High Average Efficiency Research Articles

Thickness‐Dependence of 2D g‐C3N4 Artificial Interface Layers on Lithium Metal Deposition

AbstractConstructing artificial interfacial layers using 2D materials with tunable physicochemical properties is a promising strategy to fabricate high‐performance lithium (Li) metal anodes. However, their structural evolution during solid‐electrolyte interphase (SEI) formation and the thickness effects on charge transport remain elusive. Herein, 2D g‐C3N4 layers with varied thicknesses are developed on the surface of copper foil to evaluate the thickness effects of artificial SEI on Li metal deposition. It is demonstrated that a thin g‐C3N4 layer (≈2 nm) is rapidly decomposed and fractured under the impact of Li‐ion flux, while a thick g‐C3N4 layer (≈50 nm) impedes the transport of lithium ions and electrons simultaneously, hindering the Li metal deposition underneath. Notably, a g‐C3N4 layer with moderate thickness (≈10 nm) dominates in‐situ generation of stable g‐C3N4/Li3N hybrid artificial SEI and enables fast Li‐ion transport, which induces uniform Li deposition. The lithium electrode protected by the moderate‐thickness g‐C3N4 layer exhibits outstanding cycling stability with a high average Coulombic efficiency of ≈98.92% for over 380 cycles and enables stable cycling of full cell with 50% Li excess and lean electrolyte. This proof‐of‐concept study provides essential guidance for the application of 2D materials in constructing artificial SEI for Li metal anodes.

Interfacial modulation via cationic electrostatic shielding effect for reversible and durable Zn anodes in hydrogel electrolytes

Although metallic Zn has been considered as a promising anode material in aqueous energy storage systems owing to its high theoretical capacity and intrinsic security, its practical applications are limited by dendrite growth and side reactions at the interface. To address these challenges, here we propose a cationic electrostatic shieling strategy by incorporating choline (Ch+) cations in hydrogel electrolyte (denoted as gel-ChCl electrolyte) to optimize the electrolyte-electrode interface. Theoretical and experimental findings reveal that the Ch+ cations preferentially adsorb on the Zn surface to create an electrostatic shielding layer, which functions dual effects, i.e., redistributing interfacial Zn2+ ions for the uniform deposition and fabricating water-poor interface for the inhibited side reactions. With this strategy, dendrite-free Zn anodes with high plating/stripping reversibility are realized in Zn//Zn and Zn//Cu cells for long-term lifespan and high average coulombic efficiency, respectively. More impressively, the Zn-ion hybrid capacitors (ZHCs) optimized by the gel-ChCl electrolyte deliver favorable flexibility, excellent cyclability (82.6% capacity retention after 40,000 cycles), and energy-storage applications. This work proposes a facile cationic electrostatic shielding strategy to modulate the electrolyte-electrode interface for reaching dendrite-free Zn anodes, which is favorable for advanced flexible ZHCs and beyond.

Structural reinforced NaTi2(PO4)3 composite by pillar effects for constructing a high-performance rocking-chair desalination battery

Battery deionization (BDI) technique has attracted great attention as a potential candidate to tackle the freshwater crisis, but its application is plagued by the lack of electrode materials with large desalination capacity and excellent durability. Herein, Mn dopant-reinforced NaTi2(PO4)3 (NT2–xMxP) composites with significantly enhanced structural stability and electronic/ionic conductivity were fabricated toward seawater desalination. Especially, the NT1.5M0.5P exhibits excellent desalination performance, affording a salt removal capacity (SRC) of 128.5 mg/g with a salt removal rate (SRR) of 18.4 mg g−1 min−1 and almost no capacity attenuation after 500 cycles. Furthermore, the NT1.5M0.5P further possesses favorable technical feasibility in different aqueous media, including desalination at various NaCl concentrations, temperature, solution pH, and natural seawater. Mechanism studies reveal that the NT1.5M0.5P undergoes a solid-solution reaction based on the reversible electrochemical reaction of the Ti4+/Ti3+ redox pair during the desalination/salination process. A rocking-chair desalination battery consisting of NT1.5M0.5P and NaFeHCF demonstrates a favorable desalination ability (average SRC of 49.4 mg/g and SRR of 1.73 mg g−1 min−1), outstanding cycling stability (92 % of capacity retention in 100 cycles), low energy consumption (0.288 kWh/kg-NaCl) and high average charging efficiency (86.9 %). This work sheds light on the rational design of advanced NASICON-type electrodes for seawater desalination with remarkable desalination capacity and long serving life.

Multifunctional Separator Enables High-Performance Sodium Metal Batteries in Carbonate-Based Electrolytes.

Sodium metal has become one of the most promising anodes for next-generation cheap and high-energy-density metal batteries; however, challenges caused by the uncontrollable sodium dendrite growth and fragile solid electrolyte interphase (SEI) restrict their large-scale practical applications in low-cost and wide-voltage-window carbonate electrolytes. Herein, a novel multifunctional separator with lightweight and high thinness is proposed, assembled by the cobalt-based metal-organic framework nanowires (Co-NWS), to replace the widely applied thick and heavy glass fiber separator. Benefitting from its abundant sodiophilic functional groups and densely stacked nanowires, Co-NWS not only exhibits outstanding electrolyte wettability and effectively induces uniform Na+ ion flux as a strong ion redistributor but also favors constructing the robust N,F-rich SEI layer. Satisfactorily, with 10µL carbonate electrolyte, a Na|Co-NWS|Cu half-cell delivers stable cycling (over 260 cycles) with a high average Coulombic efficiency of 98%, and the symmetric cell shows a long cycle life of more than 500h. Remarkably, the full cell shows a long-term life span (over 1500 cycles with 92% capacity retention) at high current density in the carbonate electrolyte. This work opens up a strategy for developing dendrite-free, low-cost, and long-life-span sodium metal batteries in carbonate-based electrolytes.

Lithium Dredging and Capturing Dual‐Gradient Framework Enabling Step‐Packed Deposition for Dendrite‐Free Lithium Metal Anodes

AbstractDue to the sterile lithium affinity and poor Li+ regulation ability, lithium metal tends to deposit on the top of substrate materials, which lowers the space utilization and deteriorates the dendrites growth, further increasing the risk of short circuits. It is necessary to guide lithium deposition and adjust Li+ flux at the base of substrate toward alleviating those issues of lithium metal anodes (LMAs). Herein, a dredging and capturing dual‐gradient framework is conveniently fabricated toward inducing the Li+ migration and deposition. The dual‐gradient framework combined with upper Ni3S2 nanowires with lower Li+ migration barrier and bottom Ni2P nanowires with stronger Li affinity, such reasonable distribution of components conquers the ionic concentration gradient to acquire a “step‐packed” lithium deposition mode. Moreover, the in situ formation of Li2S/Li3P‐enriched SEI further promotes Li+ transport to the interior framework. Consequently, a high average Coulombic efficiency of 98% over 230 cycles and a lifespan of 180 h (10 mA cm−2, 5 mAh cm−2) are achieved. The LiFePO4 full cells also exhibit a considerable capacity retention. This work provides a feasible strategy of step‐packing lithium deposition for significant framework design insight to boost practical lithium metal batteries (LMBs) development.

Nanosilica-filled flame-retardant copolyester electrospun composite separators for high-performance safe lithium-ion batteries

The essential role of separators in battery safety and electrochemical performance makes it necessary to create advanced separators for next-generation energy storage systems. However, conventionally commercial polyolefin separators often have problems with poor thermal stability and insufficient electrolyte wettability, resulting in restricted battery performance and serious safety issues of lithium-ion batteries. Herein, we report a separator composed of silica (SiO2) nanoparticles and intrinsically flame-retardant copolyester P(ET-co-PN)5 electrospun nanofibers, i.e. SiO2@P(ET-co-PN)5 (SP) separator. The copolyester nanofiber's three-dimensional skeleton filled with close-packed SiO2 nanoparticles endows the separator with good mechanical performance (tensile strength of 9.8 MPa) and electrolyte wettability (electrolyte uptake of 333 %), superior heatproof and fireproof properties (no shrinkage at 250 °C, PHRR of 111.6 W/g, and THR of 9.4 kJ/g). The LiFePO4/SP/Li cells exhibit high capacity of 150.2 mAh/g, high average Coulombic efficiency of nearly 100 %, and impressive capacity retention close to 100 % after 220 cycles at 0.5 C. Notably, the LiFePO4/SP/Li cells can endure 1000 cycles at 5 C with 53 % of capacity retention and approximately 100 % of Coulombic efficiency. Moreover, it delivers an initial capacity of 148 mAh/g and retains 123.2 mAh/g over 45 cycles at 120 °C.

Regulating the Interfacial Charge Density by Constructing a Novel Zn Anode-Electrolyte Interface for Highly Reversible Zn Anode.

Aqueous zinc-ion batteries (AZIBs) have attracted considerable attention. However, due to the uneven distribution of charge density at Zn anode-electrolyte interface, severe dendrites and corrosion are generated during cycling. In this work, a facile and scalable strategy to address the above-mentioned issues has been proposed through regulating the charge density at Zn anode-electrolyte interface. As a proof of concept, amidinothiourea (ATU) with abundant lone-pair electrons is employed as an interfacial charge modifier for Zn anode-electrolyte interface. The uniform and increased interfacial charge distribution on Zn anode-electrolyte interface has been obtained. Moreover, the unique Zn-bond constructed between N atoms and Zn2+ as well as the hydrogen bonds are formed among ATU and Ac- anion/active H2 O, which promote the migration and desolvation behavior of Zn2+ at anode-electrolyte interface. Accordingly, at a trace concentration of 0.01 mg mL-1 ATU, these features endow Zn anode with a long cycling life (more than 800 h), and a high average Columbic efficiency (99.52 %) for Zn||Cu batteries. When pairing with I2 cathode, the improved cycling ability (5000 cycles) with capacity retention of 77.9 % is achieved. The fundamental understanding on the regulation of charge density at anode-electrolyte interface can facilitate the development of AZIBs.

Lean-water electrolyte to stabilize zinc anode and suppress manganese dissolution of cathode for ampere-hour zinc batteries

Rechargeable Zinc battery technologies are regarded as viable candidates for large-scale energy storage due to constitutional safety and inexpensive position. Nevertheless, the strong polarity of H2O molecules initiates the deterioration of both zinc metal anode and cathode. At anode side, radical H2O molecules cause side reactions of zinc corrosion, hydrogen evolution reaction (HER) and dendrite growth. At cathode side, the dissolution of transition metal brings about severe capacity fading of cathodes. Herein, we replace the 90% H2O sheath of Zn2+ solvation with 1,3-propanediol (PDO) molecules to form a lean-water electrolyte, in which the abundant PDO molecules can significantly suppress 99.9% HER and prohibit the Zn dendrite growth, while H2O molecules with a molecular lubrication mechanism enables fast ion transportation. Consequently, at anode side, Zn plating/stripping reversibly processes over 4000 cycles with high average Coulombic efficiency of 99.24% in ZnǀǀCu cell. At cathode side, the decreased water activity and scarce solute-water dissolving surfaces suppress 98.6% dissolution of manganese species. The ZnǀǀMnHCF full cell demonstrates high capacity of 140.7 mAh·g−1 at 0.1 A·g−1 and ultra-long lifespan of 3000 cycles with 85.4% initial capacity retained. More importantly, a 1.4 Ah ZnǀǀMnHCF pouch cell shows excellent lifespan over 150 cycles with charge/discharge run time > 68 days. We expect that this work will promote the practicability of aqueous Zn-ion batteries for grid-scale energy storage.

Engineering Fluorine‐rich Double Protective Layer on Zn Anode for Highly Reversible Aqueous Zinc‐ion Batteries

AbstractThe high thermodynamic instability and side reactions of Zn‐metal anode (ZMA), especially at high current densities, greatly impede the commercialization of aqueous zinc‐ion batteries (AZIBs). Herein, a fluorine‐rich double protective layer strategy is proposed to obtain the high reversibility of AZIBs through the introduction of a versatile tetradecafluorononane‐1,9‐diol (TDFND) additive in aqueous electrolyte. TDFND molecule with large adsorption energy (−1.51 eV) preferentially absorbs on the Zn anode surface to form a Zn(OR)2− (R=−CH2−(CF2)7−CH2−) cross‐linking complex network, which balances space electric field and controls the Zn2+ ion flux, thus enabling the uniform and compact deposition of Zn (002) crystal planes. Meanwhile, TDFND with low Lowest unoccupied molecular orbital (LUMO, 0.10 eV) energy level is priorly decomposed to regulate the interfacial chemistry of ZMA by building a ZnF2‐rich solid electrode/electrolyte interface (SEI) layer. It is found that a 14 nm‐thick SEI layer delivers excellent structural integrity to suppress parasitic reactions by blocking the direct contact of active water and ZMA. Consequently, the Zn electrode exhibits a superior cycling life over 430 h at 10 mA cm−2 and a high average Coulombic efficiency of 99.8 % at 5 mA cm−2. Furthermore, a 68 mAh pouch cell delivers 80.3 % capacity retention for 1000 cycles.

Engineering Fluorine-rich Double Protective Layer on Zn Anode for Highly Reversible Aqueous Zinc-ion Batteries.

The high thermodynamic instability and side reactions of Zn-metal anode (ZMA), especially at high current densities, greatly impede the commercialization of aqueous zinc-ion batteries (AZIBs). Herein, a fluorine-rich double protective layer strategy is proposed to obtain the high reversibility of AZIBs through the introduction of a versatile tetradecafluorononane-1,9-diol (TDFND) additive in aqueous electrolyte. TDFND molecule with large adsorption energy (-1.51 eV) preferentially absorbs on the Zn anode surface to form a Zn(OR)2- (R= -CH2-(CF2)7-CH2-) cross-linking complex network, which balances space electric field and controls the Zn2+ ion flux, thus enabling the uniform and compact deposition of Zn (002) crystal planes. Meanwhile, TDFND with low Lowest unoccupied molecular orbital (LUMO, 0.10 eV) energy level is priorly decomposed to regulate the interfacial chemistry of ZMA by building a ZnF2-rich solid electrode/electrolyte interface (SEI) layer. It is found that a 14 nm-thick SEI layer delivers excellent structural integrity to suppress parasitic reactions by blocking the direct contact of active water and ZMA. Consequently, the Zn electrode exhibits a superior cycling life over 430 h at 10 mA cm-2 and a high average Coulombic efficiency of 99.8% at 5 mA cm-2. Furthermore, a 68 mAh pouch cell delivers 80.3% capacity retention for 1000 cycles.

The Rational Design of Low‐Barrier Fluorinated Aluminum Substrates for Anode‑Free Sodium Metal Battery

AbstractAnode‐free Na metal batteries are acclaimed for their high energy densities achieved through current collectors in situ plated with Na metal in the absence of active negative materials. The advancement of these devices hinges on the development of affordable current collectors for effective Na deposition and the design of advanced electrolytes with suppressed Na metal loss as measured against the poor cycling performance and safety issues associated with traditional organic electrolytes and convectional current collectors. Herein, the authors report a novel strategy for fabricating an Al current collector through annealing and fluorination using hydrofluoric acid to optimize its crystal orientation and surface properties in a bid to establish highly reversible Na deposition/dissolution processes. Through a series of characterization, electrochemical, and computational analyses, it is ascertained that the F‐rich surface of the (100)‐oriented Al substrate provides high‐affinity nucleation sites that initiate and sustain a uniform Na metal deposition and form a propitious solid electrolyte interphase layer. The present anode‐free Na metal battery prototype comprised of the treated Al substrate, a high mass loading Na3V2(PO4)3 positive electrode, and an ionic liquid electrolyte achieves a high average Coulombic efficiency (≈98%) over 50 cycles: indeed, groundbreaking performance for uncoated current collectors that do not require activation cycles.

A study on the operational performance of Chinese commercial banks considering time lag effects: A dynamic three-stage time-lag cross-efficiency model

In the multi-period and multi-stage operational process of banks, fixed assets, deposits, and non-performing loans (NPLs) are elements with time lag effects. Not or only considering one time-lag element could result in biased efficiency evaluation results. Therefore, this study proposes a dynamic three-stage time-lag range directional measure (RDM) cross-efficiency model that considers three types of time-lag elements simultaneously to assess the operational performance of banks more accurately and comprehensively. Moreover, the proposed model takes into account the following factors: non-oriented, cross-efficiency, negative data, and undesirable elements. This study conducts in-depth research on the operational performance of Chinese commercial banks and obtains the following observations. (1) The change degrees of different types of banks influenced by the different time-lag elements were inconsistent. (2) Three time-lag elements significantly influenced the operational performance of four types of banks, which was most significant for state-owned commercial banks. (3) All banks were assessed as inefficient during 2017–2021, and the highest average efficiency was found in the capital allocation stage, while the profitability stage ranked at the bottom. (4) Rural and joint-stock commercial banks had the best performance in all sub-stages, while state-owned commercial banks had the worst performance.

In-situ grown hydrophilic-zinophilic ZnCr2O4 protective layer to guide horizontal Zn2+ deposition for dendrite -free Zn anodes for aqueous Zn-ion batteries

Aqueous rechargeable Zn-ion batteries (ARZIBs) have attracted much attention owing to their safety, high energy density and environmental friendliness. However, zinc dendrites and corrosive reactions during platting/stripping on the surface of Zn anodes limit the practical applications of ARZIBs. Herein, the hydrophilic and zinophilic ZnCr2O4 interface layer is grown in situ on the surface of Zn metal to stabilize Zn anode. The in-situ grown ZnCr2O4 interface protective layer constrains the 2D diffusion of Zn2+and homogenizes the surface electric field, guiding preferentially horizontal deposition of Zn2+ along the Zn foil surface. In addition, the in situ ZnCr2O4 interface layer possesses strong hydrophilicity and zinophilicity to enable rapid desolvation of Zn(H2O)62+ and improve Zn2+ platting/stripping kinetics for dense Zn deposition without dendrite Zn growth. Consequently, the symmetric cell with ZnCr2O4-protected Zn anode can stably operate more than 1500 h at 1 mA cm−2 with 1 mAh cm−2, while the Cu||ZCO@Zn half-cell presents a high average Coulombic efficiency of over 99.7 % during cycling for more than 100 cycles. In addition, the NH4V4O10||ZCO@Zn full cell exhibits the capacity retention of 83.3 % at 3 A g−1 after 1000 cycles. This investigation provides a feasible strategy to efficiently inhibit zinc dendrites by in-situ constructing hydrophilic-zinophilic artificial protective coating on the surface of Zn anodes.

Anion-derived cathode interface engineering enables ether-based electrolytes for sodium-ion batteries

High-performance sodium-ion batteries (SIBs) require not only non-aqueous electrolytes with high ion conductivity but also high interfacial compatibility with both electrodes. Ether-based electrolytes are considered one of the most promising electrolyte systems for SIBs due to the advantages of high reduction stability and weakly desolvating power. However, conventional ether-based electrolytes are easy to decompose and deteriorate on the cathode/electrolyte interface under high voltage, which greatly restricts their practical application in SIBs. Herein, a novel and effective interfacial stabilization strategy is proposed and systemically investigated. A homogeneous and compact cathode electrolyte interphase (CEI) film rich in fluorides and borides can be successfully constructed on the cathode surface by pre-cycling of NVP@C cathode in the NaODFB-DEGDME electrolyte. The ODFB anion-derived CEI film can effectively inhibit the continuous oxidation decomposition of NaPF6-DEGDME electrolytes. As a result, the Na||NVP@C half-cell can stably cycle for 1500 cycles with high average Coulombic efficiency (CE, >99.7 %) at 5C. This work illustrates the significance of the composition and structure of CEI film for improving the interfacial stability of high-voltage SIBs with ether-based electrolytes.

Dendrite-free and gasless potassium metal anodes assisted by the mechanical-electrochemical enhancing solid K-electrode and electrolyte interface

With their high-energy density and low-price advantage, potassium (K) metal batteries have been considered the next generation of energy storage system. However, applications of K metal anode are always obstructed by severe side reactions and rapid growth of K dendrites upon cycles due to the fragile solid electrolyte interface (SEI). Herein, a novel mechanical-electrochemical stability enhancement interface is constructed through potassium salt anion structure design and in-situ ion exchange reaction, which enables SEI with reducing side reactions and relieving interface stress during cycling process. The batteries with the designed SEI could deliver excellent performances with a high average Coulombic Efficiency of 95.91 %, a critical current density of 7.5 mA cm−2 and a durable stability of more than 1350 h (0.1 mA cm−2). This work provides an effective strategy to construct a high-energy and stable K metal anode interface and will inspire the electrolyte design for other alkali metal batteries.

Honeycomb-like δ-MnO2/NCP integrated cathode for advanced aqueous zinc-ion batteries

The short cycle life and weak electrical conductivity of manganese dioxide (MnO2) are critical limitations for its application as cathode material in aqueous zinc ion batteries (AZIBs). Herein, we introduce the honeycomb-like δ-MnO2/NCP integrated cathodes, which are developed by the δ-MnO2 nanosheet in situ growing on hollow Ni@C microsphere (denoted as NBM). The hollow microsphere is self-assembled from the graphene carbon layer wrapping Ni nanoparticles (denoted as NCP) by pyrolyzing nickel-based metal-organic frameworks (MOFs). The enhanced NBM electrodes deliver a 352 mAh g − 1 ultra-high specific capacity at 0.1 A g − 1 while maintaining a 125 mAh g − 1 specific capacity at 2 A g − 1. With 81% capacity retention and 99.4% high average coulomb efficiency after 2000 cycles at 2 A g − 1, the NBM electrodes exhibit exceptional cycling stability. Experimental and theoretical results show that NBM electrodes possess excellent electrochemical properties, which are attributed to the high specific surface area of the honeycomb structure, enhanced electrical conductivity, suitable adsorption energy, and low diffusion energy barrier. Moreover, the hollow microsphere structure of NCP promotes fast diffusion of ion/electron and relieves structure collapse of δ-MnO2. This work suggests a promising avenue for developing advanced AZIBs cathode materials.

MoO3 facilitator enables ultrathin and stabilized Li metal anode for quasi-solid-state batteries

Lithium metal is considered as a highly desirable anode for high-energy and safe quasi-solid-state batteries. Nevertheless, the terrible wettability of molten lithium does not permit it to spread out on the lithiophobic current collectors, limiting their practical applications. Herein, we report an ultrathin lithium–molybdenum (Li–Mo) composite anode to settle this hurdle by reacting molten Li with α-MoO3 nanobelts. The experimental characterizations and density functional theory calculations reveal that the interfacial binding energy between molten Li and copper (Cu) foil can be decreased by adding α-MoO3, which improves the wettability toward Cu current collector and helps to realize uniform spreading of an ultrathin Li with a thickness of ∼35 μm. As a demonstration, the ultrathin Li–Mo is stabilized to provide a high average Coulombic efficiency of ∼95.2% over 300 cycles at a high current density of 1 mA cm−2, and a capacity retention of 100% is realized for a quasi-solid-state battery paired with LiFePO4 and poly(1,3-dioxolane) electrolyte. These findings open up a promising option for enhancing the wettability of molten lithium and provide a sustainable strategy for the large-scale production of ultrathin lithium for realizing next-generation high-energy and safe quasi-solid-state batteries.

Improved Interfacial Ion Migration and Deposition through the Chain‐Liquid Synergistic Effect by a Carboxylated Hydrogel Electrolyte for Stable Zinc Metal Anodes

AbstractThe large‐scale applicability of Zn‐metal anodes is severely impeded by the issues such as the dendrite growth, complicated hydrogen evolution, and uncontrollable passivation reaction. Herein, a negatively charged carboxylated double‐network hydrogel electrolyte (Gelatin/Sodium alginate‐acetate, denoted as Gel/SA‐acetate) has been developed to stabilize the interfacial electrochemistry, which restructures a type of Zn2+ ion solvent sheath optimized via a chain‐liquid synergistic effect. New hydrogen bonds are reconstructed with water molecules by the zincophilic functional groups, and directional migration of hydrated Zn2+ ions is therefore induced. Concomitantly, the robust chemical bonding of such hydrogel layers to the Zn slab exhibits a desirable anti‐catalytic effect, thereby greatly diminishing the water activity and eliminating side reactions. Subsequently, a symmetric cell using the Gel/SA‐acetate electrolyte demonstrates a reversible plating/stripping performance for 1580 h, and an asymmetric cell reaches a state‐of‐the‐art runtime of 5600 h with a high average Coulombic efficiency of 99.9 %. The resultant zinc ion hybrid capacitors deliver exceptional properties including the capacity retention of 98.5 % over 15000 cycles, energy density of 236.8 Wh kg−1, and high mechanical adaptability. This work is expected to pave a new avenue for the development of novel hydrogel electrolytes towards safe and stable Zn anodes.

Improved Interfacial Ion Migration and Deposition through the Chain-Liquid Synergistic Effect by a Carboxylated Hydrogel Electrolyte for Stable Zinc Metal Anodes.

The large-scale applicability of Zn-metal anodes is severely impeded by the issues such as the dendrite growth, complicated hydrogen evolution, and uncontrollable passivation reaction. Herein, a negatively charged carboxylated double-network hydrogel electrolyte (Gelatin/Sodium alginate-acetate, denoted as Gel/SA-acetate) has been developed to stabilize the interfacial electrochemistry, which restructures a type of Zn2+ ion solvent sheath optimized via a chain-liquid synergistic effect. New hydrogen bonds are reconstructed with water molecules by the zincophilic functional groups, and directional migration of hydrated Zn2+ ions is therefore induced. Concomitantly, the robust chemical bonding of such hydrogel layers to the Zn slab exhibits a desirable anti-catalytic effect, thereby greatly diminishing the water activity and eliminating side reactions. Subsequently, a symmetric cell using the Gel/SA-acetate electrolyte demonstrates a reversible plating/stripping performance for 1580 h, and an asymmetric cell reaches a state-of-the-art runtime of 5600 h with a high average Coulombic efficiency of 99.9 %. The resultant zinc ion hybrid capacitors deliver exceptional properties including the capacity retention of 98.5 % over 15000 cycles, energy density of 236.8 Wh kg-1 , and high mechanical adaptability. This work is expected to pave a new avenue for the development of novel hydrogel electrolytes towards safe and stable Zn anodes.

Efficient Suppression of Dendrites and Side Reactions by Strong Electrostatic Shielding Effect via the Additive of Rb2 SO4 for Anodes in Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries (AZIBs) have attracted considerable attention due to their low cost and environmental friendliness. However, the rampant dendrite growth and severe side reactions during plating/stripping on the surface of zinc (Zn) anode hinder the practicability of AZIBs. Herein, an effective and non-toxic cationic electrolyte additive of Rb2 SO4 is proposed to address the issues. The large cation of Rb+ is preferentially adsorbed on the surface of Zn metal to induce a strong shielding effect for realizing the lateral deposition of Zn2+ ions along the Zn surface and isolating water from Zn metal to effectively inhibit side reactions. Consequently, the Zn||Zn symmetric cell with the addition of 1.5mm Rb2 SO4 can cycle more than 6000h at 0.5mA cm-2 /0.25 mAh cm-2 , which is 20 times longer than that without Rb2 SO4 . Besides, the Zn||Cu asymmetric cell with Rb2 SO4 achieves a very high average Coulombic efficiency of 99.16% up to 500 cycles. Moreover, the electrolyte with Rb2 SO4 well matches with the VO2 cathode, achieving high initial capacity of 412.7 mAh g-1 at 5 A g-1 and excellent cycling stability with a capacity retention of 71.6% at 5 A g-1 after 500 cycles for the Zn//VO2 full cell.