Phase Engineering of CoMoO4 Anode Materials toward Improved Cycle Life for Li+ Storage†

Abstract

Main observation and conclusionAnode materials based on conversion reactions usually possess high energy densities for lithium‐ion batteries (LIBs). However, they suffer from poor rate performance and cycle life due to serious volume changes. Herein, α/β‐CoMoO4 heterogeneous nanorods are synthesized via a facile co‐precipitation method, and further are phase‐engineered through varying calcination temperature, accomplishing the obviously improved cycle life and rate performance as anodes for LIBs. When evaluated at a current density of 1.0 A·g–1, the optimal nanorods with an α/β phase ratio of 6.0 afford the reversible capacity of 1143.6 mAh·g–1 after 200 cycles, outperforming most of recently reported bimetal oxides. Li+ storage mechanism is further analyzed by using in‐situ X‐ray diffraction and ex‐situ transition electronic microscopy. It's revealed that β‐CoMoO4 follows a one‐step conversion reaction; while α‐CoMoO4 proceeds an intercalation pathway before the conversion reaction. Grading storage of Li+ would alleviate the volume effect of heterostructured α/β‐CoMoO4, forming electronically conductive network evenly composed of Co and Mo nanograins to enable the reversible electrochemical conversion. This work is anticipated to give some hints for the rational design of high‐performance energy materials.