Two-dimensional transition metal carbides (MXenes) are extremely competitive in electrochemical energy storage due to their highly hydrophilic surfaces and exceptional metallic conductivity. However, the easy stacking tilt of the interlayers would lead to reduced ion accessibility and available transport pathways within the MXenes, limiting their electrochemical performance.

Based on the design of nanoscale ion channels, MXene electrodes with maximum ion accessibility and high mechanical strength have been constructed and used for high-capacity zinc ion energy storage. In-plane ion channel design provides a simple, efficient, and scalable approach to improve the electrochemical energy storage capacity of MXenes and other 2D materials. Image credit: Science China Press

Numerous techniques have been developed to fully exploit the advantages of MXenes in electrochemical energy storage and prevent self-accumulation behavior. Hole etching is one of the strategies used to improve ion transport efficiency and accessibility, which can be applied to construct high-performance energy storage devices.

In particular, the ability of chemical etching to produce nanoscale electrodes with ion channels offers promising application potential. Controlling the level of chemical etching for efficient manipulation of electrochemical energy storage still presents significant difficulties.

In this study published by Scientific BulletinMXene nanosheets with in-plane ion channels are created by chemical oxidation and used as electrodes to create self-healing zinc ion microcapacitors (ZIMCs) with outstanding anti-self-discharge performance.

This work is based on the design concept of in-plane nanoscale ion channels. While maintaining the superior mechanical strength and electrical conductivity of large-sized MXene nanosheets, in-plane ion channel-equipped MXene nanosheets can reduce the ion travel distance and improve the electrochemical performance of ZIMC.

The designed MXene-based self-healing zinc ion microcapacitor has a high areal specific capacitance (532.8 mF cm-2) at a current density of 2 mA cm-2low self-discharge rate of 4.4 mV h–1and a high energy density of 145.1 μWh cm-2 at a power density of 2800 μW cm-2.

The developed ZIMC holds considerable promise for use in flexible electronics due to its superior anti-self-discharge and self-healing characteristics, which could sustain microelectronic devices for extended periods of time.

MXene electrodes with optimal ion accessibility and excellent mechanical strength have been designed and used for high-capacity zinc ion energy storage based on nanoscale ion channel construction.

In-plane ion channel design provides a simple, practical, and scalable method to significantly increase the electrochemical energy storage capability of MXenes and other 2D materials.

Journal reference

Cheng, Y. et al. (2022) Maximizing Ion Accessibility and High Mechanical Strength in Nanoscale Ion Channel MXene Electrodes for High Capacity Zinc Ion Energy Storage. Scientific Bulletin. doi:10.1016/j.scib.2022.10.003