Novel conducting solid polymer electrolytes with a zwitterionic structure boosting ionic conductivity and retarding lithium dendrite formation

Abstract

Suppressing the anionic mobility in solid polymer electrolytes (SPEs) is crucial to mitigate the ionic conductivity and internal cell polarization, thus upgrading the stability and cycle life of rechargeable lithium-ion batteries (LIBs). Now, a series of novel conducting solid polymer electrolytes (CSPEs) with a zwitterionic structure comprising TEOS which was grafted to nitrogen-centered cations connected to hydrophilic sulfonate and carboxylate groups were used as SPEs in LIBs. The quaternized 1,8-diaminonaphthalene polyvinylidene difluoride lithium-ion conducting electrolyte (DN-PF-LCP) as an SPE component in LIBs achieves outstanding ionic conductivity (8.69 × 10⁻⁴ S cm⁻¹), a sufficient capacity of 136 mA h g⁻¹ with a decent capacity retention of 96% at a current rate of 0.3C over 200 cycles at 25 °C, and superior thermo-stability (∼420 °C). The zwitterionic structure of the DN-PF-LCP CSPE provides strong molecular interactions and efficiently facilitates the disintegration of Li⁺ ions, thus stimulating the mobility of Li⁺ ions within the CSPE and enhancing the Li⁺ ion conduction properties. The hydrogen bonding and ion–dipole interactions in the DN-PF-LCP CSPE provide nanosized self-agglomeration of anions and provide interaction between anions and their structurally homologous matrix, thus impeding the mobility of anions and lithium dendritic growth. These outstanding characteristics of DN-PF-LCP make it promising as a CSPE for LIBs.