Coating material for metal batteries

Abstract

An electrochemical cell for converting chemical energy into electrical energy, the electrochemical cell formed as a pouch cell, a cylindrical cell, or a prismatic cell. The electrochemical cell includes a coating material located on one or more surfaces within the pouch cell, cylindrical cell, or prismatic cell that is in contact with an electrolyte. The coating material contains a metal oxide and / or metal hydroxide and a metal phosphate, such that the coating material is configured to reduce the amount of gas inside the cell.

Description

Coating Material for Metal BatteriesFIELD

[0001] This invention generally relates to electrochemical cells that convert chemical energy into electrical energy and to battery packs or modules that contain two or more of these electrochemical cells with each electrochemical cell being formed into a pouch cell, a cylindrical cell, or a prismatic cell. The electrochemical cells and / or battery packs or modules include a coating material located on one or more surfaces within the pouch cell, cylindrical cell, or prismatic cell that is in contact with an electrolyte, such that the coating material is configured to reduce the gas generation in the electrolyte.BACKGROUND

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] Metal-ion batteries and metal batteries include the use of soluble metal ions as the transport ions in the batteries in order to enable the occurrence of electrochemical reactions for energy storage and energy release. The main difference between metal-ion batteries and metal batteries is associated with the selection of the anode active material. When the anode active material is graphite, carbon, silicon, antimony, or a similar material, which is not the same as the metal that provides the metal-ions for energy storage / release, then the battery represents a metal-ion battery. Several examples of metal-ion batteries include lithium-ion, sodium-ion, potassium- ion, magnesium-ion, calcium-ion, and aluminum-ion batteries. In comparison, metal batteries utilize the corresponding metal that forms the metal-ions as the active anode material. Several examples of metal batteries include lithium, sodium, potassium, magnesium, calcium, and aluminum metal batteries.

[0004] In metal-ion and metal batteries, the metal-ions are typically inserted into the anode side and extracted from the cathode side of the battery cell during charging. During discharging, the metal-ions are released from the anode side and migrate back to the cathode side of the cell. Due to the high voltage stability of organic solvents, these batteries in general include organic electrolytes in order to increase their energydensities. Among these batteries, a lithium-ion battery has obtained broad commercial success.

[0005] Lithium-ion batteries are widely used in a variety of applications, such as portable electronics, electric vehicles, and grid storage, due to their long cycle life and high energy or power densities. The use of lithium-ion batteries in electric vehicles (EVs) provides the potential to reduce global greenhouse gas emissions and air pollution. State-of-the-art battery chemistries are generally based on Li-ion technology, for example, with cathodes comprising LiNiMnCoCh (NMC), LiNiCoAIO2 (NCA), LiMn2C>4 (LMO), LiFePC>4 (LFP) or LiCoCk (LCO); anodes formed of graphite or carbonaceous materials; electrolyte mixtures comprised of a combination of ethylene carbonate (EC), diethylene carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC); and a Li-salt, such as LiPFe; and an inorganic or polymeric separator located between the cathode and anode that is permeable to Li+ion migration. The battery cells are generally encased within sealed laminated foils (i.e., pouch cells) or encapsulated in metallic casings (i.e., cylindrical cells, prismatic cells).

[0006] The use of a polar organic electrolyte makes the performance of metal and metal-ion batteries highly susceptible to the presence of moisture contamination. The presence of gaseous species may arise from the decomposition of residual moisture present in the electrolyte, anode, and cathode as well as through the electrochemical decomposition of the carbonate electrolyte. For a lithium-ion battery, the situation is considered to be even worse since the LiPFe salt is highly reactive with water. During the battery fabrication process, a small amount of moisture or water may remain in the battery, even after extensively drying. When the LiPFe salt reacts with water, it generates HF and other decomposed species, with the potential to release gaseous species inside the battery.

[0007] The seriousness of the evolution of gases within lithium-ion batteries is quickly magnified when the batteries are required to function at high voltages and / or high temperatures because the electrochemical reactions that lead to the generation of the gases and other side products accelerate the degradation and aging of the cells. In addition, when gaseous species are allowed to form and accumulate inside the cells, a safety concern arises due to the swelling and outburst of the cells from the pressurized gaseous species.

[0008] Thermal runaway is a self-accelerating exothermic reaction that occurs inside a battery cell, which may be started by a hot spot (e.g., short circuit) occurring inside the cell or by a heat source arising from outside the cell (e.g., electrical failure). The occurrence of thermal runaway results in a violent reaction inside the cell that produces significant amounts of hot, toxic, and flammable gases that may be released from the cell, as well as the possible ejection of hot particles from the cell. The released gas and particles may cause serious safety and health risks, like fire, explosion, and the formation of a toxic atmosphere. The main gas compounds arising from a thermal runaway reaction include carbon dioxide (CO2), carbon monoxide (CO), hydrogen (H2) and various hydrocarbon gases. Except for CO2and H2O all of the gases that arise from a thermal runaway are flammable and / or explosive by nature. The inhibiting effect of inert gases or vapors that are present, such as CO2and water vapor, does not prevent the ignition of the flammable gas mixture during a thermal runaway.

[0009] In a lithium-ion battery, the porous polymer separator may be coated with Boehmite or alumina in order to enhance safety during the occurrence of a thermal runaway event. Compared to alumina (AI2O3), the use of Boehmite (AIOOH) is preferable because it represents a softer and less expensive material. However, the use of Boehmite in a battery may generate a significantly greater amount of gaseous species as compared to the use of AI2Os in the battery due to the relatively high moisture content and / or the presence of -OH functionality associated with Boehmite.

[0010] The presence of gaseous species within a battery cell may be mitigated by releasing the gaseous species immediately after their formation in a pouch cell. However, the release of such gaseous species after formation in a pouch cell may not be an option for large scale production of such batteries since it would delay production rate and increase production cost. For cylindrical and prismatic cells, it would be difficult to release the gas from the cell after its formation. The avoidance of the need to implement a gas releasing step during the production of a battery cell would be preferable. Therefore, there is a need to reduce the amount of gas generation arising from the use of Boehmite and other metal oxides and / or metal hydroxides in a battery cell.SUMMARY

[0011] This disclosure relates generally to an electrochemical cell for converting chemical energy into electrical energy and to a battery pack that incorporates two or more of these electrochemical cells. The electrochemical cell may be formed as a pouch cell, a cylindrical cell, or a prismatic cell. The electrochemical cell includes a coating material located on one or more surfaces within the pouch cell, cylindrical cell, or prismatic cell that is in contact with an electrolyte. This coating material comprises a metal oxide and / or metal hydroxide and a metal phosphate, such that the coating material is configured to reduce the amount of gas present inside the electrochemical cell. When desirable, the metal oxide or metal hydroxide may be Boehmite and the metal phosphate may be aluminum phosphate.

[0012] According to one aspect of the present disclosure, the coating material may be located on the surface of a separator or a current collector. The coating material includes a homogeneous mixture of the metal oxide and / or metal hydroxide and the metal phosphate or is present as a composite structure that comprises the metal oxide and / or metal hydroxide in a first layer and the metal phosphate in a second layer. The first layer generally comprises a first side and a second side, wherein the first side is in direct contact with the one or more surfaces within the pouch cell, cylindrical cell, or prismatic cell, while the second layer is in direct contact with the second side of the first layer. When desirable, the homogeneous mixture may be located within a single coating layer or within a plurality of coating layers.

[0013] According to another aspect of the present disclosure, the electrochemical cell may be a metal battery or a metal-ion battery. This metal battery or metal-ion battery generally incorporates a metal that comprises one or more of lithium, sodium potassium, magnesium, calcium, or aluminum. When desirable, the electrochemical cell may be a lithium battery or a lithium-ion battery.

[0014] In the coating material, the metal oxide or metal hydroxide may comprise aluminum oxide, aluminum oxyhydroxide with a chemical formula of AIOOH, a zeolite, a titanate, a zirconate, an aluminate, or a mixture or derivative thereof. The zeolite may comprise a structure described as FAU, LTA, CHA, BEA or ZSM-5. The metal phosphate may comprise amorphous aluminum phosphate, crystalline aluminum phosphate, an aluminum phosphate molecular sieve, or a mixture thereof. This metalphosphate generally includes a metal selected from the group consisting of Li, Mg, Ca, Sr, Ba, Ti, Zr, and a mixture thereof.

[0015] The metal oxide or metal hydroxide and the metal phosphate may be included in the coating material in a mass ratio of 99:1 to 1 :99. Alternatively, the metal oxide or metal hydroxide and the metal phosphate may be included in the coating material in a mass ratio of 90: 10 to 10:90. Alternatively, the coating material comprises the metal oxide or metal hydroxide and the metal phosphate in a mass ratio of 75:25 to 25:75.

[0016] The metal oxide or metal hydroxide may be included in the coating material in a mass percentage of 99% to 25% and the metal phosphate in a mass percentage of 1 % to 75%, relative to the overall mass of the coating material. Alternatively, the metal oxide or metal hydroxide is present in a mass percentage of 98% to 50% and the metal phosphate in a mass percentage of 2% to 50%, relative to the overall mass of the coating material. Alternatively, the coating material comprises the metal oxide or metal hydroxide in a mass percentage of 95% to 75% and the metal phosphate in a mass percentage of 5% to 25%, relative to the overall mass of the coating material.

[0017] According to another aspect of the present disclosure the coating material further comprises a polymer binder having a mass percentage of 1 % to 20%, relative to the overall mass of the coating material.

[0018] According to yet another aspect of the present disclosure a battery pack or module is provided that comprises two or more electrochemical cells as described above and further defined herein connected in series or connected parallel to one another.

[0019] According to another aspect of the present disclosure, a process for preparing an electrochemical cell formed as a pouch cell, a cylindrical cell, or a prismatic cell as described above and further defined herein is provided. This process generally comprises the steps of: 1) providing the components for the electrochemical cell including an anode, a cathode, a separator, an electrolyte, and an enclosure in the form of a pouch, a cylinder, or a prismatic package; 2) providing a coating material comprising a metal oxide and / or metal hydroxide and a metal phosphate, such that the coating material is configured to reduce the amount of gas inside the cell; 3) applying the coating material to one or more surfaces located within the electrochemical cell that is in contact with the electrolyte; and 4) assembling thecomponents of the electrochemical cell to form a pouch cell, a cylindrical cell, or a prismatic cell.

[0020] Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.DESCRIPTION OF THE DRAWINGS

[0021] In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings. The elements in each of the drawings may not necessarily be drawn to scale, but rather emphasis is placed upon illustrating the principles of the invention.

[0022] Figure 1A is a schematic representation of an electrochemical cell in the form of a pouch cell.

[0023] Figure 1 B is a schematic representation of an electrochemical cell in the form of a cylindrical cell.

[0024] Figure 1C is a schematic representation of an electrochemical cell in the form of a prismatic cell.

[0025] Figure 2 is a schematic representation of an electric vehicle with a battery pack or module that contains multiple electrochemical cells.

[0026] Figure 3A is a cross-section of a coating material applied to the surface of a component in an electrochemical cell according to the teachings of the present disclosure.

[0027] Figure 3B is a cross-section of another coating material applied to the surface of a component in an electrochemical cell according to the teachings of the present disclosure.

[0028] Figure 3C is a cross-section of yet another coating material applied to the surface of a component in an electrochemical cell according to the teachings of the present disclosure.

[0029] Figure 4 is a graphical representation of the gas generation attributed to the addition of water and Boehmite to an electrolyte.

[0030] Figure 5A is a comparison of x-ray diffraction (XRD) patterns measured for Boehmite (i.e. , y-AIO(OH)) before aging and after aging in an electrolyte.

[0031] Figure 5B is a graphical comparison of the mass loss (%) plotted as a function of temperature measured by thermogravimetric analysis (TGA) for Boehmite (i.e., y-AIO(OH)) before aging and after aging in an electrolyte.

[0032] Figure 6A is a comparison of x-ray diffraction (XRD) patterns measured for aluminum phosphate (i.e., AIPO4) before aging and after aging in an electrolyte.

[0033] Figure 6B is a graphical comparison of the mass loss (%) plotted as a function of temperature measured by thermogravimetric analysis (TGA) for aluminum phosphate (i.e., AIPO4) before aging and after aging in an electrolyte.

[0034] Figure 7 is a flowchart that describes the steps associated with a process for forming an electrochemical cell according to the teachings of the present disclosure.

[0035] Figure 8 is a flowchart that describes the steps associated with a process for forming a battery pack or module according to the teachings of the present disclosure.

[0036] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.DETAILED DESCRIPTION

[0037] The following description is merely exemplary in nature and is in no way intended to limit the present disclosure or its application or uses. For example, the electrochemical cells formed and used according to the teachings contained herein are described throughout the present disclosure in relation to a battery pack or module used in an electric vehicle in order to more fully illustrate the structural elements and the use thereof. The incorporation and use of such electrochemical cells in other applications, including without limitation, any application in which the generation of gases or vapors may be a concern, is contemplated to be within the scope of the present disclosure. It should be understood that throughout the description and drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0038] For the purpose of this disclosure, the terms "about" and "substantially" are used herein with respect to measurable values and ranges due to expected variations known to those skilled in the art (e.g., limitations and variability in measurements).

[0039] For the purpose of this disclosure, the terms "at least one" and "one or more of” an element are used interchangeably and may have the same meaning. These terms, which refer to the inclusion of a single element or a plurality of the elements, may also be represented by the suffix "(s)" at the end of the element. For example, "at least one metal oxide", "one or more metal oxides", and "metal oxide(s)" may be used interchangeably and are intended to have the same meaning.

[0040] As used herein an “electrochemical cell” is considered to be similar to or the same as a “battery cell.” For the purpose of this disclosure, a “battery cell” refers to the basic electrochemical unit of a battery that contains an anode and a cathode, as well as any components used to convert stored chemical energy to electricity, such as, for example, electrodes, a separator, and an electrolyte. In comparison, a “battery” refers to at least one battery cell placed within a housing (e.g., pouch, cylinder, prismatic enclosure) with electrical connections and possibly electronics for control and protection. A “battery pack” or “battery module” refers to a collection of more than one battery, in other words a plurality of batteries, connected either in series or parallel to one another in order to increase the voltage or capacity arising therefrom with the collection of batteries being secured within a housing.

[0041] The present disclosure generally describes electrochemical cells that convert chemical energy into electrical energy and battery packs or modules comprising two or more electrochemical cells, wherein each electrochemical cell is formed as a pouch cell, a cylindrical cell, or a prismatic cell. The electrochemical cells and hence the battery packs or modules incorporating such electrochemical cells include a coating material located on one or more surfaces within the pouch cell, cylindrical cell, or prismatic cell that is in contact with an electrolyte. The coating material generally comprises a metal oxide and / or metal hydroxide and a metal phosphate, such that the coating material is configured to reduce gas generation inside the cell.

[0042] According to one aspect of the present disclosure, the electrochemical cell may be a metal battery or a metal-ion battery. The metal battery or metal-ion battery generally incorporates one type of soluble metal ions as the transport ions in order toenable the occurrence of electrochemical reactions for energy storage and energy release. The metal comprises one or more of lithium, sodium, potassium, magnesium, calcium, or aluminum; alternatively, the metal is lithium. When lithium is the selected metal, the electrochemical cell may be a lithium battery or a lithium-ion battery.

[0043] Referring now to Figure 1 , various types of battery cells are shown in the form of a pouch cell 1A, a cylindrical cell 1 B, and a prismatic cell 1 C. In each of these batteries, the battery cells 1A, 1 B, 1 C, which includes the anode 3 (negative), separator 5, and cathode 7 (positive) are shown encapsulated within a case or enclosure 10. Both the anode 3 and cathode 7 include a layer of an active material to act as the corresponding electrode (+ / -) and a layer of a metal (e.g., Al, Cu, Ni, Ti, etc.) to act as a current collector. An electrolyte (not shown) is typically present and in contact with both the anode and cathode with the migration of ions in the electrolyte through the separator located there between.

[0044] The electrochemical cells of the present disclosure may be packaged as a pouch cell 1A, a cylindrical cell 1 B, or a prismatic cell 1C. Alternatively, the electrochemical cell is packaged as a pouch cell 1A or a cylindrical cell 1 B; alternatively, the electrochemical cell is packaged as a pouch cell 1 A. Many consumer electronic products and electric vehicles use pouch lithium-ion cells in order to provide efficient use of space, as compared to cylindrical and prismatic cell designs. However, in a pouch cell the substitution of a polymeric package for the metal container used with cylindrical and prismatic cells comes at a cost because the pouch cell may swell due to gas generation, thereby, resulting in a leakage from the sealing area.

[0045] When desirable cylindrical cells may also be used for many applications including electric vehicles due their ease of manufacturing, mechanical stability, and resistance too much higher internal pressures than pouch cells without deforming. These cells, however, will still deform and outburst if the internal gas pressure is too high. Most cylindrical cells have a safety feature, with which the cells will rupture under high pressure and the cells will leak and become unusable. Therefore, a reduction in gas generation is also desirable for cylindrical cells.

[0046] Prismatic cells may also be used in a variety of industrial applications and with certain powertrains in hybrid and electric vehicles. A prismatic cell uses a cubicshaped metal can that provides higher packaging flexibility and space efficiency thancylindrical cells. These cells have some tolerance for high internal pressure, typically at a level between that of a pouch cell and a cylindrical cell.

[0047] Referring now to Figure 2, a battery pack or module 25 is shown within an electric vehicle 30. Within this battery pack or module 25 a plurality of electrochemical cells in the form of batteries (i.e., 2 rows x 5 columns of batteries 1A-C) are present. The batteries 1A-C may be held in place through the use of a structural material 35, such as a foam. When desirable, the battery pack or module 25 may further comprise a dielectric oil (not shown) flowing through the pack or module 25 in order to provide additional cooling capability to the battery pack or module 25 as a means for thermal management.

[0048] According to one aspect of the present disclosure, the presence of a metal phosphate, such as for example, aluminum phosphate, in a coating can suppress the generation of gaseous species from a moisture contaminated electrolyte. In addition, the presence of this metal phosphate may also be capable of suppressing the generation of gaseous species that arise from other coating materials, such as Boehmite, that are used in the electrochemical cell. The presence of a Boehmite coating by itself in an electrochemical cell generates a significant amount of gaseous species.

[0049] In general, the coating material of the present disclosure combines at least one type of a metal phosphate with one or more types of a metal oxide and / or a metal hydroxide. The metal oxides and / or metal hydroxides in the coating material offers a variety of benefits including, without limitation, cost and hardness. On the other hand, although the metal phosphates in the coating material may be more costly than the metal oxides and / or metal hydroxides, the metal phosphates provide the benefit of suppressing the gas generation arising from the metal oxides and / or metal hydroxides. The combination of the metal phosphates and the metal oxides / hydroxides provides the coating material of the present disclosure with the benefits associated with both the metal phosphates and metal oxides / hydroxides.

[0050] In other words, the effectiveness of the metal phosphate in suppressing gas generation that arises from other coating components present in the electrochemical cell allows the coating material of the present disclosure to provide a variety of beneficial functions while minimizing the presence of gas generation. For example, when the coating material of the present disclosure comprises Boehmite and a metalphosphate, the coating material provides the benefits of Boehmite in the form of low cost and softness, without the serious occurrence of excessive gas generation. In another example, when the coating material of the present disclosure is composed of zeolites and a metal phosphate, the coating material provides the benefits of zeolites in removing electrolyte impurities without the occurrence of excessive gas generation. Since zeolites may bring adhered moisture into the battery cell and generate a significant amount of gaseous species, the usage of zeolites as a separator coating material generally has not been commercially viable. However, with the incorporation of a metal phosphate, the coating material of the present disclosure may also include zeolites therein without the occurrence of an issue with gas generation.

[0051] Referring again to Figures 1A, 1 B, and 1 C, the coating material 17 may be applied to one or more surfaces located within the pouch cell 1 A, cylindrical cell 1 B, or prismatic cell 1 C. Examples of such surfaces include, without limitation, the surface of the electrode layer or the current collector layer in the anode 3 and / or cathode 7, as well as the surface of the separator s. The coating material 17 may be applied to one side of the separator 5 or both sides thereof without departing from the scope of the present disclosure. Alternatively, the coating material 17 is applied as an edge coating to the current collector layer in the anode 3 and / or cathode 7. Alternatively, the coating material 17 is applied to the surface of the separator s. The coating material 17 may be applied to the entire surface or at least to a portion of the surface.

[0052] Thus, according to one aspect of the present disclosure, a coated separator for use in an electrochemical cell formed as a pouch cell, a cylindrical cell, or a prismatic cell is provided. This coated separator generally includes at least one layer of a porous polymer and at least one layer of a coating material that comprises a metal oxide and / or metal hydroxide and a metal phosphate, such that the coating material is configured to reduce the amount of gas generated when the separator is used inside the electrochemical cell with an organic electrolyte.

[0053] Referring now to Figures 3A and 3B, the coating material 17 may be applied to the one or more surfaces in the electrochemical cell 20 (e.g., separator, etc.) as a homogeneous mixture of one or more metal oxides and / or metal hydroxides 23 with at least one type of metal phosphate 27. The coating material 17 may be applied as a single coating layer (Figure 3A) or as multiple thinner coating layers (Figure 3B), e.g., a plurality of layers, applied one on top of the other.

[0054] Referring now to Figure 3C, the coating material 17 may also be applied to the one or more surfaces 20 in the electrochemical cell as a composite structure that comprises the metal oxide and / or metal hydroxide 23 in a first layer and the metal phosphate 27 in a second layer. The first layer generally comprises a first side 32 and a second side 34, the first side 32 being in direct contact with the one or more surfaces 20 within the pouch cell, cylindrical cell, or prismatic cell, while the second layer is in direct contact with the second side 34 of the first layer.

[0055] The metal oxide or metal hydroxide incorporated into the coating material may comprise aluminum oxide, aluminum oxyhydroxide with a chemical formula of AIOOH, a zeolite, a titanate, a zirconate, an aluminate, or a mixture or derivative thereof. Alternatively, the metal oxides and / or metal hydroxides may include, without limitation, one or more of MgO, CaO, SrO, BaO, TiOz, ZrO?, AI2O3, Boehmite, zeolites, and / or their hydroxides, as well as derivatives thereof. Alternatively, the metal oxides and / or metal hydroxides include aluminum oxide, Boehmite, zeolites, and mixtures thereof. The zeolites may comprise, without limitation, a structure described as FAU, LTA, CHA, BEA or ZSM-5. Alternatively, the metal oxide / hydroxide is Boehmite.

[0056] Similar to Boehmite, zeolites may include a significant amount of moisture, which could be detrimental to the electrolyte and / or generate a large amount of gas when aged. In addition, a variety of other metal oxides / hydroxides, such as alumina and titanate will also generate a significant amount of gas when aged. Each of these metal oxides / hydroxides would benefit from being blended with a metal phosphate in a coating material applied to a surface in the electrochemical cell in order to reduce the gas amount generated by such oxides / hydroxides during operation and aging.

[0057] Metal phosphates are capable of removing both HF and H2O that may be present in the electrolyte used in an electrochemical cell. The metal phosphates incorporated with the metal oxides and / or metal hydroxides to form a coating material may include, but not be limited to, magnesium phosphate, zinc phosphate, copper phosphate, iron phosphate, cobalt phosphate, nickel phosphate, silver phosphate, titanium phosphate, zirconium phosphate, aluminum phosphate, lithium phosphate, barium phosphate, calcium phosphate, strontium phosphate, and combinations or mixtures thereof. Alternatively, the metal phosphate includes a metal selected from the group consisting of Mg, Ca, Sr, Ba, Ti, Zr, and a mixture thereof. Alternatively, the metal phosphate is aluminum phosphate.

[0058] Throughout the present disclosure amorphous aluminum phosphate has been used as an example of the metal phosphate present in the coating material. However, the same gas generation suppressing effect may be extended to aluminum phosphate with other structures, including crystalline aluminum phosphate and aluminum phosphate molecular sieves without departing from the scope of the present disclosure. In addition, other metal phosphates may also be used. Alternatively, the metal in the metal phosphate resides in the family of alkaline earth metals (barium, calcium magnesium, and strontium), transition metals (titanium, zirconium), and / or lithium due to lower cost and stability upon exposure to HF, which may be present in the electrolyte. Alternatively, LisPO4 can be utilized, but is not preferred over the use of AIPO4 due to lithium being much more expensive.

[0059] The mass ratio of the metal oxides and / or metal hydroxides to the metal phosphates present in the coating material may range from 99:1 to 1 :99; alternatively, 95:5 to 5:95; alternatively, from 90:10 to 10:90; alternatively, from 80:20 to 20:80; alternatively, from 75:25 to 25:75; alternatively, from 60:40 to 40:60. Alternatively, the mass ratio of the metal oxides and / or hydroxides to the metal phosphates in the coating material is about 50:50. Alternatively, the coating material may be described as comprising the metal oxide or metal hydroxide in a mass percentage of 99% to 25% and the metal phosphate in a mass percentage of 1 % to 75%, relative to the overall mass of the coating material. Alternatively, the coating material comprises the metal oxide or metal hydroxide in a mass percentage of 98% to 50% and the metal phosphate in a mass percentage of 2% to 50%, relative to the overall mass of the coating material. Alternatively, the coating material comprises the metal oxide or metal hydroxide in a mass percentage of 95% to 75% and the metal phosphate in a mass percentage of 5% to 25%, relative to the overall mass of the coating material.

[0060] The combined mass of the metal oxides / hydroxides and the metal phosphates present in the coating material may comprise 100 wt.% relative to the overall weight of the coating material. Alternatively, the combined mass of the metal oxides / hydroxides and metal phosphates may account for > 95 wt.%; alternatively, > 90 wt.%; alternatively, at least 85 wt.%; alternatively, > 80 wt.%; alternatively, 75 wt.% or more relative to the overall weight of the coating material.

[0061] When desirable, the coating material may include additional additives, such as for example, one or more binders or adhesion promotors. These additionaladditives may be present in an overall mass amount that is generally at most 25 wt.%; alternatively, < 20 wt.%; alternatively < 15 wt.%; alternatively, < 10 wt.%; alternatively, < 5 wt.% relative to the overall weight of the coating material. Alternatively, the coating material comprises a polymer binder having a mass percentage of 1 % to 20%, relative to the overall mass of the coating material. The binder may include, but not be limited to polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyvinylpyrrolidone (PVP), polypropylene oxide (PPO), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), sodium ammonium alginate (SAA), or a mixture thereof.

[0062] Any specific examples provided in this disclosure are given to illustrate various embodiments of the invention and should not be construed to limit the scope of the disclosure. The embodiments shown in the present disclosure have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without departing from the invention. For example, it will be appreciated that all preferred features described herein are applicable to all aspects of the invention described herein.

[0063] Examples

[0064] Materials: Amorphous AIPO4 was prepared by dissolving AI(NO3)3*9H2O and H3PO4 (85 wt.%) in water to form a solution with the molar ratio of Al to P being about 1 : 1.1. Then aqueous ammonia (~28 wt.%) was added to the solution in order to raise the pH of the solution to about 8.5. The white precipitate that formed was collected by filtering and then rinsed with water. After drying the collected precipitate in an oven, the wet powder was heated at 750°C for 8 hours in air to form the amorphous AIPO4.

[0065] Boehmite was produced via a conventional hydrothermal process that utilized Gibbsite as the raw material.

[0066] Gassing studies: The powder(s) to be examined, which include the metal oxides and / or metal hydroxides, the metal phosphates, or a mixture of the metal oxides / hydroxides and metal phosphates, were dried under vacuum at 110°C for I D- 12 hours and then transferred into a glove box in order to minimize the presence of any moisture. Then a total of 12 grams of an electrolyte (1 M LiPFsin ethylene carbonate / ethyl methyl carbonate or EC / EMC (3 / 7), 1 % vinyl chloride or VC, 2% fluoroethylene carbonate or FEC) with or without 3.0 grams of the dried powder wassealed in a pouch bag. The volume of the sealed bag was determined by measuring its weight both in air and in water. The net difference of the weights was taken to represent the bag volume. After the volume measurement, the bag was stored in a pre-heated oven at 85°C for a predetermined or targeted time (i.e. , 72 hours or 95 hours). After heating, the bag was cooled down in air for >2 hours. The volume of the bag was re-measured. The volume difference before and after the heating represents the volume of gas generated during the aging process.

[0067] The gas generation rates measured forthe electrolyte with or without moisture and / or with or without metal oxides / hydroxides and / or metal phosphates upon aging at a high temperature are summarized in Table 1 below. The high aging temperature was used in order to accelerate the gas generation rate. The pouch bag with only the dry electrolyte (Sample 1 ) did not show gas generation after aging for 3 days at 85°C. As demonstrated by Sample 2, once a small among of water was added (about 442 ppm of water), a significant amount of gas (~0.4 ml) was generated. Upon increasing the amount of water present to about 1542 ppm, the generated gas amount also was observed to increase to about 1 .9 ml (Sample 3). Thus, the amount of gas generated during the aging process is shown to be directly related to the moisture content present in the electrolyte. This linear relationship is shown graphically in Figure 4.

[0068] Still referring to Table 1 and Figure 4, a total of 3 grams of Boehmite was sealed inside a pouch bag with the dry electrolyte (Sample 9) and allowed to undergo the aging process. A total of 18.4 ml of gas was measured to be generated after 3 days of aging (Sample 9). If this amount of gas was generated due to water, the measured amount suggests that as high as 25% of water may be released from Boehmite. One might expect that this relatively large amount of water could arise from the decomposition of AIOOH and the release -OH groups. In order to determine if this did occur, the x-ray diffraction (XRD) pattern measured for the Boehmite prior to aging was compared to the XRD pattern measured for the Boehmite after aging (Sample 9). As shown in Figure 5A, the crystal structure of the Boehmite did not change after the aging at 85 °C. Moreover, a comparison (Figure 5B) of thermal gravimetric analysis (TGA) conducted on the unaged Boehmite and the aged Boehmite (Sample 9) demonstrates that the mass loss of the Boehmite was not changed by the aging process. Thus, the crystal structure of Boehmite did not change during the aging process and the material was not decomposed. The large amount of gas generatedduring the aging process by the addition of Boehmite (sample 9) to the electrolyte is believed to be due to not only moisture brought into the electrolyte by the Boehmite, but also by a catalytic effect involving the occurrence of a reaction between the Boehmite and the electrolyte.

[0069] Table 1. Effect of Moisture, Boehmite, AIPO4, and Mixture Thereof on the Gas Generation of the Electrolyte

[0070] Referring once again to Table 1 , a total of 3 grams of amorphous AIPO4, was sealed inside a pouch bag with the dry electrolyte (Sample 4) and allowed to undergo the aging process. A total of only 0.1 ml of gas was measured to be generated after 3 days of aging (Sample 4). The x-ray diffraction (XRD) pattern measured for the aluminum phosphate prior to aging was compared to the XRD pattern measured for the aluminum phosphate after aging (Sample 4). As shown in the XRD comparison of Figure 6A, the amorphous structure of the metal phosphate did not change after the aging at 85°C.

[0071] However, a comparison (Figure 6B) of thermal gravimetric analysis (TGA) conducted on the unaged aluminum phosphate and the aged aluminum phosphate (Sample 4) demonstrates that the AIPO4 exhibits a significant amount of weight loss during heating or aging. The aged metal phosphate was collected from the aged electrolyte after filtering, rinsed with isopropyl alcohol, and subsequently dried at 120°C in air before the TGA measurement. Thus, the majority of the weight loss exhibited by the aged phosphate is not a result of the presence of any physically adsorbed moisture. The release of any adsorbed moisture would be expected to occur at relatively low temperatures, e.g., below 300°C or even < 200°C. Rather, it is believed that the AIPO4 has reacted with the electrolyte and remains either in solid form or liquid form through the formation of chemical bonds or via other attractive forces.

[0072] Referring once again to Table 1 , a total of 3 grams of amorphous AIPO4 along with 6.1 mg (508 ppm) water was sealed inside a pouch bag with the dry electrolyte (Sample 5) and allowed to undergo the aging process in order to check the effect that the metal phosphate may have on suppressing the generation of gas. The amount of gas expected to be generated by the additional amount of water add to Sample 5 was estimated based on the linear relationship demonstrated in Figure 4 to be on the order of 0.61 ml. However, the amount of gas generated was measured to be only 0.15 ml (Sample 5). Thus, this example demonstrates that AIPO4 can effectively suppress the generation of gas due to the presence of moisture.

[0073] Still referring to Table 1 , multiple tests were conducted using a mixture of Boehmite as the metal oxide / hydroxide and AIPO4 as the metal phosphate. More specifically, AIPO4 was blended with Boehmite at various mass ratios of 3 / 1 , 1 / 1 , 1 / 3 (Samples 6, 7, & 8), sealed with the dry electrolyte and subjected to the aging process. The amount of gas measured after aging for Samples 6, 7, and 8 ranged from 0.09 to 0.14 ml, which was much lower than the gas amount generated from Boehmite (Sample 9) and was close to the gas amount measured for only AIPO4 (Sample 4).

[0074] One would expect that the amount of gas generated would be gradually reduced corresponding to a decrease of the Boehmite amount present from 100% (Sample 9) to 75% (Sample 6) to 50% (Sample 7) to 25% (Sample 8). In other words, if there was no synergetic effect between AIPO4 and the Boehmite, the amount of gas generation would be expected to decrease from 18.42 ml (100% Boehmite) to 13.83 ml (75%), to 9.25 ml (50%), to 4.68 ml (25%). However, surprisingly, the amount of gas generation was measured to decrease from 18.42 ml (100% Boehmite, Sample 9) to 0.14 ml (75%, Sample 6), to 0.09 ml (50%, Sample 7), to 0.14 ml (25%, Sample 8). This result demonstrates that there is a synergetic interaction between Boehmite and the metal phosphate with the AIPO4 effectively suppressing the gas generation of Boehmite when the metal phosphate is mixed with the Boehmite. One would reasonably believe that either a larger content of the metal phosphate or a much smaller content of the metal phosphate could also be used to reduce the gas generation amount arising from the Boehmite.

[0075] The suppression of the gas generation arising from Boehmite in the presence of AIPO4 is consistent with the TGA measurement of the AIPO4 before and after aging (Figure 6B). Although not wanting to be strictly held to theory, it is believedthat the AIPO4 reacts with and / or captures the gas generated or released from Boehmite in the electrolyte. As a result, there is only a negligible amount of gas generation from Boehmite that is measurable in the presence of AIPO4 (Samples 6, 7, and 8).

[0076] Based on the results shown in Table 1 and as further described herein, it is possible to blend a metal phosphate (e.g., amorphous aluminum phosphate, etc.) with another metal oxide or metal hydroxide that contains a high moisture content or generates a high amount of gas during aging in order to effectively suppress such release of the moisture or generation of the gas. Thus, applying such mixture of metal oxides / hydroxides and metal phosphates as a coating material to a surface in the electrochemical cell would provide the benefit of reducing the generation of gaseous species during operation and aging of the electrochemical cell.

[0077] According to another aspect of the present disclosure, a battery pack or module is provided. This battery pack or module generally comprises two or more electrochemical or battery cells encapsulated as a pouch cell, cylindrical cell, or prismatic cell formed according to the teachings of the present disclosure. These two or more batteries may be connected to one another either in series or in parallel.

[0078] According to another aspect of the present disclosure a process or method of preparing an electrochemical cell formed as a pouch cell, a cylindrical cell, or a prismatic cell is provided. Referring now to Figure 7, this method 100 general comprises the steps of providing 105 the components for the electrochemical cell; providing 110 a coating material comprising a metal oxide and / or metal hydroxide and a metal phosphate, such that the coating material is configured to trap gas present in the electrolyte; applying 115 the coating material to one or more surfaces located within the electrochemical cell that is in contact with the electrolyte; and assembling 120 the components of the electrochemical cell into the pouch cell, the cylindrical cell, or the prismatic cell. The components of the electrochemical cell generally include an anode (active material & current collector), a cathode (active material & current collector), a separator, an electrolyte, and an enclosure in the form of a pouch, a cylinder, or a prismatic package.

[0079] According to yet another aspect of the present disclosure, a process or method of preparing a battery pack or module is provided. Referring now to Figure 8, the process 150 generally comprises the steps of providing 155 a plurality ofelectrochemical cells formed as pouch cells, cylindrical cells, or prismatic cells; providing 160 an enclosure; connecting 170 the electrochemical cells in parallel or in series; and placing 175 the connected electrochemical cells within an enclosure that surrounds the pouch cells, the cylindrical cells, or the prismatic cells.

[0080] Those ski I led-i n-the-art, in light of the present disclosure, will appreciate that many changes can be made in the specific embodiments which are disclosed herein and still obtain alike or similar result without departing from or exceeding the spirit or scope of the disclosure. One skilled in the art will further understand that any properties reported herein represent properties that are routinely measured and can be obtained by multiple different methods. The methods described herein represent one such method and other methods may be utilized without exceeding the scope of the present disclosure.

[0081] The foregoing description of various forms of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Numerous modifications or variations are possible in light of the above teachings. The forms discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various forms and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims

CLAIMSWhat is claimed is:1 . An electrochemical cell for converting chemical energy into electrical energy, the electrochemical cell formed as a pouch cell, a cylindrical cell, or a prismatic cell; wherein the electrochemical cell includes a coating material located on one or more surfaces within the pouch cell, cylindrical cell, or prismatic cell that is in contact with an electrolyte, the coating material comprising a metal oxide and / or metal hydroxide and a metal phosphate, such that the coating material is configured to reduce the amount of gas present inside the electrochemical cell.

2. The electrochemical cell according to Claim 1 , wherein the coating material is located on the surface of a separator or a current collector.

3. The electrochemical cell according to any of Claims 1 or 2, wherein the coating material includes a homogeneous mixture of the metal oxide and / or metal hydroxide and the metal phosphate or is present as a composite structure that comprises the metal oxide and / or metal hydroxide in a first layer and the metal phosphate in a second layer.

4. The electrochemical cell according to Claim 3, wherein the first layer comprises a first side and a second side, the first side being in direct contact with the one or more surfaces within the pouch cell, cylindrical cell, or prismatic cell, while the second layer is in direct contact with the second side of the first layer.

5. The electrochemical cell according to Claim 3, wherein the homogeneous mixture is located within a single coating layer or within a plurality of coating layers.

6. The electrochemical cell according to any of Claims 1 to 5, wherein the electrochemical cell is a metal battery or a metal-ion battery.

7. The electrochemical cell according to Claim 6, wherein the metal battery or metal-ion battery incorporates a metal comprising one or more of lithium, sodium potassium, magnesium, calcium, or aluminum.

8. The electrochemical cell according to any of Claims 1 to 7, wherein the electrochemical cell is a lithium battery or a lithium-ion battery.

9. The electrochemical cell according to any of Claims 1 to 8, wherein the metal oxide or metal hydroxide comprises aluminum oxide, aluminum oxyhydroxide with a chemical formula of AIOOH, a zeolite, a titanate, a zirconate, an aluminate, or a mixture or derivative thereof.

10. The electrochemical cell according to Claim 9, wherein the zeolite comprises a structure described as FAU, LTA, CHA, BEA or ZSM-5.

11. The electrochemical cell according to any of Claims 1 to 10, wherein the metal phosphate comprises amorphous aluminum phosphate, crystalline aluminum phosphate, an aluminum phosphate molecular sieve, or a mixture thereof.

12. The electrochemical cell according to any of Claims 1 to 11 , wherein the metal phosphate includes a metal selected from the group consisting of Li, Mg, Ca, Sr, Ba, Ti, Zr, and a mixture thereof.

13. The electrochemical cell according to any of Claims 1 to 12, wherein the coating material comprises the metal oxide or metal hydroxide and the metal phosphate in a mass ratio of 99:1 to 1 :99.

14. The electrochemical cell according to any of Claims 1 to 13, wherein the coating material comprises the metal oxide or metal hydroxide and the metal phosphate in a mass ratio of 90:10 to 10:90.

15. The electrochemical cell according to any of Claims 1 to 13, wherein the coating material comprises the metal oxide or metal hydroxide and the metal phosphate in a mass ratio of 75:25 to 25:75.

16. The electrochemical cell according to any of Claims 1 to 13, wherein the coating material comprises the metal oxide or metal hydroxide in a mass percentage of 99% to 25% and the metal phosphate in a mass percentage of 1 % to 75%, relative to the overall mass of the coating material.

17. The electrochemical cell according to Claim 16, wherein the coating material comprises the metal oxide or metal hydroxide in a mass percentage of 98% to 50% and the metal phosphate in a mass percentage of 2% to 50%, relative to the overall mass of the coating material.

18. The electrochemical cell according to Claim 17, wherein the coating material comprises the metal oxide or metal hydroxide in a mass percentage of 95% to 75% and the metal phosphate in a mass percentage of 5% to 25%, relative to the overall mass of the coating material.

19. The electrochemical cell according to any of Claims 1 to 18, wherein the coating material further comprises a polymer binder having a mass percentage of 1 % to 20%, relative to the overall mass of the coating material.

20. The electrochemical cell according to any of Claims 1 to 19, wherein the metal oxide or metal hydroxide is Boehmite and the metal phosphate it aluminum phosphate.

21. A battery pack or module comprising two or more electrochemical cells according to any of Claims 1 to 20 connected in series or connected parallel to one another.

22. A process for preparing an electrochemical cell formed as a pouch cell, a cylindrical cell, or a prismatic cell according to any of Claims 1 to 21 , wherein the process comprises the steps of: providing the components for the electrochemical cell including an anode, a cathode, a separator, an electrolyte, and an enclosure in the form of a pouch, a cylinder, or a prismatic package; providing a coating material comprising a metal oxide and / or metal hydroxide and a metal phosphate, such that the coating material is configured to reduce the amount of gas inside the cell; applying the coating material to one or more surfaces located within the electrochemical cell that is in contact with the electrolyte; and assembling the components of the electrochemical cell to form a pouch cell, a cylindrical cell, or a prismatic cell.

23. A process of preparing a battery pack or module, the process comprising the steps of: providing two or more of the electrochemical cells formed according to the process of Claim 22; providing an enclosure; connecting the two or more electrochemical cells in parallel or in series; placing the connected electrochemical cells within the enclosure, such that the enclosure surrounds the pouch cells, the cylindrical cells, or the prismatic cells in order to form the battery pack or module.

24. A coated separatorfor use in an electrochemical cell formed as a pouch cell, a cylindrical cell, or a prismatic cell, the coated separator comprising at least one layer of a porous polymer and at least one layer of a coating material comprising a metal oxide and / or metal hydroxide and a metal phosphate, such that the coating material is configured to reduce the amount of gas generated when the coated separator is used inside the electrochemical cell with an organic electrolyte.

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