Review of spinel LiMn2O4 cathode materials under high cut-off voltage in lithium-ion batteries: Challenges and strategies

The growing demand for high energy and power density in lithium-ion batteries mandates the utilization of cathode material with improved capacity and output voltage. Among various cathode materials, spinel structured lithium manganese oxide stands out for its acceptable energy density, high working voltage, excellent safety, and cost-effectiveness. Extending the upper cut-off voltage of cathode materials is realized to be a convenient way of increasing the energy density of lithium-ion batteries. Nevertheless, as charging to a higher voltage (>4.3 V vs Li/Li+), several derogatory issues such as surface distortions, the interfacial reaction between cathode and electrolyte, and stress-induced cracking could emerge, leading to a rapid decline in capacity and cycle life. This review summarizes the failure mechanism of LiMn2O4, focusing on high voltage stability. Additionally, various modification strategies, such as doping and surface coating, are proposed to acquire high-voltage LiMn2O4. We also discuss prominent modification approaches for structural or electrolytes, such as concentration-gradient design, electrolyte additives, and solid-state electrolytes.