Stable Photothermal Conversion Fillers Enable Subzero-Temperature Applications of PEO-Based Solid-State Lithium...

Low-temperature operational reliability remains a critical bottleneck for all-solid-state batteries (ASSBs). Polyethylene oxide (PEO)-based solid-state electrolytes (SSEs), the most widely studied SSE system, typically exhibit ionic conductivities as low as 10^-6 S cm^-1 at ambient temperature, necessitating battery operation at 60°C-80°C. This external heating requirement consumes extra electrical energy and severely limits the application of PEO-based ASSBs under low-temperature conditions. Here, we introduce lithiated poly(3,4-dioxythiophene) (LiPHT) photothermal conversion filler into PEO-based SSEs, which significantly enhances the ionic conductivity to 1.34 × 10^-4 S cm^-1 while simultaneously broadening the electrochemical window to 4.55 V vs. Li/Li⁺ at room temperature. By utilizing the PEO-LiPHT composite layer as both a "heater" and the electrolyte layer within the transparent battery, the device exhibits efficient photothermal conversion and rapid light-induced heating. Benefiting from the in situ photothermal self-heating effect that elevates the actual internal cell temperature to the optimal operating range of PEO electrolytes, the ASSB demonstrates a high discharge capacity of 131.3 mA h g^-1 at 0.5 C under an ambient temperature of -15°C. This work offers a viable pathway to circumvent the intrinsic low-temperature limitation of PEO-based electrolytes, facilitating the development of high-performance ASSBs for subzero-temperature applications.