Role of graded microstructure and electrolyte distribution in electrochemical capacitance of compressible three-dimensional carbon nanotubes-polymer foam based supercapacitor

• Published in: Electrochimica acta 2023-09, Vol.461, p.142595, Article 142595
• Main Authors: Chauhan, Pankaj Singh, Sengupta, Ria, Kumar, Sumana, Panwar, Vinod, Sahoo, Santilata, Bose, Suryasarthi, Misra, Abha
• Format: Article
• Language: English
• ISSN: 0013-4686
• DOI: 10.1016/j.electacta.2023.142595

Three-dimensional microstructure of carbon materials has a prime importance in supercapacitor for energy storage. Carbon nanotubes (CNT) provide microstructurally porous structure via entangled nodes that dynamically changes with the uniaxial compression. A unique graded CNT-polymer based three-dimensional compressible cellular foam is used as an electrode material for the solid-state supercapacitor. A direct correlation was established between the applied strain and resulting electrochemical capacitance when the foam electrode was soaked and unsoaked in the electrolyte. In a novel finding, unsoaked electrodes revealed in an extraordinary enhancement of ∼1216% in gravimetric capacitance measured at a uniaxial strain of 80% and to no surprise, the electrochemical capacitance of electrolyte-soaked electrodes remained nearly invariant from its uncompressed state. The response of electrochemical capacitance under compression is also observed varying with the mode of compression i.e. quasi-static versus pre-compressed state to a targeted strain. The role of graded microstructure during uniaxial compression was verified by using as-grown CNT mat for the electrodes of a supercapacitor. The results demonstrated a dominating contribution of dynamic variation in the density of nodes in the compressed CNT mat. The impact of macroscopic variation on the response of electrochemical capacitance of a compressed cellular CNT-polymer foam was further understood using the separators of varying pore sizes. Our results pave the way to engineer the three-dimensional compressible cellular structures for extraordinarily large energy storage capacity.