Pushing Capacities and Energy Densities Beyond Theoretical Limits of Lithium Primary Batteries Using Active Cfx Nanocapsules with X > 1

The high theoretical capacity and long shelf-life of a Li-CFx system make it most promising for portable electronics. However, the inactivation ideology of -CF3 groups in CFx hinders the development of the Li-CFx system to realize ultra-high energy density. Here, we developed a unique carbon fluoride nanocapsule (CFNC) with x > 1 using a simple thermal-assisted chemical reaction in a controlled environment. The high curvature 3D hollow structure and rich interfaces generated by the engineered wall structure of the CFNC enable activation of -CF and -CF2 groups. The resulting structure bears high mass and rich charge transfer channels which deliver a cathode capacity of 1056 mA h g(-1) and energy density up to 2487 W h kg(-1) beyond the theoretical limits of the Li-CFx system without compromising the cell voltage. To understand the role of structural engineering, density functional theory (DFT) calculations were carried out to confirm active CF2 components and the effects of various fragment sizes on the voltage plateau, where a higher discharge plateau voltage is obtained with the larger fragment. The materials design presented in this study is an effective and alternative approach to realizing primary batteries with ultra-high energy densities.