Developing efficient and cost-effective electrode materials is of essential significance to advance various energy storage technologies, among which flexible supercapacitors hold great promise to meet the growing popularity of wearable electronics. Herein, we report a homologous strategy to parallelly synthesize phosphorus-doped ZnCo₂O₄ (P-ZnCo₂O₄@NCC) and nitrogen-doped carbon (NC@NCC) both derived from ZnCo-metal-organic frameworks (MOFs) precursors in-situ grown on dopamine-modified carbon cloth (NCC) as conductive substrates. Impressively, the as-obtained P-ZnCo₂O₄@NCC can achieve a high specific capacitance of 2702.2 mF∙cm⁻² at 1 mA∙cm⁻² with the capacitance retention rate exceeding 70.6% at 10 mA∙cm⁻², demonstrating the outstanding rate capability. Moreover, flexible solid-state hybrid supercapacitors, using P-ZnCo₂O₄@NCC as positive electrode and NC@NCC as negative electrode, are assembled with poly(vinyl alcohol) (PVA)/KOH as the gel electrolyte, which deliver the energy density of 11.9 mWh∙cm⁻³ when the power density reaches up to 47.3 mW∙cm⁻³. In addition, 85.15% of the initial specific capacitance is maintained after 5000 continuous cycles and no obvious capacitance decay is observed under different bending conditions, revealing the excellent cycling stability and flexibility. As a proof-of-concept demonstration, two as-assembled hybrid supercapacitors connected in series can light up a red light-emitting diode (LED) under the bending angle of 180°, heralding the feasibility for broad practical applications.

Lithium-sulfur (Li-S) batteries with the merits of high theoretical capacity and high energy density have gained significant attention as the next-generation energy storage devices. Unfortunately, the main pressing issues of sluggish reaction kinetics and severe shuttling of polysulfides hampered their practical application. To overcome these obstacles, various strategies adopting high-efficient electrocatalysts have been explored to enable the rapid polysulfide conversions and thereby suppressing the polysulfide shuttling. This review first summarizes the recent progress on electrocatalysts involved in hosts, interlayers, and protective layers. Then, these electrocatalysts in Li-S batteries are analyzed by listing representative works, from the viewpoints of design concepts, engineering strategies, working principles, and electrochemical performance. Finally, the remaining issues/challenges and future perspectives facing electrocatalysts are given and discussed. This review may provide new guidance for the future construction of electrocatalysts and their further utilizations in high-performance Li-S batteries.

Aqueous rechargeable Zn-ion batteries are regarded as a promising alternative to lithium-ion batteries owing to their high energy density, low cost, and high safety. However, their commercialization is severely restricted by the Zn dendrite formation and side reactions. Herein, we propose that these issues can be minimized by modifying the interfacial properties through introducing electrochemically inert Al₂O₃ nanocoatings on Zn meal anodes (Al₂O₃@Zn). The Al₂O₃ nanocoatings can effectively suppress both the dendrite growth and side reactions. As a result, the Al₂O₃@Zn symmetric cells show excellent electrochemical performance with a long lifespan of more than 4,000 h at 1 mA·cm⁻² and 1 mAh·cm⁻². Meanwhile, the assembled Al₂O₃@Zn//V₂O₅ full cells can deliver a high capacity (236.2 mAh·g⁻¹) and long lifespan with a capacity retention of 76.11% after 1,000 cycles at 4 A·g⁻¹.

Due to their superior hydrophilicity and conductivity, ultra-high volumetric capacitance, and rich surface-chemistry properties, MXenes exhibit unique and excellent performance in catalysis, energy storage, electromagnetic shielding, and life sciences. Since they are derived from ceramics (MAX phase) through etching, one of the challenges in MXenes preparation is the inevitable exposure of metal atoms on their surface and embedding of anions and cations. Because the as-obtained MXenes are always in a thermodynamically metastable state, they tend to react with trace oxygen or oxygen-containing groups to form metal oxides or degrade, leading to sharply declined activity and impaired performance. Therefore, improving the stability of MXenes-based materials is of practical significance in relevant applications. Unfortunately, there lacks a comprehensive review in the literature on relevant topics. To help promote the wide applications of MXenes, we review from the following aspects: (i) insights into the factors affecting the stability of MXenes-based materials, including oxidation of MXenes flakes, stability of MXenes colloidal solutions, and swelling and degradation of MXenes thin-film, (ii) strategies for enhancing the stability of MXenes-based materials by optimizing MAX phase synthesis and modifying the MXenes preparation, and (iii) techniques for further increasing the stability of freshly prepared MXenes-based materials via controlling the storage conditions, and forming shielding on the surface and/or edge of MXenes flakes. Finally, some outlooks are proposed on the future developments and challenges of highly active and stable MXenes. We aim to provide guidance for the design, preparation, and applications of MXenes-based materials with excellent stability and activity.

Potassium-ion batteries (PIBs) are appealing alternatives to conventional lithium-ion batteries (LIBs) because of their wide potential window, fast ionic conductivity in the electrolyte, and reduced cost. However, PIBs suffer from sluggish K⁺ reaction kinetics in electrode materials, large volume expansion of electroactive materials, and the unstable solid electrolyte interphase. Various strategies, especially in terms of electrode design, have been proposed to address these issues. In this review, the recent progress on advanced anode materials of PIBs is systematically discussed, ranging from the design principles, and nanoscale fabrication and engineering to the structure-performance relationship. Finally, the remaining limitations, potential solutions, and possible research directions for the development of PIBs towards practical applications are presented. This review will provide new insights into the lab development and real-world applications of PIBs.