Clarification of underneath capacity loss for O3-type Ni, co free layered cathodes at high voltage for sodium ion batteries  

作　　者：Dong Zhou De Ning Jun Wang Jiahua Liu Gaoyuan Zhang Yinguo Xiao Jiaxin Zheng Yongli Li Jie Li Xinzhi Liu 

机构地区：[1]Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices,School of Physics,Sun Yat-sen University,Guangzhou 510275,Guangdong,China [2]School of Innovation and Entrepreneurship,Southern University of Science and Technology,Shenzhen 518055,Guangdong,China [3]Centre for Photonics Information and Energy Materials,Shenzhen Institutes of Advanced Technology,Chinese Academy of Sciences,Shenzhen 518055,Guangdong,China [4]School of Advanced Materials,Peking University Shenzhen Graduate School,Shenzhen 518055,Guangdong,China [5]Institute for Clean Energy Technology,North China Electric Power University,Beijing 102206,China [6]Department of Energy,Politecnico di Milano,Via Lambruschini 4,Milano 20156,Italy [7]Centre for Physical Mechanics and Biophysics,School of Physics,Sun Yat-sen University,Guangzhou 510275,Guangdong,China

出　　处：《Journal of Energy Chemistry》2023年第2期479-486,I0012,共9页能源化学（英文版）

基　　金：financial support of the Guangdong Basic and Applied Basic Research Foundation(2019A1515110897 and 2019B1515120028)。

摘　　要：Earth abundant O3-type NaFe_(0.5)Mn_(0.5)O_(2)layered oxide is regarded as one of the most promising cathodes for sodium ion batteries due to its low cost and high energy density.However,its poor structural stability and cycle life strongly impede the practical application.Herein,the dynamic phase evolution as well as charge compensation mechanism of O3-type NaFe_(0.5)Mn_(0.5)O_(2)cathode during sodiation/desodiation are revealed by a systemic study with operando X-ray diffraction and X-ray absorption spectroscopy,high resolution neutron powder diffraction and neutron pair distribution functions.The layered structure experiences a phase transition of O3→P3→OP2→ramsdellite during the desodiation,and a new O3’phase is observed at the end of the discharge state(1.5 V).The density functional theory(DFT)calculations and nPDF results suggest that depletion of Na^(+)ions induces the movement of Fe into Na layer resulting the formation of an inert ramsdellite phase thus causing the loss of capacity and structural integrity.Meanwhile,the operando XAS clarified the voltage regions for active Mn^(3+)/Mn^(4+)and Fe^(3+)/Fe^(4+)redox couples.This work points out the universal underneath problem for Fe-based layered oxide cathodes when cycled at high voltage and highlights the importance to suppress Fe migration regarding the design of high energy O3-type cathodes for sodium ion batteries.

关 键 词：Sodium ion batteries Layered oxide cathode Iron migration Operando X-ray absorption spectroscopy Neutron measurements 

分 类 号：TM912[电气工程—电力电子与电力传动] TQ131.12[化学工程—无机化工]