Effects of precursor treatment on the structure and electrochemical properties of spinel LiMn2O4 cathode

• The Mn–Na oxide with high valence can be easily formed and result in impurity diffraction peaks for the LiMn2O4.
• Feeding N2 and adding hydrazine could effectively prevent Mn2+ from being oxidized into the Mn–Na oxide.
• LiMn2O4 synthesized by our method delivers the excellent structural characteristics and electrochemical performances.

As a precursor of spinel LiMn2O4 cathode, manganese oxide is prepared by co-precipitation via a two-step drying method. The effects of precursor treatment on the structure, morphology, and electrochemical performance of the synthesized spinel LiMn2O4 are studied using contrasting experiments involving the addition of hydrazine, N2, and H2O2. The tests show that different treatments have a great effect on the crystal structure, morphology, tap density, and electrochemical performance of LiMn2O4. When the precursor is treated by adding hydrazine and pure N2, the synthesized LiMn2O4 shows an integral lattice, uniform particle size, a pure spinel phase with an ordered octahedral crystal structure, and high tap density (2.23 g cm−3). The electrochemical results show that spinel LiMn2O4 exhibits higher specific capacity and better cyclic stability than other samples, especially at an elevated temperature and high discharge current. The initial discharge capacity of the electrode is 110.8 mAh g−1 at a rate of 3 °C, and exhibits a good capacity retention of 96.4% after 30 cycles; at a rate of 5 °C, the initial discharge capacity is 107.5 mAh g−1, with a capacity retention of 87.3% after 50 cycles.