Aqueous Zn Research Articles

Elucidating synergistic mechanisms of an anion–cation electrolyte additive for ultra-stable zinc metal anodes

The present work presents a multi-functional 0.2 M NaI electrolyte additive to suppress Zn dendrites and water-induced parasitic reactions in aqueous Zn metal batteries, featuring an astonishing Zn deposition/stripping cyclability of 8632 h.

A covalent organic framework as a dual-active-center cathode for a high-performance aqueous zinc-ion battery.

Organic electrode materials have shown significant potential for aqueous Zn ion batteries (AZIBs) due to their flexible structure designability and cost advantage. However, sluggish ionic diffusion, high solubility, and low capacities limit their practical application. Here, we designed a covalent organic framework (TA-PTO-COF) generated by covalently bonding tris(4-formylbiphenyl)amine (TA) and 2,7-diaminopyrene-4,5,9,10-tetraone (PTO-NH2). The highly conjugated skeleton inside enhances its electron delocalization and intermolecular interaction, leading to high electronic conductivity and limited solubility. The open channel within the TA-PTO-COF provides ionic diffusion pathways for fast reaction kinetics. In addition, the abundant active sites (C[double bond, length as m-dash]N and C[double bond, length as m-dash]O) endow the TA-PTO-COF with a large reversible capacity. As a result, the well-designed TA-PTO-COF cathode delivers exceptional capacity (255 mA h g-1 at 0.1 A g-1), excellent cycling stability, and a superior rate capacity of 186 mA h g-1 at 10 A g-1. Additionally, the co-insertion mechanism of Zn2+/H+ within the TA-PTO-COF cathode is revealed in depth by ex situ spectroscopy. This study presents an effective strategy for developing high-performance organic cathodes for advanced AZIBs.

New insights into the charge storage chemistry of polymer cathodes in aqueous Zn batteries

The fractions of H+ and Zn2+ uptakes in four different polymer cathodes for aqueous Zn batteries are experimentally determined, and the dominant role of H+ in charge storage process is unveiled.

Interface regulation of the Zn anode by using a low concentration electrolyte additive for aqueous Zn batteries.

The Zn metal anode in aqueous Zn batteries faces a number of challenges including instable deposition and corrosion issues. Here, we present an interface environment regulation for a Zn electrode with a low concentration electrolyte additive of 0.1 m 3-aminobenzenesulfonic acid (ASA). ASA prefers to adsorb on the Zn surface over water and creates an ASA-rich interface. It further enters the Zn2+ solvation sheath locally, which shifts the lowest unoccupied molecular orbital from solvated water to ASA. The hydrogen evolution reaction from solvated water reduction is inhibited, and the reduction of solvated ASA generates a stable solid-electrolyte interphase composed of the ion conductor ZnS covered by organic-inorganic mixed components. With the resulting homogenized Zn deposition, continuous Zn stripping in symmetric cells reaches 99.7% depth of discharge (DOD) at a current density of 2 mA cm-2, whereas cell short-circuit takes place at 11.4% DOD in the ASA free ZnSO4 electrolyte. The repeated stripping/plating also realizes 1100 h cycle life at 2 mA cm-2, and a 99.54% stabilized coulombic efficiency is obtained for 500 cycles at 10 mA cm-2.

Rational electrolyte design and electrode regulation for boosting high-capacity Zn-iodine fiber-shaped batteries with four-electron redox reactions.

Aqueous Zn ion-based fiber-shaped batteries (AZFBs) with the merits of high flexibility and safety have received much attention for powering wearable electronic devices. However, the relatively low specific capacity provided by cathode materials limits their practical application. Herein, we first propose a simple strategy for fabricating high-capacity Zn-iodine fiber-shaped batteries with a high concentration electrolyte and a reduced graphene oxide fiber (GF) cathode. It was found that oxygen functional groups in the graphene sheet demonstrate strong interaction with polyiodides but hinder electron conductivity; thus, the optimal balance between the specific capacity and coulombic efficiency of the GF electrode can be a function of the surface properties at different hydrothermal temperatures. Besides, the regulated high concentration electrolyte effectively suppresses the diffusion of polyiodides, which is attributed to the constrained freedom of water. More importantly, a four-electron redox mechanism was experimentally revealed through in situ Raman spectra. As a result, this fiber-shaped battery delivers a superior high reversible capacity of 390 mA h cm-3 at 1 A cm-3, an excellent rate performance of 125.7 mA h cm-3 at a high current density of 8 A cm-3 and outstanding cycling life with 82% capacitance retention after 2500 cycles.

Hydrogen-bond chemistry inhibits Jahn–Teller distortion caused by Mn 3d orbitals for long-lifespan aqueous Zn//MnO2 batteries

By introducing NH4+, hydrogen-bond-modulated MnO2 nanoflowers inhibit the stretching of the [MnO6] octahedra along the z axis, reduce the occurrence of Jahn–Teller distortion, and achieve long-lifespan aqueous Zn//MnO2 batteries.

Regulation of the solvation structure and electrode interface using a succinic acid additive for highly stable aqueous Zn batteries

SA serves as an additive to reshape the solvation structure of Zn ions and adsorb on the surface of a Zn electrode, leading to a significant improvement in reversibility and cycling stability of aqueous Zn batteries.

Identifying iodide-ion regulation of early-stage zinc nucleation and growth for high-rate anode-free zinc metal batteries

An innovative approach of iodide ion-mediated regulation for the early-stage Zn nucleation and growth process is demonstrated to achieve highly reversible and high-rate anode-free aqueous Zn metal batteries.

Molecularly engineered multifunctional imide derivatives for practical Zn metal full cells

The molecularly engineered multifunctional additive of H-SU, which effectively modulates both solvated and interfacial structures, was chosen from a family of imide derivatives for practical aqueous Zn metal full cells.

Guiding uniform Zn electrodeposition through regulating pressure for stable aqueous Zn batteries

Optimal axial pressure facilitates stabilization of interphasial chemistry and enhances Zn2+ transport at the electrode–electrolyte interface, thereby guiding uniform and dense Zn deposition in aqueous Zn batteries.

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.

Novel insights into aqueous Zn–MnO2 batteries: a simple and robust approach to refute the Zn2+ intercalation mechanism

Proving minor contribution of Zn2+ intercalation in RAZMBs' reaction mechanisms regardless of electrolyte acidity by a segregated electrolyte system.

Deep ion mass transfer addressing the capacity shrink challenge of aqueous Zn‖MnO2 batteries during the cathode scaleup

This work shows that the introduction of interstitial carbon into the MnO2 lattice could reduce the affinity toward SO42− and OH−, thus suppressing the surface coverage of ZHS and improving the Zn||MnO2 battery performance under large loading mass.

Heterogeneous particles enhanced derived carbon anode for highly stable aqueous zinc-ion battery

The aqueous Zn ion battery has the advantages of high safety, low cost, and environmental friendliness. However, the dendrite growth and side reactions hinder the practical application. Advanced anode electrode materials are proposed as effective countermeasures but they show poor zinc storage performance. Herein, Ag nanoparticles with different molar ratios were doped on Zn/Co ZIF-L derived carbon by an easy silver mirror reaction. Owing to the good conductivity of silver particles and the interaction of composites, the nucleation over-potential in the Cu||Zn half-cell was reduced. This enables the full cell to maintain a specific discharge capacity of 487.6 mAh g−1 at 0.5 C and 97.6 % coulombic efficiency after long-term cycles for 3000 cycles.

Waste frying oil derived carbon nano-onions as a cost-effective cathode material for high-voltage zinc-ion hybrid supercapacitors

Energy crisis and environmental pollution are two major worldwide issues that can be solved by developing sustainable, commercial, and long-durability energy storage systems from the reutilization of waste material. Waste frying oil, a known waste, is used as a carbon source for the synthesis of carbon nano-onions (CNOs) using economically viable and environmentally friendly wick pyrolysis techniques. The as-synthesized CNOs were used as a cost-effective cathode in zinc-ions hybrid supercapacitors (Zn–HSCs). CNOs with a fractal-like structure in an interconnected network and more accessible active available surface area provide great advantage as a cathode to fabricate Zn–HSCs. The CNOs-based active cathode material in aqueous Zn–HSCs presents a high specific capacitance of 342 F g−1 at a current density of 0.5 A g−1 under a high working potential window (0–1.9 V). Zn–HSCs achieve a maximum 8.2 kW kg−1 of power density and 164.33 W h kg−1 of energy density. More significantly, excellent long-term durability with 83 % of capacity retention and 100 % retention of coulombic efficiency was also achieved after 10,000 cycles at a high 10 A g−1 of current density. The overall work represents a way of utilizing waste frying oil as a cost-effective and efficient cathode material for aqueous Zn–HSCs, which could aid-in the commercialization of Zn–HSCs.

Influence of Salt Concentration on Electrochemical Stability Window in Aqueous Electrolytes

The thermodynamic limit of water electrolysis restricts the output voltage of aqueous metal ion batteries (MIBs) due to the low electrochemical stability window of water (1.23 V) in dilute electrolytes. It occurs due to the electrolysis of free water molecules into O2 or H2. Such value is unfortunately too low for many applications. For effective utilization of this technology, the ESW needs to be expanded to at least 2 V to achieve high energy density in metal batteries. Interestingly, water electrolysis can be suppressed by binding free water content with high concentrations of salts in highly concentrated water-in-salt electrolytes.In this work, low-cost non-flammable aqueous Zn(ClO4)2 electrolytes have been studied for their electrochemical behaviour at different concentrations. The electrolytes have been evaluated via Raman spectroscopic analysis to examine the modification in local water structures associated with increasing salt concentration. We also used linear sweep voltammetry on a glassy carbon electrode to determine the electrochemical stability window of the electrolytes. Electrochemical results indicate the existence of two distinct regions in the concentration behavior of the onset potential for oxygen evolution reaction (OER) at a cut-off current density of 0.1 mA cm-2. In dilute electrolytes, the overpotential in OER increases with a low slope with increasing concentration, while there is a sharper overpotential increase at higher salt concentrations in the water-in-salt electrolytes. Raman spectroscopic analysis provides evidence of this electrochemical stability expansion as being a result of the disruption of the hydrogen bonding network present in pure water. A more compact and strongly coordinated ion hydration structure occurs in the water-in-salt electrolytes. In this way, a significant increase in oxidative stability and a decline in the Zn oxidation overpotential has been achieved in the highly concentrated water-in-salt electrolytes. Our results indicate that the Zn(ClO4)2 water-in-salt electrolytes offer more efficient Zn redox reactions and a higher electrochemical stability window than the diluted aqueous electrolytes, which is particularly beneficial for the development of high-voltage aqueous Zn ion batteries [1].

(Invited) Engineering Local Chemical Environments in Electrolytes and at Electrode-Electrolyte Interface for Efficient Aqueous Batteries

Electrolytes are an essential component of energy storage devices. Electrolyte composition has a significant impact on the environmental footprint, safety, price and performance of a battery. Aqueous electrolytes are non-flammable and can offer safer battery operation and lower toxicity. However, they suffer from a smaller electrochemical stability window compared to traditional organic electrolytes, which leads to lower energy density. To circumvent the small electrochemical stability window, highly concentrated “water-in-salt” (WIS) electrolytes, which demonstrate significantly wider stability window, were proposed and successfully applied to various aqueous energy storage systems including Li-ion and Zn metal batteries that are highly attractive for grid energy storage. However, since WIS electrolytes require large amounts of salt (often toxic) and have dramatically increased viscosity, it in turn limits their transport properties, charge-discharge rates, and usability in batteries.In this talk, the use of highly concentrated "water-in-salt" (WIS) electrolytes as a means of achieving increased charging efficiency and a wider stability window will be discussed in the context of aqueous Li-ion and Zn metal batteries. Further, we elaborate the role of cation solvation environment, electrolyte structure and hydrogen bonding on the physicochemical properties and electrochemical response of the system. We show that electrolyte composition affects the interfacial kinetics of Zn plating/stripping as well as the kinetics of the parasitic processes of electrolyte decomposition. Finally, we discuss how relatively dilute electrolytes can be engineered for efficient aqueous batteries. References Suo, O. Borodin, T. Gao, M. Olguin, J. Ho, X. Fan, C. Luo, C. Wang and K. Xu, Science, 2015, 350, 938Yamada, K. Usui, K. Sodeyama, S. Ko, Y. Tateyama and A. Yamada, Nat. Energy, 2016, 1, 16129R. Lukatskaya, J.I. Feldblyum, D.G. Mackanic, F. Lissel, D.L. Michels, Y. Cui, Z. Bao, Energy Environ. Sci., 2018, 11, 2876-2883 D.G. Vazquez, T. P. Pollard, J. Mars, J.M. Yoo, H.G. Steinrück, S. E. Bone, O. V. Safonova, M. F. Toney, O. Borodin, M.R. Lukatskaya, Energy Environ. Sci., 2023, DOI: 10.1039/D3EE00205E

Uniform Zinc Plating Enabled By Polyimide Nanofiber Network for Long-Life Aqueous Zinc Metal Batteries

The rapid development of portable electronics and emerging electric vehicles has created a pressing need for electrical energy storage systems. Among these systems, zinc metal batteries (ZMBs) have shown great potential due to their high theoretical capacity density, low reduction potential, and low-cost anodes. However, the large-scale application of rechargeable ZMBs has been limited by the well-known issues of dendrite growth and adverse side reactions in zinc metal electrodes[1].Various strategies have been proposed to overcome the challenges associated with zinc dendrite growth, including substrate structure optimization, surface modification of zinc metal, and design of novel electrolytes. Among these approaches, constructing a protective layer on the zinc anode surface is a promising strategy due to its simplicity and cost-effectiveness. A dense polyamide coating layer, prepared by the doctor blading method, has been developed to regulate the aqueous Zn deposition behavior by elevating the nucleation barrier and restricting the 2D diffusion of Zn2+ ions [2]. Additionally, an Al2O3 coating layer has been developed using atomic layer deposition to improve the rechargeability of Zn anodes for zinc-ion batteries (ZIBs)[3]. However, these dense layers face a significant challenge to ionic conductivity due to the high energy barrier that hinders the diffusion of Zn2+ ions, leading to poor battery performance, especially under high current densities.Herein, we report utilizing an electrospun polyimide network (noted as PI-Zn hereafter) to resolve this dilemma. The polyimide (PI) chain has numerous carbonyl oxygen atoms that function as electron donors, supported by theoretical calculations (Fig.1). These atoms can establish stable bonds with Zn ions, thereby reducing the activation energy for de-solvation and enhancing the kinetics of Zn ion deposition. Unlike traditional coating methods, our electrospinning polymers form a fiber-like network structure that provides ion channels, thereby enhancing ion transportation. From the Nyquist plots of symmetrical batteries (Fig. 2), the PI-Zn electrode exhibits smaller charge transfer resistance and lower activation energy compared to the bare Zn electrode. The Transmission X-Ray Microscope results (Fig.3) reveal that the deposition on the bare Zn is heterogeneous and dendritic. In contrast, the PI-Zn electrode presented a smooth surface and dendrite-free morphology. The result demonstrates that the charge transfer ability, de-solvation, and deposition kinetics have been improved by PI-Zn, which further increases the plating uniformity.The stability of the Zn anode was evaluated by long-term galvanostatic cycling of a symmetrical Zn cell (Fig. 4). The cell with bare Zn failed after cycling for 100 h at a current density of 1 mA cm-2 resulting from the short circuit. In comparison, the cell with PI-Zn exhibits a stable polarization voltage and an ultralong cycling life of over 1200 hours, indicating the extremely reversible plating/stripping enabled by the PI network. Further interrogation of the PI-Zn was carried out by stringent deep-discharge tests in symmetrical Zn cells under extremely high current density and capacity of 20 mA cm-2 and 10 mA h cm-2. The result shows that the cell with PI-Zn can cycle for more than 200 hours, two times longer than that with bare Zn, proving the advantages of the unique fiber-like network structure, which provides fast and homogeneous Zn ion transportation. Moreover, the fiber network effectively suppresses the hydrogen evolution reaction, verified by the corrosion test, despite the existence of numerous ion channels.Full prototype cells were assembled to prove the practical applications of our strategy. Two promising cathodes for aqueous ZIBs, MnVOH and MnO2, in two different electrolyte systems (Zn(OTf)2 and ZnSO4) were coupled with bare Zn or PI-Zn. For both systems, the capacity retention and Coulombic efficiency are both significantly improved with the help of PI network. The results are consistent with the lifespan difference of symmetrical Zn cells, as expected due to the same plating and stripping processes on Zn. These findings demonstrate that the strategy presented here stands to both dramatically extend battery cycle life and boost battery performance, a promising approach to solve the anode issues in advanced Zn batteries. Cao, Z., et al., Advanced Energy Materials, 2020. 10(30): p. 2001599. Zhao, Z., et al., Energy & Environmental Science, 2019. 12(6): p. 1938-1949. He, H., et al., Journal of materials chemistry A, 2020. 8(16): p. 7836-7846. Figure 1

Rechargeable Zn−MnO2 Batteries: Progress, Challenges, Rational Design, and Perspectives

AbstractAs a new type of secondary ion battery, aqueous zinc‐ion battery has a broad application prospect in the field of large‐scale energy storage due to its characteristics of low cost, high safety, environmental friendliness, and high‐power density. In recent years, manganese dioxide (MnO2)‐based materials have been extensively explored as cathodes for Zn‐ion batteries. Based on the research experiences of our group in the field of aqueous zinc ion batteries and combining with the latest literature of system, we systematically summarize the research progress of Zn−MnO2 batteries. This article first reviews the current research progress and reaction mechanism of Zn−MnO2 batteries, and then respectively expounds the optimization of MnO2 cathode, Zn anodes, and diverse electrolytes and their effects on battery performance. Additionally, primary challenges related to different components and their respective strategies for mitigating them are discussed, with the ultimate objective of offering comprehensive guidance for the design and fabrication of high‐performance Zn−MnO2 batteries. Finally, the future research and development direction of aqueous Zn−MnO2 batteries with high energy density, high safety and long life is envisioned.

Peptide Gel Electrolytes for Stabilized Zn Metal Anodes.

The rechargeable aqueous Zn ion battery (AZIB) is considered a promising candidate for future energy storage applications due to its intrinsic safety features and low cost. However, Zn dendrites and side reactions (e.g., corrosion, hydrogen evolution reaction, and inactive side product (Zn hydroxide sulfate) formation) at the Zn metal anode have been serious obstacles to realizing a satisfactory AZIB performance. The application of gel electrolytes is a common strategy for suppressing these problems, but the normally used highly cross-linked polymer matrix (e.g., polyacrylamide (PAM)) brings additional difficulties for battery assembly and recycling. Herein, we have developed a gel electrolyte for Zn metal anode stabilization, where a peptide matrix, a highly biocompatible material, is used for gel construction. Various experiments and simulations elucidate the sulfate anion-assisted self-assembly gel formation and its effect in stabilizing Zn metal anodes. Unlike polymer gel electrolytes, the peptide gel electrolyte can reversibly transform between gel and liquid states, thus facilitating the gel-involved battery assembly and recycling. Furthermore, the peptide gel electrolyte provides fast Zn ion diffusion (comparable to conventional liquid electrolyte) while suppressing side reactions and dendrite growth, thus achieving highly stable Zn metal anodes as validated in various cell configurations. We believe that our concept of gel electrolyte design will inspire more future directions for Zn metal anode protection based on gel electrolyte design.