Enhanced electrochemical properties of potassium-doped lithium-rich oxide@carbon as cathode material for lithium-ion batteries

Lithium-rich layered oxides are believed to be the most competitive cathode materials for next-generation lithium-ion batteries (LIBs) due to their high specific capacity, but the poor cycle stability and voltage attenuation severely limit their commercial applications. In this paper, a simple method combining surface treatment via pyrolysis of polyvinyl alcohol (PVA) and potassium ions (K⁺) doping, is designed to improve the above defects of the cobalt-free Lithium-rich material Li_1.2Mn_0.6Ni_0.2O₂ (LMR). The insoluble surface byproduct Li₂CO₃ and amorphous carbon nanolayer derived from the pyrolysis process of PVA alleviate the corrosion of acidic species with a favorable conductivity, while a large radius of K⁺ can enlarge the space of the lithium (Li) layer to facilitate the diffusion of Li⁺, suppress voltage polarization, and synchronously restrain the transformation from a layered structure to a spinel-like structure. After modification, the LMR material exhibits a great initial discharge capacity of 266.0 mAh g⁻¹ at 0.1C, a remarkable rate capability of 159.1 mAh g⁻¹ at 5C and an extremely high capacity retention of 98.5% over 200 cycles at 0.5C with a small voltage drop.