Synthesis and electrochemical performance enhancement of Li2MnSiO4 cathode material for lithium-ion batteries via Mn-site Cr doping

Abstract

Li₂MnSiO₄ stands out as a promising cathode material for lithium-ion batteries (LIBs) because of its remarkable theoretical capacity, excellent thermal stability, low cost, and environmental benefits. However, its practical application is hindered by poor electronic conductivity and lithium-ion diffusion rates. To overcome these challenges, Li₂Mn_1-xCr_xSiO₄ cathode materials were prepared through solid-state doping and a two-step calcination method. By doping Cr into the Mn site of Li₂MnSiO₄, the electrochemical performance can be significantly improved. TG-DTA tests were conducted to determine the optimal calcination temperature to ensure stable synthesis of the material. The research found that an optimal Cr doping level of 0.06 resulted in superior electrochemical performance, achieving a discharge capacity of 174.9 mAh g⁻¹ at 0.1C. This improvement is due to the reduction in grain size, which increases the specific surface area and enhances Li⁺ diffusion. Additionally, the larger ionic radius of Cr creates more vacancies in the lattice, facilitating electron and ion migration. The CrO bond, being stronger than the MnO bond, further contributes to improved structural stability. Thus, Cr doping effectively addresses conductivity and diffusion limitations, leading to superior electrochemical performance and advancing high-performance LIBs.