Lithiation Mechanism Change Driven by Thermally Induced Grain Fining and Its Impact on the Performance of LiMn2O4 in Lithium‐Ion Batteries

Abstract The nature of precursors employed in the synthesis of lithium‐ion battery cathode materials is a crucial performance‐dictating factor. Therefore, it is of great importance to establish a way to manipulate the precursor and seek a comprehensive understanding of its influence on the electrochemical behavior of a targeted electrode material. A thermal route is herein demonstrated for the synthesis of lithium‐excess LiMn 2 O 4 (LMO) by exploiting an intriguing thermal phenomenon, thermally induced grain fining, and sheds light on how it affects the mechanism and kinetics of lithiation, and, furthermore, the electrochemical behavior of LMO. Detailed insights into the lithiation mechanism and kinetics reveal that the use of a finely grained, porous Mn 3 O 4 , which possesses an open crystal structure, is a key to the success of incorporating excess Li. In addition, this in‐depth electrochemical investigation verifies a very recent theoretical prediction of faster Li diffusion kinetics enabled by excess Li.