Polymer electrolyte composition

Abstract

The present invention relates to a polymer electrolyte composition comprising a lithium salt of (difluoromethanesulfonyl) (trifluoromethanesulfonyl) imide and a second lithium salt. The invention also relates to an electrochemical cell or battery comprising said polymer electrolyte composition and to a method for preparing said polymer electrolyte composition.

Description

Technical Field

[0001] The present invention relates to a polymer electrolyte composition comprising a lithium salt of (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide and a second lithium salt. The present invention also relates to an electrochemical cell or battery comprising the polymer electrolyte composition and to a method for preparing the polymer electrolyte composition. Background Art

[0002] Portable electronic devices are currently being used every day and are becoming increasingly popular. In this regard, a lot of effort is being made to develop new technologies that are intended to improve the energy efficiency of the devices. Certain aspects are the subject of intensive research and relate to the ability of the battery of the device to store large amounts of energy over the entire useful life of the device. In particular, it is not only necessary for the battery to be suitable for storing large amounts of energy, but also to maintain this ability when the battery is subjected to frequent charge and discharge cycles. The charge capacity and capacity retention of the battery depend on a variety of parameters that can each be optimized independently, including the cathode material and structure, the properties of the electrolyte (or separator) and the anode material. In this regard, the use of anodes containing lithium metal has great prospects because these anodes show increased energy density if compared to conventional lithium-ion batteries. It is believed that polymer electrolytes are particularly useful in the realization of Li-metal batteries because they help prevent the formation of lithium dendrites on the electrode surface while facilitating the deposition of lithium on the anode in a uniform manner.

[0003] Polymer electrolytes are compositions comprising polymers and capable of conducting ions such as lithium cations. When used in lithium metal batteries, they are responsible for transferring lithium cations from the anode to the cathode. Lithium cations are transported through the polymer electrolyte via non-covalent interactions between the lithium cations and heteroatoms (such as halogens, O, N, and S) present on the side chains or repeating units of the polymers contained in the electrolyte. Polymer electrolytes typically also contain a lithium salt that is soluble in the medium forming the electrolyte and is responsible for pre-organizing the system and imparting conductivity to the electrolyte while limiting the formation of an ohmic drop during battery operation. Depending on the polymer that forms the electrolyte, several types of polymer electrolytes are known in the art: solid polymer electrolytes, gel polymer electrolytes, plasticized polymer electrolytes, and composite polymer electrolytes. The components used to make polymer electrolytes (e.g., polymers, lithium salts, plasticizers, or solvents, etc.) have been the subject of independent research aimed at optimizing the properties of polymer electrolytes in terms of conductivity, electrochemical stability, and the ability to maintain battery capacity after charging.

[0004] An example of such a polymer electrolyte has been reported by Yuki Kato and co-authors in “Polymer electrolyte plasticized with PEG-borateester having high ionic conductivity and thermal stability” Solid State Ionics, Vol. 150, No. 3-4, 2002, 355-361. The disclosed polymer electrolyte is prepared by the copolymerization of poly(ethylene glycol) methacrylate and poly(ethylene glycol) dimethacrylate induced by light irradiation, and uses lithium bis(trifluoromethane)sulfonyl imide (LiTFSI) as the lithium salt. Further, different amounts of poly(ethylene glycol) borate esters are used as plasticizers. According to the authors, the conductivity of the electrolyte increases with increasing the proportion of plasticizer in the electrolyte formulation. The authors conclude that the reported poly(ethylene glycol) acrylate-based electrolyte is electrochemically stable enough for application in lithium-ion batteries.

[0005] Different lithium salts that can be used for the preparation of polymer electrolytes have been reported in the art. Such salts are generally those that are soluble in polymer electrolytes and can interact with the polymer of the electrolyte via non-covalent interactions (e.g., van der Waals interactions and / or hydrophobic interactions). The strength of these interactions directly affects the ability of the electrolyte to transport lithium cations. Lithium bis(trifluoromethane)sulfonyl imide (LiTFSI) is widely used in the art as a component for polymer electrolyte compositions. Zhang and collaborators reported in "Enhanced Li-ion conductivity of polymerelectrolytes with selective introduction of hydrogen in the anion" AngewandteChemie Int.Ed.2019, Vol. 58, No. 23, 7829-7834, alternative salts (salts similar to LiTFSI) in which one or more F atoms are replaced by H atoms, in particular compounds of formula (I)

[0006]

[0007] The compounds of formula (I) are particularly shown to be effective in increasing the Li ion conductivity of polyethylene oxide-based electrolytes if compared to LiTFSI, without significantly affecting the overall conductivity of the electrolyte, thus teaching that the compounds can be used as components of polymer electrolytes.

[0008] In addition, Qiao L and co-authors disclosed an electrolyte composition comprising a mixture of an organic carbonate and lithium (difluoromethyl (trifluoromethyl) sulfonamide (LiDFTSI) as a lithium salt in “Stable non-corrosive sulfonimide salt for 4-V-class lithium metal batteries” Nature Materials 2022, Vol. 21, 455-462.

[0009] Zhang, H. and co-authors disclosed a polymer electrolyte composition comprising polyethylene oxide and lithium (difluoromethanesulfonyl) (trifluoromethanesulfonyl) imide (LiDFTFSI) as a lithium salt in “Designer Anion Enabling Solid-State Lithium-Sulfur Batteries”, Joule, Vol. 3, No. 7, 2019, pp. 1689-1702. The document further teaches that this salt forms a passivation layer comprising lithium fluoride and lithium hydride on the Li(0) anode, which helps improve the long-term cyclability of the battery by preventing the formation of lithium dendrites on the anode observed with other lithium salts such as lithium bis(trifluoromethanesulfonyl) imide LiTFSI.

[0010] From what is disclosed in the art, it can be seen that there remains a need to provide improved polymer electrolyte compositions for alkaline batteries, particularly electrolytes for lithium batteries having high charge capacity retention after cycling, electrolytes for lithium batteries operating at high voltages and / or low temperatures, and / or electrolytes that cause less corrosion when used in lithium batteries. Summary of the Invention

[0011] After exhaustive studies, the present inventors have developed a polymer electrolyte composition comprising a combination of a compound of formula (I) as defined above and an additional lithium salt. The present inventors have found in particular that the charge retention capacity of a lithium metal battery comprising a polymer electrolyte comprising the combination of the lithium salts is increased if compared to the charge retention capacity of a comparative lithium metal battery comprising a polymer electrolyte comprising each of the aforementioned lithium salts as the sole lithium salt. This synergistic effect of the two lithium salts is unexpected in view of the prior art. Furthermore, the electrolyte of the present invention advantageously allows the battery to be operated at room temperature at temperatures up to 100 % relative to Li / Li + The battery operated at a potential of 4.25 V while maintaining charge retention capacity. Batteries comprising the electrolyte of the present invention were also surprisingly less susceptible to corrosion.

[0012] Thus, in a first aspect, the present invention relates to a polymer electrolyte composition comprising:

[0013] a) polymers for electrolytes;

[0014] b) a first lithium salt of formula (I)

[0015]

[0016] and c) a second lithium salt suitable for use in lithium metal battery electrolytes.

[0017] A second aspect of the invention relates to an electrochemical cell or battery comprising the polymer electrolyte according to the first aspect of the invention.

[0018] A third aspect of the present invention relates to a method for preparing the polymer electrolyte according to the first aspect of the present invention, the method comprising the following steps:

[0019] (i) providing a lithium salt of formula (I) as defined in the first aspect of the present invention;

[0020] (ii) providing a second lithium salt as defined in the first aspect of the present invention; and

[0021] In the first alternative,

[0022] (iii) dissolving the lithium salt provided in steps (i) and (ii) in a polymer for electrolyte; or,

[0023] In the second alternative,

[0024] (iv) dissolving the lithium salt provided in steps (i) and (ii) in a solvent, and

[0025] (v) dissolving a polymer for electrolyte in the mixture obtained in step (iv);

[0026] as well as

[0027] (vi) Optionally, cross-linking the polymer for electrolyte contained in the mixture produced by step (iii) or (v). BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The specific discharge capacity (in mAh·g) of the Li cell is shown as a function of the number of charge / discharge cycles performed as disclosed in Example 2. -1 denoted by ), and contains lithium bis(oxalato)borate as the sole lithium salt ((■) charge capacity (□) discharge capacity).

[0029] Figure 2 The specific discharge capacity (in mAh·g) of the Li cell is shown as a function of the number of charge / discharge cycles performed as disclosed in Example 2. -1denoted by ), and comprising a compound of formula (I) as the sole lithium salt ((■) charge capacity (□) discharge capacity).

[0030] Figure 3 The specific discharge capacity (in mAh·g) of the Li cell is shown as a function of the number of charge / discharge cycles performed as disclosed in Example 2. -1 denoted by ), and contains a combination of lithium bis(oxalato)borate and a compound of formula (I) as a lithium salt ((■) charge capacity (□) discharge capacity).

[0031] Figure 4 The specific discharge capacity (in mAh·g) of cells 4 (filled square symbols) and 5 (open square symbols) of Example 2 is shown as a function of the number of charge / discharge cycles performed as disclosed in Example 2. -1 express). DETAILED DESCRIPTION

[0032] Unless otherwise stated, all terms used herein in this application should be understood to have their ordinary meanings as known in the art. Other more specific definitions for certain terms used in this application are set forth below and are intended to apply uniformly throughout the specification and claims unless otherwise expressly set forth a definition providing a broader definition.

[0033] For the purposes of the present invention, any range given includes both the lower and upper endpoints of the range. A given range or value (e.g., temperature, time, molar ratio, volume ratio, etc.) should be considered an approximation (i.e., with a 5% variation around the specified point) when it is defined by the term "about."

[0034] In the context of the present invention, the term "plasticizer" refers to substances which are suitable for softening polymers. Examples of plasticizers are known in the art and include, among others, organic solvents and compounds such as dimethoxyethane (DME), 1,2-diethoxyethane (DEE), 1,3-dioxolane (DOL), diethylene glycol dimethyl ether (DEGDME), triethylene glycol dimethyl ether (G3), tetraethylene glycol dimethyl ether (TEGDME), poly(ethylene glycol) dimethyl ether (PEGDME), tetrahydropyran (THP), γ-butyrolactone, tetrahydrofuran (THF), 2-methyltetrahydrofuran, diethyl ether, methyl-tert-butyl ether, succinonitrile (SN), glutaronitrile (GN), adiponitrile (AN), N,N-dimethylsulfamoyl fluoride (FSA), N,N-dimethyltrifluoromethane-sulfonamide (TFSA), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), and any mixtures thereof.

[0035] In the context of the present invention, the term "polymer electrolyte" refers to a material comprising a polymer material suitable for conducting ions (particularly lithium cations) via non-covalent interactions between polymer chains and ions. Suitable polymers for polymer electrolytes are known in the art and typically contain heteroatoms such as O, N, S or P in the repeating units of the polymer chain, which are suitable for interacting with lithium cations via lone pairs of heteroatoms. A non-exhaustive list of polymers for forming polymer electrolytes includes polyoxyalkylenes, polyalkyleneimines, polyalkylene sulfides, polyalkylene carbonates, polyacrylates, polyurethanes, polyethylene glycols optionally comprising one or more crosslinkable groups, polyphosphazenes, polysiloxanes, polyvinyl alcohol (PVA), polyvinylamine (PVAm), polyvinyl acetate (PVAc), polyvinyl halides, polyacrylonitrile (PAN), poly(vinyl pyrrolidone) (PVP), poly(2-vinyl pyridine) (P2VP), poly(ε-caprolactone) (PCL), poly(maleimide), polyaniline (PANI), chitosan (CS), and any blends or copolymers or crosslinked polymers thereof. In addition, the polymer for electrolyte according to the present invention may contain at least one crosslinkable functional group in its molecular formula, such as (meth)acrylate, epoxy, olefin, thiol, amino, hydroxyl and other crosslinkable functional groups known in the art. Alternatively, the polymer for electrolyte according to the present invention may be a crosslinked product.

[0036] In the context of the present invention, the term "acrylate" refers to a compound comprising a moiety of the formula:

[0037]

[0038] Thus, the term encompasses acrylate compounds, alkylacrylate compounds such as methacrylate compounds, cyanoacrylate compounds, and the like.

[0039] In the context of the present invention, the term "(meth)acrylate" refers to an acrylate compound or a methacrylate compound.

[0040] In the context of the present invention, the term "alkyl" refers to a saturated aliphatic hydrocarbon chain having the number of atoms disclosed in the specification and claims. Thus, "alkyl" may refer to methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, pentyl, and hexyl, among others.

[0041] As mentioned above, the first aspect of the present invention relates to a polymer electrolyte composition comprising:

[0042] a) polymers for electrolytes;

[0043] b) a first lithium salt of formula (I)

[0044]

[0045] and c) a second lithium salt suitable for use in lithium metal battery electrolytes.

[0046] The second lithium salt may be inorganic or organic. Preferably, the second lithium salt is selected from lithium perchlorate, lithium nitrate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium chlorotrifluoroborate, lithium fluoride, lithium oxide, lithium peroxide, a salt of formula LiN(SO2CF3)2, a salt of formula LiN(SO2F)2, a salt of formula LiN(SO2CF3)(SO2F), a salt of formula LiN(SO2C2F5)(SO2F), a salt of formula LiB(C2O4)2, a salt of formula LiBF2(C2O4), a salt of formula LiC(SO2CF3)3, a salt of formula LiPF3(C2F5)3, a salt of formula LiCF3SO3, and a mixture thereof.

[0047] In another embodiment, the electrolyte composition of the first aspect is an electrolyte composition wherein the second lithium salt is not lithium fluoride. The skilled person will understand that when the electrolyte is used in a lithium metal battery, this embodiment does not exclude the formation of lithium fluoride as a component of the solid electrolyte interface (SEI) between the electrolyte and the anode of the battery (e.g., by decomposition of LiDFTSI). Therefore, in a more preferred embodiment, the second lithium salt is selected from lithium perchlorate, lithium nitrate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium chlorotrifluoroborate, lithium oxide, lithium peroxide, salts of formula LiN(SO2CF3)2, salts of formula LiN(SO2F)2, salts of formula LiN(SO2CF3)(SO2F), salts of formula LiN(SO2C2F5)(SO2F), salts of formula LiB(C2O4)2, salts of formula LiBF2(C2O4), salts of formula LiC(SO2CF3)3, salts of formula LiPF3(C2F5)3, salts of formula LiCF3SO3, and mixtures thereof.

[0048] In a more preferred embodiment of the first aspect of the present invention, the second lithium salt is selected from lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium chlorotrifluoroborate, a salt of formula LiB(C2O4)2, a salt of formula LiBF2(C2O4), a salt of formula LiPF3(C2F5)3, a salt of formula LiCF3SO3, and a mixture thereof.

[0049] In another preferred embodiment of the first aspect of the present invention, the second lithium salt is an organic lithium salt preferably selected from the following: a salt of formula LiN(SO2CF3)2, a salt of formula LiN(SO2F)2, a salt of formula LiN(SO2CF3)(SO2F), a salt of formula LiN(SO2C2F5)(SO2F), a salt of formula LiB(C2O4)2, a salt of formula LiBF2(C2O4), a salt of formula LiC(SO2CF3)3, a salt of formula LiPF3(C2F5)3, a salt of formula LiCF3SO3, and a mixture thereof.

[0050] In another preferred embodiment of the first aspect of the present invention, the second lithium salt is a salt of the formula LiB(C2O4)2 (which is lithium bis(oxalato)borate). In another preferred embodiment of the first aspect of the present invention, the second lithium salt is a salt of the formula LiBF2(C2O4) (which is lithium difluoro(oxalato)borate (LiDFOB)).

[0051] In another preferred embodiment of the first aspect of the invention, the weight ratio of the first lithium salt to the second lithium salt is 1:1 to 4:1; preferably, it is 1:1 to 3:1, and more preferably, it is 1:1 to 2:1. In an even more preferred embodiment of the first aspect of the invention, the weight ratio of the first lithium salt to the second lithium salt is about 112:81. In an even more preferred embodiment of the first aspect of the invention, the weight ratio of the first lithium salt to the second lithium salt is about 114:82. In an even more preferred embodiment of the first aspect of the invention, the weight ratio of the first lithium salt to the second lithium salt is about 95:51.

[0052] In another preferred embodiment of the first aspect of the present invention, the lithium salt contained in the polymer electrolyte composition accounts for 5 wt % to 60 wt % of the composition.

[0053] In another more preferred embodiment of the first aspect of the present invention, the lithium salt is contained in the polymer electrolyte composition in an amount of 10 wt % to 50 wt % of the composition.

[0054] In another more preferred embodiment of the first aspect of the present invention, the lithium salt included in the polymer electrolyte composition accounts for 10 wt % to 30 wt % of the composition. In another more preferred embodiment of the first aspect of the present invention, the lithium salt included in the polymer electrolyte composition accounts for 15 wt % to 25 wt % of the composition.

[0055] In another more preferred embodiment of the first aspect of the present invention, the polymer electrolyte composition comprises a lithium salt in an amount of about 20% by weight of the composition.

[0056] In another embodiment of the first aspect of the present invention, the second lithium salt is lithium bis(oxalato)borate or lithium difluoro(oxalato)borate LiBF2(C2O4) (LiDFOB), and:

[0057] - the weight ratio of the first lithium salt to the second lithium salt is from 1:1 to 4:1; preferably, it is from 1:1 to 3:1, and more preferably, it is from 1:1 to 2:1; and / or

[0058] - The lithium salt contained in the polymer electrolyte composition accounts for 10 wt% to 50 wt% of the composition; preferably, the lithium salt contained in the polymer electrolyte composition accounts for 10 wt% to 30 wt% of the composition; even more preferably, the lithium salt contained in the polymer electrolyte composition accounts for 15 wt% to 25 wt% of the composition.

[0059] In another embodiment of the first aspect of the present invention, the first lithium salt of formula (I) is present in an amount of 5 to 40 weight % of the composition; preferably, it is present in an amount of 5 to 15 weight % of the composition. More preferably, the first lithium salt of formula (I) is present in an amount of about 11.2 weight % of the composition, or about 11.4 weight % of the composition, or about 9.5 weight % of the composition.

[0060] In another embodiment of the first aspect of the present invention, the second lithium salt is present in an amount of 5% to 20% by weight of the composition; preferably, 5% to 10% by weight of the composition. More preferably, the second lithium salt is present in an amount of about 8.1% of the composition. In another preferred embodiment, the second lithium salt is present in an amount of about 8.2% of the composition. In another preferred embodiment, the second lithium salt is present in an amount of about 5.1% of the composition.

[0061] In another embodiment of the first aspect of the invention, the polymer is in the form of a cross-linked polymer or in the form of a cross-linkable polymer composition.

[0062] In another embodiment of the first aspect of the invention, the polymer comprises in its molecular formula one or more crosslinkable functional groups such as (meth)acrylate, epoxy, olefin, thiol, amino, hydroxyl and other crosslinkable functional groups known in the art.

[0063] In another embodiment of the first aspect of the invention, the polymer optionally comprises one or more cross-linkable functional groups in its molecular formula and is selected from:

[0064] - polyoxyalkylenes such as polyethylene oxide (PEO) or polypropylene oxide (PPO),

[0065] - polyalkyleneimines such as polyethyleneimine (PEI),

[0066] - polyalkylene sulfides such as polyethylene sulfide (PES),

[0067] - polyalkylene carbonates such as polytrimethylene carbonate (PTMC), polyethylene carbonate (PEC) or polypropylene carbonate (PPC),

[0068] - polyacrylates, for example polymers of methyl methacrylate (PMMA), (C1-C6)alkyl acrylates, for example butyl acrylate (PBA) or ethyl acrylate (PEA), cyanoethyl acrylate (PCEA), or blends thereof or copolymers thereof or crosslinked polymers thereof with trimethylolpropane triacrylate (ETPTA) and / or pentaerythritol tetraacrylate (PETA),

[0069] - polyethylene glycol,

[0070] - polyphosphazenes, for example poly[bis(2-(2-methoxyethoxy)ethoxy)phosphazene (MEEP),

[0071] - polysiloxanes, such as poly(dimethylsiloxane) (PDMS),

[0072] - polyvinyl alcohol (PVA),

[0073] -polyvinylamine (PVAm),

[0074] - polyvinyl acetate (PVAc),

[0075] - polyvinyl halides such as polyvinyl chloride (PVC) or polyvinylidene fluoride (PVdF); polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP),

[0076] - polyacrylonitrile (PAN),

[0077] - poly(vinylpyrrolidone) (PVP),

[0078] - poly(2-vinylpyridine) (P2VP),

[0079] - poly(ε-caprolactone) (PCL),

[0080] - poly(maleimides), such as poly(alkylenemaleimides), poly(ethylene-alt-maleimide) (PEaMI),

[0081] -polyaniline (PANI),

[0082] - Chitosan (CS), and

[0083] - any blend or any copolymer or any cross-linked polymer thereof.

[0084] In another embodiment of the first aspect of the present invention, the polymer is selected from the group consisting of:

[0085] - polyoxyalkylenes such as polyethylene oxide (PEO) or polypropylene oxide (PPO),

[0086] - polyalkyleneimines such as polyethyleneimine (PEI),

[0087] - polyalkylene sulfides such as polyethylene sulfide (PES),

[0088] - polyalkylene carbonates, such as polytrimethylene carbonate (PTMC), polyethylene carbonate (PEC) or polypropylene carbonate (PPC),

[0089] - polyacrylates, for example polymers of methyl methacrylate (PMMA), (C1-C6)alkyl acrylates, for example butyl acrylate (PBA) or ethyl acrylate (PEA), cyanoethyl acrylate (PCEA), or blends thereof or copolymers thereof or crosslinked polymers thereof with trimethylolpropane triacrylate (ETPTA) and / or pentaerythritol tetraacrylate (PETA),

[0090] - polyethylene glycol optionally comprising one or more crosslinkable groups, such as poly(ethylene glycol), poly(ethylene glycol) methacrylate (PEGMA), poly(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) dimethacrylate (PEGDMA),

[0091] - polyphosphazenes, for example poly[bis(2-(2-methoxyethoxy)ethoxy)phosphazene (MEEP),

[0092] - polysiloxanes, such as poly(dimethylsiloxane) (PDMS),

[0093] - polyvinyl alcohol (PVA),

[0094] -polyvinylamine (PVAm),

[0095] - polyvinyl acetate (PVAc),

[0096] - polyvinyl halides, for example polyvinyl chloride (PVC) or polyvinylidene fluoride (PVdF); polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP),

[0097] - polyacrylonitrile (PAN),

[0098] - poly(vinylpyrrolidone) (PVP),

[0099] - poly(2-vinylpyridine) (P2VP),

[0100] - poly(ε-caprolactone) (PCL),

[0101] - poly(maleimides), such as poly(alkylenemaleimides), poly(ethylene-alt-maleimide) (PEaMI),

[0102] -polyaniline (PANI),

[0103] - Chitosan (CS), and

[0104] - any blend or any copolymer or any cross-linked polymer thereof.

[0105] In another embodiment of the first aspect of the present invention, the polymer is selected from the group consisting of:

[0106] Polyacrylates, for example polymers of methyl methacrylate (PMMA), (C1-C6)alkyl acrylates such as butyl acrylate (PBA) or ethyl acrylate (PEA), cyanoethyl acrylate (PCEA), or blends thereof or copolymers thereof or crosslinked polymers thereof with trimethylolpropane triacrylate (ETPTA) and / or pentaerythritol tetraacrylate (PETA), and

[0107] - polyethylene glycol optionally comprising one or more crosslinkable groups, such as poly(ethylene glycol), poly(ethylene glycol) methacrylate (PEGMA), poly(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) dimethacrylate (PEGDMA), or mixtures thereof and crosslinked polymers thereof.

[0108] In another embodiment of the first aspect of the present invention, the polymer is selected from the group consisting of:

[0109] - polyacrylates, for example polymers of butyl acrylate (PBA) or crosslinked polymers thereof with trimethylolpropane triacrylate (ETPTA) and / or pentaerythritol tetraacrylate (PETA), and

[0110] - polyethylene glycol optionally comprising one or more crosslinkable groups, such as poly(ethylene glycol), poly(ethylene glycol) methacrylate (PEGMA), poly(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) dimethacrylate (PEGDMA), or mixtures thereof and crosslinked polymers thereof.

[0111] In another embodiment of the first aspect of the present invention, the polymer is selected from the group consisting of:

[0112] - polyacrylates, for example polymers of butyl acrylate (PBA) or cross-linked polymers thereof with pentaerythritol tetraacrylate (PETA), and

[0113] - polyethylene glycol optionally comprising one or more crosslinkable groups, such as poly(ethylene glycol), poly(ethylene glycol) methacrylate (PEGMA), poly(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) dimethacrylate (PEGDMA), or mixtures thereof and crosslinked polymers thereof.

[0114] In another preferred embodiment of the first aspect of the present invention, the polymer is a cross-linked polymer of butyl acrylate and trimethylolpropane triacrylate (ETPTA) and / or pentaerythritol tetraacrylate (PETA). In another embodiment, the polymer is a mixture of butyl acrylate and trimethylolpropane triacrylate (ETPTA) and / or pentaerythritol tetraacrylate (PETA), i.e., the mixture before cross-linking. Preferably, the polymer is a cross-linked polymer of butyl acrylate and pentaerythritol tetraacrylate (PETA). In another embodiment, the polymer is a mixture of butyl acrylate and pentaerythritol tetraacrylate (PETA), i.e., the mixture before cross-linking.

[0115] When the polymer is a mixture of butyl acrylate and trimethylolpropane triacrylate (ETPTA) and / or pentaerythritol tetraacrylate (PETA), the weight ratio of butyl acrylate to trimethylolpropane triacrylate (ETPTA) and / or pentaerythritol tetraacrylate (PETA) is from 1:1 to 4:1; more preferably from 2:1 to 4:1; more preferably from 2:1 to 3:1, even more preferably about 3:1; and even more preferably about 113:39. More preferably, the weight ratio of butyl acrylate to trimethylolpropane triacrylate (ETPTA) and / or pentaerythritol tetraacrylate (PETA) is about 96:43 or about 98:43.

[0116] In another embodiment of the first aspect of the present invention, when polymer is the polyethylene glycol optionally comprising one or more crosslinkable groups, the crosslinkable groups are selected from (meth) acrylate, cyanoacrylate, vinyl, mercaptan, epoxy, amino and hydroxyl, and blends or copolymers thereof. Such polymer can be crosslinked via the ring-opening reaction of thiol-ene chemical reaction, free radical polymerization or epoxide and other crosslinking reactions known in the art. More preferably, polymer is crosslinked and produced by one or more poly (ethylene glycol) compounds comprising one or more crosslinkable groups, the groups being preferably as defined above, and more preferably (meth) acrylate.

[0117] In another embodiment of the first aspect of the invention, the polymer is selected from poly(ethylene glycol) methacrylate (PEGMA), poly(ethylene glycol) dimethacrylate (PEGDMA), and blends or copolymers or cross-linked polymers thereof.

[0118] In another embodiment of the first aspect of the invention, the polymer is selected from poly(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) dimethacrylate (PEGDMA), and blends or copolymers or cross-linked polymers thereof.

[0119] In another embodiment of the first aspect of the invention, the polymer is selected from poly(ethylene glycol) methyl ether methacrylate or a cross-linked polymer thereof, poly(ethylene glycol) dimethacrylate (PEGDMA) or a cross-linked polymer thereof, a cross-linked polymer of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or a polymer thereof, and blends or copolymers thereof.

[0120] In another embodiment of the first aspect of the present invention, the polymer is selected from a mixture of poly(ethylene glycol) methyl ether methacrylate (and poly(ethylene glycol) dimethacrylate (PEGDMA) and a cross-linked polymer of poly(ethylene glycol) methyl ether methacrylate (and poly(ethylene glycol) dimethacrylate (PEGDMA). The molecular weight of the polymer is preferably from 100 g / mole to 10,000 g / mole. More preferably, the molecular weight of the polymer is from 250 g / mole to 5,000 g / mole. Even more preferably, the molecular weight of the polymer is from 500 g / mole to 1,000 g / mole. In certain embodiments, it is contemplated that the polymer is selected from poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA), and the molecular weight of the polymer is from 500 g / mole to 1,000 g / mole; preferably 500 g / mole or 550 g / mole.

[0121] In another embodiment of the first aspect of the present invention, when the polymer is selected from a mixture of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) and a cross-linked polymer of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA), the poly(ethylene glycol) dimethacrylate preferably constitutes 20% to 30% by weight of the weight of the polymer in the composition.

[0122] When the polymer contains one or more crosslinkable acrylate groups in its molecular formula, the polymer electrolyte composition optionally further comprises a free radical polymerization initiator, such as azoisobutyronitrile (AIBN). The initiator compound is preferably present in an amount of 0.1% to 1% by weight of the polymer electrolyte composition; more preferably, in an amount of 0.3% by weight of the polymer electrolyte composition.

[0123] In another embodiment of the first aspect of the present invention, the polymer comprises about 15% by weight of the composition.

[0124] In another embodiment of the first aspect of the invention, the polymer is a polymer resulting from free radical polymerization of a mixture of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA). In another embodiment, the polymer is also contemplated to be a mixture of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA), i.e., a mixture prior to crosslinking.

[0125] In another embodiment of the first aspect of the invention, when the polymer is a mixture of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or a cross-linked polymer thereof, preferably the weight ratio of poly(ethylene glycol) methyl ether methacrylate to PEGDMA is 1:1 to 4:1; more preferably 2:1 to 4:1; even more preferably about 3:1; and even more preferably about 113:39.

[0126] In another embodiment of the first aspect of the invention, the polymer is selected from poly(ethylene glycol) methyl ether methacrylate or polymers thereof, poly(ethylene glycol) dimethacrylate (PEGDMA) or polymers thereof, and cross-linked polymers of poly(ethylene glycol) methyl ether methacrylate and polymers thereof with poly(ethylene glycol) dimethacrylate (PEGDMA) or polymers thereof; and:

[0127] - the polymer represents 5% to 90% by weight of the composition; preferably, the polymer represents 10% to 60% by weight of the composition; even more preferably, the polymer represents 10% to 20% by weight of the composition; and / or

[0128] When the polymer is a mixture of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or a cross-linked polymer thereof, preferably the weight ratio of poly(ethylene glycol) methyl ether methacrylate to PEGDMA is from 1:1 to 4:1; more preferably from 2:1 to 4:1; even more preferably about 3:1; and even more preferably about 113:39.

[0129] In another embodiment of the first aspect of the present invention, the polymer is selected from poly(butyl) acrylate; and a cross-linked polymer of butyl acrylate and pentaerythritol acrylate; and:

[0130] - the polymer represents 5% to 90% by weight of the composition; preferably, the polymer represents 10% to 60% by weight of the composition; even more preferably, the polymer represents 10% to 20% by weight of the composition; and / or

[0131] When the polymer is a cross-linked polymer of butyl acrylate and pentaerythritol acrylate and poly(butyl)acrylate, preferably the weight ratio of butyl acrylate to PETA is from 1:1 to 4:1; more preferably from 2:1 to 4:1; even more preferably about 3:1; and even more preferably about 113:39, or about 96:43, or about 98:43.

[0132] Thus, in a particular embodiment, the polymer electrolyte of the present invention is a polymer electrolyte wherein:

[0133] - the second lithium salt is lithium bis(oxalato)borate or lithium difluoro(oxalato)borate LiBF2(C2O4) (LiDFOB);

[0134] - the weight ratio of the first lithium salt to the second lithium salt is from 1:1 to 4:1; preferably it is from 1:1 to 3:1, and more preferably it is from 1:1 to 2:1;

[0135] - the lithium salt contained in the polymer electrolyte composition constitutes 10% to 50% by weight of the composition; preferably, the lithium salt contained in the polymer electrolyte composition constitutes 10% to 30% by weight of the composition; even more preferably, the lithium salt contained in the polymer electrolyte composition constitutes about 20% by weight of the composition; and / or

[0136] - polymers selected from (i) poly(ethylene glycol) methyl ether methacrylate or cross-linked polymers thereof, poly(ethylene glycol) dimethacrylate (PEGDMA) or cross-linked polymers thereof, cross-linked polymers of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA), and blends or copolymers thereof, and (ii) polybutyl acrylate (PBA) or cross-linked polymers thereof with pentaerythritol acrylate (PETA);

[0137] - the polymer represents from 5% to 90% by weight of the composition; preferably, the polymer represents from 10% to 60% by weight of the composition; even more preferably, the polymer represents from 10% to 20% by weight of the composition; and wherein:

[0138] When the polymer is a mixture of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or a cross-linked polymer thereof, preferably the weight ratio of poly(ethylene glycol) methyl ether methacrylate to PEGDMA is from 1:1 to 4:1; more preferably from 2:1 to 4:1; even more preferably about 3:1; and even more preferably about 113:39;

[0139] When the polymer is a cross-linked polymer of butyl acrylate and pentaerythritol acrylate or poly(butyl)acrylate, preferably the weight ratio of butyl acrylate to PETA is from 1:1 to 4:1; more preferably from 2:1 to 4:1; even more preferably about 3:1; and even more preferably about 113:39, or about 96:43, or about 98:43;

[0140] When the polymer comprises one or more crosslinkable acrylate groups in its molecular formula, the polymer electrolyte composition optionally also comprises an initiator for free-radical polymerization, such as azoisobutyronitrile (AIBN).

[0141] In a more specific embodiment, the polymer electrolyte of the first aspect of the present invention also comprises a plasticizer. Particularly suitable are plasticizer compounds that are applicable to the lithium salts of the dissolved polymer electrolyte. Such solvents are known in the art and include ether solvents, nitrile, fluorinated sulfonamide, carbonates or their combination.

[0142] In a more specific embodiment, the polymer electrolyte of the first aspect of the present invention further comprises a plasticizer selected from the group consisting of dimethoxyethane (DME), 1,2-diethoxyethane (DEE), 1,3-dioxolane (DOL), diethylene glycol dimethyl ether (DEGDME), triethylene glycol dimethyl ether (G3), tetraethylene glycol dimethyl ether (TEGDME), poly(ethylene glycol) dimethyl ether (PEGDME), tetrahydropyran (THP), γ-butyrolactone, tetrahydrofuran (THF), 2-methyltetrahydrofuran, diethyl ether, methyl-tert-butyl ether, succinonitrile (SN), glutaronitrile (GN), adiponitrile (AN), N,N-dimethylsulfamoyl fluoride (FSA), N,N-dimethyltrifluoromethane-sulfonamide (TFSA), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), and any mixture thereof.

[0143] In a more specific embodiment, the polymer electrolyte of the first aspect of the invention further comprises a plasticizer, which is a carbonate-based solvent and is preferably selected from ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), and any mixture thereof.

[0144] In a more specific embodiment, the polymer electrolyte of the first aspect of the present invention further comprises a plasticizer selected from ethyl methyl carbonate (EMC), ethylene carbonate (EC) and mixtures thereof; preferably, it is a mixture of ethyl methyl carbonate (EMC) and ethylene carbonate (EC).

[0145] When the plasticizer is a mixture of ethyl methyl carbonate (EMC) and ethylene carbonate (EC), the weight ratio of ethylene carbonate (EC) to ethyl methyl carbonate (EMC) is preferably 1:1 to 3:2. More preferably, the weight ratio is about 371:283, about 377:288, or about 405:308.

[0146] In a more specific embodiment, the polymer electrolyte of the first aspect of the present invention further comprises a plasticizer accounting for 5 wt % to 90 wt % of the polymer electrolyte composition. More preferably, the plasticizer accounts for 20 wt % to 80 wt % of the polymer electrolyte composition. Even more preferably, the plasticizer accounts for 40 wt % to 80 wt % of the polymer electrolyte composition. Even more preferably, the plasticizer accounts for 60 wt % to 80 wt % of the polymer electrolyte composition.

[0147] In a more specific embodiment, the polymer electrolyte of the first aspect of the present invention further comprises about 65.4% by weight of a plasticizer, based on the weight of the composition. In a more specific embodiment, the polymer electrolyte of the first aspect of the present invention further comprises about 66.6% by weight of a plasticizer, based on the weight of the composition. In a more specific embodiment, the polymer electrolyte of the first aspect of the present invention further comprises about 71.3% by weight of a plasticizer, based on the weight of the composition.

[0148] Thus, in a particular embodiment, the polymer electrolyte of the present invention is a polymer electrolyte wherein:

[0149] - the second lithium salt is lithium bis(oxalato)borate or lithium difluoro(oxalato)borate LiBF2(C2O4) (LiDFOB);

[0150] - the weight ratio of the first lithium salt to the second lithium salt is from 1:1 to 4:1; preferably it is from 1:1 to 3:1, and more preferably it is from 1:1 to 2:1;

[0151] - the lithium salt contained in the polymer electrolyte composition constitutes 10% to 50% by weight of the composition; preferably, the lithium salt contained in the polymer electrolyte composition constitutes 10% to 30% by weight of the composition; even more preferably, the lithium salt contained in the polymer electrolyte composition constitutes about 20% by weight of the composition; and / or

[0152] - polymers selected from: (i) poly(ethylene glycol) methyl ether methacrylate or cross-linked polymers thereof, poly(ethylene glycol) dimethacrylate (PEGDMA) or cross-linked polymers thereof, cross-linked polymers of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or polymers thereof, and blends or copolymers thereof; and (ii) polybutyl acrylate (PBA) or cross-linked polymers thereof with pentaerythritol acrylate (PETA);

[0153] - the polymer represents 5% to 90% by weight of the composition; preferably, the polymer represents 10% to 60% by weight of the composition; even more preferably, the polymer represents 10% to 20% by weight of the composition;

[0154] - the composition further comprises a plasticizer, which is a mixture of ethyl methyl carbonate (EMC) and ethylene carbonate (EC), wherein the weight ratio of ethylene carbonate (EC) to ethyl methyl carbonate (EMC) is preferably 1:1 to 3:2, and the plasticizer preferably accounts for 40% to 80% by weight of the polymer electrolyte composition; and wherein:

[0155] When the polymer is a mixture of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or a cross-linked polymer thereof, preferably the weight ratio of poly(ethylene glycol) methyl ether methacrylate to PEGDMA is from 1:1 to 4:1; more preferably from 2:1 to 4:1; even more preferably about 3:1; and even more preferably about 113:39;

[0156] When the polymer is a cross-linked polymer of butyl acrylate and pentaerythritol acrylate or poly(butyl)acrylate, preferably the weight ratio of butyl acrylate to PETA is from 1:1 to 4:1; more preferably from 2:1 to 4:1; even more preferably about 3:1; and even more preferably about 113:39, or about 96:43, or about 98:43;

[0157] When the polymer comprises one or more crosslinkable acrylate groups in its molecular formula, the polymer electrolyte composition optionally also comprises an initiator for free-radical polymerization, such as azoisobutyronitrile (AIBN).

[0158] Thus, in a particular embodiment, the polymer electrolyte of the present invention comprises:

[0159] a) a first lithium salt of formula (I) in an amount of 5 to 15 wt % of the composition, preferably 11.2 wt % or 11.4 wt % or 9.5 wt %;

[0160] b) a second lithium salt of LiB(C2O4)2 in an amount of 5 to 10 wt% of the composition, preferably 8.1 wt% or 8.2 wt%; or, alternatively, a second lithium salt of LiBF2(C2O4) in an amount of 5 to 10 wt% of the composition, preferably 5.1 wt%;

[0161] c) the polymer comprises 10% to 20% by weight of the composition and is a mixture of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or a crosslinked polymer of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or polymers thereof, and blends or copolymers thereof; preferably, the polymer comprises about 15.2% by weight of the composition, or, alternatively, the polymer comprises 10% to 20% by weight of the composition and is a crosslinked polymer of butyl acrylate and pentaerythritol acrylate or poly(butyl) acrylate, preferably, the polymer comprises about 13.9% or about 14.1% by weight of the composition,

[0162] d) a plasticizer, which comprises 40% to 80% by weight of the composition and is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC); preferably, the weight ratio of EC to EMC is 1:1 to 3:2; more preferably, the plasticizer comprises 65.5% by weight of the composition; or, alternatively, the plasticizer comprises 66.6% by weight of the composition; or, alternatively, the plasticizer comprises 71.3% by weight of the composition.

[0163] In a more preferred embodiment, the polymer electrolyte of the first aspect comprises:

[0164] a) a first lithium salt of formula (I) in an amount of 11.2% by weight of the composition;

[0165] b) a second lithium salt of LiB(C2O4)2 in an amount of about 8.1% by weight of the composition;

[0166] c) a polymer comprising about 15.2 weight percent of the composition and being a mixture of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or a crosslinked polymer of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or polymers thereof, and blends or copolymers thereof; wherein the weight ratio of poly(ethylene glycol) methyl ether methacrylate to PEGDMA is about 113:39,

[0167] d) a plasticizer comprising about 65.4% by weight of the composition and being a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC); the weight ratio of EC to EMC being about 371:283; and

[0168] e) When the polymer contains one or more cross-linkable acrylate groups in its molecular formula, the polymer electrolyte composition optionally also contains an initiator for free radical polymerization, such as azoisobutyronitrile (AIBN).

[0169] In a more preferred embodiment, the polymer electrolyte of the first aspect comprises:

[0170] a) a first lithium salt of formula (I) in an amount of 11.4% by weight of the composition;

[0171] b) a second lithium salt of LiB(C2O4)2 in an amount of about 8.2% by weight of the composition;

[0172] c) a polymer comprising 10% to 20% by weight of the composition and being a cross-linked polymer of butyl acrylate and pentaerythritol acrylate or poly(butyl) acrylate, preferably, the polymer comprises about 13.9% by weight of the composition;

[0173] d) a plasticizer comprising about 66.6% by weight of the composition and being a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC); the weight ratio of EC to EMC being about 377:288; and

[0174] e) When the polymer contains one or more cross-linkable acrylate groups in its molecular formula, the polymer electrolyte composition optionally also contains an initiator for free radical polymerization, such as azoisobutyronitrile (AIBN).

[0175] In a more preferred embodiment, the polymer electrolyte of the first aspect comprises:

[0176] a) a first lithium salt of formula (I) in an amount of 9.5% by weight of the composition;

[0177] b) a second lithium salt of LiBF2(C2O4) in an amount of about 5.1% by weight of the composition;

[0178] c) a polymer comprising 10% to 20% by weight of the composition and being a cross-linked polymer of butyl acrylate and pentaerythritol acrylate or poly(butyl) acrylate, preferably, the polymer comprises about 14.1% by weight of the composition;

[0179] d) a plasticizer comprising about 71.3% by weight of the composition and being a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC); the weight ratio of EC to EMC being about 405:308; and

[0180] e) When the polymer contains one or more cross-linkable acrylate groups in its molecular formula, the polymer electrolyte composition optionally also contains an initiator for free radical polymerization, such as azoisobutyronitrile (AIBN).

[0181] As will be apparent to the skilled artisan, the polymer electrolytes of certain embodiments of the present invention may be in the form of a crosslinked composition or in the form of a crosslinkable composition.

[0182] The polymer electrolyte of the first aspect of the invention is particularly useful in electrochemical devices such as electrochemical cells or batteries.Thus, a second aspect of the invention relates to an electrochemical cell or battery comprising the polymer electrolyte according to the first aspect of the invention.

[0183] In a preferred embodiment, the second aspect of the invention relates to an electrochemical cell or battery comprising a polymer electrolyte according to any preferred or particular embodiment of the first aspect of the invention defined above.

[0184] In a preferred embodiment, the second aspect of the present invention relates to a lithium metal battery comprising a polymer electrolyte according to any preferred or particular embodiment of the first aspect of the invention defined above. A lithium metal battery is a battery characterized in that it comprises an anode consisting essentially of metallic lithium.

[0185] In another preferred embodiment, the second aspect of the present invention relates to a lithium metal battery comprising a cathode, wherein the cathode material is selected from lithium manganese oxide, lithium nickel oxide, lithium nickel manganese cobalt oxide, lithium nickel manganese oxide, lithium manganese cobalt oxide, lithium copper oxide, lithium copper sulfide, lithium iron phosphate, lithium iron sulfide, lithium manganese iron phosphate and lithium nickel cobalt aluminum oxide.

[0186] In another preferred embodiment, the second aspect of the present invention relates to a lithium metal battery comprising a cathode, wherein the cathode material is lithium nickel manganese cobalt oxide such as NMC622.

[0187] In another preferred embodiment, the second aspect of the invention relates to a lithium metal battery comprising a membrane, such as a microporous polypropylene membrane, arranged between at least one electrode and the electrolyte in such a way that lithium cations can flow through the membrane between the polymer electrolyte and the surface of at least one electrode.

[0188] In another preferred embodiment, the second aspect of the invention relates to a lithium metal battery having a charge retention capacity of at least 70%, preferably at least 75%, and more preferably at least 80% after 100 charging cycles, wherein the first cycle is applied at a current of C / 20, the three next cycles are applied at a current of C / 10, and the remaining cycles are applied at C / 5 at a temperature of 25°C and at a voltage of 3.00V to 4.25V.

[0189] In another preferred embodiment, the second aspect of the present invention relates to a lithium metal battery wherein the cathode material is lithium nickel manganese cobalt oxide and the polymer electrolyte is a polymer electrolyte wherein:

[0190] - the second lithium salt is lithium bis(oxalato)borate or lithium difluoro(oxalato)borate LiBF2(C2O4) (LiDFOB);

[0191] - the weight ratio of the first lithium salt to the second lithium salt is from 1:1 to 4:1; preferably it is from 1:1 to 3:1, and more preferably it is from 1:1 to 2:1;

[0192] - the lithium salt contained in the polymer electrolyte composition constitutes 10% to 50% by weight of the composition; preferably, the lithium salt contained in the polymer electrolyte composition constitutes 10% to 30% by weight of the composition; even more preferably, the lithium salt contained in the polymer electrolyte composition constitutes about 20% by weight of the composition; and / or

[0193] - polymers selected from: (i) poly(ethylene glycol) methyl ether methacrylate or cross-linked polymers thereof, poly(ethylene glycol) dimethacrylate (PEGDMA) or cross-linked polymers thereof, cross-linked polymers of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or polymers thereof, and blends or copolymers thereof; and (ii) polybutyl acrylate (PBA) or cross-linked polymers thereof with pentaerythritol acrylate (PETA);

[0194] - the polymer represents 5% to 90% by weight of the composition; preferably, the polymer represents 10% to 60% by weight of the composition; even more preferably, the polymer represents 10% to 20% by weight of the composition;

[0195] - the composition further comprises a plasticizer, which is a mixture of ethyl methyl carbonate (EMC) and ethylene carbonate (EC), wherein the weight ratio of ethylene carbonate (EC) to ethyl methyl carbonate (EMC) is preferably 1:1 to 3:2, and the plasticizer preferably accounts for 40% to 80% by weight of the polymer electrolyte composition; and wherein:

[0196] When the polymer is a mixture of poly(ethylene glycol) methyl ether methacrylate (PEGDMA) and poly(ethylene glycol) dimethacrylate (PEGDMA) or a cross-linked polymer thereof, preferably the weight ratio of poly(ethylene glycol) methyl ether methacrylate to PEGDMA is from 1:1 to 4:1; more preferably from 2:1 to 4:1; even more preferably about 3:1; and even more preferably about 113:39;

[0197] When the polymer is a cross-linked polymer of butyl acrylate and pentaerythritol acrylate or poly(butyl)acrylate, preferably the weight ratio of butyl acrylate to PETA is from 1:1 to 4:1; more preferably from 2:1 to 4:1; even more preferably about 3:1; and even more preferably about 113:39, or about 96:43, or about 98:43;

[0198] When the polymer comprises one or more crosslinkable acrylate groups in its molecular formula, the polymer electrolyte composition optionally also comprises an initiator for free-radical polymerization, such as azoisobutyronitrile (AIBN).

[0199] In another preferred embodiment, the second aspect of the present invention relates to a lithium metal battery wherein the cathode material is lithium nickel manganese cobalt oxide and the polymer electrolyte comprises:

[0200] a) a first lithium salt of formula (I) as defined above in an amount of 5 to 15 wt %, preferably 11.2 wt %, of the composition;

[0201] b) a second lithium salt of LiB(C2O4)2 in an amount of 5 to 10 wt% of the composition, preferably 8.1 wt%;

[0202] c) a polymer comprising 10% to 20% by weight of the composition and being a mixture of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or a crosslinked polymer of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or polymers thereof, and blends or copolymers thereof; preferably, the polymer comprises about 15.2% by weight of the composition, and

[0203] d) a plasticizer, which accounts for 40% to 80% by weight of the composition and is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC); preferably, the weight ratio of EC to EMC is 1:1 to 3:2; more preferably, the plasticizer accounts for 65.5% by weight of the composition.

[0204] In another preferred embodiment, the second aspect of the present invention relates to a lithium metal battery wherein the cathode material is lithium nickel manganese cobalt oxide and the polymer electrolyte comprises:

[0205] a) a first lithium salt of formula (I) in an amount of 11.4% by weight of the composition;

[0206] b) a second lithium salt of LiB(C2O4)2 in an amount of about 8.2% by weight of the composition;

[0207] c) a polymer comprising 10% to 20% by weight of the composition and being a cross-linked polymer of butyl acrylate and pentaerythritol acrylate or poly(butyl) acrylate, preferably, the polymer comprises about 13.9% by weight of the composition;

[0208] d) a plasticizer, which comprises about 66.6 wt % of the composition and is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC); the weight ratio of EC to EMC is about 377:288.

[0209] In another preferred embodiment, the second aspect of the present invention relates to a lithium metal battery wherein the cathode material is lithium nickel manganese cobalt oxide and the polymer electrolyte comprises:

[0210] a) a first lithium salt of formula (I) in an amount of 9.5% by weight of the composition;

[0211] b) a second lithium salt of LiBF2(C2O4) in an amount of about 5.1% by weight of the composition;

[0212] c) a polymer comprising 10% to 20% by weight of the composition and being a cross-linked polymer of butyl acrylate and pentaerythritol acrylate or poly(butyl) acrylate, preferably, the polymer comprises about 14.1% by weight of the composition;

[0213] d) a plasticizer, which comprises about 71.3% by weight of the composition and is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC); the weight ratio of EC to EMC is about 405:308.

[0214] A method for preparing an electrochemical cell or battery according to the second aspect of the invention is also part of the invention. The method will be obvious to the skilled person using common general knowledge. In a preferred embodiment, the method comprises the following steps:

[0215] (i) providing a cathode for an electrochemical cell or battery;

[0216] (ii) providing an anode for an electrochemical cell or battery;

[0217] (iii) providing a polymer electrolyte as defined in any preferred or specific embodiment of the first aspect of the invention;

[0218] (iv) transferring the electrolyte provided in step (iii) onto the surfaces of the cathode provided in step (i) and the anode provided in step (ii), said surfaces optionally being covered with a microporous membrane; arranging the electrolyte between the cathode and the anode in such a manner that lithium cations can flow from the cathode to the anode; and

[0219] (v) Optionally, when the polymer electrolyte contains one or more cross-linkable functional groups in its molecular formula, cross-linking the polymer of the polymer electrolyte.

[0220] In a preferred embodiment, the cross-linking step is a free radical polymerization involving (meth)acrylate groups as cross-linkable functional groups, wherein the (meth)acrylate groups are preferably contained in an acrylate compound or a poly(ethylene glycol) compound such as poly(ethylene glycol) methyl ether methacrylate or PEGDMA.

[0221] Preferred materials for use in preparing electrochemical cells or batteries are as defined in preferred and specific embodiments of the second aspect of the invention.

[0222] The optional cross-linking step (v) can be performed before or after step (iv). However, it is preferably performed after step (iv) as it facilitates maximum contact surface between the electrolyte and the electrodes.

[0223] As defined above, a third aspect of the present invention relates to a method for preparing a polymer electrolyte according to the first aspect of the present invention, said method comprising the steps of:

[0224] (i) providing a lithium salt of formula (I) as defined in the first aspect of the present invention;

[0225] (ii) providing a second lithium salt as defined in the first aspect of the present invention; and

[0226] In the first alternative,

[0227] (iii) dissolving the lithium salt provided in steps (i) and (ii) in a polymer for electrolyte; or,

[0228] In the second alternative,

[0229] (iv) dissolving the lithium salt provided in steps (i) and (ii) in a solvent, and

[0230] (v) dissolving a polymer for electrolyte in the mixture obtained in step (iv);

[0231] as well as

[0232] (vi) Optionally, cross-linking the polymer for electrolyte contained in the mixture produced by step (iii) or (v).

[0233] The method of the first alternative of the third aspect of the present invention is particularly suitable when the polymer used for the electrolyte is in a liquid state.

[0234] The method of the second alternative of the third aspect of the present invention is particularly suitable when the polymer used for the electrolyte is solid and / or the lithium salt has low solubility in the polymer used for the electrolyte.

[0235] In a preferred embodiment of the third aspect of the invention, the composition of the electrolyte, the second lithium salt, the plasticizer, the polymer used for the electrolyte, and the weight ratio of the components of the electrolyte are as defined in any specific and preferred embodiment of the first aspect of the invention. In such an embodiment, the method of the second alternative of the third aspect of the invention is preferred.

[0236] In particular, when the polymer comprises one or more crosslinkable acrylate groups in its molecular formula, the optional crosslinking step (vi) is preferably carried out by free-radical polymerization, said reaction preferably being initiated with azoisobutyronitrile (AIBN).

[0237] Other cross-linking reactions are known in the art and will become apparent to the skilled artisan.

[0238] Throughout the specification and claims, the word "comprising" and variations of the word are not intended to exclude additional technical features, additives, components, or steps. Furthermore, the word "comprising" encompasses "consisting of" and "consisting essentially of." Additional objects, advantages, and features of the present invention will become apparent to those skilled in the art upon examination of the specification or may be learned through practice of the invention. The following examples are provided by way of illustration and are not intended to limit the invention.

[0239] Example

[0240] List of abbreviations

[0241] EC: Ethylene carbonate

[0242] EMC: Ethyl Methyl Carbonate

[0243] LiDFTFSI: (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide lithium salt

[0244] LiBOB: lithium bis(oxalato)borate

[0245] M n =500 g / mol of poly(ethylene glycol) methyl ether methacrylate

[0246] PEGDMA:M n =550 g / mol of poly(ethylene glycol) dimethacrylate

[0247] AIBN: Azoisobutyronitrile

[0248] rpm: revolutions per minute

[0249] RT: room temperature

[0250] Example 1: Preparation of polymer gel electrolyte

[0251] Polymer gel electrolytes having the compositions disclosed in Table 1 (expressed in wt %) were prepared according to the following general steps. In the first step, a mixture of EC and EMC was prepared by weighing appropriate amounts of EC and EMC. LiDFTFSI and / or LiBOB were weighed in a vial and the mixture of EC and EMC was added in appropriate amounts. PEGDMA and poly(ethylene glycol) methyl ether methacrylate were then added to the solution in appropriate amounts, and the resulting mixture was stirred until a homogeneous solution was obtained (approximately 2 hours at 300 rpm and RT). AIBN (0.3 wt % of the total weight of the electrolyte) was then added to the solution, and the resulting mixture was stirred at 300 rpm for 10 minutes.

[0252] Table 1

[0253]

[0254] Example 2: Preparation of lithium metal batteries containing polymer gel electrolytes

[0255] A lithium metal battery comprising the polymer gel electrolyte of Example 1 has been prepared according to the following steps:

[0256] Cathode preparation: LiNi 0.6 Mn 0.2 Co 0.2 The O2 (NMC622, purchased from Targray) cathode consisted of 90 wt% NMC622, 5 wt% conductive carbon (Super C-65), and 5 wt% polymer binder (PVdF). The slurry was prepared using N-methyl-2-pyrrolidone (NMP) as a solvent, and after homogenizing the dispersion, it was cast on a carbon-coated aluminum current collector. Finally, it was dried under vacuum at 80°C overnight, resulting in a charge of approximately 1.2 mAh cm in the case of cells prepared with the electrolytes of Comparative Examples 1 and 2 and Example 1a. -2 Up to 1.5 mAh cm -2or in the case of batteries prepared with the electrolytes of Examples 1b and 1c, about 3 mAh cm -2 The electrodes were punched with a size of 12 mm diameter and then dried again under vacuum at 50°C before cell assembly.

[0257] Anode provided: Li metal disk (China Energy Lithium, 14 mm diameter and 500 μm thickness in the case of cells prepared with the electrolytes of Comparative Examples 1 and 2 and Example 1a, or 50 μm thickness in the case of cells prepared with the electrolytes of Examples 1b and 1c).

[0258] Cell assembly: Coin cells were assembled in an argon-filled glove box using NMC622 (12 mm diameter) electrodes prepared as defined above as cathodes, Celgard 2500 as separators, and Li metal disks (China Energy Lithium, 14 mm diameter and 500 μm or 50 μm thickness as defined above) as anodes. The previously prepared electrolyte solution was cast on the separators, and the cells were closed with a crimper. The crosslinking process was then applied by keeping the cells at 70°C for 12 hours.

[0259] Following this method, the following batteries have been prepared:

[0260] - Battery 1 comprising the electrolyte of Comparative Example 1;

[0261] - Battery 2, which contains the electrolyte of Comparative Example 2;

[0262] - Battery 3 comprising the electrolyte of Example 1a;

[0263] - Cell 4 comprising the electrolyte of Example 1b; and

[0264] - Cell 5 comprising the electrolyte of Example 1c.

[0265] Using a Maccor battery tester (Series 4000), the + The charge retention capacity of the prepared batteries was tested by constant current cycling from 3.0 V to 4.25 V. The application scheme for batteries 1, 2, and 3 was based on 1 cycle at a current of C / 20 at 25° C., followed by 3 cycles at C / 10, and constant cycling at C / 5 (both charging and discharging). The application scheme for batteries 4 and 5 was based on 1 cycle at a current of C / 20 at 25° C., followed by 2 cycles at C / 10, and constant cycling at C / 10 (both charging and discharging). Figure 4The first three cycles (1 cycle at a current of C / 20, then 2 cycles at C / 10) are not shown above. The results of these experiments are shown in Figures 1 to 4 and show that the electrolyte of the present invention advantageously and unexpectedly provides a battery with improved charge retention capacity after repeated cycling. In addition, the electrolyte of the present invention advantageously allows the battery to be used at room temperature at up to 100% relative to Li / Li + The battery operated at a potential of 4.25 V while maintaining charge retention capacity. Batteries comprising the electrolyte of the present invention are also less susceptible to corrosion.

Claims

1. A polymer electrolyte composition comprising: a) polymers for electrolytes; b) a first lithium salt of formula (I) and c) a second lithium salt suitable for use in lithium metal battery electrolytes.

2. The polymer electrolyte composition of claim 1 , wherein the second lithium salt is selected from the group consisting of lithium perchlorate, lithium nitrate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium chlorotrifluoroborate, lithium fluoride, lithium oxide, lithium peroxide, a salt of formula LiN(SO2CF3)2, a salt of formula LiN(SO2F)2, a salt of formula LiN(SO2CF3)(SO2F), a salt of formula LiN(SO2C2F5)(SO2F), a salt of formula LiB(C2O4)2, a salt of formula LiBF2(C2O4), a salt of formula LiC(SO2CF3)3, a salt of formula LiPF3(C2F5)3, a salt of formula LiCF3SO3, and mixtures thereof. 3 . The polymer electrolyte composition according to claim 1 , wherein the second lithium salt is not lithium fluoride.

4. The polymer electrolyte composition according to any one of claims 1 to 3, wherein the second lithium salt is selected from lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium chlorotrifluoroborate, a salt of formula LiB(C2O4)2, a salt of formula LiBF2(C2O4), a salt of formula LiPF3(C2F5)3, a salt of formula LiCF3SO3, and a mixture thereof.

5. The polymer electrolyte composition according to any one of claims 1 to 4, wherein the second lithium salt is a salt of formula LiB(C2O4)2 or a salt of formula LiBF2(C2O4). 6 . The polymer electrolyte composition according to claim 1 , wherein a weight ratio of the first lithium salt to the second lithium salt is 1:1 to 2:

1.

7. The polymer electrolyte composition according to any one of claims 1 to 6, wherein the first lithium salt and the second lithium salt account for 10% to 30% by weight of the composition.

8. The polymer electrolyte composition according to any one of claims 1 to 6, wherein the polymer optionally comprises one or more crosslinkable functional groups in its molecular formula and is selected from: - polyoxyalkylenes such as polyethylene oxide (PEO) or polypropylene oxide (PPO), - polyalkyleneimines such as polyethyleneimine (PEI), - polyalkylene sulfides such as polyethylene sulfide (PES), - polyalkylene carbonates such as polytrimethylene carbonate (PTMC), polyethylene carbonate (PEC) or polypropylene carbonate (PPC), - polyacrylates, for example polymers of methyl methacrylate (PMMA), (C1-C6)alkyl acrylates, for example butyl acrylate (PBA) or ethyl acrylate (PEA), cyanoethyl acrylate (PCEA), or blends thereof or copolymers thereof or crosslinked polymers thereof with trimethylolpropane triacrylate (ETPTA) and / or pentaerythritol tetraacrylate (PETA), - polyethylene glycol, - polyphosphazenes, for example poly[bis(2-(2-methoxyethoxy)ethoxy)phosphazene (MEEP), - polysiloxanes, such as poly(dimethylsiloxane) (PDMS), - polyvinyl alcohol (PVA), -polyvinylamine (PVAm), - polyvinyl acetate (PVAc), - polyvinyl halides, for example polyvinyl chloride (PVC) or polyvinylidene fluoride (PVdF); polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), - polyacrylonitrile (PAN), - poly(vinylpyrrolidone) (PVP), - poly(2-vinylpyridine) (P2VP), - poly(ε-caprolactone) (PCL), - poly(maleimides), such as poly(alkylenemaleimides), poly(ethylene-alt-maleimide) (PEaMI), -polyaniline (PANI), - Chitosan (CS), and - any blend or any copolymer or any cross-linked polymer thereof.

9. The polymer electrolyte composition according to any one of claims 1 to 7, wherein the polymer is selected from: (i) - poly(ethylene glycol) methyl ether methacrylate or a cross-linked polymer thereof, - poly(ethylene glycol) dimethacrylate (PEGDMA) or a cross-linked polymer thereof, - poly(ethylene glycol) methyl ether methacrylate, a cross-linked polymer of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or a polymer thereof, and - blends or copolymers thereof; and (ii) -polybutyl acrylate, - Butyl acrylate cross-polymer with pentaerythritol tetraacrylate (PETA), and - blends or copolymers thereof.

10. The polymer electrolyte composition according to any one of claims 1 to 9, wherein the polymer comprises 10% to 20% by weight of the composition. 11 . The polymer electrolyte composition according to claim 1 , further comprising a plasticizer.

12. The polymer electrolyte composition of claim 11, wherein the plasticizer is selected from the group consisting of dimethoxyethane (DME), 1,2-diethoxyethane (DEE), 1,3-dioxolane (DOL), diethylene glycol dimethyl ether (DEGDME), triethylene glycol dimethyl ether (G3), tetraethylene glycol dimethyl ether (TEGDME), poly(ethylene glycol) dimethyl ether (PEGDME), tetrahydropyran (THP), γ-butyrolactone, tetrahydrofuran (THF), 2-methyltetrahydrofuran, diethyl ether, methyl-tert-butyl ether, succinonitrile (SN), glutaronitrile (GN), adiponitrile (AN), N,N-dimethylsulfamoyl fluoride (FSA), N,N-dimethyltrifluoromethane-sulfonamide (TFSA), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), and any mixture thereof.

13. The polymer electrolyte composition according to any one of claims 11 to 12, wherein the plasticizer is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC); preferably, the weight ratio of EC to EMC is 1:1 to 3:

2.

14. The polymer electrolyte composition according to any one of claims 11 to 13, wherein the plasticizer comprises 40% to 80% by weight of the composition.

15. The polymer electrolyte composition according to any one of claims 1 to 14, comprising: a) a first lithium salt of formula (I), wherein the amount of the first lithium salt is 5% to 15% by weight of the composition, preferably 11.2% by weight; b) a second lithium salt of LiB(C2O4)2, wherein the amount of the second lithium salt is 5% to 10% by weight of the composition, preferably 8.1% by weight; c) the polymer comprises 10% to 20% by weight of the composition and is a mixture of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or a crosslinked polymer of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) or polymers thereof, and blends or copolymers thereof; preferably, the polymer comprises about 15.2% by weight of the composition, and d) a plasticizer, which accounts for 40% to 80% by weight of the composition and is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC); preferably, the weight ratio of EC to EMC is 1:1 to 3:2; more preferably, the plasticizer accounts for 65.5% by weight of the composition.

16. An electrochemical cell or battery comprising the polymer electrolyte according to any one of claims 1 to 15.

17. A method for preparing a polymer electrolyte according to any one of claims 1 to 15, comprising the following steps: (i) providing a lithium salt of formula (I) as defined in claim 1; (ii) providing a second lithium salt as defined in any one of claims 1 to 5; as well as In the first alternative, (iii) dissolving the lithium salt provided in steps (i) and (ii) in a polymer for electrolyte; or, In the second alternative, (iv) dissolving the lithium salt provided in steps (i) and (ii) in a solvent, and (v) dissolving a polymer for electrolyte in the mixture obtained in step (iv); and (vi) Optionally, cross-linking the polymer for an electrolyte contained in the mixture produced by step (iii) or (v).

Images