Adhesive tape and battery cell

Abstract

The invention belongs to the technical field of gummed paper preparation, and particularly relates to gummed paper and a battery cell. The gummed paper comprises a base material layer and a coating layer arranged on at least one side surface of the base material layer, the base material layer comprises a plurality of fibers which are crossed and / or laminated to form pores; the number of the fiber layers is not less than 3 in the thickness direction of the gummed paper; the coating layer is partially embedded into the pores; and the puncture strength of the gummed paper is not lower than 0.8 N. The puncture strength of the gummed paper is regulated to be not lower than 0.8 N, the mechanical property of the gummed paper can be guaranteed, foreign matters such as burrs and lithium dendrites are prevented from puncturing the gummed paper, the gummed paper can play a role in protecting a diaphragm when being applied to a battery, short circuit caused by puncturing of the diaphragm is further prevented, the safety performance of the battery is improved, and meanwhile, the gummed paper is of a porous structure, so that the service life of the battery is prolonged. And the battery has relatively good electrolyte retention capability and allows electrolyte to flow, so that the battery has high energy density.

Description

Technical Field

[0001] This application belongs to the technical field of adhesive tape preparation, and specifically relates to an adhesive tape and an electric core. Background Art

[0002] Lithium-ion batteries are widely used in fields such as mobile phones, laptops, and electric vehicles. With the gradual expansion of the application market demand, new requirements for the safety of lithium-ion batteries are constantly being put forward.

[0003] Burrs at the welding points of the electrode tabs, impurities introduced during battery preparation, lithium dendrites generated during battery cycling, and the shedding of positive electrode particles can pierce the separator, resulting in the risk of short circuit due to the contact between the positive and negative electrodes, reducing the safety performance of the battery. To prevent short circuit between the positive and negative electrodes of lithium-ion batteries, adhesive tapes are often pasted at easily short-circuited parts such as the positive and negative electrode tabs and the ends of the electrode plates. However, the existing adhesive tapes with sufficient strength have poor electrolyte fluidity, and those with certain electrolyte fluidity have insufficient strength, unable to eliminate the short-circuit risk. Summary of the Invention

[0004] Therefore, the technical problem to be solved by this application is how to simultaneously improve the strength and ion permeability of the adhesive tape, improve the safety performance of the battery and take into account the energy density, so as to provide an adhesive tape and an electric core.

[0005] For this reason, this application provides the following technical solutions.

[0006] In the first aspect of this application, an adhesive tape is provided. The adhesive tape includes a base material layer and a coating layer provided on at least one surface of the base material layer; the base material layer includes a plurality of fibers, and pores are formed by the intersection and / or lamination of the plurality of fibers; along the thickness direction of the adhesive tape, the number of fiber layers is not less than 3 layers; the coating layer includes inorganic particles, and the coating layer is partially embedded in the pores; the puncture strength of the adhesive tape is not less than 0.8 N.

[0007] As an optional implementation manner, the number of fiber layers is 3 to 7 layers; and / or,

[0008] the thickness of the adhesive tape is 12 μm to 50 μm; and / or,

[0009] the porosity of the adhesive tape is 30% to 80%; and / or,

[0010] the film-breaking temperature of the adhesive tape is not less than 200 °C; and / or,

[0011] the thermal shrinkage rate of the adhesive tape in the TD direction at 120 °C / 30 min ≤ 2%; and / or,

[0012] the thermal shrinkage rate of the adhesive tape in the MD direction at 120 °C / 30 min ≤ 2%.

[0013] As an alternative embodiment, the thickness of the adhesive tape is 16 μm to 26 μm; and / or,

[0014] the composition of the substrate layer includes a polymer; and / or,

[0015] the thickness of the substrate layer is 9 μm to 45 μm; and / or,

[0016] the average diameter of the fibers is 3 μm to 15 μm; and / or,

[0017] the pore diameter of the pores is 0.1 μm to 30 μm.

[0018] As an alternative embodiment, the polymer includes at least one of polyethylene terephthalate, polyethylene, polypropylene, polyimide, polyvinyl chloride, and ethylene-propylene copolymer; and / or,

[0019] the weight-average molecular weight of the polymer is not less than 1×10 6 ; and / or,

[0020] the melting point of the polymer is not less than 130 °C; and / or,

[0021] the thickness of the substrate layer is 10 μm to 24 μm; and / or,

[0022] the average diameter of the fibers is 3 μm to 8 μm; and / or,

[0023] the pore diameter of the pores is 0.5 μm to 15 μm.

[0024] As an alternative embodiment, the coating layer includes a first coating layer on the surface of the substrate layer and a second coating layer embedded in the pores; the thickness of the first coating layer is 2 μm to 15 μm; and / or,

[0025] the first coating layer and the second coating layer include inorganic particles and / or an adhesive.

[0026] As an alternative embodiment, the average particle size of the inorganic particles is 150 nm to 2 μm; and / or,

[0027] the weight-average molecular weight of the adhesive is not less than 1.5×10 5 ; and / or,

[0028] calculated based on 100% of the total mass fraction of the coating layer, the coating layer includes 40 wt% to 80 wt% inorganic particles; and / or,

[0029] calculated based on 100% of the total mass fraction of the coating layer, the coating layer includes 20 wt% to 60 wt% adhesive.

[0030] The second aspect of the present application provides an electric core, which includes a positive electrode tab, a negative electrode tab, a separator, and the above-mentioned adhesive tape. The separator is disposed between the positive electrode tab and the negative electrode tab; the adhesive tape is disposed at least at least part of at least one surface of the positive electrode tab; and / or,

[0031] The adhesive tape is disposed at least at least part of at least one surface of the negative electrode tab; and / or,

[0032] The adhesive tape is disposed at least at least part of at least one surface of the separator.

[0033] The third aspect of the present application provides an electric core, which includes a positive electrode tab, a negative electrode tab, a separator disposed between the positive electrode tab and the negative electrode tab, and the above-mentioned adhesive tape. The positive electrode tab, the separator, and the negative electrode tab are stacked and wound multiple times along the winding direction to form a wound electric core. The wound electric core includes a flat region and an arc region. At least a part of the adhesive tape is located in the arc region. The adhesive tape is disposed at least at one of the positive electrode tab, the negative electrode tab, and the separator; and / or,

[0034] The positive electrode tab is provided with a positive electrode ear, and at least a part of the adhesive tape is located in the welding area of the positive electrode ear; and / or,

[0035] The negative electrode tab is provided with a negative electrode ear, and at least a part of the adhesive tape is located in the welding area of the negative electrode ear.

[0036] As an optional implementation manner, the positive electrode tab includes a positive electrode current collector and a positive electrode active material layer located on at least one surface of the positive electrode current collector. At least a part of the adhesive tape covers the surface of the end of the positive electrode active material layer; and / or,

[0037] The negative electrode tab includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector. At least a part of the adhesive tape covers the surface of the end of the negative electrode active material layer.

[0038] As an optional implementation manner, the electric core satisfies the following relationship:

[0039]

[0040] Wherein, S 1 is the area of the ear welding area, in mm 2 , S 2 is the area of the adhesive tape located in the ear welding area, in mm 2 , and H is the swelling thickness of the adhesive tape in the electrolyte, in μm.

[0041] As an alternative embodiment, the adhesive strength between the adhesive tape and the positive electrode tab is 0.5 to 20 N / mm;

[0042] The S 1 is 10 mm 2 to 900 mm 2 ; and / or,

[0043] The S 2 is 16 mm 2 to 1500 mm 2 ; and / or,

[0044] The H is 0.1 μm to 1.5 μm.

[0045] The technical solution of the present application has the following advantages:

[0046] 1. The adhesive tape provided by the present application, the adhesive tape includes a base material layer and a coating layer provided on at least one surface of the base material layer; the base material layer includes a plurality of fibers, and pores are formed by crossing and / or laminating between the plurality of fibers; along the thickness direction of the adhesive tape, the number of fiber layers is not less than 3 layers; the coating layer is partially embedded in the pores; the puncture strength of the adhesive tape is not less than 0.8 N. The present application regulates the puncture strength of the adhesive tape to be not less than 0.8 N, which can ensure the mechanical properties of the adhesive tape, prevent foreign objects such as burrs and lithium dendrites from piercing the adhesive tape, and can play a role in protecting the diaphragm when the adhesive tape is applied to the battery, further preventing the diaphragm from being pierced and causing a short circuit, thereby improving the safety performance of the battery. At the same time, the base material of the adhesive tape contains pores, has good electrolyte retention ability, and allows the electrolyte to flow, enabling the battery to have both high energy density. The number of fiber layers is not less than 3 layers, which strengthens the piercing strength of the adhesive tape and improves the puncture resistance safety of the adhesive tape; the more the number of fiber layers, the smaller the pore diameter formed between the fibers, which is beneficial to improving the puncture resistance safety of the adhesive tape. The pores formed by the fibers of the present application are embedded with a part of the coating layer, which can improve the adhesion between the base material layer and the coating layer and the puncture strength of the adhesive tape, reduce the occurrence of short circuits in the battery, and improve the safety performance and electrical performance of the battery. In addition, when the adhesive tape is applied to the battery, it can also prevent burrs or the shedding of the active material layer from piercing the diaphragm, play a role in isolating the positive electrode and the negative electrode, further reduce the short circuit risk, and improve the battery safety performance. At the same time, the adhesive tape allows the electrolyte to flow, avoiding the accumulation of the electrolyte under the adhesive tape and causing the adhesive tape to bulge. The lithium ions under the adhesive tape can normally vertically penetrate the adhesive tape, improving the actual negative electrode capacity and positive electrode capacity ratio at the edge of the adhesive tape, and preventing lithium deposition at the negative electrode opposite to the edge position of the adhesive tape. Description of the Drawings

[0047] To more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0048] Figure 1 It is a schematic structural diagram of the adhesive tape in Embodiment 1 of the present application;

[0049] Figure 2 It is an SEM image of the surface of the coating layer of the adhesive tape in Embodiment 1 of the present application;

[0050] Figure 3 It is an SEM image of the surface of the base material layer of the adhesive tape in Embodiment 1 of the present application;

[0051] Reference numerals:

[0052] 1 - coating layer; 2 - base material layer. Specific embodiments

[0053] The following embodiments are provided to better further understand the present application. They are not limited to the best embodiments, and do not limit the content and protection scope of the present application. Any product that is the same as or similar to the present application obtained by anyone under the inspiration of the present application or by combining the features of the present application with other prior art features falls within the protection scope of the present application.

[0054] For those not specifying specific experimental steps or conditions in the embodiments, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For reagents or instruments not specifying the manufacturer, they are all conventional reagent products that can be obtained through commercial purchase.

[0055] Burrs at the welding points of the tabs in the battery system, impurities introduced during battery preparation, lithium dendrites generated during battery cycling, and shedding of the positive electrode particles can pierce the separator, posing a short - circuit risk and reducing the safety performance of the battery. To prevent short - circuit between the positive and negative electrodes of the lithium - ion battery, adhesive tapes are often pasted at the tabs of the positive and negative electrodes and the ends of the electrode sheets and other parts prone to short - circuit. One implementation is to use a porous adhesive tape with a through - hole structure, which can make the electrolyte have a certain fluidity at the taping position, but it will reduce the strength of the adhesive tape, resulting in insufficient anti - piercing safety. Another implementation is to use a non - continuously coated adhesive layer, which can make the electrolyte have a certain fluidity at the taping position, but it is prone to cause the adhesive tape to fall off or increase the risk of dendrite generation at the taping position. To solve the above problems, the present application provides the following technical solutions.

[0056] In a first aspect, the present application provides a sticker, which includes a substrate layer and a coating layer provided on at least one surface of the substrate layer; the substrate layer includes a plurality of fibers, and pores are formed by crossing and / or laminating between the plurality of fibers; along the thickness direction of the sticker, the number of fiber layers is not less than 3 layers; the coating layer includes inorganic particles, and the coating layer is partially embedded in the pores; the puncture strength of the sticker is not less than 0.8 N. It should be noted that the sticker provided by the present application is not easily punctured by foreign objects such as burrs, lithium dendrites, impurities, positive active material particles or negative active material particles. When this sticker is applied to a battery, it can prevent the separator from being punctured and reduce the risk of battery short circuit, especially reducing the risk of the positive active material particles and ear burrs puncturing the separator; the sticker of the present application also has good electrolyte retention ability, can make the electrolyte flow, allows lithium ions to shuttle, will not accumulate under the sticker resulting in problems such as bulging of the sticker, and lithium ions can normally pass through the sticker, improving the capacity at the edge of the sticker, preventing lithium deposition or dendrite generation at the negative electrode, and reducing battery energy loss and short circuit risk. The sticker provided by the present application has good electrolyte retention ability, and on the basis of not affecting the electrolyte flow in the sticking area, the sticker takes into account high puncture resistance safety, thereby reducing the risk of battery short circuit and making the battery have both high energy density, cycle performance and safety.

[0057] Further, the present application regulates the puncture strength of the sticker to be not less than 0.8 N, so that the sticker has high puncture resistance safety, can ensure the mechanical properties of the sticker, prevent foreign objects such as burrs and lithium dendrites from puncturing the sticker, and can protect the separator from being punctured and prevent short circuit when the sticker is applied to a battery, improving the safety performance of the battery. The number of fiber layers is not less than 3 layers, which strengthens the puncture strength of the sticker and improves the puncture resistance safety of the sticker; the more the number of fiber layers, the smaller the pore diameter formed between the fibers, which is beneficial to improving the puncture resistance safety. The pores formed by the fibers of the present application are embedded with a part of the coating layer, which can improve the adhesion between the substrate layer and the coating layer and the puncture strength of the sticker, reduce the occurrence of battery short circuit, and improve the safety performance and electrical performance of the battery. In addition, when this sticker is applied to a battery, it can also prevent the active material layer from falling off and powdering, play a role in isolating the positive electrode and the negative electrode, further reduce the risk of battery short circuit, and improve the safety performance of the battery. Further, the sticker of the present application can adsorb the electrolyte and has a certain electrolyte retention ability. When it is applied to a battery, the sticker can conduct ions and allow lithium ions to freely and quickly shuttle in the area where the sticker is pasted. On the one hand, it does not affect the capacity of the active material in the area where the sticker is pasted, ensuring that the battery has a high energy density; on the other hand, it can prevent dendrites from being generated at the sticker part and puncturing the separator to cause short circuit. The sticker provided by the present application has better puncture resistance safety on the basis of having the effect of electrolyte flow and lithium ion transmission and reducing the bulging phenomenon of the sticker, reducing the risk of battery short circuit, and making the battery have both high energy density, cycle performance and safety.

[0058] This application uses a method well-known in the art to test the puncture strength of the adhesive tape. One such method for testing the puncture strength is as follows: Use a universal testing machine to measure according to GB / T 2679.7 Puncture Strength of Paperboard; use a steel needle with a diameter of 1.0 mm and a spherical tip radius of 0.5 mm to pierce the adhesive tape at a speed of 50 mm / min, and read the maximum puncture force when the steel needle penetrates the test piece, which is the puncture strength. The fiber layer refers to a single-layer structure formed by the intersection of fibers in the same plane along the length direction of the adhesive tape. The number of fiber layers refers to the number of single-layer structures along the thickness direction of the adhesive tape. The method for testing the number of fiber layers includes: using an argon ion milling instrument to cut the cross-section of the adhesive tape in a liquid nitrogen environment to obtain an SEM image of the cross-section of the adhesive tape, and the number of single-layer structures in the thickness direction of the adhesive tape is recorded as the number of fiber layers. Exemplarily, the puncture strength of the adhesive tape is 0.8 N, 1.2 N, 1.6 N, 2 N, 2.5 N, 3 N, 3.5 N, 4 N, 4.5 N, 5 N, 5.5 N, 6 N, 6.5 N, 7 N, 7.5 N, 7 N or within the range formed by any two of the above values.

[0059] In an alternative embodiment, the number of fiber layers is 3 to 7 layers; and / or,

[0060] the thickness of the adhesive tape is 12 μm to 50 μm; and / or,

[0061] the porosity of the adhesive tape is 30% to 80%; and / or,

[0062] the film-breaking temperature of the base material layer is not lower than 200 °C; and / or,

[0063] the thermal shrinkage rate of the adhesive tape in the TD direction at 120 °C / 30 min ≤ 2%; and / or,

[0064] the thermal shrinkage rate of the adhesive tape in the MD direction at 120 °C / 30 min ≤ 2%.

[0065] Increasing the number of fiber layers helps improve the puncture resistance safety of the adhesive tape. However, as the number of fiber layers increases, it will affect the ion permeability of the adhesive tape and make the adhesive tape too hard. The number of fiber layers of the adhesive tape in this application is 3 to 7 layers, which is beneficial to improving the puncture resistance safety of the adhesive tape and reducing the hardness of the adhesive tape, better protecting the separator, further reducing the puncture of the separator and enhancing the battery safety performance. Controlling the thickness, porosity, and thermal shrinkage rate of the adhesive tape in this application to meet the above ranges helps further improve the puncture safety. The adhesive tape in this application meeting the above ranges is beneficial to further improving the puncture resistance safety of the adhesive tape on the basis of ensuring that the battery has an appropriate thickness and high energy density. Regulating the porosity of the adhesive tape in this application to meet the above ranges can further increase the electrolyte retention capacity of the adhesive tape, enhance ion transport and battery energy density. The film-breaking temperature of the adhesive tape in this application is not lower than 200 °C, which helps reduce the thermal shrinkage rate and improve the thermal stability of the adhesive tape, thereby enhancing the thermal safety of the battery. When the battery temperature is too high, the adhesive tape in this application has good thermal stability and is not easily damaged, playing a role in protecting the battery and improving the safety of the battery. The thermal shrinkage rates of the adhesive tape in this application in the TD direction and MD direction are both ≤ 2%, preventing the adhesive tape from shrinking and causing battery short circuit at high temperatures, which helps further improve the thermal stability of the adhesive tape and the thermal safety of the battery.

[0066] It should be noted that the number of fiber layers and the thickness of the adhesive tape are obtained by testing using well-known methods in the art. Here is an example. Obtain the SEM image of the cross-section of the adhesive tape along the thickness direction to obtain the number of fiber layers and the thickness of the adhesive tape. A fiber layer refers to a single-layer structure formed by fibers intersecting in the same plane along the length direction of the adhesive tape. Randomly select 20 positions in the SEM image of the cross-section of the adhesive tape along the thickness direction to obtain the number of fibers along the thickness direction of each position, and record the fiber number with the largest proportion as the number of fiber layers. Exemplarily, the number of fiber layers is 3 layers, 4 layers, 5 layers, 6 layers, 7 layers or within the range composed of any two of the above values. The thickness of the adhesive tape is 12 μm, 16 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or within the range composed of any two of the above values.

[0067] The porosity of the adhesive tape is obtained by testing using well-known methods in the art. Here is an example. Weigh the adhesive tape sample, soak it in n-butanol solvent for 2 h, take it out and wipe off the surface liquid and then weigh it. The porosity is calculated by the following formula:

[0068]

[0069] where, W 2 is the weight of the adhesive tape sample after soaking in n-butanol, in g; W 1 is the weight of the adhesive tape before soaking, in g; A is the area of the adhesive tape sample, in cm 2; d is the average thickness of the adhesive tape sample, in cm; ρ is the density of n-butanol, 0.811 g / mL. Exemplarily, the porosity of the adhesive tape is 30%, 40%, 50%, 60%, 70%, 80% or within the range composed of any two of the above values.

[0070] The thermal shrinkage rate of the adhesive tape is tested by using methods well-known in the art. The testing methods for the thermal shrinkage rates in the TD direction and MD direction of the adhesive tape are the same. Here is one example. Take an adhesive tape sample and measure the original length dimension L of the adhesive tape sample at room temperature. 0 Place the adhesive tape sample in a vacuum drying oven at 120°C ± 2°C and heat it for 30 minutes, then take it out and measure the length dimension L of the adhesive tape sample after heating at room temperature. 1 The thermal shrinkage rate is calculated according to the following formula:

[0071]

[0072] Exemplarily, the thermal shrinkage rate of the adhesive tape in the TD direction is 0.05%, 0.1%, 0.15%, 2% or within the range composed of any two of the above values. The thermal shrinkage rate of the adhesive tape in the MD direction is 0.05%, 0.1%, 0.15%, 2% or within the range composed of any two of the above values.

[0073] The film-breaking temperature of the adhesive tape is obtained by using methods well-known in the art. Here is one example. The testing method for the film-breaking temperature of the adhesive tape includes: fixing the adhesive tape sample on a stainless steel rack, placing it in an oven that has been heated to a preset temperature for 2 minutes, taking out the sample and observing its deformation, and taking the temperature at which the deformation first occurs as its film-breaking temperature. The film-breaking temperature of the base material layer is 200°C, 250°C, 300°C, 350°C, 400°C or within the range composed of any two of the above values.

[0074] In an optional embodiment, the composition of the base material layer includes a polymer; and / or,

[0075] The thickness of the base material layer is 9 μm to 45 μm; and / or,

[0076] The average diameter of the fibers is 3 μm to 15 μm; and / or,

[0077] The pore diameter of the pores is 0.1 μm to 30 μm.

[0078] The composition of the base material layer of this application includes a polymer. The polymer has high crystallinity and regularity, good mechanical strength, which helps to further improve the puncture strength of the adhesive tape, is beneficial to improving the puncture resistance safety of the adhesive tape, further reduces the diaphragm from being punctured, and improves the battery safety performance. The polymer also has good heat resistance and has characteristics such as shape stability at high temperatures, which can further improve the thermal stability of the adhesive tape and is beneficial to the thermal safety of the battery. By adjusting the thickness of the base material layer of this application to meet the above range, it is possible to further improve the puncture strength and puncture resistance safety of the adhesive tape on the basis of ensuring the mechanical strength of the adhesive tape and the battery having an appropriate thickness, and reduce the situation where foreign objects such as burrs and lithium dendrites pierce the adhesive tape and pierce the diaphragm, thereby further improving the safety performance of the battery. The average diameter of the fibers in this application is 3μm to 15μm, which helps the coating layer to embed into the base material layer, prevents the adhesive tape from having through holes, and further improves the puncture resistance safety of the adhesive tape. The pore diameter of the pores in this application is 0.1μm to 30μm, which is beneficial to improving the puncture strength of the adhesive tape. In addition, when the average diameter of the fibers in this application is within the above range, it also helps to increase the electrolyte retention amount of the adhesive tape. The fibers maintain appropriate swelling under the immersion of the electrolyte, improve the bonding force between the coating layer and the base material layer, enhance the liquid retention ability of the adhesive tape, help the lithium ions to shuttle, promote the electrolyte flow, prevent problems such as bulging caused by the accumulation of electrolyte under the adhesive tape, and prevent lithium deposition on the negative electrode. When the pore diameter of the pores is within the above range, the embedding amount of the coating layer in the base material layer can be appropriate, which helps to increase the electrolyte retention amount of the adhesive tape, enables the adhesive tape to adsorb more electrolyte, and improves the lithium ion transmission.

[0079] It should be noted that the thickness of the base material layer, the average diameter of the fibers, and the pore diameter of the pores are all obtained by testing methods well-known in the art. Here, a testing method is listed. Average diameter of the fibers: Take an adhesive tape sample, take 10 SEM images of different positions of the adhesive tape sample under the electron microscope, measure the diameters of any 80 fibers in each SEM image, take the average value, calculate the data of the 10 SEM images and then take the average value to obtain the average diameter of the fibers. The pore diameter of the pores refers to the pore diameter with the largest proportion in the pore size distribution diagram. The pore diameter of the pores is obtained by testing methods well-known in the art. Here, a method is listed: Take an adhesive tape sample, soak it in benzene solution for 4h, take out the adhesive tape sample and dry it, test the pore diameter of the adhesive tape sample with a pore size meter, and take the pore diameter with the largest proportion in the pore size distribution diagram as the pore diameter of the pores. Exemplarily, the thickness of the base material layer is 9μm, 12μm, 16μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm or within the range composed of any two of the above values. The average diameter of the fibers is 3μm, 5μm, 7μm, 9μm, 11μm, 13μm, 15μm or within the range composed of any two of the above values. The pore diameter of the pores is 0.1μm, 0.5μm, 1μm, 3μm, 7μm, 11μm, 16μm, 23μm, 30μm or within the range composed of any two of the above values.

[0080] In an alternative embodiment, the polymer comprises at least one of polyethylene terephthalate, polyethylene, polypropylene, polyimide, polyvinyl chloride, ethylene-propylene copolymer; and / or,

[0081] The weight-average molecular weight of the polymer is not less than 1×10 6 ; and / or,

[0082] The melting point of the polymer is not less than 130 °C; and / or,

[0083] The thickness of the adhesive tape is 16 μm to 26 μm; and / or,

[0084] The thickness of the base material layer is 10 μm to 24 μm; and / or,

[0085] The average diameter of the fiber is 3 μm to 8 μm; and / or,

[0086] The pore diameter of the pore is 0.5 μm to 10 μm.

[0087] The composition of the base material layer of this application includes at least one of polyethylene terephthalate, polyethylene, polypropylene, polyimide, polyvinyl chloride, ethylene-propylene copolymer. The weight-average molecular weight of the polymer in this application is not less than 1×10 6 , which can form longer molecular chains, provide more cross-linking points between fibers, enhance the strength of the fibers, easily form uniform fibers, further improve the mechanical properties and puncture resistance safety of the adhesive tape, reduce the puncture of the adhesive tape and the separator, cause short circuits, and is beneficial to improving the battery safety performance. The melting point of the polymer in this application is not less than 130 °C, which can make the adhesive tape have higher thermal stability, prevent the adhesive tape from being damaged and causing battery short circuits under high temperature or high voltage, and improve the thermal safety of the battery. The pore diameter of the controlled pores in this application is 0.5 μm to 10 μm, which is beneficial to the filling of the pores by the coating layer and preventing the coating layer from falling off and causing through holes in the adhesive tape, further improving the mechanical properties and puncture resistance safety of the adhesive tape, and reducing the risk of battery short circuits.

[0088] It should be noted that the weight-average molecular weight of the polymer is obtained by testing using a method well-known in the art. Here, a gel permeation chromatography method is listed. The melting point of the polymer is obtained by testing using a method well-known in the art. Here, a DSC is listed as an example. Exemplarily, the weight-average molecular weight of the polymer is 1×10 6 、2×10 6 、5×10 6 、8×10 6 、2×10 7etc. The melting point of the polymer is 130 °C, 150 °C, 200 °C, 250 °C, 300 °C, 350 °C, 400 °C or within the range composed of any two of the above values.

[0089] In an alternative embodiment, the coating layer includes a first coating layer on the surface of the substrate layer and a second coating layer embedded in the pores; the thickness of the first coating layer is 2 μm to 15 μm; and / or,

[0090] The first coating layer and the second coating layer include inorganic particles and / or adhesives.

[0091] The thickness of the first coating layer of this application meets the above range, which helps to further improve the puncture resistance of the adhesive tape. The inorganic particles have high hardness, which can further improve the puncture strength of the adhesive tape, thereby enhancing the puncture resistance safety; in addition, the inorganic particles also help to increase the electrolyte retention capacity of the adhesive tape. The adhesive in the coating can improve the puncture strength of the adhesive tape. It should be noted that both the first coating layer and the second coating layer contain inorganic particles and / or adhesives. Exemplarily, the thickness of the first coating layer is 2 μm, 4 μm, 8 μm, 10 μm, 13 μm, 15 μm or within the range composed of any two of the above values.

[0092] In an alternative embodiment, the average particle size of the inorganic particles is 150 nm to 2 μm; and / or,

[0093] The molecular weight of the adhesive is not less than 1.5×10 5 ; and / or,

[0094] Based on the total mass fraction of the coating layer being 100%, the coating layer includes 40 wt% to 80 wt% inorganic particles; and / or,

[0095] Based on the total mass fraction of the coating layer being 100%, the coating layer includes 20 wt% to 60 wt% adhesive.

[0096] It should be noted that the average particle size of the inorganic particles is obtained by testing using methods well-known in the art. Here is an example. Under SEM, measure the diameters of 100 particles randomly on the surface of the adhesive tape coating layer, calculate the average value, measure 10 times at 10 different positions, and take the average value, which is recorded as the average particle size of the inorganic particles. The weight-average molecular weight of the adhesive is obtained by testing using methods well-known in the art. Here is an example, gel permeation chromatography. The test method for the mass content of the inorganic particles in the coating layer is obtained by using methods well-known in the art. Here is an example. Weigh the adhesive tape sample and record it as M. Immerse it in benzene solution for 4 h. The coating layer peels off from the substrate layer. Take out the substrate layer, dry it and weigh it, and record it as M 1 , the total mass of the coating layer is M - M 1 ; use a mass of M0 Filter the benzene solution with filter paper. The binder in the coating layer dissolves in benzene, and the inorganic particles adhere to the filter paper. After drying the filter paper, weigh it and record it as M2. The mass of the inorganic particles is M 2 -M 0 , and the mass content of the inorganic particles in the coating layer is (M 2 -M 0 ) / (M - M 1 ). It should be noted that the adhesive tape sample can also be immersed in organic solvents such as toluene. This application does not limit the type of immersion solvent, as long as the coating layer can be separated from the substrate. Further, the mass content of the binder in the coating layer is calculated by the following formula: binder mass content = 1 - inorganic particle mass content.

[0097] Exemplarily, the average particle size of the inorganic particles is 150nm, 200nm, 300nm, 500nm, 800nm, 1μm, 1.2μm, 1.5μm, 2μm or within the range composed of any two of the above values. Based on the total mass fraction of 100% of the coating layer, the mass content of the inorganic particles in the coating layer is 40wt%, 50wt%, 60wt%, 70wt%, 80wt% or within the range composed of any two of the above values.

[0098] It should be noted that the inorganic particles include alumina, boehmite, Li 7 La 3 Zr 2 O 12 (LLZO), Li 3x La(2 / 3 - x ) / 3 TiO 3 (LLTO), Li 1+x Al x Ti 2-x (PO 4 ) 3 (LATP), magnesium oxide, titanium oxide, hafnium dioxide, tin dioxide, cerium dioxide, nickel oxide, zirconium oxide, zinc oxide, calcium oxide, magnesium hydroxide, aluminum hydroxide, barium hydroxide, barium sulfate, calcium silicate or at least one of titanium dioxide. The binder includes at least one of polyisobutene, styrene-isoprene copolymer, polyvinylidene fluoride, copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene and styrene-butadiene rubber.

[0099] In a second aspect, the present application provides an electrode assembly, which includes a positive electrode tab, a negative electrode tab, a separator, and the above-mentioned adhesive tape. The separator is disposed between the positive electrode tab and the negative electrode tab; the adhesive tape is disposed at least partially on at least one surface of the positive electrode tab; and / or,

[0100] the adhesive tape is disposed at least partially on at least one surface of the negative electrode tab; and / or,

[0101] the adhesive tape is disposed at least partially on at least one surface of the separator.

[0102] The positive electrode tab, the negative electrode tab, and the separator each have two surfaces, and the adhesive tape is disposed at least partially on at least one surface of these surfaces. It should be noted that the partial position includes the case where the adhesive tape covers a part of the surface or the entire surface.

[0103] In a third aspect, the present application provides an electrode assembly, which includes a positive electrode tab, a negative electrode tab, a separator disposed between the positive electrode tab and the negative electrode tab, and the above-mentioned adhesive tape. The positive electrode tab, the separator, and the negative electrode tab are stacked and wound multiple times along the winding direction to form a wound electrode assembly. The wound electrode assembly includes a flat region and an arc region. At least a part of the adhesive tape is located in the arc region, and the adhesive tape is disposed at least at one of the positive electrode tab, the negative electrode tab, and the separator; and / or,

[0104] the positive electrode tab is provided with a positive electrode ear, and at least a part of the adhesive tape is located in the welding area of the positive electrode ear; and / or,

[0105] the negative electrode tab is provided with a negative electrode ear, and at least a part of the adhesive tape is located in the welding area of the negative electrode ear.

[0106] In the present application, the adhesive tape is disposed on the surface of the electrode tab or the separator located in the arc region, which can prevent the separator from being punctured due to the expansion of the system during cycling and the short circuit caused by dendrites piercing the separator, thereby improving the safety performance of the battery. In the present application, the adhesive tape is disposed in the welding area of the electrode tab ear, which can prevent the burrs at the welding point from piercing the separator and causing a short circuit, thereby improving the safety performance of the battery. In addition, disposing the adhesive tape on the electrode assembly can also improve the electrical properties such as the energy density of the battery.

[0107] In an optional embodiment, the positive electrode tab includes a positive electrode current collector and a positive electrode active material layer located on at least one surface of the positive electrode current collector, and at least a part of the adhesive tape covers the surface at the end of the positive electrode active material layer; and / or,

[0108] the negative electrode tab includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, and at least a part of the adhesive tape covers the surface at the end of the negative electrode active material layer.

[0109] In this application, the adhesive tape is applied to the ends of the positive or negative electrodes, which can prevent the short - circuit risk caused by the shedding of active substances in the electrode sheets; the adhesive tape can also play a role in separating the positive and negative electrodes, further reducing the short - circuit risk. In addition, when the adhesive tape is applied to the ends of the electrode sheets, it can also reduce problems such as the shedding of the active material layer and powder falling off. It should be noted that the end refers to the position where the coating meets the current collector, that is, the end of the wound battery cell.

[0110] In an alternative embodiment, the following relationship is satisfied:

[0111]

[0112] where S 1 is the area of the tab welding area, in mm 2 , S 2 is the area of the adhesive tape located in the tab welding area, in mm 2 , and H is the swelling thickness of the adhesive tape in the electrolyte, in μm.

[0113] When the existing ion - impermeable adhesive tape is applied to the battery cell, it will hinder the transmission of lithium ions between the tab and the electrolyte, increasing the internal resistance of the battery cell. The adhesive tape of this application has a liquid - holding capacity, which can improve the transmission of lithium ions between the tab and the electrolyte and reduce the internal resistance of the battery cell. However, when there is too much electrolyte, on the one hand, it is easy to cause the adhesive tape to lose its adhesion and fail to play a protective role; on the other hand, it is also easy to cause side reactions between the tab welding area and the electrolyte. Although the risk of local side reactions can be reduced by increasing the tab welding area, making the overall current distribution of the tab more uniform and reducing the local current density; it can also reduce the contact resistance and heat generation, avoiding side reactions caused by high temperature. However, too large a welding area may lead to uneven welding quality, increasing the risk of welding defects (such as pores and cracks), and it is also easy to cause mechanical stress to concentrate in the welding area, increasing the risk of tab detachment or fracture. It is also possible to reduce the reaction area between the electrolyte and the welding area by reducing the tab welding area to achieve the purpose of reducing side reactions. However, reducing the tab welding area will increase the internal resistance of the battery. Through research, it is found that by regulating the area S 1 of the tab welding area and the area S 2 of the adhesive tape located in the tab welding area to satisfy the above formula (1), the area S 1 of the tab welding area and the area S 2The swelling thickness of the adhesive tape in the electrolyte satisfies Equation 2, which can make the electrolyte content at the tab welding area and the tab position match. On the one hand, it can avoid the side reaction between the tab welding area and the electrolyte, and there is no need to sacrifice the internal resistance of the battery cell or the tab welding quality to reduce the side reaction. On the other hand, it is beneficial to make the current distribution more uniform, reduce the situation of too high local current density, etc., so as to avoid the aggravation of local heating and further reduce the side reaction caused by high temperature. In addition, it can make the adhesive tape have appropriate adhesiveness to prevent the adhesive tape from falling off and ensure the safety performance of the battery; satisfying the above Equations 1-2 is also beneficial to improving the welding quality, reducing the generation of welding defects, relieving the mechanical stress in the welding area, further reducing the risk of tab detachment or fracture, and making the battery have an appropriate thickness, further improving the battery energy density.

[0114] In an optional embodiment, the adhesion strength between the adhesive tape and the positive electrode plate is 0.5-20 N / mm.

[0115] The S 1 is 10 mm 2 ~900 mm 2 ; and / or,

[0116] The S 2 is 16 mm 2 ~1500 mm 2 ; and / or,

[0117] The H is 0.1 μm~1.5 μm.

[0118] This application makes the area S of the tab welding area 1 satisfy the above range. On the one hand, it makes the current distribution more uniform, reduces the too high local current density, and thus reduces the risk of local side reaction; on the other hand, it can also reduce the contact resistance, reduce heat generation, and avoid the side reaction caused by high temperature. In addition, when the area S of the tab welding area 1 satisfies the above range, it can also improve the uniformity of the welding quality, further reduce welding defects such as pores and cracks, reduce the situation of mechanical stress concentration in the welding area, and is beneficial to reducing tab detachment or fracture.

[0119] The area S of the adhesive tape located in the tab welding area of this application 2 satisfies the above range. On the one hand, it makes the area of the adhesive tape match the tab welding area, ensures that the battery has an appropriate thickness, and is beneficial to further improving the battery energy density; on the other hand, the matching of the adhesive tape area and the tab welding area can give full play to the protective role of the adhesive tape, reduce the situation of battery short circuit, and can make the electrolyte distribution at the tab position more uniform, reducing the internal resistance of the battery.

[0120] It should be noted that the swelling thickness H of the adhesive tape in the electrolyte is obtained by testing with a method well-known in the art. Exemplarily, the testing method for the swelling thickness H of the adhesive tape: After removing the adhesive tape from the battery and drying it, measure the initial thickness of the dried adhesive tape as h 1 , immerse the adhesive tape in the electrolyte at 85 °C for 24 h and then measure the thickness as h 2 , H = h 2 - h 1 . Exemplarily, H is 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 0.9 μm, 1.1 μm, 1.3 μm, 1.5 μm or within the range composed of any two of the above values.

[0121] The area S of the tab welding region 1 and the area S of the adhesive tape located in the tab welding region 2 are obtained by testing and calculating with a method well-known in the art. Exemplarily, when the tab welding region is rectangular, the area S 1 = length × width.

[0122] The adhesion strength is obtained by testing with a method well-known in the art. Here is one example: Lay the electrode sheet containing the adhesive tape flat on the table, use a transparent adhesive tape with the same width as the adhesive tape and paste it on the surface of the adhesive tape. On the side of the electrode sheet without the adhesive tape, stick it to the OPP film through double-sided tape, roll it back and forth three times with a 2 kg roller, and use a universal testing machine to test the adhesion strength. In this application, the adhesion strength between the adhesive tape and the electrode sheet is regulated to meet the above range, and the adhesive tape is not likely to shift, ensuring the safety and puncture resistance of the battery.

[0123] In an optional embodiment, the composition of the positive electrode active material layer includes a positive electrode active material, which is a common raw material in the art, such as at least one of lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide (LiCoO 2 ), lithium manganese oxide, lithium manganese iron phosphate or lithium titanate, etc. The composition of the positive electrode active material layer also includes additives, such as a binder, a conductive agent, etc., and the binder and the conductive agent are common raw materials in the art. The conductive agent includes at least one of conductive carbon black, carbon nanotubes, etc.; the binder includes at least one of PVDF, HSV, PTFE, SBR, PAA, etc. The positive electrode current collector uses a common current collector in the art, such as aluminum foil, titanium foil, etc.

[0124] In an alternative embodiment, 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 current collector can be a common current collector in the art, such as copper foil, nickel foil, iron-nickel alloy foil, copper-nickel alloy foil, etc. The composition of the negative electrode active material layer includes active materials, which are common raw materials in the art, such as at least one of carbon-based materials, silicon-based materials, tin-based materials, and titanium-based materials; specifically, it includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, silicon alloys, elemental tin, tin oxide compounds, tin alloys, elemental titanium, titanium oxide compounds, and titanium alloys. It can be understood that the composition of the negative electrode active material layer can also include additives, such as conductive agents, binders, etc. The conductive agent includes at least one of carbon black, carbon nanotubes, etc., and the content of the conductive agent in the negative electrode active material layer is not higher than 3 wt%. The binder includes at least one of SBR binder, PAA binder, etc., and the content of the binder in the negative electrode active material layer is not higher than 3 wt%. The active materials, conductive agents, and binders in the negative electrode active material layer adopt conventional dosage ratios in the art.

[0125] In an alternative embodiment, the separator includes a base film and a coating located on at least one surface of the base film, and the coating includes at least one layer structure of a ceramic layer and an adhesive layer. The material of the base film is selected from well-known raw materials in the art and is not limited thereto; as an example, the material of the base film includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polyphenylene sulfide, polyimide, polystyrene, polytetrafluoroethylene, polymethyl methacrylate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, cellulose, etc. The composition of the ceramic layer includes inorganic particles and a binder. Optionally, the mass ratio of the inorganic particles to the binder is (40-95):(5-60); the inorganic particles include at least one of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin oxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium dioxide, zirconium titanate, barium titanate, and magnesium fluoride; the binder includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinyl pyrrolidone, polyethylene ether, polytetrafluoroethylene, and polyhexafluoropropylene. The adhesive layer is a polymer coating; the polymer is a common compound in the art; for example, the polymer includes a copolymer or homopolymer formed by at least one monomer of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, styrene, α-methylstyrene, vinyltoluene, ethylene, vinyl acetate, acrylonitrile, vinylidene fluoride, hexafluoropropylene, chlorophthalic anhydride; the polymer can also be at least one of polyetherimide, polyamideimide, polyimide, and a copolymer of vinylidene fluoride-hexafluoropropylene.

[0126] In an alternative embodiment, the battery cell further includes an electrolyte, which includes an electrolyte salt and a solvent. It can be understood that the electrolyte is a common raw material for preparing battery cells in the art. The electrolyte salt includes lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluoro(bis(oxalato))phosphate (LiDFOP), and lithium tetrafluoro(bis(oxalato))phosphate (LiTFOP), at least one of which. The solvent includes at least one of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE). The electrolyte further includes an additive, and the type and amount of the additive added are determined according to requirements.

[0127] Example 1

[0128] This example provides a battery, including:

[0129] (1) The structure of the adhesive tape is as Figure 1 shown. The adhesive tape includes a base layer 2 and a coating layer 1 provided on one side of the surface of the base layer. The material of the base layer includes polyethylene terephthalate (molecular weight of about 1.25 million, melting point of about 255 °C), with a thickness of 10 μm. The base layer includes a number of fibers, the average diameter of the fibers is 3.5 μm, the pore diameter of the pores formed between the fibers is 3 μm, and the number of layers of the fiber layer is 3 layers; the coating layer includes boehmite particles and a styrene-isoprene (molecular weight of about 150,000) copolymer adhesive with a mass ratio of 3:2. The average particle size of the inorganic particles is 0.8 μm, and the thickness of the first coating layer is 6 μm; the porosity of the adhesive tape is 35%. Figure 2 is the SEM image of the surface of the coating layer of the adhesive tape. It can be seen from the figure that inorganic particles and adhesives are distributed on the surface. Figure 3It is an SEM image of the surface of the adhesive tape base material layer. The base material layer contains several fibers, and a network structure is formed between the several fibers.

[0130] The cathode active material lithium cobalt oxide, the binder PVDF, and the conductive carbon black are dispersed in N-methylpyrrolidone according to a mass ratio of 97:2:1 to obtain a uniform cathode active material slurry; the above slurry is evenly coated on both surfaces of the aluminum foil, and after drying, an active material layer is formed; in a certain area of the active material layer, the coating is removed by cleaning to expose the aluminum foil, and then roll-pressed; a tab is welded in the area where the aluminum foil is exposed above to obtain a pole piece, which is slit and the positive tab is welded. An adhesive tape is pasted at the end of the active material layer to obtain a positive pole piece, and the bonding strength between the adhesive tape and the positive pole piece is 5 N / mm.

[0131] (2) Graphite, the binder styrene-butadiene rubber, the thickener sodium carboxymethyl cellulose, and the conductive agent conductive carbon black are mixed and dispersed in deionized water according to a mass ratio of 97:1:1.5:0.5 to obtain a negative electrode slurry. The negative electrode slurry is evenly coated on both surfaces of the copper foil; after the coated pole piece is dried, the coating is removed by cleaning in a certain area in the middle of the active coating to expose the current collector, and then roll-pressed; a tab is welded in the cleaning area to prepare a negative pole piece.

[0132] (3) The above positive pole piece, separator, and negative pole piece are stacked in sequence, wound to support the core, encapsulated with an aluminum-plastic film, baked in a vacuum state for 24 h to remove moisture, injected with electrolyte, formed, aged, vacuum-sealed, and sorted to obtain a soft-pack lithium-ion battery. Among them, the electrolyte includes an organic solvent and the lithium salt LiPF6. The organic solvent includes diethyl carbonate, dimethyl carbonate, and ethylene carbonate with a volume ratio of 1:1:1, and the concentration of the lithium salt in the electrolyte is 1 mol / L.

[0133] Example 2-16

[0134] Examples 2-16 respectively provide a battery, which is basically the same as Example 1, except that the adhesive tapes are different, and the adhesive tape parameters are shown in Table 1.

[0135] Examples 17-26

[0136] Examples 17-26 respectively provide a battery, which is basically the same as Example 9, except that the area S1 of the tab welding area and the area of the adhesive tape located in the tab welding area are different, and the parameters are shown in Table 1.

[0137] Comparative Example 1

[0138] Comparative Example 1 provides a battery, which is basically the same as Example 1, except that the adhesive tape is different, and the adhesive tape parameters are shown in Table 1.

[0139] Comparative Example 2

[0140] Comparative Example 1 provides a battery, which is basically the same as Example 1, except that the adhesive tape is different. The parameters of the adhesive tape are shown in Table 1.

[0141] Table 1 Adhesive Tape Parameters of Each Example and Comparative Example

[0142] Table 1-1

[0143]

[0144] Table 1-2

[0145]

[0146]

[0147] Test Example

[0148] This test example provides the performance of the batteries of the above examples and comparative examples:

[0149] Cycle life: ① Under the condition of 25°C, charge at a constant current of 0.5C to 4.5V, and charge at a constant voltage until it cuts off at 0.05V; ② Discharge at a constant current of 0.5C until it cuts off at 3.0V, and record the first discharge capacity as the initial capacity Q 1 ; ③ Repeat steps ①-②, and the obtained discharge capacity is used as the capacity Q of the battery 2 , and calculate the capacity retention rate (%) according to the following formula. When the capacity retention rate decays to 80%, the test stops, and record the number of cycles at this time, which is the cycle life of the battery.

[0150] Energy density: Under the condition of 25°C, charge to full capacity at 0.2C and let it stand for 10 minutes. Discharge at 0.2C to 3.0V to measure the capacity of the battery. Calculate the energy density through the following formula.

[0151]

[0152] Test K value: The K value is the voltage decay value of the battery per hour, mV / h; test the voltage internal resistance at different times, and calculate through the formula K = (OCV1 - OCV2) / time interval between two tests.

[0153] Test method for battery internal resistance: Use an internal resistance tester of model ZX5563.

[0154] Process processing situation: After the battery is prepared, disassemble the battery and observe whether the adhesive tape has phenomena such as loss of adhesion, displacement, and shedding. If there is no such situation, it is recorded as no abnormality.

[0155] Table 2 Test Results of Examples and Comparative Examples

[0156]

[0157]

[0158] As can be seen from the above results, when the adhesive tape of the present application is applied to a battery, it can improve the puncture resistance safety of the separator on the basis of ensuring the electrical properties such as the energy density and cycle performance of the battery, thereby reducing the risk of battery short circuit and improving the battery safety performance. The present application is conducive to optimizing the battery energy density and cycle performance by further optimizing the number of fiber layers. From Comparative Examples 1-2, the present application controls the puncture strength of the adhesive tape to be not less than 0.8 N, and the number of fiber layers to be not less than 3 layers, which is conducive to improving the puncture resistance safety of the adhesive tape on the basis of ensuring the electrolyte retention amount and allowing lithium ions to shuttle, reducing the battery short circuit risk, and making the battery have both high energy density, cycle performance and safety.

[0159] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made on the basis of the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A tape, characterized in that: The adhesive tape comprises a substrate layer and a coating layer arranged on at least one side of the substrate layer; the substrate layer comprises a plurality of fibers, and the fibers are crossed and / or stacked to form pores; along the thickness direction of the adhesive tape, the number of fiber layers is not less than 3; the coating layer comprises inorganic particles, and a portion of the coating layer is embedded in the pores; the puncture strength of the adhesive tape is not less than 0.8N.

2. The adhesive tape according to claim 1, characterized in that: The number of fiber layers is 3 to 7; and / or, The thickness of the adhesive tape is 12 μm to 50 μm; and / or, The porosity of the adhesive tape is 30% to 80%; and / or, The film breaking temperature of the adhesive tape is not less than 200°C; and / or, The thermal shrinkage rate of the adhesive tape in the TD direction at 120°C / 30min is ≤2%; and / or, The thermal shrinkage rate of the adhesive tape in the MD direction at 120° C. / 30 min is ≤2%.

3. The adhesive tape according to claim 1, characterized in that: The composition of the substrate layer includes a polymer; and / or, The thickness of the substrate layer is 9 μm to 45 μm; and / or, The average diameter of the fibers is 3 μm to 15 μm; and / or, The pores have a pore diameter of 0.1 μm to 30 μm.

4. The adhesive tape according to claim 3, characterized in that: The polymer includes at least one of polyethylene terephthalate, polyethylene, polypropylene, polyimide, polyvinyl chloride, and ethylene-propylene copolymer; and / or, The weight average molecular weight of the polymer is not less than 1×10 6 and / or, The melting point of the polymer is not less than 130°C; and / or, The thickness of the adhesive tape is 16 μm to 26 μm; and / or, The thickness of the substrate layer is 10 μm to 24 μm; and / or, The average diameter of the fibers is 3 μm to 8 μm; and / or, The pores have a pore diameter of 0.5 μm to 15 μm.

5. The adhesive tape according to claim 1, characterized in that: The coating layer comprises a first coating layer located on the surface of the substrate layer and a second coating layer embedded in the pores; the thickness of the first coating layer is 2 μm to 15 μm; and / or, The first coating layer and the second coating layer include inorganic particles and / or a binder.

6. The adhesive tape according to claim 5, characterized in that: The average particle size of the inorganic particles is 150 nm to 2 μm; and / or, The weight average molecular weight of the adhesive is not less than 1.5×10 5 and / or, Based on 100% of the total mass fraction of the coating layer, the coating layer comprises 40wt% to 80wt% of inorganic particles; and / or, Based on 100% of the total mass fraction of the coating layer, the coating layer includes 20wt% to 60wt% of adhesive.

7. A battery cell, characterized in that: The battery cell comprises a positive electrode sheet, a negative electrode sheet, a separator and the adhesive tape according to any one of claims 1 to 6, wherein the separator is arranged between the positive electrode sheet and the negative electrode sheet; the adhesive tape is arranged on at least a part of at least one surface of the positive electrode sheet; and or, The adhesive tape is disposed on at least a portion of at least one surface of the negative electrode plate; and or, The adhesive tape is disposed on at least a portion of at least one surface of the diaphragm.

8. A battery cell, characterized in that: The battery cell comprises a positive electrode sheet, a negative electrode sheet, a separator arranged between the positive electrode sheet and the negative electrode sheet, and the adhesive tape according to any one of claims 1 to 6, wherein the positive electrode sheet, the separator and the negative electrode sheet are stacked and wound multiple times in a winding direction to form a wound battery cell, the wound battery cell comprises a straight area and an arc area, at least a portion of the adhesive tape is located in the arc area, and the adhesive tape is arranged at at least one of the positive electrode sheet, the negative electrode sheet and the separator; and / or, The positive electrode sheet is provided with a positive electrode tab, and at least a portion of the adhesive tape is located in a welding area of ​​the positive electrode tab; and / or, The negative electrode plate is provided with a negative electrode tab, and at least a portion of the adhesive tape is located at a welding area of ​​the negative electrode tab; and / or, The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer located on at least one surface of the positive electrode current collector, and at least a portion of the adhesive tape covers a surface at a terminal end of the positive electrode active material layer; and / or, The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, and at least a portion of the adhesive tape covers the surface of the end of the negative electrode active material layer.

9. The battery cell according to claim 8, characterized in that: The following relationship is satisfied: Among them, S1 is the area of ​​the tab welding area, in mm 2 , S2 is the area of ​​the adhesive tape located in the tab welding area, in mm 2 , H is the swelling thickness of the adhesive tape in the electrolyte, in μm.

10. The battery cell according to claim 9, characterized in that: The adhesive strength between the adhesive tape and the positive electrode plate is 0.5 to 20 N / mm; and / or, The S1 is 10 mm 2 ~900mm 2 and / or, The S2 is 16mm 2 ~1500mm 2 and / or, The H is 0.1 μm to 1.5 μm.

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