Fast Charge-Transport Interface on Primary Particles Boosts High-Rate Performance of Li-Rich Mn-Based Cathode Materials.

Abstract

A Li-rich Mn-based layered oxide cathode (LLO) is one of the most promising cathode materials for achieving high-energy lithium-ion batteries. Nevertheless, the intrinsic problems including sluggish kinetics, oxygen evolution, and structural degradation lead to unsatisfactory performance in rate capability, initial Coulombic efficiency, and stability of LLO. Herein, different from the current typical surface modification, an interfacial optimization of primary particles is proposed to improve the simultaneous transport of ions and electrons. The modified interfaces containing AlPO4 and carbon can effectively increase the Li+ diffusion coefficient and decrease the interfacial charge-transfer resistance, thereby achieving fast charge-transport kinetics. Moreover, the in situ high-temperature X-ray diffraction confirms that the modified interface can improve the thermal stability of LLO by inhibiting the lattice oxygen release on the surface of the delithiated cathode material. In addition, the chemical and visual analysis of the cathode-electrolyte interface (CEI) composition clarifies that a highly stable and conductive CEI film generated on the modified electrode can facilitate interfacial kinetic transmission during cycling. As a result, the optimized LLO cathode exhibits a high initial Coulombic efficiency of 87.3% at a 0.2C rate and maintains superior high-rate stability with a capacity retention of 88.2% after 300 cycles at a 5C high rate.