Cross-Linked Poly(vinyl alcohol)–Malonic Acid Water-Soluble Binder for High-Performance Silicon Anodes in Lithium-Ion batteries

In lithium-ion batteries (LIBs), silicon (Si) is the most promising alternative anode material to graphite owing to its high theoretical capacity (4200 mAh/g), high energy density, low cost, and easy availability. However, the practical applications of Si-based anodes are restricted owing to their massive volume expansion (>300%), which leads to the pulverization of Si and fast capacity fading of the electrodes. The optimization of polymer binders has been considered an effective strategy for decreasing the volume expansion of Si electrodes during the charge/discharge process. In this study, a cross-linked poly(vinyl alcohol) (PVA)–malonic acid (MA) water-soluble polymeric binder was prepared through the polymerization of PVA and MA. The synthesized cross-linked PVA–MA composite binder with hydroxyl groups (OH) and ester bonds remarkably enhanced the mechanical and adhesion properties. A Si electrode with a composite binder containing PVA and 10 wt %MA exhibited a high initial capacity of 3558 mAh/g and maintained 2267 mAh/g after 100 cycles at a rate of 0.3 C compared to the traditional PVdF binder (2306 mAh/g at a rate of 0.3C). This study offers a method to fabricate stable Si electrodes using sustainable Si sources and eco-friendly carboxylic acid–based cross-linkers for synthesizing cross-linked polymer binders.