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  • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
  • H01M10/0562—Solid materials
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  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/431—Inorganic material
  • H01M50/434—Ceramics
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  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
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  • 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
  • H01M50/497—Ionic conductivity
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  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
  • H01M8/1018—Polymeric electrolyte materials
  • H01M8/1041—Polymer electrolyte composites, mixtures or blends
  • H01M8/1046—Mixtures of at least one polymer and at least one additive
  • H01M8/1048—Ion-conducting additives, e.g. ion-conducting particles, heteropolyacids, metal phosphate or polybenzimidazole with phosphoric acid
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
  • B29C64/10—Processes of additive manufacturing
  • B29C64/141—Processes of additive manufacturing using only solid materials
  • B29C64/153—Processes of additive manufacturing using only solid materials using layers of powder being selectively joined, e.g. by selective laser sintering or melting
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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  • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
  • B29C64/10—Processes of additive manufacturing
  • B29C64/165—Processes of additive manufacturing using a combination of solid and fluid materials, e.g. a powder selectively bound by a liquid binder, catalyst, inhibitor or energy absorber
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  • H01M2300/00—Electrolytes
  • H01M2300/0088—Composites
  • H01M2300/0091—Composites in the form of mixtures
• • 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
  • 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
  • Y02E60/13—Energy storage using capacitors
• • 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
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells

Definitions

• the present disclosure relates to ion-conducting electrolytes and assemblies incorporating ion-conducting electrolytes.
• Ion-conducting electrolytes have been proposed for use in a wide variety of technological applications including lithium ion batteries, sodium sulfur batteries, solid oxide fuel cells, oxygen separators, electrolyzers, sensors, chemical reactors, etc.
• Ion-conducting composite electrolytes comprise path-engineered ion-conducting ceramic electrolyte particles positioned in a solid polymeric matrix and can be configured to confer flexibility and strain tolerance that exceeds that which is possible with a conventional ceramic electrolytes.
• an ion-conducting composite electrolyte comprising path- engineered ion-conducting ceramic electrolyte particles and a solid polymeric matrix.
• the path-engineered particles are characterized by an anisotropic crystalline micro structure where the ionic conductivity of the crystalline structure in a preferred conductivity direction H associated with one of the crystal planes of the path-engineered particle is larger than the ionic conductivity of the crystalline structure in a reduced conductivity direction L associated with another of the crystal planes of the path-engineered particle.
• the path-engineered particles are sized and positioned in the polymeric matrix such that a majority of the path-engineered particles breach both of the opposite major faces of the matrix body and are oriented in the polymeric matrix such that the preferred conductivity direction H is more closely aligned with a minimum path length spanning a thickness of the matrix body than is the reduced conductivity direction L.
• an ion-conducting composite electrolyte where the path-engineered particles are characterized by an isotropic crystalline structure.
• methods of preparing ion-conducting composite electrolytes involve preparing path-engineered particles for inclusion in a polymeric matrix by subjecting ceramic precursor crystals to thermally- induced microcracking.
• the micro-cracked precursor crystals can be separated into individual path-engineered ion-conducting ceramic electrolyte particles.
• FIG. 1 A is a schematic illustration of a portion of one type of ion-conducting composite electrolyte according to the present disclosure
• Figs. IB and 1C present schematic illustrations of some of the many ways in which path engineered particles can be oriented in an ion-conducting composite electrolyte according to the present disclosure
• Fig. 2 is a detailed schematic illustration of a path-engineered particle for use in ion- conducting composite electrolytes according to the present disclosure
• Fig. 3 illustrates particles comprising impeded linear ion-conducting paths
• Fig. 4 illustrates an electrochemical device comprising a cathode and an anode separated by a composite electrolyte
• Fig. 5 is a plot of area specific resistance versus membrane thickness.
• a portion of an ion-conducting composite electrolyte 10 is illustrated schematically and comprises path-engineered ion-conducting ceramic electrolyte particles 20, a solid polymeric matrix 30, and, optionally, a fiber stiffener component 40 distributed throughout the polymeric matrix 30.
• the respective shapes of the path-engineered particles 20 may vary significantly from particle to particle and is not illustrated with particular precision in Fig. 1A. Rather, the path-engineered particles 20 of Fig. 1 A are merely presented to show their presence in the polymeric matrix 30 and to show that their size and shape will typically vary across the composite electrolyte 30. Similarly, the size and shape of the path-engineered particles illustrated in Figs. IB and 1 C, described in further detail below, have been intentionally simplified for illustrative purposes.
• the polymeric matrix defines a pair of opposite major faces 32, 34 defining a matrix body there between.
• the path-engineered particles 20 are sized and positioned in the polymeric matrix 30 such that a majority of the path-engineered particles 20 breach, i.e., are flush with or extend beyond, both of the opposite major faces 32, 34 of the matrix body. It is contemplated that the path-engineered particles may be advantageously characterized by an anisotropic crystalline structure, although isotropic crystalline structures are also contemplated.
• the path-engineered particles 20 can be selected such that they are characterized by an anisotropic crystalline structure.
• the particles can be selected such that the ionic conductivity of the crystalline structure in a preferred conductivity direction H associated with one of the crystal planes of the path-engineered particle 20 is larger than the ionic conductivity of the crystalline structure in a reduced conductivity direction L associated with a different crystal plane of the path-engineered particle 20.
• substantially all, or at least a majority of, the path engineered particles 20 can be oriented in the polymeric matrix 30 such that the preferred conductivity direction H is more closely aligned with a minimum path length x spanning a thickness of the matrix body, i.e., more closely aligned than the reduced conductivity direction L.
• This alignment is illustrated schematically in Figs. IB and 1 C and can lead to a composite electrolyte with enhanced ionic conductivity, typically on the order of approximately 10 "4 S/cm or greater.
• the ionic conductivity of the crystalline structure in the preferred conductivity direction H is approximately one order of magnitude larger than the ionic conductivity of the crystalline structure in the reduced conductivity direction L.
• the path engineered particles 20 can be sized such that a size dimension of the path-engineered particle 20 in the preferred conductivity direction H is smaller than a size dimension of the path-engineered particle 20 in the reduced conductivity direction L.
• the difference in the respective size dimensions of the path-engineered particle 20 can be used to encourage self- alignment of the path engineered particles in the aforementioned orientation because, in many of the contemplated fabrication processes described herein a particle will naturally tend to settle in an orientation that is strongly influenced by the relative size dimensions of the particle in different directions.
• path-engineered particles characterized by an isotropic crystalline structure the aforementioned selective orientation would not typically be necessary.
• suitable isotropic crystalline structures include, but are not limited to, lithium ion conductors with the cubic garnet structure such as aluminum-stabilized or with the perovskite structure such as Li 3x Lao.67- x Ti0 3 , and typically lead to a composite electrolyte with enhanced ionic conductivity typically on the order of approximately lxlO 4 S/cm or greater.
• Particular embodiments of the present disclosure relate to the advantageous use of path-engineered particles 20 that are characterized by hexagonal crystalline structures. More specifically, referring to Fig.
• the present inventors have recognized that the ionic conductivity of the composite electrolyte 10 can be enhanced by ensuring that a majority, or substantially all, of the path engineered particles 20 are oriented in the polymeric matrix 30 such that the minimum path length x spanning a thickness of the matrix body is more closely aligned with the relatively high conductivity crystallographic direction H than with the relatively low conductivity crystallographic direction L.
• the path-engineered particles 20 will comprise an ion-conducting ceramic, such as, for example, a lithium ion-conducting ceramic like LATP or a derivative thereof. Such materials may possess internal inclusions that typically comprise aluminum phosphate, titanium dioxide, aluminum oxide, or combinations thereof. Additional contemplated embodiments will include path engineered particles comprising an ion-conducting ceramic selected from lithium metal phosphates, sodium zirconia phosphates, sodium beta aluminate, fluorites, and ceramic oxides with garnet- type crystalline structures.
• composition or choice of material is selected partly based upon the ability to grow crystals by a convenient technique like the Czochralski process.
• examples of such materials are LiNb0 3 , YV0 4 , A1 2 0 3 , and Ce 2 0 3 -doped Y 3 A1 5 0 12 (YAG:Ce). It is noted that the compositional profile of contemplated composite electrolytes can be controlled by doping to attain desired properties.
• path-engineered particles 20 may comprise internal inclusions in the form of primary inclusions 22 and secondary phase inclusions 24, grain boundaries 26, pores 28, or combinations thereof.
• the path-engineered particles 20 can be oriented in the polymeric matrix 30 to comprise a breaching cross section, examples of which are illustrated schematically in Figs. 1 and 2.
• the breaching cross section defines a cross-body, linear ion- conducting path (+) that is unimpeded by the internal inclusions 22, 24, the grain boundaries 26, and the pores 28 of the particle 20.
• linear ion-conducting path composite electrolytes eliminate, or substantially reduce, the impact of grain boundaries on ionic transport.
• a face -breaching, path-engineered particle 20 may comprise a single crystal majority, by volume, that is free of grain boundaries, although a remaining volume of the particle itself comprises a minority of grain boundaries 26, internal inclusions 22, 24 and pores 28.
• the remaining volume comprises primary phase inclusions of distinct crystal orientation, secondary phase inclusions, pores, or combinations thereof and occupies between approximately 0.1% and approximately 20%, by volume, of the face-breaching, path-engineered particle 20.
• the aforementioned unimpeded linear ion-conducting paths (+) may be more readily achieved by ensuring that the grain boundaries 26 of the path engineered particles 20 span less than a majority of the breaching cross section of the face- breaching, path-engineered particles in a direction substantially parallel to the major faces of the matrix body.
• An example of a grain boundary satisfying this condition is illustrated in Fig. 2, while the right-hand side particle 20' illustrated in Fig. 3 includes a grain boundary 26' that does not satisfy this condition.
• At least a majority of the path-engineered particles 20 are oriented in the polymeric matrix 30 such that respective breaching cross sections of the particles 20 define a cross-body, linear ion-conducting path that is unimpeded by the secondary phase inclusions 24, grain boundaries 26, and closed pores 28 of the face- breaching, path-engineered particle 20.
• volumetric composition of the composite electrolyte 10 it is contemplated that particular embodiments will comprise (i) between approximately 10% and approximately 95% of the face -breaching, path-engineered particles 20 (ii) between approximately 5% and approximately 90% of the polymeric matrix 30, and (iii) between approximately 0.1% and approximately 20% of impeded -path ion-conducting ceramic electrolyte particles 20', by volume.
• impeded-path ion-conducting particles 20' are particles that do not comprise the above-described unimpeded cross-body, linear ion-conducting path, either because they are dominated by inclusions 24', grain boundaries 26', and/or pores 28', are primarily polycrystalline, or do not breach both of the opposite major faces of the matrix body. More preferably, it is contemplated that, in some embodiments, the composite electrolyte 10 comprises at least approximately 20% of the face-breaching, path-engineered particles 20, by volume.
• the path-engineered particles will define an average size (dso) of between approximately ⁇ ⁇ and approximately 1mm with a size dispersion ((dcio-dio)/d 5 o) that is less than approximately 1.0. It is also contemplated that the composite electrolyte 10 will often advantageously define a thickness of between approximately ⁇ and approximately 50 ⁇ . It is contemplated that the thickness of a composite electrolyte according to the present disclosure for any given application is a function of its conductivity, mechanical strength, and methods of preparation. It may range from a few microns up to about 1 mm.
• Crystalline structures used for the composite electrolytes of the present disclosure need not be regular in shape nor compositionally uniform or free of inclusions. Crystals of the type required for the composite electrolyte can be prepared efficiently by techniques such as prolonged sintering to allow grain growth or by slow cooling from the melt. The product of either process can then be ground and selectively sized by sieving, air-classification, etc.
• Methods of preparing ion-conducting composite electrolytes 10 involve preparing the path-engineered particles 20 for inclusion in the polymeric matrix 30 by subjecting ceramic precursor crystals to thermally- induced microcracking. The microcracked precursor crystals can subsequently be separated into individual path-engineered ion-conducting ceramic electrolyte particles 20.
• the composite electrolyte 10 including the path-engineered particles 20 and the polymeric matrix 30 may be assembled by a variety of suitable techniques including, without limitation, injection molding, compression molding, roll molding, film casting, spin coating alone on in conjunction post forming techniques like plasma etching, mechanical abrasion, laser ablation to expose the particles and enable ionic conduction.
• contemplated composite electrolyte membranes can be formed by polymer processing techniques without sintering.
• LATP lithium ion- conducting LATP
• the reactants for the two batches listed in the table below were dry blended in a total amount of about 2 kg each, transferred into platinum crucibles, reacted for 12 hours at 190°C, reacted 12 hours and 800°C to partially form the LATP crystalline structure, and then vibratory milled.
• the milled powder was formed into ⁇ 25 mm diameter pills by uniaxially pressing.
• the pills were sintered at temperatures and times listed in Table #2 to induce grain growth.
• the grains in the pills were further processed into a powder that is made of particles that are themselves predominantly single crystals. Although it is possible to imagine grinding, jet milling or another high energy technique to separate the particles and reduce their sizes, this was not necessary with LATP.
• the crystalline structure of LATP is not cubic, and is subject to microcracking as a result of its large thermal expansion anisotropy.
• the critical grain size for microcracking is estimated to be about 0.5 ⁇ . This critical grain size is almost two orders of magnitude smaller than those obtained by extended sintering.
• the pills were extensively microcracked and with only the mildest of forces crumbled into individual crystals.
• LATP crystals were grown starting with the reactants listed in the following table:
• spin-coating and chemical etching were applied to produce a composite electrolyte membrane by starting with 4g of a 5: 1 PDMS solution, 1 g of 625 EQU ground and sieved to give particles with sizes ranging from 250-355 ⁇ , spin coating at 500 rpm for 10 seconds, and lastly etching both surfaces in a batch of NMB/TBAF for 15 minutes to remove residual silicone.
• the thickness of the silicone in the as- finished membrane, i.e. between the LATP particles was about 140 ⁇ , which is significantly thinner than the lithium ion-conducting crystal particles.
• the DC resistance of the membrane was taken as approximately 175 ⁇ . With geometric factors of the electrolyte membrane taken into account, this translates to a lithium ion conductivity of 2.7x 10 "4 S/cm, more than four-fold greater than the highest value reported for a
• a residual overcoat of polymer on the surface of the conducting particles will be an inherent result of the process. This residual is likely to block movement of the mobile ion that the electrolyte carries and degrade conductivity.
• the residual can be removed by a variety of techniques, including, but not limited to, chemical etching, polishing, mechanical abrasion, refractive ion etching, ozone plasma treatment, and laser ablation.
• composite electrolytes 10 provide several parameters that may be adjusted and tailored to improve the performance of electrochemical devices 50 incorporating the electrolyte 10.
• Contemplated parameters include, but are not limited to average particle size, the dispersion in their size, the conductivity of single crystal components of the particles, their orientation, the thickness of the polymer membrane, and the degree of exposure of the particles beyond the major faces of the polymeric matrix in which they are positioned.
• These and other parameters may be selected to improve electrochemical performance attributes such as power density or response speed and/or mechanical performance attributes that facilitate handling, in-service durability, or device lifetime.
• the primary benefits created by a composite electrolyte are a higher ionic conductivity and equivalent or lower area specific resistance (ASR) than what can be achieved in an optimized polycrystalline membrane that conducts the same ionic species.
• ASR area specific resistance
• the ionic conductivity within a crystal of doped polycrystalline lithium titanium phosphate and lithium germanium phosphate ceramics is a factor of 50 to 100 times greater than realized in the polycrystalline state as a whole.
• the single crystal conductivity of these doped titanium and germanium phosphates approaches or exceeds 10 "3 S/cm.
• ASR is a key figure of merit used to judge the power generating capability of an electrochemical device or its components, i.e., its electrolyte membrane.
• the ASR of the electrolyte is the dominant contributor to the total ASR of a device if its conductivity is low and the membrane thickness is large.
• the ASR of a composite electrolyte C based upon single crystals of the composition
• Li 1.3 Alo. 3 Ti 1 .7(P0 3 )3 is compared to a sintered polycrystalline electrolyte P of the same composition as a function of membrane thickness x.
• the figure illustrates two solids loadings, 25% and 50%, of single crystals in the composite electrolyte. It also assumes that the single crystals are flush with the polymer surface, that is to say they do not bulge from the surface of the electrolyte. It is also assumed that the surfaces of the single crystals are fully exposed, i.e. no polymer overcoat, and that the crystals have a uniform cross-section and are oriented normal to the plane of the membrane.
• the composite electrolyte even with only a 25% volume loading in the membrane provide an ASR that is a factor of four lower than the polycrystalline electrolyte of the same thickness.
• the ASR of a polycrystalline electrolyte that is thin may be acceptable from and electrochemical standpoint for application in a device. However, its thin nature might make manufacturing difficult or compromise the durability of the device.
• the composite electrolyte because of its inherently higher conductivity can be made with an equivalent ASR but with a much greater thickness to overcome such issues.
• Another possibility is to impart a maximum level of flexibility to the membrane. This can be accomplished by minimizing the amount of single crystal ion conductor within the composite.
• the ASR calculation represented in Fig. 5 provides the basis for both of these possibilities.
• composite electrolytes described herein can be the source of numerous advantages with respect to the start of the art. For example, contemplated composite electrolytes are likely to exhibit ionic conductivity that is greater than that which would be available from comparable polycrystalline ceramic electrolytes. Further, contemplated composite electrolyte structures are likely to be more easily handled during processing and device assembly steps and are less likely to be subject to abrupt or unpredictable mechanical failure. The ionic conductivity of contemplated composite electrolyte structures can be traded for increased mechanical integrity by thickening the electrolyte while still maintaining sufficiently high electrochemical performance.
• Fig. 4 illustrates an electrochemical device 50 comprising a cathode 60 and an anode 70 separated by a composite electrolyte 10.

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• 2012
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