Improved Electrochemical Performance of Spinel LiNi0.5Mn1.5O4 Cathode Materials with a Dual Structure Triggered by LiF at Low Calcination

High-voltage spinel LiNi0.5Mn1.5O4 (LNMO), which has the advantages of high energy density, low cost, environmental friendliness, and being cobalt-free, is considered one of the most promising cathode materials for the next generation of power lithium-ion batteries. However, the side reaction at the interface between the LNMO cathode material and electrolyte usually causes a low specific capacity, poor rate, and poor cycling performance. In this work, we propose a facilitated method to build a well-tuned dual structure of LiF coating and F- doping LNMO cathode material via simple calcination of LNMO with LiF at low temperatures. The experimental results and DFT analysis demonstrated that the powerful interface protection due to the LiF coating and the higher lithium diffusion coefficient caused by F- doping effectively improved the electrochemical performance of LNMO. The optimized LNMO-1.3LiF cathode material presents a high discharge capacity of 140.3 mA h g-1 at 1 C and 118.7 mA h g-1 at 10 C. Furthermore, the capacity is retained at 75.4% after the 1000th cycle at 1 C. Our research provides a concrete guidance on how to effectively boost the electrochemical performance of LNMO cathode materials.