Zinc ion Batteries: Bridging the Gap from Academia to Industry for Grid-Scale Energy Storage.

Zinc ion batteries (ZIBs) exhibit significant promise in the next generation of grid-scale energy storage systems owing to their safety, relatively high volumetric energy density, and low production cost. Despite substantial advancements in ZIBs, a comprehensive evaluation of critical parameters impacting their practical energy density (Epractical) and calendar life is lacking. Hence, we suggest using formulation-based study as a scientific tool to accurately calculate the cell-level energy density and predict the cycling life of ZIBs. By combining all key battery parameters, such as the capacity ratio of negative to positive electrode (N/P), into one formula, we assess their impact on Epractical. When all parameters are optimized, we urge to achieve the theoretical capacity for a high Epractical. Furthermore, we propose a formulation that correlates the N/P and Coulombic efficiency of ZIBs for predicting their calendar life. Finally, we offer a comprehensive overview of current advancements in ZIBs, covering cathode and anode, along with practical evaluations. This Minireview outlines specific goals, suggests future research directions, and sketches prospects for designing efficient and high-performing ZIBs. It aims at bridging the gap from academia to industry for grid-scale energy storage.

The effect of Ge doping concentration on the electrochemical performance of silicene anode for lithium-ion batteries: a first-principles study.

Two-dimensional materials have been considered as novel anode materials for LIBs because of their large surface area, small volume change, and low Li diffusion barrier. Among them, the two-dimensional material SixGey has many excellent properties as an anode. However, Ge is expensive and not suitable for mass production. Therefore, proper Ge doping is of great significance to improve performance and reduce cost. Herein, we systematically study the effect of Ge doping and its concentration on the structure and electrochemical performance of two-dimensional SixGey by density functional theory (DFT) calculations. The incorporation of low concentration Ge can improve the horizontal and vertical diffusion ability of Li atoms compared to silicene. However, excessive Ge will increase the horizontal diffusion energy barrier of Li and reduce the theoretical capacity, where Si6Ge2 has a relatively high theoretical capacity and a low diffusion energy barrier. In addition, fully lithiated 2D SixGey shows poor electrical conductivity and increasing Ge concentration seems to be effective in improving the electrical conductivity of the material. This study will provide significant theoretical guidance for the design and preparation of two-dimensional silicon-based materials.

Solvent control of water O-H bonds for highly reversible zinc ion batteries.

Aqueous Zn-ion batteries have attracted increasing research interest; however, the development of these batteries has been hindered by several challenges, including dendrite growth, Zn corrosion, cathode material degradation, limited temperature adaptability and electrochemical stability window, which are associated with water activity and the solvation structure of electrolytes. Here we report that water activity is suppressed by increasing the electron density of the water protons through interactions with highly polar dimethylacetamide and trimethyl phosphate molecules. Meanwhile, the Zn corrosion in the hybrid electrolyte is mitigated, and the electrochemical stability window and the operating temperature of the electrolyte are extended. The dimethylacetamide alters the surface energy of Zn, guiding the (002) plane dominated deposition of Zn. Molecular dynamics simulation evidences Zn2+ ions are solvated with fewer water molecules, resulting in lower lattice strain in the NaV3O8·1.5H2O cathode during the insertion of hydrated Zn2+ ions, boosting the lifespan of Zn|| NaV3O8·1.5H2O cell to 3000 cycles.

Regulating the reduction reaction pathways via manipulating the solvation shell and donor number of the solvent in Li-CO2 chemistry.

Transforming CO2 into valuable chemicals is an inevitable trend in our current society. Among the viable end-uses of CO2, fixing CO2 as carbon or carbonates via Li-CO2 chemistry could be an efficient approach, and promising achievements have been obtained in catalyst design in the past. Even so, the critical role of anions/solvents in the formation of a robust solid electrolyte interphase (SEI) layer on cathodes and the solvation structure have never been investigated. Herein, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in two common solvents with various donor numbers (DN) have been introduced as ideal examples. The results indicate that the cells in dimethyl sulfoxide (DMSO)-based electrolytes with high DN possess a low proportion of solvent-separated ion pairs and contact ion pairs in electrolyte configuration, which are responsible for fast ion diffusion, high ionic conductivity, and small polarization. The 3 M DMSO cell delivered the lowest polarization of 1.3 V compared to all the tetraethylene glycol dimethyl ether (TEGDME)-based cells (about 1.7 V). In addition, the coordination of the O in the TFSI- anion to the central solvated Li+ ion was located at around 2 Å in the concentrated DMSO-based electrolytes, indicating that TFSI- anions could access the primary solvation sheath to form an LiF-rich SEI layer. This deeper understanding of the electrolyte solvent property for SEI formation and buried interface side reactions provides beneficial clues for future Li-CO2 battery development and electrolyte design.

Organic pH Buffer for Dendrite-Free and Shuttle-Free Zn-I2 Batteries.

Aqueous Zn-Iodine (I2 ) batteries are attractive for large-scale energy storage. However, drawbacks include, Zn dendrites, hydrogen evolution reaction (HER), corrosion and, cathode "shuttle" of polyiodines. Here we report a class of N-containing heterocyclic compounds as organic pH buffers to obviate these. We evidence that addition of pyridine /imidazole regulates electrolyte pH, and inhibits HER and anode corrosion. In addition, pyridine and imidazole preferentially absorb on Zn metal, regulating non-dendritic Zn plating /stripping, and achieving a high Coulombic efficiency of 99.6 % and long-term cycling stability of 3200 h at 2 mA cm-2 , 2 mAh cm-2 . It is also confirmed that pyridine inhibits polyiodines shuttling and boosts conversion kinetics for I- /I2 . As a result, the Zn-I2 full battery exhibits long cycle stability of >25 000 cycles and high specific capacity of 105.5 mAh g-1 at 10 A g-1 . We conclude organic pH buffer engineering is practical for dendrite-free and shuttle-free Zn-I2 batteries.

Monolithic Phosphate Interphase for Highly Reversible and Stable Zn Metal Anode.

Zinc metal battery (ZMB) is promising as the next generation of energy storage system, but challenges relating to dendrites and corrosion of the zinc anode are restricting its practical application. Here, to stabilize Zn anode, we report a controlled electrolytic method for a monolithic solid-electrolyte interphase (SEI) via a high dipole moment solvent dimethyl methylphosphonate (DMMP). The DMMP-based electrolytes can generate a homogeneous and robust phosphate SEI (Zn3 (PO4 )2 and ZnP2 O6 ). Benefiting from the protecting impact of this in situ monolithic SEI, the zinc electrode exhibits long-term cycling of 4700 h and a high Coulombic efficiency 99.89 % in Zn|Zn and Zn|Cu cell, respectively. The full V2 O5 |Zn battery with DMMP-H2 O hybrid electrolyte exhibits a high capacity retention of 82.2 % following 4000 cycles under 5 A g-1 . The first success in constructing the monolithic phosphate SEI will open a new avenue in electrolyte design for highly reversible and stable Zn metal anodes.

Understanding H2 Evolution Electrochemistry to Minimize Solvated Water Impact on Zinc-Anode Performance.

H2 evolution is the reason for poor reversibility and limited cycle stability with Zn-metal anodes, and impedes practical application in aqueous zinc-ion batteries (AZIBs). Here, using a combined gas chromatography experiment and computation, it is demonstrated that H2 evolution primarily originates from solvated water, rather than free water without interaction with Zn2+ . Using linear sweep voltammetry (LSV) in salt electrolytes, H2 evolution is evidenced to occur at a more negative potential than zinc reduction because of the high overpotential against H2 evolution on Zn metal. The hypothesis is tested and, using a glycine additive to reduce solvated water, it is confirmed that H2 evolution and "parasitic" side reactions are suppressed on the Zn anode. This electrolyte additive is evidenced to suppress H2 evolution, reduce corrosion, and give a uniform Zn deposition in Zn|Zn and Zn|Cu cells. It is demonstrated that Zn|PANI (highly conductive polyaniline) full cells exhibit boosted electrochemical performance in 1 M ZnSO4 -3 M glycine electrolyte. It is concluded that this new understanding of electrochemistry of H2 evolution can be used for design of relatively low-cost and safe AZIBs for practical large-scale energy storage.

From room temperature to harsh temperature applications: Fundamentals and perspectives on electrolytes in zinc metal batteries.

As one of the most competitive candidates for the next-generation energy storage systems, the emerging rechargeable zinc metal battery (ZMB) is inevitably influenced by beyond-room-temperature conditions, resulting in inferior performances. Although much attention has been paid to evaluating the performance of ZMBs under extreme temperatures in recent years, most academic electrolyte research has not provided adequate information about physical properties or practical testing protocols of their electrolytes, making it difficult to assess their true performance. The growing interest in ZMBs is calling for in-depth research on electrolyte behavior under harsh practical conditions, which has not been systematically reviewed yet. Hence, in this review, we first showcase the fundamentals behind the failure of ZMBs in terms of temperature influence and then present a comprehensive understanding of the current electrolyte strategies to improve battery performance at harsh temperatures. Last, we offer perspectives on the advance of ZMB electrolytes toward industrial application.

Electrolyte Engineering Enables High Performance Zinc-Ion Batteries.

Zinc-ion batteries (ZIBs) feature high safety, low cost, environmental-friendliness, and promising electrochemical performance, and are therefore regarded as a potential technology to be applied in large-scale energy storage devices. However, ZIBs still face some critical challenges and bottlenecks. The electrolyte is an essential component of batteries and its properties affect the mass transport, energy storage mechanisms, reaction kinetics, and side reactions of ZIBs. The adjustment of electrolyte formulas usually has direct and obvious impacts on the overall output and performance. In this review, advanced electrolyte strategies are overviewed for optimizing the compatibility between cathode materials and electrolytes, inhibiting anode corrosion and dendrite growth, extending electrochemical stability windows, enabling wearable applications, and enhancing temperature tolerance. The underlying scientific mechanisms, electrolyte design principles, and recent progress are presented to provide a better understanding and inspiration to readers. In addition, a comprehensive perspective about electrolyte design and engineering for ZIBs is included.

Electron-Injection-Engineering Induced Phase Transition toward Stabilized 1T-MoS2 with Extraordinary Sodium Storage Performance.

Phase transition engineering, with the ability to alter the electronic structure and physicochemical properties of materials, has been widely used to achieve the thermodynamically unstable metallic phase MoS2 (1T-MoS2), although the complex operating conditions and low yield of previous strategies make the large-scale fabrication of 1T-MoS2 a big challenge. Herein, we report a facile electron injection strategy for phase transition engineering and fabricate a composite of conductive TiO chemically bonded to 1T-MoS2 nanoflowers (TiO-1T-MoS2 NFs) on a large scale. The underlying mechanism analysis reveals that electron-injection-engineering triggers a reorganization of the Mo 4d orbitals and results in a 100% phase transition of MoS2 from 2H to 1T. In the TiO-1T-MoS2 NFs composite, the 1T-MoS2 demonstrates a higher electronic conductivity, a lower Na+ diffusion barrier, and a more restricted S release than 2H-MoS2. In addition, conductive TiO bonding successfully resolves the stability challenge of the 1T phase. These merits endow TiO-1T-MoS2 NFs electrodes with an excellent rate capability (650/288 mAh g-1 at 50/20 000 mA g-1, respectively) and an outstanding cyclability (501 mAh g-1 at 1000 mA g-1 after 700 cycles) in sodium ion batteries. Such an improvement signifies that this facile and scalable phase-transition engineering combined with a deep mechanism analysis offers an important reference for designing advanced materials for various applications.

Lithium Metal Electrode with Increased Air Stability and Robust Solid Electrolyte Interphase Realized by Silane Coupling Agent Modification.

The quality of the solid electrolyte interphase (SEI) layer is the decisive factor for the electrochemical performance of Li-metal-based batteries. Due to the absence of effective bonding, a natural SEI layer may exfoliate from the Li anode during interfacial fluctuations. Here, a silane coupling agent is introduced to serve as an adhesion promoter to bridge these two dissimilar materials via both chemical bonding and physical intertwining effects. Its inorganic reactive groups can combine with the Li substrate by forming LiOSi bonds, while organic functional groups can take part in the formation of the SEI layer and thereby bond with SEI components. Li metal electrodes with silane coupling agent modification exhibit excellent electrochemical performance, even under extreme testing conditions. This modification layer with dense structure could also protect the Li metal from corrosion by air, evidenced by the comparable electrochemical activity of the modified Li metal electrodes even after being exposed in air for 2 h. This design provides a promising pathway for the development of Li metal electrodes that will be stable both in electrolyte and in air.

Electrolyte Design for In Situ Construction of Highly Zn2+ -Conductive Solid Electrolyte Interphase to Enable High-Performance Aqueous Zn-Ion Batteries under Practical Conditions.

Rechargeable aqueous Zn-ion batteries promise high capacity, low cost, high safety, and sustainability for large-scale energy storage. The Zn metal anode, however, suffers from the dendrite growth and side reactions that are mainly due to the absence of an appropriate solid electrolyte interphase (SEI) layer. Herein, the in situ formation of a dense, stable, and highly Zn2+ -conductive SEI layer (hopeite) in aqueous Zn chemistry is demonstrated, by introducing Zn(H2 PO4 )2 salt into the electrolyte. The hopeite SEI (≈140 nm thickness) enables uniform and rapid Zn-ion transport kinetics for dendrite-free Zn deposition, and restrains the side reactions via isolating active Zn from the bulk electrolyte. Under practical testing conditions with an ultrathin Zn anode (10 µm), a low negative/positive capacity ratio (≈2.3), and a lean electrolyte (9 µL mAh-1 ), the Zn/V2 O5 full cell retains 94.4% of its original capacity after 500 cycles. This work provides a simple yet practical solution to high-performance aqueous battery technology via building in situ SEI layers.

Manipulating the Solvation Structure of Nonflammable Electrolyte and Interface to Enable Unprecedented Stability of Graphite Anodes beyond 2 Years for Safe Potassium-Ion Batteries.

Potassium-ion batteries (PIBs) are attractive for low-cost and large-scale energy storage applications, in which graphite is one of the most promising anodes. However, the large size and the high activity of K+ ions and the highly catalytic surface of graphite largely prevent the development of safe and compatible electrolytes. Here, a nonflammable, moderate-concentration electrolyte is reported that is highly compatible with graphite anodes and that consists of fire-retardant trimethyl phosphate (TMP) and potassium bis(fluorosulfonyl)imide (KFSI) in a salt/solvent molar ratio of 3:8. It shows unprecedented stability, as evidenced by its 74% capacity retention over 24 months of cycling (over 2000 cycles) at the 0.2 C current rate. Electrolyte structure and surface analyses show that this excellent cycling stability is due to the nearly 100% solvation of TMP molecules with K+ cations and the formation of FSI- -derived F-rich solid electrolyte interphase (SEI), which effectively suppresses the decomposition of the solvent molecules toward the graphite anode. Furthermore, excellent performance on high-mass loaded graphite electrodes and in a full cell with perylenetetracarboxylic dianhydride cathode is demonstrated. This study highlights the importance of the compatibility of both electrolyte and the interface, and offers new opportunities to design the electrolyte-SEI nexus for safe and practical PIBs.

An In-Depth Study of Zn Metal Surface Chemistry for Advanced Aqueous Zn-Ion Batteries.

Although Zn metal has been regarded as the most promising anode for aqueous batteries, it persistently suffers from serious side reactions and dendrite growth in mild electrolyte. Spontaneous Zn corrosion and hydrogen evolution damage the shelf life and calendar life of Zn-based batteries, severely affecting their industrial applications. Herein, a robust and homogeneous ZnS interphase is built in situ on the Zn surface by a vapor-solid strategy to enhance Zn reversibility. The thickness of the ZnS film is controlled via the treatment temperature, and the performance of the protected Zn electrode is optimized. The dense ZnS artificial layer obtained at 350 °C not only suppresses Zn corrosion by forming a physical barrier on the Zn surface, but also inhibits dendrite growth via guiding the Zn plating/stripping underneath the artificial layer. Accordingly, a side reaction-free and dendrite-free Zn electrode is developed, the effectiveness of which is also convincing in a MnO2 /ZnS@Zn full-cell with 87.6% capacity retention after 2500 cycles.

An Intrinsically Non-flammable Electrolyte for High-Performance Potassium Batteries.

Potassium-ion batteries are promising for low-cost and large-scale energy storage applications, but the major obstacle to their application is the lack of safe and effective electrolytes. A phosphate-based fire retardant such as triethyl phosphate is now shown to work as a single solvent with potassium bis(fluorosulfonyl)imide at 0.9 m, in contrast to previous Li and Na systems where phosphates cannot work at low concentrations. This electrolyte is optimized at 2 m, where it exhibits the advantages of low cost, low viscosity, and high conductivity, as well as the formation of a uniform and robust salt-derived solid-electrolyte interphase layer, leading to non-dendritic K-metal plating/stripping with Coulombic efficiency of 99.6 % and a highly reversible graphite anode.

Anion Vacancies Regulating Endows MoSSe with Fast and Stable Potassium Ion Storage.

Vacancy engineering is a promising approach for optimizing the energy storage performance of transition metal dichalcogenides (TMDs) due to the unique properties of vacancies in manipulating the electronic structure and active sites. Nevertheless, achieving effective introduction of anion vacancies with adjustable vacancy concentration on a large scale is still a big challenge. Herein, MoS2(1-x)Se2x alloys with anion vacancies introduced in situ have been achieved by a simple alloying reaction, and the vacancy concentration has been optimized through adjusting the chemical composition. Experimental and density functional theory calculation results suggest that the anion vacancies in MoS2(1-x)Se2x alloys could enhance the electronic conductivity, induce more active sites, and alleviate structural variation in the alloys during the potassium storage process. When applied as potassium ion battery anodes, the most optimized vacancy-rich MoSSe alloy delivered high reversible capacities of 517.4 and 362.4 mAh g-1 at 100 and 1000 mA g-1, respectively. Moreover, a reversible capacity of 220.5 mAh g-1 could be maintained at 2000 mA g-1 after 1000 cycles. This work demonstrates a practical approach to modifying the electronic and defect properties of TMDs, providing an effective strategy for constructing advanced electrode materials for battery systems.