Mesocarbon Microbeads Boost the Electrochemical Performances of LiFePO4||Li4Ti5O12 through Anion Intercalation

Li-ion batteries with LiFePO4 cathode and Li4Ti5O12 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 Li4Ti5O12 anode can achieve a high output voltage of >3.0 V. In this study, mesocarbon microbeads (MCMB)@LiFePO4||Li4Ti5O12 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||Li4Ti5O12 manifests much better electrochemical performance than LiFePO4||Li4Ti5O12 and MCMB||Li4Ti5O12. 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).