Synthesis and enhanced electrochemical performance of LiNi0.5Mn1.5O4 cathode materials under the assistance of polyvinylpyrrolidone

LiNi 0 .5 Mn 1 .5 O 4 materials with hierarchical microsphere structure are prepared by PVP-assisted coprecipitation-hydrothermal method followed by high-temperature calcination. Effects of PVP molecular weights on the structure, morphology, and electrochemical properties of LiNi 0.5 Mn 1.5 O 4 are investigated. It is found that PVP addition improves the crystallinity and disordering degree of LiNi 0.5 Mn 1.5 O 4 . PVP molecular weights exert great influence on the particle morphology. With the increase of molecular weight, primary particle size gradually decreases and secondary particle distribution becomes more uniform. Compared with LNMO-PVP M and LNMO-PVP H , LNMO-PVP L particle possesses extra {110} surface besides {111} and {100} surfaces. Electrochemical results show that PVP addition enhances the electrochemical performance of LiNi 0.5 Mn 1.5 O 4 , due to higher crystallinity, higher cation disordering degree, smaller primary particle size, and more uniform secondary particle distribution. LNMO-PVP L material exhibits the optimal electrochemical performance, due to extra {110} exposed surface and higher disordering degree, as well as relatively large primary particle size and slightly severe agglomerate structure.