Functionalized polymeric separator membranes for mitigating transition metal dissolution and capturing acidic species

Abstract

The present invention provides a functionalized polymer separator membrane comprising a polymer backbone selected from an aramid-based polymer, a polyamide-based polymer, or a polyimide-based polymer, or a combination thereof; and further comprising one or more functional pendant groups (-FSG) capable of capturing transition metal ions and acidic species. The functionalized polymer separator membrane may be a sulfonated polyarylamide separator membrane. Sulfonating of the polyarylamide separator membrane adds functional groups that capture both acidic species and TM ions, thereby inhibiting anode damage caused by TM deposition onto the anode by a two-step process. The functionalized polymer separator membranes may be used with lithium ion, lithium metal, or sodium ion batteries.

Description

Technical Field

[0001] The present disclosure relates to functionalized polymer separator films for rechargeable secondary batteries. More specifically, aspects of the present disclosure relate to lithium ion batteries, lithium metal batteries, or sodium ion batteries for electric motor vehicles and other electric devices. Specifically, the present disclosure relates to functionalized polymer separator films having polyaramid, polyamide, and / or polyimide backbones. Background Art

[0002] The present disclosure relates to functionalized polymer separator films for rechargeable secondary batteries. More specifically, aspects of the present disclosure relate to lithium ion batteries, lithium metal batteries, or sodium ion batteries for electric motor vehicles and other electric devices. Specifically, the present disclosure relates to functionalized polymer separator films having polyaramid, polyamide, and / or polyimide backbones.

[0003] Rechargeable batteries can be used to power a variety of items such as toys, consumer electronics, motor vehicles, and aircraft. A full electric vehicle (FEV) – colloquially known as an "electric vehicle" – is a class of electrically driven vehicle configurations that completely omits the internal combustion engine and accompanying peripheral components from the powertrain system, instead relying on a rechargeable energy storage system (RESS) and traction motors for vehicle propulsion. In a battery-based FEV, the engine components, fuel supply system, and exhaust system of an internal combustion engine-based vehicle are replaced by a single or multiple traction motors, rechargeable battery tanks, and battery cooling and charging hardware. In contrast, a hybrid electric vehicle (HEV) powertrain employs a variety of traction power sources to propel the vehicle, most commonly operating the internal combustion engine components in conjunction with a battery-powered or fuel tank-powered traction motor. Because a hybrid electric drive vehicle derives its power from a source other than the engine, the HEV engine can be fully or partially shut down when the vehicle is driven by the electric motor(s).

[0004] High voltage (HV) electrical systems control the transfer of power between traction motors and rechargeable battery packs to provide the power required to operate many hybrid electric and all-electric powertrains. To provide the power capacity and energy density required to propel the vehicle for the required mileage at the required speed, modern traction battery packs group multiple battery cans (e.g., 8-16+ cans / stack) into individual battery modules (e.g., 10-40+ modules / stack) that are electrically interconnected in series or parallel and mounted to the vehicle chassis, such as via a battery pack housing or support tray. Located on the battery side of the HV power system is a front-end DC-DC power converter that is electrically connected to the (one or more) traction battery packs to increase the voltage supply to the main DC bus and the DC-AC power inverter module (PIM). High frequency bulk capacitors can be arranged across the positive and negative terminals of the main DC bus to provide electrical stability and store supplemental electrical energy. A dedicated Electronic Battery Control Module (EBCM) controls the operation of the battery pack(s) and traction motor(s) by operating in cooperation with the Powertrain Control Module (PCM) and the power electronics packages for each motor.

[0005] Battery arrays such as battery modules, battery packs, etc. typically include multiple battery cans positioned relatively close to each other. Batteries can be broadly classified into primary batteries and secondary batteries. Primary batteries, also known as disposable batteries, are intended to be used until exhausted, after which they can simply be replaced with new batteries. Secondary batteries, more commonly known as rechargeable batteries, employ specific chemistries that allow such batteries to be repeatedly recharged and reused, thus offering economic, environmental, and ease-of-use benefits over disposable batteries.

[0006] Lithium-ion batteries age with time and use, resulting in a decrease in energy storage capacity. Undesirable growth of a passivation surface layer (solid electrolyte interface, SEI) on the anode creates resistance to lithium ion flow, resulting in increased charge transfer resistance and anode impedance. The SEI layer is made of compounds decomposed from the electrolyte combined with anode surface materials (such as graphite). Some of these compounds include, but are not limited to, lithium carbonate, alkyl lithium, and lithium fluoride compounds.

[0007] Graphite is one of the common anode materials for lithium-ion batteries operating in organic electrolytes such as LiPF6 with co-solvents such as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC). The reaction of the anode with the electrolyte solution leads to the formation of species such as ROCO2Li and CO2OLi on the anode surface. The layer formed by these species is called the SEI layer. ROCO2Li can undergo a reduction reaction with CO2 and trace amounts of H2O in the electrolyte to form lithium carbonate, which further reacts with EC to form transesterification products such as DMDOHC (dimethyl 2,5-dioxahexanecarboxylate), (dimethyl 2,5-dioxahexanecarboxylate), EMDOHC (ethyl methyl-2,5-dioxahexanecarboxylate), and DECDOHC (diethyl methyl-2,5-dioxahexanecarboxylate)

[0008] In addition, anionic pollutants such as F from HF and PF5 - , which readily reacts with lithium to form insoluble reaction products that are uneven, electronically insulating, and unstable on the graphite anode surface. In addition, due to the presence of transition metal (TM) ions such as Mn in the electrolyte 3+ (becomes Mn 2+ and Mn 4+ ) are disproportionated by trace amounts of hydrofluoric acid (HF), and the cathode electrode metal dissolves from the lattice into the electrolyte, resulting in the deposition of cationic contaminants such as Mn, Co, and Fe on the anode electrode surface. The consequences of TM ion dissolution and subsequent deposition can include: (1) material loss and capacity fade at the positive electrode, and (2) deposition (i.e., reduction) on the negative electrode, which under certain conditions can degrade the thin, initial protective SEI layer while also blocking (desirable) lithium ion insertion into the negative electrode. Therefore, TM dissolution can be an inherent challenge for lithium-ion batteries, especially for high energy density nickel-manganese-cobalt (NMC) lithium-ion batteries.

[0009] In lithium-based batteries, the SEI layer (also known as the passivation layer) is a layer of material that forms between the negative electrode and the liquid electrolyte. It is spontaneously generated by the decomposition of electrolyte compounds at the high reduction potential inherent in these systems. The SEI layer is an important factor controlling the efficiency, safety and life of lithium batteries. A stable SEI layer can ensure good, long-term charge capacity retention stability, while an unstable (growing) SEI layer will eventually consume lithium ions, thereby reducing the charge capacity while increasing the internal charge transfer resistance. Therefore, unstable SEI layer formation is one of the main reasons for the poor capacity retention of high-capacity electrodes, which usually have large volume changes during charge and discharge.

[0010] Therefore, there is a need for a method of forming a polymer separator film that mitigates: (1) battery capacity fade caused by acidic species (eg, HF and other acidic species in the electrolyte solution), and (2) dissolution of transition metal ions from the cathode of the battery. Summary of the invention

[0011] A functionalized polymer separator membrane comprising a polymer backbone selected from an aramid-based polymer, a polyamide-based polymer, or a polyimide-based polymer, or a combination thereof; and further comprising one or more functional side groups (-FSG) capable of capturing transition metal ions and acidic substances. The functionalized polymer separator membrane can be a sulfonated polyaramid separator membrane. Sulfonation of the polyaramid separator adds functional groups that capture both acidic substances and TM ions, thereby inhibiting anode damage caused by TM deposition onto the anode through a two-step process. The functionalized polymer separator membrane can be used with lithium-ion, lithium metal, or sodium-ion batteries.

[0012] The present disclosure also teaches a method for functionalizing a separator membrane based on polyaramid, polyamide or polyimide for use with a rechargeable battery. During battery operation, the functional sulfonate groups will capture acidic species from the electrolyte solution, as well as capture transition metal ions dissolved from the cathode. Capturing acidic species will also reduce the amount of transition metal dissolved from the cathode, and capturing transition metal (TM) ions will prevent them from migrating to the anode and depositing on the anode, thereby slowing down battery degradation.

[0013] Sulfonation of the polyaramid separator adds functional groups that capture both acidic species and TM ions, thereby inhibiting anode damage caused by TM deposition onto the anode through a two-step process. Amination of the aromatic backbone can also provide acid scavenging capabilities. Functionalization of the polyamide backbone can also provide acid scavenging capabilities. Functionalized polymer separator membranes can be used with lithium-ion, lithium metal, or sodium-ion batteries.

[0014] The functional groups disclosed herein provide a two-step protection against the consequences of TM deposition at the anode, including: (1) reducing the amount of acidic species in the electrolyte solution (and thus, partially reducing the amount of TM ions dissolved from the cathode through acid scavenging chemistry); (2) trapping those TM ions that still dissolve from the cathode in the separator membrane, and (3) preventing TM ions from reaching the anode. There are two defense mechanisms at work: (1) acid scavenging, which addresses the root cause of the DMDCR (dissolution from cathode - migration through electrolyte solution - deposition at anode - catalytic electrolyte solution decomposition reaction at anode) degradation mechanism by preventing dissolution altogether (thus, interfering with the first "D (dissolution)"); and (2) trapping TM ions that manage to be removed from the cathode (thus, interfering with the second "D (deposition)").

[0015] In some embodiments, the functionalized polymer separator membrane comprises a polymer backbone selected from an aromatic polyamide-based polymer chain, a polyamide-based polymer chain, or a polyimide-based polymer chain, or a combination thereof; and further comprises one or more functional side groups, wherein the one or more functional side groups are capable of capturing transition metal ions and acidic substances.

[0016] In some embodiments, the functionalized polyaramid separator membrane comprises a polyaramid polymer backbone defined by two benzene rings joined by a carboxamide group (—C(═O)NH 2 ).

[0017] In some embodiments, the functionalized polyaramid separator film may include pendant urethane derivative groups.

[0018] In some embodiments, the functionalized polyaramid separator membrane may contain urea derivative pendant groups.

[0019] In some embodiments, the functionalized polymer spacer membrane comprises one or more functional side groups selected from: (a) thiol (-SH); (b) carboxylate (-COO-); (c) amino (-NH2); (d) hydroxyl (-OH); or (e) pyridine (-C5NH4); or a combination thereof.

[0020] In some embodiments, the functionalized polyaromatic amide isolation membrane comprises a polyaromatic amide polymer backbone defined by two benzene rings joined by a carboxamide group (-C(=O)NH2); and further comprises one or more metal capture side groups (-M) capable of capturing transition metal ions; and further comprises one or more acid capture side groups (-A) capable of capturing acidic substances.

[0021] In some embodiments, one or more metal capture side groups (-M) may include -SO3Li.

[0022] In some embodiments, one or more of the acid-trapping pendant groups (—A) may include amine groups (—NH 2 ).

[0023] In some embodiments, one or more of the acid-trapping side groups (-A) may include an amide derivative.

[0024] In some embodiments, one or more of the acid-trapping pendant groups (-A) may include a urea derivative.

[0025] In some embodiments, the pendant acid capture groups may include EDTA acid capture groups made by treating a polyaramid separator membrane with EDTA anhydride.

[0026] In some embodiments, the functionalized polyaromatic amide isolation membrane comprises: one or more nitrogen atoms and one or more acid capture functional groups attached to the one or more nitrogen atoms; wherein the one or more acid capture functional groups comprise an isocyanate bond having an amine group (-NH2), and the amine group (-NH2) replaces O==C==N on the diisocyanate bond.

[0027] In some embodiments, the method of forming a functionalized polymer separator film comprises: first, contacting a solution containing functional side groups with a precursor polymer separator film to form a functionalized polymer separator film; second, rinsing the functionalized polymer separator film in deionized water or an alkaline solution to form a workpiece; and third, drying the workpiece in an oven to completely remove adsorbed water, thereby forming a functionalized polymer separator film having functional side groups.

[0028] In some embodiments, the polymer separator film can be a polyaramid separator film.

[0029] In some embodiments, the solution can be at least one of sulfuric acid, chlorosulfonic acid, or aminosulfonic acid, or a combination thereof; and the method further includes contacting diluted LiOH or lithium sulfate with the functionalized polyaramid separator membrane to form a workpiece; and thereafter rinsing the functionalized polyaramid separator membrane in deionized water.

[0030] In some embodiments, the solution can be a nitrating solution, and second, the nitrated polyaromatic amide separator membrane is placed in a reducing bath to form a reduced workpiece; third, the reduced workpiece is contacted with deionized water; and fourth, the reduced workpiece is dried in an oven to completely remove adsorbed water; thereby forming a nitrated polyaromatic amide separator membrane.

[0031] In some embodiments, the nitrating solution can be a mixture of nitric acid (HNO3) and sulfuric acid (H2SO4); and wherein the reducing bath can be sodium dithionite NaS2O4.

[0032] In some embodiments, the solution may be a mixture of a diisocyanate and 1,4-diazabicyclo[2.2.2]octane (DABCO).

[0033] In some embodiments, the method may include replacing deionized water with a first solution comprising an alcohol to form pendant carbamate derivative groups or replacing deionized water with a second solution comprising an amine to form pendant urea derivative groups.

[0034] In some embodiments, the solution may include an activated thiol-reactive agent; wherein the activated thiol-reactive agent may include a thiol-reactive agent mixed with a solvent comprising water or dimethyl sulfoxide; and second, combining the activated thiol-reactive agent with the polyaromatic amide solution to form a functionalized polyaromatic amide separator membrane functionalized with -SH groups.

[0035] In some embodiments, the thiol-reactive agent can be 2-iminothiolane, N-succinimidyl 3-(2-pyridyldithio)propionate.

[0036] In some embodiments, the solution may include a carboxylate precursor; thereby forming a functionalized polyaramid separator membrane having -COO- pendant groups.

[0037] In some embodiments, the carboxylate precursor may be selected from a carboxylic acid, a carboxylate-containing compound, acetic acid (CH3COOH), or succinic anhydride (C4H4O3), or a combination thereof.

[0038] The present invention discloses the following scheme:

[0039] Scheme 1. A functionalized polymer spacer membrane comprising:

[0040] a polymer backbone selected from an aramid-based polymer, a polyamide-based polymer, or a polyimide-based polymer, or a combination thereof; and

[0041] According to (I), further comprising one or more functional side groups (-FSG), wherein the one or more functional side groups are capable of capturing transition metal ions and acidic substances:

[0042]

[0043] Scheme 2. A functionalized polymer separator membrane according to Scheme 1, wherein according to (II), the polymer backbone comprises a polyaromatic amide backbone defined by two benzene rings joined by a carboxamide group (-C(=O)NH2):

[0044]

[0045] Scheme 3. The functionalized polymer separator membrane according to Scheme 2, comprising a carbamate derivative pendant group according to (III):

[0046]

[0047] Wherein R = alkyl, aromatic or non-reactive group.

[0048] Scheme 4. The functionalized polymer separator membrane according to Scheme 2, comprising a carbamate derivative pendant group according to (III):

[0049]

[0050] Wherein R = alkyl, aromatic or non-reactive group.

[0051] Scheme 5. The functionalized polymer spacer membrane according to Scheme 2, comprising a urea derivative pendant group according to (IV):

[0052]

[0053]

[0054] Wherein R = alkyl, aromatic or non-reactive group.

[0055] Scheme 6. The functionalized polymer spacer membrane according to Scheme 2, comprising a urea derivative pendant group according to (IV):

[0056]

[0057] Wherein R = alkyl, aromatic or non-reactive group.

[0058] Embodiment 7. The functionalized polymer spacer membrane according to embodiment 1, wherein the one or more functional side groups are selected from:

[0059] (a) Sulfhydryl group (-SH);

[0060] (b) carboxylate group (-COO-);

[0061] (c) amino group (-NH2);

[0062] (d) hydroxyl (-OH); or

[0063] (e) pyridine group (-C5NH4);

[0064] or a combination thereof.

[0065] Scheme 8. A functionalized polyaromatic amide separator membrane, comprising:

[0066] A polyaramid polymer backbone defined by two benzene rings joined by a carboxamide group (-C(=O)NH2); and according to (V), further comprising:

[0067] one or more metal-capturing pendant groups (-M); and

[0068] one or more acid-trapping side groups (-A),

[0069] wherein the one or more metal capture side groups (-M) are capable of capturing transition metal ions; and

[0070] wherein the one or more acid-capturing side groups (-A) are capable of capturing acidic species:

[0071]

[0072] Scheme 9. The functionalized polyaromatic amide separator membrane according to Scheme 8, wherein according to (VI), the one or more metal capture side groups (-M) include -SO3Li:

[0073]

[0074] Scheme 10. The functionalized polyaromatic amide separator membrane according to Scheme 8, wherein according to (VII), the one or more acid-capturing side groups comprise an amine group (—NH 2 ):

[0075]

[0076] 11. The functionalized polyaromatic amide separator membrane according to 8, wherein according to (VIII), the one or more acid-capturing side groups comprise an amide derivative:

[0077]

[0078] Wherein R' = alkyl, aromatic or non-reactive group.

[0079] 12. The functionalized polyaromatic amide separator membrane according to 8, wherein according to (IX), the one or more acid-capturing side groups comprise a urea derivative:

[0080]

[0081] Wherein R' = alkyl, aromatic or non-reactive group.

[0082] Scheme 13. The functionalized polyaramid separator membrane according to Scheme 8, wherein according to (X), the acid-capturing side groups include EDTA acid-capturing groups prepared by treating the polyaramid separator membrane with EDTA anhydride:

[0083]

[0084] Embodiment 14. The functionalized polyaromatic amide separator membrane according to embodiment 8, comprising one or more nitrogen atoms; and

[0085] one or more acid capture functional groups attached to the one or more nitrogen atoms;

[0086] Wherein according to (XI), the one or more acid capture functional groups comprise an isocyanate bond having an amine group (-NH2) which replaces the O==C==N on the diisocyanate bond:

[0087]

[0088] Wherein R = alkyl, aromatic or non-reactive group.

[0089] Embodiment 15. A method for forming a functionalized polymer separator membrane, the method comprising:

[0090] First, contacting a solution containing one or more functional pendant groups with a precursor polymer spacer membrane to form a functionalized polymer spacer membrane;

[0091] second, rinsing the functionalized polymer separator film in deionized water or an alkaline solution to form a workpiece; and

[0092] Third, the workpiece is dried in an oven to completely remove the adsorbed water;

[0093] A functionalized polymer separator membrane having functional pendant groups is thereby formed.

[0094] Embodiment 16. The method according to embodiment 15, wherein the functionalized polymer separator membrane comprises a functionalized polyaramid separator membrane.

[0095] Scheme 17. The method according to Scheme 16,

[0096] wherein the solution comprises at least one of sulfuric acid, chlorosulfonic acid or aminosulfonic acid or a combination thereof; and the method further comprises:

[0097] Diluted LiOH or lithium sulfate is contacted with the functionalized polyaramid separator membrane to form a workpiece, and then secondly, the functionalized polyaramid separator membrane is rinsed in the deionized water.

[0098] Scheme 18. The method according to Scheme 16,

[0099] wherein the solution comprises a nitrating solution; thereby forming a nitrated polyaramid separator membrane; and

[0100] second, placing the nitrated polyaramid separator film in a reducing bath to form a reduced workpiece;

[0101] third, contacting the reduced workpiece with deionized water; and

[0102] Fourth, the reduced workpiece is dried in an oven to completely remove the adsorbed water.

[0103] Thus, a nitrated polyaramide separator membrane is formed.

[0104] Scheme 19. The method according to Scheme 18,

[0105] wherein the nitrating solution comprises a mixture of nitric acid (HNO3) and sulfuric acid (H2SO4); and

[0106] The reducing bath comprises sodium dithionite NaS2O4.

[0107] Embodiment 20. The method according to embodiment 16, wherein the solution comprises a mixture of a diisocyanate and 1,4-diazabicyclo[2.2.2]octane (DABCO).

[0108] Solution 21. The method according to Solution 20, further comprising:

[0109] replacing the deionized water with a first solution comprising an alcohol to form pendant carbamate derivative groups; or

[0110] The deionized water is replaced with a second solution comprising an amine to form the urea derivative pendant groups.

[0111] Solution 22. The method according to Solution 16, further comprising:

[0112] mixing a thiol-reactive agent with a solvent comprising water or dimethyl sulfoxide to form an activated thiol-reactive agent;

[0113] wherein said solution comprises said activated thiol-reactive agent; and

[0114] The solution is combined with a polyaramid solution to form a functionalized polyaramid separator membrane functionalized with -SH groups. BRIEF DESCRIPTION OF THE DRAWINGS

[0115] Figure 1 A schematic cross-sectional view of an example of a lithium-ion battery stack according to the present disclosure is shown.

[0116] Figure 2A Shown is the chemical structure of an example of a polyaramid backbone (meta-aramid) of a separator film according to the present disclosure.

[0117] Figure 2B The chemical structure of an example of a modified polyaramid backbone (meta-aramid) after sulfonation with -SO3H groups according to the present disclosure is shown.

[0118] Figure 2C The chemical structure of an example of a modified polyaramid backbone (meta-aramid) after lithium ion exchange according to the present disclosure is shown.

[0119] Figure 2D The chemical structure of an example of a modified polyaramid backbone (meta-aramid) after capturing transition metal manganese ions according to the present disclosure is shown.

[0120] Figure 3 is a graphical illustration of the light transmittance as a function of wave number for treated (modified) polyaramid separator films according to the present disclosure compared to untreated polyaramid material.

[0121] Figure 4A Shown is the chemical structure of an example of a polyaramid backbone (meta-aramid) according to the present disclosure.

[0122] Figure 4B The chemical structure of an example of a modified polyaramid backbone (meta-aramid) treated with a mixture of HNO3 and H2SO4 according to the present disclosure is shown.

[0123] Figure 4C The chemical structure of an example of a modified polyaramid backbone (meta-aramid) after NaS2O4 treatment according to the present disclosure is shown.

[0124] Figure 5A Shown is the chemical structure of an example of a polyaramid backbone (meta-aramid) according to the present disclosure.

[0125] Figure 5B Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) treated with a mixture of DABCO (1,4-diazabicyclo[2.2.2]octane) and diisocyanate according to the present disclosure.

[0126] Figure 5C The chemical structure of an example of a modified polyaramid backbone (meta-aramid) after final treatment with H2O according to the present disclosure is shown.

[0127] Figure 5D Shown are chemical structures of examples of diisocyanate linkages according to the present disclosure, where R = alkyl, aromatic, or non-reactive groups.

[0128] Figure 6 Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having amide derivative acid-trapping pendant groups according to the present disclosure, where R' = alkyl, aromatic, or non-reactive groups.

[0129] Figure 7 Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having urea derivative acid-trapping pendant groups according to the present disclosure, where R' = alkyl, aromatic, or non-reactive groups.

[0130] Figure 8Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having EDTA acid-trapping pendant groups made by treating a polymer separator membrane with EDTA anhydride in accordance with the present disclosure.

[0131] Fig. 9 Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having urethane derivative acid-trapping pendant groups according to the present disclosure, where R = alkyl, aromatic, or non-reactive group.

[0132] Fig.10 Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having urea derivative acid-trapping pendant groups according to the present disclosure, where R = alkyl, aromatic, or non-reactive group.

[0133] Fig.11 Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having hydroxyl (—OH) functional pendant groups according to the present disclosure.

[0134] Fig.12 Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having thiol (—SH) functional pendant groups according to the present disclosure.

[0135] Fig.13 Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having carboxylate (—COO—) functional pendant groups according to the present disclosure.

[0136] Fig.14 Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having lithiated carboxylate (—COOLi) functional pendant groups according to the present disclosure.

[0137] Fig.15 The chemical structure of an example of a modified polyaramid backbone (meta-aramid) having pyridine (-C5NH4) functional pendant groups according to the present disclosure is shown.

[0138] Fig.16 An example of a block diagram for forming a functionalized polyaramid separator film according to the present disclosure is shown.

[0139] Fig.17 An example of a block diagram for forming a sulfonated polyaramid separator membrane according to the present disclosure is shown.

[0140] Fig.18 An example of a block diagram for forming a nitrated polyaramid separator film according to the present disclosure is shown.

[0141] Fig.19An example of a block diagram for forming a modified polyaramide separator film having pendant aminated diisocyanate groups according to the present disclosure is shown.

[0142] Fig. 20 An example of a block diagram for forming a functionalized polyaramid separator film having -SH pendant groups according to the present disclosure is shown.

[0143] Fig.21 An example of a block diagram for forming a functionalized polyaramid separator film having -COO- groups according to the present disclosure is shown.

[0144] Fig. 22 Shown is the chemical structure of an example of a polyaramid backbone (meta-aramid) of a separator membrane having metal-capturing side groups (—M) and acid-capturing side groups (—A) according to the present disclosure.

[0145] Fig.23 Shown is the chemical structure of an example of a polyaramid backbone (meta-aramid) of a separator membrane having pendant functional groups (—FSG) according to the present disclosure.

[0146] Fig.24 A schematic perspective view of an example of an electric vehicle according to the present disclosure is shown. DETAILED DESCRIPTION

[0147] The present disclosure can be implemented in many different forms. Representative embodiments of the present disclosure are shown in the drawings and will be described in detail herein, and it should be understood that these embodiments are provided as examples of the disclosed principles, rather than limitations on the broad aspects of the present disclosure. In this regard, elements and limitations such as those described in the abstract, background technology, summary of the invention, and detailed description but not explicitly set forth in the claims should not be incorporated into the claims individually or collectively by implication, inference, or otherwise.

[0148] For the purposes of this Detailed Description, unless expressly stated otherwise: the singular includes the plural and vice versa; the words "and" and "or" shall be both conjunctions and disjunctions; the words "any" and "all" shall mean "any and all"; and the words "include," "contain," "includes," "have," and the like shall each mean "including but not limited to." In addition, approximate words such as "about," "almost," "substantially," "roughly," "approximately," and the like may each be used herein in the sense of "within, close to, or nearly within," for example, or "within 0-5% of" or "within an acceptable manufacturing tolerance," or their logical combinations.

[0149] Unless otherwise specified from the context, as used herein, the term "about" should be understood to be within the normal tolerance range in the art, such as within 2 standard deviations of the mean. "About" can be understood to be within 10%, 5%, 1%, 0.5%, 0.1%, 0.05% or 0.01% of the stated value. "About" can alternatively be understood to imply the exact value specified. Unless the context clearly indicates otherwise, the numerical values ​​provided herein are modified by the term "about".

[0150] Finally, directional adjectives and adverbs, such as front, rear, inside, outside, right, left, vertical, horizontal, up, down, front, rear, left, and the like, may be relative to the motor vehicle, such as the forward direction of travel of the motor vehicle when the vehicle is operably oriented on a level driving surface.

[0151] The terms "separator" and "separator film" are used interchangeably herein. The terms "treated" and "modified" are used interchangeably herein. The phrases "polymer backbone" and "polyaramid backbone" refer to a polymer chain of linked repeating subunits.

[0152] The present separator films can be used with a variety of different battery chemistries including, but not limited to, lithium ion, lithium metal, and sodium ion battery chemistries.

[0153] Figure 1A schematic cross-sectional view of an example of a lithium-ion battery stack 10 is shown. The five stacked battery layers of the lithium-ion battery stack 10 include: a negative current collector layer 12; a negative electrode layer 14 disposed adjacent to the negative current collector layer 12; a porous separator layer 16 disposed adjacent to the negative electrode layer 14; a positive electrode layer 18 disposed adjacent to the porous separator layer 16 opposite to the negative electrode layer 14; and a positive current collector layer 20 disposed adjacent to the positive electrode layer 18. The negative current collector layer 12 may include a copper sheet. The negative electrode layer 14 may include a material selected from the following: lithium, graphite, lithium titanate, silicon / carbon, or tin / cobalt alloy, or a combination thereof. The porous separator layer 16 may include a microporous polymer selected from the following: microporous polyethylene (PE), microporous polypropylene (PP), microporous polyethylene terephthalate (PET), microporous polyaramide (PA), or a ceramic coating on one or both sides of a microporous polymer film, or a combination thereof. The ceramic coating material may include: aluminum oxide, silicon oxide, titanium oxide, boehmite, magnesium oxide, zeolite, lithiated zeolite or a combination thereof. The positive electrode layer 18 may include a compound selected from the following: lithium metal oxide, LiCoO2 (LCO), LiMn2O4 (LMO), LiFePO4 (LFP), nickel manganese cobalt oxide (NMC) or nickel cobalt aluminum oxide (NCA) or a combination thereof. Finally, in some embodiments, the positive current collector layer 20 may include aluminum. The five stacked battery layers may be contained in a sealed prismatic or cylindrical battery can (i.e., housing) having a positive electrode tab and a negative electrode tab protruding from the top of the can.

[0154] The aromatic polyaramid separator membranes described herein are highly porous materials (eg, microporous membranes and nanoporous membranes).

[0155] Figure 2A The chemical structure of an example of a precursor polyaromatic amide backbone (e.g., meta-aramid) according to the present disclosure is shown. The polyaromatic amide polymer is named polyparaphenylene terephthalamide or polymetaphenylene terephthalamide. In some embodiments, para-aramid polymers can be used to replace meta-aramid polymers. In some embodiments, a combination of meta-aramid polymers and para-aramid polymers can be used together. The precursor polyaromatic amide backbone comprises a repeating unit comprising two benzene rings joined by a carboxamide group (-C(=O)NH2). The two benzene rings are alternately attached to two NH groups or two CO groups. The term "polyaromatic amide" is an abbreviation for "aromatic polyaromatic amide".

[0156] Figure 2BThe chemical structure of an example of a modified polyaramid backbone (meta-aramid) after sulfonation with -SO3H groups according to the present disclosure is shown. Sulfonation of the aramid polymer involves replacing protons on the polyaramid backbone with sulfonic acid groups (-SO3H) by treatment with sulfuric acid, H2SO4. Due to the presence of the sulfonic acid groups (which have a high affinity for metal ions), the sulfonated polyaramid captures transition metals (e.g., manganese). The sulfonation process may include passing diluted and heated sulfuric acid (e.g., heated to about 70°C to 90°C) through Figure 2A The polyaramid separator membrane is immersed in or passes through. The concentration of sulfuric acid may be about 5 parts by weight to about 30 parts by weight based on 100 parts by weight of the aqueous sulfuric acid solution.

[0157] Figure 2C The chemical structure of an example of a modified polyaramid backbone (meta-aramid) after lithium ion exchange according to the present disclosure is shown. The lithium ion exchange may include passing diluted and heated LiOH (e.g., heated to about 70° C. to 90° C.) through Figure 2B The modified polyaramid separator membrane is immersed in or passed through.

[0158] Figure 2D The chemical structure of an example of a modified polyaramid backbone (meta-aramid) after capturing transition metal manganese ions during battery use and recharging according to the present disclosure is shown. In this step, manganese preferentially replaces lithium ions in the -SO3Li functional group (this is also true for other transition metal ions (e.g., cobalt and iron)).

[0159] Figure 3 A graphical representation of the measured results of light transmittance of treated (modified) polyaramid materials according to the present disclosure as a function of photon wave number is shown compared to untreated polyaramid materials. There is no substantial difference between the untreated and modified polyaramid materials, indicating that the sulfonation treatment of the polyaramid materials does not impair the structural properties of the modified polyaramid.

[0160] Table 1 summarizes the experimental measurements of the amount (concentration) of manganese and sulfur adsorption in three different types of modified separator membranes. According to the test standard "GLIProcedure ME-70", the samples were first exposed to an excess of 0.1M manganese salt for 10 minutes, and then the amount (concentration) of Mn or S adsorbed by the separator membrane samples was measured using an inductively coupled plasma mass spectrometer system (ICP-MS). The measured concentrations of adsorbed manganese and sulfur for sample #1 (modified LG Chem alumina-coated polyethylene (PE) separator) were very low, with manganese being 0.842% and sulfur being <0.029%. This is because sample #1 was not sulfonated. The measured adsorbed manganese concentration for sample #2 (modified sulfonated polyaramide separator) was much higher at 2.47%, while the adsorbed sulfur concentration was lower at only 0.408%. Sample #3 (modified sulfonated polyaramide separator coated with lithium-zeolite) had a similarly high measured adsorbed manganese concentration (2.77%) and a lower adsorbed sulfur concentration (0.293%). These results indicate that the sulfonated polyaramide separator membrane can result in a significant adsorption amount of the transition metal element manganese.

[0161] Table 1 Adsorption of manganese and sulfur in sulfonated polyamide separator membranes

[0162]

[0163] Figure 4A The chemical structure of an example of a precursor polyaramid backbone (meta-aramid) according to the present disclosure is shown.

[0164] Figure 4B The chemical structure of an example of a modified polyaramid backbone (meta-aramid) according to the present disclosure after nitration with a solution containing nitric acid (HNO3) or a mixture of nitric acid and sulfuric acid (H2SO4) is shown. The relative ratio of nitric acid and sulfuric acid in the nitration solution can be 1:1. In some embodiments, concentrated nitric acid can be used alone. In some embodiments, acyl nitrates can be used. The nitration treatment replaces protons on the benzene ring with -NO2 groups.

[0165] Figure 4C The chemical structure of an example of a modified polyaramid backbone (meta-aramid) after treatment with a reducing agent (e.g., sodium dithionite, NaS2O4) according to the present disclosure is shown. This step replaces the Figure 4B The -NO2 groups in the NH4Cl provide enhanced acid scavenging functionality.

[0166] Figure 5A The chemical structure of an example of a precursor polyaramid backbone (meta-aramid) according to the present disclosure is shown.

[0167] Figure 5BThe chemical structures of examples of modified polyaramid backbones (meta-aramids) after functionalization with a mixture of DABCO (1,4-diazabicyclo[2.2.2]octane) and diisocyanates according to the present disclosure are shown. They are used in a molar ratio of 1DABCO:100 diisocyanate, ranging from 1:20 to 1:200. Isocyanates are functional groups with the formula -RN=C=O. Diisocyanates are generally defined as: OCN-R-OCN. Examples of suitable diisocyanates include: (NCO)2 and hexamethylene diisocyanate (CH2)6(NCO)2.

[0168] Figure 5C It shows that according to the present disclosure Figure 5B Chemical structure of an example of a modified polyaramid backbone (meta-aramid) of a functionalized separator membrane after H2O treatment.

[0169] Figure 5D The chemical structure of an example of a diisocyanate bond according to the present disclosure is shown, where R = alkyl, aromatic group or non-reactive group. A diisocyanate bond is defined as:

[0170]

[0171] Wherein R = alkyl, aromatic or non-reactive group according to the present disclosure. Common examples of R may include: ethyl, propyl, hexyl, benzyl, toluene and cyclohexyl. In other embodiments, R may include: alkyl (hexamethylene diisocyanate), aromatic (1,3-diisocyanatobenzene), or cyclic (isophorone diisocyanate), or a combination thereof.

[0172] Figure 6 Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having amide derivative acid-trapping pendant groups according to the present disclosure, where R' = alkyl, aromatic, or non-reactive groups.

[0173] Figure 7 Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having urea derivative acid-trapping pendant groups according to the present disclosure, where R' = alkyl, aromatic, or non-reactive groups.

[0174] Figure 8 The chemical structure of an example of a modified polyaramid backbone (meta-aramid) having EDTA acid-trapping side groups prepared by treating a polymer separator membrane with EDTA anhydride according to the present disclosure is shown. EDTA stands for ethylenediaminetetraacetic acid (C 10 H 16 N2O8), and is a metal ion (including Mn 2+)Bound Metal Chelators. In some embodiments, other compounds may be used to treat the polymeric spacer membrane including: acid chlorides, anhydrides, or isocyanates, or combinations thereof.

[0175] Fig. 9 Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having urethane derivative acid-trapping pendant groups according to the present disclosure, where R = alkyl, aromatic, or non-reactive group.

[0176] Fig.10 Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having urea derivative acid-trapping pendant groups according to the present disclosure, where R = alkyl, aromatic, or non-reactive group.

[0177] In some embodiments, the following polymer spacer membranes may be functionalized according to the techniques presented above, including but not limited to: (a) spacer membranes based on aromatic polyamides (e.g., meta-aromatic polyamide, para-aromatic polyamide); (b) spacer membranes based on polyimides, and (c) spacer membranes based on polyamides.

[0178] In some embodiments, the following functional groups may be added to the polymer backbone of the separator membrane, which can capture acidic species and / or transition metal ions:

[0179] 1.Sulfhydryl group (-SH);

[0180] 2. Carboxylate group (-COO-);

[0181] 3. Amino group (-NH2);

[0182] 4. Hydroxyl (-OH); and

[0183] 5. Pyridine group (-C5NH4).

[0184] Fig.11 Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having hydroxyl (—OH) functional pendant groups according to the present disclosure.

[0185] Fig.12 Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having thiol (—SH) functional pendant groups according to the present disclosure.

[0186] Fig.13 Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having carboxylate (—COO—) functional pendant groups according to the present disclosure.

[0187] Fig.14Shown is the chemical structure of an example of a modified polyaramid backbone (meta-aramid) having lithiated carboxylate (—COOLi) functional pendant groups according to the present disclosure.

[0188] Fig.15 The chemical structure of an example of a modified polyaramid backbone (meta-aramid) having pyridine (-C5NH4) functional pendant groups according to the present disclosure is shown.

[0189] Fig.16 A method for functionalizing a polyaromatic amide separator membrane (such as Fig. 22 An example of a block diagram of the invention is shown in FIG. 1 . The method comprises:

[0190] (1) contacting a solution containing functional side groups with a precursor polyaramid separator membrane to form a functionalized polyaramid separator membrane (step 36);

[0191] (2) rinsing the functionalized polyaramid separator film in deionized water or an alkaline solution to form a workpiece (step 38); and

[0192] (3) The workpiece is dried in an oven to completely remove the adsorbed water, thereby forming a sulfonated polyaramid separator membrane (step 39).

[0193] Fig.17 A sulfonated precursor polyaramid separator membrane (eg Figures 2A-2D An example of a block diagram of a device as shown in FIG. 1 ) comprising:

[0194] (1) contacting at least one of dilute sulfuric acid, chlorosulfonic acid, or aminosulfonic acid, or a combination thereof, with a precursor polyaramid separator membrane to form a sulfonated polyaramid separator membrane (step 40);

[0195] (2) contacting diluted LiOH or lithium sulfate with the sulfonated polyaramid separator membrane to form a workpiece (step 42);

[0196] (3) contacting the workpiece with deionized water (step 44); and

[0197] (4) Drying the workpiece in an oven to completely remove the adsorbed water to form the sulfonated polyaramid separator membrane (step 46). Step 40 may include diluting sulfuric acid, chlorosulfonic acid, or aminosulfonic acid and heating to about 70°C to 90°C. Step 44 may include washing off excess salt, lithium hydroxide, or lithium sulfate. Step 46 may include drying the workpiece in a vacuum oven at about 150°C to completely remove the adsorbed water. Longer times and lower temperatures (e.g., >100°C) may also be used.

[0198] Fig.18 A polyaramid separator membrane (eg Figures 4A-4CAn example of a block diagram of a device as shown in FIG. 1 ) comprising:

[0199] (1) contacting a nitrating solution with a precursor polyaramid separator film to form a nitrated polyaramid separator film (step 50);

[0200] (2) placing the nitrated polyaramid separator film in a reducing bath to form a reduced workpiece (step 52);

[0201] (3) contacting the reduced workpiece with deionized water (step 54); and

[0202] (4) Drying the reduced workpiece in an oven to completely remove adsorbed water, thereby forming a nitrated polyaromatic amide spacer membrane (step 56). In some embodiments, the nitrating solution may include a mixture of nitric acid and sulfuric acid. The reducing bath may include sodium dithionite. In some embodiments, further reaction with acid chlorides, anhydrides, or isocyanates may be used to add additional functionalization (s) of the polyaromatic amide spacer membrane. For example, EDTA anhydride (a common multidentate chelating agent) can be used to capture metal ions, as described below.

[0203] Fig.19 An example of a block diagram for a sulfonated precursor polyaramid separator membrane is shown (eg Figures 5A-5D ), which includes:

[0204] (1) contacting a mixture of diisocyanate and 1,4-diazabicyclo[2.2.2]octane (DABCO) with a precursor polyaramide separator film to form a modified polyaramide separator film (step 60);

[0205] (2) contacting deionized water with the modified polyaramide separator membrane to form an aminated workpiece (step 62); and

[0206] (3) Drying the aminated workpiece in an oven to completely remove the adsorbed water, thereby forming a functionalized polyaramid spacer membrane having aminated diisocyanate pendant groups (step 64). Step 62 produces amine groups -R-NH2, where R = alkyl, aromatic group or non-reactive group. In some embodiments, step 62 may alternatively include exposing the modified polyaramid spacer membrane to a solution containing an alcohol (i.e., to prepare a carbamate derivative) or an amine solution (i.e., to prepare a urea derivative), or a combination thereof, instead of contacting with deionized water. Generally speaking, the presence of amine groups provides acid scavenging.

[0207] In some embodiments, additional intermediate isocyanate treatments may be used to add various functional pendant groups using isocyanate chemistry by forming, for example, urethane bonds and / or ureas.

[0208] Fig. 20An example of a method for functionalizing a precursor polyaramide separator membrane with a thiol group (-SH) is shown (eg Fig.12 ), which includes:

[0209] (1) activating the thiol reactant with a solvent comprising water or dimethyl sulfoxide to form an activated thiol reactant (step 70);

[0210] (2) combining the activated thiol reactant with the polyaramid solution to form a precursor polyaramid separator film (step 72);

[0211] (3) incubating the precursor polyaramide membrane for a certain incubation time to form a functionalized polyaramide separator membrane (step 74);

[0212] (4) contacting the functionalized polyaramid separator membrane with deionized water to form a workpiece (step 76); and

[0213] (5) The workpiece is dried in an oven to completely remove the adsorbed water, thereby forming a functionalized polyaramide separator film with -SH side groups (step 78).

[0214] Fig.21 An example of a method for functionalizing a precursor polyaramide separator membrane with carboxylate (-COO-) groups is shown (eg Fig.13 ), which includes:

[0215] (1) preparing a solution containing a carboxylate precursor (step 80);

[0216] (2) contacting the solution with a precursor polyaramid separator membrane to form a functionalized polyaramid separator membrane (step 82);

[0217] (3) rinsing the functionalized polyaramid separator membrane in deionized water or an alkaline solution to form a workpiece (step 84);

[0218] (4) rinsing the workpiece with deionized water to remove unreacted reagents or byproducts (step 86); and

[0219] (5) Drying the workpiece in an oven to completely remove the adsorbed water, thereby forming a functionalized polyaramide separator film with -COO- side groups (step 88). In some embodiments, the carboxylate precursor used in step 80 can be acetic acid (CH3COOH) or succinic anhydride (C4H4O3).

[0220] Fig. 22 Shown is the chemical structure of an example of a polyaramid backbone (meta-aramid) of a separator membrane having metal-capturing side groups (—M) and acid-capturing side groups (—A) according to the present disclosure.

[0221] Fig.23 Shown is the chemical structure of an example of a polyaramid backbone (meta-aramid) of a separator membrane having pendant functional groups (—FSG) according to the present disclosure.

[0222] Fig.24 A schematic perspective view of an example of an electric motor vehicle 22 having a rechargeable battery pack 30 according to the present disclosure is shown. The electric motor vehicle 22 includes a body 24, a passenger compartment 26, a plurality of wheels 28, 28', etc. attached to the body 24, and a rechargeable battery pack 30 located at a rear end of the electric motor vehicle 22. The electric motor vehicle 22 also includes an electric traction motor 32 attached to the body 24, which is operable to drive one or more of the wheels 28, 28', etc. to propel the electric motor vehicle 22. The rechargeable battery 30 is attached to the body 24 and electrically connected to the traction motor 32 via a power cable 34.

[0223] HF is a common acid in the battery environment. Other acids that may be present in battery cells include: trifluoromethanesulfonic acid (CF3SO3H). This acid can be a decomposition product of certain lithium salts, such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), a common lithium-ion battery salt. Other acids may include: acetic acid (CH3COOH), which may be introduced via impurities or contaminants during the manufacturing process; and formic acid (HCOOH), which can also be a byproduct of certain decomposition reactions in the battery.

Claims

1. A functionalized polymer spacer membrane comprising: a polymer backbone selected from an aramid-based polymer, a polyamide-based polymer, or a polyimide-based polymer, or a combination thereof; and According to (I), further comprising one or more functional side groups (-FSG), wherein the one or more functional side groups are capable of capturing transition metal ions and acidic substances:

2. The functionalized polymer spacer membrane of claim 1, wherein the one or more functional side groups are selected from: (a) Sulfhydryl group (-SH); (b) carboxylate group (-COO-); (c) amino group (-NH2); (d) hydroxyl (-OH); or (e) pyridine group (-C5NH4); or a combination thereof.

3. A functionalized polyaromatic amide separator membrane, comprising: A polyaromatic amide polymer backbone defined by two benzene rings joined by a carboxamide group (-C(=O)NH2); and further comprising one or more metal-capturing side groups; according to (II), the one or more metal-capturing side groups include -SO3Li:

4. The functionalized polyaromatic amide separator membrane of claim 3, wherein according to (III), the one or more acid-trapping side groups comprise an amine group (-NH2):

5. The functionalized polyaramid separator membrane of claim 2, wherein according to (IV), the one or more functional side groups comprise an amide derivative: Wherein R' = alkyl, aromatic or non-reactive group.

6. A method of forming a functionalized polymer separator film, the method comprising: First, contacting a solution containing one or more functional pendant groups with a precursor polymer spacer membrane to form a functionalized polymer spacer membrane; second, rinsing the functionalized polymer spacer membrane in deionized water or an alkaline solution to form a workpiece; and Third, the workpiece is dried in an oven to completely remove the adsorbed water; A functionalized polymer separator membrane having functional pendant groups is thereby formed.

7. The method of claim 6, wherein the functionalized polymer separator membrane comprises a functionalized polyaramid separator membrane.

8. The method according to claim 7, wherein the solution comprises at least one of sulfuric acid, chlorosulfonic acid or aminosulfonic acid or a combination thereof; and the method further comprises: Diluted LiOH or lithium sulfate is contacted with the functionalized polyaramid separator membrane to form a workpiece, and then the functionalized polyaramid separator membrane is rinsed with the deionized water.

9. The method according to claim 7, wherein the solution comprises a nitrating solution; thereby forming a nitrated polyaramid separator membrane; and second, placing the nitrated polyaramid separator film in a reducing bath to form a reduced workpiece; third, contacting the reduced workpiece with deionized water; and Fourth, the reduced workpiece is dried in an oven to completely remove the adsorbed water, thereby forming a nitrated polyaramid separator membrane.

10. The method according to claim 7, wherein the nitrating solution comprises a mixture of nitric acid (HNO3) and sulfuric acid (H2SO4); and The reducing bath comprises sodium dithionite NaS2O4.

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