Reversible cationic-anionic redox in disordered rocksalt cathodes enabled by fluorination-induced integrated structure design  

作　　者：Feng Wu Jinyang Dong Jiayu Zhao Qi Shi Yun Lu Ning Li Duanyun Cao Wenbo Li Jianan Hao Yu Zheng Lai Chen Yuefeng Su 

机构地区：[1]School of Materials Science and Engineering,Beijing Key Laboratory of Environmental Science and Engineering,Beijing Institute of Technology,Beijing 100081,China [2]Beijing Institute of Technology Chongqing Innovation Center,Chongqing 401120,China [3]BTR New Material Group Co.,Ltd,Shenzhen 518000,Guangdong,China

出　　处：《Journal of Energy Chemistry》2023年第7期158-169,I0004,共13页能源化学（英文版）

基　　金：supported by the National Key R&D Program of China(2021YFB2401800);the National Natural Science Foundation of China(22179008,21875022);the Natural Science Foundation of Chongqing,China(cstc2020jcyj-msxmX0589,cstc2020jcyjmsxmX0654);the support from Beijing Institute of Technology Research Fund Program for Young Scholars;the 4B7B beamlines radiation equipment of Beijing Synchrotron Radiation Facility(2021-BEPC-PT-005924,2021-BEPC-PT-005967)。

摘　　要：Cation-disordered rocksalt oxides(DRX)have been identified as promising cathode materials for high energy density applications owing to their variable elemental composition and cationic-anionic redox activity.However,their practical implementation has been impeded by unwanted phenomena such as irrepressible transition metal migration/dissolution and O_(2)/CO_(2)evolution,which arise due to parasitic reactions and densification-degradation mechanisms during extended cycling.To address these issues,a micron-sized DRX cathode Li_(1.2)Ni_(1/3)Ti_(1/3)W_(2/15)O_(1.85)F_(0.15)(SLNTWOF)with F substitution and ultrathin LiF coating layer is developed by alcohols assisted sol-gel method.Within this fluorination-induced integrated structure design(FISD)strategy,in-situ F substitution modifies the activity/reversibility of the cationic-anionic redox reaction,while the ultrathin LiF coating and single-crystal structure synergistically mitigate the cathode/electrolyte parasitic reaction and densification-degradation mechanism.Attributed to the multiple modifications and size effect in the FISD strategy,the SLNTWOF sample exhibits reversible cationic-anionic redox chemistry with a meliorated reversible capacity of 290.3 mA h g^(-1)at 0.05C(1C=200 mA g^(-1)),improved cycling stability of 78.5%capacity retention after 50 cycles at 0.5 C,and modified rate capability of 102.8 mA h g^(-1)at 2 C.This work reveals that the synergistic effects between bulk structure modification,surface regulation,and engineering particle size can effectively modulate the distribution and evolution of cationic-anionic redox activities in DRX cathodes.

关 键 词：Cation-disordered rocksalt oxides Fluorine substitution Ultrathin LiF coating Micron-sized single-crystal Reversible cationic-anionic redox 

分 类 号：TM912[电气工程—电力电子与电力传动] O646.541[理学—物理化学]