Wetting agent, negative electrode slurry and secondary battery thereof

Abstract

The invention provides a wetting agent, negative electrode slurry and a secondary battery thereof. The wetting agent comprises a vinyl benzene unit, a vinyl acrylate unit and a vinyl functional unit; the glass transition temperature of the wetting agent is-50 to 30 DEG C; the mass swelling ratio of the wetting agent in the electrolyte is 500%-3000%, and the volume swelling ratio of the wetting agent in the electrolyte is 50%-1000%. The wetting agent provided by the invention has relatively high electrolyte absorption rate and electrolyte retention rate, so that the secondary battery has relatively good cycle performance.

Description

Technical Field

[0001] The invention belongs to the technical field of secondary batteries, and in particular relates to a wetting agent, anode slurry and a secondary battery thereof. Background Art

[0002] Secondary batteries have the advantages of high voltage, high specific energy, stable discharge voltage, good cycle performance, good safety performance and long service life. They are widely used in power vehicles, energy storage and other fields.

[0003] In the current traditional preparation process of negative electrode (or anode) pole pieces, traditional styrene-butadiene rubber (SBR) emulsion and sodium carboxymethyl cellulose (CMC) are used together as dispersion and adhesive. During use, since CMC is a solid dry powder, it must be fully dissolved before use to obtain a uniform solution, which greatly hinders the improvement of production efficiency. In addition, CMC has medium viscosity and high brittleness, and the pole pieces are prone to cracking during charge and discharge. At the same time, the electrolyte with SBR as a binder swells greatly. During the use of the negative electrode cell made of it, due to the repeated expansion and contraction of the volume of the graphite negative electrode and the silicon-based negative electrode during the charge and discharge cycle, the bonding force of the binder drops sharply, causing the negative electrode material to fall off the current collector, resulting in the degradation of the cell performance or even complete failure, especially the degradation of high-temperature storage and high-temperature cycle performance.

[0004] CN 104247109A discloses a lithium ion secondary battery having a positive electrode, a negative electrode, an electrolyte and a separator, wherein the negative electrode comprises a negative electrode active material layer formed by a negative electrode slurry composition, wherein the negative electrode slurry composition comprises a negative electrode binder composition and a negative electrode active material, wherein the negative electrode binder composition comprises a particulate polymer A containing an aliphatic conjugated diene monomer unit, wherein the negative electrode binder composition has a solubility parameter of 8 to 13 (cal / cm 3 ) 1 / 2 The swelling degree of the electrolyte formed by the solvent is 1 to 2 times, and the repeated tensile strength of the negative electrode binder composition after swelling with the electrolyte is 0.5 to 20 Kg / cm at a low elongation modulus of 15%. 2 The positive electrode contains a positive electrode active material layer formed by a positive electrode slurry composition, the positive electrode slurry composition contains a positive electrode binder composition and a positive electrode active material, the positive electrode binder composition includes a particulate polymer B containing an ethylenically unsaturated carboxylic acid monomer unit; a binder with a specified swelling degree and repeated tensile strength, which can inhibit the expansion of the battery even when a silicon-based material is used as the negative electrode active material, and a lithium-ion secondary battery with good performance can be obtained even in high temperature and low temperature environments, but the battery fast charging performance cannot be solved.

[0005] Therefore, based on the above research, how to provide a negative electrode sheet with a higher electrolyte absorption rate and electrolyte retention rate so that the secondary battery has better cycle performance and lithium and sodium ions have a faster diffusion rate in the negative electrode sheet is an urgent problem that needs to be solved. Summary of the invention

[0006] The invention provides a wetting agent, anode slurry and a secondary battery thereof. The wetting agent has a higher electrolyte absorption rate and a higher electrolyte retention rate, so that the secondary battery has a better cycle performance.

[0007] In order to solve the above technical problems, the present invention provides a wetting agent, which includes vinylbenzene units, vinyl acrylate units and vinyl functional units; The glass transition temperature of the wetting agent is -50 to 30° C.; the mass swelling rate of the wetting agent in the electrolyte is 500% to 3000%, and the volume swelling rate is 50% to 1000%.

[0008] Preferably, the weight ratio of the vinylbenzene units, the vinyl acrylate units and the vinyl functional units is (1-100):(100-400):(5-100).

[0009] Preferably, the weight ratio of the vinylbenzene units, the vinyl acrylate units and the vinyl functional units is (5-50):(120-350):(10-80).

[0010] Preferably, the vinylbenzene unit is a structural unit obtained by polymerization of a vinylbenzene monomer, and the vinylbenzene monomer is selected from one or more of styrene, α-methylstyrene, vinyltoluene, 2-vinylnaphthalene, methylvinylnaphthalene, vinylanthracene, methylvinylanthracene, phenoxyethyl methacrylate, 2-butyleneethoxyphthalate, benzyl acrylate, 2-phenoxyethyl acrylate, biphenyl acrylate, phenoxydiethylene glycol acrylate, ethoxypolyethylene glycol o-phenylphenol acrylate, benzyl methacrylate, ethoxylated bisphenol A dimethacrylate, phenyl acrylate, and benzyl acrylate.

[0011] Preferably, the vinyl acrylate unit is a structural unit obtained by polymerization of a vinyl acrylate monomer, and the vinyl acrylate monomer is selected from one or more of methoxydiethylene glycol methacrylate, stearic methacrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, 2-methoxyethyl acrylate, isopentyl acrylate, pentyl acrylate, octyl acrylate, hexyl acrylate, isopropyl acrylate, isodecyl acrylate, butyl acrylate, hexadienyl acrylate, vinyl acrylate, 3,4-epoxycyclohexyl methacrylate, methylhexyl acrylate, allylhexyl acrylate, formyloxyethyl acrylate, lauryl acrylate, lauryl methacrylate, octadecyl acrylate, octadecyl methacrylate, behenyl acrylate, behenyl methacrylate, and caprolactone acrylate.

[0012] Preferably, the vinyl functional unit is a structural unit obtained by polymerization of a vinyl functional monomer, and the vinyl functional monomer is selected from one or more of acrylamide, 2-(tetrahydro-2-furanyl) methyl acrylate, cyclotrimethylolpropane formal acrylate, 2-hydroxymethylpropyl acrylate, acrylonitrile, 4-hydroxybutyl acrylate, vinyltrimethoxysilane, vinyltriethoxysilane, methylvinyldimethoxysilane, vinyldimethoxysilane, vinylethoxysilane, vinylpyrrolidone, hydroxyethyl acrylate, and hydroxypropyl acrylate.

[0013] Preferably, the vinyl functional monomer is selected from one or more of methylvinyldimethoxysilane, vinyldimethoxysilane, vinyltrimethoxysilane and vinyltriethoxysilane.

[0014] In a second aspect, the present application provides a negative electrode slurry, comprising a negative electrode active material and a wetting agent as described in any one of the above.

[0015] Preferably, based on 100% of the mass of the negative electrode slurry, the mass content of the wetting agent is 0.1% to 0.5%.

[0016] In a third aspect, the present application provides a secondary battery, comprising a negative electrode sheet, an electrolyte and a positive electrode sheet, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode material layer is prepared from the negative electrode slurry as described above; After the negative electrode material layer is immersed in the electrolyte, the chromaticity of the electrolyte is less than 10.

[0017] The wetting agent provided in the present application contains vinylbenzene units, vinyl acrylate units and vinyl functional units, so that it has a high absorption mass of 500% to 3000% for the electrolyte, increases the transmission channels of lithium and sodium ions, and improves the migration rate of lithium and sodium ions in the active material. During the battery cycle, the high liquid absorption and high liquid retention properties of the wetting agent make it easy to replenish the electrolyte in time, thereby improving the cycle performance of the secondary battery. And the volume swelling rate of the wetting agent is within 50% to 1000%, which prevents the powder on the negative electrode sheet from falling off due to excessive volume swelling. DETAILED DESCRIPTION

[0018] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] An embodiment of the present application provides a wetting agent, which includes vinyl benzene units, vinyl acrylate units and vinyl functional units.

[0020] The glass transition temperature of the wetting agent is -50 to 30° C.; the mass swelling rate of the wetting agent in the electrolyte is 500% to 3000%, and the volume swelling rate is 50% to 1000%.

[0021] The wetting agent provided in this embodiment contains vinylbenzene units, vinyl acrylate units and vinyl functional units, so that it has a high absorption mass of 500% to 3000% for the electrolyte, increases the transmission channels of lithium and sodium ions, and improves the migration rate of lithium and sodium ions in the active material. During the battery cycle, the high liquid absorption and high liquid retention properties of the wetting agent make it easy to replenish the electrolyte in time, thereby improving the cycle performance of the secondary battery. And the volume swelling rate of the wetting agent is within 50% to 1000%, which prevents the powder on the negative electrode sheet from falling off due to excessive volume swelling.

[0022] In some embodiments, the weight ratio of the vinyl benzene units, vinyl acrylate units and vinyl functional units is (1-100): (100-400): (5-100). By adjusting the weight ratio of the vinyl benzene units, vinyl acrylate units and vinyl functional units, the glass transition temperature of the wetting agent is within -50-30°C, and the vinyl benzene units, vinyl acrylate units and vinyl functional units in the wetting agent present a three-dimensional network structure, thereby improving the liquid absorption and liquid retention performance of the wetting agent.

[0023] Specifically, the weight ratio of the vinylbenzene units, the vinyl acrylate units and the vinyl functional units includes, but is not limited to, 1:200:50, 50:200:100, 50:400:50, 100:300:70 or 100:200:100.

[0024] In a preferred embodiment, the weight ratio of the vinylbenzene units, vinyl acrylate units and vinyl functional units is (5-50): (120-350): (10-80).

[0025] In some embodiments, the vinylbenzene unit is a structural unit obtained by polymerization of vinylbenzene monomers, and the vinylbenzene monomers are selected from one or more of styrene, α-methylstyrene, vinyltoluene, 2-vinylnaphthalene, methylvinylnaphthalene, vinylanthracene, methylvinylanthracene, phenoxyethyl methacrylate, 2-butylene ethoxyphthalate, benzyl acrylate, 2-phenoxyethyl acrylate, biphenyl acrylate, phenoxydiethylene glycol acrylate, ethoxypolyethylene glycol o-phenylphenol acrylate, benzyl methacrylate, ethoxylated bisphenol A dimethacrylate, phenyl acrylate, and benzyl acrylate. By selecting the above-mentioned vinylbenzene monomers with a rigid structure, a relatively loose spatial structure can be formed in the molecular chain of the wetting agent, providing space for the storage of the liquid and improving the liquid retention performance of the wetting agent.

[0026] In a preferred embodiment, the vinyl acrylate monomer is selected from at least one of styrene and ethoxylated bisphenol A dimethacrylate.

[0027] In some embodiments, the vinyl acrylate unit is a structural unit obtained by polymerization of vinyl acrylate monomers, and the vinyl acrylate monomers are selected from one or more of methoxydiethylene glycol methacrylate, stearic methacrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, 2-methoxyethyl acrylate, isopentyl acrylate, amyl acrylate, octyl acrylate, hexyl acrylate, isopropyl acrylate, isodecyl acrylate, butyl acrylate, hexadienyl acrylate, vinyl acrylate, 3,4-epoxycyclohexyl methacrylate, methylhexyl acrylate, allylhexyl acrylate, formyloxyethyl acrylate, lauryl acrylate, lauryl methacrylate, octadecyl acrylate, octadecyl methacrylate, behenyl acrylate, behenyl methacrylate, and caprolactone acrylate. By selecting the above-mentioned vinyl acrylate monomers, when the vinyl acrylate monomers, vinylbenzene monomers, and vinyl functional monomers undergo polymerization, a wetting agent with a three-dimensional network cross-linked structure is formed, which enhances the toughness and elasticity of the wetting agent and improves the liquid absorption performance of the wetting agent.

[0028] In a preferred embodiment, the vinyl acrylate monomer is selected from one or more of methyl acrylate, 2-methoxyethyl acrylate, and cyclohexyl acrylate.

[0029] In some embodiments, the vinyl functional unit is a structural unit obtained by polymerization of a vinyl functional monomer, and the vinyl functional monomer is selected from one or more of acrylamide, 2-(tetrahydro-2-furanyl) methyl acrylate, cyclotrimethylolpropane methyl acrylate, 2-hydroxymethylpropyl acrylate, acrylonitrile, 4-hydroxybutyl acrylate, vinyl trimethoxysilane, vinyl triethoxysilane, methyl vinyl dimethoxysilane, vinyl dimethoxysilane, vinyl ethoxysilane, vinyl pyrrolidone, hydroxyethyl acrylate, and hydroxypropyl acrylate. The wetting agent with a three-dimensional network structure obtained by reacting the above vinyl functional monomers with vinyl acrylate monomers and vinyl benzene monomers has more sites for interaction with liquid molecules, which helps to improve the liquid absorption performance of the wetting agent.

[0030] In a preferred embodiment, the vinyl functional monomer is selected from one or more of vinyl dimethoxy silane, vinyl trimethoxy silane and vinyl triethoxy silane.

[0031] Specifically, the wetting agent is formed by polymerization of vinylbenzene monomers, vinyl acrylate monomers, and vinyl functional monomers under the action of an emulsifier, and the mass ratio of the emulsifier to the vinyl functional monomer is (0.5-5): (50-100). The mass ratio of the initiator to the vinyl functional monomer is (0.5-5): (50-100). The initiator can be any type of initiator commonly used in the art, and has no special effect in the present invention. Specifically, the initiator can be azobisisobutyronitrile.

[0032] The specific method of the emulsion polymerization is commonly used in the field of chemical synthesis, for example, each raw monomer is mixed with an emulsifier and stirred, and then heated to 40-80° C. under stirring, and then an initiator is added and reacted for 12-36 hours.

[0033] The wetting agent is an emulsion with a solid content of 30% to 50%.

[0034] In some embodiments, the emulsifier is selected from one or more of sodium dodecylbenzene sulfonate, phosphate esters, ammonium nonylphenol polyoxyethylene ether sulfate, sodium dodecyl sulfate, sodium octanoate, polyethoxyoctanol ether, octylphenol polyoxyethylene ether, sodium octyl sulfonate, sodium stearate, polyethoxyoctanol, polyethylene glycol octyl ether, sodium octyl sulfate, octyl alcohol polyoxyethylene ether, polyethylene ether phytate, octylphenol ethoxylate, phytate, polyethylene ether octyl ether, dodecyl polyoxyethylene ether, sodium polyethoxyoctyl ether sulfate, sodium polyethylene ether phytate, and polyethylene octanoate.

[0035] In a preferred embodiment, the emulsifier is selected from one or more of nonylphenol polyoxyethylene ether ammonium sulfate, sodium dodecylbenzene sulfonate, octylphenol ethoxylate, and polyethylene glycol octyl ether.

[0036] An embodiment of the present application provides a negative electrode slurry, comprising a negative electrode active material and a wetting agent as described above.

[0037] In some embodiments, the mass content of the wetting agent is 0.1% to 0.5% based on the mass of the negative electrode slurry being 100%. By controlling the content of the wetting agent within the above range, the liquid absorption rate and liquid retention rate of the negative electrode sheet to the electrolyte can be improved, so that the battery has better cycle performance.

[0038] In a third aspect, an embodiment of the present application provides a secondary battery, comprising a negative electrode sheet, an electrolyte and a positive electrode sheet, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode material layer is prepared from the negative electrode slurry as described above; After the negative electrode material layer is immersed in the electrolyte, the chromaticity of the electrolyte is less than 10.

[0039] By selecting the negative electrode sheet containing the wetting agent of this embodiment, on the one hand, the negative electrode sheet has a good liquid absorption rate and liquid retention rate, increases the transmission channel of lithium and sodium ions, improves the migration rate of lithium and sodium ions in the active material, and replenishes the exhausted electrolyte during the cycle process, thereby improving the cycle performance of lithium and sodium ion batteries. On the other hand, the wetting agent absorbs impurities in the electrolyte, improves the chemical stability of the electrolyte, and makes the migration of lithium ions in the electrolyte smoother, thereby improving the charge and discharge efficiency and cycle life of the battery.

[0040] The present invention is further described below by way of examples.

[0041] The wetting agent, negative electrode slurry and secondary battery disclosed in the present invention are specifically described.

[0042] Example 1 Wetting Agents Under nitrogen, 50 parts of styrene, 300 parts of methacrylate stearate, 70 parts of methyl vinyl dimethoxy silane, and 3 parts of nonylphenol polyoxyethylene ether ammonium sulfate were mixed, and stirred at a speed of 50 r / min for 30 seconds to obtain a mixed solution; The mixed solution was heated to 50°C under a nitrogen atmosphere, and then 1.5 parts of azobisisobutyronitrile were added. The temperature was kept at 50°C and stirred continuously at a speed of 50 r / min. The reaction was stopped after 24 hours. 250 parts of N-methylpyrrolidone were added to the obtained polymer solution and heated to remove the solvent by rotary evaporation to obtain a wetting agent.

[0043] Preparation of negative electrode After mixing 0.3% wetting agent, 96% negative electrode active material graphite, 1% negative electrode conductive agent conductive carbon black, and 2.7% thickener sodium carboxymethyl cellulose (CMC), deionized water is added for stirring to prepare negative electrode slurry. Then the negative electrode slurry is coated on both surfaces of the negative electrode current collector Cu foil, and after drying, cold pressing, slitting and other processes, the negative electrode sheet is obtained.

[0044] Preparation of positive electrode The positive electrode active material lithium manganese oxide, conductive carbon black, and positive electrode binder are mixed in a mass ratio of 90:3:7, and NMP is added to prepare positive electrode slurry. The positive electrode slurry is coated on aluminum foil and dried to obtain a positive electrode sheet.

[0045] Secondary battery preparation The negative electrode sheet, isolation film (PE film), and positive electrode sheet are stacked in order, with the isolation film placed between the positive and negative electrodes to play an isolating role, to form an electrode assembly, which is placed in an outer package, injected with commercially available electrolyte and packaged, and then subjected to processes such as liquid injection, formation, and exhaust to obtain a secondary battery.

[0046] Example 2 Most of the steps of Example 2 are the same as those of Example 1, except that the raw material composition of the wetting agent includes 100 parts of vinyldimethoxysilane.

[0047] Example 3 Most of the steps of Example 3 are the same as those of Example 1, except that the raw material composition of the wetting agent includes 50 parts of vinyldimethoxysilane.

[0048] Example 4 Most of the steps of Example 4 are the same as those of Example 1, except that the raw material composition of the wetting agent includes 150 parts of vinyldimethoxysilane.

[0049] Example 5 Most of the steps of Example 5 are the same as those of Example 1, except that the raw material composition of the wetting agent includes 30 parts of vinyldimethoxysilane.

[0050] Example 6 Example 6 is similar to Example 1 in most of the steps except that 400 parts of stearyl methacrylate are included.

[0051] Example 7 Example 7 is similar to Example 1 in most of the steps except that 200 parts of stearyl methacrylate are included.

[0052] Example 8 Most of the steps of Example 8 are the same as those of Example 1, except that the raw material composition of the wetting agent includes 150 parts of stearic methacrylate.

[0053] Example 9 Most of the steps of Example 9 are the same as those of Example 1, except that the raw material composition of the wetting agent includes 500 g of stearic methacrylate.

[0054] Example 10 Example 10 is similar to Example 1 in most of its steps except that 1 part of styrene is included.

[0055] Embodiment 11 Example 11 was performed in much the same manner as Example 1, except that 100 parts of styrene was included.

[0056] Example 12 Example 12 is similar to Example 1 in most of its steps, except that the raw material composition of the wetting agent includes 150 parts of styrene.

[0057] Example 13 Most of the steps of Example 13 are the same as those of Example 1, except that the raw material composition of the wetting agent includes 50 parts of ethoxylated bisphenol A dimethacrylate, 300 parts of 3,4-epoxycyclohexyl methacrylate, and 70 parts of 2-(tetrahydro-2-furanyl)methyl acrylate.

[0058] Embodiment 14 Most of the steps of Example 14 are the same as those of Example 1, except that the raw material composition of the wetting agent includes 50 parts of ethoxy polyethylene glycol o-phenylphenol acrylate, 300 parts of 2-methoxyethyl 2-acrylate, and 70 parts of cyclotrimethylolpropane formal acrylate.

[0059] Embodiment 15 Most of the steps of Example 15 are the same as those of Example 1, except that the raw material composition of the wetting agent includes 50 parts of 2-butenoylethoxyphthalate, 300 parts of cyclohexyl acrylate, and 70 parts of 2-hydroxymethylpropyl acrylate.

[0060] Example 16 Most of the steps of Example 16 are the same as those of Example 1, except that the raw material composition of the wetting agent includes 50 parts of phenoxydiethylene glycol acrylate, 300 parts of formyloxyethyl acrylate, and 70 parts of vinyltrimethoxysilane.

[0061] Comparative Example 1 Most of the steps of Comparative Example 1 are the same as those of Example 1, except that the raw material composition of the wetting agent includes 50 parts of styrene and 300 parts of stearic methacrylate.

[0062] Comparative Example 2 Most of the steps of Comparative Example 2 and Example 1 are the same, except that the raw material composition of the wetting agent includes 300 parts of stearic methacrylate and 70 parts of vinyldimethoxysilane.

[0063] Comparative Example 3 Comparative Example 3 is similar to Example 1 in most of the steps, except that the raw material composition of the wetting agent includes 100 parts of styrene and 50 parts of vinyldimethoxysilane.

[0064] Comparative Example 4 Comparative Example 4 is similar to Example 1 in most of the steps, except that no wetting agent is added to the negative electrode slurry.

[0065] Electrical performance test: The wetting agents, negative electrode sheets, and secondary batteries prepared in the above examples and comparative examples were subjected to the following tests.

[0066] 1) Electrolyte swelling rate test: Mass swelling rate: Under standard atmospheric pressure and 25°C, add 1M lithium hexafluorophosphate to a mixed solution of ethylene carbonate and ethyl methyl carbonate in a mass ratio of 1:1 as the electrolyte. Take two containers and add the electrolyte, make the wetting agent into a thin film and dry and weigh it to obtain Winitial. The film specification is a circular sheet with a diameter of 20mm and a thickness of 20μm. Immerse the wetting agent film in the electrolyte, place it for 72 hours, take it out and wipe off the electrolyte on the surface to weigh it to obtain Wbalance. Mass swelling rate = (Wbalance-Winitial) / Winitial*100%.

[0067] Volume swelling rate: Under standard atmospheric pressure and 25°C, add 1M lithium hexafluorophosphate to a mixed solution of ethylene carbonate and ethyl methyl carbonate in a mass ratio of 1:1 as the electrolyte. Take two containers and add electrolyte, make the wetting agent into a thin film and dry it. The film specification is a circular sheet with a diameter of 20mm and a thickness of 20μm. Immerse the wetting agent film in the electrolyte and mark the volume change as Vinitial. After 72 hours, take out and wipe off the electrolyte on the surface, place it in another container with electrolyte, mark the volume change as Vbalance, and the volume swelling rate = (Vbalance-Vinitial) / Vinitial*100%.

[0068] 2) Normal temperature cycle test The specific method is: let the soft pack battery stand until the temperature reaches 25℃±2℃, test the capacity of the soft pack battery, record it as the capacity before storage, discharge the soft pack battery at 0.5C constant current to 2.7V, charge at 1C constant current to 4.3V, then charge at constant voltage to the cut-off current of 0.05C, and then discharge at 1C constant current to 2.75V after charging is completed; cycle 500 times in this way and record the capacity retention rate.

[0069] 3) Electrolyte color test Take 100 mL of the electrolyte sample after soaking the wetting agent film in the above mass swelling rate test and put it in a 250 mL beaker. Use a colorimeter to test the colorimetric test Pt-co reading. The colorimetry of the electrolyte is determined in accordance with the provisions of GB / T 3143.

[0070] The test results are shown in Table 1 below.

[0071] Table 1

[0072] From the test results of Example 1 and Comparative Examples 1 to 4, it can be seen that after using the wetting agent of this example, both the volume swelling and the mass swelling are greatly improved, and the chromaticity of the electrolyte is not greatly affected. The cycle performance of Example 1 is greatly improved compared with Comparative Example 1.

[0073] From the test results of Examples 1, 13 to 16, and Comparative Examples 1 to 3, it can be seen that when the wetting agent contains vinylbenzene units, vinyl acrylate units, and vinyl functional units, the wetting agent has a high absorption quality for the electrolyte, and the cycle performance of the batteries of Examples 1 and 13 to 16 is greatly improved compared with Comparative Examples 1 to 3.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A wetting agent, characterized in that The wetting agent comprises vinylbenzene units, vinyl acrylate units and vinyl functional units; The glass transition temperature of the wetting agent is -50 to 30° C.; the mass swelling rate of the wetting agent in the electrolyte is 500% to 3000%, and the volume swelling rate is 50% to 1000%.

2. The wetting agent according to claim 1, characterized in that The weight ratio of the vinylbenzene units, the vinyl acrylate units and the vinyl functional units is (1-100): (100-400): (5-100).

3. The wetting agent according to claim 2, characterized in that The weight ratio of the vinylbenzene units, the vinyl acrylate units and the vinyl functional units is (5-50): (120-350): (10-80).

4. The wetting agent according to claim 1, characterized in that The vinylbenzene unit is a structural unit obtained by polymerization of vinylbenzene monomers, and the vinylbenzene monomers are selected from one or more of styrene, α-methylstyrene, vinyltoluene, 2-vinylnaphthalene, methylvinylnaphthalene, vinylanthracene, methylvinylanthracene, phenoxyethyl methacrylate, 2-butyleneethoxyphthalate, benzyl acrylate, 2-phenoxyethyl acrylate, biphenyl acrylate, phenoxydiethylene glycol acrylate, ethoxypolyethylene glycol o-phenylphenol acrylate, benzyl methacrylate, ethoxylated bisphenol A dimethacrylate, phenyl acrylate, and benzyl acrylate.

5. The wetting agent according to claim 1, characterized in that The vinyl acrylate unit is a structural unit obtained by polymerization of vinyl acrylate monomers, and the vinyl acrylate monomers are selected from one or more of methoxydiethylene glycol methacrylate, stearic methacrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, 2-methoxyethyl acrylate, isopentyl acrylate, pentyl acrylate, octyl acrylate, hexyl acrylate, isopropyl acrylate, isodecyl acrylate, butyl acrylate, hexadienyl acrylate, vinyl acrylate, 3,4-epoxycyclohexyl methacrylate, methylhexyl acrylate, allylhexyl acrylate, formyloxyethyl acrylate, lauryl acrylate, lauryl methacrylate, octadecyl acrylate, octadecyl methacrylate, behenyl acrylate, behenyl methacrylate, and caprolactone acrylate.

6. The wetting agent according to claim 1, characterized in that The vinyl functional unit is a structural unit obtained by polymerization of a vinyl functional monomer, and the vinyl functional monomer is selected from one or more of acrylamide, 2-(tetrahydro-2-furanyl) methyl acrylate, cyclotrimethylolpropane formal acrylate, 2-hydroxymethylpropyl acrylate, acrylonitrile, 4-hydroxybutyl acrylate, vinyltrimethoxysilane, vinyltriethoxysilane, methylvinyldimethoxysilane, vinyldimethoxysilane, vinylethoxysilane, vinylpyrrolidone, hydroxyethyl acrylate, and hydroxypropyl acrylate.

7. The wetting agent according to claim 6, characterized in that The vinyl functional monomer is selected from one or more of vinyl dimethoxy silane, vinyl trimethoxy silane and vinyl triethoxy silane.

8. A negative electrode slurry, characterized in that: The invention comprises a negative electrode active material and the wetting agent according to any one of claims 1 to 7.

9. The negative electrode slurry according to claim 8, characterized in that: Based on the mass of the negative electrode slurry being 100%, the mass content of the wetting agent is 0.1% to 0.5%.

10. A secondary battery, characterized in that: It comprises a negative electrode sheet, an electrolyte and a positive electrode sheet, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer arranged on at least one side of the negative electrode current collector, wherein the negative electrode material layer is prepared from the negative electrode slurry according to claim 8 or 9; After the negative electrode material layer is immersed in the electrolyte, the chromaticity of the electrolyte is less than 10.

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