Selective interfacial polymerization improves reversibility of Si anodes

The volume swelling issues and corresponding negative effects of Si-based anodes exclude them from practical applications. Among varied novel strategies, electrolyte engineering, with its high operability, can effectively optimize the solid electrolyte interface (SEI) to enhance its ion transport and anti-swelling properties. Especially, the preference of SEI for LiF-rich inorganics and viscoelastic oligomers makes lithium bis(fluorosulfonyl)imide (LiFSI) and 1,3-dioxolane (DOL) ideal components of the electrolyte. However, LiFSI triggers the in-situ polymerization of DOL, resulting in the complete solidification of the electrolyte, which will lead to even more serious interfacial problems. To address this, a polymerization inhibitor-containing electrolyte was designed to enable stable coexistence of DOL and LiFSI. The inhibitor will decompose preferentially than the initiator at the electrode surface during the lithiation of Si anode, losing the inhibition effect on the polymerization reaction, and DOL will polymerize (PDOL) only at the Si surface to form a strain-resistant interface. While outside the PDOL-rich polymer layer, due to the invariably presence of inhibitor, DOL will not polymerize, and the electrolyte maintains good wettability to the electrode. Benefiting from such a selective interfacial polymerization electrolyte (SIPE), the SEI exhibits excellent tensile resistance and ionic conductivity, which survives repeated volume changes and mitigates the negative effects caused by continuous SEI formation and Si particle pulverization. As a result, at a current density of 1500 mA g −1 (≈ 0.42 C), the SIPE-equipped silicon anode still has a reversible capacity of 1739 mAh g −1 after 200 cycles, with an improved capacity retention rate from 45.4 % to 84.3 %.