Enabling Solid-State Li Metal Batteries by In Situ Forming Ionogel Interlayers

The pressing need for advanced energy storage devices with high energy density and safety is leading research to solid-state Li metal batteries (SSLMBs). However, the advancement of this type of battery is impeded by the incompatibility and the inferior interfacial contact between solid-state electrolytes and electrodes. In this work, the issues are addressed by introducing the PEGDA/Pyr₁₃TFSI ionogel into the interfaces between a NASICON-type Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) solid electrolyte and the electrodes via a simple drop-coating and in situ polymerization method. It is demonstrated that the formed robust and elastic ionogel interlayers not only preclude the adverse reactions between the LATP pellet and the Li metal anode but also significantly reduce the interfacial resistances. As a result, the cycling life of the Li/Li symmetric cell with the ionogel interlayers reaches up to 300 h, whereas the cell using the bare LATP dies after only 10 h. More notably, the Li/ionogel/LATP/ionogel/LiFePO₄ full battery delivers a high capacity of 152.5 mAh g^–1 at 0.5 C at 60 °C with a retention of 91.5% after 200 cycles, in a sharp contrast to the value of as low as 46 mAh g^–1 even at 0.1 C given by the Li/ionogel/LATP/LiFePO₄ cell. These encouraging results demonstrate that the interfacial modification strategy proposed in this work is effective in constructing stable, compact, and durable interfaces between solid electrolytes and electrodes, thereby paving the way for high-performance SSLMBs.