US20010055717A1 - Electrochemical cell having a surface modified electrode and associated fabrication process - Google Patents
Electrochemical cell having a surface modified electrode and associated fabrication process Download PDFInfo
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- US20010055717A1 US20010055717A1 US09/902,235 US90223501A US2001055717A1 US 20010055717 A1 US20010055717 A1 US 20010055717A1 US 90223501 A US90223501 A US 90223501A US 2001055717 A1 US2001055717 A1 US 2001055717A1
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- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- 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
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
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- 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
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
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- 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
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- 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
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
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- 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
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- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- 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
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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- 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
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- 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
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- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- 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
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49108—Electric battery cell making
Definitions
- the present invention relates in general to electrochemical cells, and more particularly, to an electrochemical cell having an electrode with a modified surface layer.
- the present invention is further directed to a process for fabricating the same.
- Lithium based electrochemical cells have been known in the art for several years. Furthermore, experimentation associated with lithium based cells having intercalation type electrodes has been explored. While batteries utilizing intercalation type electrodes have exhibited some promising performance characteristics, compatibility between the active material layer of such electrodes and associated electrolyte remains largely problematic.
- electrochemical cells based on lithiated transition metal oxide electrodes deintercalate lithium ions at relatively high potentials in order to utilize their full capacity—above approximately 4 volts. This high charge voltage coupled with the naturally oxidizing character of the active material facilitates decomposition of the associated electrolyte. Such decomposition of the electrolyte, among other things, adversely affects coulombic efficiency, decreases net capacity as well as increases self-discharge rates of the cell.
- the present invention is directed to an electrode for use in an electrochemical cell comprising: a) a current collecting substrate; b) an active material associated with the substrate; and c) a surface modifying component applied to at least a portion of the active material, wherein the surface modifying component is fabricated from at least one of the group consisting essentially of lithium niobates and lithium tantalates.
- the electrode further comprises means for increasing the compatibility of the electrode with an associated electrolyte.
- the compatibility increasing means comprises the surface-modifying component.
- the surface modifying component is fabricated from a lithium niobate species or lithium tantalate species having the chemical structure Li x NbO y or Li x TaO y , wherein x and y range from about 1 to 5.
- the surface-modifying component is in a crystalline or glassy state.
- the surface modifying component is doped with at least one carbonaceous particle and/or at least one additive selected from the group consisting essentially of transition metal oxides, metal oxides, non-metal oxides, rare earth metal oxides, and metal phosphates, sulfates, and sulfides.
- the present invention is also directed to a process for manufacturing an electrochemical cell comprising the steps of: a) associating a surface modifying component with an active material; b) modifying the surface of the active material c) fabricating a first electrode by applying the surface modified active material to a current collecting substrate; d) fabricating a second electrode; and e) associating at least one electrolyte with the first and second electrodes.
- the step of associating the surface modifying component includes the steps of: a) dissolving at least one of a lithium niobate species and a lithium tantalate species in a solvent and, in turn, preparing a solution; b) applying the prepared solution to the active material; and c) substantially removing the solvent from the solution.
- the step of preparing the solution includes the step of doping the solution with at least one carbonaceous species and/or the step of doping the solution with at least one of the group of transition metal oxides, non-metal oxides, rare earth metal oxides, and metal phosphates, sulfates, and sulfides.
- FIG. 1 of the drawings is a schematic representation of a prior art electrochemical cell before an initial charge
- FIG. 2 of the drawings is a schematic representation of a prior art electrochemical cell after an initial charge
- FIG. 3 of the drawings is a schematic representation of an electrochemical cell in accordance with the present invention.
- FIG. 4 of the drawings is a plot of cell voltage versus time for a cell fabricated in accordance with the present invention
- FIG. 5 of the drawings is a plot of cell capacity versus time at different cycle rates for a cell fabricated in accordance with the present invention
- FIG. 6 of the drawings is a plot of normalized capacity versus cycle number for both a test cell as well as a cell fabricated in accordance with the present invention.
- FIG. 7 of the drawings is a plot of normalized capacity versus cycle time for both a test cell as well as a cell fabricated in accordance with the present invention.
- Prior art electrochemical cell 10 is shown in FIG. 1, prior to an application of an initial electrical charge, as generally comprising first electrode 12 , second electrode 14 , and electrolyte 16 .
- First electrode 12 is conventionally fabricated from lithium, carbon, or a mixture thereof and second electrode 14 is conventionally fabricated from a lithium transition metal oxide, such as LiMn 2 O 4 , LiCoO 2 , or LiNiO 2 .
- Electrolyte 16 can include an organic solvent 18 such as propylene carbonate (PC) or ethylene carbonate (EC).
- PC propylene carbonate
- EC ethylene carbonate
- Prior art electrochemical cell 10 is shown in FIG. 2, after a charge/discharge cycle, as generally comprising first electrode 12 , second electrode 14 , electrolyte 16 , and decomposition products 20 .
- generation of decomposition products 20 can result in an electrochemical cell exhibiting poor coulombic efficiency, diminished capacity, and increased self-discharge rates as well as shortened cell life.
- the solvent within electrolyte 16 can chemically interact with the electrode surface and subsequently form a gas species upon decomposition, which can render the cell not only inoperative, but also dangerous during its operation.
- Electrochemical cell 100 of the present invention is shown in FIG. 3 prior to an application of an initial electrical charge, as generally comprising first electrode 112 , second electrode 114 , electrolyte 116 , and surface modifying component 115 .
- First electrode 112 is preferably fabricated from lithium, carbon, or a mixture of lithium and carbon and second electrode 114 is preferably fabricated from a lithium transition metal oxide, such as LiMn 2 O 4 , LiCoO 2 , or LiNiO 2 .
- a lithium transition metal oxide such as LiMn 2 O 4 , LiCoO 2 , or LiNiO 2 .
- any one of a number of conventional electrode materials is likewise contemplated for use.
- electrolyte 116 includes a conventional salt, such as LiPF 6 or LiAsF 6 , dissolved in a conventional solvent 118 , such as propylene carbonate (PC) or ethylene carbonate (EC), although other commercially available and conventionally used solvents and salts or electrochemical systems (such as liquid, polymer, gel, and plastic systems) as would be readily understood to those having ordinary skill in the art having the present disclosure before them, are likewise contemplated for use.
- a conventional salt such as LiPF 6 or LiAsF 6
- solvent 118 such as propylene carbonate (PC) or ethylene carbonate (EC)
- PC propylene carbonate
- EC ethylene carbonate
- Surface modifying component 115 is associated with second electrode 114 .
- Surface modifying component 115 is preferably fabricated from lithium niobates and/or lithium tantalates such as LiMO 2 , LiMO 3 , Li 5 MO 5 , where M is Nb and/or Ta.
- lithium niobates and tantalates include those represented by the chemical formula Li 1-5 NbO 1-5 and Li 1-5 TaO 1-5 . While specific niobates and tantalates have been disclosed, for illustrative purposes only, it will be understood that other species and/or derivatives that would be known to those will ordinary skill in the art having the present disclosure before them are likewise contemplated for use.
- surface modifying component 115 is fabricated into or exists in a crystalline or “glassy” state.
- surface modifying component 115 can be “doped” or associated with one or more carbonaceous particles, such as carbon black or graphite.
- the surface modifying component can also be “doped” or associated with other components, such as transition metal oxides, metal oxides including Fe and Cr, non-metal oxides, rare earth metal oxides, and metal phosphates, sulfates, and sulfides.
- surface modifying component 115 substantially increases the compatibility of electrode 114 with electrolyte 116 .
- electrochemical cell 100 will not readily generate a substantial quantity of a decomposition product after an initial charge/discharge cycle as does cell 10 of the prior art.
- the present invention is further directed to a process for fabricating electrochemical cell 100 comprising the following steps: First, surface modifying component 115 is associated with an active material, such as LiNiO 2 , LiCoO 2 , or LiNiO 2 .
- Surface modifying component 115 is preferably associated with the active material by dissolving one or more lithium niobate or lithium tantalate species in a conventional solvent and then applying the prepared solution to at least a portion of the active material. The solvent can then be substantially removed by evaporation, to, in turn, result in a surface modified active material. Of course removal of the solvent can be hastened with the use of heat and/or a reduced pressure environment.
- electrode 114 is fabricated by applying the active material associated with surface modifying component 115 to a current collecting substrate, such as aluminum (not shown). After electrode 114 is fabricated, electrode 112 is fabricated.
- electrode 112 will be an anode and 114 will comprise a cathode. Of course, in a secondary cell configuration, the anode and cathode will become interchangeable with each other, depending on whether the cell is in a state of charging or discharging. Electrodes 112 and 114 are fabricated using conventional techniques.
- Electrolyte 116 is associated with electrodes 112 and 114 , respectively.
- Electrolyte 116 may comprise a salt, such as LiPF 6 or LiAsF 6 , dissolved in at least one solvent, such as PC or EC.
- the electrolyte is fabricated using conventional techniques.
- the solution can be doped with a carbonaceous species and/or other additives such as transition metal oxides, metal oxides, non-metal oxides, rare earth metal oxides, and metal phosphates, sulfates, and sulfides.
- a carbonaceous species and/or other additives such as transition metal oxides, metal oxides, non-metal oxides, rare earth metal oxides, and metal phosphates, sulfates, and sulfides.
- LiNiO 2 powder (LectroTM Plus 200 cathode material, FMC Corp., Gastonia, N.C.) was placed in a dry, clean 6 fluid ounce jar.
- a magnetic stirring bar was then placed in the beaker, and the beaker was placed on a conventional stirring plate.
- the contents in the jar were dried in an air oven having a temperature set point of approximately 100 degrees centigrade for approximately 48 hours. The contents were then dried for an additional 24 hours in a vacuum oven having a temperature set point of approximately 100 degrees centigrade.
- the dried powder was transferred into an alumina tray for pyrolysis in an oxygen enriched atmosphere.
- the pyrolysis conditions were: Temperature Set Point Duration at Set In Degrees Centigrade Point in Hours 400 1.0 450 0.5 500 0.5 550 0.5 600 0.5 650 0.5 700 0.5 750 5.0
- LiNiO 2 niobate function gradient material was cooled down in the oven over 16 hours and then transferred to a clean dry jar for storage.
- FIG. 4 shows the first charge/discharge cycle of a LiNiO 2 niobate FGM electrode coin cell tested at about C/24. The profile is consistent with a LiNiO 2 cathode.
- FIG. 5 shows the effect of cycle rate on the LiNiO 2 niobate FGM electrode coin cells at C, C/4, and C/8 rates. Note that there is very little loss of cell capacity even after 700 hours of testing.
- FIG. 6 shows a comparison of capacity versus cycles number for a LiNiO 2 niobate FGM electrode coin cell and a LiNiO 2 electrode coin cell tested at about the C/4 rate.
- the cell with the LiNiO 2 niobate FGM electrode has retained its capacity much better than the cell with the LiNiO 2 electrode. This indicates that secondary, irreversible reactions on the electrode surface of the LiNiO 2 niobate FGM electrode are occurring at a significantly lower rate than in the cell with the LiNiO 2 electrode. Therefore, the LiNiO 2 niobate FGM electrode has demonstrated, among other things, a substantially improved electrolyte compatibility relative to a LiNiO 2 electrode.
- FIG. 7 shows the cumulative effect of normalized capacity as a function of cycle time for a LiNiO 2 electrode as well as for a LiNiO 2 niobate FGM electrode.
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Abstract
An electrode for use in an electrochemical cell comprising a current collecting substrate, an active material associated with the substrate; and a surface modifying component applied to at least a portion of the active material, wherein the surface modifying component is fabricated from at least one of the group consisting essentially of lithium niobates and lithium tantalates.
A process for manufacturing an electrochemical cell comprising the steps of associating a surface modifying component with an active material, modifying the surface of the active material, fabricating a first electrode by applying the surface modified active material to a current collecting substrate, fabricating a second electrode, and associating at least one electrolyte with the first and second electrodes.
Description
- 1. Field of the Invention
- The present invention relates in general to electrochemical cells, and more particularly, to an electrochemical cell having an electrode with a modified surface layer. The present invention is further directed to a process for fabricating the same.
- 2. Background Art
- Lithium based electrochemical cells have been known in the art for several years. Furthermore, experimentation associated with lithium based cells having intercalation type electrodes has been explored. While batteries utilizing intercalation type electrodes have exhibited some promising performance characteristics, compatibility between the active material layer of such electrodes and associated electrolyte remains largely problematic. For example, electrochemical cells based on lithiated transition metal oxide electrodes deintercalate lithium ions at relatively high potentials in order to utilize their full capacity—above approximately 4 volts. This high charge voltage coupled with the naturally oxidizing character of the active material facilitates decomposition of the associated electrolyte. Such decomposition of the electrolyte, among other things, adversely affects coulombic efficiency, decreases net capacity as well as increases self-discharge rates of the cell.
- It is therefore as object of the present invention to provide an electrode structure and associated fabrication process that remedies, among other things, the aforementioned detriments and/or complications associated with intercalation type electrodes.
- The present invention is directed to an electrode for use in an electrochemical cell comprising: a) a current collecting substrate; b) an active material associated with the substrate; and c) a surface modifying component applied to at least a portion of the active material, wherein the surface modifying component is fabricated from at least one of the group consisting essentially of lithium niobates and lithium tantalates.
- In a preferred embodiment of the invention, the electrode further comprises means for increasing the compatibility of the electrode with an associated electrolyte. In this embodiment the compatibility increasing means comprises the surface-modifying component.
- In another preferred embodiment of the invention, the surface modifying component is fabricated from a lithium niobate species or lithium tantalate species having the chemical structure LixNbOy or LixTaOy, wherein x and y range from about 1 to 5.
- In yet another preferred embodiment of the invention, the surface-modifying component is in a crystalline or glassy state.
- Preferably the surface modifying component is doped with at least one carbonaceous particle and/or at least one additive selected from the group consisting essentially of transition metal oxides, metal oxides, non-metal oxides, rare earth metal oxides, and metal phosphates, sulfates, and sulfides.
- The present invention is also directed to a process for manufacturing an electrochemical cell comprising the steps of: a) associating a surface modifying component with an active material; b) modifying the surface of the active material c) fabricating a first electrode by applying the surface modified active material to a current collecting substrate; d) fabricating a second electrode; and e) associating at least one electrolyte with the first and second electrodes.
- In a preferred embodiment of the invention, the step of associating the surface modifying component includes the steps of: a) dissolving at least one of a lithium niobate species and a lithium tantalate species in a solvent and, in turn, preparing a solution; b) applying the prepared solution to the active material; and c) substantially removing the solvent from the solution.
- In another preferred embodiment of the invention the step of preparing the solution includes the step of doping the solution with at least one carbonaceous species and/or the step of doping the solution with at least one of the group of transition metal oxides, non-metal oxides, rare earth metal oxides, and metal phosphates, sulfates, and sulfides.
- The invention will now be described with reference to the drawings wherein:
- FIG. 1 of the drawings is a schematic representation of a prior art electrochemical cell before an initial charge;
- FIG. 2 of the drawings is a schematic representation of a prior art electrochemical cell after an initial charge;
- FIG. 3 of the drawings is a schematic representation of an electrochemical cell in accordance with the present invention;
- FIG. 4 of the drawings is a plot of cell voltage versus time for a cell fabricated in accordance with the present invention;
- FIG. 5 of the drawings is a plot of cell capacity versus time at different cycle rates for a cell fabricated in accordance with the present invention;
- FIG. 6 of the drawings is a plot of normalized capacity versus cycle number for both a test cell as well as a cell fabricated in accordance with the present invention; and
- FIG. 7 of the drawings is a plot of normalized capacity versus cycle time for both a test cell as well as a cell fabricated in accordance with the present invention.
- While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail several specific embodiments with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiments illustrated.
- Prior art
electrochemical cell 10 is shown in FIG. 1, prior to an application of an initial electrical charge, as generally comprisingfirst electrode 12,second electrode 14, andelectrolyte 16.First electrode 12 is conventionally fabricated from lithium, carbon, or a mixture thereof andsecond electrode 14 is conventionally fabricated from a lithium transition metal oxide, such as LiMn2O4, LiCoO2, or LiNiO2.Electrolyte 16 can include anorganic solvent 18 such as propylene carbonate (PC) or ethylene carbonate (EC). - Prior art
electrochemical cell 10 is shown in FIG. 2, after a charge/discharge cycle, as generally comprisingfirst electrode 12,second electrode 14,electrolyte 16, anddecomposition products 20. As will be discussed in greater detail below, generation ofdecomposition products 20 can result in an electrochemical cell exhibiting poor coulombic efficiency, diminished capacity, and increased self-discharge rates as well as shortened cell life. Additionally, the solvent withinelectrolyte 16 can chemically interact with the electrode surface and subsequently form a gas species upon decomposition, which can render the cell not only inoperative, but also dangerous during its operation. -
Electrochemical cell 100 of the present invention is shown in FIG. 3 prior to an application of an initial electrical charge, as generally comprisingfirst electrode 112,second electrode 114,electrolyte 116, andsurface modifying component 115. -
First electrode 112 is preferably fabricated from lithium, carbon, or a mixture of lithium and carbon andsecond electrode 114 is preferably fabricated from a lithium transition metal oxide, such as LiMn2O4, LiCoO2, or LiNiO2. Of course, any one of a number of conventional electrode materials is likewise contemplated for use. - For purposes of the present disclosure,
electrolyte 116 includes a conventional salt, such as LiPF6 or LiAsF6, dissolved in aconventional solvent 118, such as propylene carbonate (PC) or ethylene carbonate (EC), although other commercially available and conventionally used solvents and salts or electrochemical systems (such as liquid, polymer, gel, and plastic systems) as would be readily understood to those having ordinary skill in the art having the present disclosure before them, are likewise contemplated for use. -
Surface modifying component 115 is associated withsecond electrode 114.Surface modifying component 115 is preferably fabricated from lithium niobates and/or lithium tantalates such as LiMO2, LiMO3, Li5MO5, where M is Nb and/or Ta. Other suitable niobates and tantalates include those represented by the chemical formula Li1-5NbO1-5 and Li1-5TaO1-5. While specific niobates and tantalates have been disclosed, for illustrative purposes only, it will be understood that other species and/or derivatives that would be known to those will ordinary skill in the art having the present disclosure before them are likewise contemplated for use. Preferablysurface modifying component 115 is fabricated into or exists in a crystalline or “glassy” state. Although not shown, it is further contemplated thatsurface modifying component 115 can be “doped” or associated with one or more carbonaceous particles, such as carbon black or graphite. In addition, the surface modifying component can also be “doped” or associated with other components, such as transition metal oxides, metal oxides including Fe and Cr, non-metal oxides, rare earth metal oxides, and metal phosphates, sulfates, and sulfides. As will be discussed in greater detail belowsurface modifying component 115 substantially increases the compatibility ofelectrode 114 withelectrolyte 116. As will be discussed in greater detail belowelectrochemical cell 100 will not readily generate a substantial quantity of a decomposition product after an initial charge/discharge cycle as doescell 10 of the prior art. - The present invention is further directed to a process for fabricating
electrochemical cell 100 comprising the following steps: First,surface modifying component 115 is associated with an active material, such as LiNiO2, LiCoO2, or LiNiO2.Surface modifying component 115 is preferably associated with the active material by dissolving one or more lithium niobate or lithium tantalate species in a conventional solvent and then applying the prepared solution to at least a portion of the active material. The solvent can then be substantially removed by evaporation, to, in turn, result in a surface modified active material. Of course removal of the solvent can be hastened with the use of heat and/or a reduced pressure environment. - Next,
electrode 114 is fabricated by applying the active material associated withsurface modifying component 115 to a current collecting substrate, such as aluminum (not shown). Afterelectrode 114 is fabricated,electrode 112 is fabricated. For purposes of the present disclosure,electrode 112 will be an anode and 114 will comprise a cathode. Of course, in a secondary cell configuration, the anode and cathode will become interchangeable with each other, depending on whether the cell is in a state of charging or discharging. Electrodes 112 and 114 are fabricated using conventional techniques. - Next,
electrolyte 116 is associated withelectrodes Electrolyte 116 may comprise a salt, such as LiPF6 or LiAsF6, dissolved in at least one solvent, such as PC or EC. The electrolyte is fabricated using conventional techniques. - In an alternative embodiment of the process, the solution can be doped with a carbonaceous species and/or other additives such as transition metal oxides, metal oxides, non-metal oxides, rare earth metal oxides, and metal phosphates, sulfates, and sulfides.
- In support of the present invention, the following experimental procedure was conducted:
- First, 6.00 grams of LiNiO2 powder (
Lectro™ Plus 200 cathode material, FMC Corp., Gastonia, N.C.) was placed in a dry, clean 6 fluid ounce jar. Second, approximately 13 milliliters of clean steel balls was added to the jar as a grinding medium. Third, 20 millimoles of LiNb(OCH2CH3)6 (Gelest, Inc., Tulleytown, Pa.) was measured into a 100 milliliter beaker as a 25.0 gram solution in anhydrous alcohol. A magnetic stirring bar was then placed in the beaker, and the beaker was placed on a conventional stirring plate. Fourth, 30 milliliters of H2O was mixed with 20 milliliters of dry 2-methoxyethanol (Aldrich Chemical Co., Milwaukee, Wis.), which was then added to the 100 milliliter beaker. Fifth, 20 milliliters of anhydrous 2-methoxyethanol was added to the 6 fluid ounce jar. Sixth, the contents in the beaker were vigorously agitated for approximately 10 minutes. Seventh, the contents in the 100 milliliter beaker was charged into the 6 fluid ounce jar containing the LiNiO2 powder. Eight, the jar was capped with a polytetrafluoroethylene (PTFE) lined cap and placed on a ball mill roller for approximately 48 hours. Next the contents in the jar were dried in an air oven having a temperature set point of approximately 100 degrees centigrade for approximately 48 hours. The contents were then dried for an additional 24 hours in a vacuum oven having a temperature set point of approximately 100 degrees centigrade. Next, the dried powder was transferred into an alumina tray for pyrolysis in an oxygen enriched atmosphere. The pyrolysis conditions were:Temperature Set Point Duration at Set In Degrees Centigrade Point in Hours 400 1.0 450 0.5 500 0.5 550 0.5 600 0.5 650 0.5 700 0.5 750 5.0 - Finally, the LiNiO2 niobate function gradient material was cooled down in the oven over 16 hours and then transferred to a clean dry jar for storage.
- First, 5.0661 grams of the above prepared LiNiO2 niobate functional gradient material, 0.5970 grams of acetylene black (C-100, Cheveron Oil Co., Richmond, Calif.) and 0.2979 grams of polyvinylidene fluoride powder (534,000 molecular weight, Aldrich Chemical Co.) were charged into a dry, clean 6 fluid ounce jar. Ceramic grinding balls were added to the jar until the jar was half full. Next, enough hexane was charged into the jar so that the ceramic grinding balls were then covered with solvent. The jar was then capped with a PTFE lined cap and placed on a ball mill roller for approximately 24 hours. After milling, 3.0 milliliters of N,N-dimethyl formamide (Aldrich Chemical Co.) was added to the solvent paste. The resulting paste was then coated onto primed aluminum foil using a 0.003 inch gap coating knife. The coated material was dried atmospherically and then further dried in a vacuum oven having a temperature set point of approximately 100 degrees centigrade. Next, test electrodes were punched from the coated foil using a 9 millimeter die. Coin cells were then assembled using lithium metal as the counter electrode and a 1 Molar solution of LiAsF6 in propylene carbonate (PC) as the electrolyte.
- The above assembled cells were placed on a standard battery cycling test machine (Arbin BT-2043, Arbin Instruments, College Station, Tex.) and cycled at various rates of discharge and charge calculated from the estimated theoretical cell capacity of the cell's test electrode. The test results of the LiNiO2 niobate FGM electrode coin cells can be seen in FIGS. 4 and 5. Comparative test results of coin cells fabricated from LiNiO2 both with and without the niobate can be seen in FIGS. 6 and 7.
- FIG. 4 shows the first charge/discharge cycle of a LiNiO2 niobate FGM electrode coin cell tested at about C/24. The profile is consistent with a LiNiO2 cathode.
- FIG. 5 shows the effect of cycle rate on the LiNiO2 niobate FGM electrode coin cells at C, C/4, and C/8 rates. Note that there is very little loss of cell capacity even after 700 hours of testing.
- FIG. 6 shows a comparison of capacity versus cycles number for a LiNiO2 niobate FGM electrode coin cell and a LiNiO2 electrode coin cell tested at about the C/4 rate. As can be seen, the cell with the LiNiO2 niobate FGM electrode has retained its capacity much better than the cell with the LiNiO2 electrode. This indicates that secondary, irreversible reactions on the electrode surface of the LiNiO2 niobate FGM electrode are occurring at a significantly lower rate than in the cell with the LiNiO2 electrode. Therefore, the LiNiO2 niobate FGM electrode has demonstrated, among other things, a substantially improved electrolyte compatibility relative to a LiNiO2 electrode.
- FIG. 7 shows the cumulative effect of normalized capacity as a function of cycle time for a LiNiO2 electrode as well as for a LiNiO2 niobate FGM electrode.
- The foregoing description merely explains and illustrates the invention and the invention is not limited thereto except insofar as the appended claims are so limited, as those skilled in the art who have the disclosure before them will be able to make modifications without departing the scope of the invention.
Claims (20)
1. An electrode for use in an electrochemical cell comprising:
a current collecting substrate;
an active material associated with the substrate; and
a surface modifying component applied to at least a portion of the active material, wherein the surface modifying component is fabricated from at least one of the group consisting essentially of lithium niobates and lithium tantalates.
2. The electrode according to , further comprising means for increasing the compatibility of the electrode with an associated electrolyte.
claim 1
3. The electrode according to , wherein the compatibility increasing means comprises the surface modifying component.
claim 2
4. The electrode according to , wherein the surface modifying component is fabricated from at least one lithium niobate species having the chemical structure LixNbOy, wherein x and y range from about 1 to 5.
claim 1
5. The electrode according to , wherein the surface modifying component is fabricated from at lest one lithium tantalate species having the chemical structure LixTaOy, wherein x and y range from about 1 to 5.
claim 1
6. The electrode according to , wherein the surface modifying component is in a crystalline or glassy state.
claim 1
7. The electrode according to , wherein the surface modifying component is doped with at least one carbonaceous particle.
claim 1
8. The electrode according to , wherein the surface modifying component is doped with at least one of the group consisting essentially of transition metal oxides, metal oxides, non-metal oxides, rare earth metal oxides, and metal phosphates, sulfates, and sulfides.
claim 1
9. An electrochemical cell comprising:
an electrolyte;
a first electrode and a second electrode wherein at least one of the first and second electrodes comprises:
a current collecting substrate;
an active material associated with the substrate; and
a surface modifying component applied to at least a portion of the active material, wherein the surface modifying component is fabricated from at least one of the group consisting essentially of lithium niobates and lithium tantalates.
10. The electrochemical cell according to , further comprising means for increasing the compatibility of the electrode with the electrolyte.
claim 9
11. The electrochemical cell according to , wherein the compatibility increasing means includes the surface modifying component.
claim 10
12. The electrochemical cell according to , wherein the surface modifying component is fabricated from at least one lithium niobate species having the chemical structure LixNbOy, wherein x and y range from about 1 to 5.
claim 9
13. The electrochemical cell according to , wherein the surface modifying component is fabricated from at lest one lithium tantalate species having the chemical structure LixTaOy, wherein x and y range from about 1 to 5.
claim 9
14. The electrochemical cell according to , wherein the surface modifying component is in a crystalline or glassy state.
claim 9
15. The electrochemical cell according to , wherein the surface modifying component is doped with at least one carbonaceous particle.
claim 9
16. The electrochemical cell according to , wherein the surface modifying component is doped with at least one of the group consisting essentially of transition metal oxides, metal oxides, non-metal oxides, rare earth metal oxides, and metal phosphates, sulfates, and sulfides.
claim 9
17. A process for manufacturing an electrochemical cell comprising the steps of:
associating a surface modifying component with an active material;
modifying the surface of the active material;
fabricating a first electrode by applying the surface modified active material to a current collecting substrate;
fabricating a second electrode; and
associating at least one electrolyte with the first and second electrodes.
18. The process according to , wherein the step of associating the surface modifying component includes the steps of:
claim 17
dissolving at least one of a lithium niobate species and a lithium tantalate species in a solvent and, in turn, preparing a solution;
applying the prepared solution to at least a portion of the active material; and
substantially removing the solvent from the solution.
19. The process according to , wherein the step of preparing the solution includes the step of doping the solution with at least one carbonaceous species.
claim 18
20. The process according to , wherein the step of preparing the solution includes the step of doping the solution with at least one of the group of transition metal oxides, non-metal oxides, rare earth metal oxides, and metal phosphates, sulfates, and sulfides.
claim 18
Priority Applications (1)
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US09/902,235 US20010055717A1 (en) | 1999-07-15 | 2001-07-10 | Electrochemical cell having a surface modified electrode and associated fabrication process |
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US09/353,979 US6258486B1 (en) | 1999-07-15 | 1999-07-15 | Electrochemical cell having a surface modified electrode and associated fabrication process |
US09/902,235 US20010055717A1 (en) | 1999-07-15 | 2001-07-10 | Electrochemical cell having a surface modified electrode and associated fabrication process |
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US09/353,979 Continuation US6258486B1 (en) | 1999-07-15 | 1999-07-15 | Electrochemical cell having a surface modified electrode and associated fabrication process |
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US09/902,235 Abandoned US20010055717A1 (en) | 1999-07-15 | 2001-07-10 | Electrochemical cell having a surface modified electrode and associated fabrication process |
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JP (1) | JP2001043847A (en) |
Cited By (7)
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US20090104500A1 (en) * | 2004-12-23 | 2009-04-23 | Universitetet I Oslo | Proton Conductors |
US20090155692A1 (en) * | 2007-12-18 | 2009-06-18 | Samsung Sdi Co., Ltd. | Surface treated anode active material and method of making the same, anode including the same, and lithium battery including the same |
US20140227606A1 (en) * | 2011-09-30 | 2014-08-14 | Toyota Jidosha Kabushiki Kaisha | All solid state battery and method for producing same |
US10658661B2 (en) | 2011-08-30 | 2020-05-19 | Semiconductor Energy Laboratory Co., Ltd. | Power storage device and method for manufacturing electrode |
WO2020249659A1 (en) | 2019-06-13 | 2020-12-17 | Basf Se | Coated particulate material comprising complex layered oxide for use as electrode active material, respective methods of making and uses thereof |
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US4465747A (en) * | 1983-06-29 | 1984-08-14 | Union Carbide Corporation | Alkali metal or alkaline earth metal compound additive for manganese dioxide-containing nonaqueous cells |
JP3347555B2 (en) * | 1994-12-01 | 2002-11-20 | キヤノン株式会社 | Method for manufacturing negative electrode of lithium secondary battery |
-
1999
- 1999-07-15 US US09/353,979 patent/US6258486B1/en not_active Expired - Lifetime
-
2000
- 2000-07-12 JP JP2000211295A patent/JP2001043847A/en active Pending
-
2001
- 2001-07-10 US US09/902,235 patent/US20010055717A1/en not_active Abandoned
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US20090104500A1 (en) * | 2004-12-23 | 2009-04-23 | Universitetet I Oslo | Proton Conductors |
US8426077B2 (en) | 2004-12-23 | 2013-04-23 | Universitetet I Oslo | Proton conductors |
US20090155692A1 (en) * | 2007-12-18 | 2009-06-18 | Samsung Sdi Co., Ltd. | Surface treated anode active material and method of making the same, anode including the same, and lithium battery including the same |
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US10658661B2 (en) | 2011-08-30 | 2020-05-19 | Semiconductor Energy Laboratory Co., Ltd. | Power storage device and method for manufacturing electrode |
US20140227606A1 (en) * | 2011-09-30 | 2014-08-14 | Toyota Jidosha Kabushiki Kaisha | All solid state battery and method for producing same |
WO2020249659A1 (en) | 2019-06-13 | 2020-12-17 | Basf Se | Coated particulate material comprising complex layered oxide for use as electrode active material, respective methods of making and uses thereof |
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Also Published As
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US6258486B1 (en) | 2001-07-10 |
JP2001043847A (en) | 2001-02-16 |
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