A screening method for film-forming additive in high-voltage graphite/LiCoO2

Abstract

Using film-forming additive is an important approach to address the incompatibility between high-reactive electrodes and electrolytes. However, the design and screening of these film-forming additives still rely on a trial-and-error method, which is inefficient and costly. Herein, we established a method for screening additives based on theoretical calculations, and supplemented by short-term experiments. Four sulfur-containing additives, 1,3,2-dioxathiane 2-oxide (PRS), 1,3-propanediolcyclic sulfate (PCS), 1,5,2,4-dioxadithiane 2,2,4,4-tetraoxide (MMDS), sulfolane (Sul), were selected for investigation. The theoretical calculation results indicated that the additive with a greater negative adsorption energy on the cathode than the solvent facilitate film formation on the cathode. This principle can also be applied to screen the anode film-forming additive. However, the calculated results can only provide the insight into the additives’ capacity to participate in film formation, without revealing the stability of the resulting interfacial film or the improvement in the battery’s electrochemical performance. To address this limitation, three efficient short-term experimental methods were designed to characterize the stability of interfacial film: electrochemical impedance spectroscopy, high-temperature (45 °C) storage, and chronoamperometry. The proposed method, combing experiments and theoretical calculation, improves the accuracy for screening of film-forming additives.