Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
  • B29C41/003—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor characterised by the choice of material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
  • B29C41/02—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor for making articles of definite length, i.e. discrete articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
  • B29C71/02—Thermal after-treatment
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/20—Manufacture of shaped structures of ion-exchange resins
  • C08J5/22—Films, membranes or diaphragms
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
  • C09K5/08—Materials not undergoing a change of physical state when used
• • 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
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
  • H01M50/491—Porosity
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
  • H01M50/494—Tensile strength
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/06—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts
  • B29K2105/20—Inserts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2709/00—Use of inorganic materials not provided for in groups B29K2703/00 - B29K2707/00, for preformed parts, e.g. for inserts
  • B29K2709/02—Ceramics
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2715/00—Condition, form or state of preformed parts, e.g. inserts
  • B29K2715/003—Cellular or porous
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2031/00—Other particular articles
  • B29L2031/34—Electrical apparatus, e.g. sparking plugs or parts thereof
  • B29L2031/3468—Batteries, accumulators or fuel cells
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2220/00—Batteries for particular applications
  • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2220/00—Batteries for particular applications
  • H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
• • 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
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/60—Other road transportation technologies with climate change mitigation effect
  • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

Definitions

• the present disclosure relates generally to the field of porous membranes and to electric current producing cells and separators for use in electric current producing cells. More particularly, this disclosure pertains to a porous separator membrane comprising an inorganic oxide or other inorganic material where the membrane has increased thermal conductivity compared to porous separator membranes consisting of polyolefin materials. Also, the present disclosure pertains to electric current producing cells, such as lithium ion cells and capacitors, comprising such porous separators with increased thermal conductivity.
• Lithium batteries including rechargeable or secondary lithium ion batteries, non-rechargeable or primary lithium batteries, and other types such as lithium-sulfur batteries, are typically made by interleaving a plastic separator, a metal substrate with a cathode layer coated on both sides, another plastic separator, and another metal substrate with an anode layer coated on both sides. To maintain the alignment of the strips of these materials and for other quality reasons, this interleaving is usually done on automatic equipment, which is complex and expensive. Also, in order to achieve sufficient mechanical strength and integrity, the separators and the metal substrates are relatively thick, such as 10 ⁇ or more in thickness.
• a typical thickness of the copper metal substrate for the anode coating layers is 10 ⁇
• a typical thickness of the aluminum metal substrate for the cathode coating layers is 12 ⁇
• the plastic separators typically have thicknesses ranging from 12-20 ⁇ .
• One aspect of the present disclosure pertains to a porous battery separator including ceramic particles and a polymeric binder, wherein the porous separator has a porosity between 35-50% and an average pore size between 10-50 nm.
• the ceramic particles are selected from the group consisting of inorganic oxide particles and inorganic nitride particles.
• the porous separator exhibits less than 1 % shrinkage when exposed to a temperature of 200°C for at least one hour.
• the ceramic particles include at least one of AI2O3, AIO(OH) or boehmite, A1N, BN, SiN, ZnO, Zr02, S1O 2 , and combinations thereof.
• the ceramic particles include between 65-95%> boehmite and a remainder of BN. In some cases, the ceramic particles include between 65-95%> boehmite and a remainder of A1N. In some cases, the average pore size is between 10-90 nm. In some cases, less than 1% of the pores have a size outside of 10-90 nm. In some cases, the porosity is between 35-50%.
• the polymeric binder includes a polymer selected from polyvinylidene difluoride (PVdF) and copolymers thereof, polyvinyl ethers, urethanes, acrylics, cellulosics, styrene-butadiene copolymers, natural rubbers, chitosan, nitrile rubbers, silicone elastomers, PEO or PEO copolymers, polyphosphazenes, and combinations thereof.
• the porous separator has a thermal conductivity that increases when temperature is raised from 25 °C to 50°C and tested using one of ASTM E1461 and ASTM 1530.
• the separator has a pore volume and greater than 90% of the pore volume includes pores having a pore diameter of less than 100 nm.
• an electrochemical cell including an anode, a cathode, an inorganic electrolyte, comprising a lithium salt, and a porous separator layer including an organic polymer and a ceramic material, wherein the porous separator layer has a porosity between 35-50% and an average pore size between 10-90 nm and exhibits less than 1% shrinkage when exposed to a temperature of 200°C for at least one hour.
• the inorganic ceramic particles are selected from the group consisting of inorganic oxide particles and inorganic nitride particles.
• the inorganic ceramic particles include A1 2 0 3 , AIO(OH) or boehmite, A1N, BN, SiN, ZnO, Zr0 2 , Si0 2 , and combinations thereof; and the organic polymer includes PVdF and copolymers thereof, polyvinyl ethers, urethanes, acrylics, cellulosics, styrene -butadiene copolymers, natural rubbers, chitosan, nitrile rubbers, silicone elastomers, PEO or PEO copolymers, polyphosphazenes, and combinations thereof.
• the average pore size is between 25-35 nm.
• the porosity is between 40-45%.
• Another aspect of the present disclosure pertains to a method of manufacturing a flexible porous composite separator.
• the method includes formulating a dispersion, wherein the dispersion includes an organic polymeric material, an inorganic ceramic material, and a solvent; applying the dispersion to a substrate to form a coating; drying and curing the coating; and removing the coating from the substrate thereby forming a flexible porous composite separator, wherein the porous separator has a porosity between 35-50% and an average pore size between 10-50 nm and exhibits less than 1 % shrinkage when exposed to a temperature of 200°C for at least one hour.
• the average pore size is between 20-40 nm and the porosity of the porous composite separator is between 40-45%.
• the inorganic ceramic material includes at least one of boehmite, BN, and A1N.
• Another aspect of the present disclosure pertains to a method of transferring heat through a battery including raising the temperature of an electrode in a lithium ion battery, and transferring heat from the electrode through a separator to a second electrode, the separator comprising porous ceramic particles and a polymer, wherein the separator has a porosity of 35-50% and an average pore size between 10-50 nm. In some cases, the average pore size is between 20-40 nm. In some cases, the separator has a plurality of pores and each of the pores has a diameter between 10-50 nm. In some cases, the separator has a plurality of pores and none of the pores has a diameter greater than 100 nm.
• the separator has a porosity between 40-45%. In some cases, the separator exhibits less than 1% shrinkage when exposed to a temperature of 200°C for at least one hour.
• a flexible composite ceramic separator including a polymer; a first inorganic particulate material dispersed uniformly in the polymer; a second inorganic particulate material dispersed uniformly in the polymer, the second inorganic particulate material differing in either particle size or composition from the first inorganic particulate material; and wherein the flexible composite ceramic separator exhibits a thermal conductivity that is greater than the thermal conductivity of a comparative composite ceramic separator of the same composition that differs only in that it only includes a single inorganic particulate material at the same weight loading as the sum of the loadings of the first and second inorganic particulate materials.
• the single inorganic particulate in the comparative composite ceramic separator is the same as one of the inorganic part
• Figures 1-2 show thermograms of a polymeric separator and boehmite-based separator prepared according to an embodiment of the present disclosure.
• Figure 3 shows a chart of the thermal conductivity (measured in W/m- ) of a polymeric separator compared to that of a nanoporous composite separator prepared according to an embodiment of the present disclosure.
• Figure 4 shows a chart of the thermal conductivity (measured in W/m-K) of a polymeric separator material, a ceramic-coated polymeric separator material, and a nanoporous composite separator material prepared according to an embodiment of the present disclosure.
• Figures 5-6 are graphs of the dimensional stability of various separator materials, including a nanoporous composite separator prepared according to an embodiment of the present disclosure.
• Figures 7-8 are graphs of the dimensional stability of various separator materials, including a nanoporous composite separator prepared according to an embodiment of the present disclosure.
• Figure 9 is a graph of the differential intrusion as a function of pore size diameter of a polymeric separator material and a nanoporous composite separator material prepared according to an embodiment of the present disclosure.
• Figure 10 is a graph of the tensile stress as a function of percent extension of two separator materials, including a nanoporous composite separator material prepared according to an embodiment of the present disclosure.
• Figure 11 is a graph of the particle size distribution of various boehmite and boron nitride (BN) blends, according to various embodiments of the present disclosure.
• Figure 12 is a graph of the particle size distribution of various boehmite and alumina nitride (A1N) blends, according to various embodiments of the present disclosure.
• Figure 13 is a graph of the viscosity profiles for various boehmite and BN blends, in liquid form, according to various embodiments of the present disclosure.
• Figure 14 is a flow chart illustrating a method for preparing a nanoporous composite separator, according to an embodiment of the present invention DETAILED DESCRIPTION OF THE DISCLOSURE
• Nanoporous composite separators comprising a composite of porous/nanoporous inorganic material and an organic polymer material. Such composite separators may be used, for instance, in batteries and/or capacitors.
• the inorganic material may comprise AI2O3, AIO(OH) or boehmite, A1N, BN, SiN, ZnO, Zr0 2 , Si0 2 , or combinations thereof.
• the organic polymer material may include, for example, polyvinylidene difluoride (PVdF) and/or copolymers thereof, polyvinyl ethers, urethanes, acrylics, cellulosics, styrene -butadiene copolymers, natural rubbers, chitosan, nitrile rubbers, silicone elastomers, polyethylene oxide (PEO) or PEO copolymers, polyphosphazenes, or combinations thereof.
• PVdF polyvinylidene difluoride
• copolymers thereof polyvinyl ethers, urethanes, acrylics, cellulosics, styrene -butadiene copolymers, natural rubbers, chitosan, nitrile rubbers, silicone elastomers, polyethylene oxide (PEO) or PEO copolymers, polyphosphazenes, or combinations thereof.
• the flexible nanoporous composite separator has
• the separator may be formed by coating a substrate with a dispersion including the inorganic material, organic material, and a solvent. Once dried, the coating may be removed from the substrate, thus forming the nanoporous composite separator.
• a nanoporous composite separator may provide thermal conductivity and dimensional stability at temperatures above 200°C.
• the porous separator serves a key role in battery designs including prevention of physical contact between the anode and cathode, while facilitating ion transport for electrochemical energy supply as needed.
• Large format Li-ion batteries may operate in an average temperature range between 20-70°C; however, spikes in battery charge and/or discharge can push short term temperatures of such batteries beyond 110°C.
• Separators used for lithium ion batteries are typically polyolefm separators, such as polypropylene or polyethylene that may shrink and/or melt at such high temperatures due to, among other things, chemical breakdown.
• plastic separators Although these plastic separators have the low electrical conductivity needed to insulate the electrodes of batteries from each other, plastic separators also have very low thermal conductivity and are therefore slow or inefficient in dissipating heat within a battery. As lithium ion batteries are increasingly utilized for higher capacity applications, such as for electric and/or hybrid vehicles, the need for improved safety is greatly increased because of the large size and high power rates of these batteries. In some cases, the battery separators may be required to maintain dimensional stability (i.e., ⁇ 5.0% shrinkage of the separator material) at temperatures at or above 200°C in order to ensure battery performance and safety.
• dimensional stability i.e., ⁇ 5.0% shrinkage of the separator material
• Coating of polyolefm separators with ceramic-based materials, and/or selecting higher melting polymer-based materials (PET, polyamides, PVdF, etc.) may increase the thermal stability/battery failure temperature somewhat; however, such techniques increase costs and fail to address a fundamental separator design issue: rapid, efficient, and uniform heat transfer throughout the cell.
• nanoporous inorganic separator materials are disclosed which are electrically isolating, thermally conductive, and maintain dimensional stability at temperatures above 200°C.
• a nanoporous separator layer includes an inorganic material (also called ceramic and/or ceramic filler material) and an organic polymer which acts as a binder to hold the inorganic material together.
• This nanoporous composite separator exhibits a balance of mechanical strength, ionic conductivity, thermal conductivity, and electrical insulation rendering it suitable as a separator membrane for electrochemical cells.
• Suitable inorganic ceramic materials may include, for example, high thermal-conductivity ceramic particles such as AI2O3, AIO(OH) or boehmite, A1N, BN, SiN, ZnO, Zr0 2 , Si0 2 , and combinations of the above.
• a nanoporous composite separator may be formed, in some embodiments, by dispersing one or more of these inorganic materials with an organic or inorganic polymer material including, but not limited to: PVdF and/or copolymers thereof, polyvinyl ethers, urethanes, acrylics, cellulosics, styrene -butadiene copolymers, natural rubbers, chitosan, nitrile rubbers, silicone elastomers, PEO or PEO copolymers, polyphosphazenes, and combinations of the above.
• an organic or inorganic polymer material including, but not limited to: PVdF and/or copolymers thereof, polyvinyl ethers, urethanes, acrylics, cellulosics, styrene -butadiene copolymers, natural rubbers, chitosan, nitrile rubbers, silicone elastomers, PEO or PEO copolymers, poly
• Table 1 provides a number of suitable example inorganic ceramic materials suitable for forming the nanoporous composite separator disclosed herein.
• the inorganic materials are listed along with their corresponding thermal and electrical properties.
• the thermal conductivity of hexagonal-Boron Nitride may be 600 or 30, in some embodiments, depending on its orientation.
• the inorganic material may include boehmite, or a combination of any of these materials.
• Boehmite is a hydrated form of alumina that may be stable up to temperatures exceeding 600°C.
• the crystal structure of boehmite is octahedral and is arranged in corrugated layers and is thus less prone to moisture pick-up than other aluminum based materials.
• the various properties of the nanoporous composite separator may be tailored by adjusting, for example, particle size, organic polymer, particle size distribution, porosity of the inorganic material, specific surface area, and/or surface treatment of the nanoporous material.
• the particle size distribution of the composite separator may be customized by blending boehmite with the various other inorganic materials in various proportions.
• the nanoporous separator material may be pure boehmite (having less than 1% impurities), may be 90% boehmite and 10% BN or A1N, or it may be 70% boehmite and 30% BN or A1N.
• the nanoporous composite separator includes inorganic particles and an organic polymeric to bond the inorganic particles together to form a homogeneous separator.
• a nanoporous composite separator was prepared by mixing a 4: 1 by weight blend of a boehmite pigment with a PVdF polymer and dispersants in an organic solvent blend comprising N-methylpyrrolidone (NMP) and 2-butanone and coating this mixture onto a silicone release film.
• the solvent may comprise other suitable solvents or combinations of solvents such as, for example, benzene, ethyl benzene, toluene, xylene, MEK, NMP, or 2-butanone.
• a porous boehmite-based separator of 20 ⁇ in thickness was obtained. The porosity of this separator was about 42%, and the separator showed less than 1% shrinkage when heated in an oven at 220°C for 1 hour.
• the nanoporous composite separator showed less than 0.5% shrinkage under similar heating conditions.
• the organic polymer material may be a high molecular weight grade of PVdF, such as Solvay® Solef 130 PVdF.
• This particular organic material can provide strong adhesion to current collectors, and in one specific example the nanoporous composite separator includes 4.5 parts boehmite to 1 part Solef 5130 by weight.
• incorporation of a small amount of co- monomer may enhance the cohesive strength of the separator material.
• decreasing the ratio of inorganic oxide to organic polymer will lower the porosity and cycling rate capability of the separator material while increasing its mechanical strength.
• the nanoporous composite separator may have a porosity between 35-50%, a uniform pore distribution over the entire separator material, and/or an average pore diameter of between 20-40 nm. In different sets of embodiments, the porosity of the separator is between 40-45%.
• the inorganic material may include no pores greater than 100 nm, 90 nm, 80 nm, 70 nm, 60 nm, 50 nm, or 40 nm. In still other sets of embodiments, less than 1% or less than 0.1% of the pores are greater than 100 nm, 90 nm, 80 nm, 70 nm, 60 nm, 50 nm, or 40 nm.
• the average pore size is between 10-50 nm, 20-40 nm, or 25-35 nm. In still other sets of embodiments, more than 99% or 99.9% of the pores of the composite separator are between 10-90 nm, 10- 50 nm, 20-40 nm, or 25-35 nm.
• the nanoporous composite separator may exhibit similar properties in the machine direction (along the length of the sample) as in the transverse direction (along the width of the sample) if the separator material is not oriented during manufacturing.
• lithium batteries for vehicles are of a flat or prismatic design.
• manufacturing high energy and economical lithium batteries for vehicles or other applications may involve increasing the proportion or percentage of the volume of the electroactive material in each battery and reducing the complexity and expense of the automated equipment to fabricate the battery.
• a lithium battery may increase the content of electroactive material by implementing thinner separator and/or metal substrate layers.
• Such lithium batteries may be fabricated, for example, on less complex and less expensive automated processing equipment than, for example, the winding equipment utilized for portable computer batteries.
• automated processing equipment may be particularly adapted for making flat or prismatic batteries.
• a dispersion may be prepared including the inorganic material, a polymer material, and a solvent in the desired proportions.
• the dispersion may then be coated on a temporary carrier substrate and allowed to dry and/or cure in order to obtain the desired mechanical properties prior to removal from the substrate.
• the composite material may be removed from the substrate (or the substrate may be removed from the composite material), thus forming a nanoporous composite separator.
• the porous separator layer may be a film with a thickness between 5-50 ⁇ , 10-30 ⁇ , 7-20 ⁇ , 10-20 ⁇ , or 2015-25 ⁇ .
• Figures 1-2 show thermograms produced using an infrared camera (FLIR Model 8300) of a polymeric separator and boehmite-based separator prepared according to an embodiment of the present disclosure.
• Figure 1 is a thermogram of a polyethylene separator film upon exposure to a heated stainless steel substrate
• Figure 2 is a thermogram of a boehmite-based separator film of similar thickness exposed in like manner to the heated stainless steel substrate.
• the bright patches 101 in Figure 1 correspond to areas of increased heat concentration
• the darker patches 103 correspond to areas of decreased heat concentration.
• the uniform heat distribution observed in the boehmite-based separator of Figure 2 is evident compared to the uneven heat distribution seen with the plastic separator.
• Figure 3 shows a chart of the thermal conductivity (measured in W/m-K) of a polymeric separator compared to that of a nanoporous composite separator prepared according to an embodiment of the present disclosure.
• the measurements in Figure 3 were done according to ASTM El 461 by the laser flash (transient) method using an LFA-447 from Netszch® Instruments, Burlington, MA. These measurements illustrate the higher thermal conductivity of the nanoporous composite separator compared to a typical polyolefm separator material.
• Columns 301 and 303 chart the thermal conductivity of the nanoporous composite separator exposed to temperatures of 25°C and 50°C, respectively, while columns 305 and 307 chart the thermal conductivity of the polyolefm separator material exposed to 25°C and 50°C, respectively.
• the polyolefm separator material used was 18 ⁇ thick Tonen® tri-layer
• the nanoporous composite separator was 21 ⁇ thick and comprised a 4.5:1 ratio of Boehmite (Disperal® 10SR) to Solvay® Solef 5130.
• the thermal conductivity of the nanoporous composite separator is more than four times greater than that of the polyolefin separator of a similar thickness.
• This enhanced thermal conductivity is further increased, in some embodiments, when the temperature is increased from 25°C to 50°C.
• This property of increasing thermal conductivity as the temperature increases is particularly useful for safety in lithium ion batteries since they typically operate at temperatures around 50°C due to the heat generated during cell operation. It is important to rapidly and evenly distribute the heat throughout the cell to minimize the localized buildup of heat from any "hot spots" or other unevenly heated areas.
• Figure 4 shows a chart of the thermal conductivity (measured in W/m-K) of a polymeric separator material, a ceramic-coated polymeric separator material, and a nanoporous composite separator prepared according to an embodiment of the present disclosure.
• the thermal conductivities charted in Figure 4 were measured according to the ASTM El 530 guarded hot plate (steady state) method with an estimated variation of +3.0%. These measurements illustrate the higher thermal conductivity of the nanoporous composite separator compared to a typical polymeric separator material and a ceramic-coated polymeric separator material.
• the samples measured include the two separator materials measured in Figure 3, as well as a third sample made from coating each side of the 18 ⁇ thick Tonen® tri- layer with a 3.5 ⁇ layer comprising a 5.5: 1 ratio of boehmite to polymeric binder material.
• Columns 401 and 403 chart the thermal conductivity of the nanoporous composite separator measured at 25°C and 50°C, respectively;
• columns 405 and 407 chart the thermal conductivity of the polyolefin separator material measured at 25 °C and 50°C, respectively;
• columns 409 and 411 chart the thermal conductivity of the ceramic-coated polymeric separator material measured at 25°C and 50°C, respectively.
• the thermal conductivity of the nanoporous composite separator is about twice that of the polyolefin separator material of a similar thickness, while the ceramic-coated separator material shows a slight improvement of about 20% in thermal conductivity over that of the polyolefin separator material.
• Figures 5-6 are graphs of the dimensional stability of various separator materials, including a nanoporous composite separator prepared according to an embodiment of the present disclosure. Figure 5 graphs the dimensional change (measured in ⁇ ) as a function of temperature of the various separator materials measured along the length of the samples, while Figure 6 graphs the dimensional change measured along the width of the material samples.
• 501 graphs the dimensional change of a polymeric separator material
• 503 graphs the dimensional change of a one-side ceramic-coated polymeric separator material
• 505 graphs the dimensional change of a two-side ceramic-coated polymeric separator material
• 507 graphs the dimensional change of a nanoporous composite separator prepared according to an embodiment of the present disclosure.
• the polymeric separator corresponding to graph 501 was a Tonen® tri-layer polyolefm with a thickness of 18 ⁇ and a Gurley air permeability of 300sec/100 cc.
• the separator corresponding to graph 503 was coated on a single side with a 3.5 ⁇ layer comprising a 5.5: 1 ratio of Boehmite (Disperal® 10SR) to Arkema Kynar® 761, and the separator had a Gurley air permeability of 470 sec/ 100 cc.
• the separator corresponding to graph 505 was coated on two sides with a 3.5 ⁇ layer comprising a 5.5:1 ratio of Boehmite (Disperal® 10SR) to Arkema Kynar® 761, and the separator had a Gurley air permeability of 600 sec/100 cc.
• the nanoporous composite separator corresponding to graph 507 comprised a 4.5: 1 ratio of Boehmite (Disperal® 10SR) to Solvay® Solef 5130, was 21 ⁇ thick, had a Gurley air permeability of 900 sec/100 cc, and a porosity of 40%.
• the dimensional stability of the polymeric separator 501 and the ceramic-coated polymeric separators 503-505 changes greatly between 100-170°C, while the nanoporous composite separator 507 maintains a high dimensional stability well beyond 200°C.
• Figures 7-8 are graphs of the dimensional stability (measured as percent shrinkage) of various separator materials, including a nanoporous composite separator prepared according to an embodiment of the present disclosure.
• Figure 7 graphs the percent shrinkage as a function of temperature of the various separator materials measured along the length of the samples
• Figure 8 graphs the percent shrinkage measured along the width of the various material samples.
• the percent shrinkage graphed in Figures 7-8 was measured unrestrained over one hour according to the ASTM 1204 standard test method for measuring linear dimensional changes.
• 701 graphs the percent shrinkage of a polymeric separator material
• 703 graphs the percent shrinkage of a one-side ceramic-coated polymeric separator material
• 705 graphs the percent shrinkage of a two-side ceramic- coated polymeric separator material
• 707 graphs the percent shrinkage of a nanoporous composite separator prepared according to an embodiment of the present disclosure.
• the various separators corresponding to graphs 701, 703, 705, and 707 were the same separators described above in reference to graphs 501, 503, 505, and 507, respectively.
• Figure 9 is a graph of the log of the differential intrusion (measured as mL/g) as a function of pore size diameter (measured in ⁇ ) of a polymeric separator material and a nanoporous flexible composite separator prepared according to an embodiment of the present disclosure.
• 901 graphs the differential intrusion of a nanoporous composite separator 20 ⁇ thick, with a porosity of about 40%, and comprising a 4.5:1 ratio of boehmite (Disperal® 10SR) to Solvay® Solef 5130; and 903 graphs the differential intrusion of a 18 ⁇ thick Tonen® tri-layer polymeric separator material.
• the pore size distribution 901 corresponding to the nanoporous composite separator is concentrated at around 30 nm, and has a smaller mean size compared to the distribution 903 corresponding to the polymeric separator.
• such a narrow pore size distribution and small average size may minimize the risk of dendritic penetration of the separator, which may cause localized short-circuits.
• the pore size distribution of the nanoporous composite separator may be concentrated between 10-90 nm, 10-50 nm, 20-40 nm, or 25-35 nm.
• the pore size may be tailored, in some embodiments, through the formulation parameters of the nanoporous composite separator. As discussed above, decreasing the ratio of inorganic oxide to organic polymer will lower the porosity and cycling rate capability while increasing the mechanical strength of the material.
• Figure 10 is a graph of the tensile stress (measured in psi) as a function of percent extension of two separator materials, including a nanoporous composite separator prepared according to an embodiment of the present disclosure.
• 1001 graphs the tensile stress of a 18 ⁇ thick Tonen® tri- layer polymeric separator material; while 1003 graphs the tensile stress of a nanoporous composite separator 20 ⁇ thick, with a porosity of about 40%, and comprising a 4.5:1 ratio of boehmite (Disperal® 10SR) to Solvay® Solef 5130.
• the separators corresponding to graphs 1001, and 1003 were the same separators described above in reference to graphs 501, 503, 505, and 507, respectively.
• the U.S. Advanced Battery Consortium (USABC) target tensile stress is 1000 psi, and is shown by line 1005.
• the tensile stresses graphed in Figure 10 were measured along the length of the material samples using the ASTM D882-00 standard method for measuring the tensile properties of thin plastic sheeting.
• the nanoporous composite separator 1003 has more than twice the compression strength of the polymeric separator material 1001.
• Figure 11 is a graph of the particle size distribution (volume percent as a function of particle size in ⁇ ) of various boehmite and boron nitride (BN) blends, according to various embodiments of the present disclosure.
• the BN used is Saint-Gobain® Carbotherm PCTP05.
• 1101 plots the particle size distribution of a 100% boehmite material
• 1103 plots the particle size distribution of a composition including 90% boehmite and 10% BN
• 1105 plots the particle size distribution of a composition including 70% boehmite and 30%> BN, according to three embodiments of the present disclosure.
• the mode of the boehmite material distribution 1101 is at about 0.1 ⁇ .
• the boehmite material distribution 1101 includes a single mode, while the 90% boehmite composition 1103 and the 70% boehmite composition 1105 each display a bimodal distribution with modes at about 0.15-0.19 ⁇ , and at about 2-3 ⁇ .
• Figure 12 is a graph of the particle size distribution (volume percent as a function of particle size in ⁇ ) of various boehmite and alumina nitride (A1N) blends, according to various embodiments of the present disclosure.
• 1201 plots the particle size distribution of a separator material comprising 100% boehmite
• 1203 plots the particle size distribution of a separator material comprising 90% boehmite and 10% A1N
• 1205 plots the particle size distribution of a separator material comprising 70% boehmite and 30% A1N, according to three embodiments of the present disclosure.
• the mode of the boehmite material 1201 distribution is at about 0.1 ⁇ , similar to the mode of the boehmite material distribution 1101 graphed in Figure 11.
• the boehmite material distribution 1201 includes a single mode, while the 90% boehmite material 1203 and the 70% boehmite material 1205 each display a bimodal distribution.
• the modes of the 90% boehmite material distribution 1203 are at about 0.15-0.19 ⁇ , and at about 8-11 ⁇ , while the modes of the 70% boehmite material distribution 1205 are at about 0.12-0.18 ⁇ and about 7-10 ⁇ .
• the inorganic particles may be of different sizes that are grouped around two, three or more modes. It is believed that by using a multi-modal distribution of particles of different sizes, the particles may be packed in a configuration in the separator that provides for increased heat transfer and better compression strength while maintaining or even improving porosity of the separator.
• the particles grouped around different modes may be of the same or different composition. For example, boehmite particles having a modal distribution centered at about 100 nm may be combined with additional boehmite particles having a modal distribution centered at about 2 ⁇ .
• boehmite particles having a modal distribution centered at about 100 nm may be combined with A1N or BN particles having a modal distribution centered at about 2 ⁇ .
• the ratio of the particle size at a first mode to the particle size at a second mode can be, for example, greater than 1 :2, 1 :3, 1 :5 or 1 :10. In other embodiments, the ratio of the particle sizes of the two modes can be, for example, less than 1 :100, 1 :50, 1 :20, 1 : 10, 1 :5 or 1 :3.
• the ratio (wt wt) of the amounts of the two different sized particles used in a separator can be greater than 1 : 1, 2:1, 5: 1 or 10: 1.
• Figure 13 is a graph of the viscosity profiles (measured as viscosity in cPs as a function of spindle speed in rpms) for the various boehmite and BN blends, in liquid form, according to various embodiments of the present disclosure.
• 1301 plots the viscosity profile of a 100% boehmite material
• 1303 plots the viscosity profile of a composition including 90% boehmite and 10% BN
• 1305 plots the viscosity profile of a composition including 70% boehmite and 30% BN, according to three embodiments of the present disclosure.
• the BN-modified compositions 1103-1105 and 1303- 1305 may have higher thermal conductivities than a pure boehmite composition due to a dense packing of the blended filler that is enabled by the bimodal particle size distribution.
• the AlN-modified compositions 1203- 1205 may have higher thermal conductivities than a pure boehmite composition due to the bimodal particle size distribution of the AlN-modified composition.
• Figure 14 is a flow chart illustrating a method for preparing a nanoporous composite separator, according to an embodiment of the present invention.
• the method may begin by mixing 1401 inorganic particles with a solvent.
• the inorganic particles may include AI2O3, AIO(OH) or boehmite, A1N, BN, SiN, ZnO, Zr0 2 , S1O2, or combinations thereof
• the solvent may include toluene, xylene, ME , NMP, 2-butanone, or any other suitable solvent or combinations thereof.
• the method may continue with adding 1402 the polymeric binder material in order to form a dispersion.
• the polymeric binder material may include polyvinylidene difluoride (PVdF) and copolymers thereof, polyvinyl ethers, urethanes, acrylics, cellulosics, styrene -butadiene copolymers, natural rubbers, chitosan, nitrile rubbers, silicone elastomers, PEO or PEO copolymers, polyphosphazenes, or combinations thereof.
• the method may continue with coating 1403 the dispersion onto a substrate and drying/curing 1404 the dispersion, thus forming the nanoporous composite separator. Once dried, the method may continue with removing 1405 the nanoporous composite separator from the substrate.

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