A hybrid superconcentrated electrolyte enables 2.5 V carbon-based supercapacitors

Confined Water Dynamics in Topological Networks Hydrogel for Aqueous Electrochemical Devices

The unique properties of confined water molecules within polymer networks have garnered extensive research interest in energy storage, catalysis, and sensing. Confined water molecules exhibit higher thermodynamic stability compared to free water, which reduces decomposition and evaporation of water in hydrogel electrolyte system. Herein, a facile strategy is developed to limit active water molecules in a hydrogel network via hydrogen bonding within a topological network. The design of this gel enhances hydrogen bonding between the gel network and water molecules, thereby improving stability by constructing interpenetrating networks. Using this design, the topological network gel is selected as the electrolyte for batteries, demonstrating an extended electrochemical window from 2.37 V with polyvinyl alcohol gel to 2.96 V, indicating superior confinement of water molecules by hydrogen bonds in the topological network. Additionally, batteries and capacitors assembled with the topological gel exhibit high-capacity retention rates of 94.25% after 20 000 cycles at a current density of 1.0 A g-1 and 87.63% after 10 000 cycles at a current density of 0.5 A g-1, respectively. This study demonstrates the feasibility of using a topological gel design to enhance gel electrolyte stability, offering a promising avenue for future research in regulating topological networks within gels for various applications.

Challenges and prospects of high-voltage aqueous electrolytes for energy storage applications

Aqueous electrolytes have attracted widespread attention as they are safe, environmentally benign and cost effective, holding great promise for future low-cost and sustainable energy storage devices. Nonetheless, the narrow electrochemical stability window caused by water electrolysis, as well as the trade-off between the stability window and other properties remain the bottleneck problem for the practical applications of aqueous electrolytes. Deep insights into the correlations between the microscopic physicochemical and electrochemical mechanisms and the macroscopic properties of aqueous electrolyte are essential for the envisaged applications, yet a systematic analysis of the recent progress in this area is still lacking. In this Perspective article, the basic mechanisms and influencing factors of water electrolysis including the hydrogen evolution and oxygen evolution reactions is critically examined. We systematically review the current state-of-the-art on high-voltage aqueous electrolytes focusing on the fundamental mechanisms of ion kinetics leading to dynamic electrolyte restructuring. Recent advances on the optimization of high-voltage aqueous electrolytes are also summarized. The existing challenges are identified and perspectives for exploring and developing future high-voltage aqueous electrolytes are provided.

Scalable 18,650 aqueous-based supercapacitors using hydrophobicity concept of anti-corrosion graphite passivation layer

Scalable aqueous-based supercapacitors are ideal as future energy storage technologies due to their great safety, low cost, and environmental friendliness. However, the corrosion of metal current collectors e.g., aluminium (Al) foil in aqueous solutions limits their practical applications. In this work, we demonstrate a low-cost, scalable, and simple method to prepare an anti-corrosion current collector using a concept of hydrophobicity by coating the hydrophobic graphite passivation layer on the Al foil via a roll-to-roll coating technology at the semi-automation scale of production pilot plant of 18,650 cylindrical supercapacitor cells. All qualities of materials, electrodes, and production process are therefore in the quality control as the same level of commercial supercapacitors. In addition, the effects of the graphite coating layer have been fundamentally evaluated. We have found that the graphite-coated layer can improve the interfacial contact without air void space between the activated carbon active material layer and the Al foil current collector. Importantly, it can suppress the corrosion and the formation of resistive oxide film resulting in better rate capability and excellent cycling stability without capacitance loss after long cycling. The scalable supercapacitor prototypes here in this work may pave the way to practical 18,650 supercapacitors for sustainable energy storage systems in the future.