Additive composition, electrode plate and secondary battery

Abstract

The invention relates to the technical field of batteries, in particular to an additive composition, an electrode plate and a secondary battery, and the additive composition comprises a plasticizer; the plasticizer comprises a phosphorus-containing compound modified by a bridging agent; the phosphorus-containing compound comprises a compound as shown in a formula I and / or a formula II; the electrode plate formed by the additive composition has high compaction density, can improve the energy density of the secondary battery, and improves the cycle performance of the secondary battery. # imgabs0 #

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to an additive composition, an electrode plate and a secondary battery. Background Art

[0002] Secondary batteries are a type of clean energy with excellent performance. In recent years, with the advancement of science and technology, people's demand for secondary batteries has increased, and their requirements for performance have also become higher and higher.

[0003] In the prior art, the active materials of secondary batteries are easily broken when forming electrode plates, and the electrode plates are highly brittle, making it difficult for the active materials to be compacted. Therefore, the compaction density of the electrode plates of secondary batteries is low, resulting in poor cycle performance of the secondary batteries.

[0004] Therefore, it is crucial to develop an additive for electrode plates that can overcome the above-mentioned defects. Summary of the invention

[0005] In view of the above problems, the present application provides an additive composition, an electrode plate and a secondary battery. The electrode plate formed by the additive composition has a high compaction density, which can increase the energy density of the secondary battery and improve the cycle performance of the secondary battery.

[0006] [Additive composition]

[0007] The present application provides an additive composition, the additive composition comprising a plasticizer;

[0008] The plasticizer includes a phosphorus-containing compound modified by a bridging agent;

[0009] The phosphorus-containing compound includes compounds represented by formula I and / or formula II;

[0010]

[0011] Among them, R1, R2, R1 ′ , R2 ′ , R4, R5, R4 ′ and R5 ′ Each is independently selected from hydroxyl, substituted or unsubstituted C1-C40 (e.g., C2, C5, C10, C15, C20, C25, C30, C35, etc.) alkyl, substituted or unsubstituted polyoxyalkylene ether group;

[0012] R3 and R6 are each independently selected from a single bond, a substituted or unsubstituted C1-C40 (e.g., C2, C5, C10, C15, C20, C25, C30, C35, etc.) alkylene group, a substituted or unsubstituted polyoxyalkylene ether group;

[0013] m and n are each independently selected from 0 or 1;

[0014] L1 and L2 are each independently selected from a single bond, hydrogen, hydroxyl, substituted or unsubstituted C1-C40 (e.g., C2, C5, C10, C15, C20, C25, C30, C35, etc.) alkyl, substituted or unsubstituted C6-C12 (e.g., C7, C8, C9, C10, C11, etc.) aryl, substituted or unsubstituted C1-C40 (e.g., C2, C5, C10, C15, C20, C25, C30, C35, etc.) C0, C25, C30, C35, etc.) heteroalkyl, substituted or unsubstituted C1-C40 (e.g., C2, C5, C10, C15, C20, C25, C30, C35, etc.) alkylene, substituted or unsubstituted C6-C12 arylene, substituted or unsubstituted C1-C40 (e.g., C2, C5, C10, C15, C20, C25, C30, C35, etc.) heteroalkylene;

[0015] R1, R2 and L1 are not hydroxyl groups at the same time, and R4, R5 and L2 are not hydroxyl groups at the same time;

[0016] The substituent is selected from hydroxyl, amino, carboxyl, ester, amide, C1-C6 alkyl, and C6-C12 aryl.

[0017] In the present application, when m=0, L1 is selected from hydrogen, hydroxyl, substituted or unsubstituted C1-C40 alkyl, substituted or unsubstituted C6-C12 aryl, substituted or unsubstituted C1-C40 heteroalkyl; when m=1, L1 is selected from single bond, substituted or unsubstituted C1-C40 alkylene, substituted or unsubstituted C6-C12 arylene, substituted or unsubstituted C1-C40 heteroalkylene. When n=0 or 1, L2 has similar selection. The reason for the above setting is to meet the compound valence rule.

[0018] In the present application, C1~C40 alkyl refers to an alkyl group with 1 to 40 carbon atoms, such as C2, C5, C10, C15, C20, C25, C30, C35, etc., and other similar expressions are the same.

[0019] The polyoxyalkylene ether group refers to a divalent group formed by removing a hydrogen atom from the polyoxyalkylene ether group described in the present application.

[0020] Heteroalkyl refers to an alkyl group containing a heteroatom, and the heteroatom can be selected from oxygen atom, sulfur atom, nitrogen atom and the like.

[0021] When the aforementioned alkyl group contains an oxygen atom, it may be an alkoxy group.

[0022] In the technical solution of the implementation mode of the present application, the plasticizer includes a phosphorus-containing compound modified by a bridging agent, which can form a three-dimensional ionic network structure, improve the uniformity of the distribution of the main materials (such as active materials, conductive agents and binders, etc.) in the electrode plate, reduce the friction between the active materials, and improve the problem of active materials being damaged during the process of forming the electrode plate; moreover, the additive composition can improve the toughness of the electrode plate, therefore, the electrode plate formed by the additive composition has a high compaction density, which can improve the energy density of the secondary battery and improve the cycle performance of the secondary battery.

[0023] In some embodiments, R1, R2, R1 ′ , R2 ′ , R4, R5, R4 ′ and R5 ′ Each is independently selected from substituted or unsubstituted polyoxyalkylene ether groups.

[0024] In the technical solution of the implementation mode of the present application, the polyoxyalkylene ether group has a high affinity with the solvent and the surface of the main material, and can quickly infiltrate the surface of the main material particles with the help of the solvent. After drying, it can also assist other additives such as plasticizers to form a uniform coating on the surface of the main material particles.

[0025] In some embodiments, R1, R2, R1 ′ , R2 ′ , R4, R5, R4 ′ and R5 ′ Each independently contains 6 to 36 (e.g., 8, 10, 15, 20, 25, 30, 35, etc.) carbon atoms, more preferably 6 to 18 carbon atoms.

[0026] In some embodiments, the R3 and R6 are each independently selected from a single bond, a substituted or unsubstituted polyoxyalkylene ether group.

[0027] In some embodiments, R3 and R6 each independently contain 6-36 (e.g., 8, 10, 15, 20, 25, 30, 35, etc.) carbon atoms, more preferably 6 to 18 carbon atoms.

[0028] In some embodiments, L1 and L2 are each independently selected from a single bond, hydrogen, hydroxyl, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted phenyl, substituted or unsubstituted C1-C6 heteroalkyl, substituted or unsubstituted C1-C6 alkylene, substituted or unsubstituted phenylene, substituted or unsubstituted C1-C6 heteroalkylene.

[0029] In some embodiments, the polyoxyalkylene ether group includes any one of a fatty alcohol polyoxyalkylene ether group, a fatty amine polyoxyalkylene ether group, a fatty acid ester polyoxyalkylene ether group, or a fatty amide polyoxyalkylene ether group, or a combination of at least two of them.

[0030] In the present application, the polyoxyalkylene ether group is derived from a polyoxyalkylene ether containing a terminal hydroxyl substituent, and the polyoxyalkylene ether containing a terminal hydroxyl substituent is usually prepared from aliphatic hydrocarbons, fatty amines, fatty acid esters, fatty amides, etc. containing hydroxyl substituents as starting reactants, and then alkoxylated (such as ethoxylated, propoxylated, etc.) by reaction with epoxy hydrocarbons, and after reaching the designed molecular weight, a capping agent is added to obtain the polyoxyalkylene ether.

[0031] In some embodiments, the polyoxyalkylene ether group includes any one of -CH2CH2O-, -CH2CH2CH2O-, -CH2CH(CH3)O-, -CH2CH2CH2CH2O-, -CH(CH3)CH2CH2O-, -CH2CH(CH3)CH2O-, -CH2CH(CH3)CH2O-, or a combination of at least two of them.

[0032] As an example, the structural formula of the polyoxyalkylene ether group is as follows:

[0033] -(CH2CH2O) a (CH2CH2CH2O) b (CH2CHCH3O) c -(CH2CH2CH2CH2O) d -(CH(CH3)CH2CH2O) e -、-(CH2CH(CH3)CH2O) f 、-(CH2CH2CH(CH3)O) g -R7, -CH2CH2O-, -CH2CH2CH2O-, -CH2CHCH3O-, -CH2CH2CH2CH2O-, -CH(CH3)CH2CH2O-, -CH2CH(CH3)CH2O-, -CH2CH2CH(CH3)O- seven structural units are connected in any order;

[0034] R7 is selected from hydrogen, substituted or unsubstituted C1-C40 (e.g., C2, C5, C10, C15, C20, C25, C30, C35, etc.) alkyl, substituted or unsubstituted C1-C40 (e.g., C2, C5, C10, C15, C20, C25, C30, C35, etc.) alkoxy, substituted or unsubstituted C2-C24 (e.g., C2, C5, C10, C15, C20, C25, C30, C35, etc.) alkoxycarbonyl, substituted or unsubstituted C2-C36 (e.g., C2, C5, C10, C15, C20, C25, C30, C35, etc.) C15, C20, C25, C30, C35, etc.) ester group, substituted or unsubstituted C2-C36 (e.g., C2, C5, C10, C15, C20, C25, C30, C35, etc.) amide group, substituted or unsubstituted C1-C18 (e.g., C2, C4, C6, C8, C10, C12, C14, C16, etc.) monoalkylamine group, substituted or unsubstituted C2-C36 (e.g., C5, C10, C15, C20, C25, C30, C35, etc.) dialkylamine group;

[0035] a, b, c, d, e, f, and g are each independently selected from an integer of 0-200 (e.g., 2, 5, 10, 20, 40, 60, 80, 100, 120, 140, 160, 180, etc.), and a, b, c, d, e, f, and g are not 0 at the same time.

[0036] The alkoxycarbonyl group is represented by -OC(=O)-R', wherein R' is an alkyl group as described herein.

[0037] The ester group is represented by -C(=O)-OR', wherein R' is an alkyl group or an aryl group as described in the present application.

[0038] The amide group is represented by -C(=O)-NH-R', -S(=O)2-NR'R", wherein R', R" are alkyl, alkoxy or aryl groups as described in the present application.

[0039] A monoalkylamine group is represented by -NH-R', wherein R' is an alkyl group as described herein.

[0040] The dialkylamine group is represented by -NR'R", wherein R' and R" are alkyl groups as described herein.

[0041] In some embodiments, the number average molecular weight of the polyoxyalkylene ether group is 200-4000 g / mol, for example, 500 g / mol, 1000 g / mol, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, 3500 g / mol, etc.

[0042] As an example, the phosphorus-containing compound includes at least one of the following compounds:

[0043]

[0044] In some embodiments, the bridging agent comprises a fatty amine.

[0045] In the technical solution of the implementation mode of the present application, the bridging agent is preferably a fatty amine, which has the advantages of fast reaction speed, high efficiency and good bridging stability compared with other bridging agents.

[0046] In some embodiments, the functionality of the fatty amine is ≥ 2, such as 3, 4, 5, etc.

[0047] In some embodiments, the bridging agent includes any one of hexamethylenediamine, decanediamine, N,N,N',N'-tetraethylethylenediamine, N,N,N',N'-tetramethyldecanediamine, piperazine, N,N'-dimethylpiperazine, 1,4-diazabicyclo[2.2.2]octane, diethylenetriamine, triethylenetetramine or polyethyleneimine, or a combination of at least two thereof.

[0048] In some embodiments, the mass ratio of the phosphorus-containing compound to the bridging agent is (9-99):1, wherein 9-99 can be 10, 20, 30, 40, 50, 60, 70, 80, 90, etc.

[0049] In the technical solution of the embodiment of the present application, the mass ratio of the phosphorus-containing compound to the bridging agent is within the above range. The reason is that if the mass ratio of the two is too high, the content of the bridging agent in the additive composition will be too low, and the phosphorus-containing compound cannot be effectively bridged, which is not conducive to the improvement of the electrode performance of the additive composition; if the mass ratio of the two is too low, the content of the bridging agent in the additive composition will be too high, causing the additive composition to produce a cross-linked gel, which loses the inherent properties of the plasticizer. In some embodiments, the additive composition also includes a pH regulator.

[0050] In some embodiments, the pH adjuster includes any one or a combination of at least two of ammonia, tetramethylammonium hydroxide, amino alcohol, monofunctional higher fatty amine or alkali metal hydroxide.

[0051] In the present application, the monofunctional amine refers to a compound containing only one N atom, and illustratively may be a primary amine, a secondary amine, or a tertiary amine.

[0052] In the technical solution of the implementation mode of the present application, the pH regulator, on the one hand, adjusts the pH value of the system within the required range, and on the other hand, cooperates with the plasticizer to interact with the phosphorus-containing sites of the plasticizer, and uses the phosphorus-containing sites to stabilize the overall charge distribution of the plasticizer, so that the additive composition can be effectively dispersed and attached to the surface of the main material with the same charge, thereby increasing the compaction density of the electrode plate formed by the additive composition, thereby increasing the energy density of the secondary battery and improving the cycle performance of the secondary battery.

[0053] In some embodiments, the amino alcohol has 1 to 6 carbon atoms, such as 2, 3, 4, 5, etc.

[0054] In some embodiments, the amino alcohol includes any one of ethanolamine, diethanolamine, triethanolamine, 3-aminopropanol, 1-amino-2-propanol, 2-amino-1-propanol, 1-amino-2-methyl-2-propanol, 2-amino-2-methyl-propanol, 2-(methylamino)ethanol, N,N-dimethylethanolamine, N-methyldiethanolamine, bis(2-hydroxypropyl)amine, tris(2-hydroxypropyl)amine or 2-amino-1-butanol, or a combination of at least two thereof.

[0055] In some embodiments, the monofunctional higher fatty amine has the structural formula N(R8)(R9)(R 10 ).

[0056] Among them, R8, R9, R 10 Each is independently selected from hydrogen or C8-C36 (e.g., C10, C15, C20, C25, C30, C35, etc.) alkyl;

[0057] R8, R9, R 10 Not hydrogen at the same time.

[0058] In some embodiments, the pH value of the additive composition is 3.0 to 11.0, such as 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, etc.

[0059] In the present application, the pH value test method is: adding the additive composition into deionized water to obtain an aqueous solution with a concentration of 10 wt %, and testing the solution using a pH meter.

[0060] In the technical solution of the implementation mode of the present application, the pH value of the additive composition is within the above range. The reason is that too high or too low pH value of the additive composition will lead to instability of the electrode slurry, resulting in uneven coating and dark marks, affecting the quality of the electrode plate.

[0061] In some embodiments, the additive composition further includes a dispersant and / or a solvent.

[0062] In some embodiments, the dispersant includes polyvinyl pyrrolidone and / or a derivative of polyvinyl pyrrolidone.

[0063] In some embodiments, the derivative of polyvinyl pyrrolidone includes a copolymer of N-vinyl pyrrolidone and a monomer containing an unsaturated double bond.

[0064] In some embodiments, the monomer containing an unsaturated double bond includes any one of acrylonitrile monomers, acrylic acid monomers, acrylamide monomers, acrylate monomers, aromatic vinyl monomers, N-vinyl caprolactam or vinyl methyl oxazolidinone, or a combination of at least two thereof.

[0065] In some embodiments, the acrylic monomer includes any one or a combination of at least two of acrylic acid, methacrylic acid, maleic acid, or itaconic acid.

[0066] In some embodiments, the acrylonitrile monomer includes acrylonitrile and / or methacrylonitrile.

[0067] In some embodiments, the acrylamide monomer includes any one of acrylamide, N-methylacrylamide, N-ethylacrylamide, N-butylacrylamide, 2-methylacrylamide, diacetoneacrylamide, N-methoxymethylacrylamide, N-isopropyloxymethylacrylamide, N-hydroxymethylacrylamide, N-hydroxyethylacrylamide, N-butoxymethylacrylamide, N-isobutyloxymethylacrylamide, N-octyloxymethylacrylamide or N-carboxymethoxymethylacrylamide, or a combination of at least two thereof.

[0068] In some embodiments, the acrylic acid ester monomer includes methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-pentyl acrylate, isopentyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate; any one of methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, octadecyl acrylate, hydroxyethyl acrylate or hydroxypropyl acrylate, or a combination of at least two thereof.

[0069] In some embodiments, the aromatic vinyl monomer includes any one or a combination of at least two of styrene, α-methylstyrene, tert-butylstyrene, vinylanthracene, vinylanthraquinone, vinylpyridine, vinylimidazole or vinylcarbazole.

[0070] In some embodiments, the mass ratio of the plasticizer to the dispersant is (1.5-9):1, wherein 1.5-9 can be 2, 3, 4, 5, 6, 7, 8, etc.

[0071] In some embodiments, the solvent includes any one or a combination of at least two of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, toluene, xylene, tetrahydrofuran, dioxane or water.

[0072] [Preparation of Additive Composition]

[0073] In some embodiments, the method for preparing the additive composition described in the present application comprises the following steps:

[0074] The plasticizer and the pH adjuster are mixed to obtain the additive composition.

[0075] In some embodiments, the mixed raw materials further include a dispersant and / or a solvent.

[0076] In some embodiments, the method for preparing the plasticizer comprises the following steps:

[0077] The phosphorus-containing compound and the bridging agent are mixed and reacted at 20° C. to 60° C. for 2 hours to obtain the plasticizer.

[0078] In some embodiments, the preparation of the phosphorus-containing compound is carried out by a method commonly used in the art, for example, a phosphating agent is used to react with different proportions of C1-C40 alkyl groups containing terminal hydroxyl substituents and polyoxyalkylene ethers containing terminal hydroxyl substituents. The phosphating agent generally includes phosphoric acid, phosphorus pentoxide, polyphosphoric acid, pyrophosphoric acid, etc.; the polyoxyalkylene ethers containing terminal hydroxyl substituents are generally prepared from aliphatic hydrocarbons, fatty amines, fatty acid esters, and fatty amides containing hydroxyl substituents as starting reactants, and then alkoxylated (such as ethoxylation, propoxylation, etc.) by reacting with epoxy hydrocarbons, and after reaching the designed molecular weight, a capping agent is added to obtain the compound.

[0079] [Electrode Plate]

[0080] The present application provides an electrode plate, wherein the electrode plate comprises the additive composition.

[0081] In the present application, the electrode plate includes a positive electrode plate or a negative electrode plate.

[0082] As an example, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector (such as aluminum foil, etc.). The positive electrode film layer includes a positive electrode active material (such as lithium iron phosphate, etc.), a conductive agent (such as carbon black, carbon nanotubes, etc.) and a binder (such as polytetrafluoroethylene, polyvinylidene fluoride, etc.), and optionally, the above-mentioned additive composition is also included. The present application does not limit the types of positive electrode active materials, conductive agents and binders, and well-known materials can be selected.

[0083] As an example, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector (such as copper foil, etc.). The negative electrode film layer includes a negative electrode active material (such as graphite, etc.), a conductive agent (such as carbon black, carbon nanotubes, etc.) and a binder (such as polytetrafluoroethylene, polyvinylidene fluoride, etc.), and optionally, the above-mentioned additive composition is also included. The present application does not limit the types of negative electrode active materials, conductive agents and binders, and well-known materials can be selected.

[0084] The additive composition is disposed in the positive electrode film layer and / or the negative electrode film layer.

[0085] In some embodiments, based on the total mass of the electrode sheet film layer as 100%, the mass of the non-volatile component in the additive composition is 0.01%-0.5%, such as 0.1%, 0.2%, 0.3%, 0.4%, etc. The above mass relationship refers to the component in the additive composition that does not volatilize after forming the electrode sheet.

[0086] [Secondary battery]

[0087] The present application provides a secondary battery, which includes the additive composition or the electrode plate.

[0088] In the present application, the secondary battery can be a lithium ion battery, a sodium ion battery, a sodium lithium ion battery, a lithium metal battery, a sodium metal battery, a lithium sulfur battery, a magnesium ion battery, a nickel hydrogen battery, a nickel cadmium battery, a lead storage battery, etc., and the embodiments of the present application are not limited to this.

[0089] As an example, the secondary battery includes a positive electrode plate, a separator, a negative electrode plate and an electrolyte. The present application does not limit the types of the separator and the electrolyte, and any known material can be selected.

[0090] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. DETAILED DESCRIPTION

[0091] The following is a detailed description of the embodiments of the technical solution of the present application. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0092] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the description and claims of this application and any variations thereof are intended to cover non-exclusive inclusions.

[0093] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0094] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0095] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "2-10" means that all real numbers between "2-10" are listed in this document, and "2-10" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0096] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0097] Example 1

[0098] Additive composition:

[0099] (1) Add 95 g of phosphorus-containing compound 1 and 95 g of solvent N-methylpyrrolidone into a 500 mL three-necked flask and stir thoroughly to dissolve to form a uniform clear solution;

[0100] (2) heating to 40° C., adding 5 g of a bridging agent, decanediamine, and stirring the mixture for 2 h to form plasticizer 1;

[0101] (3) The system was cooled to room temperature, and tetramethylammonium hydroxide, a pH adjuster, was added until the pH value of the system was 6.9, thereby obtaining the additive composition.

[0102] Positive electrode:

[0103] (1) In parts by weight, 95.5 parts of lithium iron phosphate (Hunan Yuneng New Energy Battery Materials Co., Ltd., model Y9C), 1.5 parts of conductive carbon black Super P, 0.5 parts of conductive carbon nanotubes (Tian Nai Technology, model LB156), and 2.5 parts of binder polyvinylidene fluoride (US Solvay, model PVDF5130) were added to N-methylpyrrolidone at a total solid content of 68% (solid components are lithium iron phosphate, conductive carbon black Super P, conductive carbon nanotubes and binder PVDF) to prepare a slurry matrix, and then the additive composition prepared in each embodiment and comparative example was added to the slurry matrix at a total solid content of 0.2% by weight, and mixed evenly using a double planetary mixer to obtain an electrode slurry;

[0104] (2) After the uniformly dispersed electrode slurry is passed through a 100-mesh sieve, it is coated on an aluminum foil with a thickness of 12 μm using an electric scraper with adjustable height, dried in an oven at 120°C, and then heated at room temperature at 1×10 4 The positive electrode sheet is rolled by a unit length load of N / m.

[0105] Negative electrode sheet: The negative electrode active material graphite, conductive carbon black Super P, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are fully stirred and mixed in a deionized water solvent at a mass ratio of 96.5:1.0:1.0:1.5 to form a uniform negative electrode slurry, which is coated on the negative electrode current collector copper foil, dried and roll-pressed at 80°C to obtain a negative electrode sheet.

[0106] Secondary battery: The positive electrode sheet, PP separator, and negative electrode sheet are stacked in order to obtain a battery cell. The electrolyte (the volume ratio of EC:EMC:DEC is 1:1:1 (1.0M lithium salt)) is injected, and the secondary battery is prepared through processes such as tableting, shelving, and formation.

[0107] Example 2-14

[0108] Except for the parameters in Table 1, a secondary battery was prepared according to the method of Example 1.

[0109] Table 1: Components of the additive composition

[0110]

[0111]

[0112] In the table, “——” refers to items not involved; polyvinyl pyrrolidone was purchased from BASF with the brand name K30; the copolymer of N-vinyl pyrrolidone and methacrylic acid was synthesized using the commonly used method in the technical field, such as mixing N-vinyl pyrrolidone and methacrylic acid and adding an initiator to react.

[0113] The structural formula and preparation method of the phosphorus-containing compound 1 in Example 1 of the present application are as follows:

[0114] Phosphorus compounds 1:

[0115] Preparation method: Add 54mmol methoxypolyethylene glycol (HO(CH2CH2O) 12 CH3), add 30mL toluene, stir and dissolve to form a uniform solution. Then add 33mmol pyrophosphoric acid and stir at 25°C for 3 days. Add ether to the reaction mixture for extraction, wash the ether layer with water, and then separate the ether layer. After drying and removing the ether, the phosphorus-containing compound 1 is obtained as a light yellow oily liquid.

[0116] The structural formulas of the phosphorus-containing compounds 1 to 9 in Examples 2 to 14 of the present application are as follows:

[0117] Phosphorus compounds 2:

[0118] Phosphorus compounds 3:

[0119] Phosphorus compounds 4:

[0120] Phosphorus compounds 5:

[0121] Phosphorus compounds 6:

[0122] Phosphorus compounds 7:

[0123] Phosphorus compounds 8:

[0124] Phosphorus compounds 9:

[0125] Comparative Example 1

[0126] The difference between this comparative example and Example 1 is that the positive electrode plate does not include the additive composition, and the rest is the same as Example 1.

[0127] Comparative Example 2

[0128] The difference between this comparative example and Example 1 is that the plasticizer does not include a bridging agent, and the rest is the same as Example 1.

[0129] [Performance test]

[0130] (1) Compacted density: 30 small discs with an area of ​​S were cut from the positive electrode sheet, and their average weight m1 and average thickness H1 were measured; 30 small discs with an area of ​​S were cut from the aluminum foil, and their average weight m0 and average thickness H0 were measured. The compacted density of the electrode sheet was calculated using the following formula:

[0131] Compacted density = (m1-m0) / ((H1-H0)×S).

[0132] (2) Cycle performance: At 25°C, the secondary battery prepared as above was charged to 4.2V at a constant current of 0.33C, then charged to a cutoff current of 0.02C at a constant voltage, left for 5 min, discharged to 2.5V at 0.33C, left for 5 min, and the discharge capacity after the first cycle was recorded. Again, the battery was charged to 4.2V at a constant current of 0.33C, then charged to a cutoff current of 0.02C at a constant voltage, left for 5 min, discharged to 2.5V at 0.33C, left for 5 min, and the cycle was repeated. After 100 cycles of charge / discharge, the discharge capacity after the 100th cycle was recorded.

[0133] The capacity retention rate of a lithium-ion secondary battery after 100 cycles is calculated using the following formula:

[0134] Capacity retention rate after 100 cycles (%) = discharge capacity after 100th cycle / discharge capacity after first cycle.

[0135] The test results are summarized in Table 2.

[0136] Table 2

[0137]

[0138]

[0139] According to the data in Table 2, the compaction density of the electrode sheet formed by the additive composition described in this application is 2.54 g / cm 3 As mentioned above, the capacity retention rate after 100 cycles is above 88.6%. The electrode plate formed by the additive composition described in the present application has a high compaction density, which can increase the energy density of the secondary battery and improve the cycle performance of the secondary battery.

[0140] Analysis of Comparative Example 1 and Example 1 shows that the performance of Comparative Example 1 is not as good as that of Example 1, which proves that the electrode plate containing the additive composition described in the present application has better performance.

[0141] Analysis of Comparative Example 2 and Example 1 shows that the performance of Comparative Example 2 is not as good as that of Example 1, which proves that the additive composition formed by the plasticizer is more conducive to improving the performance of the electrode plate and the secondary battery.

[0142] Analysis of Examples 11-12 and Example 1 shows that the performance of Examples 11-12 is not as good as that of Example 1, which proves that the performance of the additive composition is better within the pH range.

[0143] Analysis of Example 13 and Example 1 shows that Example 13 is not as good as Example 1, which proves that the additive composition formed by the combination of the plasticizer and the pH adjuster is more conducive to improving the performance of the electrode plate and the secondary battery.

[0144] Analysis of Example 14 and Example 1 shows that Example 14 is not as good as Example 1, which proves that it is better to contain polyoxyalkylene ether group or suboxyalkylene ether group in the structure of the additive composition.

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. An additive composition, characterized in that The additive composition includes a plasticizer; The plasticizer includes a phosphorus-containing compound modified by a bridging agent; The phosphorus-containing compound includes compounds represented by formula I and / or formula II; Among them, R1, R2, R1 ′ , R2 ′ , R4, R5, R4 ′ and R5 ′ Each is independently selected from a hydroxyl group, a substituted or unsubstituted C1-C40 alkyl group, and a substituted or unsubstituted polyoxyalkylene ether group; R3 and R6 are each independently selected from a single bond, a substituted or unsubstituted C1-C40 alkylene group, a substituted or unsubstituted polyoxyalkylene ether group; m and n are each independently selected from 0 or 1; L1 and L2 are each independently selected from a single bond, hydrogen, hydroxyl, substituted or unsubstituted C1-C40 alkyl, substituted or unsubstituted C6-C12 aryl, substituted or unsubstituted C1-C40 heteroalkyl, substituted or unsubstituted C1-C40 alkylene, substituted or unsubstituted C6-C12 arylene, substituted or unsubstituted C1-C40 heteroalkylene; R1, R2 and L1 are not hydroxyl groups at the same time, and R4, R5 and L2 are not hydroxyl groups at the same time; The substituent is selected from hydroxyl, amino, carboxyl, ester, amide, C1-C6 alkyl, and C6-C12 aryl.

2. The additive composition according to claim 1, characterized in that R1, R2, R1 ′ , R2 ′ , R4, R5, R4 ′ and R5 ′ Each independently selected from substituted or unsubstituted polyoxyalkylene ether groups; Preferably, R1, R2, R1 ′ , R2 ′ , R4, R5, R4 ′ and R5 ′ Each independently contains 6 to 36 carbon atoms, more preferably 6 to 18 carbon atoms; Preferably, said R3 and R6 are each independently selected from a single bond, a substituted or unsubstituted polyoxyalkylene ether group; Preferably, R3 and R6 each independently contain 6 to 36 carbon atoms, more preferably 6 to 18 carbon atoms.

3. The additive composition according to claim 1 or 2, characterized in that L1 and L2 are each independently selected from a single bond, hydrogen, hydroxyl, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted phenyl, substituted or unsubstituted C1-C6 heteroalkyl, substituted or unsubstituted C1-C6 alkylene, substituted or unsubstituted phenylene, substituted or unsubstituted C1-C6 heteroalkylene.

4. The additive composition according to any one of claims 1 to 3, characterized in that: The polyoxyalkylene ether group includes any one of a fatty alcohol polyoxyalkylene ether group, a fatty amine polyoxyalkylene ether group, a fatty acid ester polyoxyalkylene ether group or a fatty amide polyoxyalkylene ether group, or a combination of at least two thereof; Preferably, the polyoxyalkylene ether group includes any one of -CH2CH2O-, -CH2CH2CH2O-, -CH2CH(CH3)O-, -CH2CH2CH2CH2O-, -CH(CH3)CH2CH2O-, -CH2CH(CH3)CH2O-, -CH2CH(CH3)CH2O-, or a combination of at least two of them.

5. The additive composition according to any one of claims 1 to 4, characterized in that: The number average molecular weight of the polyoxyalkylene ether group is 200-4000 g / mol.

6. The additive composition according to any one of claims 1 to 5, characterized in that: The bridging agent includes a fatty amine; Preferably, the functionality of the fatty amine is ≥2; Preferably, the bridging agent comprises any one or a combination of at least two of hexamethylenediamine, decanediamine, N,N,N',N'-tetraethylethylenediamine, N,N,N',N'-tetramethyldecanediamine, piperazine, N,N'-dimethylpiperazine, 1,4-diazabicyclo[2.2.2]octane, diethylenetriamine, triethylenetetramine or polyethyleneimine; Preferably, the mass ratio of the phosphorus-containing compound to the bridging agent is (9-99):

1.

7. The additive composition according to any one of claims 1 to 6, characterized in that: The additive composition also includes a pH adjuster; Preferably, the pH adjuster comprises any one or a combination of at least two of ammonia, tetramethylammonium hydroxide, amino alcohol, monofunctional higher fatty amine or alkali metal hydroxide; Preferably, the amino alcohol has 1 to 6 carbon atoms; Preferably, the amino alcohol comprises any one or a combination of at least two of ethanolamine, diethanolamine, triethanolamine, 3-aminopropanol, 1-amino-2-propanol, 2-amino-1-propanol, 1-amino-2-methyl-2-propanol, 2-amino-2-methyl-propanol, 2-(methylamino)ethanol, N,N-dimethylethanolamine, N-methyldiethanolamine, bis(2-hydroxypropyl)amine, tris(2-hydroxypropyl)amine or 2-amino-1-butanol; Preferably, the structural formula of the monofunctional higher fatty amine is N(R8)(R9)(R 10 ); Among them, R8, R9, R 10 Each independently selected from hydrogen or C8-C36 alkyl; R8, R9, R 10 Not at the same time hydrogen; Preferably, the pH value of the additive composition is 3.0-11.

0.

8. The additive composition according to any one of claims 1 to 7, characterized in that: The additive composition also includes a dispersant and / or a solvent; Preferably, the dispersant comprises polyvinyl pyrrolidone and / or a derivative of polyvinyl pyrrolidone; Preferably, the derivative of polyvinyl pyrrolidone comprises a copolymer of N-vinyl pyrrolidone and a monomer containing an unsaturated double bond; Preferably, the monomer containing unsaturated double bonds includes any one or a combination of at least two of acrylonitrile monomers, acrylic acid monomers, acrylamide monomers, acrylate monomers, aromatic vinyl monomers, N-vinyl caprolactam or vinyl methyl oxazolidinone; Preferably, the acrylic monomer includes any one or a combination of at least two of acrylic acid, methacrylic acid, maleic acid or itaconic acid; Preferably, the acrylonitrile monomer includes acrylonitrile and / or methacrylonitrile; Preferably, the acrylamide monomer includes any one of acrylamide, N-methylacrylamide, N-ethylacrylamide, N-butylacrylamide, α-methylacrylamide, diacetoneacrylamide, N-methoxymethylacrylamide, N-isopropyloxymethylacrylamide, N-hydroxymethylacrylamide, N-hydroxyethylacrylamide, N-butoxymethylacrylamide, N-isobutyloxymethylacrylamide, N-octyloxymethylacrylamide or N-carboxymethoxymethylacrylamide, or a combination of at least two thereof; Preferably, the acrylic acid ester monomers include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-pentyl acrylate, isopentyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate; any one or a combination of at least two of methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, octadecyl acrylate, hydroxyethyl acrylate or hydroxypropyl acrylate; Preferably, the aromatic vinyl monomer includes any one or a combination of at least two of styrene, α-methylstyrene, tert-butylstyrene, vinylanthracene, vinylanthraquinone, vinylpyridine, vinylimidazole or vinylcarbazole; Preferably, the mass ratio of the plasticizer to the dispersant is (1.5-9):1; Preferably, the solvent includes any one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, toluene, xylene, tetrahydrofuran, dioxane or water, or a combination of at least two thereof.

9. An electrode plate, characterized in that: The electrode plate comprises the additive composition according to any one of claims 1 to 8.

10. A secondary battery, characterized in that: The secondary battery comprises the additive composition according to any one of claims 1 to 8, or the electrode plate according to claim 9.

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