Local electric field effect of montmorillonite in solid polymer electrolytes for lithium metal batteries

Solid polymer electrolytes (SPEs) with in-built inorganic fillers are very promising for building safe solid-state batteries, owing to their excellent flexibility, prominent interfacial wettability and low costs. However, the morphology and surface state of inorganic fillers greatly affect ionic conductivity of SPEs. Here, we report that ultraviolet (UV) initiates in situ cross-linking of poly(ethylene glycol) methyl ether acrylate (MPEGA), poly (ethylene glycol) diacrylate (PEGDA) and montmorillonite (MMT) between cathodes and anodes of cell, to produce a solid composite electrolyte (CMP/MMT) that is composed of a robust interpenetrating polymer network matrix and layered MMT nanosheets. Surprisingly, the CMP/MMT delivers a high room-temperature ionic conductivity (similar to 1.06 mS cm(-1)), large lithium-ions transference number (t(Li+) = 0.79). The large ionic conductivity enhancement is ascribed to the local electric field effect of montmorillonite (MMT), which accelerates the lithium-ions fast transport in the interlayer of the MMT nanosheets. In addition, the density functional theory (DFT) is conducted to demonstrate the mechanism of improving ionic conductivity. As a result, a solid-state battery with CMP/MMT demonstrates a high capacity of similar to 140 mAh g(-1) and excellent capacity retention of >98% at 0.3 C after 400 cycling.

Automated summary

Solid polymer electrolytes (SPEs) with in-built inorganic fillers show great potential for safe solid-state batteries due to their flexibility, interfacial wettability, and cost-effectiveness. This study demonstrates the in situ cross-linking of polymer compounds and montmorillonite (MMT) using ultraviolet (UV) light, resulting in a solid composite electrolyte (CMP/MMT) with high ionic conductivity and lithium-ions transference number. The enhanced ionic conductivity is attributed to the electric field effect of MMT, facilitating rapid lithium-ion transport. Density functional theory (DFT) is used to explain the mechanism behind the improved ionic conductivity, showcasing the high capacity and excellent capacity retention of the solid-state battery with CMP/MMT after cycling.