High-performance spherical LiVPO4F/C cathode enabled by facile spray pyrolysis

LiVPO4F suffers problems of difficulty in synthesis and poor conductivity. To solve these,herein sub-micro spherical LiVPO4F/C is synthesized from a highly-reactive hollow VPO4/C sphere that is derived from a facile and fast spray pyrolysis for the first time. Uniform carbon coating layer with a thickness of 5–8 nm is observed on the surface of the particles,helping to improve the electronic conductivity,suppress the particle growth and protect the particles from corrosion by the electrolyte. The particles are shaped as fine sub-micro spheres,which are beneficial for shortening the distance for Li+ transport. Rietveld refinement for the X-ray diffraction pattern of as-prepared sample shows high-purity triclinic LiVPO4F with an enlarged lattice volume,enabling faster Li+ transport in the prepared material. Accordingly,the resulted LiVPO4F/C demonstrates superior electrochemical properties,delivering 135.4,91.1 mA hg-1 at 1,40 C respectively,and remaining the capacity of 93.3 mA hg-1 after 500 cycles at 20 C with the retention of 95.0%. The method introduced here provides an efficient way to address the serious problems of preparing high-purity Li VPO4F with good conductivity.