LiCr0.2Ni0.4Mn1.4O4 spinels exhibiting huge rate capability at 25 and 55 °C: Analysis of the effect of the particle size

The comparison of the rate capability of LiCr_0.2Ni_0.4Mn_1.4O₄ spinels synthesized by the sucrose aided combustion method at 900, 950 and 1000 °C is presented. XRD and TEM studies show that the spinel cubic structure remains unchanged on heating but the particle size is notably modified. Indeed, it increases from 695 nm at 900 °C to 1465 nm at 1000 °C. The electrochemical properties have been evaluated by galvanostatic cycling at 25 and 55 °C between 1 C and 60 C discharge rates. At both temperatures, all samples exhibit high working voltage (∼4.7 V), elevated capacity (∼140 mAh g⁻¹) and high cyclability (capacity retention ∼99% after 50 cycles even at 55 °C). The samples also have huge rate capability. They retain more than 70% of their maximum capacity at the very fast rate of 60 C. The effect of the particle size on the rate capability at 25 and at 55 °C has been investigated. It was demonstrated that LiCr_0.2Ni_0.4Mn_1.4O₄ annealed at 900 °C, with the lowest particle size, has the best electrochemical performances. In fact, among the LiNi_0.5Mn_1.5O₄-based cathodes, SAC900 exhibits the highest rate capability ever published. This spinel, able to deliver 31,000 W kg⁻¹ at 25 °C and 27,500 W kg⁻¹ at 55 °C is a really promising cathode for high-power Li-ion battery.