Reinforcing the surface conductivity and stability of primary particles for high-performance Li-rich layered Li1.18Mn0.52Co0.15Ni0.15O2via an integrated strategy

Abstract

A Li-rich layered oxide material of Li_1.18Mn_0.52Co_0.15Ni_0.15O₂ with Li₃PO₄ as an outer modification layer and a spinel as an inner modification layer on the surface of primary particles was synthesized by a facile synchronous method. A series of physical characterization techniques indicate that Li₃PO₄ and the spinel simultaneously form not only on the surface but also in the bulk of the cathode material during the preparation process. Consequently, a stable protective layer and a highly conductive interlayer are fabricated by the formation of the Li₃PO₄ and spinel phase on the primary particle surface of the cathode material. The modified sample exhibits an improved initial coulombic efficiency of approximately 88.5%. Moreover, the capacity retention of the modified sample increases to 92% after 100 cycles at a rate of 0.2C from 2.0 to 4.8 V compared to that of the pristine sample (62.7%). Moreover, the modified sample also exhibits an excellent rate capability of 171.4 mA h g⁻¹ at a 5C rate relative to the pristine sample (134.1 mA h g⁻¹). Our facile modification approach combines the merits of the spinel phase and the Li₃PO₄ compound. Also, our approach can remarkably suppress the structural transformation from layered to spinel-like and decrease the loss of active materials by mitigating the formation of corrosion pits on the particles as well as enhancing the dynamic performance of Li⁺ diffusion of Li-rich layered oxides.