Polycrystalline secondary particle size regulation boosts the cycle performance of ultra-high-nickel layered oxide cathode materials

Abstract

The ultra-high-nickel layered oxide cathodes of LiNixCoyMn1-x-yO2 (NCM, and x ≥ 0.9) have been considered promising candidates to meet the growing demand for high-energy-density lithium-ion batteries (LIBs) due to their high specific capacity. However, their capacity retention tends to be low in practical applications due to the instability of their structure during charge and discharge cycles. Herein, a strategy for regulating secondary particle size is put forward to alleviate the crystal volume change and suppress the H2-H3 phase transitions, ultimately stabilizing the structure against microcrack development and improving the cycle performance of the ultra-high-nickel layered oxide cathodes. The results show that LiNi0.90Co0.05Mn0.05O2 (NCM90) with a D50 of 8.6 μm (NCM90–9) exhibits the optimum electrochemical performance compared to its counterparts, which delivers a high cycling stability (91.86 % capacity retention after 200 cycles at 0.5 C) and a good rate performance (127.3 mAh·g-1 at 6 C). The superior performance of NCM90–9 is attributed to the suppression of microcracks within secondary particles and parasitic reactions with the electrolyte, which are determined by its secondary particle size. This result provides valuable guidelines for the development of ultra-high-nickel layered oxide cathodes.