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Abstract Aqueous trivalent metal batteries represent a compelling candidate for energy storage due to the intriguing three‐electron transfer reaction and the distinct properties of trivalent cations. However, little research progress has been achieved with trivalent batteries due to the inappropriate redox potentials and drastic ion hydrolysis side reactions. Herein, the appealing yet underrepresented trivalent indium is selected as an advanced metal choice and the crucial effect of substrate on its plating mechanism is revealed. When copper foil is used, an indiophilic indium‐copper alloy interface can be formed in situ upon plating, exhibiting favorable binding energies and low diffusion energy barriers for indium atoms. Consequently, a planar, smooth, and dense indium metal layer is uniformly deposited on the copper substrate, leading to outstanding plating efficiency (99.8–99.9%) and an exceedingly long lifespan (6.4–7.4 months). The plated indium anode is further paired with a high‐mass‐loading Prussian blue cathode (2 mAh cm⁻²), and the full cell (negative/positive electrode capacity, N/P = 2.5) delivers an excellent cycling life of 1000 cycles with 72% retention. This work represents a significant advancement in the development of high‐performance trivalent metal batteries. 

Aqueous sodium-ion batteries (ASIBs) represent a promising battery technology for stationary energy storage, due to their attractive merits of low cost, high abundance, and inherent safety. Recently, a variety of advanced cathode, anode, and electrolyte materials have been developed for ASIBs, which not only enhance our fundamental understanding of the Na insertion mechanism, but also facilitate the research and development of practical ASIB systems. Among these electrode materials, iron-based materials are of particular importance because of the high abundance, low price, and low toxicity of Fe elements. However, to our knowledge, there are no review papers that specifically discuss the properties of Fe-based materials for ASIBs yet. In this review, we present the recent research progress on Fe-based cathode/anode materials, which include polyanionic compounds, Prussian blue, oxides, carbides, and selenides. We also discuss the research efforts to build Fe-based ASIB full cells. Lastly, we share our perspectives on the key challenges that need to be addressed and suggest alternative directions for aqueous Na-ion batteries. We hope this review paper can promote more research efforts on the development of low-cost and low-toxicity materials for aqueous battery applications. 

Abstract High‐voltage lithium metal batteries with nickel‐rich oxide cathodes (LiNi_0.8Co_0.1Mn_0.1O₂, NCM811) represent one of the most promising approaches to achieve high energy density up to 500 Wh kg⁻¹. However, severe interfacial side reactions occur at both NCM811 cathode and lithium anode at ultrahigh voltages (>4.6 V). To address these issues, various electrolytes have been developed, but they still suffer from electrolyte decomposition, leading to moderate voltages and insufficient cycling. Herein, we introduce (3,3,3‐trifluoropropyl)trimethoxy silane (TTMS) as an asymmetrically fluorinated single solvent, which incorporates both strongly solvating (─OCH₃) and weakly solvating (─CF₃) groups. The designed 2.1 mol L⁻¹(M) LiFSI/TTMS electrolyte achieves excellent compatibility with both NCM811 cathode and Li metal anode due to its unique anion‐dominating solvation structures and inorganic‐rich interphase formation. Consequently, it enables stable cycling in the Li||NCM811 battery at an ultrahigh voltage of 4.8 V, with 84.5% capacity retention after 300 cycles. Even under more aggressive conditions, including high temperature (60 °C) and anode‐less configuration (N/P ratio = 1.76), the Li||NCM811 battery exhibits remarkable capacity retention (>80%) over 300 cycles. This work underscores the effectiveness of electrolyte engineering for developing ultrahigh‐voltage and long‐cycling battery systems. 

Abstract Solid‐state batteries (SSBs) are competitive contenders for energy storage due to their inherent safety and high energy. However, the lack of an appropriate anode has hindered their development. Graphite and lithium metal are widely used anode materials, but graphite suffers from a low capacity, whereas lithium metal presents severe dendrite and reactivity challenges. Herein, the promising performance of micro‐sized alloys is demonstrated as high‐capacity and long‐cycling anodes for SSBs. Using antimony as a model anode, its full theoretical capacity (660 mAh g⁻¹), high‐rate capability (3 A g⁻¹), and long cycling life (1000–2000 cycles) is achieved at room temperature. Comparative studies further reveal an overlooked “micro‐size effect”, where micro‐sized alloys establish more efficient electron/ion conduction pathways, significantly exceeding their nano‐sized counterparts. This micro‐size effect challenges the conventional belief that nano‐sized alloys always outperform micro‐sized ones. Based on this discovery, similarly high performance of other micro‐alloys (lead and bismuth) in SSBs is further demonstrated. Given the additional benefits of easy synthesis, low cost, high tap density, and high stability, micro‐sized alloys hold great promise as excellent anode candidates for SSBs. 

Abstract Iron ion batteries using Fe²⁺as a charge carrier have yet to be widely explored, and they lack high‐performing Fe²⁺hosting cathode materials to couple with the iron metal anode. Here, it is demonstrated that VOPO₄∙2H₂O can reversibly host Fe²⁺with a high specific capacity of 100 mAh g⁻¹and stable cycling performance, where 68% of the initial capacity is retained over 800 cycles. In sharp contrast, VOPO₄∙2H₂O's capacity of hosting Zn²⁺fades precipitously over tens of cycles. VOPO₄∙2H₂O stores Fe²⁺with a unique mechanism, where upon contacting the electrolyte by the VOPO₄∙2H₂O electrode, Fe²⁺ions from the electrolyte get oxidized to Fe³⁺ions that are inserted and trapped in the VOPO₄∙2H₂O structure in an electroless redox reaction. The trapped Fe³⁺ions, thus, bolt the layered structure of VOPO₄∙2H₂O, which prevents it from dissolution into the electrolyte during (de)insertion of Fe²⁺. The findings offer a new strategy to use a redox‐active ion charge carrier to stabilize the layered electrode materials. 

Abstract A non‐aqueous proton electrolyte is devised by dissolving H₃PO₄into acetonitrile. The electrolyte exhibits unique vibrational signatures from stimulated Raman spectroscopy. Such an electrolyte exhibits unique characteristics compared to aqueous acidic electrolytes: 1) higher (de)protonation potential for a lower desolvation energy of protons, 2) better cycling stability by dissolution suppression, and 3) higher Coulombic efficiency owing to the lack of oxygen evolution reaction. Two non‐aqueous proton full cells exhibit better cycling stability, higher Coulombic efficiency, and less self‐discharge compared to the aqueous counterpart.