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
  • H01M4/62—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
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
  • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
  • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
• • 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
  • H01M4/0402—Methods of deposition of the material
• • 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
  • H01M4/0402—Methods of deposition of the material
  • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
• • 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
• • 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
• • 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
  • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• • 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
  • H01M4/364—Composites as mixtures
• • 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
• • 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
• • 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
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
  • H01M4/623—Binders being polymers fluorinated polymers
• • 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
  • H01M2004/021—Physical characteristics, e.g. porosity, surface area
• • 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
  • H01M2004/028—Positive electrodes
• • 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
• • 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

Definitions

• cathode formulations comprising graphenes, cathodes made therefrom, and methods of making such cathode formulations.
• M uch effort has been focused on improving the performance of rechargeable batteries, such as those containing lithium ion-based cathodes.
• the active cathode material is capable of absorbing and desorbing lithium ions under a voltage differential to the anode in repeatable fashion. Because these materials are typically poor conductors, conductive carbon-based additives are often added to impart conductivity to the cathode.
• conductive carbon-based additives are often added to impart conductivity to the cathode.
• One embodiment provides a cathode formulation comprising: an electroactive material; and graphene interspersed with the electroactive material; wherein a ratio of (mean electroactive material domain size) / (mean graphene lateral domain size) ranges from 3:2 to 15:1.
• Another embodiment provides a cathode comprising: an electroactive material; and graphene interspersed with the electroactive material; wherein a ratio of (mean electroactive material domain size) / (mean graphene lateral domain size) ranges from 3:2 to 15:1.
• Another embodiment provides a method of making a cathode, comprising: combining particles comprising an electroactive material, a graphene, and a binder in the presence of a solvent to produce a paste having a solids loading of at least 80%, wherein a ratio of (mean electroactive material domain size) / (mean graphene lateral domain size) ranges from 3:2 to 15:1; and depositing the paste onto a substrate; and forming the cathode.
• Another embodiment provides a cathode paste containing particles comprising: an electroactive material; a graphene; and a binder; wherein a ratio of (mean electroactive material domain size) / (mean graphene lateral domain size) ranges from 3:2 to 15:1, and wherein the paste has a solids loading of at least 65%.
• FIG. 1 is a schematic cross-section of the domains of electroactive material and graphene, and features the short range and long range conductivity pathways;
• FIG. 2A is a schematic cross-section of the relative domain sizes of electroactive material and graphene in a ratio ranging from 3:2 to 15:1;
• FIG. 2B is a schematic cross-section of the relative domain sizes of electroactive material and graphene in a ratio below the range of 3:2 to 15:1.
• cathode formulations comprising graphenes.
• One embodiment provides a cathode formulation comprising: an electroactive material; and graphene interspersed with the electroactive material; wherein a ratio of (mean electroactive material domain size) / (mean graphene lateral domain size) ranges from 3:2 to 15:1.
• the cathode formulation comprises the graphene interspersed with the electroactive material. It has been discovered that the use of graphene as a conductive carbon-based material results in improved cathode performance (and thus, overall battery performance) compared to cathodes comprising more traditional conductive carbon materials such as graphite, carbon black, carbon nanotubes, etc.
• the cathode formulation can take the form of a paste or slurry in which particulate electroactive material and graphene is combined in the presence of a solvent.
• the cathode formulation is a solid material resulting from solvent removal from the paste/slurry.
• the cathode formulation is provided in a cathode.
• cathode performance can be enhanced by optimizing the relationship between mean domain size of the electroactive material and the graphene lateral domain size, wherein the ratio of (mean electroactive material domain size) / (mean graphene lateral domain size) ranges from 3:2 to 15:1, e.g., a ratio ranging from 3:2 to 10:1.
• Domain size can be used to define the size of discrete particles or regions of a material within a solid.
• electroactive material domain size as used herein encompasses the largest dimension of the electroactive material domain (e.g., particle).
• the domain can take the form of various shapes, e.g., cuboids, spheroids, plates, or irregular shapes, whether discrete, encompassed in a paste, or encompassed in a solid matrix.
• the electroactive material can be comprised of 2 ⁇ particles agglomerated into a discrete 10 ⁇ larger particle.
• the domain size of the electroactive material is 10 ⁇ .
• the cathode formulation comprises electroactive material having a mean domain size ranging from 3 to 20 ⁇ , e.g., from 3 to 15 ⁇ , from 5 to 20 ⁇ or from 5 to 12 ⁇ .
• domain size (e.g., in a solid cathode material) can be determined by scanning electron microscopy (SEM), e.g., field emission SEM (FE-SEM), or other methods known in the art.
• SEM scanning electron microscopy
• FE-SEM field emission SEM
• Graphene as used herein comprises stacked sheets, in which each sheet comprises sp 2 -hybridized carbon atoms bonded to each other to form a honey-comb lattice.
• the graphene comprises few-layer graphenes (FLG), having 2 or more stacked graphene sheets, e.g., a 2-20 layer graphene.
• the graphene i.e., the FLG
• the FLG comprises a 3-15 layer graphene.
• a portion of the graphene (i.e., the FLG) can include single-layer graphene and/or graphene having more than 15 or more than 20 layers so long as at least 80%, at least 85%, at least 90%, or at least 95% of the graphene comprises 2-20 layer graphene. In another embodiment, at least 80%, at least 85%, at least 90%, or at least 95% of the graphene comprises 3-15 layer graphene.
• the dimensions of graphenes are typically defined by thickness and lateral domain size.
• Graphene thickness generally depends on the number of layered graphene sheets. The dimension transverse to the thickness is referred to herein as the "lateral" dimension or domain.
• the graphene has a mean lateral domain size ranging from 0.5 to 10 ⁇ , e.g., ranging from 1 ⁇ to 5 ⁇ .
• the graphenes can exist as discrete particles and/or as aggregates.
• Aggregates refers to a plurality of graphene particles (FLG) that are adhered to each other.
• mean lateral domain size refers to the longest indivisible dimension or domain of the aggregate. Thickness of the aggregates is defined as the thickness of the individual graphene particle.
• the surface area of the graphene is a function of the number of sheets stacked upon each other and can be calculated based on the number of layers.
• the graphene has no microporosity.
• the surface area of a graphene monolayer with no porosity is 2700 m 2 /g.
• the surface area of a 2-layer graphene with no porosity can be calculated as 1350 m 2 /g.
• the graphene surface area results from the combination of the number of stacked sheets and amorphous cavities or pores.
• the graphene has a microporosity ranging from greater than 0% to 50%, e.g., from 20% to 45%.
• the graphene has a BET surface area ranging from 40 to 1600 m 2 /g, from 60 to 1000 m 2 /g, or a BET surface area ranging from 80 to 800 m 2 /g.
• the electroactive material is a lithium ion-based material. Lithium ion batteries have proven useful for consumer electronics as well as electric and hybrid electric vehicles due to high energy and power densities, allowing them to charge and discharge rapidly. Exemplary lithium ion materials include:
• LiMP0 4 wherein M represents one or more metals selected from Fe, Mn, Co, and Ni;
• M' represents one or more metals selected from Ni, Mn, Co, Al, Mg, Ti, V, Cr, Fe, Zr, Ga, and Si;
• M represents one or more metals selected from Ni, Mn, Co, Al, Mg, Ti, V, Cr, Fe, Zr, Ga, and Si (e.g., Li[Mn(M")] 2 0 4 );
• LiFe x Mn y Co z P0 4 where x varies from 0.01-1, y varies from 0.01-1, z varies from 0.01-0.2, and x+y+z l; LiNii- x _ y Mn x CO y 0 2 , wherein x ranges from 0.01 to 0.99 and y ranges from 0.01 to 0.99; and layer-layer compositions containing an Li 2 Mn0 3 phase or a LiMn 2 0 3 phase.
• the electroactive material is selected from at least one of Li 2 Mn0 3 ; LiNii- x _ y Mn x CO y 0 2 wherein x ranges from 0.01 to 0.99 and y ranges from 0.01 to 0.99; LiNi 0 .5M ni. 5 O 4 ; Lii +x (Ni y Coi_ y _ z Mn z )i_ x 0 2 , wherein x ranges from 0 to 1, y ranges from 0 to 1 and z ranges from 0 to 1; and layer-layer compositions containing at least one of an Li 2 Mn0 3 phase and an LiMn 2 0 3 phase.
• the graphene is obtained from commercially available sources.
• the graphene can be formed by separation of graphene sheets (e.g., via exfoliation) from a graphite or carbon fiber material by, e.g., subjecting the graphite or carbon fiber material to acidic conditions (e.g., sulfuric or nitric acid), followed by shearing processes such as milling, sonification, etc.
• acidic conditions e.g., sulfuric or nitric acid
• Another embodiment provides a cathode, comprising: an electroactive material; and graphene interspersed with the active material; wherein a ratio of (mean electroactive material domain size) / (mean graphene lateral domain size) ranges from 3:2 to 15:1.
• the cathode comprises graphene interspersed with the electroactive material wherein the electroactive material is the majority component in the cathode formulation.
• the choice of electroactive material may depend on specific capacity desired, as each active material has a theoretical specific capacity relating to the maximum amount of capacity that it can store. Table 1 lists the specific capacities for various electroactive materials.
• the cathode comprises 90% active material
• the theoretical specific capacity of the cathode will approximate 90 % of the value for that particular active material.
• the graphenes disclosed herein can be included in sufficiently small amounts to maximize the amount of electroactive material and thereby maximize the specific capacity of the cathode.
• the graphene is present in the cathode in an amount ranging from 0.1 to 2.5% by weight relative to the total weight of the cathode, such as an amount ranging from 0.1 to 2%, from 0.5 to 2%, from 0.1 to 1.5%, or an amount ranging from 0.1 to 1.25%.
• the graphene is present in the cathode in an amount sufficient to form an electrically conductive pathway across a dimension of the cathode.
• FIG. 1 schematically illustrates the conductive pathway provided by the graphenes disclosed herein.
• Cathode formulation 2 comprises a plurality of domains of an electroactive material 4, each domain being substantially surrounded by a plurality of graphenes 6a to provide short range conductivity about each domain 4.
• Another plurality of graphenes 6b are collectively arranged to form a pathway extending along the plurality of domains 4 to provide long range conductivity throughout a cathode dimension.
• Some graphenes may be positioned to provide both short range and long range conductivity.
• the mean lateral domain size of the graphene e.g., ranging from 0.5 to 10 ⁇ or from 1 ⁇ to 5 ⁇
• the relatively small thickness of the graphene e.g., 2-20 layer or 3-15 layer
• FIGs. 2A and 2B show the dimensions of the electroactive material 14 in relation to graphene 16 in accordance with the embodiments disclosed herein.
• FIG. 2B shows domain sizes of the electroactive material 14' domain and graphene 16' lateral domain where the ratio is less than 3:2.
• the short range conductivity can be interrupted due to the large size of the lateral graphene domain, resulting in a reduction in cathode productivity.
• having a (mean electroactive material domain) / (mean graphene lateral domain) ratio of less than 3:2 results in insufficient graphene coating of the electroactive material and therefore poorer short range conductivity.
• the graphene-electroactive material overlap is maximized at lower domain size for the graphene.
• the beneficial contact of the graphene- electroactive contacts is overweighed by the detrimental effects of short domain size on the graphene-graphene overlap.
• the cathode dimension is a thickness of at least 10 ⁇ , such as a thickness of at least 50 ⁇ , or a thickness ranging from 50 ⁇ to 200 ⁇ , e.g., a thickness ranging from 50 ⁇ to 100 ⁇ .
• thinner cathodes can be constructed to have dimensions ranging from 10 ⁇ to 50 ⁇ , e.g., from 20 ⁇ to 50 ⁇ .
• the cathode comprising the materials disclosed herein has a performance, as defined by a discharge capacity at 4C current, of at least 130 mAh/g, e.g., ranging from 140 mAh/g to 200 mAh/g.
• the cathode further comprises a binder.
• binder materials include but are not limited to fluorinated polymers such as
• PVDF poly(vinyldifluoroethylene)
• PVDF-HFP poly(vinyldifluoroethylene-co-hexafluoropropylene)
• PTFE poly(tetrafluoroethylene)
• PVA poly(ethylene) oxide
• PVA polyvinyl-alcohol
• CMC carboxymethylcellulose
• PVP polyvinyl pyrrolidone
• binders include polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene- butadiene rubber (SBR), and fluoro rubber and copolymers and mixtures thereof.
• EPDM ethylene-propylene-diene terpolymer
• SBR styrene- butadiene rubber
• Another embodiment provides a method of making a cathode, comprising: combining particles comprising an electroactive material, a graphene, and a binder in the presence of a solvent to produce a paste, wherein a ratio of (mean
• electroactive material domain size (mean graphene lateral domain size) ranges from 3:2 to 15:1 (e.g., from 3:2 to 10:1); depositing the paste onto a substrate; and; and forming the cathode.
• the paste is the product of combining particles comprising electroactive material with graphene and binder in the presence of a solvent.
• the paste has a sufficiently high solids loading to enable deposition onto a substrate while minimizing the formation of inherent defects (e.g., cracking) that may result with a less viscous paste (e.g., having a lower solids loading).
• a higher solids loading reduces the amount of solvent needed.
• the solids loading is at least 65%, e.g., a solids loading ranging from 65% to 85% or ranging from 74% to 81%.
• the particles can be combined in the solvent in any order so long as the resulting paste is substantially homogeneous, which can be achieved by shaking, stirring, etc.
• the particles can be formed in situ or added as already formed particles having the domain sizes disclosed herein.
• Exemplary solvents include e.g., N-methylpyrrolidone, acetone, alcohols, and water.
• the method comprises depositing the paste onto a substrate, such as a current collector (e.g., an aluminum sheet), followed by forming the cathode.
• a substrate such as a current collector (e.g., an aluminum sheet)
• "forming the cathode” comprises removing the solvent.
• the solvent is removed by drying the paste either at ambient temperature or under low heat conditions, e.g., temperatures ranging from 20° to 100°C.
• forming the cathode can be accomplished in several steps.
• the forming can comprise depositing the paste onto a current collector (e.g., an aluminum sheet), and drying the paste on the current collector to form the solid.
• the solvent removal is subsumed in the forming step.
• the forming can further comprise cutting the deposited cathode/AI sheet to the desired dimensions followed by calendering to achieve a desired cathode porosity.
• cathode porosity results in improved ionic (e.g., Li ion) conductivity.
• Calendering can be performed with stainless steel rollers to achieve a desired cathode porosity, as known in the art.
• the cathode has a porosity ranging from 10 to 50 %, e.g., a porosity ranging from 15 to 30 %.
• the cathode paste comprises particles comprising: an electroactive material; a graphene; and a binder; wherein a ratio of (mean electroactive material particle size) / (mean graphene lateral size) ranges from 3:2 to 15:1 (e.g., from 3:2 to 10:1), and wherein the paste has a solids loading of at least 65%.
• the graphene dimensions disclosed herein contribute to a higher solids loading due to the thin, platelike structure when compared to, e.g., carbon black, which has a higher structure or other graphene particles having dimensions outside the claimed range.
• the paste has a solids loading ranging from 65% to 85%, such as a solids loading ranging from 74% to 81%.
• the higher solids loading translates to higher viscosities, such as a viscosity ranging from 100 cP to 10,000 cP, such as a viscosity ranging from 2,000 cP to 7,000 cP when measured with a Brookfield Viscometer Model HB using a SC4-18 type spindle at 10 RPM.
• Another embodiment provides an electrochemical cell (battery) comprising the cathodes comprising the materials disclosed herein.
• the use of the disclosed cathode formulations can result in a cathode/cell having one or more improved properties, including:
• This Example describes the preparation of cathode pastes incorporating various graphenes as a conductive aid.
• the surface area, lateral domain, and thickness properties of these graphenes are listed in Table 2 below.
• Graphenes A and B are aggregates whereas Graphene C and Comparative Graphene D are platelets.
• Ext. SA is external surface area which is defined as the BJH desorption cumulative surface area of pores that are greater than 1.7 nm in diameter.
• NMP N-methylpyrrolidone
• the solids loading of the cathode pastes are listed in Table 3 below.
• pastes according to the embodiments disclosed herein are capable of high solids loading (e.g., of at least 65%), enabled by the lower loading of graphenes. It can be seen that a high solids loading is achieved at 0.25 wt% graphene compared to the Comp Paste slurry prepared with carbon black at 3 wt%.
• This Example describes the preparation of cathodes from cathode pastes.
• the pastes were prepared in the same manner as described in Example 1, in proportions outlined in Table 4.
• Comparative Sample 1 incorporates the Comparative CB described in Example 1, and Comparative Sample 2 incorporates Comparative Graphene D as the conductive filler.
• the paste was mechanically drawndown on an etched aluminum sheet (17 ⁇ thickness) and subsequently dried at 80°C for 1 h. After drying, circular disks were cut out of the sheet and calendered between two stainless steel rollers to a desired porosity, as listed in Table 4. These disks were dried overnight at 80°C and placed in a glovebox for coin cell manufacture where the coin cell cathodes have thicknesses (including the Al foil) as listed in Table 4.
• This Example describes the physical and electrochemical testing of the coin cells of Example 2.
• the cathodes were examined via FE-SEM cross-section spectroscopy.
• the electrochemical properties were investigated via cyclic voltammetry and charge-discharge tests. The specific capacity at specified charge and discharge rates as well as voltage response.
• Power density (W/g) is calculated as V(V)*l(A)/m (g) where V is average discharge voltage , I is discharge current and m is weight of active powder in the cathode. Table 5
• the domain size of the electroactive material can also be a contributing effect to the improved performance of cathodes containing graphenes versus carbon black.
• Table 8 below provides data for LiNio.33Coo.33M no.33O2 having a domain size of 2 ⁇
• electroactive material domain size (mean graphene lateral domain size) ratio is less than 3:2 (see Tables 5-7).

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