Zinc-based energy storage has lately gained popularity due to natural abundance, operational safety, high energy density. Unfortunately, dendrite growth is a common and intractable issue faced in existing zinc-ion batteries to shorten cycle lifespan/stability. This review summarizes recent progress in assembly component (e. g., anode, electrolyte, separator) engineering for dendrite-free zinc-ion batteries. First, diversiform strategies of Zn surface modification and Zn host design are presented to shield the fundamental adverse effect aroused by uneven zinc deposition on the anode. Then, subtle deployments of electrolyte constituents are illustrated to optimize the Zn2+ solvation structure for ultimate dendrite control and Coulombic efficiency elevation in aqueous systems and beyond (e.g., eutectic electrolytes). Furthermore, rational manipulation of advanced separators and the upgrade of zinc metal-free Zn2+-storage devices are briefly discussed to explore the dendrite-free and high-level Zn2+-storage. Finally, challenges and perspectives are proposed to offer research inspirations toward safe, high-efficiency and long-lifespan zinc storage.

Dendrite-Free Engineering toward Efficient Zinc Storage: Recent Progress and Future Perspectives.

The reversibility and cyclability of aqueous zinc-ion batteries (ZIBs) are largely determined by the stabilization of the Zn anode. Therefore, a stable anode/electrolyte interface capable of inhibiting dendrites and side reactions is crucial for high-performing ZIBs. In this study, we investigated the adsorption of 1,4-dioxane (DX) to promote the exposure of Zn (002) facets and prevent dendrite growth. DX appears to reside at the interface and suppress the detrimental side reactions. ZIBs with the addition of DX demonstrated a long-term cycling stability of 1000 h in harsh conditions of 10 mA cm-2 with an ultrahigh cumulative plated capacity of 5 Ah cm-2 and shows a good reversibility with an average Coulombic efficiency of 99.7%. The Zn//NH4V4O10 full battery with DX achieves a high specific capacity (202 mAh g-1 at 5 A g-1) and capacity retention (90.6% after 5000 cycles), much better than that of ZIBs with the pristine ZnSO4 electrolyte. By selectively adjusting the Zn2+ deposition rate on the crystal facets with adsorbed molecules, this work provides a promising modulation strategy at the molecular level for high-performing Zn anodes and can potentially be applied to other metal anodes suffering from instability and irreversibility.

Addition of Dioxane in Electrolyte Promotes (002)-Textured Zinc Growth and Suppressed Side Reactions in Zinc-Ion Batteries.

Dual-atom catalysts (DACs) have emerged as efficient electrocatalysts for CO2 reduction owing to the synergistic effect between the binary metal sites. However, rationally modulating the electronic structure of DACs to optimize the catalytic performance remains a great challenge. Herein, we report the electronic structure modulation of three Ni2 DACs (namely, Ni2-N7, Ni2-N5C2 and Ni2-N3C4) by the regulation of the coordination environments around the dual-atom Ni2 centres. As a result, Ni2-N3C4 exhibits significantly improved electrocatalytic activity for CO2 reduction, not only better than the corresponding single-atom Ni catalyst (Ni-N2C2), but also higher than Ni2-N7 and Ni2-N5C2 DACs. Density functional theory (DFT) calculations revealed that the high electrocatalytic activity of Ni2-N3C4 for CO2 reduction could be attributed to the electronic structure modulation to the Ni centre and the resulted proper binding energies to COOH* and CO* intermediates.

Modulating the Electronic Structures of Dual-Atom Catalysts via Coordination Environment Engineering for Boosting CO2 Electroreduction.

The most commonly used zinc foil anode for aqueous zinc‐ion batteries suffers from poor cycle stability and low zinc utilization. Zinc‐plated anodes on the host materials with high zincophilicity and stability are receiving increasing attention to alleviate these above issues. Here, the high zinc deposition activity of Cu (2 2 0) is confirmed through experimental observations and theoretical calculations and then Cu (2 2 0) substrates are prepared with the highly preferred orientation through an industrial electrolysis strategy. The prepared Cu (2 2 0) substrate can consistently modulate dense zinc growth by inducing the Zn (0 0 1) growth with the lowest surface energy and exposing high‐index zinc facets due to its exceptional grain size, high deposition activity, and homogeneous crystal orientation, which result in the high zinc plating/stripping reversibility of this Cu (2 2 0) substrate. When assembled into the Zn//MnO2 battery, the zinc‐plated Cu (2 2 0) can deliver capacity retention of 93.9% after 640 cycles at high zinc utilization (≈20%). This scalable orientation design strategy provides a new perspective for realizing dendrite‐free metal deposition with special textures.

High‐Index Zinc Facet Exposure Induced by Preferentially Orientated Substrate for Dendrite‐Free Zinc Anode

Ultrathin separators are indispensable to high‐energy‐density zinc‐ion batteries (ZIBs), but their easy failure caused by zinc dendrites poses a great challenge. Herein, 23 µm‐thick functional ultrathin separators (FUSs), realizing superb electrochemical stability of zinc anodes and outstanding long‐term durability of ultrathin separators, are reported. In the FUSs, an ultrathin but mechanically strong nanoporous membrane substrate benefits fast and flux‐homogenized Zn2+ transport, while a metal–organic framework (MOF)‐derived C/Cu nanocomposite decoration layer provides rich low‐barrier zinc nucleation sites, thereby synergistically stabilizing zinc anodes to inhibit zinc dendrites and dendrite‐caused separator failure. Investigation of the zinc affinity of the MOF‐derived C/Cu nanocomposites unravels the high zincophilicity of heteroatom‐containing C/Cu interfaces. Zinc anodes coupled with the FUSs present superior electrochemical stability, whose operation lifetime exceeds 2000 h at 1 mA cm−2 and 600 h at 10 mA cm−2, 40–50 times longer than that of the zinc anodes using glass‐fiber separators. The reliability of the FUSs in ZIBs and zinc‐ion hybrid supercapacitors is also validated. This work proposes a new strategy to stabilize zinc anodes and provides theoretical guidance in developing ultrathin separators for high‐energy‐density zinc‐based energy storage.

Functional Ultrathin Separators Proactively Stabilizing Zinc Anodes for Zinc‐Based Energy Storage

Resource‐abundant metal (e.g., zinc) batteries feature intrinsic advantages of safety and sustainability. Their practical feasibility, however, is impeded by the poor reversibility of metal anodes, typically caused by the uncontrollable dendrite enlargement. Significant effort is exerted to completely prevent dendrites from forming, but this seems less effective at high current densities. Herein, this work presents an alternative dendrite regulation strategy of forming tiny, homogeneously distributed, and identical zinc dendrites by facet matching, which effectively avoids undesirable dendrite enlargement. Confirmed by multiscale theoretical screening and characterization, the regularly exposed Cu(111) facets at the ridges of a copper nanowire are capable of such dendrite regulation by forming a low‐mismatched Zn(002)/Cu(111) interface. Consequently, reversible zinc electroplating/stripping is achieved at an unprecedentedly high rate of 100 mA cm−2 for over 30 000 cycles, corresponding to an accumulative areal capacity up to 30 Ah cm−2. A full cell using this anode shows a high capacity of 308.3 mAh g−1 and a high capacity retention of 91.4% after 800 cycles. This strategy is also viable for magnesium and aluminum anodes, thus opening up a promising and universal avenue toward long‐life and high‐rate metal anodes.

An Ultrahigh Rate and Stable Zinc Anode by Facet‐Matching‐Induced Dendrite Regulation

Encapsulating metal‐based catalysts inside carbon sheaths is a frequently‐adopted strategy to enhance their durability under various harsh situations and improve their catalytic activity simultaneously. Such carbon encapsulation, however, imposes significant complications for directly modifying materials’ surface atomic/electronic configurations, fundamentally impeding the accurate tuning of their catalytic capabilities. Herein, a universal single‐atom alloy (SAA) strategy is reported to indirectly yet precisely manipulate the surface electronic structure of carbon‐encapsulated electrocatalysts. By versatilely constructing a SAA core inside an N‐doped carbon sheath, material's electrocatalytic capability can be flexibly tuned. The one with Ru‐SAA cores serves as an excellent bifunctional electrocatalyst for oxygen/hydrogen evolution, exhibiting minimal cell voltage of 1.55 V (10 mA cm−2) and outstanding mass activity of 1251 mA m gRu−1${\rm{g}}_{{\rm{Ru}}}^{ - 1}$ for overall water splitting, while the one with Ir‐SAA cores possesses superior oxygen reduction activity with a half‐wave potential of 919 mV. Density functional theory calculations reveal that the doped atoms can simultaneously optimize the adsorption of protons (H*) and oxygenated intermediates (OH*, O*, and OOH*) to achieve the remarkable thermoneutral hydrogen evolution and enhanced oxygen evolution. This work thus demonstrates a versatile strategy to precisely modify the surface electronic properties of carbon‐shielded materials for optimized performances.

Carbon‐Shielded Single‐Atom Alloy Material Family for Multi‐Functional Electrocatalysis

Abstract Electrocatalytic production of hydrogen peroxide (H 2 O 2 ) via the 2e − transfer route of the oxygen reduction reaction (ORR) offers a promising alternative to the energy-intensive anthraquinone process, which dominates current industrial-scale production of H 2 O 2 . The availability of cost-effective electrocatalysts exhibiting high activity, selectivity, and stability is imperative for the practical deployment of this process. Single-atom catalysts (SACs) featuring the characteristics of both homogeneous and heterogeneous catalysts are particularly well suited for H 2 O 2 synthesis and thus, have been intensively investigated in the last few years. Herein, we present an in-depth review of the current trends for designing SACs for H 2 O 2 production via the 2e − ORR route. We start from the electronic and geometric structures of SACs. Then, strategies for regulating these isolated metal sites and their coordination environments are presented in detail, since these fundamentally determine electrocatalytic performance. Subsequently, correlations between electronic structures and electrocatalytic performance of the materials are discussed. Furthermore, the factors that potentially impact the performance of SACs in H 2 O 2 production are summarized. Finally, the challenges and opportunities for rational design of more targeted H 2 O 2 -producing SACs are highlighted. We hope this review will present the latest developments in this area and shed light on the design of advanced materials for electrochemical energy conversion. Graphical abstract 

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Electrocatalytic Oxygen Reduction to Produce Hydrogen Peroxide: Rational Design from Single-Atom Catalysts to Devices

Electrocatalytic nitrogen reduction reaction (eNRR) is a sustainable alternative to the traditional Haber–Bosch process due to its eco‐friendly nature and capability of utilizing renewable energy. However, its low Faradic efficiency (FE), caused by the excessive adsorption and reduction of protons, has been regarded as the main challenge, which leads to low ammonia yield as well. Herein, a carbon‐supported iron electrocatalyst is reported, which is fabricated by low‐temperature (300 °C) potassium vapor reduction of FeF3‐intercalated graphite fluoride, for efficient electrochemical nitrogen reduction. The strategy enables the unique formation of exposed Fe nanoparticles uniformly anchored on graphene and in situ doped with fluorine heteroatoms. These specific features can alter the electronic configuration of the Fe nanoparticles, leading to strong surface polarization that boosts nitrogen absorption capability for eNRR, resulting in high FE (41.6%) and ammonia yield rate (53.3 μg h‐1 mg‐1) simultaneously. First‐principle calculation attributes this enhanced eNRR capability to more empty orbitals carried by the Fe atoms through the electron transfer with F dopant and substrate. As a versatile strategy for synthesizing various ultrafine and highly dispersed metal nanoparticles on the carbon support, this work might shed light on rational designing essential electrocatalysts with effective electronic structure manipulation.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/adfm.202111733

Feng Hou

Papers

An Ultrahigh Rate and Stable Zinc Anode by Facet‐Matching‐Induced Dendrite Regulation

Carbon‐Shielded Single‐Atom Alloy Material Family for Multi‐Functional Electrocatalysis

Electrocatalytic Oxygen Reduction to Produce Hydrogen Peroxide: Rational Design from Single-Atom Catalysts to Devices

Regulating the Electronic Configuration of Supported Iron Nanoparticles for Electrochemical Catalytic Nitrogen Fixation

Photoelectrochemical nitrogen reduction: A step toward achieving sustainable ammonia synthesis