Gradient hydrogen bonding and π-π interactions: A dual-mechanism binder for resilient and high-performance silicon-based anodes

Abstract

Polydopamine–glutathione (PDG) is mixed with carboxymethyl cellulose (CMC) to synthesize a new functional CMC–PDG binder. PDG additive significantly improves the mechanical strength, adhesiveness, and elasticity of the corresponding electrode compared with a pristine CMC binder. This is due to the multiple hydrogen-bonding groups in PDG, which form strong interactions with Si and CMC, effectively dispersing the internal stress caused by the volume expansion of Si. The Si electrode containing CMC–PDG binder exhibits greater capacity retention, and a superior cycle life compared with CMC in both SiOx and Si/C composite electrodes. When applied to SiOx electrode, the CMC-PDG-based electrode achieves a high capacity retention of 72.6 % after 100 cycles. Density functional theory and noncovalent interaction simulations confirm that PDG forms hydrogen bonds with Si and CMC and strengthens π–π interactions with graphite and styrene–butadiene rubber. In addition, full-cell with high loading density electrodes shows a high capacity retention of 68.5 % after 300 cycles for the CMC–PDG electrode. This new binder is a key technology for high-performance Si-based anodes at low cost through a simple manufacturing process and is expected to accelerate the commercialization of next-generation high-energy-density lithium-ion batteries.