Lithiophilic gel polymer electrolyte to stabilize the lithium anode for a quasi-solid-state lithium–sulfur battery

Abstract

Lithium–sulfur batteries are the most promising candidates for high energy battery systems due to their high theoretical energy density. However, the severe degradation of the lithium anode during cycling is a significant issue that hinders the practical application of lithium–sulfur batteries. Herein, a gel polymer electrolyte, fabricated via the self-polymerization of polydopamine (PDA) on the surface of polyvinylidene fluoride (PVDF) gel polymer electrolyte, was introduced for the first time to stabilize the lithium anode in a quasi-solid-state lithium–sulfur battery. Specifically, polydopamine with pyrrolic nitrogen in the structure is identified to be lithiophilic owing to its Lewis acid–base interactions. Such a lithiophilic gel polymer electrolyte plays a key role in regulating the nucleation and stripping/plating process of the lithium anode, leading to a smooth anode surface with a stable solid electrolyte interphase (SEI) during long-term cycling. Moreover, polydopamine is beneficial for confining polysulfides through their strong interaction, thus reducing the polysulfide side reaction with the anode. As a result, the quasi-solid-state cell with the multifunctional gel polymer electrolyte not only possesses a stable lithium anode, but also demonstrates excellent cycling performance. Moreover, the amount of electrolyte in the quasi-solid-state cell is lower compared with the conventional cell with a liquid electrolyte, which favors an increase in energy density of the battery.