Chao Geng

Rechargeable seawater battery (RSWB) is a promising candidate for low‐cost energy storage while solar seawater desalination (SSD) can produce clean water from seawater, yet no attempts have been made to integrate them, preferably with a mutual enhancement effect. In this study, we report an ε‐MnO ₂ material with bifunctions of ion storage for RSWB and photothermal effect for SSD. The integration of RSWB and SSD leads to a mutual enhancement effect, in sharp contrast to traditional integrations. The ε‐MnO ₂ displays a high specific capacity of 265 mAh g ⁻¹ for RSWB. When coupled with SSD, the specific capacity obviously increases, and meanwhile the seawater evaporation rate also increases substantially during the charge/discharge process. The mutual enhancement effect is attributed to the temperature increase in cathode caused by the photothermal effect of ε‐MnO ₂ and the weakened hydrogen‐bonding interaction arising from the charge/discharge process. This work would provide new perspectives on energy storage and clean water production.

Rechargeable seawater batteries are emerging as sustainable electrochemical energy‐storage systems that directly exploit natural seawater as an abundant electrolyte and ion reservoir. Beyond conventional seawater‐activated primary batteries and half‐seawater rechargeable systems, fourth‐generation seawater batteries represent a distinct concept in which both electrodes operate directly in natural seawater without nonaqueous anolytes or NASICON‐type ceramic separators. This review clarifies the conceptual boundary between seawater‐based batteries, where seawater mainly serves as a solvent, catholyte, or supporting medium, and genuine rechargeable seawater batteries, where intrinsic seawater ions participate in charge storage and charge compensation. We discuss the fundamental electrochemistry of seawater electrolytes, including ion transport, oxygen/chlorine side reactions, and seawater–electrode interfacial chemistry. Recent advances in cathode materials, including cation‐intercalation hosts and oxygen electrocatalysts, are summarized together with emerging anode materials for single‐ion storage and multi‐ion costorage. Key challenges involving chloride‐induced corrosion, competitive ion storage, interfacial instability, and marine deployment are critically assessed. Future directions are proposed to guide the development of efficient, durable, and scalable rechargeable seawater batteries for marine energy storage.

Rechargeable aqueous zinc‐ion batteries have garnered considerable attention due to their intrinsic safety, high theoretical capacity, and low cost. However, problems such as zinc dendrite growth, hydrogen evolution reaction, and severe corrosion hinder their practical deployment. Herein, we fabricate a homogeneous high‐entropy oxide powder (Co _0.2 Cu _0.2 Mg _0.2 Ni _0.2 Zn _0.2 )O with a single‐phase rock‐salt structure, as a protective artificial interphase for the Zn anode. The multicomponent oxide layer enables selective Zn ²⁺ adsorption and enhanced ion migration uniformity. Furthermore, its intrinsic hydrophobicity and strong desolvation ability suppress parasitic side reactions, thereby facilitating uniform and reversible Zn plating/stripping. As a result, the modified Zn anode exhibits an ultralong cycling lifespan of 1800 h at 10 mA cm ⁻² in a 2 M ZnSO ₄ electrolyte, and retains 750 h of stable cycling even in a natural seawater‐based ZnSO ₄ system at 20 mA cm ⁻² . This approach is further validated with a compositional variation—(Co _0.2 Cu _0.2 Mn _0.2 Ni _0.2 Zn _0.2 )O—demonstrating robust cycling over 1300 h at 10 mA cm ⁻² . Furthermore, full cells assembled with an I ₂ cathode show enhanced electrochemical performance. These findings highlight the dual roles of high‐entropy materials in simultaneously accelerating the kinetics of Zn ²⁺ transport and homogenizing zinc deposition, offering a promising strategy for the stabilization of zinc metal anodes in aqueous batteries.

Aqueous ammonium‐ion battery has recently gained attention as a safe, high‐power, and cost‐effective energy storage device; yet the development in cathode materials that can simultaneously deliver high capacity, high potential, and stable cycling performance is limited. Herein, a Prussian blue analog with three redox‐active sites (Co, Mn, and Fe) as a high‐performance cathode material for aqueous ammonium‐ion batteries by a dual function doping strategy is reported. It achieves a high reversible capacity of 153 mAh g ⁻¹ and superior cycling stability over 2500 cycles with negligible capacity decay. Density functional theory calculations and electrochemical analysis reveal that Mn activates the redox activity of Co via the enhanced electron depletion, while Co effectively suppresses the Jahn–Teller effect through splitting the degenerate orbitals of Mn, preserving the long‐range structural integrity of the framework. Paring this cathode with the VO _x @polypyrrole anode, a high specific energy of 145.7 Wh kg ⁻¹ can be achieved at a high specific power of 810.9 W kg ⁻¹ . This work offers a viable design strategy for the optimization of electrode materials through unlocking multiple active sites and stabilizing lattice frameworks.