Aqueous Zn Batteries Research Articles

Correction: Preferred planar crystal growth and uniform solid electrolyte interfaces enabled by anion receptors for stable aqueous Zn batteries

Correction for ‘Preferred planar crystal growth and uniform solid electrolyte interfaces enabled by anion receptors for stable aqueous Zn batteries’ by Xinyu Wang et al., Energy Environ. Sci., 2023, 16, 4572–4583, https://doi.org/10.1039/D3EE01580G.

Enhanced kinetics and stability for aqueous Zn battery enabled by low-cost additive chemistry

Rechargeable aqueous zinc(Zn) batteries are a sustainable alternative to lithium-based energy storage devices due to their high safety, low cost, and scalability. Unfortunately, the Zn/Zn2+ redox chemistry is significantly plagued by undesirable interface caused by the instability of water, which directly dictates the low Zn reversibility and dendrite growth behavior. Here, we report an aqueous electrolyte in which low-cost ammonium dihydrogen phosphate is utilized as an electrolyte additive to enable the in-situ construction of phosphate-based interphase on the Zn-metal surface. Importantly, such interphase not only effectively eliminates water-related parasitic reactions and enables a highly reversible Zn deposition/dissolution, as demonstrated by its high Coulombic efficiency of 99.3 %, but also contributes a dendrite-free Zn morphology. Apart from the improved stability of the Zn anode, the addition of NH4H2PO4 also grants the enhanced reaction kinetics of Zn2+, bringing a lower Zn2+ de-solvation energy barrier and much-improved rate performance. Benefiting from the synergistic factors, excellent cycling performances of the Zn0.25V2O5·nH2O (ZVO)/Zn batteries are guaranteed. Additionally, a 31.2 mAh ZVO/Zn pouch cell also demonstrates a stable long life of 400 cycles, and capacity retention of 67.8 % is also retained. The low-cost and efficient electrolyte strategy points out a promising direction for practical Zn batteries.

Regeneration of Spent Lithium Manganate Batteries into Al-Doped MnO2 Cathodes toward Aqueous Zn Batteries.

Large quantities of spent lithium-ion batteries (LIBs) will inevitably be generated in the near future because of their wide application in many fields. It will cause not only resource waste but also environmental pollution if these spent batteries are not properly handled. Until now, the recycling of spent lithium manganate batteries has centered on high-valuable elements such as lithium; however, manganese element and current collector Al foil have not yet attracted wide attention. In this work, aluminum-doped manganese dioxide was synthesized by overall recycling cathode active materials and current collector Al foil from a spent lithium manganate battery. Employing such aluminum-doped manganese dioxide as the cathode material of aqueous Zn batteries, it displays better electrochemical performance than manganese dioxide prepared by only recycling the cathode active materials. The overall recycling not only simplifies the recycling process but also realizes high-value recycling of spent lithium manganate batteries. We offer new tactics for overall recycling of cathodes from spent LIBs and designing high-performance manganese dioxide cathodes for aqueous Zn batteries.

Long‐cycling Zinc Metal Anodes Enabled by an In Situ Constructed ZnO Coating Layer

AbstractSuppressing dendrite growth in zinc (Zn) anodes for aqueous Zn batteries remains a significant challenge. Modifying the Zn/electrolyte interface stands out as one of the most promising strategies to tackle this problem. In this study, a nanometer‐thick ZnO coating layer with a uniform concave surface geometry is in situ constructed to modify the Zn anode for the first time. The chemical bond formed between the ZnO layer and the Zn foil enhances the structural stability of the synthesized ZnO modified‐Zn anode. Finite element simulations indicate that the ZnO coating layer facilitates uniform electric field distribution and zinc flux on the Zn electrode. In situ optical observations unveil how the modification interface regulates zinc plating behaviors on the Zn anode. Impressively, the symmetrical ZnO‐Zn cell displays a remarkable cycling stability of 1765 h at a current density of 5 mA cm−2 with an areal capacity of 1 mAh cm−2. Even when subjected to a very high current density of 50 mA cm−2, it maintains stable operation over 3800 cycles. This success highlights the immense application potential of the rationally tailored ZnO‐Zn anode.

The Zn Deposition Mechanism and Pressure Effects for Aqueous Zn Batteries: A Combined Theoretical and Experimental Study

AbstractA new reactive force field based on quantum mechanical data for describing formation of the Zn electrode‐electrolyte interface (EEI) chemistry in aqueous zinc‐ion batteries (ZIBs) is developed. This is the first demonstration in which Reactive Molecular Dynamics (RMD) simulation is used to follow the Zn reduction and anode structural evolution at the EEI. It is found that under axial pressure, Zn dendrite formation is inhibited. This is associated with accelerated ion transport and reduction while increasing preference towards horizontal (002) plane growth. Pressure‐induced desolvation of Zn ions within the electric double layer, which promotes faster reduction kinetics is observed. It is found that axial pressure stabilizes adatoms on the (002) plane by decreasing axial atom stress during nucleation and by increasing favorable lateral adatom diffusion, which reduces atomic scale dendrite formation. Finally, these are confirmed results by experimental characterization and electrochemical tests.

Phase-Field Simulation of a Dynamic Protective Layer for the Inhibition of Dendrite Growth in Zinc Metal Batteries.

Metallic zinc (Zn) has been considered one of the most promising anode materials for next-generation aqueous Zn batteries due to its low redox potential and high storage capacity. However, excessive dendrite formation in Zn metal, corrosion, the evolution of hydrogen gas during the cycling process, and the poor Zn-ion (Zn2+) transport from the electrolyte to the electrode limit its practical application. One of the most effective strategies to suppress Zn dendrite growth and promote Zn2+ transport is to introduce suitable protective layers between the Zn metal electrode and the electrolyte. Herein, we mathematically simulated the dynamic interactions between the Zn deposition on the anode and the resulting displacement of a protective layer that covers the anode, the latter of which can simultaneously inhibit Zn dendrite growth and enhance the Zn2+ transport through the interface between the Zn anode and the protective layer. Our simulation results indicate that a protective layer of high Zn2+ diffusivity not only improves the deposition rate of the Zn metal but also prevents dendrite growth by homogenizing the Zn2+ concentration at the anode surface. In addition, it is revealed that the anisotropic Zn2+ diffusivity in the protective layer influences the 2D diffusion of Zn2+. Higher Zn2+ diffusivity perpendicular to the Zn metal surface inhibits dendrite growth, while higher diffusivity parallel to the Zn metal surface promotes dendrite growth. Our work thus provides a fundamental understanding and a design principle for controlling anisotropic Zn2+ diffusion in the protective layer for better suppression of dendrite growth in Zn metal batteries.

Hetero-Solvation-Diluted Strongly-Coordinated Zn2+-Cosolvent Pairs Downshifting Zn Electrode Potential for High-Voltage Hybrid Batteries.

Mild aqueous Zn batteries (AZBs) generally suffer a low-voltage/energy dilemma, which compromises their competitiveness for large-scale energy storage. Pushing Zn anode potential downshift is an admissible yet underappreciated approach for high-voltage/energy AZBs. Herein, with a mild hybrid electrolyte containing in situ-derived diluted strongly-coordinated Zn2+-cosolvent pairs, a considerable Zn anode potential downshift is initially achieved for high-voltage Zn-based hybrid batteries. The chosen butylpyridine cosolvent not only strongly coordinates Zn2+ ions but also acts as a hydrogen-bond end-capping agent to inhibit hydrogen evolution reaction (HER). The electrolyte environment with hetero-solvation-diluted strongly-coordinated Zn2+-cosolvent pairs remarkably lowers Zn2+ activity, responsible for the Zn electrode potential downshift (-0.330V vs Zn), confirming to modified Nernst law (ΔE = ln[a(Zn2 + )/a(coordinated solvent)]). With the diluted Zn2+-containing hybrid electrolyte, the Zn//Zn symmetric cell in the hybrid electrolyte shows a long lifespan over 1270h at a stripping/plating capacity of 0.4mA h cm-2. Compared with in common hybrid electrolytes, the as-assembled Zn-MnO2 hybrid battery delivers a ca. 0.278 V enhanced voltage plateau (1.57V) and a long-term cyclability of over 736 cycles. This work opens a new avenue toward Zn anode potential downshift for high-voltage AZBs, which can extend to other mild metal batteries.

Understanding the Super-Theoretical Capacity Behavior of VO2 in Aqueous Zn Batteries.

VO2 material, as a promising intercalation host, is widely investigated not only in aqueous lithium-ion batteries, but also in aqueous zinc-ion batteries (AZIBs) owing to its stable tunnel-like framework and multivalence of vanadium. Different from lithium-ion storage, VO2 can provide higher capacity when storing zinc ions, even exceeding its theoretical capacity (323mAhg-1), but the specific reason for this unconventional performance in AZIBs is still unclear. The present study proposes a catalytic oxygen evolution reaction (OER) coupled with an interface oxidation mechanism of VO2 during the initial charging to a high voltage. This coupling induces a phase transformation of VO2 into a high oxidation state of V5O12∙6H2O, enabling a nearly two-electron reaction and providing additional zinc storage sites to achieve super-theoretical capacity. Furthermore, it is demonstrated that these vanadium oxide cathodes (V2O3, VO2, and V2O5) will all undergo phase change after the first charge or short cycle. Notably, water molecules participate in the final formation of layered vanadium-based hydrate, highlighting their crucial role as "pillars" for stabilizing the structure. This work significantly enhances the understanding of vanadium-based oxide cathodes.

Rationally Designed ZnTe@C Nanowires with Superior Zinc Storage Performance for Aqueous Zn Batteries (Small 52/2023)

Rationally Designed ZnTe@C Nanowires with Superior Zinc Storage Performance for Aqueous Zn Batteries (Small 52/2023)

Quinone carbonyl activation for in situ constructing kinetic-boosted zincophilic polymer interphase toward high performance Zn metal anode

A facile interfacial engineering on Zn foil anode to boost fast Zn-ion kinetics for uniform Zn deposition is highly desired in rechargeable Zn batteries. Herein, we report a 3 s dipping method to in situ construct a quinone carbonyl rich polymer interphase on Zn foil with fast Zn-ion capture-transfer-deposition kinetics. Quinone carbonyl obtained through “hydroxyl to carbonyl” oxidation on tannic acid (TA) molecule shows high adsorption to Zn-ion, effectively activating Zn-ion conduction on TA. The quinone carbonyl rich TA based polymer interphase possesses abundant zincophilic carbonyl sites, which facilitate rapid Zn-ion transfer through ample channels, accelerated Zn-ion deposition with carbonyl-assisted [Zn(H2O)6]2+ desolvation, moreover, quick Zn-ion capture from the electrolyte. The fast Zn-ion kinetics regulate super-uniform and flat Zn deposition by promoting multisite Zn nucleation and reducing concentration polarization induced Zn dendrites. Consequently, as-prepared OTA-SO@Zn anode shows high cycling stability (3200 h at 1 mA cm−2/1 mA h cm−2; 550 h at 5 mA cm−2/5 mA h cm−2) in symmetric cell. The OTA-SO@Zn||CNT@MnO2 full cell delivers capacity retention of 99.2% after 1500 cycles, ranking the top-level of aqueous Zn batteries. This work sheds light on exploration of quinone carbonyl in electrochemical ion-transport and provides an efficient Zn metal protective method with large-scale implementation potential.

Activating Organic Electrode via Trace Dissolved Organic Molecules.

Organic electrode materials have gained attention for their tunable structures and sustainability, but their low electronic conductivity requires the use of large amounts of carbon additives (30 wt %) and low mass loadings (<2 mg cm-2) in electrodes. Here, we synthesize dibenzo[b,i]phenazine-5,7,12,14-tetrone (DPT) as a cathode active material for an aqueous Zn battery and find that Zn2+ storage dominates the cathode reaction. This battery demonstrates high capacity (367 mAh g-1), high-rate performance, and superlong life (12000 cycles). Remarkably, despite DPT's insulative nature, even with a high mass loading (10 mg cm-2) and only 10 wt % carbon additives, the DPT-based cathode exhibits promising performance due to trace dissolved discharge product (DPTx-). During discharge, the DPT is reduced to trace amounts of dissolved DPTx- at the cathode surface, which in turn reduces the remaining solid DPT as a redox mediator. Furthermore, dissolution-redeposition results in the reduction of DPT size and the formation of pores, further activating the electrode.

Chemisorption Effect Enables High-Loading Zinc-Iodine Batteries

Rechargeable Zn-I2 batteries featuring intrinsic safety and high energy density demonstrate promising energy storage prospects. However, the poor interface stability of the Zn anode and the undesirable shuttle effect severely hinder the device stability due to the diffusive characteristics of the soluble polyiodides in aqueous media. Here, a synergetic physicochemical strategy that combines physical constraints and chemical absorption was proposed by developing a composite host matrix with a core/porous-sheath structure, which can effectively confine iodine species. Initial I− ions bind securely with carboxylated multi-walled carbon nanotubes (c-MCNTs) to form the C–I bonds through chemical interactions. Furthermore, the pore structure of microporous carbon (MPC) not only restricts the iodine species in the pores through physisorption (secondary adsorption) but also facilitates the diffusion of Zn2+. The as-prepared carbon nanotubes coated with microporous carbon (glucose as the carbon source, and its ratio to CNT is 12:1) can serve as a host material (CNT@MPC12), and adsorb iodide ions to derive CNT@MPC12-I−. As a result, the developed aqueous Zn battery with CNT@MPC12-I− cathode delivers superior reversible rate capacity (0.35mAh cm–2 at 20mAcm–2) and remarkable cycling performance (12000 cycles at 10mAcm–2). Notably, such cathode can also exhibit an impressive capacity retention of 97% after 8600 cycles, even at an ultrahigh loading mass of 16.05mgcm–2. As such, our strategy can be extended to design other metal I2 batteries with high loading and long-life expectancy.

Conversion-type Cathode Materials for Aqueous Zn Metal Batteries in Non-Alkaline Aqueous Electrolytes: Progress, Challenges, And Solutions.

Aqueous Zn metal batteries are attractive as safe and low-cost energy storage systems. At present, due to the narrow window of the aqueous electrolyte and the strong reliance of the Zn2+ ion intercalated reaction on the host structure, the current intercalated cathode materials exhibit restricted energy densities. In contrast, cathode materials with conversion reactions can promise higher energy densities. Especially, the recently reported conversion-type cathode materials that function in non-alkaline electrolytes have garnered increasing attention. This is because the use of non-alkaline electrolytes can prevent the occurrence of side reactions encountered in alkaline electrolytes and thereby enhance cycling stability. However, there is a lack of comprehensive review on the reaction mechanisms, progress, challenges, and solutions to these cathode materials. In this review, four kinds of conversion-type cathode materials including MnO2 , halogen materials (Br2 and I2 ), chalcogenide materials (O2 , S, Se, and Te), and Cu-based compounds (CuI, Cu2 O, Cu2 S, CuO, CuS, and CuSe) are reviewed. First, the reaction mechanisms and battery structures of these materials are introduced. Second, the fundamental problems and their corresponding solutions are discussed in detail in each material. Finally, future directions and efforts for the development of conversion-type cathode materials for aqueous Zn batteries are proposed. This article is protected by copyright. All rights reserved.

Surface Adsorption and Proton Chemistry of Ultra-Stabilized Aqueous Zinc-Manganese Dioxide Batteries.

Aqueous rechargeable Zinc (Zn) batteries incorporating MnO2 cathodes possess favorable sustainability properties and are being considered for low-cost, high-safety energy storage. However, unstable electrode structures and unclear charge storage mechanisms limit their development. Here, advanced transmission electron microscopy, electrochemical analysis, and theoretical calculations are utilized to study the working mechanisms of a Zn/MnO2 battery with a Co2+ -stabilized, tunnel-structured α-MnO2 cathode (Cox MnO2 ). It is shown that Co2+ can be pre-intercalated into α-MnO2 and occupy the (2×2) tunnel structure, which improves the structural stability of MnO2 , facilitates the proton diffusion and Zn2+ adsorption on the MnO2 surface upon battery cycling. It is further revealed that for the MnO2 cathode, the charge storage reaction proceeds mainly by proton intercalation with the formation of α-Hy Cox MnO2 , and that the anode design (with or without Zn metal) affects the surface adsorption of by-product Zn4 SO4 (OH)6 ·nH2 O on MnO2 surface. This work advances the fundamental understanding of rechargeable Zn batteries and also sheds light on efficient electrode modifications toward performance enhancement.

Tuning the Valence of MnOx Cathodes Reveals the Universality of the Proton‐Coupled Electrodissolution/Electrodeposition Mechanism in Rechargeable Aqueous Zn Batteries

AbstractThe charge storage mechanism of manganese oxides (MnOx) in rechargeable mild aqueous Zn batteries is still a matter of debate, with no consensus on mechanism and charge carriers. In this work, this issue is addressed by relying on a quantitative and comparative electrochemical study of low‐valence crystalline MnOx cathodes in a range of aqueous electrolytes, with a primary focus on spinel Mn3O4. The results demonstrate that the oxidation state of Mn in MnOx structures as well as their degree of crystallinity have little impact on the electrochemical reactivity, all MnOx being fully converted into soluble Mn2+ upon discharge. It is further revealed that this electrodissolution mechanism is affected by Mn3O4 dismutation in the most acidic electrolytes. Accordingly, the true thermodynamics and kinetics of Mn3O4 are only accessible at mildly acidic to neutral pHs. In addition, the study confirms the phase transformation of Mn3O4 to Mn5O8 upon galvanostatic oxidation, and demonstrates that this transformation only proceeds in Mn2+‐free electrolytes, since otherwise amorphous MnO2 electrodeposits on top of Mn3O4. Finally, it is concluded that regardless of the starting MnOx material, after the first discharge or a first charge/discharge cycle, subsequent charge/discharge cycles rely on a reversible proton‐coupled electrodeposition of amorphous MnO2.

Revealing the missing puzzle piece of concentration in regulating Zn electrodeposition.

Despite achievements in suppressing dendrites and regulating Zn crystal growth, secondary aqueous Zn batteries are still rare in the market. Existing strategies mainly focus on electrode modification and electrolyte optimization, while the essential role of ion concentration in liquid-to-solid electrodeposition is neglected for a long time. Herein, the mechanism of concentration regulation in Zn electrodeposition is investigated in depth by combining electrochemical tests, post hoc characterization, and multiscale simulations. First, initial Zn electrodeposition is thermodynamically controlled epitaxial growth, whereas with the rapid depletion of ions, the concentration overpotential transcends the thermodynamic influence to kinetic control. Then, the evolution of the morphology from 2D sheets to 1D whiskers due to the concentration change is insightfully revealed by the morphological characterization and phase-field modeling. Furthermore, the depth of discharge (DOD) results in large concentration differences at the electrode-electrolyte interface, with a mild concentration distribution at lower DOD generating (002) crystal plane 2D sheets and a heavily varied concentration distribution at higher DOD yielding arbitrarily oriented 3D blocks. As a proof of concept, relaxation is introduced into two systems to homogenize the concentration distribution, revalidating the essential role of concentration in regulating electrodeposition, and two vital factors affecting the relaxation time, i.e., current density and electrode distance, are deeply investigated, demonstrating that the relaxation time is positively related to both and is more sensitive to the electrode distance. This work contributes to reacquainting aqueous batteries undergoing phase transitions and reveals a missing piece of the puzzle in regulating Zn electrodeposition.

Corn Husk‐Derived Activated Carbon as High‐Performance Anode Constituent for Rechargeable Aqueous Zn/α‐MnO2 Batteries

Zinc (Zn) aqueous batteries have gained significant research interest for large‐scale electrochemical energy storage applications due to their rich abundance of raw materials, high energy density, environmental friendliness, low capital, and maintenance expenditure. However, the progress of metallic Zn anode in the aqueous Zn battery chemistry is hindered by several critical challenges, including low Coulombic efficiency and the formation of Zn dendrites, irrespective of the pH of the electrolyte. Herein, the application of porous activated carbon (AC) derived from waste corn husk as Zn anode constituent to improve the cyclability of the aqueous Zn battery is reported. In the full cell study, it is observed that the battery containing 15 wt% of AC as anode coupled with α‐MnO2 nanorods cathode shows excellent capacity retention of 86.42% (initial discharge capacity = 211.67 mAh g−1) after 125 charge/discharge cycles at current rate of 100 mA g−1. Moreover, herein, insights into converting waste to energy by utilizing the biowaste precursor to develop stable and durable rechargeable aqueous Zn‐based batteries are provided.

Molecular engineering of self-assembled monolayers for highly utilized Zn anodes

Stabilizing the Zn anode under high utilization rates is highly applauded yet very challenging in aqueous Zn batteries. Here, we rationally design a zincophilic short-chain aromatic molecule, 4-mercaptopyridine (4Mpy), to construct self-assembled monolayers (SAMs) on a copper substrate to achieve highly utilized Zn anodes. We reveal that 4Mpy could be firmly bound on the Cu substrate via Cu–S bond to form compact and uniform SAMs, which could effectively isolate the water on the electrode surface and thus eliminate the water-related side reactions. In addition, the short-chain aromatic ring structure of 4Mpy could not only ensure the ordered arrangement of zincophilic pyridine N but also facilitate charge transfer, thus enabling uniform and rapid Zn deposition. Consequently, the Zn/4Mpy/Cu electrode not only enables the symmetric cell to stably cycle for over 180 ​h at 10 ​mA ​cm−2 under a high depth-of-discharge of 90%, but also allows the MnO2-paired pouch cell to survive for 100 cycles under a high Zn utilization rate of 78.8%. An anode-free 4Mpy/Cu||graphite cell also operates for 150 cycles without obvious capacity fading at 0.1 ​A ​g−1. This control of interfacial chemistry via SAMs to achieve high utilization rates of metal anodes provides a new paradigm for developing high-energy metal-based batteries.

High Energy Density Aqueous Zinc–Chalcogen (S, Se, Te) Batteries: Recent Progress, Challenges, and Perspective

AbstractZinc‐ion batteries with chalcogen‐based (S, Se, Te) cathodes have emerged as a promising candidate for utility‐scale energy storage systems and portable electronics, which have attracted rapid attention and offer tremendous opportunities owing to their excellent energy density, on top of the advantages of aqueous Zn batteries including cost‐effectiveness, inherent safety, and eco‐friendliness. Here, a comprehensive overview on the basic mechanism of zinc–chalcogen batteries with their great advantages and intrinsic issues is provided. More detailed recent progress is summarized and the existing challenges with promising strategies are provided as well. First, four specific types of batteries are presented, including: zinc–sulfur, zinc–selenium, zinc–selenium sulfide, and zinc–tellurium batteries. Second, the remaining challenges within chalcogen‐based cathodes in the material preparation, physicochemical properties, and battery performance are summarized and discussed. Meanwhile, a series of constructive strategies are comprehensively put forward for optimizing electrochemical performance. Finally, the future research perspectives of zinc–chalcogen batteries are proposed for the exploration and innovation of next‐generation green zinc storage applications.

Reversible Zn electrodeposition enabled by interfacial chemistry manipulation for high-energy anode-free Zn batteries

Aqueous Zn batteries have attracted intensive interest in terms of the high safety and sustainable raw materials with low cost. However, the excess use of Zn anode greatly limits the practical energy density of batteries and arouses a threat to their real-life application. Here, a robust heterointerface composed of 0D metal nanodots and 2D metal carbide nanosheets with triple synergistic effects is designed to manipulate interfacial chemistry for anode-free Zn batteries. An interface of in situ anchoring ultrafine Sn nanodots on Na+ decorated MXene nanosheets is used as a model. The 2D Na-MXene promotes the Zn plating/stripping kinetics and homogenizes the distributions of electric field and ion flux. The high-affinity Zn binding sites of 0D Sn nanodots reduce the plating energy barrier and consequently manipulate the uniform Zn nucleation/growth. The in situ formed ZnF2 layer during Zn plating allows Zn ions to diffuse and shields side reactions. Consequently, the stable Zn plating/stripping with a high accumulated areal capacity of 5,000 mAh cm−2 is realized at high current density and plating capacity (10 mA cm−2∼20 mAh cm−2). Benefitting from triply synergistic effects derived from built cooperative interfaces, an anode-free Zn cell is constructed, proving ameliorative cyclic stability.