An In Situ Polysol Electrolyte by Salt-in-Sol Nanoparticle Cross-Linking for Quasi-Solid-State Batteries

Transforming liquid electrolytes into solids by lithium salt-triggered in situ polymerization-based solidification has been of great interest for the manufacturing of solid-state batteries. However, this strategy faces a tricky obstacle in simultaneously achieving high ionic conductivity and mechanical properties due to the poor controllability of the reaction process and electrolyte microstructures. Here, to overcome this challenge, we propose a neuron-like in situ polysol electrolyte (Neu-iPE) by salt-in-sol cross-linking that realizes a lithium-salt-regulated physical cross-linking of poly(vinylidene fluoride) (PVDF) sol nanoparticles. It is found that lithium salt can effectively regulate the sol-gel transition of PVDF sol, as well as the sol-cross-linking via a salt-in-sol microphase reorganization. Benefiting from the well-controlled neuron-like microstructures, the Neu-iPE integrates the advantages of separator and liquid electrolytes and simultaneously achieves a high room-temperature ion-conductivity of 0.42 mS/cm, mechanical strength of 15.7 MPa, and puncture toughness of 34.4 MJ/m³. Enabled by this Neu-iPE, a component-integrated quasi-solid-state battery is successfully fabricated to achieve structural flexibility and interface stability as compared with conventional batteries. This study on Neu-iPE presents not only a promising alternative to conventional in situ polymerization-based electrolyte solidification but also a salt-in-sol cross-linking strategy for the fabrication of biomimetic functional materials and devices.