Aqueous zinc-ion batteries (ZIBs) have emerged as promising candidates for safe and sustainable energy storage systems. However, conventional ZIBs face critical challenges, such as zinc dendrite formation, corrosion, and passivation, primarily due to their unstable deposition‒dissolution mechanism compared with the “rocking-chair” mechanism of lithium-ion batteries. This review presents a critical assessment of the past decade’s significant advances in “rocking-chair” ZIBs, with a particular focus on Zn²⁺-intercalation anodes. Four major classes of zinc-metal-free anodes are systematically discussed, highlighting their distinctive physicochemical features and zinc storage mechanisms. The development trajectory of anode materials is traced from early developments in transition metal dichalcogenides to emerging hybrid materials, with a focus on key challenges in ionic diffusion and electronic conductivity. Furthermore, we summarize the underlying working principles, essential design criteria, and material optimization strategies. Finally, future research opportunities and technological challenges are outlined to advance rocking-chair ZIBs toward practical deployment in applications ranging from grid-scale storage to portable electronics. This review provides critical insights and design guidance for enabling the next generation of high-performance, commercially viable ZIBs.

The shift towards green hydrogen production is imperative for accomplishing sustainable energy goals, particularly through seawater electrolysis. However, the simultaneous occurrence of the chlorine evolution reaction (CER) poses a substantial challenge by competing with the oxygen evolution reaction at the anode, thereby reducing the catalyst's efficiency and selectivity. This review critically examines the modern strategies for mitigating CER, focusing on the development and application of advanced nanomaterials. The emphasis is on transition metals and their oxides, 2D materials, layered double hydroxide-based electrocatalysts, and core–shell nanostructure-based electrocatalysts, highlighting their electrocatalytic properties, structural advantages, and potential drawbacks. Moreover, this review presents a balanced assessment of their benefits, including improved catalytic activity and stability, and their limitations, such as cost and scalability. Furthermore, this review reports the advantages and disadvantages of the CER, revealing that competing CERs can suppress the HER Faradaic efficiency by 20%–30% in chloride-rich electrolytes (~ 0.5 mol L⁻¹ Cl⁻). The conclusion and future outlook focus on the key findings, highlighting the necessity for continued innovation in material design and engineering. This review aims to guide researchers and industry stakeholders in developing more efficient and sustainable technologies for seawater electrolysis.

Solid-state lithium batteries (SSLBs) are approaching practical deployment, following breakthroughs in overcoming remaining interfacial transport barriers. A pragmatic solution has emerged: the introduction of a small quantity of liquid electrolyte to wet rough interfaces, restore contact, and open fast-ion pathways. Although such liquid additives are now widely adopted across laboratories, the evidence base remains scattered and terminology inconsistent. This review consolidates recent progress and distills design principles for integrating a fraction of liquid into nominally solid-state batteries. We classify chemistries as conventional salt-in-solvent electrolytes, ionic liquids, and gel polymer electrolytes, and map their implementation at solid electrolyte/electrode interfaces. Mechanisms are discussed through which fractional liquid additives reduce interfacial impedance, suppress void growth, and tune interphase chemistry. Improvements in electrochemical performance, including cycling stability and rate capability, are compared alongside trade-offs such as safety risks (flammability, volatility, parasitic reactions, and lithium penetration). Protocols are outlined to quantify the minimum effective additive content while retaining the intrinsic advantages of SSLBs (high-energy density and superior safety). Finally, future research directions are proposed to guide translation from bench to market, including operando mapping of liquid distribution, durability under practical areal loadings and stack pressures, and scalable delivery methods.

Ion-exchange membrane fuel cells (IEMFCs) and ion-exchange membrane water electrolyzers (IEMWEs) have become the focus of research in the field of clean energy conversion. However, the problem of membrane and electrode species transport is still a bottleneck for their industrialization. Biological behavior in nature provides valuable insights into the design of energy conversion devices. The phenomenon in which fish groups achieve efficient passage through orderly arrangement reveals the unique advantage of aligned transport structures in increasing the transport efficiency of species. This evolutionary law from disorder to order is reflected in energy devices as the oriented design of membrane electrode assemblies (MEAs). Conventional MEAs suffer from inefficient mass transport, catalyst agglomeration, and insufficient ion conductivity, which are rooted in transport disorder caused by isotropic channels. Novel uniaxial transport structures construct a directly connected path for ion conduction, gas diffusion, and water transport through-plane to the overall alignment of the MEAs, and this design significantly reduces the internal resistance and increases the energy density and conversion efficiency. Starting with ion-exchange membranes, this review describes the importance of overall alignment from membranes to electrodes for ion, gas, and water transport and systematically compares the differences in transport mechanisms among isotropic, anisotropic, and through-plane aligned structures. The synthesis methods and fabrication techniques for achieving these aligned transport architectures are summarized, and their structural stability and device stability are evaluated. The prospects for the industrialization of uniaxially oriented MEAs are envisioned, and possible solutions to existing challenges are proposed.

Two-dimensional (2D) materials have emerged as promising candidates for electrochemical energy storage and conversion applications, owing to their unique structural features and exceptional physicochemical properties. However, the large-scale practical deployment of these materials remains highly dependent on the development of efficient and scalable fabrication techniques. Notably, salt-assisted synthesis strategies have gained significant attention as a versatile approach, enabling precise structural modulation and performance optimization of 2D materials while maintaining cost efficiency and procedural simplicity. This review systematically summarizes recent advances in the salt-assisted synthesis of 2D materials and highlights their emerging roles in electrochemical applications. The influences of salt media on crystal nucleation, growth behavior, and surface properties for synthesizing 2D materials are discussed firstly in this review. Furthermore, representative 2D materials synthesized via this strategy are categorized and evaluated for applications in metal-ion batteries, supercapacitors, and electrocatalysis. Finally, the prevailing challenges and future research directions are critically assessed, targeting scalable production, mechanistic understanding, and multifunctional integration of salt-assisted synthesis for 2D materials. This comprehensive overview aims to provide fundamental insights and practical guidelines for the design of high-performance 2D electrochemical materials.

Na-ion batteries (NIBs) have gained attention as a cost-effective option for large-scale energy storage, offering electrochemical properties similar to lithium-ion batteries (LIBs). To improve safety and energy density, solid-state electrolytes (SSEs) are being incorporated into NIBs, paving the way for high-performance all-solid-state sodium-ion batteries (ASSNIBs). This review summarises recent progress in Na-based SSEs, categorised into oxides, sulfides, and halides, with particular emphasis on their crystal structures, ion conduction mechanisms, and electrochemical performance. We then critically examine the key challenges facing ASSNIBs, including low ionic conductivity, unstable electrode/electrolyte interfaces, and the reliance on rare or costly materials. To gain deeper insights into these issues, we highlight advanced characterisation and modelling techniques, including cryogenic electron microscopy, in-situ/operando characterisation, and machine learning approaches—all of which contribute to understanding Na-ion transport mechanisms and interfacial dynamics more comprehensively, and comparing with conventional electrochemical tests, structural characterisation and modelling methods. Building on these insights, we explore promising strategies such as microstructural design, mixed-ion approaches, and interface engineering to overcome the current limitations in Na SSEs. Finally, we offer perspectives on future research directions to support the rational design and optimisation of Na SSEs, ultimately advancing the development of next-generation ASSNIBs. The advanced characterisation and machine learning methodologies emphasised herein will also prove valuable for broader applications in electrochemical energy storage systems.