Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/362—Composites
  • H01M4/366—Composites as layered products
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
  • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
  • C23C16/308—Oxynitrides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
  • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
  • C23C16/40—Oxides
  • C23C16/405—Oxides of refractory metals or yttrium
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
  • C23C16/455—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for introducing gases into reaction chamber or for modifying gas flows in reaction chamber
  • C23C16/45523—Pulsed gas flow or change of composition over time
  • C23C16/45525—Atomic layer deposition [ALD]
  • C23C16/45555—Atomic layer deposition [ALD] applied in non-semiconductor technology
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/24—Alkaline accumulators
  • H01M10/30—Nickel accumulators
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/04—Processes of manufacture in general
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/24—Electrodes for alkaline accumulators
  • H01M4/244—Zinc electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/624—Electric conductive fillers
  • H01M4/625—Carbon or graphite
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M12/00—Hybrid cells; Manufacture thereof
  • H01M12/04—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type
  • H01M12/06—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type with one metallic and one gaseous electrode
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/027—Negative electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2300/00—Electrolytes
  • H01M2300/0002—Aqueous electrolytes
  • H01M2300/0014—Alkaline electrolytes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• Batteries can be generally described as comprising three components: an anode that contains a material that is oxidized (yields electrons) during discharge of the battery (i.e., while it is providing power), a cathode that contains a material that is reduced (accepts electrons) during discharge of the battery, and an electrolyte that provides for transfer of ions between the cathode and anode.
• anode that contains a material that is oxidized (yields electrons) during discharge of the battery (i.e., while it is providing power)
• a cathode that contains a material that is reduced (accepts electrons) during discharge of the battery
• an electrolyte that provides for transfer of ions between the cathode and anode.
• the anode is the negative pole of the battery
• the cathode is the positive pole.
• Batteries can also be generally categorized as being “primary,” where the electrochemical reaction is essentially irreversible, so that the battery becomes unusable once discharged, and “secondary,” where the electrochemical reaction is, at least in part, reversible so that the battery can be “recharged” and used more than once.
• Secondary batteries are increasingly used in many applications because of their convenience (particularly in applications where replacing batteries can be difficult), reduced cost (by reducing the need for replacement), and environmental benefits (by reducing the waste from battery disposal).
• Secondary batteries utilizing faradaic energy storage mechanisms are the most prominent systems among the EES technologies.
• LIBs lithium-ion batteries
• Neutral and alkaline electrolytes are two major classes of aqueous electrolytes for zinc anodes.
• BMKPIYOMIJSM aQUK IUVLMZ QU UM ⁇ [YIS MSMK[YVS ⁇ [MZ Z ⁇ KP IZ f ⁇ I[MYnQUnZIS[g MSMK[YVS ⁇ [MZ IUL TVS[MU hydrate electrolytes have been investigated.
• HER In an alkaline electrolyte with pH 14, the Zn/ZnO standard reduction potential (-1.26 V vs the standard hydrogen electrode (SHE)) is lower than that of the HER (-0.83 V vs SHE).
• SHE standard hydrogen electrode
• HER is thermodynamically favored during charging, which causes low Coulombic efficiency, electrolyte drying, bubble accumulation, and eventually cell failure.
• GC battery-gas chromatography
• Rechargeable Zn-based aqueous batteries have immense potential in large-scale energy storage systems due to their high gravimetric capacity (specific capacity) of 820 milliampere hours per gram (mA•h/g; hereinafter “mAh/g” or similar units) and high volumetric capacity of 5854 milliampere hours per cubic centimeter (mA•h/cm 3 ; hereinafter “mAh/cm 3 ”, “mAh/mL” or similar units), cost effectiveness, and high chemical stability in air and aqueous solution.
• Zn has roughly three times the volumetric capacity compared to Li (2062 mAh/cm 3 ).
• aqueous Zn-based batteries do not require the comparably complex subsystems required for lithium-based batteries including thermal management, sophisticated electronic controls, and structural protection to manage any catastrophic events.
• aqueous electrolyte zinc-based batteries not only are safer, but also can be manufactured in ambient air rather than dry room, and have much higher tolerance to moisture and air during operation. Having two valence electrons and high density, zinc metal has three times the volumetric capacity of lithium metal.
• Zn-air has a theoretical volumetric energy density (energy density) of 4400 watt-hour per liter (W•h/L; hereinafter “Wh/L” or similar units), that is more than three times of conventional Li-ion batteries (1400 Wh/L), and approaching Li-S batteries (5200 Wh/L).
• Wh/L volumetric energy density
• Primary Zn-air batteries have already been the battery of choice for hearing aids, which require extremely high energy density and safety.
• zinc is abundant, low-cost, and environmentally benign, rendering them suitable for large scale applications.
• 3 ⁇ 4 evolution dries out the electrolyte, enhances internal pressure of the battery, and gas bubbles block the ionic pathway, which leads to a low Coulombic efficiency ( ⁇ 60%) and even sudden battery failure.
• Zn dendrites are formed during the charging process (i.e. , electrodeposition of Zn metal) when and/or Zn 2+ ions are deposited unevenly, with faster growth occurring along energetically favorable crystallographic directions, resulting in internal short circuit. Furthermore, incomplete reduction of zincate ions coupled with non-uniform redistribution of Zn electrode material during the charging process leads to densification of the electrode at specific regions over many charge/discharge cycles, causing loss of usable capacity.
• the passivation layer on the bulk zinc anode shortens the cycle life because active Zn is transformed into relatively insulating ZnO, which increases the internal resistance of the Zn electrode.
• This passivation inhibits the discharge process as the insulating ZnO film on the Zn surface blocks the migration of the discharge products and/or hydroxide ions, causing significant loss of energy efficiency for the charge/discharge cycles.
• the passivation mechanism of the Zn anode in alkali electrolytes has been investigated, effective methods for resolving this problem have yet to be proposed. [0028] Attempts have been made in the past to overcome one or two of the challenges of passivation, dissolution, and HER.
• a recent attempt has been made to mitigate dendrite formation and shape change of the Zn electrode by altering the Zn electrode design.
• a 3D-zinc sponge anode was prepared to improve the rechargeability of Zn-based batteries.
• problems persist: (1) passivation is still present in the 3D-zinc anodes, especially with a high depth of discharge (DOD); (2) the larger electrode-electrolyte contact area accelerates the dissolution of zinc, leading to shape change and capacity fading; and (3) the volume capacity decreases because of the porosity of the zinc sponge and the low depth-of-discharge.
• An exemplary electrode would include anodic core elements comprising core material, the core material having a passivation interface size and an intrinsic dissolution rate, and a conformal shell coating on an outer surface of the anodic core elements forming core/shell structures, wherein the anodic core elements comprise a feature size smaller than the core material passivation interface size, and wherein a dissolution rate of the core material from the core/shell structures is less than the intrinsic dissolution rate.
• the shell should be made of material that has low activity towards the HER of reduction of water to hydrogen as a side reaction.
• core/shell nanoscale structures provide deeply rechargeable anodes, and can overcome intrinsic limitations of other battery materials that involve soluble intermediates or insulating discharge products.
• Starting with a nanomaterial with high-surface area could avoid the passivation layer problem. However, the dissolution problem is more severe.
• a nonporous coating could prevent ZnO dissolution, but would also block the OH- transport necessary for the zinc redox reaction to occur. Therefore, simultaneously solving the dilemmas of passivation and dissolution are an answer.
• the present invention encompasses a myriad of core material/coatings that with optimization of the core and shell materials, from aspects of pore size, porosity, and surface charge, leads to various improvements of anode performance and stability.
• Many materials with controlled ion-sieving and HER suppressing properties are contemplated herein.
• the design principles can be applied to other morphologies (e.g. particles) of starting materials for large scale production.
• the mechanistic understanding and design principles cover many types of rechargeable high-energy aqueous batteries.
• the concept of separating ions and molecules by size using selective membranes is known.
• an electrode comprises anodic core elements comprising a core material of zinc, the core material having a core material passivation interface size of approximately 2 ⁇ m, a core material intrinsic dissolution rate, and a core material hydrogen evolution reaction (HER) rate.
• the electrode further comprises a conformal shell coating of TiO2 on an outer surface of the anodic core elements, thus forming ZnO@TiO2 core/shell structures.
• the electrode can be a sub-micron zinc anode sealed with an ion-sieving coating that suppresses hydrogen evolution reaction.
• ZnO nanorods are coated with TiO2, which overcomes passivation, dissolution, and hydrogen evolution issues simultaneously. It achieves superior reversible deep cycling performance with a high discharge capacity of approximately 616 mAh/g and Coulombic efficiency of approximately 93.5% when cycled with 100% depth of discharge at lean electrolyte. It can also deeply cycle ⁇ 350 times in a beaker cell.
• the electrode further comprises a conformal shell coating of TiN x O y on an outer surface of the anodic core elements, thus forming ZnO@TiN x O y core/shell structures.
• the anodic core elements are nanoscale, so as to comprise a feature size smaller than the zinc passivation interface size.
• the anodic core elements can be nanorods with a diameter of less than approximately 2 ⁇ m, and more preferably less than approximately 500 nm.
• the dissolution rate of zinc from the core/shell structures is less than the Zn intrinsic dissolution rate, as the relatively thin (having a thickness of less than approximately 10 nm) and conformal TiNxOy coating mitigates Zn dissolution in an alkaline electrolyte.
• the ZnO@TiNxOy core/shell nanorod structures provide a deeply rechargeable Zn anode. The small diameter of ZnO limits to fully prevents passivation, and allows near to full utilization of active materials, while the relatively thin and conformal TiNxOy coating not only mitigates the Zn dissolution, but also mechanically maintains the morphology of the nanostructures, and delivers electrons to the nanorods.
• the ZnO@TiN x O y core/shell nanorod anode achieves superior specific capacity and cycle life compared with bulk Zn foil and uncoated ZnO nanorod anodes.
• the discharge capacity of the ZnO@TiN x O y core/shell nanorod anode is approximately twice as large as that of an uncoated ZnO nanorod anode. It was surprisingly found that the ZnO@TiNxOy nanorod anode achieves a much higher specific discharge capacity of approximately 508 mAh/g than that of conventional zinc anodes.
• an electrode comprises anodic core primary elements comprising a core material of zinc, the core material having a core material passivation interface size of approximately 2 ⁇ m, a core material intrinsic dissolution rate, and a core material HER rate.
• the electrode further comprises a conformal shell coating of carbon on an outer surface of the anodic core primary elements, thus forming ZnO@C core/shell structures.
• the anodic core primary elements are nanoscale, so as to comprise a feature size smaller than the zinc passivation interface size.
• the anodic core primary elements can be particles with a diameter of less than approximately 2 ⁇ m, and more preferably are nanoparticles (NPs) with a diameter of less than approximately 100 nm.
• NPs nanoparticles
• the dissolution rate of zinc from the core/shell structures is less than the Zn intrinsic dissolution rate, as the relatively thin (having a thickness of less than approximately 15 nm) and conformal amorphous, microporous, and conductive carbon coating mitigates Zn dissolution in an alkaline electrolyte.
• An assembly (secondary cluster) of these core/shell structures form Zn-pome microspheres (pomegranate-like nanoporous carbon-coated ZnO clusters).
• Each secondary cluster/Zn-pome microsphere can be approximately 6 mm in size and comprise on the order of approximately 10 5 ZnO NPs individually encapsulated by an amorphous, microporous, and conductive carbon shell that slows down the dissolution of zincate intermediate species during cycling. The shell further suppresses zinc dissolution by decreasing the electrode-electrolyte contact area.
• the nanoscale, pomegranate-structured Zn anode can be fabricated via a bottom-up microemulsion approach.
• the in the Zn-pome, primary ZnO NPs assemble into secondary clusters after which they are individually encapsulated by a conductive, microporous carbon framework.
• the small size of ZnO NPs overcomes the problematic issue of passivation, whereas the secondary structure and ion-sieving carbon shell mitigates the dissolution problem.
• ICP Inductively coupled plasma
• an electrode comprises anodic passivation interface size of approximately 2 ⁇ m, a core material intrinsic dissolution rate, and a core material HER rate.
• the electrode further comprises a conformal shell coating of an ion-sieving carbon on an outer surface of the anodic core elements, thus forming ZnO@C core/shell structures.
• the anodic core primary elements are nanoscale, so as to comprise a feature size smaller than the zinc passivation interface size.
• the anodic core primary elements can be particles with a diameter of less than approximately 2 ⁇ m, and more preferably are nanoparticles (NPs) with a diameter of less than approximately 100 nm.
• the dissolution rate of zinc from the core/shell structures is less than the Zn intrinsic dissolution rate, as the relatively thin (having a thickness of less than approximately 30 nm) and conformal ion-sieving carbon coating mitigates Zn dissolution in an alkaline electrolyte.
• the ion-sieving carbon nanoshell coated ZnO nanoparticle anode can be synthesized in a scalable way with controllable shell thickness.
• the nanosized ZnO prevents passivation, while the microporous carbon shell slows down Zn species dissolution. Under extremely harsh testing conditions (closed cell, lean electrolyte, no ZnO saturation), this Zn anode shows significantly improved performance compared to Zn foil and bare ZnO nanoparticles.
• the ion-sieving nanoshell can be beneficial to other electrodes such as sulfur cathode for Li-S batteries.
• an electrode comprises anodic core elements comprising core material, the core material having a core material passivation interface size, a core material intrinsic dissolution rate, and a core material hydrogen evolution reaction (HER) rate, a conformal shell coating on an outer surface of the anodic core elements forming core/shell structures, wherein the anodic core elements comprise a feature size smaller than the core material passivation interface size, wherein a dissolution rate of the core material from the core/shell structures is less than the core material intrinsic dissolution rate; and wherein the HER rate of the shell is less than the core material HER rate.
• the electrode can be deeply rechargeable.
• the electrode can have a DOD of greater than 50%.
• the core material can be selected from the group comprising a metal, metal oxide, metal sulfide, and combinations thereof.
• the core material can be selected from the group comprising Zn, Li, Na, Mg, Ca, ZnO, Li 2 O, Na 2 O, MgO, CaO, ZnS, LLS, Na 2 SS MgS, CaS, and combinations thereof.
• the conformal shell coating can comprise a cermet.
• the conformal shell coating can comprise carbon.
• the core/shell structures can have a specific discharge capacity of at least 70% of the theoretical limit of the specific discharge capacity of the core material.
• the electrode can have a coulombic efficiency greater than about 93.5%.
• the anodic core/shell structures can be formed by a deposition technique of layers of the conformal shell coating over a deposition cycling series, and wherein a morphology of the anodic core elements prior to the deposition cycling series is substantially the same as a morphology of the core/shell structures after the deposition cycling series.
• the anodic core/shell structures can be formed by an atomic layer deposition (ALD) technique of layers of the conformal shell coating over an ALD cycling series, and wherein a morphology of the anodic core elements prior to the ALD cycling series is substantially the same as a morphology of the core/shell structures after the ALD cycling series.
• ALD atomic layer deposition
• the anodic core elements are nanorod structures, the core material comprises ZnO, and the conformal shell coating comprises TiNxOy.
• the diameter of the nanorods can be less than approximately 2 pm.
• the diameter of the nanorods can be less than approximately 500 nm.
• the conformal shell coating can have a thickness of less than 10 nm.
• the conformal shell coating can have a thickness of less than approximately 6 nm.
• the anodic core elements are nanoparticles
• the core material comprises ZnO
• the conformal shell coating comprises carbon
• the conformal shell coating can comprise an amorphous, microporous, and conductive carbon.
• An assembly of core/shell structures can form Zn-pome microspheres (pomegranate-like nanoporous carbon-coated ZnO clusters).
• Each Zn-pome microsphere can have a diameter of approximately 6 ⁇ m.
• Each Zn-pome microsphere can comprise on the order of approximately 10 5 core/shell structures.
• the diameter of the nanoparticles can be less than approximately 2 ⁇ m.
• the diameter of the nanoparticles can be less than approximately 100 nm.
• the conformal shell coating can have a thickness of less than 15 nm.
• the conformal shell coating can have a thickness of less than approximately 10 nm.
• the anodic core elements are nanoparticles
• the core material comprises ZnO
• the conformal shell coating comprises an ion- sieving carbon shell.
• a rechargeable battery system comprises anodic core/shell structures comprising a ZnO core coated with a shell layer of TiN x O y, an aqueous electrolyte, and a cathode.
• a rechargeable battery system comprises anodic Zn-pome microspheres each comprising a pomegranate-like assembly of individual ZnO nanoparticles coated with a shell layer of carbon, an aqueous electrolyte, and a cathode.
• a rechargeable battery system comprises anodic core/shell nanoparticles comprising a ZnO core coated with a shell layer of ion- sieving carbon, an aqueous electrolyte, and a cathode.
• the rechargeable battery system can be deeply rechargeable.
• the rechargeable battery system can have a DOD of greater than 50%.
• the cathode can comprise Ni(OH) 2 .
• the anodic core/shell structures can be formed by a deposition technique of the conformal shell on the core over a deposition cycling series, and wherein a morphology of the core prior to the deposition cycling series can remain substantially the same as the morphology of the core/shell structures after the deposition cycling series.
• FIG. 1 is illustrative of typical issues of Zn anode in alkaline electrolyte and design of a high-performance Zn anode by overcoming the issues, and includes schematic diagrams of passivation (FIG. 1A) and dissolution (FIG. 1B) issues of zinc anodes.
• FIG. 1C is a schematic diagram of the battery-GC quantitative analysis method developed to quantitatively identify the influence of HER on Coulombic efficiency of zinc anodes by measuring the H 2 evolved in the reactor after charging/discharging the zinc anode for 1 cycle.
• FIGS. 2A-C present a schematic diagram (FIG. 2A), experiment setup (FIG. 2B), and reactor design (FIG. 2C) of the battery-GC quantitative analysis method used to quantitatively identify the influence of HER on Coulombic efficiency of zinc anodes.
• PRR pressure reducing regulator
• MFC mass flow controller
• GC gas chromatography.
• FIGS. 3A-B include a graph (FIG. 3A) and schematic diagram (FIG.
• FIG. 4 is a schematic illustration of the presently inventive HER suppressing sealed nanorod (HSSN) zinc anode design principle: sealed sub-micron-sized anodes with an HER suppressing ion-sieving coating to overcome passivation, dissolution, and hydrogen evolution issues simultaneously in alkaline electrolytes.
• FIGS. 5A-C illustrate the fabrication of an HSSN anode. Schematic diagrams and scanning electron microscopy (SEM) images of carbon paper (FIG. 5A), ZnO nanorod anode (FIG.5B), and HSSN anode (FIG.5C).
• FIGS. 6A-C are SEM images of an uncoated ZnO nanorod anode with a mass loading of ZnO nanorods ranging from 0.5 mg/cm 2 to 5.5 mg/cm 2 .
• FIG. 7A is a schematic diagram of T1O2 coating process.
• FIGS. 7B-C are SEM images of ZnO nanorods before (FIG. 7B) and after T1O2 coating (FIG. 7C).
• FIG. 7D is a SEM image and elemental mappings of the present HSSN anode.
• FIGS. 8-11 are a characterization of a single ZnO@TiO 2 nanorod collected from the present HSSN anode.
• FIGS. 8A-8C include a scanning transmission electron microscopy (STEM) image and elemental mappings of a ZnO@TiO 2 nanorod.
• STEM scanning transmission electron microscopy
• FIGS. 9A-B shows spatial distributions of Zn and Ti elements and energy-dispersive X-ray (EDX) spectroscopies in the core and shell regions.
• EDX energy-dispersive X-ray
• FIG. 10 is a transmission electron microscopy (TEM) diffraction image of a ZnO@TiO 2 nanorod, showing the diffraction pattern of hexagonal ZnO.
• TEM transmission electron microscopy
• FIG. 11 is a TEM image of a ZnO@TiO 2 nanorod, showing the thickness ( ⁇ 30 nm) of a T1O2 coating.
• FIGS. 12A-C are varying magnitude SEM images of the present HSSN anode after etching ZnO away.
• FIG. 13 presents ICP results showing dissolved Zn concentration after soaking the present HSSN and uncoated ZnO anodes in 4M KOH solution. 90% ZnO dissolution is suppressed in the HSSN anode, which means that the TiO 2 coating effectively blocks zincate ions.
• FIGS. 14A-B are varying magnitude SEM images and elemental mappings of the uncoated ZnO (FIG. 14A) and HSSN (FIG. 14B) anodes after soaking in 4M KOH solution.
• the reservation of Zn in the HSSN anode supports the assumption that a TiO 2 coating can effectively block zincate ions.
• FIG. 15 is a graph of X-ray diffraction (XRD) patterns of uncoated ZnO and HSSN anodes before and after charging.
• the weak ZnO peaks of the HSSN anode after charging is from residual unreacted ZnO.
• FIGS. 16-17 are SEM images before and after charging of an uncoated ZnO anode (FIG. 16) and HSSN anode (FIG. 17).
• FIGS. 18-19 are SEM images of an uncoated ZnO nanorod anode (FIG. 18) and HSSN anode (FIG. 19) after five galvanostatic cycles with 25 ⁇ L electrolyte. They were cycled at ⁇ 0.25 mA/cm 2 for 2 hours of charge and ⁇ 0.25 mA/cm 2 discharge to 1.5V. The mass loadings of ZnO nanorods on both anodes are ⁇ 3.3 mg/cm 2 .
• FIG.20 is a STEM image of a ZnO@TiO2 nanorod after charging.
• FIG.21 is a STEM image and elemental mappings of a ZnO@TiO2 nanorod after charging.
• FIG.22 is a SEM image and elemental mappings of the present HSSN anode after charge.
• FIGS.23A-B are graphs illustrating the Brunauer-Emmett-Teller (BET) pore width distribution (FIG.23A) and surface areas (FIG. 23B) of uncoated ZnO and HSSN anodes. After TiO 2 coating, nanopores are measured which indicates that TiO 2 coating is nanoporous.
• FIG.24 is an X-ray photoelectron spectroscopy (XPS) survey of the ZnO@TiN x O y anode.
• XPS X-ray photoelectron spectroscopy
• FIG. 25 is a schematic diagram of a three-electrode cell in 4M KOH electrolyte with a TiO2 or TiNxOy electrode as the working electrode, an Hg/HgO electrode as the reference electrode, and Pt foil as the counter electrode.
• FIG.26 is a schematic of TiN ALD recipe.
• FIG.27 shows IR-corrected polarization curves of TiNxOy and TiO2 electrodes. At any fixed potential, the hydrogen evolution on TiNxOy electrode is severer than TiO2 electrode. Scan rate: 2 mV/s.
• FIG.28 shows IR-corrected polarization curves of a CP substrate, and TiN x O y and TiO 2 electrodes. HER can be suppressed with the existence of TiO 2 .
• CP carbon paper.
• Scan rate 2 mV/s.
• FIG.29A is an XPS survey spectra of the TiO 2 coating.
• FIG.29B is an XPS survey spectra of the TiN x O y coating.
• FIG. 29C is a table that shows sheet resistance and resistivity of TiN x O y and TiO 2 coatings measured using a four-point probe system.
• FIG.29A is an XPS survey spectra of the TiO 2 coating.
• FIG.29B is an XPS survey spectra of the TiN x O y coating.
• FIG. 29C is a table that shows sheet resistance and resistivity of TiN x O y and TiO 2 coatings measured using a four-point probe system.
• FIG. 30A shows basic models of TiO2, TiNxOy-1 and TiNxOy-2 clusters, and FIG. 30B an adsorption free energy diagram of each cluster.
• FIG.31A shows basic models of TiO 2 , TiN x O y -3 and TiN x O y -4 clusters, and FIG. 31B an adsorption free energy diagram of each cluster.
• FIG.32 is a table of a summary of simulated energy of clusters (M) and H-adsorbed clusters (M-H), binding energy, and free energy. Atoms in clusters: smallest “atom”, N; larger, H; larger still, Ti; and largest, O. [00116] FIG.
• FIG. 33 illustrates ICP results showing dissolved Zn concentration after soaking the uncoated ZnO, HSSN and ZnO@TiNxOy anodes in 4M KOH solution. 90% ZnO dissolution is suppressed in the HSSN and ZnO@TiNxOy anodes. This shows HSSN and ZnO@TiNxOy anodes have very similar ion-sieving capability.
• FIG.34 contains SEM images and elemental mappings of the ZnO@TiN x O y anode after soaking in 4M KOH solution. The reservation of Zn in the ZnO@TiN x O y anode supports that TiN x O y coating can effectively block zincate ions.
• FIG. 35A shows cell components of a pouch cell, and FIG. 35B the assembled pouch cell.
• the separator has a 1.5 cm diameter.
• the anode has a 1 cm diameter.
• FIG. 36 illustrates voltage profiles of Zn-Ni batteries with HSSN and ZnO@TiNxOy as anodes. The Coulombic efficiency of the present HSSN anode is higher with better HER suppressing capability.
• FIG. 37A shows cycling performance of the ZnO@TiNxOy and HSSN anodes in lean electrolyte at 100% DOD.
• FIG. 37B shows cycling performance of the HSSN and ZnO@TiNxOy anodes at various C rates. State of charge: 20%.
• FIGS. 38A-B are graphs illustrating BET pore width distribution (FIG. 38A) and surface areas (FIG.38B) of HSSN and ZnO@TiN x O y anodes.
• FIG. 39 is a table showing a comparison of Coulombic efficiency of the present HSSN anode with conventional zinc-based anodes (100% DOD) in alkaline electrolytes.
• FIG.40 shows cycling performance of the present HSSN anode in a lean electrolyte at 40% DOD
• FIG. 41 illustrates charge-discharge profiles of the present HSSN anode in a lean electrolyte at 40% DOD.
• FIG. 42 are CV curves of CP-TiO 2 and HSSN electrodes. There is no capacity contribution from TiO 2 during the electrochemical reaction. Scan rate: 10 mV/s.
• FIG. 43 are optic microscope images of the HSSN anode before and after battery failure.
• FIG. 44 shows cycling performance of the present HSSN anode in a beaker cell with a large amount of electrolyte at 100% DOD.
• FIGS. 45A-B are voltage profiles (from cycle 50 th to 70 th ) of the HSSN anode cycled in a lean electrolyte at 40% DOD (FIG.
• FIG.46 is a table comparing the present HSSN anode with conventional zinc-based anodes in aspects of electrolyte-to-discharge-capacity (E/DC) ratio and Coulombic efficiency in alkaline electrolyte.
• the DOD of Anode No. 0 is 40%.
• the DOD of the remaining Anode Nos. 1-22 are 100%.
• FIG. 47 illustrates via graph a comparison of the HSSN anode and conventional anodes (with 100% DOD) in aspects of E/DC ratio and Coulombic efficiency.
• FIG. 48 is another schematic similar to FIG.
• FIG.49 is a graph of 1 cycle discharge and charge test for Zn foil under 10 mA, showing that Zn foil can only deliver ⁇ 1.7 mAh capacity (1% utilization) and charge capacity is only 1/5 th of discharge capacity.
• FIG.50 is an SEM image of ZnO passivation layer on Zn mesh (Dexmet), formed by discharging Zn mesh under 1 mA with a 10 ⁇ L electrolyte. The separator used was Celgard 3501. [00134] FIG.
• FIG. 51 is a schematic of morphological changes of zinc electrode during electrochemical cycling, where the feature size of an uncoated ZnO nanorod of the prior art is smaller than the critical passivation size, however, the large electrode-electrolyte surface area accelerates anode dissolution and promotes electrode shape change.
• FIG. 52 is a schematic of morphological changes of zinc electrode during electrochemical cycling, where the shape of the present ZnO@TiN x O y nanorod anode retains during cycling with the inventive sealed nanorod structure.
• FIG.53 is a schematic of a TiN ALD recipe.
• FIGS.54A-54C are pictures of a beaker cell (FIG.54A), a coin cell (FIG.54B) and scalability of Zn-Ni single coin cell (FIG.54C). Top and bottom cases have an approximate 2 cm diameter. The separator has an approximate 1.5 cm diameter. The working electrode (WE) has an approximate 1 cm diameter.
• FIG.55 is an optical picture of a pouch cell.
• FIG. 56 is a schematic of the fabrication process for the present ZnO@TiN x O y core/shell nanorod anode.
• FIG.57 is a low magnification SEM image of a ZnO nanorod anode.
• FIG.59 is an SEM image of a ZnO@TiNxOy nanorod anode.
• FIG.60 is a TEM image of a ZnO@TiNxOy nanorod.
• FIG.61 is a high resolution transmission electron microscopy (HRTEM) image of a ZnO@100TiNxOy nanorod, showing the thickness ( ⁇ 6.1 nm) of the TiNxOy coating.
• HRTEM transmission electron microscopy
• FIG.62 is an HRTEM image of a ZnO@TiNxOy nanorod, showing the lattice of ZnO, G))+H% L e )'+/ UT'
• FIG. 63 is an electron diffraction pattern of a ZnO@TiN x O y nanorod, showing the diffraction pattern of ZnO.
• FIG.64 is an SEM image and elemental mapping of ZnO@TiN x O y nanorods.
• FIGS.65-67 are graphs of an XPS survey of ZnO nanorod and ZnO@TiNxOy nanorod anodes (FIG.65); a high-resolution XPS spectra of Zn 2p peaks (FIG.66); and a high-resolution XPS spectra of Ti 2p peaks (FIG.67).
• the samples shown in FIGS.59-67 are all deposited by ALD for 100 cycles.
• FIGS. 68-69 are XPS survey spectra (FIG. 68) and high-resolution Zn 2p and Ti 2p spectra (FIG. 69) of a ZnO@TiN x O y nanorod anode with 200 cycles ALD.
• FIG. 70 illustrates ICP results and an image (inset) showing dissolved Zn concentration after soaking the ZnO@TiN x O y and uncoated ZnO anodes in 4M KOH solution.
• FIGS. 71-72 are SEM images of an uncoated ZnO nanorod anode (FIG. 71) and a ZnO@TiN x O y nanorod anode (FIG. 72) before and after a 2 hour charge with a 25 ⁇ L electrolyte.
• FIG. 74 are SEM images of approximately 0.5 mg/cm 2 ZnO@TiN x O y nanorod anode with 200 cycles ALD after a 1 hour constant current charge at 1C rate with a 25 ⁇ L electrolyte. Tin was used as anode current collector.
• FIG. 74 is an SEM image and elemental mapping of a ZnO@TiN x O y nanorod anode after a 2 hour charge.
• FIG. 75 is an TEM image of a ZnO@TiN x O y nanorod anode after 2 hour charge.
• FIGS. 72 and 74-75 are from the same anode sample with 100 cycles ALD.
• FIG. 76 are XRD results of a ZnO nanorod and a ZnO@TiN x O y nanorod anode before and after charge.
• the weak ZnO peaks of ZnO@TiN x O y nanorod anode with 200 cycles ALD after charge is from residual unreacted ZnO.
• Tin foils were used as anode current collectors.
• FIG. 77 is an electrochemical impedance spectroscopy (EIS) result and equivalent circuit of an uncoated ZnO anode and a ZnO@TiN x O y nanorod anode.
• EIS electrochemical impedance spectroscopy
• FIGS. 78-80 are SEM images of a pristine ZnO@TiN x O y nanorod anode with 200 cycles ALD (FIG. 78), after a 3 hour constant current charge at 0.33C with a 25 ⁇ L electrolyte (FIG. 79), and after further constant current discharge at 0.33C (0.7 hours) to 1.5 V with a 25 ⁇ L electrolyte (FIG. 80). All SEM images are from same sample with a mass density of ⁇ 1.7 mg/cm 2 . This result indicates that there is almost no shape change during the charge and discharge step.
• FIGS. 81-82 are SEM images of a pristine uncoated ZnO nanorod anode (FIG. 81), and after a 3 hour constant current charge at 0.33C with a 25 ⁇ L electrolyte (FIG. 82). All SEM images are from same sample with a mass density of- 1.7 mg/cm 2 . Some nanorods were detached from the beginning as shown in FIG. 81, due to external mechanical force during transfer. After charge, most ZnO nanorods grown on the top layer of carbon fibers detached. Because of the small amount of electrolyte, the ZnO nanorods grown on the inner carbon fibers were not in contact with electrolyte in the first charge, and remained.
• FIG. 83 is a schematic diagram of beaker cell and coin cell.
• FIG. 84 shows cycling performance of pure current collector in the beaker cell and coin cell. Real: count all the zinc in the electrolyte. Pseudo: calculation without counting zinc in the electrolyte. One dot every four data points.
• FIG. 85 illustrates discharge capacity for the first 32 galvanostatic cycles of an uncoated ZnO nanorod and the ZnO@TiN x O y nanorod anodes with ⁇ 2.1 mg/cm 2 at 0.5C rate in a coin cell with ZnO-free electrolyte. 50 ⁇ L electrolyte was dropped onto a separator and 10 ⁇ L electrolyte was dropped onto cathode. Inset: optical image of a coin cell.
• FIG. 86 is a graph of the charge voltage profiles of the ZnO and ZnO@TiN x O y anodes.
• FIG. 86 illustrates discharge capacity retention of uncoated ZnO nanorod and ZnO@TiN x O y nanorod anodes with - 1.5 mg/cm 2 at 0.25C rate in coin cells. 25 ⁇ L electrolyte was dropped onto separator. The cut-off voltages are approximately - 1.5/1.9V. The maximum discharge capacity (corresponding to approximately 100%) of uncoated ZnO nanorod and ZnO@TiN x O y nanorod anodes are approximately 235.2 mAh/g and approximately 153.5 mAh/g, respectively.
• FIG. 88 shows cycling performance of - 1.1 mg/cm 2 ZnO@TiN x O y nanorod anodes in pouch cells with ZnO saturated and ZnO-free electrolytes, respectively. They were cycled at 1C for charge and 5C for discharge with approximately 1.4/2V cut-off voltages.
• FIG. 89 is a comparison of specific discharge capacity between the present anode and previously reported anodes. Zinc in the electrode and electrolyte are both counted.
• FIG. 90 shows cycling performance of the ZnO@TiN x O y nanorod anode ( ⁇ 2 mg/cm 2 ) with 200 cycles with ALD at 0.5C charge and 2C discharge rates in beaker cell with 10 mL ZnO saturated 4M KOH electrolyte.
• the cut-off voltages are approximately 1.4/2 V. One dot every five data points.
• FIG. 91 is a cyclic voltammogram (CV) for ZnO@TiN x O y anode in a coin cell at approximately 0.1 mV/s scan rate. The CV was done using two electrodes with ZnO@TiN x O y anode and Ni(OH) 2 cathode in ZnO free electrolyte.
• FIGS. 92-93 are CVs for ZnO@TiN x O y anodes in a pouch cell (FIG. 92) and beaker cell (FIG. 93) at an approximately 0.1 mV/s scan rate.
• the CV for the anode in pouch cell was done using two electrodes with ZnO@TiN x O y anode and Ni(OH) 2 cathode in ZnO saturated electrolyte.
• the CV for the anode in beaker cell was done using three electrodes with ZnO@TiN x O y anode, Hg/HgO reference electrode and graphite counter electrode in ZnO saturated 4M KOH electrolyte.
• FIG. 94 is a current density profile as cycled under start-stop conditions in coin cells.
• FIG. 95 shows long-term discharge capacity retention of Zn foil and a ZnO@TiN x O y nanorod anode as cycled under start-stop conditions with 100 ⁇ L electrolyte.
• the Zn foil with approximately 0.02% DOD and the ZnO@TiN x O y nanorod anode with approximately 1% DOD were cycled at the same current density, which is shown in FIG. 94.
• Tin foils were used as anode current collectors. Cells were cycled between approximately 0 and 2 V.
• FIG. 96 are voltage profiles of a ZnO@TiN x O y nanorod anode of the 2000 th and 4000 th cycles under start-stop conditions.
• FIGS. 97-98 are photos of cells, with a ZnO@TiN x O y nanorod anode (FIG. 97) and Zn foil (FIG. 98) as anode respectively, after long-term start-stop conditions at the same current density (shown in FIG. 94).
• FIG. 99 shows the discharge capacity of a ZnO@TiN x O y nanorod anode under rate test conditions, showing electrochemical stability at different rate after several activation cycles.
• FIG. 100A illustrates ZnO NPs with fast dissolution rate in alkaline aqueous solution
• FIG. 100B illustrates ZnO NPs coated with carbon
• FIG. lOOC illustrates the present Zn-pomegranate in which carbon filled into the free space of ZnO clusters plays an important role in ion sieving, conductivity, and structure stabilization of the electrode
• FIG. 100D shows the calculated surface area in contact with electrolyte and the number of primary nanoparticles in one Zn pomegranate cluster versus its diameter. The smaller the surface contact with the electrolyte, the lower the capacity fading.
• FIG. 101 is a cross-sectional SEM image of Zn mesh with a ZnO passivation layer formed on it after discharging the Zn mesh under 1 mA with a 100 ⁇ L electrolyte comprising 2M KF, 2M K 2 CO 3 and 4M KOH. The passivation layer is approximately 2 ⁇ m.
• FIG. 102 illustrates the synthesis of a Zn-pome.
• FIG. 102A shows the Zn-pome were prepared by a bottom-up microemulsion approach.
• FIG.102B is a picture of ZnO NPs.
• FIGS.103A-C are SEM images of clusters of ZnO nanoparticles assembled via a microemulsion approach.
• FIGS.103D-F are SEM images of Zn-pome (nano-porous carbon- coated ZnO cluster).
• FIG. 103G is a TEM image of Zn-pome.
• FIG. 103H is a TEM image of the carbon framework of Zn-pome after etching away ZnO in 1M HCl for 24 hours.
• FIG. 103I is a cross-sectional SEM image of one Zn-pome microparticle obtained by focused ion beam (FIB) analysis.
• FIG. 104A is a TEM image of a Zn-pome.
• FIG. 104B is a schematic of etching ZnO.
• FIGS.104C-F are TEM images of the Zn-pome after etching away ZnO in 1M HCl.
• FIGS. 105-106 are FIB milling of Zn-pome.
• FIG. 105 is a top-view image of Zn- pome after FIB milling.
• FIG.106 is a cross-section image of Zn-pome after FIB milling.
• FIG. 107A illustrates XRD patterns and FIG. 107B XPS spectra of ZnO NPs, ZnO@C NPs and Zn-pome.
• FIG. 107C is a high-resolution XPS spectra of ZnO NPs and Zn- pome.
• FIG. 107A illustrates XRD patterns and FIG. 107B XPS spectra of ZnO NPs, ZnO@C NPs and Zn-pome.
• FIG. 107C is a high-resolution X
• FIG. 107D is a TGA weight loss curve and FIG. 107E is a BET pore size distribution of Zn-pome.
• FIG. 107F shows dissolved and undissolved portions of zinc in 4M KOH electrolyte for ZnO NPs, ZnO@C NPs and Zn-pome; embedded pictures show the electron microscopy images of ZnO NPs, ZnO@C NPs and Zn-pome.
• FIG.108 includes a picture of CR2032 coin cell cases (left) and a schematic of coin cell components and their arrangement used (right).
• FIG. 109A is a graph of specific capacity of ZnO NPs and Zn-pome.
• FIG. 109A is a graph of specific capacity of ZnO NPs and Zn-pome.
• FIG. 109B is voltage profiles of Zn-pome/Ni(OH)2.
• FIG. 109C is a graph of specific capacity of ZnO NPs/Ni(OH)2 and Zn-pome/Ni(OH)2 at a 5C discharge rate.
• FIG. 109D illustrates testing of self- discharge of Zn-pome cell cycling at 0.5C for one cycle, resting for 24 hours, then cycling at 1C.
• FIG. 109E is a SEM image of Zn-pome anode before cycling (FIGS.109F and G) and after two [00183]
• FIG.110A is a graph of specific capacity of Zn-pome, ZnO NPs@C and ZnO NPs.
• FIG.110B shows additional battery cycling data of bare ZnO and Zn-pome anodes (1C rate).
• FIG. 111 illustrates the performance of bare ZnO and Zn-pome anodes at 5C discharge rate.
• FIG. 112 presents the cycle performance of bare ZnO and Zn-pome anodes (charged at 1C, discharged at 5C), after resting for 24 hours followed by the first cycle at 0.5C.
• FIGS. 113A-F are SEM images of Zn-pome anode after cycling at 1C.
• FIGS. 113A-D after cycling 10 cycles.
• FIGS.113E-L after cycling 20 cycles.
• FIG. 113A-F SEM images of Zn-pome anode after cycling at 1C.
• FIGS. 113A-D after cycling 10 cycles.
• FIGS.113E-L after cycling 20 cycles.
• FIG. 114A is a SEM image of commercial ZnO nanoparticles with a short rod- like shape.
• FIG.114B is a TEM image of a ZnO@C nanoparticle.
• FIG. 114C are TGA results used to determine the carbon content in ZnO@C nanoparticles.
• FIG. 114D is SEM image of carbon-coated ZnO nanoparticles (ZnO@C).
• FIG.114E is a TEM image of HCl etched ZnO@C particles, resulting in a uniform hollow carbon nanoshell.
• FIG. 114F are XRD results for bare ZnO and ZnO@C nanoparticles. [00188] FIG.
• FIG. 115 is a SEM image of nanoparticles ZnO@C at 5.0 kV. The ZnO@C core- shell structure is visible.
• FIG. 116 contains SEM images of ZnO@C particles with different carbon shell thickness, synthesized using different mass of dopamine hydrochloride. The mass of dopamine hydrochloride is 100 mg (1:1), 200 mg (2:1), and 300 mg (3:1).
• FIG. 117 shows TGA data of ZnO@polydopamine nanoparticles under an Ar environment. Above about 680 °C, there is a dramatic sample weight loss, suggesting that ZnO gets reduced by carbon and escapes from the carbon shell. [00191] FIG.
• FIG. 118A illustrates the structure and size of hydroxide ion and zincate ion calculated by DFT.
• FIG. 118B is XPS spectra for bare ZnO and ZnO@C nanoparticles.
• FIG. 118C is XPS high-resolution Zn spectra for bare ZnO and ZnO@C nanoparticles.
• FIG.118D is a graph of N2 adsorption/desorption isotherms of ZnO and ZnO@C nanoparticles.
• FIG. 118E is a graph of BET pore width distribution of ZnO and ZnO@C nanoparticles.
• FIG. 118F is a graph of ICP-AES quantification of ZnO dissolution in KOH electrolyte from bare ZnO and ZnO@C nanoparticles for 5 minutes, 1 day, and 10 days. Bare ZnO dissolves much faster than ZnO@C.
• FIG.119 illustrates specific capacity and Coulombic efficiency of bare ZnO (1.03 mg), ZnO@C (0.94 mg), and bulk Zn foil anodes during discharge process, the inset shows a typical 2032 coin cell fabricated during the experiment.
• FIG. 120 is a second set of cycling data of bare ZnO and ZnO@C anodes.
• FIG.121 is a comparison of voltage profile between bare ZnO and ZnO@C for the first charging process, ZnO@C particles show a lower overpotential.
• FIG.122 is a comparison of voltage profile between bare ZnO and ZnO@C for all the cycles, ZnO@C particles show a lower overpotential for every cycle.
• FIG. 123 shows voltage profiles of the cell with ZnO@C anode at 1 st , 10 th , 20 th , 30 th , 40 th cycles.
• FIG. 124A is a SEM image of bare ZnO anode before cycling.
• FIG. 124B is a SEM image of bare ZnO anode after three cycles, showing a dramatic shape change. Pores are indicated by yellow arrows.
• FIG.124C is a SEM image of ZnO@C anode before cycling.
• FIG. 124D is a SEM image of ZnO@C anode after three cycles, the nanoparticles maintained a spherical shape as before cycling.
• FIG.125 is a TEM image of a ZnO@C particle after charging, the active material is still well confined inside the nanoshell.
• FIG. 124A is a SEM image of bare ZnO anode before cycling.
• FIG. 124B is a SEM image of bare ZnO anode after three cycles, showing a dramatic shape change. Pores are indicated by yellow arrows.
• FIG.124C is a SEM image of Z
• FIG. 126 illustrates the performance of ZnO@C batteries with different thickness of nanoshell coating.
• the mass of active material is ⁇ 1mg and the batteries are tested at 1C rate and 100% DOD.
• ZnO@C 2:1 shown in the main text demonstrates superior performance.
• FIG. 127 presents the Coulombic efficiency in a ZnO@C pouch cell with ZnO saturated electrolyte at 1C and 100% DOD.
• FIG. 128 presents the Coulombic efficiency of a ZnO@C pouch cell with >95% Coulombic efficiency and ⁇ 100% retention for 500 cycles, with an actual rate of 12C.
• Ranges can be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, another exemplary embodiment includes from the one particular value and/or to the other particular value.
• Using “comprising” or “including” or like terms means that at least the named compound, element, particle, or method step is present in the composition or article or method, but does not exclude the presence of other compounds, materials, particles, method steps, even if the other such compounds, material, particles, method steps have the same function as what is named. [00207] Mention of one or more method steps does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Similarly, it is also to be understood that the mention of one or more components in a device or system does not preclude the presence of additional components or intervening components between those components expressly identified.
• Exemplary embodiments of the present invention comprise innovative components of a deeply rechargeable battery system, and an innovative system and method of rechargeable batteries.
• a core/shell nanoscale structure provides deeply rechargeable anodes that overcome intrinsic limitations of conventional battery materials that involve soluble intermediates or insulating discharge products.
• the present invention simultaneously overcomes the dilemmas of passivation and dissolution.
• An ion-sieving concept is applied to a Zn anode that confines larger zincate ions and allows smaller hydroxide ions to permeate, can limit/prevent ZnO dissolution and [00209]
• Examples of the present invention include sealing ZnO nanorods for deeply rechargeable high-energy aqueous battery anodes, a deeply rechargeable zinc anode with pomegranate-inspired nanostructure for high-energy aqueous batteries, ion-sieving carbon nanoshells for deeply rechargeable Zn-based aqueous batteries, and a deeply rechargeable and hydrogen-evolution-suppressing zinc anode in alkaline aqueous electrolyte.
• FIG. 1A is illustrative of the passivation issue
• FIG. IB is illustrative of the dissolution issue.
• these issues are due to the following processes: (i) the insulating discharge product ZnO passivates the surface of zinc anodes, preventing the latter from further discharging or recharging back to metallic zinc, and (ii) the intermediate zincate is soluble in alkaline electrolytes, which leads to active material loss, random ZnO precipitation on the electrode, and morphology change of the electrode over cycling.
• a GC quantitative analysis method (FIGS. 1C and 2A-C) is used herein to identify the influence of HER on the capacity loss of zinc anodes. This is achieved by measuring the evolved 3 ⁇ 4 using GC after charging/discharging the zinc anode in alkaline electrolyte (ZnO-saturated 4M KOH) for one cycle (FIGS. 3A-B).
• the present invention comprises sealed sub-micronsized anodes, coated with a HER suppressing ion-sieving layer to simultaneously tackle passivation, dissolution, and HER issues (FIG. 4).
• a design features at least the following advantages: (i) sub-micron-sized ZnO avoids passivation and allows complete utilization of the active materials; (ii) the ion-sieving coating layer confines zincate inside and mitigates shape changes of the electrode; and (iii) the coating layer is made of a HER suppressing material, which represses side reactions.
• HER suppressing sealed nanorod (HSSN) zinc anodes exhibit long cycle life, high Coulombic efficiency, and high specific discharge capacity.
• the critical thickness of ZnO passivation layer has previously been quantified to be ⁇ 2 ⁇ m when a zinc metal anode is completely passivated.
• sub-micron-sized zinc anodes are believed to be able to overcome the passivation problem.
• decreasing the feature size to be nanoscale will intensify the dissolution and HER problems, due to increased electrode- electrolyte contact area. Therefore, sealing sub-micron-sized anodes by uniformly coating a HER suppressing ion-sieving layer is developed, which can suppress HER and selectively block larger zincate ions inside the coating while enabling OH-/H2O transport (FIG.4).
• Coat technology is important, as conventional attempts with non-uniform coatings creates structures that still suffer dissolution and HER issues, which might be a reason these prior results had short cycle life ( ⁇ 20 cycles) and low specific discharge capacity.
• a TiO 2 coating material is investigated to demonstrate it is stable with alkaline electrolytes and has a low HER activity.
• the present HSSN anode was successfully fabricated as shown in FIGS.5A-C. ZnO nanorods were first grown on the carbon paper hydrothermally. The mass loading of ZnO nanorods on carbon paper can be tuned from 0.5 mg/cm 2 to 5.5 mg/cm 2 .
• the ZnO precursor solution was prepared by mixing 50 mL zinc nitrate hexahydrate (30 mM, Alfa Aesar), 50 mL hexamethylenetetramine (30 mM, Sigma Aldrich), and ammonia (28.0-30.0% NH3 basis, Sigma Aldrich). [00220]
• the seeded carbon paper was placed in the solution, followed by heating in an oven at 90 °C. After DI-H2O washing and drying at 80 °C for 3 hours, the white-colored product on carbon paper was obtained.
• Different mass loadings (0.5 ⁇ 5.5 mg/cm 2 ) of ZnO nanorods on carbon paper were achieved by adjusting reaction conditions, as summarized in TABLE 1 and shown in FIGS. 6A-C.
• the “Repeat” column means that the ZnO nanorods-loaded carbon paper from the first reaction was put into a new precursor solution to repeat the reaction.
• the XRD patterns (Panalytical XPert PRO Alpha-1) were carried out with Cu K-Alpha radiation.
• the XPS was measured with Thermo Scientific K-Alpha system.
• the specific BET surface areas and pore size distribution were determined by physisorption (BELSORP-max, MicrotracBEL Corp.).
• the dissolved Zn concentration of samples in 4M KOH electrolyte was measured with an ICP measurement. Cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy were conducted using a VSP system (BioLogic). Battery cycling tests were carried out using LANHE operating in galvanostatic mode. [00231] In the battery-gas chromatography quantitative analysis measurement, the airtight battery system (FIGS.
• Coin Cell [00235] CR2032 cases (MTI Corporation) were used to make coin cells.
• the aqueous electrolyte consists of 4M KOH (Sigma Aldrich, 99.99%), 2M KF (Alfa Aesar, 99.99%) and 2M K2CO3 #5SNI 5MZIY% 22'220"$' +.
• Pouch-type batteries (FIGS. 35A-B) were assembled using Ampac’s SealPAK.
• the mass loading of active material (ZnO) on the anode is 1.5 mg/cm 2 .
• the aqueous electrolyte comprises 4M KOH (Sigma Aldrich, 99.99%), 2M KF (Alfa Aesar, 99.99%) and 2M K2CO3 (Alfa Aesar, 99.997%) with saturated ZnO. 100 mT electrolyte was used. Glass fiber (GE Healthcare, WhatmanTM 10370003) was used as the separator. Ti wires were used as electrode terminals.
• Cells are galvanostatically cycled at a charge rate of 1C and a discharge rate of 5C between 1.4 and 1.9 V.
• the anodes were activated by being pre- cycled in pouch cells for 6 cycles.
• the charge capacity limit cut-off is 658 mAh/g (theoretical specific capacity of ZnO).
• the anodes were activated by being pre-cycled with 100% active material utilization for 1 cycle and then being fully charged.
• the mass loading of active material (ZnO) on the anode is 1.6 mg/cm 2 .
• 10 mL ZnO-saturated 4M KOH (Sigma Aldrich) was used as the electrolyte.
• Cells are galvanostatically cycled at 100% DOD at a charge rate of 1 C and a discharge rate of 5C between 1.4 and 1.9 V.
• the anodes were activated by being pre-cycled in beaker cells for 50 cycles.
• the charge capacity limit cut-off is 658 mAh/g.
• Ag wire was used as the anode terminal.
• Stainless steel wire was used as the cathode terminal.
• charge capacity was limited to the theoretical capacity of ZnO (approximately 658 mAh/g).
• charge capacity was calculated by:
• MW is the molar weight of active material
• n is the number of electrons transferred in the relevant reaction
• F is the Faraday’s constant.
• MW of ZnO 81.38 g/mol
• n 2
• F 96485 C/mol.
• the ZnO in the core has a hexagonal close packed crystal structure and the TiO2 coating is amorphous.
• the TiO2 layer has a thickness of ⁇ 31.7 nm (FIG. 11).
• the mass loading of TiO2 is ⁇ 0.35 mg/cm 2 , which is only ⁇ 10.4 wt% of the present HSSN anode (with approximately 3 mg/cm 2 ZnO nanorods).
• the hollow nanoarrays stayed in place (FIGS. 12A-C), displaying that the TiO 2 coating, although only ⁇ 30 nm thick, is mechanically strong and firmly supports the ZnO nanorods.
• the dissolved Zn of the HSSN anode (1.9%) was much lower than that of the uncoated ZnO anode ( ⁇ 16.9%).
• ⁇ 90% ZnO dissolution is suppressed in the HSSN anode, which displays that the TiO2 shell effectively blocks zincate ions.
• Both anodes were imaged after soaking in 4M KOH solution (FIGS. 14A-B), which also supports that TiO2 coating can effectively confine zincates inside the shell.
• the zinc-based anodes were also characterized before and after a single charge in coin cells. As shown in FIG. 15, XRD patterns confirmed the existence of the charging product, metallic Zn.
• TiO2 layer has nanosized pores, which block larger zincate ion inside the shell and enable OH-/H 2 O transport through the shell.
• the porosity of TiO 2 can likely be further engineered to optimize its ion-sieving performance.
• an ion-sieving coating layer is important for nanostructured Zn anodes to effectively suppress active material dissolution.
• such an ion- sieving coating layer should be HER suppressing.
• HER activities of TiO2 and TiNxOy were investigated. [00262] TiNxOy (Fig.
• the HER on the TiNxOy electrode was more severe (higher current density at a fixed HER potential) than on TiO2.
• These experimental results reveal that the TiO2 is more hydrogen suppressive than TiNxOy.
• the HER activities of the TiO2 electrode were also compared with the carbon paper substrate, which experimentally indicates that the existence of TiO2 coating can suppress HER (FIG. 28).
• the sheet resistance of TiO2 and TiNxOy was measured using a four-point probe system (FIGS.29A-C). [00264] TiO2 has lower electrical conductivity, which may be part of the reason for its lower HER activity and better HER suppressing capability.
• AGH* represents the free energy for FI adsorption.
• FISSN and ZnO@TiN x O y anodes have very similar ion-sieving capability. With hydrogen suppressing capability, the present FISSN anode shows higher Coulombic efficiency compared to the ZnO@TiN x O y counterpart.
• cathodes with excess capacity were harvested to pair with Zn anodes.
• the calculation of the specific capacity of zinc anodes is based on the mass of ZnO (theoretical capacity: 658 mAh/g) if not otherwise specified. Cells were galvanostatically cycled at a charge rate of 1C and a discharge rate of 5C.
• the anodes were cycled in pouch cells (FIGS. 35A- B) instead of coin cells to avoid the FIER on stainless steel coin cell cases. They were cycled at 100% DOD. Thus, the extent of side reactions on them can be directly indicated by the cell Coulombic efficiency. Fligher “clean” Coulombic efficiency means fewer side reactions.
• the present HSSN anode when cycled at 40% DOD in a lean electrolyte, the present HSSN anode (with 1.05 mg/cm 2 ZnO) demonstrated long-term stable cycling for more than 170 cycles. There was no capacity contribution from the TiO2 shell during the electrochemical reactions (FIG. 42).
• the present HSSN anode When cycled at 100% DOD in a lean electrolyte, the present HSSN anode (with ⁇ 1.5 mg/cm 2 ZnO) achieved an average Coulombic efficiency of 93.5% and average discharge capacity of 616 mAh/g in the first 12 galvanostatic cycles (FIG.37A). [00271] The capacity fading occurs after 33 cycles.
• the battery failure can be attributed to (1) the structural collapse of the HSSN anode (FIG.43) due to the shape and volume changes of Zn/ZnO inside the shell, and (2) the limited mass transfer of Zn species caused by electrolyte decomposition and hydrogen accumulation.
• the anode was also evaluated in a beaker cell with a large amount of ZnO-saturated electrolyte. As shown in FIG. 44, the present HSSN anode (with ⁇ 1.6 mg/cm 2 ZnO) was cycled more than 350 times with Coulombic efficiency of 94.3% and a discharge capacity of 621 mAh/g. [00272] Voltage profiles for the batteries shown in FIGS.40 and 44 can be found in FIGS. 45A-45B.
• cycle life of Zn anodes in a lean electrolyte is much shorter than in a large amount of ZnO-saturated electrolyte. This can be explained by the electrochemistry of alkaline Zn anodes. In a large amount of ZnO-saturated electrolyte, the effect of minor electrolyte decomposition can be minimized with excess water. Moreover, there is excess zincate in the electrolyte, which is the active material for Zn anodes.
• the long cycle life of Zn anodes can be IKPQM]ML ⁇ M[ Q[ QZ QUI ⁇ [PMU[QK' ⁇ U SMIU MSMK[YVS ⁇ [M #*)) m>$% JI[[MYQMZ NIQS X ⁇ QKRMY IZ I YMZ ⁇ S[ VN complicated synergistic effects caused by electrolyte decomposition and limited mass transfer of Zn species.
• Electrolyte-to-discharge-capacity (E/DC) ratio is also critical for device-level energy density and is crucial for practical applications.
• the tested Coulombic efficiency of alkaline Zn anodes is highly correlated to the E/DC ratio. Thus, it is necessary to provide E/DC ratios to get a fair comparison on the Coulombic efficiency of different Zn anode materials. However, only a few previous works (summarized in the table of FIG.46) reported this ratio or provided necessary information for its calculation.
• Prior results were summarized, and the anode compared with them in terms of Coulombic efficiency and E/DC ratio in FIG. 47.
• HER suppressing core/shell Zn anode (1) Zn species are confined inside the shell so there is minimized active material loss; and (2) minimized HER and less electrolyte decomposition can be achieved with the HER suppressing property. These enable the present anode to achieve high Coulombic efficiency in lean electrolyte.
• the overall real and specific discharge capacities of the present HSSN anode were ⁇ 0.9 mAh/cm 2 and ⁇ 91 mAh/g, respectively, after considering the mass of the current collector. Due to its specially featured core/shell nanorod structure, its overall capacity was unable to meet design parameters for practical Zn anodes (11.7 mAh/cm 2 ), however the present design principals achieves practically high energy-density Zn anodes.
• the present zinc anode design namely sealing sub-micron-sized ZnO with a HER suppressing and ion-sieving layer, to overcome simultaneously passivation, dissolution, and hydrogen evolution issues in alkaline electrolytes is disclosed.
• a ZnO nanorod anode and TiO2 shell were chosen to demonstrate this concept.
• the fabricated HSSN anode achieves superior reversible deep cycling performance at lean electrolyte. While the Coulombic efficiency of the present HSSN anode is higher than that of most of the previously reported zinc anodes, it will be improved to approach the efficiency of LIBs (99.9%).
• the passivation problem (nonconductive property of ZnO) of Zn foil limits the utilization ( ⁇ approximately 1%) of Zn foil anode and makes it non-rechargeable. Under approximately 10 mA discharge, one can only get ⁇ 1.7 mAh capacity of Zn foil with approximately 0.25 mm thickness and approximately 1 cm diameter in a coin cell. As shown in FIG. 50, the thickness of the passivation layer (or the critical passivation size) is ⁇ 2 ⁇ m. Microporous Zn sponges are known, and enhance rechargeability, yet the Zn sponge feature size is ⁇ 10 ⁇ m (greater than the critical passivation size of approximately 2 ⁇ m), so only approximately 40% DOD of them can be achieved.
• the feature size of an uncoated ZnO nanorod is smaller than the critical passivation size, however, the large electrode-electrolyte surface area accelerates anode dissolution and promotes electrode shape change. Moreover, due to the relatively insulating property of ZnO, electrons can only be distributed on carbon paper, which leads to fast complexation and electroreduction reactions on the root of nanorods in charging. As a result, the nanorods of FIG.51 detach from carbon paper. [00283] In an exemplary embodiment of the present invention as shown in FIG.
• each ZnO nanorod is smaller than the critical passivation size; (ii) a carbon paper framework and TiN x O y coating, which encapsulates the ZnO nanorod, function as an electrical pathway so that all ZnO nanorods are electrochemically active; and (iii) the TiNxOy coating enables fast hydroxide/water diffusion as well as blocks large zincates from escaping during electrochemical cycling, thus effectively preventing anode structure fracture.
• Carbon paper (Fuel Cell Store) was first heat-treated at 500 °C for 1 hour in air to increase its wettability.
• ZnO nanorods were grown on the carbon paper by a wet chemical process.
• carbon paper was soaked in an aqueous solution containing 0.1M KMnO 4 (Sigma Aldrich) for 1 hour to form a seed layer.
• the seeded carbon paper was then dipped into a glass bottle with a precursor solution containing 50 mL zinc nitrate hexahydrate (30 mM, Alfa Aesar), 50 mL hexamethylene-tetramine (30 mM, Sigma Aldrich), and ammonia (28.0 ⁇ 30.0% NH 3 basis, Sigma Aldrich).
• the sealed bottle was placed into an oven at 90 °C.
• the white-colored carbon paper ZnO nanorods were obtained by water washing and drying at 80 °C for 3 hours.
• different mass loadings of ZnO nanorods on carbon paper ranging from 0.5 mg/cm 2 to 5.5 mg/cm 2 were synthesized by adjusting: the carbon paper area per bottle, the NH3 concentration, the hydrothermal time, and the hydrothermal times.
• TABLE 2 [00288] Synthesis of ZnO@TiNxOy Core/Shell Nanorods [00289] The synthesis of ZnO@TiN x O y core/shell nanorods was conducted in Cambridge FIJI Plasma ALD system. First, the TiN was deposited onto the ZnO nanorods.
• the precursors of TiN were Tetrakis(dimethylamido)Titanium(IV) (TDMAT, Sigma Aldrich) and N2.
• TDMAT Tetrakis(dimethylamido)Titanium(IV)
• N2 Tetrakis(dimethylamido)Titanium(IV)
• TDMAT Tetrakis(dimethylamido)Titanium(IV)
• TDMAT Tetrakis(dimethylamido)Titanium(IV)
• N2 Tetrakis(dimethylamido)Titanium(IV)
• Electrochemistry [00291] To investigate the Zn anode, full batteries were made using Ni(OH)2 as the rechargeable cathode. The Ni(OH)2 cathodes were harvested from commercial Ni-Zn AA batteries from PowerGenix. [00292] Coin Cell [00293] Coin-type batteries were assembled using CR2032 cases (MTI Corporation), the present zinc anodes (round disk, approximately 1 cm diameter) and Ni(OH)2 cathodes with excess capacity, as shown in FIGS.54A-54C. The coin cell has a small volume of electrolyte, which is required for practical application.
• the aqueous electrolyte comprises 4M KOH (Sigma Aldrich, 99.99%), 2M KF (Alfa Aesar, 99.99%) and 2M K 2 CO 3 (Alfa Aesar, 99.997%).
• Glass fiber GE Healthcare, Whatman TM 10370003 was used as the separator.
• the ZnO@TiNxOy nanorod anode and Zn foil were pre- activated.
• the ZnO@TiNxOy nanorod anode was pre-cycled three times at 0.5C between approximately 1.4 and 2 V.
• the Zn foil (approximately 0.02% DOD) was firstly discharged for 2 hours and re-charged for 2 hours at a constant current of approximately 1.35 mA. Then it was discharged twice and charged once at the same time interval of 1 hour at approximately 1.35 mA. [00295]
• the Zn foil (approximately 1% DOD) was pre-cycled twice at a constant current of approximately 1 mA.
• the cathode harvested from commercial Ni-Zn AA batteries was electrochemically oxidized to approximately 0.6 V vs an HgO/Hg reference electrode in a beaker cell with 2M KOH as the electrolyte.
• Pouch Cell [00296] Pouch Cell [00297] Pouch-type batteries (FIG. 55) were assembled using Ampac’s SealPAK, the present zinc anodes (round disk, approximately 1 cm diameter) and Ni(OH) 2 cathodes with excess capacity.
• the aqueous electrolyte comprises 4M KOH (Sigma Aldrich, 99.99%), 2M KF (Alfa Aesar, 99.99%) and 2M K2CO3 (Alfa Aesar, 99.997%).
• Celgard 3501 close to anode
• Freudenberg 700/28K close to cathode
• ZnO nanorods are synthesized on carbon paper with mass loading ranging from approximately 0.5 to approximately 5.5 mg/cm 2 (FIGS. 56-58C) by adjusting the area of carbon paper placed in hydrothermal reactor, NH 3 concentration, hydrothermal time, etc. (TABLE 1). In the ALD process (FIG. 53), the recipe was run 100 or 200 cycles.
• the TiN x O y mass loadings of 100 cycles and 200 cycles are approximately 0.057 mg/cm 2 and approximately 0.19 mg/cm 2 , which are only approximately 0.6 wt% and approximately 1.9 wt% of ZnO@TiNxOy nanorod anode, respectively (for approximately 3 mg/cm 2 ZnO nanorods).
• the nanorod morphology does not change after TiNxOy coating (FIGS.59 and 64). HRTEM images show uniform TiNxOy coating with a thickness of approximately 6.1 nm for ZnO@TiNxOy nanorod with 100 cycles ALD (FIGS. 60-61).
• ZnO nanorod is hexagonal and TiNxOy coating is amorphous, which are evident from TEM (FIGS.62-63) and XRD results (FIG. 76).
• TEM TEM
• XRD results FIG. 76
• XPS results also indicate complete coverage of TiN x O y on ZnO (FIGS. 65-66 and 68-69), which is important for encapsulating zincate during cycling.
• nitrogen peak in the XPS survey spectra (FIG. 65) and three Ti 2p peaks in the high- resolution XPS spectra (FIG. 67), which belong to TiO 2 indicate that ALD TiN is partially oxidized to TiN x O y .
• the TiN x O y coating although only a few nanometers thick, firmly supports the ZnO nanorod, blocks zincates, and enables OH-/H2O to pass through.
• a ZnO@TiNxOy anode and an uncoated ZnO anode (1 cm diameter disk) were soaked into two tubes with 2 mL 4M KOH solution, respectively. Then the dissolved Zn concentration was measured in both solutions using ICP atomic emission spectroscopy (ICP-AES). The dissolved Zn of the TiN x O y coating effectively blocks zincates.
• ICP-AES ICP atomic emission spectroscopy
• EIS was also employed to investigate the electrochemical influence of conductive TiNxOy coating.
• the charge-transfer resistance (Rct) of the ZnO@TiNxOy nanorod anode is much lower than that of the uncoated ZnO anode. This can be attributed to the good conductivity of TiNxOy and the high zincate concentration inside the TiNxOy coating.
• Zinc anodes were tested in coin-type cells with lean zinc-free electrolyte here to evaluate their real performance (FIGS.
• the pure current collector without any active material in the beaker cell can show excellent cycling performance with a pseudo specific discharge capacity of approximately 600 mAh/g (assuming there is approximately 1.5 mg ZnO on the anode, which has approximately 1 mAh theoretical capacity).
• the real specific discharge capacity in the beaker cell is only approximately 4 mAh/g, while that in the coin cell is approximately 150 mAh/g.
• electrolyte When testing zinc anodes in beaker cells with 10 mL ZnO saturated 4M KOH electrolyte, electrolyte can contribute a large capacity, which is 100 times that of in coin cells with 100 ⁇ L electrolyte (TABLE 3). With this big contribution, it is hard to evaluate the true performance of zinc anodes with less amount of active materials.
• Coin-type cells use minimum amount of electrolyte and have a higher volumetric capacity compared with beaker cells, which is a better testing choice even though the testing environment is harsh.
• TABLE 3 - Calculation Of Equivalent ZnO Quantity And Capacity [00311] (*) ICP Emission Spectroscopy result. [00312] (**) used to make FIG.84.
• the reversible discharge capacity of the ZnO@TiNxOy nanorod anode at the tenth galvanostatic cycle is approximately 279 mAh/g, which is twice as large as that of an uncoated ZnO nanorod anode (approximately 148 mAh/g) at a rate of C/2.
• the discharge capacity of the ZnO@TiN x O y nanorod anode decays to below approximately 150 mAh/g after 30 cycles, versus only 9 cycles for uncoated ZnO nanorod anode.
• the TiNxOy coating did not change the over-potential of the ZnO anode with almost the same charge profile as the uncoated ZnO (FIG. 86). Cycled at a lower rate (C/4) with approximately 50% SOC, the capacity difference between coated and uncoated ZnO nanorod anodes in initial cycles is small, yet the ZnO@TiNxOy nanorod anode shows better capacity retention than uncoated ZnO nanorod anode (FIG. 87). The discharge capacities of uncoated and sealed ZnO nanorod anodes decay to approximately 50% after 31 and 53 cycles, respectively.
• the electrodes were imaged after three galvanostatic cycles at 0.33C.
• the ZnO@TiNxOy nanorod anode keeps its original morphology after cycling, whereas almost no nanorods can be found on the carbon paper for the uncoated ZnO nanorod anode.
• the superior performance of ZnO@TiN x O y nanorod anode can be attributed to the small feature size of ZnO and conformal TiN x O y coating. Below the critical passivation thickness, the anode passivation problem is nearly if not fully eliminated.
• the TiNxOy coating serves as an electrical pathway, confines large zincate molecules, yet allows OH- and water to pass. As a mechanical backbone, the TiNxOy coating protects ZnO nanorods from detaching from the carbon paper substrate, and thus provides a short zincate mass transfer path for the reaction. [00318] Without a TiNxOy coating, the ZnO nanorod will detach from substrate upon charging (FIG. 89). This on one hand leads to a much slower mass transport for electrically disconnected ZnO to dissolve in electrolyte to form zincate and then diffuse to current collector. On the other hand, detached ZnO or dissolved zincate may migrate far from anode and never participate in further cycling. Both mechanisms will cause capacity decay over cycling.
• the utilization of Zn could be potentially modeled by quantitative comparison of electroreduction rate and mass transfer rate of ,7 ( )% )G I N .
• the ZnO@TiNxOy nanorod anode was also tested in pouch cell with a ZnO-free electrolyte (FIG. 88). It achieves a specific discharge capacity of approximately 408 mAh/g (based on ZnO if not otherwise stated), which is 508 mAh/g(Zn).
• FIG. 89 the present ZnO@TiN x O y nanorod anode demonstrates a much higher specific capacity than that of many previously reported zinc anodes shown in TABLE 5.
• FIG. 90 shows the CV of the ZnO@TiN x O y nanorod anode in a coin cell with ZnO free electrolyte.
• FIGS. 92-93 The CV of the ZnO@TiNxOy nanorod anode in pouch and beaker cells is shown in FIGS. 92-93.
• the ZnO@TiN x O y nanorod anode has excellent performance under start-stop operations, demonstrating potential to replace lead acid batteries in micro-hybrid vehicles. Engine restart, rest and pulse discharge are involved in the start-stop operation.
• the procedure of a test is showed in FIG.94.
• the capacity of ZnO@TiNxOy nanorod anode was kept at approximately 1% DOD per duty cycle.
• the ZnO@TiNxOy nanorod anode maintained 100% discharge capacity for more than 7500 cycles (FIG. 95) at approximately 1% DOD.
• Voltage profile of the ZnO@TiNxOy nanorod anode is shown in FIGS. 96-98. Under the same current density (FIG.
• the Zn foil died after 3400 cycles, which is less than half of cycle number of ZnO@TiNxOy nanorod anode, even though the DOD of Zn foil is only approximately 0.02% (1/50 th of that of ZnO@TiN x O y nanorod anode).
• This Zn foil cell died with a sudden voltage drop to ⁇ 0 V because Zn is completely passivated by ZnO. And the cell was severely swelled, possibly due to accumulation of hydrogen evolved on the anode (FIGS.96-98). Severe hydrogen evolution occurs after the passivation of Zn anode.
• the cell with a ZnO@TiN x O y nanorod anode only slightly swelled, which indicated less side reaction and higher utilization of zinc. Less swelling further indicates the present ZnO@TiN x O y nanorod anode does not passivate and retains its activity over thousands of cycles.
• Zn foil start stop performance was tested with approximately 1% DOD at the same time interval as shown in FIG. 94, which showed dramatically discharge capacity decay (FIG.95). This result indicates the high stability of ZnO@TiNxOy nanorod anode.
• the ZnO@TiNxOy nanorod anode also demonstrated stable cycling at different cycling rates from 0.25C to 4C in FIG. 99.
• the ZnO@TiNxOy nanorod anode achieves very high specific discharge capacity and superior reversibility when testing in a coin cell with lean ZnO-free electrolyte.
• commercial PowerGenix AA batteries which are made of a Zn metal anode and NiOOH cathode, the discharge capacity decayed to approximately 50% of its initial capacity after only 9 cycles (0.5C, 20 °C, charged to approximately 105% theoretical capacity).
• NiOOH cathodes are very reversible, and the Zn anode is the main cause of the poor reversibility.
• the present ZnO@TiN x O y core/shell nanorod anode structure successfully overcomes problems of ZnO passivation and zincate dissolution simultaneously, and significantly improves the cycle life of Zn anode. Because electrolyte consumption and bubble accumulation resulted from hydrogen evolution side reaction, anodes degraded ultimately when cycled in coin cells with lean electrolyte. This can be further improved by coating hydrogen evolution suppressive materials. In addition, the mechanistic understanding and design principles provide guidance to future designs of zinc and other metal anodes (e.g.
• the present invention comprises a ZnO pomegranate (Zn-pome) material in which the zinc oxide nanoparticles (ZnO NPs) are analogous to seeds that are individually encapsulated and held in clusters by a carbon shell diaphragm.
• FIG. 100 shows the schematic of zincate motion during battery cycling of ZnO NPs (FIG. 100A), ZnO@C NPs (FIG. 100B) and Zn-pome (FIG. 100C).
• Zn-pome electrode There are several distinctive advantages of the Zn-pome electrode.
• multi-layered carbon acts as a conductor, protector, and ion barrier in Zn- pome to adequately constrain the migration of ,7()%) G I N (the discharge product), thus mitigating the dendrite formation and shape change of the Zn electrode.
• the thickness of the passivation layer is ⁇ 2 ⁇ m, which indicates that the Zn anode cannot be consumed entirely in the discharge process if the size of the Zn material is larger than ⁇ 2 ⁇ m regardless of the shape (foil, rod, particle, etc.).
• the nanoscale ZnO primary material is chosen to build Zn-pome.
• the robust carbon shell on ZnO NPs is both electrically and ionically conducting, which not only allows for effective kinetics, but also improves the mechanical strength of the Zn anode.
• the Zn-pome has a smaller solid-electrolyte contact area than ZnO@C NPs (as shown in FIG. 100D), which can significantly reduce the dissolution rate during cycling.
• the longstanding limitations that have impeded the rechargeability of Zn electrode i.e., Zn dendrite formation, Zn electrode shape change and ZnO passivation
• Zn electrode shape change and ZnO passivation can be significantly alleviated by the electrode design of the Zn-pome.
• Microemulsion-Based Assembly Of ZnO Nanoparticles Into Clusters [00336] The synthesis of Zn-pome is schematically illustrated in FIGS. 102A-H.
• ZnO ZnONPs, Aldrich, 100 mg
• ODE 8 mL1-octadecene
• emulsion stabilizer amphiphilic block copolymer, Hypermer 2524, Croda USA
• the morphology of Zn-pome and the carbon shell after etching the ZnO cluster was determined using TEM (Hitachi HT7700).
• the cross-sectioned images of clusters after being etched in 1M HCl were generated using FEI Nova Nanolab 200 FIB/SEM that included SEM imaging and FIB milling.
• the XRD pattern (Panalytical XPert PRO Alpha-1) for bare ZnO, ZnONPs@C, and Zn-pome were carried out with CuK-Alpha radiation. [00341]
• the XPS was measured with AlK-Alpha (Thermo K-alpha).
• XPS survey spectra and high resolution spectra of Zn2p O1s and C1s were measured
• the weight percentage of ZnO in Zn-pome was determined from the weight loss curves measured under air atmosphere on a thermogravimetric analysis (TGA) instrument (TA instrument, Q500) with a heating rate of 5 °C/min to 850 °C.
• TGA thermogravimetric analysis
• the specific BET surface areas and pore size distribution were determined by physisorption (BELSORP-MAX, Microtrac BEL Japan, Inc.).
• the dissolved concentration of bare ZnO, ZnONPs@C, Zn-pome in 4M KOH electrolyte was measured with an ICP measurement: three samples with the same amount of active material were immersed into 4M KOH for 5 minutes, IUL [PM Z ⁇ WMYUI[IU[ IN[MY KMU[YQN ⁇ OI[QVU ⁇ IZ TMIZ ⁇ YML' DPM ⁇ 6A ZITWSMZ ⁇ MYM NQS[MYML ⁇ Q[P )'+ mT Acrodisc IC PES filters and diluted 100 times in ICP Matrix Solution.
• Electrode preparation Approximately 151 mg synthesized Zn-pome was gently ground in a mortar and transferred into a 4 mL vial with 0.5 g N-Methyl-2-pyrrolidone (NMP) (Aldrich), then the 1.2 g NMP solution containing PVDF (MTI, ⁇ 10 wt% of PVDF) was added to the sample and stirred for 30 minutes. The slurry was then cast onto Sn foil (Alfa) with a Doctor’s blade and dried at 80 °C for 30 minutes.
• NMP N-Methyl-2-pyrrolidone
• Electrochemistry 2032 coin cells were assembled under ambient environment, with Zn-pome anode, Ni(OH)2 cathode obtained from commercial Zn-Ni batteries (PowerGenix), and a separator (GF 6, Whatman).
• the aqueous electrolyte contains 4M KOH (Aldrich), 2M K2CO3 (Aldrich) and 2M KF (Aldrich).
• the control cells were assembled using the same process as Zn-pome anode batteries, just with the Zn-pome anode replaced by the bare ZnO anode.
• the cells were charged and discharged at 1C for comparison between bare ZnO and Zn-pome, and the performances of the 5C rate discharge and self-discharge were investigated, respectively.
• the SEM images of ZnO clusters were investigated under various magnifications (FIGS. 103A-C). These clusters with diameters in the range of approximately 1-6 ⁇ m primarily contained ZnO NPs. The rounded edge of the Zn-pome (FIGS. 103D-F) indicated that the ZnO clusters were adequately coated with a thin layer of carbon framework.
• the detailed structure of the Zn-pome was investigated using HRTEM and FIB analysis. According to TEM images (FIGS.
• the diameter of a typical Zn-pome microparticle was ⁇ 6 ⁇ m.
• the Zn-pome was treated with 1M HCl to etch away ZnO, the hollow carbon framework could be clearly observed in TEM images (FIGS. 103H and 104C-F).
• TEM images FIGS. 103H and 104C-F.
• each ZnO NP was individually coated by a thin layer of carbon framework with [00348]
• the coated carbon framework was stable even without the solid “seeds,” i.e., ZnO NPs, which is important for the structural stability of Zn-pome, especially when the active Zn material is mainly oxidized and dissolved after the deep discharge process.
• FIG.103I exhibits the cross-sectional images of the Zn-pome microparticle obtained by FIB analysis.
• a secondary Zn-pome microparticle comprises ZnO NP clusters, in which each ZnO NP with a rounded surface was uniformly encapsulated by the carbon framework. More cross-sectional images are illustrated in FIGS. 105-106.
• the abovementioned morphology investigations of Zn-pome reveal that Zn- pome fabricated by bottom-up approach, comprising a robust carbon framework and ZnO nanoparticles, can be used as an anode in zinc-based batteries.
• XRD and XPS were used to characterize the crystal structure and chemical composition of Zn-pome (FIGS.107A-C).
• Zn-pome is characterized as ZnO NP clusters uniformly coated with an amorphous carbon layer.
• the content of carbon is found to be approximately 40% in Zn-pome based on TGA in air, as shown in FIG.107D.
• the BET results reveal that the average pore size of the carbon shell is ⁇ 10 ⁇ (FIG.107E). This indicates that the carbon framework can properly mitigate the permeation of zincate through the shell structure.
• the dissolution rate of ZnO in an aqueous alkaline electrolyte was investigated. Samples of ZnO NPs, ZnO@C NPs and Zn- pome containing equal amounts of zinc were immersed in 1 mL 4M KOH solutions at the same time.
• Zn-pome significantly reduced the portion of dissolved Zn in KOH (approximately 1.05%) in comparison with ZnO NPs (approximately 30.8%) and ZnO@C NPs (approximately 11%). This effect is ascribed to the synergistic function of carbon shell and secondary structure in Zn-pome. The diffusion of zincate in alkaline media is confined within the secondary particles, whereas the confined zincate can still be electrochemically reduced.
• the pomegranate structure is also expected to alleviate Zn dendrite formation and shape change (i.e., localized densification) during the charge/discharge process.
• Zn dendrite formation and shape change i.e., localized densification
• the electrochemical performances of Zn-pome and ZnO NPs were evaluated by a full cell configuration comprising Ni(OH)2 cathode with excess capacity obtained from commercial zinc-nickel batteries. The cells were cycled at 1C in a voltage window between 1.5 and 2.0 V in 2M KF, 2M K2CO3 and 4M KOH.
• 109B presents the typical charge/discharge profiles voltage of the Zn-pome/Ni(OH) 2 cell is maintained at approximately 1.80 V after 40 cycles, indicating excellent cycling stability.
• the improved performance of Zn-pome/Ni(OH)2 cells compared to that of Zn NPs/Ni(OH)2 is due to the ion-sieving ability of the carbon shell and secondary particle structure.
• the increase in charging voltage in consecutive cycling is possibly due to the accumulation of hydrogen evolved in the reduction of water.
• hydrogen evolution can be effectively suppressed by the adjustments of electrolyte (such as the use of water-in-salt or solid state additives).
• the electrochemical performance of Zn-pome/Ni(OH)2 is also superior to that of Zn NPs/Ni(OH) 2 at a higher discharge rate (5C), as shown in FIGS. 109C and 111.
• the discharge capacity of Zn-pome/Ni(OH) 2 is maintained approximately 400 mAh/g for 45 cycles (e.g., 411 mAh/g at the 44 th cycle).
• Zn NPs/Ni(OH) 2 suffers from a quick decay of discharge capacity after the 3 rd cycle (merely approximately 186 mAh/g at the 21 st cycle).
• Zn-pome/Ni(OH)2 still exhibited high capacity after resting and maintained approximately 84% of capacity even after 40 cycles (on the basis of the 3rd cycle), indicating that Zn-pome anode is effective in retaining Zn active species due to the carbon framework.
• the morphology evolution of Zn-pome was investigated by SEM (FIGS.109E- G, and 113A-L). The Zn-pome anode maintained the microspheric morphology after ten charge/discharge cycles, indicating the robust morphology of the pomegranate structure.
• Zn-pome is considered to be a novel Zn anode material that can mitigate the Zn dendrite formation, shape change and passivation issues in alkaline Zn-ion batteries.
• a nanoscale pomegranate-inspired hierarchical Zn anode material (Zn-pome) is fabricated via a bottom-up microemulsion approach.
• Each Zn-pome microsphere is around 6 ⁇ m in size and is composed of on the order of 10 5 ZnO nanoparticles individually encapsulated by an amorphous, microporous, and conductive carbon shell that slows down the dissolution of zincate intermediate species during cycling.
• the secondary structure further suppresses the zinc dissolution by decreasing the electrode-electrolyte contact area.
• Zn-pome exhibits significantly suppressed dissolution of zinc compared to ZnO NP nano-particles and ZnO@C nanoparticles.
• the Zn-pome anode demonstrates remarkable capacity and cycle stability under extremely harsh testing conditions (limited electrolyte, ZnO-free electrolyte, and 100% DOD); it also retains high capacity after long-term resting in a discharged state, in which ZnO in the electrode has a massive tendency to dissolve.
• Zn-pome anode The success of the Zn-pome anode can be ascribed to inventive design principles that manage soluble intermediates during repeated electrochemical cycling; this is important for future designs of Zn aqueous anodes as well as other battery systems involving soluble intermediates (e.g., lithium-sulfur batteries).
• Ion-Sieving Carbon Nanoshells for Deeply Rechargeable Zn-Based Aqueous Batteries [00363] An optimized structure to solve Zn anodes’ passivation and dissolution problems simultaneously is fashioned. Specifically, the structure features (1) a sub-micrometer ZnO particle as the core, and (2) an ion-sieving carbon coating as the shell.
• nanoparticles with even smaller diameter offer no further benefit to reversibility but have much more severe dissolution concerns.
• the carbon shell is deposited on the ZnO nanoparticles through carbonization of a uniform polydo-pamine coating.
• the ability of polydopamine coatings to form a uniform shell with controllable thickness has been confirmed before.
• the present two-step synthesis method is relatively simple and scalable, and the carbon shell thickness is controllable by simply adjusting the dopamine mass during synthesis.
• ZnO@C Synthesis 100 mg commercial ZnO nanoparticles ( ⁇ approximately 100 nm, Aldrich) were buffer (pH 8.5, Alfa) and 100 (1:1), 200 (2:1) and 300 (3:1) mg of dopamine hydrochloride (Aldrich) were added and mixed for different nanoshell thickness, and then stirred for 24 hours. The fabricated polydopamine-coated ZnO nanoparticles ZnO@P were collected and washed with DI water two times in the centrifuge and dried overnight.
• the threshold ZnO@P calcination temperature was measured with TGA by heating the sample in Ar gas to 900 °C with a heating rate of 5 °C/min.
• the XRD pattern Panalytical XPert PRO Alpha-1 for both bare ZnO and ZnO@C nanoparticles were carried out with CuK-Alpha radiation. The specific BET surface areas and pore size distribution were determined by physisorption (BELSORP-MAX, Microtrac BEL Japan, Inc.). The XPS was measured with AlK-Alpha (Thermo K-alpha), XPS survey spectra and high- resolution Zn 2p, O1s, C1s spectra were measured.
• Electrode Preparation [00372] Synthesized ZnO@C or as-received ZnO nanoparticles was mixed with carbon black (MTI) and PVDF (MTI) of an 80:10:10 ratio and grinded in a mortar, then NMP (Aldrich) of two times the mass of slurry was added to the sample and stirred in a 4 mL vial for 8 hours to ensure the slurry uniformity. The slurry was then casted onto Sn foil (Alfa) with a Doctor’s blade and dried at 90°C for 1 hour then calendared.
• MMI carbon black
• PVDF PVDF
• Electrochemistry 2032 coin cells were assembled under atmosphere environment with the can at the bottom, followed by the ZnO anode, 100 ⁇ L electrolyte immersed separator, then the Ni(OH) 2 cathode, spacer, spring and the cap. A commercial Ni(OH)2 electrode (PowerGenix) was used as the cathode. The separator used for battery testing was glass fiber filter (GF 6, Whatman) unless otherwise noted. [00375] The composition of the electrolyte was KOH (4M, Aldrich) with K2CO3 (2M, Aldrich) and KF (2M, Aldrich) added to enhance ionic conductivity.
• Zn mesh (Dexmet) was discharged with 1 mA in 10 ⁇ L with a Celgard 3501 separator.
• Zn foil (0.25 mm, Alfa) was used for the anode while other battery parts remained the same and the GCPL (galvanostatic cycling with potential limitation) test was performed with 2 mAh at 1C.
• the voltage cutoff for GCPL was 2 V and 1.5 V for the charging and discharging processes, the cells were charged and discharged at 1C for comparison between bare ZnO and ZnO@C nanoparticles.
• the mass loading of bare ZnO and ZnO@C was 1.03 mg and 0.904 mg for the comparison at low mass loading.
• the pore size of the carbon nanoshell is tailored to allow hydroxide ions to pass through while blocking transport of zincate ions.
• the zincate intermediate is trapped inside the carbon shell and reacts with Zn within the shell, preventing deposition of Zn in another location.
• the OH j by-product can diffuse out freely through the micropores in the shell due to their smaller size.
• the uniform polydopamine shell is first coated onto ZnO nanoparticles by stirring the particles with dopamine hydrochloride in Tris buffer (pH 8.5) for 24 hours at room temperature in the presence of air. After carbonization at 600 °C, ZnO@C nanoparticles are obtained. [00383] The particles are of short rod-like shapes. An SEM image shows a quasi-spherical morphology of ZnO@C (FIGS.114B and 115), which indicates the coating is successful, and the particles are of slightly larger size than bare ZnO. The TEM image in FIG.
• 114B shows a single ZnO@C nanoparticle with an amorphous carbon shell coated uniformly on the surface and the thickness of the carbon shell is approximately 20-30 nm. Notice that the coating thickness is tunable by simply changing the dopamine hydrochloride mass.
• TEM images of single coated particles with different coating thickness are shown in FIG.116. 600 °C was selected as the carbonization temperature because the ZnO core is reduced to Zn vapor and escapes at above 680 °C, determined from the TGA results above, and FIG.117. [00385] TEM results confirm partial ZnO loss inside the carbon shell at 700 °C and complete loss at 800 °C.
• the BET method is used to analyze the pore size of carbon-coated ZnO (FIG.118D).
• the pore width is calculated from the adsorption/desorption isotherm to be around 5-8 ⁇ (FIG.118E), between the sizes of hydroxide and zincate ions plus the solvation shell.
• Hydroxide species are expected to be more mobile and zincate species to be less mobile when diffusing through the nanoshell. In comparison, uncoated ZnO particles do not have pores in the same range.
• both ZnO and ZnO@C powders are soaked in KOH (4M) for 5 minutes, 1 day, and 10 days and the dissolved ,7()%) G I N are quantified using inductively coupled plasma atomic emission spectroscopy (ICP-AES). As shown in FIG.118F, although Zn still dissolves into the electrolyte, the dissolved ,7()%) G I N from bare ZnO is much lower and slower than that from ZnO@C, which confirms that the carbon nanoshell functions as a barrier to slow down the zincate escape.
• ICP-AES inductively coupled plasma atomic emission spectroscopy
• FIG.119 compares the specific capacity of ZnO@C anode with a bare ZnO anode at similar mass loading. Performance of Zn foil, which degrades quickly in only seven cycles due to severe ZnO passivation is also shown in the same plot. The bare ZnO anode lasts for 20 cycles before severe capacity degradation is evident, indicating the success of decreasing feature size in mitigating passivation.
• the carbon shell also increases the conductivity of the anode material, which is helpful for preventing the formation of a passivation layer, also with the help of the carbon nanoshell the overpotential for every single cycle of the battery with ZnO@C is lower than that of bare ZnO (FIGS.121-122).
• the nitrogen doping also facilitates the conductivity of the carbon layer and charge transfer at the interface.
• FIG. 123 shows the voltage versus specific capacity during the charging and discharging processes. The performances of the charging processes are similar, indicating a stable performance.
• FIGS.124A-D shows the SEM images of both bare and coated ZnO anodes before cycling and after three cycles.
• the dissolution and passivation problems of Zn anode materials is simultaneously solved by applying an ion- sieving carbon nanoshell coating onto ZnO nanoparticles which are well below the critical passivation thickness.
• the carbon nanoshell is uniform and complete. The micropores ions to pass freely, and the nanoshells’ rigidity prevents anode shape change and dendrite growth.

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