`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`
`WATCO
`
`JUL 1 0 2015
`
`UNITED STATES DEPARTMENT OF COMMERCE
`United States Patent and Trademark Office
`PO Box 145
`Address: CLAMMIBSIQNER FOR PATENTS
`Alexandna, Vii 22313-1450
`Www uspto.g
`
`APPLICATION
`
`NUMBER
`
`62/230,502
`
`FILING or
`
`371(c) DATE
`
`06/08/2015
`
`GRP ART
`
`UNIT
`
`FIL =—D
`
`WatCo, Office of Research
`of Water]
`200University Avenue West
`
`Waterloo, ON N2L 3G1
`
`ATTY.DOCKET.NO
`
`TOT CLAIMSHIND CLAIMS
`
`CONFIRMATION NO. 8739
`FILING RECEIPT
`ONL
`
`Date Mailed: 06/30/2015
`
`Receipt is acknowledged ofthis provisional patent application.
`It will not be examined for patentability and will
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`
`Inventor(s)
`
`Applicant(s)
`
`Linda Faye Nazar, Waterloo, CANADA;
`Dipan Kundu, Kitchener, CANADA;
`Brian Adams, Mitchell, CANADA;
`
`Linda Faye Nazar, Waterloo, CANADA;
`Dipan Kundu, Kitchener, CANADA;
`Brian Adams, Mitchell, CANADA;
`
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`** SMALLENTITY **
`
`Aqueous Zn-lon batteries using a metallic zinc negative electrode and vanadate positive electrodes
`
`UW Exhibit 1003, pg. 1
`
`

`

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`UW Exhibit 1003, pg. 2
`
`

`

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`UW Exhibit 1003, pg. 3
`
`

`

`Aqueous Zn-Ion Batteries Using a Metallic Zinc Negative Electrode
`and Vanadate Positive Electrodes
`
`Inventors:
`
`Dr. Linda Faye Nazar, (Professor, University of Waterloo), 225-45 Benjamin Rd. Waterloo,
`Ontario, N2V 1Z3 (Canadian Citizen)
`
` Dr. Dipan Kundu, (Researcher, University of Waterloo), 11 Overlea Dr, # 1012, Kitchener ON
`N2M 5C8 (Indian Citizen)
`
`Brian David Garnett Adams, (Researcher, University of Waterloo), 228 Morenz Dr., Mitchell
`ON N0K 1N0 (Canadian Citizen)
`
`The United States Government has rights in this invention pursuant to DOE-FOA-0000559,
`Energy Innovation Hub — Batteries and Energy Storage, and [ANL Subcontract No. 3F-32281],
`issued under DOE Prime Contract No. DE-AC02-06CH11357 between the United States
`Government and UChicago Argonne, LLC representing Argonne National Laboratory.
`
`What is claimed here are material composition and method of synthesis for Aqueous Zn-Ion
`Batteries Using a Metallic Zinc Negative Electrode and Vanadate Positive Electrodes, related to
`the field of rechargeable Zinc-Ion batteries and their applications in power storage, as generally
`and as specifically described herein;
`
`Abstract
`The present invention pertains to claims related to a low cost rechargeable Zn battery based on a
`cathode comprised of nanostructured hydrated vanadium oxides as robust materials for high rate
`and long term reversible Zn2+ ion intercalation storage at the cathode, that are coupled with a
`metallic Zn anode, and an aqueous electrolyte. Vanadium possesses a range of oxidation states
`(+2 to +5), which allows for multiple redox and hence large specific capacities. Layered
`MxVnOm oxides (M = metal ion) of compositions such as V2O5, V3O8, V4O11 - that are made of
`two dimensional sheet structures - have been the subject of intense investigation for both non-
`aqueous and aqueous alkali (Li and Na) ion batteries. The additional presence of interlayer metal
`ions and/or water of hydration in such layered oxides act as pillars, providing structural stability
`during long term charge discharge cycling. Two vanadates that embody such qualities are
`H2V3O8 and ZnxV2O5, which we have synthesized in nanofiber morphology by a simple and
`rapid microwave hydrothermal method, without using any toxic or corrosive chemical. These
`are converted to freestanding film electrodes by adopting a low-cost and green, water based
`electrode fabrication process. The nanomorphology of the product and compact film structure
`allows for facile release of strain resulting upon Zn2+ cycling, short ion diffusion paths, good
`interaction with carbon additives with the active material and robust conductive wiring at the
`cathode. An additional contribution to the technology is the use of a titanium or titanium coated
`
`UW Exhibit 1003, pg. 4
`
`

`

`current collector for Zn deposition at the negative electrode. This material has a substantial
`overpotential for hydrogen evolution, which is comparable to Zn itself. This combination
`facilitates high specific capacities of up to 350 mAh g-1 and long term cyclabilities up to 1000
`cycles at 100% coulombic efficiency using fast current rates. It thus gives rise to predicted
`gravimetric energy densities up to 280 Wh/kg for the cathode alone, and between 200 – 250
`Wh/kg including the mass of the zinc anode.
`
`
`Introduction
`
`The energy driven technological revolution of the past century has made our lives easy in
`many ways. However, in doing so, we have relied solely on the combustion of fossil fuels that
`has led to severe environmental damage and now we are on the verge of a global climate change.
`This has raised the call for an environmentally responsible energy economy relying on cheap and
`sustainable energy generation and storage. In this backdrop, renewable energy resources (solar,
`wind, etc.) along with electrochemical energy storage devices based on batteries have gained
`prominence as a result of considerable breakthroughs in the last two decades. Primary batteries
`have been replaced with rechargeable (secondary) types for all uses, with the exception of small
`consumer portable electronics. Four main types of secondary batteries currently dominate the
`commercial market: lead-acid, nickel-cadmium, nickel metal-hydride, and lithium-ion. Lead-acid
`batteries have remained as the leader (for the past century) for certain applications where their
`low gravimetric energy density is not a major concern; specifically automotive starter sources
`and backup power supplies. Nickel-cadmium cells made their way into markets of portable
`power tools in the 1980s and 1990s, but have been since replaced by nickel metal-hydride cells
`due to the toxicity of cadmium. Nickel metal-hydride are still used today for certain applications,
`but are being replaced by lithium ion batteries (LIBs) which have become the frontrunner by
`revolutionizing the portable electronics market and raising the stake of electrified transportation.
`Unfortunately, despite the high energy and high power of some LIBs, concerns over the future
`cost of lithium and the sustainability of the resources, and safety hazards of using highly
`flammable and toxic organic electrolyte limit their application to some extent. In this context,
`rechargeable aqueous batteries which utilize cheap and safe water based electrolytes, and do not
`involve the dry atmospheric assembly conditions of non-aqueous batteries, are attracting
`tremendous attention. In addition, the high ionic conductivities of aqueous electrolytes (1 S cm-1)
`compared to non-aqueous electrolytes (1-10 mS cm-1) favor high rate capabilities suitable for
`emerging applications.
`
`The use of metallic negative electrodes in either primary or secondary type batteries is
`also quite attractive as a means to achieve high energy densities and for ease of battery assembly
`(and ultimately lowering costs). In general, the most reducing metals (Table 1) happen to be the
`lightest weight, and thus, have the highest theoretical gravimetric capacities. On the other hand,
`the heavier metals have greater densities, which in turn lead to higher volumetric capacities.
`There is a trade-off between the reduction potential of a metal – low values giving higher cell
`
`UW Exhibit 1003, pg. 5
`
`

`

`voltages – and safety concerns. Since all metals listed in Table 1 have E° values below 0 V vs.
`SHE (defined by 2H+ + 2e- → H2), they all have the potential to react with water to evolve
`hydrogen. Particularly, the lightweight metals (lithium, potassium, calcium, sodium, and
`magnesium) spontaneously react with even trace amounts of water from the atmosphere.
`
`Of all the metals, zinc is the most reducing candidate which is stable in water. For this
`reason, zinc has been utilized as the negative electrode in primary aqueous battery systems
`including Leclanché cells (i.e., modern zinc-carbon cells), zinc-chloride cells, alkaline cells,
`zinc-air cells, and mercury oxide cells. In most of these battery types, an alkaline electrolyte is
`used, where zinc metal is oxidized to form the soluble zincate ion (eq. 1) or further can be
`irreversibly oxidized to ZnO precipitates (eq. 2,3):
`
`2- + 2e-
`Zn + 4OH- → Zn(OH)4
`(1)
`Zn + 2OH- → Zn(OH)2 + 2e-
`(2)
`(3)
`Zn(OH)2 → ZnO + H2O
`Table 1. Comparison of various metals for use as battery anodes (negative electrodes).
`Metal
`E°
`Theoretical
`Theoretical
`Commercial Battery
`Issues with Metal Anodes in
`(V vs.
`Gravimetric
`Volumetric
`Types*
`Commercial Battery Systems
`Capacity (mAh g-1)
`SHE)
`Capacity
`(mAh cm-3)
`2061
`
`590
`
`2060
`
`1131
`
`3837
`
`8046
`
`5845
`
`7554
`
`4149
`
`8138
`
`Li-SO2 (P), Li-SOCl2 (P),
`Li-FeS2 (P), Li-I2 (P), Li-
`MnO2 (P), Li-(CF)n (P)
`None
`
`Reactive with atmosphere.
`
`Extremely reactive.
`
`None
`
`Reactive with atmosphere.
`
`Sodium-Sulfur (S)
`
`Reactive with atmosphere.
`
`Mg-CuCl (P)
`
`Aluminum-Air (P)
`
`Leclanché (P), Alkaline (P),
`Zinc-Air (P), Zinc-Chloride
`(P), Mecury Oxide (P)
`Iron Nickel (S), Iron-Air
`(S), Iron Silver (S)
`Mercury Oxide (P), Nickel
`Cadmium (S)
`None
`
`High self discharge rate of Mg-CuCl
`cells requires them to be made “dry
`charged” and add water when energy is
`required. Mg plating/stripping is difficult
`in non-aqueous electrolytes inhibiting
`development of secondary cells.
`Primary or mechanically rechargeable
`only.
`Dissolution of Zn at high pH.
`
`Self-discharge of iron electrode due to H2
`evolution (Fe + 2H2O → Fe(OH)2 + H2).
`Toxic element.
`
`Batteries based off of nickel typically
`utilize NiOOH as the cathode in an
`alkaline electrolyte. Ni is a good catalyst
`for H2 evolution, inhibiting its use as a
`negative electrode.
`Heavy
`element,
`capacity.
`
`gravimetric
`
`low
`
`Lithium
`Li+ + e- → Li(s)
`
`-3.04
`
`3861
`
`Potassium
`K+ + e- → K(s)
`Calcium
`Ca2+ + 2e- → Ca(s)
`Sodium
`Na+ + e- → Na(s)
`Magnesium
`Mg2+ + 2e- → Mg(s)
`
`-2.92
`
`686
`
`-2.76
`
`1337
`
`-2.71
`
`1166
`
`-2.38
`
`2205
`
`-1.66
`
`2980
`
`-0.76
`
`820
`
`Aluminum
`Al3+ + 3e- → Al(s)
`Zinc
`Zn2+ + 2e- → Zn(s)
`
`Iron
`Fe2+ + 2e- → Fe(s)
`Cadmium
`Cd2+ + 2e- → Cd(s)
`Nickel
`Ni2+ + 2e- → Ni(s)
`
`-0.41
`
`-0.40
`
`-0.23
`
`960
`
`477
`
`913
`
`259
`
`-0.13
`Lead
`Pb2+ + 2e- → Pb(s)
`* P=primary, S=secondary
`
`8934
`
`Lead-Acid (S)
`
`UW Exhibit 1003, pg. 6
`
`

`

`Additionally, irreversibility in these systems can arise at the cathode. For example, in the
`case of modern zinc-chloride and alkaline batteries where MnO2 is the active cathode material,
`the following chemistry occurs:
`MnO2 + H2O + e- → MnOOH + OH-
`(4)
`(5) MnOOH + H2O + e- → Mn(OH)2 + OH-
`
`Rechargeable aqueous batteries are extremely appealing for emerging energy storage
`markets as discussed above. In particular, Li+-based shuttle systems have been extensively
`researched. However, in attempts to move beyond lithium, naturally abundant Na+ and K+
`systems, and very recently, the intercalation chemistry of divalent cations are being explored.
`Zn2+ based systems are promising for multiple reasons: (a) the high abundance and large
`production of zinc which makes it very low-cost; (b) the high corrosion resistance of zinc in
`atmospheric and other environments; (c) the non-toxicity of zinc; (d) the low redox potential of
`the Zn anode (-0.76 V vs. SHE) compared to the redox potential of host materials used in other
`aqueous batteries; (e) the high potential volumetric energy density of the zinc negative electrode,
`owing to its density (7.14 g cm-3); and lastly, the extremely small exchange current for hydrogen
`evolution on zinc from solutions with Zn2+ concentrations higher than 10-4 M, which renders Zn
`deposition the major electrochemical reaction at low cathodic potential. The last feature
`facilitates a much larger kinetic voltage window (~2.5 V) for Zn2+ based rechargeable batteries
`containing aqueous electrolytes, a Zn2+ host, and a Zn anode, compared to the small
`thermodynamic window of 1.23 V of aqueous electrolytes. This concept of a zinc-ion battery is
`depicted in Figure 1. Nonetheless, the inventory of host materials capable of reversible Zn2+
`storage is currently sparse and only a few materials, namely MnO2 (α, β, γ, λ, and todorokite),
`zinc hexacyanoferrate, and copper hexacyanoferrate have been explored. Among the different
`polymorphs of MnO2, the alpha version delivers a large initial specific capacity of ~210 mAh g-1
`at a discharge potential of 1.3 V. Poor rate performance and sharp initial capacity fading due to
`manganese dissolution in the electrolyte bar its practical application, however.Error! Bookmark not
`defined. Even though open framework metal hexacyanaoferrates offer possibilities of a range of
`multivalent cation insertion and a rather high operational voltage (~1.7 V for Zn/Zn-
`hexacyanoferrate) for zinc insertion, a very low specific capacity (65 mAh g-1 at 1C) dampens
`their contention. Therefore, new host materials and chemistries are required favoring multiple
`redox per molecular unit for high specific capacities, and stable architectures with facile zinc ion
`pathways that enable fast and reversible cycling.
`
`UW Exhibit 1003, pg. 7
`
`

`

`
`
`
`
` Figure 1. Conceptual scheme of a zinc-ion battery.
`
`
`
`Herein, we introduce two vanadium oxide based compounds with layered crystal
`structures containing crystalline water and a nanostructured morphology as robust host materials
`for high rate and long term reversible Zn2+ ion storage in aqueous electrolyte. Vanadium is a
`low-cost metal possessing a range of oxidation states (+2 to +5), which allows for multiple redox
`and hence large specific capacities for vanadium based electrode materials. Particularly, oxides
`of vanadium e.g., V2O5 which is produced in large quantities, display numerous crystal and
`compositional chemistries for reversible metal ion storage. Layered MxVnOm oxides (M = metal
`ion) with pure oxide compositions such as V2O5, V3O8, V4O11 have been the subject of intense
`investigation for both non-aqueous and aqueous alkali (Li and Na) ion batteries. However, as we
`demonstrate here, interlayer metal ions and/or water of hydration in these layered oxides can act
`as pillars, providing structural stability during long term cycling and facilitating the mobility of
`divalent cations such as Zn2+ and Mg2+. Hydrated vanadium oxides that possess such qualities
`are H2V3O8 and ZnxV2O5, which we have synthesized in nanofiber morphology by a simple and
`rapid microwave hydrothermal treatment of V2O5, without using any toxic or corrosive
`chemicals. Their nanomorphology and compact film structure allows for facile release of strain
`
`UW Exhibit 1003, pg. 8
`
`

`

`resulting upon Zn2+ cycling, short ion diffusion paths, good interaction of carbon additives and
`robust conductive wiring. They were converted to freestanding film electrodes by adopting a
`“green”, low cost water based electrode fabrication process. This facilitates high specific
`capacities of ~350 mAh g-1 and long term cyclabilities up to 1000 cycles at high coulombic
`efficiency using fast current rates. Predicted gravimetric energy densities are up to 280 Wh/kg
`for the cathode alone, and between 200 – 250 Wh/kg including the mass of the zinc anode.
`
`
`
`Experimental Methods
`
`Synthesis of H2V3O8 and ZnxV2O5: Microwave solvothermal methods developed over the last
`two decades are now often used to prepare cathode materials for lithium ion batteries. In our
`study we have modified a time consuming and energy expensive hydrothermal approach used in
`the synthesis of single crystalline H2V3O8 nanobelts to a rapid and scalable microwave
`hydrothermal method for the synthesis of highly homogeneous H2V3O8 and ZnxV2O5 nanofibers.
`In a typical procedure, 3-4 mmol V2O5 was dispersed in 15:1 water/acetone (v) mixture with or
`without a stoichiometric amount of zinc chloride (for ZnxV2O5) and transferred to a sealed
`TeflonTM vessel. The vessels were fitted to a rotor equipped with temperature and pressure
`sensors and placed in an Anton Parr microwave synthesis system (Synthos 3000). The system
`temperature was raised to 180°C in 10 minutes and maintained for 60 to 90 minutes. The as-
`synthesized product was thoroughly washed with distilled water followed by a small amount of
`isopropanol and dried at 60°C for 24 h.
`
`Characterization Methods: Powder X-ray diffraction was performed on a Bruker D8-Advance
`powder diffractometer equipped with Vantec-1 detector, using Cu-Kα radiation (λ= 1.5405Å) in
`the range from 5° to 80° (2θ) at a step size of 0.025° using Bragg-Brentano geometry. X-ray data
`refinement was carried out by conventional Rietveld refinement method using the Bruker-AXS
`TOPAS 4.2 software (Bruker-AXS, 2008). The background, scale factor, zero point, lattice
`parameters, atomic positions and coefficients for the peak shape function were iteratively refined
`until convergence was achieved. The morphologies of the samples were examined by field-
`emission scanning electron microscopy (FE-SEM, LEO 1530) equipped with an energy
`dispersive X-ray spectroscopy (EDX) attachment. For high resolution transmission electron
`microscopy (HRTEM), samples were dispersed in iso-propanol by ultrasonication and loaded
`onto a carbon coated copper grid for imaging on a FEI Titan 80-300.
`
`Battery Cycling: For electrochemical performance evaluation, a freestanding film type electrode
`was fabricated by a facile green approach. In a typical process, nanofibers were mixed with
`conducting nanocarbon Super P® and a water based composite binder carboxymethylcellulose
`(CMC) and styrene-butadiene rubber(SBR) (CMC/SBR= 2:1) in 70:27:3 weight ratio. The
`mixture was dispersed in small amount of water using an ultrasonic mixer to obtain a stable
`homogeneous ink which was filtered through a Durapore® DVPP 0.65 µm filtration membrane.
`
`UW Exhibit 1003, pg. 9
`
`

`

`After drying at 60°C the composite film was then punched into 1 cm2 electrode coins and further
`dried at 180°C for 1 h. The electrochemical properties were investigated in PFA based
`Swagelok® type cells using 1 M ZnSO4 in water as the electrolyte and titanium or stainless steel
`rods as the current collector. Galvanostatic cycling studies were performed using a multichannel
`Biologic VMP3 potentiostat/galvanostat.
`
`Three-Electrode Electrochemical Measurements: The voltammetric electrochemical
`experiments were performed with a three-electrode cell consisting of the working electrode, Pt
`mesh (1 cm2) as the counter electrode, and an Ag/AgCl (3 M KCl) reference electrode. The
`working electrodes were a Zn disk (φ = 2 mm), a Ti disk (φ = 2 mm), a stainless steel rod (316
`grade, φ = 12 mm), and the H2V3O8 composite electrode. Cyclic voltammetry was performed at a
`scan rate of 5 mV/s and linear sweep voltammograms were acquired at 1 mV/s. These techniques
`were controlled with a CHI700E potentiostat (CH Instruments, Inc.). The electrolytes used were
`1 M Na2SO4 for the hydrogen evolution reaction and 1 M ZnSO4 for zinc plating/stripping and
`the oxygen evolution reaction. All experiments were performed at room temperature (23 ± 2
`°C).
`
`
`
`Results and Discussion
`
`Electrochemistry.
`
`
`The operating voltage of all secondary aqueous batteries is limited by the potentials for
`hydrogen evolution and oxygen evolution from water electrolysis. Since both the hydrogen and
`oxygen evolution reactions (HER and OER, respectively) are pH dependent (see equations 7-10)
`and catalytic in nature, the precise potential at which they occur is sensitive to the electrolyte
`composition and electrode material. HER and OER occur during charge at the negative and
`positive electrodes, respectively, and are displayed below:
`
`Cathodic Reactions:
`Zinc Deposition:
`Zn2+ + 2e- → Zn
`
`(6)
`Hydrogen Evolution:
`2H2O + 2e- → H2 + 2OH-
`
`(7)
`
`
`
`
`
`
`
`
`
`
`
`(8)
`
`2H+ + 2e- → H2
`
`
`
`Anodic Reactions:
`
`
`
`
`
`
`
`Oxygen Evolution:
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`(9)
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`4OH- → O2 + 2H2O + 4e-
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`(10)
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`2H2O → O2 + 4H+ + 4e-
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`E°= -0.76 V vs. SHE
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`E°= -0.83 V vs. SHE
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`E°= 0.00 V vs. SHE
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`E°= 0.40 V vs. SHE
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`E°= 1.23 V vs. SHE
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`UW Exhibit 1003, pg. 10
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`To examine the suitability of a metallic zinc negative electrode for secondary zinc-ion
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`batteries, linear sweep voltammetry was used to probe the HER. In Figure 1, a zinc-ion-free (1
`M Na2SO4) electrolyte was used which contained the same concentration of the sulfate anion and
`similar pH value (4-5) as the 1 M ZnSO4 electrolyte used for all other studies. It can be seen that
`the hydrogen evolution reaction has an overpotential of ~0.4 V with respect to Pt on both zinc
`metal and titanium metal.
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`Figure 1. Linear sweep voltammograms at 1 mV/s on Pt, Ti, and Zn in 1 M Na2SO4 showing the
`onset of the hydrogen evolution reaction.
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`Stainless steel was deemed to be unsuitable as a current collector for the negative electrode as it
`catalyzes the HER and competes with zinc electrodeposition, but titanium was found to be an
`excellent current collector for the negative, comparable to Zn itself (Figure 2a,b).
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`UW Exhibit 1003, pg. 11
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`Figure 2. Linear sweep voltammograms at 1 mV/s in 1 M Na2SO4 showing the hydrogen
`evolution reaction. The dashed red voltammogram in (a) shows zinc deposition on a zinc disk
`electrode in 1 M ZnSO4 for comparison.
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`Furthermore, zinc deposition and stripping was completely reversible on titanium as
`displayed in Figure 3a. The Coulombic efficiency (Qox/Qred) was 100 % over 100 cycles on
`titanium with no loss in the electrical charge (Q) for deposition or stripping. Stainless steel
`suffered from a decay in both Qred and Qox, even for the first 10 cycles (Figure 3b). On stainless
`steel the Coulombic efficiency was only 87 % for the first cycle and 74 % for the tenth cycle.
`This shows that the excess charge during reduction (Qred) goes towards the HER.
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`UW Exhibit 1003, pg. 12
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`Figure 3. Cyclic voltammograms at 5 mV/s on (a) a Ti disk electrode and (b) stainless steel rod
`in 1 M ZnSO4.
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`Since the OER dictates the maximum potential for the positive electrode, this was first
`examined on stainless steel, a practical current collector material. Titanium also has a high
`overpotential for OER, however, we suspect that OER on many Zn2+-intercalation materials will
`have activity similar to stainless steel which is why we show the result for OER on stainless steel
`rather than titanium. Figure 4 displays the linear voltammograms for Zn electrodeposition onto
`a Zn disk and OER on a stainless steel rod in 1 M ZnSO4 at 1 mV/s. This plot shows the
`maximum possible operating voltage window of a secondary Zn-ion battery using 1 M ZnSO4,
`which is ~2.4 V. Obviously, the positive electrode of choice must be within this window,
`particularly if a high-voltage material is to be used. In our case, the upper voltage cut-off for
`batteries with H2V3O8 and ZnxV2O5 are 1.1 V, which is well below the limit at which OER will
`occur at these materials.
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`UW Exhibit 1003, pg. 13
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`Figure 4. Linear sweep voltammograms on a zinc disk electrode (red) and a stainless steel disk
`electrode (blue) at 1 mV/s in 1 M ZnSO4. The cathodic sweep on zinc shows zinc deposition and
`the anodic sweep on the stainless steel shows the oxygen evolution reaction. These two
`electrochemical reactions dictate the potential operating window for aqueous zinc-ion batteries
`using this electrolyte.
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`Figure 5 displays the chronopotentiometric curves for charging α-MnO2 (which has been
`explored as a Zn-ion intercalation host previously) and H2V3O8 electrodes without prior
`discharge. This gives an indication of the possible upper voltage cut-off which can be used for a
`given material. Clearly, the H2V3O8 material undergoes structural transitions between 1.5 V and
`2.4 V, at which point OER occurs. In contrast, with α-MnO2, the voltage quickly rises to 2.4 V
`where a flat OER plateau arises. Thus, upper voltages of 1.1 V for H2V3O8 and 1.8 V for α-
`MnO2 were used in all subsequent battery cycling protocols.
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`UW Exhibit 1003, pg. 14
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`Figure 5. Galvanostatic charging of H2V3O8 (red) and α-MnO2 (black) electrodes at 0.5 mA/cm2
`in 1 M ZnSO4 with metallic zinc negative electrodes.
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`Cathode Materials: Synthesis and Characterization. The hydrothermal method has evolved
`into an important wet chemistry method for the synthesis of nanostructured vanadium oxide
`materials. However, such process can be time consuming, as in the synthesis of H2V3O8
`nanobelts which requires hydrothermal treatment of V2O5 in water for 2-3 days at 210°C. By
`introducing a microwave heat treatment, we have developed a versatile and scalable synthetic
`approach for the rapid synthesis of ultralong H2V3O8 and ZnxV2O5 nanofibers. Water is known to
`strongly interact with the microwave radiation via a dipolar-microwave interaction, leading to
`rapidly superheated local regions in the reaction media. In contrast to typical hydrothermal
`methods where slow heating mainly occurs via thermal conduction mechanism, heating of the
`entire reaction media through penetration of microwaves triggers rapid intercalation-exfoliation
`and cleavage of V2O5 into nanosheets and finally into H2V3O8 or ZnxV2O5 nanofibers. The phase
`purity of the as-synthesi