Breakthrough binder enhances silicon anode stability in lithium-ion batteries
Binder-induced interphase regulation in electric double layer for enhanced stability of silicon anode
image: Breakthrough Binder Enhances Silicon Anode Stability in Lithium-Ion Batteries
Credit: ©Science China Press
The Promise of Silicon Anodes and the SEI Dilemma
Silicon anodes hold great promise for next-generation LIBs due to their exceptionally high theoretical capacity (3579 mAh g-1), low working voltage (~0.4 V vs Li/Li+), and abundance. However, silicon's significant volume expansion during lithiation/delithiation (over 300%) leads to the rupture and erratic regeneration of the SEI layer. This instability results in parasitic reactions, continuous electrolyte consumption, and capacity degradation, severely limiting the cycle life of silicon anodes.
Innovative Binder Design
The research team, led by Professors Shujiang Ding and Dongyang Zhang, proposed a new binder synthesized by grafting branched chains with polar functional groups (sulfonic acid and amino groups) onto polysaccharide guar gum. This binder, termed GGSN, was designed to modulate the electric double layer (EDL) structure at the electrode/electrolyte interface, thereby influencing the formation and composition of the SEI layer.
Mechanism of Action
The polar functional groups in GGSN exhibit a strong affinity for Li+, competing with the solvent molecules and reducing the desolvation energy. This interaction leads to a redistribution of Li+ and electrolyte solvent molecules, decreasing the free solvent content and suppressing organic solvent reduction. Consequently, the binder promotes the formation of an ultrathin SEI layer (11 nm) with a unique double-layer structure: an inorganic inner layer (Li2CO3, LiF, Li2O) and an organic outer layer. This configuration enhances ionic conductivity, provides robust mechanical support, and effectively inhibits electrolyte penetration and uncontrolled SEI growth.
Implications for Future Battery Technology
This study not only provides a new strategy for designing binders for silicon anodes but also deepens the understanding of the interfacial regulation mechanism between binders and electrolyte components. The insights gained from this research could accelerate the development of high-performance silicon-based anodes, bringing the vision of longer-range electric vehicles and faster-charging batteries one step closer to reality.