Rechargeable Alkaline Research Articles

Stretchable Textile Rechargeable Zn Batteries Enabled by a Wax Dyeing Method

AbstractThe development of smart electronic textiles faces one challenge that the power devices should be as comfortable, lightweight, and flexible as that of common fabrics. Herein, a stretchable textile‐based rechargeable Zn microbattery fabricated through a method analogous to Chinese traditional Batik wax dyeing is reported. Conductive metal coatings (Ni and Cu) in arbitrary patterns are prepared on a variety of fabrics, either hydrophobic or hydrophilic. The resistance of a knitted conductive textile is fully recoverable and extremely stable even after 1000 cycles of stretching to 50% tensile strain, due to the absence of damage in the conformal metal coatings. An in‐plane rechargeable alkaline Zn microbattery is then fabricated on the conductive textile using Zn as the anode and NiCo bimetallic oxyhydroxide as the cathode, achieving an areal capacity about 0.45 mAh cm−2. Stable stretchability of the textile Zn microbattery is also demonstrated. The stretchable textile conductors and rechargeable Zn microbatteries suggest great potentials in stretchable electronics or electronic textiles.

Toward more efficient and stable bifunctional electrocatalysts for oxygen electrodes using FeCo2O4/carbon nanofiber prepared by electrospinning

In the present work, an iron-cobaltite spinel supported on N-containing carbon nanofibers (CNFs) shows a remarkable activity for the oxygen evolution reaction (OER) in alkaline solution, with an overpotential (η10mAcm-2) of 130 mV, one of the lowest values in literature so far. This material is also an excellent catalyst for the oxygen reduction reaction (ORR), what leads to an extraordinary reversible behavior (ΔE = EOER – EORR=480 mV), being an economic and easy scalable candidate for the air electrode of metal-air batteries or for electrochemical devices where the oxygen evolution or the oxygen reduction is involved. In the present research, Fe partially replaces Co atoms in the Co3O4 spinel structure to obtain a more economically feasible material, leading to a FeCo2O4/CNF, by using an electrospinning preparation procedure previously adopted for the Co3O4/CNF synthesis. The substitution of iron in the Co3O4/CNF spinel entails an outstanding onset potential toward the OER of 1.36 V vs. reversible hydrogen electrode, which is 120 mV lower compared with the pure spinel (Co3O4/CNF). An optimal distribution of the FeCo2O4 particles on the CNF surface, with 3-nm-size particles, allows exposing abundant active sites, mainly Co3+ and Fe3+, responsible for the enhanced activity toward the OER, and Fe-Nx moieties and N-sites (N-graphitic/pyridinic), more active for the ORR. Besides, FeCo2O4/CNF shows a well-developed porous structure, favoring the mass transfer, a parameter particularly important for the ORR. To assess the stability of the catalysts for rechargeable alkaline metal-air batteries, cycling operation and chronopotentiometric experiments are carried out, showing a stable potential for 24 h.

Modification of Corroded Metal (Ni or Fe) Foam for High‐Performance Rechargeable Alkaline Ni/Fe Batteries

AbstractAqueous rechargeable Ni/Fe batteries with low cost and high safety have attracted tremendous attention for large‐scale energy storage. However, their application is limited by the poor conductivity and cycle performance of electrode materials. Herein, one high‐performance Ni/Fe battery with binder‐free electrodes is successfully designed and fabricated. Both of cathode and anode are initially synthesized by in‐situ corrosion process. Then, the cathode is treated by electrochemical activation (NiO‐NiF2/NF). The smooth nanoparticles transform into porous nanospheres, increasing the electrochemical activity. The anode is decorated with carbon and Bi2S3 (C@Fe‐based/Bi/FF), which can enhance the conductivity and overcome hydrogen evolution reaction. The rate capacity and the cyclic stability are promoted evidently. We assemble the Ni/Fe battery based on C@Fe‐based/Bi/FF anode and NiO‐NiF2/NF cathode, exhibiting a high energy density of 75.72 mWh cm−3 at a power density of 136.30 mW cm−3, and two batteries in series also can lighten a red LED.

Breakdown and Reformation of Birnessite in Rechargeable, Bismuth Modified MnO2 Alkaline Batteries

Rechargeable Zn-MnO2 alkaline batteries have been identified as a viable option for the modernization of grid scale energy storage due to their projected cost (<$100/kWh), scalability, and safer components when compared to non-aqueous alternatives.1 For this system to reach its maximum capability, the full Mn4+/2+ redox couple must be reversible over thousands of cycles with high mass loading. This was successfully demonstrated with the incorporation of various electrode constituents which alter the fundamental discharge and charge process of MnO2 to Mn(OH)2.1 Using non-destructive, synchrotron diffraction techniques, we detail the effect of Bi on the breakdown and reformation of birnessite (\U0001d6ff-MnO2) during cycling. Further spectroscopic evidence including Raman and X-ray absorption spectroscopy during cycling also provides crucial insights into amorphous phases and variations in redox activity, with and without additives.Early demonstrations of Bi3+ containing constituents with MnO2 in alkaline batteries increased the cyclability of these systems up to hundreds of cycles with low mass loading.2,3 Later investigations followed up by hypothesizing the presence of Bi3+ could potentially catalyze the reduction of Mn3+ to Mn2+ and that upon subsequent charge promotes the formation of a layered, birnessite, MnO2 structure.4 The quick reduction of Mn3+/2+ is critical because the presence of Mn3+ is associated with the irreversible phase change to the Mn3O4 spinel structure.5 Figure 1 shows the birnessite (001) reflection at ~7.1 Å rapidly shift to lower d-spacings upon discharge until ~6.9 Å then directly convert to Mn(OH)2 where the corresponding ~4.8 Å reflection appears. Notably, no crystalline intermediates such as MnOOH or Mn3O4 form during cycling. Also, upon charge the birnessite (001) reflection does not appear until the third potential plateau even though the Mn(OH)2 (001) reflection fades linearly until the end of charge. Due to these observations, further spectroscopic techniques were used to probe these reactions. Using operando Raman spectroscopy we observed a limited formation of an amorphous Mn3O4 during discharge and a disordered birnessite phase formation occurring on the second plateau of charge in the presence of Bi3+. These investigations provide new insight into the intermediates and formation mechanisms of Mn-based alkaline battery electrodes in the presence of Bi2O3.The presence of both Cu and Bi additives are necessary to stabilize the reversible processes occurring during electrochemical cycling. However, the synergistic relationship between Cu and Bi is not extensively investigated. Previous synchrotron XANES and XRF mapping showed that the Cu2+/0 redox couple was occurring during the Mn3+/2+ reduction. It was hypothesized that the Cu acts as a redox mediator and rapidly forms the Mn2+ species during discharge.6 Here we use a X-ray absorption spectroscopy quick scanning to monitor the Mn, Bi, and Cu redox activity which are all relating to the possible mediation of Mn reduction and oxidation. Using multiple techniques, we provide a complete understanding of the role of both bismuth and copper containing constituents on the redox transitions of MnO2 in alkaline electrolyte. Wholistic investigations combining multiple operando techniques are critical to the development of rechargeable alkaline batteries by advancing the fundamental design of these systems. Figure 1 (a) Operando X-ray diffraction data between 3-7.5 Å of the first cycle of Bi2O3-modified birnessite electrode in KOH electrolyte. (b) Corresponding galvanostatic discharge and charge at a rate of C/3. (c) Lattice parameter ‘c’, the interlayer spacing, of the birnessite phase during the first cycle. (d) The relative peak intensities of the birnessite and Mn(OH)2 (001) reflection during the first cycle.

A Mechanistic Understanding of the Electrochemical Activity of Zinc Oxide in Alkaline Batteries

Rechargeable zinc alkaline batteries are of great interest for stationary storage applications because they are inherently safe, energy dense, environmentally friendly, and low-cost. However, these batteries have not been commercialized on a large scale because of their low cycle life at high depths of discharge. One cause is the buildup of ZnO on the electrode. It has been shown recently that ZnO produced in zinc alkaline electrodes inserts protons and electrons and undergoes electrochromic color changes as a function of electrode potential. This dynamic behavior increases hydrogen catalysis, contributes capacity to the electrode, and changes oxide conductivity as a function of electrode potential. In this work we investigate the disorder and nonstoichiometry of ZnO that allow the material to become electrochemically active. We used 1H, 2H, and 67Zn solid-state MAS NMR to better understand structure, defects, order, and the hydrogen insertion mechanism of the ZnO. Understanding the physical properties of the ZnO will enable better design of electrodes and additives for zinc alkaline batteries in the future.

Fabricating architected zinc electrodes with unprecedented volumetric capacity in rechargeable alkaline cells

Recasting zinc electrodes into sponge form factors enables dendrite-free, rechargeable zinc batteries. Prior versions of these electrodes suffer from poor volumetric capacity and insufficient mechanical strength to scale beyond a few square centimeters. Most approaches to fortify zinc electrodes involve adding supportive inactive materials that decrease capacity. In contrast, we boost electrode strength through zinc/zinc-oxide fabrication advances that increase capacity. The resulting electrodes reach a tensile strength of 1 ​MPa, which now affords large-format scaling of zinc sponges. The tuned architecture achieves a 102% increase in rechargeable volumetric capacity over previously reported electrodes, yielding 928 ​mA ​h cmZn−3 in a nickel–zinc battery cycled 115 times with a coulombic efficiency near 100%. These advances in strength, scalability, manufacturability, and rechargeable capacity expand Zn-battery capabilities for a variety of applications including grid storage, personal electronics, and electric vehicles.

Monolithic Nanoporous Zn Anode for Rechargeable Alkaline Batteries.

The fabrication of monolithic nanoporous zinc bears its significance in safe and inexpensive energy storage; it can provide the much needed electrical conductivity and specific area in a practical alkaline battery to extend the short cycle life of a zinc anode. Although this type of structure has been routinely fabricated by dealloying, that is, the selective dissolution of an alloy, it has not led to a rechargeable zinc anode largely because the need for more reactive metal as the dissolving component in dealloying limits the choices of alloy precursors. Here, we apply the mechanism of dealloying, percolation dissolution, to design a process of reduction-induced decomposition of a zinc compound (ZnCl2) for nanoporous zinc. Using naphthalenide solution, we confine the selective dissolution of chloride to the compound/electrolyte interface, triggering the spontaneous formation of a network of 70 nm wide percolating zinc ligaments that retain the shape of a 200 μm thick monolith. We further reveal that this structure, when electrochemically oxidized and reduced in an alkaline electrolyte, undergoes surface-diffusion-controlled coarsening toward a quasi-steady-state with a length scale of ∼500 nm. The coarsening dynamics preserves the continuous zinc phase, enabling its uniform reaction and 200 cycles of stable performance at 40% depth of discharge (328 mAh/g) in a Ni-Zn battery.

Ab Initio Studies of Discharge Mechanism of MnO2 in Deep-Cycled Rechargeable Zn/MnO2 Batteries

Rechargeable alkaline Zn/MnO2 batteries are an attractive solution for large-scale energy storage applications. Recently, Bi and Cu additives have been used to increase the cycle life and capacity of rechargeable Zn/MnO2 batteries, with an equivalent of the full two-electron capacity realized for many cycles, in the absence of zinc. However, the mechanism of the effect of Bi and Cu on the performance of rechargeable Zn/MnO2 batteries has not been investigated in detail. We apply first-principles density functional computational methods to study the discharge mechanisms of the unmodified and Bi/Cu-modified γ-MnO2 electrodes in rechargeable alkaline Zn/MnO2 batteries. Using the results of our calculations, we analyze the possible redox reaction pathways in the γ-MnO2 electrode and identify the electrochemical processes leading to the formation of irreversible discharge reaction products, such as hausmannite and hetaerolite. Our study demonstrates the possibility of formation of intermediate Bi-Mn and Cu-Mn oxides in deep-cycled Bi/Cu-modified MnO2 electrodes. The formation of intermediate Bi-Mn and Cu-Mn oxides could reduce the rate of accumulation of irreversible reaction products in the MnO2 electrode and improve the rechargeability and cyclability of Zn/MnO2 batteries.

Bismuth Enables the Formation of Disordered Birnessite in Rechargeable Alkaline Batteries

Recent advances in rechargeable Zn/MnO2 alkaline batteries have shown promise for scalable energy storage systems which provide a safe, low-cost alternative with a demonstrated lifetime over thousands of cycles. This cathode technology is based on a 2-electron Mn redox process where a layered birnessite-type phase has been shown to form after the first cycle with excellent reversibility between the discharge product, Mn(OH)2. Herein, we investigate the reversible reaction between birnessite and Mn(OH)2 with and without a Bi2O3 additive using multimodal structural characterization techniques during active battery cycling. Diffraction results provide evidence of Bi3+ residing in the interlayer of birnessite which prevents irreversible Mn3O4 formation by limiting Mn3+ diffusion within the crystal lattice. Also, upon charge no MnOOH intermediate phases are observed. Instead, X-ray absorption and Raman spectroscopy indicate a disordered, non-crystalline birnessite-type phase consisting of mostly neutral H2O within the interlayer. Birnessite phases will reform without Bi2O3 present, but Mn3O4 formation severely polarizes the potential they are formed at, leading to capacity fade. Also, we discuss the reversible Bi2O3 conversion to Bi0 and its contribution to the observed capacity. We expect the results will provide crucial insight into the development of aqueous, rechargeable battery systems utilizing MnO2.

Effect of ZnO-Saturated Electrolyte on Rechargeable Alkaline Zinc Batteries at Increased Depth-of-Discharge

Rechargeable alkaline batteries containing zinc anodes suffer from redistribution of active material due to the high solubility of ZnO in the electrolyte, limiting achievable capacity and lifetime. Here, we investigate pre-saturating the KOH electrolyte with ZnO as a strategy to mitigate this issue, utilizing rechargeable Ni–Zn cells. In contrast to previous reports featuring this approach, we use more practical limited-electrolyte cells and systematically study ZnO saturation at different levels of zinc depth-of-discharge (DODZn), where the pre-dissolved ZnO is included in the total system capacity. Starting with 32 wt. % KOH, cells tested at 14%, 21%, and 35% DODZn with ZnO-saturated electrolyte exhibit 191%, 235%, and 110% longer cycle life respectively over identically tested cells with ZnO-free electrolyte, with similar energy efficiency and no voltage-related energy losses. Furthermore, anodes cycled in ZnO-saturated electrolyte develop more favorable compact zinc deposits with less overall mass loss. The effect of initial KOH concentration was also studied, with ZnO saturation enhancing cycle life for 32 wt % and 45 wt % KOH but not for 25 wt % KOH, likely due to cell failure by passivation rather than shorting. The simplicity of ZnO addition and its beneficial effect at high zinc utilization make it a promising means to make secondary alkaline zinc batteries more commercially viable.

Interface engineering of Co3O4 nanowire arrays with ultrafine NiO nanowires for high-performance rechargeable alkaline batteries.

Interface engineering multi-component core-shell nanostructures with highly efficient and reversible faradaic reactions for energy conversion storage devices is still a challenge. Here, Co3O4 nanowires@NiO ultrafine nanowires on Ni foam were well fabricated via coating the NiO ultrafine nanowires on porous Co3O4 nanowire arrays. The combination of structural and compositional advantages endows the Co3O4@NiO core-shell composites with excellent electrochemical performance, such as a favorable specific capacity of 0.71 mA h cm-2 at 3 mA cm-2, excellent rate capability and 85% retention rate up to 10,000 cycles. Rechargeable alkaline batteries with the Co3O4@NiO core-shell composites and AC as cathode and anode, respectively, had a high specific capacity of 0.51 mA h cm-2 and stable cycling ability (81% retention after 5000 cycles). The hierarchical core-shell heterostructure electrode exhibits excellent electrochemical performance, making it a very promising material for next-generation energy storage device applications.

Dendritic Nanostructured Waste Copper Wires for High-Energy Alkaline Battery

HighlightsElectronic waste Cu wires were successfully used as a cost-effective current collector for high-energy wire-type rechargeable alkaline batteries.The scalable approach was applied to reduce, reuse, and recycle electronic waste.A developed wire-type rechargeable alkaline battery exhibited a high-energy-density of 82.42 Wh kg−1 with long-term cycling stability.

Ultrafast lithium diffusion in bilayer buckled graphene: A comparative study of Li and Na

A spectacular enhancement of Li interlayer diffusion constant parallel to the folding axis is found. The ratio of the parallel to the perpendicular diffusion constant depends on the buckling direction and stacking, and increases with the degree of buckling. The strongest anisotropy is observed in the case of fixed zig-zag edges. A comparison with the diffusion of Na suggests that the strong asymmetry in the vibrational states of buckled graphene and also the smaller mass of Li are likely to contribute to the observed diffusion enhancement. This work opens a new pathway to develop highly-efficient anodes for rechargeable alkaline batteries.

EDTA-Co(II) sodium complex derived Co(OH)2/Co3O4/Co nanoparticles embedded in nitrogen-enriched graphitic porous carbon as lithium-ion battery anode with superior cycling stability

Transition metal hydroxides (TMHOs) can be applied either as pseudocapacitive materials for high-power supercapacitors or as positive electrode materials for rechargeable alkaline batteries. However, TMHOs have been seldom studied as anode materials for lithium-ion batteries (LIBs) although they are very competitive similarly to electrochemical active metal oxides. Here, we reported a facile synthesis of Co(OH)2/Co3O4/Co nanoparticles embedded in nitrogen-enriched graphitic porous carbon using EDTA-Co(II) sodium complex as the precursor. The composite delivers a high reversible capacity of 553 mAh g−1 at a current density of 100 mA g−1, and remains around 540 mA h g−1 after 300 cycles without significant fading. Moreover, the composite demonstrates high-rate performance as well, a high specific capacity of around 280 mAh g−1 can still be achieved at 800 mA g−1. Overall, the reported composite and synthesis methodology may stimulate further research of TMHOs and their composite as excellent energy-storage anode materials for LIBs.

Construction of sugar gourd-like yolk-shell Ni–Mo–Co–S nanocage arrays for high-performance alkaline battery

Mixed transition metal sulfides (TMSs) with hollow and complex hollow structures have attracted intensive attentions as high-performance cathode materials for rechargeable alkaline batteries. However, these powder-based electrode materials should be further mixed with insulative polymer binders and suffered from complicate electrode fabrication process. Herein, for the first time, we demonstrate the delicate design and synthesis of the sugar gourd-like multi-component yolk-shell Ni–Mo–Co–S nanocage arrays (NCAs) on Ni foam (NF) through a facile metal-organic framework (MOF)-engaged strategy. The synthetic process includes the growth of Co-based zeolitic imidazolate framework (ZIF-67) polyhedra onto the NiMoO4·xH2O nanorod arrays (NRAs) at room temperature and followed by a sufficient sulfidation reaction. Benefiting from the intriguing structural and compositional advantages, the yolk-shell Ni–Mo–Co–S NCAs/NF binder-free electrode exhibits an extremely high areal capacity of 1.96 mAh cm−2 at a current density of 5 mA cm−2 and excellent cycling stability. The electrode kinetics analysis confirms the diffusion-controlled battery-type behavior of the yolk-shell Ni–Mo–Co–S NCAs/NF electrode. The corresponding full cell delivers an high energy density of 92.6 Wh kg−1 at the power density of 1029.1 W kg−1 with the yolk-shell Ni–Mo–Co–S NCAs/NF as cathode electrode and Bi2O3 as anode electrode, indicating the potential for real applications. This work would make contribution to the realization of directly growing multi-component hollow and complex hollow structures on conductive substrate for high-performance electrochemical energy storage.

Effect of ZnO-Saturated Electrolyte on Rechargeable Alkaline Zn–Ni and Zn–MnO2 Batteries at High Zinc Depth-of-Discharge

The transition from fossil fuels toward a clean, renewable energy-based economy has generated significant interest in rechargeable batteries for grid-level storage, electric vehicles, and portable electronics. Although lithium-ion batteries are currently the predominant technology for such applications, they have relatively expensive raw materials and serious safety hazards due to their use of flammable electrolyte. Rechargeable alkaline MnO2–Zn and Ni–Zn batteries are promising alternatives that have a theoretical specific energy rivaling Li-ion systems, along with inexpensive, environmentally compatible raw materials and non-flammable aqueous electrolyte. Unfortunately, alkaline Zn anodes suffer from irreversible shape change, redistribution of active material, and passivation over repeated charge­–discharge, limiting their achievable capacity and lifetime. One simple strategy to overcome these issues is to pre-saturate the electrolyte with ZnO, which minimizes dissolution and long-range migration of zinc from the anode, and also reduces the rate of hydrogen evolution.[1] Although the use of ZnO-saturated electrolyte in Ni–Zn cells has been previously reported, most of the relevant literature uses flooded cells and does not account for the large excess of Zn species in the electrolyte relative to the anode, which artificially inflates the specific capacity. In addition, there has been no systematic study to date on the effect of ZnO-saturated electrolyte at different Zn depth-of-discharge (DODZn­). Here, we present a comprehensive investigation of ZnO-saturated electrolyte in more commercially relevant, non-flooded Ni–Zn cells at various high DODZn­ (10+%), analyzing its impact on cycle life and Zn electrochemistry. With additive-free KOH electrolyte, such high levels of Zn utilization limit the cells to only ~100 cycles, but cells with saturated electrolyte can achieve 180+ cycles at 10+% DODZn, even when this DOD accounts for ZnO in the electrolyte. Besides standard anodes consisting only of a mixture of Zn and ZnO particles with a polymeric binder, we examine ZnO-saturated electrolyte with Zn anodes containing Ca- and/or Bi-based additives, which have previously been shown to improve cycle life at 15% DODZn in additive-free electrolyte.[2] Changes in the morphology, distribution, and size of the active material particles in the anodes during cycling are characterized by ex situ scanning electron microscopy. Finally, we evaluate ZnO-saturated electrolyte in a MnO2–Zn system, which offers significantly higher theoretical energy density and lower cost per kWh than Ni–Zn but has heretofore not been studied with ZnO-saturated electrolyte because zincate can react with MnO2 to form electrochemically inactive compounds. As a path forward, we are developing zincate-blocking polymeric membranes that can essentially isolate the MnO2 cathode from zincate while maintaining good hydroxide conductivity, thereby allowing for reversible cycling of a MnO2–Zn cell at high DODZn. Various aspects of this work will also be presented. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. Dr. Imre Gyuk, Energy Storage Program Manager, Office of Electricity Delivery and Energy Reliability is also thanked for his financial support of this project. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government. [1] A.R. Mainar, E. Iruin, L.C. Colmenares, J.A. Blázquez, H.-J. Grande, Energy Science & Engineering 6 (2018), 174–186. [2] D.E. Turney, J.W. Gallaway, G.G. Yadav, et al., Chem. Mater. 29 (2017), 4819–4832.

A Study of Practical Obstacles in Primary and Rechargeable Alkaline Zinc-Air Batteries

As one of the proposed post lithium-ion battery technologies, metal-air batteries have received revived interest recently. Among the different types of metal-air batteries, rechargeable zinc-air battery (RZAB) is a promising electrochemical energy storage device with the advantages of high theoretical energy density of 1086 Wh kg-1, high abundance, low toxicity and intrinsic safety.1 However, current RZAB still suffer from poor energy efficiency and cycle life, owing mainly to the zinc-anodes, electrolytes, and air-cathodes. To improve the low energy efficiency, many efforts have been made to promote both of the sluggish oxygen reduction/evolution reactions in the air-cathodes by engineering bifunctional catalyst materials with high reactivity. Although significant progress has been made in developing suitable catalyst materials for the air-cathode, many technical challenges still remain in electrolyte to achieve the long cycle life while maintaining high performance. Aqueous electrolytes, predominantly alkaline electrolytes, have been adopted by the RZAB system since its birth. Potassium hydrogen (KOH) is the most commonly used alkaline electrolyte because of its high ionic conductivity, high activity for both the zinc and air electrodes as well as good low temperature performance.2 Despite its desirable properties, the usage of KOH in RZAB raises several technical problems: i) zinc dendrite formation, shape change, surface passivation from complicated reaction between zinc and OH- as well as the dissolution and migration of Zn(OH)4 2-; ii) corrosion of the carbon-based air cathode in concentrated alkaline electrolyte; iii) formation of insoluble K2CO3 arising from the reaction of aerial CO2 with KOH; iv) reduced cell shelf due to the high corrosive ability of concentrated alkaline electrolyte to the stainless steel used in the experimental cell component. In this work, specific attention is given to the obstacles caused by the alkaline electrolytes with the focus on the fundamental understanding of zinc-anode reaction mechanisms, carbonization of electrolyte as well as the precipitation of carbonates on the air cathode. Furthermore, the effects of the practical operating conditions on battery performance and durability are discussed, including the experimental cell configuration for RZAB as well as the contaminants commonly encountered in ambient air (e.g. carbon dioxide). The approaches to overcome the challenges are also presented and analyzed for facilitating further research and development of the electrolyte for RZAB. Reference Li, Y.; Dai, H., Recent advances in zinc-air batteries. Chemical Society reviews 2014, 43 (15), 5257-75.R. Mainar, A.; Leonet, O.; Bengoechea, M.; Boyano, I.; de Meatza, I.; Kvasha, A.; Guerfi, A.; Alberto Blázquez, J., Alkaline aqueous electrolytes for secondary zinc-air batteries: an overview. International Journal of Energy Research 2016, 40 (8), 1032-1049.

Morphology and Phase Changes in Fe Anodes for Rechargeable Alkaline Batteries

Rechargeable alkaline batteries may become promising non-flammable alternatives to Li-ion batteries for the applications where achieving the highest energy density is less critical than safety, environmental friendliness and low cost of energy storage systems. A renewed interest on Ni-Fe aqueous batteries awakes due to the aforementioned advantages as well as long life and robustness against harsh conditions. The challenges for improved Ni-Fe batteries, however, remain limiting their utilization for large-scale energy storage systems: electrolyte decomposition, high self-discharge and poor cell efficiency. Such drawbacks can be overcome by sound understanding on the cell reactions happening at the electrodes. By conducting systematic studies on Fe anodes using cyclic voltammetry and a broad range of characterization tools, four distinct stages of Fe anode evolution were revealed: development, retention, fading and failure, where each stage is associated with very specific changes in the morphology and phase of Fe anodes. The particle fragmentation with the consequent gain in the surface area resulted in the increase in the Fe anode capacity during the initial cycles of deep charge/discharge. Most importantly, it was discovered that the irreversible formation of monocrystalline maghemites (γ-Fe2O3) with low reactivity is responsible for the eventual Fe anode capacity fading. We confirmed that the microstructure change takes over during early charge-discharge cycles of Fe anodes while their phase change is dominant at later stage which is the key for the rationale explaining the failure mechanism of Fe anodes in Ni-Fe batteries. Ultimately, our study correlates the changes in the electrochemical behavior of micro-scale Fe upon deep cycling in alkaline conditions with the changes in its morphology and phase. * DOI: 10.1021/acsenergylett.8b00063

Rechargeable Solid-State Copper Sulphide Cathodes for Alkaline Batteries

For energy storage to become ubiquitous in the electric grid, safe, reliable low-cost electrochemical storage technologies that can be manufactured at high volumes with low capital expenditures are needed. Rechargeable alkaline batteries based on abundant and low cost materials with high capacities, such as a Zinc (Zn) anode (820 mAh g-1) paired with a Sulphur (S) cathode (1675 mAh g-1, based on the idealized redox couple of S2-/S) could serve as high energy dense systems if sufficient cycle life and energy densities can in fact be realized. S has a suitable terrestrial abundance and overall economics for wide-spread battery use; however, to date Zn/S batteries have been primary in nature and hindered by crossover of sulphide, which reacts with the Zn anode during discharge, forming an insulating ZnS layer and rendering the Zn anode inert to re-charge. In this talk we will report on the first use of a solid-state sulphide/polysulphide electrochemical couple(s) in alkaline electrolyte.1 Specifically, a new battery chemistry that consists of a solid-state Cu2S cathode paired with a Zn anode in alkaline electrolyte, which gives a nominal >1.2 V cell voltage based on the sulfide/polysulfide redox cathode chemistry, will be presented. It was found that in order for the S cathode to have the best cycle life in the solid-state it must not only be bound to Cu ions but bound to Cu ions in the +1 valence state, forming Cu2S as a discharge product. Zn/Cu2S batteries cycled between 1.45 V and 0.4 V vs Zn displayed capacities of ~ 1500 mAh g-1 (based on mass of S) or ~ 300 mAh g-1 (based on mass of Cu2S) and high areal (> 23 mAh cm-2) and energy densities (> 135 Wh L-1), but suffered from moderate cycle life (~ 250 cycles). The failure mechanism of this electrode is proposed to be the conversion of the charged S species into irreversible sulphite and/or sulphide, releasing the bound Cu ions. The Cu ions become free to perform Cu specific redox reactions which slowly changes the battery redox chemistry from that of S to that of Cu with a S additive. Batteries utilizing the Cu2S cathode and a 50% depth of charge (DOC) cathode cycling protocol, with 5 wt. % Na2S added to the electrolyte, retained a cathode capacity of 838 mAh g−1 (based on the mass of S) or 169 mA h g−1 (based on mass of Cu2S) after 450 cycles with > 99.7% coulombic efficiency as shown in the accompanying Figure. These Zn/Cu2S batteries provided a grid storage relevant energy density of > 42 W h L−1 (at 65 wt. % Cu2S loading), despite only using a 3% depth of discharge (DOD) for the Zn anode. These results represent the first example of a rechargeable solid-state sulphur cathode in an alkaline battery and augur for the further development of a new class of energy dense grid storage batteries based on high capacity solid-state S-based cathodes. Various aspects of the battery chemistry and its cycling properties will be presented. This work was supported by the U.S. Department of Energy, Office of Electricity, Energy Storage Program, Dr. Imre Gyuk, Program Manager, and the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government. [1]. J. Duay, T. N. Lambert, M. A. Kelly, I. Pineda-Dominguez “Rechargeable Solid-State Copper Sulphide Cathodes for Alkaline Batteries: Importance of the Copper Valence State” J. Electrochem. Soc. 2019 166 (4), A687-A694. DOI: 10.1149/2.0261904jes. Figure 1

Mesoporous Fe3S4 microparticles as a novel anode material for rechargeable alkaline aqueous batteries

Transition metal chalcogenide as a novel class of materials has recently drawn increasing attention in the field of energy storage. Herein, the Fe2O3 precursor was first synthesized by ionic liquid–assisted hydrothermal method and further sulfurized by hydrothermal approach to obtain mesoporous Fe3S4 microparticles. When used as anode materials for rechargeable alkaline aqueous batteries for the first time, the Fe3S4 electrode exhibits enhanced electrochemical properties compared with the Fe3O4 counterpart. The Fe3S4 electrode delivers a high specific capacity of 110.6 mAh g−1 at 2 A g−1, good rate performance, and superior cycling stability with 75.8% of capacity retention at 2 A g−1 after 3000 cycles. The excellent electrochemical behaviors are mainly ascribed to the unique mesoporous structure with large specific surface area, high total pore volume, and superior electronic conductivity. These results indicate that the mesoporous Fe3S4 microparticles can be considered as a promising anode material for rechargeable alkaline aqueous batteries.