Key Takeaways & Executive Findings
- •• MXenes exhibit superior electrical conductivity and chemical tunability compared to traditional electrode materials, making them highly promising for supercapacitors. • The main challenge is balancing high volumetric capacitance with rapid ion transport, as modification strategies often increase ion channels but reduce packing density. • The review covers recent preparation methods and modification strategies aimed at achieving both high volumetric capacitance and high ion transport for applications in wearable and microdevices. • Structural engineering of MXenes is critical to overcome stacking issues and enhance rate performance and electrochemical activity.
Abstract
Supercapacitors (SCs) stand out among various energy storage devices owing to their high power density and long-term cycling stability. As new two-dimensional material, MXenes have become a research hotspot in recent years owing to their unique structure and rich surface functional groups. Compared with other materials, MXenes are more promising for SCs owing to their tunable precursors, structural stability, and excellent electrical conductivity. However, the rate performance and electrochemical reaction activity of MXene materials are poor, and stacking severely limits their application. Therefore, various modification strategies are employed to improve the electrochemical performance of MXene materials. As the modification strategy of MXene electrode materials often involves increasing the number of ion transport channels to expose more active sites, the packing density is also affected to different degrees. Therefore, achieving a balance between high volumetric capacitance and rapid ion transport has become a key issue for the application of MXene-based SCs in wearable devices and microdevices. In this paper, the latest progress in the preparation methods and modification strategies of MXenes in recent years is reviewed with the aim of achieving both high volumetric capacitance and high ion transport for expanding the application of MXene-based SCs in microdevices and wearable devices.
1. Introduction
Among the current major energy storage devices, lithium-ion batteries have attracted considerable attention owing to their high energy density and wide range of sources. However, they still face important challenges such as slow reaction rates that cannot withstand excessive currents, limited service life, and relatively high safety risks [1]. In contrast, supercapacitors (SCs) display superior power density and excellent cycle stability, making them ideal for applications in electric vehicles, regenerative braking systems, and emergency backup power supplies [2–3]. Although the current energy density of supercapacitors is relatively low, this deficiency is gradually improving with in-depth research on advanced materials and continuous technological progress. Supercapacitors are expected to occupy a key position in the field of energy storage technologies in the future [4].
Numerous electrode materials with unique physicochemical properties have been explored to enhance the electrochemical performance of supercapacitors (SCs) [5]. Carbon-based materials, such as activated carbon (AC) and graphene, have been widely studied due to their large specific surface areas and excellent electrical conductivities. However, their surface chemical activity is relatively low, which limits their charge storage mechanism primarily to electric double-layer capacitance (EDLC). As a result, these materials suffer from low energy storage density, restricting their further application in high-energy SCs. In addition, their limited chemical tunability hinders further structural and functional optimization at the molecular level. [6–7]. Transition metal oxides, including manganese dioxide (MnO2) and nickel oxide (NiO), offer high theoretical capacities owing to their multiple oxidation states. Nevertheless, their inherently poor electrical conductivity and structural instability during cycling significantly impair their rate capability and long-term performance [8]. Conductive polymers, such as polyaniline (PANI) and polypyrrole (PPy), exhibit reversible redox reactions and relatively high pseudocapacitive activity. However, their cycling stability is limited. For instance, PPy relies on the conjugated structure of its molecular backbone and doped ions for charge transport, resulting in lower electron mobility and carrier concentration than MXenes. Furthermore, the electrochemical properties of PPy are highly sensitive to environmental conditions, often leading to structural degradation and reduced stability, particularly in acidic electrolytes, where PPy undergoes severe degradation that shortens the device’s lifespan [9–11]. MXenes, as a new class of 2D materials, exhibit superior electrical conductivity compared to metal oxides and greater chemical tunability than carbon materials. Their structure contains transition-metal active sites with variable oxidation states, enabling faradaic charge storage.
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Yan Liu, Kaiyang Guo, Yuanmeng Ge, Wenzheng Yan, Kai Gu, Yapeng Tian, Xinwei Cui (2025). Structural engineering of MXenes towards high electrochemical performance in supercapacitors. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-025-3146-2
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Frequently Asked Questions
What are MXenes and why are they promising for supercapacitors?
MXenes are a new class of two-dimensional materials with unique structure, rich surface functional groups, tunable precursors, structural stability, and excellent electrical conductivity. These properties make them highly promising for supercapacitors, offering high power density and long-term cycling stability.
What are the main challenges in using MXenes for supercapacitors?
The main challenges include poor rate performance and electrochemical reaction activity, as well as severe stacking of MXene layers, which limits ion transport and reduces accessible active sites. Additionally, modification strategies to increase ion transport channels often reduce packing density, creating a trade-off between volumetric capacitance and ion transport.
How can the electrochemical performance of MXenes be improved?
Various modification strategies are employed, such as structural engineering to increase ion transport channels and expose more active sites. The goal is to achieve a balance between high volumetric capacitance and rapid ion transport, which is crucial for applications in wearable devices and microdevices.
What is the significance of this review paper?
This review summarizes the latest progress in preparation methods and modification strategies of MXenes, aiming to achieve both high volumetric capacitance and high ion transport. It provides insights into expanding the application of MXene-based supercapacitors in microdevices and wearable devices.
What are the potential applications of MXene-based supercapacitors?
MXene-based supercapacitors are ideal for applications requiring high power density and long-term stability, such as electric vehicles, regenerative braking systems, emergency backup power supplies, and especially wearable devices and microdevices where both high volumetric capacitance and rapid ion transport are essential.
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