Macromonomer and solid polymer electrolyte

Abstract

The present invention provides a macromonomer, an electrolyte precursor composition comprising the macromonomer, a method for preparing a solid polymer electrolyte, a solid polymer electrolyte, a solid lithium secondary battery, an electrochemical device, and an apparatus.

Description

TECHNICAL FIELD

[0001] The present invention relates to a polymer electrolyte, which is particularly useful for solid-state lithium ion batteries. BACKGROUND

[0002] In solid-state batteries, the solid-state electrolyte replaces the function of both separator and electrolyte. To function as a separator to prevent short circuit between anode and cathode, the solid-state electrolyte needs mechanical stability, while having high ionic conductivity at room temperature to enable shuttling of lithium ions between anode and cathode.

[0003] Zhang, X.; Daigle, J. C.; Zaghib, K. Comprehensive review of polymer architecture for all-solid-state lithium rechargeable batteries. Materials (Basel). 2020, 13, 2488 summarizes the influence of polymer architecture on the physical and electrochemical properties of SPEs (solid-state polymer electrolytes) in lithium solid-state polymer batteries. The discussion focuses on four main categories: linear polymers, comb-like polymers, hyperbranched polymers, and cross-linked polymers. There are still three main issues to be addressed in PEO-based SPEs: low ionic conductivity at low temperature, low transference number, and relatively narrow electrochemical window when using high-voltage cathodes.

[0004] Nair, J. R., Destro, M., Gerbaldi, C. et al. Novel multiphase electrode / electrolyte composites for next generation of flexible polymeric Li-ion cells. J Appl Electrochem 43, 137-145 (2013) discloses a methacryl-based polymer electrolyte formed in situ directly at the interface of different electrode films (i.e. commercial graphite and hydrothermally synthesized LiFeP04). The polymer electrolyte was prepared under UV-irradiation using materials including bisphenol A ethoxylate (15EO / phenol) dimethacrylate (BEMA), a methacryl-based difunctional oligomer with an average molecular weight of 1,700, and poly(ethylene glycol) methyl ether methacrylate (PEGMA-475, average Mn: 475). After exposure to UV-irradiation, the polymer electrolyte film obtained by copolymerization of the reactive mixture including BEMA, PEGMA-475, LiTFSI and EDEC (1:1 w / w) solution and a photoinitiator was found to be transparent, self-standing, flexible, non-sticky and easy to handle.

[0005] Michiyuki Kono et al 1998 J. Electrochem. Soc. 145 1521 discloses a polymer electrolyte. When preparing the electrolyte, the terminal hydroxyl groups of poly(ethylene oxide-co-propylene oxide) triol (MW 7940) are partially methylated and the remaining hydroxyl groups are esterified with acrylic acid. The resulting macromonomer is crosslinked by photoirradiation in the presence of an electrolyte salt to prepare a network polymer electrolyte. However, the electrochemical and mechanical properties remain to be further improved.

[0006] St-Onge, V., Cui, M., Rochon, S. et al. Reducing crystallinity in solid polymer electrolytes for lithium-metal batteries via statistical copolymerization. Commun Mater 2, 83 (2021) discloses EO-PO polyether copolymer alcohols that exhibit high ionic conductivity. Copolymers prepared contain about 300 EO units and some comonomer units. It was found that about 26 mol% of comonomer is sufficient to completely eliminate polymer crystallinity, resulting in a PEO-rich material that is thermodynamically unable to crystallize. Statistical copolymers containing 18 mol% of comonomer and 18 wt% of LiTFSI are completely free of crystallinity. In contrast to the nature of the comonomer side chains, the comonomer content strongly influences the ionic conductivity. A small amount of comonomer leads to a decrease in crystallite size and a reduction in crystallinity content. Thus, by adding only 10 mol% of comonomer, the ionic conductivity increases from 5 x 10 -8 to 0.3 x 10 -4 S cm -1 . Introducing larger amounts of comonomer in the SPE leads to a decrease in conductivity because the comonomer is not as effective as the EO unit in dissolving and complexing the Li+ salt. Thus, 10 mol% of comonomer units in the copolymer is the optimal trade-off between reducing crystallinity and increasing the necessary EO content for ionic conductivity. For PO, BO, and TO units, these copolymers have crystallinity contents of 19%, 12%, and 4%, respectively, and T g g of -44°C, -50°C, and -72°C, respectively. After copolymerization, the copolymer was precipitated with 600 mL of hexane and filtered. The precipitated polymer was dried under vacuum at room temperature for 24 h to obtain a white-yellowish powder. Polymer electrolytes were prepared as follows: 820 mg of polymer was dissolved in 5 to 10 mL of anhydrous THF in a nitrogen-filled glovebox. Then, 180 mg of LiTFSI was added to the solution and dissolved at 65°C. The solvent was then evaporated under reduced pressure and dried under vacuum for 24 h. The electrolyte was kept in the nitrogen glovebox. However, the polymer electrolytes prepared using the copolymer alcohols show poor mechanical properties.

[0007] US6933078B2 discloses crosslinked polymer electrolytes comprising poly(ethylene glycol) methyl ether methacrylate (POEM) monomers crosslinked with low Tg second monomers. Crosslinked polymer electrolytes are disclosed, for example, POEM-X-PDMSD-LiN(CF3SO2)2 and POEM-X-PDMSM-PEGDME-LiN(CF3SO2)2. US6933078B2 does not disclose the preparation of POEM-X-PDMSM-PEGDME-LiN(CF3SO2)2 but mentions that "it was found that PDMSM can be easily grafted onto POEM monomers, but PDMSD can be easily crosslinked with POEM monomers by using free radical synthesis method. (PDMSM crosslinked polymers can be prepared by using alternative synthesis method). POEM-g-PDMSM polymers are soluble electrolytes with relatively lower conductivity and poor mechanical properties." Example 4 discloses the preparation of POEM-X-PDMSD-LiN(CF3SO2)2 by solution casting using POEM (14.8 ml), methacryloyloxypropyl terminated polydimethylsiloxane (PDMSD) (4.0 ml, ethyl acetate (96 ml), LiN(CF3SO2)2 (1.8 g) plus AIBN (0.072 g). The patent does not disclose the specific mechanical properties of the crosslinked polymer electrolytes prepared in the examples.

[0008] US20030180624A1 discloses interpenetrating network solid state polymer electrolytes comprising at least one branched siloxane polymer having one or more poly(alkylene oxide) branches as side chains, at least one crosslinking agent, at least one monofunctional monomeric compound for controlling crosslinking density, at least one metal salt, and at least one free radical reaction initiator. In Examples 1 to 2, 0.4 to 2.0 g of branched siloxane polymer, 0.4 g of poly(ethylene glycol-600) dimethacrylate) (PEGDMA600) and 1.2 to 1.6 g of poly(ethylene glycol) ethyl ether methacrylate (PEGEEMA) were used to prepare SPEs. During the preparation, a porous polycarbonate membrane was used as a support for the IPN SPEs. Both of the IPN SPEs showed high ionic conductivities of over 10 -5 S / cm at room temperature, and the ionic conductivities increased as the content of the branched siloxane polymer increased. SUMMARY

[0009] The present invention aims to solve at least some of the problems in the art. The present invention improves the manufacturing process of solid state polymer electrolytes by using liquid feedstock formulations that can be crosslinked and cured during the production of solid state batteries. This is achieved by (meth-)acrylate monomers with amorphous side chains that suppress crystallization. Furthermore, the use of polymer electrolytes of (meth-)acrylate monomers crosslinked by siloxane monomers achieves surprisingly good mechanical properties and surprisingly high ionic conductivities at low temperatures, for example below 40°C, in particular below 20°C.

[0010] By designing polyether-co-polymer (meth-)acrylate macromonomers, the mechanical properties related to the molecular weight of the polymer can be tuned by polymerization. In this polymerization, a crosslinker is used to adjust the elastic properties of the resulting elastomeric material.

[0011] The present invention provides a macromonomer represented by the following general formula (I):

[0012]

[0013] wherein R1represents methyl or H;

[0014] wherein z is the number of repetitions of the ethylene glycol spacer and represents 0, 1, 2 or 3;

[0015] R2represents methyl or a C2 to C10 aliphatic or aromatic group, preferably methyl or ethyl, more preferably methyl;

[0016] n represents a positive integer from 10 to 200, preferably a positive integer from 10 to 100, more preferably a positive integer from 40 to 80; n defines the degree of polymerization of the random copolymer with the comonomer ratio of x and y; and

[0017] y = 1 % to 40 %, preferably 5 % to 25 %, more preferably 10 % to 20 %, even more preferably 12 % to 18 %, x = 1 - y.

[0018] The number average molecular weight of the macromonomer is typically from 500 to 10000, preferably from 500 to 5000, for example from 600 to 4500, more preferably from 750 to 4000, or from 750 to 2000, even more preferably from 800 to 1500, for example about 1000.

[0019] Preferably, the macromonomer is liquid at room temperature. Such liquid macromonomers include the following macromonomers, wherein in formula (I),

[0020] wherein R1represents methyl or H;

[0021] wherein z is the number of repetitions of the ethylene glycol spacer and represents 0, 1, 2 or 3;

[0022] R2represents a methyl group or a C2to C5aliphatic group, preferably a methyl group or an ethyl group, more preferably a methyl group;

[0023] n represents a positive integer from 10 to 100; n defines the degree of polymerization of the random copolymer having a comonomer ratio of x and y;

[0024] y = 10% to 25%, preferably 14% to 20%, x = 1 - y; and

[0025] The number average molecular weight of the macromonomer is from 500 to 5000, preferably from 750 to 2000, more preferably from 800 to 1500, for example about 1000.

[0026] The macromonomer is a poly(ethylene glycol-co-propylene glycol) alkyl ether (meth-)acrylate.

[0027] The macromonomer of the present application does not have crystalline domains. In other words, the polyether-co-polymer (meth-)acrylate macromonomer is amorphous. The macromonomer is anhydrous. It is a liquid at room temperature. Therefore, no solvent is required for handling it and it can be used as a reactive diluent for formulations which does not need to be removed after the reaction and does not result in volatile organic compounds (VOC).

[0028] Furthermore, using the macromonomer of the present application, electrolytes having good electrochemical properties (e.g. high ionic conductivity, in particular at low temperatures) and good mechanical properties (e.g. mechanical stability or strength) can be prepared.

[0029] The present application further provides a macromonomer composition comprising:

[0030] The macromonomer of the present application, and

[0031] less than 5 wt%, for example less than 4 wt%, less than 3 wt%, less than 2 wt%, preferably less than 1 wt%, for example less than 0.9 wt%, less than 0.8 wt%, less than 0.7 wt%, less than 0.6 wt%, less than 0.5 wt%, less than 0.4 wt%, less than 0.3 wt%, less than 0.2 wt%, even less than 0.1 wt% of solvent based on the total weight of the macromonomer composition;

[0032] wherein the number average molecular weight of the macromonomer is from 500 to 5000, preferably from 750 to 2000, more preferably from 800 to 1500.

[0033] The macromonomer composition is a liquid at room temperature.

[0034] The solvent can include water and a suitable organic solvent, such as an alcohol, an ester, an ether, a ketone.

[0035] The amount of macromer, based on the total weight of the macromonomer composition, is typically 90 wt% or more, preferably 95 wt% or more, such as 96 wt%, 97 wt%, 98 wt% or more, more preferably 99 wt% or more, such as 99.1 wt%, 99.2 wt%, 99.3 wt%, 99.4 wt%, 99.5 wt%, 99.6 wt%, 99.7 wt%, 99.8 wt% or 99.9 wt% or more.

[0036] The macromonomer of formula (I) can be synthesized via transesterification, direct esterification with (meth-)acrylic acid or via esterification with activated (meth-)acrylic acid derivatives such as (meth-)acrylic anhydride or (meth)acrylic acid chloride. The amorphous monomer can be synthesized using methods known in the art (or slight variations thereof), such as WO2010003710A1 or WO2020035315A1 or EP0780360B1.

[0037] In some embodiments, the method of preparing the macromonomer of the present application comprises the steps of:

[0038] I) reacting a primary alcohol with ethylene oxide (EO) and propylene oxide (PO) under catalysis; and

[0039] II) reacting the reaction product of step I) with a (meth-)acrylic ester under catalysis to obtain the macromonomer.

[0040] The macromonomer is an amorphous poly(ethylene glycol-co-propylene glycol) alkyl ether (meth-)acrylate.

[0041] The person skilled in the art can adjust the molar ratio of EO to PO and the molar ratio of EO and PO to the primary alcohol to obtain a macromonomer with the desired repeating units and molecular weight.

[0042] The primary alcohol can be any monofunctional alcohol. For example, the monofunctional alcohol can be selected from the group consisting of methanol, diethylene glycol monomethyl ether, ethylene glycol monomethyl ether, triethylene glycol monomethyl ether, methoxypolyethylene glycol ((MPEG) and other polar monofunctional alcohols.

[0043] In some embodiments, the method of preparing the macromonomer of the present application comprises the steps of:

[0044] I) reacting a primary alcohol with ethylene oxide and propylene oxide to obtain a polyether; and

[0045] II) reacting the polyether with a (meth-)acrylic acid methyl ester to obtain a poly(ethylene glycol-co-propylene glycol) methyl ether (meth-)acrylate.

[0046] The present application further provides an electrolyte precursor composition (i.e. electrolyte formulation) comprising:

[0047] A) a macromer of the present application;

[0048] B) a siloxane monomer, in particular an acrylate-functional siloxane monomer; and

[0049] C) a lithium salt,

[0050] and optionally D) a free radical initiator.

[0051] The lithium salt and free radical initiator (which can be either radiation or thermal) can be selected from those conventional in the art.

[0052] The electrolyte precursor composition can be free of any solvent including water and organic solvents. The electrolyte precursor composition preferably comprises less than 10 wt%, for example less than 9 wt%, less than 8 wt%, less than 7 wt%, less than 6 wt%, more preferably less than 5 wt%, for example less than 4 wt%, less than 3 wt%, less than 2 wt%, even more preferably less than 1 wt%, for example less than 0.9 wt%, less than 0.8 wt%, less than 0.7 wt%, less than 0.6 wt%, less than 0.5 wt%, less than 0.4 wt%, less than 0.3 wt%, less than 0.2 wt%, even less than 0.1 wt% of a solvent including water and organic solvents, based on the total weight of the electrolyte precursor composition. In some embodiments, the electrolyte precursor composition is free of any organic solvent or water.

[0053] The electrolyte precursor composition can further comprise a filler. Examples of the filler can include silicon oxides and metal oxides.

[0054] The present application therefore provides a liquid electrolyte precursor formulation which can be used to prepare a solid-state electrolyte for a solid-state battery. The liquid formulation can be solidified after the formulation is coated onto an electrode.

[0055] The present application further provides a method of preparing a solid polymer electrolyte comprising the steps of:

[0056] a) providing an electrolyte precursor composition of the present application; and

[0057] b) cross-linking the liquid electrolyte precursor composition with irradiation or heat treatment in the presence of a free radical initiator.

[0058] The methods of irradiation (e.g. UV, electron) and heat treatment can be conventional.

[0059] The present application further provides a solid-state polymer electrolyte prepared according to the method of the present application, or obtained by curing the electrolyte precursor composition.

[0060] The electrolyte can be free of any solvent including water and organic solvent, and preferably free of any solvent including water and organic solvent.

[0061] A transparent and elastic film can be obtained via the method of the present application. The electrolyte is superior to PEO SPE benchmark, especially at low temperature.

[0062] The present application further provides a lithium ion battery comprising the solid-state polymer electrolyte of the present application.

[0063] The present application further provides a solid-state lithium secondary battery comprising a cathode, the solid copolymer electrolyte of the present application, and an anode, preferably a lithium metal anode. This solid-state lithium secondary battery does not include a separator used in a liquid-state lithium secondary battery.

[0064] The present application further provides a method of preparing a solid-state lithium secondary battery, comprising:

[0065] Assembling a cathode, the solid copolymer electrolyte of the present application, and an anode, preferably a lithium metal anode, to form a solid-state lithium secondary battery.

[0066] In the present application, the term "solid-state polymer electrolyte" refers to an all-solid-state polymer electrolyte and / or a quasi-solid-state polymer electrolyte. The solid-state polymer electrolyte in the present application is preferably an all-solid-state polymer electrolyte. Unless otherwise specified, the term "copolymer electrolyte" is used interchangeably with "polymer electrolyte" when it refers to the solid-state polymer electrolyte of the present application.

[0067] In the present application, "lithium secondary battery" includes a lithium ion secondary battery and a lithium metal secondary battery.

[0068] The present application further provides an electrochemical device comprising the solid-state polymer electrolyte of the present application.

[0069] In some examples, the electrochemical device is a secondary battery, such as a lithium ion battery, and particularly a lithium metal secondary battery.

[0070] The present application further provides an apparatus comprising the electrochemical device of the present application. The apparatus includes, but is not limited to, an electric vehicle, an electric home appliance, an electric power tool, a portable communication device such as a mobile phone, a consumer electronic product, and any other product suitable for incorporating the electrochemical device or lithium secondary battery of the present application as an energy source.

[0071] The present application further provides the use of the macromonomer of the present application or the use of the electrolyte precursor composition of the present application for the preparation of a solid state polymer electrolyte in a lithium secondary battery, in particular a lithium metal secondary battery, in particular for improving properties such as electrolyte mechanical properties, ionic conductivity (in particular at low temperatures, e.g. 0 to 40 °C, in particular 0 to 20 °C, e.g. 0 to 10 °C) and / or cycling performance.

[0072] Siloxane monomer

[0073] The siloxane monomer is selected from organomodified siloxanes having ethylenically unsaturated free-radically polymerizable groups. The ethylenically unsaturated free-radically polymerizable groups are preferably selected from (meth-)acryloyloxy functional groups. The siloxane monomer is preferably selected from (meth-)acryloyloxy functionalized siloxanes having ethylenically unsaturated free-radically polymerizable groups. The acryloyloxy functional groups are necessary for efficient crosslinking.

[0074] The number of free-radically polymerizable groups in the siloxane monomer is typically 3 or more to ensure efficient crosslinking.

[0075] The siloxane monomer is preferably selected from (meth-)acryloyloxy functionalized siloxanes having 4 to 40 silicon atoms, wherein 15% to 100% of the silicon atoms have ethylenically unsaturated free-radically polymerizable groups.

[0076] In some embodiments, the siloxane monomer further comprises non-free-radically polymerizable ester groups.

[0077] In some embodiments, the siloxane monomer is a compound of formula (II),

[0078] M 1 e M 3 f D 1 g D 3 h (II)

[0079] wherein

[0080] M 1 = [R 1 3SiO 1 / 2 ],

[0081] M 3 = [R 1 2R 3 SiO 1 / 2 ],

[0082] D 1 = [R 12 SiO 2 / 2 ],

[0083] D 3 = [R 1 R 3 SiO 2 / 2 ],

[0084] e = 0 to 2,

[0085] f = 0 to 2, preferably 0, and e + f = 2,

[0086] g = 0 to 38, preferably 10 to 26,

[0087] h = 0 to 20, for example 1 to 20, or 2 to 20, or 3 to 20, preferably 4 to 15,

[0088] and the ratio of the sum (f + h) to the sum (g + h + 2) is from 0.15 up to 1, preferably 0.2 to 0.5,

[0089] and the sum (g + h + 2) is 4 to 40, preferably 10 to 30,

[0090] R 1 denote identical or different aliphatic hydrocarbon radicals having 1 to 10 carbon atoms or aromatic hydrocarbon radicals having 6 to 12 carbon atoms, preferably methyl and / or phenyl, particularly preferably methyl,

[0091] R 3 denote identical or different hydrocarbon radicals having 1 to 5 identical or different ester groups, preferably (meth-)acryloyloxy functional groups, which are linear, cyclic, branched and / or aromatic, preferably linear or branched, and which are selected from the group consisting of ethylenically unsaturated free-radically polymerizable ester groups and non-free-radically polymerizable ester groups, the ethylenically unsaturated free-radically polymerizable ester groups preferably being (meth-)acryloyloxy functional groups.

[0092] R 3 The ester functions of the radicals R

[0093] Preferably, in the siloxane monomers, the free-radically polymerizable groups are present in a number fraction of 80 to 90 %, based on the number of all ester functions of the compounds of the formula (II).

[0094] The radicals R 3The ethylenically unsaturated, free-radically polymerizable ester functionality of the compound of formula (II) is preferably selected from those of an acrylate functionality and / or a methacrylate functionality, more preferably an acrylate functionality.

[0095] The radicals R in the compound of formula (II) 3 The non-free-radically polymerizable ester group of the compound of formula (II) is preferably a monocarboxylic acid radical. The non-free-radically polymerizable ester group is preferably selected from the acid radicals of the acid class of acetic acid, propionic acid, butyric acid, valeric acid and benzoic acid, more preferably the acid radical of acetic acid. More preferably, the monocarboxylic acid radical is present in a number fraction of 3% to 20%, preferably 5% to 15%, based on the number of all ester functionalities of the compound of formula (II).

[0096] In some preferred embodiments, the siloxane monomer is a compound of formula (II), wherein

[0097] e = 2,

[0098] f = 0,

[0099] h = 4 to 15,

[0100] and the sum (g + h + 2) is 5 to 40, preferably 10 to 30,

[0101] R 3 denote identical or different hydrocarbon radicals, which have 1 to 5 identical or different ester groups, which are linear, cyclic, branched and / or aromatic, preferably linear or branched, and which are selected from the group consisting of ethylenically unsaturated, free-radically polymerizable ester groups and non-free-radically polymerizable ester groups, the ethylenically unsaturated, free-radically polymerizable ester groups being preferably (meth-)acryloyloxy-functional groups; and

[0102] wherein the number of free-radically polymerizable groups in the siloxane monomer is 3 or more.

[0103] The organomodified silicone can be prepared by the method described in US 10,465,032 B2 or US Patent No. 4,978,726.

[0104] A preferred example of the above siloxane monomer can be commercially available from Evonik Industries AG as V-Si 7255.

[0105] V-Si 7255 is a comb acryloyloxy functional polysiloxane. Its chemical name is: Siloxane and silicone, 3-[3-(acetyloxy)-2-hydroxypropoxy]propylmethyl, dimethyl, 3-[2-hydroxy-3-[(1-oxo-2-propen-1-yl)oxy]propoxy]propylmethyl; CAS No.: 125455-51-8.

[0106] Preferably, the weight ratio of the siloxane monomer to the macromonomer of the present application is from 1 :0.4 to 1 :80, in particular from 1 :0.8 to 1 :52, preferably from 1 :1.6 to 1 :55, in particular from 1 :1.6 to 1 :52, more preferably from 1 :12.8 to 1 :55, even more preferably from 1 :20 to 1 :52, in particular from 1 :12.8 to 1 :52.

[0107] Lithium salt

[0108] The lithium salt is a material that is dissolved in the non-aqueous electrolyte to thereby cause lithium ions to dissociate.

[0109] The lithium salt can be those conventionally used in the art, but which are thermally stable during in-situ polymerization (e.g. at 80°C), non-limiting examples can be at least one selected from the group consisting of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluoro(oxalato)borate (LiODFB), LiAsF6, LiClO4, LiN(CF3SO2)2, LiBF4, LiSbF6, and LiCl, LiBr, LiI, LiB 10 Cl 10 , LiCF3SO3, LiCF3CO2, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, chloroborane lithium, lithium lower aliphatic carboxylate, lithium tetraphenylborate and imide. The lithium salt is preferably selected from the group consisting of LiTFSI, LiFSI and LiClO4. These materials can be used alone or in any combination thereof.

[0110] Radical initiator

[0111] The radical initiator for the polymerization reaction is used for thermal polymerization or radiation polymerization, such as photopolymerization, of the reactive monomer, and can be those conventional in the art.

[0112] Examples of the radical initiator or polymerization initiator can include azo compounds such as 2,2-azobis(2-cyanobutane), 2,2-azobis(methyl butyronitrile), 2,2'-azoisobutyronitrile (AIBN), azobisdimethyl-valeronitrile (AMVN), and the like, peroxide compounds such as benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-t-butyl peroxide, cumyl peroxide, hydrogen peroxide, and the like, and hydroperoxides. Preferably, AIBN, 2,2'-azobis(2,4-dimethylvaleronitrile) (V65), di-(4-t-butylcyclohexyl)-peroxydicarbonate (DBC), and the like can also be used.

[0113] Preferably, the radical thermal initiator can be selected from the group consisting of azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (ABVN), benzoyl peroxide (BPO), lauryl peroxide (LPO), and the like. More preferably, the radical initiator is benzoyl peroxide (BPO) or azobisisobutyronitrile (AIBN).

[0114] The radical photoinitiator generates radicals when exposed to UV light, and then starts polymerization. Examples of the photoinitiator can include benzoyl compounds such as 2,2-dimethoxy-l,2-diphenyl-ethane-l-one (DMPA), benzil dimethyl ketal, diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO), 2-hydroxy-2-methylpropiophenone (HMPP), 1-hydroxycyclohexyl phenyl ketone (HCPK), and the like, and analogs can also be employed.

[0115] Preferably, the radical photoinitiator can be selected from the group consisting of 2,2-dimethoxy-l,2-diphenyl-ethane-l-one (DMPA), benzil dimethyl ketal, diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO), and the like. More preferably, the radical photoinitiator is 2,2-dimethoxy-l,2-diphenyl-ethane-l-one (DMPA).

[0116] The amount of the radical initiator is conventional. Preferably, the amount of the radical initiator is 0.1 wt% to 3 wt%, more preferably about 0.5 wt%, based on the total weight of the monomers of the copolymer.

[0117] In some embodiments, the amount of the photoinitiator or thermal initiator can be 0.2 wt% to 2 wt%, preferably about 0.5 wt%, based on the total weight of the macromonomer and the siloxane monomer of the present application. The photoinitiator or thermal initiator generates radicals to initiate polymerization under UV irradiation or heating.

[0118] In some embodiments, the polymerization initiator decomposes at a specific temperature of 40 to 80°C to form a free radical and is reactive with monomers via free radical polymerization to form a polymer electrolyte. Generally, this free radical polymerization proceeds by sequential reactions consisting of initiation, which involves the formation of transient molecules with highly reactive or active sites; propagation, which involves the reformation of active sites at chain ends by the addition of monomers to the active chain ends; chain transfer, which involves the transfer of the active sites to other molecules; and termination, which involves the destruction of active chain centers.

[0119] Preferably, the solid-state lithium secondary battery can be a coin cell or a pouch cell.

[0120] The electrochemical device encompasses all kinds of devices that undergo electrochemical reactions. Examples of the electrochemical device include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, capacitors, etc., preferably secondary batteries.

[0121] Generally, a secondary battery is manufactured by including an electrolyte in an electrode assembly composed of a cathode and an anode, which are opposite to each other with a separator therebetween (or without a separator for an SPE).

[0122] For example, a cathode is manufactured by applying a mixture of a cathode active material, a conductive material, and a binder to a cathode current collector, and then drying and pressing. If necessary, a filler can be further added to the above mixture.

[0123] The cathode current collector is generally manufactured to have a thickness of 3 to 500 μm. The materials used for the cathode current collector are not particularly limited as long as they have high conductivity without causing chemical changes in the manufactured battery. Examples of the materials used for the cathode current collector can include stainless steel, aluminum, nickel, titanium, sintered carbon, and aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver. The current collector can be manufactured to have fine irregularities on its surface in order to enhance adhesion to the cathode active material. In addition, the current collector can take various forms, including a film, a sheet, a foil, a mesh, a porous structure, a foam, and a nonwoven fabric.

[0124] Examples of the cathode active material that can be used in the present application can include, but are not limited to, a layered compound such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals such as LiNi x Co y Mn 1-x-y(NCM); lithium manganese oxides such as compounds of formula Li 1+x Mn 2-x O4(0≦x≦0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxides (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; lithium nickel oxides of formula LiNi 1-x M x O2(M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and 0.01 < x < 0.3); lithium manganese oxides of formula LiMn 2- x M x O2(M = Co, Ni, Fe, Cr, Zn, or Ta, and 0.01 < x < 0.1) or Li2Mn3MO8(M = Fe, Co, Ni, Cu, or Zn); LiMn2O4, wherein a portion of Li is substituted with an alkaline earth metal ion; a disulfide compound; and Fe2(MoO4)3, LiFe3O4, and the like.

[0125] In some embodiments, the cathode active material is selected from LiFePO4, LiCoO2, LiNi 0.8 Mn 0.1 Co 0.1 O2, LiNi 0.6 Mn 0.2 Co 0.2 O2, LiNi 0.85 Co 0.05 Al 0.1 O2, all of which are commercially available common cathodes.

[0126] In some embodiments, a cathode slurry is obtained by blending a cathode active material, super-p, a binder, and lithium perchlorate (LiClO4) in a solvent, then directly loading the slurry onto an aluminum foil by blade casting and drying under vacuum to remove the solvent. In some embodiments, the weight ratio of the cathode active material, super-p, binder, and LiClO4 is (67% to 89%):(5% to 20%):(5% to 10%):(1% to 3%).

[0127] Preferably, the weight ratio of the cathode active material, super-p, binder, and LiClO4 is 78.94%:9.87%:9.87%:1.32%.

[0128] Preferably, the solvent used in preparing the cathode slurry is acetonitrile or N-methyl pyrrolidone. Typically, acetonitrile is used when the binder is PEO. N-methyl pyrrolidone is used when the binder is PVDF.

[0129] Preferably, the temperature of the dried cathode slurry is 60°C to 120°C. The time for drying the cathode slurry can be preferably 10 to 24 hours, more preferably 12 hours.

[0130] The conductive material is generally added in an amount of 1 to 50% by weight, based on the total weight of the mixture including the cathode active material. The conductive material is not particularly limited as long as it has a suitable conductivity without causing a chemical change in the manufactured battery. Examples of the conductive material can include the following conductive materials including: graphite, such as natural or artificial graphite; carbon black, such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers, such as carbon fibers and metal fibers; metal powders, such as carbon fluoride powder, aluminum powder, and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and polyphenylene derivatives.

[0131] The binder is a component that helps adhesion between the active material and the conductive material and adhesion with the current collector. The binder is generally added in an amount of 1 to 50% by weight, based on the total weight of the mixture including the cathode active material. Examples of the binder can include polyvinylidene fluoride, poly(ethylene oxide) (PEO), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluoro rubber, and various copolymers.

[0132] In some embodiments, the polymeric binder is poly(ethylene oxide) (PEO) or poly(vinylidene fluoride) (PVDF).

[0133] The filler is an optional ingredient for suppressing swelling of the cathode. The filler is not particularly limited as long as it does not cause a chemical change in the manufactured battery and is a fibrous material. As examples of the filler, there are available olefin polymers, such as polyethylene and polypropylene; and fibrous materials, such as glass fibers and carbon fibers. The anode is manufactured by applying the anode active material to the anode current collector, and then drying. If necessary, other components as described above can be further included.

[0134] The negative current collector is generally manufactured to have a thickness of 3 to 500 μm. The materials used for the negative current collector are not particularly limited as long as they have a suitable conductivity without causing chemical changes in the manufactured battery. Examples of the materials used for the negative current collector can include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel having a surface treated with carbon, nickel, titanium, or silver, and an aluminum cadmium alloy. Similar to the positive current collector, the negative current collector can also be treated to form fine irregularities on its surface in order to enhance the adhesion strength to the negative active material. In addition, the negative current collector can be used in various forms including a film, a sheet, a foil, a mesh, a porous structure, a foam, and a nonwoven fabric.

[0135] Examples of the negative active material that can be used in the present application include carbon such as non-graphitizable carbon and graphite-based carbon; metal complex oxides such as Li x Fe2O3(0≦x≦1), Li x WO2(0≦x≦1), and Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, or Ge; Me': Al, B, P, Si, Group I, II, and III elements of the periodic table, or halogen; 0≦x≦1; 1≦y≦3; and 1≦z≦8); lithium metal; lithium alloys; silicon-based alloys; tin-based alloys; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; conductive polymers such as polyacetylene; and Li-Co-Ni based materials. In some embodiments of the present application, lithium metal is used as the negative electrode.

[0136] The secondary battery of the present application can be, for example, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, a lithium ion polymer secondary battery, or the like. The secondary battery can be manufactured in various forms. For example, the electrode assembly can be constructed in a jelly-roll structure, a stacked structure, a stacked / folded structure, or the like. The battery can employ a configuration in which the electrode assembly is mounted inside a battery case of a cylindrical can, a prismatic can, or a laminate including a metal layer and a resin layer. Such configurations of the battery are widely known in the art.

[0137] Using the macromonomer and electrolyte precursor composition of the present invention, a solid state polymer electrolyte having high ionic conductivity and good mechanical stability / strength can be prepared. Furthermore, the macromonomer and electrolyte precursor composition of the present invention is free of liquids and water. No solvent is required for processing the macromonomer and electrolyte precursor composition of the present invention. After crosslinking and preparation of the solid state polymer electrolyte using the electrolyte precursor composition of the present invention, no solvent needs to be removed.

[0138] Due to the further crosslinking of the macromonomer with the siloxane monomer, the solid state polymer electrolyte of the present invention has better mechanical properties compared to the prior art polymer electrolytes using PEO polymers or PEOPO copolymers. The solid state polymer electrolyte of the present invention has particularly better mechanical properties at temperatures above the melting point of PEO polymers or PEOPO copolymers which lose their mechanical strength above the melting point.

[0139] In contrast to the solid state polymer electrolyte benchmark poly(ethylene oxide) (PEO), the solid state electrolyte of the present invention has no crystallization ability. The complete amorphous structure of the electrolyte of the present invention shows superior ionic conductivity at lower temperatures. This is due to the absence of any crystallization which hinders the movement of ions at lower temperatures as well as the reduction of complexation of the amorphous poly(ethylene glycol-co-propylene glycol) with PEG or PEO structures. Furthermore, the comonomer propylene oxide in the polyether side chains of the present invention reduces the chelation of lithium ions, thus increasing their mobility. In contrast to the prior art involving non-crosslinked polyethers with molecular weights below 15,000 g / mol which do not have any mechanical integrity above the melting point, the macromonomer of the present invention with polyether side chains can be polymerized with siloxane monomers to form high molecular weight with better mechanical properties at such temperatures. By crosslinking with a crosslinker, a transparent and highly elastic film can be obtained which has the function of both electrolyte and separator in a solid state battery. The elastic film can withstand deformation and thus improve the safety of the battery.

[0140] The method of the present invention simplifies the production process and allows the manufacturers of lithium ion batteries to use the established equipment for lithium ion batteries with liquid electrolytes. In the method of the present invention, the drying step is replaced by a crosslinking step, where the solid state electrolyte is formed from the monomer formulation, compared to the conventional production process of lithium ion batteries with liquid electrolytes. Furthermore, no electrolyte filling step is required anymore. Due to the simplified production process, the cell factory cost is expected to be 20% lower than the current equivalent capacity factory.

[0141] In current battery production, liquid electrolytes are handled. The formulation can also be handled as a liquid before crosslinking. After it has been applied to the battery electrode, it can be solidified by crosslinking. This simplifies the manufacturing process, as no additional solvents or extrusion equipment are needed.

[0142] The solid-state electrolytes prepared with high conductivity at room temperature contribute to the electrification of mobility.

[0143] Other advantages of the present application will become apparent to those skilled in the art upon reading the specification. BRIEF DESCRIPTION OF DRAWINGS

[0144] Figure 1 The ionic conductivities of the crosslinked polymer electrolytes prepared in Examples 1 to 2 and Comparative Examples 1 to 3 at different temperatures are shown. DETAILED DESCRIPTION

[0145] The present application will now be described in detail by the following examples. The scope of the present application should not be limited to the embodiments of the examples.

[0146] Material

[0147] The following materials were used in the examples.

[0148] MPEG 1005MA W represents 50 wt% methoxypolyethylene glycol 1000-methacrylate in water. It is a highly polar monomer with excellent water solubility (50 wt% in water). The monomer can be represented by the following formula (III):

[0149]

[0150] wherein the molecular weight is 1005. MPEG 1005MA W was freeze-dried to remove water and obtain a solid monomer. MPEG 1005MA W freeze-dried to remove water and obtain a solid monomer.

[0151] to remove water and obtain a solid monomer.

[0152] MPEG 2005MA W represents 50 wt% methoxypolyethylene glycol 2000-methacrylate in water. It is a highly polar monomer with excellent water solubility (50 wt% in water). The monomer can be represented by the above formula (III) wherein the molecular weight is 2005. MPEG 2005MA W was freeze-dried to remove water and obtain a solid monomer.

[0153] MPEG 2005MA W freeze-dried to remove water and obtain a solid monomer.

[0154] MPEG 1005MA W and MPEG 2005MA W both are commercially available from Evonik Industries AG.

[0155] Analytical methods

[0156] Electrochemical impedance spectroscopy measurements were performed using a SP-300 potentiostat (BioLogic Science Instruments) in the temperature range from 0 to 70 °C. Impedance measurements were performed in the frequency range from 1 MHz to 500 mHz (and back) with an amplitude of 20 mV. The heating cycle included a gradual temperature increase from 0 to 70 °C in steps of 10 °C. The temperature was increased with a heating / cooling rate of 60 °C h -1 for 10 minutes, after which the temperature was kept constant for another 50 minutes to obtain the impedance spectra. At a temperature of 70 °C, the heating profile was reversed and a gradual cooling was performed in similar temperature steps. The ionic conductivity, s, was calculated according to the following equation:

[0157] s = 1 / R b *L / A

[0158] R b is the bulk electrolyte resistance which can be obtained from the Nyquist plot, L is the membrane thickness, and A is the membrane area.

[0159] Example 1

[0160] Synthesis of poly(ethylene glycol-co-propylene glycol) ether alcohol (diethylene glycol monomethyl ether + 16 EO / 3 PO):

[0161] In a 17 liter autoclave, 1556 g of diethylene glycol monomethyl ether and 45.4 g of potassium methoxide catalyst were added and the reactor content was inertized with nitrogen. The stirred reaction mixture was heated to 60 °C and stirred for 15 minutes. The internal pressure of the reactor was reduced to 100 mbar and the reaction mixture was heated to a reaction temperature of 115 °C. During a period of 2.5 hours, a mixture of 9595 g of ethylene oxide and 2370 g of propylene oxide was added under stirring and cooled to an internal temperature maximum of 115 °C and an internal pressure of 2.3 bar (abs.). After complete addition, the mixture was kept at 115 °C for 1.5 hours, after which the reaction mixture was degassed. Volatile components, such as residual ethylene oxide and propylene oxide, were removed by vacuum distillation. The basic product was cooled to 90 °C, aqueous phosphoric acid was added for neutralization and the mixture was stirred for 30 minutes. As antioxidant, 6.78 g of Irganox® 1076 was added. The product was discharged and analyzed by GPC. The results are shown in Table 1. 20 (high molecular weight hindered phenolic antioxidant and primary stabilizer from SI Group). Water was removed by distillation under reduced pressure (<20 mbar) and with increasing temperature up to 110 °C. The mixture was cooled to 70 °C and precipitated phosphates were removed by filtration. The yield of the liquid colorless polyether was 13.5 kg. The obtained poly(ethylene glycol-co-propylene glycol) ether alcohol had a hydroxyl value of 56.4 mg KOH / g and an acid value of 0.2 mg KOH / g.

[0162] Synthesis of poly(ethylene glycol-co-propylene glycol) methyl ether methacrylate 1000:

[0163] The above prepared poly(ethylene glycol-co-propylene glycol) ether alcohol (4400 g, 4.40 moles, Mw 1000 g / mole) and methyl methacrylate (11013 g, 110.0 moles) were weighed into a reaction vessel. Hydroquinone monomethyl ether (MEHQ) (0.94 g, 200 ppm rel. to product) was added and (lean) air was passed through the reaction mixture. Dehydration of the mixing tank was performed by azeotropic distillation of water / methyl methacrylate until the initially present water was completely distilled off. The amount of methyl methacrylate distilled off during the dehydration was subsequently replenished by adding an appropriate amount to the mixture. Catalyst titanium tetraisopropoxide (44.0 g, 0.155 moles, 1 wt% rel. to alcohol) was added and the mixture was heated to reflux, gradually distilling off the methanol / methyl methacrylate azeotrope. Complete conversion of the starting materials was achieved after 3 h. The mixture was cooled to 60-85 °C and the catalyst was precipitated with dilute sulfuric acid (1 wt%). After neutralization with Na2CO3 (10 wt%) a filter aid (Celite) was added. Water and a part of the excess methyl methacrylate were distilled off under vacuum and elevated temperature. Then the reaction mixture was filtered using a pressure filter and residual solvents were removed under vacuum. The product was obtained as a clear liquid.

[0164] Yield: 4613 g (98 wt%).

[0165] Water content: 0.015 wt% (determined by Karl-Fischer titration), GPC analysis was in agreement with the expected Mw distribution of the product and based on the starting materials.

[0166] Preparation of a solid state polymer electrolyte:

[0167] The prepared amorphous poly(ethylene glycol-co-propylene glycol) methyl ether methacrylate 1000 (840 mg, 84 wt% based on the total weight of the reaction mixture) was mixed with V-Si 7255 (30 mg, 3 wt%), photoinitiator (phenyl-di-(2,4,6-trimethylbenzoyl)- phosphine oxide, BAPO) (30 mg, 3 wt%) and lithium bis(trifluoromethanesulfonyl) imide (LITFSI) (100 mg, 10 wt%) were mixed. The mixture was stirred overnight in the dark and then dried overnight at 60 °C. The final material was poured directly on top of a stainless steel pan and then exposed to light (TLC, λ = 365 nm) at room temperature for 3 h.

[0168] Example 2

[0169] Using the same method as in Example 1, except that only half the amount of diethylene glycol monomethyl ether described in Example 1 and half the amount of potassium methanolate catalyst were used in Example 2, poly(ethylene glycol-co- propylene glycol) ether alcohol with twice the molecular weight of that prepared in Example 1 was prepared.

[0170] Synthesis of poly(ethylene glycol-co-propylene glycol) methyl ether methacrylate 2000:

[0171] The poly(ethylene glycol-co-propylene glycol) ether alcohol prepared above (1437.8 g, 0.72 moles, Mw 2000 g / mole) and methyl methacrylate (3063.5 g, 30.6 moles) were weighed into a reaction vessel. MEHQ (0.297 g, 200 ppm relative to product) was added and (lean) air was passed through the reaction mixture. Calcium oxide (11.21 g, 200 mmol, 0.78% relative to alcohol) and lithium chloride (3.16 g, 74.5 mmol, 0.22% relative to alcohol) were added and the mixture was heated to reflux while continuously distilling off the methanol / methyl methacrylate azeotrope. After 4 to 6 hours complete conversion was achieved and filter aid (Celite) was added. The excess methyl methacrylate was distilled off under vacuum at elevated temperature with stirring, followed by filtration of the mixture using a pressure filtration device. Residual methyl methacrylate was removed under vacuum. The product was obtained as a clear liquid.

[0172] Yield: 1346 g (91 wt%, loss on filter plate).

[0173] Water content: 0.01 wt% (determined by Karl Fischer titration), GPC analysis was consistent with the product and expected Mw distribution based on the raw materials.

[0174] Preparation of a solid state polymer electrolyte:

[0175] A solid state polymer electrolyte was prepared according to the same method as in example 1, except that the amorphous poly(ethylene glycol-co-propylene glycol) methyl ether methacrylate 2000 was used as raw material.

[0176] Example 3

[0177] Synthesis of poly(ethylene glycol-co-propylene glycol) methyl ether methacrylate 4000

[0178] Poly(oxyalkylen) ether alcohol (4008.6 g, 1.00 mol, Mw ~ 4068 g / mol) and methyl methacrylate (6019.3 g, 60.12 mol) were weighed into a reaction vessel. MEHQ (0.82 g, 200 ppm relative to product) was added and (lean) air was passed through the reaction mixture. Dehydration of the mixture was performed by azeotropic distillation of water / methyl methacrylate until the initially present water was completely distilled off. The amount of methyl methacrylate distilled off during the dehydration was subsequently replenished by adding the appropriate amount to the mixture.

[0179] Catalyst titanium tetraisopropoxide (40.1 g, 0.141 mol, 1 wt% relative to alcohol) was added and the mixture was heated to reflux, gradually distilling off the methanol / methyl methacrylate azeotrope. Complete conversion of the raw materials was achieved after 2 h. The mixture was cooled to 60-85 °C and the catalyst was precipitated with dilute sulfuric acid (1 wt%) under constant stirring. After neutralization with Na2CO3 (10 wt%), a filter aid (Tonsil) was added. Water and a part of the excess methyl methacrylate were distilled off under vacuum and at elevated temperature. Then, the reaction mixture was filtered (using a filter press) and residual solvents were removed under vacuum. The product was obtained as a clear liquid.

[0180] Yield: 3582 g (88 wt%, loss on filter plate).

[0181] Water content: 0.03 wt% (Karl Fischer), Ti < 1 ppm (AES), MEHQ 177 ppm, GPC analysis was consistent with the product and the expected Mw distribution based on the raw materials.

[0182] Example 4

[0183] Synthesis of poly(ethylene glycol-co-propylene glycol) methyl ether methacrylate 4600

[0184] Poly(oxyalkylene)ether alcohol (874 g, 0.19 moles, Mw ~ 4600 g / mole) and methyl methacrylate (2377.9 g, 23.75 moles) were weighed into a reaction vessel. MEHQ (0.18 g, 200 ppm relative to product) was added and (lean) air was passed through the reaction mixture. Dehydration of the mixture was carried out by azeotropic distillation of water / methyl methacrylate until the initially present water was completely distilled off. The amount of methyl methacrylate distilled off during the dehydration was subsequently replenished by adding the appropriate amount to the mixture.

[0185] LiCI (2.31 g, 0.05 moles, 0.26 wt% relative to alcohol) and CaO (8.18 g, 0.15 moles, 0.94 wt% relative to alcohol) were added and the mixture was heated to reflux, gradually distilling off the methanol / methyl methacrylate azeotrope. Complete conversion of the starting materials was achieved after 2.5 hours, after which excess methyl methacrylate was partially distilled off (1101 g) at 200 mbar. The mixture was cooled to 60-85°C and filter aid (15.7 g Tonsil) was added. The mixture was stirred for 15 minutes and filtered (using a filter press). Residual methyl methacrylate was removed by vacuum distillation. The product was obtained as a clear liquid.

[0186] Yield: 839.8 g (95 wt%).

[0187] Water content: 0.02 wt% (Karl Fischer), OH value <0.50, acid value 0.08, MEHQ 176 ppm, GPC analysis consistent with the product and expected Mw distribution based on the starting materials, D = 1.18.

[0188] Comparative Example 1 : PEO electrolyte

[0189] Poly(ethylene oxide) (PEO) (Mw = 200,000 g / mole) (900 mg, 90 wt%) was mixed with lithium bis(trifluoromethanesulfonyl)imide (LITFSI) (100 mg, 10 wt%) in 1 mL of acetonitrile and stirred overnight. Then, the mixture was cast into a Teflon mold and dried in an oven at 60 °C for 2 days to remove any trace of solvent before use. The ionic conductivity was measured in a CR2032 coin cell battery by sandwiching the solid electrolyte between two stainless steel (SS).

[0190] Comparative Example 2: photo-crosslinked MPEG 1005MA electrolyte

[0191] Freeze-dried monomers MPEG 1005MA W (840 mg, 84 wt% based on the total weight of the reaction mixture) was mixed with V-Si 7255 (30 mg, 3 wt%), a photoinitiator (phenyl-di-(2,4,6-trimethylbenzoyl)-phosphine oxide, BAPO) (30 mg, 3 wt%) and lithium bis(trifluoromethanesulfonyl)imide (LITFSI) (100 mg, 10 wt%) were mixed and 0.5 mL of acetonitrile was added to obtain a homogeneous solution. The mixture was stirred overnight in the dark, then cast into a Teflon mold and dried in an oven at 60 °C for 2 days to remove any traces of solvent before use. The material was exposed to light (TLC, λ = 365 nm) at room temperature for 3 h.

[0192] Comparative Example 3: photo-crosslinked MPEG 2005MA electrolyte

[0193] The freeze-dried monomer MPEG 2005MA W (840 mg, 84 wt% based on the total weight of the reaction mixture) was mixed with V-Si 7255 (30 mg, 3 wt%), a photoinitiator (phenyl-di-(2,4,6-trimethylbenzoyl)-phosphine oxide, BAPO) (30 mg, 3 wt%) and lithium bis(trifluoromethanesulfonyl)imide (LITFSI) (100 mg, 10 wt%) were mixed and 0.5 mL of acetonitrile was added to obtain a homogeneous solution. The mixture was stirred overnight in the dark, then cast into a Teflon mold and dried in an oven at 60 °C for 2 days to remove any traces of solvent before use. The material was exposed to light (TLC, λ = 365 nm) at room temperature for 3 h.

[0194] The electrochemical properties and mechanical properties of the electrolytes prepared in the examples and comparative examples were determined according to the methods as described above.

[0195] The ionic conductivities of the electrolytes tested are summarized in Table 1 below.

[0196] Table 1:

[0197]

[0198] As above Figure 1As shown in Table 1, the electrolyte prepared in Example 2 exhibits better ionic conductivity than the electrolyte prepared in Comparative Example 3 at various temperatures of 0 to 10°C, particularly at a low temperature of 0°C, and even exhibits better ionic conductivity than those of Comparative Examples 1 and 2 at various temperatures of 0 to 30°C. More surprisingly, the electrolyte prepared in Example 1 exhibits higher ionic conductivity than that of Comparative Example 2 at various temperatures of 0 to 50°C, particularly at a low temperature of 0 to 20°C, and also exhibits better ionic conductivity than those of Comparative Examples 1 and 3 at least at a low temperature of 0 to 20°C.

[0199] Likewise Figure 1 As shown in FIG5 , when the temperature is reduced from 50° C. to 0° C., the ionic conductivities of the electrolytes of Comparative Examples 1 to 3 decrease more significantly than those of Examples 1 to 2. Such temperature-dependent ionic conductivity characteristics of the electrolyte of the present invention are very advantageous, particularly when the electrolyte is used in an environment having a low temperature or a variation between low and high temperatures.

[0200] On the other hand, the mechanical properties of the electrolytes of Examples 1 to 2 are superior to those of Comparative Examples 1 to 3. The electrolytes of Examples 1 to 2 are self-supporting, very elastic solids. The electrolyte membranes are easily handled with tools such as tweezers and remain intact when handled with tweezers. In contrast, the electrolytes of Comparative Examples 1 to 3 are solid but not elastic. Their electrolyte membranes easily break when handled with tweezers and must be handled with extreme care.

[0201] As used herein, terms such as "including" and the like as used herein are open-ended terms meaning "including at least" unless expressly stated otherwise.

[0202] All references, tests, standards, documents, publications, etc. mentioned herein are incorporated herein by reference. Where numerical limits or ranges are stated, the endpoints are included. In addition, all values ​​and subranges within the numerical limits or ranges are specifically included as if expressly written.

[0203] The above description is presented to enable those skilled in the art to make and use the present invention, and the above description is provided in the context of a specific application and its requirements. Various modifications to the preferred embodiments will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown, but to conform to the widest scope consistent with the principles and features disclosed herein. In this regard, it is broadly considered that certain embodiments within the present invention may not illustrate each benefit of the present invention.

Claims

1. A macromonomer represented by the following general formula (I): wherein R1 represents a methyl group or H; wherein z is the number of repetitions of the ethylene glycol spacer and represents 0, 1, 2, or 3; R2 represents a methyl group or a C2 to C10 aliphatic or aromatic group, preferably a methyl group or an ethyl group, more preferably a methyl group; n represents a positive integer from 10 to 200, preferably a positive integer from 10 to 100, more preferably a positive integer from 40 to 80; n defines the degree of polymerization of the random copolymer having a comonomer ratio of x and y; and y=1% to 40%, preferably 5% to 25%, more preferably 10% to 20%, even more preferably 12% to 18%, x=1-y.

2. The macromonomer according to claim 1, wherein the macromonomer has a number average molecular weight of 500 to 10,000, preferably 500 to 5,000, such as 600 to 4,500, more preferably 750 to 4,000, or 750 to 2,000, even more preferably 800 to 1,500, such as about 1,000. The macromonomer according to claim 1 , wherein the macromonomer is liquid at room temperature.

4. The macromonomer according to claim 1, wherein in formula (I), R1 represents a methyl group or H; z is the number of repetitions of the ethylene glycol spacer and represents 0, 1, 2, or 3; R2 represents a methyl group or a C2 to C5 aliphatic group, preferably a methyl group or an ethyl group, more preferably a methyl group; n represents a positive integer from 10 to 100; n defines the degree of polymerization of the random copolymer having a comonomer ratio of x and y; y=10% to 25%, preferably 14% to 20%, x=1-y; and The macromonomer has a number average molecular weight of 500 to 5000, preferably 750 to 2000, more preferably 800 to 1500, for example about 1000.

5. An electrolyte precursor composition comprising: A) the macromonomer according to claim 1; B) siloxane monomers, particularly acrylate-functional siloxane monomers; and C) lithium salts, and optionally D) a free radical initiator.

6. The electrolyte precursor composition according to claim 5, wherein the siloxane monomer is a compound of formula (II), M 1 e M 3 f D 1 g D 3 h (II) in, M 1 =[R 1 3SiO 1 / 2 ], M 3 =[R 1 2R 3 SiO 1 / 2 ], D 1 =[R 1 2SiO 2 / 2 ], D 3 =[R 1 R 3 SiO 2 / 2 ], e=0 to 2, f=0 to 2, preferably 0, and e+f=2, g = 0 to 38, preferably 10 to 26, h=0 to 20, such as 1 to 20, or 2 to 20, or 3 to 20, preferably 4 to 15, and the ratio of the sum (f+h) to the sum (g+h+2) is from 0.15 to at most 1, preferably from 0.2 to 0.5, and the sum (g+h+2) is 4 to 40, preferably 10 to 30, R 1 represents the same or different aliphatic hydrocarbon groups having 1 to 10 carbon atoms or aromatic hydrocarbon groups having 6 to 12 carbon atoms, preferably methyl and / or phenyl, particularly preferably methyl, R 3 represents identical or different hydrocarbon radicals having 1 to 5 identical or different ester groups, preferably (meth-)acryloyloxy-functional groups, the hydrocarbon radical being linear, cyclic, branched and / or aromatic, preferably linear or branched, and the ester groups, preferably (meth-)acryloyloxy-functional groups, being selected from ethylenically unsaturated, free-radically polymerizable ester groups and non-free-radically polymerizable ester groups, the ethylenically unsaturated, free-radically polymerizable ester groups preferably being (meth-)acryloyloxy-functional groups.

7. The electrolyte precursor composition according to claim 5, wherein the siloxane monomer is a compound of formula (II), wherein: e＝2， f＝0， h=4 to 15, and the sum (g+h+2) is 5 to 40, preferably 10 to 30, R 3 represents identical or different hydrocarbon groups, said hydrocarbon groups having 1 to 5 identical or different ester groups, said hydrocarbon groups being linear, cyclic, branched and / or aromatic, preferably linear or branched, and said ester groups being selected from ethylenically unsaturated free-radically polymerizable ester groups and non-free-radically polymerizable ester groups, said ethylenically unsaturated free-radically polymerizable ester groups preferably being (meth-)acryloyloxy functional groups; and The number of free radical polymerizable groups in the siloxane monomer is 3 or more.

8. The electrolyte precursor composition according to claim 5, wherein the weight ratio of the siloxane monomer to the macromonomer is 1:0.4 to 1:80, in particular 1:0.8 to 1:52, preferably 1:1.6 to 1:55, in particular 1:1.6 to 1:52, more preferably 1:12.8 to 1:55, even more preferably 1:20 to 1:52, in particular 1:12.8 to 1:

52.

9. A method for preparing a solid polymer electrolyte comprising the steps of: a) providing the electrolyte precursor composition according to claim 5; and b) crosslinking the liquid electrolyte precursor composition by irradiation or heat treatment in the presence of a free radical initiator.

10. A solid polymer electrolyte prepared according to the method of claim 9, or obtained by curing the electrolyte precursor composition according to claim 5.

11. A solid-state lithium secondary battery comprising a positive electrode, a solid copolymer electrolyte and a negative electrode, wherein the negative electrode is preferably a lithium metal negative electrode, wherein the solid copolymer electrolyte is the solid copolymer electrolyte according to claim 10.

12. An electrochemical device comprising the solid polymer electrolyte according to claim 10.

13. An apparatus comprising the electrochemical device according to claim 12.

14. A macromonomer composition comprising: The macromonomer according to claim 3 or 4, and less than 5 wt %, e.g., less than 4 wt %, less than 3 wt %, less than 2 wt %, preferably less than 1 wt %, e.g., less than 0.9 wt %, less than 0.8 wt %, less than 0.7 wt %, less than 0.6 wt %, less than 0.5 wt %, less than 0.4 wt %, less than 0.3 wt %, less than 0.2 wt %, even less than 0.1 wt % of solvent, based on the total weight of the macromer composition; and The number average molecular weight of the macromonomer is 500 to 5000, preferably 750 to 2000, more preferably 800 to 1500.

15. Use of the macromonomer according to any one of claims 1 to 4, or use of the electrolyte precursor composition according to any one of claims 5 to 8, in the preparation of solid polymer electrolytes in lithium secondary batteries, in particular lithium metal secondary batteries, in particular for improving performance, such as electrolyte mechanical properties, ionic conductivity, in particular ionic conductivity at low temperatures, and / or cycling performance.

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