Hybrid Aluminum-Ion Capacitors for High-Temperature Energy Storage: Commercial Viability and Performance Evaluation

초록

Hybrid capacitors capable of stable operation at 85 degrees C remain underdeveloped despite the demand for energy-storage systems in electric vehicles, grid storage, aerospace systems, and other thermally demanding applications, where additional cooling increases system size and complexity. Conventional supercapacitors (SCs) and lithium-ion capacitors (LICs) are constrained at elevated temperatures by organic-electrolyte instability and interfacial degradation. Herein, we present a hybrid aluminum-ion capacitor (AIC) using commercially available activated carbon (AC) as the cathode, aluminum foil as the anode, and an AlCl3/[EMIm]Cl ionic liquid electrolyte. At 25 degrees C, the AIC delivered 14 mWh cm-3 at 81 mW cm-3, approximately twice that of the AC-based SC and comparable to that of an LIC. At 85 degrees C, the energy density increased to 25.4 mWh cm-3, 1.8 times the room-temperature value, with performance comparable to that reported for SCs and an LIC developed for high-temperature operation. This improvement is associated with increased ionic conductivity and temperature-dependent changes in the charge-storage behavior. Above 55 degrees C, the capacitance increase is associated with an increased diffusion-controlled contribution, which may include thermally facilitated ion transport within confined pores of the AC cathode and enhanced aluminum interfacial charge-transfer kinetics. Structural and surface analyses indicated no significant degradation of the AC cathode or aluminum anode during high-temperature operation. The AIC retains 83.5% of its initial capacitance after 10 000 cycles at 85 degrees C, and pouch-type cells power an LED at 25 degrees C and 85 degrees C. These findings demonstrate the potential of AICs based on commercially available electrode materials for thermally demanding energy-storage applications.image

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