Beneficial Effect of LiFePO4/C coating on Li0.9Mn1.6Ni0.4O4 obtained by microwave heating

Abstract

There is increasing interest in 5 V vs. Li/Li+ cathodes due to their high energy density; however, unfavourable reactions occur at potentials higher than 4.8 V vs. Li/Li+. In order to avoid degradation of the active material, the L0.9MNO (Li0.9Mn1.6Ni0.4O4) with spinel type structure was coated with nanoplates of LFP/C (LiFePO4 /C) with olivine type structure and a carbon layer of ∼ 2 nm, seeking to improve the stability of the L0.9NMO spinel phase and retain active sites for lithium intercalation. L0.9MNO-LFP/C composite was prepared by microwave heating at power of 10 W obtaining a thin LFP/C layer of around 20 nm on L0.9MNO particles. Homogeneous layer and a low formation of by-products in the electrolyte-cathode interphase were obtained with LFP/C amounts of 4 and 6 wt%. The highest cycling stability was achieved with LFP/C amount of 4 wt% (96.8% after 100 cycles). The high rate capability was obtained in the composite with 2 wt% of LFP/C (89% retention at 20C), the effect of which is attributed to the charge transfer kinetic improvement in L0.9MNO spinel phase that the carbon coating of LFP/C provided without affecting the lithium mobility within active material.