High-energy density cellulose nanofibre supercapacitors enabled by pseudo-solid water molecules

Compared with conventional electrochemical supercapacitors and lithium-ion batteries, the novel amorphous cellulose nanofibre (ACF) supercapacitor demonstrates superior electric storage capacity with a high-power density, owing to its fast-charging capability and high-voltage performance. This study unveils introduces an ACF supercapacitor characterised by a substantial energy density. This is achieved by integrating a singular layer of pseudo-solid water molecules (electrical resistivity of 1.11 × 10⁸ Ω cm) with cellulose nanofibers (CNFs), establishing forming an electric double layer at the electrode interface. The enhanced energy storage in these high-energy density capacitors (8.55 J/m²) is explicated through the polarisation of protons and lone pair electrons on oxygen atoms during water electrolysis, commencing at 1.23 V. Improvements in energy density are attainable through CNF density enhancements and charging-current optimisation. The proposed ACF supercapacitor offers substantial promise for integration into the power sources of flexible and renewable paper-based electronic devices.