B/Al Codoped/Coated Ultra-High Nickel Cobalt-Free Material with Excellent High Voltage/Rate Cycle Stability

Ultrahigh nickel cobalt-free cathode materials have high energy density and are very promising materials for application in lithium-ion batteries. However, they face severe challenges of overall degradation in the interface/lattice structure stability during charge and discharge, resulting in poor safety and a short cycle life. In this paper, the B/Al codoping/coating is applied to LiNi0.9Mn0.1O2 (NM90). The LiAlO2/LiBO2 coating formed in situ by B/Al and surface residual alkali helps to reduce O2 evolution and restrain side reactions on surface. The B/Al codoping resulting from high-temperature thermal diffusion significantly expands the layer spacing, thus improving the Li+ diffusion rate. After 300 cycles, the optimized NM90-1% AB material achieves 86.5% capacity retention (1 C, 2.7–4.3 V, 25 °C) compared to 68.5% for the pristine NM90 material. Furthermore, its capacity retention can reach 84.7% after 300 cycles at 4.4 V and 5 C, which is much higher than the 58.9% of NM90 material. Even at 10 C, the specific discharge capacity of the NM90-1% AB material can still reach 155.1 mA h/g, but the NM90 material only has 142.8 mA h/g. It is obvious that the B/Al codoped/coated strategy can enhance the interface/lattice structural stability of NM90 material.