Enhancement of the Li ion transfer reaction at the LiCoO2 interface by 1,3,5-trifluorobenzene

This work presents a method of enhancing the kinetics of the interfacial reaction using 1,3,5-trifluorobenzene (TFB) which is used as an electron acceptor due to its locally biased polarity and as a source of rearranging the layer of the electrolyte around LiCoO₂ electrode, not a SEI layer source. The full cells with TFB show a decrease in irreversible capacity loss during the first charge-to-discharge process, regardless of the SEI layer formation, and also show better discharge properties even at high rate conditions. The charge transfer resistance (R_ct) of the LiCoO₂ half cell with TFB shows the smaller resistance than that of the TFB free half cell, and the activation energy calculated from the R_ct was 24.7 kJ/mol for the TFB free half cell and 19.3 kJ/mol for the half cell with TFB. In addition, the film resistance of the half cell with TFB shows higher value when the temperature is below 283 K. Since R_ct is related to the transfer resistance of the solvated Li⁺ ions on the surface of the LiCoO₂ electrode, it will help design the electrolyte to improve the transfer velocity of Li⁺ ions around the cathode electrode for high power Li ion battery.