γ-Ray irradiated polyacrylamide networks enable high-performance Li||S pouch cells

Abstract

Binders are essential for maintaining positive electrode integrity in Li||S batteries and significantly affect their performance. However, commercial linear binders often have disordered networks, poor binding efficiency, and insufficient mechanical strength. To address these challenges, three-dimensional covalent binders offer a promising solution. Traditional methods for producing cross-linked binders require additives and result in poorly controlled polymer networks due to the stochastic nature of liquid-phase polymerization. Moreover, the mechanisms by which reticulated binders stabilize the positive electrode remain unclear, requiring investigation under operando conditions. Herein, we present an approach to tailor cross-linked polyacrylamide networks using solid-state operando γ-ray irradiation chemistry, which eliminates additives and produces a pure, ordered network with remarkable binding capabilities. By integrating in situ high-resolution optical frequency domain reflectometry, multiscale synchrotron radiation characterization, and virtual simulations, this study reveals the role of binders in dynamically encaging and confining sulfur. Specifically, γ-ray-enabled polyacrylamide networks enhance battery performance through mechanical strengthening, optimized sulfur regeneration, and improved re-occupancy. Consequently, the well-designed composite positive electrode structure with only 5.0 wt% binder improves soft-packaged Li||S battery performance across various scenarios. Notably, a 1.2-Ah pouch cell achieves 410.1 Wh kg⁻¹ specific energy with a low electrolyte/sulfur ratio of 3.0 µL mg^–1.