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

Abstract

The high theoretical capacity and long shelf-life of the Li-CF x system make it most promising for portable electronics. However, the inactivation ideology of -CF 3 groups in CF x hinders the development of the Li-CF x system to realize ultra-high energy density. Here, we developed a unique carbon fluoride nanocapsule (CFNC) having x >1 using a simple thermal-assisted chemical reaction in a controlled environment. The highly curvature 3D hollow structure and rich interfaces generated by the engineered wall structure of CFNC enable activation of -CF and -CF 2 groups. The resulted structure bears high mass and rich charge transfer channels which deliver cathode capacity of 1056 mAh g -1 and energy density up to 2444 Wh kg -1 beyond the theoretical limits of the Li-CF x system without compromising the cell voltage. To understand the role of structural engineering, the density functional theory (DFT) calculations were carried out to confirm active CF 2 components and the effect of various fragment sizes on voltage plateau, where 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.

Keywords: Fluorinated carbon, nanocapsule, high-capacity, Energy density, lithium primary battery