Application of 2D Materials to Potassium-Ion Hybrid Capacitors

A Comprehensive Review of Anode Materials in Rechargeable Calcium-Ion Batteries

Recently, rechargeable calcium-ion batteries (CIB) have been investigated extensively due to their safety, environmental friendliness, abundant storage capacity, low cost, and their energy density and power density characteristics. This paper presents a systematic review of recent research advancements in anode materials, including alloys, organic materials, carbon-based materials, and transition metal oxide. First, the basic properties of CIBs and the challenges associated with anode materials are described. Then, the reaction mechanism and improvement strategies of anode materials for CIBs are highlighted. Finally, the advantages and disadvantages of the identified anode materials are summarized, and potential future research directions are highlighted.

Recent Advances in Current Collectors for Aqueous Zinc-ion Batteries

Aqueous zinc-ion batteries (AZIBs) are promising options for large-scale electrical energy storage because of their safety, affordability, and environmental friendliness. As an indispensable component of AZIBs, a current collector plays a crucial role in supporting electrode materials and collecting the accumulated electrical energy. Recently, some progress has been made in the study of current collectors for AZIBs; however, only few comprehensive reviews on this topic are available. In this review, the systematic summary and discussion of research progress on current collectors for AZIBs is presented. Furthermore, the main challenges and key prospects for the future development of current collectors for AZIBs are discussed.

Research Advances of Cathode Materials for Rechargeable Aluminum Batteries

Rechargeable aluminum ion batteries (AIBs) have recently gained widespread research concern as energy storage technologies because of their advantages of being safe, economical, environmentally friendly, sustainable, and displaying high performance. Nevertheless, the intense Coulombic interactions between the Al3+ ions with high charge density and the lattice of the electrode body lead to poor cathode kinetics and limited cycle life in AIBs. This paper reviews the recent advances in the cathode design of AIBs to gain a comprehensive understanding of the opportunities and challenges presented by current AIBs. In addition, the advantages, limitations, and possible solutions of each cathode material are discussed. Finally, the future development prospect of the cathode materials is presented.

Recent Advances in Graphene-Based Materials for Zinc-Ion Batteries

Zinc-ion batteries (ZIBs) are a promising alternative for large-scale energy storage due to their advantages of environmental protection, low cost, and intrinsic safety. However, the utilization of their full potential is still hindered by the sluggish electrode reaction kinetics, poor structural stability, severe Zn dendrite growth, and narrow electrochemical stability window of the whole battery. Graphene-based materials with excellent physicochemical properties hold great promise for addressing the above challenges foe ZIBs. In this review, the energy storage mechanisms and challenges faced by ZIBs are first discussed. Key issues and recent progress in design strategies for graphene-based materials in optimizing the electrochemical performance of ZIBs (anode, cathode, electrolyte, separator and current collector) are then discussed. Finally, some potential challenges and future research directions of graphene-based materials in high-performance ZIBs are proposed for practical applications.

Recent development of manganese dioxide-based materials as zinc-ion battery cathode

The development of advanced cathode materials for zinc-ion batteries (ZIBs) is a critical step in building large-scale green energy conversion and storage systems in the future. Manganese dioxide is one of the most well-studied cathode materials for zinc-ion batteries due to its wide range of crystal forms, cost-effectiveness, and well-established synthesis processes. This review describes the recent research progress of manganese dioxide-based ZIBs, and the reaction mechanism, electrochemical performance, and challenges of manganese dioxide-based ZIBs materials are systematically introduced. Optimization strategies for high-performance manganese dioxide-based materials for ZIBs with different crystal forms, nanostructures, morphologies, and compositions are discussed. Finally, the current challenges and future research directions of manganese dioxide-based cathodes in ZIBs are envisaged.

3D ordered amorphous and porous TiO2 framework anode with low insertion barrier and fast kinetics for K-ion hybrid capacitors

TiO₂ is considered as a low cost, long-term stable, and safe anode for high power K-ion hybrid capacitors (KICs) due to its abundant reserve, small volume expansion rate, and sloping voltage plateau that avoids K-ion plating at high voltage polarization. However, the enhancement of its low capacity and sluggish kinetics caused by poor electroconductivity and high insertion barrier is still challenging to further develop high-performance KICs. Herein, the reduced graphene oxide (rGO) is embedded in the walls of 3D ordered macro-/mesoporous TiO₂ (termed as TiO₂@rGO framework) to create intimate TiO₂/rGO interfaces, ensuring the effectively electron transportation during potassiation/depotassiation of TiO₂ while maintaining rapid ions/electrolyte diffusion. Furthermore, the controlled amorphous TiO₂ framework can further lower the lattice insertion energies, contributing to a fast accommodation of K-ion. As expected, the amorphous TiO₂@rGO framework (TiO₂@rGO-1) exhibits a superior rate capability (148.8 mAh g^-1 at 5 A g^-1) and cycling stability (171.2 mAh g^-1 at 1 A g^-1 after 800 cycles). The assembled KICs can reach a high energy/power density of 125.2 Wh kg^-1/4267.4 W kg^-1 as well as a long-term lifespan. This tactic provides a reliable and general way to design a TiO₂-based anode with fast kinetics toward high-performance KICs.

Two-Dimensional Materials Applied in Membranes of Redox Flow Battery

Redox flow batteries (RFBs) are one of the most promising techniques to store and convert green and renewable energy, benefiting from their advantages of high safety, flexible design and long lifespan. Membranes with fast and selective ions transport are required for the advances of RFBs. Remarkably, two-dimensional (2D) materials with high mechanical and chemical stability, strict size exclusion and abundantly modifiable functional groups, have attracted extensive attentions in the applications of energy fields. Herein, the improvements and perspectives of 2D materials working for ionic transportation and sieving in RFBs membranes are presented. The characteristics of various materials and their advantages and disadvantages in the applications of RFBs membranes particularly are focused. This review is expected to provide a guidance for the design of membranes based on 2D materials for RFBs.

Hierarchical MXene/transition metal oxide heterostructures for rechargeable batteries, capacitors, and capacitive deionization

2D MXenes have attracted considerable attention due to their high electronic conductivity, tunable metal compositions, functional termination groups, low ion diffusion barriers, and abundant active sites. However, MXenes suffer from sheet stacking and partial surface oxidation, limiting their energy storage and water treatment development. To solve these problems and enhance the performance of MXenes in practical applications, various hierarchical MXene/transition metal oxide (MXene/TMO) heterostructures are rationally designed and constructed. The hierarchical MXene/TMO heterostructures can not only prevent the stacking of MXene sheets and improve the electronic conductivity and buffer the volume change of TMOs during the electrochemical reaction process. The synergistic effect of conductive MXenes and active TMOs also makes MXene/TMO heterostructures promising electrode materials for energy storage and seawater desalination. This review mainly introduces and discusses the recent research progress in MXene/TMO heterostructures, focusing on their synthetic strategies, heterointerface engineering, and applications in rechargeable batteries, capacitors, and capacitive deionization (CDI). Finally, the key challenges and prospects for the future development of the MXene/TMO heterostructures in rechargeable batteries, capacitors, and CDI are proposed.

Recent Advances in Layered Metal-Oxide Cathodes for Application in Potassium-Ion Batteries

To meet future energy demands, currently, dominant lithium-ion batteries (LIBs) must be supported by abundant and cost-effective alternative battery materials. Potassium-ion batteries (KIBs) are promising alternatives to LIBs because KIB materials are abundant and because KIBs exhibit intercalation chemistry like LIBs and comparable energy densities. In pursuit of superior batteries, designing and developing highly efficient electrode materials are indispensable for meeting the requirements of large-scale energy storage applications. Despite using graphite anodes in KIBs instead of in sodium-ion batteries (NIBs), developing suitable KIB cathodes is extremely challenging and has attracted considerable research attention. Among the various cathode materials, layered metal oxides have attracted considerable interest owing to their tunable stoichiometry, high specific capacity, and structural stability. Therefore, the recent progress in layered metal-oxide cathodes is comprehensively reviewed for application to KIBs and the fundamental material design, classification, phase transitions, preparation techniques, and corresponding electrochemical performance of KIBs are presented. Furthermore, the challenges and opportunities associated with developing layered oxide cathode materials are presented for practical application to KIBs.

Expanded Graphite-Based Materials for Supercapacitors: A Review

Supercapacitors have gained e wide attention because of high power density, fast charging and discharging, as well as good cycle performance. Recently, expanded graphite (EG) has been widely investigated as an effective electrode material for supercapacitors owing to its excellent physical, chemical, electrical, and mechanical properties. Based on charge storage mechanism, supercapacitors have been divided into symmetric, asymmetric, and hybrid supercapacitors. Here, we review the study progress of EG-based materials to be electrode materials. Furthermore, we discuss the application prospects and challenges of EG-based materials in supercapacitors.

Application of expanded graphite-based materials for rechargeable batteries beyond lithium-ions

New types of rechargeable batteries other than lithium-ions, including sodium/potassium/zinc/magnesium/calcium/aluminum-ion batteries and non-aqueous batteries, are rapidly advancing towards large-scale energy storage applications. A major challenge for these burgeoning batteries is the absence of appropriate electrode materials, which gravely hinders their further development. Expanded graphite (EG)-based electrode materials have been proposed for these emerging batteries due to their low cost, non-toxic, rich-layered structure and adjustable layer spacing. Here, we evaluate and summarize the application of EG-based materials in rechargeable batteries other than Li⁺ batteries, including alkaline ion (such as Na⁺, K⁺) storage and multivalent ion (such as Mg²⁺, Zn²⁺, Ca²⁺ and Al³⁺) storage batteries. Particularly, this article discusses the composite strategy and performance of EG-based materials, which enables them to function as an electrode in these emerging batteries. Future research areas in EG-based materials, from the fundamental understanding of material design and processing to reaction mechanisms and device performance optimization strategies, are being looked forward to.