Key Takeaways & Executive Findings
- •• A novel high-entropy metal–organic frameworks (HE-MOFs) electrode for fast sodium-ion storage devices has been realized by introducing five metallic elements. • The platform capacity/voltage of the electrode materials are precisely regulated by the adjustable metal species/content of HE-MOFs. • The sodium-ion capacitors assembled based on high-entropy MOFs electrode exhibit high-power density (20,000 W kg-1) and high-energy density (99.4 Wh kg-1). • The HE-MOFs material maintains a reversible specific capacity of 89 mAh g−1 at 20 A g−1 and an ideal sodium storage voltage plateau of ~0.5 V, with platform capacity increased to 122.7 mAh g−1.
Abstract
Precise regulation of the platform capacity/voltage of electrode materials contributes to the efficient operation of sodium-ion fast-charging devices. However, the design of such electrode materials is still in a blank stage. Herein, based on tunable metal–organic frameworks, we have designed a novel material system—two-dimensional high-entropy metal–organic frameworks (HE-MOFs), which exhibits unique properties in sodium storage and is of vital importance for realizing fast-charging batteries. Furthermore, we have found that the high-entropy effect can regulate the electronic structure, the sodium-ion migration environment, and the sodium-ion storage active sites, thereby meeting the requirements of electrode materials for sodium-ion fast-charging devices. Impressively, the HE-MOFs material still maintains a reversible specific capacity of 89 mAh g−1 at a current density of 20 A g−1. It presents an ideal sodium storage voltage plateau of approximately 0.5 V, and its platform capacity is increased to 122.7 mAh g−1, far superior to that of Mn-MOFs (with no platform capacity). This helps to reduce safety hazards during the fast-charging process and demonstrates its great application value in the fields of fast-charging sodium-ion batteries and capacitors. Our research findings have broken the barriers to the application of non-conductive MOFs as energy storage materials, enhanced the understanding of the regulation of platform capacity and voltage, and paved the way for the realization of high-security sodium-ion fast-charging devices.
1. Introduction
The development and application of advanced materials have provided a constant impetus to improve the energy/power density of energy storage devices [1–4]. In recent decades, the widespread use of lithium-ion batteries has propelled the development of human civilization [5–7]. However, the limited availability of lithium resources constrains the widespread use of lithium-ion batteries in large-scale fast energy storage devices [8, 9]. Sodium-ion energy storage devices, characterized by their low cost, abundant raw materials, and more evenly distributed global sodium resources, represent a better solution for large-scale fast energy storage [10, 11]. Nevertheless, developing sodium-ion energy storage devices with both rapid charging capability and high-energy density poses significant challenges. During fast charging, sodium ions may precipitate in metallic form, thereby affecting the safety performance of the entire battery [12, 13]. Meanwhile, the electrode material, which is the "heart" of the energy storage device, exhibits an uncontrollable voltage plateau and platform capacity. The realization of controllable voltage plateau and plateau capacity is conducive to the reduction of the risk factor in the operation of sodium-ion energy storage devices and the improvement of their energy/power density.
Metal–organic frameworks with adjustable metal components and variable contents provide the possibility of regulating the voltage platform and platform capacity [14–16]. In recent years, the development of conductive metal–organic frameworks (MOFs) has expanded the prospects of direct application of MOFs in energy storage [17–19]. However, the synthesis of conductive MOFs is complex, costly, and limited in variety [20–22]. On the contrary, non-conductive MOFs are numerous and simple to synthesize, and their derivatives are widely used in energy storage [23, 24]. Nevertheless, their poor chemical stability and conductivity seriously hinder their direct use as electrode materials [25]. In disordered multi-component systems, a large conformational entropy can often stabilize the crystal structure and promote its chemical and structural diversity [26–30]. To date, a large number of high-entropy materials, such as initial high-entropy alloys (HEAs) and subsequently high-entropy oxides (HEOs), have been used in applications such as environmental protection, electrochemical energy storage, and catalysis [31–35]. Whether high-entropy (HE) strategies can effectively modify non-conductive MOFs materials and induce them to become excellent sodium fast storage electrode materials deserves in-depth investigation.
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Shusheng Tao, Ziwei Cao, Xuhuan Xiao, Zirui Song, Dengyi Xiong, Ye Tian, Wentao Deng, Youcai Liu, Hongshuai Hou, Guoqiang Zou, Xiaobo Ji (2025). Tunable Platform Capacity of Metal–Organic Frameworks via High-Entropy Strategy for Ultra-Fast Sodium Storage. Nano-Micro Letters. https://doi.org/10.1007/s40820-025-01706-3
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Frequently Asked Questions
What are high-entropy metal-organic frameworks (HE-MOFs)?
HE-MOFs are a novel class of metal-organic frameworks that incorporate multiple metallic elements (typically five or more) in near-equimolar ratios, leveraging the high-entropy effect to stabilize the structure and tune electronic properties for enhanced electrochemical performance.
How does the high-entropy strategy improve sodium storage performance?
The high-entropy effect regulates the electronic structure, sodium-ion migration environment, and active sites, leading to improved reversible capacity, a desirable voltage plateau (~0.5 V), and increased platform capacity, enabling fast and safe sodium storage.
What are the key performance metrics of the HE-MOFs electrode?
The HE-MOFs electrode maintains a reversible specific capacity of 89 mAh g−1 at a high current density of 20 A g−1, and exhibits an ideal sodium storage voltage plateau of approximately 0.5 V with a platform capacity of 122.7 mAh g−1.
What applications can benefit from this research?
The findings are directly applicable to fast-charging sodium-ion batteries and sodium-ion capacitors, offering high power density (20,000 W kg−1) and high energy density (99.4 Wh kg−1), which are crucial for large-scale energy storage systems.
How does this work address the limitations of non-conductive MOFs?
By introducing the high-entropy strategy, the researchers successfully modified non-conductive MOFs to become excellent sodium storage electrode materials, overcoming the barriers of poor conductivity and stability, thus expanding the direct application of MOFs in energy storage.
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