Electrolyte, semi-solid secondary battery, and preparation method and application thereof

Abstract

The application provides an electrolyte, a semi-solid secondary battery and a preparation method and application thereof. The electrolyte comprises a first solution and a second solution. The first solution comprises a first electrolyte, a first solvent, a polymerization monomer, a copolymerization monomer and an initiator. The polymerization monomer comprises at least one compound with a structure shown in formula I. In formula I, o represents a central group selected from a heterocyclic group or a linear group; at least two of R1, R2,..., and Rn contain a carbon-carbon double bond or a carbon-carbon triple bond, and n is an integer from 2 to 6; and the copolymerization monomer comprises an alkali metal salt containing an unsaturated bond. The electrolyte, the polymerization monomer and the copolymerization monomer are used in cooperation, so that the ion conductivity of a polymer network is improved, and the impedance of the electrolyte is reduced. When the electrolyte is used in the semi-solid secondary battery, the safety of the battery can be improved, and the rate performance and the cycle performance of the battery can be improved.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to an electrolyte, a semi-solid secondary battery, a preparation method thereof, and its application. Background Technology

[0002] As the energy density of power batteries increases, safety issues become increasingly prominent, and using solid-state or semi-solid-state technology to improve battery safety performance is the current mainstream direction.

[0003] In-situ solidified electrolyte is produced by adding polymeric monomers to the electrolyte. After injection, polymerization is initiated by temperature, which seals the liquid electrolyte within a polymer network. This reduces the amount of liquid components and the risk of contact between the positive and negative electrodes, thus improving safety performance in areas such as thermal runaway.

[0004] However, traditional in-situ solidification still has some drawbacks. For example, a related technology discloses a solid polymer electrolyte that improves the battery's high-voltage resistance and safety. In this approach, the polymer monomers used are molecules containing unsaturated double bonds, such as 1,1,1,3,3,3-hexafluoroisopropyl isobutylene ester, vinyl-terminated polydimethylsilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2,4,6-triallyloxy-1,3,5-triazine, pentaerythritol tetraacrylate, and tripropylene phosphate. Although polymerization improves battery safety, it also reduces the lithium-ion conductivity of the polymer network, leading to deterioration in the battery's rate performance, low-temperature performance, and even cycle performance.

[0005] Therefore, there is an urgent need for an electrolyte that can improve battery safety performance without affecting or even enhancing ion conductivity, and without degrading or even improving battery rate performance and cycle performance. Summary of the Invention

[0006] In view of this, one object of this application is to provide an electrolyte containing a polymeric monomer and a comonomer, wherein the polymeric monomer is selected from compounds having the structure shown in Formula I, and the comonomer is selected from alkali metal salts containing unsaturated bonds. The combined use of these two monomers can enhance the ion-conducting capacity of the polymeric network and reduce the impedance of the electrolyte. Using this electrolyte in a semi-solid-state secondary battery can improve both battery safety and rate and cycle performance.

[0007] Another objective of this application is to provide a semi-solid secondary battery.

[0008] Another objective of this application is to provide a method for preparing a semi-solid secondary battery.

[0009] Another object of this application is to provide an electrical device.

[0010] To achieve the above objectives, a first aspect of this application provides an electrolyte comprising a first solution and a second solution, wherein the first solution comprises a first electrolyte, a first solvent, a polymeric monomer, a comonomer, and an initiator, and the polymeric monomer comprises at least one compound having the structure shown in Formula I:

[0011]

[0012] In Formula I, ○ represents a central group, which is selected from heterocyclic groups or linear groups; R1, R2...Rn are each independently selected from one of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, saturated or unsaturated carboxylic acid ester, saturated or unsaturated amide, saturated or unsaturated isocyanate, alkoxy, alkenyloxy, alkynyloxy, saturated or unsaturated acyl, and at least two of R1, R2...Rn contain carbon-carbon double bonds or carbon-carbon triple bonds, and n is an integer from 2 to 6;

[0013] The comonomer includes alkali metal salts containing unsaturated bonds.

[0014] In some embodiments, the heterocyclic group is selected from one of nitrogen-containing C2-C5 heterocyclic groups, oxygen-containing C2-C5 heterocyclic groups, and sulfur-containing C2-C5 heterocyclic groups.

[0015] In some embodiments, the linear group is selected from one of the following: single atom, C1-6 alkyl, C1-6 alkoxy, phosphate ester, phosphite ester, sulfonate ester, and borate ester.

[0016] In some embodiments, R1, R2...Rn are each independently selected from one of the following: substituted or unsubstituted C1-6 alkyl, substituted or unsubstituted C2-5 alkenyl, substituted or unsubstituted C2-5 alkynyl, saturated or unsaturated C1-6 carboxylic acid ester, saturated or unsaturated C1-6 amide, saturated or unsaturated C1-6 isocyanate, C1-6 alkoxy, C2-6 alkenoxy, C2-6 alkynoxy, and saturated or unsaturated C1-6 acyl.

[0017] In some embodiments, the substituents in the substituted alkyl, substituted alkenyl, and substituted alkynyl groups include, but are not limited to, at least one of halogen atoms, cyano groups, phenyl groups, etc.

[0018] In some embodiments, the heterocyclic group is selected from one of the following structures:

[0019] In some embodiments, the single atom includes, but is not limited to, one of nitrogen atoms, carbon atoms, silicon atoms, phosphorus atoms, boron atoms, etc.

[0020] In some implementations, R1, R2...R n Each is independently selected from one of the following: unsubstituted C2-5 alkenyl, unsubstituted C2-5 alkynyl, unsaturated C1-6 amide, C2-6 alkenoxy, C2-6 alkynoxy, unsaturated C1-6 acyl, or unsaturated C1-6 carboxylic acid ester.

[0021] In some embodiments, the linear group is selected from one of the following structures:

[0022] In some implementations, R1, R2...R n Each independently selected

[0023] One of them.

[0024] In some embodiments, the compound having the structure shown in Formula I includes at least one of compounds T1-T9:

[0025]

[0026]

[0027] In some embodiments, the alkali metal salt containing unsaturated bonds includes at least one of compounds having the structure of Formula II, Formula III, and Formula IV:

[0028]

[0029] Among them, X1, X2, and X6 are each independently selected from one of the C2-6 alkenyl or C2-6 alkynyl groups, X3, X4, and X5 are all F, and Y1, Y2, Y3, and Y4 are each independently selected from one of the alkali metals.

[0030] In some embodiments, X1, X2, and X6 are each independently selected from one of C2-6 alkenyl groups, and Y1, Y2, Y3, and Y4 are each independently selected from one of lithium and sodium.

[0031] In some embodiments, the alkali metal salt containing unsaturated bonds includes at least one of compounds P1-P5:

[0032]

[0033] In some embodiments, the compound having the structure shown in Formula I has a mass content of a% in the electrolyte, and the alkali metal salt containing unsaturated bonds has a mass content of b% in the electrolyte, wherein a and b satisfy:

[0034] 1≤a+b≤10; and / or,

[0035] 1 / 5 ≤ a / b ≤ 10.

[0036] In some embodiments, the compound having the structure shown in Formula I and the alkali metal salt containing unsaturated bonds form a gel polymer under the action of the initiator, the gel polymer having the polymer structure shown in Formula V:

[0037]

[0038] In formula V, Y is an alkali metal.

[0039] In some embodiments, the mass of the first solution accounts for 5-30% of the total mass of the electrolyte.

[0040] In some embodiments, the first electrolyte includes at least one of alkali metal salts.

[0041] In some embodiments, the concentration of the first electrolyte in the electrolyte is 0.5-1.4 mol / L.

[0042] In some embodiments, the first solvent includes at least one of carbonate, carboxylic acid ester, fluorocarbonate, and fluorocarboxylic acid ester.

[0043] In some embodiments, the initiator includes at least one of azobisisobutyronitrile (AIBN) and benzoyl peroxide (BPO).

[0044] In some embodiments, the initiator has a mass content of 0.1-0.3% in the electrolyte.

[0045] In some embodiments, the second solution includes a second electrolyte, a second solvent, and an additive, said additive including at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl sulfate (DTD), 1,3-propanesulfonate lactone (PS), lithium difluorobis(oxalato) phosphate (LiODFP), lithium difluorobis(oxalato) borate (LiODFB), ethylene ethylene carbonate (VEC), 1,3-propenesulfonate lactone (PST), methyl methylene disulfonate (MMDS), vinyl sulfate (ESa), tetravinylsilane (TVSI), and lithium difluorophosphate (LiPO2F2).

[0046] In some embodiments, the second electrolyte may be the same as or different from the first electrolyte, and the second solvent may be the same as or different from the first solvent.

[0047] In some embodiments, the concentration of the second electrolyte in the electrolyte is 0.5-1.4 mol / L.

[0048] In some embodiments, the additive is present in the electrolyte at a mass content of 2.5-4.5%.

[0049] A second aspect of this application provides a semi-solid secondary battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte comprises the electrolyte described in this application.

[0050] A third aspect of this application discloses a method for preparing a semi-solid-state secondary battery, comprising:

[0051] The second solution is injected into the dry cell containing the electrolyte to be injected, and then the cells are formed to obtain a cell after one injection.

[0052] The first solution is injected into the battery after the first injection, followed by a first settling and a second settling to obtain the semi-solid secondary battery.

[0053] The temperature of the second settling period is higher than that of the first settling period.

[0054] In some implementations, the temperature of the first settling period is room temperature.

[0055] In some implementations, the first settling time is 48-72 hours.

[0056] In some embodiments, the temperature of the second settling period is 40-80°C.

[0057] In some implementations, the second settling time is 4-48 hours.

[0058] In some embodiments, the method for preparing the semi-solid secondary battery further includes a third settling step of placing the dry cell containing the second solution into a stand before the formation; the temperature of the third settling is 20-30°C, and the time of the third settling is 24-48 hours.

[0059] The fourth aspect of this application discloses an electrical device comprising the semi-solid secondary battery described in this application or a semi-solid secondary battery prepared by the preparation method of the semi-solid secondary battery described in this application.

[0060] The electrolyte of this application can bring at least the following beneficial effects:

[0061] This electrolyte contains polymeric monomers and comonomers. The polymeric monomers are compounds with the structure shown in Formula I, and the comonomers are alkali metal salts containing unsaturated bonds. When used together, the three-dimensional network structure formed by the polymeric monomers effectively absorbs free solvent molecules in the electrolyte, while reducing crosstalk between the positive and negative electrode materials, thus improving battery safety. Simultaneously, the copolymerization of the alkali metal salts with unsaturated bonds forms freely moving side chains, and the anions provide ion conduction, thereby reducing the electrolyte impedance. Using this electrolyte in semi-solid-state rechargeable batteries can improve both battery safety and rate and cycle performance.

[0062] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Detailed Implementation

[0063] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0064] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0065] Unless otherwise specified, all raw materials and equipment involved in this application are self-made through commercial means or known methods; and all methods involved are conventional methods unless otherwise specified.

[0066] In this application, "room temperature" refers to 20-30℃.

[0067] definition:

[0068] The term "alkyl" refers to a saturated hydrocarbon group, including both straight-chain and branched structures. Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl (e.g., n-propyl, isopropyl), butyl (e.g., n-butyl, isobutyl, sec-butyl, tert-butyl), and pentyl (e.g., n-pentyl, isopentyl, neopentyl). In various embodiments, C1-10 alkyl groups, i.e., alkyl groups, may contain 1 to 10 carbon atoms.

[0069] The term "alkenyl" refers to an unsaturated hydrocarbon group containing carbon-carbon double bonds, including both straight-chain and branched structures, and the number of carbon-carbon double bonds can be one or more. Examples of alkenyl groups include, but are not limited to, vinyl, propenyl, allyl, and butadienyl. In various embodiments, C2-5 alkenyl groups, i.e., alkenyl groups, can contain 2 to 5 carbon atoms.

[0070] The term "alkynyl" refers to an unsaturated hydrocarbon group containing a carbon-carbon triple bond, including both straight-chain and branched structures, and the number of carbon-carbon triple bonds can be one or more. Examples of alkynyl groups include, but are not limited to, ethynyl, propynyl, butynyl, and butadiynyl. In various embodiments, the C2-5 alkynyl group, i.e., the alkynyl group, can contain 2 to 5 carbon atoms.

[0071] The term "alkoxy" refers to an alkyl group containing an oxygen atom (-O-).

[0072] The term "alkenyl group" refers to an alkenyl group containing an oxygen atom (-O-).

[0073] The term "alkynyl group" refers to an alkynyl group containing an oxygen atom (-O-).

[0074] The term "carboxylic acid ester group" refers to both C-carboxylic acid ester groups and O-carboxylic acid ester groups. Specifically, "C-carboxylic acid ester group" refers to a -C(=O)-OR' terminal group or a -C(=O)-O- linker, while "O-carboxylic acid ester group" refers to an -OC(=O)R' terminal group or a -OC(=O)- linker, where R' can be alkenyl, alkynyl, alkyl, etc. Carboxylic acid ester groups can be linear or cyclic.

[0075] The term "amide group" refers to the R"-C(=O)-NH- or -NH-C(=O)-R" group, where R" can be a monobond, alkenyl, alkynyl, alkyl, etc.

[0076] The term "isocyanate group" refers to an R"'-N=C=O group, where R"' is a monobond, alkenyl, alkynyl, alkyl, etc.

[0077] The term "acyl" refers to the atomic group remaining after removing one or more hydroxyl groups from an organic or inorganic oxyacid. R0 can be alkenyl, alkynyl, alkyl, etc.

[0078] The term "phosphate group" refers to

[0079] The term "phosphite group" refers to

[0080] The term "sulfonate group" refers to the –S(=O)2-R' terminal group or the –S(=O)2- linker group, where R' is an alkenyl, alkynyl, alkyl, etc.

[0081] The term "boronate group" refers to

[0082] The asterisk (*) indicates the connection between identical or different atoms, or between chemical formulas.

[0083] The term "heterocyclic group" refers to a cycloalkyl group in which at least one carbon atom is replaced by a non-carbon atom, which can be an N atom, O atom, S atom, etc., and can be a saturated ring or a partially unsaturated ring. Phrases containing this term, such as "C4-9 heterocyclic group," refer to heterocyclic groups containing 4-9 carbon atoms, and each occurrence can be independently C4, C6, C7, C8, or C9 heteroalkyl. Suitable examples include, but are not limited to: dihydropyridyl, tetrahydropyridyl (piperidinyl), tetrahydrothiophenyl, sulfur-oxidized tetrahydrothiophenyl, tetrahydrofuranyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, and dihydroindolyl.

[0084] Throughout this specification, substituents of compounds are disclosed by groups or ranges. It is expressly intended that such description include each individual sub-combination of members of these groups and ranges. For example, it is expressly intended that the term "C1-6 alkyl" individually discloses alkyl groups of C1, C2, C3, C4, C5, C6, C1-6, C1-5, C1-4, C1-3, C1-2, C2-6, C2-5, C2-4, C2-3, C3-6, C3-5, C3-4, C4-6, C4-5, and C5-6.

[0085] In this document, when a substituent refers to a group consisting of certain groups, it includes groups formed by these groups being bonded together by single bonds. For example, when a substituent refers to "at least one of a composition consisting of a hydroxyl group, a C1-18 monovalent alkyl group, and a C6-18 monovalent aryl group", the substituent individually discloses a hydroxyl group, a C1-18 monovalent alkyl group, a C6-18 monovalent aryl group, a hydroxyl-substituted C1-18 monovalent alkyl group, a hydroxyl-substituted C6-18 monovalent aryl group, and a C1-18 monovalent alkyl-substituted C6-18 monovalent aryl group.

[0086] In this article, when each substituent is "monovalent", it refers to a group formed by removing one H atom from the molecule; when each substituent is "divalent", it refers to a group formed by removing two H atoms from the molecule; when each substituent is "trivalent", it refers to a group formed by removing three H atoms from the molecule; and when each substituent is "tetravalent", it refers to a group formed by removing four H atoms from the molecule.

[0087] Electrolyte

[0088] In a first aspect, the electrolyte of this application embodiment includes a first solution and a second solution. The first solution includes a first electrolyte, a first solvent, a polymeric monomer, a comonomer, and an initiator. The polymeric monomer includes at least one compound having the structure shown in Formula I.

[0089]

[0090] In formula I,

[0091] ○ indicates a central group, which is selected from heterocyclic groups or linear groups;

[0092] R1, R2...Rn are each independently selected from one of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, saturated or unsaturated carboxylic acid ester, saturated or unsaturated amide, saturated or unsaturated isocyanate, alkoxy, alkenyloxy, alkynyloxy, saturated or unsaturated acyl, and at least two of R1, R2...Rn contain carbon-carbon double or carbon-carbon triple bonds, where n is an integer from 2 to 6;

[0093] The comonomer includes alkali metal salts containing unsaturated bonds.

[0094] It is understood that the compounds having the structure shown in Formula I in the embodiments of this application are polyene or polyynyl polymer monomers. Furthermore, based on the different central groups, compounds having the structure shown in Formula I can be divided into two main categories: when the central group is a heterocyclic group, the compounds having the structure shown in Formula I are polyene or polyynyl heterocyclic compounds; when the central group is a linear group, the compounds having the structure shown in Formula I are polyene or polyynyl linear compounds.

[0095] In some embodiments, the heterocyclic group is selected from one of nitrogen-containing C2-5 heterocyclic groups, oxygen-containing C2-5 heterocyclic groups, and sulfur-containing C2-5 heterocyclic groups.

[0096] As an alternative example, the heterocyclic group is selected from one of the following structures:

[0097] In some embodiments, the linear group is selected from one of the following: single atom, C1-6 alkyl, C1-6 alkoxy, phosphate ester, phosphite ester, sulfonate ester, and borate ester.

[0098] For example, the single atom includes, but is not limited to, one of nitrogen atoms, carbon atoms, silicon atoms, phosphorus atoms, boron atoms, etc.

[0099] For example, C1-6 alkyl groups include, but are not limited to, methyl (-CH3), ethyl (-C2H5), n-propyl (-CH2CH2CH3), isopropyl (-CH(CH3)2), and cyclopropyl. n-Butyl (-CH2CH2CH2CH3), isobutyl (-CH(CH3)CH2CH3), sec-Butyl (-CH2CH(CH3)2), tert-Butyl (-C(CH3)3), cyclobutyl -CH2CH2CH2CH2CH3, -CH(CH3)CH2CH2CH3, -CH2CH(CH3)CH2CH3, -CH2CH2CH(CH3)2, -CH(C2H5)CH2CH3, -C(CH3)2CH2CH3, -CH(CH3)CH(CH3)2, -CH2C(CH3)3, cyclopentyl wait.

[0100] For example, C1-6 alkoxy groups include, but are not limited to, methoxy (CH3O-), ethoxy (C2H5O-), propoxy (C3H7O-), butoxy (C4H9O-), and pentoxy (C5H5O-). 11 O-) etc.

[0101] As an alternative example, the linear group is selected from one of the following structures:

[0102] In some embodiments, R1, R2...Rn are each independently selected from one of the following: substituted or unsubstituted C1-6 alkyl, substituted or unsubstituted C2-5 alkenyl, substituted or unsubstituted C2-5 alkynyl, saturated or unsaturated C1-6 carboxylic acid ester, saturated or unsaturated C1-6 amide, saturated or unsaturated C1-6 isocyanate, C1-6 alkoxy, C2-6 alkenoxy, C2-6 alkynoxy, and saturated or unsaturated C1-6 acyl.

[0103] For example, unsubstituted C2-5 alkenyl groups include, but are not limited to, vinyl (-CH=CH2), propenyl (-CH=CH-CH3), -CH=CH2-CH2-CH3, and -CH=CH2-CH=CH2. wait.

[0104] For example, unsubstituted C2-5 ynyl groups include, but are not limited to, ethynyl (-C≡CH), propynyl (-C≡C-CH3), butynyl (-C≡C-CH2-CH3), etc.

[0105] For example, substituted C1-6 alkyl groups include, but are not limited to, alkyl groups in which one or more H atoms of the unsubstituted C1-6 alkyl groups described above are replaced by substituents.

[0106] For example, substituted C2-5 alkenyl groups include, but are not limited to, alkenyl groups in which one or more H atoms in the unsubstituted C2-5 alkenyl groups described above are replaced by substituents.

[0107] For example, substituted C2-5 ynyl groups include, but are not limited to, ynyl groups in which one or more H atoms of the unsubstituted C2-5 ynyl groups described above are replaced by substituents.

[0108] In some embodiments, the substituents in the substituted alkyl, substituted alkenyl, and substituted alkynyl groups include, but are not limited to, at least one of halogen atoms, cyano groups, phenyl groups, etc.

[0109] For example, the halogen atom includes a fluorine atom (F), a chlorine atom (Cl), a bromine atom (Br), or an iodine atom (I), optionally a fluorine atom (F).

[0110] Exemplary examples include, but are not limited to, saturated or unsaturated C1-6 carboxylic acid ester groups. wait.

[0111] Exemplary examples include, but are not limited to, saturated or unsaturated C1-6 amide groups. wait.

[0112] For example, C1-6 alkoxy groups include, but are not limited to, methoxy, ethoxy, propoxy, etc.

[0113] For example, C2-6 olefins include, but are not limited to, wait.

[0114] For example, C2-6 acetylated groups include, but are not limited to, those containing, acetylated groups. wait.

[0115] As an optional example, R1, R2…R n Each is independently selected from one of the following: unsubstituted C2-5 alkenyl, unsubstituted C2-5 alkynyl, unsaturated C1-6 amide, C2-6 alkenoxy, C2-6 alkynoxy, and unsaturated C1-6 acyl ester.

[0116] As a more alternative example, R1, R2…R n Each independently selected

[0117] One of them.

[0118] In some embodiments, the compound having the structure shown in Formula I includes, but is not limited to, at least one of compounds T1-T9:

[0119]

[0120]

[0121] Of the compounds T1-T9 mentioned above, compounds T1-T5 are cyclic polyene (alkynyl) compounds, and compounds T6-T9 are chain polyene (alkynyl) compounds. Specifically, compound T1 is triallyl isocyanurate (TAIC, CAS number 1025-15-6), compound T2 is 2,4,6-tris(allyloxy)-1,3,5-triazine (CAS number 101-37-1), compound T3 is 1,3,5-triacryloylhexahydro-1,3,5-triazine (CAS number 959-52-4), compound T4 is 1,4-diaceryloylpiperazine (CAS number 6342-17-2), and compound T5 is tris(2-hydroxyethyl)isocyanurate. The compounds are: triacrylate (THEICTA, CAS No. 40220-08-4), compound T6 is triargyl phosphate (also known as triargyl phosphate, CAS No. 1779-34-6), compound T7 is glycerol propoxyacid (1PO / OH) triacrylate (CAS No. 52408-84-1), compound T8 is pentaerythritol tetraacrylate (CAS No. 4986-89-4), and compound T9 is N,N-diallyl acrylamide (CAS No. 3085-68-5).

[0122] The compounds having the structure shown in Formula I in this application can all be synthesized by commonly used organic synthesis mechanisms and methods, which will not be elaborated here.

[0123] In some embodiments, the alkali metal salt containing unsaturated bonds includes at least one of compounds having the structure of Formula II, Formula III, and Formula IV:

[0124]

[0125] Among them, X1, X2, and X6 are each independently selected from one of the C2-6 alkenyl or C2-6 alkynyl groups, X3, X4, and X5 are all F, and Y1, Y2, Y3, and Y4 are each independently selected from one of the alkali metals.

[0126] For example, the alkenyl groups of C2-6 include, but are not limited to, vinyl (-CH=CH2), propenyl (-CH2-CH=CH2), butenyl (-CH2-CH2-CH=CH2), etc.

[0127] For example, alkali metals include, but are not limited to, lithium (Li), sodium (Na) or potassium (K), with lithium (Li) being an option.

[0128] As an optional example, X1, X2, and X6 are each independently selected from one of C2-6 alkenyl groups, and X3, X4, and X5 are all F; Y1, Y2, Y3, and Y4 are each independently selected from one of lithium and sodium, with lithium being optional.

[0129] As a more alternative example, the alkali metal salt containing unsaturated bonds includes, but is not limited to, at least one of compounds P1-P5:

[0130]

[0131] Of the compounds P1-P5 mentioned above, compound P1 is lithium propylene sulfate, compound P2 is lithium butenyl sulfate, compound P3 is lithium propylene sulfate (boron trifluoride), compound P4 is lithium propylene sulfonate, and compound P5 is lithium propylene diphosphate.

[0132] Compounds having the structure of Formula II, Formula III, and Formula IV can all be synthesized using common organic synthesis mechanisms and methods. For example:

[0133] Taking a compound with the structure of Formula III as an example, its synthesis method includes the following steps:

[0134] (1) Under N2 atmosphere, 0.5 mol of lithium carbonate was added to 600 ml of ethanol to prepare a suspension. The suspension was heated to 90 °C and refluxed. 0.97 mol of diethyl sulfate was added dropwise for 45 min. After the addition was completed, the reaction was kept at the temperature for 3 h to obtain the reaction solution. The reaction solution was filtered in a glove box and concentrated under reduced pressure at -0.1 MPa and 45 °C for 1.5 h. Finally, it was vacuum dried at -0.1 MPa and 60 °C for 18 h to obtain lithium ethyl sulfate.

[0135] (2) Preparation of unsaturated lithium sulfate. In a N2 atmosphere, 1.0 mol of lithium ethyl sulfate prepared in step (1) was dissolved in 1000 ml of acetonitrile, 1.6 g of KOH was added, the temperature was raised to 82 °C, and 2.2 mol of 3-buten-1-ol was added dropwise for 2 h. After the addition was completed, the reaction was kept at the temperature for 12 h to obtain crude unsaturated lithium sulfate. The crude unsaturated lithium sulfate was filtered and then washed twice with dichloromethane (DCM) to make the product more loose. Finally, it was vacuum dried at -0.1 MPa and 40 °C for 16 h to obtain a white solid.

[0136] In some embodiments, the compound having the structure shown in Formula I has a mass content of a% in the electrolyte, and the alkali metal salt containing unsaturated bonds has a mass content of b% in the electrolyte, wherein a and b satisfy:

[0137] 1≤a+b≤10.

[0138] That is, the total mass content of the compound having the structure shown in Formula I and the alkali metal salt containing unsaturated bonds in the electrolyte is 1-10%. In the embodiments of this application, when the total mass of the compound having the structure shown in Formula I and the alkali metal salt containing unsaturated bonds in the electrolyte is within the above range, it can improve safety without increasing (or even improving) the conduction impedance of cations, thus improving the rate performance of the battery; if it is less than 1%, it has no significant impact on the performance of the battery and does not improve safety; if it is more than 10%, it may cause volume shrinkage during polymerization, resulting in contact interface problems, and the polymer has many crosslinking points, resulting in excessively high impedance and overall deterioration of battery performance.

[0139] For example, the total mass content (a% + b%) of the compound having the structure shown in Formula I and the alkali metal salt containing unsaturated bonds in the electrolyte includes, but is not limited to, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0140] As an optional example, the total mass content (a% + b%) of the compound having the structure shown in Formula I and the alkali metal salt containing unsaturated bonds in the electrolyte is 1.5-5%.

[0141] In some embodiments, the compound having the structure shown in Formula I has a mass content of a% in the electrolyte, and the alkali metal salt containing unsaturated bonds has a mass content of b% in the electrolyte, wherein a and b satisfy:

[0142] 1 / 5 ≤ a / b ≤ 10.

[0143] That is, the mass ratio of the compound having the structure shown in Formula I to the alkali metal salt containing unsaturated bonds is 10:1 to 1:5. In the embodiments of this application, when the mass ratio of the compound having the structure shown in Formula I to the alkali metal salt containing unsaturated bonds is within the above range, the effects mentioned above can be achieved, improving safety without significant degradation of electrical performance or even improving it; if it is less than 1 / 5, it is difficult to completely lock in free electrolyte solvents and other components after polymerization, making it difficult to improve battery safety; if it is greater than 10, although safety is improved, the impedance of ion conduction is increased, causing the rate capability, cycle life and other electrical performance to be affected.

[0144] For example, the mass ratio (a / b) of the compound having the structure shown in Formula I and the alkali metal salt containing unsaturated bonds includes, but is not limited to, 1 / 5, 1 / 2, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0145] As an alternative example, the mass ratio (a / b) of the compound having the structure shown in Formula I and the alkali metal salt containing unsaturated bonds is 1:2.5 to 5:1.

[0146] In some embodiments, the compound having the structure shown in Formula I and the alkali metal salt containing unsaturated bonds form a gel polymer under the action of the initiator, the gel polymer having the polymer structure shown in Formula V:

[0147]

[0148] In Formula V, Y is an alkali metal, including but not limited to lithium, sodium, or potassium.

[0149] It should be noted that the choice of Y in the polymer structure shown in Formula V is the same as the choices of Y1, Y2, Y3, and Y4 mentioned above. For example, when Y1, Y2, Y3, and Y4 are lithium, Y is also lithium.

[0150] In the embodiments of this application, when the electrolyte is used in a semi-solid secondary battery, after the battery is placed at a high temperature, the compound having the structure shown in Formula I and the alkali metal salt containing unsaturated bonds can polymerize under the action of the initiator to form a gel polymer. The polymerizing monomer having the structure shown in Formula I serves as the polymer backbone, providing a certain strength and liquid absorption / retention capacity; the comonomer containing the alkali metal salt with unsaturated bonds provides a channel for the transport of alkali metal ions such as lithium ions, improving the rate performance of the battery.

[0151] In some embodiments, the mass of the first solution accounts for 5-30% of the total mass of the electrolyte. In the embodiments of this application, the proportion of the mass of the first solution to the total mass of the electrolyte is within the above range, which can achieve the effects described above; if it is less than 5%, the amount of polymerizable monomers is insufficient, and it is difficult to completely lock in the free electrolyte solvent and other components after polymerization, making it difficult to improve battery safety; if it is greater than 30%, the content of electrolyte II is too small, which will cause the risk of incomplete wetting after the first injection, resulting in insufficient formation and film formation, making it difficult to exert the capacity, and thus affecting the overall battery performance.

[0152] For example, the mass of the first solution as a percentage of the total mass of the electrolyte includes, but is not limited to, 5%, 7.5%, 10%, 12.5%, 15%, 17.5%, 20%, 22.5%, 25%, 27.5%, or 30%.

[0153] As an alternative example, the mass of the first solution accounts for 10-25% of the total mass of the electrolyte.

[0154] In some embodiments, the first electrolyte includes at least one of alkali metal salts.

[0155] For example, alkali metal salts include, but are not limited to, at least one of lithium salts, sodium salts, potassium salts, etc.

[0156] As an alternative example, an alkali metal salt is a lithium salt.

[0157] For example, lithium salts include, but are not limited to, at least one of lithium hexafluorophosphate and lithium bisfluorosulfonylimide.

[0158] In some embodiments, the first electrolyte (e.g., lithium salt) has a mass content of 7-20% in the electrolyte, including but not limited to 7%, 10%, 12.5%, 15%, 17.5%, or 20%.

[0159] In some embodiments, the concentration of the first electrolyte in the electrolyte is 0.5-1.4 mol / L, including but not limited to 0.5 mol / L, 0.7 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L or 1.5 mol / L.

[0160] In some embodiments, the first solvent includes, but is not limited to, at least one of carbonates, carboxylic esters, fluorocarbonates, fluorocarboxylic esters, etc.

[0161] For example, the carbonate includes, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC).

[0162] For example, the carboxylic acid esters include, but are not limited to, at least one of methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), ethyl propionate (EP), propyl propionate (PP), and butyl acetate (PA).

[0163] For example, the fluorocarbonate includes, but is not limited to, at least one of bis(2,2,2-trifluoroethyl)carbonate (TFEC), ethyltrifluoroethylcarbonate (ETFEC), methyltrifluoroethylcarbonate (MTFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0164] For example, the fluorocarboxylic acid esters include, but are not limited to, at least one of methyl difluoroacetate (MDFA), ethyl difluoroacetate (EDFA), ethyl difluoroacetate (DFEA), and ethyl trifluoroacetate (ETFA).

[0165] In some embodiments, the initiator includes, but is not limited to, at least one of azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), etc.

[0166] In some embodiments, the initiator has a mass content of 0.1-0.3% in the electrolyte, including but not limited to 0.1%, 0.15%, 0.2%, 0.25%, or 0.3%.

[0167] In some embodiments, the second solution includes a second electrolyte, a second solvent, and an additive.

[0168] In the embodiments of this application, the second solution and the first solution are set independently to facilitate separate liquid injection during the preparation of the semi-solid secondary battery, as detailed in the preparation method of the semi-solid secondary battery below.

[0169] In some embodiments, the additives include, but are not limited to, at least one of the following: fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl sulfate (DTD), 1,3-propanesulfonate lactone (PS), lithium difluorobis(oxalato) phosphate (LiODFP), lithium difluorooxalatoborate (LiODFB), ethylene ethylene carbonate (VEC), 1,3-propenesulfonate lactone (PST), methylene disulfonate (MMDS), vinyl sulfate (ESa), tetravinylsilane (TVSI), and lithium difluorophosphate (LiPO2F2). In the embodiments of this application, the additives function to improve the overall performance of the battery.

[0170] In some embodiments, the second electrolyte is the same as the first electrolyte.

[0171] In other embodiments, the second electrolyte is different from the first electrolyte. For example, when the first electrolyte salt is lithium hexafluorophosphate, the second electrolyte salt may be lithium difluorosulfonylimide.

[0172] In some embodiments, the second solvent is the same as the first solvent.

[0173] In other embodiments, the second solvent may be different from the first solvent. For example, when the first solvent is the aforementioned carbonate, the second solvent may be the aforementioned carboxylic acid ester used as the first solvent.

[0174] In some embodiments, the concentration of the second electrolyte in the electrolyte is 0.5-1.4 mol / L, including but not limited to 0.5 mol / L, 0.7 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L or 1.5 mol / L.

[0175] It should be noted that in the electrolyte of this application embodiment, if there is no second solution, the safety of the subsequent battery will be degraded.

[0176] In some embodiments, the additive is present in the electrolyte at a mass content of 2.5-4.5%.

[0177] The electrolyte of this application embodiment contains a polymeric monomer and a comonomer. The polymeric monomer is selected from compounds having the structure shown in Formula I, and the comonomer is selected from alkali metal salts containing unsaturated bonds. The combined use of these two monomers can enhance the ion-conducting capacity of the polymeric network and reduce the impedance of the electrolyte. Using this electrolyte in a semi-solid-state secondary battery can improve both battery safety and rate and cycle performance.

[0178] Semi-solid secondary batteries

[0179] The semi-solid secondary battery of this application embodiment includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte includes the electrolyte of this application embodiment.

[0180] In some embodiments, the positive electrode sheet includes a positive electrode material and a positive electrode current collector. The positive electrode material includes a positive electrode active material, a positive electrode binder, a positive electrode conductive agent, and a positive electrode dispersant.

[0181] 1) Positive electrode plate

[0182] In some embodiments, when the semi-solid secondary battery is a semi-solid lithium-ion battery, the positive electrode active material includes, but is not limited to, lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), lithium cobalt phosphate (LiCoPO4), lithium cobalt oxide (LiCoO2), spinel-type lithium manganese oxide (LiMn2O4), spinel-type lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4), layered lithium manganese oxide (LiMnO2), lithium nickel oxide (LiNiO2), lithium niobate (LiNbO2), lithium nickel cobalt aluminum oxide (LiNi x Co y Al 1-x-y O2, 0 < x < 1, 0 < y < 1, 0 < x + y < 1, for example, LiNi 0.8 Co 0.15 Al 0.05 O2), lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1-x-y O2, 0 < x < 1, 0 < y < 1, 0 < x + y < 1, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, etc.), lithium nickel manganese aluminum oxide (LiNi x Mn y Al 1-x-y O2, 0 ≤ x, y ≤ 1, 0 ≤ x + y ≤ 1)), lithium iron manganese phosphate (LiFe a Mn 1- a PO4, 0 ≤ a ≤ 1), lithium-rich materials (such as lithium-rich nickel cobalt manganese oxide) and at least one of their respective modified compounds. These materials can be used alone or in combination of two or more.

[0183] In some other embodiments, the positive electrode active material can also be selected from compounds that can reversibly intercalate and deintercalate Na + . As an example, the positive electrode active material includes transition metal oxides, polyanion compounds, Prussian blue analogs, etc.

[0184] In some other embodiments, the modified compounds of the above positive electrode active materials can be doping modification, surface coating modification or simultaneous doping and coating modification of the positive electrode active material.

[0185] In some embodiments, the positive current collector may be a metal foil, such as aluminum foil.

[0186] In some embodiments, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylates, polyamides, polyimides, polyurethanes, polyacrylonitrile, and polyacrylic acid.

[0187] In some embodiments, the positive electrode binder accounts for 0.1-3.5% of the total weight of the positive electrode material, optionally 0.5-2.5%.

[0188] In some embodiments, the positive electrode conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, and carbon nanofibers.

[0189] In some embodiments, the positive electrode conductive agent accounts for 0.05-5% of the total weight of the positive electrode material, optionally 0.5-3%.

[0190] In some embodiments, the positive electrode dispersant includes, but is not limited to, at least one of sodium dodecylbenzenesulfonate (SDBS), polyvinylpyrrolidone (PVP), etc.

[0191] The components used to prepare the positive electrode sheet, such as positive active material, positive conductive agent, positive binder and any other components, are dispersed in a solvent (e.g. N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0192] 2) Negative electrode plate

[0193] In some embodiments, the negative electrode sheet includes a negative electrode material and a negative electrode current collector. The negative electrode material includes a negative electrode active material, a negative electrode binder, a negative electrode conductive agent, and a negative electrode dispersant.

[0194] In some embodiments, the negative electrode active material includes, but is not limited to, artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0195] In some embodiments, the negative current collector may be a metal foil, such as copper foil or aluminum foil.

[0196] In some embodiments, the negative electrode binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0197] In some embodiments, the negative electrode conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, and carbon nanofibers.

[0198] In some embodiments, the negative electrode dispersant includes, but is not limited to, at least one of polyvinyl alcohol, carboxymethyl cellulose, etc.

[0199] In some embodiments, the negative electrode material may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0200] The components used to prepare the negative electrode sheet, such as negative electrode active material, negative electrode conductive agent, negative electrode binder and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0201] 3) Diaphragm

[0202] In some embodiments, the diaphragm includes, but is not limited to, at least one of polyethylene (PE) diaphragms, polypropylene (PP) diaphragms, composite diaphragms (e.g., PE / PP), ceramic diaphragms, etc.

[0203] <Preparation Methods of Semi-Solid-State Secondary Batteries>

[0204] The method for preparing a semi-solid-state secondary battery according to embodiments of this application includes the following steps:

[0205] S101. The second solution is injected into the dry cell containing the electrolyte to be injected, and then the cells are formed to obtain the cell after one injection.

[0206] In some embodiments, the preparation method of the above-mentioned semi-solid secondary battery further includes the step of preparing the electrolyte.

[0207] For example, the method for preparing the electrolyte includes the following steps:

[0208] (1) Preparation of the first solution: Mix the first electrolyte, the first solvent, the polymer monomer and the initiator to obtain the first solution.

[0209] (2) Preparation of the second solution: Mix the second electrolyte, the second solvent and the additive to obtain the second solution.

[0210] In some embodiments, the method for preparing the semi-solid secondary battery described above further includes the step of preparing a dry cell containing the electrolyte to be injected.

[0211] For example, the method for preparing the dry cell to be injected with electrolyte includes the following steps:

[0212] The positive electrode, negative electrode, and separator are wound, packaged, and dried to obtain the dry cell to be injected with electrolyte.

[0213] In some embodiments, the method for preparing the semi-solid secondary battery further includes a third settling step of placing the dry cell containing the second solution before the formation.

[0214] In some embodiments, the temperature of the third settling period is 20-30°C, including but not limited to 20°C, 22.5°C, 25°C, or 27.5°C.

[0215] In some implementations, the third settling time is 24-48 hours, including but not limited to 24 hours, 30 hours, 36 hours, 40 hours, or 46 hours.

[0216] S102. The first solution is injected into the battery after the first injection, followed by a first settling and a second settling to obtain the semi-solid secondary battery.

[0217] In some embodiments, the temperature of the second settling period is higher than that of the first settling period. The purpose of this arrangement in the embodiments of this application is to ensure that the in-situ curing polymerization needs to be carried out at a high temperature, but it is also necessary to avoid high temperature-induced reactions before complete impregnation; therefore, it is necessary to settling at room temperature first, and then settling at a high temperature.

[0218] In some implementations, the temperature of the first settling period is room temperature.

[0219] In some implementations, the first settling time is more than 48 hours.

[0220] As an optional example, the first settling time is 48-72 hours, including but not limited to 54 hours, 60 hours, 66 hours, or 70 hours.

[0221] In some embodiments, the temperature of the second settling period is 40-80°C, including but not limited to 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C.

[0222] As an optional example, the temperature of the second settling period is 45-55°C.

[0223] In some implementations, the second settling time is more than 4 hours.

[0224] As an optional example, the second settling time is 4-48 hours, including but not limited to 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, or 45 hours.

[0225] The method for preparing a semi-solid secondary battery according to the embodiments of this application adopts a multi-step liquid injection approach, which reduces the consumption of the polymer network during the formation stage and further reduces the film-forming impedance. While improving battery safety, it does not deteriorate the rate performance and cycle performance of the battery, making it an excellent semi-solid solution.

[0226] <Electrical Appliances>

[0227] The electrical device in this application includes the semi-solid secondary battery of this application, or the semi-solid secondary battery prepared by the preparation method of the semi-solid secondary battery of this application.

[0228] In some embodiments, the aforementioned electrical devices include, but are not limited to, electric vehicles, electronic devices, and lighting equipment.

[0229] The following non-limiting embodiments further illustrate certain features of the present technology.

[0230] I. Examples and Comparative Examples

[0231] The polymer monomers involved in the following examples are selected from the compounds shown in Table 1.

[0232] Table 1 shows the polymer monomers involved in each embodiment.

[0233]

[0234]

[0235] The comonomers used in the following examples are selected from the compounds shown in Table 2.

[0236] Table 2 shows the comonomers involved in each embodiment.

[0237]

[0238] The electrolyte raw materials used in the following examples and comparative examples were all purchased from new energy or chemical companies such as Do-Fluoride Chemicals, Shanghai Rukun, Hebei Shengtai, and Anaiji.

[0239] Example 1

[0240] (electrolyte)

[0241] The electrolyte in this embodiment consists of a first solution and a second solution, which are set separately, with a mass ratio of 2:8. Wherein:

[0242] The first solution consists of: 12.5 wt% polymeric monomer, 5 wt% comonomer, 0.875 wt% initiator, and the balance being the first electrolyte and the first solvent. The concentration of the first electrolyte is 1 M. The polymeric monomer is compound T1, the comonomer is compound P1, the initiator is azobisisobutyronitrile (AIBN), the first electrolyte is LiPF6, and the first solvent is a mixture of EC, PC, DEC, and EMC in a mass ratio of 5:20:15:60.

[0243] The second solution consists of 4.49 wt% additives, with the remainder being a second electrolyte and a second solvent. The concentration of the second electrolyte is 1 M. The additives are composed of VC, FEC, DTD, PS, and LiPO2F2, with mass contents of 0.63 wt%, 1.3 wt%, 1.3 wt%, 0.63 wt%, and 0.63 wt%, respectively, in the second solution. The second electrolyte is LiPF6, and the second solvent is a mixture of EC, PC, DEC, and EMC in a mass ratio of 5:20:15:60.

[0244] After conversion, the contents of the other components in the first and second solutions, excluding the first and second solvents, in the entire electrolyte are as follows: 2.5 wt% polymeric monomer, 1 wt% comonomer, 0.175% initiator, 0.5% VC, 1% FEC, 1% DTD, 0.5% PS, 0.5% LiPO2F2, and the concentrations of the first and second electrolytes are both 1 M.

[0245] (Preparation of electrolyte)

[0246] The electrolyte preparation method of this embodiment includes the following steps:

[0247] (1) Preparation of the first solution: In a glove box, the first electrolyte, the first solvent, the polymer monomer and the initiator are stirred and mixed to obtain the first solution.

[0248] (2) Preparation of the second solution: In a glove box, the second electrolyte, the second solvent and the additive are stirred and mixed to obtain the second solution.

[0249] (Preparation method of semi-solid lithium-ion battery)

[0250] The method for preparing a semi-solid-state lithium-ion battery in this embodiment includes the following steps:

[0251] 1) Preparation of the positive electrode: The positive electrode active material is a nickel-cobalt-manganese ternary material NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 02) 97wt% of positive electrode conductive agent SP 1wt% + CNT 0.5wt% and positive electrode binder PVDF 1.5wt% are dispersed in solvent N-methylpyrrolidone to form a positive electrode slurry; the positive electrode slurry is coated on the opposite two sides of the positive electrode current collector aluminum foil, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0252] 2) Preparation of the negative electrode sheet: 96wt% of artificial graphite (negative electrode active material), 1wt% of SP (negative electrode conductive agent), 2wt% of SBR (negative electrode binder), and 1wt% of CMC (negative electrode thickener) are dispersed in deionized water to form a negative electrode slurry. The negative electrode slurry is coated onto the opposite surfaces of the copper foil (negative electrode current collector). After drying and cold pressing, the negative electrode sheet is obtained. The N / P ratio (i.e., the ratio of the reversible capacity of the negative electrode to the reversible capacity of the positive electrode) of the negative electrode sheet to the positive electrode sheet is 1.08.

[0253] 3) Diaphragm selection: Select PE diaphragm.

[0254] 4) Preparation of dry cell to be injected with electrolyte: The positive electrode, negative electrode and separator are wound, packaged and dried to form the dry cell to be injected with electrolyte.

[0255] 5) Fluid injection: The fluid injection process includes:

[0256] A. The second solution is injected into the dry cell containing the electrolyte, then sealed and left at 25°C for 36 hours to undergo formation, resulting in a cell after one electrolyte injection.

[0257] B. After the first electrolyte injection, cut open the gas bag of the battery, inject the first solution, seal it, and then let it stand at room temperature (25°C) for 48 hours. Then, heat it to 50°C and let it stand for 5 hours to obtain the semi-solid-state lithium-ion battery of this embodiment. The injection volumes of the second solution and the first solution are 80% and 20% of the total injection volume (i.e., the total mass of the electrolyte), respectively.

[0258] Examples 2-27 and Comparative Examples 1-10 are basically the same as Example 1, except that the selection and amount of some substances in the first solution are different. The specific differences are shown in Table 3.

[0259] Table 3. Differences between the electrolyte formulations of Examples 1-27 and Comparative Examples 1-10 and Example 1.

[0260]

[0261]

[0262] Example 28 (mass ratio of first solution to second solution is 1:9)

[0263] This embodiment is basically the same as embodiment 3, except that:

[0264] In the electrolyte, the mass ratio of the first solution to the second solution is 1:9; the first solution contains 25 wt% polymeric monomer, 10 wt% comonomer, and 1.75 wt% initiator; the second solution contains 3.88 wt% additives, specifically 0.56% VC, 1.1% FEC, 1.1% DTD, 0.56% PS, and 0.56% LiPO2F2.

[0265] Example 29 (The mass ratio of the first solution and the second solution is the lower limit of 1:19—the first solution accounts for 5% of the electrolyte)

[0266] This embodiment is basically the same as embodiment 3, except that:

[0267] In the electrolyte, the mass ratio of the first solution to the second solution is 1:19; the first solution contains 50 wt% polymeric monomer, 20 wt% comonomer, and 3.5 wt% initiator; the second solution contains 3.69 wt% additives, specifically 0.53% VC, 1.05% FEC, 1.05% DTD, 0.53% PS, and 0.53% LiPO2F2.

[0268] Example 30 (The mass ratio of the first solution and the second solution is at the upper limit of 3:7—the first solution accounts for 30% of the electrolyte)

[0269] This embodiment is basically the same as embodiment 3, except that:

[0270] In the electrolyte, the mass ratio of the first solution to the second solution is 3:7; the first solution contains 8.333 wt% polymeric monomer, 3.333 wt% comonomer, and 0.583 wt% initiator; the second solution contains 3.69 wt% additives, specifically 0.714% VC, 1.429% FEC, 1.429% DTD, 0.714% PS, and 0.714% LiPO2F2.

[0271] Comparative Example 11 (Single Injection)

[0272] This comparative example is basically the same as Example 3, except that:

[0273] The electrolyte in this comparative example comprises the following components by mass percentage: polymeric monomer compound T3 2.5%, comonomer compound P1 1%, initiator AIBN 0.175%, 0.5% VC, 1% FEC, 1% DTD, 0.5% PS, 0.5% LiPO2F2, with the balance being electrolyte and solvent. The electrolyte is LiPF6, with a concentration of 1M in the electrolyte solution; the solvent is a mixture of EC, PC, DEC, and EMC in a mass ratio of 5:20:15:60.

[0274] The electrolyte was prepared by mixing the electrolyte, solvent, polymerizing monomer, initiator, VC, FEC, DTD, PS, and LiPO2F2 in a glove box to obtain the electrolyte of this comparative example.

[0275] In the preparation method of semi-solid lithium-ion batteries:

[0276] Step 5) involves injecting the electrolyte of this comparative example into the dry cell containing the electrolyte, then sealing it, and then letting it stand at room temperature (25°C) for 48 hours, followed by standing at 50°C for 5 hours. Finally, after formation and capacity testing, the battery of this comparative example is obtained.

[0277] II. Performance Testing

[0278] 1. Electrochemical testing

[0279] (1) Room temperature DCR test

[0280] The batteries prepared in each embodiment or comparative example were placed in a 25°C constant temperature oven and the discharge capacity Ci was extracted using a 1CC / 1DC method. After being fully charged with 1CC, they were discharged at 1Ci for 30 minutes until reaching 50% SOC. Then, they were discharged at 4Ci for 30 seconds, and the discharge rate (DCR) for 30 seconds was calculated. Here, CC represents the charge rate, DC represents the discharge rate, and Ci in 1Ci also represents the discharge capacity.

[0281] (2) Rate Discharge Test

[0282] In a constant temperature oven at 25°C, the batteries prepared in each embodiment or comparative example were charged to 4.25V (0.05C cutoff) using a 1C constant current and constant voltage method, and then discharged to 2.75V using a 1C constant current method to obtain C0; then, they were charged to 4.25V using a 1C current and constant voltage method, and then discharged to 2.75V using a 3C constant current method to obtain C1. C1 / C0*100% is the discharge capacity at the 3C rate.

[0283] (3) 25℃ Cyclic Test

[0284] In a constant temperature oven at 25°C, the batteries prepared in each example or comparative example were subjected to charge-discharge tests at a current of 0.5CC / 1DC under conditions of 2.75-4.25V. After 500 cycles, the battery capacity retention rate was recorded.

[0285] (4) 45℃ Cyclic Test

[0286] In a constant temperature oven at 45°C, the batteries prepared in each example or comparative example were subjected to charge-discharge tests at a current of 0.5CC / 1DC under conditions of 2.75-4.25V. After 500 cycles, the battery capacity retention rate was recorded.

[0287] 2. Battery thermal chamber safety test

[0288] The batteries prepared in each embodiment or comparative example were charged to 4.25V (0.05C cutoff) using a constant current and constant voltage method at 1C, and then placed in a test chamber. The test chamber was heated at a rate of 5℃ / min to 130℃ and held for 30 minutes. The changes in battery surface temperature and voltage were recorded. If the battery did not catch fire, explode, or leak, the hot chamber test was considered passed. Three batteries were tested in each group, and the pass rate of the hot chamber test was recorded.

[0289] In a constant-temperature oven at 25°C, the batteries prepared in each example or comparative example were charged to 4.25V (0.05C cutoff) using a 1C constant-current and constant-voltage method, and then discharged to 2.75V using a 1C constant-current method to obtain C0. They were then charged to 4.25V using a 1C constant-current and constant-voltage method, and then discharged at 1C0 for 6 minutes to obtain a battery with 90% SOC. The batteries were placed in a test chamber, and the test chamber was heated to 150°C at a heating rate of 5°C / min, and held for 30 minutes. The changes in battery surface temperature and voltage were recorded. If the battery did not catch fire, explode, or leak, the hot chamber test was considered passed. Three batteries were prepared for each group, and the pass rate of the hot chamber test was recorded.

[0290] The electrochemical and safety performance test results of each embodiment and comparative example are shown in Table 4.

[0291] Table 4. Electrochemical and safety performance test results of each example and comparative example.

[0292]

[0293]

[0294] Note: The concentration of the second solution in Comparative Example 8 was too high, making it difficult to inject.

[0295] Electrochemical performance test results show:

[0296] (1) Comparing Examples 1-13, 28 with Comparative Examples 2, 3, 4, 8, it can be found that using a single polymer monomer or insufficient comonomer can easily lead to an increase in battery DCR, a significant deterioration in rate performance, and a certain impact on cycle performance.

[0297] (2) Comparison of Example 3 with Comparative Examples 7 and 8 shows that the amount of polymerized monomer needs to be controlled within a certain range. Too much monomer will cause the electrolyte viscosity to increase and the lithium salt solubility to decrease.

[0298] (3) Comparing Example 3 with Example 13 and Comparative Example 10, it was found that too much comonomer is not beneficial to high temperature performance and rate discharge performance.

[0299] The results of the hot box experiment show that:

[0300] (1) The comparison between the examples and Comparative Example 1 shows that the polymer monomers disclosed in this application can improve the thermal box safety of the battery.

[0301] (2) Compared with Comparative Examples 2-7 and 10, it is shown that the monomers that ensure the improvement of battery safety are mainly polymeric monomers, while copolymeric monomers do not improve safety. Moreover, too little polymeric monomer (Comparative Example 7) cannot guarantee safety well.

[0302] Comparative Examples 3, 28 and 11 show that using polymerizable monomers to achieve in-situ polymerization, combined with a two-injection method, allows polymerization to occur after formation. Compared with a one-injection method, this can significantly reduce DCR and improve rate performance.

[0303] In summary, this application discloses an in-situ curing scheme and a semi-solid-state battery prepared using this scheme. This scheme improves battery safety without degrading the cell's kinetic performance through the interaction of polymeric monomers and comonomers. Furthermore, by employing a stepwise liquid injection method, it further reduces DCR, providing a new approach to enhancing the safety of highly active positive and negative electrodes.

[0304] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0305] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order, or primary and secondary relationship of the indicated technical features.

[0306] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0307] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0308] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), and similarly, "multiple groups" refers to two or more (including two groups).

[0309] All embodiments of this application can be executed individually or in combination with other embodiments, and are all considered to be within the scope of protection claimed by this application.

Claims

1. An electrolyte, characterized in that, The solution comprises a first solution and a second solution. The first solution comprises a first electrolyte, a first solvent, a polymerizing monomer, a comonomer, and an initiator. The polymerizing monomer comprises at least one compound having the structure shown in Formula I. In formula I, ○ indicates a central group, which is selected from heterocyclic groups or linear groups; R1, R2...Rn are each independently selected from one of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, saturated or unsaturated carboxylic acid ester, saturated or unsaturated amide, saturated or unsaturated isocyanate, alkoxy, alkenyloxy, alkynyloxy, saturated or unsaturated acyl, and at least two of R1, R2...Rn contain carbon-carbon double or carbon-carbon triple bonds, where n is an integer from 2 to 6; The comonomer includes alkali metal salts containing unsaturated bonds.

2. The electrolyte according to claim 1, characterized in that, The heterocyclic group is selected from one of nitrogen-containing C2-5 heterocyclic groups, oxygen-containing C2-5 heterocyclic groups, and sulfur-containing C2-5 heterocyclic groups; and / or, The linear group is selected from one of the following: monatomic, C1-6 alkyl, C1-6 alkoxy, phosphate ester, phosphite ester, sulfonate ester, and borate ester; and / or, R1, R2...Rn are each independently selected from one of the following: substituted or unsubstituted C1-6 alkyl, substituted or unsubstituted C2-5 alkenyl, substituted or unsubstituted C2-5 alkynyl, saturated or unsaturated C1-6 carboxylic acid ester, saturated or unsaturated C1-6 amide, saturated or unsaturated C1-6 isocyanate, C1-6 alkoxy, C2-6 alkenoxy, C2-6 alkynoxy, and saturated or unsaturated C1-6 acyl; and / or, The substituents in the substituted alkyl, substituted alkenyl, and substituted alkynyl groups all include at least one of halogen atoms, cyano groups, and phenyl groups.

3. The electrolyte according to claim 2, characterized in that, The heterocyclic group is selected from one of the following structures: And / or, The single atom includes one of nitrogen, carbon, silicon, phosphorus, and boron atoms; and / or, R1, R2…R n Each is independently selected from one of the following: unsubstituted C2-5 alkenyl, unsubstituted C2-5 alkynyl, unsaturated C1-6 amide, C2-6 alkenoxy, C2-6 alkynoxy, unsaturated C1-6 acyl, or unsaturated C1-6 carboxylic acid ester.

4. The electrolyte according to claim 3, characterized in that, The linear group is selected from one of the following structures: And / or, R1, R2…R n Each independently selected One of them.

5. The electrolyte according to claim 1, characterized in that, The compound having the structure shown in Formula I includes at least one of compounds T1-T9:

6. The electrolyte according to claim 1, characterized in that, The alkali metal salt containing unsaturated bonds includes at least one of the following: compounds having the structure of Formula II, compounds having the structure of Formula III, and compounds having the structure of Formula IV: Among them, X1, X2, and X6 are each independently selected from one of the C2-6 alkenyl or C2-6 alkynyl groups, X3, X4, and X5 are all F, and Y1, Y2, Y3, and Y4 are each independently selected from one of the alkali metals.

7. The electrolyte according to claim 6, characterized in that, X1, X2, and X6 are each independently selected from one of the C2-6 alkenyl groups, and Y1, Y2, Y3, and Y4 are each independently selected from one of lithium and sodium.

8. The electrolyte according to claim 7, characterized in that, The alkali metal salt containing unsaturated bonds includes at least one of compounds P1-P5: 。 9. The electrolyte according to claim 1, characterized in that, The compound having the structure shown in Formula I has a mass content of a in the electrolyte, and the alkali metal salt containing unsaturated bonds has a mass content of b in the electrolyte, wherein a and b satisfy: 1≤a+b≤10; and / or, 1 / 5 ≤ a / b ≤ 10.

10. The electrolyte according to claim 1, characterized in that, The compound having the structure shown in Formula I and the alkali metal salt containing unsaturated bonds form a gel polymer under the action of the initiator, and the gel polymer has the polymer structure shown in Formula V: In formula V, Y is an alkali metal.

11. The electrolyte according to claim 1, characterized in that, The first solution accounts for 5-30% of the total mass of the electrolyte; and / or, The first electrolyte includes at least one alkali metal salt; and / or, The concentration of the first electrolyte in the electrolyte solution is 0.5-1.4 mol / L; The first solvent comprises at least one of carbonates, carboxylic esters, fluorocarbonates, and fluorocarboxylic esters; and / or, the initiator comprises at least one of azobisisobutyronitrile and benzoyl peroxide; and / or, The initiator has a mass content of 0.1-0.3% in the electrolyte.

12. The electrolyte according to any one of claims 1 to 11, characterized in that, The second solution comprises a second electrolyte, a second solvent, and an additive, wherein the additive comprises at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, 1,3-propanesulfonate lactone, lithium difluorobis(oxalato) phosphate, lithium difluoro(oxalato) borate, ethylene carbonate, 1,3-propenesulfonate lactone, methylene disulfonate, vinyl sulfate, tetravinylsilane, and lithium difluorophosphate.

13. The electrolyte according to claim 12, characterized in that, The second electrolyte may be the same as or different from the first electrolyte; the second solvent may be the same as or different from the first solvent; and / or, The concentration of the second electrolyte in the electrolyte solution is 0.5-1.4 mol / L; The additive has a mass content of 2.5-4.5% in the electrolyte.

14. A semi-solid-state secondary battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The electrolyte includes the electrolyte as described in any one of claims 1 to 13.

15. A method for preparing a semi-solid-state secondary battery as described in claim 14, characterized in that, include: The second solution is injected into the dry cell containing the electrolyte to be injected, and then the cells are formed to obtain a cell after one injection. The first solution is injected into the battery after the first injection, followed by a first settling and a second settling to obtain the semi-solid secondary battery. The temperature of the second settling period is higher than that of the first settling period.

16. The preparation method according to claim 15, characterized in that, The first settling temperature is room temperature; and / or, The first settling time is 48-72 hours; and / or, The second settling temperature is 40-80℃; and / or, The second settling time is 4-48 hours; and / or, The method for preparing the semi-solid secondary battery further includes a third settling step of placing the dry cell containing the second solution into a stand before the formation; the temperature of the third settling is 20-30°C, and the time of the third settling is 24-48h.

17. An electrical appliance, characterized in that, This includes the semi-solid secondary battery as described in claim 14 or the semi-solid secondary battery prepared by the preparation method as described in claim 15 or 16.

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