Waterproof breathable film and lithium ion battery

Abstract

The utility model discloses a waterproof breathable film and a lithium ion battery. The waterproof breathable film comprises a breathable waterproof layer, a water absorption layer and a breathable fixing layer which are sequentially stacked from bottom to top. The breathable fixing layer is adopted to combine the breathable waterproof film layer and the water absorbing material into a whole, so that the formed three-layer structure allows gas to pass through but does not allow water vapor to pass through, the waterproof breathable film is applied to the lithium ion battery, gas discharge can be performed without using a dry dew point environment, water vapor can be prevented from entering the battery, and the service life of the battery is prolonged. The production cost and the process complexity of the battery are reduced, and the battery is continuously effective.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, specifically to a waterproof and breathable membrane and a lithium-ion battery. Background Technology

[0002] In recent years, lithium-ion batteries have been widely used in aerospace, automotive, and mobile devices. However, with socio-economic development, market competition among suppliers has intensified, making the control of process complexity and production costs particularly crucial. The manufacturing process of lithium-ion batteries involves complex steps, including electrode fabrication, stacking, electrolyte injection, aging, formation, and capacity testing. Controlling the moisture content of the electrolyte and electrodes is critical in these stages. Therefore, the formation stage and the lithium replenishment agent decomposition stage in lithium-ion batteries require ensuring gas removal while preventing moisture from entering the battery to avoid battery failure. Related technologies aim to remove gas while preventing moisture from entering the battery in a dry dew point environment. However, maintaining a dry dew point environment requires expensive equipment such as dehumidifiers, increasing process complexity and battery production costs. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in the related art. Therefore, one objective of this invention is to provide a waterproof and breathable membrane that, when applied to lithium-ion batteries, allows gas to escape without requiring a dry dew point environment, thereby reducing battery production costs and process complexity.

[0004] Specifically, the first aspect of this utility model provides a waterproof and breathable membrane, comprising: a breathable and waterproof layer, a water-absorbing layer, and a breathable fixing layer stacked sequentially from bottom to top.

[0005] This invention uses a breathable fixing layer to combine a breathable but waterproof membrane layer and a water-absorbing material into a whole. The resulting three-layer structure allows gas to pass through but not water vapor. When this waterproof and breathable membrane is applied to lithium-ion batteries, the internal gas of the battery can be discharged without the need for a dry dew point environment. This can prevent water vapor from entering the battery, reduce the production cost and process complexity of the battery, and maintain the battery's continuous effectiveness.

[0006] According to some embodiments of this utility model, the waterproof and breathable membrane further includes a gas-expanding layer, which is disposed on the side of the breathable but waterproof layer away from the absorbent layer. The gas-expanding layer can dissolve gas, increasing the gas permeation rate and promoting rapid gas discharge.

[0007] According to some embodiments of this invention, the air-expanding layer is a cellulose layer, a polyamide layer, a polysulfone layer, or a silicone rubber layer. The resulting waterproof and breathable membrane has good waterproof and breathable properties.

[0008] According to some embodiments of this utility model, the thickness ratio of the air-purifying layer to the breathable and waterproof layer is 0.3:1-3:1. Optimizing the thickness ratio of the air-purifying layer to the breathable and waterproof layer is beneficial to further improve the waterproof and breathable effect and maintain the battery's continuous effectiveness.

[0009] According to some embodiments of this utility model, the thickness ratio of the air-expanding layer to the air-permeable but waterproof layer is 0.5:1-2:1.

[0010] According to some embodiments of the present invention, the thickness of the gas-promoting layer is 3μm-30μm.

[0011] According to some embodiments of this utility model, the breathable and waterproof layer has a microporous structure, and the pore size of the micropores is 1μm-10μm. The micropore size on the breathable and waterproof layer is larger than the size of gas molecules but smaller than the size of liquid water molecules, thereby allowing gas to pass through but not water vapor.

[0012] According to some embodiments of this utility model, the thickness of the breathable but waterproof layer is 5μm-10μm.

[0013] According to some embodiments of this utility model, the breathable fixing layer has a microporous structure, and the pore size of the micropores is 1μm-10μm. The fixing layer serves to fix the absorbent layer and the breathable but waterproof layer, as well as to provide insulation; at the same time, the fixing layer is breathable, allowing gas to pass through, but with a pore size of 1μm-10μm, water vapor cannot pass through, thereby improving the waterproof effect.

[0014] According to some embodiments of this utility model, the thickness of the breathable fixing layer is 4μm-6μm.

[0015] According to some embodiments of this utility model, the thickness of the absorbent layer is 20μm-25μm.

[0016] According to some embodiments of this utility model, the breathable and waterproof layer is a polyethylene terephthalate layer, a polyvinylidene fluoride layer, or an expanded polytetrafluoroethylene layer; the absorbent layer is a silica gel layer, an activated carbon layer, a calcium chloride layer, a calcium phosphate layer, a magnesium oxide layer, a soda lime layer, a magnesium chloride layer, or an iron powder layer; and the breathable fixing layer is a polyethylene layer or a polyethylene terephthalate layer. The resulting waterproof and breathable membrane has good waterproof and breathable properties.

[0017] A second aspect of this invention provides a lithium-ion battery, comprising a battery casing and a battery cell disposed inside the battery casing, wherein the battery casing has a liquid injection hole; the lithium-ion battery further comprises a waterproof and breathable membrane according to the first aspect of this invention, the waterproof and breathable membrane covering the liquid injection hole of the battery casing. Due to the use of the waterproof and breathable membrane of this invention, the lithium-ion battery has good waterproof and breathable performance, allowing gas to escape without requiring a dry dew point environment, reducing battery production costs and process complexity, and maintaining the battery's continuous effectiveness.

[0018] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] The above and / or additional aspects and advantages of this utility model will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0020] Figure 1 This is a schematic diagram of the structure of a waterproof and breathable membrane according to some embodiments of this utility model.

[0021] Figure 2 This is a structural schematic diagram of a waterproof and breathable membrane according to other embodiments of this utility model.

[0022] Figure 3 This is a schematic diagram of the structure of a lithium-ion battery according to some embodiments of the present invention.

[0023] Figure label:

[0024] 100. Waterproof and breathable membrane; 101. Breathable but waterproof layer; 102. Absorbent layer; 103. Breathable and fixing layer; 104. Air-purifying layer; 200. Battery casing; 201. Liquid injection hole. Detailed Implementation

[0025] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0026] In recent years, lithium-ion batteries have been widely used in aerospace, automotive, and mobile devices. However, with socio-economic development, competition among suppliers is becoming increasingly fierce, making the control of process complexity and production costs particularly important. The manufacturing process of lithium-ion batteries involves complex steps, including electrode fabrication, stacking, electrolyte injection, aging, formation, and capacity testing. Controlling the electrolyte and electrode moisture content is crucial in all these stages.

[0027] During the battery formation stage, the initial charging process generates a large amount of gas due to the formation of an SEI film (solid electrolyte interphase) at the negative electrode. Additionally, in some lithium-ion battery systems, the decomposition of the lithium replenishment agent also produces significant amounts of gas. A common venting method is to maintain a dry dew point environment by using vents to allow the gas to escape smoothly while preventing water molecules from entering. However, maintaining a dry dew point environment requires expensive equipment such as dehumidifiers, increasing the complexity of the process and the manufacturing cost of the battery.

[0028] To address the above issues, this invention proposes a waterproof and breathable membrane. This membrane combines a breathable, waterproof membrane layer and an absorbent material into a single unit using a breathable fixing layer. The resulting three-layer structure allows gas to pass through but prevents water vapor from passing through. When this waterproof and breathable membrane is applied to lithium-ion batteries, it eliminates the need for a dry dew point environment to allow gas to escape from the battery while preventing water vapor from entering. This reduces battery production costs and process complexity, ensuring the battery remains effective.

[0029] Specifically, such as Figure 1 As shown, the first aspect of this utility model provides a waterproof and breathable membrane 100, comprising: a breathable and waterproof layer 101, a water-absorbing layer 102, and a breathable fixing layer 103 stacked sequentially from bottom to top.

[0030] In the waterproof and breathable membrane 100, the breathable but waterproof layer 101 prevents liquid water (water vapor) from passing through while allowing gas molecules to pass through. The absorbent layer 102 absorbs water vapor from the air, preventing it from entering the battery while allowing gases generated during battery formation or lithium replenishment decomposition to escape. The breathable fixing layer 103 is made of a heat-sealing material, which, through a heat-sealing process, fixes the absorbent layer 102 and the breathable but waterproof layer 101 together, serving to secure them as a single unit and providing insulation while allowing gas molecules to pass through.

[0031] The waterproof and breathable membrane of this invention can be reused after drying and dehydration. Furthermore, the waterproof and breathable membrane is simple to prepare, easy to operate, inexpensive, and cost-effective.

[0032] In some embodiments, such as Figure 2 As shown, the waterproof and breathable membrane 100 also includes an air-expanding layer 104, which is disposed on the side of the breathable but waterproof layer 101 away from the water-absorbing layer 102. The air-expanding layer 104 can adsorb or dissolve gas, thereby increasing the gas permeation rate, promoting rapid gas discharge, shortening the opening time of the vent (such as the liquid injection hole on the battery casing), and reducing the entry of water vapor into the battery.

[0033] In some embodiments, the gas-expanding layer 104 is a cellulose layer, a polyamide layer, a polysulfone layer, or a silicone rubber layer. These organic materials can effectively dissolve gases, increasing the gas permeation rate, thereby forming a waterproof and breathable membrane with good waterproof and breathable properties.

[0034] In some embodiments, the thickness ratio of the air-purifying layer 104 to the breathable and waterproof layer 101 can be 0.3:1 to 3:1. Optimizing the thickness ratio of the air-purifying layer to the breathable and waterproof layer helps to further improve the waterproof and breathable effect and maintain the battery's continuous effectiveness.

[0035] In some embodiments, the thickness ratio of the air-expanding layer 104 to the air-permeable but waterproof layer 101 can be 0.5:1-2:1.

[0036] In some specific embodiments, the thickness ratio of the air-expanding layer 104 to the air-permeable but waterproof layer 101 can be 0.3:1, 0.5:1, 0.7:1, 1:1, 1.2:1, 1.5:1, 1.7:1, 2:1, 2.2:1, 2.5:1, 2.7:1 or 3:1.

[0037] In some embodiments, the thickness of the gas-expanding layer 104 can be 3μm-30μm. Optimizing the thickness of the gas-expanding layer facilitates rapid gas discharge, shortens the opening time of the vent, and reduces the entry of moisture into the battery. The resulting waterproof and breathable membrane has good waterproof and breathable properties.

[0038] In some specific embodiments, the thickness of the gas-promoting layer 104 may be 3μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 15μm, 20μm, 25μm or 30μm.

[0039] In some embodiments, the breathable but waterproof layer 101 has a microporous structure, and the pore size of the micropores can be 1-10 μm. The micropore size on the breathable but waterproof layer is larger than the size of gas molecules but smaller than the size of liquid water molecules, thereby allowing gas to pass through but not water vapor to pass through, achieving the effect of being breathable but waterproof.

[0040] In some specific embodiments, the pore size of the micropores can be 1μm-5μm, 2μm-8μm, or 5μm-10μm.

[0041] In some embodiments, the thickness of the breathable but waterproof layer 101 can be 5μm-10μm. The resulting waterproof and breathable membrane has good waterproof and breathable properties.

[0042] In some specific embodiments, the thickness of the breathable but waterproof layer 101 can be 5μm, 6μm, 7μm, 8μm, 9μm or 10μm.

[0043] In some embodiments, the breathable fixing layer 103 has a microporous structure, wherein the pore size is 1μm-10μm. The fixing layer serves to fix the absorbent layer and the breathable but waterproof layer, as well as to provide insulation; at the same time, the fixing layer is breathable, allowing gas to pass through and be expelled; however, with a micropore size of 1μm-10μm, water vapor cannot pass through, thereby improving the waterproof effect.

[0044] In some specific embodiments, the pore size of the micropores can be 1μm-5μm, 2μm-8μm, or 5μm-10μm.

[0045] In some embodiments, the thickness of the breathable fixing layer 103 can be 4μm-6μm. Optimizing the thickness of the breathable fixing layer is beneficial for fixing the breathable and waterproof layer and the absorbent layer together, thereby forming a waterproof and breathable membrane with good waterproof and breathable effects.

[0046] In some specific embodiments, the thickness of the breathable fixing layer 103 may be 4μm, 4.5μm, 5μm, 5.5μm or 6μm.

[0047] In some embodiments, the thickness of the absorbent layer 102 can be 20μm-25μm. Optimizing the thickness of the absorbent layer helps to improve the waterproof and breathable membrane's ability to adsorb moisture from the air, reducing the amount of moisture entering the battery.

[0048] In some specific embodiments, the thickness of the absorbent layer 102 may be 20μm, 21μm, 22μm, 23μm, 24μm or 25μm.

[0049] In some embodiments, the breathable and waterproof layer 101 is a polyethylene terephthalate (PET) layer, a polyvinylidene fluoride (PVDF) layer, or an expanded polytetrafluoroethylene (e-PTFE) layer. Using these material layers helps to improve the waterproof and breathable properties of the membrane.

[0050] In some embodiments, the absorbent layer 102 is a silica gel layer, activated carbon layer, calcium chloride layer, calcium phosphate layer, magnesium oxide layer, soda lime layer, magnesium chloride layer, or iron powder layer. Using these material layers helps to improve the membrane's ability to adsorb moisture from the air. The absorbent layer is formed by pressing absorbent material under pressure; it has a porous structure that allows gas molecules to pass through, while its absorbent capacity adsorbs moisture from the air, preventing moisture from entering the battery.

[0051] In some embodiments, the breathable fixing layer 103 is a polyethylene (PE) layer or a polyethylene terephthalate (PET) layer. Using these high-temperature heat-sealing material layers helps to improve the fixation of the breathable and waterproof layers and the absorbent layer, while also improving the membrane's breathability and insulation properties.

[0052] In some embodiments, the waterproof and breathable membrane 100 may be prepared by a method including the following steps:

[0053] Lay out the breathable but waterproof layer 101 flat;

[0054] Spread the absorbent material on the breathable but impermeable layer 101;

[0055] The absorbent material is flattened under pressure and fixed into a cake shape as the absorbent layer 102.

[0056] The breathable fixing layer 103 is laid flat on the water-absorbing layer 102 and then pressed and assembled into a waterproof and breathable membrane 100 through a heat-sealing process.

[0057] This preparation method is simple, easy to operate, inexpensive, and cost-effective. The resulting waterproof and breathable membrane can be reused after water removal.

[0058] In some embodiments, the absorbent material is silica gel, activated carbon, calcium chloride, calcium phosphate, magnesium oxide, quicklime, magnesium chloride, or iron powder.

[0059] In some embodiments, the absorbent material is flattened under a pressure of 1400N-1600N (e.g., 1400N, 1450N, 1500N, 1550N, or 1600N) at 35℃±3℃ (e.g., 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, or 38℃).

[0060] In some embodiments, the parameters of the heat sealing process may be a heat sealing temperature of 170℃-185℃ (e.g., 170℃, 175℃, 180℃, or 185℃) and a heat sealing time of 1s-2s (e.g., 1s, 1.2s, 1.4s, 1.6s, 1.8s, or 2s). Preferably, the heat sealing temperature is 180℃ and the heat sealing time is 1.2s.

[0061] In some embodiments, after assembly, the method further includes: applying an organic solution to the surface of the breathable but waterproof layer away from the absorbent layer, and drying it to form an air-purifying layer 104.

[0062] In some specific embodiments, the organic material is cellulose, polyamide, polysulfone, or silicone rubber. An organic solution refers to a solution of the organic material in a solvent. The solvent is at least one selected from polyethylene glycol, isopropanol, ethanol, water, N-methylpyrrolidone, etc.

[0063] In some specific embodiments, the drying temperature may be 100°C-150°C, for example 100°C, 110°C, 120°C, 130°C, 140°C or 150°C.

[0064] In some embodiments, the areas of the breathable and waterproof layer 101 and the breathable fixing layer 103 are both larger than the area of ​​the absorbent layer 102. After being pressed by a heat-sealing process, the edges of the breathable and waterproof layer 101 and the breathable fixing layer 103 are fixed together, and the absorbent layer 102 is sandwiched between the two layers.

[0065] The second aspect of this utility model provides a lithium-ion battery, such as... Figure 3 As shown, the battery includes a battery casing 200 and a battery cell (not shown) disposed inside the battery casing 200. The battery casing 200 has a liquid injection hole 201. The lithium-ion battery also includes a waterproof and breathable membrane 100 of the first aspect of this invention, which covers the liquid injection hole 201 of the battery casing 200. Due to the use of the waterproof and breathable membrane of this invention, the lithium-ion battery has good waterproof and breathable properties, allowing gas to escape without requiring a dry dew point environment, reducing battery production costs and process complexity, and maintaining the battery's continuous effectiveness.

[0066] In some embodiments, the area of ​​the absorbent layer in the waterproof and breathable membrane 100 is larger than the area of ​​the injection hole 201, which is beneficial to improving the water absorption effect. In some embodiments, the area of ​​the air-expanding layer 104 in the waterproof and breathable membrane 100 is larger than the area of ​​the injection hole 201, and can completely cover the injection hole, which is beneficial to improving the water absorption effect.

[0067] In some embodiments, a lithium-ion battery includes a battery casing, a battery cell disposed inside the battery casing, and an electrolyte. The battery casing includes a body and a cover plate. The body may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The body has an opening communicating with the receiving cavity, and the cover plate can be placed over the opening to close the receiving cavity. The cover plate is provided with an injection hole. The battery cell may be manufactured from a positive electrode, a negative electrode, and a separator through a winding process or a stacking process. The electrolyte is immersed in the battery cell.

[0068] During battery formation and lithium replenishment agent decomposition, a waterproof and breathable membrane 100 covers the injection hole 201 to prevent moisture in the air from entering. This allows the battery to control the moisture content during the venting process, avoiding the use of a dew point environment and reducing battery production costs and process complexity.

[0069] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0070] Example 1

[0071] A PET film (purchased from DuPont, USA) with a micropore size of 1μm-10μm and a thickness of 10μm was laid flat as a breathable but waterproof layer. Silica gel (purchased from Shenzhen Minghui Antibacterial Technology Co., Ltd.) was spread on top of the breathable but waterproof layer. At 35℃, the silica gel was pressed flat with a pressure of 1500N to fix it into a disc shape as an absorbent layer with a thickness of 25μm. A PE film (purchased from DuPont, USA) with a micropore size of 1μm-10μm and a thickness of 6μm was laid flat on top of the absorbent layer as a breathable fixing layer. The layers were then assembled into a membrane using a heat-sealing process at 180℃ for 1.2s. Finally, a cellulose solution in ethanol (cellulose concentration 40mg / mL, purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.) was coated onto the surface of the breathable but waterproof layer away from the absorbent layer. After drying at 120℃ for 5 minutes, a degassing layer with a thickness of 10μm was formed. The final product has a four-layer structure, consisting of a breathable fixing layer, a water-absorbing layer, a breathable but waterproof layer, and a gas-expanding layer.

[0072] Example 2

[0073] The waterproof and breathable membrane was prepared according to the method described in Example 1, except that no air-expanding layer was formed. The final product has a three-layer structure, consisting of a breathable fixing layer, a water-absorbing layer, and a breathable but impermeable layer.

[0074] Examples 3-15

[0075] Examples 3-15 were prepared according to the method described in Example 1, with differences shown in Table 1 below.

[0076] Comparative Example 1

[0077] The PET film with a micropore size of 1μm-10μm and a thickness of 10μm, as described in Example 1, was used as the waterproof and breathable membrane.

[0078] Comparative Example 2

[0079] The waterproof and breathable membrane was prepared according to the method described in Example 1, except that no water-absorbing layer and air-purifying layer were formed. The final product was a two-layer structure consisting of a breathable fixing layer and a breathable but waterproof layer.

[0080] The waterproof and breathable membranes prepared in the above embodiments and comparative examples were applied to the electrolyte injection holes of lithium-ion batteries. After formation, the first efficiency (i.e., initial coulombic efficiency) of the lithium-ion batteries was tested. Since moisture is related to the formation of the SEI film in the battery, it will affect the first irreversible capacity loss of the battery, that is, affect the first efficiency of the battery.

[0081] Preparation of lithium-ion batteries:

[0082] (1) Preparation of positive electrode sheet

[0083] It is made of carbon-coated aluminum foil and positive electrode paste, with a certain size of aluminum foil exposed on one side of the electrode width direction as the electrode tab.

[0084] Positive electrode manufacturing process: The positive electrode active material lithium iron phosphate (LFP), conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 90:5:5 and added to the solvent N-methylpyrrolidone (NMP). The mixture is stirred evenly under vacuum to obtain a positive electrode slurry with a solid content of 47wt%. The positive electrode slurry is uniformly coated onto carbon-coated aluminum foil for the positive electrode current collector and dried at 85°C. Then, it is cold-pressed, trimmed, cut, and slit. Finally, it is dried under vacuum at 85°C to obtain the positive electrode sheet.

[0085] (2) Preparation of negative electrode sheet

[0086] It is made of copper foil and negative electrode slurry. Electrode manufacturing process: The negative electrode active material artificial graphite, conductive agent Super P, thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber latex (SBR) are mixed in a mass ratio of 90:5:1:4 and added to the solvent deionized water. The mixture is stirred evenly under vacuum to obtain the negative electrode slurry, in which the solid content is 40wt%. The negative electrode slurry is uniformly coated on a copper foil negative electrode current collector with a thickness of 6μm. After the negative electrode slurry is evenly coated on both sides, it is dried at 85℃. Finally, the negative electrode sheet is made by rolling, slitting, and die-cutting.

[0087] (3) Preparation of electrolyte

[0088] A commonly used carbonate electrolyte was selected, with the organic solvent being a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC), wherein the volume ratio of EC to EMC was 20:30. Thoroughly dried lithium hexafluorophosphate was dissolved in the above organic solvent in an argon-atmosphere glove box with a water content of <10 ppm. Then, additives VC and FEC were added and mixed thoroughly to obtain the electrolyte. The concentration of lithium hexafluorophosphate was 1 mol / L.

[0089] (4) Diaphragm

[0090] PE membranes are selected, with a thickness of 20 micrometers.

[0091] (5) Assemble lithium-ion batteries

[0092] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. They are then wound into a square bare cell, and tabs are welded on. The bare cell is then fixed with a Mylar film by heat fusion, followed by welding on a steel battery casing and cover plate. Electrolyte is injected through the reserved injection hole, and the injection hole is covered with a waterproof and breathable membrane. After processes such as standing, hot and cold pressing, formation, decomposition, and aging, the waterproof and breathable membrane is removed under dew point conditions, and the injection port is welded and sealed, completing the preparation of the finished battery.

[0093] First-time efficiency test of lithium-ion batteries: During the first charge and discharge of the battery, record the charging and discharging capacities, and then calculate their percentages, i.e., first-time efficiency = (first discharge capacity / first charge capacity) * 100%. The specific test procedure is as follows: At 25℃, charge the battery at 0.05C for 2 hours, let it rest for 10 minutes, and then charge it again at a constant current of 0.2C to 3.8V. The sum of the capacities obtained from the two charging cycles is recorded as C1. After resting for another 10 minutes, discharge it again at a constant current of 0.2C to 2V, and record this discharge capacity as C2. Therefore, the first-time efficiency of the battery is P = C2 / C1 * 100%.

[0094] The test results are shown in Table 1 below.

[0095] Table 1

[0096]

[0097]

[0098]

[0099] By comparing the embodiments and comparative examples, it can be seen that with the waterproof and breathable membrane of this utility model, gas can be discharged without the need for a dry dew point environment, which can prevent water vapor from entering the battery, reduce the production cost and process complexity of the battery, and maintain the battery's continuous effectiveness.

[0100] In addition, by setting up a gas-expanding layer, the gas permeation rate can be increased, promoting rapid gas discharge, shortening the opening time of the liquid injection hole on the battery casing, reducing the entry of water vapor into the battery, and keeping the battery continuously effective.

[0101] The terms "first" and "second" used in this document are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature marked "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0102] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0103] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A waterproof, breathable membrane, characterized in that, Comprising: a water vapor permeable and water impermeable layer, a water absorbing layer, and a water vapor permeable fixing layer stacked in order from bottom to top, the water vapor permeable and water impermeable layer, the water vapor permeable and water impermeable layer has a microporous structure, and the water vapor permeable fixing layer has a microporous structure.

2. The waterproof, breathable film of claim 1, wherein The air exhaust promoting layer is a cellulose layer, a polyamide layer, a polysulfone layer, or a silicone rubber layer.

3. The waterproof, breathable film of claim 1, wherein The thickness ratio of the air exhaust promoting layer to the water vapor permeable and water impermeable layer is 0.3:1-3:

1.

4. The waterproof, breathable film of claim 3, wherein, The thickness ratio of the air exhaust promoting layer to the water vapor permeable and water impermeable layer is 0.5:1-2:

1.

5. The waterproof, breathable film of claim 1, wherein The thickness of the air exhaust promoting layer is 3-30 microns.

6. The waterproof, breathable film of claim 1, wherein The pore size of the micropores of the water vapor permeable and water impermeable layer is 1-10 microns.

7. The waterproof, breathable film of claim 1, wherein The thickness of the water vapor permeable and water impermeable layer is 5-10 microns.

8. The waterproof, breathable film of claim 1, wherein The pore size of the micropores of the water vapor permeable fixing layer is 1-10 microns.

9. The waterproof, breathable film of claim 1, wherein, The thickness of the water vapor permeable fixing layer is 4-6 microns.

10. The waterproof, breathable film of claim 1, wherein The thickness of the water absorbing layer is 20-25 microns.

11. The waterproof, breathable film of claim 1, wherein The water vapor permeable and water impermeable layer is a polyethylene terephthalate layer, a polyvinylidene fluoride layer, or an expanded polytetrafluoroethylene layer; The water absorbing layer is a silica gel layer, an activated carbon layer, a calcium chloride layer, a calcium phosphate layer, a magnesium oxide layer, a soda lime layer, a magnesium chloride layer, or an iron powder layer; The water vapor permeable fixing layer is a polyethylene layer or a polyethylene terephthalate layer.

12. A lithium-ion battery, characterized by, The lithium ion battery comprises a battery shell and an electric core arranged inside the battery shell, and a liquid injection hole is arranged on the battery shell; the lithium ion battery further comprises the water vapor permeable and water impermeable film according to any one of claims 1-11, and the water vapor permeable and water impermeable film covers the liquid injection hole of the battery shell.

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