POLYACRYLAMIDE ELECTROLYTES FOR BATTERIES CYCLING LITHIUM IONS AND BATTERIES CONTAINING THEM

Abstract

An electrolyte for a lithium-ion cycling battery comprises a polyacrylamide and a liquid electrolyte immobilized within the polyacrylamide. The polyacrylamide comprises acrylamide monomers covalently bonded to each other. The liquid electrolyte comprises a lithium salt in an organic solvent.

Description

INITIATIONThe information included in this section serves to generally illustrate the context of the disclosure. Work of the present inventors, insofar as described in this introduction, as well as aspects of the description that may not otherwise be considered prior art at the time of filing, is neither expressly nor silently admitted as prior art against this disclosure.The present disclosure relates to electrolytes for batteries that cycle lithium ions, and more particularly to electrolytes comprising a polymer matrix and a liquid electrolyte immobilized in the polymer matrix.Batteries that cycle lithium ions generally include a positive electrode, a negative electrode spaced from the positive electrode, and an ionically conductive electrolyte that provides a medium for the conduction of lithium ions between the positive and negative electrodes during the discharge and charging of the batteries. The electrolyte may be formulated to exhibit certain desirable properties including high ionic conductivity, good heat resistance, a wide electrochemical stability window, the ability to form a stable ionically conductive solid electrolyte intermediate phase on the surface of the positive electrode and / or the negative electrode, and chemical compatibility with other components of the batteries.SUMMARYAn electrolyte for a battery that cycles lithium ions according to one or more aspects of the present disclosure includes a polyacrylamide and a liquid electrolyte immobilized in the polyacrylamide. The polyacrylamide comprises acrylamide monomers covalently bonded together. The liquid electrolyte comprises a lithium salt in an organic solvent.The acrylamide monomers may include acrylamide, N-alkylacrylamide, N-cycloalkylacrylamide, dialkylacrylamide, hydroxyalkylacrylamides, N-arylacrylamides, methacrylamide, N-alkylmethacrylamide, N-cycloalkylmethacrylamide, dialkylmethacrylamide, dialkylaminoalkylmethacrylamide, hydroxyalkylmethacrylamide, N-arylmethacrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, or a combination thereof.At least one of the acrylamide monomers may comprise a substituent selected from the group consisting of silyl, siloxy, alkoxysilyl, sulfo, phosphate, and carboxamide.The polyacrylamide may further comprise an alkylenebisacrylamide cross-linker. In this case, the acrylamide monomers and the alkylenebisacrylamide cross-linker can be covalently attached to each other to form a three dimensional network of interconnected polyacrylamide chains.The polyacrylamide may further comprise an acrylonitrile monomer. In this case, the acrylamide monomers and the acrylonitrile monomer may be covalently bonded to each other.The polyacrylamide may comprise a polymer of formula (1): wherein: m is an integer; n is zero or an integer; p is zero or an integer; q is zero or 1; R 1, R 3, R 4 and R 5 are each individually H, hydroxyl, hydrocarbyl, heterohydrocarbyl, silyl, siloxy, alkoxysilyl, sulfo, phosphate, or carboxamide moiety; R 2 is a divalent hydrocarbyl or heterohydrocarbyl; and the sum of m+n+p is greater than or equal to 100 and less than or equal to 200,000.The organic solvent may include an ether-based solvent. The lithium salt may comprise lithium hexafluorophosphate (LiPF 6), lithium bis(trifluoromethane)sulfonylimide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), or a combination thereof.The electrolyte may further comprise an additive comprising lithium nitrate (LiNOs).A battery that cycles lithium ions according to one or more aspects of the present disclosure includes a negative electrode, a positive electrode spaced apart from the negative electrode by a gap, and a polymer electrolyte disposed in the gap between the negative electrode and the positive electrode. The negative electrode comprises an electroactive negative electrode material. The positive electrode comprises an electroactive positive electrode material. The polymer electrolyte comprises a polyacrylamide and a liquid electrolyte immobilized in the polyacrylamide. The polyacrylamide comprises acrylamide monomers covalently bonded together. The liquid electrolyte comprises a lithium salt in an organic solvent.The acrylamide monomers may include acrylamide, N-alkylacrylamide, N-cycloalkylacrylamide, dialkylacrylamide, hydroxyalkylacrylamides, N-arylacrylamides, methacrylamide, N-alkylmethacrylamide, N-cycloalkylmethacrylamide, dialkylmethacrylamide, dialkylaminoalkylmethacrylamide, hydroxyalkylmethacrylamide, N-arylmethacrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-acrylamido-2-methyl-propanesulfonic acid, or a combination thereof.At least one of the acrylamide monomers may comprise a substituent selected from the group consisting of silyl, siloxy, alkoxysilyl, sulfo, phosphate, and carboxamide.The polyacrylamide may further comprise an alkylenebisacrylamide cross-linker. In this case, the acrylamide monomers and the alkylenebisacrylamide cross-linker can be covalently attached to each other to form a three dimensional network of interconnected polyacrylamide chains.The polyacrylamide may further comprise an acrylonitrile monomer. In this case, the acrylamide monomers and the acrylonitrile monomer may be covalently bonded to each other.The polyacrylamide may comprise a polymer of formula (1): wherein: m is an integer; n is zero or an integer; p is zero or an integer; q is zero or 1; R 1, R 3, R 4 and R 5 are each individually H, hydroxyl, hydrocarbyl, heterohydrocarbyl, silyl, siloxy, alkoxysilyl, sulfo, phosphate, or carboxamide moiety; R 2 is a divalent hydrocarbyl or heterohydrocarbyl; and the sum of m+n+p is greater than or equal to 100 and less than or equal to 200,000.The organic solvent may include an ether-based solvent. The lithium salt may comprise lithium hexafluorophosphate (LiPF 6), lithium bis(trifluoromethane)sulfonylimide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), or a combination thereof.The liquid electrolyte may further comprise an additive comprising lithium nitrate (LiNO 3).The electroactive positive electrode material may comprise a sulfur-based material.The electroactive negative electrode material may comprise nonporous lithium.A method for manufacturing a lithium ion cycling battery according to one or more aspects of the present disclosure includes a step of assembling a stack including a negative electrode and a positive electrode, the negative electrode and the positive electrode being spaced apart from each other by a gap. The stack is infiltrated with an electrolyte precursor comprising acrylamide monomers, a radical initiator, and a liquid electrolyte. Free radical polymerization of the acrylamide monomers is initiated such that the acrylamide monomers covalently bond to each other to form a polyacrylamide.The radical initiator may comprise an azo compound, an organic peroxide, or a combination thereof. The free radical polymerization of the acrylamide monomers is initiated by heating the electrolyte precursor to a temperature greater than or equal to 70 degrees Celsius.Further areas of applicability of the present disclosure will become apparent from the detailed description, claims and drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.BRIEF DESCRIPTION OF THE DRAWINGSThe present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: FIG. 1 is a schematic perspective view of a motor vehicle powered by a battery pack including a plurality of battery modules. FIG. 2 is a schematic cross-sectional view of a portion of one of the battery modules of FIG. 1, wherein the battery module comprises multiple electrochemical cells or batteries that cycle lithium ions. FIG. 3 is a schematic cross-sectional view of a battery that cycles lithium ions, the battery including a positive electrode, a negative electrode, and a polymer electrolyte disposed between the positive electrode and the negative electrode.In the drawings, reference numerals may be reused to identify similar and / or identical elements.DETAILED DESCRIPTIONDefinitions"Hydrocarbyl" refers to a functional group containing only hydrogen and carbon atoms, including branched or unbranched, saturated or unsaturated, cyclic, polycyclic, or acyclic groups. Hydrocarbyls are formed by removing at least one hydrogen atom from a hydrocarbon molecule. According to the number of removed hydrogen atoms, a hydrocarbyl may be monovalent (formed by removing one hydrogen atom, also referred to as a hydrocarbyl group), divalent (formed by removing two hydrogen atoms, also referred to as a hydrocarbylene group), and the like. Examples of monovalent hydrocarbyls include alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and alkynyl groups. Examples of divalent hydrocarbyl groups include alkylene, cycloalkylene, alkenylene, alkynylene and arylene groups."Heterohydrocarbyl" refers to a hydrocarbyl wherein at least one of the carbon atoms is replaced with a heteroatom, e.g., nitrogen, oxygen, sulfur, phosphorus, boron, or silicon. Examples of heterohydrocarbyls include alkoxy, aryloxy, -CH 2 OCH 3 and oxyalkylene (e.g., -CH 2 CH 2 O-)."Carboxamide" refers to a compound, moiety or functional group having the formula R'-C(=O)-NR"R"', wherein R', R", and R"' are each individually H, hydrocarbyl, or heterohydrocarbyl."Substituted" refers to a compound, moiety, or functional group in which at least one hydrogen atom bonded to a carbon atom is replaced with a substituent that is a functional group. Examples of substituents include hydroxyl (-OH), heterohydrocarbyl, phosphate, amino, halo, silyl and sulfo groups."Silyl" refers to a functional group having the formula -SiR'R "R'" wherein R', R" and R"' are each individually H, hydrocarbyl or heterohydrocarbyl."Siloxy" refers to a functional group having the formula -OSiR'R "R'" wherein R', R" and R"' are each individually H, hydrocarbyl or heterohydrocarbyl."Alkoxysilyl" refers to a functional group having the formula -Si(OR) 3, wherein R is H, hydrocarbyl, heterohydrocarbyl, or -Si(OR) 3."Sulfo" refers to a functional group having the formula -SO 3 R wherein R is H, hydrocarbyl, or heterohydrocarbyl."Phosphate" refers to a functional group having the formula -OPO(OR) 2, wherein R is H, hydrocarbyl, or heterohydrocarbyl.Terms such as "at least one of A, B, and / or C" should be construed as being logical (A ORed with B ORed with C) using a non-exclusive logical OR operation, and should not be understood as "at least one of A, at least one of B, and at least one of C".The term "and / or" includes combinations of one or more of the associated listed items.The singular forms "a", "an" and "the" may also include the plural forms unless the context clearly indicates otherwise.The terms "comprise," "comprising," "include," and "have" are inclusive and therefore specify the presence of stated features, elements, compositions, steps, integers, operations, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Although the open terms "comprises," "comprising," "including," and "having" are to be understood as non-limiting terms that describe and claim various configurations set forth herein, in certain aspects, the term may alternatively be understood as a more restrictive and restrictive term, such as "consisting of" or "consisting essentially of.". Therefore, for any given configuration specifying compositions, materials, components, elements, constituents, features, integers, operations, and / or method steps, the present disclosure expressly also encompasses configurations consisting of or consisting essentially of such specified compositions, materials, components, elements, constituents, features, integers, operations, and / or method steps.The terms "composition" and "material" are used interchangeably to refer generally to a substance containing at least the preferred chemical components, elements or compounds, but which may also contain additional elements, compounds or substances, including traces of impurities (i.e., in amounts less than or equal to 0.1%). An "X-based" composition or material generally refers to compositions or materials in which "X" is the largest single component of the composition or material on a weight percent (%) basis. This may comprise both compositions or materials with a weight proportion greater than 50% X and those with a weight proportion less than 50% X, such that X is the largest individual constituent of the composition or of the material, based on its total weight. When a composition or material is referred to as being "substantially free" of a substance, the composition or material may comprise less than 5%, optionally less than 3%, optionally less than 1%, or optionally less than 0.1%, by weight, of the substance.The term "metal" may refer to a pure elemental metal or to an elemental metal and one or more other metal or non-metal elements. The term "elemental metal" means that the metal in question is in its purest form and does not contain any other elements except in traces, i.e. as impurities.EmbodimentsThe presently disclosed polymer electrolytes can be used in batteries that cycle lithium ions to help reduce the interfacial resistance between the electrolyte and the positive and negative electrodes, which can improve the electrochemical performance of the batteries. When used in batteries comprising sulfur-based electroactive positive electrode materials, the polymer electrolytes may help prevent or inhibit polysulfide dissolution and hunting between the positive and negative electrodes, which may improve cycle life and coulombic efficiency of the batteries. Moreover, when used in batteries comprising nonporous lithium metal negative electrodes, the polymer electrolytes can help promote homogeneous deposition of metallic lithium and thereby avoid the undesirable nucleation and growth of lithium dendrites. The presently disclosed polymer electrolytes include a polyacrylamide and a liquid electrolyte immobilized in the polyacrylamide. The amide groups in the polyacrylamide can help bind acid species, chelate metal ions, and absorb polysulfide species, thereby improving cycle life of the batteries.FIG. 1 shows a motor vehicle 2 powered by an electric motor 4 that draws current from a battery pack 6 that includes one or more battery modules 8. The battery modules 8 may be electrically coupled in series and / or in parallel to meet the desired capacity and power requirements of the electric motor 4. The vehicle 2 may be a pure electric vehicle and powered solely by the electric motor 4, or the vehicle 2 may be a hybrid electric vehicle and powered by the electric motor 4 and an internal combustion engine (not shown).As shown in FIG. 2, each battery module 8 includes one or more electrochemical cells or batteries 10 that cycle lithium ions. In practice, the batteries 10 in the battery module 8 are often configured as a stack of layers including negative electrode layers 12, negative electrode current collectors 13, positive electrode layers 14, positive electrode current collectors 15, and separator layers 16. Each battery 10 is defined by a negative electrode layer 12 and a positive electrode layer 14 separated from each other by a separator layer 16. In practice, the separator layer 16 may be infiltrated with an electrolyte that provides a medium for conducting lithium ions between the negative electrode layer 12 and the positive electrode layer 14, or the separator layer 16 itself may function as an electrolyte. The negative electrode layers 12 are disposed on and in electrical communication with the negative electrode current collectors 13, and the positive electrode layers 14 are disposed on and in electrical communication with the positive electrode current collectors 15. As shown in FIG. 2, for efficiency, the layers may be stacked such that some of the negative electrode current collectors 13 and some of the positive electrode current collectors 15 are double-sided and include negative electrode layers 12 or positive electrode layers 14, respectively, on both sides thereof. In this arrangement, adjacent negative electrode layers 12 and positive electrode layers 14 share a single negative electrode current collector 13 or a positive electrode current collector 15, respectively.FIG. 3 shows an electrochemical cell or battery 20 that cycles lithium ions. The battery 20 may generate an electric current during discharge, which may be used to supply power to a load device (e.g., an electric motor 4), and may be charged by connection to a power source. Like the batteries 10 shown in FIGS. 1 and 2, in aspects, the battery 20 may be used to power an electric motor 4 of a motor vehicle 2. Additionally or alternatively, the battery 20 may also be used in other transportation applications (e.g., motorcycle, boat, tractor, bus, motorcycle, recreational vehicle, recreational vehicle, tank, and plane) and may be used to power stationary and / or portable electronic devices, components, and devices used in a variety of other industries and applications including, but not limited to, industrial, residential, and commercial buildings, consumer goods, industrial devices and machines, agricultural devices, and heavy machinery.The battery 20 includes a negative electrode 22, a positive electrode 24, and a polymer electrolyte 28 disposed between a facing surface 38 of the negative electrode 22 and an opposing facing surface 40 of the positive electrode 24. The negative electrode 22 is disposed on a main surface of a negative electrode current collector 30, and the positive electrode 24 is disposed on a main surface of a positive electrode current collector 32. In practice, the negative electrode current collector 30 and the positive electrode current collector 32 are electrically connected to a power source or load 34 (e.g., the electric motor 4) via an external circuit 36. The negative electrode 22 and the positive electrode 24 are formulated such that when the battery 20 is at least partially charged, an electrochemical potential difference arises between the negative electrode 22 and the positive electrode 24. During discharge of the battery 20, the electrochemical potential established between the negative electrode 22 and the positive electrode 24 drives spontaneous reduction and oxidation reactions (redox reactions) within the battery 20 and the release of lithium ions and electrons from the negative electrode 22. The liberated lithium ions migrate from the negative electrode 22 to the positive electrode 24 through the polymer electrolyte 28, while the electrons migrate from the negative electrode 22 to the positive electrode 24 via the external electric circuit 36 which generates an electric current. After the negative electrode 22 is partially or completely depleted of lithium, the battery 20 may be charged by connecting the negative electrode 22 and the positive electrode 24 to the energy source 34, thereby driving non-spontaneous redox reactions within the battery 20 and the release of the lithium ions and electrons from the positive electrode 24. The repeated discharging and charging of the battery 20 may be referred to herein as "cycling", wherein a full charging operation followed by a full discharging operation is considered a full cycle.The positive electrode 24 is formulated to store and release lithium ions upon discharging and charging of the battery 20. The positive electrode 24 may be disposed in the form of a continuous porous layer on the major surface of the positive electrode current collector 32 and have open pores extending therethrough. The positive electrode 24 comprises an electrochemically active (electroactive) material (electroactive positive electrode material), a polymeric binder, and optionally an electrically conductive material. In aspects, the positive electrode electroactive material 24 may be a particulate material, and the positive electrode electroactive material particles 24 may be mixed with the polymeric binder and the electrically conductive material.The positive electrode electroactive material 24 may store and release lithium ions by undergoing a reversible redox reaction with lithium at a higher electrochemical potential than the negative electrode electroactive material 22, such that there is an electrochemical potential difference between the negative electrode 22 and the positive electrode 24. The positive electrode electroactive material 24 may include a material capable of undergoing lithium intercalation and deintercalation, or a material capable of undergoing a conversion reaction with lithium. In embodiments where the positive electrode electroactive material 24 comprises an intercalation host material capable of undergoing the reversible intercalation or intercalation of lithium ions, the positive electrode electroactive material 24 may comprise a lithium transition metal oxide. For example, the positive electrode electroactive material 24 may comprise a layered lithium transition metal oxide represented by the formula LiMeO 2 and / or Li 2 MeO 3, a layered lithium-rich transition metal oxide represented by the formula Li 1+x Me 1-x O 2( where 0<x≤0.33), an olivine-type lithium transition metal oxide represented by the formula LiMePO4, a monoclinic-type lithium transition metal oxide represented by the formula Li 3 Me 2( PO 4)3, a spinel-type lithium transition metal oxide represented by the formula LiMe 2 O 4, a tavorite represented by one or both of the following formulas LiMeSO 4 F or LiMePO 4 F, or a combination thereof, wherein Me is a transition metal (e.g., Co, Ni, Mn, Fe, Al, V, or a combination thereof). In embodiments where the positive electrode electroactive material 24 comprises a conversion material, the positive electrode electroactive material 24 may comprise sulfur, selenium, tellurium, iodine, a halide (e.g., a fluoride or chloride), sulfide, selenide, telluride, iodide, phosphide, nitride, oxide, oxysulfide, oxyfluoride, sulfur fluoride, sulfur oxyfluoride, or a lithium and / or metal compound thereof (e.g., a compound of iron, manganese, nickel, copper, and / or cobalt).In embodiments, the positive electrode electroactive material 24 may comprise a sulfur-based material. In embodiments, the positive electrode electroactive material 24 may comprise a composite comprising sulfur and / or a sulfur-based material dispersed in an electrically conductive matrix material. Examples of electrically conductive matrix materials include carbon-based materials, metal compounds, conductive polymers, and combinations thereof. Examples of carbon-based electrically conductive matrix materials include graphene, reduced graphene oxide, carbon nanotubes (CNTs), hierarchical porous carbon, hollow structured carbon, and combinations thereof. Examples of matrix materials of metal compounds include manganese oxide (MnO 2), titanium oxide (TiO 2), iron oxide (Fe 2 O 3), vanadium oxide (V 2 O 5), cobalt sulfide (CoS 2 and / or Co 9 S 8), titanium sulfide (TiS), titanium nitride (TiN), titanium carbide (Ti 2 C), lithium sulfide (Li2S), and combinations thereof. Examples of electrically conductive polymeric matrix materials include polyacrylonitrile (PAN), polypyrrole, polythiophene, poly(3,4-ethylenedioxythiophene) (PEDOT), and combinations thereof. In embodiments, the positive electrode electroactive material 24 may comprise sulfurized polyacrylonitrile (SPAN).The positive electrode electroactive material 24 may constitute greater than or equal to about 50%, optionally greater than or equal to about 60%, or optionally greater than or equal to about 70%, and less than or equal to about 95%, optionally less than or equal to about 90%, or optionally less than or equal to about 80%, by weight of the positive electrode 24.The polymeric binder is electrochemically inactive and may be incorporated into the positive electrode 24 to provide structural integrity to the positive electrode 24 and / or to adhere the positive electrode 24 to the major surface of the positive electrode current collector 32. Examples of polymeric binders include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), ethylene propylene diene monomer (EPDM) rubber, styrene butadiene rubber (SBR), carboxymethylcellulose (CMC), nitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), styrene ethylene butylene styrene copolymer (SEBS), polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), polyacrylates, alginates, polyacrylic acid, and combinations thereof. The polymeric binder may constitute greater than or equal to about 1%, or optionally greater than or equal to about 5%, and less than or equal to about 10% by weight of the positive electrode 24.The optional electrically conductive material is electrochemically inactive and may be incorporated into the positive electrode 24 to provide sufficient electrical conductivity to the positive electrode 24 to aid in the percolation of electrons therethrough. Examples of electrically conductive materials include carbon-based materials, metals (e.g., nickel), and / or electrically conductive polymers. Examples of carbon-based electrically conductive materials include carbon black (CB) (e.g., acetylene black), graphite, graphene (e.g., graphene nanoplatelets, GNP), graphene oxide, carbon nanotubes (CNT), and / or carbon fibers (e.g., carbon nanofibers). Examples of electrically conductive polymers include polyaniline, polythiophene, polyacetylene and / or polypyrrole. When included in the positive electrode 24, the optional electrically conductive material may comprise greater than 0%, optionally greater than or equal to about 1%, or optionally greater than or equal to about 5%, and less than or equal to about 10% of the positive electrode 24 by weight.The negative electrode 22 is formulated to store and release lithium ions to facilitate charging and discharging of the battery 20. The negative electrode 22 may be disposed in the form of a continuous layer on a main surface of the negative electrode current collector 30. The negative electrode 22 includes an electrochemically active (electroactive) material (electroactive negative electrode material) that can store and release lithium ions by undergoing a reversible redox reaction with lithium upon charging and discharging of the battery 20. Examples of electroactive negative electrode materials include lithium, lithium-based materials (e.g., alloys of lithium and silicon, aluminum, indium, and / or tin), carbon-based materials (e.g., graphite, activated carbon, carbon black, hard carbon, soft carbon, and / or graphene), silicon-based materials (e.g., alloys of silicon and lithium, tin, iron, aluminum, and / or cobalt), silicon oxide, silicon oxide-based materials (e.g., lithium silicon oxide), tin oxide, aluminum, indium, zinc, germanium, titanium oxide, lithium titanate, and combinations thereof.In some embodiments, the negative electrode 22 may be porous and have open pores extending therethrough. In this case, the electroactive negative electrode material 22 may be a particulate material, and the particles of electroactive negative electrode material 22 may be mixed with a polymeric binder and optionally an electrically conductive material. In this case, the electroactive negative electrode material 22 may comprise greater than or equal to about 50%, optionally greater than or equal to about 60%, or optionally greater than or equal to about 70%, and less than or equal to about 95%, optionally less than or equal to about 90%, or optionally less than or equal to about 80%, by weight of the negative electrode 24. The same polymeric binders and / or electrically conductive materials described above with respect to the positive electrode 24 may be used in the negative electrode 22 in substantially the same amounts.In other embodiments, the electroactive material of the negative electrode 22 may be comprised of lithium, and the negative electrode 22 may be in the form of a nonporous metal film or foil, such as a lithium metal film or foil. In this case, the negative electrode 22 may comprise greater than 97% lithium by weight, or optionally greater than 99% lithium. In embodiments where the electroactive material of the negative electrode 22 is comprised of lithium, the negative electrode 22 may be substantially free of elements or compounds that undergo a reversible redox reaction with lithium during operation of the battery 20. Moreover, in such embodiments, the negative electrode 22 may be substantially free of a polymeric binder.The polymer electrolyte 28 is ionically conductive and is formulated to provide a medium for conducting lithium ions between the negative electrode 22 and the positive electrode 24. The polymer electrolyte 28 physically separates and electrically isolates the negative electrode 22 and the positive electrode 24 while permitting lithium ions to pass through. The polymer electrolyte 28 may be sandwiched between the negative electrode 22 and the positive electrode 24, and may be in direct physical contact with the opposing facing surfaces 38, 40 of the negative electrode 22 and the positive electrode 24. In embodiments where the negative electrode 22 and / or the positive electrode 24 are porous, the polymer electrolyte 28 may at least partially infiltrate the open pores thereof. The polymer electrolyte 28 comprises a polyacrylamide, a liquid electrolyte immobilized in the polyacrylamide, and optionally a support structure. The polymer electrolyte 28 may have a thickness of greater than or equal to 5 micrometers (μm), optionally greater than or equal to 10 μm, or optionally greater than or equal to 20 μm and less than or equal to 500 μm, optionally less than or equal to 200 μm, or optionally less than or equal to 50 μm.The polyacrylamide is formulated to provide flexibility to the polymer electrolyte 28 and the ability to make robust interfacial contact with the facing surface 38 of the negative electrode 22 and with the facing surface 40 of the positive electrode 24, which may contribute to reducing interfacial resistance between the polymer electrolyte 28 and the negative and positive electrodes 22, 24. In embodiments where the electroactive positive electrode material 24 comprises a sulfur-based material, the polyacrylamide may also help prevent the polysulfides formed in the positive electrode 24 from diffusing through the polymer electrolyte 28 and undesirably reacting with the lithium metal in the negative electrode 22 to form insoluble polysulfides, thereby reducing cycle life and coulombic efficiency of the battery 20 (a phenomenon known as triggering or swinging polysulfides). Moreover, in embodiments where the negative electrode 22 is comprised of nonporous lithium, the polyacrylamide may help provide the battery 20 with a low ion concentration polarization at the interface between the negative electrode 22 and the polymer electrolyte 28, which may promote homogeneous deposition of metallic lithium on the facing surface 38 of the negative electrode 22 and thereby prevent the undesirable nucleation and growth of lithium dendrimers. The polyacrylamide may be greater than or equal to 1%, optionally greater than or equal to 5%, and less than or equal to 30%, optionally less than or equal to 20%, or optionally less than or equal to 10% by weight of the polymer electrolyte 28.The polyacrylamide comprises an acrylamide monomer, optionally an alkylenebisacrylamide crosslinker, and optionally an acrylonitrile monomer. In polyacrylamide, the acrylamide monomer, the optional alkylenebisacrylamide cross-linker, and the optional acrylonitrile monomer are covalently bonded together. In embodiments, the polyacrylamide may be a homopolymer or copolymer having formula (1): wherein X is an acrylamide monomer; Y is an alkylenebisacrylamide crosslinker; Z is an acrylonitrile monomer; m is an integer; n is zero or an integer; p is zero or an integer; q is zero or 1; R 1, R 3, R 4 and R 5 are each individually H, a hydroxyl, hydrocarbyl, heterohydrocarbyl, silyl, siloxy, alkoxysilyl, sulfo, phosphate, or carboxamide moiety; and R 2 is a divalent hydrocarbyl or heterohydrocarbyl moiety. In embodiments, the sum of m+n+p may be greater than or equal to 100 and less than or equal to 200,000.Examples of acrylamide monomers include acrylamide, N-alkylacrylamides (e.g., N-methylacrylamide, N-ethylacrylamide, N-n-propylacrylamide, N-isopropylacrylamide, N-n-butylacrylamide, and N-tert-butylacrylamide), N-cycloalkylacrylamides (e.g., N-cyclohexylacrylamide), dialkylacrylamides (e.g., N,N-dimethylacrylamide, and N,N-diallylacrylamide); dialkylaminoalkylacrylamides; hydroxyalkylacrylamides; N-arylacrylamides; methacrylamide; N-alkyl methacrylamides (e.g., N-methyl methacrylamide, N-ethyl methacrylamide, N-n-propyl methacrylamide, N-isopropyl methacrylamide, N-n-butyl methacrylamide, and N-tert-butyl methacrylamide); N-cycloalkyl methacrylamides; dialkyl methacrylamides (e.g., N,N-dimethyl methacrylamide); dialkylaminoalkyl methacrylamides; hydroxyalkyl methacrylamides; N-aryl methacrylamides; 2-acrylamido-2-methyl-1-propanesulfonic acid; 2-acrylamido-2-methyl-propanesulfonic acid; and combinations thereof.Examples of alkylenebisacrylamide crosslinkers include N,N'-methylenebisacrylamide, N,N'-ethylenebisacrylamide, and combinations thereof.Examples of acrylonitrile monomers include acrylonitrile, methacrylonitrile, 2-hydroxyethylacrylonitrile, methoxyacrylonitrile, methoxymethacrylonitrile, and combinations thereof.In embodiments, the acrylamide monomers, the optional alkylenebisacrylamide crosslinker, the optional acrylonitrile monomer, and / or the functional groups thereof may be substituted or unsubstituted.In embodiments where the polyacrylamide comprises the optional alkylenebisacrylamide cross-linker (i.e., where n is an integer greater than or equal to 1), the acrylamide monomers and the alkylenebisacrylamide cross-linker are covalently attached to each other and may form a three-dimensional network of interconnected polyacrylamide chains, each polyacrylamide chain comprising two or more acrylamide monomers.The liquid electrolyte infiltrates the polyacrylamide and is formulated to provide good ionic conductivity to the polymer electrolyte 28. The liquid electrolyte comprises an organic solvent, a lithium salt in the organic solvent, and optionally an additive. The liquid electrolyte may be greater than or equal to 70%, or optionally greater than or equal to 80%, and less than or equal to 99%, or optionally less than or equal to 95%, or optionally less than or equal to 90%, by weight of the polymer electrolyte 28.The organic solvent may comprise a non-aqueous aprotic organic solvent. Non-limiting examples of non-aqueous aprotic organic solvents include cyclic carbonates (e.g., ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC)); linear carbonates (e.g., dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC)); aliphatic ethers (e.g., triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dimethoxypropane, 1,2-dimethoxyethane (DME), 1-2-diethoxyethane, and / or ethoxymethoxyethane); cyclic ethers (e.g., 1,4-dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, and / or 1,3-dioxolane (DOL)), and combinations thereof. In embodiments, the organic solvent may comprise an ether-based solvent. For example, in embodiments, the organic solvent may comprise a mixture of a cyclic ether (e.g., DOL) and an aliphatic ether (e.g., DME). In this case, the cyclic ether and the aliphatic ether may be contained in the liquid electrolyte in a volumetric ratio of about 1:1.The lithium salt is soluble in the organic solvent and allows lithium ions to pass through the polymer electrolyte 28. Examples of lithium salts include lithium hexafluorophosphate (LiPF 6), lithium difluorophosphate (LiPO 2 F 2), lithium perchlorate (LiClO 4), lithium tetrachloroaluminate (LiAlCl 4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiF 4), lithium hexafluoroarsenate (Li-AsF 6), lithium trifluoromethanesulfonate (LiCF 3 SO 3), Lithium bis(trifluoromethanesulfonyl)imide (LiN(CF 3 SO 2)2) ( LiTFSI), lithium bis(fluorosulfonyl)imide (LiN(FSO 2)2) ( LiFSI), lithium tetraphenylborate (LiB(C 6 H 5)4), lithium bis(oxalato)borate (LiB(C 2 O 4)2) ( LiBO), Lithium difluoro(oxalato)borate (LiB 2( C 2 O 4)) ( LiDFOB), and combinations thereof. In aspects, the lithium salt may comprise LiFSI, LiTFSI, LiPF 6 or a combination thereof. The lithium salt may be dissolved in the organic solvent at a concentration of greater than or equal to about 0.5 molar and less than or equal to about 1.5 molar. In aspects, the lithium salt may be dissolved in the organic solvent at a concentration of about 1 molar. The lithium salt may constitute greater than or equal to about 5%, optionally greater than or equal to about 10%, and less than or equal to about 20%, or optionally less than or equal to about 15%, by weight of the polymer electrolyte 28.The optional additive is soluble in the organic solvent and can be formulated to help prevent or suppress the release and hunting of polysulfide. Examples of additives include lithium nitrate (LiNO 3). When present, the optional additive may be dissolved in the organic solvent at a concentration of greater than or equal to about 0.1 molar and less than or equal to about 0.5 molar. In aspects, the optional additive may be dissolved in the organic solvent at a concentration of about 0.3 molar.The optional support structure may help provide mechanical stability to the polymer electrolyte 28, and may comprise a microporous nonwoven material impregnated, infiltrated, and / or encapsulated within the polymer electrolyte 28. The support structure may comprise, for example, a mat of nonwoven fibers. The fibers may comprise a polymer (e.g., a polyolefin and / or a polyamide), glass, or a combination thereof. The support structure may comprise, for example, a mat of nonwoven fibers of polypropylene (PP), polyethylene (PE) and / or polyethylene terephthalate (PET). The carrier may have a thickness of greater than or equal to 5 μm, optionally greater than or equal to 10 μm and less than or equal to 200 μm, optionally less than or equal to 100 μm or optionally less than or equal to 50 μm,The negative electrode current collector 30 and the positive electrode current collector 32 are electrically conductive and provide an electrical connection between the external circuit 36 and the negative electrode 22 and the positive electrode 24, respectively. In aspects, the negative electrode current collector 30 and the positive electrode current collector 32 may be made of metal and may be in the form of nonporous metal foils, perforated metal foils, porous metal nets, or a combination thereof. The negative electrode current collector 30 may be made of copper, nickel or their alloys, stainless steel or other suitable electrically conductive material. The positive electrode current collector 32 may be made of aluminum (Al) or other suitable electrically conductive material.MethodThe battery assembly 20 may be manufactured by assembling a stack including the negative electrode 22 and the positive electrode 24, the negative electrode 22 and the positive electrode 24 being spaced apart from each other by a gap, and infiltrating the stack with an electrolyte precursor and then initiating polymerization by free radicals thereof. The electrolyte precursor comprises acrylamide monomers, the optional alkylene bisacrylamide cross-linker, the optional acrylonitrile monomer, a radical initiator, and a liquid electrolyte. The acrylamide monomers, the optional alkylenebisacrylamide crosslinker, the optional acrylonitrile monomer, and the liquid electrolyte may have substantially the same composition as the acrylamide monomer, the optional alkylenebisacrylamide crosslinker, the optional acrylonitrile monomer, and the liquid electrolyte described above with respect to the polymer electrolyte 28, and may be present in the electrolyte precursor in substantially the same proportions.The radical initiator may comprise a thermal polymerization initiator or a photopolymerization initiator. Examples of thermal polymerization initiators include azo compounds, organic peroxides, and combinations thereof. Examples of azo compound initiators include azobisisobutyronitrile (AIBN), 1,1'-azobis(cyclohexanecarbonitrile) (ACHN), and combinations thereof. Examples of organic peroxide initiators include benzoyl peroxide, tert-butylperoxyacetate, and combinations thereof. Examples of photopolymerization initiators include methylbenzoyl formate (MBF). In embodiments, the radical initiator may comprise AIBN.Free radical polymerization of the electrolyte precursor can be initiated such that the acrylamide monomers, the optional alkylenebisacrylamide crosslinker, and the optional acrylonitrile monomer are covalently bonded together to form a polyacrylamide. The polymerization of the electrolyte precursor by free radicals can be initiated, for example, by heating the electrolyte precursor and / or by irradiating the electrolyte precursor with ultraviolet (UV) light. In embodiments where the polymerization of the electrolyte precursor is initiated by free radicals by heating, the electrolyte precursor may be heated to a temperature of greater than or equal to 50 degrees Celsius (° C.), optionally greater than or equal to 70° C., or optionally greater than or equal to 100° C.The above description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or its use. The broad teachings of the disclosure may be practiced in a wide variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be limited to the same as other changes will become apparent after studying the drawings, the specification, and the following claims. It should be appreciated that one or more steps within a method may be performed in different order (or simultaneously) without altering the principles of the present disclosure. Further, although the embodiments are described above as each having particular features, any one or more of those features described with respect to one embodiment of the disclosure may be implemented with and / or combined with features of any of the other embodiments, even if that combination is not expressly described. In other words, the described embodiments are not mutually exclusive, and an exchange of one or more embodiments with one another remains within the scope of this disclosure.

Claims

A battery that cycles lithium ions, the battery comprising: a negative electrode comprising an electroactive negative electrode material; a positive electrode spaced from the negative electrode by a gap, the positive electrode comprising an electroactive positive electrode material; and a polymer electrolyte disposed in the gap between the negative electrode and the positive electrode, the polymer electrolyte comprising: a polyacrylamide comprising acrylamide monomers covalently bonded to each other, and a liquid electrolyte immobilized in the polyacrylamide, the liquid electrolyte comprising a lithium salt in an organic solvent.The battery of claim 1, wherein the acrylamide monomers comprise acrylamide, N-alkylacrylamide, N-cycloalkylacrylamide, dialkylacrylamide, hydroxyalkylacrylamides, N-arylacrylamides, methacrylamide, N-alkylmethacrylamide, N-cycloalkylmethacrylamide, dialkylmethacrylamide, dialkylaminoalkylmethacrylamide, hydroxyalkylmethacrylamide, N-arylmethacrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-acrylamido-2-methyl-propanephosphonic acid, or a combination thereof.The battery of claim 1, wherein at least one of the acrylamide monomers comprises a substituent selected from the group consisting of silyl, siloxy, alkoxysilyl, sulfo, phosphate, and carboxamide.The battery of claim 1, wherein the polyacrylamide further comprises an alkylenebisacrylamide cross-linker, and wherein the acrylamide monomers and the alkylenebisacrylamide cross-linker are covalently bonded together to form a three-dimensional network of interconnected polyacrylamide chains.The battery of claim 1, wherein the polyacrylamide further comprises an acrylonitrile monomer, and wherein the acrylamide monomers and the acrylonitrile monomer are covalently bonded to each other.The battery of claim 1, wherein the polyacrylamide comprises a polymer having formula (1): wherein: m is an integer; n is zero or an integer; p is zero or an integer; q is zero or 1; R 1, R 3, R 4 and R 5 are each individually H, hydroxyl, hydrocarbyl, heterohydrocarbyl, silyl, siloxy, alkoxysilyl, sulfo, phosphate, or carboxamide moieties; R 2 is a divalent hydrocarbyl or heterohydrocarbyl, and the sum of m + n + p is greater than or equal to 100 and less than or equal to 200,000.The battery of claim 1, wherein the organic solvent comprises an ether-based solvent, and wherein the lithium salt comprises lithium hexafluorophosphate (LiPF 6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), or a combination thereof.The battery of claim 1, wherein the liquid electrolyte further comprises an additive comprising lithium nitrate (LiNO 3).The battery of claim 1, wherein the electroactive positive electrode material comprises a sulfur-based material.The battery of claim 1, wherein the electroactive negative electrode material comprises non-porous lithium.

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