Electrode Optimization using Bimodal Sized Particles in Ni-Rich NCM Cathodes for Enhanced Volumetric Energy Density and Cycle Life

초록

High-nickel-layered oxide cathodes have emerged as promising candidates for high-energy lithium-ion batteries, owing to their high capacity and reduced cobalt content. In this study, LiNi0.93Co0.03Mn0.04O2 (NCM9334) cathode materials were synthesized through co-precipitation, including a smallparticle variant (~2 μm secondary particles) and a conventional larger-particle variant (~15–20 μm). The small-particle cathode achieved higher initial discharge capacity (≈209mAh·g−1 at 0.1C) compared with the larger-particle cathode (≈190 mAh·g−1) because of the shorter lithium-ion diffusion pathways. However, small particles exhibited slightly faster capacity fading over 100 cycles (retaining ~76% versus ~78% for large particles). To combine the advantages of both materials, bimodal cathodes were prepared by blending small and large particles in various ratios. An optimal 50:50 bimodal composite achieved a high volumetric discharge capacity of ~306 mAh·cc−1 at 1C with ~80% capacity retention over 100 cycles. All bimodal electrodes exhibited improved cycle stability compared with single-sized cathodes, with even a 5% small-particle blend yielding ~85% retention. The findings indicate that decreasing the dimensions of secondary particles and implementing a bimodal particle size distribution can markedly improve the performance of Ni-rich cathodes. This approach offers a promising avenue for enhancing the energy density and prolonging the lifespan of lithium-ion batteries utilized in electric vehicles.

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