Graphene Oxide‐Based Solid Electrolytes with 3D Prepercolating Pathways for Efficient Proton Transport

Abstract Graphene oxide (GO) with unprecedentedly fast ion transport ability has become emerging building blocks for solid electrolytes. However, the inferior through‐plane transport properties, along with the agglomeration and discontinuity of GO nanosheets in composite electrolytes represent a major obstacle for efficient proton conduction. Herein, a 3D prepercolating sulfonated GO (3D sGO) network is designed by a freeze‐casting method, and further fabricated composite electrolytes by infusing polymer electrolytes into the 3D sGO networks. The sGO laminates are well integrated into percolative nanoarchitectures, which enables the 3D sGO networks a high proton conduction capability (five times higher than Nafion membrane, a state‐of‐art solid electrolyte) and isotropic transport feature. The prepercolating strategy avoids sGO nanosheets agglomeration and provides continuously proton‐conductive pathways that percolate throughout the whole electrolytes. Consequently, the composite electrolytes exhibit a remarkable and simultaneous improvement in both in‐plane and through‐plane proton conductivity, which is unattainable for the existing 2D nanofiller–polymer electrolytes. Particularly, the highest through‐plane proton conductivity reaches 0.29 S cm⁻¹, outperforming the current 2D nanofiller‐based composite electrolytes. This prepercolating strategy may open a new avenue to fully utilizing the inherently rapid conduction of 2D materials for efficient transport of diverse ions/molecules.