Radially Microstructural Design of LiNi_0.8Co_0.1Mn_0.1O₂ Cathode Material toward Long-Term Cyclability and High Rate Capability at High Voltage

Abstract

Layered LiNi0.8Co0.1Mn0.1O2 oxide (NCM811) has attracted wide attention as a candidate for the high-energy cathode in lithium-ion batteries (LIBs). It is necessary to amend both the insufficient cycling life caused by microstructural degradation and the poor rate capability due to the restricted kinetics, especially at high voltage. Here we design and synthesize a special NCM811 (R-NCM), containing primary particles arranged radially from the surface to the interior, to address these issues. Compared with the structure of primary particles randomly distributed in conventional NCM811 (C-NCM), this special microstructure in R-NCM shows more reversible cell volume variation, providing more open paths for Li+ transfer, and, more importantly, it significantly alleviates the mechanical stress induced by volume variation inside the particle when cycled to high voltage. Consequently, R-NCM delivers high reversible capacity (221.5 mAh g–1 at a current rate of 0.2 C) and increased rate capability (143 mAh g–1 at a current rate of 10 C) under a cutoff voltage of 4.6 V. Moreover, the long-term cycling stability in R-NCM at 4.6 V is remarkably increased due to the special microstructure. This morphological design provides a method for preparing advanced cathode materials for practical applications.