Lithium-ion and solvent co-intercalation enhancing the energy density of fluorinated graphene cathode

Abstract

Fluorinated carbons CF_x hold the highest theoretical energy density (e.g., 2180 W h kg⁻¹ when x = 1) among all cathode materials of lithium primary batteries. However, the low conductivity and severe polarization limit it to achieve its theory. In this study, we design a new electrolyte, namely 1 M LiBF₄ DMSO:DOL (1:9 vol.), achieving a high energy density in Li/CF_x primary cells. The DMSO with a small molecular size and high donor number successfully solvates Li⁺ into a defined Li⁺-solvation structure. Such solvated Li⁺ can intercalate into the large-spacing carbon layers and achieve an improved capacity. Consequently, when discharged to 1.0 V, the CF_1.12 cathode demonstrates a specific capacity of 1944 mA h g⁻¹ with a specific energy density of 3793 W h kg⁻¹. This strategy demonstrates that designing the electrolyte is powerful in improving the electrochemical performance of CF_x cathode.