面向高电压固态锂电池的明胶/聚氧化乙烯复合电解质的制备与性能

Preparation and performances of gelatin/polyethylene oxide composite electrolyte for high-voltage solid-state lithium batteries

聚氧化乙烯(PEO)基电解质在高电压下不稳定的界面严重阻碍了其在高能量密度固态锂电池中的实际应用。本文利用明胶的羧基与PEO链端羟基形成氢键,减缓了高电压下PEO端羟基氧化,进而构建基于PEO/明胶复合电解质的高电压固态锂电池。研究结果表明,PEO电解质链端羟基氧化分解是Li|PEO|NCM811在大于4.0 V时产生“电压噪声”行为的主要原因。加入明胶后,由于明胶与PEO之间的氢键作用,PEO/明胶复合电解质在4.0~4.3 V下的端羟基氧化副反应得以抑制。同时,大分子明胶的加入,降低了PEO的结晶度,形成快速的锂离子导体通路,提升了复合电解质的离子电导率,因此提升了匹配三元正极NCM811的电化学性能。该工作为面向高电压固态锂电池的PEO聚合物电解质的简便构建提供了新思路。

The unstable interface of polyethylene oxide(PEO)-based electrolytes at high voltage seriously hinders their practical application in high-energy density solid-state lithium batteries.This study presents a new approach of constructing high-voltage solid-state lithium batteries based on the PEO/gelatin composite electrolyte.The results indicate that the oxidative decomposition of the hydroxyl groups at the end of the PEO-based electrolyte chain mainly causes the voltage noise behavior of the Li | PEO | NCM811 at voltages greater than 4.0 V.To address this issue,the gelatin carboxyl group is utilized to form hydrogen bonds with the hydroxyl end groups of the PEO chain,slowing down the PEO hydroxyl group oxidation under a high voltage.The hydroxyl terminal oxidation side reaction of the PEO/gelatin composite electrolyte is suppressed at 4.0—4.3 V after gelatin addition.The results show that adding macromolecular gelatin reduces the PEO crystallinity and forms a fast Li ion conductor pathway that improves the ion conductivity of the composite electrolyte,which consequently improves the high-voltage stability of the matched high-voltage cathode,NCM811.This work presents a simple approach of constructing PEO-based polymer electrolytes for high-voltage solid-state lithium batteries.