Challenges and Approaches for High-Voltage Spinel Lithium-Ion Batteries

Lithium‐ion (Li‐ion) batteries have been developed for electric vehicle (EV) applications, owing to their high energy density. Recent research and development efforts have been devoted to finding the next generation of cathode materials for Li‐ion batteries to extend the driving distance of EVs and lower their cost. LiNi0.5Mn1.5O4 (LNMO) high‐voltage spinel is a promising candidate for a next‐generation cathode material based on its high operating voltage (4.75 V vs. Li), potentially low material cost, and excellent rate capability. Over the last decade, much research effort has focused on achieving a fundamental understanding of the structure–property relationship in LNMO materials. Recent studies, however, demonstrated that the most critical barrier for the commercialization of high‐voltage spinel Li‐ion batteries is electrolyte decomposition and concurrent degradative reactions at electrode/electrolyte interfaces, which results in poor cycle life for LNMO/graphite full cells. Despite scattered reports addressing these processes in high‐voltage spinel full cells, they have not been consolidated into a systematic review article. With this perspective, emphasis is placed herein on describing the challenges and the various approaches to mitigate electrolyte decomposition and other degradative reactions in high‐voltage spinel cathodes in full cells. Danger, high voltage! LiNi0.5Mn1.5O4 high‐voltage spinel is a promising candidate for next‐generation cathode materials, but its commercialization is hampered by electrolyte instability and concurrent parasitic reactions at electrode/electrolyte interfaces (see figure). The known challenges in LiNi0.5Mn1.5O4/graphite full‐cell systems are reviewed. In addition, multiple strategies to overcome the issues and prolong the cycle life of full cells are introduced.