Selenium-regulated band structure engineering in CFx cathodes enables high-power and wide-temperature Li/CFx primary batteries.

Li/CF_x primary batteries are renowned for their exceptional energy density, yet their practical deployment is hindered by the inherently sluggish kinetics of the CF_x cathode. This study addresses this limitation by incorporating selenium (Se) into CF_x (denoted as CF_x/Se) via a facile low-temperature thermal treatment, significantly enhancing its electrochemical performance. Comprehensive spectroscopic and electrochemical analyses reveal that Se doping induces the formation of CSe bonds, which promote semi-ionic CF bonding, thereby accelerating Li⁺ diffusion and reducing charge transfer resistance. Density functional theory calculations further demonstrate that Se doping modulates the electronic structure of CF_x, narrowing its bandgap to establish an efficient conductive network and markedly improving electronic conductivity. The optimized CF_x/Se-1 composite (Se:CF_x = 1:9) delivers outstanding performance, achieving a discharge capacity of 383.9 mAh g^-1 at a high current density of 20 A g^-1 with an energy density of 765.7 Wh kg^-1 and a power density of 3.99 × 10⁴ W kg^-1. Moreover, CF_x/Se-1 exhibits remarkable wide-temperature operability (-35 to 60 °C), retaining a capacity of 485.3 mAh g^-1 at 0.5 A g^-1 with a stable 2.0 V plateau even at -35 °C. This work underscores the pivotal role of Se doping in tailoring the band structure of CF_x, unlocking its potential for high-power and extreme-temperature Li/CF_x batteries.