The enhancement of the fluorination degree of carbon fluorides (CF_x) compounds is the most effective method to improve the energy densities of Li/CF_x batteries because the specific capacity of CF_x is proportional to the molar ratio of F to C atoms (F/C). In this study, B-doped graphene (BG) is prepared by using boric acid as the doping source and then the prepared BG is utilized as the starting material for the preparation of CF_x. The B-doping enhances the F/C ratio of CF_x without hindering the electrochemical activity of the C–F bond. During the fluorination process, B-containing functional groups are removed from the graphene lattice. This facilitates the formation of a defect-rich graphene matrix, which not only enhances the F/C ratio due to abundant perfluorinated groups at the defective edges but also serves as the active site for extra Li⁺ storage. The prepared CF_x exhibits the maximum specific capacity of 1204 mAh g⁻¹, which is 39.2% higher than that of CF_x obtained directly from graphene oxide (without B-doping). An unprecedented energy density of 2974 Wh kg⁻¹ is achieved for the as-prepared CF_x samples, which is significantly higher than the theoretically calculated energy density of commercially available fluorinated graphite (2180 Wh kg⁻¹). Therefore, this study demonstrates a great potential of B-doping to realize the ultrahigh energy density of CF_x cathodes for practical applications.

Lithium primary batteries are widely used in various fields where high energy densities and long storage times are in demand. However, studies on lithium primary batteries are currently focused on the gravimetric energy densities of active materials and rarely account for the volumetric energy requirements of unmanned devices. Herein, CuF₂/CF_x composites are prepared via planetary ball milling (PBM) to improve the volumetric energy densities of lithium primary batteries using the high mass density of CuF₂, achieving a maximum volumetric energy density of 4163.40 Wh L⁻¹. The CuF₂/CF_x hybrid cathodes exhibit three distinct discharge plateaus rather than simple combinations of the discharge curves of their components. This phenomenon is caused by charge redistribution and lattice modulation on the contact surfaces of CuF₂ and CF_x during PBM, which change the valence state of Cu and modify the electronic structures of the composites. As a result, CuF₂/CF_x hybrid cathodes exhibit unique discharge behaviors and improved rate capabilities, delivering a maximum power density of 11.16 kW kg⁻¹ (25.56 kW L⁻¹). Therefore, it is a promising strategy to further improve the comprehensive performance of lithium primary batteries through the use of interfacial optimization among different fluoride cathodes.