Growth of Polyhedral LiNi0.5Co0.2Mn0.3O₂ Crystals in a Molten Li₃BO₃ Flux and Their Role in Electrode Density and Dispersion Design

Electrode structure design is a crucial aspect for realizing high output and energy density batteries. Although secondary particles are generally used as active materials in batteries, it is difficult to improve the electrode density as well as the dispersibility of active materials. Primary particles with well-developed crystal faces are candidates to replace secondary particle active materials as usual cases. Since the crystalline material is harder than the secondary particles, the electrode structure can be changed to a different structure than before. In this study, we grow LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) crystals with reasonable capacity and investigate the effect of crystal particles on the electrode structure. The Li 3 BO 3 flux-grown polyhedral NCM523 crystal particles exhibit battery performance similar to that of the NCM523 secondary particles. Using these NCM523 crystals, we fabricate two types of electrodes: one composed of NCM523 crystals and the other composed of a mixture of NCM523 secondary particles and crystals. The electrode density and dispersibility of the active materials are increased by applying high pressing pressure or pulverizing the secondary particles and efficient filling and dispersion, respectively. By the addition of crystal particles, the discharge capacity at 10 C is improved by up to approximately 350 mA h cm –3, which is 170% of the capacity of commercial NCM523. Our findings indicate that the addition of crystal particles drastically improves the electrode structure without replacing the secondary particles. This insight provides the guidelines for electrode designing and manufacturing processes to achieve enhanced battery performance at low cost with various active materials.