High-Capacity Dual-Ion Batteries Based on Concentrated Solutions of LiPF6-Methyl Acetate

The electrolyte plays a pivotal role in determining the performance of graphite cathodes in dual-ion batteries (DIBs). Although LiPF₆-methyl acetate (MA)-based electrolytes have shown potential in DIBs, the discharge capacity of the cells is unsatisfied using a conventional electrolyte concentration. Herein, we demonstrate that concentrated LiPF₆-MA electrolytes effectively enhance the performance of lithium/graphite DIBs. As the electrolyte concentration increases from 1 to 6 mol kg^–1, the discharge capacity of the cell increases from 79 to 121 mAh g^–1. In situ X-ray diffraction (XRD) combined with electrochemical dilatometry (ECD) reveals the anion storage behavior of PF₆^– in graphite cathodes, exhibiting superior reversibility at higher concentrations. Moreover, the concentrated LiPF₆-MA electrolytes effectively suppress lithium dendrite growth, improving the safety and stability of the cells. This study highlights the critical role of electrolyte concentration in optimizing DIB performance, providing a feasible strategy for developing high-capacity and stable DIB systems.