Zn/V2O5 Aqueous Hybrid-Ion Battery with High Voltage Platform and Long Cycle Life.

Electrochemical Energy Storage with Mediator-Ion Solid Electrolytes

Rechargeable aqueous batteries are of high interest for future stationary grid-scale energy storage applications where high safety is needed (1). Copper hexacyanoferrate (CuHCF), a Prussian Blue Analogue (PBA) material, has recently gained interest as positive electrode for aqueous Zn-ion batteries (ZIBs) (2,3). Reversible Zn2+ ion insertion is facilitated by its open-framework with large channels that can host a variety of monovalent and divalent cations. Recent studies have shown that the charge compensation process takes place via Zn2+ ions swapping position between tunnel sites and vacancy sites (4).Among aqueous ZIBs, the Zn/CuHCF cell has attracted noticeable attention, as it can combine abundant and inexpensive materials with a good trade-off between capacity and performance. Zinc can supply a high capacity (820 mAh g-1), while CuHCF typically provides a moderate capacity of ca. 60-80 mAh g-1.However, it exhibits one of the highest operating voltages among PBA-type cathodes (1.7 V vs. Zn2+/Zn) and exhibits a cubic-type structure with wide channels. In comparison to many other materials, CuHCF undergoes minimal volume and structural changes during ion insertion/de-insertion, exhibits a high Coulombic efficiency of ca. 99%, and can be cycled at high rates without compromising the capacity, which makes it an interesting material for high-power applications.Nevertheless, CuHCF suffers from capacity fade owing to instabilities of Cu, which we have demonstrated in details in a recent investigation (5). In that study, we also highlighted that the characteristic aging effect, observed as a growth of a two-phase plateau in the charge/discharge profiles and associated with capacity loss (6), can be explained by Cu dissolution and thereby a displacement of the two Cu2+/Cu+ and Fe3+/Fe2+ redox-couples (5). Alkali metal cations (Li+, Na+, K+, Rb+, Cs+) have recently been shown to impact the capacity of the Zn/CuHCF cell along with a modulation of the characteristic redox-features in the voltammetric profiles (7). Cycling of large cations (Rb+, Cs+) was linked to a reduced capacity, while moderately sized cations (K+) resulted in optimal capacity and higher charge retention. This has motivated us to investigate the effect of the alkali metal cations on the charge compensation and redox processes in CuHCF in more detail in this study.By employing X-ray photoelectron spectroscopy (XPS), we show that small cations (Li+) have negligible impact on the Cu and Fe redox processes, while moderately sized cations (K+) suppress Cu redox and enhance Fe redox, which optimizes the capacity and improves the cycling stability, accordingly. Large cations (Cs+), on the other hand, prevent reversible redox and lock both metal centers in their most reduced states (Cu+, Fe2+), which impedes the charge compensation process and reduces the capacity. Our study unveils how alkali metal cations influence the performance of ZIBs by affecting the synergy of the Cu2+/Cu+ and Fe3+/Fe2+ redox couples in CuHCF and demonstrates how tailoring the electrolyte formulation can conveniently impact the capacity retention of this compound in PBA-type ZIBs. Figure 1. The aqueous Zn/CuHCF cell. (a) Schematic figures illustrating the structure of the CuHCF cathode and its wide channels that can host ions. (b) Cyclic voltammograms (CV) of the Zn/CuHCF cell in pure 1M ZnSO4 and in presence of 0.2 M alkali metal cation additives (Li+, K+, Cs+). (c) X-ray photoelectron spectroscopy (XPS) showing the Cu 2p3/2 and Fe 2p3/2 spectra of the same electrolytes as shown in (b). References J. Shin, and J. W. Choi, Advanced Energy Materials, 10, 2001386–2001386 (2020).R. Trócoli, and F. La Mantia, ChemSusChem, 8, 481–485 (2015).Z. Jia, B. Wang, and Y. Wang, Materials Chemistry and Physics, 149–150, 601–606 (2015).V. Renman, D. O. Ojwang, M. Valvo, C. P. Gómez, T. Gustafsson, G. Svensson, Journal of Power Sources, 369, 146–153 (2017).M. Görlin, D. O., Ojwang, M.-T. Lee, V. Renman, C.-W. Tai, and M. Valvo, ACS Applied Materials & Interfaces, 13, 59962–59974 (2021)R. Trócoli, G. Kasiri, and F. La Mantia, Journal of Power Sources, 400, 167–171 (2018).D. Phadke, R. Mysyk, and M. Anouti, Journal of Energy Chemistry 40, 31–38 (2020). Figure 1

With the rapid consumption of fossil energy resources and the increasing pollution problems, the efficient use of energy and the development of renewable energy sources is urgently needed, which demand for the large-scale electrical energy storage system with properties of high-security, low-cost, environmentally benign, remarkable capacity and long-life span. In this regard, achieving some breakthroughs in this system will have extremely important strategic impacts on future energy structure adjustments and smart grid construction. Although lithium ion battery has dominated the energy market for decades, the intrinsic drawbacks of high cost and safety issues, to a great extent, impedes its utilization in scale-up energy storage system. And recent years witnessed the significant progress of rechargeable multivalent metal ions batteries, such as Mg2+-ion, Al3+-ion, Ca2+-ion and Zn2+-ion batteries. With the unique features of high safety, low-cost, environmental friendly, abundant resources stockpile, low redox potential (–0.76 V vs. SHE), high capacity (up to 820 mAh g–1 theoretically) and energy density (5851 mAh mL−1) of metallic Zn as well as remarkable ionic conductivity of aqueous electrolyte, aqueous rechargeable zinc battery has attracted plenty of interest in recent years and exhibits great potential to be an important candidate for the next generation of high-safe and large scale energy storage system. Many researchers have paid great attention to the development of high performance aqueous rechargeable zinc battery system, including cathode materials, electrolytes and anode. And some great achievements have been obtained. Henceforth, in this review, we have systematically reviewed the research progress of aqueous rechargeable zinc battery, summarized and discussed the existing problems faced by this system and the related solutions. Based on the author’s best knowledge and understanding of aqueous rechargeable zinc battery, we have looked forward to its future research direction and made some perspectives, which is expected to pave the pathway for the understanding and further development of aqueous rechargeable zinc battery. In our view, the development of advanced solid/gel electrolyte should be attached great significance, which is a promising way to solve a series of problems existing in anode and cathode, such as cathode material dissolution, zinc anode dendrite growth, passivation and corrosion, as well as the by-products existing in the system. Moreover, the research on solid/gel electrolyte also offers some opportunities of constructing wearable and flexible electronic devices, such as smart watch, which is greatly beneficial to put forward to the practical application of aqueous rechargeable zinc battery. In addition, development of high performance cathode materials with remarkable strength of both high-voltage and high-capacity, and in-depth researches on the modification and optimization of zinc anode are the further trends of high-performance aqueous rechargeable zinc battery.

Both high safety and low cost give aqueous rechargeable sodium-ion batteries (ARSB) the opportunity for application in stationary energy storage, but the low operating potential of the existing cathode materials limits its energy density. Here, we introduce a hydrothermal-assisted strategy to prepare the Na7V4(P2O7)4(PO4)/C nanorod and employ it as a novel high-property cathode material for ARSB. The hierarchical structure is formed by direct in situ carbonization of the surfactants (CTAB and oxalic acid) along with the crystallization of Na7V4(P2O7)4(PO4). The prepared Na7V4(P2O7)4(PO4) with a well-defined 1D nanostructure and uniform particle size is wrapped with a thin carbon layer. For the first time, its sodium intercalation chemistry in an aqueous electrolyte was investigated. Based on the reversible phase transformation and high sodium diffusion coefficient, it is demonstrated to be reliable in an aqueous electrolyte with the rapid ion transport capability. A pair of redox plateaus is observed in the charge and discharge curves at 0.961 and 0.944 V (vs. SCE) respectively with the capacity of 51.2 mA h g(-1) at 80 mA g(-1). Favored by the open ion channel and 1D morphology, the composite exhibits superior high rate capability and 72% of the capacity remains at 1000 mA g(-1). The results not only demonstrate a high-property cathode material for ARSB, but also are helpful for design and synthesis of mixed-polyanion electrode materials with tailored architecture.

Charging up Stationary Energy Storage

LiV 3O 8: characterization as anode material for an aqueous rechargeable Li-ion battery system

Solar energy has the characteristics of intermittent and unstable, and it results in the negative impact on power quality of the utility grid while the penetration rate of the grid-connected photovoltaic generation system is increased. The energy storage system (ESS) can alleviate the negative impact on power quality of the utility grid so as to increase the penetration rate of the grid-connected photovoltaic generation system. Aqueous Hybrid Ion (AHI) battery contains no heavy metals or toxic chemicals, and it is non-flammable and non-explosive. Besides, AHI battery has the characteristics of high cycle life, safety and sustainability. A 5kW DC-coupling distribution power generation system (DPGS) based on photovoltaic and AHI battery set is presented in this paper. The operation modes of this DPGS are divided into self-consumption, charging/discharging schedule and stand-alone. The maximum power efficiency from the solar cell array to the grid is 97.1%. The maximum power efficiency of the bidirectional DC-DC converter is 97.3% and the maximum power efficiency from the AHI battery set to the grid is 94.5%. Therefore, the power efficiency of this DPGS is very high.

Aqueous rechargeable batteries have drawn wide attention owing to the advantages of low cost, high safety, and rapid kinetic process. In recent years, the use of NH4+ ions and other nonmetallic ions as carrier batteries has come into researchers’ view. The storage of NH4+ shows fast diffusion kinetics and the ability to achieve highly reversible redox processes by forming hydrogen bonds between NH4+ and electrode materials. Designing and exploration of advanced materials for NH4+ storage are of high significance in building high‐performance aqueous battery systems. This review summarizes the latest advances of critical materials, including Prussian blue analogs, transition metal oxides, and organic compounds for NH4+ batteries. Comparison of properties among different materials is discussed in detail. Different NH4+ storage behaviors according to several kinds of materials are demonstrated. Finally, the challenges and valuable perspectives for the further development of aqueous NH4+ batteries are also provided.

[Introduction] The development of environmentally friendly batteries, such as rechargeable aqueous metal-air batteries, has been required for sustainable energy supply. Aqueous zinc-air batteries, composed of zinc as the anode, O2 in the air as the cathode, and a very base aqueous solution (e.g., 6 M KOH aqueous solution) as the electrolyte, are one of the representative environmentally friendly batteries, because of their high energy density (1353 W h kg−1 excluding oxygen) compared to conventional lithium-ion batteries (limited to be <350 W h kg−1 based on the intercalation chemistry).[1] However, these batteries usually have extremely low cyclability because of dendrite formation on the anode and carbonate salt clogging (i.e., the reaction between CO2 in the air and the base) in the electrolyte during charging and discharging.To improve their cyclability, we previously reported a rechargeable organic polymer-air battery using a redox polymer with an anthraquinone derivative (which has a one-step two-electron redox capability in an acidic aqueous solution).[2] This rechargeable organic polymer-air battery exhibits a very high Coulombic efficiency of 99% because of the distorted structure of the anthraquinone derivative. However, organic redox polymers with linear polymer structures are not sufficiently robust for long-term use as an anode-active material in aqueous air batteries.On the other hand, Prof. Yu et al. have recently fabricated a rechargeable organic polymer-air battery using a networked polymer based on anthraquinone as an anode-active material and demonstrated very high cyclability of presumably 99% capacity retention even after 60,000 cycles.[3] This is presumably because the networked polymer forms a robust three-dimensional network that prevents it from decomposing or dissociating from the electrode. However, the Coulombic efficiency was lower than that of organic polymer-air batteries with organic linear polymers, and was only 95%.To achieve both the sufficiently high cyclability and high Coulombic efficiency as an aqueous air battery, the anode-active material must possess high hydrophilicity, exhibit high diffusivity of compensating ions in the material, and have a robust structure that is not decomposed or dissociated from the electrode during charging and discharging.In this work, as the anode-active material, we focused on the anthraquinone molecule itself, which has a reversible redox capacity at the very negative potential close to the potential window in aqueous electrolytes and whose redox properties can be modulated by facile organic synthesis. To improve anthraquinone’s hydrophilicity and inhibit its aggregation, we synthesized 2-propoxyethyl anthraquinone-2-carboxylate. 2-propoxyethyl anthraquinone-2-carboxylate had a reversible redox potential in an acidic aqueous solution, and we established a novel rechargeable organic molecule-air battery using2-propoxyethyl anthraquinone-2-carboxylate as the anode-active material and an acidic aqueous solution as the electrolyte. [Results & Discussions] The battery was chargeable and dischargeable, with the very high Coulombic efficiency of >99% at 15 C. The discharge capacity was almost full capacity, indicating that almost all the molecules contributed to charging and discharging. The discharge capacity remained >99% even after 100 cycles, indicating that the battery had a very high cyclability. Even at 60 C, the discharge capacity of the battery was almost the same as that at 15 C, indicating a high-rate capability. Moreover, the results confirm that this novel rechargeable organic molecule-air battery exhibits the highest cyclability and Coulombic efficiency in rechargeable organic-based aqueous air batteries. Using 2-propoxyethyl anthraquinone-2-carboxylate as an anode-active material in aqueous air batteries will potentially achieve almost the same energy density and increase power density by several times or more, compared to the polymer-air batteries demonstrated. Therefore, the energy density of the aqueous air battery using 2-propoxyethyl anthraquinone-2-carboxylatewill be almost the same as that of metal-air batteries (e.g., zinc-air batteries), and its power density is expected to be higher than that of lithium-ion batteries.We want to discuss this in more detail at the poster session. [Reference] [1] J. Zhang et al., Chem. Sci. 2019, 10, 8924-8929.[2] K. Oka et al., Macromolecules 2021, 54, 4854-4859.[3] L. Zhong et al., Angew. Chem. Int. Ed. 2021, 60, 10164-10171. Figure 1

A key aspect of any future battery technology development is safety. Although lithium-based batteries are ubiquitous, there are still challenges related to their energy density, cycle life, cost and safety. In regard to safety, compared with organic electrolyte, aqueous rechargeable batteries may provide a safer alternative for reliable, low-cost and large-scale energy storage systems. As seen from the penetration test in Fig. 1a-1b, the battery with organic electrolyte catches fire, yet the battery with aqueous electrolyte is relatively safe. Moreover, aqueous batteries have high ion conductivity and cost effectiveness. Generally, the cell voltage and energy density of aqueous batteries are lower than those of organic-based batteries (e.g. Li-ion) because of the relatively smaller electrochemical stability window of water. Among all the metals that are stable in water, zinc is the most active and has the lowest possible operating potential. This means using Zn anode can increase overall cell voltage of aqueous batteries. Moreover, zinc is globally available, inexpensive (3.19 USD kg-1), and has high capacity (820 Ah kg-1 and 5854 Ah L-1). Zinc-based aqueous batteries also possess the stability to be operated in ambient air. Accordingly, Zn aqueous rechargeable batteries are promising to become a safer energy storage system. Among zinc-based aqueous batteries, Zn-air batteries have high theoretical volumetric energy density, which is around three times that of conventional Li-ion batteries (LIB). Zn anodes have been investigated in neutral/mild acidic aqueous electrolytes. Yet in order to pair them with oxygen cathode to reach the highest energy density, alkaline aqueous electrolyte is ideal, in which the oxygen electrode has low polarization. In alkaline aqueous electrolyte, Zn anode undergoes a Zn (s) ↔ Zn(OH)4 2- (aq) ↔ ZnO (s) conversion. This solid-solute-solid transformation and insulating discharge product ZnO lead to three vital challenges: 1) ZnO passivates Zn surface and prevents further discharging, leading to low Zn utilization; 2) ZnO is insulating and can hardly be charged back to Zn; 3) diffusion of Zn(OH)4 2- causes the loss of active material and change of electrode morphology. Thus, anode modification and protection are needed to alleviate the passivation and dissolution. We firstly designed a Zn mesh@GO anode (Fig 1c). Graphene oxide (GO) layers on the Zn mesh surface deliver electrons across insulating ZnO and can slow down the Zn dissolution. However, the utilization of zinc is still low because passivation problem is not completely solved. Through SEM investigation, critical passivation size was found to be ~ 2 µm. Thus, we further designed a lasagna-inspired ZnO@GO anode (Fig 1d). ZnO nanoparticles are encapsulated by GO. ZnO lasagna structure has three features: 1) the size of ZnO nanoparticles is smaller than the critical size of passivation; 2) the fabrication of ZnO lasagna anode starts with commercially available ZnO nanoparticles (~100 nm), and is compatible with the roll-to-roll process, which is ideal for large-scale manufacturing; 3) GO allows permeation of OH- and water, and prevents loss of Zn active material through blocking bigger Zn(OH)4 2-. As a result, such lasagna anode achieves a high volumetric capacity of 2308 Ah/L and a remarkable capacity retention of 86% after 150 cycles. In contrast, the open-structured ZnO nanoparticle anode, without the protection of GO, completely died after 90 cycles. Figure 1

Modelling, simulation, and validation of the 12-volt battery pack using a 20 Ah lithium–nickel–manganese–cobalt–oxide cell is presented in this paper. The cell characteristics influenced by thermal effects are also considered in the modelling. The parameters normalized directly from a single cell experiment are foundations of the model. This approach provides a systematic integration of actual cell monitoring with a module model that contains four cells connected in series. The validated battery module model then is utilized to form a high fidelity 80 Ah 12-volt battery pack with 14.4 V nominal voltage. The battery cell thermal effectiveness and battery module management system functions are constructed in the MATLAB/Simulink platform. The experimental tests are carried out in an industry-scale setup with cycler unit, temperature control chamber, and computer-controlled software for battery testing. As the 12-volt lithium-ion battery packs might be ready for mainstream adoption in automotive starting–lighting–ignition (SLI), stop–start engine idling elimination, and stationary energy storage applications, this paper investigates the influence of ambient temperature and charging/discharging currents on the battery performance in terms of discharging voltage and usable capacity. The proposed simulation model provides design guidelines for lithium-ion polymer batteries in electrified vehicles and stationary electric energy storage applications.

The eminent global energy crisis and growing ecological concerns in the past two decades lead to intensive development in the fields of clean energy sources such as wind and solar power. The successful penetration of green energy technologies highly depends on the deployment of large scale energy storage systems (ESS) with low cost, safe, and longevity. Lithium ion batteries (LIB) have been well acknowledged as EES with high energy density and long cycling life, and are superior to other conventional batteries. However, their inherent safety and cost issues related to the use of expensive, toxic and flammable organic electrolyte and superfast charging performance are still challenges for their applications in large-scale EES such as electric vehicles and smart grids [1]. To meet the needs of EES, batteries based on aqueous electrolytes are attractive candidates compared to the present LIB utilizing flammable and expensive organic electrolytes because of their improved safety and low cost. For these reasons, aqueous batteries, including Pb-Acid, Ni-Cd and Ni-MH batteries, are widely used in many markets such as electric scooters and automatically guided vehicles. However, the Pb-Acid batteries and Ni-Cd batteries raise the problem of toxic heavy-metal pollution, while the market of Ni-MH batteries is limited by its high cost due to the use of rare-earth metal for anodes [2]. So it is necessary to develop a new type of aqueous battery with qualities of low cost, safety, environmental benignity, long cycle life and acceptable energy density. Zn is an ideal anode for aqueous rechargeable batteries due to its abundance in the nature and possesses a high theoretical capacity (820 mAh/g) and a low negative potential (-0.762 V vs. SHE). Various rechargeable Zn-based batteries have been investigated (Ni-Zn, Zn-air and Zn-Br flow battery etc.) [3]. Recently, a promising aqueous Zn-LiMn2O4 (LMO) rechargeable battery system has attracted attentions as a low cost, ecologically friendly and safe battery. The estimated energy density of the system is 50-80 Wh/kg, which is comparable to conventional aqueous systems such as Lead-Acid batteries [4]. However, shape change and dendritic shorting of the Zn electrode prevent the commercialization of these battery technologies [3]. Herein, we present an innovative design of aqueous battery based on Zn-LMO system, which used the concept of immobilized Zn2+ions to prevent the metal dendrite in Zn-based batteries and optimized a nontoxic, high conductivity, noncorrosive, and low-cost neutral aqueous solution as electrolyte. Therefore, this new design of Zn-LMO aqueous battery exhibits an improved rate capability and delivers good cycling performance while still maintaining an acceptable energy density. As shown in Fig.1 and Fig.2, the Zn-LMO pouch cell provides a high discharge capacity of 120 mAh/g (based on the weight of LMO) at 0.5C at room temperature with an average discharge potential of 1.88 V. The system showed a good rate capability, maintaining 99, 92.5, and 74.3% of the 0.5C value at rates of 1C, 2C, and 4C, respectively. In addition, the battery also exhibited an excellent good cycle performance even at higher temperature of 60℃（Fig.2）which were attributed to the well optimized negative, positive and electrolyte combination and composition. Given the unique advantages (performance, scalability, low cost, safety and environmental benignity) of this cell, it’s optimal for stationary storage applications of renewable energies, such as solar and wind, and energy integration into the grid. Fig. 1. Charge/Discharge profiles (25℃) of Zn-LMO battery at various current densities from 0.5C to 4C. Cut voltage is 1.5 V-2.3 V. Fig. 2. Cycle performances and coulombic efficiency (25℃ and 60℃) of Zn-LMO battery at 4C. Reference [1] J.M. Tarascon, Nature 414 (2001) 359. [2] F. Beck, Electrochimica Acta 45 (2000) 2467. [3] X.G. Zhang, Encyclopedia of Electrochemical Power Sources (2009) 454. [4] J. Yan, Journal of Power Sources 216 (2012) 222. Figure 1

Zinc metal has emerged as seeded anode material in the field of high-efficiency aqueous metal-air battery system due to the advantages of abundant reserves, strong reversibility and high capacity. Unfortunately, the conventional zinc electrodes commonly adopt a flat structure, and the dendrite accumulation and corrosion during the cycle process lead to sub-optimal efficiency and performance. Herein, the zinc electrode is designed as a three-dimensional (3D) spiral structure to improve the utilization efficiency of zinc and the quality of the battery. Compared with the zinc plate, the 3D spiral zinc electrode can shorten the movement distance of the particles in space and the operation period in time, increase the specific surface area of the reaction, reduce the resistance of mass and charge transfer, and achieve the effect of optimizing the performance of the battery system. The results show that the aqueous zinc-air battery made of 3D spiral zinc electrode exhibits better charge-discharge characteristics, higher power density and narrower voltage windows. This study demonstrates a zinc anode with simple feasibility properties and a special structure, aiming to provide a new research direction and innovation strategy for the development of high-performance rechargeable zinc-air battery systems.

Aqueous hybrid ion batteries – An environmentally friendly alternative for stationary energy storage?

Ultrafast charge in Zn-based batteries through high-potential deposition