Abstract
The hybrid ion capacitor (HIC) is a hybrid electrochemical energy storage device that combines the intercalation mechanism of a lithium-ion battery anode with the double-layer mechanism of the cathode. Thus, an HIC combines the high energy density of batteries and the high power density of supercapacitors, thus bridging the gap between batteries and supercapacitors. Two-dimensional (2D) carbon materials (graphite, graphene, carbon nanosheets) are promising candidates for hybrid capacitors owing to their unique physical and chemical properties, including their enormous specific surface areas, abundance of active sites (surface and functional groups), and large interlayer spacing. So far, there has been no review focusing on the 2D carbon-based materials for the emerging post-lithium hybrid capacitors. This concept review considers the role of 2D carbon in hybrid capacitors and the recent progress in the application of 2D carbon materials for post-Li (Na+, K+, Zn2+) hybrid capacitors. Moreover, their challenges and trends in their future development are discussed.
Highlights
Based on the energy storage mechanism, supercapacitors can be classified into three types [2]: (1) electrochemical double-layer capacitors (EDLCs), which store energy through the adsorption of ions on the surfaces of the electrodes; (2) pseudocapacitors (PCs), which have a storage mechanism based on fast surface redox reactions; and (3) hybrid capacitors, which store energy through a combination of the adsorption of ions on the surface of the electrodes and redox reactions of their electrodes
We have summarized the recent progress on the application of 2D carbon materials in post-Li hybrid capacitors, including sodium-ion hybrid capacitors, potassium-ion hybrid capacitors, and zinc-ion hybrid capacitors
This article provides a comprehensive overview of the mechanisms and variety of hybrid capacitors, the functions of 2D carbon materials in hybrid capacitors, and current problematic issues for hybrid capacitors
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The commercial supercapacitors show high power density of up to 10 kW kg−1 and long-term durability through the reversible adsorption/desorption of ions on the electrode surface but have low specific energy densities (
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