Polyacrylamide-containing polymer electrolyte and method for producing the same

Abstract

The present invention relates to a polymer electrolyte comprising a polymer backbone derived from acrylamide monomers and a bis-acrylamide crosslinker that effectively encapsulates deep eutectic solvents (DES) and is compatible with high potential electrodes. The present invention further relates to composite cathodes and electrochemical cells comprising the polymer electrolyte, and their uses.

Description

[Technical Field]

[0001] The present invention relates to polymer electrolytes comprising polymer networks with a polyacrylamide backbone, which are particularly suitable for use with electrolyte compositions comprising deep eutectic solvents. The present invention also relates to methods for making such polymer electrolytes, as well as to the use of such polymer electrolytes in electrochemical cells and the like. [Background technology]

[0002] In recent years, electronic products, electronic devices, and communication devices have rapidly become smaller and lighter. Similarly, electric vehicles, which have emerged as an environmentally friendly means of transportation, have become widely used. These factors have led to a demand for higher performance in secondary batteries used as power sources for these products. Furthermore, lithium secondary batteries have attracted attention as high-performance batteries due to their high energy density and high reference electrode potential.

[0003] Conventional lithium secondary batteries contain liquid electrolytes, such as organic solvents. A significant drawback of liquid electrolytes is that the compositions, particularly the solvents, are flammable, posing a significant safety risk during normal operation, especially in the event of an accident. Another drawback, inherent to the liquid nature of the electrolyte, is the increased risk of leakage and environmental contamination in the event of a spill or leak.

[0004] In recent years, efforts have been made to develop solid-state electrolytes that can provide solid-state lithium-ion batteries. Such solid-state batteries have significantly reduced EHS (environment, health, and safety) hazards. Conventional solid electrolytes can include oxide-based solid electrolytes, polymer-based solid electrolytes, and sulfide-based electrolytes. Polymer-based electrolytes are commonly used due to their low flammability, high flexibility, excellent thermal stability, and safety.

[0005] The difficulty in developing solid electrolytes with high ionic conductivity, wide electrochemical window, and mechanical / thermal stability has led to the concept of solid-liquid composite materials such as solid composite electrolytes (SCEs). These electrolytes include liquid lithium-ion conducting electrolytes encapsulated within a solid framework or network. Examples include ionic liquids confined within inorganic (e.g., silica) or polymer (e.g., poly(ethylene glycol) diacrylate (PEODA)) solid frameworks.

[0006] A major challenge in the fabrication of solid composite electrolytes is the selection of a polymer backbone that is stable to sol-gel synthesis and can effectively encapsulate the liquid lithium-ion electrolyte. Furthermore, it is difficult to develop a solid composite electrolyte that is compatible with high-potential cathode materials such as NMC622 or NMC811 and exhibits satisfactory anode stability. For example, the most common solid polymer electrolyte, PEO (polyethylene oxide), is poorly resistant to Li + It has anodic stability limited to a potential of about 4.0 V vs. Li.

[0007] Energy Environ. Sci., 2021, 14, 931-939 contemplates the use of alkali metal bis(trifluoromethane)-sulfonimide (TFSI) salts in polymer electrolytes containing an N-isopropylacrylamide (NIPAM) polymer backbone.

[0008] Chem. Mater. 2020, 32, 3783-3793 proposes the use of lithium bis(trifluoromethane)-sulfonimide lithium salt (LiTFSI) and N-methylacetamide (MAc) based deep eutectic solvent in a polymer electrolyte containing an ethylene glycol 4-acryloylmorpholine (AcMo) backbone.

[0009] U.S. Patent Application Publication No. 2020 / 0343586(A1) contemplates the use of various deep eutectic solvents in polymer electrolytes containing various polymer backbones, including a polymer electrolyte containing lithium bis(trifluoromethane)-sulfonimide lithium salt (LiTFSI) and N-methylacetamide (MAc)-based deep eutectic solvent in a polymer network containing an acrylate backbone.

[0010] It is an object of the present invention to provide a polymer electrolyte comprising a polymer network that is compatible with deep eutectic solvents.

[0011] It is a further object of the present invention to provide a polymer electrolyte that is compatible with high voltage cathode active materials, particularly NMC622.

[0012] It is a further object of the present invention to provide a polymer electrolyte having high anodic stability.

[0013] A further object of the present invention is to provide a polymer electrolyte having good mechanical flexibility. Summary of the Invention

[0014] The inventors have discovered that polymer electrolytes comprising polymer networks with specific acrylamide monomers and bisacrylamide crosslinkers effectively encapsulate deep eutectic solvents (DES) and are surprisingly compatible with the high-potential electrodes described herein. As shown in the accompanying examples, the polymer electrolytes described herein have excellent cycling stability when combined with high-potential electrodes such as NMC622, and have been found to outperform polymer electrolytes based on the same monomers but using bisacrylate crosslinkers. Furthermore, the inventors have discovered that the polymer electrolyte can be conveniently pre-synthesized, but can also be synthesized in the presence of the cathode active material, thereby providing the cathode material. One or more of the objects of the present invention are achieved by different aspects of the invention described herein.

[0015] Thus, in a first aspect of the present invention, there is provided a polymer electrolyte comprising an electrolyte composition and a polymer network, wherein the electrolyte composition preferably comprises a deep eutectic solvent (DES), and the polymer electrolyte is obtained by polymerizing a precursor composition comprising the electrolyte composition, a first monomer according to formula (I) and a crosslinker according to formula (II), [ka] [ka] [In the formula, R 1 is selected from C1-C6 hydroxyalkyl; R 2 is selected from H, methyl, or ethyl; n is an integer ranging from 0 to 5, R 3 and R 4 are each independently selected from H, methyl, or ethyl; R 5 and R 6 are each independently selected from H or methyl; X is an alkanediyl or polyoxyalkylene, preferably X is (—CH—) o or -CH2-CH2(-O-CH2-CH2) p - and o is an integer ranging from 1 to 10; and p is an integer in the range of 1 to 200], a polymer electrolyte is provided.

[0016] In a preferred embodiment of the present invention, the first crosslinking agent is contained in the precursor composition in an amount such that the molar ratio of the total amount of the first monomers contained in the precursor composition to the total amount of the first crosslinking agent contained in the precursor composition is within a range of 99.5:0.5 to 80:20, preferably within a range of 98:2 to 80:20, and more preferably within a range of 95:5 to 85:15.

[0017] In another aspect, the present invention provides a method for preparing the polymer electrolyte of the present invention, comprising the steps of: (a) providing a precursor composition comprising an electrolyte composition and a first monomer according to formula (I) described herein, wherein the electrolyte composition preferably comprises a deep eutectic solvent (DES); (b) polymerizing the precursor composition.

[0018] In another aspect, the present invention provides a composite cathode comprising the polymer electrolyte of the present invention.

[0019] In another aspect, the present invention provides an electrochemical cell comprising a polymer electrolyte according to the present invention.

[0020] In another aspect of the present invention there is provided the use of a polymer electrolyte according to the present invention as an electrolyte for an electrochemical cell.

[0021] In another aspect of the present invention, there is provided a battery, more particularly a lithium ion battery or a lithium metal battery, comprising at least one electrochemical cell comprising the polymer electrolyte described herein, e.g., two or more electrochemical cells according to the present invention.

[0022] In another aspect of the present invention, there is provided a method of manufacturing or operating stationary applications such as cars, computers, personal digital assistants, cell phones, watches, camcorders, digital cameras, thermometers, calculators, laptop BIOS, communications equipment, remote car locks, and energy storage devices for power plants by using at least one battery or at least one electrochemical cell comprising the polymer electrolyte material described herein.

[0023] Another aspect of the present invention provides the use of an electrochemical cell comprising a polymer electrolyte of the present invention in a motorized vehicle, a bicycle powered by an electric motor, a robot, an aircraft (e.g., an unmanned aerial vehicle including a drone), a ship, a satellite, or a stationary energy store. [Brief explanation of the drawings]

[0024] [Figure 1] 1 shows EIS characterization of a symmetric cell containing an NMC622 electrode and the polymer electrolyte of Comparative Example 1. [Figure 2] 1 shows EIS characterization of a symmetric cell containing an NMC622 electrode and the polymer electrolyte of Example 1. [Figure 3] 1 shows the cycling capacity of cells containing NMC622 and Li electrodes along with Comparative Example and Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0025] In the following detailed description, preferred embodiments are described in detail to enable the practice of the present invention. While the present invention is described with reference to these particular preferred embodiments, it will be understood that the present invention is not limited to these preferred embodiments. To the contrary, however, the present invention encompasses numerous alternatives, modifications, and equivalents, as will become apparent from a consideration of the following detailed description.

[0026] As used herein, the expression "comprise" and its variations, such as "comprises" and "comprising," should be interpreted in an open and inclusive sense, meaning that the described embodiments include the recited features, but do not exclude the presence of other features unless doing so would render the embodiment inoperable.

[0027] As used herein, the phrases "one embodiment," "a particular embodiment," "an embodiment," and the like should be interpreted to mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Thus, the appearances of such phrases in various places throughout this specification do not necessarily all refer to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. For example, particular features of the present disclosure that are described in this specification in the context of separate embodiments are also expressly contemplated as being combined in a single embodiment.

[0028] As used herein, the singular forms "a," "an," and "the" should be construed to include plural referents unless the content clearly dictates otherwise. It should also be noted that the term "or" is generally used in its broadest sense, i.e., meaning "and / or," unless the content clearly dictates otherwise.

[0029] As used herein, the expression "cathode active material" is also interchangeably referred to as "positive electrode active material." As will be understood by those skilled in the art, cathode polarity can be positive or negative depending on the operating mode of the electrochemical cell containing the cathode active material. As used herein and in the claims, the term "cathode active material" or "positive electrode active material" is defined as a material that is electrochemically active in a positive electrode or cathode. An active material is understood to be a material that can capture and release Li-ions when exposed to a voltage change over a period of time.

[0030] As used herein, the expression "(meth)acrylamide" should be interpreted as "methacrylamide, acrylamide, or a combination thereof." For example, N-dialkyl(meth)acrylamide should be interpreted as "N-dialkylmethacrylamide, N-dialkylacrylamide, or a combination thereof."

[0031] The parameters x, y, z, and a referred to herein in the context of the composition of the cathode active material are measured by inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0032] Ionic conductivity referred to herein refers to the ionic conductivity determined by electrochemical impedance spectroscopy (EIS) (using a Biologic SP-300) of the polymer electrolyte in a symmetrical stainless steel|electrolyte|stainless steel Swagelok-type cell at a specific temperature by perturbing the open circuit potential with an AC sinusoidal potential of 10 mV amplitude in the frequency range of 10 kHz to 100 mHz.

[0033] The "anodic stability limit" referred to herein is determined by linear sweep voltammetry (preferably using a Bio-Logic SP-300) of a polymer electrolyte sandwiched between a stainless steel working electrode and lithium metal reference and counter electrodes in a coin cell setup, with the working electrode voltage exceeding 10 mV s. -1 At a scan rate of , the anodic scan is performed from the open circuit potential to Li+ The potential was swept up to 6 V vs. / Li. The stability limit was determined as the onset of electrolyte oxidation, which can be observed by a sudden increase in the measured current.

[0034] The polymer electrolyte of the present invention In a first aspect of the present invention, there is provided a polymer electrolyte comprising an electrolyte composition and a polymer network, wherein the electrolyte composition preferably comprises a deep eutectic solvent (DES), and the polymer electrolyte is obtained by polymerizing a precursor composition comprising the electrolyte composition, a first monomer according to formula (I) and a first crosslinker according to formula (II), [ka] [ka] [In the formula, R 1 is selected from C1-C6 hydroxyalkyl; R 2 is selected from H, methyl, or ethyl; n is an integer ranging from 0 to 5, R 3 and R 4 are each independently selected from H, methyl, or ethyl; R 5 and R 6 are each independently selected from H or methyl; X is an alkanediyl or polyoxyalkylene, preferably X is (—CH—) o or -CH2-CH2(-O-CH2-CH2) p - and o is an integer in the range of 1 to 10; and p is an integer in the range of 1 to 200], a polymer electrolyte is provided.

[0035] The polymer network referred to in this disclosure is a three-dimensional network obtained by polymerization of one or more monomers according to formula (I) in the presence of a crosslinker according to formula (II). Such three-dimensional polymer networks are also called gels, and the polymer electrolytes of the present invention are also called "gel polymer electrolytes." For the purposes of this disclosure, a gel polymer refers to a polymer network (i.e., a three-dimensional crosslinked system) that does not exhibit flow when in a steady state but allows the diffusion of a liquid phase through the polymer network. Preferably, the gel is self-supporting. Such gels typically exhibit a combination of flexibility, mechanical robustness, low vapor pressure, and preferably non-flammability.

[0036] As one skilled in the art will understand based on this disclosure, the electrolyte composition is contained within a polymer network. The electrolyte composition is typically confined within the polymer network, meaning that substantially no electrolyte composition spontaneously flows from the polymer electrolyte of the present invention when placed on a surface (e.g., a ceramic lab bench) without the application of external pressure. In all aspects of the present invention, it is highly preferred that the electrolyte composition, absent the polymer network, is a liquid at 20°C.

[0037] In a preferred embodiment, R 1 is selected from C1-C6 hydroxyalkyl, preferably R 1 In a more preferred embodiment, the polymer electrolyte of the present invention is provided, wherein R is selected from C1 to C3 hydroxyalkyl, more preferably selected from C1 to C2 hydroxyalkyl. 1 is selected from C1-C6 hydroxyalkyl containing one or two hydroxyl functional groups, preferably R 1 is selected from C1-C3 hydroxyalkyl containing one or two hydroxyl functional groups, more preferably selected from C1-C2 hydroxyalkyl containing one or two hydroxyl functional groups. 1 contains one hydroxyl functional group. Most preferably, R 1 is 2-hydroxyethyl.

[0038] In a preferred embodiment, R 2 is selected from H or methyl, most preferably H.

[0039] In a preferred embodiment, there is provided a polymer electrolyte of the present invention, wherein n is an integer in the range of 0 to 5, more preferably in the range of 0 to 3, more preferably in the range of 0 to 2, and in a highly preferred embodiment, n is equal to 0.

[0040] Therefore, according to a highly preferred embodiment of the present invention: ·R 1 is selected from C1-C6 hydroxyalkyl containing one or two hydroxyl functional groups, preferably R 1 is selected from C1-C3 hydroxyalkyl containing one or two hydroxyl functional groups, more preferably selected from C1-C2 hydroxyalkyl containing one or two hydroxyl functional groups, most preferably R 1 is 2-hydroxyethyl, ·R 2 is selected from H or methyl, most preferably H, and n is an integer in the range of 0 to 5, more preferably in the range of 0 to 3, more preferably in the range of 0 to 2, and most preferably n is equal to 0. From the above, it will be understood by those skilled in the art that the first monomer according to formula (I) is preferably selected from N-(2-hydroxyethyl)acrylamide, N-(2-hydroxyethyl)methacrylamide, and combinations thereof, and most preferably N-(2-hydroxyethyl)acrylamide.

[0041] In preferred embodiments of the invention, the first monomer constitutes at least 80 mol%, preferably at least 90 mol%, and more preferably at least 95 mol% of all monomers in the precursor composition. In highly preferred embodiments of the invention, the first monomer constitutes at least 98 mol%, 99 mol%, or about 100 mol% of all monomers in the composition. For purposes of determining the total amount of monomers in the precursor composition, any compound polymerizable with the first monomer and having a functionality of 1 is considered a monomer, with the functionality being determined based on the acrylamide functionality and the free-radically polymerizable functionality of the first monomer.

[0042] Crosslinking agent According to the present invention, the precursor composition further comprises a first crosslinker according to formula (II) described herein. Because the first monomer (acrylamide according to formula (I)) is monofunctional, the inclusion of a crosslinker in the precursor composition allows for the formation of a three-dimensional polymer network. As shown in the accompanying examples, the use of a crosslinker according to formula (II) has been found to result in significantly improved cycling stability of the polymer network of the present invention compared to when a bisacrylate crosslinker is used.

[0043] In a preferred embodiment of the present invention, R 3 and R 4 are each independently selected from H or methyl, preferably H. In a highly preferred embodiment of the present invention, R 3 and R 4 are the same and are selected from H or methyl, most preferably R 3 and R 4 are both H.

[0044] In a preferred embodiment of the present invention, R 5 and R 6 are each independently selected from H or methyl. In a preferred embodiment, R 5 and R 6 are the same and are selected from H or methyl, most preferably R 5 and R 6are both H.

[0045] As will be appreciated by those skilled in the art, X may be -CH2-CH2(-O-CH2-CH2) p -, the compound of formula (II) is in fact provided in the form of a mixture of compounds with different degrees of ethoxylation and therefore different numbers of p. The precursor composition comprises one or more crosslinkers according to formula (II), where X is -CH2-CH2(-O-CH2-CH2). p -, it is preferred that the number average p determined over all compounds of formula (II) in the precursor composition is in the range of 1 to 200, preferably in the range of 2 to 20.

[0046] In a preferred embodiment of the present invention, X is (—CH—) o wherein o is in the range of 1 to 10, preferably in the range of 1 to 5, and more preferably o is equal to 1. In other words, it is highly preferred that X is methanediyl.

[0047] Therefore, as will be appreciated by those skilled in the art based on the above, in a preferred embodiment of the present invention: ·R 3 and R 4 are each independently selected from H or methyl, preferably H; ·R 5 and R 6 are each independently selected from H or methyl; X is (-CH2-) o wherein o is in the range of 1 to 10, preferably in the range of 1 to 5, and more preferably o is equal to 1. Therefore, in a preferred embodiment of the present invention, ·R 1 is selected from C1-C6 hydroxyalkyl, wherein C1-C6 hydroxyalkyl contains one or two hydroxyl functional groups, preferably R 1is selected from C1-C3 hydroxyalkyl, wherein C1-C3 hydroxyalkyl contains one or two hydroxyl functional groups, more preferably C1-C2 hydroxyalkyl, wherein C1-C2 hydroxyalkyl contains one or two hydroxyl functional groups, most preferably R 1 is 2-hydroxyethyl, ·R 2 is selected from H or methyl, most preferably H; n is an integer in the range of 0 to 5, more preferably in the range of 0 to 3, more preferably in the range of 0 to 2, and most preferably n is equal to 0, ·R 3 and R 4 are each independently selected from H or methyl, preferably H; ·R 5 and R 6 are each independently selected from H or methyl; X is (-CH2-) o wherein o is in the range of 1 to 10, preferably in the range of 1 to 5, and more preferably o is equal to 1.

[0048] The precursor composition may further comprise a second crosslinker different from the first crosslinker, which may be selected from any crosslinker polymerizable with the first monomer and having a functionality of 2 or greater, the functionality being determined based on the acrylamide functionality and the free-radically polymerizable functionality of the first monomer. The second crosslinker different from the first crosslinker may be selected from allyl (-CH3-CH=CH2), oxiranyl (-C2H3O), glycidyl (-CH2-C2H3O), vinyl ether (-O-CH=CH2), vinyl ester (-C(O)-O-CH=CH2), vinylamide (-C(O)-NH-CH=CH2), vinylamine (-NH-CH=CH2), norbornene, maleate, fumarate, itaconate, alkynyl [ka] It is preferably selected from crosslinkers containing two or more functional groups selected from the group consisting of styrene (-Ph-CH=CH2), acrylamide (-NH-C(O)-CH=CH2), methacrylamide (-NH-C(O)-C(CH3)=CH2), acrylate (-OC(O)-CH=CH2), methacrylate (-OC(O)-C(CH3)=CH2), and combinations thereof, and more preferably selected from crosslinkers containing two or more functional groups selected from acrylamide (-NH-C(O)-CH=CH2), methacrylamide (-NH-C(O)-C(CH3)=CH2), acrylate (-OC(O)-CH=CH2), methacrylate (-OC(O)-C(CH3)=CH2), and combinations thereof. In some embodiments of the present invention, the second crosslinker comprises two, three, or four functional groups selected from the functional groups set forth in the preceding sentence, although it is preferred that the second crosslinker comprise two of the same or different functional groups selected from the functional groups set forth in the preceding sentence.

[0049] Generally, it is preferred that the average functionality determined across all crosslinkers in the precursor composition be in the range of 2 to 3, preferably in the range of 2 to 2.5, and most preferably in the range of 2 to 2.2. For purposes of determining this average functionality, any compound polymerizable with the first monomer and having a functionality of 2 or greater is considered a crosslinker, with functionality determined based on the acrylamide functionality and the free-radically polymerizable functionality of the first monomer.

[0050] In a preferred embodiment of the present invention, the first crosslinker constitutes at least 80 wt. % of all crosslinkers in the precursor composition (based on the total weight of all crosslinkers contained in the precursor composition), preferably at least 90 wt. % (based on the total weight of all crosslinkers contained in the precursor composition), and more preferably at least 95 wt. % (based on the total weight of all crosslinkers contained in the precursor composition). In a highly preferred embodiment of the present invention, the first crosslinker is the only crosslinker present in the precursor composition. Any compound polymerizable with the first monomer and having a functionality of 2 or greater is considered a crosslinker, with the functionality being determined based on the acrylamide functionality and the free-radically polymerizable functionality of the first monomer.

[0051] As will be appreciated by those skilled in the art, the amount of crosslinker used in the precursor composition affects the mechanical and electrochemical properties of the resulting polymer electrolyte. In a preferred embodiment of the present invention, the first crosslinker is included in the precursor composition in an amount such that the molar ratio of the total amount of first monomers included in the precursor composition to the total amount of first crosslinker included in the precursor composition is within the range of 99.5:0.5 to 80:20, preferably 98:2 to 80:20, and more preferably 95:5 to 85:15. When the precursor composition includes additional crosslinkers other than the first crosslinker, the total amount of crosslinkers in the precursor composition is preferably within the range of 99.5:0.5 to 80:20, preferably 98:2 to 80:20, and more preferably 95:5 to 85:15. For purposes of determining the total amount of crosslinker, any compound polymerizable with the first monomer and having a functionality of 2 or greater is considered a crosslinker, with the functionality being determined based on the acrylamide functionality and free-radically polymerizable functional groups of the first monomer. As previously described, it is highly preferred that the first crosslinker be the predominant crosslinker (80% by weight or more of all crosslinkers previously described herein) or the only crosslinker present in the precursor composition.

[0052] According to a preferred embodiment of the present invention, the precursor composition further comprises one or more radical initiators, preferably one or more radical initiators selected from thermal initiators, photoinitiators, and combinations thereof.

[0053] Suitable radical thermal initiators include benzoyl peroxide, dibenzoyl peroxide, succinic acid peroxide, dilauroyl peroxide, didecanoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, di-t-amyl peroxide, α,α'-di(t-butylperoxy)diisopropyl-benzene, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di-( t-Butylperoxy)hexyne-3, t-butylcumyl peroxide, α-cumylperoxyneodecanoate, α-cumylperoxyneopheptanoate, t-amylperoxyneodecanoate, t-butylperoxyneodecanoate, di-(2-ethylhexyl)peroxydicarbonate, t-amylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2 ,5-bis(2-ethyl-hexanoylperoxy)hexane, dibenzoyl peroxide, t-amylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, 1,1-di-(t-amylperoxy)cyclohexane, 1,1-di-(t-butylperoxy)3,3,5-trimethylcyclohexane, 1,1-di-(t-butylperoxy)cyclohexane, OO-t-amyl-O(2-ethylhexanoylperoxy)hexane sil) monoperoxycarbonate, OO-t-butyl O-isopropyl monoperoxycarbonate, OO-t-butyl O-(2-ethylhexyl) monoperoxycarbonate, t-amyl peroxybenzoate, t-butyl peroxyacetate, t-butyl peroxybenzoate, ethyl 3,3-di-(t-amylperoxy)butyrate, ethyl 3,3-di-(t-butylperoxy)butyrate, dicumyl peroxide;and azo compounds such as 4,4'-azobis(4-cyanovaleric acid), 1,1'-azobis(cyclohexanecarbonitrile), azobisisobutyronitrile (AIBN), and 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis[2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane disulfate dihydrate, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate Examples of suitable azobis include, but are not limited to, 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane}dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis(1-imino-1-pyrrolidino-2-ethylpropane)dihydrochloride, 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], cumene hydroperoxide, and ammonium persulfate;

[0054] Suitable radical photoinitiators include benzophenone (e.g., "IRGACURE 500"), 3-methylbenzophenone, 2-methylbenzophenone, 3,4-dimethylbenzophenone, 3-hydroxybenzophenone, 4-hydroxybenzophenone, 4,4'-dihydroxybenzophenone, 4-benzoylbenzoic acid, 2-benzoylbenzoic acid, methyl 2-benzoylbenzoate, 4,4'-carbonyldiphthalic anhydride, methyl benzoyl formate (e.g., "DAROCUR MBF"), 1-hydroxy-cyclohexyl-phenyl-ketone (e.g., "IRGACURE 184"), 2-hydroxy-2-methyl-1-phenyl-1-propanone (e.g., "DAROCUR 1173"), 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone (e.g., "IRGACURE 1173"). 2959"), oxy-phenyl-acetic acid 2-[2oxo-2phenyl-acetoxy-ethoxy]-ethyl ester and oxy-phenyl-acetic acid 2-[2-hydroxy-ethoxy]-ethyl ester (e.g., "IRGACURE 754"), α,α-dimethoxy-α-phenylacetophenone (also known as 2,2-dimethoxy-2-phenyl-acetophenone (DMPA), e.g., "IRGACURE 651"), 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone (e.g., "IRGACURE 369"), 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone (e.g., "IRGACURE 907"), diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide (e.g., "DAROCURE 754"). TPO), phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl) (e.g., IRGACURE 819), bis(η5-2,4-cyclopentadien-1-yl)bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]titanium (e.g., "IRGACURE 784"), 1-hydroxy-cyclohexyl-phenyl-ketone (e.g., ("IRGACURE 184"), 2-hydroxy-2-methyl-1-phenyl-1-propanone (e.g., "DAROCUR 1173"), 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one (e.g., "IRGACURE 127"), 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone (e.g., "IRGACURE 127"). 2959"), phenyl glyoxylate, oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester, oxy-phenyl-acetic acid 2-[2-hydroxy-ethoxy]-ethyl ester, phenyl glyoxylic acid methyl ester (e.g., "DAROCUR MBF"), 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (e.g., "LUCIRIN TPO"), 2,4,6-trimethylbenzoyl-diphenylphosphinate (e.g., "LUCIRIN TPO-L"), liquid blends of acylphosphine oxides (e.g., "IRGACURE 2100"), bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (e.g., "IRGACURE 819"), titanocene, bis(η5-2,4-cyclopentadien-1-yl)bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl] (e.g., "IRGACURE 784"), [1-(4-phenylsulfanylbenzoyl)heptylideneamino]benzoate (e.g., "IRGACURE OXE 01"), [1-[9-ethyl-6-(2-methylbenzoyl)carbazol-3-yl]ethylideneamino]acetate (e.g., "IRGACURE OXE 02"), 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (e.g., "IRGACURE 907"), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (e.g., "IRGACURE 907"). 369"), 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one (e.g., "IRGACURE 379"), benzil dimethyl ketal, 2,2-dimethoxy-1,2-diphenylethan-1-one (e.g., "IRGACURE 651"), camphorquinone, acetophenone, 4'-hydroxyacetophenone, 3'-hydroxyacetophenone, 4-(dimethylamino)-benzophenone, 4,4'-bis(dimethylamino)-benzophenone, 4,4'-bis(diethylamino)-benzophenone, 4,4'-dichlorobenzophenone, 4-phenylbenzophenone, 1,4-dibenzoylbenzene, 4-(p-tolylthio)-benzophenone, dibenzosuberenone, benzyl, p-anisyl, methylbenzoylformate, 9,10-phenanthrenequinone, 2-benzoyl- 2-Propanol, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 1-benzoylcyclohexanol, benzoin, anisoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-diethoxyacetophenone, benzil dimethyl ketal, 2-methyl-4'-(methylthio)-2-morpholinopropiophenone, 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone, 2-isonitrosopropiophenone, 9,Examples of suitable thiol compounds include, but are not limited to, 10-phenanthrenequinone, 2-ethylanthraquinone, sodium anthraquinone-2-sulfonate, 2-chlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2-isopropylthioxanthone, 2,4-diethylthioxanthen-9-one, 2,7-dimethyloxythioxanthone, 2,2'-bis(2-chlorophenyl)4,4',5,5'-tetraphenyl-1,2'-biimidazole, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, lithium phenyl-(2,4,6-trimethylbenzoyl)phosphinate, and ferrocene.

[0055] In some embodiments of the present invention, the precursor composition further comprises one or more radical initiators selected from 2,2-dimethoxy-2-phenyl-acetophenone (DMPA), azobisisobutyronitrile (AIBN), and combinations thereof.

[0056] The one or more radical initiators are preferably used in an amount such that the molar ratio of the total amount of the first monomer contained in the precursor composition to the total amount of the one or more radical initiators contained in the precursor composition is within a range of 99.8:0.2 to 80:20, preferably within a range of 99:1 to 85:15, and more preferably within a range of 98:2 to 90:10.

[0057] electrolyte composition As will be understood by those skilled in the art, to obtain a gel-type polymer electrolyte, the polymer is preferably synthesized in the presence of the electrolyte composition, thereby effectively encapsulating the electrolyte composition within the polymer network. However, without being bound by any theory, other methods of obtaining a polymer electrolyte other than those described herein may be possible, such as exchanging another liquid composition (e.g., a solvent) encapsulated in the polymer for the electrolyte composition, absorbing the electrolyte composition into a preformed polymer network, or injecting the electrolyte composition into a preformed polymer network. Thus, according to the present invention, a polymer electrolyte can be obtained by polymerizing a precursor composition containing the polymer electrolyte and other components discussed throughout this disclosure (e.g., monomers, crosslinkers, initiators, etc.). In all aspects of the present invention, it is highly preferred that the electrolyte composition, absent the polymer network, be liquid at 20°C.

[0058] As shown in the accompanying examples, the inventors have discovered that deep eutectic solvent (DES)-filled polymer electrolytes exhibit exceptional performance, particularly in combination with high potential cathode active materials such as NMC622. Thus, in accordance with highly preferred embodiments of the present invention, the electrolyte composition comprises or consists of a deep eutectic solvent (DES). The deep eutectic solvent is preferably liquid at 20°C.

[0059] Various relative amounts of DES to polymer have been found to result in functional electrolyte materials. The precursor composition preferably comprises about 45-95% by volume (based on the total volume of the precursor composition), preferably about 55-90% by volume, and more preferably about 70-90% by volume of deep eutectic solvent (DES). Precursor compositions having about 85% by volume of DES have been found to provide excellent ionic conductivity and mechanical properties (increased flexibility). Thus, in highly preferred embodiments of the present invention, the precursor composition comprises about 75-90% by volume (based on the total volume of the precursor composition), preferably about 80-90% by volume, and most preferably about 83-87% by volume of deep eutectic solvent (DES). The remainder of the precursor composition consists of a first monomer, optionally additional monomers, a first crosslinker, optionally additional crosslinkers, one or more radical initiators, and optional additional components. In some embodiments, the remainder of the precursor composition consists essentially of a first monomer, optionally additional monomers, a first crosslinker, optionally additional crosslinkers, and one or more radical initiators.

[0060] Deep eutectic solvents (DES) preferably have a eutectic point of 25° C. or less, preferably a eutectic point of 15° C. or less, more preferably 0° C. or less. In a highly preferred embodiment of the present invention, the deep eutectic solvent (DES) has a eutectic point of −15° C. or less, most preferably −25° C. or less, allowing the DES to remain in a liquid state over the typical operating temperature window of electrochemical cells for typical applications such as automobiles. The eutectic points referred to herein are determined at a pressure of about 101 kPa.

[0061] The deep eutectic solvent (DES) preferably comprises at least one hydrogen bond acceptor and at least one hydrogen bond donor. The molar ratio of hydrogen bond acceptor to hydrogen bond donor is preferably at least 1:1, more preferably at least 1:2, and more preferably at least 1:3. In a preferred embodiment of the present invention, the electrolyte composition comprises or consists of (preferably consists of) a deep eutectic solvent (DES) comprising at least one hydrogen bond acceptor and at least one hydrogen bond donor, and the molar ratio of hydrogen bond acceptor to hydrogen bond donor is in the range of 1:1 to 1:8, preferably in the range of 1:2 to 1:6, and more preferably in the range of 1:3 to 1:5. A highly preferred molar ratio of hydrogen bond acceptor to hydrogen bond donor (particularly when the hydrogen bond acceptor is lithium bis(trifluoromethanesulfonyl)imide, as described elsewhere herein, and / or when the hydrogen bond donor is N-methylacetamide, as described elsewhere herein) is in the range of 1:3.5 to 1:4.5, e.g., about 1:4.

[0062] In a preferred embodiment of the present invention, the hydrogen bond acceptor comprises a lithium salt, a zinc salt, or a combination thereof, preferably a lithium salt. In a more preferred embodiment, the hydrogen bond acceptor is selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiOTf), lithium chloride (LiCl), lithium hexafluorophosphate (LiPF), lithium polysulfide, lithium perchlorate (LiClO), lithium bromide (LiBr), lithium iodide (LiI), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF), lithium hexafluoroarsenate (LiAsF), lithium bis(oxalato)borate (LiBOB), lithium fluoroalkylphosphate (LFAP[LiPF(CFCF)]), and combinations thereof, preferably lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and / or the hydrogen bond donor is selected from the group consisting of urea, N-methylurea, N,N-dimethylurea, N,N'- Dimethylurea, N,N,N'-trimethylurea, thiourea, N-methylthiourea, N,N-dimethylthiourea, N,N'-dimethylthiourea, N,N,N'-trimethylthiourea, ethylene glycol, propane-1,2-diol, propane-1,3-diol, butane-1,4-diol, 1,2,3-propanetriol, acetic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecane The alkyl acrylate is selected from the group consisting of candiedioic acid, benzoic acid, glycolic acid, citric acid, 2-hydroxypropionic acid, 2-hydroxyisobutyric acid, o-phenylenediamine, choline chloride, acetamide, N-methylacetamide, trifluoroacetamide, N-methyltrifluoroacetamide, benzamide, benzenesulfonic acid, p-toluenesulfonic acid, o-toluenesulfonic acid, m-toluenesulfonic acid, and combinations thereof, preferably N-methylacetamide.

[0063] Thus, in some embodiments of the present invention, the electrolyte composition comprises a deep eutectic solvent (DES) comprising, preferably consisting of, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and N-methylacetamide, wherein the molar ratio of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to N-methylacetamide is in the range of 1:1 to 1:8, preferably in the range of 1:2 to 1:6, more preferably in the range of 1:3 to 1:5, e.g., about 1:4.

[0064] The electrolyte composition preferably comprises at least 90 wt. % (based on the total weight of the electrolyte composition), preferably at least 95 wt. %, and more preferably at least 99 wt. % DES. In some embodiments, the electrolyte composition comprises water, e.g., 0.1 to 30 wt. % (based on the total weight of the electrolyte composition) water, or 0.1 to 10 wt. % (based on the total weight of the electrolyte composition) water. In other preferred embodiments, the electrolyte composition comprises less than 5 wt. % water, preferably less than 0.1 wt. % water, and more preferably less than 0.01 wt. % water. In some embodiments, the electrolyte composition is substantially free of water. The latter is particularly preferred for use in combination with moisture-sensitive electrodes such as Li or graphite. In all embodiments described herein, the electrolyte composition preferably comprises a deep eutectic solvent (DES).

[0065] As will be understood by those skilled in the art, in the context of the present disclosure, a precursor composition consists essentially of the electrolyte composition described herein in combination with a first monomer, a first crosslinker, and one or more initiators described herein. Thus, according to preferred embodiments of the present invention, the precursor composition comprises at least 90 wt % (based on the total weight of the precursor composition), preferably at least 95 wt % (based on the total weight of the precursor composition), and more preferably at least 99 wt % (based on the total weight of the precursor composition) of the electrolyte composition, the first monomer, optionally additional monomers, the first crosslinker, optionally additional crosslinkers, and one or more radical initiators. In some embodiments, the precursor composition comprises at least 90 wt % (based on the total weight of the precursor composition), preferably at least 95 wt % (based on the total weight of the precursor composition), and more preferably at least 99 wt % (based on the total weight of the precursor composition) of the electrolyte composition, the first monomer, the first crosslinker, and one or more radical initiators. As previously described herein, any compound polymerizable with a first monomer and having a functionality of 1 is considered a monomer, and any compound polymerizable with a first monomer and having a functionality of 2 or greater is considered a crosslinker, with the functionality being determined based on the acrylamide functionality and the free-radically polymerizable functionality of the first monomer. Thus, according to preferred embodiments of the present invention, the polymer electrolyte comprises at least 90 wt. % (based on the total weight of the polymer electrolyte), more preferably at least 98 wt. % (based on the total weight of the polymer electrolyte), and most preferably at least 99 wt. % (based on the total weight of the polymer electrolyte) of the combined weight of the polymer network and the electrolyte composition. In some embodiments, the polymer electrolyte consists essentially of the polymer network and the electrolyte composition.

[0066] In a preferred embodiment of the present invention, at least Li + 4.6V vs. Li, preferably Li + A polymer electrolyte is provided having an anode stability limit of at least 4.7 V vs. / Li.

[0067] Method for preparing the polymer electrolyte of the present invention In another aspect, the present invention provides a method for preparing the polymer electrolyte of the present invention, comprising the steps of: (i) providing a precursor composition as described herein; (ii) polymerizing the precursor composition.

[0068] Embodiments described herein relating to polymer electrolytes apply mutatis mutandis to methods of preparing polymer electrolytes. For example, various embodiments relating to the identity and amounts of monomers, crosslinkers, initiators, and electrolyte compositions described herein in the context of polymer electrolytes are equally applicable to methods of preparing polymer electrolytes.

[0069] In a preferred embodiment of the method for preparing a polymer electrolyte, the precursor composition comprises one or more radical initiators, as described hereinbefore, and step (ii) comprises activating the radical initiators. Activation is preferably carried out by UV irradiation of the precursor composition or by heating the precursor composition to a temperature of at least 50° C., preferably at least 60° C. Step (ii) is preferably carried out under an inert gas atmosphere, preferably an inert atmosphere such as nitrogen or argon.

[0070] In some embodiments of the present invention, step (ii) comprises (ii)a contacting the precursor composition with a cathode active material and (ii)b polymerizing the precursor composition in the presence of the cathode active material. Step (ii) preferably comprises mixing the precursor composition with the cathode active material, which is preferably granular, or depositing the precursor composition on the surface of a porous cathode active material. The contacting is preferably carried out for at least 1 minute before polymerization to ensure complete mixing or impregnation. In this manner, a composite cathode comprising the polymer electrolyte of the present invention and the cathode active material can be obtained.

[0071] The cathode active material can be any cathode active material, preferably a cathode active material suitable for secondary lithium ion batteries.

[0072] As shown in the accompanying examples, the inventors have found that polymer electrolytes exhibit surprisingly good electrochemical performance when used in combination with high potential cathode active materials. Thus, the cathode active material is preferably Li + At least 4.3V vs. Li / , preferably Li + / Li, more preferably at least 4.4V + The cathode active material preferably comprises Li, M, and O, where M comprises Ni and one or both of Mn and Co, and preferably M is Ni with a content x, where 50.0 mol%≦x≦95.0 mol%, preferably 55.0 mol%≦x≦95.0 mol%, Mn with a content y, where 0.0 mol%≦y≦40.0 mol%; Co with a content z, where 0.0 mol%≦z≦40.0 mol%; and D having a content a, where a is 0.0 mol%≦a≦2.0 mol%, and D is at least one element other than Li, Ni, Mn, Co, and O; x+y+z+a is 100.0 mol%, More preferably, M is Ni with a content x, where 50.0 mol%≦x≦85.0 mol%; Mn with a content y, where 7.5 mol%≦y≦25.0 mol%; Co with a content z, where 7.5 mol%≦z≦25.0 mol%; and D having a content a, where a is 0.0 mol%≦a≦2.0 mol%, and D is at least one element other than Li, Ni, Mn, Co, and O; x+y+z+a is 100.0 mol%, More preferably, M is Ni with a content x, where 55.0 mol%≦x≦80.0 mol%; Mn with a content y, where 10.0 mol%≦y≦30.0 mol%; Co with a content z of 10.0 mol%≦z≦30.0 mol%; and D having a content a, where a is 0.0 mol%≦a≦2.0 mol%, and D is at least one element other than Li, Ni, Mn, Co, and O; x+y+z+a is 100.0 mol%, More preferably, M is Ni with a content x, where 55.0 mol%≦x≦75.0 mol%, Mn with a content y, where 12.5 mol%≦y≦22.5 mol%; Co with a content z, where 12.5 mol%≦z≦22.5 mol%; and D having a content a, where a is 0.0 mol%≦a≦2.0 mol%, and D is at least one element other than Li, Ni, Mn, Co, and O; x+y+z+a is 100.0 mol%, Most preferably, M is Ni with a content x, where 55.0 mol%≦x≦70.0 mol%; Mn with a content y, where 15.0 mol%≦y≦22.5 mol%; Co with a content z of 15.0 mol%≦z≦22.5 mol%; and D having a content a, where a is 0.0 mol%≦a≦2.0 mol%, and D is at least one element other than Li, Ni, Mn, Co, and O; x+y+z+a is 100.0 mol%.

[0073] As known to those skilled in the art, NMC cathode active materials can contain impurities or be doped or coated to result in an overall cathode active material that includes one or more elements other than Li, Ni, Mn, Co, and O, which is reflected in the parameter "D" used herein. In preferred embodiments of the present invention, D is an element selected from the group consisting of Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zr, and Zn; preferably, Al, B, Cr, Nb, S, Si, Ti, Y, Zr, and W; more preferably, B, Nb, Ti, Zr, and W.

[0074] Examples of suitable cathode active materials are NMC532, NMC622, NMC811, preferably NMC622 or NMC811, more preferably NMC622.

[0075] Composite cathodes containing the polymer electrolytes of the present invention In another aspect of the invention, there is provided a composite cathode comprising a polymer electrolyte described herein and a cathode active material described herein.

[0076] Embodiments described herein relating to polymer electrolytes apply mutatis mutandis to composite cathodes comprising polymer electrolytes. For example, various embodiments relating to the identity and amounts of monomers, crosslinkers, initiators, and electrolyte compositions described herein in the context of polymer electrolytes are equally applicable to methods of preparing polymer electrolytes.

[0077] The active cathode material included in the composite cathode can be any active cathode material, preferably a cathode active material suitable for secondary lithium-ion batteries.

[0078] As shown in the accompanying examples, the inventors have found that polymer electrolytes exhibit surprisingly good electrochemical performance when used in combination with high potential cathode active materials. Thus, the cathode active material is preferably Li + At least 4.3V vs. Li / , preferably Li + / Li, more preferably at least 4.4V + The cathode active material preferably comprises Li, M, and O, where M comprises Ni and one or both of Mn and Co, and preferably M is Ni with a content x, where 50.0 mol%≦x≦95.0 mol%, preferably 55.0 mol%≦x≦95.0 mol%, Mn with a content y, where 0.0 mol%≦y≦40.0 mol%; Co with a content z, where 0.0 mol%≦z≦40.0 mol%; and D having a content a, where a is 0.0 mol%≦a≦2.0 mol%, and D is at least one element other than Li, Ni, Mn, Co, and O; x+y+z+a is 100.0 mol%, More preferably, M is Ni with a content x, where 50.0 mol%≦x≦85.0 mol%; Mn with a content y, where 7.5 mol%≦y≦25.0 mol%; Co with a content z, where 7.5 mol%≦z≦25.0 mol%; and D having a content a, where a is 0.0 mol%≦a≦2.0 mol%, and D is at least one element other than Li, Ni, Mn, Co, and O; x+y+z+a is 100.0 mol%, More preferably, M is Ni with a content x, where 55.0 mol%≦x≦80.0 mol%; Mn with a content y, where 10.0 mol%≦y≦30.0 mol%; Co with a content z of 10.0 mol%≦z≦30.0 mol%; and D having a content a, where a is 0.0 mol%≦a≦2.0 mol%, and D is at least one element other than Li, Ni, Mn, Co, and O; x+y+z+a is 100.0 mol%, More preferably, M is Ni with a content x, where 55.0 mol%≦x≦75.0 mol%, Mn with a content y, where 12.5 mol%≦y≦22.5 mol%; Co with a content z, where 12.5 mol%≦z≦22.5 mol%; and D having a content a, where a is 0.0 mol%≦a≦2.0 mol%, and D is at least one element other than Li, Ni, Mn, Co, and O; x+y+z+a is 100.0 mol%, Most preferably, M is Ni with a content x, where 55.0 mol%≦x≦70.0 mol%; Mn with a content y, where 15.0 mol%≦y≦22.5 mol%; Co with a content z of 15.0 mol%≦z≦22.5 mol%; and D having a content a, where a is 0.0 mol%≦a≦2.0 mol%, and D is at least one element other than Li, Ni, Mn, Co, and O; x+y+z+a is 100.0 mol%.

[0079] As known to those skilled in the art, NMC cathode active materials can contain impurities or be doped or coated to result in an overall cathode active material that includes one or more elements other than Li, Ni, Mn, Co, and O, which is reflected in the parameter "D" used herein. In preferred embodiments of the present invention, D is an element selected from the group consisting of Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zr, and Zn; preferably, Al, B, Cr, Nb, S, Si, Ti, Y, Zr, and W; more preferably, B, Nb, Ti, Zr, and W.

[0080] Examples of suitable cathode active materials are NMC532, NMC622, NMC811, preferably NMC622 or NMC811, more preferably NMC622.

[0081] The composite cathode may comprise a homogeneous mixture of cathode particles and polymer electrolyte particles. Alternatively, the composite cathode may comprise a polymer electrolyte coated on and / or at least partially embedded in a cathode active material. Such a composite cathode may be obtained by the method for preparing a polymer electrolyte described hereinabove, in which step (ii) comprises contacting a (ii)a precursor composition with a cathode active material and polymerizing the (ii)b precursor composition in the presence of the cathode active material.

[0082] An optional but preferred additional component of the composite cathode material of the present invention is a conductive additive, particularly a carbon-based conductive additive. The carbon-based conductive additive may be any carbon-rich material, for example, any material containing at least 95% by weight of carbon, preferably at least 99% by weight of carbon. Examples of suitable materials are graphite, carbon black, carbon fiber, carbon nanotubes, graphene, and combinations thereof. Carbon black is known to those skilled in the art and includes variants such as acetylene black or Super C65.

[0083] In a preferred embodiment, the carbon-based conductive aid described herein is present in the solid composite cathode composition of the present invention in an amount of at least 0.5 wt% (based on the combined weight of the polymer electrolyte and the cathode active material), preferably at least 1 wt% (based on the combined weight of the polymer electrolyte and the cathode active material), and more preferably at least 3 wt% (based on the combined weight of the polymer electrolyte and the cathode active material). Typically, the carbon-based conductive aid is present in an amount of less than 12 wt% (based on the combined weight of the polymer electrolyte and the cathode active material), preferably less than 9 wt% (based on the combined weight of the polymer electrolyte and the cathode active material), and more preferably less than 7 wt% (based on the combined weight of the polymer electrolyte and the cathode active material).

[0084] In another aspect of the present invention, there is provided a composite cathode obtainable by the method for preparing a polymer electrolyte as described hereinabove, wherein step (ii) comprises contacting a (ii)a precursor composition with a cathode active material, and polymerizing the (ii)b precursor composition in the presence of the cathode active material.

[0085] The composite cathode material may be formulated into a cathode using techniques known to those skilled in the art. In particular, some embodiments of the present invention provide a cathode comprising the solid composite cathode material of the present invention combined with a binder, such as a polymer binder. The binder is not particularly limited and can be any suitable polymer binder, such as polyimide (PI), polyvinylidene chloride (PVdC), polyethylene oxide (PEO), polyvinylidene fluoride (PVdF), etc.

[0086] Electrochemical cells comprising the polymer electrolyte of the present invention In another aspect of the present invention, there is provided an electrochemical cell comprising the polymer electrolyte herein.

[0087] Embodiments described in this disclosure relating to polymer electrolytes apply mutatis mutandis to electrochemical cells comprising polymer electrolytes. For example, various embodiments relating to the identity and amounts of monomers, crosslinkers, initiators, and electrolyte compositions described herein in the context of polymer electrolytes are equally applicable to electrochemical cells comprising polymer electrolytes.

[0088] The electrochemical cell preferably includes an anode, a cathode, and an electrolyte.

[0089] The anode comprises an active anode material. Suitable electrochemically active anode materials are known in the art. For example, the anode can comprise graphitic carbon, metallic lithium, or a metal alloy containing lithium as the active anode material.

[0090] The cathode includes an active cathode material, which may be any active cathode material, preferably a cathode active material suitable for secondary lithium-ion batteries.

[0091] As shown in the accompanying examples, the inventors have found that polymer electrolytes exhibit surprisingly good electrochemical performance when used in combination with high potential cathode active materials. Thus, the cathode active material is preferably Li +At least 4.3V vs. Li / , preferably Li + / Li, more preferably at least 4.4V + The cathode active material preferably comprises Li, M, and O, where M comprises Ni and one or both of Mn and Co, and preferably M is Ni with a content x, where 50.0 mol%≦x≦95.0 mol%, preferably 55.0 mol%≦x≦95.0 mol%, Mn with a content y, where 0.0 mol%≦y≦40.0 mol%; Co with a content z, where 0.0 mol%≦z≦40.0 mol%; and D having a content a, where a is 0.0 mol%≦a≦2.0 mol%, and D is at least one element other than Li, Ni, Mn, Co, and O; x+y+z+a is 100.0 mol%, More preferably, M is Ni with a content x, where 50.0 mol%≦x≦85.0 mol%; Mn with a content y, where 7.5 mol%≦y≦25.0 mol%; Co with a content z, where 7.5 mol%≦z≦25.0 mol%; and D having a content a, where a is 0.0 mol%≦a≦2.0 mol%, and D is at least one element other than Li, Ni, Mn, Co, and O; x+y+z+a is 100.0 mol%, More preferably, M is Ni with a content x, where 55.0 mol%≦x≦75.0 mol%, Mn with a content y, where mol%≦y≦22.5 mol%; Co with a content z, where 12.5 mol%≦z≦22.5 mol%; and D having a content a, where a is 0.0 mol%≦a≦2.0 mol%, and D is at least one element other than Li, Ni, Mn, Co, and O; x+y+z+a is 100.0 mol%, Most preferably, M is Ni with a content x, where 55.0 mol%≦x≦70.0 mol%; Mn with a content y, where 15.0 mol%≦y≦22.5 mol%; Co with a content z of 15.0 mol%≦z≦22.5 mol%; and D having a content a, where a is 0.0 mol%≦a≦2.0 mol%, and D is at least one element other than Li, Ni, Mn, Co, and O; x+y+z+a is 100.0 mol%.

[0092] As known to those skilled in the art, NMC cathode active materials can contain impurities or be doped or coated to result in an overall cathode active material that includes one or more elements other than Li, Ni, Mn, Co, and O, which is reflected in the parameter "D" used herein. In preferred embodiments of the present invention, D is an element selected from the group consisting of Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zr, and Zn; preferably, Al, B, Cr, Nb, S, Si, Ti, Y, Zr, and W; more preferably, B, Nb, Ti, Zr, and W. Examples of suitable cathode active materials are NMC532, NMC622, NMC811, preferably NMC622 or NMC811, more preferably NMC622.

[0093] An optional but preferred additional component of the cathode included in the electrochemical cell of the present invention is a conductive additive, particularly a carbon-based conductive additive. The carbon-based conductive additive may be any carbon-rich material, for example, any material containing at least 95% by weight of carbon, preferably at least 99% by weight of carbon. Examples of suitable materials are graphite, carbon black, carbon fiber, carbon nanotubes, graphene, and combinations thereof. Carbon black is known to those skilled in the art and includes variants such as acetylene black or Super C65.

[0094] In a preferred embodiment, the carbon-based conductive aid described herein is present in the cathode included in the electrochemical cell of the present invention in an amount of at least 0.5 wt. % (based on the total weight of the cathode), preferably at least 1 wt. % (based on the total weight of the cathode), and more preferably at least 3 wt. % (based on the total weight of the cathode). Typically, the carbon-based conductive aid is present in an amount of less than 12 wt. % (based on the total weight of the cathode), preferably less than 9 wt. % (based on the total weight of the cathode), and more preferably less than 7 wt. % (based on the total weight of the cathode).

[0095] In some embodiments of the present invention, the cathode included in the electrochemical cell of the present invention further comprises a binder, such as a polymer binder. The binder is not particularly limited and can be any suitable polymer binder, such as polyimide (PI), polyvinylidene chloride (PVdC), polyethylene oxide (PEO), polyvinylidene fluoride (PVdF), etc. In a preferred embodiment of the present invention, the electrochemical cell comprises a polymer electrolyte of the present invention disposed in contact with the cathode active material.

[0096] For example, an electrochemical cell can include a polymer electrolyte of the present invention disposed between and in contact with an anode and a cathode.

[0097] For example, an electrochemical cell can include a polymer electrolyte of the present invention in the form of a coating on the anode and / or cathode.

[0098] For example, an electrochemical cell may include the polymer electrolyte of the present invention in the form of a composite cathode as described hereinabove and an electrode active material. In such embodiments, the electrochemical cell preferably includes an additional electrolyte disposed between the composite cathode and the anode, which may be the polymer electrolyte of the present invention or another electrolyte.

[0099] The polymer electrolyte of the present invention having a gel-like consistency is considered a solid electrolyte for the purposes of this disclosure, which, as will be appreciated by those skilled in the art, can also function as a separator in an electrochemical cell.

[0100] The electrochemical cells described herein preferably have charge transport in a Li + The electrochemical cell is a lithium-ion-containing cell operated by ions. The electrochemical cell can have a disk-like or prismatic shape. The electrochemical cell can include a housing that can be made from steel or aluminum. Multiple electrochemical cells can be combined into an all-solid-state battery with both solid electrodes and a solid electrolyte.

[0101] In particularly preferred embodiments, the cathode active materials described herein are the only cathode active materials contained in the cathode of the electrochemical cell.

[0102] Method for manufacturing an electrochemical cell of the present invention In another aspect, the present invention provides a method for manufacturing an electrochemical cell, comprising: (a) providing a cathode; (b) providing an anode; (c) providing an electrolyte; (d) forming an electrochemical cell by assembling the cathode, the anode, and the polymer electrolyte into an electrochemical cell; The method of manufacture is provided wherein the electrolyte comprises a polymer electrolyte of the present invention and / or the cathode is provided in the form of a composite cathode comprising a cathode active material of the present invention and a polymer electrolyte.

[0103] Embodiments described in this disclosure relating to electrochemical cells or polymer electrolytes apply mutatis mutandis to methods of making electrochemical cells. For example, various embodiments relating to the identity and amounts of monomers, crosslinkers, initiators, and electrolyte compositions described herein in the context of polymer electrolytes are equally applicable to methods of preparing electrochemical cells.

[0104] Uses of the Polymer Electrolyte of the Invention In another aspect of the present invention, there is provided the use of a polymer electrolyte as described herein as an electrolyte for an electrochemical cell.

[0105] Embodiments described in this disclosure relating to polymer electrolytes apply mutatis mutandis to the use of polymer electrolytes. For example, various embodiments relating to the identity and amounts of monomers, crosslinkers, initiators, and electrolyte compositions described herein in the context of polymer electrolytes are equally applicable to the use of polymer electrolytes.

[0106] The electrochemical cell is preferably an electrochemical cell as described herein in the context of another aspect of the present invention.

[0107] Batteries containing electrochemical cells of the present invention and uses thereof Another aspect of the present invention relates to a battery, more particularly a lithium ion battery or a lithium metal battery, comprising at least one electrochemical cell comprising the gel polymer electrolyte described herein, e.g., two or more electrochemical cells described herein.

[0108] The electrochemical cells described herein can be combined with one another, for example, in series or parallel connections. Series connections are preferred. The electrochemical cells or batteries described herein can be used to manufacture or operate stationary applications such as energy storage devices for cars, computers, personal digital assistants, cell phones, watches, camcorders, digital cameras, thermometers, calculators, laptop BIOS, communications equipment, satellites, or remote car locks, and power generation plants.

[0109] A further aspect of the present invention is a method of manufacturing or operating stationary applications such as energy storage devices for cars, computers, personal digital assistants, cell phones, watches, camcorders, digital cameras, thermometers, calculators, laptop BIOS, communications equipment, satellites, remote car locks, and power plants by using at least one battery or at least one electrochemical cell described herein comprising the polymer electrolyte of the present invention.

[0110] A further aspect of the present invention is the use of an electrochemical cell or battery described herein comprising a polymer electrolyte of the present invention in a motorized vehicle, a bicycle powered by an electric motor, a robot, an aircraft (e.g., an unmanned aerial vehicle including a drone), a watercraft, a satellite, or a stationary energy storage device.

[0111] A further aspect of the present invention is a method of providing electrical power to a device, wherein the power is supplied by an electrochemical cell or battery as described herein comprising a polymer electrolyte of the present invention, and wherein the electrochemical cell or battery as described herein, preferably the electrochemical cell, operates at a voltage greater than 4.4 V, preferably greater than 4.5 V, more preferably greater than 4.6 V, for example greater than 4.7 V. The device may be any battery-powered device, but is preferably selected from motorized vehicles, computers, personal digital assistants, mobile phones, watches, camcorders, digital cameras, thermometers, calculators, laptop BIOS, communications equipment, satellites, remote car locks, stationary applications such as energy storage devices for power plants, bicycles operated by electric motors, robots, aircraft (e.g., unmanned aerial vehicles including drones), watercraft, satellites, etc.

[0112] The present invention further provides a device comprising at least one battery or electrochemical cell described herein, which comprises the polymer electrolyte of the present invention. Preferred are mobile devices, such as vehicles, e.g., automobiles, bicycles, aircraft, satellites, or water vehicles, e.g., boats or ships. Other examples of mobile devices are portable, such as computers, particularly laptops, telephones, or power tools, e.g., from the construction sector, particularly drills, battery-powered screwdrivers, or battery-powered tackers. [Example]

[0113] 1. Preparation of Materials An electrolyte composition consisting of a deep eutectic solvent (DES) was prepared by mixing lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and N-methylacetamide in a 1:4 molar ratio and vigorously stirring until a homogeneous, clear liquid was obtained. The precursor composition was prepared by mixing the monomers listed in Table 1, the crosslinker listed in Table 1, and the free radical initiator listed in Table 1 into a premix with a molar ratio of (monomer:crosslinker:initiator) of 90:10:5, and then combining the DES with the premix in a volume ratio of 85:15 DES:premix. The resulting mixture was stirred to obtain a homogeneous blend and polymerized by UV irradiation (365 nm) for 1 hour.

[0114] A cathode containing NMC622 as the cathode active material (LiNi 0.6 Mn 0.2 Co 0.2 O2) is 80% by weight of LiNi 0.6 Mn 0.2 Co 0.2 O2, 10 wt% carbon black, and 10 wt% poly(vinylidene fluoride) (PVDF) were compounded by mixing in N-methyl-2-pyrrolidone (NMP). The thoroughly mixed slurry was tape-cast onto aluminum foil and dried in air at 110 °C to a thickness of approximately 18.7 μm and a density of 0.622 mg cm. -2 An electrode with an active material loading of 0.109 mAh cm was obtained. -2 , the theoretical capacity of NMC622 is 175mAh g -1 (Assuming that).

[0115] For use in coin cells, the polymer electrolyte and cathode were cut to the appropriate size with a hollow punch. Li|polymer electrolyte|NMC622 cells were assembled by placing the positive electrode in front of the Li foil negative electrode, separated by a P-ETG electrode in between. [Table 1]

[0116] 2. Electrochemical Performance Determination Ionic conductivity was determined by electrochemical impedance spectroscopy (EIS) (using a Biologic SP-300) of the polymer electrolyte in a symmetrical stainless steel|electrolyte|stainless steel Swagelok-type cell at a specific temperature by perturbing the open-circuit potential with an AC sinusoidal potential of 10 mV amplitude in the frequency range of 10 kHz to 100 mHz.

[0117] The anodic stability limit was determined by linear sweep voltammetry (using a Bio-Logic, SP-300) of the polymer electrolyte sandwiched between a stainless steel working electrode and lithium metal reference and counter electrodes in a coin cell setup, with the working electrode voltage maintained at 10 mV s -1 At a scan rate of , the anodic scan is performed from the open circuit potential to Li + The voltage was swept up to 6 V vs. / Li. The stability limit was determined as the onset of electrolyte oxidation, which can be observed by a sudden increase in the measured current. Without being bound by any theory, the inventors believe that electrolyte oxidation is due to the TFSI - It is believed that this may be due to oxidation of the anion.

[0118] The electrochemical compatibility of the polymer electrolyte with high-voltage cathode materials was studied by electrochemical impedance spectroscopy (EIS) in NMC622|polymer electrolyte|NMC622 symmetric cells.

[0119] Cycling performance was determined for Li|polymer electrolyte|NMC622 cells prepared as described above using a TOYO battery cycler. + The electrode underwent a 16-hour open circuit potential (OCP) period before galvanostatic cycling from 3.0 to 4.3 V vs. Li. + The cells were activated by two galvanostatic charge / discharge cycles at C / 20 between 3.0 V and 4.3 V vs. Li. The cycling protocol consisted of five cycles each at C / 20, C / 10, C / 5, C / 2, and 1C rates, followed by 100 cycles at C / 10. The capacity values ​​were normalized to the weight of the cathode active material (NMC), and the results were reproducible.

[0120] 3.Results The results of electrochemical characterization of the polymer electrolyte of the present invention are shown in Figures 1-3 and Table 2. Table 2 shows the excellent ionic conductivity of the polymer electrolyte of the present invention at three different temperatures. Table 2 also highlights the compatibility of the polymer electrolyte of the present invention with NMC622 cathode active material, particularly as can be derived from Figure 3. The cycling performance using the crosslinker of Example 1 shows improved performance compared to the crosslinker of the comparative example. [Table 2]

[0121] As can be seen from FIG. 3, precursor compositions including a first crosslinker according to the present invention provide improved cycling performance.

Claims

1. A polymer electrolyte comprising an electrolyte composition and a polymer network, The electrolyte composition preferably comprises a deep eutectic solvent (DES), The polymer electrolyte is obtained by polymerizing a precursor composition comprising the electrolyte composition, a first monomer according to formula (I) and a first crosslinker according to formula (II). 【Chemical 1】 【Chemistry 2】 [In the formula, R １ is C １ ~C ６ hydroxyalkyl; R ２ is selected from H, methyl, or ethyl; n is an integer ranging from 0 to 5; R ３ and R ４ are each independently selected from H, methyl, or ethyl; R ５ and R ６ are each independently selected from H or methyl; X is an alkanediyl or polyoxyalkylene, preferably X is (—CH ２ -) ｏ or -CH ２ -CH ２ (-O-CH ２ -CH ２ ) ｐ - and o is an integer ranging from 1 to 10; p is an integer in the range of 1 to 200], a polymer electrolyte.

2. 2. The polymer electrolyte of claim 1, wherein the first crosslinker is included in the precursor composition in an amount such that the molar ratio of the total amount of the first monomers included in the precursor composition to the total amount of the first crosslinker included in the precursor composition is in the range of 99.5:0.5 to 80:20, preferably in the range of 98:2 to 80:20, and more preferably in the range of 95:5 to 85:

15.

3. 10. The polymer electrolyte of claim 1, wherein the first monomer comprises at least 80 mol%, preferably at least 90 mol%, and more preferably at least 95 mol% of all monomers in the precursor composition.

4. 10. The polymer electrolyte of claim 1, wherein the first crosslinker constitutes at least 80 wt % (based on the total weight of all crosslinkers in the precursor composition), preferably at least 90 wt % (based on the total weight of all crosslinkers in the precursor composition), and more preferably at least 95 wt % (based on the total weight of all crosslinkers in the precursor composition) of all crosslinkers in the precursor composition.

5. 10. The polymer electrolyte of claim 1, wherein the precursor composition further comprises one or more radical initiators, preferably one or more radical initiators selected from thermal initiators, photoinitiators, and combinations thereof.

6. ・R ３ and R ４ are each independently selected from H or methyl, preferably H; ・R ５ and R ６ are each independently selected from H or methyl; ・X is (-CH ２ -) ｏ 2. The polymer electrolyte of claim 1, wherein o is selected from the formula:

7. ・R １ contains one or two hydroxyl functional groups, １ ~C ６ hydroxyalkyl, preferably R １ contains one or two hydroxyl functional groups, １ ~C ３ hydroxyalkyl, more preferably containing one or two hydroxyl functional groups, C １ ~C ２ hydroxyalkyl, most preferably R １ is 2-hydroxyethyl, ・R ２ is selected from H or methyl, most preferably H; A polymer electrolyte according to claim 1, wherein n is an integer in the range of 0 to 5, more preferably in the range of 0 to 3, more preferably in the range of 0 to 2, and most preferably n is equal to 0.

8. 2. The polymer electrolyte of claim 1, wherein the deep eutectic solvent (DES) has a eutectic point of 25° C. or less.

9. 2. The polymer electrolyte of claim 1, wherein the deep eutectic solvent (DES) comprises at least one hydrogen bond acceptor and at least one hydrogen bond donor, and the at least one hydrogen bond acceptor comprises a lithium salt, a zinc salt, or a combination thereof, preferably a lithium salt.

10. The at least one hydrogen bond acceptor may be selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiOTf), lithium chloride (LiCl), lithium hexafluorophosphate (LiPF ６ ), lithium polysulfide, lithium perchlorate (LiClO ４ ), lithium bromide (LiBr), lithium iodide (LiI), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF ４ ), lithium hexafluoroarsenate (LiAsF ６ ), lithium bis(oxalato)borate (LiBOB), lithium fluoroalkylphosphate (LFAP [LiPF ３ (CF ２ CF ３ ) ３ 10. The polymer electrolyte of claim 9, wherein the polymer electrolyte is selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and combinations thereof.

11. The at least one hydrogen bond donor may be urea, N-methylurea, N,N-dimethylurea, N,N'-dimethylurea, N,N,N'-trimethylurea, thiourea, N-methylthiourea, N,N-dimethylthiourea, N,N'-dimethylthiourea, N,N,N'-trimethylthiourea, ethylene glycol, propane-1,2-diol, propane-1,3-diol, butane-1,4-diol, 1,2,3-propanetriol, acetic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sucralose ...

10. The polymer electrolyte of claim 9, wherein the carboxylic acid is selected from the group consisting of benzoic acid, undecanedioic acid, dodecanedioic acid, benzoic acid, glycolic acid, citric acid, 2-hydroxypropionic acid, 2-hydroxyisobutyric acid, o-phenylenediamine, choline chloride, acetamide, N-methylacetamide, trifluoroacetamide, N-methyltrifluoroacetamide, benzamide, benzenesulfonic acid, p-toluenesulfonic acid, o-toluenesulfonic acid, m-toluenesulfonic acid, and combinations thereof, preferably N-methylacetamide.

12. 2. The polymer electrolyte of claim 1, wherein the precursor composition comprises about 75-90% by volume (based on the total volume of the precursor composition) of a deep eutectic solvent (DES), preferably about 80-90% by volume, and most preferably about 83-87% by volume.

13. A method for preparing the polymer electrolyte according to any one of claims 1 to 12, comprising the steps of: (a) providing a precursor composition according to any one of claims 1 to 12; (b) polymerizing said precursor composition.

14. Use of the polymer electrolyte according to any one of claims 1 to 12 as an electrolyte for an electrochemical cell.

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