Boosting the Energy Density of Li||CF_x Primary Batteries Using a 1,3-Dimethyl-2-imidazolidinone-Based Electrolyte

Elevating the discharge voltage plateau is regarded as the most effective strategy to improve the energy density of Li||CF_x batteries in consideration of the finite capacity of CF_x (x ∼ 1) cathodes. Here, an electrolyte, with LiBF₄ in 1,3-dimethyl-2-imidazolidinone (DMI)/1,2-dimethoxyethane (DME), is developed for the first time to substantially promote the discharge voltage of CF_x without compromising the available discharge capacity. DME possesses the property of low viscosity, while DMI functions to increase the voltage plateau during discharge owing to its moderate nucleophilicity and donor number, which decreases the energy barrier for breaking C–F bonds. The optimized electrolyte exhibits a significantly high average discharge voltage of 2.69 V at a current density of 10 mA g^–1, which is 11.6% higher than the control electrolyte (2.41 V). In addition, a high energy density of 2099 Wh kg^–1 is achieved in the optimized electrolyte (vs 1905 Wh kg^–1 in the control electrolyte), showing great potential for practical applications.