Impact of Local Separation on the Structural and Electrochemical Behaviors in Li2MoO3LiCrO2 Disordered Rock‐Salt Cathode Material. Issue 3 (20th November 2020)

• Record Type: Journal Article
• Authors: Lee, Hayeon; Choi, Woosung; Lee, Wontae; Shim, Jae‐Hyun; Kim, Young‐Min; Yoon, Won‐Sub
• Is Part Of: Advanced energy materials. Volume 11:Issue 3(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-11-20
• Subjects: disordered rock‐salt cathodes -- domain separation -- Li‐ion batteries -- metal–metal bond -- short‐range order; Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.202002958
• Languages: English
• ISSNs: 1614-6832

Abstract

Abstract: Li‐excess disordered rock‐salt oxides have emerged as a promising group of cathode materials for Li‐ion batteries. However, the real cation distribution and short‐range order of various disordered oxides have not been fully determined, making it difficult to understand their actual structures and reaction processes. Here, Li1.233 Mo0.467 Cr0.3 O2 (LMCO), as a cathode material that undergoes a unique in situ cation‐disorder is investigated. Through synchrotron‐ and lab‐based multiscale characterizations, it is observed that the as‐prepared material has separate domains resembling Li2 MoO3 and LiCrO2 even in a single‐phase bulk crystal structure. The Mo/Li‐rich and Cr/Li‐poor domains are maintained even after significant cation‐disorder. The formation and dissociation of short MoMo bonds along with a unique MoO6 distortion in Mo/Li‐rich domain of disordered LMCO leads to minimal lattice parameter changes during Mo redox reactions. This phenomenon is intensified when the structure becomes more disordered owing to the dissipation of anisotropy. In disordered LMCO, the Mo 4+/6+ redox is highly reversible, while Cr 3+/4+ redox is not. Finally, based on the local separation that induces different 0‐TM diffusion abilities according to the different domains in disordered LMCO, the mechanisms of the domain‐dependent kinetics, asymmetric Li + diffusion, and linked hysteresis/degradation processes are explained. Abstract : This work shows how specific atomic arrangements can significantly affect the structural and electrochemical behaviors of disordered rock‐salt materials. Combined anisotropic local distortions involving a formation–dissociation of short metal–metal bonds lead to minimal lattice volume changes during cycling. Fast/sluggish Li + diffusion in Li‐rich/Li‐poor domains and accompanying asymmetric Li + diffusion increase voltage hysteresis and cause element‐specific degradation.