Photothermally enhanced ion-transport in solid-state, non-Faradic energy storage devices for sub-freezing operability

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-11, Vol.500, p.156617, Article 156617
• Main Authors: Villan, Mohammed Aslam, Chowdhury, Arnab, Parker, Bradyn J., Bhardwaj, Bhupesh, Cameron, Neil R., Subramaniam, Chandramouli
• Format: Article
• Language: English
• Subjects: Hard-carbons; Ionic liquids; Low temperature tolerance; Non-Faradic energy storage; Photothermal supercapacitor; Solar-thermal conversion
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.156617

[Display omitted] •Multifunctional, porosity-engineered, non-graphitizable nanocarbon florets (NCF).•Synergistic harvesting of electrical and photothermal energy with NCF.•Achieving sub-zero (−30 °C) and ultrafast (90 ms) operability of NCF- supercapacitor.•Demonstrating 45% higher energy storage at −30 °C, to rival their ambient performance.•Engineered extraction of full photothermal and electrical potential in energy storage. The universal direct dependence of ionic mobility on temperature severely restricts the low-temperature operation of energy storage devices. We overcome this limitation by synergizing photothermal conversion with electrochemical energy storage, using non-graphitizable nanocarbon florets (NCF) as multi-functional electrodes. NCF-based supercapacitors leverage the photothermal energy, directing it to the High Internal Phase Emulsion polymer (poly-HIPE) infused ionic conductor [BMIm]-[TFSI], resulting in 15% increase in specific capacitance (Csp) at 30 °C and a 45% at −30 °C. This is the first solid-state energy storage device usable at sub-freezing conditions (< − 4 °C) without compromising its performance. Importantly, the device exhibits identical characteristics at 10 °C (with sunlight) and 30 °C (in the dark), thereby offsetting a temperature difference of 20 °C. Experimental evidences points to the reduction in electrolyte resistance by 86% and 34% in relaxation time constant as the origin of such improved functioning. Furthermore, the advantage of processability is translated to configurational form-factor to efficiently heat the ionic conductor and thereby realise a 15% increase in Csp.