Effect of Oxidative Synthesis Conditions on the Performance of Single‐Crystalline LiMn2‐xMxO4 (M = Al, Fe, and Ni) Spinel Cathodes in Lithium‐Ion Batteries

Abstract LiMn 2 O 4 (LMO) spinel cathode materials attract much interest due to the low price of manganese and high power density for lithium‐ion batteries. However, the LMO cathodes suffer from the Mn dissolution problem at particle surfaces, which accelerates capacity fade. Herein, the authors report that the oxidative synthesis condition is a key factor in the cell performance of single‐crystalline LiMn 2‐ x M x O 4 (0.03 ≤ x ≤ 0.1, M = Al, Fe, and Ni) cathode materials prepared at 1000 °C. The use of oxygen flow during the spinel‐phase formation minimizes the presence of oxygen vacancies generated at 1000 °C, thereby yielding a stoichiometrically doped LMO product; otherwise, the spinel cathode prepared in atmospheric air readily loses capacity due to the oxygen vacancies in the structure. As a way of circumventing the use of oxygen flow, a one‐pot, two‐step heating in air at 1000 °C and subsequently at 600 °C is used to yield the stoichiometric LMO product. The lithiation heating at 1000–600 ⁰C resulted in a significant improvement in the cycling stability of the prepared LMO cathode in graphite‐based full cells. This study on oxidative synthesis conditions also confirms the advantage of minimizing the surface area of the cathode particles.