Solid-state supercapacitors with enhanced performance using AI3+-doped Li+ ion perovskite electrolyte integrated with carbon aerogel electrode

Abstract

We report the performance of solid-state ceramic supercapacitors (SSCs) based on a novel composite electrolyte comprising aluminum-doped lithium lanthanum titanate perovskite, Li0.36La0.56Ti0.995Al0.005O3 (Al3+-doped LLTO), and the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM BF4). Rietveld refinement of X-ray diffraction data confirms the preservation of the tetragonal perovskite phase after Al3+ substitution, indicating structural stability of the host lattice. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy further corroborate the successful incorporation of Al3+ without forming secondary phases. The addition of ∼6 wt % EMIM BF4 into Al-LLTO matrix significantly enhances the room-temperature ionic conductivity to ∼10–3 Ω–1 cm–1, nearly 3 orders of magnitude greater than that of pristine LLTO, resulting into improved long-range electrical transport. Further, novel SSCs have been fabricated by sandwiching the composite electrolyte between high surface area freeze-dried carbon aerogel (FD-CA) coated copper electrodes and assembled using a low-cost hot-roll lamination approach. The devices at 35 °C exhibited a high specific capacitance of ∼370 F g–1 at 1 mA/2 V, excellent cycling stability with ∼87% capacitance retention over 15,000 cycles at 2 V and 2 mA (1 A g–1), and stable Coulombic efficiency of ∼99%. These symmetric SSCs demonstrate ideal electric double-layer capacitive behavior for operating potential ≤ 2 V. These results highlight the potential of Al3-doped LLTO/EMIM BF4 composite electrolytes in combination with FD-CA-based electrodes for the development of safe, efficient, stable and scalable solid-state supercapacitors.