Plasticized composite electrolytes with mesoporous silica nanoparticle-reinforced PVDF–HFP for solid-state lithium–metal batteries

Abstract

The solid-state lithium polymer battery is emerging as a preferred alternative to liquid lithium-ion batteries due to its enhanced safety and superior interfacial compatibility. This study proposes a solid polymer electrolyte (SPE) design that integrates inorganic mesoporous silica nanoparticles (MSN) and plasticizer succinonitrile (SCN) into a PVDF–HFP/LiTFSI matrix, creating abundant electrochemically stable lithium-ion transport pathways and structural void spaces. Experimental results demonstrated that the as-fabricated SPEs exhibited a wide electrochemical window of 5.6 V and an ionic conductivity of 3.1 × 10⁻⁵ S cm⁻¹ at room temperature. Notably, the symmetric cell employing this SPEs demonstrated stable operation exceeding 500 hours under 0.2 mA cm⁻² current density and 0.2 mA h cm⁻² areal capacity, while maintaining consistently low polarization levels. Further investigations reveal that the all-solid-state LFP|SPEs|PDDA-TFSI@Li battery, featuring a poly(diallyl dimethyl ammonium)-bis(trifluoromethanesulfonyl)imide (PDDA-TFSI) polycationic protective layer on the lithium metal surface, delivered an impressive initial discharge capacity of 167.6 mA h g⁻¹ at 25 °C and 0.1C rate. After 200 cycles at 0.5C rate, it retained a high reversible capacity of 153.8 mA h g⁻¹ with exceptional capacity retention rate (97.2%).