Electrolyte distribution — One of the key factors to improve the high-rate performance of gel polymer Li ion batteries

This work describes the importance of the electrolyte distribution in gel polymer Li ion batteries, which can be a key factor to improve the high-rate cycle performance. After thermal curing of the pre-gel solution, it was changed to the sticky gel which is enough to tether not only liquid components but also battery parts tightly. The 5.0 C cycling performance of the single full cell with gel polymer electrolyte was superior to the cell with its liquid electrolyte, even though it had the lower ionic conductivity (2.5 mS cm−1) compared to the liquid electrolyte (7.8 mS cm−1) at room temperature. A careful analysis of the 1st dQ/dV curve revealed that there was no significant difference in the formation of the solid–electrolyte interface layer between two electrolyte systems. In LSV experiments by the Pt probe over the LiCoO2 substrate with 4.8 V (Li/Li+), the EC-related peak increased with the probe approaching the substrate in case of the liquid electrolyte, whereas the current density of the peak was hardly changed in the gel polymer electrolyte. These results indicate that the gel polymer electrolyte with a uniform electrolyte distribution can be a good candidate for the electrolyte of the Li ion batteries with outstanding high-rate performance.

► This work describes the importance of the electrolyte distribution.
► Battery with better performance has more uniform distribution of the electrolyte.
► This mechanism applies to gel polymer electrolyte.