Kwun Nam Hui

Aqueous zinc‐sulfur batteries combine sulfur's high theoretical specific capacity with the safety, resource abundance and manufacturing compatibility of aqueous zinc chemistry. However, their progression from high‐capacity concepts to practical devices is hindered by the poor electronic conductivity of sulfur and zinc sulfide, sluggish solid‐state conversion kinetics, large volume changes, water‐induced parasitic reactions, redox‐mediator failure and unstable zinc deposition. Because these processes interact across cell components, optimizing the cathode, electrolyte, separator, or anode in isolation often fails to achieve the ultimate goal of improving device performance. This Review presents a reaction‐to‐device framework for understanding recent advances in aqueous zinc‐sulfur batteries. Cathode hosts and catalysts are evaluated according to their ability to integrate electronic conduction, species confinement, catalytic conversion and mechanical buffering; redox mediators and electrolyte formulations according to their control over conversion pathways, solvation structures, water activity and interfacial chemistry; and selective membranes and zinc‐protective interfaces according to their regulation of ion transport and electrode compatibility. Flexible, stretchable, planar and pouch‐cell configurations are further examined as tests of system‐level integration. This reaction‐to‐device perspective establishes design and benchmarking principles for advancing zinc‐sulfur batteries toward safe, economical and scalable energy‐storage technologies.

Seawater zinc‐sulfur (Zn‐S) batteries could support marine energy systems, but their development is hindered by sluggish sulfur redox kinetics, chloride‐induced Zn corrosion, and poorly understood biological risks from electrolyte additives. Here, 4‐formylphenyl β‐D‐allopyranoside, a saccharide‐derived glycoside, is introduced as a biologically compatible electrolyte regulator for rechargeable seawater Zn–S batteries. The glycoside promotes reversible sulfur‐ZnS conversion and suppresses hydrogen evolution, corrosion, and dendritic Zn deposition. This dual regulation enables an energy density of approximately 542 Wh/kg _sulfur and stable cycling over 6000 cycles, while supporting flexible pouch cells under mechanical deformation and low‐temperature conditions. Zebrafish embryo, rat implantation, and human keratinocyte assays indicate that the glycoside‐regulated electrolyte is less toxic than electrolytes containing conventional organic additives. By integrating molecular interfacial regulation with biosafety assessment, this work establishes a design strategy for durable and environmentally compatible seawater batteries, with potential applications in marine renewable‐energy storage, distributed monitoring, and wearable technologies for ocean deployment.

Seawater zinc‐sulfur (Zn‐S) batteries could support marine energy systems, but their development is hindered by sluggish sulfur redox kinetics, chloride‐induced Zn corrosion, and poorly understood biological risks from electrolyte additives. Here, 4‐formylphenyl β‐D‐allopyranoside, a saccharide‐derived glycoside, is introduced as a biologically compatible electrolyte regulator for rechargeable seawater Zn–S batteries. The glycoside promotes reversible sulfur‐ZnS conversion and suppresses hydrogen evolution, corrosion, and dendritic Zn deposition. This dual regulation enables an energy density of approximately 542 Wh/kg _sulfur and stable cycling over 6000 cycles, while supporting flexible pouch cells under mechanical deformation and low‐temperature conditions. Zebrafish embryo, rat implantation, and human keratinocyte assays indicate that the glycoside‐regulated electrolyte is less toxic than electrolytes containing conventional organic additives. By integrating molecular interfacial regulation with biosafety assessment, this work establishes a design strategy for durable and environmentally compatible seawater batteries, with potential applications in marine renewable‐energy storage, distributed monitoring, and wearable technologies for ocean deployment.

P2‐type layered transition metal (TM) oxides have emerged as promising cathode candidates for sodium‐ion batteries (SIBs) owing to their intrinsic air stability and open prismatic diffusion pathways. However, at moderate (de)sodiation, severe structural breakdown and performance failure associated with the intra‐particle anisotropic lattice strain and stress are habitually neglected. In this study, we reveal the intrinsic correlation between strain evolution and capacity diving in P2−type layered cathodes, where strain expansion, rather than conventional phase transitions or oxygen loss, is identified as the center of cathodic degradation. Upon the build‐up of lattice strain beyond a structural threshold during cycling, lattice fracture and amorphization are triggered to block the reversible Na‐ion transport, as confirmed by ex situ XAS, EBSD analysis, and intuitive structural observations. By integrating highly matched conformal octahedra into the host lattice as a structural ‘buffer’, the pernicious strain expansion is significantly mitigated by nearly 30% per cycle relative to the bare counterpart, as evidenced by in situ XRD and mechanical simulations. The resulting cathode exhibits exceptional cycling durability with improved 81.0% capacity retention over 1000 cycles at 3 C. These findings highlight the mechanistic role of strain expansion on cathode degradation and rationalize the design of long‐lived layered oxide cathodes.

P2‐type layered transition metal (TM) oxides have emerged as promising cathode candidates for sodium‐ion batteries (SIBs) owing to their intrinsic air stability and open prismatic diffusion pathways. However, at moderate (de)sodiation, severe structural breakdown and performance failure associated with the intra‐particle anisotropic lattice strain and stress are habitually neglected. In this study, we reveal the intrinsic correlation between strain evolution and capacity diving in P2−type layered cathodes, where strain expansion, rather than conventional phase transitions or oxygen loss, is identified as the center of cathodic degradation. Upon the build‐up of lattice strain beyond a structural threshold during cycling, lattice fracture and amorphization are triggered to block the reversible Na‐ion transport, as confirmed by ex situ XAS, EBSD analysis, and intuitive structural observations. By integrating highly matched conformal octahedra into the host lattice as a structural ‘buffer’, the pernicious strain expansion is significantly mitigated by nearly 30% per cycle relative to the bare counterpart, as evidenced by in situ XRD and mechanical simulations. The resulting cathode exhibits exceptional cycling durability with improved 81.0% capacity retention over 1000 cycles at 3 C. These findings highlight the mechanistic role of strain expansion on cathode degradation and rationalize the design of long‐lived layered oxide cathodes.

The direct recycling of spent LiFePO ₄ is essential for building a sustainable circular economy for lithium‐ion batteries, yet conventional methods suffer from high energy consumption and environmental pollution. Here, we develop a continuous redox flow battery using regenerable ascorbic acid as a redox mediator for efficient ambient‐temperature relithiation. The electrochemical regeneration of ascorbic acid enables a near‐closed‐loop process with minimal reagent consumption. The regenerated LiFePO ₄ achieves a specific capacity of 123.6 mAh/g at 0.5 C, comparable to spent LiFePO ₄ , and achieve a capacity restoration efficiency of 44.3%. Structural and elemental analyses confirm successful restoration of the crystal lattice and lithium content. This work provides a green, economical, and scalable strategy for direct recycling of spent LiFePO ₄ , demonstrating strong potential for industrial‐scale battery reclamation.

Achieving high‐safety, high‐voltage, and long‐life lithium metal batteries (LMBs) requires electrolytes capable of simultaneously stabilizing lithium (Li) metal and withstanding severe oxidative environments. Here we report an anion‐regulated electrolyte constructed by co‐optimizing lithium difluoro(oxalato)borate (LiDFOB) and lithium nitrate (LiNO ₃ ) in nonflammable triethyl phosphate. Combined theoretical simulations and experimental investigations reveal that the DFOB ⁻ /NO ₃ ⁻ dual‐anion synergy reconstructs the Li ⁺ solvation sheath from solvent‐dominated, solvent‐separated ion pairs into anion‐rich structure dominated by contact ion pairs and small‐sized aggregated clusters. This solvation transformation weakens Li ⁺ ‐solvent interactions, facilitates rapid desolvation, and induces preferential anion redox, thereby forming uniform lithium fluoride, lithium nitride, and B–O/F‐rich solid‐electrolyte interphases at both the anode and cathode. These robust, anions‐derived, and inorganic‐rich electrode‐electrolyte interphases suppress dendrite initiation, mitigate parasitic reactions, stabilizing high‐voltage LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811) cathode and improve interfacial Li ⁺ transport and de‐solvation kinetics. Benefiting from this synergistic solvation and interphase co‐engineering, Li||NCM811 cells with anion‐regulated electrolyte deliver 226 mAh g ⁻¹ at 0.1 C, retain 136 mAh g ⁻¹ at 4 C, and maintain 152 mAh g ⁻¹ after 500 cycles (0.5 C discharge). This work establishes anion‐regulated solvation as a scalable route toward safe, high‐voltage, and long‐cycling LMBs.

Metal–organic frameworks (MOFs) constitute an exceptional class of porous crystalline materials, distinguished by their structural tunability, extensive surface areas, and multifunctional chemical attributes. Their intrinsic diversity and adaptability have positioned them at the forefront of numerous technological domains, including catalysis, gas sorption, and electrochemical energy storage. These applications are particularly significant in the context of wearable technologies, where mechanical flexibility, low weight, and high energy density are imperative. The inherent limitations of conventional energy-storage materials whether in geometric rigidity, insufficient energy density, or inadequate mechanical resilience underscore the pressing need to develop MOF architectures. This review synthesizes recent advancements in supercapacitors and battery systems, with a focus on the role of MOFs in enhancing device performance across key metrics such as energy density, charge–discharge kinetics, and operational long life. Owing to their thin-film compatibility and deformable profiles, these devices are poised for seamless integration into next-generation wearable platforms. MOFs, characterized by their dual functionality, mechanical compliance, and highly porous frameworks, exhibit significant promise in driving the evolution of wearable energy-storage technologies. Future progress will hinge on overcoming persistent challenges related to stability, scalability, and long-term performance. Continued advances in synthesis strategies, processing techniques, and fundamental understanding will be critical to unlocking the broader industrial potential of MOFs, spanning energy systems, pharmaceutical delivery, electronic devices, and environmental remediation. Ultimately, the incorporation of MOFs into wearable energy-storage systems may catalyze transformative developments in portable electronics, redefining both operational capabilities and user experience.