Chain Conformation and Crosslink Density as Independent Mechanistic Levers in Comb-Brush Particle Artificial Solid Electrolyte Interfaces for Lithium-Metal Batteries.

Artificial solid electrolyte interfaces (aSEIs) based on organic-inorganic hybrids offer a promising strategy to stabilize lithium-metal anodes by combining mechanical strength and ionic conductivity. Herein, entanglement- and crosslink-enabled comb-brush particles (CBPs) were synthesized by grafting oligo-(ethylene oxide) methyl ether methacrylate (OEOMA500) and 2-(dimethylamino)-ethyl methacrylate (DMAEMA) from silica nanoparticles via atom transfer radical polymerization. Systematic variation of DMAEMA content enabled control over polymer conformation and mechanical properties. Increasing DMAEMA incorporation reduced polymer extension and enhanced chain entanglement, resulting in higher storage moduli and decreased creep deformation. Blended with LiTFSI, higher DMAEMA contents led to reduced ionic conductivity. Despite this trade-off, CBPs containing 5 - 25 wt % DMAEMA demonstrated stable symmetric cycling over 2000 h with low overpotentials and uniform lithium deposition. Higher DMAEMA fractions, on the other hand, resulted in soft shorting and dendrite formation. Topical crosslinking via quaternization further tuned interphase stability. Bromide-based crosslinkers provided improved cycling stability compared to their triflate analogs. Long-chain Br-PEO2k-Br enabled interparticle crosslinking and overpotentials as low as 40 mV. These results demonstrate that balancing entanglements, ionic conductivity, and controlled crosslinking density is critical for designing robust hybrid aSEIs for lithium-metal batteries.