Mesocarbon Microbeads Boost the Electrochemical Performances of LiFePO₄ ||Li₄ Ti₅ O₁₂ through Anion Intercalation

Li-ion batteries with LiFePO₄ cathode and Li₄ Ti₅ O₁₂ anode show promise for storing renewable energy. However, their low output voltage results in a low energy density. In contrast, dual-ion batteries with graphite cathode and Li₄ Ti₅ O₁₂ anode can achieve a high output voltage of >3.0 V. In this study, mesocarbon microbeads (MCMB)@LiFePO₄ ||Li₄ Ti₅ O₁₂ dual-ion batteries are developed to address these issues. In the cathode, MCMB improves the conductivity of LiFePO₄ and increases the output voltage by the intercalation of anions in the cell voltage range of 2.1-3.5 V. Moreover, the LiFePO₄ shell sustains the structural integrity of MCMB and generates in situ a cathode-electrolyte interphase (CEI) with rich LiF. Owing to these unique compositional and structural features, MCMB@LiFePO₄ ||Li₄ Ti₅ O₁₂ manifests much better electrochemical performance than LiFePO₄ ||Li₄ Ti₅ O₁₂ and MCMB||Li₄ Ti₅ O₁₂ . It sustains 89.6 % of the initial capacity after 1200 cycles at 0.2 A g^-1 and achieves a specific energy up to 128 Wh kg^-1 at 179 W kg^-1 .