A 12 μm-Thick, Mechanically Stable Ionogel Electrolyte with Directed Li Transport Channels for High-Performance Lithium Metal Batteries.

The ionogel polymer electrolyte (IGPE) has emerged as a promising polymer electrolyte for lithium metal batteries (LMBs) due to its high safety and a wide electrochemical window. To achieve an energy density comparable to that of liquid electrolyte (LEs)-based cells, ultrathin IGPE electrolytes with high Li conductance are desired. However, their development still suffers from intrinsically poor mechanical stability and the low Li transference number () of IGPEs. Here, we design a 12 μm-thick, mechanically reliable, and highly Li conductive IGPE electrolyte (PET-IGPE) by incorporating a poly(butyl acrylate) (PBA)/solvate ionic liquid (SIL)-based ionogel with a polyethylene terephthalate (PET) track-etched membrane. The PET membrane as the scaffold enables the resultant IGPE electrolyte to have a high tensile strength of 65 MPa and a puncture strength of >340 gf mil, preventing the Li symmetrical cell from short-circuiting for over 700 h of cycling. Meanwhile, the vertically aligned pores in the PET membrane function as the directional Li motion pathway, which enables an ultrahigh areal ionic conductance of 308.3 mS cm, improves to 0.61, and steady Li plating/stripping without impairing the thermal and electrochemical oxidative stability of IGPEs. As a result, the Li|12PET-IGPE|LiFePO cell shows high capacity, high cycling stability in a wide temperature range of 25-90 °C, and high tolerance to abuse, such as folding, cutting, or nail penetration.