Ab Initio Studies of the Electrochemical Reactivity of Carbon Allotropes in Rechargeable Li-ion Batteries.

Lithium-ion batteries are broadly used in consumer electronics, electric vehicles, and large-scale energy storage due to their high capacity, high energy density, long cycle life, and low self-discharge characteristics. Primary Li/CF_x batteries are known to possess an extremely high theoretical capacity (>800 mAh/g). However, attempts to make rechargeable Li/CF_x batteries have so far not been successful, due to the poor rechargeability and low discharge rates of CF_x electrodes. Recent studies have shown that low-dimensional carbon materials could enhance the capacity and improve the cycling stability and electrochemical performance of Li-ion batteries. We apply ab initio density functional computational methods to model the fluorination process across various derivatives of low-dimensional carbon allotropes and investigate the interaction of Li ions with both partially and fully fluorinated carbon allotropes and their derivatives. Our study predicts the fluorination energies of the studied carbon allotropes to be in the range of 1.5 – 2.5 eV, whereas the estimated Li insertion energies are found to be in the range from 1.5 to 2.9 eV. The results of our calculations demonstrate a significant influence of low-dimensional carbon allotropes on the electrochemical properties of CF_x electrodes in rechargeable Li/CF_x batteries.