Bicontinuous-Structured Elastomeric Electrolytes for High-Energy Solid-State Lithium-Metal Batteries

Abstract

The use of lithium (Li) metal anodes in solid-state batteries is a strong strategy as a next-generation battery technology for surpassing the energy density and safety of conventional Li-ion batteries. However, in practice, current solid-state electrolytes have been limited to realize Li metal batteries due to their insufficient electrochemical and mechanical properties. Here, we design a new class of elastomeric electrolytes having a 3D interconnected plastic-crystal phase within the elastomer matrix—plastic crystal-embedded elastomer electrolytes (PCEEs).1 To elucidate the effects of structural changes in PCEEs on Li-ion transport property, mechanical elasticity, and electrochemical performance, we investigate various phase-separated structures of PCEEs by adjusting each phase’s volume ratio. Among these structures, we reveal that bicontinuous-structured PCEE, consisting of an equal volume ratio of elastomer to plastic-crystal phase, is well-balanced to develop the efficient ion-conducting, plastic-crystal pathways within a mechanically robust, cross-linked elastomer matrix. Hence, this optimal PCEE shows a combination of high ionic conductivity (>10-3 S cm-1) at ambient temperature, high Li-ion transference number (>0.70), and good mechanical resilience (elongation at break ≈ 300%). A full cell configured with the optimized PCEE, a limited Li source, and a high loading LiNi0.83Mn0.6Co1.1O2 cathode delivers a high energy density exceeding 430 Wh kganode+cathode+electrolyte -1. Understanding the structure-property-electrochemical performance relationship of PCEE through structural control can form the basis of structure-controlled elastomeric electrolytes, holding substantial promise in various electrochemical energy storage systems.