All-Solid-State Capacitors Using Li<sub>3</sub>YCl<sub>6</sub> and Carbon Composites

The development of all-solid-state capacitors (ASSCs) using lithiumion-conducting inorganic solid electrolytes (SEs) with good formability and a wide electrochemical potential window is highly desired.Herein, we present ASSCs employing Li 3 YCl 6 (LYC) as one of the chloride SEs.Exploiting the favorable processability and electrochemical stability of LYC, 2 V-class ASSCs were fabricated by room-temperature pressing.Furthermore, the effects of the mixing conditions of composite electrodes comprising LYC and single-walled carbon nanotubes on device performance was investigated.Under the most intense mixing condition, the device achieved a specific capacitance of 15.4 F g -1 at 0-2 V and 0.13 mA cm -2 .Further, the electrode produced under the most intense mixing conditions yielded a homogeneous LYC-defect-enriched-carbon composite.These features are expected to enhance the effective interfacial area and facilitate greater charge accumulation, thereby improving the capacitance and mitigating voltage drop.Overall, this study demonstrates the potential of LYC for high-performance ASSCs and highlights the advantage of integrating SEs with both mechanical formability and a wide electrochemical potential window as a promising strategy for next-generation solid-state energy storage devices.