Investigation on Spinel LiNi_0.5Mn_1.5O₄ Synthesized by MnCO₃ Prepared under Different Conditions for Lithium-Ion Batteries

LiNi_0.5Mn_1.5O₄(LNMO) is synthesized using MnCO₃ as manganese source in this paper. MnCO₃ is prepared by precipitation reaction between MnSO₄ and NH₄HCO₃. Two different adding processes of precipitant, slow dropping and rapid addition, are compared. MnCO₃ particles have core-shell structure. When the precipitant is added slowly, the shell occupies a larger proportion in MnCO₃ particles. Compared to slow dropping process, rapid addition of precipitant may reduce particle size and improve dispersity of MnCO₃ and LNMO particles. LNMO prepared by large MnCO₃ particles (>8 μm) and small MnCO₃ particles (∼1 μm) have core-shell structure and hollow structure, respectively. LNMO with hollow structure are not stable and break easily during cycling. Slow addition process for precipitant can improve the rate performance of LNMO. When the concentration of MnSO₄ solution is 0.04 mol L⁻¹ and precipitant is added slowly, LNMO exhibits the best electrochemical performances. Its particle size is 8 μm and its discharge capacities at 0.2C and 20 C are 123 and 62 mAh g⁻¹, respectively. After 500 cycles at 1 C, its discharge capacity is still as high as 114.1mAh g⁻¹, which maintains 92.4 % of its initial capacity.