Enhancing LiNi0.5Mn1.5O4 Cathode Stability via Al Doping for High-Voltage Lithium-Ion Batteries

Abstract

Spinel-type LiNi_0.5Mn_1.5O₄ is a promising high-voltage cathode material due to its advantages of high charge–discharge potential platform and high-energy density. However, the dissolution behavior of transition metal ions under high operating voltage can cause rapid degradation of the electrochemical performance of the battery, severely restricting the commercial application process of this material. To address the aforementioned bottleneck issues, this study introduced Al element doping during the precursor preparation stage and successfully synthesized Al-doped modified spinel cathode materials. The structural characterization results indicate that Al doping can effectively regulate the crystal morphology of the material, promote the evolution of particles from spherical to regular crystal forms, and reduce the relative content of Mn³⁺, thereby achieving effective suppression of Mn dissolution. Electrochemical testing shows that among the series of doped samples, LiNi_0.5Mn_1.48Al_0.02O₄ exhibits the best rate performance and long-cycle stability: its first discharge specific capacity at 0.2 C can reach 126.7 mAh·g⁻¹, and after 500 cycles at 1 C, the capacity retention rate is still as high as 98.4%. The excellent electrochemical performance mentioned above confirms that in situ doping in the precursor stage is an efficient and feasible strategy for spinel positive electrode modification.