High-Performance Ni-Rich Li[Ni0.92−XCo0.04Mn0.04Alx]O2 Cathodes for High Energy Density Lithium-Ion Batteries

Abstract

A high-performing Ni-rich Li[Ni1−x−y−zCoxMnyAlz]O2 (NCMA) is developed by comparing the electrochemical performance of Li[Ni0.92−xCo0.04Mn0.04Alx]O2 cathodes (x = 0, 0.01, 0.03, and 0.05). Excessive Al leads to the accumulation of Al on secondary particle surfaces and at grain boundaries, resulting in the refinement of the cathode microstructure. Increasing the Al content enhances the degree of refinement, including primary particle elongation and radial alignment. A well-refined microstructure effectively dissipates the strain caused by the rapid contraction of unit cells during the H2 phase → H3 phase transition near the charge end, thereby suppressing the formation of internal cracks. An Al content of 3 mol% provides optimal overall electrochemical performance. The full cell with an optimized Li[Ni0.894Co0.041Mn0.034Al0.031]O2 cathode exhibits excellent long-term cycling stability, retaining >90% of its initial capacity after 500 cycles and an energy density of 740 Wh Kg-1. In contrast, a Li[Ni0.91Co0.04Mn0.04Al0.01]O2 cathode, in which Li and Ni cation mixing is prevented, loses 38.3% of its initial capacity after 500 cycles. This research demonstrates that an NCMA cathode with the optimal Al content can surpass existing layered cathodes and represents a new class of Ni-rich layered cathodes suitable for high-performance electric vehicles.