The Effect of Boron Doping on Structure and Electrochemical Performance of Lithium-Rich Layered Oxide Materials.

Polyanion doping shows great potential to improve electrochemical performance of Li-rich layered oxide (LLO) materials. Here, by optimizing the doping content and annealing temperature, we obtained boron-doped LLO materials Li1.2Mn0.54Ni0.13Co0.13BxO2 (x = 0.04 and 0.06) with comprehensively improved performance (94% capacity retention after 100 cycles at 60 mA/g current density and a rate capability much higher compared to that of the pristine sample) at annealing temperatures of 750 and 650 °C, respectively, which are much lower than the traditional annealing temperature of similar material systems without boron. The scenario of the complex crystallization process was captured using Cs-corrected high-angle annular dark field scanning transmission electron microscopic (HAADF-STEM) imaging techniques. The existence of layered, NiO-type, and spinel-like structures in a single particle induced by boron doping and optimization of annealing temperature is believed to contribute to the remarkable improvement of cycling stability and rate capability.