Synthesis of LiNi 0.5 Mn 1.5 O 4 via Ammonia‐free Co‐precipitation Method: Insight in the Effects of the Lithium Additions on the Morphology, Structure and Electrochemical properties

Stoichiometric sphere‐like Ni 0.25 Mn 0.75 CO 3 precursors have been synthesized by the ammonia‐free co‐precipitation via adjusting the Na 2 CO 3 precipitant feeding. As an important factor in LiNi 0.5 Mn 1.5 O 4 synthesis process, the effects of lithium additions on the physicochemical and electrochemical properties of the LiNi 0.5 Mn 1.5 O 4 were extensively investigated. The lithium additions increase can strengthen the LiNi 0.5 Mn 1.5 O 4 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 LiNi 0.5 Mn 1.5 O 4 with lithium additions of 0.505 delivers 135.8 mAh•g ‐1 at 147.0 mA•g ‐1 with capacity retention of 90.06 % after 300 cycles. Even at 2940 mA•g ‐1 , the discharge capacity can reach to 96.7 mAh•g ‐1 . These excellent electrochemical performances are mainly ascribed to the Ni 0.25 Mn 0.75 CO 3 precursors with homogenous elements distributions, the good morphology and crystal structure of LiNi 0.5 Mn 1.5 O 4 at appropriate amounts of lithium additions.