The effects of a mixed precipitant on the morphology and electrochemical performance of LiNi0.5Mn1.5O4cathode materials

Abstract

A series of LiNi0.5Mn1.5O4(LNMO) samples were synthesized by adjusting the molar ratio of (NH4)2CO3to Na2CO3in a mixed precipitant for evaluating the effects of ammonia from (NH4)2CO3as a complexing agent and Na2CO3as a precipitant on the morphology and electrochemical performances of LNMO. In this research, a rapid precipitation method followed by hydrothermal treatment was used to prepare the precursors of LNMO, and different molar ratios (0:1, 1:2, 1:1, 2:1, 1:0) of (NH4)2CO3to Na2CO3were used for mixed precipitants. The test results revealed that the cathode material exhibits the best electrochemical performance when the molar ratio of (NH4)2CO3to Na2CO3is set at 1:2, displaying a specific discharge capacity of 129.4 mA h g–1at 0.5 C and a capacity retention of 82.3% after 200 charge–discharge cycles. In addition, it still shows a high rate performance with a discharge capacity of 112.7 mA h g–1at 10 C and 98.8 mA h g–1at 20 C, which is attributed to an accurate Ni/Mn ratio, smaller primary particle sizes and a porous spherical morphology.