Polymer‐Clay Nanocomposite Solid‐State Electrolyte with Selective Cation Transport Boosting and Retarded Lithium Dendrite Formation

Commercialized lithium‐ion batteries (LIBs) with a liquid electrolyte have a high potential for combustion or explosion. The use of solid electrolytes in LIBs is a promising way to overcome the drawbacks of conventional liquid electrolyte‐based systems, but they generally have a lower ionic conductivity and lithium ion mobility. Here, a UV‐crosslinked composite polymer‐clay electrolyte (U‐CPCE) that is composed of a durable semi‐interpenetrating polymer network (semi‐IPN) ion transportive matrix (ETPTA/PVdF‐HFP) and 2D ultrathin clay nanosheets that are fabricated by a one‐step in situ UV curing method, are reported. The U‐CPCE exhibits robust and flexible properties with an ionic conductivity of more than 10−3 S cm−1 at room temperature with the help of exfoliated clay nanosheets. As a result, the U‐CPCE‐based LIBs show an initial discharge capacity of 152 mAh g−1 (at 0.2 C for a LiCoO2 half‐cell), which is comparable to that of conventional liquid electrolyte‐based cells. In addition, they show excellent cycling performance (96% capacity retention after 200 cycles at 0.5 C) due to a significantly enhanced Li+ transference number (tLi+ = 0.78) and inhibition of lithium dendrite formation on the lithium metal surface. Furthermore, a molecular dynamics (MD) study is conducted to elucidate the mechanism of improving ionic conductivity. The U‐CPCE design can offer opportunities for future all‐solid‐state Li‐ion batteries. Montmorillonite clay is an attractive material, which is eco‐friendly and abundant on earth. By applying it to an electrolyte, it is possible to design a solid‐state electrolyte for lithium‐ion batteries with improved ionic conductivity, lithium ion transference number (t+ = 0.78), and stability with lithium metal anodes.