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Sodium-ion storage technologies are promising candidates for large-scale grid systems due to the abundance and low cost of sodium. However, compared to well-understood lithium-ion storage mechanisms, sodium-ion storage remains relatively unexplored. Herein, we systematically determine the sodium-ion storage properties of anatase titanium dioxide (TiO2(A)). During the initial sodiation process, a thin surface layer (~3 to 5 nm) of crystalline TiO2(A) becomes amorphous but still undergoes Ti4+/Ti3+ redox reactions. A model explaining the role of the amorphous layer and the dependence of the specific capacity on the size of TiO2(A) nanoparticles is proposed. Amorphous nanoparticles of ~10 nm seem to be optimum in terms of achieving high specific capacity, on the order of 200 mAh g-1, at high charge/discharge rates. Kinetic studies of TiO2(A) nanoparticles indicate that sodium-ion storage is due to a surface-redox mechanism that is not dependent on nanoparticle size in contrast to the lithiation of TiO2(A) which is a diffusion-limited intercalation process. The surface-redox properties of TiO2(A) result in excellent rate capability, cycling stability and low overpotentials. Moreover, tailoring the surface-redox mechanism enables thick electrodes of TiO2(A) to retain high rate properties, and represents a promising direction for high-power sodium-ion storage.

Electrolyte regulation in Zn‐based aqueous batteries (ZABs) has been extensively reported, and a broad range of strategies has been proposed. However, there is currently a lack of systematic summaries and a comprehensive understanding of the impact of hydrogen bond (H‐bond) networks on electrolyte performance. This work presents the electrolyte structure model, encompassing solvation structure, electrolyte/Zn anode interface, and H‐bond network. Through emphasizing and summarizing the reconstruction, strengthening, and breaking of the H‐bond network within the electrolyte structure, various specific regulation strategies are identified, such as high Gutmann donor number solvent, organic co‐solvent, molecular crowding additives, structure‐breaking ions, and solid‐state design. A critical appraisal is then provided on the key performance metrics influenced by these regulation methods, including Coulomb efficiency, voltage hysteresis, freezing point, and lifespan. This work is expected to illustrate electrolyte structure design to improve the comprehensive performance of ZABs. Last, a data‐driven summary and outlook on hydrogen bond network regulation in electrolyte structure is provided, to objectively evaluate the overall performances of ZABs. [ABSTRACT FROM AUTHOR]

The virtues of electrolytic MnO2 aqueous batteries are high theoretical energy density, affordability and safety. However, the continuous dead MnO2 and unstable Mn2+/MnO2 electrolysis pose challenges to the practical output energy and lifespan. Herein, we demonstrate bifunctional cationic redox mediation and catalysis kinetics metrics to rescue dead MnO2 and construct a stable and fast electrolytic Zn–Mn redox-flow battery (eZMRFB). Spectroscopic characterizations and electrochemical evaluation reveal the superior mediation kinetics of a cationic Fe2+ redox mediator compared with the anionic ones (e.g. I– and Br–), thus eliminating dead MnO2 effectively. With intensified oxygen vacancies, density functional theory simulations of the reaction pathways further verify the concomitant Fe-catalysed Mn2+/MnO2 electrolysis kinetics via charge delocalization and activated O 2p electron states, boosting its rate capability. As a result, the elaborated eZMRFB achieves a coulombic efficiency of nearly 100%, ultra-high areal capacity of 80 mAh cm–2, rate capability of 20 C and a long lifespan of 2500 cycles. This work may advance high-energy aqueous batteries to next-generation scalable energy storage. [ABSTRACT FROM AUTHOR]

Electrochromic (EC) devices represent an emerging energy-saving technology, exhibiting the capability to dynamically modulate light and heat transmittance. Despite their promising potential, the commercialization of EC devices faces substantial impediments such as high cost, intricate fabrication process, and low optical contrast inherent in conventional EC materials relying on the ion insertion/extraction mechanism. In this study, we introduce an innovative "electrode-free" electrochromic (EC) device, termed the EECD, which lacks an EC-layer on the electrodes during device assembling and in the bleached state. This device features a simplified fabrication process and delivers superior optical modulation. It achieves a high optical contrast ranging from 68-85% across the visible spectrum and boasts a rapid response time, reaching 90% coloring in just 17 seconds. In addition, EECD exhibits stable cycling for over 10,000 cycles without noticeable degradation and maintains functionality across a broad temperature range (0 °C to 50 °C). Furthermore, the fabricated large-area devices (40 cm × 40 cm) demonstrate excellent tinting uniformity, suggesting excellent scalability of this approach. Our study establishes a paradigmatic breakthrough for EC smart windows. Cheng Yang and co-workers develop an "electrode-free" electrochromic window, featuring a simplified fabrication process and delivering superior optical modulation capability. [ABSTRACT FROM AUTHOR]

Aqueous Zn–CO2 batteries can not only convert CO2 into high‐value chemicals but also store/output electric energy for external use. However, their performance is limited by sluggish and complicated CO2 electroreduction at the cathode. Herein, a dual‐anion regulated Bi electrocatalyst is developed to selectively reduce CO2 to formate with a Faradaic efficiency of up to 97% at a large current density of 250 mA cm−2. With O and/or F, the rate‐determine step of CO2 electroreduction has been manipulated (from the first hydrogenation to *HCOOH desorption step) with a reduced energy barrier. Significantly, the fabricated Zn–CO2 battery exhibits a high discharge voltage of 1.2 V, optimal power density of 4.51 mW cm−2, remarkable energy density of 802 Wh kg−1, and energy‐conversion efficiency of 70.74%, stability up to 200 cycles and 68 h. This study provides possible strategies to fabricate reversible and energetic aqueous Zn–CO2 batteries by addressing cathodic problems. [ABSTRACT FROM AUTHOR]

Rechargeable Zn‐air batteries (ZAB) represent a promising avenue for sustainable energy storage, boasting high energy density, cost‐effectiveness, scalability, and environmental friendliness. However, the sluggish redox kinetics and limited cycle life of bifunctional oxygen evolution/reduction (OER/ORR) electrocatalysts impede the further practical development of ZABs. In this study, homogenic boundary effect within α/β‐NiMoO4 is introduced as a superior electrocatalyst for ZAB. Through in situ poikilothermic X‐ray diffraction, X‐ray absorption spectroscopy, and theoretical investigations, the active Ni atoms exhibit more effective electron transfer at α/β‐NiMoO4 due to the homogenic boundary effect is unveiled. Furthermore, the presence of oxygen vacancies and lattice distortions at these boundaries significantly reduces the thermodynamic barrier of OER to a mere 0.46 V. Consequently, α/β‐NiMoO4 demonstrates a remarkably low overpotential of 270 mV at 10 mA cm−2 for the bottlenecked OER, along with prolonged durability (150 h) and a high specific capacity (745 mAh g−1 at 5 mA cm−2) for ZAB. This study underscores the efficacy of homogenic boundary effects in enhancing electrocatalytic activities, offering great promise for the advancement of sustainable energy systems. [ABSTRACT FROM AUTHOR]

Zinc‐based aqueous batteries (ZABs) are attracting extensive attention due to the low cost, high capacity, and environmental benignity of the zinc anode. However, their application is still hindered by the undesired zinc dendrites. Despite Zn‐surface modification being promising in relieving dendrites, a thick separator (i.e. glass fiber, 250–700 μm) is still required to resist the dendrite puncture, which limits volumetric energy density of battery. Here, we pivot from the traditional interphase plus extra separator categories, proposing an all‐in‐one ligand buffer layer (ca. 20 μm) to effectively modulate the Zn2+ transfer and deposition behaviors proved by in situ electrochemical digital holography. Experimental characterizations and density functional theory simulations further reveal that the catechol groups in the buffer layer can accelerate the Zn2+ reduction reaction (ZRR) through the electron‐donating p‐π conjugation effect, decreasing the negative charge in the coordination environment. Without extra separators, the elaborated system endows low polarization below 28.2 mV, long lifespan of 4950 h at 5 mA cm−2 in symmetric batteries, and an unprecedented volumetric energy density of 99.2 Wh L−1 based on the whole pouch cells. The concomitantly "separator‐free" and "dendrite‐free" conjugation effect with an accelerated ZRR process could foster the progression of metallic anodes and benefit energetic aqueous batteries. [ABSTRACT FROM AUTHOR]

Zinc ion batteries (ZIBs) exhibit significant promise in the next generation of grid‐scale energy storage systems owing to their safety, relatively high volumetric energy density, and low production cost. Despite substantial advancements in ZIBs, a comprehensive evaluation of critical parameters impacting their practical energy density (Epractical) and calendar life is lacking. Hence, we suggest using formulation‐based study as a scientific tool to accurately calculate the cell‐level energy density and predict the cycling life of ZIBs. By combining all key battery parameters, such as the capacity ratio of negative to positive electrode (N/P), into one formula, we assess their impact on Epractical. When all parameters are optimized, we urge to achieve the theoretical capacity for a high Epractical. Furthermore, we propose a formulation that correlates the N/P and Coulombic efficiency of ZIBs for predicting their calendar life. Finally, we offer a comprehensive overview of current advancements in ZIBs, covering cathode and anode, along with practical evaluations. This Minireview outlines specific goals, suggests future research directions, and sketches prospects for designing efficient and high‐performing ZIBs. It aims at bridging the gap from academia to industry for grid‐scale energy storage. [ABSTRACT FROM AUTHOR]