Structural and enhanced electrochemical performance of Co-free lithium-rich layered manganese-based Li1.2Mn0.6Ni0.2O2 cathodes via Na-doping at Li site for lithium-ion batteries

Abstract

Li-rich Co-free Mn-based cathode materials have attracted considerable attention in the development of lithium-ion batteries (LIBs) due to their impressive theoretical capacity and cost-effectiveness. Nevertheless, the inherent shortcomings in cycling stability and rate capability hinder their widespread application. Herein, Na-doped Li_1.2-xNa_xMn_0.6Ni_0.2O₂ (x = 0, 0.01, 0.03, 0.05, 0.08, 0.10) is synthesized using Na₂CO₃ as the source of Na. Density functional theory (DFT) calculations reveal that the presence of Na⁺ introduction enlarges the between-layer spacing of Li_1.2Mn_0.6Ni_0.2O₂, reduces the band gap width, reduces the cation mixing phenomenon, and increases the Li⁺ diffusion rate and electronic conductivity. Experimental electrochemical assessments demonstrate that the cathode material with a Na doping level of 0.03 exhibits remarkable performance: it achieves a discharge specific capacity of 204 mAh·g⁻¹ at 0.1C and retains 87.4% of its capacity after 100 cycles. These findings underscore the efficacy of Na doping in enhancing the electrochemical properties of Li-rich Mn-based cathode materials, thereby advancing their potential for practical application in LIBs.