The choice of organic acids as complexing agent affecting on the electrochemical properties of spinel LiNi0.5Mn1.5O4

In this work, three organic acids were, respectively, used as complexing agent to synthesize LiNi0.5Mn1.5O4 (LNMO) materials. Lactic and malic acid were applied for the first time to prepare LNMO successfully. The materials are well crystallized and show a disordered Fd3m structure. Citric acid is conducive to grain refinement and has the smallest grain size and biggest surface area among these samples. Material with citric acid presents a better stability of the coulombic efficiency exceeding 95% at 1 C rate after 500 cycles and retains more than 70% capacity retention, while lactic acid shows a fast capacity decay during the charging and discharging circulation. EIS spectra indicate that small grain size is good for the charge transfer, and LNMO with citric acid possesses the greatest DLi+ of 5.39 × 10−12 cm2 s−1, while it is two times bigger than that with malic acid and almost ten times as fast as LNMO by lactic acid. Citric acid has the optimal electrochemical performance than lactic and malic acid. Our work could provide a pretty reference for the researchers to select a special acid.