Multicomponent copolymers, methods for their preparation, polymer electrolytes and lithium ion batteries

Abstract

The application relates to the technical field of lithium ion batteries, and discloses a multi-component copolymer, a preparation method thereof, a polymer electrolyte and a lithium ion battery. The multi-component copolymer comprises a core structure unit shown in formula (1), a plurality of extension structure units shown in formula (2) and a plurality of end-capping structure units shown in formula (3), the core structure unit is connected with the plurality of end-capping structure units through the plurality of extension structure units, and a structure is formed at the connection, wherein R1 and R2 are each independently a C2-C12 linear or branched alkylene; and n and m are each independently a positive integer. 10 The application further discloses a preparation method of the multi-component copolymer, a polymer electrolyte containing the multi-component copolymer and a lithium ion battery comprising the polymer electrolyte. The polymer electrolyte provided by the application can have strong mechanical strength and high ionic conductivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a multi-component copolymer, a preparation method thereof, a polymer electrolyte and a lithium ion battery. BACKGROUND

[0002] Solid polymer electrolyte (SPE) has strong plasticity, which is convenient for battery shape design and assembly, and can meet the development requirements of miniaturization, thinning and lightening of electronic products. Solid polymer electrolyte is composed of lithium salt and polymer matrix. The most commonly used matrix for polymer electrolyte is polyether (polyethylene oxide (PEO), polyphenyl ether (PPO), polyether polyol (PEPO) and the like). Polyether can provide high enough electron donor group density and has flexible polyether chain segment, so it can effectively dissolve cations by cage effect. However, most polyethers have high crystallinity, which hinders the migration of lithium ions, and have low solubility for lithium salt, resulting in low room temperature ionic conductivity.

[0003] With the increasing demand for the capacity of energy storage devices, the mechanical properties of solid polymer electrolyte have also been improved. During the charging and discharging cycle of the battery, the carrier ions are continuously embedded / extracted in the electrode material, causing the volume expansion / contraction of the electrode, so the solid electrolyte needs to have high enough mechanical strength to resist the volume change of the electrode. The existing technology of polymer electrolyte has the problem that the mechanical properties and ionic conductivity are incompatible.

[0004] Therefore, there is an urgent need to develop a new technology for preparing electrolyte materials with strong mechanical strength and high ionic conductivity. SUMMARY

[0005] The purpose of the present application is to overcome the problem that the existing electrolyte materials cannot have strong mechanical strength and high ionic conductivity, and to provide a multi-component copolymer, a preparation method thereof, a polymer electrolyte and a lithium ion battery.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a multi-component copolymer, wherein the multi-component copolymer comprises a core structure unit represented by formula (1), a plurality of extension structure units represented by formula (2) and a plurality of end structure units represented by formula (3), the core structure unit and the plurality of end structure units are connected through the plurality of extension structure units, and the connection forms structure:

[0007]

[0008] wherein R1 and R2 are each independently a linear or branched alkylene group with 2-10 carbon atoms; n and m are each independently a positive integer. 10 The present application has the advantages that the multi-component copolymer has strong mechanical strength and high ionic conductivity, and the polymer electrolyte and the lithium ion battery prepared by using the multi-component copolymer have high ionic conductivity and good mechanical properties.

[0009] A second aspect of the present invention provides a method for preparing a multi-component copolymer, wherein the method comprises the following steps:

[0010] (1) in the presence of an initiator and an organic solvent, subjecting the monomer represented by formula (I) and the monomer represented by formula (II) to a first polymerization reaction to obtain a first polymer product;

[0011]

[0012] (2) subjecting the first polymer product to a second polymerization reaction with a monomer represented by formula (III) to obtain a second polymer product;

[0013]

[0014] (3) adding methanol to the second polymer product to cause an end-capping reaction to obtain the multi-component copolymer;

[0015] Wherein, X is halogen, R1 and R2 are each independently C2-C 10 wherein n and m are each independently a positive integer.

[0016] Wherein, X is halogen, R1 and R2 are each independently C2-C 10 wherein n and m are each independently a positive integer.

[0017] The third aspect of the present invention provides a multi-component copolymer prepared by the aforementioned preparation method.

[0018] A fourth aspect of the present invention provides a polymer electrolyte, wherein the polymer electrolyte comprises the aforementioned multi-polymer, a lithium salt, a plasticizer, and a filler.

[0019] A fifth aspect of the present invention provides a lithium-ion battery comprising the aforementioned polymer electrolyte.

[0020] Through the above technical solution, the beneficial effects achieved by the present invention are as follows:

[0021] (1) The present invention provides a multi-component copolymer having polyoxyalkylene segments widely distributed within its branched structure, which improves the copolymer's flexibility. When used as a polymer matrix in a polymer electrolyte for lithium-ion batteries, the copolymer can improve its ability to dissolve lithium ions and significantly increase its ionic conductivity. Furthermore, the multi-component copolymer contains a structure with m-phenylimide groups, which significantly enhances the mechanical strength of the polymer electrolyte.

[0022] (2) Compared with conventional chain polymer electrolytes, the polymer electrolyte provided by the present invention can have both strong mechanical strength and high ionic conductivity. The polymer electrolyte has the advantages of high mechanical strength and high ionic conductivity.

[0023] (3) The polymer electrolyte provided by the present application has simple preparation conditions and is easy to realize industrialization. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a schematic diagram of the multi-copolymer of the present application;

[0025] Figure 2 is a structural formula of 2,4,6-trifluoromethylacetamide;

[0026] Figure 3 is a structural formula of 2,4-trifluoromethylacetamide-6-polyoxyethylene alcohol;

[0027] Figure 4 is a structural schematic diagram of the multi-copolymer of the present application, wherein A1=A2=A3;

[0028] Figure 5 shows the specific structure of the multi-copolymer, taking A3 as an example. DETAILED DESCRIPTION

[0029] The endpoints of the ranges and any values claimed herein are not to be understood as limited to the exact values recited as implicitly split into a narrower range between each pair of endpoints. The ranges should be understood to include values near the recited values within the range. For values that are less than one, the ranges should be understood to include values within one unit of the recited value, for example, 1.0, 1.1, 1.2, etc.

[0030] The first aspect of the present application provides a multi-copolymer, wherein the multi-copolymer comprises a core structural unit shown in formula (1), a plurality of extension structural units shown in formula (2), and a plurality of end-capping structural units shown in formula (3), the core structural unit is connected with a plurality of the end-capping structural units through a plurality of the extension structural units, and the connection forms a structure shown in formula (4).

[0031]

[0032] wherein R1 and R2 are each independently a C2-C 10 straight-chain or branched alkylene; n and m are each independently a positive integer.

[0033] The multi-copolymer provided by the present application, the core structural unit is connected with a plurality of the end-capping structural units through a plurality of the extension structural units, and the connection forms a structure shown in formula (4). wherein a plurality of the extension structural units continuously extend and expand around the core structural unit through a structure shown in formula (5). ​​

[0034] The multi-polymer provided by the present application has a core structure unit as shown in formula (1), an extended structure unit as shown in formula (2), and a terminal structure unit as shown in formula (3), for example Figure 1 The branched structure of the multi-polymer is widely distributed with polyalkylene oxide segments, which improves the flexibility of the multi-polymer. When the multi-polymer is used as a polymer matrix for preparing a lithium ion battery, the ability to dissolve lithium ions can be improved, and the ionic conductivity can be greatly increased. In addition, the multi-polymer contains a structure of m-phenyl imide group, which greatly improves the mechanical strength of the polymer electrolyte.

[0035] In some preferred embodiments of the present application, the polyalkylene oxide segment can be a polypropylene oxide segment, a polyethylene oxide segment, and a copolymer segment of propylene oxide and ethylene oxide.

[0036] In some preferred embodiments of the present application, when the number of extended structure units is 1, 3 or 7, they can be named as 1st generation, 2nd generation, and 3rd generation polymerization, respectively, and the number of terminal structure units is 2, 4, and 8, respectively.

[0037] For example, the multi-polymer in formula (1) is polymerized to the 3rd generation, and then polymerized with excess polyalkylene oxide alcohol, and finally terminated with methyl. Figure 5 For example, the multi-polymer in formula (1) is polymerized to the 3rd generation, and then polymerized with excess polyalkylene oxide alcohol, and finally terminated with methyl.

[0038] In the present application, examples of the linear or branched alkylene group of C2-C 10 , for example, can be any one of ethylene, n-propylene, iso-propylene, n-butylene, sec-butylene, iso-butylene, tert-butylene, n-pentylene, iso-pentylene, tert-pentylene, neopentylene, n-hexylene, iso-hexylene, n-heptylene, iso-heptylene, 2-methylhexylene, 2-ethylhexylene, 1-methylheptylene, 2-methylheptylene, n-octylene, iso-octylene, n-nonylene, iso-nonylene, and 3,5,5-trimethylhexylene, n-decylene, and iso-decylene.

[0039] In the present application, the values of n and m can be independently selected as positive integers, for example, 1, 2, 10, 20, 50, 100, 200, 500, etc.

[0040] In the present application, the corresponding structure of m in the terminal structure unit as shown in formula (3) can be different or the same in the terminal of different positions in the multi-polymer. That is, the multi-polymer can have different or the same terminal structure units, and correspondingly, the values of m are different or the same.

[0041] In some embodiments of the present application, in the multi-copolymer, the value of m in the end-capping structural unit at different positions has at least two different values. That is, the value of m (which can be marked as m1, m2, m3,...) in the end-capping structural unit at different positions in the multi-copolymer can be different.

[0042] When the value of m in the end-capping structural unit at different positions is different, it indicates that the length of the outermost polyoxyalkylene segment is in a dispersed state distribution, at which the ionic conductivity is the largest and can capture and complex lithium ions to the maximum extent.

[0043] In some preferred embodiments of the present application, R1 and R2 are each independently a C2-C6 linear or branched alkylene group, preferably ethylene and / or propylene.

[0044] In some preferred embodiments of the present application, n is a positive integer of 1-100, for example 1, 2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, and any value within the range between any two of the above values, preferably 3-60, and further preferably 3-25.

[0045] In some preferred embodiments of the present application, m is a positive integer of 1-100, for example 1, 2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, and any value within the range between any two of the above values, preferably 3-60, and further preferably 3-25.

[0046] In some embodiments of the present application, the molar ratio of the core structural unit represented by formula (1), the extension structural unit represented by formula (2), and the end-capping structural unit represented by formula (3) in the multi-copolymer is 1: (3-100): (6-200).

[0047] In some embodiments of the present application, the weight average molecular weight of the multi-copolymer is 6x10 5 -2x10 6 g / mol, for example, and any value within the range between any two of the above values, preferably 7x10 5 -1x10 6 g / mol. In the present application, controlling the weight average molecular weight of the multi-copolymer within the above specific range can maximize the ionic conductivity.

[0048] In the present application, the weight average molecular weight of the multi-copolymer is tested by gel chromatography.

[0049] In some embodiments of the present application, the multi-copolymer has a structure represented by formula (4),

[0050]

[0051] wherein A1, A2 and A3 are structurally identical.

[0052] In the present application, when the multi-copolymer has the structure shown in formula (4), the three branched chains have the same structure, are in the same dispersion state, and have the same distribution. At this time, the stress in each direction is uniform, and the ability to capture and complex lithium ions in each direction is equivalent. When it is used as a polymer electrolyte matrix, the obtained polymer electrolyte has the advantages of uniform mechanical strength, high toughness, high ionic conductivity, good thermal stability and high interface stability.

[0053] The second aspect of the present application provides a method for preparing a multi-copolymer, wherein the method comprises the following steps:

[0054] (1) a first polymerization reaction of a monomer shown in formula (I) and a monomer shown in formula (II) in the presence of an initiator and an organic solvent to obtain a first polymerization product;

[0055]

[0056] (2) a second polymerization reaction of the first polymerization product and a monomer shown in formula (III) to obtain a second polymerization product;

[0057]

[0058] (3) an end-capping reaction of the second polymerization product by adding methanol to obtain the multi-copolymer;

[0059] wherein X is halogen, R1 and R2 are each independently a C2-C6 linear or branched alkylene, and n and m are each independently a positive integer. 10

[0060] In the present application, the above preparation method has the characteristics of easy implementation, and brings the effect of less impurities in the product.

[0061] In some embodiments of the present application, X is selected from at least one of F, Cl and Br.

[0062] In some preferred embodiments of the present application, R1 and R2 are each independently a C2-C6 linear or branched alkylene, preferably ethylene and / or propylene.

[0063] In some preferred embodiments of the present application, n is a positive integer of 1-100, for example 1, 2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, and any value within the range of any two of the above values, preferably 3-60, and further preferably 3-25. ​

[0064] In some preferred embodiments of the present application, m is a positive integer from 1 to 100, such as 1, 2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, and any value within a range between any two of the above-mentioned values, preferably from 3 to 60, and further preferably from 3 to 25.

[0065] In some preferred embodiments of the present application, the monomer of formula (I) is 2,4,6-trifluoromethylacetamide, as shown in formula (I): 10 Examples of the straight-chain or branched-chain alkylene group are as described above in the first aspect of the present application, which will not be repeated here.

[0066] In some preferred embodiments of the present application, the monomer of formula (I) is 2,4,6-trifluoromethylacetamide, as shown in formula (I): Figure 2 In some preferred embodiments of the present application, the monomer of formula (II) is 2,4-trifluoromethylacetamide-6-polyoxyethylene alcohol, as shown in formula (II): Figure 3 In some preferred embodiments of the present application, the monomer of formula (III) is polyoxyethylene alcohol.

[0067] In some preferred embodiments of the present application, the molar ratio of the monomer of formula (I), the monomer of formula (II), the monomer of formula (III) and methanol is 1: (3-100): (6-200): (6-200).

[0068] In some embodiments of the present application, the initiator is selected from at least one of dibutyltin dilaurate, azobisisobutyronitrile and methyl peroxide.

[0069] In some preferred embodiments of the present application, the amount of the initiator is 0.1-1 wt% of the total weight of the monomer of formula (I) and the monomer of formula (II), preferably 0.4-0.5 wt%.

[0070] In some preferred embodiments of the present application, the organic solvent is selected from at least one of dimethylformamide, tetrahydrofuran and toluene.

[0071] In some preferred embodiments of the present application, the temperature of the first polymerization reaction is 60-100°C, such as 60°C, 70°C, 80°C, 90°C, 100°C, and any value within a range between any two of the above-mentioned values, preferably from 70°C to 85°C. The time of the first polymerization reaction is 10-30h, such as 10h, 15h, 20h, 25h, 30h, and any value within a range between any two of the above-mentioned values, preferably from 15h to 25h.

[0072] In some preferred embodiments of the present application, the temperature of the second polymerization reaction is 60-100℃, such as 60℃, 70℃, 80℃, 90℃, 100℃, and any value within the range between any two of the above-mentioned values, preferably 70-85℃. The time of the second polymerization reaction is 10-30h, such as 10h, 15h, 20h, 25h, 30h, and any value within the range between any two of the above-mentioned values, preferably 15-25h.

[0073] In some preferred embodiments of the present application, the temperature of the end-capping reaction is 60-100℃, such as 60℃, 70℃, 80℃, 90℃, 100℃, and any value within the range between any two of the above-mentioned values, preferably 70-85℃. The time of the end-capping reaction is 3-10h, such as 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, and any value within the range between any two of the above-mentioned values, preferably 4-6h.

[0074] According to a particularly preferred embodiment of the present application, a method for preparing a multi-component copolymer, wherein the method comprises the following steps:

[0075] (1) a first polymerization reaction of a monomer represented by formula (I) and a monomer represented by formula (II) is carried out in the presence of dibutyltin dilaurate and dimethylformamide at 70-85℃ for 15-25h to obtain a first polymerization product;

[0076]

[0077] (2) a second polymerization reaction of the first polymerization product and a monomer represented by formula (III) is carried out in the presence of tetrahydrofuran at 70-85℃ for 15-25h to obtain a second polymerization product;

[0078]

[0079] (3) an end-capping reaction of the second polymerization product with methanol is carried out at 70-85℃ for 4-6h to obtain the multi-component copolymer;

[0080] wherein X is at least one of F, Cl and Br, R1and R2are each independently ethylene and / or propylene, n is any integer from 3 to 25, and m is any integer from 3 to 25;

[0081] The molar ratio of the monomer represented by formula (I), the monomer represented by formula (II), the monomer represented by formula (III) and methanol is 1:(3-100):(6-200):(6-200);

[0082] The amount of dibutyl tin dilaurate is 0.4-0.5 wt% of the total weight of the monomer of formula (I) and the monomer of formula (II).

[0083] The third aspect of the present application provides a multi-copolymer, which is prepared by the aforementioned preparation method.

[0084] The fourth aspect of the present application provides a polymer electrolyte, wherein the polymer electrolyte comprises the aforementioned multi-copolymer, a lithium salt, a plasticizer and a filler.

[0085] In some embodiments of the present application, the polymer electrolyte comprises, in parts by weight, 25-50 parts of the multi-copolymer, 20-40 parts of the lithium salt, 20-40 parts of the plasticizer and 1-4 parts of the filler.

[0086] The multi-copolymer can be selected from 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, and any value within a range defined by any two of the above values.

[0087] The lithium salt can be selected from 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, and any value within a range defined by any two of the above values.

[0088] The plasticizer can be selected from 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, and any value within a range defined by any two of the above values.

[0089] The filler can be selected from 1 part, 2 parts, 3 parts, 4 parts, and any value within a range defined by any two of the above values.

[0090] In some preferred embodiments of the present application, the polymer electrolyte comprises, in parts by weight, 35-45 parts of the multi-copolymer, 25-35 parts of the lithium salt, 25-35 parts of the plasticizer and 1.5-2.5 parts of the filler.

[0091] In some preferred embodiments of the present application, the molar ratio of the oxygen atoms contained in the multi-copolymer to the lithium ions in the lithium salt in the polymer electrolyte is 6-40:1, for example, 6:1, 8:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, and any value within a range defined by any two of the above values. In the present application, controlling the molar ratio of the oxygen atoms contained in the multi-copolymer to the lithium ions in the lithium salt within the above range can maximize the ionic conductivity value.

[0092] In some preferred embodiments of the present application, the lithium salt is selected from at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluorosilicate (LiSiF6), lithium tetraphenylborate (LiB(C6H5)4), lithium chloride (LiCl), lithium bromide (LiBr), lithium chloroaluminate (LiAlCl4), and lithium fluorocarbon sulfonate (e.g., LiC(SO2CF3)3), LiCH3SO3, LiN(SO2CF3)2, LiN(SO2C2F5)2). To obtain higher room temperature ionic conductivity, lithium bis(pentafluoroethylsulfonyl)imide (LiN(SO2C2F5)2) or lithium hexafluorophosphate (LiPF6) is preferred.

[0093] In some preferred embodiments of the present application, the plasticizer is selected from at least one of phthalate ester, aliphatic dibasic acid ester, fatty acid ester, benzenepolyacid ester, polyhydric alcohol ester, epoxy hydrocarbon, and alkyl sulfonate.

[0094] In some preferred embodiments of the present application, the filler is selected from at least one of Al2O3, SiO2, TiO2, BaTiO3, zeolite, and clay. In the present application, the filler as an additive can improve the interface performance between the electrolyte and the electrode, reduce the crystallinity and glass transition temperature of the polymer, and increase the ionic conductivity of the electrolyte.

[0095] The polymer electrolyte composition provided by the present application can further add other dopes disclosed in the art to improve performance, such as adding small molecule liquid plasticizer to reduce the crystalline region content of the polymer matrix and improve the ionic conductivity.

[0096] The small molecule liquid plasticizer includes organic liquid, organic small molecule substance (such as oligomer), and electrolyte, which generally causes the polymer matrix to swell and transform into a gel state, and can greatly improve the ionic conductivity. The commonly used organic liquid is carbonate such as DMC (dimethyl carbonate), DEC (diethyl carbonate), PC (polycarbonate), EC (ethylene carbonate), etc., and the organic small molecule substance is PEG (polyethylene glycol), PEGDMA (polyethylene glycol dimethyl acrylate), etc.

[0097] According to a particularly preferred embodiment of the present application, a polymer electrolyte includes, in parts by weight, 35-45 parts of a multi-copolymer, 25-35 parts of a lithium salt, 25-35 parts of a plasticizer, and 1.5-2.5 parts of a filler.

[0098] In the polymer electrolyte, the molar ratio of the oxygen atoms in the multi-copolymer to the lithium ions in the lithium salt is 6-40:1.

[0099] The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorosilicate, lithium tetraphenylborate, lithium chloride, lithium bromide, lithium chloroaluminate, and lithium fluorohydrocarbylsulfonate;

[0100] The plasticizer is selected from at least one of phthalate ester, aliphatic dibasic acid ester, fatty acid ester, benzenepolyacid ester, polyhydric alcohol ester, epoxy hydrocarbon, and alkyl sulfonate ester.

[0101] The filler is selected from at least one of Al2O3, SiO2, TiO2, BaTiO3, zeolite, and clay.

[0102] In the polymer electrolyte provided by the present application, the polyoxyalkylene chain segments are widely distributed in the branched structure of the multi-copolymer, which improves the flexibility of the multi-copolymer and the ability to dissolve lithium ions, greatly increasing the ionic conductivity. In addition, the structure containing m-phenyl imide groups in the multi-copolymer can adjust the complexing strength of lithium ions, greatly improving the mechanical strength of the polymer electrolyte. Therefore, compared with the traditional chain polymer electrolyte, the polymer electrolyte provided by the present application can have strong mechanical strength and high ionic conductivity.

[0103] In some embodiments of the present application, a method for preparing a polymer electrolyte, wherein the method comprises the following steps:

[0104] (a) mixing the aforementioned multi-copolymer with a filler and forming a film;

[0105] (b) immersing the film-1 obtained in step (a) into a lithium-containing solution and drying to form a film;

[0106] (c) contacting the film-2 obtained in step (b) with propylene carbonate to swell and form a film, thereby obtaining the polymer electrolyte.

[0107] In some preferred embodiments of the present application, the lithium-containing solution is an ethyl acetate solution of lithium salt.

[0108] In some embodiments of the present application, the raw materials in the method are as follows in terms of weight parts: multi-copolymer 25-50 parts, lithium salt 20-40 parts, plasticizer 20-40 parts, and filler 1-4 parts.

[0109] In some preferred embodiments of the present application, the raw materials in the method are as follows in terms of weight parts: multi-copolymer 35-45 parts, lithium salt 25-35 parts, plasticizer 25-35 parts, and filler 1.5-2.5 parts.

[0110] In some preferred embodiments of the present application, the molar ratio of oxygen atoms contained in the multi-copolymer to lithium ions in the lithium-containing solution is 6-40:1.

[0111] In some preferred embodiments of the present application, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorosilicate, lithium tetraphenylborate, lithium chloride, lithium bromide, lithium chloroaluminate, lithium fluorocarbonsulfonate.

[0112] In some preferred embodiments of the present application, the plasticizer is selected from at least one of phthalate ester, aliphatic dibasic acid ester, fatty acid ester, benzenepolyacid ester, polyhydric alcohol ester, epoxy hydrocarbon, and alkyl sulfonate.

[0113] In some preferred embodiments of the present application, the filler is selected from at least one of AI2O3, SiO2, TiO2, BaTiO3, zeolite, and clay.

[0114] The fifth aspect of the present application provides a lithium ion battery comprising the aforementioned polymer electrolyte.

[0115] The lithium ion battery provided by the present application comprises a positive electrode, a negative electrode, and the aforementioned polymer electrolyte, wherein the polymer electrolyte is located between the positive electrode and the negative electrode.

[0116] The positive electrode comprises a positive electrode current collector and a positive electrode active material supported thereon. The positive electrode current collector is an aluminum foil, and the positive electrode active material comprises a positive electrode active substance, a binder, and a conductive agent. The positive electrode active substance can be any of the positive electrode materials that have been commercially available so far, such as LiFePO4, LiMnO2, LiNiO2, LiCoO2, LiVPO4F, LiFeO2, or a ternary system.

[0117] The negative electrode comprises a negative electrode current collector and a negative electrode active material supported thereon. The negative electrode current collector is a copper foil, and the negative electrode active material comprises a negative electrode active substance, a binder, and a conductive agent. The negative electrode active substance can be any of the negative electrode materials that have been commercially available so far, such as natural graphite, artificial graphite, hard carbon, soft carbon, lithium titanate, or a mixture of one or more thereof.

[0118] The binder can be any of the binders commonly used in the art, for example, one or more of polyvinylidene fluoride, polytetrafluoroethylene, butadiene styrene rubber, and polyacrylate. The conductive agent can be any of the conductive agents commonly used in the art, for example, one or more of graphite, carbon fiber, carbon black, metal powder, metal oxide, and fiber.

[0119] The method for preparing the lithium ion battery comprising the polymer electrolyte is not particularly limited in the present application, and any of the methods commonly used in the art can be used.

[0120] For example, a solution of the polymer electrolyte is coated on the surface of the positive electrode sheet and the negative electrode sheet, a polymer electrolyte film is formed by drying to remove the solvent, the positive electrode sheet and the negative electrode sheet coated with the polymer electrolyte are wound or stacked to prepare a core, which is placed in a battery case, sealed, formed, sealed, packaged; or a polymer electrolyte film is prepared first, then attached to the surface of the positive electrode sheet or the negative electrode sheet, then the positive electrode sheet and the negative electrode sheet are wound or stacked to prepare a core, which is placed in a battery case, sealed, formed, sealed, packaged; or the prepared polymer electrolyte is added between the positive electrode sheet and the negative electrode sheet to which the polymer electrolyte provided by the present application is attached, then the positive electrode sheet and the negative electrode sheet are wound or stacked to prepare a core, which is placed in a battery case, sealed, formed, sealed, packaged, and the added polymer electrolyte includes the polymer electrolyte provided by the present application, and also includes other polymer electrolytes and separator materials. The sealing and formation operations are performed by using the methods commonly used in the art.

[0121] The present application will be described in detail below by way of examples.

[0122] In the following examples and comparative examples, the specific conditions not specified are performed according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be obtained by market purchase.

[0123] In the following examples and comparative examples, the parts of the raw materials are by weight.

[0124] Preparation Example 1

[0125] This preparation example is used to illustrate the preparation of the multi-copolymer.

[0126] Into a polymerization reactor, 2,4,6-trifluoromethylacetamide, Figure 2 2,4-trifluoromethylacetamide-6-polyethylene oxide alcohol, Figure 3 and dry dimethylformamide and dibutyltin dilaurate are added, heated to 80℃, and the reaction is continued for 24h; then tetrahydrofuran and polyethylene oxide alcohol are added to the polymerization reactor, and the reaction is continued at 80℃ for 24h; finally, methanol is added to the polymerization reactor, and the end-capping reaction is carried out at 80℃ for 5h, to finally obtain the multi-copolymer S-1. The molar ratio of 2,4,6-trifluoromethylacetamide, 2,4-trifluoromethylacetamide-6-polyethylene oxide alcohol, polyethylene oxide alcohol and methanol is 1:21:24:24.

[0127] The structure of the multi-copolymer S-1 is shown in Figure 4 and Figure 5 wherein the value of n and the values of m1-m8 are shown in Table 1.

[0128] Preparation Examples 2-12

[0129] The multipolymer S-2 to S-12 were prepared according to the method of Preparation 1, except that in each preparation, the 2,4-trifluoromethylacetamide-6-polyoxyethylene alcohol and the polyoxyethylene alcohol were different.

[0130] The structure of the multipolymer S-2 to S-12 is shown in Figure 4 and Figure 5 wherein the values of n and m1-m8 are shown in Table 1.

[0131] Preparation 13

[0132] The multipolymer S-13 was prepared according to the method of Preparation 1, except that the molar ratio of 2,4,6-trifluoromethylacetamide, 2,4-trifluoromethylacetamide-6-polyoxyethylene alcohol (value of n is 3), polyoxyethylene alcohol (value of m is 3) and methanol was 1:14:17:17.

[0133] Table 1

[0134] Number n value Values of m1-m8 Preparation Example 1 3 m1 = m2 = m3 = m4 = m5 = m6 = m7 = m8 = 3 Preparation Example 2 3 m1 = m2 = m3 = m4 = m5 = m6 = m7 = m8 = 9 Preparation Example 3 3 m1 = m2 = m3 = m4 = m5 = m6 = m7 = m8 = 15 Preparation Example 4 3 m1 = m2 = m3 = m4 = m5 = m6 = m7 = m8 = 20 Preparation Example 5 9 m1 = m2 = m3 = m4 = m5 = m6 = m7 = m8 = 3 Preparation Example 6 9 m1 = m2 = m3 = m4 = m5 = m6 = m7 = m8 = 9 Preparation Example 7 9 m1 = m2 = m3 = m4 = m5 = m6 = m7 = m8 = 15 Preparation Example 8 9 m1 = m2 = m3 = m4 = m5 = m6 = m7 = m8 = 20 Preparation Example 9 3 m1 = m2 = 3, m3 = m4 = 9, m5 = m6 = 15, m7 = m8 = 25 Preparation Example 10 9 m1 = m2 = 3, m3 = m4 = 9, m5 = m6 = 15, m7 = m8 = 25 Preparation Example 11 15 m1 = m2 = 3, m3 = m4 = 9, m5 = m6 = 15, m7 = m8 = 25 Preparation Example 12 25 m1 = m2 = 3, m3 = m4 = 9, m5 = m6 = 15, m7 = m8 = 25

[0135] Example 1

[0136] This example is illustrative of the preparation of a polymer electrolyte.

[0137] To 35 parts of the multipolymer S-1 was added 1.5 parts of SiO2 and heated to 120°C with stirring until homogeneous. The resulting prepolymer melt was poured onto a glass sheet and heated to 120°C in a vacuum oven overnight. The resulting film was removed from the glass sheet and weighed and immersed in a solution of lithium hexafluorophosphate (25 parts) in ethyl acetate for 24 hours to swell. After swelling, the film was dried in a vacuum oven at 60°C overnight and weighed to determine the amount of lithium hexafluorophosphate. The film was immediately transferred to an argon filled glove box to avoid picking up moisture from the air. In the glove box, 35 parts of propylene carbonate was added and the film was allowed to swell for at least two hours and reach equilibrium to produce the final polymer electrolyte M1 which was in the form of a film.

[0138] The molar ratio of oxygen atoms in the multipolymer to lithium ions in the lithium containing solution was 10:1.

[0139] Example 2

[0140] This example is illustrative of the preparation of a polymer electrolyte.

[0141] Example 1

[0142] The molar ratio of oxygen atoms contained in the multi-copolymer to lithium ions in the lithium-containing solution is 8:1.

[0143] Example 2

[0144] This example is used to illustrate the preparation of a polymer electrolyte.

[0145] Example 3

[0146] The molar ratio of oxygen atoms contained in the multi-copolymer to lithium ions in the lithium-containing solution is 40:1.

[0147] Example 4

[0148] This example is used to illustrate the preparation of a polymer electrolyte.

[0149] A 25 parts of the multicomponent copolymer S-4 was heated to 120°C with 1 part of Si02 and stirred until homogeneous. The resulting prepolymer melt was poured onto a glass sheet and heated to 120°C in a vacuum chamber overnight. The resulting film was removed from the glass sheet, weighed, and immersed in a solution of lithium hexafluorophosphate (20 parts) in ethyl acetate for 24 h for swelling. After swelling, the film was dried in a vacuum chamber at 60°C overnight and weighed to calculate the amount of lithium salt. The prepared film was immediately transferred to an argon-filled glove box to avoid the absorption of moisture from the air. In the glove box, 20 parts of propylene carbonate were added and the film was allowed to swell for at least two hours and reach equilibrium to produce the final polymer electrolyte M4, which was in the form of a film.

[0150] The molar ratio of oxygen atoms contained in the multicomponent copolymer to lithium ions in the lithium-containing solution is 6:1.

[0151] Example 5

[0152] This example is used to illustrate the preparation of a polymer electrolyte.

[0153] A 50 parts of the multicomponent copolymer S-5 was heated to 120°C with 4 parts of Si02 and stirred until homogeneous. The resulting prepolymer melt was poured onto a glass sheet and heated to 120°C in a vacuum chamber overnight. The resulting film was removed from the glass sheet, weighed, and immersed in a solution of lithium tetrafluoroborate (40 parts) in ethyl acetate for 24 h for swelling. After swelling, the film was dried in a vacuum chamber at 60°C overnight and weighed to calculate the amount of lithium tetrafluoroborate. The prepared film was immediately transferred to an argon-filled glove box to avoid the absorption of moisture from the air. In the glove box, 40 parts of propylene carbonate were added and the film was allowed to swell for at least two hours and reach equilibrium to produce the final polymer electrolyte M5, which was in the form of a film.

[0154] The molar ratio of oxygen atoms contained in the multicomponent copolymer to lithium ions in the lithium-containing solution is 30:1.

[0155] Examples 6-13

[0156] The polymer electrolytes were prepared according to the method of Example 1, except that the multicomponent copolymer S-1 was replaced with the multicomponent copolymers S-6 to S-13 to obtain the polymer electrolytes M6 to M13.

[0157] Comparative Example 1

[0158] A 0.683 g of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and 1 g of polyethylene oxide (PEO) with a weight average molecular weight of 400,000 g / mol were added to an appropriate amount of anhydrous acetonitrile, stirred at room temperature for 24 h, and then cast into a film in polytetrafluoroethylene, which was then vacuum dried at 50°C for 48 h to obtain a polymer electrolyte RM1.

[0159] Test Example

[0160] Crystallinity: tested by differential scanning calorimeter (DSC-Q2000), calibrated by indium standard, sample weight 8-10 mg, temperature range -70-150℃, heating and cooling rate 10℃ / min. The crystallinity of thin film polymer electrolyte samples M1-M13 and RM1-RM3 was recorded.

[0161] Tensile strength: tested by tensile testing equipment Instron 5565, strain rate of the instrument 100% / min.

[0162] Ionic conductivity: thin film polymer electrolyte samples M1-M13 and RM1 were cut into thin films with an area of 2 cm 2 , thickness of 0.4 mm, and assembled into 2032 button cells by sandwiching the polymer electrolyte between two parallel stainless steel sheets in a glove. The cell model was "stainless steel sheet | polymer electrolyte film | stainless steel sheet", and the CHI660B electrochemical workstation of Shanghai Chenhua Instrument Co., Ltd. was used to test the frequency range of 1-100 kHz, the temperature was -20℃, -15℃, 20℃, 50℃, 80℃, 110℃, and the bulk resistance (Rh) of the polymer electrolyte was the intersection of the Nyquist curve and the real axis. The ionic conductivity was calculated according to the formula σ = I / (A·Rh), where σ is the ionic conductivity, I is the thickness of the polymer electrolyte film, and A is the contact area of the elastic polymer electrolyte film and the electrode.

[0163] The test results are shown in Table 2.

[0164] Table 2

[0165]

[0166]

[0167] From the test results in Table 2, compared with the polymer electrolyte prepared in the comparative example, the polymer electrolyte prepared by using the multi-component copolymer provided by the application as the polymer matrix has higher ionic conductivity and lower crystallinity, and the mechanical property of tensile strength is not only not reduced but also better than that of the electrolyte prepared in the comparative example, which can effectively improve the safety performance of lithium ion batteries.

[0168] From the experimental data of Examples 1-12, it can be seen that when n is 9, the ionic conductivity and mechanical strength can be maximized; when n is the same and m1-m8 has different values, the length of the outermost polyalkylene oxide segment of the multi-component copolymer is in a dispersed state, the ionic conductivity is the largest, and the lithium ions can be maximally captured and complexed.

[0169] From the experimental data of Example 1 and Example 13, it can be seen that when the three branched structures of the multi-polymer are different, the polymer electrolyte prepared by the polymer matrix is slightly worse in ionic conductivity and tensile strength performance than the polymer electrolyte prepared by the polymer matrix with the same branched structure, but still better than the performance obtained in the comparative example.

[0170] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A multi-component copolymer, characterized in that: The multi-component copolymer comprises a core structural unit represented by formula (1), a plurality of extended structural units represented by formula (2), and a plurality of end-capping structural units represented by formula (3), wherein the core structural unit and the plurality of end-capping structural units are connected via the plurality of extended structural units, and the connection forms structure: Formula (1) Formula (2) Formula (3) Wherein, R1 and R2 are each independently C2-C 10 A straight or branched alkylene group; n and m are each independently a positive integer; The molar ratio of the core structural unit represented by formula (1), the extended structural unit represented by formula (2) and the end-capping structural unit represented by formula (3) in the multi-polymer is 1:(3-100):(6-200).

2. The multi-component copolymer according to claim 1, wherein In the multi-component copolymer, the values ​​of m in the end-capping structural units at different positions have at least two different values.

3. The multi-component copolymer according to claim 1, wherein R1 and R2 are each independently a C2-C6 linear or branched alkylene group.

4. The multi-component copolymer according to claim 3, wherein R1 and R2 are each independently ethylene and / or propylene.

5. The multi-component copolymer according to claim 1, wherein n is a positive integer from 1 to 100.

6. The multi-component copolymer according to claim 5, wherein n is a positive integer from 3 to 60.

7. The multi-component copolymer according to claim 6, wherein n is a positive integer from 3 to 25.

8. The multi-component copolymer according to claim 1, wherein m is a positive integer from 1 to 100.

9. The multi-component copolymer according to claim 8, wherein m is a positive integer from 3 to 60.

10. The multi-component copolymer according to claim 9, wherein m is a positive integer from 3 to 25.

11. The multi-component copolymer according to claim 1 or 2, wherein The weight average molecular weight of the multi-component copolymer is 6×10 5 -2×10 6 g / mol.

12. The multi-component copolymer according to claim 11, wherein The weight average molecular weight of the multi-component copolymer is 7×10 5 -1×10 6 g / mol.

13. The multi-component copolymer according to claim 1, characterized in that The multi-component copolymer has a structure shown in formula (4), Formula (4), Among them, A1, A2 and A3 are identical in structure.

14. A method for preparing a multi-component copolymer, characterized in that: The method comprises the following steps: (1) in the presence of an initiator and an organic solvent, subjecting the monomer represented by formula (I) and the monomer represented by formula (II) to a first polymerization reaction to obtain a first polymer product; Formula (I), Formula (II); (2) subjecting the first polymer product to a second polymerization reaction with the monomer represented by formula (III) to obtain a second polymer product; Formula (III); (3) adding methanol to the second polymer product to cause an end-capping reaction to obtain the multi-component copolymer; wherein the molar ratio of the monomer represented by formula (I), the monomer represented by formula (II), the monomer represented by formula (III) and methanol is 1:(3-100):(6-200):(6-200); Wherein, X is halogen, R1 and R2 are each independently C2-C 10 wherein n and m are each independently a positive integer.

15. The preparation method according to claim 14, wherein X is at least one selected from F, Cl and Br.

16. The preparation method according to claim 14, wherein R1 and R2 are each independently a C2-C6 linear or branched alkylene group.

17. The preparation method according to claim 16, wherein R1 and R2 are each independently ethylene and / or propylene.

18. The preparation method according to claim 14, wherein n is a positive integer from 1 to 100.

19. The preparation method according to claim 18, wherein n is a positive integer from 3 to 60.

20. The preparation method according to claim 19, wherein n is a positive integer from 3 to 25.

21. The preparation method according to claim 14, wherein m is a positive integer from 1 to 100.

22. The preparation method according to claim 21, wherein m is a positive integer from 3 to 60.

23. The preparation method according to claim 22, wherein m is a positive integer from 3 to 25.

24. The preparation method according to claim 14, wherein The initiator is dibutyltin dilaurate.

25. The preparation method according to claim 14, wherein The amount of the initiator used is 0.1-1 wt % of the total weight of the monomer represented by formula (I) and the monomer represented by formula (II).

26. The preparation method according to claim 25, wherein The amount of the initiator used is 0.4-0.5 wt% of the total weight of the monomer represented by formula (I) and the monomer represented by formula (II).

27. The preparation method according to claim 14, wherein The organic solvent is selected from at least one of dimethylformamide, tetrahydrofuran and toluene.

28. The preparation method according to claim 14, wherein The temperature of the first polymerization reaction is 60-100° C.; the time of the first polymerization reaction is 10-30 hours.

29. The preparation method according to claim 28, wherein The temperature of the first polymerization reaction is 70-85° C.; the time of the first polymerization reaction is 15-25 hours.

30. The preparation method according to claim 14, wherein The temperature of the second polymerization reaction is 60-100° C.; the time of the second polymerization reaction is 10-30 hours.

31. The preparation method according to claim 30, wherein The temperature of the second polymerization reaction is 70-85° C.; the time of the second polymerization reaction is 15-25 hours.

32. The preparation method according to claim 14, wherein The temperature of the end-capping reaction is 60-100° C.; the time of the end-capping reaction is 3-10 hours.

33. The preparation method according to claim 32, wherein The temperature of the end-capping reaction is 70-85° C.; the time of the end-capping reaction is 4-6 hours.

34. A multi-component copolymer prepared by the preparation method according to any one of claims 14 to 33.

35. A polymer electrolyte, characterized in that The polymer electrolyte comprises the multi-component copolymer according to any one of claims 1 to 13 and 34, a lithium salt, a plasticizer and a filler.

36. The polymer electrolyte according to claim 35, wherein In parts by weight, the polymer electrolyte comprises: 25-50 parts of a multi-component copolymer, 20-40 parts of a lithium salt, 20-40 parts of a plasticizer, and 1-4 parts of a filler.

37. The polymer electrolyte according to claim 36, wherein In parts by weight, the polymer electrolyte comprises: 35-45 parts of a multi-component copolymer, 25-35 parts of a lithium salt, 25-35 parts of a plasticizer, and 1.5-2.5 parts of a filler.

38. The polymer electrolyte according to claim 35, wherein In the polymer electrolyte, the molar ratio of oxygen atoms in the multi-component copolymer to lithium ions in the lithium salt is 6-40:

1.

39. The polymer electrolyte according to claim 35, wherein The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorosilicate, lithium tetraphenylborate, lithium chloride, lithium bromide, lithium chloroaluminate and lithium fluoroalkylsulfonate.

40. The polymer electrolyte according to claim 35, wherein The plasticizer is selected from at least one of phthalates, aliphatic dibasic acid esters, fatty acid esters, benzene polyesters, polyol esters, epoxy hydrocarbons and alkyl sulfonates.

41. The polymer electrolyte according to claim 35, wherein the filler is selected from at least one of Al2O3, SiO2, TiO2, BaTiO3, zeolite and clay.

42. A lithium ion battery comprising the polymer electrolyte according to any one of claims 35 to 41.

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