MXenes: A comprehensive review of synthesis, properties, and progress in supercapacitor applications

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Top Highlights

• Supercapacitors find extensive applications across various sectors like industrial-energy recovery, smart-grids, consumer electronics, electric-vehicle industry, and the solar energy generation systems

• Through a combination of theoretical insights and experimental findings, the potential of MXenes to revolutionize supercapacitor technology emerges, offering prospects for high-energy-density and long-lasting energy storage solutions.

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• MXenes exhibit high electrical conductivity, large surface areas, and tailored surface chemistry, making them promising candidates for energy storage in supercapacitors.

• including novel electrode designs, electrolyte engineering, and hybrid materials,

• Bimetallic MXenes

• To achieve quick energy storage, the electrolyte ions can quickly undergo adsorption and desorption on the surface of the supercapacitor electrodes, facilitated by the electric field.

• Pseudocapacitors store electrical energy through rapid and reversible faradaic reactions that occur either on or in close proximity to the electrode surface [5]. While the faradaic charge transfer in pseudocapacitors may be slower compared to electrostatic adsorption of electrolyte-ions in EDLCs, it offers the advantage of achieving a higher energy storage density.

• EDLCs rely on adsorption of electrolyte ions at the interfaces between electrodes and electrolytes to facilitate the energy storage process. At the same time, the aggregation of ions on the electrolyte side induces the migration of electrons towards the electrode surface, leading to electric double layer formation.

• The MXene's hydrophilic surface is a result of the chemical etching process and the presence of surface termination groups [15].

• Researchers intercalated MXene with one-dimensional cellulose nanofibers (CNF) and carboxylic single-walled carbon nanotubes (SWCNT), resulting in well-dispersed MXene/SWCNT/CNF aqueous suspensions and their hybrid hydrogels.

• Pseudocapacitors often have an energy density that is higher than EDLCs. Pseudocapacitors typically have better power densities as compared to batteries

• The material's flexibility features enable it to take on any shape, and its mechanical properties also include strength, elasticity, tractability, and machenability.

• MXenes have outperformed the best-known carbon supercapacitors in terms of capacitance performance, including graphene supercapacitors [77,78], which have a capacitance of 78 F/g, as well as more widely used commercial supercapacitors [79], which typically have capacitances between 80 and 200 F/g.