Synthesis of LiNi0.5Mn1.5O4 via Ammonia-free Co-precipitation Method: Insight in the Effects of the Lithium Additions on the Morphology, Structure and Electrochemical properties

Stoichiometric sphere-like Ni0.25Mn0.75CO3 precursors have been synthesized by the ammonia-free co-precipitation via adjusting the Na2CO3 precipitant feeding. As an important factor in LiNi0.5Mn1.5O4 synthesis process, the effects of lithium additions on the physicochemical and electrochemical properties of the LiNi0.5Mn1.5O4 were extensively investigated. The lithium additions increase can strengthen the LiNi0.5Mn1.5O4 crystal growth and crystallization. Lack of lithium additions causes the formation of the lithium deficient compounds, while the excess of lithium additions induces the phase transformation from Fd-3m to P4(3)32 accompanied by the formation of the rock salt phase. The as-prepared spinel LiNi0.5Mn1.5O4 with lithium additions of 0.505 delivers 135.8 mAh center dot g(-1) at 147.0 mA center dot g(-1) with capacity retention of 90.06 % after 300 cycles. Even at 2940 mA center dot g(-1), the discharge capacity can reach to 96.7 mAh center dot g(-1). These excellent electrochemical performances are mainly ascribed to the Ni0.25Mn0.75CO3 precursors with homogenous elements distributions, the good morphology and crystal structure of LiNi0.5Mn1.5O4 at appropriate amounts of lithium additions.