CN116979221A - Secondary battery and electric equipment - Google Patents

Secondary battery and electric equipment Download PDF

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Publication number
CN116979221A
CN116979221A CN202310638079.XA CN202310638079A CN116979221A CN 116979221 A CN116979221 A CN 116979221A CN 202310638079 A CN202310638079 A CN 202310638079A CN 116979221 A CN116979221 A CN 116979221A
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CN
China
Prior art keywords
secondary battery
average thickness
film
adhesive layer
negative electrode
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Pending
Application number
CN202310638079.XA
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Chinese (zh)
Inventor
谢易昊
李柳
王宝玉
张耀
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Xinwangda Power Technology Co ltd
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Xinwangda Power Technology Co ltd
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Priority to CN202310638079.XA priority Critical patent/CN116979221A/en
Publication of CN116979221A publication Critical patent/CN116979221A/en
Pending legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/423—Polyamide resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
    • H01M50/461—Separators, membranes or diaphragms characterised by their combination with electrodes with adhesive layers between electrodes and separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties

Abstract

The application discloses a secondary battery and electric equipment, wherein a first adhesive layer is arranged on one surface of a base film of a diaphragm, which faces an anode pole piece, and a second adhesive layer is arranged on one surface of the base film, which faces a cathode pole piece, the average thickness of the first adhesive layer is smaller than that of the second adhesive layer, on the premise of ensuring the bonding strength with the anode pole piece, the material cost is reduced, the internal resistance of the secondary battery can be reduced, the charge and discharge power is improved, the average thickness of the second adhesive layer is relatively thicker, the expansion deformation of an active material in the cathode pole piece in the charge and discharge cycle process of the secondary battery can be restrained, the bonding strength of the diaphragm and the cathode pole piece is improved, and the deformation resistance strength of the cathode pole piece is enhanced, so that the secondary battery has better charge and discharge power at normal temperature and low temperature, and has higher cycle capacity retention rate and lower DCR growth rate.

Description

Secondary battery and electric equipment
Technical Field
The application relates to the technical field of batteries, in particular to a secondary battery and electric equipment.
Background
As one of the important components of the secondary battery, the design of the separator is continuously optimized, and plays an important role in the process of developing a secondary battery with high power, long life and high safety performance. The basic function of the diaphragm is to separate the positive pole piece from the negative pole piece to prevent contact short circuit and to transmit active metal ions.
In the existing secondary battery, the bonding strength between the diaphragm and the pole piece is low, the hardness of the winding core is easy to be low in the aspect of manufacturing the winding core, the transportation and assembly of the winding core are affected, the bonding strength between the diaphragm and the pole piece is high, although the hardness of the winding core can be improved, the diffusion of active metal ions between the positive pole piece and the negative pole piece can be affected, the internal resistance of the secondary battery is increased, and the cycle performance of the secondary battery is deteriorated.
Disclosure of Invention
The embodiment of the application provides a secondary battery and electric equipment, which can solve the problem between a pole piece and a diaphragm in the existing secondary battery.
A first aspect of the present application provides a secondary battery including a positive electrode tab, a separator, and a negative electrode tab; the diaphragm comprises a base film, a first adhesive layer is arranged on one surface of the base film facing the positive pole piece, and a second adhesive layer is arranged on one surface of the base film facing the negative pole piece; wherein, the average thickness of first glue film is T1, the average thickness of second glue film is T2, satisfies: t2> T1.
Optionally, at least one of the following conditions is satisfied: (1) T1/T2 is not less than 0.1 and not more than 0.8; (2) T1 is less than or equal to 1 μm and less than or equal to 4 μm; (3) T2 is less than or equal to 3 μm and less than or equal to 8 μm.
Optionally, the adhesive further comprises a first ceramic coating, wherein the first ceramic coating is arranged between the first adhesive layer and the base film, and the average thickness of the first ceramic coating is T3, so that T3/T1 is more than or equal to 0.1 and less than or equal to 5; and/or T3 is less than or equal to 0.1 μm and less than or equal to 5 μm.
Optionally, the adhesive further comprises a second ceramic coating, wherein the second ceramic coating is arranged between the second adhesive layer and the base film, and the average thickness of the second ceramic coating is T4, so that T4/T2 is more than or equal to 0.01 and less than or equal to 1.3; and/or T4 is less than or equal to 0.1 μm and less than or equal to 5 μm.
Optionally, the thickness of the base film is 5 μm to 30 μm.
Optionally, the first adhesive layer and the second adhesive layer each independently comprise at least one of sodium carboxymethyl cellulose, polystyrene-butadiene emulsion, styrene butadiene rubber emulsion, nitrile butadiene rubber emulsion, silicone rubber emulsion, ethylene-vinyl acetate copolymer emulsion, polytetrafluoroethylene emulsion, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polymethyl methacrylate, polyethylene oxide, polyethyl acrylate, ethylene tetrafluoroethylene copolymer.
Optionally, the first ceramic coating and the second ceramic coating each independently comprise at least one of alumina, magnesia, silica, magnesium hydroxide, boehmite, titania.
Optionally, the base film includes at least one of a polypropylene film, a polyethylene film, a cellulose film, a polyethylene terephthalate film, a nonwoven fabric film, a polyimide film, and an electrospun film.
Optionally, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector; the negative electrode active material layer includes a silicon-based negative electrode material.
The second aspect of the application also provides electric equipment, which comprises the secondary battery, wherein the secondary battery is used as a power supply of the electric equipment.
The application has the beneficial effects that the secondary battery and the electric equipment are provided, the first adhesive layer is arranged on one surface of the base film of the diaphragm, which faces the positive electrode plate, and the second adhesive layer is arranged on one surface of the base film, which faces the negative electrode plate, and the average thickness of the first adhesive layer is smaller than that of the second adhesive layer, so that the material cost is reduced, the internal resistance of the secondary battery can be reduced, the charge and discharge power is improved, the average thickness of the second adhesive layer is relatively thicker, the expansion deformation of the active material in the negative electrode plate in the charge and discharge cycle process of the secondary battery can be restrained, the bonding strength of the diaphragm and the negative electrode plate is improved, and the deformation resistance strength of the negative electrode plate is enhanced, so that the secondary battery has better charge and discharge power at normal temperature and low temperature, and has higher cycle capacity retention rate and lower DCR growth rate.
Detailed Description
The following description of the embodiments of the present application will be made clearly and completely, and it is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application. Furthermore, it should be understood that the detailed description is presented herein for purposes of illustration and description only, and is not intended to limit the application.
In the detailed description and claims, a list of items connected by the term "at least one of" may mean any combination of the listed items. For example, if items a and B are listed, the phrase "at least one of a and B" means only a; only B; or A and B. In another example, if items A, B and C are listed, then the phrase "at least one of A, B and C" means only a; or only B; only C; a and B (excluding C); a and C (excluding B); b and C (excluding A); or A, B and C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements. At least one of the terms "has the same meaning as at least one of the terms".
In the present specification, a numerical range shown by using "to" means a range including numerical values described before and after "to" as a minimum value and a maximum value, respectively.
The embodiment of the application provides a secondary battery and electric equipment with the secondary battery, wherein a first adhesive layer is arranged on one surface of a base film of a diaphragm facing a positive electrode plate, a second adhesive layer is arranged on one surface of the base film facing a negative electrode plate, the average thickness of the first adhesive layer is smaller than that of the second adhesive layer, the material cost is reduced, the internal resistance of the secondary battery can be reduced, the charge and discharge power is improved on the premise of ensuring the bonding strength with the positive electrode plate, the average thickness of the second adhesive layer is relatively thicker, the expansion deformation of an active material in the negative electrode plate in the charge and discharge cycle process of the secondary battery can be restrained, the bonding strength of the diaphragm and the negative electrode plate is improved, and the deformation resistance strength of the negative electrode plate is enhanced, so that the secondary battery has better charge and discharge power at normal temperature and low temperature, and has higher cycle capacity retention rate and lower DCR growth rate.
The embodiment of the application provides a secondary battery, which comprises a positive pole piece, a negative pole piece, a diaphragm, electrolyte and a shell, wherein the diaphragm is arranged between the positive pole piece and the negative pole piece.
I. Diaphragm
In some embodiments, the diaphragm includes basic film, first glue film and second glue film, and first glue film sets up in basic film towards anodal pole piece one side, and first glue film's average thickness is T1, and the second glue film sets up in basic film towards negative pole piece one side, and the average thickness of second glue film is T2, satisfies: t1 < T2.
The average thickness T1 of the first adhesive layer is relatively smaller, so that the diffusion of active metal ions (such as lithium ions) is ensured on the premise of ensuring the bonding strength of the diaphragm and the positive electrode plate, and the internal resistance of the secondary battery (such as a lithium ion battery) is reduced. The average thickness T2 of the second adhesive layer is relatively large, so that one surface of the diaphragm, facing the negative electrode plate, has enough adhesive coating amount to ensure the bonding strength between the diaphragm and the negative electrode plate, and because the negative electrode material in the negative electrode plate, particularly the silicon-based negative electrode material, is easy to expand in volume in the charge and discharge process, the negative electrode plate of the secondary battery is easy to expand and deform in the circulation process, and therefore, the sufficient adhesive coating amount is required to inhibit the expansion and deformation of the negative electrode plate. Therefore, the average thickness T1 of the first adhesive layer and the average thickness T2 of the second adhesive layer cannot be the same, if t1=t2, and the average thicknesses of the first adhesive layer and the second adhesive layer are both equal to the average thickness of T2, although the bonding strength between the separator and the negative electrode plate is ensured, the average thickness of T1 is too large, which can affect the diffusion of active metal ions and increase the internal resistance of the secondary battery; if t1=t2, and the average thickness of T1, the bonding strength between the separator and the positive electrode sheet and the diffusion of the active metal ions are ensured, but the bonding strength between the separator and the negative electrode sheet cannot be satisfied, so that the negative electrode sheet of the secondary battery is expanded and deformed in the cycle process.
In some embodiments of the application, 0.1.ltoreq.T1/T2.ltoreq.0.8, in particular the ratio T1/T2 may be in the range of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or any two numbers thereof.
In some embodiments of the application, 1 μm.ltoreq.T1.ltoreq.4μm, in particular, the value of T1 may be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or a range of any two numbers therein.
In some embodiments of the application, 3 μm.ltoreq.T2.ltoreq.8μm, in particular, the value of T2 may be 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm or a range of any two numbers therein.
In some embodiments of the present application, the first and second gum layers each independently comprise at least one of sodium carboxymethyl cellulose, polystyrene-butadiene emulsion, styrene-butadiene rubber emulsion, nitrile rubber emulsion, silicone rubber emulsion, ethylene-vinyl acetate copolymer emulsion, polytetrafluoroethylene emulsion, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polymethyl methacrylate, polyethylene oxide, polyethyl acrylate, ethylene tetrafluoroethylene copolymer.
In some embodiments of the application, the means for applying the first and second glue layers comprises at least one of gravure roll coating and rotary spraying.
In some embodiments of the application, the separator further comprises a first ceramic coating layer disposed between the first glue layer and the base film, the first ceramic coating layer having an average thickness T3, 0.1.ltoreq.T3/T1.ltoreq.5, and in particular, the value of T3/T1 may be 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or a range consisting of any two thereof. When T3/T1 is in the above range, the bonding strength between the diaphragm and the positive electrode plate is ensured, the diffusion of active metal ions is ensured, and the internal resistance of the secondary battery is reduced.
In some embodiments of the application, 0.1 μm.ltoreq.T3.ltoreq.5 μm, in particular, T3 may be 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or a range of any two numbers therein. When the average thickness T3 of the first ceramic coating layer is within the above range, the heat resistance of the separator may be improved, thereby improving the overall safety performance of the secondary battery. Wherein, as the average thickness T3 of the first ceramic coating layer increases, the thermal shrinkage rate of the separator decreases and the heat resistance is enhanced, but, too low T3 may cause the thermal shrinkage rate of the separator to increase, the heat resistance decreases, and too high T3 may affect the diffusion of active metal ions, resulting in the increase of the internal resistance of the secondary battery, and thus the cycle capacity retention rate of the secondary battery decreases and the cycle discharge DCR growth rate increases.
In some embodiments of the application, the separator further comprises a second ceramic coating layer disposed between the second glue layer and the base film, the second ceramic coating layer having an average thickness T4, 0.01.ltoreq.T4/T2.ltoreq.1.7, in particular, the value of T4/T2 may be 0.01, 0.05, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0, 1.3, 1.5, 1.7 or a range of any two numbers therein. When T4/T2 is in the above range, the bonding strength between the diaphragm and the negative electrode plate is ensured, the diffusion of active metal ions is ensured, and the internal resistance of the secondary battery is reduced.
In some embodiments of the application, 0.1 μm.ltoreq.T4.ltoreq.5 μm, in particular T4 may be 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or a range of any two numbers therein. When the average thickness T4 of the second ceramic coating layer is within the above range, the heat resistance of the separator may be improved, thereby improving the overall safety performance of the secondary battery. Wherein, as the average thickness T4 of the second ceramic coating layer increases, the thermal shrinkage rate of the separator decreases and the heat resistance is enhanced, but, too low T4 may cause the thermal shrinkage rate of the separator to increase, the heat resistance decreases, and too high T4 may affect the diffusion of active metal ions, resulting in the increase of the internal resistance of the secondary battery, and thus the cycle capacity retention rate of the secondary battery decreases and the cycle discharge DCR growth rate increases.
In some embodiments of the application, the first ceramic coating and the second ceramic coating each independently comprise at least one of alumina, magnesia, silica, magnesium hydroxide, boehmite, titania.
In some embodiments of the application, the thickness of the base film is 5 μm to 30 μm, specifically, the thickness of the base film may be 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 17 μm, 20 μm, 22 μm, 25 μm, 27 μm, 30 μm or a range of any two numbers therein.
In some embodiments of the application, the base film comprises at least one of a polypropylene film, a polyethylene film, a cellulose film, a polyethylene terephthalate film, a nonwoven fabric film, a polyimide film, an electrospun separator.
II. Positive electrode plate
The positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer arranged on the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, a positive electrode conductive agent and a positive electrode binder.
The positive electrode active material includes, but is not limited to, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium-containing phosphates, lithium cobaltate, and the like.
The kind of the positive electrode conductive agent is not limited, and any known conductive agent may be used. The positive electrode conductive agent may include, but is not limited to, natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, graphene, and the like. The above positive electrode conductive agents may be used alone or in any combination.
The type of positive electrode binder used in the production of the positive electrode active material layer is not particularly limited as long as it is a material that is soluble or dispersible in a liquid medium used in the production of the electrode.
The type of solvent used to form the positive electrode slurry is not limited as long as it is a solvent capable of dissolving or dispersing the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder. Examples of the solvent used to form the positive electrode slurry may include any one of an aqueous solvent and an organic solvent. Examples of the aqueous medium may include, but are not limited to, water, a mixed medium of alcohol and water, and the like. Examples of the organic-based medium may include, but are not limited to, diethylenetriamine, N-dimethylaminopropylamine, diethyl ether, propylene oxide, tetrahydrofuran (THF), N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, hexamethylphosphoramide, dimethylsulfoxide, and the like.
III, negative pole piece
The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector.
In some embodiments of the application, the negative electrode active material layer comprises a silicon-based negative electrode material.
In some embodiments of the application, the silicon-based negative electrode material comprises at least one of silicon, a silicon-based alloy, a silicon oxide, a silicon/carbon composite, a silicon oxide/carbon composite.
IV, electrolyte
The electrolyte includes a lithium salt, an organic solvent, and an additive.
The lithium salt comprises at least one of lithium hexafluorophosphate, organic lithium borate, lithium perchlorate and sulfonimide lithium salt. The content of the lithium salt is not particularly limited as long as the effect of the present application is not impaired.
Organic solvents include cyclic carbonates and chain carbonates. The cyclic carbonate includes EC (ethylene carbonate), and the chain carbonate includes at least one of DEC (diethyl carbonate), DMC (dimethyl carbonate) and EMC (methyl ethyl carbonate).
The additive comprises at least one of vinylene carbonate, 1, 3-propane sultone, vinyl sulfate, lithium difluorophosphate, fluoroethylene carbonate (FEC), lithium difluorooxalato borate, tripropynyl phosphate, triallyl isocyanurate.
The secondary battery provided by the embodiment of the application can be applied to electric equipment, and the secondary battery is used as a power supply of the electric equipment, wherein the electric equipment can be used for electric toys, electric tools, battery cars, electric automobiles, energy storage equipment, ships, spacecrafts and the like without limitation.
The following description is made of a method for manufacturing a secondary battery according to the present application with reference to specific examples:
example 1
(1) Preparation of positive electrode plate
The positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM 622), conductive agent acetylene black (Super P) and binder polyvinylidene fluoride (PVDF) are uniformly mixed according to the mass ratio NCM622:super P:PVDF=94:3:3, uniformly dispersed in N-methyl pyrrolidone (NMP) to prepare uniform slurry, and the slurry is coated on two sides of an aluminum foil, baked, rolled and cut into pieces to obtain the positive electrode plate.
(2) Preparation of negative electrode plate
Uniformly mixing SiO-C, conductive agent acetylene black (Super P) and binder SBR according to the mass ratio of SiO-C to Super P SBR=94:3:3, uniformly dispersing in deionized water to prepare uniform slurry, coating the slurry on two sides of a copper foil, baking, rolling and cutting to obtain a negative electrode plate.
(3) Preparation of electrolyte
Mixing Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) according to a mass ratio of 1:1:1, and then adding 1mol/L LiPF 6 Mixing uniformly, and then adding 1, 3-propane sultone and vinyl sulfate to prepare electrolyte.
(4) Preparation of separator
Selecting a PP (polypropylene) base film with the thickness of 12 mu m, coating alumina slurry on two sides of the base film in a gravure coating mode to form ceramic coatings with the thickness of 1 mu m respectively, namely, the average thickness T3 of the first ceramic coating and the average thickness T4 of the second ceramic coating are 1 mu m, drying, coating PVDF slurry on the ceramic coatings in a rotary spraying mode to form a first adhesive layer and a second adhesive layer, controlling the average thickness of the adhesive layers by spraying quantity, wherein the average thickness T1 of the first adhesive layer is 2 mu m, the average thickness T2 of the second adhesive layer is 5 mu m, T1/T2=0.4, T3/T1=0.5 and T4/T2=0.2.
(5) Fabrication of secondary battery
And sequentially stacking the prepared positive electrode plate, the diaphragm and the negative electrode plate, wherein a first adhesive layer of the diaphragm faces the positive electrode plate, a second adhesive layer of the diaphragm faces the negative electrode plate, winding to form a winding core, hot-pressing and shaping, welding the electrode lugs to obtain a bare cell, placing the cell in an outer packaging aluminum-plastic film, placing in an oven at 85+/-10 ℃ for baking for 24 hours, injecting electrolyte into the dried aluminum-plastic film, sealing, standing, forming and separating, and thus completing the manufacture of the secondary battery.
Example 2
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the average thickness T1 of the first glue layer is 1 μm, t1/t2=0.2.
Example 3
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the average thickness T1 of the first glue layer is 3 μm, t1/t2=0.6.
Example 4
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the average thickness T1 of the first glue layer was 4 μm, T1/t2=0.8.
Example 5
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the average thickness T2 of the second glue layer was 8 μm, T1/t2=0.25.
Example 6
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the average thickness T2 of the second glue layer was 10 μm, T1/t2=0.2.
Example 7
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the average thickness T2 of the second glue layer is 3 μm, T1/t2=0.67.
Example 8
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the average thickness T3 of the first ceramic coating is 2 μm, T3/t1=1, the average thickness T4 of the second ceramic coating is 2 μm, T4/t2=0.4.
Example 9
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the average thickness T3 of the first ceramic coating is 0.1 μm, t3/t1=0.05, and the average thickness T4 of the second ceramic coating is 0.1 μm, t4/t2=0.02.
Example 10
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the average thickness T3 of the first ceramic coating is 3 μm, t3/t1=1.5, and the average thickness T4 of the second ceramic coating is 3 μm, t4/t2=0.6.
Example 11
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the average thickness T3 of the first ceramic coating was 5 μm, T3/t1=2.5, T4 of the second ceramic coating was 5 μm, T4/t2=1.
Example 12
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the average thickness T3 of the first ceramic coating is 2 μm, T3/t1=1, the average thickness T4 of the second ceramic coating is 3 μm, T4/t2=0.6.
Example 13
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the average thickness T3 of the first ceramic coating is 2 μm, T3/t1=1, the average thickness T4 of the second ceramic coating is 5 μm, T4/t2=1.7.
Example 14
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the separator was free of the first ceramic coating and the second ceramic coating, the average thickness T1 of the first glue layer was 2 μm, and the average thickness T2 of the second glue layer was 5 μm.
Comparative example 1
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the average thickness T1 of the first glue layer is 2 μm and the average thickness T2 of the second glue layer is 2 μm.
Comparative example 2
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the average thickness T1 of the first glue layer is 10 μm and the average thickness T2 of the second glue layer is 10 μm.
Comparative example 3
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the separator was free of the first ceramic coating and the second ceramic coating, the average thickness T1 of the first glue layer was 2 μm, and the average thickness T2 of the second glue layer was 2 μm.
Comparative example 4
A secondary battery was prepared as described in example 1, except for the following differences, which were the same as in example 1:
the separator was free of a first ceramic coating and a second ceramic coating, the average thickness T1 of the first glue layer being 10 μm and the average thickness T2 of the second glue layer being 10 μm.
Diaphragm heat shrinkage test:
test methods see GB/T12027-2004, the separator was cut into 10cm squares, heat treated in an oven at 150℃for 1 hour, the film area before and after heat treatment was calculated, the ratio of the area contracted to the area before heat treatment was taken as the heat shrinkage of the separator, and the test results were shown in Table 2 with MD in the machine direction and TD in the transverse direction.
Secondary battery performance test:
the secondary batteries prepared in examples 1 to 14 and comparative examples 1 to 4 were subjected to a short-term power test and a cycle performance test, respectively.
1. Short-term power test:
the test conditions were 25 ℃,50% soc,10s peak power test.
At an ambient temperature of 25 ℃, the secondary battery was charged for 10s in a state of charge of 50%, the charging peak power A1 of the secondary battery was tested, and the test results are referred to table 2.
The secondary battery was charged at an ambient temperature of-20 c for 10s in a state of charge of 50%, and the charging peak power A2 of the secondary battery was measured, and the measurement results are shown in table 2.
At an ambient temperature of 25 ℃, the secondary battery was discharged in a state of charge of 50% for 10s, and the discharge peak power B1 of the secondary battery was tested, and the test results are referred to table 2.
At an ambient temperature of-20 ℃, the secondary battery was discharged in a state of charge of 50% for 10s, and the discharge peak power B2 of the secondary battery was tested, and the test results are shown in table 2.
And (3) testing the cycle performance:
the test conditions were 45℃and 10C/10C cycle tests, the 8000-cycle capacity retention rate and 25℃and 50% SOC and 10s discharge DCR growth rate were recorded, and the test results were shown in Table 2. Parameters of the separators in the secondary batteries prepared in examples 1 to 14 and comparative examples 1 to 4 are shown in table 1.
TABLE 1
The short-term charge and discharge power test results, cycle performance test results, and thermal shrinkage test results of the separators of the secondary batteries prepared in examples 1 to 14 and comparative examples 1 to 4 are shown in table 2.
TABLE 2
As can be seen from table 2, by comparing the average thickness T1 of the first adhesive layer in the separator prepared in example 1, the average thickness T2 of the second adhesive layer in the separator prepared in example 1, and the average thickness T2 of the first adhesive layer in the separator prepared in comparative example 1, was 2 μm, the average thickness T2 of the second adhesive layer in the separator prepared in comparative example 2 was 2 μm, the average thickness T1 of the first adhesive layer in the separator prepared in comparative example 2 was 10 μm, the average thickness T2 of the second adhesive layer was 10 μm, the thickness of the separator prepared in comparative example 1 was the smallest, the secondary battery prepared in comparative example 1 exhibited the best peak charge-discharge power at normal temperature (25 ℃) and peak charge-discharge power at low temperature (-20 ℃), example 2 was worst, showing that the increase in the average thickness of the adhesive layer, the internal resistance of the secondary battery was increased, and the charge-discharge power of the secondary battery was reduced. However, the secondary battery prepared in example 1, which had the highest cycle capacity retention rate after 8000 cycles and the lowest cycle discharge DCR growth rate, was the secondary battery prepared in comparative example 1, which had the lowest cycle capacity retention rate after 8000 cycles and the highest cycle discharge DCR growth rate, for comparative example 2 times, showed that comparative example 1 had insufficient adhesive coating amount, insufficient adhesive strength and insufficient deformation resistance due to the total thickness of the adhesive layer, and further, poor adhesion between the separator and the pole piece during the cycle, pole piece expansion caused pole piece deformation, electrolyte infiltration deteriorated, and eventually, the secondary battery had a sufficient adhesive coating amount, but the cycle performance was inferior to that of example 1 due to the increase of interface impedance due to the excessive adhesive layer thickness.
As is apparent from comparative examples 1 to 4, as the average thickness T1 of the first adhesive layer increases, the cyclic capacity retention rate of the secondary battery exhibits a parabolic trend of increasing first and then decreasing, and the cyclic discharge DCR growth rate of the secondary battery exhibits a parabolic trend of decreasing first and then increasing, for example, the cyclic capacity retention rate of the secondary battery reaches the maximum at T1 of 2 μm and the cyclic discharge DCR growth rate of the secondary battery is the minimum at T1 of 2 μm, because when the average thickness T1 of the first adhesive layer is thin, the adhesive strength between the separator and the positive electrode sheet is weak, resulting in deterioration of the interface of the secondary battery during cycling, affecting the cyclic capacity retention rate of the secondary battery, and resulting in a higher cyclic discharge DCR growth rate of the secondary battery. When the average thickness T1 of the first adhesive layer is thicker, the diffusion of the active metal ions is affected, resulting in an increase in the internal resistance of the secondary battery, a decrease in the cycle capacity retention rate of the secondary battery, and an increase in the cycle discharge DCR growth rate.
As is apparent from comparative examples 1 and examples 5 to 7, as the average thickness T2 of the second adhesive layer increases, the cyclic capacity retention rate of the secondary battery exhibits a parabolic trend of increasing first and then decreasing, the cyclic discharge DCR growth rate of the secondary battery exhibits a parabolic trend of decreasing first and then increasing, for example, when T2 is 5 μm, the cyclic capacity retention rate of the secondary battery reaches the maximum, and the cyclic discharge DCR growth rate is lowest when T2 is 5 μm, because when the average thickness T2 of the second adhesive layer is too thin, the adhesive strength between the separator and the negative electrode tab is weak, resulting in swelling deformation of the negative electrode tab during the cycle of the secondary battery, affecting the cyclic capacity retention rate of the secondary battery, resulting in a higher cyclic discharge DCR growth rate of the secondary battery. When the average thickness T2 of the second adhesive layer is thicker, the diffusion of active metal ions is affected, resulting in an increase in the internal resistance of the secondary battery, a decrease in the cycle capacity retention rate of the secondary battery, and an increase in the cycle discharge DCR growth rate.
The secondary battery and the electric equipment provided by the embodiment of the application are described in detail, and specific examples are applied to illustrate the principle and the implementation of the application, and the description of the above embodiments is only used for helping to understand the method and the core idea of the application; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in light of the ideas of the present application, the present description should not be construed as limiting the present application.

Claims (10)

1. The secondary battery is characterized by comprising a positive electrode plate, a diaphragm and a negative electrode plate;
the diaphragm comprises a base film, a first adhesive layer is arranged on one surface of the base film facing the positive pole piece, and a second adhesive layer is arranged on one surface of the base film facing the negative pole piece;
wherein, the average thickness of first glue film is T1, the average thickness of second glue film is T2, satisfies: t2> T1.
2. The secondary battery according to claim 1, wherein at least one of the following conditions is satisfied:
(1)0.1≤T1/T2≤0.8；
(2)1μm≤T1≤4μm；
(3)3μm≤T2≤8μm。
3. the secondary battery according to claim 1, further comprising a first ceramic coating layer disposed between the first adhesive layer and the base film, wherein the first ceramic coating layer has an average thickness of T3, then 0.1.ltoreq.t3/t1.ltoreq.5; and/or T3 is less than or equal to 0.1 μm and less than or equal to 5 μm.
4. The secondary battery according to claim 3, further comprising a second ceramic coating layer disposed between the second adhesive layer and the base film, wherein the second ceramic coating layer has an average thickness of T4, then 0.01 +.t4/t2 +.1.7; and/or T4 is less than or equal to 0.1 μm and less than or equal to 5 μm.
5. The secondary battery according to claim 1, wherein the thickness of the base film is 5 μm to 30 μm.
6. The secondary battery of claim 1, wherein the first and second adhesive layers each independently comprise at least one of sodium carboxymethyl cellulose, polystyrene-butadiene emulsion, styrene-butadiene rubber emulsion, nitrile rubber emulsion, silicone rubber emulsion, ethylene-vinyl acetate copolymer emulsion, polytetrafluoroethylene emulsion, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polymethyl methacrylate, polyethylene oxide, polyethyl acrylate, ethylene tetrafluoroethylene copolymer.
7. The secondary battery of claim 4, wherein the first ceramic coating and the second ceramic coating each independently comprise at least one of alumina, magnesia, silica, magnesium hydroxide, boehmite, titania.
8. The secondary battery according to claim 1, wherein the base film comprises at least one of a polypropylene film, a polyethylene film, a cellulose film, a polyethylene terephthalate film, a nonwoven fabric film, a polyimide film, and an electrospun film.
9. The secondary battery according to claim 1, wherein the negative electrode tab includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector;
the negative electrode active material layer includes a silicon-based negative electrode material.
10. An electric device comprising the secondary battery according to any one of claims 1 to 9 as a power supply source of the electric device.
CN202310638079.XA 2023-05-31 2023-05-31 Secondary battery and electric equipment Pending CN116979221A (en)

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