Batteries, and electrochemical and electronic devices containing them.

Abstract

The present invention provides a battery, as well as electrochemical and electronic devices including the same, wherein the battery comprises an electrode assembly and an outer bag, the electrode assembly comprises electrode pieces and a separator, the separator comprises a porous substrate, at least one surface of the porous substrate is provided with a first coating layer, the first coating layer comprises a first polymer and a second polymer having different melting points, and the battery satisfies 0.077 ≤ (3.0 - D2 / D1) / T ≤ 0.118. The present invention can provide the battery with good electrochemical performance, and further can provide the battery with a wide hot box test safety tolerance and a high hot box test pass rate.

Description

[Technical Field]

[0001] This invention claims priority to a Chinese patent application filed with the China Intellectual Property Administration on August 11, 2023, application number 202311017486.5, with the title of the invention "Battery, and electrochemical and electronic apparatus containing the same," the entirety of which is incorporated into this invention by reference.

[0002] The present invention belongs to the field of electrochemical technology, and more specifically, relates to batteries, as well as electrochemical and electronic devices including them. [Background technology]

[0003] Rapid charging and high energy density are major trends in battery development. With the rapid improvement in battery charging rates and the increase in battery energy density, the safety tolerances for battery hot-box testing are becoming increasingly narrow. Currently, improving the pass rate of battery hot-box testing often affects the battery's electrochemical performance under normal use. Therefore, a pressing technical challenge for those skilled in the art is how to broaden the safety tolerances for battery hot-box testing and improve the pass rate without affecting the battery's electrochemical performance under normal use. [Overview of the project]

[0004] The present invention provides a battery having good electrochemical performance, a wide safety tolerance range for hot box testing, and a high pass rate for hot box testing, as well as electrochemical and electronic devices containing the same.

[0005] A first aspect of the present invention provides a battery comprising an electrode assembly and an outer bag, wherein the electrode assembly comprises an electrode piece and a separator.

[0006] The separator includes a porous substrate, and a first coating layer is provided on at least one surface of the porous substrate, and the first coating layer includes a first polymer and a second polymer having different melting points.

[0007] The battery satisfies 0.077 ≤ (3.0 - D2 / D1) / T ≤ 0.118. D1 is the thickness of the battery, measured after it has been fully charged at 25°C, and its unit is mm. D2 is the thickness of the battery, measured again after it has been fully charged, placed vertically in a hot box, heated from 25°C to 130°C at a rate of 5°C / min for 60 minutes, and then allowed to cool down to 25°C, and its unit is mm. T is the adhesive force between the first coating layer of the separator and the electrode piece adjacent to the first coating layer, and its unit is N / m.

[0008] A battery satisfying 0.077 ≤ (3.0 - D2 / D1) / T ≤ 0.118 can have a wide safety tolerance range and a high pass rate in hot box testing, as well as good electrochemical performance.

[0009] A battery that satisfies 0.077 ≤ (3.0 - D2 / D1) / T ≤ 0.118 can have a sufficiently open interface between the electrode and the separator during the heat generation phase. This allows for timely transfer of gas and heat at the interface to the outer bag, thereby reducing heat buildup at the interface, expanding the safety tolerance range for the battery's hot box test, and improving the pass rate of the battery's hot box test.

[0010] A battery satisfying 0.077 ≤ (3.0 - D2 / D1) / T ≤ 0.118 further possesses appropriate interfacial adhesion under normal operating conditions, thereby reducing the probability of electrode assembly deformation after battery charge-discharge cycles and further enabling the battery to exhibit good electrochemical performance.

[0011] In any embodiment, the electrode piece includes a positive electrode piece and a negative electrode piece, and a first coating layer is provided on the surface of the porous substrate facing the positive electrode piece.

[0012] In any embodiment, the battery satisfies 0.096 ≤ (3.0 - D2 / D1) / T ≤ 0.110. By further adjusting (3.0 - D2 / D1) / T within the above range, the battery can better combine good electrochemical performance with a high pass rate in hot box testing.

[0013] In any embodiment, T is between 5.42 N / m and 10.23 N / m, and / or D2 / D1 is between 2.12 and 2.42.

[0014] In any embodiment, T is 5.91 N / m to 7.91 N / m and / or D2 / D1 is 2.21 to 2.38.

[0015] By adjusting the adhesive force T between the first coating layer of the separator and the electrode piece adjacent to the first coating layer within the above range, the battery can have appropriate interfacial adhesion during normal use, thereby reducing the probability of deformation of the electrode assembly after the battery's charge-discharge cycle, and further enabling the battery to have good electrochemical performance. Adjusting the adhesive force T between the first coating layer of the separator and the electrode piece adjacent to the first coating layer within the above range is also advantageous in that the interface between the electrode piece and the separator opens sufficiently when the battery is in the heat generation phase, thereby enabling the timely transfer of gas and heat at the interface to the outer bag, reducing heat accumulation at the interface, further expanding the safety tolerance range for the battery's hot box test, and improving the pass rate of the battery's hot box test.

[0016] When D2 / D1 is within the above range, when the battery is in the heat generation stage, the interface between the electrode plate and the separator can be fully opened, so that the gas and heat at the interface can be timely transmitted to the outer packaging bag, thereby reducing the heat accumulation at the interface. Furthermore, the safety tolerance range of the battery's hot box test can be expanded, and the passing rate of the battery's hot box test can be improved.

[0017] In any embodiment, let the melting point of the first polymer be T (1) , (2) , m1 ,

[0019] , , (2) , , (1) and the melting point of the second polymer be T m2 In this case, T m1 is 60°C to 100°C, T m2 is 130°C or higher, and T<​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​The following conditions must be met: 50 ≤ 1.25, and the particle size Dv in the volume-based particle size distribution of the first polymer particles (1) 90 and the particle size Dv in the volume-based particle size distribution of the second polymer particles (2) 50 is 2.0 ≤ Dv (1) 90 / Dv (2) The condition satisfies 50 ≤ 5.0.

[0020] In any embodiment, Dv (2) 50 / Dv (1) 50 is 0.60 ≤ Dv (2) 50 / Dv (1) Satisfying 50 ≤ 0.83, and Dv (1) 90 / Dv (2) 50 is 3.00 ≤ Dv (1) 90 / Dv (2) The condition satisfies 50 ≤ 4.17.

[0021] Dv (2) 50 / Dv (1) 50 and Dv (1) 90 / Dv (2) By adjusting 50 within the above range, it is advantageous to disperse the second polymer around the first polymer, thereby improving the film formation of the first polymer, and also to ensure that the first coating layer possesses appropriate adhesion and breathability. Furthermore, it is possible to give the battery good electrochemical performance and a high pass rate in hot box testing.

[0022] In any embodiment, the particle size Dv in the volume-based particle size distribution of the first polymer particles (1) 50 corresponds to a particle size of 0.8 μm to 2.0 μm.

[0023] In any embodiment, the particle size Dv in the volume-based particle size distribution of the first polymer particles (1) 90 corresponds to a particle size of 2.0 μm to 5.0 μm.

[0024] Particle size Dv in the volume-based particle size distribution of the first polymer (1) 50 and / or Dv (1)By adjusting 90 within the above range, the first coating layer can be given appropriate adhesion and breathability, thereby enabling the battery to have good electrochemical performance and a high pass rate in hot box testing.

[0025] In any embodiment, the particle size Dv in the volume-based particle size distribution of the second polymer particles (2) 50 corresponds to a size of 0.54 μm to 1.5 μm.

[0026] Particle size Dv in the volume-based particle size distribution of the second polymer (2) By adjusting 50 within the above range, the first coating layer can be given appropriate adhesion and breathability, thereby enabling the battery to have good electrochemical performance and a high pass rate in hot box testing.

[0027] In any embodiment, if the weight content of the first polymer is m1 and the weight content of the second polymer is m2, then, based on the total weight of the first coating layer, m1 is 50% to 86% and m2 is 9% to 45%.

[0028] In any given embodiment, m1 is 70% to 82%, and m2 is 13% to 25%.

[0029] By adjusting the weight content m1 of the first polymer and the weight content m2 of the second polymer within the above range, it is advantageous that the separator and the electrode piece have appropriate adhesion, and that the interface between the electrode piece and the separator opens sufficiently when the battery is in the heat generation stage. This allows gas and heat at the interface to be transferred to the outer bag in a timely manner, thereby reducing heat accumulation at the interface. Furthermore, it is possible to broaden the safety tolerance range for the battery's hot box test and improve the pass rate of the battery's hot box test. In addition, the first coating layer can be given appropriate adhesion and breathability, thus enabling the battery to have good electrochemical performance.

[0030] In any embodiment, the weight-average molecular weight of the first polymer is M. w1 The weight-average molecular weight of the second polymer is set to M. w2 In that case, M w1 It is between 150,000 and 260,000, M w2 The range is 1.18 million to 2 million.

[0031] M w1 and M w2 By adjusting the values ​​within the above range, it is possible to give the battery good electrochemical performance, further widen the safety tolerance range for the battery's hot box test, and improve the pass rate of the battery's hot box test.

[0032] In any embodiment, the first polymer comprises at least one homopolymer and copolymer of at least one monomer from among ethylene, propylene, vinylidene fluoride, acrylic acid, acrylic acid ester, styrene, acrylonitrile, maleic anhydride, vinyl chloride, and chloropropene.

[0033] In any embodiment, the second polymer comprises at least one of the monomers and copolymers selected from vinylidene fluoride, hexafluoropropylene, propylene, vinyl chloride, styrene, butadiene, acrylic acid esters, and acrylic acid.

[0034] In any embodiment, a first coating layer is provided on one surface of the porous substrate, and a second coating layer is provided on the other surface of the porous substrate, wherein the second coating layer comprises a third polymer, and the third polymer comprises at least one of the monomers and copolymers selected from butyl acrylate, octyl acrylate, isooctyl acrylate, styrene, and butadiene, and the melting point of the third polymer is 50°C to 70°C. This reduces the probability of deformation of the electrode assembly after the battery's charge-discharge cycle, and furthermore, allows the battery to have good electrochemical performance.

[0035] In any embodiment, the coating weight of the first coating layer is 0.5 mg / 5000 mm 2 ~3mg / 5000mg 2 That is the case.

[0036] By adjusting the coating weight of the first coating layer within the above range, the first coating layer can be given appropriate tackiness. Specifically, the first coating layer has good tackiness under normal battery operation conditions and low tackiness when the battery is in the heat generation phase. This is advantageous because it allows the interface between the electrode pieces and the separator to open sufficiently when the battery is in the heat generation phase, thereby enabling timely transfer of gas and heat at the interface to the outer bag, reducing heat accumulation at the interface. Furthermore, it is possible to broaden the safety tolerance range for the battery's hot box test, improve the pass rate of the battery's hot box test, reduce the probability of deformation of the electrode assembly after the battery's charge-discharge cycle, and further, give the battery good electrochemical performance.

[0037] In any embodiment, the thickness of the first coating layer is 0.5 μm to 2.8 μm.

[0038] By adjusting the thickness of the first coating layer within the above range, the first coating layer can be given appropriate tackiness. Specifically, the first coating layer has good tackiness under normal battery operation conditions and low tackiness when the battery is in the heat generation phase. This is advantageous because it allows the interface between the electrode pieces and the separator to open sufficiently when the battery is in the heat generation phase, thereby enabling timely transfer of gas and heat at the interface to the outer bag, reducing heat accumulation at the interface. Furthermore, it is possible to broaden the safety tolerance range for the battery's hot box test, improve the pass rate of the battery's hot box test, reduce the probability of deformation of the electrode assembly after the battery's charge-discharge cycle, and further, give the battery good electrochemical performance.

[0039] In any embodiment, the battery is a pouch battery.

[0040] In any embodiment, the positive electrode piece comprises a positive electrode active material, the positive electrode active material comprising at least one of lithium cobaltate, lithium nickel cobalt aluminate, lithium nickel cobalt manganeseate, lithium iron phosphate, and each of these modified compounds, the modification comprising doping modification, surface coating modification, or simultaneous doping and coating modification.

[0041] In any embodiment, the negative electrode piece comprises a negative electrode active material, the negative electrode active material comprises at least one of graphite and silicon-based materials, and the weight content of the silicon-based material in the negative electrode active material is 0% to 25%.

[0042] A second aspect of the present invention provides an electrochemical apparatus including the battery of the first aspect of the present invention.

[0043] A third aspect of the present invention provides an electronic device including a battery according to the first aspect of the present invention and / or an electrochemical device according to the second aspect of the present invention. [Modes for carrying out the invention]

[0044] To further clarify the object, technical proposal, and advantages of the present invention, the technical proposal of the present invention will be described clearly and completely below with reference to examples. Obviously, the examples described are some, but not all, examples of the present invention. The relevant examples described herein are illustrative and are intended to provide a basic understanding of the present invention. The examples of the present invention should not be construed as limiting the present invention. All other examples that a person skilled in the art could obtain without creative work based on the technical proposal and examples provided by the present invention are all within the scope of protection of the present invention.

[0045] For the sake of brevity, this specification specifically discloses only a few numerical ranges. However, any lower limit can be combined with any upper limit to form an unexpressly specified range. Furthermore, any lower limit can be combined with other lower limits to form an unexpressly specified range, and similarly, any upper limit can be combined with any other upper limit to form an unexpressly specified range. In addition, each individually disclosed point or single numerical value itself can, as a lower or upper limit, be combined with any other point or single numerical value, or with any other lower or upper limit, to form an unexpressly specified range.

[0046] In this specification, unless otherwise specified, "above" and "below" include this numerical value.

[0047] Unless otherwise specified, the terms used in this invention have the meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of each parameter mentioned in this invention can be measured by various measurement methods commonly used in the art (for example, by the methods described in the embodiments of this invention). Unless otherwise specified, the test temperature for each parameter mentioned in this invention is 25°C and the test pressure is standard atmospheric pressure.

[0048] A list of items connected by the terms "at least one of," "at least one of," "at least one kind of," or other similar terms can 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 A only, B only, or A and B. In other specific examples, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means A only, B only, C only, A and B (excluding C), A and C (excluding B), B and C (excluding A), or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0049] The term "plural" means two or more.

[0050] The battery referred to in the embodiments of the present invention may include any apparatus in which an electrochemical reaction occurs. In some embodiments, the battery may include a lithium-ion battery.

[0051] The failure process of a battery as determined by hot-box testing can be divided into three stages: the heat generation stage, the heat accumulation stage, and the thermal runaway stage. The reactions involved in thermal runaway are very complex and mainly include the decomposition of the solid electrolyte interface film (hereinafter abbreviated as SEI film), the reaction between the positive electrode and the electrolyte, the reaction between the negative electrode and the electrolyte, and the decomposition reaction of the electrolyte itself.

[0052] In the heat generation phase, the heat generated by the decomposition of the SEI film leads to the initial heat accumulation of the battery, and as heat continues to accumulate, the battery reaches the heat accumulation phase. In the heat accumulation phase, the electrolyte continues to be reduced as the SEI film continues to decompose, which triggers a reaction between the positive electrode and the electrolyte. At this stage, the battery may vent and produce a large amount of smoke, and as heat continues to accumulate, it enters the thermal runaway phase. In the thermal runaway phase, the positive and negative electrodes react rapidly, causing a sharp rise in temperature, which can lead to combustion and potentially cause the battery to explode.

[0053] Currently, common methods used to broaden the safety tolerance range for battery hot box testing and improve the pass rate include adjusting the electrolyte system composition and applying a low-tack coating layer to the separator surface. However, adjusting the electrolyte system composition tends to affect the electrochemical performance of the battery under normal use. Applying a low-tack coating layer to the separator surface tends to reduce the interfacial adhesion of the battery, which makes deformation of the electrode assembly more likely after the battery's charge-discharge cycle, and further affects the electrochemical performance, such as the cycle characteristics, of the battery under normal use.

[0054] Embodiments of the present invention provide a battery that has good electrochemical performance, a wide hot-box safety tolerance range, and a high hot-box pass rate.

[0055] The battery provided in the embodiment of the present invention includes an electrode assembly and an outer packaging bag.

[0056] The electrode assembly includes an electrode piece and a separator. The separator includes a porous substrate, and a first coating layer is provided on at least one surface of the porous substrate, the first coating layer comprising a first polymer and a second polymer having different melting points.

[0057] The battery satisfies the condition 0.077 ≤ (3.0 - D2 / D1) / T ≤ 0.118. D1 is the thickness of the battery, measured after it has been fully charged at 25°C, in units of mm. D2 is the thickness of the battery, measured again after it has been fully charged, placed vertically in a hot box, heated from 25°C to 130°C at a rate of 5°C / min for 60 minutes, and allowed to cool down to 25°C. T is the adhesive force between the first coating layer of the separator and the electrode piece adjacent to the first coating layer, in units of N / m.

[0058] The thickness direction of the battery is perpendicular to the main surface of the battery (i.e., the surface with the largest surface area).

[0059] The battery thickness D1 can be measured by following the procedure below. Under conditions of 25°C, the battery is left to stand for 5 minutes, charged with a constant current of 0.5C, and the cutoff current is set to 0.025C. During the charging process, when the battery voltage reaches the charging termination voltage, the charging is changed to constant voltage charging and continued until the charging current ≤ cutoff current. After that, the battery is left to stand for 60 minutes, and the battery thickness is measured and defined as D1.

[0060] The adhesive force T between the first coating layer of the separator and the adjacent electrode piece can be measured according to the following procedure: After the hot box test, wait for the battery temperature to drop to 25°C, then disassemble and remove the separator and electrode piece together from the battery. Subsequently, measure the adhesive force T between the first coating layer of the separator and the adjacent electrode piece using a 180° peel test standard. The test standard can be GB / T 2790-1995. The measuring device may be a tensile testing machine. After the measurement is complete, the ratio of the average value of the applied force at the plateau of the peel force curve to the sample width is taken as the adhesive force T between the first coating layer of the separator and the adjacent electrode piece. The tensile speed (i.e., peel speed) of the tensile testing machine should be 50 mm / min. The measurement temperature should be 25°C.

[0061] When performing a 180° peel test, the separator and electrode pieces, which are removed from the battery along with the battery itself, can be cut into small strips measuring 15 mm x 54.2 mm before the test can be conducted.

[0062] Polymers with different melting points generally have different film-forming properties and tackiness. Generally, polymers with lower melting points have better film-forming properties and stronger tackiness. When used as the first coating layer of a separator, the separator is at increased risk of the polymer in the first coating layer softening and clogging pores during the battery manufacturing process (e.g., baking of electrode assemblies, hot pressing, etc.) and normal use of the battery, thus affecting the electrochemical performance of the battery. The first coating layer of the separator provided in the embodiments of the present invention comprises a first polymer and a second polymer with different melting points. By using a combination of polymers having different film-forming properties and / or tackiness, the polymer with the higher melting point can be dispersed around the polymer with the lower melting point. This reduces the risk of the polymer in the first coating layer of the separator softening and clogging pores during the battery manufacturing process (e.g., baking of electrode assemblies, hot pressing, etc.) and normal use of the battery, and further allows the first coating layer to have appropriate tackiness and breathability.

[0063] The adhesive force T between the first coating layer of the separator and the electrode piece adjacent to the first coating layer can reflect the adhesive properties between the first coating layer of the separator and the electrode piece adjacent to the first coating layer during normal battery use. Increasing the adhesive force T between the first coating layer of the separator and the electrode piece adjacent to the first coating layer reduces the probability of deformation of the electrode assembly after the battery's charge-discharge cycle, but is disadvantageous to the interface between the electrode piece and the separator opening sufficiently when the battery is in the heat generation phase, and is therefore disadvantageous to reducing heat accumulation at the interface.

[0064] D2 / D1 can reflect the change in thickness of a fully charged battery before and after hot box testing. A relatively large D2 / D1 indicates that the interface between the electrode and separator can open sufficiently when the battery is in the heat generation phase, but during normal battery use, the adhesion between the first coating layer of the separator and the electrode adjacent to the first coating layer may be low, which increases the probability of electrode assembly deformation after the battery's charge-discharge cycle and degrades the battery's electrochemical performance. A relatively small D2 / D1 indicates that the interface between the electrode and separator cannot open or opens insufficiently when the battery is in the heat generation phase, which is unfavorable for reducing heat buildup at the interface.

[0065] A battery satisfying 0.077 ≤ (3.0 - D2 / D1) / T ≤ 0.118 can have a wide safety tolerance range and a high pass rate in hot box testing, as well as good electrochemical performance.

[0066] A battery that satisfies 0.077 ≤ (3.0 - D2 / D1) / T ≤ 0.118 can have a sufficiently open interface between the electrode and the separator during the heat generation phase. This allows for timely transfer of gas and heat at the interface to the outer bag, thereby reducing heat buildup at the interface, expanding the safety tolerance range for the battery's hot box test, and improving the pass rate of the battery's hot box test.

[0067] A battery satisfying 0.077 ≤ (3.0 - D2 / D1) / T ≤ 0.118 further possesses appropriate interfacial adhesion under normal operating conditions, thereby reducing the probability of electrode assembly deformation after battery charge-discharge cycles and further enabling the battery to exhibit good electrochemical performance.

[0068] On the other hand, batteries that satisfy the condition that (3.0-D2 / D1) / T is less than 0.077 have a relatively large adhesive force T between the first coating layer of the separator and the electrode piece adjacent to the first coating layer after the hot box test. When the battery is in the heat generation stage, the adhesive force between the first coating layer of the separator and the electrode piece is relatively large, so the interface between the electrode piece and the separator cannot open or opens to an insufficient degree. As a result, gas and heat at the interface cannot be transferred to the outer bag in a timely manner, and heat continues to accumulate at the interface. Therefore, batteries that satisfy the condition that (3.0-D2 / D1) / T is less than 0.077 have a relatively low pass rate in the hot box test. A battery satisfying the condition (3.0-D2 / D1) / T being less than 0.077 indicates that, after hot-box testing, the design of the separator's first coating layer is unreasonable, as evidenced by the relatively large adhesive force T between the separator's first coating layer and the electrode piece adjacent to the first coating layer. This results in excessive tackiness of the first and / or second polymers in the first coating layer, and relatively strong fluidity after the first and / or second polymers are softened by heat, thereby increasing the risk of the separator pores becoming clogged during the battery manufacturing process (e.g., baking of electrode assemblies, hot pressing, etc.) and normal use of the battery, and further affecting the battery's electrochemical performance.

[0069] On the other hand, batteries that satisfy the condition (3.0-D2 / D1) / T greater than 0.118 have relatively low interfacial adhesion during normal use, as evidenced by the relatively small adhesive force T between the first coating layer of the separator and the electrode piece adjacent to the first coating layer after the hot box test. This makes them prone to deformation of the electrode assembly after the battery's charge-discharge cycle and further affects the electrochemical performance of the battery during normal use. In batteries that satisfy the condition (3.0-D2 / D1) / T greater than 0.118, during the heat generation phase, the interface between the electrode piece and the separator may not open, or may not open sufficiently. This prevents the timely transfer of gas and heat at the interface to the outer bag, and furthermore, heat continues to accumulate at the interface. Consequently, batteries that satisfy the condition (3.0-D2 / D1) / T greater than 0.118 also have a relatively low pass rate in the hot box test.

[0070] In some embodiments, the battery satisfies 0.088≦(3.0-D2 / D1) / T≦0.118, 0.090≦(3.0-D2 / D1) / T≦0.115, 0.092≦(3.0-D2 / D1) / T≦0.113, 0.094≦(3.0-D2 / D1) / T≦0.113, or 0.096≦(3.0-D2 / D1) / T≦0.110.

[0071] By further adjusting (3.0-D2 / D1) / T within the above range, the battery can better combine good electrochemical performance with a high pass rate in hot box testing.

[0072] In some embodiments, the electrode pieces include a positive electrode piece and a negative electrode piece, and a first coating layer is provided on the surface of the porous substrate facing the positive electrode piece.

[0073] In some embodiments, the adhesive force T between the first coating layer of the separator and the pole adjacent to the first coating layer may be 5.42 N / m to 10.23 N / m, for example, 5.42 N / m, 5.56 N / m, 5.72 N / m, 5.91 N / m, 6.04 N / m, 6.16 N / m, 6.40 N / m, 6.58 N / m, 6.78 N / m, 6.9 The adhesive force T between the first coating layer of the separator and the electrode adjacent to the first coating layer may be 5.91 N / m to 7.91 N / m.

[0074] By adjusting the adhesive force T between the first coating layer of the separator and the electrode piece adjacent to the first coating layer within the above range, the battery can be given appropriate interfacial adhesion during normal use, thereby reducing the probability of deformation of the electrode assembly after the battery's charge-discharge cycle, and further, the battery can be given good electrochemical performance. By adjusting the adhesive force T between the first coating layer of the separator and the electrode piece adjacent to the first coating layer within the above range, it is advantageous that the interface between the electrode piece and the separator opens sufficiently when the battery is in the heat generation phase, thereby allowing gas and heat at the interface to be transmitted to the outer bag in a timely manner, reducing heat accumulation at the interface, further expanding the safety tolerance range for the battery's hot box test, and improving the pass rate of the battery's hot box test.

[0075] In some embodiments, D2 / D1 is between 2.12 and 2.42, and may be, for example, 2.12, 2.15, 2.17, 2.20, 2.21, 2.23, 2.25, 2.27, 2.29, 2.31, 2.35, 2.38, 2.40, 2.42, or any two of the above values. Optionally, D2 / D1 may be between 2.21 and 2.38.

[0076] When D2 / D1 is within the above range, the interface between the electrode and the separator can open sufficiently when the battery is in the heat generation phase. This allows gas and heat at the interface to be transferred to the outer bag in a timely manner, thereby reducing heat buildup at the interface. Furthermore, it expands the safety tolerance range for the battery's hot box test and improves the pass rate of the battery's hot box test.

[0077] The above parameters D2 / D1 and T can be adjusted by adjusting parameters such as the melting point of the first polymer and the second polymer, particle size in the volume-based particle size distribution, weight-average molecular weight, and weight content, as well as parameters such as the coating weight and thickness of the first coating layer.

[0078] In some examples, the melting point of the first polymer is set to T m1 The melting point of the second polymer is set to T m2 In that case, T m1 The temperature can be 60°C to 100°C, T m2 It may be 130℃ or higher, and T m2 -T m1 The temperature can be between 40°C and 120°C.

[0079] Melting point T of the first polymer in the first coating layer m1If the above range is maintained, the first coating layer can be given good film formation characteristics and appropriate tackiness. That is, the first coating layer has good tackiness under normal battery usage conditions and low tackiness when the battery is in the heat generation phase, which is advantageous in reducing the probability of electrode assembly deformation after the battery's charge-discharge cycle. Furthermore, it can give the battery good electrochemical performance. In addition, when the battery is in the heat generation phase, the interface between the electrode piece and the separator can open sufficiently, allowing gas and heat at the interface to be transmitted to the outer bag in a timely manner, thereby reducing heat accumulation at the interface. Moreover, it can broaden the safety tolerance range for the battery's hot box test and improve the pass rate of the battery's hot box test.

[0080] Melting point T of the second polymer in the first coating layer m2 If the above range is present, the first coating layer can be given appropriate breathability, thereby enabling the battery to have good electrochemical performance.

[0081] T m2 -T m1 By adjusting the above range, the second polymer can be dispersed around the first polymer, thereby reducing the risk of the polymer in the first coating layer of the separator softening and blocking the pores during the battery manufacturing process (e.g., processes such as baking and hot pressing of the electrode assembly) and the normal use of the battery, thereby enabling the battery to have good electrochemical performance. Furthermore, when the battery is in the heat generation stage, the interface between the electrode piece and the separator can be sufficiently opened, allowing gas and heat at the interface to be transferred to the outer bag in a timely manner, thereby reducing heat accumulation at the interface. In addition, the safety tolerance range for the battery's hot box test can be expanded, and the pass rate of the battery's hot box test can be improved.

[0082] Therefore, the melting point T of the first polymer m1 , the melting point T of the second polymer m2 , and T m2-T m1 By adjusting the values ​​within the above range, the battery can be given good electrochemical performance, and furthermore, the safety tolerance range for the battery's hot box test can be expanded, improving the pass rate of the battery's hot box test.

[0083] Melting point T of the first polymer m1 When the melting point T of the first polymer is relatively high, the first coating layer has relatively low tackiness and film-forming ability under normal battery use conditions. This reduces the interfacial tackiness of the battery, making the electrode assembly more susceptible to deformation after the battery's charge-discharge cycle, and further affecting the electrochemical performance of the battery under normal use conditions. m1 When the temperature is relatively high, the first coating layer, when the battery is in the heat generation phase, softens due to the heat, increasing the adhesive force between the first coating layer of the separator and the electrode piece. This is detrimental to the opening of the interface between the electrode piece and the separator, preventing the timely transfer of gas and heat at the interface to the outer bag. Furthermore, heat continues to accumulate at the interface, resulting in a relatively low pass rate for the battery's hot box test.

[0084] Melting point T of the first polymer m1 When this value is relatively low, the fluidity of the first polymer after it softens due to heat increases during the battery manufacturing process (e.g., processes such as baking and heat pressing of the electrode assembly) and during normal battery use. This increases the risk of the separator pores becoming clogged, and further affects the electrochemical performance of the battery during normal use.

[0085] Melting point T of the second polymer m2 If the melting point T of the second polymer is relatively low, the fluidity of the second polymer after it softens due to heat increases during the battery manufacturing process (e.g., baking of electrode assemblies, hot pressing, etc.) and during normal battery use, which increases the risk of the separator pores becoming clogged and further affects the electrochemical performance of the battery during normal use. m2When the temperature is relatively low, the second polymer softens due to the heat when the battery is in the heat generation phase, increasing the adhesive force between the first coating layer of the separator and the electrode piece adjacent to the first coating layer. This is detrimental to the opening of the interface between the electrode piece and the separator, preventing the timely transfer of gas and heat at the interface to the outer bag. Furthermore, heat continues to accumulate at the interface, resulting in a relatively low pass rate for the battery's hot box test.

[0086] T m2 -T m1 When the ratio is relatively low, it is disadvantageous for dispersing the second polymer around the first polymer, thereby increasing the risk of the separator pores becoming clogged during the battery manufacturing process (e.g., baking of electrode assemblies, hot pressing, etc.) and during normal battery use. Furthermore, it affects the electrochemical performance of the battery during normal use. Additionally, when the battery is in the heat generation phase, it is disadvantageous for the interface between the electrode pieces and the separator to open sufficiently. As a result, gas and heat at the interface cannot be transferred to the outer bag in a timely manner, and heat continues to accumulate at the interface, leading to a relatively low pass rate in the battery's hot box test.

[0087] In some examples, the melting point of the first polymer is set to T m1 The melting point of the second polymer is set to T m2 In that case, T m1 The temperature can be 70°C to 90°C, T m2 The temperature may be between 135°C and 160°C, and T m2 -T m1 The temperature can be between 50°C and 80°C.

[0088] This allows for better electrochemical performance in batteries, expands the safety tolerance range for hot box testing, and improves the pass rate of hot box testing.

[0089] The method for adjusting the melting points of the first polymer and the second polymer is not particularly limited as long as the object of the present invention can be achieved. For example, the melting points of the first polymer and the second polymer can be adjusted by adjusting one or more of the weight-average molecular weight, crystallinity, composition and ratio of the copolymerized monomers, etc.

[0090] In some embodiments, the particle diameter Dv in the volume-based particle size distribution of the particles of the first polymer (1) 50 and the particle diameter Dv in the volume-based particle size distribution of the particles of the second polymer (2) 50 satisfy 0.50 ≦ Dv (2) 50 / Dv (1) 50 ≦ 1.25, for example, Dv (2) 50 / Dv (1) 50 may be in the range consisting of 0.50, 0.60, 0.67, 0.75, 0.83, 0.90, 1.00, 1.10, 1.25 or any two of the above numerical values. Optionally, Dv (1) 50 and Dv (2) 50 satisfy 0.60 ≦ Dv (2) 50 / Dv (1) 50 ≦ 0.83.

[0091] Dv (2) 50 / Dv (1) By adjusting Dv

[0092] 50 within the above range, the film formation of the first polymer can be improved, and the first coating layer can be made to have appropriate adhesiveness and air permeability, so that the battery can have good electrochemical performance and a high qualified rate in the hot box test. (2) 50 / Dv (1) When Dv

[0093] 50 is relatively large, the first coating layer has relatively low adhesiveness in the normal use state of the battery, and thereby the interfacial adhesiveness of the battery decreases, so that the electrode assembly is likely to deform after the charge and discharge cycles of the battery, and further affects the electrochemical performance of the battery during normal use. (2) 50 / Dv (1)When 50 is relatively small, the first coating layer has relatively strong adhesiveness when the battery is in the heat generation stage, which is disadvantageous for the interface between the electrode sheet and the separator to fully open, and thus the gas and heat at the interface cannot be timely transmitted to the outer packaging bag. Furthermore, the heat at the interface will continue to accumulate, resulting in a relatively low pass rate of the battery's hot box test. At the same time, Dv (2) 50 / Dv (1) When 50 is relatively small, it is disadvantageous to disperse the second polymer around the first polymer, which will deteriorate the air permeability of the separator. Moreover, during the manufacturing process of the battery (such as processes like baking of the electrode assembly, thermal pressing formation, etc.) and the normal use process of the battery, the risk of the pores of the separator being blocked increases, further affecting the electrochemical performance of the battery. <000067​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​(1) 90 / Dv (2) When 50 is relatively large, the first coating layer has relatively low tackiness under normal battery use conditions. This reduces the interfacial tackiness of the battery, making the electrode assembly more susceptible to deformation after charge-discharge cycles and further affecting the electrochemical performance of the battery under normal use.

[0097] Dv (1) 90 / Dv (2) When 50 is relatively small, the first coating layer is relatively sticky when the battery is in the heat generation phase, which is detrimental to the sufficient opening of the interface between the electrode and the separator. As a result, gas and heat at the interface cannot be transferred to the outer bag in a timely manner, and furthermore, heat continues to accumulate at the interface, resulting in a relatively low pass rate for the battery's hot box test. (1) 90 / Dv (2) When 50 is relatively small, it is disadvantageous to disperse the second polymer around the first polymer, which reduces the permeability of the separator and increases the risk of the separator pores becoming clogged during the battery manufacturing process (e.g., baking of electrode assemblies, hot pressing, etc.) and during normal use of the battery, further affecting the electrochemical performance of the battery.

[0098] In some examples, the particle size Dv in the volume-based particle size distribution of the first polymer particles (1) Particle size Dv in the volume-based particle size distribution of 50 and second polymer particles (2) 50 is 0.50 ≤ Dv (2) 50 / Dv (1) The condition 50 ≤ 1.25 is satisfied, and the particle size Dv in the volume-based particle size distribution of the first polymer particles is satisfied. (1) Particle size Dv in the volume-based particle size distribution of 90 and the second polymer (2) 50 is 2.0 ≤ Dv (1) 90 / Dv (2) The condition satisfies 50 ≤ 5.0. Arbitrarily, Dv (2) 50 / Dv (1) 50 is 0.60 ≤ Dv (2) 50 / Dv (1)Satisfying 50 ≤ 0.83, and Dv (1) 90 / Dv (2) 50 is 3.00 ≤ Dv (1) 90 / Dv (2) The condition satisfies 50 ≤ 4.17.

[0099] Dv (2) 50 / Dv (1) 50 and Dv (1) 90 / Dv (2) By adjusting 50 within the above range, it is advantageous to disperse the second polymer around the first polymer, thereby improving the film formation of the first polymer, and also to ensure that the first coating layer possesses appropriate adhesion and breathability. Furthermore, it is possible to give the battery good electrochemical performance and a high pass rate in hot box testing.

[0100] In some examples, the particle size Dv in the volume-based particle size distribution of the first polymer particles (1) 50 may be 0.8 μm to 2.0 μm, and may be arbitrarily 1.0 μm to 2.0 μm, or 1.0 μm to 1.5 μm.

[0101] In some examples, the particle size Dv in the volume-based particle size distribution of the first polymer particles (1) 90 may be 2.0 μm to 5.0 μm.

[0102] Particle size Dv in the volume-based particle size distribution of the first polymer (1) 50 and / or Dv (1) By adjusting 90 within the above range, the first coating layer can be given appropriate adhesion and breathability, thereby enabling the battery to have good electrochemical performance and a high pass rate in hot box testing.

[0103] Particle size Dv in the volume-based particle size distribution of the first polymer (1) 50 and / or Dv (1)When 90 is relatively large, the first coating layer has relatively low tackiness under normal battery use conditions. This reduces the interfacial tackiness of the battery, making the electrode assembly more susceptible to deformation after charge-discharge cycles and further affecting the electrochemical performance of the battery under normal use.

[0104] Particle size Dv in the volume-based particle size distribution of the first polymer (1) 50 and / or Dv (1) When 90 is relatively small, the first coating layer is relatively sticky when the battery is in the heat generation phase, which is detrimental to the sufficient opening of the interface between the electrode piece and the separator. As a result, gas and heat at the interface cannot be transferred to the outer bag in a timely manner, and furthermore, heat continues to accumulate at the interface, resulting in a relatively low pass rate for the battery's hot box test. At the same time, the particle size Dv in the volume-based particle size distribution of the first polymer particles (1) 50 and / or Dv (1) If 90 is relatively small, the permeability of the separator will be poor, and the risk of the separator pores becoming clogged during the battery manufacturing process (e.g., baking of electrode assemblies, heat pressing, etc.) and during normal use of the battery will increase, further affecting the electrochemical performance of the battery.

[0105] In some examples, the particle size Dv in the volume-based particle size distribution of the second polymer particles (2) 50 may be 0.54 μm to 1.5 μm.

[0106] Particle size Dv in the volume-based particle size distribution of the second polymer (2) By adjusting 50 within the above range, the first coating layer can be given appropriate adhesion and breathability, thereby enabling the battery to have good electrochemical performance and a high pass rate in hot box testing.

[0107] Particle size Dv in the volume-based particle size distribution of the second polymer (2)When 50 is relatively large, the first coating layer has relatively low tackiness under normal battery use conditions. This reduces the interfacial tackiness of the battery, making the electrode assembly more susceptible to deformation after charge-discharge cycles and further affecting the electrochemical performance of the battery under normal use.

[0108] Particle size Dv in the volume-based particle size distribution of the second polymer (2) When 50 is relatively small, the first coating layer is relatively sticky when the battery is in the heat generation phase, which is detrimental to the sufficient opening of the interface between the electrode piece and the separator. As a result, gas and heat at the interface cannot be transferred to the outer bag in a timely manner, and furthermore, heat continues to accumulate at the interface, resulting in a relatively low pass rate for the battery's hot box test. At the same time, the particle size Dv in the volume-based particle size distribution of the second polymer particles... (2) If 50 is relatively small, the permeability of the separator will be reduced, and the risk of the separator pores becoming clogged during the battery manufacturing process (e.g., baking of electrode assemblies, heat pressing, etc.) and during normal battery use will increase, further affecting the electrochemical performance of the battery.

[0109] In some examples, the particle size Dv in the volume-based particle size distribution of the first polymer particles (1) 10 may be 0.1 μm to 0.7 μm.

[0110] Particle size Dv in the volume-based particle size distribution of the first polymer (1) By further adjusting 10 within the above range, the electrolyte transport capacity of the separator can be further improved, thereby improving the battery's cycle characteristics.

[0111] In some examples, the particle size Dv in the volume-based particle size distribution of the second polymer particles (2) 10 may be 0.1 μm to 0.5 μm.

[0112] In some examples, the particle size Dv in the volume-based particle size distribution of the second polymer particles(2) 90 may be 2.0 μm to 5.0 μm.

[0113] Particle size Dv in the volume-based particle size distribution of the second polymer (2) 10 and / or Dv (2) By further adjusting 90 within the above range, the electrolyte transport capacity of the separator can be further improved, thereby improving the battery's cycle characteristics.

[0114] Dv10 represents the particle size at which the volume accumulation reaches 10% in the volume-based particle size distribution of the material, measured from the smallest particle size side. Dv50 represents the particle size at which the volume accumulation reaches 50% in the volume-based particle size distribution of the material, measured from the smallest particle size side. Dv90 represents the particle size at which the volume accumulation reaches 90% in the volume-based particle size distribution of the material, measured from the smallest particle size side.

[0115] In some embodiments, when the weight content of the first polymer is m1 and the weight content of the second polymer is m2, m1 may be 50% to 86% and m2 may be 9% to 45% based on the total weight of the first coating layer. Optionally, m1 may be 70% to 82% and m2 may be 13% to 25%.

[0116] By adjusting the weight content m1 of the first polymer and the weight content m2 of the second polymer within the above range, it is advantageous that the separator and the electrode piece have appropriate adhesion, and that the interface between the electrode piece and the separator opens sufficiently when the battery is in the heat generation stage. This allows gas and heat at the interface to be transferred to the outer bag in a timely manner, thereby reducing heat accumulation at the interface. Furthermore, it is possible to broaden the safety tolerance range for the battery's hot box test and improve the pass rate of the battery's hot box test. In addition, the first coating layer can be given appropriate adhesion and breathability, thus enabling the battery to have good electrochemical performance.

[0117] When the weight content m1 of the first polymer is relatively small and the weight content m2 of the second polymer is relatively large, the first coating layer has relatively low tackiness under normal battery operation conditions. This reduces the interfacial tackiness of the battery, making the electrode assembly more susceptible to deformation after the battery's charge-discharge cycle, and further affecting the battery's electrochemical performance under normal operation.

[0118] When the weight content m1 of the first polymer is relatively large and the weight content m2 of the second polymer is relatively small, the first coating layer is relatively sticky when the battery is in the heat generation phase. This is detrimental to the sufficient opening of the interface between the electrode pieces and the separator when the battery is in the heat generation phase. As a result, gas and heat at the interface cannot be transferred to the outer bag in a timely manner, and heat continues to accumulate at the interface, leading to a relatively low pass rate in the battery's hot box test. At the same time, when the weight content m1 of the first polymer is relatively large and the weight content m2 of the second polymer is relatively small, it is detrimental to the dispersion of the second polymer around the first polymer. This reduces the permeability of the separator and increases the risk of the separator pores becoming blocked during the battery manufacturing process (e.g., baking of electrode assemblies, heat pressing and chemical formation) and during normal use of the battery, further affecting the electrochemical performance of the battery.

[0119] In some examples, the weight-average molecular weight of the first polymer is set to M. w1 In that case, M w1 This can be between 50,000 and 500,000, for example, 50,000, 100,000, 150,000, 180,000, 200,000, 230,000, 260,000, 300,000, 350,000, 400,000, 450,000, 500,000, or any two of the above numbers. Optionally, M w1 It could be between 150,000 and 260,000.

[0120] Weight-average molecular weight M of the first polymer w1By adjusting the above range, the first coating layer can be given appropriate tackiness, and the battery can be given appropriate interfacial tackiness. This is advantageous because when the battery is in the heat generation phase, the interface between the electrode piece and the separator can open sufficiently. This allows gas and heat at the interface to be transferred to the outer bag in a timely manner, thereby reducing heat accumulation at the interface. Furthermore, it is possible to broaden the safety tolerance range for the battery's hot box test, improve the pass rate of the battery's hot box test, reduce the probability of deformation of the electrode assembly after the battery's charge-discharge cycle, and furthermore, give the battery good electrochemical performance.

[0121] Weight-average molecular weight M of the first polymer w1 When this value is relatively low, the fluidity of the first polymer after it softens due to heat increases during the battery manufacturing process (e.g., processes such as baking and heat pressing of the electrode assembly) and during normal battery use. This increases the risk of the separator pores becoming clogged, and further affects the electrochemical performance of the battery during normal use.

[0122] Weight-average molecular weight M of the first polymer w1 When the coefficient of friction is relatively high, the first coating layer has relatively low tackiness under normal battery use conditions. This reduces the interfacial tackiness of the battery, making the electrode assembly more susceptible to deformation after charge-discharge cycles and further affecting the electrochemical performance of the battery under normal use conditions.

[0123] In some examples, the weight-average molecular weight of the second polymer is set to M. w2 In that case, M w2 This can be between 700,000 and 2,200,000, for example, 700,000, 800,000, 900,000, 1,000,000, 1,180,000, 1,340,000, 1,500,000, 1,810,000, 2,000,000, or a range consisting of any two of the above numbers. Optionally, M w2 It could be between 1.18 million and 2 million.

[0124] Weight-average molecular weight M of the second polymer w2By adjusting the weight-average molecular weight M of the second polymer, the second polymer can be dispersed around the first polymer, thereby reducing the risk of the separator pores becoming clogged during the battery manufacturing process (e.g., baking of electrode assemblies, hot pressing, etc.) and the normal use of the battery, and furthermore, enabling the battery to have good electrochemical performance. w2 By adjusting the above range, it is advantageous that the separator and electrode pieces have appropriate adhesive strength, and that the interface between the electrode pieces and the separator opens sufficiently when the battery is in the heat generation stage. This allows gas and heat at the interface to be transferred to the outer bag in a timely manner, thereby reducing heat accumulation at the interface. Furthermore, it is possible to broaden the safety tolerance range for the battery's hot box test and improve the pass rate of the battery's hot box test.

[0125] Weight-average molecular weight M of the second polymer w2 When the weight-average molecular weight M of the second polymer is relatively low, when the battery is in the heat generation phase, the second polymer softens due to the heat, increasing the adhesive force between the first coating layer of the separator and the electrode piece. This is detrimental to the opening of the interface between the electrode piece and the separator, preventing the timely transfer of gas and heat at the interface to the outer bag. Furthermore, heat continues to accumulate at the interface, resulting in a relatively low pass rate for the battery's hot box test. At the same time, the weight-average molecular weight M of the second polymer w2 When this is relatively low, the fluidity of the second polymer after it softens due to heat increases during the battery manufacturing process (e.g., baking of electrode assemblies, heat pressing, etc.) and during normal battery use. This increases the risk of pore blockage during the heat pressing of the separator, further affecting the electrochemical performance of the battery.

[0126] Weight-average molecular weight M of the second polymer w2When the coefficient of friction is relatively high, the second polymer has poor film-forming properties, and the first coating layer has relatively low tackiness under normal battery use conditions. This reduces the interfacial tackiness of the battery, making the electrode assembly more susceptible to deformation after the battery's charge-discharge cycle, and further affecting the battery's electrochemical performance under normal use.

[0127] In some embodiments, M w1 It can be between 150,000 and 260,000, M w2 It could be between 1.18 million and 2 million.

[0128] M w1 and M w2 By adjusting the values ​​within the above range, it is possible to give the battery good electrochemical performance, further widen the safety tolerance range for the battery's hot box test, and improve the pass rate of the battery's hot box test.

[0129] In some embodiments, M w1 and M w2 700,000 ≤ M w2 -M w1 The condition satisfies ≤2.3 million, and arbitrarily, 980,000 ≤ M w2 -M w1 It satisfies the condition ≤ 1.61 million.

[0130] M w2 -M w1 By adjusting the values ​​within the above range, it is advantageous to disperse the second polymer around the first polymer, thereby reducing the risk of the separator pores becoming clogged during the battery manufacturing process (e.g., processes such as baking and hot pressing of the electrode assembly) and during normal battery use. Furthermore, the first coating layer can be given appropriate adhesion and breathability, and the battery can be given good electrochemical performance and a high pass rate in hot box testing.

[0131] In some examples, the weight-average molecular weight of the first polymer is set to M. w1 The weight-average molecular weight of the second polymer is M. w2 In that case, Mw1 It can be between 50,000 and 500,000, M w2 It may be between 700,000 and 2,200,000, and M w1 and M w2 700,000 ≤ M w2 -M w1 The condition ≤ 2.3 million is satisfied. Arbitrarily, M w1 It can be between 150,000 and 260,000, M w2 It may be between 1.18 million and 2 million, and M w1 and M w2 980,000 ≤ M w2 -M w1 It satisfies the condition ≤ 1.61 million.

[0132] This allows for better electrochemical performance in batteries, expands the safety tolerance range for hot box testing, and improves the pass rate of hot box testing.

[0133] In some examples, the first polymer may contain at least one of the monomers and copolymers selected from ethylene, propylene, vinylidene fluoride, acrylic acid, acrylic acid esters, styrene, acrylonitrile, maleic anhydride, vinyl chloride, and chloropropene. The first polymer may contain a homopolymer, a copolymer, or a mixture thereof.

[0134] In some examples, the second polymer may contain at least one of the monomers and copolymers selected from vinylidene fluoride, hexafluoropropylene, propylene, vinyl chloride, styrene, butadiene, acrylic acid esters, and acrylic acid. The second polymer may contain a homopolymer, a copolymer, or a mixture of both.

[0135] In some examples, the coating weight of the first coating layer was 0.5 mg / 5000 mm 2 ~3mg / 5000mg 2 It may also be 0.5 mg / 5000 ml 2 , 0.8 mg / 5000 ml2 , 1 mg / 5000 ml 2 , 1.5 mg / 5000 ml 2 , 2mg / 5000mg 2 , 2.5 mg / 5000 ml 2 3 mg / 5000 ml 2 Alternatively, it may be within a range consisting of any two of the above values. Optionally, the coating weight of the first coating layer may be 0.5 mg / 5000 mm 2 ~1.5mg / 5000mg 2 That's fine.

[0136] By adjusting the coating weight of the first coating layer within the above range, the first coating layer can be given appropriate tackiness. Specifically, the first coating layer has good tackiness under normal battery operation conditions and low tackiness when the battery is in the heat generation phase. This is advantageous because it allows the interface between the electrode pieces and the separator to open sufficiently when the battery is in the heat generation phase, thereby enabling timely transfer of gas and heat at the interface to the outer bag, reducing heat accumulation at the interface. Furthermore, it is possible to broaden the safety tolerance range for the battery's hot box test, improve the pass rate of the battery's hot box test, reduce the probability of deformation of the electrode assembly after the battery's charge-discharge cycle, and further, give the battery good electrochemical performance.

[0137] When the coating weight of the first coating layer is relatively low, the first coating layer has relatively low tackiness under normal battery operation conditions. This reduces the interfacial tackiness of the battery, making the electrode assembly more susceptible to deformation after the battery's charge-discharge cycle, and further affecting the battery's electrochemical performance under normal operation.

[0138] When the coating weight of the first coating layer is relatively high, the first coating layer is relatively sticky when the battery is in the heat generation stage. This is detrimental to the sufficient opening of the interface between the electrode pieces and the separator, which prevents the timely transfer of gas and heat at the interface to the outer bag. Furthermore, heat continues to accumulate at the interface, resulting in a relatively low pass rate for the battery's hot box test.

[0139] In some embodiments, the thickness of the first coating layer may be 0.5 μm to 2.8 μm, for example, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 2.8 μm, or any two of the above values. Optionally, the thickness of the first coating layer may be 1 μm to 2 μm.

[0140] By adjusting the thickness of the first coating layer within the above range, the first coating layer can be given appropriate tackiness. Specifically, the first coating layer has good tackiness under normal battery operation conditions and low tackiness when the battery is in the heat generation phase. This is advantageous because it allows the interface between the electrode pieces and the separator to open sufficiently when the battery is in the heat generation phase, thereby enabling timely transfer of gas and heat at the interface to the outer bag, reducing heat accumulation at the interface. Furthermore, it is possible to broaden the safety tolerance range for the battery's hot box test, improve the pass rate of the battery's hot box test, reduce the probability of deformation of the electrode assembly after the battery's charge-discharge cycle, and further, give the battery good electrochemical performance.

[0141] When the thickness of the first coating layer is relatively thin, the first coating layer has relatively low tackiness under normal battery operation conditions. This reduces the interfacial tackiness of the battery, making the electrode assembly more susceptible to deformation after the battery's charge-discharge cycle, and further affecting the electrochemical performance of the battery under normal operation conditions.

[0142] When the thickness of the first coating layer is relatively thick, the first coating layer is relatively sticky when the battery is in the heat generation stage. This is detrimental to the sufficient opening of the interface between the electrode pieces and the separator, which prevents the timely transfer of gas and heat at the interface to the outer bag. Furthermore, heat continues to accumulate at the interface, resulting in a relatively low pass rate for the battery's hot box test.

[0143] In some embodiments, the first coating layer may further contain a thickener, a wetting agent, etc. In the present invention, the thickener is not particularly limited and may be, for example, at least one of sodium carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, methylhydroxyethylcellulose, and ethylhydroxyethylcellulose. In the present invention, the wetting agent is not particularly limited and may be, for example, at least one of polyoxyethylene ether, dimethylsiloxane, sucrose ester, and alkyl ether sulfate sodium.

[0144] In some embodiments, a first coating layer is provided on one surface of a porous substrate, and a second coating layer is provided on the other surface of the porous substrate, the second coating layer comprising a third polymer, the third polymer may comprise at least one of the monomers and copolymers selected from butyl acrylate, octyl acrylate, isooctyl acrylate, styrene, and butadiene. The third polymer may comprise a homopolymer, a copolymer, or a mixture thereof.

[0145] This reduces the probability of electrode assembly deformation occurring after battery charge-discharge cycles, and furthermore, allows the battery to have good electrochemical performance.

[0146] In some examples, the melting point of the third polymer may be 50°C to 70°C.

[0147] The present invention does not have any particular limitations on the thickness of the second coating layer, as long as the objective of the present invention is achieved. For example, the thickness of the second coating layer may be 0.5 μm to 3 μm.

[0148] The present invention does not have any particular limitations on the coating weight of the second coating layer, as long as the objective of the present invention is achieved. For example, the coating weight of the second coating layer may be 0.5 mg / 5000 mm 2 ~3mg / 5000mg 2 That's fine.

[0149] In some embodiments, an inorganic coating layer may be provided between the porous substrate and the first coating layer. Providing an inorganic coating layer between the porous substrate and the first coating layer can also improve the thermal shrinkage resistance, puncture resistance, and / or electrolyte transportability of the separator.

[0150] In some embodiments, the inorganic coating layer may include, but is not limited to, a ceramic, which may include at least one of alumina, boehmite, titania, silica, zirconia, tin dioxide, magnesium hydroxide, magnesium oxide, zinc oxide, barium sulfate, boron nitride, and aluminum nitride.

[0151] In some embodiments, the inorganic coating layer may further contain a binder, and in the present invention, the type of binder is not particularly limited and may include, for example, at least one of polyacrylate, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethylcellulose, potassium carboxymethylcellulose, sodium hydroxymethylcellulose, and potassium hydroxymethylcellulose.

[0152] The present invention does not have any particular limitations on the thickness of the inorganic coating layer, as long as the objective of the present invention is achieved. For example, the thickness of the inorganic coating layer may be 0.5 μm to 6 μm.

[0153] The present invention does not have any particular limitations on the coating weight of the inorganic coating layer, as long as the objective of the present invention is achieved. For example, the coating weight of the inorganic coating layer is 3 mg / 5000 mm 2 ~20mg / 5000mg 2 That's fine.

[0154] The present invention is not particularly limited in terms of the separator substrate, as long as it can achieve the objectives of the present invention. For example, the separator substrate may be a nonwoven fabric, film, or composite film having a porous structure, and the material of the separator substrate may include at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyamide, spandex, and aramid. Optionally, a polypropylene porous film, polyethylene porous film, polypropylene nonwoven fabric, polyethylene nonwoven fabric, or polypropylene-polyethylene-polypropylene porous composite film may be used.

[0155] [Positive electrode piece] The materials, composition, and manufacturing methods of the positive electrode pieces may include techniques known in any prior art.

[0156] In some embodiments, the positive electrode piece may include a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector.

[0157] In some embodiments, the shape of the positive electrode current collector may be plate-shaped or foil-shaped, and the embodiments of the present invention are not limited thereto.

[0158] In some embodiments, the thickness of the positive electrode current collector may be 6 μm to 25 μm.

[0159] In some embodiments, the material of the positive electrode current collector is not particularly limited, and an electronically conductive material can be selected. For example, a single element or alloy (e.g., stainless steel) containing at least one element from among C, Ti, Cr, Mo, Ru, Rh, Ta, W, Os, Ir, Pt, Au, and Al may be used.

[0160] From the standpoint of high conductivity, high stability in electrolytes, and good oxidation resistance, carbon (C) layer, aluminum foil, and stainless steel foil can be selected. From the standpoint of further reducing production costs, aluminum foil can be selected. Those skilled in the art can make adjustments according to the actual situation.

[0161] The positive electrode film layer contains a positive electrode active material. The positive electrode active material can be selected from materials capable of intercalating and releasing lithium. Optionally, the positive electrode active material may include at least one of lithium cobalt oxide (LiCoO2), lithium nickel cobalt aluminate, lithium nickel cobalt manganese oxide, lithium iron phosphate (LiFePO4), and modified compounds of each thereof.

[0162] For example, lithium nickel-cobalt aluminate is LiNi 0.8 Co 0.15 Al 0.05 It may contain, but is not limited to, O2.

[0163] For example, lithium nickel cobalt manganese oxide is LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiLiLi 0.5 Co 0.2 Mn 0.3 O2, LiLiLi 0.6 Co 0.2 Mn 0.2 O2 and LiNi 0.8 Co 0.1 Mn 0.1 It may contain, but is not limited to, at least one of the O2 species.

[0164] The modified compounds for each of the above positive electrode active materials may be compounds obtained by doping modification, surface coating modification, or simultaneous doping and coating modification of the positive electrode active material.

[0165] In some embodiments, the positive electrode film layer may contain a positive electrode conductive agent. The specific type of positive electrode conductive agent is not particularly limited and can be appropriately selected as needed. For example, the positive electrode conductive agent may contain conductive carbon powder. As an example, the positive electrode conductive agent may contain, but is not limited to, at least one of conductive carbon black, acetylene black (AB), Ketjen black (KB), graphite, carbon fiber, carbon tube, graphene, amorphous carbon, hard carbon, soft carbon, glassy carbon, carbon nanofiber, or carbon nanotube (CNT). These materials may be used individually or in combination of two or more.

[0166] In some embodiments, the positive electrode film layer may include a positive electrode adhesive. The specific type of positive electrode adhesive is not particularly limited and can be appropriately selected as needed. For example, the positive electrode adhesive may include, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and polyvinyl alcohol (PVA).

[0167] In some embodiments, the thickness of the positive electrode film layer may be 15 μm to 150 μm, and the embodiments of the present invention are not limited thereto. The thickness of the positive electrode film layer refers to the thickness of the positive electrode film layer located on one side of the positive electrode current collector.

[0168] The positive electrode sheet can be prepared according to the conventional methods in the art. Generally, the positive electrode active material, and any positive electrode conductive agent, positive electrode adhesive, etc. are dispersed in a solvent to form a positive electrode slurry. The positive electrode slurry is applied to the positive electrode current collector, and through processes such as drying and compression, a positive electrode sheet is obtained. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.

[0169] The coating method may be a coating method known in the art. For example, extrusion coating may be used, or methods such as gravure coating, microgravure coating, electrospray coating, transfer coating, etc. may be used. The embodiments of the present invention do not limit this.

[0170] [Negative electrode sheet] The material, composition, and manufacturing method of the negative electrode sheet can include any technology known in the prior art.

[0171] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector.

[0172] In some embodiments, the shape of the negative electrode current collector may be plate-like or foil-like, and the embodiments of the present invention do not limit this.

[0173] In some embodiments, the thickness of the negative electrode current collector may be 4 μm to 25 μm.

[0174] In some embodiments, the material of the negative electrode current collector is not particularly limited, and a material having good electronic conductivity can be selected. For example, a single substance or alloy containing at least one element of C, Cu, Ni, Fe, V, Nb, Ti, Cr, Mo, Ru, Rh, Ta, W, Os, Ir, Pt, Au, Ag (such as stainless steel, etc.) may be used. Also, it may be a composite material obtained by plating a different conductive material on a conductive material. For example, Cu may be plated on Fe.

[0175] From the viewpoint of high conductivity, high stability in electrolytes, and good oxidation resistance, copper foil, nickel foil, and stainless steel foil can be selected. From the viewpoint of further reducing production costs, copper foil and nickel foil can be selected. Those skilled in the art can adjust according to the actual situation.

[0176] The negative electrode film layer contains a negative electrode active material. The negative electrode active material may contain at least one of graphite and silicon-based materials.

[0177] The weight content of silicon-based materials in the negative electrode active material may be between 0% and 25%. A weight content of 0% silicon-based materials means that the negative electrode active material does not contain any silicon-based materials.

[0178] For example, graphite includes natural graphite, artificial graphite, or mixtures thereof.

[0179] As an example, silicon-based materials include at least one of silicon, silicon oxides, silicon-carbon materials, and silicon alloys.

[0180] In some embodiments, the negative electrode film layer may contain a negative electrode conductive agent. The specific type of negative electrode conductive agent is not particularly limited and can be selected as needed. For example, the negative electrode conductive agent may contain conductive carbon powder. As an example, the negative electrode conductive agent may contain, but is not limited to, at least one of conductive carbon black, acetylene black (AB), Ketjen black (KB), graphite, carbon fiber, carbon tube, graphene, amorphous carbon, hard carbon, soft carbon, glassy carbon, carbon nanofiber, or carbon nanotube (CNT). These materials may be used individually or in combination of two or more.

[0181] In some embodiments, the negative electrode film layer may include a negative electrode adhesive. The specific type of negative electrode adhesive is not particularly limited and can be selected as needed. As an example, the negative electrode adhesive may include at least one of styrene-butadiene rubber (SBR), acrylonitrile polypolymer (e.g., LA-based aqueous adhesive, optionally LA132 or LA133), polyacrylic acid (PAA) and its salts, styrene-acrylic resin, polyvinyl alcohol (PVA), and derivatives of each thereof. Derivatives generally refer to products obtained by substituting hydrogen atoms or groups of atoms in a polymer with other atoms or groups of atoms.

[0182] In some embodiments, the negative electrode film layer may contain a negative electrode dispersant. This can improve the film formation quality of the negative electrode film layer. For example, the negative electrode film layer may contain at least one of carboxymethylcellulose sodium (CMC) and its derivatives. A derivative generally refers to a product obtained by substituting a hydrogen atom or group of atoms in the polymer with another atom or group of atoms (e.g., an amino group).

[0183] In some embodiments, the thickness of the negative electrode film layer may be 30 μm to 150 μm, and the embodiments of the present invention are not limited thereto. The thickness of the negative electrode film layer refers to the thickness of the negative electrode film layer located on one side of the negative electrode current collector.

[0184] Negative electrode pieces can be prepared according to conventional methods in the art. Generally, a negative electrode active material, a metal salt, and an optional negative electrode conductive agent, negative electrode adhesive, negative electrode dispersant, etc., are dispersed in a solvent to form a negative electrode slurry. The negative electrode slurry is then applied to a negative electrode current collector, and negative electrode pieces are obtained through processes such as drying and compression. The solvent may include at least one of water, ethanol, acetone, butanone, dimethylformamide, N-methylpyrrolidone, diethylformamide, dimethyl sulfoxide, and tetrahydrofuran, and the examples of the present invention are not limited thereto.

[0185] The coating method may be any coating method known in the art, such as extrusion coating, gravure coating, microgravure coating, electrospray coating, or transfer coating, and the embodiments of the present invention are not limited thereto.

[0186] The negative electrode pieces provided in the embodiments of the present invention do not preclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode piece may further include a conductive undercoat layer (e.g., consisting of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and provided on the surface of the negative electrode current collector. In some embodiments, the negative electrode piece may further include a protective layer covering the surface of the negative electrode film layer.

[0187] [Electrolytes] A battery further contains an electrolyte. The electrolyte may be a solid electrolyte, a gel electrolyte, or a liquid electrolyte (also called an electrolyte solution).

[0188] In some embodiments, the electrolyte may be an electrolyte solution. The electrolyte solution may contain an electrolyte salt containing lithium ions and a solvent.

[0189] The type of electrolyte salt and solvent is not particularly limited and can be selected as needed.

[0190] In some examples, the electrolyte salt may include, but is not limited to, at least one of the following: lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), and lithium bis(oxalato)borate (LiBOB). The electrolyte salt may be used individually, or in combination of two or more types.

[0191] In some embodiments, the solvent may contain at least one of a carbonate compound, a carboxylic acid ester compound, an ether compound, and a sulfone compound. As an example, the solvent may include ethylene carbonate (EC), fluoroethylene carbonate (FEC), 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), γ-butyrolactone, sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), diethyl sulfone (ESE), methyl sulfolane, dimethyl sulfoxide, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl- 1,3-dioxolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethyl ether, diethyl ether, nitromethane, N,N-dimethylformamide, etc., but is not limited thereto. The above solvents may be used alone or in combination of two or more.

[0192] In some embodiments, the electrolyte solution may further contain additives, such as additives for improving various characteristics of the battery.

[0193] The electrolyte solution can be prepared according to conventional methods in the art. For example, a solvent, an electrolyte salt, and any other components can be uniformly mixed to obtain the electrolyte solution. The addition order of each material is not particularly limited. For example, the electrolyte salt and any other components can be added to the solvent and uniformly mixed to obtain the electrolyte solution.

[0194] The components in the electrolyte and their content can be measured according to conventional methods in the art. For example, they can be detected by gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), etc.

[0195] In some embodiments, the positive electrode piece, negative electrode piece, and separator can be manufactured as an electrode assembly by a winding or lamination process.

[0196] In some embodiments, the battery may be a pouch battery.

[0197] In some embodiments, the outer packaging may be a pouch, for example, a bag-shaped pouch. The material of the pouch may be aluminum laminate film or plastic. For example, the plastic may include at least one of polypropylene (PP), polybutylene terephthalate (PBT), or polybutylene succinate (PBS).

[0198] Separator Embodiments of the present invention further provide a separator.

[0199] The separator includes a porous substrate, and a first coating layer is provided on at least one surface of the porous substrate, the first coating layer comprising a first polymer and a second polymer having different melting points.

[0200] In some examples, the melting point of the first polymer is set to T m1 The melting point of the second polymer is set to T m2 In that case, T m1 The temperature can be 60°C to 100°C, T m2 It may be 130℃ or higher, and T m2 -T m1 The temperature can be between 40°C and 120°C.

[0201] Melting point T of the first polymer m1 , the melting point T of the second polymer m2 , and Tm2 -T m1 By adjusting the values ​​within the above range, the battery can be given good electrochemical performance, and furthermore, the safety tolerance range for the battery's hot box test can be expanded, improving the pass rate of the battery's hot box test.

[0202] In some examples, the melting point of the first polymer is set to T m1 The melting point of the second polymer is set to T m2 In that case, T m1 The temperature can be 70°C to 90°C, T m2 The temperature may be between 135°C and 160°C, and T m2 -T m1 The temperature can be between 50°C and 80°C.

[0203] This allows for better electrochemical performance in batteries, expands the safety tolerance range for hot box testing, and improves the pass rate of hot box testing.

[0204] In some examples, the particle size Dv in the volume-based particle size distribution of the first polymer particles (1) Particle size Dv in the volume-based particle size distribution of 50 and second polymer particles (2) 50 is 0.50 ≤ Dv (2) 50 / Dv (1) Satisfying 50 ≤ 1.25, for example, Dv (2) 50 / Dv (1) 50 may be a range consisting of 0.50, 0.60, 0.67, 0.75, 0.83, 0.90, 1.00, 1.10, 1.25, or any two of the numbers listed above. Optionally, Dv (1) 50 and Dv (2) 50 is 0.60 ≤ Dv (2) 50 / Dv (1) The condition satisfies 50 ≤ 0.83.

[0205] Dv (2) 50 / Dv (1)By adjusting 50 within the above range, the film formation of the first polymer can be improved, and the first coating layer can be given appropriate adhesion and breathability, thereby enabling the battery to have good electrochemical performance and a high pass rate in hot box testing.

[0206] In some examples, the particle size Dv in the volume-based particle size distribution of the first polymer particles (1) Particle size Dv in the volume-based particle size distribution of 90 and the second polymer (2) 50 is 2.0 ≤ Dv (1) 90 / Dv (2) Satisfying 50 ≤ 5.0, for example, Dv (1) 90 / Dv (2) 50 may be a range consisting of 2.0, 2.25, 2.50, 2.80, 3.00, 3.25, 3.50, 3.75, 4.0, 4.17, 5.0, or any two of the numbers listed above. Optionally, Dv (1) 90 and Dv (2) 50 is 3.00 ≤ Dv (1) 90 / Dv (2) The condition satisfies 50 ≤ 4.17.

[0207] Dv (1) 90 / Dv (2) By adjusting 50 within the above range, the film formation of the first polymer can be improved, and the first coating layer can be given appropriate adhesion and breathability, thereby enabling the battery to have good electrochemical performance and a high pass rate in hot box testing.

[0208] In some examples, the particle size Dv in the volume-based particle size distribution of the first polymer particles (1) Particle size Dv in the volume-based particle size distribution of 50 and second polymer particles (2) 50 is 0.50 ≤ Dv (2) 50 / Dv (1) The condition 50 ≤ 1.25 is satisfied, and the particle size Dv in the volume-based particle size distribution of the first polymer particles is satisfied. (1) Particle size Dv in the volume-based particle size distribution of 90 and the second polymer (2) 50 is 2.0 ≤ Dv(1) 90 / Dv (2) The condition satisfies 50 ≤ 5.0. Arbitrarily, Dv (2) 50 / Dv (1) 50 is 0.60 ≤ Dv (2) 50 / Dv (1) Satisfying 50 ≤ 0.83, and Dv (1) 90 / Dv (2) 50 is 3.00 ≤ Dv (1) 90 / Dv (2) The condition satisfies 50 ≤ 4.17.

[0209] Dv (2) 50 / Dv (1) 50 and Dv (1) 90 / Dv (2) By adjusting 50 within the above range, it is advantageous to disperse the second polymer around the first polymer, thereby improving the film formation of the first polymer, and also to ensure that the first coating layer possesses appropriate adhesion and breathability. Furthermore, it is possible to give the battery good electrochemical performance and a high pass rate in hot box testing.

[0210] In some examples, the particle size Dv in the volume-based particle size distribution of the first polymer particles (1) 50 may be 0.8 μm to 2.0 μm, and may be arbitrarily 1.0 μm to 2.0 μm, or 1.0 μm to 1.5 μm.

[0211] In some examples, the particle size Dv in the volume-based particle size distribution of the first polymer particles (1) 90 may be 2.0 μm to 5.0 μm.

[0212] Particle size Dv in the volume-based particle size distribution of the first polymer (1) 50 and / or Dv (1) By adjusting 90 within the above range, the first coating layer can be given appropriate adhesion and breathability, thereby enabling the battery to have good electrochemical performance and a high pass rate in hot box testing.

[0213] In some examples, the particle size Dv in the volume-based particle size distribution of the second polymer particles (2) 50 may be 0.54 μm to 1.5 μm.

[0214] Particle size Dv in the volume-based particle size distribution of the second polymer (2) By adjusting 50 within the above range, the first coating layer can be given appropriate adhesion and breathability, thereby enabling the battery to have good electrochemical performance and a high pass rate in hot box testing.

[0215] In some examples, the particle size Dv in the volume-based particle size distribution of the first polymer particles (1) 10 may be 0.1 μm to 0.7 μm.

[0216] Particle size Dv in the volume-based particle size distribution of the first polymer (1) By further adjusting 10 within the above range, the electrolyte transport capacity of the separator can be further improved, thereby improving the battery's cycle characteristics.

[0217] In some examples, the particle size Dv in the volume-based particle size distribution of the second polymer particles (2) 10 may be 0.1 μm to 0.5 μm.

[0218] In some examples, the particle size Dv in the volume-based particle size distribution of the second polymer particles (2) 90 may be 2.0 μm to 5.0 μm.

[0219] Particle size Dv in the volume-based particle size distribution of the second polymer (2) 10 and / or Dv (2) By further adjusting 90 within the above range, the electrolyte transport capacity of the separator can be further improved, thereby improving the battery's cycle characteristics.

[0220] In some embodiments, when the weight content of the first polymer is m1 and the weight content of the second polymer is m2, m1 may be 50% to 86% and m2 may be 9% to 45% based on the total weight of the first coating layer. Optionally, m1 may be 70% to 82% and m2 may be 13% to 25%.

[0221] By adjusting the weight content m1 of the first polymer and the weight content m2 of the second polymer within the above range, it is advantageous that the separator and the electrode piece have appropriate adhesion, and that the interface between the electrode piece and the separator opens sufficiently when the battery is in the heat generation stage. This allows gas and heat at the interface to be transferred to the outer bag in a timely manner, thereby reducing heat accumulation at the interface. Furthermore, it is possible to broaden the safety tolerance range for the battery's hot box test and improve the pass rate of the battery's hot box test. In addition, the first coating layer can be given appropriate adhesion and breathability, thus enabling the battery to have good electrochemical performance.

[0222] In some examples, the weight-average molecular weight of the first polymer is set to M. w1 In that case, M w1 This can be between 50,000 and 500,000, for example, 50,000, 100,000, 150,000, 180,000, 200,000, 230,000, 260,000, 300,000, 350,000, 400,000, 450,000, 500,000, or any two of the above numbers. Optionally, M w1 It could be between 150,000 and 260,000.

[0223] Weight-average molecular weight M of the first polymer w1By adjusting the above range, the first coating layer can be given appropriate tackiness, and the battery can be given appropriate interfacial tackiness. This is advantageous because when the battery is in the heat generation phase, the interface between the electrode piece and the separator can open sufficiently. This allows gas and heat at the interface to be transferred to the outer bag in a timely manner, thereby reducing heat accumulation at the interface. Furthermore, it is possible to broaden the safety tolerance range for the battery's hot box test, improve the pass rate of the battery's hot box test, reduce the probability of deformation of the electrode assembly after the battery's charge-discharge cycle, and furthermore, give the battery good electrochemical performance.

[0224] In some examples, the weight-average molecular weight of the second polymer is set to M. w2 In that case, M w2 This can be between 700,000 and 2,200,000, for example, 700,000, 800,000, 900,000, 1,000,000, 1,180,000, 1,340,000, 1,500,000, 1,810,000, 2,000,000, or a range consisting of any two of the above numbers. Optionally, M w2 It could be between 1.18 million and 2 million.

[0225] Weight-average molecular weight M of the second polymer w2 By adjusting the weight-average molecular weight M of the second polymer, the second polymer can be dispersed around the first polymer, thereby reducing the risk of the separator pores becoming clogged during the battery manufacturing process (e.g., baking of electrode assemblies, hot pressing, etc.) and the normal use of the battery, and furthermore, enabling the battery to have good electrochemical performance. w2 By adjusting the above range, it is advantageous that the separator and electrode pieces have appropriate adhesive strength, and that the interface between the electrode pieces and the separator opens sufficiently when the battery is in the heat generation stage. This allows gas and heat at the interface to be transferred to the outer bag in a timely manner, thereby reducing heat accumulation at the interface. Furthermore, it is possible to broaden the safety tolerance range for the battery's hot box test and improve the pass rate of the battery's hot box test.

[0226] In some embodiments, M w1 It can be between 150,000 and 260,000, M w2 It could be between 1.18 million and 2 million.

[0227] M w1 and M w2 By adjusting the values ​​within the above range, it is possible to give the battery good electrochemical performance, further widen the safety tolerance range for the battery's hot box test, and improve the pass rate of the battery's hot box test.

[0228] In some embodiments, M w1 and M w2 700,000 ≤ M w2 -M w1 The condition satisfies ≤2.3 million, and arbitrarily, 980,000 ≤ M w2 -M w1 It satisfies the condition ≤ 1.61 million.

[0229] M w2 -M w1 By adjusting the values ​​within the above range, it is advantageous to disperse the second polymer around the first polymer, thereby reducing the risk of the separator pores becoming clogged during the battery manufacturing process (e.g., processes such as baking and hot pressing of the electrode assembly) and during normal battery use. Furthermore, the first coating layer can be given appropriate adhesion and breathability, and the battery can be given good electrochemical performance and a high pass rate in hot box testing.

[0230] In some examples, the weight-average molecular weight of the first polymer is set to M. w1 The weight-average molecular weight of the second polymer is set to M. w2 In that case, M w1 It can be between 50,000 and 500,000, M w2 It may be between 700,000 and 2,200,000, and M w1 and M w2 700,000 ≤ M w2 -M w1 The condition ≤ 2.3 million is satisfied. Arbitrarily, Mw1 It can be between 150,000 and 260,000, M w2 It may be between 1.18 million and 2 million, and M w1 and M w2 980,000 ≤ M w2 -M w1 It satisfies the condition ≤ 1.61 million.

[0231] This allows for better electrochemical performance in batteries, expands the safety tolerance range for hot box testing, and improves the pass rate of hot box testing.

[0232] In some examples, the first polymer may contain at least one of the monomers and copolymers selected from ethylene, propylene, vinylidene fluoride, acrylic acid, acrylic acid esters, styrene, acrylonitrile, maleic anhydride, vinyl chloride, and chloropropene. The first polymer may contain a homopolymer, a copolymer, or a mixture thereof.

[0233] In some examples, the second polymer may contain at least one of the monomers and copolymers selected from vinylidene fluoride, hexafluoropropylene, propylene, vinyl chloride, styrene, butadiene, acrylic acid esters, and acrylic acid. The second polymer may contain a homopolymer, a copolymer, or a mixture of both.

[0234] In some examples, the coating weight of the first coating layer was 0.5 mg / 5000 mm 2 ~3mg / 5000mg 2 It may also be 0.5 mg / 5000 ml 2 , 0.8 mg / 5000 ml 2 , 1 mg / 5000 ml 2 , 1.5 mg / 5000 ml 2 , 2mg / 5000mg 2 , 2.5 mg / 5000 ml 2 3 mg / 5000 ml 2Alternatively, it may be within a range consisting of any two of the above values. Optionally, the coating weight of the first coating layer may be 0.5 mg / 5000 mm 2 ~1.5mg / 5000mg 2 That's fine.

[0235] By adjusting the coating weight of the first coating layer within the above range, the first coating layer can be given appropriate tackiness. Specifically, the first coating layer has good tackiness under normal battery operation conditions and low tackiness when the battery is in the heat generation phase. This is advantageous because it allows the interface between the electrode pieces and the separator to open sufficiently when the battery is in the heat generation phase, thereby enabling timely transfer of gas and heat at the interface to the outer bag, reducing heat accumulation at the interface. Furthermore, it is possible to broaden the safety tolerance range for the battery's hot box test, improve the pass rate of the battery's hot box test, reduce the probability of deformation of the electrode assembly after the battery's charge-discharge cycle, and further, give the battery good electrochemical performance.

[0236] In some embodiments, the thickness of the first coating layer may be 0.5 μm to 2.8 μm, for example, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 2.8 μm, or any two of the above values. Optionally, the thickness of the first coating layer may be 1 μm to 2 μm.

[0237] By adjusting the thickness of the first coating layer within the above range, the first coating layer can be given appropriate tackiness. Specifically, the first coating layer has good tackiness under normal battery operation conditions and low tackiness when the battery is in the heat generation phase. This is advantageous because it allows the interface between the electrode pieces and the separator to open sufficiently when the battery is in the heat generation phase, thereby enabling timely transfer of gas and heat at the interface to the outer bag, reducing heat accumulation at the interface. Furthermore, it is possible to broaden the safety tolerance range for the battery's hot box test, improve the pass rate of the battery's hot box test, reduce the probability of deformation of the electrode assembly after the battery's charge-discharge cycle, and further, give the battery good electrochemical performance.

[0238] In some embodiments, the first coating layer may further contain a thickener, a wetting agent, etc. In the present invention, the thickener is not particularly limited and may be, for example, at least one of sodium carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, methylhydroxyethylcellulose, and ethylhydroxyethylcellulose. In the present invention, the wetting agent is not particularly limited and may be, for example, at least one of polyoxyethylene ether, dimethylsiloxane, sucrose ester, and alkyl ether sulfate sodium.

[0239] In some embodiments, a first coating layer is provided on the surface of the porous substrate facing the positive electrode piece. This is advantageous in broadening the safety tolerance range for the battery's hot box test and improving the pass rate of the battery's hot box test.

[0240] In some embodiments, a first coating layer is provided on one surface of the porous substrate, and a second coating layer is provided on the other surface of the porous substrate. Optionally, the first coating layer is provided on the surface of the porous substrate facing the positive electrode piece, and the second coating layer is provided on the surface of the porous substrate facing the negative electrode piece.

[0241] The second coating layer comprises a third polymer, which may comprise at least one of the monomers and copolymers selected from butyl acrylate, octyl acrylate, isooctyl acrylate, styrene, and butadiene. The third polymer may comprise a homopolymer, a copolymer, or a mixture thereof.

[0242] This reduces the probability of electrode assembly deformation occurring after battery charge-discharge cycles, and furthermore, allows the battery to have good electrochemical performance.

[0243] In some examples, the melting point of the third polymer may be 50°C to 70°C.

[0244] The present invention does not have any particular limitations on the thickness of the second coating layer, as long as the objective of the present invention is achieved. For example, the thickness of the second coating layer may be 0.5 μm to 3 μm.

[0245] The present invention does not have any particular limitations on the coating weight of the second coating layer, as long as the objective of the present invention is achieved. For example, the coating weight of the second coating layer may be 0.5 mg / 5000 mm 2 ~3mg / 5000mg 2 That's fine.

[0246] In some embodiments, an inorganic coating layer may be provided between the porous substrate and the first coating layer. Providing an inorganic coating layer between the porous substrate and the first coating layer can also improve the thermal shrinkage resistance, puncture resistance, and / or electrolyte transportability of the separator.

[0247] In some embodiments, the inorganic coating layer may include, but is not limited to, a ceramic, which may include at least one of alumina, boehmite, titania, silica, zirconia, tin dioxide, magnesium hydroxide, magnesium oxide, zinc oxide, barium sulfate, boron nitride, and aluminum nitride.

[0248] In some embodiments, the inorganic coating layer may further contain a binder, and in the present invention, the type of binder is not particularly limited and may include, for example, at least one of polyacrylate, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethylcellulose, potassium carboxymethylcellulose, sodium hydroxymethylcellulose, and potassium hydroxymethylcellulose.

[0249] The present invention does not have any particular limitations on the thickness of the inorganic coating layer, as long as the objective of the present invention is achieved. For example, the thickness of the inorganic coating layer may be 0.5 μm to 6 μm.

[0250] The present invention does not have any particular limitations on the coating weight of the inorganic coating layer, as long as the objective of the present invention is achieved. For example, the coating weight of the inorganic coating layer is 3 mg / 5000 mm 2 ~20mg / 5000mg 2 That's fine.

[0251] The present invention is not particularly limited in terms of the separator substrate, as long as it can achieve the objectives of the present invention. For example, the separator substrate may be a nonwoven fabric, film, or composite film having a porous structure, and the material of the separator substrate may include at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyamide, spandex, and aramid. Optionally, a polypropylene porous film, polyethylene porous film, polypropylene nonwoven fabric, polyethylene nonwoven fabric, or polypropylene-polyethylene-polypropylene porous composite film may be used.

[0252] The separator can be prepared according to the following method: The first polymer, the second polymer, and the solvent are uniformly stirred to obtain a slurry for the first coating layer. The slurry for the first coating layer is applied to at least one surface of a porous substrate and dried to obtain the separator.

[0253] In some embodiments, the slurry for the first coating layer may further contain a thickener, a wetting agent, and the like.

[0254] Electrochemical apparatus Embodiments of the present invention further provide an electrochemical apparatus including a battery as described in any one of the above embodiments.

[0255] In one embodiment, the electrochemical apparatus includes a housing, and the batteries are located within the housing. The number of batteries may be multiple, and multiple batteries are located within the housing.

[0256] In one embodiment, the electrochemical apparatus may be a battery module or a battery pack.

[0257] electronic equipment Embodiments of the present invention further provide electronic devices including a battery and / or electrochemical device as described in any one of the above embodiments.

[0258] The electronic device of the present invention is not particularly limited and may be any known electronic device used in the prior art. In some embodiments, the electronic device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an e-book player, a mobile phone, a portable facsimile, a portable copier, a portable printer, a stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CC player, a MiniDisc, a transceiver, an electronic notebook, a calculator, a memory card, a portable tape recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, an electric assist bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household storage battery, and a lithium-ion capacitor.

[0259] Examples The following examples illustrate the contents of the present invention in more detail, but since various modifications and changes within the scope of the invention will be obvious to those skilled in the art, these examples are used merely for illustrative purposes. Unless otherwise specified, all parts, percentages and ratios reported in the following examples are by weight. Furthermore, all reagents used in the examples are commercially available or obtained by conventional methods and are ready for direct use without further processing. Furthermore, all equipment used in the examples is commercially available.

[0260] Test section (1) Measurement of the melting points of the first polymer and the second polymer The melting points of the first polymer and the second polymer are measured using a differential scanning calorimeter (DSC). The sample mass can be 8 mg to 15 mg, the test temperature range is 25°C to 400°C, and the heating rate is 10°C / min.

[0261] (2) Measurement of the weight-average molecular weight of the first polymer and the weight-average molecular weight of the second polymer The weight-average molecular weight of the first polymer and the weight-average molecular weight of the second polymer are measured using gel permeation chromatography (GPC).

[0262] (3) Measurement of particle size in the volume-based particle size distribution of the first polymer and the second polymer Referring to GB / T 19077-2016, the particle size in the volume-based particle size distribution of the first polymer and the particle size in the volume-based particle size distribution of the second polymer are measured, and the measuring device can be a laser diffraction particle size distribution analyzer, for example, the Mastersizer 3000 laser diffraction particle size distribution analyzer from Malvern GmbH, UK.

[0263] (4) Hot box test Under conditions of 25°C, the lithium-ion battery is left standing for 5 minutes, charged to 4.5V with a constant current of 0.5C, then charged again to 0.025C with a constant voltage of 4.5V, left standing for 60 minutes, and then subjected to a hot box test. Before the hot box test, the appearance of the lithium-ion battery is inspected and photographed, a temperature sensor cable is attached, the lithium-ion battery is placed vertically in the hot box, and the temperature is raised from 25°C to 130°C at a rate of 5°C / min and maintained for 60 minutes. If the lithium-ion battery does not ignite or explode, it is considered to have passed the hot box test. The sample size of lithium-ion batteries for testing is set at 100, and the number of batteries that pass the hot box test is tallied to calculate the pass rate of the hot box test.

[0264] (5) Measurement of the thickness of lithium-ion batteries Under conditions of 25°C, the lithium-ion battery is left standing for 5 minutes, charged to 4.5V with a constant current of 0.5C, then charged again to 0.025C with a constant voltage of 4.5V, left standing for 60 minutes, and the thickness of the lithium-ion battery is measured and designated as D1, i.e., the thickness before the hot box test. After the hot box test described above, remove the lithium-ion battery, wait for the temperature of the lithium-ion battery to drop to 25°C, and measure the thickness of the lithium-ion battery again. This measurement is then designated as D2.

[0265] The thickness of a lithium-ion battery can be measured using a laser thickness gauge. To ensure the accuracy of the measurement results, five lithium-ion battery samples may be taken for each example and comparative example, and measurements may be taken at three points for each lithium-ion battery sample, with the average value being taken.

[0266] (6) Measurement of the adhesive force between the first coating layer of the separator and the electrode adjacent to the first coating layer. The test standard can be found in GB / T 2790-1995. After the hot box test described above, the lithium-ion battery is removed, and after waiting for the temperature of the lithium-ion battery to drop to 25°C, the separator and electrode pieces are disassembled and removed from the lithium-ion battery together. These are then cut into small strips of 15 mm × 54.2 mm, and the adhesive force between the first coating layer of the separator and the electrode piece adjacent to the first coating layer is measured using a 180° peel test standard and defined as T. The measuring device is a universal tensile testing machine. After the measurement is completed, the ratio of the average value of the applied force at the plateau of the peel force curve to the sample width is defined as the adhesive force T between the first coating layer of the separator and the electrode piece adjacent to the first coating layer. The tensile speed (i.e., peel speed) of the tensile testing machine can be set to 50 mm / min. To ensure the accuracy of the measurement results, five lithium-ion battery samples can be taken and measured for each example and comparative example, and the average value can be used as the measurement result.

[0267] In the following examples and comparative examples, the adhesive force T measured in Examples 1-13 is the adhesive force between the first coating layer of the separator and the negative electrode piece, while the adhesive force T measured in the other examples and comparative examples is the adhesive force between the first coating layer of the separator and the positive electrode piece.

[0268] (7) Cycle characteristics test The measurement temperature will be 12°C. After letting the lithium-ion battery stand for 5 minutes, charge it to 4.45V with a constant current of 2C, then charge it to 0.05C with a constant voltage. After letting it stand for 5 minutes, discharge the lithium-ion battery to 3.0V with a constant current of 0.2C. Repeat the above procedure three times (i.e., charge at 2C and discharge at 0.2C), and record the discharge capacity of the third cycle. After letting the lithium-ion battery stand for 5 minutes, charge it to 4.45V with a constant current of 2C, then charge it to 0.05C with a constant voltage. After letting it stand for 5 minutes, discharge it to 3.0V with a constant current of 1C. Repeat the above procedure for 47 cycles (i.e., charge at 2C and discharge at 1C). After letting the lithium-ion battery stand for 5 minutes, charge it to 4.45V with a constant current of 2C, then charge it to 0.05C with a constant voltage. After letting it stand for 5 minutes, discharge it to 3.0V with a constant current of 0.2C. Repeat the above procedure 750 times (i.e., charge at 2C and discharge at 0.2C), for a total of 800 cycles, and record the discharge capacity at the 800th cycle. The cycle capacity retention rate (%) after 800 cycles of a lithium-ion battery is calculated as follows: (Discharge capacity at the 800th cycle / Discharge capacity at the 3rd cycle) × 100%.

[0269] To ensure the accuracy of the measurement results, five lithium-ion battery samples can be taken and measured for each example and comparative example, and the average value can be used as the measurement result.

[0270] Example 1-1 (1) Preparation of separators Boehmite with a volume-average particle size Dv50 of 1 μm and a polyacrylic acid ester binder were dispersed in deionized water in a mass ratio of 90:10 to form an inorganic coating layer slurry with a solid content of 50%. Using a microgravure coating method, the inorganic coating layer slurry was uniformly applied to one surface of a 5 μm thick porous PE substrate, dried in an oven, and then an inorganic coating layer was obtained. The thickness of the inorganic coating layer was 2 μm.

[0271] Polymer particles of the first polymer, which uses propylene as the base monomer, and polymer particles of the second polymer, which uses vinylidene fluoride as the base monomer, as shown in Table 1, were added to a stirrer and mixed uniformly. Sodium carboxymethylcellulose was added to the stirrer and mixed uniformly. Dimethylsiloxane, a wetting agent, was added to the stirrer, and then deionized water was added and mixed to adjust the viscosity of the slurry to 40 MPa·s and the solid content to 5%, thereby obtaining the slurry for the first coating layer. The slurry for the first coating layer was uniformly applied to the inorganic coating layer and dried in an oven to obtain the first coating layer. The coating weight of the slurry for the first coating layer was 1 mg / 5000 mm 2 The thickness of the first coating layer was 1.5 μm. The mass ratio of the first polymer, the second polymer, sodium carboxymethylcellulose, and dimethylsiloxane was 75:20:0.5:4.5. In Table 1, T m1 indicates the melting point of the first polymer, T m2 The symbol indicates the melting point of the second polymer. w1 This indicates the weight-average molecular weight of the first polymer, M w2 This indicates the weight-average molecular weight of the second polymer. Dv (1) 50 and Dv (1) 90 represents the particle size in the volume-based particle size distribution of the first polymer particles, and Dv (2) 50 represents the particle size in the volume-based particle size distribution of the second polymer. m1 represents the weight content of the first polymer, and m2 represents the weight content of the second polymer, both based on the total weight of the first coating layer.

[0272] The third polymer, styrene-butyl acrylate-isooctyl acrylate copolymer, was added to a stirrer, and sodium carboxymethylcellulose was added and mixed uniformly. Dimethylsiloxane, a wetting agent, was added to the stirrer, and then deionized water was added and mixed to adjust the viscosity of the slurry to 40 MPa·s and the solid content to 5%, thereby obtaining the slurry for the second coating layer. The slurry for the second coating layer was uniformly applied to the other surface of the porous PE substrate and dried in an oven to obtain the second coating layer. The coating weight of the slurry for the second coating layer was 1 mg / 5000 mm 2 The thickness of the second coating layer was 1.5 μm. The mass ratio of the third polymer, carboxymethylcellulose sodium, and dimethylsiloxane was 95:0.5:4.5.

[0273] (2) Preparation of the negative electrode piece Artificial graphite, acetylene black, styrene-butadiene rubber, and sodium carboxymethylcellulose were mixed in a mass ratio of 96:1:1.5:1.5. Deionized water was then added as a solvent to prepare a slurry with a solid content of 70%, which was then uniformly stirred. The slurry was uniformly applied to one surface of an 8 μm thick copper foil, dried at 110°C, and cold-pressed to obtain a negative electrode piece coated on one side, with a negative electrode film layer thickness of 150 μm. The above procedure was then repeated on the other surface of the copper foil to obtain a negative electrode piece coated on both sides. The negative electrode pieces were cut to a standard size of 74 mm × 867 mm, tabs were welded on, and then they were set aside for use.

[0274] (3) Preparation of positive electrode piece LiCoO2, acetylene black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 94:3:3. Then, N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75%, which was then uniformly stirred. The slurry was uniformly applied to one surface of a 12 μm thick aluminum foil, dried at 90°C, and cold-pressed to obtain a positive electrode piece coated on one side, with a positive electrode film layer thickness of 100 μm. The above procedure was then repeated on the other surface of the aluminum foil to obtain a positive electrode piece coated on both sides. The positive electrode pieces were cut to a standard size of 74 mm × 867 mm, tabs were welded on, and then they were set aside for use.

[0275] (4) Preparation of electrolyte Under conditions with a moisture content of less than 10 ppm, ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propyl propionate (PP), and vinylene carbonate (VC) were mixed in a mass ratio of 20:30:20:28:2. LiPF6 was then added and mixed uniformly to obtain an electrolyte. The mass fraction of LiPF6 in the electrolyte was 8%.

[0276] (5) Preparation of lithium-ion batteries The positive electrode piece, separator, and negative electrode piece prepared as described above were stacked in order, the first coating layer of the separator was brought into contact with the positive electrode piece, and the assembly was wound to obtain an electrode assembly. The electrode assembly was placed in an aluminum laminate film outer bag, moisture was removed at 80°C, the prepared electrolyte was injected, and after processes such as vacuum sealing, standing, hot pressing, and shaping, a pouch-type lithium-ion battery was obtained.

[0277] Examples 1-2 to 1-12 In the preparation of the separator, the other preparation steps were the same as in Example 1-1, except that the melting point and weight-average molecular weight of the first polymer and / or the second polymer were different. The specific parameters are shown in Table 1.

[0278] Examples 1-13 In the preparation of the lithium-ion battery, the other preparation steps were the same as in Example 1-1, except that the first coating layer of the separator was brought into contact with the negative electrode piece.

[0279] Examples 1-14 Aside from the separator preparation process, the other preparation steps were the same as in Example 1-1.

[0280] (1) Preparation of separators Boehmite with a volume-average particle size Dv50 of 1 μm and a polyacrylic acid ester binder were dispersed in deionized water in a mass ratio of 90:10 to form an inorganic coating layer slurry with a solid content of 50%. Using a microgravure coating method, the inorganic coating layer slurry was uniformly applied to both sides of a 5 μm thick porous PE substrate and dried in an oven to obtain an inorganic coating layer. The thickness of the inorganic coating layer (thickness on one side) was 2 μm.

[0281] Polymer particles of the first polymer, based on propylene as the monomer, and polymer particles of the second polymer, based on vinylidene fluoride as the monomer, as shown in Table 1, were added to a stirrer and mixed uniformly. Sodium carboxymethylcellulose was added to the stirrer and mixed uniformly. Dimethylsiloxane, a wetting agent, was added to the stirrer, and then deionized water was added and mixed to adjust the viscosity of the slurry to 40 MPa·s and the solid content to 5%, thereby obtaining the slurry for the first coating layer. The slurry for the first coating layer was uniformly applied to the inorganic coating layer and dried in an oven to obtain the first coating layer. The coating weight (coating weight on one side) of the slurry for the first coating layer was 1 mg / 5000 mm 2 The thickness of the first coating layer (thickness on one side) was 1.5 μm. The mass ratio of the first polymer, the second polymer, sodium carboxymethylcellulose, and dimethylsiloxane was 75:20:0.5:4.5. In Table 1, T m1 indicates the melting point of the first polymer, T m2 The symbol indicates the melting point of the second polymer. w1 This indicates the weight-average molecular weight of the first polymer, Mw2 This indicates the weight-average molecular weight of the second polymer. Dv (1) 50 and Dv (1) 90 represents the particle size in the volume-based particle size distribution of the first polymer particles, and Dv (2) 50 represents the particle size in the volume-based particle size distribution of the second polymer. m1 represents the weight content of the first polymer, and m2 represents the weight content of the second polymer, both based on the total weight of the first coating layer.

[0282] Examples 1-15 In the preparation of the separator, the other preparation steps were the same as in Example 1-1, except that the melting point and weight-average molecular weight of the first polymer were different. The specific parameters are shown in Table 1.

[0283] Comparative Example 1 Aside from the separator preparation process, the other preparation steps were the same as in Example 1-1.

[0284] Boehmite with a volume-average particle size Dv50 of 1 μm and a polyacrylic acid ester binder were dispersed in deionized water in a mass ratio of 90:10 to form an inorganic coating layer slurry with a solid content of 50%. Using a microgravure coating method, the inorganic coating layer slurry was uniformly applied to one surface of a 5 μm thick porous PE substrate, dried in an oven, and then an inorganic coating layer was obtained. The thickness of the inorganic coating layer was 2 μm.

[0285] Polymer particles with propylene as the base monomer of the first polymer shown in Table 1 were added to a stirrer and mixed uniformly. Sodium carboxymethylcellulose was added to the stirrer and mixed uniformly. Dimethylsiloxane, a wetting agent, was added to the stirrer, and then deionized water was added and mixed to adjust the viscosity of the slurry to 40 MPa·s and the solid content to 5%, thereby obtaining the slurry for the first coating layer. The slurry for the first coating layer was uniformly applied to the inorganic coating layer and dried in an oven to obtain the first coating layer. The coating weight of the slurry for the first coating layer was 1 mg / 5000 mm 2The thickness of the first coating layer was 1.5 μm. The mass ratio of the first polymer, carboxymethylcellulose sodium, and dimethylsiloxane was 95:0.5:4.5.

[0286] The third polymer, styrene-butyl acrylate-isooctyl acrylate copolymer, was added to a stirrer, and sodium carboxymethylcellulose was added and mixed uniformly. Dimethylsiloxane, a wetting agent, was added to the stirrer, and then deionized water was added and mixed to adjust the viscosity of the slurry to 40 MPa·s and the solid content to 5%, thereby obtaining the slurry for the second coating layer. The slurry for the second coating layer was uniformly applied to the other surface of the porous PE substrate and dried in an oven to obtain the second coating layer. The coating weight of the slurry for the second coating layer was 1 mg / 5000 mm 2 The thickness of the second coating layer was 1.5 μm. The mass ratio of the third polymer, carboxymethylcellulose sodium, and dimethylsiloxane was 95:0.5:4.5.

[0287] As can be seen from the measurement results in Table 1, batteries that satisfy 0.077 ≤ (3.0 - D2 / D1) / T ≤ 0.118 can have a high pass rate in the hot box test and simultaneously possess good electrochemical performance.

[0288] The battery prepared in Comparative Example 1 did not satisfy 0.077 ≤ (3.0 - D2 / D1) / T ≤ 0.118, and therefore the battery could not achieve both a high pass rate in the hot box test and good electrochemical performance.

[0289] The first coating layer of the separator prepared in Comparative Example 1 uses only the first polymer. The first polymer has a relatively low melting point, and during the battery manufacturing process (e.g., baking of the electrode assembly, hot pressing, etc.) and the normal use of the battery, its fluidity after softening due to heat is relatively strong, increasing the risk of the separator pores becoming clogged. Therefore, the electrochemical performance of the battery prepared in Comparative Example 1 is inferior. At the same time, when the battery is in the heat generation stage, the interface between the electrode piece and the separator of the battery prepared in Comparative Example 1 cannot open, or opens insufficiently. As a result, gas and heat at the interface cannot be transferred to the outer bag in a timely manner, and heat continues to accumulate at the interface. Therefore, the pass rate of the hot box test for the battery prepared in Comparative Example 1 is also relatively low.

[0290] Furthermore, as can be seen from the measurement results of Examples 1-1 to 1-15, the melting point T of the first polymer m1 , the melting point T of the second polymer m2 , and the difference T between the two m2 -T m1 By further adjusting the range, the overall performance of the battery can be further improved.

[0291] [Table 1] Examples 2-1 to 2-15 In Examples 2-1 to 2-13, in the preparation of the separator, the particle size Dv in the volume-based particle size distribution of the first polymer particles was (1) 50 and Dv (1) 90, or particle size Dv in the volume-based particle size distribution of the second polymer particles (2) Aside from the difference of 50, the other preparation steps were the same as in Example 1-1. The specific parameters are shown in Table 2.

[0292] In Examples 2-14 to 2-15, in the preparation of the separator, the particle size Dv in the volume-based particle size distribution of the second polymer particles was (2) 50. Melting point T of the second polymer m2Aside from the difference in one parameter, the other preparation steps were the same as in Example 2-3. The specific parameters are shown in Table 2.

[0293] [Table 2] As can be seen from the measurement results of Examples 1-1 and 2-1 to 2-13, the particle size Dv in the volume-based particle size distribution of the first polymer particles (1) 50 and Dv (1) 90. Particle size Dv in the volume-based particle size distribution of the second polymer (2) 50, Dv (2) 50 / Dv (1) 50, Dv (1) 90 / Dv (2) By further adjusting one or more of the 50 ranges, the overall performance of the battery can be further improved.

[0294] As can be seen from the measurement results of Examples 2-14 to 2-15, the difference T between the melting point of the second polymer and the melting point of the first polymer m2 -T m1 , as well as particle size Dv in the volume-based particle size distribution of the particles of the first polymer and the second polymer. (2) 50 / Dv (1) 50, Dv (1) 90 / Dv (2) By further adjusting the range of 50, the pass rate of the battery's hot box test can be further improved, and the battery's cycle characteristics can be further enhanced.

[0295] Examples 3-1 to 3-7 In the preparation of the separator, the other preparation steps were the same as in Example 1-1, except that the weight content of the first polymer and the second polymer was different. The specific parameters are shown in Table 3.

[0296] [Table 3] As can be seen from the measurement results of Examples 1-1 and 3-1 to 3-7, the overall performance of the battery can be further improved by further adjusting the range of the weight content m1 of the first polymer and the weight content m2 of the second polymer in the first coating layer.

[0297] Examples 4-1 to 4-6 In preparing the separator, the other preparation steps were the same as in Example 1-1, except that the coating weight of the slurry for the first coating layer and / or the thickness of the first coating layer were different. The specific parameters are shown in Table 4.

[0298] [Table 4] As can be seen from the measurement results of Examples 1-1 and 4-1 to 4-6, the overall performance of the battery can be further improved by further adjusting the coating weight and / or thickness of the first coating layer.

[0299] Examples 5-1 to 5-5 In the preparation of the separator, the preparation steps were the same as in Example 1-1, except that the types, melting points, and weight-average molecular weights of the first and second polymers were different. The specific parameters are shown in Table 5.

[0300] [Table 5] As can be seen from the measurement results of Examples 1-1 and 5-1 to 5-5, there are differences in the improvement effect on battery performance depending on the type of first polymer and second polymer, but in all cases, the battery can be given a high pass rate in the hot box test and good electrochemical performance.

[0301] In each of the above examples and comparative examples, the first polymer and the second polymer may be obtained by directly purchasing commercially available materials, or by performing a polymerization reaction using methods known in the art. The first polymer or the second polymer having different volume-based particle size distributions can be obtained by grinding and classifying the resin particles obtained after the polymerization reaction is complete, or by directly purchasing commercially available resin particles.

[0302] The above are merely specific embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. Any equivalent modifications or substitutions that can be easily conceived by any skilled craftsman familiar with the art within the scope of the art disclosed herein should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A battery comprising an electrode assembly and an outer bag, the electrode assembly comprising an electrode piece and a separator, The separator includes a porous substrate, and a first coating layer is provided on at least one surface of the porous substrate, and the first coating layer includes a first polymer and a second polymer having different melting points. The aforementioned battery is 0.077 ≤ (3.0 - D ２ / D １ ) / T ≤ 0.118, The aforementioned D １ This is the thickness of the battery obtained by measuring it after fully charging the battery under conditions of 25°C, and the unit is mm. The aforementioned D ２ This refers to the thickness of the battery obtained by placing the fully charged battery vertically in a hot box, raising the temperature from 25°C to 130°C at a rate of 5°C / min and holding it for 60 minutes, and then measuring it again after the battery temperature has dropped to 25°C. The unit is mm. The aforementioned T is the adhesive force between the first coating layer of the separator and the electrode adjacent to the first coating layer, and its unit is N / m. A battery characterized by the following features.

2. The battery according to claim 1, characterized in that the electrode piece includes a positive electrode piece and a negative electrode piece, and a first coating layer is provided on the surface of the porous substrate facing the positive electrode piece.

3. The aforementioned battery is 0.096 ≤ (3.0 - D ２ / D １ The battery according to claim 1, characterized in that it satisfies ) / T ≤ 0.

110.

4. T is between 5.42 N / m and 10.23 N / m, and / or D ２ / D １ The battery according to any one of claims 1 to 3, characterized in that the ratio is 2.12 to 2.

42.

5. T is between 5.91 N / m and 7.91 N / m, and / or D ２ / D １ The battery according to claim 4, characterized in that D / D is 2.21 to 2.

38.

6. The melting point of the first polymer is T ｍ１ The melting point of the second polymer is set to T ｍ２ In that case, T ｍ１ The temperature range is 60°C to 100°C, ｍ２ The temperature is 130°C or higher, and T ｍ２ -T ｍ１ The battery according to any one of claims 1 to 3, characterized in that the temperature range is 40°C to 120°C.

7. T ｍ１ The temperature range is 70°C to 90°C, ｍ２ The temperature is between 135°C and 160°C, and T ｍ２ -T ｍ１ The battery according to claim 6, characterized in that the temperature is 50°C to 80°C.

8. Particle size Dv in the volume-based particle size distribution of the first polymer particles （１） 50 and the particle size Dv in the volume-based particle size distribution of the second polymer particles （２） 50 is 0.50 ≤ Dv （２） 50 / Dv （１） 50 ≤ 1.25 satisfies, Particle size Dv in the volume-based particle size distribution of the first polymer particles （１） 90 and the particle size Dv in the volume-based particle size distribution of the second polymer particles （２） 50 is 2.0 ≤ Dv （１） 90 / Dv （２） A battery according to any one of claims 1 to 3, characterized in that 50 ≤ 5.

0.

9. Dv （２） 50 / Dv （１） 50 is 0.60 ≤ Dv （２） 50 / Dv （１） 50 ≤ 0.83 and Dv （１） 90 / Dv （２） 50 is 3.00 ≤ Dv （１） 90 / Dv （２） The battery according to claim 8, characterized in that 50 ≤ 4.

17.

10. The first coating layer is (1) Particle size Dv in the volume-based particle size distribution of the first polymer particles （１） 50 is between 0.8 μm and 2.0 μm. (2) Particle size Dv in the volume-based particle size distribution of the first polymer particles （１） 90 is between 2.0 μm and 5.0 μm, and (3) Particle size Dv in the volume-based particle size distribution of the second polymer particles （２） 50 is between 0.54 μm and 1.5 μm. A battery according to any one of claims 1 to 3, characterized in that it satisfies at least one of the following conditions.

11. The battery according to any one of claims 1 to 3, characterized in that, when the weight content of the first polymer is m1 and the weight content of the second polymer is m2, in both cases, m1 is 50% to 86% and m2 is 9% to 45% based on the total weight of the first coating layer.

12. The battery according to claim 11, characterized in that m1 is 70% to 82% and m2 is 13% to 25%.

13. The weight-average molecular weight of the first polymer is M. ｗ１ The weight-average molecular weight of the second polymer is set to M. ｗ２ In that case, M ｗ１ It is between 150,000 and 260,000, M ｗ２ The battery according to any one of claims 1 to 3, characterized in that the power is between 1.18 million and 2 million.

14. The first polymer comprises at least one of the monomers and copolymers selected from ethylene, propylene, vinylidene fluoride, acrylic acid, acrylic acid ester, styrene, acrylonitrile, maleic anhydride, vinyl chloride, and chloropropene, and / or The second polymer comprises at least one of the monomers and copolymers selected from vinylidene fluoride, hexafluoropropylene, propylene, vinyl chloride, styrene, butadiene, acrylic acid esters, and acrylic acid. A battery according to any one of claims 1 to 3, characterized in that

15. A first coating layer is provided on one surface of the porous substrate, and a second coating layer is provided on the other surface of the porous substrate, and the second coating layer contains a third polymer. The third polymer comprises at least one of the monomers and copolymers selected from butyl acrylate, octyl acrylate, isooctyl acrylate, styrene, and butadiene. The battery according to any one of claims 1 to 3, characterized in that the melting point of the third polymer is 50°C to 70°C.

16. The aforementioned separator is, (1) The coating weight of the first coating layer is 0.5 mg / 5000 mm ２ ~3mg / 5000mm ２ Being, and (2) The thickness of the first coating layer shall be 0.5 μm to 2.8 μm. A battery according to any one of claims 1 to 3, characterized in that it satisfies at least one of the following conditions.

17. The aforementioned battery is (1) The battery is a pouch battery. (2) The positive electrode piece comprises a positive electrode active material, the positive electrode active material comprises at least one of lithium cobalt oxide, lithium nickel cobalt aluminate, lithium nickel cobalt manganese oxide, lithium iron phosphate, and each of these modified compounds, the modification includes doping modification, surface coating modification, or simultaneous doping and coating modification, and (3) The negative electrode piece contains a negative electrode active material, the negative electrode active material contains at least one of graphite and silicon-based materials, and the weight content of the silicon-based material in the negative electrode active material is 0% to 25%. The battery according to claim 2, characterized in that it satisfies at least one of the following conditions.

18. An electrochemical apparatus characterized by comprising a battery according to any one of claims 1 to 17.

19. An electronic device characterized by including a battery according to any one of claims 1 to 17, or an electrochemical device according to claim 18.

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