Rational Design of a LiVPO4F@C Microsphere Cathode Enabled by a One-Step Hydrothermal Reaction for Lithium-Ion Batteries

LiVPO4F is an attractive cathode material due to its high operating voltage, high energy density, and stable structure, but its application is still hindered by low electrical conductivity and complicated synthesis processes. Here, the microsphere LiVPO4F@C cathode material with a high discharge plateau and stable structures is synthesized by a simple hydrothermal reaction. The formation mechanisms of the microsphere LiVPO4F are clarified. Surfactant hexadecyl trimethylammonium bromide is self-assembled into a spherical micelle matrix during the hydrothermal reaction and formed the microsphere LiVPO4F@C particles through multilayer adsorption. Meanwhile, the effects of pH value and the content of LiF on the morphology, structure, and electrochemical performance of the LiVPO4F@C cathode material are investigated. When the value of pH is close to neutral, the fluorine can be effectively deposited to form spherical LiVPO4F. With the addition of LiF at a ratio of 1.4, the prepared LiVPO4F@C exhibits better crystallinity and uniform spherical morphology, with excellent rate capability and cycling stability and a capacity retention of 93.60% at 5C. This work provides a simple and effective preparation solution for exploring a high-performance LiVPO4F@C cathode material for lithium-ion batteries.