The Modulation of Cross-Linking Density in Gel Polymer Electrolyte for the Inhibition of Lithium Dendrite

Abstract

The high theoretical capacity and low electrochemical potential make lithium metal the most promising material to replace the graphite anode. However, lithium dendrite growth is the key problem that limits the development of lithium metal batteries. As a solid electrolyte, the gel polymer electrolyte (GPE) possesses a certain ability to inhibit the growth of lithium dendrites compared with a liquid electrolyte, but the inhibition mechanism is not very clear. In this work, through the regulation of GPE cross-linking density, we verify that the cross-linked GPE network has a certain influence on the solvation structure of lithium ions. The increased cross-linking density of GPE induces the Li⁺ solvated sheath dominated by contact ion pairs/solvent-separated ion pairs and Li⁺ aggregates, which is conducive to the formation of stable LiF-rich SEIs to resist lithium dendrites. The high cross-linked GPE-based LiFePO₄ full battery also exhibits a high capacity retention rate of 81.9% even after 220 cycles at a rate of 0.2C and 90.1% after 140 cycles at a rate of 0.5C. The inhibiting mechanism of lithium dendrites by the cross-linked GPE is described for the first time, which provides a better idea for the design of GPE.