Ionic conductive rubber quasi-solid polymer electrolyte for solid-state lithium-metal batteries

Abstract

Rubber is a material renowned for its exceptional mechanical properties, including excellent elasticity, tensile strength, and low cost. However, conventional rubber lacks ionic conductivity, significantly limiting its application in solid-state electrolytes. In this work, we propose the concept of ionic conductive rubber (ICR) electrolyte to improve the ionic conductivity of conventional rubber and create a quasi-solid polymer electrolyte (QPE) suitable for lithium metal batteries. The developed ICR QPE exhibits outstanding elasticity, ensuring good dynamic contact during lithium stripping and plating processes. Consequently, these allow assembled symmetric cells demonstrate low polarization voltage and highly stable lithium stripping/plating cycles, sustaining over 1300 h at a current density of 0.1 mA cm⁻². Additionally, ICR QPE exhibits superior ionic conductivity of 0.4 × 10⁻³ S cm⁻¹ at room temperature, and ultrahigh Li⁺ transference number of 0.758. Moreover, the assembled LFP|ICR QPE|Li battery demonstrats excellent long-term cycle stability at 0.5 C and 25 °C, with an average coulomb efficiency of 99.6 % over 600 cycles. Our proposed ICR QPE breaks the traditional rubber ion conduction problem, and its unique low cost characteristics, superior mechanical properties and excellent ion conductivity provide a promising solution for long-cycle stable solid lithium metal batteries.