Electric Double Layer Regulator Design through a Functional Group Assembly Strategy towards Long-lasting Zinc Metal Batteries.

Regulating the electric double layer (EDL) structure of the zinc metal anode by using electrolyte additives is an efficient way to suppress interface side reactions and facilitate uniform zinc deposition. Nevertheless, there are no reports investigating the proactive design of EDL-regulating additives before the start of experiments. Herein, a functional group assembly strategy is proposed to design electrolyte additives for modulating the EDL, thereby realizing a long-lasting zinc metal anode. Specifically, by screening ten common functional groups, N, N-dimethyl-1H-imidazole-1-sulfonamide (IS) is designed by assembling an imidazole group, characterized by its high adsorption capability on the zinc anode, and a sulfone group, which exhibits strong binding with Zn2+ ions. Benefiting from the adsorption functionalization of the imidazole group, the IS molecules occupy the position of H2O in the inner Helmholtz layer of the EDL, forming a molecular protective layer to inhibit H2O-induced side reactions. Meanwhile, the sulfone group in IS, acting as a binding site to Zn2+, promotes the de-solvation of Zn2+ ions, facilitating compact zinc deposition. Consequently, the utilization of IS significantly extending the cycling stability of Zn||Zn and Zn||NaV3O8·1.5H2O full cell. This study offers an innovative approach to the design of EDL regulators for high-performance zinc metal batteries.

Understanding the charge transfer effects of single atoms for boosting the performance of Na-S batteries.

The effective flow of electrons through bulk electrodes is crucial for achieving high-performance batteries, although the poor conductivity of homocyclic sulfur molecules results in high barriers against the passage of electrons through electrode structures. This phenomenon causes incomplete reactions and the formation of metastable products. To enhance the performance of the electrode, it is important to place substitutable electrification units to accelerate the cleavage of sulfur molecules and increase the selectivity of stable products during charging and discharging. Herein, we develop a single-atom-charging strategy to address the electron transport issues in bulk sulfur electrodes. The establishment of the synergistic interaction between the adsorption model and electronic transfer helps us achieve a high level of selectivity towards the desirable short-chain sodium polysulfides during the practical battery test. These finding indicates that the atomic manganese sites have an enhanced ability to capture and donate electrons. Additionally, the charge transfer process facilitates the rearrangement of sodium ions, thereby accelerating the kinetics of the sodium ions through the electrostatic force. These combined effects improve pathway selectivity and conversion to stable products during the redox process, leading to superior electrochemical performance for room temperature sodium-sulfur batteries.

Routes to high-performance layered oxide cathodes for sodium-ion batteries.

Sodium-ion batteries (SIBs) are experiencing a large-scale renaissance to supplement or replace expensive lithium-ion batteries (LIBs) and low energy density lead-acid batteries in electrical energy storage systems and other applications. In this case, layered oxide materials have become one of the most popular cathode candidates for SIBs because of their low cost and comparatively facile synthesis method. However, the intrinsic shortcomings of layered oxide cathodes, which severely limit their commercialization process, urgently need to be addressed. In this review, inherent challenges associated with layered oxide cathodes for SIBs, such as their irreversible multiphase transition, poor air stability, and low energy density, are systematically summarized and discussed, together with strategies to overcome these dilemmas through bulk phase modulation, surface/interface modification, functional structure manipulation, and cationic and anionic redox optimization. Emphasis is placed on investigating variations in the chemical composition and structural configuration of layered oxide cathodes and how they affect the electrochemical behavior of the cathodes to illustrate how these issues can be addressed. The summary of failure mechanisms and corresponding modification strategies of layered oxide cathodes presented herein provides a valuable reference for scientific and practical issues related to the development of SIBs.

A Critical Review on Room-Temperature Sodium-Sulfur Batteries: From Research Advances to Practical Perspectives.

Room-temperature sodium-sulfur (RT-Na/S) batteries are promising alternatives for next-generation energy storage systems with high energy density and high power density. However, some notorious issues are hampering the practical application of RT-Na/S batteries. Besides, the working mechanism of RT-Na/S batteries under practical conditions such as high sulfur loading, lean electrolyte, and low capacity ratio between the negative and positive electrode (N/P ratio), is of essential importance for practical applications, yet the significance of these parameters has long been disregarded. Herein, it is comprehensively reviewed recent advances on Na metal anode, S cathode, electrolyte, and separator engineering for RT-Na/S batteries. The discrepancies between laboratory research and practical conditions are elaborately discussed, endeavors toward practical applications are highlighted, and suggestions for the practical values of the crucial parameters are rationally proposed. Furthermore, an empirical equation to estimate the actual energy density of RT-Na/S pouch cells under practical conditions is rationally proposed for the first time, making it possible to evaluate the gravimetric energy density of the cells under practical conditions. This review aims to reemphasize the vital importance of the crucial parameters for RT-Na/S batteries to bridge the gaps between laboratory research and practical applications.

Linearly Interlinked Fe-Nx -Fe Single Atoms Catalyze High-Rate Sodium-Sulfur Batteries.

Linearly interlinked single atoms offer unprecedented physiochemical properties, but their synthesis for practical applications still poses significant challenges. Herein, linearly interlinked iron single-atom catalysts that are loaded onto interconnected carbon channels as cathodic sulfur hosts for room-temperature sodium-sulfur batteries are presented. The interlinked iron single-atom exhibits unique metallic iron bonds that facilitate the transfer of electrons to the sulfur cathode, thereby accelerating the reaction kinetics. Additionally, the columnated and interlinked carbon channels ensure rapid Na+ diffusion kinetics to support high-rate battery reactions. By combining the iron atomic chains and the topological carbon channels, the resulting sulfur cathodes demonstrate effective high-rate conversion performance while maintaining excellent stability. Remarkably, even after 5000 cycles at a current density of 10 A g-1 , the Na-S battery retains a capacity of 325 mAh g-1 . This work can open a new avenue in the design of catalysts and carbon ionic channels, paving the way to achieve sustainable and high-performance energy devices.

Defect-Free Prussian Blue Analogue as Zero-Strain Cathode Material for High-Energy-Density Potassium-Ion Batteries.

Prussian blue analogues (PBAs) have been widely studied as cathodes for potassium-ion batteries (PIBs) due to their three-dimensional framework structure and easily adjustable composition. However, the phase transition behavior and [Fe(CN)6]4- anionic defects severely deteriorate electrochemical performances. Herein, we propose a defect-free potassium iron manganese hexacyanoferrate (K1.47Fe0.5Mn0.5[Fe(CN)6]·1.26H2O, KFMHCF-1/2) as the cathode material for PIBs. The Fe-Mn binary synergistic and defect-free effects can inhibit the cell volume change and octahedral slip during the K-ion insertion/extraction process, so that the phase transformation behavior (monoclinic ↔ cubic) is effectively inhibited, achieving a zero-strain solid solution mechanism employing Fe and Mn as dual active-sites. Thus, KFMHCF-1/2 contributes the highest initial capacity of 155.3 mAh·g-1 with an energy density of 599.5 Wh·kg-1 at 10 mA·g-1 among the reported PBA cathodes, superior rate capability, and cyclic stability over 450 cycles. The assembled K-ion full battery using K deposited on graphite (K@G) as anode also delivers high reversible specific capacity of 131.1 mAh·g-1 at 20 mA·g-1 and ultralong lifespans over 1000 cycles at 50 mA·g-1 with the lowest capacity decay rate of 0.044% per cycle. This work will promote the rapid application of high-energy-density PIBs.

Lithium-Ion Charged Polymer Channels Flattening Lithium Metal Anode.

The concentration difference in the near-surface region of lithium metal is the main cause of lithium dendrite growth. Resolving this issue will be key to achieving high-performance lithium metal batteries (LMBs). Herein, we construct a lithium nitrate (LiNO3)-implanted electroactive ß phase polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) crystalline polymorph layer (PHL). The electronegatively charged polymer chains attain lithium ions on the surface to form lithium-ion charged channels. These channels act as reservoirs to sustainably release Li ions to recompense the ionic flux of electrolytes, decreasing the growth of lithium dendrites. The stretched molecular channels can also accelerate the transport of Li ions. The combined effects enable a high Coulombic efficiency of 97.0% for 250 cycles in lithium (Li)||copper (Cu) cell and a stable symmetric plating/stripping behavior over 2000 h at 3 mA cm-2 with ultrahigh Li utilization of 50%. Furthermore, the full cell coupled with PHL-Cu@Li anode and LiFePO4 cathode exhibits long-term cycle stability with high-capacity retention of 95.9% after 900 cycles. Impressively, the full cell paired with LiNi0.87Co0.1Mn0.03O2 maintains a discharge capacity of 170.0 mAh g-1 with a capacity retention of 84.3% after 100 cycles even under harsh condition of ultralow N/P ratio of 0.83. This facile strategy will widen the potential application of LiNO3 in ester-based electrolyte for practical high-voltage LMBs.

Covalent Organic Frameworks: Their Composites and Derivatives for Rechargeable Metal-Ion Batteries.

Covalent organic frameworks (COFs) have attracted considerable interest in the field of rechargeable batteries owing to their three-dimensional (3D) varied pore sizes, inerratic porous structures, abundant redox-active sites, and customizable structure-adjustable frameworks. In the context of metal-ion batteries, these materials play a vital role in electrode materials, effectively addressing critical issues such as low ionic conductivity, limited specific capacity, and unstable structural integrity. However, the electrochemical characteristics of the developed COFs still fall short of practical battery requirements due to inherent issues such as low electronic conductivity, the tradeoff between capacity and redox potential, and unfavorable micromorphology. This review provides a comprehensive overview of the recent advancements in the application of COFs, COF-based composites, and their derivatives in rechargeable metal-ion batteries, including lithium-ion, lithium-sulfur, sodium-ion, sodium-sulfur, potassium-ion, zinc-ion, and other multivalent metal-ion batteries. The operational mechanisms of COFs, COF-based composites, and their derivatives in rechargeable batteries are elucidated, along with the strategies implemented to enhance the electrochemical properties and broaden the range of their applications.

Salt Anion Amphiphilicity-Activated Electrolyte Cosolvent Selection Strategy toward Durable Zn Metal Anode.

One effective solution to inhibit side reactions and Zn dendrite growth in aqueous Zn-ion batteries is to add a cosolvent into the Zn(CF3SO3)2 electrolyte, which has the potential to form a robust solid electrolyte interface composed of ZnF2 and ZnS. Nevertheless, there is still a lack of discussion on a convenient selection method for cosolvents, which can directly reflect the interactions between solvent and solute to rationally design the electrolyte solvation structure. Herein, logP, where P is the octanol-water partition coefficient, a general parameter to describe the hydrophilicity and lipophilicity of chemicals, is proposed as a standard for selecting cosolvents for Zn(CF3SO3)2 electrolyte, which is demonstrated by testing seven different types of solvents. The solvent with a logP value similar to that of the salt anion CF3SO3- can interact with CF3SO3-, Zn2+, and H2O, leading to a reconstruction of the electrolyte solvation structure. To prove the concept, methyl acetate (MA) is demonstrated as an example due to its similar logP value to that of CF3SO3-. Both the experimental and theoretical results illustrate that MA molecules not only enter into the solvation shell of CF3SO3- but also coordinate with Zn2+ or H2O, forming an MA and CF3SO3- involved core-shell solvation structure. The special solvation structure reduces H2O activity and contributes to forming an anion-induced ZnCO3-ZnF2-rich solid electrolyte interface. As a result, the Zn||Zn cell and Zn||NaV3O8·1.5H2O cell with MA-involved electrolyte exhibit superior performances to that with the MA-free electrolyte. This work provides an insight into electrolyte design via salt anion chemistry for high-performance Zn batteries.

Advanced Anode Materials for Rechargeable Sodium-Ion Batteries.

Rechargeable sodium-ion batteries (SIBs) have been considered as promising energy storage devices owing to the similar "rocking chair" working mechanism as lithium-ion batteries and abundant and low-cost sodium resource. However, the large ionic radius of the Na-ion (1.07 Å) brings a key scientific challenge, restricting the development of electrode materials for SIBs, and the infeasibility of graphite and silicon in reversible Na-ion storage further promotes the investigation of advanced anode materials. Currently, the key issues facing anode materials include sluggish electrochemical kinetics and a large volume expansion. Despite these challenges, substantial conceptual and experimental progress has been made in the past. Herein, we present a brief review of the recent development of intercalation, conversion, alloying, conversion-alloying, and organic anode materials for SIBs. Starting from the historical research progress of anode electrodes, the detailed Na-ion storage mechanism is analyzed. Various optimization strategies to improve the electrochemical properties of anodes are summarized, including phase state adjustment, defect introduction, molecular engineering, nanostructure design, composite construction, heterostructure synthesis, and heteroatom doping. Furthermore, the associated merits and drawbacks of each class of material are outlined, and the challenges and possible future directions for high-performance anode materials are discussed.

Electrolyte and Additive Engineering for Zn Anode Interfacial Regulation in Aqueous Zinc Batteries.

Aqueous Zn-metal batteries (AZMBs) have gained great interest due to their low cost, eco-friendliness, and inherent safety, which serve as a promising complement to the existing metal-based batteries, e.g., lithium-metal batteries and sodium-metal batteries. Although the utilization of aqueous electrolytes and Zn metal anode in AZMBs ensures their improved safety over other metal batteries meanwhile guaranteeing their decent energy density at the cell level, plenty of challenges involved with metallic Zn anode still await to be addressed, including dendrite growth, hydrogen evolution reaction, and zinc corrosion and passivation. In the past years, several attempts have been adopted to address these problems, among which engineering the aqueous electrolytes and additives is regarded as a facile and promising approach. In this review, a comprehensive summary of aqueous electrolytes and electrolyte additives will be given based on the recent literature, aiming at providing a fundamental understanding of the challenges associated with the metallic Zn anode in aqueous electrolytes, meanwhile offering a guideline for the electrolytes and additives engineering strategies toward stable AZMBs in the future.

A Dual Organic Solvent Zn-Ion Electrolyte Enables Highly Stable Zn Metal Batteries.

Aqueous zinc (Zn) batteries have been regarded as an alternative to lithium-ion batteries due to their high abundance, low cost, and higher intrinsic safety. However, the low Zn plating/stripping reversibility, Zn dendrite growth, and continuous water consumption have hindered the practical application of aqueous Zn anodes. Herein, a hydrous organic Zn-ion electrolyte based on a dual organic solvent, namely hydrated Zn(BF4)2 zinc salt dissolved in dimethyl carbonate (DMC) and vinyl carbonate (EC) solvents [denoted as Zn(BF4)2/DMC/EC], can address these problems, which not only inhibits the side reactions but also promotes uniform Zn plating/stripping through the formation of a stable solid state interface layer and Zn2+-EC/2DMC pairs. This electrolyte enables the Zn electrode to stably undergo >700 cycles at a rate of 1 mA cm-2 with a Coulombic efficiency of 99.71%. Moreover, the full cell paired with V2O5 also demonstrates excellent cycling stability without capacity decay at 1 A g-1 after 1600 cycles.

A quasi-solid polymer electrolyte initiated by two-dimensional functional nanosheets for stable lithium metal batteries.

Lithium-metal batteries (LMBs) are expected to serve as next-generation energy storage systems due to their high theoretical energy density. However, their practical application is largely impeded due to the safety risks that arise from the uncontrollable Li dendrite growth and the high reactivity between high flammability liquid organic electrolytes and metallic lithium. Here, we report a highly safe quasi-solid gel polymer electrolyte (GPE) to achieve stable cycling of lithium metal with high coulombic efficiency, and it is prepared by in situ polymerization of 1,3-dioxolane (DOL) assisted by multi-functional H3Sb3P2O14 sheets. H3Sb3P2O14 acts as an initiator and a functional additive simultaneously that promotes the formation of a stable solid electrolyte interface (SEI) layer, thereby regulating the uniform deposition of Li and improving the Li plating/stripping efficiency. The obtained quasi-solid GPE exhibits high ionic conductivity and enhanced oxidative stability, favoring a stabilized electrode/electrolyte interface. Using the GPE, the electrochemical performance of the quasi-solid-state LMB with a LiFePO4 cathode and a lithium metal anode is significantly improved, delivering a discharge capacity of 125.7 mA h g-1 even after 1000 cycles. Therefore, the high reversibility and remarkable battery cyclability suggest that such a GPE is a promising choice of electrolyte for LMBs, while its facile preparation makes its large-scale application possible in the future.

Double design of host and guest synergistically reinforces the Na-ion storage of sulfur cathodes.

Development of room-temperature sodium-sulfur batteries is significantly hampered by the shuttle effect of soluble intermediates and intrinsically sluggish conversion kinetics. In this work, a double design host and guest strategy (i.e., implantation of a polar V2O3 adsorbent into a carbon substrate and selenium doping of a sulfur guest) is proposed to synergistically reinforce the electrochemical properties of sulfur electrodes in sodium ion storage. The V2O3 adsorbent efficiently immobilizes sulfur species via strong polar-polar interactions, while the selenium dopant improves the electronic conductivity of sulfur cathodes and accelerates the redox conversion of sulfur cathodes. The synergistic effect between the V2O3 adsorbent and selenium dopant is shown to inhibit the shuttle effect and improve the redox kinetics, thus realizing greatly enhanced Na-ion storage properties of sulfur cathodes. The as-designed sulfur cathode delivers a superior rate capability of 663 mA h g-1 at 2.0 A g-1 and demonstrates excellent cyclability of 405 mA h g-1 over 700 cycles at 1.0 A g-1.

Orthorhombic Nb2 O5 Decorated Carbon Nanoreactors Enable Bidirectionally Regulated Redox Behaviors in Room-Temperature Na-S Batteries.

Regulating redox kinetics is able to spur the great-leap-forward development of room-temperature sodium-sulfur (RT Na-S) batteries, especially on propelling their Na-ion storage capability. Here, an innovative metal oxide kinetics accelerator, orthorhombic Nb2 O5 Na-ion conductor, is proposed to functionalize porous carbon nanoreactors (CNR) for S cathodes. The Nb2 O5 is shown to chemically immobilize sodium polysulfides via strong affinity. Theoretical and experimental evidence reveals that the Nb2 O5 can bidirectionally regulate redox behaviors of S cathodes, which accelerates reduction conversions from polysulfides to sulfides as well as promotes oxidation reactions from sulfides to S. In situ and ex situ characterization techniques further verify its electrochemical lasting endurance in catalyzing S conversions. The well-designed S cathode demonstrates a high specific capacity of 1377 mA h g-1 at 0.1 A g-1 , outstanding rate capability of 405 mA h g-1 at 2 A g-1 , and stable cyclability with a capacity retention of 617 mA h g-1 over 600 cycles at 0.5 A g-1 . An ultralow capacity decay rate of 0.0193% per cycle is successfully realized, superior to those of current state-of-the-art RT Na-S batteries. This design also suits emerging Na-Se batteries, which contribute to outstanding electrochemical performance as well.

Anode optimization strategies for aqueous zinc-ion batteries.

Zinc-ion batteries (ZIBs) have received much research attention due to their advantages of safety, non-toxicity, simple manufacture, and element abundance. Nevertheless, serious problems still remain for their anodes, such as dendrite development, corrosion, passivation, and the parasitic hydrogen evolution reaction due to their unique aqueous electrolyte system constituting the main issues that must be addressed, which are blocking the further advancement of anodes for Zn-ion batteries. Herein, we conduct an in-depth analysis of the problems that exist for the zinc anode, summarize the main failure types and mechanisms of the zinc anode, and review the main modification strategies for the anode from the three aspects of the electrolyte, anode surface, and anode host. Furthermore, we also shed light on further modification and optimization strategies for the zinc anode, which provide directions for the future development of anodes for zinc-ion batteries.

Trimodal hierarchical porous carbon nanorods enable high-performance Na-Se batteries.

Technical bottlenecks of polyselenide shuttling and material volume variation significantly hamper the development of emerging sodium-selenium (Na-Se) batteries. The nanopore structure of substrate materials is demonstrated to play a vital role in stabilizing Se cathodes and approaching superior Na-ion storage properties. Herein, an ideal nanorod-like trimodal hierarchical porous carbon (THPC) host is fabricated through a facile one-step carbonization method for advanced Na-Se batteries. The THPC possesses a trimodal nanopore structure encompassing micropores, mesopores, and macropores, and functions as a good accommodator of Se molecules, a reservoir of polyselenide intermediates, a buffer for volume expansion of Se species during sodiation, and a promoter for electron/ion transfer in the electrochemical process. As a result, Na-Se batteries assembled with the Se-THPC composite cathode realize high utilization of Se, fast redox kinetics, and excellent cyclability. Furthermore, the Na-ion storage mechanism of the well-designed Se-THPC composite is profoundly revealed by in situ visual characterization techniques.

Nonionic Surfactant-Assisted In Situ Generation of Stable Passivation Protective Layer for Highly Stable Aqueous Zn Metal Anodes.

A highly stable interface for aqueous rechargeable Zn batteries is of importance to inhibit the growth of Zn dendrites and suppress the side reactions. In this work, we have developed a stable honeycomb-like ZnO passivation protective layer on the Zn surface, which is in situ generated with the assistance of a nonionic surfactant additive (polyethylene glycol tert-octylphenyl ether, denoted as PEGTE). The ZnO passivation layer can facilitate the uniform distribution of the electric field, guiding the uniform deposition of Zn2+ and inhibit the generation of dendrites. As a result, the symmetric cell using the electrolyte with PEGTE shows an excellent performance at high areal capacity, reflected by stable cycling for over 2400 h at 5 mAh/cm2 and 1300 h at 10 mAh/cm2. The full cell paired with V2O5 demonstrates a long lifespan for more than 600 cycles at a low negative/positive capacity ratio.

Honeycomb-like 3D carbon skeletons with embedded phosphorus-rich phosphide nanoparticles as advanced anodes for lithium-ion batteries.

Phosphorus-rich iron phosphides (FeP2) have been regarded as excellent anode candidates for lithium storage owing to their low cost, high natural abundance, high theoretical capacity, and reasonable redox potential. However, FeP2 suffers from a few challenging problems such as low reversibility, fast capacity degradation, and big volume variation. Herein, we have designed and synthesized a 3D honeycomb-like carbon skeleton with embedded FeP2 nanoparticles (denoted as FeP2 NPs@CK), which can significantly promote the kinetics and maintain the structural stability during the cycling, resulting in an excellent electrochemical performance reflected by high reversibility and long-term cycling stability. FeP2 NPs@CK shows high reversibility, delivering a reversible capacity as high as 938 mA h g-1 at 0.5 A g-1. It also shows excellent cycling stability, delivering a capacity of 620 mA h g-1 after 500 cycles at 1 A g-1. Moreover, the fast kinetics and lithium storage mechanism of FeP2 NPs@CK are investigated by quantitative analysis and in situ X-ray diffraction. Such superior performance demonstrates that FeP2 NPs@CK could be a promising and attractive anode candidate for lithium storage.