Anode Material For Aqueous Batteries Research Articles

A multifunctional protective layer filled with 2D anionic nanosheets enabling a dendrite-free zinc anode

Metallic zinc (Zn) has been considered as an ideal anode material for aqueous batteries, but its development is hampered by the growth of Zn dendrites and side reactions with aqueous electrolytes.

Heterostructured Interface Enables Uniform Zinc Deposition for High-Performance Zinc-Ion Batteries.

Zinc metal has considerable potential as a high-energy anode material for aqueous batteries due to its high theoretical capacity and environmental friendliness. However, dendrite growth and parasitic reactions at the electrode/electrolyte interface remain two serious problems for the Zn metal anode. Here, the heterostructured interface of ZnO rod array and CuZn5 layer is fabricated on the Zn substrate (ZnCu@Zn) to address these two issues. The zincophilic CuZn5 layer with abundant nucleation sites ensures the initial uniform Zn nucleation process during cycling. Meanwhile, the ZnO rod array grown on the surface of the CuZn5 layer can guide the subsequent homogeneous Zn deposition via spatial confinement and electrostatic attraction effects, leading to the dendrite-free Zn electrodeposition process. Consequently, the derived ZnCu@Zn anode exhibits an ultra-long lifespan of up to 2500h with symmetric cells at the current density and capacity of 0.5mAcm-2 /0.5mAhcm-2 . Besides, a remarkable cyclability (75% retention for 2500 cycles at 2Ag-1 ) is achieved in the ZnCu@Zn||MnO2 full cell with a capacity of 139.7mAhg-1 . This heterostructured interface with specific functional layers provides a feasible strategy for the design of high-performance metal anodes.

In-situ grown porous protective layers with high binding strength for stable Zn anodes

Zinc (Zn) metal is a promising anode material for aqueous batteries. Unfortunately, undesirable issues such as dendrite growth, intricate side reactions, and limited reversibility restrict its large-scale applications. Herein, a porous ZIF-8 protecting layer is in-situ constructed on the Zn surface (named as Zn@ZIF8) to effectively manipulate the Zn plating/stripping behavior. The in-situformation of porous ZIF-8 layer not only shows excellent bonding strength with Zn substrate but also affords low nucleation overpotential and uniform Zn2+ electrolyte flux and reduces intricate side reactions, thus leading to homogeneous Zn plating/stripping behavior. These merits enable substantially stable symmetric Zn cells and Zn-based electrochemical energy storage devices. In detail, the Zn ion capacitor based on Zn@ZIF8 anodes demonstrates superior cycling stability (∼100% capacity retention after 20 000 cycles), much better than those with bare Zn anodes. This work presents a facile and effective approach for manipulating Zn dendrites growth and realizing ultra-stable Zn-based batteries.

Dendrites-Free Zn Metal Anodes Enabled by an Artificial Protective Layer Filled with 2D Anionic Nanosheets.

Metallic zinc (Zn) has been considered to be an ideal anode material for aqueous batteries, but is impeded by the growth of Zn dendrites and its side reactions with an aqueous electrolyte. Here, it is reported that an artificial protective layer filled with novel 2D Zn2+ adsorbed Sb3 P2 O14 3- (denoted as Zn-Sb3 P2 O14 ) nanosheets provide an effective route to mitigate the above challenging problems. The Zn-Sb3 P2 O14 protection layer not only avoids the direct contact with the aqueous electrolyte to suppress the side reactions but also allows for Zn-ions to pass through the protection layer rapidly. Moreover, the 2D Sb3 P2 O14 3- skeleton with negative charge also confines the 2D diffusion of Zn-ion along the lateral surface of Zn anode, resulting in a uniform electron-deposition. This unique protection layer not only enables dendrite-free Zn plating/stripping with an average Coulombic efficiency of 99.2% for 200 cycles, but also sustains the symmetric Zn||Zn cell over 1300 h at 1mA cm-2 and 1 mAh cm-2 as well as for 450 h at 10mA cm-2 and 10 mAh cm-2 . Such advantages bring high reversibility to full Zn batteries with MnO2 cathodes, which deliver a discharge capacity of 111.7 mAh g-1 after 1000 cycles.

Highly reversible and dendrite-free Zn electrodeposition enabled by a thin metallic interfacial layer in aqueous batteries

• A thin metallic interfacial layer enables highly reversible Zn electrodeposition. • High average Coulombic efficiency of 99.7% for 3000 cycles is achieved at 1 mAh cm −2 . • Dendrite-free Zn electrodeposition for 2500 cycles is attained at 1 mA cm −2 . Zinc (Zn) metal is regarded as a promising anode material for aqueous batteries owing to its high natural abundance, high theoretical capacity and low redox potential. However, aqueous Zn metal anodes suffer from poor reversibility, as shown by their low Coulombic efficiency (CE) and dendrite growth during long-term plating/stripping. In this study, we report that a thin metallic Cu or Ag interfacial layer, made by a facile thermal evaporation method, can enable highly reversible and nondendritic plating/stripping of Zn metal anodes in aqueous batteries. This is attributed to the synergy of fast Zn-ion migration through the tiny gaps in the interfacial layer as well as its high interfacial affinity for Zn metal. High average CE of 99.7% are achieved over 3000 plating/stripping cycles at 10 mA cm −2 and 1 mAh cm −2 . The modified Zn anode can stably cycle for more than 2500 cycles (5000 h) of plating/stripping at 1 mA cm −2 and a 500 cycle-life is realized for a full cell paired with a MnO 2 cathode. This finding opens up a promising avenue to develop the next-generation Zn metal-based energy storage technologies.

(Europe Section Alessandro Volta Medal Award) Electrolytes and Metallic Anodes: About an Old Argument That Marks the Fundamental Understanding of Modern Metal Anodes in Advanced Battery Systems

Simple, yet meaningful, experiments, already carried out in the 18th century by Galvani and Volta, are at the very base of modern batteries that shape our society. From the very first muscle twitch to batteries found nowadays in nearly every part of modern life, with the best known example of a modern battery represented by the lithium ion battery (LIB), the same basic principles are present. The comparably fast and seminal development of LIBs through assiduous collective efforts was granted the 2019 Nobel Prize in Chemistry.[1] Besides all modern perspectives, fundamental principles are still being derived from the early works of Volta and Galvani, which have not been always in agreement.Because the LIB technology is more and more approaching its ceiling in terms of specific energy (Wh kg−1) and energy density (Wh L−1) imposed by the nature of intercalation chemistry, metal-based anodes, such as Li, Na, Mg, Ca, Zn and Al, are currently considered for the next evolutional step of battery technology.[2,3,4] Independent of the chosen materials, the chemistry of the anodes (graphite, silicon or metal anodes) with the electrolyte plays a crucial role in the development of the batteries. In LIBs, the formation of a solid electrolyte interphase (SEI) on graphite in organic media induced by an external current/voltage and involving the reduction of the electrolyte components was key for the stable operation of such anodes.[5] Similar processes for metal-based anodes do not necessarily require electrode polarization conditions and can occur spontaneously. For example, supplementary to SEI formation on the Li surface, induced by the extremely low redox potential of metallic lithium (−3.04 V vs. SHE), other processes of Li deterioration, namely galvanic corrosion (worth also considering here: dendrite growth, volume changes of the Li anode, low Coulombic efficiency), have to be scrutinized. Recently, battery researchers revisited the corrosion phenomena in lithium metal batteries (LMBs).[6,7] A systematic study focused on the corrosion-related processes in model Li anodes (using Li powder) revealed the great significance that such processes exercise on the performance of LMBs.[7]From a different perspective, flammable non-aqueous electrolytes, widely used in the LIB/LMB systems, are causing increased safety concerns. As an alternative, Zn has been regarded as a potential anode material for aqueous batteries because of its high theoretical volumetric capacity and suitable redox potential (−0.76 V vs. SHE), along with an intrinsic safety from the aqueous electrolyte nature. Similar to the Li anode in nonaqueous electrolytes, the Zn anode has also long-standing challenges in conventional alkaline electrolytes, such as chemical instability (e.g. corrosion) and electrochemical irreversibility (e.g. non-uniform electrodeposition/-dissolution, dendrite growth).[8]In this perspective, the two worlds of Li-based and Zn-based battery systems are united and attributed to the lessons by Volta and Galvani. Metals from the Volta pile (Cu and Zn) and modern metals (Li) are discussed side by side and in correlation to each other. Solutions to address their challenges, and thus overcome the barriers of their application, in rechargeable systems will be highlighted. It is emphasized that the combination of metals (e.g. Li) with metal ions (e.g. Zn2+) can result in formation of intermetallic phases, able to improve stability of the electrodes under cell operation conditions. This can further result in an increase in safety and cycle life of the batteries utilizing metals as negative electrodes.[9] Special attention will be also given to the obstacles caused by the alkaline electrolytes with focus on the fundamental understanding of Zn reaction mechanisms. Approaches to overcome the challenges are presented and evaluated for their potential to facilitate further research and development of electrolytes in these systems.

Deeply Rechargeable and Hydrogen-Evolution-Suppressing Zinc Anode in Alkaline Aqueous Electrolyte.

Metallic zinc as a rechargeable anode material for aqueous batteries has gained tremendous attention. Zn-air batteries, which operate in alkaline electrolytes, are promising with the highest theoretical volumetric energy density. However, rechargeable zinc anodes develop slowly in alkaline electrolytes due to passivation, dissolution, and hydrogen evolution issues. In this study, we report the design of a submicron zinc anode sealed with an ion-sieving coating that suppresses hydrogen evolution reaction. The design is demonstrated with ZnO nanorods coated by TiO2, which overcomes passivation, dissolution, and hydrogen evolution issues simultaneously. It achieves superior reversible deep cycling performance with a high discharge capacity of 616 mAh/g and Coulombic efficiency of 93.5% when cycled with 100% depth of discharge at lean electrolyte. It can also deeply cycle ∼350 times in a beaker cell. The design principle of this work may potentially be applied to other battery electrode materials.

An approaching-theoretical-capacity anode material for aqueous battery: Hollow hexagonal prism Bi2O3 assembled by nanoparticles

At present, various strategies are utilized to improve the specific capacity of electrode materials to overcome the low energy density problem of aqueous battery, while their specific capacity is still far away from the theoretical value, especially for anode materials. Herein, we designed and synthesized nanoparticles assembled hollow hexagonal prism Bi2O3 (HHP Bi2O3) through template inducing synthesis. When used as an anode material for aqueous battery, it demonstrated a remarkable specific capacity of 327 mAh/g at 1 A/g, which reaches 94.8% of its theoretical capacity and is the highest value of its kind. Besides the high specific capacity, the as-fabricated HHP Bi2O3 also exhibits superior rate capability (220 mAh/g at 20 A/g) and long-term stability (~80%, 3000 cycles). Such high performance originates from high atom utilization and fast reaction kinetics for electrochemical reaction brought by its unique structures. Notably, when the HHP Bi2O3 is paired with the cathode material NixCo1-x (OH)2 to form an aqueous alkaline battery, its high electrochemical property is well exhibited. The designed HHP Bi2O3 with scalable synthesis process provides guidance for the preparation of other high capacity energy-storage materials, and paves the way to promote their practicality.

Visualising and Characterising Zinc Ion Transport for Zinc Ion Batteries By Fluorescence Microscopy

Zinc has been regarded as a promising anode material for aqueous batteries in view of its advantages including high specific capacity, abundance and intrinsic safety. Aqueous zinc ion batteries have attracted growing attention as a potential alternative to lithium ion batteries, especially for medium and large-scale energy storage. Aqueous zinc ion batteries consist of a zinc anode and a zinc intercalating cathode in a zinc-salt-containing electrolyte and use zinc ions as charge carriers. The electrolyte transporting zinc ions between the anode and the cathode plays an essential role in determining battery performance and life. Visualising ion transport in the electrolytes of zinc ion batteries can give insights into electrolyte dynamics as well as battery processes. Yet, this is limited by the spatial-temporal resolution of the existing techniques. Moreover, most of the existing in-situ visualisation techniques are very expensive and not easily accessible. Fluorescence microscopy provides a powerful tool for probing tiny structures and tracking species in real time. It relies on fluorescence which occurs when molecules absorb light with a certain wavelength followed by the re-emission of light with a longer wavelength. These excitation and emission wavelengths are usually unique fingerprints of certain substances. Fluorescent sensors, with high sensitivity of fluorescence assays, have been widely exploited as a useful tool for species detection and mechanistic studies in biology and chemistry. In this study, a novel microfluidics-based fluorescence microscopy platform is developed for visualising and characterising zinc ion transport in the electrolytes of zinc ion batteries. The platform is calibrated by comparing the measurement results with the literature data. Key transport properties of zinc ions are quantified under different electrolyte conditions. The developed platform is demonstrated to be a simple and versatile tool for electrolyte characterisation, which provides key information guiding future electrolyte development and battery performance improvement.

Highly reversible zinc metal anode for aqueous batteries.

Metallic zinc (Zn) has been regarded as an ideal anode material for aqueous batteries because of its high theoretical capacity (820 mA h g-1), low potential (-0.762 V versus the standard hydrogen electrode), high abundance, low toxicity and intrinsic safety. However, aqueous Zn chemistry persistently suffers from irreversibility issues, as exemplified by its low coulombic efficiency (CE) and dendrite growth during plating/ stripping, and sustained water consumption. In this work, we demonstrate that an aqueous electrolyte based on Zn and lithium salts at high concentrations is a very effective way to address these issues. This unique electrolyte not only enables dendrite-free Zn plating/stripping at nearly 100% CE, but also retains water in the open atmosphere, which makes hermetic cell configurations optional. These merits bring unprecedented flexibility and reversibility to Zn batteries using either LiMn2O4 or O2 cathodes-the former deliver 180 W h kg-1 while retaining 80% capacity for >4,000 cycles, and the latter deliver 300 W h kg-1 (1,000 W h kg-1 based on the cathode) for >200 cycles.

Morphology and Phase Changes in Iron Anodes Affecting their Capacity and Stability in Rechargeable Alkaline Batteries

Rechargeable alkaline batteries may become attractive nonflammable alternatives to lithium-ion (Li-ion) batteries for applications where achieving the highest energy density is less critical than safety, environmental friendliness, and low cost of energy storage. The broad abundance and low price of iron (Fe) make it attractive as a rechargeable anode material for aqueous batteries. Through cyclic voltammetry and post-mortem analysis, we revealed four distinct stages of Fe anode evolution: development, retention, fading, and failure, where each stage is associated with very specific changes in the morphology and phase of Fe anodes. We observed the Fe particle fragmentation resulted in the capacity increase during the initial cycles of charge–discharge. Most importantly, we discovered the irreversible formation of maghemite (γ-Fe2O3) with low reactivity is responsible for the eventual Fe anode capacity fading. This unexpected discovery changes the paradigm on possible routes to stabilize Fe anodes and cont...

Direct Growth of Bismuth Film as Anode for Aqueous Rechargeable Batteries in LiOH, NaOH and KOH Electrolytes.

As promising candidates for next-generation energy storage devices, aqueous rechargeable batteries are safer and cheaper than organic Li ion batteries. But due to the narrow voltage window of aqueous electrolytes, proper anode materials with low redox potential and high capacity are quite rare. In this work, bismuth electrode film was directly grown by a facile hydrothermal route and tested in LiOH, NaOH and KOH electrolytes. With low redox potential (reduction/oxidation potentials at ca. −0.85/−0.52 V vs. SCE, respectively) and high specific capacity (170 mAh·g−1 at current density of 0.5 A·g−1 in KOH electrolyte), Bi was demonstrated as a suitable anode material for aqueous batteries. Furthermore, by electrochemical impedance spectroscopy (EIS) analysis, we found that with smaller Rs and faster ion diffusion coefficient, Bi electrode film in KOH electrolyte exhibited better electrochemical performance than in LiOH and NaOH electrolytes.