Cell-nucleus structured electrolyte for low-temperature aqueous zinc batteries

Given their intrinsic safety, low cost, and high energy density, aqueous zinc (Zn) batteries hold substantial promise in large-scale energy storage applications. However, Zn dendrite formation and serious side reactions in metallic Zn anodes significantly compromise the reversibility of electrochemical Zn plating/stripping, restricting their lifespan and practical applications. Herein, we demonstrate that the polyvinyl alcohol (PVA) coated Zn anode can alleviate those issues. The PVA molecules at the Zn anode/electrolyte interface enable homogeneous Zn plating/stripping behavior by regulating the nucleation and ion diffusion barriers and effectively suppress the corrosion and hydrogen evolution reaction in mildly acidic electrolytes. As a result, a highly reversible and dendrite-free Zn anode can be obtained. The content of PVA plays a critical role in governing the cycling lifetime and stability. With the optimized content of PVA, stable Zn plating/stripping with a cycling capacity of 1 mAh cm-2 over 1500 hours has been achieved at 1 mA cm-2. In contrast, the bare Zn anode showed an unstable plating/stripping behavior with obvious polarization and limited cycling lifetime. Even at a high current density of 5 mA cm-2, the PVA-coated Zn anode remained stable for 1000 cycles. The present work provides a promising strategy to stabilize Zn anodes towards long-lifespan, cost-effective, and scalable aqueous rechargeable zinc-based batteries.

Aqueous rechargeable zinc batteries (ARZBs) are desirable for energy storage devices owing to their low cost and abundance of the Zn anode, but their further development is limited by a dearth of ideal cathode materials that can simultaneously possess high capacity and stability. Herein, we employ a layered structure of ammonium vanadium bronze (NH4)0.5V2O5 as the cathode material for ARZBs. The large interlayer distance supported by the NH4+ insertion not only facilitates the Zn2+-ion intercalation/deintercalation but also improves the electrochemical stability in ARZBs. As a result, the layered structural (NH4)0.5V2O5 cathode delivers a high capacity up to 418.4 mA h g-1 at a current density of 0.1 A g-1. A reversible capacity of 248.8 mA h g-1 is still retained after 2000 cycles and a capacity retention of 91.4% was maintained at 5 A g-1. Furthermore, in comparison with previously reported Zn-ion batteries, the Zn/(NH4)0.5V2O5 battery achieves a prominent high energy density of 418.4 W h kg-1 while delivering a high power density of 100 W kg-1. The results would enlighten and push the ammonium vanadium compounds to a brand new stage for the application of aqueous batteries.

Despite the impressive merits of low‐cost and high‐safety electrochemical energy storage for aqueous zinc ion batteries, researchers have long struggled against the unresolved issues of dendrite growth and the side reactions of zinc metal anodes. Herein, a new strategy of zinc‐electrolyte interface charge engineering induced by amino acid additives is demonstrated for highly reversible zinc plating/stripping. Through electrostatic preferential absorption of positively charged arginine molecules on the surface of the zinc metal anode, a self‐adaptive zinc‐electrolyte interface is established for the inhibition of water adsorption/hydrogen evolution and the guidance of uniform zinc deposition. Consequently, an ultra‐long stable cycling up to 2200 h at a high current density of 5 mA cm−2 is achieved under an areal capacity of 4 mAh cm−2. Even cycled at an ultra‐high current density of 10 mA cm−2, 900 h‐long stable cycling is still demonstrated, demonstrating the reliable self‐adaptive feature of the zinc‐electrolyte interface. This work provides a new perspective of interface charge engineering in realizing highly reversible bulk zinc anode that can prompt its practical application in aqueous rechargeable zinc batteries.

Crystal water improves electrochemical performance of the layered manganese oxide for aqueous rechargeable zinc batteries.

Metal–organic framework for dendrite-free anodes in aqueous rechargeable zinc batteries

Solid-electrolyte interphases (SEIs) are essential for stabilizing metal anodes in aqueous zinc (Zn) batteries (AZBs), yet their formation remains intrinsically uncontrolled, leaving the interphase vulnerable to dissolution and water-driven parasitic reactions. Herein, we report an electron-induced molecular programming strategy that uses only 1mM of 4-bromobenzenediazonium tetrafluoroborate (BDTF) to in situ construct a Zn2+-favored molecular lock on the ZnF2-rich SEI surface. Electrochemically generated p-bromoaniline becomes molecularly woven into the inorganic layer, forming an ultrathin molecular-lock shell (∼1nm) atop a graded hybrid SEI. Through N-Zn coordination coupled with Br-induced interfacial polarization, the molecular lock reorganizes the local electrostatic environment, stabilizes ZnF2, limits water access, and promotes desolvation-facilitated Zn2+ transport. As a result, the programmed SEI enables highly reversible Zn plating/stripping with a 99.8% average Coulombic efficiency, and stable cycling under 80% depth of discharge at 10mA cm- 2. Moreover, it displays broad cathode compatibility, extending cycling stability in vanadium-, manganese-, and iodine-based full cells. In Ah-level pouch cells with ultrahigh vanadium-based cathode loading (21mg cm-2), the system delivers 1.2 Ah with 81% retention after 100 cycles, surpassing state-of-the-art aqueous Zn batteries that typically fail at high mass loading.

With the advantages of low cost, good safety, and easy assembly, aqueous zinc batteries (AZBs) are expected to be a promising energy storage device. However, AZBs are compromised by Zn dendrites and the hydrogen evolution reaction. Herein, we use polyethylene glycol-200 (PEG-200) and benzylidene acetone (BDA) as additives in the electrolyte of AZBs in order to inhibit Zn dendrite growth and side reactions, thus improving the cycle performance of the Zn electrode. PEG-200 can be not only used as a co-solvent for BDA but also as a surfactant to achieve a uniform interfacial electric field. As a brightening agent, BDA forms a diffusion layer on the plating substrate, which increases the electrochemical polarization and nucleation overpotential, increases the number of active nucleation sites, and finally refines the grain size of the zinc deposit. The surface of the symmetric battery electrode with electrolyte containing PEG-200 additive is smooth after cycling, and dendrite formation is successfully suppressed. The Zn–Zn symmetric cell with additive-containing electrolyte has a higher nucleation overpotential and a cyclic stability for as long as 890 h (only 48 h for the unmodified symmetric cell). This is due to the adsorption of the additive on the negative electrode, which homogenizes the deposition interface and reduces the contact of the negative electrode with water.

Artificial solid electrolyte interphase for thermally stable rechargeable aqueous zinc batteries

Regulating the redox reversibility of zinc anode toward stable aqueous zinc batteries

Towards reusable 3D-printed graphite framework for zinc anode in aqueous zinc battery

Aqueous zinc batteries (ZIBs) have attracted considerable attention in recent years because of their high safety and eco-friendly features. Numerous studies have shown that adding Mn2+ salts to ZnSO4 electrolytes enhanced overall energy densities and extended the cycling life of Zn/MnO2 batteries. It is commonly believed that Mn2+ additives in the electrolyte inhibit the dissolution of MnO2 cathode. To better understand the role of Mn2+ electrolyte additives, the ZIB using a Co3 O4 cathode instead of MnO2 in 0.3m MnSO4 + 3m ZnSO4 electrolyte is built to avoid interference from MnO2 cathode. As expected, the Zn/Co3 O4 battery exhibits electrochemical characteristics nearly identical to those of Zn/MnO2 batteries. Operando synchrotron X-ray diffraction (XRD), ex situ X-ray absorption spectroscopy (XAS), and electrochemical analyses are carried out to determine the reaction mechanism and pathway. This work demonstrates that the electrochemical reaction occurring at cathode involves a reversible Mn2+ /MnO2 deposition/dissolution process, while a chemical reaction of Zn2+ /Zn4 SO4 (OH)6 ∙5H2 O deposition/dissolution is involved during part of the charge/discharge cycle due to the change in the electrolyte environment. The reversible Zn2+ /Zn4 SO4 (OH)6 ∙5H2 O reaction contributes no capacity and lowers the diffusion kinetics of the Mn2+ /MnO2 reaction, which prevents the operation of ZIBs at high current densities.

Zn interfacial issues involved dendrite evolution and undesired parasitic reactions are tough challenges to impede the progress of Zn ion battery. Herein, dendrite‐free Zn anode with boosted stability is achieved by four‐in‐one functional additive triethyl phosphate (TEP). Experiments and theoretical calculation reveal that TEP additive participates in the generation of compact inorganic interface to prevent Zn from corrosion. Meanwhile, the interfacial electrical double layer (EDL) is reconstructed with adsorbed TEP molecules in inner layer and weakened Zn2+ solvation structure in diffusion layer, which efficiently shields Zn from active H2O and moderate electrochemical kinetics, thereby preventing water‐related secondary reaction and Zn electroplating on tip region. Additionally, TEP additive manipulates zinc growth direction by adsorbing on the (002) facet, thus enabling long‐lasting dendrite‐free deposition. Accordingly, Zn||Zn symmetric cell demonstrates an ultralong lifespan over 5000 h (almost 7 months) at 1 mA cm−2, 1 mAh cm−2 and remarkable coulombic efficiency (CE) of ≈97.6% for 1500 cycles. For practical demonstration, Zn||LiFePO4 full cell demonstrates an improved rate capability and an elevated capacity of 116.0 mAh g−1. These findings highlight interface chemistry manipulated by multifunctional additives as an efficient approach to stabilize Zn anode, holding promise for top‐notch Zn‐based batteries with improved longevity.

Aqueous zinc batteries have emerged as promising alternatives to conventional lithium-ion batteries, offering an environmentally friendly and cost-effective solution to our growing energy storage needs. However, one of the critical obstacles to realizing their full potential lies in addressing the dendritic structure growth challenges within zinc batteries. These dendrites, unwanted metal protrusions that form during the charging and discharging cycles, can lead to adverse implications, including short circuits, reduced battery performance, and safety concerns. To overcome these challenges, researchers and engineers have been diligently devising strategies. This paper delves into the complexities of dendrite formation in aqueous zinc batteries, outlining their adverse implications for battery performance and safety. Various strategies to address the dendrite challenge are explored, with a focus on their effectiveness and limitations. One promising avenue involves developing innovative three-dimensional (3D) structural designs within the battery architecture to inhibit dendrite formation. Conclusively, harnessing the potential of aqueous zinc batteries hinges on the successful mitigation of dendrite formation through the concerted implementation of ingenious 3D structural designs and other innovative strategies, steering the pathway towards safer and more efficient energy storage solutions.

An increasingly growing market for electricity energy will be projected to double by 2050. Renewable energies, such as solar and wind, can be an effective way to address the challenge. However, the incompatibility between generation and consumption of electricity arises a considerable trouble when a huge amount of electricity coming from renewable sources finds no users, which could result in miserable failure of an aging grid. To secure the grid, the utilization and development of efficient energy storage technologies are highly demanded. Among the energy storage system (ESS), aqueous Zinc (Zn) batteries based organic material cathode have been regarded as an attractive candidate on account of its outstanding superiorities compared with inorganic compounds. Although it has gained huge success in lab‐scale, the long‐standing challenges like inferior energy density, low power density, narrow operation temperature range and poor cycling life still restrict their practical application in aqueous Zn batteries (AZBs). In this minireview, we firstly provide a comprehensive insight into the different storage mechanisms that are proposed in varieties of organic cathodes. Based on the clear understanding on mechanisms, we further summarize the major progress and offer several promising research directions on promoting electrochemical performance of Zn‐organic batteries.

Rechargeable aqueous zinc (Zn) batteries are a promising candidate for large‐scale energy storage, but the noncompact and dendritic Zn deposition, water‐induced parasitic reaction, and narrow operating temperature range severely hinder their practical application. Here, it is demonstrated that these challenges can be conquered by introducing low‐cost acetamide (Ace) into aqueous electrolytes. The non‐sacrificial Ace molecules with both donor and acceptor groups can disrupt the original H‐bonded network of water, replace the solvating‐H2O in Zn2+‐solvation sheath, form dynamic adsorption on Zn, and create an H2O‐poor electrical double‐layer. Consequently, the presence of Ace suppresses water erosion on Zn, homogenizes Zn nucleation/growth, reduces water reactivity, and depresses the freezing point of electrolyte. The formulated Ace‐containing electrolyte features a wide temperature range from −20 to 60 °C and enables highly compact and dendrite‐free Zn electrodeposition even at 25 mAh cm−2 using a non‐pressure electrolytic cell. Moreover, the Ace‐containing electrolyte allows Zn electrodes to achieve a long‐term lifespan across −20–60 °C and excellent deep cycling stability under 85.3% depth‐of‐discharge (25 mAh cm−2) with over 400 h, and supports the stable operation of Zn–Iodine full batteries under harsh conditions.