Solid-state battery binder and preparation method thereof

Abstract

The present invention belongs to the technical field of polymer binders, and particularly relates to a solid-state battery binder and a preparation method thereof, the solid-state battery binder comprises: a viscous monomer which is an acrylate monomer having a C3-C12 alkyl side chain; the lithium-supplying monomer is a monomer containing phosphate ester or a monomer which contains hydroxyl and amino and is easy to prepare phosphate ester through a phosphate esterification reaction; the lithium-conducting monomer is polyethylene glycol acrylate containing an ethyoxyl structure and a derivative of the polyethylene glycol acrylate; the adhesive monomer, the lithium-supplying monomer and the lithium-conducting monomer are polymerized together through a multifunctional integrated design, the adhesive has high solubility in an ester solvent due to a large number of ester groups contained in the adhesive, so that the bonding effect and the ionic conductivity of the solid-state battery can be improved, and the adhesive provided by the invention has high bonding force, and can be applied to the lithium-ion battery. The composite material has the advantages of high conductivity, high flexibility, high ionic conductivity, high solubility, high electrochemical stability, high temperature resistance and excellent comprehensive performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer binders, and particularly relates to a solid-state battery binder and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries are widely used in various portable mobile power sources. Currently, commercial lithium ion batteries generally use liquid electrolyte, and there is a risk of combustion and explosion under extreme conditions. Solid-state batteries use solid-state electrolyte, have advantages of high energy density, safety, wide temperature range performance, and are an important direction of development of lithium ion batteries. However, solid-state batteries mainly have a solid-solid interface contact problem, that is, the interface contact of the positive electrode sheet, the solid-state electrolyte and the negative electrode sheet, and the rigid contact of the electrode active material, the solid-state electrolyte and the conductive agent directly lead to the problems of high interface impedance and low ionic conductivity of the solid-state battery.

[0003] In liquid lithium ion batteries, the binder is usually added during the preparation of the positive and negative electrode slurries to bond the active material, the conductive agent and the electrode sheet. However, in solid-state batteries, there are higher requirements for the binder, which needs to have high bonding ability to bond the solid-state electrolyte, the positive and negative electrode active materials, the electrode sheet, the conductive agent and other additives, and also should have certain ionic conductivity to assist ion transmission.

[0004] However, the current mainstream lithium ion battery binder has the problems of poor ionic conductivity and inability to effectively adapt to the complex interface of the solid-state battery. Such a binder is difficult to meet the dual requirements of high adhesion and high ionic conductivity of the solid-state battery, leading to poor interface contact inside the battery, increasing the interface impedance and reducing the ion transmission efficiency, thereby affecting the improvement of the overall performance of the solid-state battery.

[0005] Therefore, overcoming the defect that the adhesion and ionic conductivity of the solid-state battery binder are incompatible is a technical problem that needs to be solved in the field.

[0006] It should be noted that the above information disclosed in the background section is only used to understand the background of the present application, and therefore, the above description is not considered to constitute prior art information. SUMMARY

[0007] The embodiments of the present disclosure at least provide a solid-state battery binder and a preparation method thereof.

[0008] In a first aspect, the embodiments of the present disclosure provide a solid-state battery binder, comprising: a sticky monomer, the sticky monomer being a C3-C 12an alkyl side chain acrylate monomer; a lithium-donating monomer, which is a monomer containing a phosphate ester or a monomer containing a hydroxyl group, an amino group, which is easily prepared into a phosphate ester through a phosphate esterification reaction; a lithium-conducting monomer, which is a polyethylene glycol acrylate containing an ethoxy structure and derivatives thereof.

[0009] In an alternative embodiment, the viscous monomer has a structure represented by formula (1): Formula (1) wherein R1 is selected from C3-C 12 long-chain alkane structure.

[0010] In an alternative embodiment, the lithium-donating monomer has a structure represented by formula (2-a) or formula (2-b): Formula (2-a) or Formula (2-b) wherein R2 is selected from -COOR, substituted or unsubstituted -(CH2) m -CH3, R is selected from C1-C6 alkyl, and m has a value ranging from 0 to 6; R3 is selected from -H, -(CH2) k -CH3, k has a value ranging from 0 to 6; and R4 is selected from C1-C6 alkyl having an end group comprising any one or more of -OH, -NH2, -Cl, -Br, -I.

[0011] In an alternative embodiment, the lithium-conducting monomer has a structure represented by formula (3): Formula (3) wherein R5 is selected from any one of methyl, ethyl, propyl, and butyl, x has a value ranging from 3 to 20, and the lithium-conducting monomer has a molecular weight Mn = 300-1000.

[0012] In an alternative embodiment, the mole fraction of the viscous monomer is 30%-70% based on the total moles of the solid-state battery binder; and / or, the mole fraction of the lithium-donating monomer is 15%-40% based on the total moles of the solid-state battery binder; and / or, the mole fraction of the lithium-conducting monomer is 15%-40% based on the total moles of the solid-state battery binder.

[0013] In an alternative embodiment, the solid-state battery binder has a weight average molecular weight of 300,000-3,000,000.

[0014] In a second aspect, the present disclosure also provides a preparation method of the solid-state battery binder as described above, comprising the following steps: S1, dissolving a tacky monomer, a lithium-providing monomer, a lithium-conducting monomer and a molecular weight control agent in an organic solvent A in a reaction kettle, and then adding an initiator to perform a polymerization reaction under a protective gas atmosphere to obtain a polymer solution; S2, reacting the polymer solution with a phosphate esterification reagent, wherein if the lithium-providing monomer itself contains phosphate, step S2 is skipped; S3, mixing a lithium salt with the reaction product of the previous step in an organic solvent B to obtain the binder, wherein if the organic solvent A and the organic solvent B are different substances, the reaction product of the previous step needs to be dried or rotary evaporated to remove the solvent first.

[0015] In an optional embodiment, step S1 satisfies at least one of the following characteristics: the mass ratio of the tacky monomer, the lithium-providing monomer and the lithium-conducting monomer is (1-8):1:(0.3-2), and the solid content is 40%; the molecular weight control agent includes at least one of dodecyl mercaptan, isooctyl mercaptan, 3-mercapto propionic acid methyl ester, sodium allyl sulfonate, cyanoisopropyl disulfide, 2-cyano-2-propyl dodecyl trithiocarbonate, and methionine; the organic solvent A includes at least one of N-methyl pyrrolidone, dimethyl sulfoxide, cyclohexanone, toluene, and ethyl acetate; the initiator includes at least one of azobisisobutyronitrile, azobis cyanovaleric acid, tert-butyl peroxy-2-ethylhexanoate, benzoyl peroxide, lauroyl peroxide, and potassium persulfate; the protective atmosphere includes at least one of nitrogen, argon, and helium; the temperature of the polymerization reaction is 60-100°C; and the time of the polymerization reaction is 4-10 h.

[0016] In an optional embodiment, step S2 satisfies at least one of the following characteristics: the phosphate esterification reagent includes at least one of phosphoric acid, phosphorus oxychloride, phosphoric acid chloride, phosphite, cyclic phosphorus oxychloride reagent, and diphosphorus pentoxide; the esterification reaction temperature is 40-80°C; and the esterification reaction time is 3-8 h.

[0017] In an optional embodiment, step S3 satisfies at least one of the following characteristics: the lithium salt includes at least one of lithium perchlorate, lithium tetrafluoroborate, lithium bisfluorosulfonimide, lithium bis-trifluoromethanesulfonimide, lithium bisfluoroborate, lithium bisfluoroglyoxalate borate, lithium bisfluorophosphate, lithium trifluoromethanesulfonate, lithium bisfluoropropenoate, and lithium trifluoroacetate; the molar ratio of the lithium salt to the hydroxyl group in the phosphate ester group is 1:1, and the monomer input amount is adjusted so that the molar ratio of the lithium salt to the EO repeating unit in the polymer is 1:(2-20); the organic solvent B includes at least one of toluene, n-heptane, xylene, anisole, acetonitrile, tetrahydrofuran, and N-methyl pyrrolidone; the temperature of the mixing is 50-90°C; and the time of the mixing is 4-24 h.

[0018] In a third aspect, the embodiments of the present disclosure further provide a solid-state electrolyte, comprising at least one of an oxide solid-state electrolyte and a sulfide solid-state electrolyte, and the solid-state battery binder as described above or the solid-state battery binder prepared by the preparation method as described above.

[0019] The present application has the advantages that the solid-state battery binder and the preparation method thereof polymerize the adhesive monomer, the lithium-providing monomer and the lithium-conducting monomer together through multifunctional integration design. The adhesive monomer is a long-chain acrylate monomer, which can reduce the polymer glass transition temperature and increase the molecular chain entanglement density. Meanwhile, the long alkyl group provides a similar "intermolecular lubrication" effect, enhances the interface diffusion capacity, and realizes high adhesion and high peel strength. The phosphate group in the lithium-providing monomer can strongly adsorb lithium ions through dipole-ion interaction, and the binding energy thereof is about 120 kJ / mol. After mixing with lithium salt, the lithium-providing monomer can carry lithium ions. The lithium-conducting monomer is a polyethylene glycol acrylate monomer, in which the oxygen atoms of ethylene oxide continuously undergo the process of "complexation-decomplexation-recomplexation" with lithium ions, thereby achieving the effect of rapid migration of lithium ions, so that the binder has high ionic conductivity. The large number of ester groups contained in the binder make the binder have high solubility in ester solvents, thereby improving the adhesion effect and ionic conductivity of the solid-state battery. Therefore, the binder provided by the present application has high adhesion, high flexibility, high ionic conductivity and high solubility, and has high electrochemical stability and high temperature resistance, and has excellent comprehensive performance.

[0020] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application will be realized and achieved by the structures particularly pointed out in the description.

[0021] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the following preferred embodiments are specifically described as follows. DETAILED DESCRIPTION

[0022] In order to make the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0023] As used herein, the phrases "in one embodiment", "according to one embodiment", "in some embodiments", and the like generally mean the particular feature, structure, or characteristic following the phrase is that one of the many embodiments of the disclosure. Features, structures, or characteristics can be included in more than one embodiment of the disclosure, and the phrases, therefore, do not necessarily refer to the same embodiment. As used herein, the terms "for example," "e.g.," and the like indicate that the example is one of a possible, non-limiting scenario. Any embodiment described herein as "for example" or "e.g." is not necessarily to be construed as preferred or advantageous over other embodiments. Rather, the use of terms such as "for example" or "e.g." is intended to present concepts in a particular manner.

[0024] In this document, relational terms such as "at least one of" or "one or more of" are used to indicate that items in a list include any single item, any combination of two or more items, or all of the items in the list. For example, the phrase "at least one of A and B" means A alone, B alone, or A and B together. The phrase "one or more of A and B" means A alone, B alone, or A and B together.

[0025] The terminology used herein is for the purpose of describing particular example configurations only and is not intended to be limiting. As used herein, the singular articles "a," "an," and "the" can be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having" are inclusive and therefore specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order in which they are described or illustrated, unless specifically identified as an order of performance. Additional or alternative steps can be employed.

[0026] Some embodiments of the present application are described in detail below. The following embodiments and features of the embodiments can be combined with each other, without conflict, if necessary.

[0027] The embodiments of the present disclosure provide a solid-state battery binder, comprising: a tacky monomer, the tacky monomer being a C3-C 12 an alkyl side chain acrylate monomer; a lithium-donating monomer, the lithium-donating monomer being a monomer containing a phosphate ester or a monomer containing a hydroxyl group, an amino group, which is easy to prepare a phosphate ester through a phosphate esterization reaction; a lithium-conducting monomer, the lithium-conducting monomer being a polyethylene glycol acrylate containing an ethoxy structure and derivatives thereof.

[0028] In an alternative embodiment, the tacky monomer has a structure shown in formula (1): Formula (1) Wherein, R1 is selected from C3~C 12 long-chain alkane structure.

[0029] Specifically, the adhesive monomer includes but is not limited to one or more of n-propyl acrylate, isobutyl acrylate, n-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, isooctyl acrylate, n-octyl acrylate, n-decyl acrylate, lauryl acrylate, etc.

[0030] In some embodiments, specifically, the lithium-donating monomer has a structure shown in Formula (2-a) or Formula (2-b): Formula (2-a) or Formula (2-b) Wherein, R2 is selected from -COOR, substituted or unsubstituted -(CH2) m -CH3, R is selected from C1 to C6 alkyl, m is in the range of 0 to 6; R3 is selected from -H, -(CH2) k -CH3, k ranges from 0 to 6; R4 is selected from a C1 to C6 alkyl group including any one or more of -OH, -NH2, -Cl, -Br, and -I.

[0031] Specifically, the lithium-donating monomer includes, but is not limited to, one or more of the monomers containing phosphate groups such as hydroxyethyl methacrylate phosphate, bis(2-ethylhexyl)phosphate acrylate, polyethylene glycol methyl ether phosphate acrylate, glycidyl ether phosphate acrylate, and brominated neopentyl glycol phosphate acrylate, and may also be one or more of the monomers capable of undergoing phosphate esterification reaction such as hydroxyethyl acrylate, hydroxypropyl acrylate, aminoethyl acrylate, chloroethyl acrylate, and bromoethyl acrylate.

[0032] In some embodiments, specifically, the lithium-conducting monomer has a structure shown in formula (3): Formula (3) Wherein, R5 is selected from any one of methyl, ethyl, propyl and butyl, the value range of x is 3 to 20, and the molecular weight Mn of the lithium-conducting monomer is 300 to 1000.

[0033] Specifically, the lithium-conducting monomer includes but is not limited to one or more of methoxy polyethylene glycol acrylate (400), methoxy polyethylene glycol acrylate (480), methoxy polyethylene glycol acrylate (750), methoxy polyethylene glycol acrylate (1000), ethyl polyethylene glycol acrylate, propyl polyethylene glycol acrylate, butyl polyethylene glycol acrylate, etc.

[0034] In some embodiments, specifically, the mole fraction of the viscous monomer is 30% to 70% based on the total moles of the solid-state battery binder; and / or, the mole fraction of the lithium-providing monomer is 15% to 40% based on the total moles of the solid-state battery binder; and / or, the mole fraction of the lithium-conducting monomer is 15% to 40% based on the total moles of the solid-state battery binder.

[0035] In some embodiments, specifically, the weight average molecular weight of the solid-state battery binder is 30,000 to 300,000.

[0036] The present disclosure also provides a preparation method of the solid-state battery binder as described above, comprising the following steps: S1, dissolving the viscous monomer, the lithium-providing monomer, the lithium-conducting monomer and the molecular weight control agent in an organic solvent A in a reaction kettle, adding an initiator, and then performing a polymerization reaction under a protective gas atmosphere to obtain a polymer solution; S2, reacting the polymer solution with a phosphate esterification reagent, wherein if the lithium-providing monomer itself contains phosphate, step S2 is skipped; S3, mixing a lithium salt with the reaction product of the previous step in an organic solvent B to obtain the binder, wherein if the organic solvent A and the organic solvent B are different substances, the reaction product of the previous step needs to be dried or rotary evaporated to remove the solvent first.

[0037] In some embodiments, specifically, step S1 satisfies at least one of the following characteristics: the mass ratio of the viscous monomer, the lithium-providing monomer and the lithium-conducting monomer is (1 to 8): 1: (0.3 to 2), and the solid content is 40%; the molecular weight control agent includes at least one of dodecyl mercaptan, isooctyl mercaptoacetate, 3-mercaptopropionic acid methyl ester, sodium allyl sulfonate, cyanoisopropyl disulfide benzoate, 2-cyano-2-propyl dodecyl trithiocarbonate, and methionine; the organic solvent A includes at least one of N-methyl pyrrolidone, dimethyl sulfoxide, cyclohexanone, toluene, and ethyl acetate; the initiator includes at least one of azobis isobutyronitrile, azobis cyanovaleric acid, tert-butyl peroxy-2-ethylhexanoate, benzoyl peroxide, lauroyl peroxide, and potassium persulfate; the protective atmosphere includes at least one of nitrogen, argon, and helium; the temperature of the polymerization reaction is 60°C to 100°C; and the time of the polymerization reaction is 4 h to 10 h.

[0038] In some embodiments, specifically, step S2 satisfies at least one of the following characteristics: the phosphate esterification reagent includes at least one of phosphoric acid, phosphorus oxychloride, phosphoric acid chloride, phosphite, cyclic phosphorus oxychloride reagent, and diphosphorus pentoxide; the esterification reaction temperature is 40°C to 80°C; and the esterification reaction time is 3 h to 8 h.

[0039] In some embodiments, specifically, step S3 satisfies at least one of the following features: the lithium salt comprises at least one of lithium perchlorate, lithium tetrafluoroborate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium bisfluoroborate, lithium bisfluoroglyoxalate borate, lithium bisfluorophosphate, lithium trifluoromethanesulfonate, lithium bisfluoropropenoate, lithium trifluoroacetate, etc.; the molar ratio of the lithium salt to the hydroxyl group in the phosphate group is 1:1, the monomer input amount is adjusted so that the molar ratio of the lithium salt to the EO repeating unit in the polymer is 1:(2-20); the organic solvent B comprises at least one of toluene, n-heptane, xylene, anisole, acetonitrile, tetrahydrofuran, N-methyl pyrrolidone; the mixing temperature is 50-90°C; and the mixing time is 4-24 h.

[0040] The embodiments of the present disclosure also provide a solid-state electrolyte comprising at least one of an oxide solid-state electrolyte and a sulfide solid-state electrolyte, and the solid-state battery binder as described above or the solid-state battery binder prepared by the preparation method as described above.

[0041] Embodiment 1, S1: 16.42 g of viscous monomer isooctyl acrylate, 7.73 g of lithium-providing monomer hydroxypropyl acrylate, 15.85 g of lithium-conducting monomer methoxy polyethylene glycol acrylate (480), and 0.1 g of molecular weight control agent methionine are dissolved in 60 g of N-methyl pyrrolidone in a reaction kettle, heated to 80°C under a nitrogen atmosphere, then 0.2 g of initiator azobisisobutyronitrile is added, the rotation speed is 400 rpm, and the reaction is performed for 8 h.

[0042] S2: 60 g of the obtained polymer solution is taken into a three-necked flask equipped with a magnetic stirrer, heated to 75°C, then 3.5 g of phosphoric acid is added, and the reaction is performed under vacuum for 6 h to obtain a phosphate-containing polymer.

[0043] S3: 20 g of lithium bis-trifluoromethanesulfonylimide is dissolved in 60 g of the obtained polymer solution, stirred at 90°C under a nitrogen atmosphere for 24 h, then distilled under reduced pressure for 8 h to remove the lithium bis-trifluoromethanesulfonylimide generated after the reaction, and the desired binder material is obtained.

[0044] S4: 5.4 g of lithium aluminum titanium phosphate is mixed with 1.5 g of the binder material solution (0.6 g of the binder is 10% of the solid content) and 3.1 g of N-methyl pyrrolidone solvent, stirred at 1000 rpm for 1 h to obtain a solid-state electrolyte slurry with a solid content of 60%, and the solid-state electrolyte is obtained by drying at 120°C for 2 h.

[0045] Example 2, S1: In a reaction kettle, 14.32 g of viscous monomer isooctyl acrylate, 11.83 g of lithium-donating monomer hydroxyethyl methacrylate phosphate, 13.85 g of lithium-conducting monomer methoxy polyethylene glycol acrylate (480), and 0.25 g of molecular weight controller 2-cyano-2-propyl dodecyl trithiocarbonate, dissolved in 60 g of N-methyl pyrrolidone, were heated to 80°C under a nitrogen atmosphere, and then 0.3 g of initiator benzoyl peroxide was added, with a rotation speed of 400 rpm, and reacted for 10 h.

[0046] Skip step S2, and the remaining steps are the same as S3 and S4 in Example 1.

[0047] Example 3, S1: The same as the S1 step of Example 1.

[0048] S2: 60 g of the obtained polymer solution was placed in a three-necked flask equipped with a magnetic stirrer, heated to 70°C, and then 3.17 g of phosphoryl chloride was added, and reacted under vacuum for 6 h to obtain a phosphate-containing polymer.

[0049] S3: 20 g of lithium bis-trifluoromethanesulfonimide was dissolved in 60 g of the obtained polymer solution, and reacted at 90°C under a nitrogen atmosphere for 24 h with stirring. Then, the bis-trifluoromethanesulfonimide produced after the reaction was removed by distillation under reduced pressure for 8 h to obtain the desired binder material. The solvent of the binder material was removed by rotary evaporation.

[0050] S4: 4.5 g of lithium phosphorus sulfur chloride was mixed with 0.5 g of the above binder (containing 10% by solid weight) and 5 g of solvent (30% isopropyl ether and 70% n-hexane) to obtain a solid electrolyte slurry with a solid content of 50% by stirring at 1000 rpm for 1 h. The solid electrolyte was obtained by drying at 120°C for 2 h.

[0051] Example 4, the 0.1 g of molecular weight controller methionine added in S1 of Example 1 was replaced with 0.1 g of molecular weight controller dodecyl mercaptan, and the remaining steps were the same.

[0052] Example 5, the 0.1 g of molecular weight controller methionine added in S1 of Example 1 was replaced with 0.1 g of molecular weight controller cyanoisopropyl dithio benzoate, and the remaining steps were the same.

[0053] Example 6, the amount of monomer added in S1 of Example 1 was replaced with 19.02 g of viscous monomer isooctyl acrylate, 4.48 g of lithium-donating monomer hydroxypropyl acrylate, and 16.51 g of lithium-conducting monomer methoxy polyethylene glycol acrylate (480), and the remaining steps were the same.

[0054] Comparative Example 1: The binder prepared in Example 1 was replaced by PVDF, and other steps were the same.

[0055] Comparative Example 2: In S1 of Example 1, the molecular weight control agent was not added, and other steps were the same.

[0056] Table 1: Binder characterization results of Examples 1-5 and Comparative Examples 1-2

[0057] wherein the monomer ratio is viscous monomer: lithium-providing monomer: lithium-conducting monomer.

[0058] Performance test: Preparation of positive electrode slurry: In this example, N-methyl pyrrolidone, corresponding solid-state electrolyte, carbon black, binder and positive electrode active material (lithium iron phosphate, etc.) were weighed in sequence, the solid content was 60%, and the mass ratio of solid-state electrolyte, carbon black, binder and positive electrode active material was 2:0.3:1:0.67. In the defoaming machine, first pre-mix at 800 rpm for 30 s, then stir at 2000 rpm for 20 min to obtain a positive electrode slurry with a solid content of 60%.

[0059] Peeling strength test: The uniformly dispersed slurry was uniformly coated on the substrate of the positive electrode tab with aluminum foil as the substrate by a coating machine at a thickness of 200 um, and the finished positive electrode tab was placed in a 105℃ oven for 1 h. Then the wet thickness of the finished tab was 200 um, and the peeling strength was tested after rolling. The tab was cut into a sample strip of 15 mm x 200 mm after rolling to a compacted density of 2.4 g / m3, and a 180° horizontal peeling strength tester was used for testing at a speed of 150 mm / min and a test temperature of 25℃.

[0060] Measurement of ionic conductivity: In this example, the solid-state polymer electrolyte was tested by AC impedance method, and the frequency range of AC impedance test was 0.1 Hz-100 kHz, and the amplitude was 5 mv. The specific method is as follows: the prepared solid-state electrolyte slurry was evenly applied on a circular stainless steel sheet with a diameter of 16 mm, dried in a 120℃ oven, and then another identical stainless steel sheet was covered on the solid-state electrolyte, and then the AC impedance spectrum of the solid-state electrolyte sample was measured by an electrochemical workstation. The ionic conductivity σ of the electrolyte is calculated according to the following formula:

[0061] wherein L is the thickness of the solid-state electrolyte (cm), Rb is the bulk impedance of the electrolyte (Ω), and S is the effective contact area of the electrolyte (cm2).

[0062] Table 2: Test results of Examples 1-5 and Comparative Examples 1-2

[0063] In the present application, it can be seen from Examples 1-6 and Comparative Example 1 that the solid-state electrolyte and electrode sheet using the binder of the present application have higher ionic conductivity and peel strength than when using conventional PVDF.

[0064] It can be seen from Examples 1-6 and Comparative Example 2 that the binder with the molecular weight control agent has higher ionic conductivity and peel strength due to its narrow molecular weight distribution.

[0065] Comparing Examples 1-6, it can be seen from the comparison of Examples 1 and 2 that the binder with higher molecular weight can result in higher peel strength; from the comparison of Examples 1 and 3 that the binder of the present application can be used for oxide and sulfide electrolytes; from the comparison of Examples 1, 4, and 5 that the narrower the molecular weight distribution, the higher the peel strength when using different molecular weight control agents; and from the comparison of Examples 1 and 6 that increasing the content of the tacky monomer in the binder can improve the peel strength.

[0066] In summary, the solid-state battery binder and the preparation method thereof of the present application polymerize the tacky monomer, the lithium-providing monomer, and the lithium-conducting monomer together through multifunctional integrated design. The tacky monomer is a long-chain acrylate monomer, which can reduce the glass transition temperature of the polymer, increase the entanglement density of the molecular chain, and at the same time, the long alkyl group provides a similar "intermolecular lubrication" effect to enhance the interface diffusion capacity, achieving high tackiness and high peel strength. The lithium-providing monomer contains phosphate groups, which can strongly adsorb lithium ions through dipole-ion interaction with a binding energy of about 120 kJ / mol, and can carry lithium ions after mixing with lithium salts. The lithium-conducting monomer is a polyethylene glycol acrylate monomer, in which the oxygen atoms of the ethylene oxide groups constantly undergo the process of "complexation-decomplexation-recomplexation" with lithium ions, thereby achieving the effect of rapid migration of lithium ions, so that the binder has high ionic conductivity. The large number of ester groups in the binder make the binder have high solubility in ester solvents, thereby improving the binding effect and ionic conductivity of the solid-state battery. Therefore, the binder provided by the present application has high adhesion, high flexibility, high ionic conductivity, and high solubility, and has high electrochemical stability and high temperature resistance, and has excellent comprehensive performance.

[0067] Based on the above ideal embodiments according to the present application, through the above description, relevant personnel can make various changes and modifications without deviating from the technical idea of the present application. The technical scope of the present application is not limited to the contents in the specification, and must be determined by the scope of the claims.

Claims

1. A solid-state battery binder, characterized in that: include: The adhesive monomer is a monomer having C3 to C 12 Acrylate monomers with alkyl side chains; A lithium-donating monomer, wherein the lithium-donating monomer is a monomer containing phosphate or a monomer containing hydroxyl or amino groups and easily prepared into phosphate by phosphatization reaction; The lithium-conducting monomer is polyethylene glycol acrylate containing an ethoxy structure and its derivatives.

2. The solid-state battery binder according to claim 1, wherein The adhesive monomer has a structure shown in formula (1): Formula (1) Wherein, R1 is selected from C3~C 12 long-chain alkane structure.

3. The solid-state battery binder according to claim 1, wherein The lithium supply monomer has a structure shown in formula (2-a) or formula (2-b): Formula (2-a) or Formula (2-b) Wherein, R2 is selected from -COOR, substituted or unsubstituted -(CH2) m -CH3, R is selected from C1 to C6 alkyl, and the value of m ranges from 0 to 6; R3 is selected from -H, -(CH2) k -CH3, the value of k ranges from 0 to 6; R4 is selected from C1 to C6 alkyl groups including any one or more of -OH, -NH2, -Cl, -Br, and -I.

4. The solid-state battery binder according to claim 1, wherein The lithium-conducting monomer has a structure shown in formula (3): Formula (3) Wherein, R5 is selected from any one of methyl, ethyl, propyl and butyl, the value range of x is 3 to 20, and the molecular weight Mn of the lithium-conducting monomer is 300 to 1000.

5. The solid-state battery binder according to claim 1, wherein Based on the total molar amount of the solid-state battery binder, the molar fraction of the adhesive monomer is 30% to 70%; and / or, based on the total molar amount of the solid-state battery binder, the molar fraction of the lithium-donating monomer is 15% to 40%; and / or, based on the total molar amount of the solid-state battery binder, the molar fraction of the lithium-conducting monomer is 15% to 40%; The weight average molecular weight of the solid-state battery binder is 30,000 to 300,000.

6. A method for preparing the solid-state battery binder according to any one of claims 1 to 5, characterized in that: The steps include: S1, dissolving a viscous monomer, a lithium-donating monomer, a lithium-conducting monomer, and a molecular weight control agent in an organic solvent A in a reaction kettle, adding an initiator, and conducting a polymerization reaction under a protective gas atmosphere to obtain a polymer solution; S2, reacting the polymer solution with a phosphate reagent, wherein if the lithium-donating monomer itself contains phosphate, step S2 is skipped; S3, mixing the lithium salt and the reaction product of the above step in an organic solvent B to obtain a binder, wherein if the organic solvent A and the organic solvent B are different substances, the reaction product of the above step needs to be dried or evaporated to remove the solvent.

7. The preparation method according to claim 6, wherein Step S1 satisfies at least one of the following characteristics: The molar ratio of the adhesive monomer, the lithium-donating monomer and the lithium-conducting monomer is (1-8):1:(0.3-2), and the solid content is 40%; The molecular weight control agent includes at least one of dodecyl mercaptan, isooctyl thioglycolate, methyl 3-mercaptopropionate, sodium allyl sulfonate, cyanoisopropyl dithiobenzoate, 2-cyano-2-propyl dodecyl trithiocarbonate, and methionine; The organic solvent A comprises at least one of N-methylpyrrolidone, dimethyl sulfoxide, cyclohexanone, toluene, and ethyl acetate; The initiator includes at least one of azobisisobutyronitrile, azobiscyanovaleric acid, tert-butyl peroxy-2-ethylhexanoate, benzoyl peroxide, lauroyl peroxide, and potassium persulfate; The protective atmosphere includes at least one of nitrogen, argon and helium; The polymerization reaction temperature is 60°C to 100°C; The polymerization reaction time is 4 h to 10 h.

8. The preparation method according to claim 6, wherein Step S2 satisfies at least one of the following characteristics: The phosphating agent includes at least one of phosphoric acid, phosphorus oxychloride, phosphate acyl chloride, phosphite, cyclic phosphating agent, and phosphorus pentoxide; The esterification reaction temperature is 40°C to 80°C; The esterification reaction time is 3h to 8h.

9. The preparation method according to claim 6, wherein Step S3 satisfies at least one of the following characteristics: The lithium salt includes at least one of lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluoroborate), lithium bis(fluorooxalatoborate), lithium bis(fluorophosphate), lithium trifluoromethanesulfonate, lithium bis(fluoroacrylate), lithium trifluoroacetate, etc.; The molar ratio of the lithium salt to the hydroxyl group in the phosphate group is 1:1, and the amount of monomer input is adjusted so that the molar ratio of the lithium salt to the EO repeating unit in the polymer is 1:(2-20); The organic solvent B comprises at least one of toluene, n-heptane, xylene, anisole, acetonitrile, tetrahydrofuran, and N-methylpyrrolidone; The mixing temperature is 50°C to 90°C; The mixing time is 4 hours to 24 hours.

10. A solid electrolyte, characterized in that It comprises at least one of an oxide solid electrolyte and a sulfide solid electrolyte, and the solid-state battery binder according to any one of claims 1 to 5 or the solid-state battery binder prepared by the preparation method according to any one of claims 6 to 9.

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