Battery separator, battery, and electric device

Abstract

Provided in the present application are a battery separator, a battery, and an electric device. The battery separator comprises a base membrane and a polymer adhesive material arranged on at least one side of the surfaces of the base membrane. The swelling rate of the polymer adhesive material in an electrolyte is less than 15%.

Description

A battery separator, a battery, and an electrical device.

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202510496066.2, filed on April 18, 2025, entitled “A Battery Separator, a Battery, and an Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, and in particular to a battery separator, a battery, and an electrical device. Background Technology

[0004] The battery separator is one of the main components of a battery. It separates the positive and negative electrodes while allowing ions to pass through, enabling the battery to charge and discharge. The battery separator prevents the positive and negative electrodes from coming into contact, which could cause a short circuit and prevent the battery from swelling or exploding.

[0005] In related technologies, when battery separators are immersed in electrolyte, they are prone to problems in maintaining their adhesion performance for a long time. This leads to weak interfacial bonding between the separator and the electrode in the battery, resulting in peeling or delamination, which in turn affects the battery's safety, charge and discharge performance, and cycle life, thus causing a decline in battery performance. Summary of the Invention

[0006] The technical problem to be solved by this application is to provide a battery separator, a battery, and an electrical device to improve the bonding performance of the battery separator.

[0007] To address the aforementioned issues, this application discloses a battery separator comprising a base film and a polymer adhesive disposed on at least one surface of the base film, wherein the swelling rate of the polymer adhesive in the electrolyte is less than 15%.

[0008] In some embodiments of this application, the swelling rate of the polymer adhesive in the electrolyte is less than 10%.

[0009] In some embodiments of this application, the D50 particle size of the polymer adhesive material ranges from 500 nm to 1.5 μm, preferably from 800 nm to 1.2 μm.

[0010] In some embodiments of this application, the polymer adhesive has a melting point greater than 115°C, and / or the initial melting point range of the polymer adhesive is 60–85°C.

[0011] In some embodiments of this application, the polymer adhesive includes a first adhesive and a second adhesive, wherein the initial melting point of the first adhesive is in the range of 60 to 85°C, and the initial melting point of the second adhesive is in the range of greater than 115°C.

[0012] In some embodiments of this application, the mass ratio between the first adhesive material and the second adhesive material is 4:6 to 2:8.

[0013] In some embodiments of this application, the polymeric adhesive includes polymethacrylate and / or polyethylene materials.

[0014] In some embodiments of this application, the battery separator further includes nano-ceramics, which are mixed with polymer adhesives and disposed on at least one side of the base film.

[0015] In some embodiments of this application, the D50 particle size of the nanoceramics is 500 nm to 800 nm.

[0016] In some embodiments of this application, the weight ratio between the polymer adhesive and the nano-ceramic ranges from 7:3 to 3:7.

[0017] In some embodiments of this application, the coating amount of the polymer adhesive on one side is 0.2–1.5 g / m². 2 .

[0018] In some embodiments of this application, the polymer adhesive is applied to at least one side of the base film by spraying or roller coating.

[0019] In some embodiments of this application, when using a spraying method, the coating amount of the polymer adhesive on one side is 0.2–0.8 g / m². 2 .

[0020] In some embodiments of this application, when using a roller coating method, the coating amount of the polymer adhesive on one side is 0.6–1.5 g / m². 2 .

[0021] This application also provides a battery, including the battery separator of this application embodiment.

[0022] This application also provides an electrical device, which includes a battery as described in the embodiments of this application.

[0023] Compared with the prior art, this application has the following advantages:

[0024] The battery separator provided in this application includes a base film and a polymer adhesive disposed on at least one surface of the base film. The swelling rate of the polymer adhesive in the electrolyte is less than 15%. Because the swelling rate of the polymer adhesive in the electrolyte is less than 15%, the polymer adhesive is unlikely to swell significantly in the electrolyte. This avoids reducing the cohesive force after the polymer adhesive swells, allowing the battery separator to maintain good adhesion in the electrolyte. This ensures good bonding between the battery separator and the electrode, resulting in a battery with good performance. Attached Figure Description

[0025] Figure 1 is an SEM image of the battery separator in Embodiment 1 of this application;

[0026] Figure 2 is a schematic diagram of the SEM image of the battery separator in Embodiments 1, 7, 8, 10, 11, 13, 14, 16, 17, 18 and Comparative Example 1 of this application.

[0027] Figure 3 is a schematic diagram of the thermal stability test of the battery separator in Embodiments 1, 2, 4, 9, 13 and Comparative Example 1 of this application;

[0028] Figure 4 is a schematic diagram of the three-point bending force test used in this application;

[0029] Figure 5 is a schematic diagram of the core hardness of Embodiment 1 and Comparative Example 1 of this application;

[0030] Figure 6 is a schematic diagram of electrolyte wetting observation in Examples 1, 11, 12, 15, 19 and Comparative Example 1 of this application;

[0031] Figure 7 is a schematic diagram of the narrow-face extrusion and large-face extrusion tests used in this application;

[0032] Figure 8 is a schematic diagram of the results of the cell extrusion test in Embodiment 1 and Comparative Example 1 of this application;

[0033] Figure 9 is a schematic diagram of the mechanical impact test conditions used in this application. Detailed Implementation

[0034] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] This application provides a battery separator, which includes a base film and a polymer adhesive disposed on at least one surface of the base film. The swelling rate of the polymer adhesive in the electrolyte is less than 15%.

[0036] Specifically, the battery separator may include a base membrane, which can be made of materials with good mechanical properties, such as polyolefin materials, polyester materials, and polyamide materials. Among them, polyolefin materials may specifically include polyethylene (PE) and polypropylene (PP), etc., and this application does not limit this.

[0037] The battery separator can have a microporous structure, which provides channels for ion transport within the battery, allowing ions in the electrolyte to pass smoothly through the separator and enabling the battery's charging and discharging functions. The porosity of the battery separator is related to the battery's ion conduction efficiency. In some embodiments of this application, the porosity of the base membrane can be in the range of 25% to 80%, such as 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc., and this application does not impose any limitation on this.

[0038] Generally, for battery separators made of materials such as polyolefins, after the separator and electrode sheets are stacked to form the electrode core, the electrode core usually needs to be hot-pressed to ensure that the stacked structure of the electrode core is not loose and the separator is not wrinkled. After hot pressing, the separator and electrode sheets are tightly bonded. However, the tight bonding between the separator and electrode sheets in the electrode core can prevent the electrolyte from effectively wetting the electrode sheets and separator inside the battery, which to some extent affects the migration and transport of lithium ions in lithium-ion batteries or sodium ions in sodium-ion batteries, thus affecting battery performance. In some embodiments of this application, a polymer adhesive can be provided on at least one surface of the base film. Through the adhesive effect of the polymer adhesive, the battery separator can be better bonded to the electrode sheets, avoiding peeling or delamination of the stacked structure in the electrode core. This can maintain good charge-discharge performance and cycle life of the battery, thereby improving battery performance.

[0039] In some embodiments of this application, in order to improve the bonding effect between the polymer adhesive and the base film, as well as the bonding effect between the polymer adhesive and the electrode, a polymer adhesive with a swelling rate of less than 15% in the electrolyte can be used.

[0040] The electrolyte may contain organic solvents, lithium salts, and additives. This application does not limit the use of organic solvents such as ethylene carbonate, propylene carbonate, ethyl acetate, and dimethylformamide.

[0041] When polymeric adhesives have a high swelling rate in the electrolyte, they can undergo significant swelling. After swelling, the overall structure of the polymeric adhesive becomes loose, the intermolecular interactions weaken, and the cohesive force decreases. Consequently, the adhesive's bonding ability deteriorates, making it prone to peeling or delamination.

[0042] In some embodiments of this application, by using a polymer adhesive with a swelling rate of less than 15% in the electrolyte, the polymer adhesive will not swell significantly even after long-term immersion in the electrolyte, and can always maintain good cohesion. This allows it to maintain good adhesion in the electrolyte, so that the battery separator with the polymer adhesive can maintain good bonding with the electrode, and the prepared battery can maintain good performance.

[0043] Because the battery separator maintains good adhesion to the electrode, it is also less prone to wrinkling. Even under severe vibration, the battery separator can still maintain good adhesion to the electrode, allowing the battery to maintain good cycle life.

[0044] In practice, the swelling rate can be measured as follows: Before immersing the polymer material in the electrolyte, measure its mass. Then, immerse the polymer material in the electrolyte for a certain period, allowing it to expand. Once the polymer material in the electrolyte stops swelling and reaches a stable state, remove it and measure its mass. The ratio of the difference in mass before and after swelling to the mass before swelling is the swelling rate of the polymer material.

[0045] In some embodiments of this application, the polymer particles in the polymer adhesive can agglomerate to a certain extent, forming adhesive particles (secondary particles). These particles can have a certain height, and after the battery separator and electrode are bonded together, they can be supported between the battery separator and the electrode, creating a gap between them. After electrolyte injection, on the one hand, the polymer adhesive itself can be wetted by the electrolyte, allowing for normal ion conduction between the battery separator and the electrode. On the other hand, the gaps formed by the adhesive particles allow electrolyte to flow in, further enabling the electrolyte to more fully wet the battery separator and the electrode, thus maintaining good charge / discharge performance and cycle life of the battery.

[0046] The battery separator provided in this application includes a base film and a polymer adhesive disposed on at least one surface of the base film. The swelling rate of the polymer adhesive in the electrolyte is less than 15%. Because the swelling rate of the polymer adhesive in the electrolyte is less than 15%, the polymer adhesive is unlikely to swell significantly in the electrolyte. This avoids reducing the cohesive force after the polymer adhesive swells, allowing the battery separator to maintain good adhesion in the electrolyte. The polymer adhesive adheres tightly to the surface of the base film and the electrode surface, thus maintaining good bonding between the battery separator and the electrode. This prevents interface peeling or delamination during subsequent processing and long-term use, resulting in a battery that maintains good performance.

[0047] In some embodiments of this application, the swelling rate of the polymer adhesive in the electrolyte is less than 10%. In this case, the expansion of the polymer adhesive in the electrolyte can be smaller, the battery separator is less likely to wrinkle, and better cohesion can be maintained, thereby maintaining better adhesion performance in the electrolyte.

[0048] In some embodiments of this application, the D50 particle size of the polymer adhesive material ranges from 500 nm to 1.5 μm. The D50 particle size can be 500 nm, 600 nm, 800 nm, 900 nm, 1 μm, 1.1 μm, 1.2 μm, etc.

[0049] Specifically, polymer adhesives contain particles of different sizes, thus yielding a particle distribution. The D50 particle size represents the value at which 50% of the particles in the distribution are smaller than or equal to this value; that is, the D50 particle size can be considered the median particle size in the polymer adhesive. In specific experiments, particle size can be measured using methods such as laser scattering or dynamic light scattering. For example, a Mastersizer 3000 laser particle size analyzer can be used to measure D50, and this application does not impose any limitations on this method. In related technologies, when other materials are coated onto the surface of a base film to modify it or to form a composite base film, the adhesive dots formed by the aggregation of multiple adhesive particles on the coated material (e.g., PVDF is formed by the aggregation of multiple 100–200 nm adhesive particles) are typically large, with diameters ranging from 300–500 μm and heights from 5–20 μm.

[0050] In some embodiments of this application, by using polymer adhesives with larger particle sizes, the polymer adhesives can be more uniformly disposed on the substrate during the application of the base film to at least one side surface, and are less prone to agglomeration that could lead to a sudden increase in particle size. Therefore, the adhesive dots formed by the agglomeration of multiple adhesive particles on the coating can maintain a small diameter and height, and a relatively concentrated size distribution. This avoids the possibility of excessively large adhesive dots protruding from the base film surface and detaching under physical friction during processing and application, thus affecting the integrity of the polymer adhesives on the base film surface and consequently the bonding effect between the battery separator and the electrode.

[0051] In some embodiments of this application, Figure 1 is an SEM image of the battery separator in Example 1. It can be seen that in this embodiment, after the polymer adhesive is coated onto the surface of the base film, multiple adhesive dots formed by the aggregation of adhesive particles are visible at a scale of 100 μm. These adhesive dots have relatively small diameters and a concentrated size distribution, making them difficult to detach under physical friction during battery separator processing and application, thus maintaining the integrity of the base film surface.

[0052] In some embodiments of this application, when polymer adhesive is simultaneously disposed on both sides of the base film, the polymer adhesive can provide good adhesion for both the positive and negative electrode sheets. Even when immersed in the electrolyte, the battery separator can still maintain a high-strength bond with both the positive and negative electrode sheets. Therefore, the battery core, composed of the positive electrode sheet, battery separator, and negative electrode sheet, can remain rigid and difficult to bend even without a rigid outer shell such as an aluminum casing. This avoids the soft, collapsing bending of battery cores in existing technologies. Due to the high strength of the battery core, it can withstand higher compressive forces and is less prone to deformation, reducing the risk of short circuits and thermal runaway due to separator rupture or puncture.

[0053] In some embodiments of this application, the D50 particle size of the polymer adhesive material ranges from 800 nm to 1.2 μm.

[0054] Specifically, if the particle size is too large, the polymer adhesive particles may be too dispersed, resulting in poor controllability of the adhesive dot morphology in the coated polymer adhesive layer and making it prone to uneven thickness, thus affecting the bonding effect between the battery separator and the electrode. If the particle size is too small, the high surface energy, van der Waals forces, electrostatic forces, and other interactions of the nanoscale particles may cause powder agglomeration, leading to uneven particle size and thickness on the polymer adhesive coating.

[0055] Therefore, the D50 particle size range of the polymer adhesive can be set to 800 nm to 1.2 μm. With a D50 particle size range of 800 nm to 1.2 μm, the polymer adhesive can avoid uneven distribution of polymer dots in the coating due to excessively large or small particle sizes. The adhesive dots formed by particle agglomeration can be evenly distributed on the base film surface, with relatively uniform particle size and small thickness fluctuations. It also avoids the situation where individual oversized adhesive dots protrude from the base film surface during processing and use, making them prone to detachment under physical friction, thus affecting the integrity of the polymer adhesive on the base film surface and consequently the bonding effect between the battery separator and the electrode.

[0056] In some embodiments of this application, the melting point of the polymer adhesive is greater than 115°C, and / or the initial melting point range of the polymer adhesive is 60–85°C. For example, the melting point can be 115°C, 120°C, 125°C, 130°C, 140°C, etc. The initial melting point can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, etc.

[0057] In some embodiments of this application, the polymer adhesive material can possess adhesive properties in a dry state, i.e., without contact with the electrolyte. Therefore, during battery fabrication, the battery electrodes and separator can be bonded together under hot-pressing conditions. After bonding, the electrolyte can be added to prepare the battery.

[0058] To achieve good adhesion between the battery electrodes and the battery separator during hot pressing, the polymer adhesive material typically needs to be in a relatively soft state during the process. This allows the battery electrodes to fully contact the polymer adhesive material, utilizing intermolecular forces to achieve a good interfacial bonding effect between the battery electrodes and the battery separator. Therefore, a polymer adhesive material with an initial melting point range of 60–85℃ can be used.

[0059] The initial melting point can refer to the temperature at which a material begins to absorb heat during the melting point test, i.e., the temperature at which the melting endothermic peak begins to rise, which corresponds to the temperature at which the material begins to absorb heat and soften.

[0060] In some embodiments of this application, the initial melting point can be measured using a Mettler Toledo DSC1 differential scanning calorimeter (DSC). The sample is placed in an aluminum crucible and heated to 150°C at a rate of 10°C / min, then cooled to 25°C at a rate of 10°C / min. The heat flow curve is recorded, and the peak point at which the curve begins to show endothermic activity is taken as the initial melting point.

[0061] With an initial melting point range of 60–85°C, the temperature during hot pressing can be no lower than the initial melting point range. As a result, the polymer adhesive can soften during hot pressing, allowing it to better contact the battery electrode and improve the interfacial bonding effect between the battery electrode and the battery separator.

[0062] In some embodiments of this application, the battery separator can be baked during the battery manufacturing process to remove any excess impurities such as moisture and volatile organic compounds. However, if the polymer adhesive completely melts during the baking process, it may cause a large amount of polymer adhesive to penetrate into the microporous structure of the base membrane, affecting the ion conductivity of the base membrane.

[0063] Therefore, the melting point of the polymer adhesive can be set to be greater than 115℃. Under this condition, during the baking process, the baking temperature does not exceed the melting point of the polymer adhesive. At this time, although the polymer adhesive softens to a certain extent, it will not completely turn into a liquid state and will not easily penetrate into the base film and block the microporous structure of the base film, thereby maintaining the base film with good ion conductivity.

[0064] In practice, measurements can be taken using a Mettler Toledo DSC1 differential scanning calorimeter (DSC). The sample is placed in an aluminum crucible and heated to 150°C at a rate of 10°C / min, then cooled to 25°C at a rate of 10°C / min. The heat flow curve is recorded, and the peak of the liquid absorption melting curve is taken as the melting point of the material.

[0065] To ensure that the melting point of polymer adhesives exceeds 115°C, materials with suitable melting points can be selected based on their molecular structure characteristics. In some embodiments of this application, generally, materials such as polyethylene exhibit better molecular symmetry and a more compact molecular arrangement, requiring higher energy to break the crystal lattice, thus increasing their melting point. Simultaneously, higher molecular weight or a higher degree of cross-linking in the cross-linked network structure also contributes to a higher melting point. Furthermore, selecting materials containing benzene ring structures, such as polyethylene terephthalate, or materials with polar groups, such as polyamides, also helps to increase the melting point.

[0066] To ensure that the initial melting point of the polymer adhesive is within the range of 60–85°C, materials that meet the initial melting point requirement can be selected based on the characteristics of their molecular structure. In some embodiments of this application, for example, low molecular weight polyolefin materials, the lower the molecular weight, the lower the intermolecular forces and the lower the melting point; alternatively, grafting polybutyl acrylate with a low glass transition temperature (Tg) and a flexible structure onto higher molecular weight polyolefins can disrupt the polymer's crystal structure, thus allowing the initial melting point of the polymer material to be within the range of 60–85°C.

[0067] In some embodiments of this application, the polymer adhesive may specifically include at least two materials, namely a first adhesive and a second adhesive. The first adhesive has an initial melting point range of 60–85°C, and the second adhesive has an initial melting point range greater than 115°C.

[0068] Therefore, by using a first adhesive material with a lower initial melting point temperature, the polymer adhesive material softens during hot pressing, allowing for better contact with the battery electrodes and improving the interfacial bonding between the battery electrodes and the battery separator. Simultaneously, by using a second adhesive material with a higher initial melting point temperature, the baking temperature does not exceed the overall melting point of the polymer adhesive material. At this point, although the polymer adhesive material softens to some extent, it does not completely transform into a liquid state, making it less likely to penetrate into the base film and block its microporous structure, thus maintaining the base film's good ion conductivity.

[0069] In some embodiments of this application, the mass ratio between the first adhesive material and the second adhesive material is 4:6 to 2:8. For example, 4:6, 3.5:6.5, 3:7, 2.5:7.5, 2:8, etc. By reasonably setting the mass ratio between the first adhesive material and the second adhesive material, situations where the battery electrode and the battery separator cannot bond or where the polymer adhesive material melts and blocks the microporous structure of the base film can be avoided.

[0070] In some embodiments of this application, the polymeric adhesive includes polymethacrylate and / or polyethylene materials.

[0071] Specifically, the polymer adhesive can include polymethyl methacrylate and / or polyethylene materials. High-molecular-weight polymethyl methacrylate and / or polyethylene materials can achieve a swelling rate of less than 15% in the electrolyte. This allows the battery separator to maintain good adhesion in the electrolyte, and the polymer adhesive adheres tightly to the base film and electrode, ensuring good bonding between the battery separator and the electrode, resulting in a battery with good performance.

[0072] In some embodiments of this application, highly cross-linked copolymer methacrylate can be selected, with a glass transition temperature (Tg) of approximately 90 ± 5°C. This allows for better bonding with the battery electrode during hot pressing, achieving a good interfacial bond between the battery electrode and the battery separator. Simultaneously, with a glass transition temperature of approximately 90 ± 5°C, it will not penetrate the microporous structure of the base film during baking.

[0073] Polyethylene materials can include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), oxidized high-density polyethylene (OHDPE), chlorinated high-density polyethylene (CHDPE), acrylic acid-modified polyethylene, and maleic anhydride-modified polyethylene, etc. Their melting points can be greater than 115℃.

[0074] In practical implementation, polyethylene with an initial melting point of 60–85°C is used as the first adhesive material, and oxidized polyethylene with a melting point greater than 115°C is used as the second adhesive material. The first and second adhesive materials are then mixed. The resulting polymer adhesive material allows the battery electrodes to fully contact the polymer adhesive material during hot pressing, resulting in a good interfacial bonding effect between the battery electrodes and the battery separator. Simultaneously, the polymer adhesive material does not completely transform into a liquid state during baking, avoiding blockage of the microporous structure of the base film and maintaining the base film's good ion conductivity. This allows for the preparation of a battery with superior overall performance.

[0075] In some embodiments of this application, the battery separator further includes nano-ceramics, which are mixed with polymer adhesives and disposed on at least one side surface of the base film.

[0076] In some embodiments of this application, the battery separator may further include nanoceramics. The nanoceramics can be mixed with a polymer adhesive and then disposed on at least one side surface of the base membrane. Nanoceramics are polar materials and are easily wetted by the electrolyte. When nanoceramics are disposed on the electrode separator, they can alter the surface properties of the battery separator, making the entire battery separator more easily wetted by the electrolyte, thereby further improving the ion conductivity of the battery separator.

[0077] The nanoceramics can be oxide ceramics, nitride ceramics, carbide ceramics, etc. Oxide ceramics can be alumina, zirconium oxide, silicon dioxide, etc. Nitride ceramics can be silicon nitride, aluminum nitride, boron nitride, etc. Carbide ceramics can be silicon carbide, tungsten carbide, titanium carbide, etc. Preferably, the nanoceramics in this application can be at least one of alumina, boehmite, silicon dioxide, zirconium oxide, titanium dioxide, and cerium oxide.

[0078] In some embodiments of this application, the D50 particle size of the nanoceramics is 500 nm to 800 nm. For example, the D50 particle size can be 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, etc.

[0079] In some embodiments of this application, the D50 particle size of the nanoceramic can be 500 nm to 800 nm. In this case, the D50 particle size of the nanoceramic is relatively close to that of the polymer adhesive, which will not significantly affect the uniformity of the distribution of the polymer adhesive on the substrate surface, so that the prepared battery separator has good overall distribution uniformity.

[0080] The D50 particle size of ceramics is smaller than that of polymer adhesives, allowing ceramics to be embedded in the gaps between polymer adhesives, which can better prevent polymer adhesives from clogging the microporous structure of the base film.

[0081] In some embodiments of this application, the weight ratio between the polymer adhesive and the nano-ceramic material ranges from 7:3 to 3:7. For example, 7:3, 6:4, 5:5, 4:6, 3:7, etc.

[0082] In some embodiments of this application, the weight ratio of the polymer adhesive to the nanoceramic material ranges from 7:3 to 3:7. A higher proportion of polymer adhesive provides better adhesion to the battery separator. A higher proportion of nanoceramic material provides better wetting properties to the battery separator.

[0083] In some embodiments of this application, the coating amount of the polymer adhesive is 0.2–1.5 g / m². 2 For example, the coating amount can be 0.2 g / m². 2 0.3g / m 2 0.4g / m2 0.5g / m 2 0.6g / m 2 0.7g / m 2 0.8g / m 2 0.9g / m 2 1.0g / m 2 1.1g / m 2 1.2g / m 2 1.3g / m 2 1.4g / m 2 1.5g / m 2 wait.

[0084] In practical implementation, the coating amount of the polymer adhesive can be 0.2–1.5 g / m². 2 At this coating amount, the overall thickness of the polymer adhesive is moderate, providing good bonding performance and preventing it from easily detaching due to physical friction.

[0085] In some embodiments of this application, the polymer adhesive is applied to at least one side of the base film by spraying or roller coating.

[0086] In some embodiments of this application, the polymer adhesive can be applied to at least one surface of the base film by spraying or roller coating. When using a spraying method, the polymer adhesive can typically achieve a lower and more uniform thickness compared to existing materials such as polyvinylidene fluoride (PVDF), providing better adhesion and reducing the likelihood of detachment due to physical friction.

[0087] When using a roller coating method, nano-ceramics can be easily added during the construction process, thereby improving the adhesion and wetting properties of the battery separator through the combination of polymer adhesives and nano-ceramics.

[0088] In some embodiments of this application, when using a spraying method, the coating amount of the polymer adhesive is 0.2–0.8 g / m². 2 .

[0089] In some embodiments of this application, when using a spraying method, the polymer adhesive can be sprayed onto the surface of the base film in the form of mist droplets, forming uniformly aggregated adhesive dots. The coating amount of the polymer adhesive can be 0.2–0.8 g / m³. 2 At this point, the polymer adhesive can provide good bonding performance while avoiding excessive polymer adhesive causing excessive battery impedance and overly tight electrode core bonding, which is not conducive to electrolyte wetting.

[0090] In some embodiments of this application, when using a roller coating method, the coating amount of the polymer adhesive is 0.6–1.5 g / m².2 .

[0091] In some embodiments of this application, when using a roller coating method, the polymer adhesive can be applied to the surface of the base film by roller coating to form a uniform coating. The coating amount of the polymer adhesive can be 0.6–1.5 g / m³. 2 At this point, the polymer adhesive can provide better bonding performance.

[0092] Simultaneously, nano-ceramics can be added during the construction process according to actual needs, thereby improving the adhesion and wetting properties of the battery separator through the combination of polymer adhesives and nano-ceramics. Specifically, when nano-ceramics are added, the coating amount of the mixture of nano-ceramics and polymer adhesives can be 0.6–1.5 g / m³. 2 .

[0093] This application also provides a method for preparing a battery separator as described in this application embodiment, wherein the method includes:

[0094] Step 101: Obtain the base film and polymer adhesive;

[0095] Step 102: Apply polymer adhesive to at least one side surface of the base film to obtain a battery separator.

[0096] In practice, a base film and a polymer adhesive can be obtained, and the polymer adhesive can be applied to at least one side of the base film using spraying or roller coating to obtain a battery separator. Since the swelling rate of the polymer adhesive in the electrolyte is less than 15%, it is difficult for the polymer adhesive to swell significantly in the electrolyte. This avoids reducing the cohesive force after the polymer adhesive swells, allowing the battery separator to maintain good adhesion in the electrolyte and ensuring good bonding between the battery separator and the electrode. The resulting battery can maintain good performance.

[0097] This application also provides a battery, including the battery separator of this application embodiment, or including a battery separator prepared by the battery separator preparation method of this application embodiment.

[0098] The battery can take many forms, such as a single cell, a battery pack, a battery module, a battery system, a battery stack, a battery array, etc., and this application does not limit it.

[0099] This application also provides an electrical device, which includes a battery as described in the embodiments of this application.

[0100] Among them, the electrical equipment can be 3C (Computer, Communication, Consumer Electronics) electronic equipment, new energy vehicles, electric bicycles, etc. This application does not restrict this.

[0101] To enable those skilled in the art to better understand this application, the following describes the preparation method of the battery separator of this application through several specific embodiments.

[0102] Example 1

[0103] (1) A polymer adhesive is sprayed onto one side surface of a microporous polyethylene (PE) base film with a thickness of 12 μm and a porosity of 40%.

[0104] (2) Dry at 85°C and cut to obtain battery separator.

[0105] The polymer adhesive has an overall D50 particle size of 1 μm, an initial melting point of 70℃, a melting point Tm of 125℃, and a swelling rate of 5% in the electrolyte. The coating weight of the polymer adhesive is 0.4 g / m². 2 / noodle.

[0106] The polymer adhesive comprises polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 125°C, which are melt-mixed at a mass ratio of polyethylene:oxidized polyethylene = 3:7. The polymer adhesive is then prepared as an aqueous emulsion and sprayed onto the surface of a base film.

[0107] The electrolyte comprises lithium salt, solvent, and additives. The lithium salt consists of 1.2 mol / L LiPF6. The solvent comprises ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). The volume ratio of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) is 1:1:1. The additives include 2% vinylene carbonate (VC), 2% fluoroethylene carbonate (FEC), and 1% trimethyl phosphate (TMP) by mass fraction.

[0108] For example, the polymer adhesive used in this embodiment is the Kar series from Guangdong Carbon Language New Materials Co., Ltd.

[0109] Example 2

[0110] The difference from Example 1 is that the overall D50 particle size of the polymer adhesive is 1 μm, the initial melting point is 60°C, the melting point Tm is 125°C, and the swelling in the electrolyte is 5%. The coating amount of the polymer adhesive is 0.4 g / m² / surface.

[0111] The polymer adhesive includes polyethylene with an initial melting point of 60°C and a melting point Tm of 80°C, and oxidized polyethylene with a melting point Tm of 125°C, which are obtained by melt mixing polyethylene and oxidized polyethylene in a mass ratio of 3:7.

[0112] Example 3

[0113] The difference from Example 1 is that the overall D50 particle size of the polymer adhesive is 1 μm, the initial melting point is 85°C, the melting point Tm is 125°C, and the swelling in the electrolyte is 5%. The coating amount of the polymer adhesive is 0.4 g / m². 2 / noodle.

[0114] The polymer adhesive includes polyethylene with an initial melting point of 85°C and a melting point Tm of 110°C, and oxidized polyethylene with a melting point Tm of 125°C, which are obtained by melt mixing polyethylene and oxidized polyethylene in a mass ratio of 3:7.

[0115] Example 4

[0116] The difference from Example 1 is that the overall D50 particle size of the polymer adhesive is 1 μm, the initial melting point is 70°C, the melting point Tm is 115°C, and the swelling in the electrolyte is 5%. The coating amount of the polymer adhesive is 0.4 g / m². 2 / noodle.

[0117] The polymer adhesive includes polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 115°C, which are obtained by melt mixing polyethylene and oxidized polyethylene in a mass ratio of 3:7.

[0118] Example 5

[0119] The difference from Example 1 is that the overall D50 particle size of the polymer adhesive is 1 μm, the initial melting point is 70°C, the melting point Tm is 125°C, and the swelling in the electrolyte is 5%. The coating amount of the polymer adhesive is 0.4 g / m². 2 / noodle.

[0120] The polymer adhesive includes polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 125°C, which are obtained by melt mixing polyethylene and oxidized polyethylene in a mass ratio of 4:6.

[0121] Example 6

[0122] The difference from Example 1 is that the overall D50 particle size of the polymer adhesive is 1 μm, the initial melting point is 70°C, the melting point Tm is 125°C, and the swelling in the electrolyte is 5%. The coating amount of the polymer adhesive is 0.4 g / m². 2 / noodle.

[0123] The polymer adhesive includes polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 125°C, which are obtained by melt mixing polyethylene and oxidized polyethylene in a mass ratio of 2:8.

[0124] Example 7

[0125] The difference from Example 1 is that the overall D50 particle size of the polymer adhesive is 0.5 μm, the initial melting point is 70°C, the melting point Tm is 125°C, and the swelling in the electrolyte is 5%. The coating amount of the polymer adhesive is 0.4 g / m². 2 / noodle.

[0126] The polymer adhesive comprises polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 125°C, which are melt-mixed at a mass ratio of polyethylene:oxidized polyethylene = 3:7. The polymer adhesive is then prepared as an aqueous emulsion and sprayed onto the surface of a base film.

[0127] Example 8

[0128] The difference from Example 1 is that the overall D50 particle size of the polymer adhesive is 1.5 μm, the initial melting point is 70°C, the melting point Tm is 125°C, and the swelling in the electrolyte is 5%. The coating amount of the polymer adhesive is 0.4 g / m². 2 / noodle.

[0129] The polymer adhesive comprises polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 125°C, which are melt-mixed at a mass ratio of polyethylene:oxidized polyethylene = 3:7. The polymer adhesive is then prepared as an aqueous emulsion and sprayed onto the surface of a base film.

[0130] Example 9

[0131] (1) Polymethyl methacrylate (PMMA) was sprayed onto one side of a microporous polyethylene (PE) base film with a thickness of 12 μm and a porosity of 40%. PMMA with a glass transition temperature (Tg) of 90 °C was used as the polymer material. Its D50 particle size was 1 μm. The swelling in the electrolyte was 14%. An aqueous emulsion of PMMA was prepared and sprayed onto the base film surface.

[0132] (2) Dry at 85°C and cut to obtain battery separator.

[0133] The electrolyte comprises lithium salt, solvent, and additives. The lithium salt consists of 1.2 mol / L LiPF6. The solvent comprises ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). The volume ratio of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) is 1:1:1. The additives include 2% vinylene carbonate (VC), 2% fluoroethylene carbonate (FEC), and 1% trimethyl phosphate (TMP) by mass fraction.

[0134] For example, the polymethacrylate used in this embodiment is Indira FS430H.

[0135] Example 10

[0136] The difference from Example 1 is that the overall D50 particle size of the polymer adhesive is 1 μm, the initial melting point is 70°C, the melting point Tm is 125°C, and the swelling in the electrolyte is 5%. The coating amount of the polymer adhesive is 0.2 g / m². 2 / noodle.

[0137] The polymer adhesive comprises polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 125°C, which are melt-mixed at a mass ratio of polyethylene:oxidized polyethylene = 3:7. The polymer adhesive is then prepared as an aqueous emulsion and sprayed onto the surface of a base film.

[0138] Example 11

[0139] The difference from Example 1 is that the overall D50 particle size of the polymer adhesive is 1 μm, the initial melting point is 70°C, the melting point Tm is 125°C, and the swelling in the electrolyte is 5%. The coating amount of the polymer adhesive is 0.8 g / m². 2 / noodle.

[0140] The polymer adhesive comprises polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 125°C, which are melt-mixed at a mass ratio of polyethylene:oxidized polyethylene = 3:7. The polymer adhesive is then prepared as an aqueous emulsion and sprayed onto the surface of a base film.

[0141] Example 12

[0142] The difference from Example 1 is that both sides of the base film are coated with polymer adhesive by spraying.

[0143] The polymer adhesive has an overall D50 particle size of 1μm, an initial melting point of 70℃, a melting point Tm of 125℃, and a swelling rate of 5% in the electrolyte. The overall coating weight of the polymer adhesive on both sides is 0.8g / m². 2 .

[0144] The polymer adhesive comprises polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 125°C, which are melt-mixed at a mass ratio of polyethylene:oxidized polyethylene = 3:7. The polymer adhesive is then prepared as an aqueous emulsion and sprayed onto the surface of a base film.

[0145] Example 13

[0146] The difference from Example 1 is that a mixture of polymer adhesive and nano-ceramic (boehmite) is coated onto one side of the base film by roller coating. The mass ratio of polymer adhesive to nano-ceramic is 5:5. The D50 particle size of the nano-ceramic is 0.5 μm. The coating amount of the polymer adhesive and nano-ceramic mixture is 0.8 g / m³. 2 / noodle.

[0147] The polymer adhesive has an overall D50 particle size of 1μm, an initial melting point of 70℃, a melting point Tm of 125℃, and a swelling rate of 5% in the electrolyte.

[0148] The polymer adhesive comprises polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 125°C, which are melt-mixed at a mass ratio of polyethylene:oxidized polyethylene = 3:7. The polymer adhesive is then prepared as an aqueous emulsion and sprayed onto the surface of a base film.

[0149] Example 14

[0150] The difference from Example 13 is that a mixture of polymer adhesive and nano-ceramic (boehmite) is coated onto one side of the base film using a roller coating method. The coating amount of the polymer adhesive and nano-ceramic mixture is 0.6 g / m². 2 / noodle.

[0151] The polymer adhesive and nano-ceramics are in a 5:5 mass ratio. The D50 particle size of the nano-ceramics is 0.5 μm.

[0152] The polymer adhesive has an overall D50 particle size of 1μm, an initial melting point of 70℃, a melting point Tm of 125℃, and a swelling rate of 5% in the electrolyte.

[0153] The polymer adhesive comprises polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 125°C, which are melt-mixed at a mass ratio of polyethylene:oxidized polyethylene = 3:7. The polymer adhesive is then prepared as an aqueous emulsion and sprayed onto the surface of a base film.

[0154] Example 15

[0155] The difference from Example 13 is that a mixture of polymer adhesive and nano-ceramic (boehmite) is coated onto one side of the base film using a roller coating method. The coating amount of the polymer adhesive and nano-ceramic mixture is 1.5 g / m².2 / noodle.

[0156] The polymer adhesive and nano-ceramics are in a 5:5 mass ratio. The D50 particle size of the nano-ceramics is 0.5 μm.

[0157] The polymer adhesive has an overall D50 particle size of 1μm, an initial melting point of 70℃, a melting point Tm of 125℃, and a swelling rate of 5% in the electrolyte.

[0158] The polymer adhesive comprises polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 125°C, which are melt-mixed at a mass ratio of polyethylene:oxidized polyethylene = 3:7. The polymer adhesive is then prepared as an aqueous emulsion and sprayed onto the surface of a base film.

[0159] Example 16

[0160] The difference from Example 13 is that a mixture of polymer adhesive and nano-ceramic (boehmite) is coated onto one side of the base film by roller coating. The mass ratio of polymer adhesive to nano-ceramic is 5:5. The D50 particle size of the nano-ceramic is 0.8 μm. The coating amount of the polymer adhesive and nano-ceramic mixture is 0.8 g / m³. 2 / noodle.

[0161] The polymer adhesive has an overall D50 particle size of 1μm, an initial melting point of 70℃, a melting point Tm of 125℃, and a swelling rate of 5% in the electrolyte.

[0162] The polymer adhesive comprises polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 125°C, which are melt-mixed at a mass ratio of polyethylene:oxidized polyethylene = 3:7. The polymer adhesive is then prepared as an aqueous emulsion and sprayed onto the surface of a base film.

[0163] Example 17

[0164] The difference from Example 13 is that a mixture of polymer adhesive and nano-ceramic (boehmite) is coated onto one side of the base film by roller coating. The mass ratio of polymer adhesive to nano-ceramic is 7:3. The D50 particle size of the nano-ceramic is 0.5 μm. The coating amount of the polymer adhesive and nano-ceramic mixture is 0.8 g / m³. 2 / noodle.

[0165] The polymer adhesive has an overall D50 particle size of 1μm, an initial melting point of 70℃, a melting point Tm of 125℃, and a swelling rate of 5% in the electrolyte.

[0166] The polymer adhesive comprises polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 125°C, which are melt-mixed at a mass ratio of polyethylene:oxidized polyethylene = 3:7. The polymer adhesive is then prepared as an aqueous emulsion and sprayed onto the surface of a base film.

[0167] Example 18

[0168] The difference from Example 13 is that a mixture of polymer adhesive and nano-ceramic (boehmite) is coated onto one side of the base film by roller coating. The mass ratio of polymer adhesive to nano-ceramic is 3:7. The D50 particle size of the nano-ceramic is 0.5 μm. The coating amount of the polymer adhesive and nano-ceramic mixture is 0.8 g / m³. 2 / noodle.

[0169] The polymer adhesive has an overall D50 particle size of 1μm, an initial melting point of 70℃, a melting point Tm of 125℃, and a swelling rate of 5% in the electrolyte.

[0170] The polymer adhesive comprises polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 125°C, which are melt-mixed at a mass ratio of polyethylene:oxidized polyethylene = 3:7. The polymer adhesive is then prepared as an aqueous emulsion and sprayed onto the surface of a base film.

[0171] Example 19

[0172] The difference from Example 13 is that both sides of the base film are coated with a mixture of polymer adhesive and nano-ceramic (boehmite) by roller coating. The mass ratio of polymer adhesive to nano-ceramic is 5:5. The D50 particle size of the nano-ceramic is 0.5 μm. The total coating weight of the polymer adhesive and nano-ceramic mixture on both sides is 1.6 g / m². 2 .

[0173] The polymer adhesive has an overall D50 particle size of 1μm, an initial melting point of 70℃, a melting point Tm of 125℃, and a swelling rate of 5% in the electrolyte.

[0174] The polymer adhesive comprises polyethylene with an initial melting point of 70°C and a melting point Tm of 90°C, and oxidized polyethylene with a melting point Tm of 125°C, which are melt-mixed at a mass ratio of polyethylene:oxidized polyethylene = 3:7. The polymer adhesive is then prepared as an aqueous emulsion and sprayed onto the surface of a base film.

[0175] Comparative Example 1

[0176] The difference from Example 1 is that PVDF (polyvinylidene fluoride) is coated onto one side of the base film by spraying. PVDF has a melting point of 150°C and swells to 45% in the electrolyte. The coating amount is 0.6 g / m³. 2 / noodle.

[0177] Comparative Example 2

[0178] The difference from Example 1 is that PVDF (polyvinylidene fluoride) was sprayed onto both surfaces of the base film. PVDF has a melting point of 150°C and swells to 45% in the electrolyte. The total coating weight on both sides is 1.2 g / m². 2 .

[0179] The battery separator provided in this application includes a base film and an adhesive material disposed on at least one surface of the base film. The swelling rate of the adhesive material in the electrolyte is less than 15%. Because the swelling rate of the adhesive material in the electrolyte is less than 15%, the adhesive material is unlikely to swell in the electrolyte. This avoids reducing the cohesive force after swelling, allowing the battery separator to maintain good adhesion in the electrolyte. Consequently, the battery separator and the electrode are well bonded, and the prepared battery maintains good performance. The following specific experimental data illustrates some of the advantages of this application embodiment compared to the prior art.

[0180] I. Morphology Test: The morphology of the separators prepared in Examples 1, 7, 8, 10, 11, 13, 14, 16, 17, 18 and Comparative Example 1 was observed by scanning electron microscope (SEM). SEM images of some of the battery separators of the examples and comparative examples are shown in Figure 2.

[0181] As can be seen, the battery separators obtained in the embodiments of this application have relatively smooth morphology, resulting in battery separators with relatively uniform particle size distribution. In contrast, in Comparative Example 1, due to the excessively small particle size, the adhesive particles agglomerate severely, resulting in an overall poor morphology of the sprayed coating.

[0182] Specifically, for Examples 1, 7, 8, 10, and 11, it can be seen that the agglomerates formed by the aggregation of adhesive particles on the surface of Examples 1, 7, 8, 10, and 11 are more uniformly distributed, and their size is significantly smaller than that of the agglomerates formed in Comparative Example 1. Furthermore, the size distribution of the agglomerates is relatively concentrated. Compared to the agglomerates formed in Comparative Example 1, there are no obvious protrusions, and the agglomerate height is lower. By forming smaller agglomerates, physical friction detachment during battery separator processing and application can be avoided, the battery separator surface can remain intact, and the battery separator and electrode can be better bonded.

[0183] For Examples 13, 14, 16, 17, and 18, it can be seen that when a roller coating method is used and a mixture of polymer adhesive and nano-ceramics is coated on the surface of the base film, the polymer adhesive particles and nano-ceramics formed in Examples 13, 14, and 16 are mixed with each other and dispersed relatively uniformly on the surface of the base film. The uniform distribution of nano-ceramics on the surface of the base film can further improve the ion conductivity of the battery separator.

[0184] II. Diaphragm Thermal Stability Test

[0185] Examples 1, 2, 4, 9, and 13 were baked in an oven at 110°C for 12 hours, and the changes in the coating were observed. The results are shown in Figure 3.

[0186] As can be seen, the battery separators prepared in Examples 1, 2, 4, 9, and 13 of this application have good surface morphology and are not significantly damaged by heating, indicating that the embodiments have good thermal stability and can provide good adhesion performance during the bonding process between the battery separator and the electrode.

[0187] III. Diaphragm Hot-Pressure Peel Strength Test

[0188] The separators prepared in Examples 1-19 and Comparative Examples 1-2 were bonded to the positive electrode sheets and then hot-pressed. The hot-pressing conditions were 90°C, 1.5MPa, and 60s. The 180° peel strength between the separator and the electrode sheet was then tested to obtain the bonding strength between the coating and the electrode sheet. The results are shown in Table 1.

[0189] Table 1 Results of hot-press peel strength test

[0190] As can be seen, the dry bonding force between the diaphragm and the electrode sheet in this embodiment is strong, and the dry bonding performance is close to that of the comparative example, which can ensure good adhesion between the cell manufacturing process and the electrode sheet interface.

[0191] IV. Diaphragm wet adhesion peel strength test

[0192] The samples obtained by hot-pressing the separators and positive electrodes prepared in Examples 1-19 and Comparative Examples 1-2 were immersed in electrolyte for 12 hours, and then the wet adhesion peel strength between the separator and the electrode was tested by peeling them at 180°. The results are summarized in Table 2.

[0193] Table 2 Results of wet peel strength test

[0194] As can be seen, the battery separator in this embodiment exhibits stronger wet adhesion performance compared to the comparative example. The wet peel strength of the comparative example is significantly lower than its dry peel strength. This is because the comparative example uses polyvinylidene fluoride with an excessively high swelling ratio, which fails to maintain good cohesion under electrolyte immersion conditions, resulting in a substantial reduction in adhesion performance.

[0195] In this embodiment, a polymer adhesive with a swelling rate of less than 15% in the electrolyte is used. Even after prolonged immersion in the electrolyte, the polymer adhesive does not exhibit significant swelling and maintains good cohesion, thus ensuring good adhesion performance in the electrolyte. Furthermore, the wet peel strength of the polymer adhesive in this embodiment shows a smaller decrease compared to the dry peel strength. The polymer adhesive in this embodiment maintains good bonding performance under both wet and dry adhesive conditions, making it more suitable for application in battery manufacturing processes.

[0196] V. Core Hardness Test

[0197] Examples 1-19 and Comparative Examples 1-2 were prepared by stacking 45 layers of positive electrode, 46 layers of negative electrode, and 92 layers of separator to obtain electrode cores. The electrode cores were preheated at 90°C for 300s, then hot-pressed at 1.5MPa for 60s. After hot pressing, the maximum bending force at three points of the electrode core was tested. The hot-pressed electrode cores were then assembled in a shell or encapsulated in an aluminum-plastic film, immersed in electrolyte for 24h, and then disassembled and tested for the maximum bending force at three points. The schematic diagram of the three-point bending force test is shown in Figure 4. The test results are shown in Table 3.

[0198] Table 3 Core Hardness Test

[0199] As can be seen, the electrode core prepared in this embodiment maintains good hardness under both dry and wet electrode core conditions. In subsequent battery production, the electrode core can be assembled without additional mechanical fixation or adhesive bonding. In contrast, the electrode core prepared in the comparative example softens significantly under wet electrode core conditions due to excessive swelling, making it difficult to measure its hardness.

[0200] Furthermore, as shown in Figure 5, Figure 5(a) shows the electrode core prepared in Example 1 of this application. It can be seen that after being immersed in electrolyte for 24 hours, it can maintain its original hardness. Other Examples 2-19 maintained the same effect. Figure 5(b) shows the electrode core of Comparative Example 1. It can be seen that it cannot maintain its hardness and forms a bent shape.

[0201] VI. Electrolyte wetting observation

[0202] The electrode cores of Examples 1-19 were disassembled after electrolyte impregnation to observe whether the internal electrolyte impregnation was sufficient. The results are shown in Table 4 and Figure 6.

[0203] Table 4. Results of Immersion Observation Test

[0204] As can be seen, in the electrode core prepared in the embodiments of this application, the electrolyte can wet the battery separator and electrode to varying degrees, and there is no situation where the battery separator and electrode cannot be wetted at all.

[0205] As can be seen from Figure 6, in Example 1, the electrolyte almost completely wets the battery separator and the electrode, while in Examples 11, 12, 15, and 19, the electrolyte wets only a portion of the battery separator and the electrode.

[0206] The embodiments of this application can maintain good electrolyte wetting of the battery separator and electrodes, thereby maintaining good charge and discharge performance and cycle life of the battery.

[0207] VII. Cell Extrusion Test

[0208] The fully charged cells prepared in Examples 1-19 and Comparative Examples 1-2 were subjected to narrow-area extrusion and large-area extrusion, respectively, as shown in Figure 7, until the core short-circuited and became uncontrollable. The maximum extrusion force required to achieve short-circuit uncontrollability was recorded. The results are shown in Figure 8 and Table 5.

[0209] Table 5. Results of Cell Extrusion Test

[0210] Referring to Table 4 and Figure 8(a) for the test results of Example 1, and Figure 8(b) for the test results of Comparative Example 1, compared with the PVDF cells of Comparative Examples 1 and 2, the extrusion resistance of the examples is significantly improved. In particular, some examples did not experience short circuits or runaway even under the large-area pressure over-extrusion equipment range (400kN), while Comparative Examples 1 and 2 experienced short circuits and runaway under lower extrusion pressure conditions. It is evident that the embodiments of this application can maintain good bonding between the battery separator and the electrode in the electrolyte, allowing the cell to maintain good hardness and further improving the extrusion resistance of the cell, thus effectively enhancing battery safety performance.

[0211] 8. Mechanical Shock Test of Battery Cells: Fully charged battery cells manufactured from the production line undergo mechanical shock testing, as shown in Figure 9. The test conditions are: shock waveform - half-sine wave, acceleration 300 m / s². 2 The impact duration was 6 ms, and the number of impacts was 10 (the acceleration direction was the same as the impact acceleration direction of the car driving - i.e. the X direction of the battery). The voltage drop (mV) and ACIR increase (mΩ) of the cell after the impact were observed to evaluate the stability of the cell under the working conditions. The results are shown in Table 6.

[0212] Table 6 Results of Mechanical Shock Test on Battery Cells

[0213] As can be seen, compared with Comparative Examples 1-2, Examples 1-19 show significantly smaller voltage reduction and significantly lower ACIR increase, indicating that the embodiments of this application maintain good bonding between the battery separator and the electrode in the electrolyte through polymer adhesive, resulting in a more stable battery cell that is beneficial for the battery to maintain good performance under operating conditions for a long time.

[0214] IX. Cell Life Test

[0215] ① Prepare test batteries containing separators for the batteries in the examples and comparative examples respectively: Prepare positive electrode sheets and negative electrode sheets. The positive electrode sheet includes a positive current collector (specifically, aluminum foil) and a positive active material layer. The positive active material includes positive active material (specifically lithium iron phosphate, LiFePO4), conductive agent (specifically Super P), and binder (specifically polyvinylidene fluoride, PVDF) in a mass ratio of 95:2.6:2.4. The negative electrode sheet includes a negative current collector (specifically, copper foil) and negative active material (specifically graphite), conductive agent (specifically Super P), and binder (specifically CMC+SBR=1+1.6) in a mass ratio of 96.00:1.40:2.60.

[0216] The separators of each embodiment and the comparative example were placed between the positive and negative electrode sheets to separate them. 45 layers of positive electrode, 46 layers of negative electrode, and 92 layers of separator were stacked to obtain each dry cell. The dry cells were preheated to 90°C for 300 seconds and hot-pressed at 1.5 MPa for 60 seconds. Each dry cell was placed in an aluminum-plastic film outer packaging and dried under vacuum at 95°C for 12 hours. After cooling, electrolyte was injected, and then the cells were vacuum-sealed and left to soak at 50°C for 48 hours. Afterward, they underwent pressure formation at 25°C, high-temperature aging at 45°C, secondary encapsulation, degassing, and capacity testing to obtain batteries S1-S10 of each embodiment and batteries D12, D17, and D18 of the comparative examples.

[0217] ②Room temperature cycling test:

[0218] Under conditions of 45±1℃, the battery was subjected to charge-discharge cycle testing at a rate of 1.0C charge and 1.0C discharge. The steps were as follows: rest for 30 minutes; charge at a constant current of 1.0C to 3.8V, then charge at a constant voltage of 0.05C to cut off; rest for 30 minutes; discharge at a constant current of 1.0C to 2.0V, which constitutes one cycle. This process was repeated, and the number of cycles when the battery capacity retention rate reached 85% was recorded as the battery's cycle life. Five batteries were used in each group, and the average value was taken. The results are shown in Table 7.

[0219] Table 7 Cell life test results

[0220] As can be seen, the cycle life performance of the embodiments is superior to that of the comparative examples. The embodiments of this application effectively improve the cycle life of the battery by maintaining good adhesion between the battery separator and the electrode in the electrolyte using polymer adhesives.

[0221] In summary, the battery separator provided in this application includes a base film and an adhesive material disposed on at least one surface of the base film. The swelling rate of the adhesive material in the electrolyte is less than 15%. Because the swelling rate of the adhesive material in the electrolyte is less than 15%, the adhesive material is unlikely to swell significantly in the electrolyte. This avoids reducing the cohesive force after the adhesive material swells, allowing the battery separator to maintain good adhesion in the electrolyte. Consequently, the battery separator and the electrode maintain good adhesion throughout their entire life cycle, and the prepared battery maintains good safety and electrical performance.

[0222] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0223] The foregoing has provided a detailed description of a battery separator, a battery, and an electrical device provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A battery separator, wherein, The battery separator includes a base film and a polymer adhesive material disposed on at least one surface of the base film, wherein the swelling rate of the polymer adhesive material in the electrolyte is less than 15%.

2. The battery separator according to claim 1, wherein, The swelling rate of the polymer adhesive in the electrolyte is less than 10%.

3. The battery separator according to claim 1 or 2, wherein, The D50 particle size range of the polymer adhesive is 500 nm to 1.5 μm, preferably 800 nm to 1.2 μm.

4. The battery separator according to any one of claims 1 to 3, wherein, The polymer adhesive has a melting point greater than 115°C, and / or the initial melting point range of the polymer adhesive is 60–85°C.

5. The battery separator according to any one of claims 1 to 4, wherein, The polymer adhesive includes a first adhesive and a second adhesive, wherein the initial melting point of the first adhesive is in the range of 60 to 85°C, and the initial melting point of the second adhesive is in the range of greater than 115°C.

6. The battery separator according to claim 5, wherein, The mass ratio between the first adhesive material and the second adhesive material is 4:6 to 2:

8.

7. The battery separator according to any one of claims 1 to 6, wherein, The polymer adhesive includes polymethyl methacrylate and / or polyethylene materials.

8. The battery separator according to any one of claims 1 to 7, wherein, The battery separator also includes nano-ceramics, which are mixed with the polymer adhesive and disposed on at least one side of the base film.

9. The battery separator according to claim 8, wherein, The D50 particle size of the nanoceramic is 500nm to 800nm.

10. The battery separator according to claim 8 or 9, wherein, The weight ratio between the polymer adhesive and the nano-ceramic ranges from 7:3 to 3:

7.

11. The battery separator according to any one of claims 1 to 10, wherein, The coating amount of the polymer adhesive on one side is 0.2–1.5 g / m². 2 .

12. The battery separator according to any one of claims 1 to 11, wherein, The polymer adhesive is applied to at least one side of the base film by spraying or roller coating.

13. The battery separator according to claim 12, wherein, When using a spraying method, the coating amount of the polymer adhesive on one side is 0.2–0.8 g / m². 2 .

14. The battery separator according to claim 12 or 13, wherein, When using a roller coating method, the coating weight of the polymer adhesive on one side is 0.6–1.5 g / m². 2 .

15. A battery, wherein, Includes the battery separator as described in any one of claims 1 to 14.

16. An electrical appliance, wherein, The electrical device includes the battery as described in claim 15.

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