Cu Doping-Enabled Control of Grain Boundary Fusion and Particle Size in Single-Crystal LiNi0.5Co0.2Mn0.3O2 Cathode Materials

Copper (Cu) doping is recognized as an effective strategy to enhance the electrochemical properties of LiNi1−x−yCoxMnyO2 (NCM) cathode materials. However, the influence of Cu2+ doping on particle size and grain boundary fusion remains insufficiently explored. A simple microwave-assisted solution combustion synthesis method was used to introduce Cu2+ into LiNi0.5Co0.2Mn0.3O2 (NCM523), aiming to regulate particle size and grain boundary fusion. The results demonstrate that increasing the Cu2+ doping content promotes particle growth, while an appropriate doping level reduces the degree of grain boundary fusion and cation mixing. Benefiting from these structural improvements, the optimized LiNi0.5Co0.2Mn0.29Cu0.01O2 (Cu–1) cathode exhibits significantly enhanced electrochemical performance, delivering a discharge capacity of 128.6 mAh g−1 after 100 cycles at 0.2 C, which is 32 mAh g−1 higher than value of the undoped sample (96.6 mAh g−1). These findings underscore that tailored Cu2+ doping can effectively optimize the microstructure of NCM523, leading to superior cycling stability, and provide new insights into the design of high-performance NCM cathodes.