Nanohybrid Gel Polymer Electrolytes Based on Vinyl-Functionalized Mesoporous Silica Nanoparticles for Lithium Metal Batteries

For the development of high-energy-density lithium metal batteries (LMBs), we designed nanohybrid gel polymer electrolytes (NGPEs). In NGPEs, vinyl-functionalized mesoporous silica nanoparticles (VMSNs, as reinforcement fillers) are integrated with cross-linkable poly(ethylene glycol) (PEG) oligomers and an ionic species mixture of ionic liquid and Li salt via a UV curing process. Two types of mesoporous silica nanoparticles with and without vinyl groups (VMSN vs MSN) are synthesized via the surface grafting method and used to prepare NGPE-VMSN and NGPE-MSN, where the corresponding silica nanoparticles are chemically and physically dispersed into the PEG network, respectively. The hybrid PEG network-derived NGPEs with mesoporous silica nanoparticles show attractive electrolyte properties, i.e., high shear storage modulus (G′ = 1.1 × 10⁶ Pa), high ionic conductivity (σ_dc = 1 × 10^–4 S cm^–1), and wide electrochemical stability window (ESW ∼ 4.5 V), at room temperature. The resultant NGPE in the Li|Li cell also shows long-term cyclic stability without short-circuiting over 1000 h under 0.1 mA cm^–2, suggesting the NGPE’s effectiveness in dendrite inhibition. Furthermore, the LiFePO₄|NGPE|Li full cell presents a high specific capacity of 124 mAh g^–1 at 0.5C and stable cycling performances with 100% capacity retention and 99.5% Coulombic efficiency after 190 cycles at 25 °C. The NGPE demonstrates a simple design principle for replacing liquid electrolytes with solid-state electrolytes, allowing for a perfect complex between inorganic silica nanoparticles and organic PEG gel network through vinyl bonds on the MSN surface and PEG terminal group for high-energy-density LMBs.