provide reference for the development of high-performance DRX materials.
具有低成本、长循环寿命、资源丰富且功率和能量密度高优势的富锂无序岩盐阴极（DRX）材料引起了大量学术关注。然而，低成本元素体系中较差的循环稳定性以及阳离子和阴离子氧化还原活性的实现尚不明确，严重阻碍了高性能DRX的构建。在此，设计并成功合成了一类有前景的基于Ti-Mn的阴极材料LiMnNbTiO和LiMnTiOF，以构建高能量密度DRX并研究氟化对阳离子和阴离子氧化还原活性的影响。结果表明，氟化和未氟化的DRX都具有相似的结构（Fm-3 m），但充放电曲线明显不同。氟化阴极显示出高初始充放电容量，分别为317.3/283.9 mAh g，比能量密度为1370.4/735.5 Wh kg，并且在20 mA g下循环20次后具有稳定的容量保持率，放电容量为202.6 mAh g。结合相关光谱结果和高分辨透射电子显微镜图像，我们揭示了LiMnTiOF优异的循环性能源于适度的氧氧化还原的不利影响减弱以及Mn导致的 Jahn-Teller 畸变效应降低，赋予氟化DRX更好的结构稳定性和更大的Mn/Mn储库。构建低成本氟氧化物的策略以及对氟化诱导阳离子和阴离子氧化还原活性机制的理解将为高性能DRX材料的开发提供参考。
