AlPO4-Li3PO4 dual shell for enhancing interfacial stability of Co-free Li-rich Mn-based cathode

Abstract

Li-rich Mn-based cathode materials (LRM) have attracted extensive attention as key cathode material for achieving high energy density in lithium ion batteries. However, the irreversible oxygen precipitation and structural transformation during its cycling process, resulting in capacity and voltage degradation have heavily hindered practical applications. The Co-free Li-rich Mn-based cathode material Li1.2Ni0.185Mn0.585Fe0.03O2 by the modified Pechini method, the AlPO4-Li3PO4 double shell was formed in situ on its surface. The AlPO4 protective layer formed by the highly electronegative (PO4)3- with not only effectively inhibits the precipitation of surface oxygen, but also suppresses the interfacial side reactions and transition metal dissolution, thus raising the cycling performances. The formation of the outer Li3PO4 helps to remove the residual Li+ on the surface, accelerates the diffusion and charge transfer process of Li+ at the electrode/electrolyte interface. The synergistic modification of the AlPO4-Li3PO4 dual shell can significantly improve the cycling stability and rate performance. In particular, the 3% modified sample with a capacity retention of 74.8% after 200 cycles at 0.2 C. The first discharge specific capacity is 260.73 mAh g-1 at 0.1 C, and the initial coulombic efficiency reaches 84.96%. The lithium-ion full cell employing 3% and graphite exhibit a specific energy density of 440 Wh kg-1 at 0.1 C, and shows the best cycling stability with 78.3% capacity retention over 100 cycles at 1 C.