Battery separator, battery and electrical device

Abstract

A battery separator, a battery and an electrical device. The separator comprises a substrate layer and bonding particles dispersed within the substrate layer, the bonding particles being exposed from the outer surface of at least one side of the substrate layer in the thickness direction. The bonding particles are distributed within the substrate layer of the separator, and, when the separator is applied to a battery, the portions of the bonding particles exposed from the substrate layer can bond the separator to an electrode sheet; and the substrate layer can be prepared simply by means of single-pass coating, thus reducing process steps and reducing the separator production cost. In addition, the separator having the described structure can reduce the risk of bubble generation at the interface between the separator and an electrode sheet during a battery formation process, so as to improve the structural stability of battery cells, thus helping to ensure better performance of batteries.

Description

Battery separators, batteries, and electrical equipment

[0001] This disclosure claims priority to the Chinese patent application filed with the China Patent Office on December 28, 2023, with application number 202311836352.6 and application name “Battery Diaphragm, Battery and Electrical Equipment”, the entire contents of which are incorporated by reference into this disclosure. Technical Field

[0002] The embodiments of the present disclosure relate to the field of battery technology, and more particularly to a battery separator, a battery, and an electrical device. Background Art

[0003] In secondary batteries, a separator is typically placed between the positive and negative electrodes to prevent direct contact. However, prior art techniques have shown that separators are prone to swelling and wrinkling, resulting in an unstable interface between the separator and the electrode surface and prone to delamination, leading to suboptimal battery production processes. Gases generated during battery formation also tend to accumulate at the separator interface, forming bubbles and causing degradation of the battery interface.

[0004] In order to solve the above problems, the industry usually uses a diaphragm with a stacked double-coating structure, including a stacked substrate, a ceramic coating and an organic coating. Among them, the ceramic coating is used to improve the performance of the diaphragm, and the organic coating is used to achieve soft contact and bonding between the diaphragm and the surface of the electrode pole piece, which is beneficial to the pole core shaping, while alleviating the diaphragm wrinkles and optimizing the battery interface. However, the above-mentioned diaphragm adhesion is unstable and prone to stratification, resulting in poor battery production process. In addition, the above-mentioned double-coating structure needs to be coated twice. Specifically, the ceramic coating is first coated on the substrate, and then the organic layer is coated on the ceramic coating. Its preparation process is complicated, the cost is high, the production efficiency is low, and the thickness of the final diaphragm is large.

[0005] Summary of the Invention

[0006] In view of this, the present disclosure provides a battery diaphragm, a battery and an electrical device, wherein bonding particles are distributed in the base layer of the diaphragm. When the diaphragm is applied to the battery, the exposed portion of the bonding particles relative to the base layer can bond the diaphragm to the electrode plate, and can be stably adhered to the surface of the electrode plate. Moreover, the base layer can be prepared by only a single coating, which saves process and reduces the production cost of the battery diaphragm. In addition, the diaphragm can also reduce the risk of bubbles generated at the interface between the diaphragm and the electrode plate during the battery formation process, thereby improving the structural stability of the battery cell and ensuring better performance of the battery.

[0007] A first aspect of the present disclosure provides a battery separator, comprising a base layer and binding particles dispersed in the base layer, wherein the binding particles are exposed on at least one outer surface of the base layer in a thickness direction.

[0008] The bonding particles are exposed on at least one side in the thickness direction of the substrate layer. When applied to the battery, good contact between the bonding particles and the electrode pole piece can be achieved. The bonding particles can give full play to their bonding effect, bond the diaphragm and the electrode pole piece, and improve the structural stability of the battery cell. In addition, the bonding particles are exposed relative to the substrate layer, which can leave a gap between the electrode pole piece and the base layer, reserving an exhaust channel for the gas generated during battery formation, reducing the risk of bubbling and deterioration at the interface, leading to lithium precipitation (for lithium-ion batteries) or sodium precipitation (for sodium-ion batteries). More importantly, the above-mentioned base layer can be directly obtained by one-time coating, which saves the process, greatly improves production efficiency and reduces production costs.

[0009] A second aspect of the present disclosure provides a battery, comprising a positive electrode sheet, a negative electrode sheet, and the separator provided by the first aspect of the present disclosure; wherein the separator is arranged between the positive electrode sheet and the negative electrode sheet.

[0010] The above-mentioned diaphragm has good thermal stability and mechanical stability, and the diaphragm has good adhesion to the positive and negative electrode plates. Therefore, the above-mentioned diaphragm is not easy to be dislocated during the manufacturing, storage, and circulation of the battery; it can also provide a good exhaust channel for the gas generated during the battery formation process, improve the problem of diaphragm and electrode stratification, and the internal structure stability of the battery is good, which is conducive to the long-term and stable performance of the battery; in addition, the use of the above-mentioned battery diaphragm can reduce the production cost of the battery.

[0011] The third aspect of the present disclosure provides an electric device, comprising the battery provided in the second aspect of the present disclosure. Since the battery provided in the present disclosure is used for power supply, the electric device has stable power supply and high market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG1A is a simplified structural diagram of one structure of a battery separator provided in an embodiment of the present disclosure.

[0013] FIG1B is a simplified structural diagram of one structure of a battery separator provided in another embodiment of the present disclosure.

[0014] 2A and 2B are scanning electron microscope (SEM) photos of the battery separator of Example 1 of the present disclosure at different angles, and FIG. 2C is a SEM photo of the battery separator of Example 1 after hot pressing.

[0015] 3A and 3B are SEM photos of the battery separator of Example 4 at different angles, and FIG. 3C is a SEM photo of the battery separator of Example 4 after hot pressing.

[0016] 4A and 4B are SEM photographs of the battery separator of Example 14 at different angles, and FIG. 4C is an SEM photograph of the battery separator of Example 14 after hot pressing.

[0017] FIG5 is a SEM photograph of the surface of the battery electrode disassembled after the normal temperature cycle test of the battery in Example 4.

[0018] FIG6 is a simplified schematic diagram of the structure of a battery provided in an embodiment of the present disclosure.

[0019] FIG7 is a simplified structural diagram of an electrical device provided in an embodiment of the present disclosure.

[0020] Explanation of reference numerals: 100-diaphragm; 1-base layer; 10-substrate; 20-composite coating; 21-ceramic base layer; 2-bonding particles; 60-battery; 61-positive electrode sheet; 63-negative electrode sheet; 70-electrical equipment. DETAILED DESCRIPTION

[0021] At present, in order to improve the thermal stability, mechanical properties and electrolyte wetting ability of polyolefin membranes so that they can be used as battery separators, the industry usually sets a ceramic coating on the surface of the polyolefin membrane. However, the existing ceramic coating does not have adhesion to the electrode pole piece, and it is impossible to obtain a structurally stable battery cell. Therefore, it is usually necessary to set an organic material layer (usually a polyvinylidene fluoride layer, PVDF) on the surface of the above-mentioned ceramic coating to "bridge" the diaphragm and the electrode pole piece. Although there are also methods in the prior art to add binder particles to the ceramic coating itself, these binder particles are only used to bond the ceramic particles and improve the strength of the ceramic coating itself. An additional organic material layer is still required. Obviously, the above two coatings need to be applied twice, and the process is more complicated. In industrial production, it will greatly increase production costs and reduce production efficiency. In addition, the organic material layer generally needs to adopt a spin coating process, which makes the consistency of the organic material layer poor. In the hot pressing process of the battery cell process, the adhesion between the diaphragm and the pole piece is poor, and the battery cell produced is prone to stratification and other problems. In order to solve the above problems, an embodiment of the present disclosure provides a battery separator, comprising a substrate and a composite coating arranged on the surface of at least one side of the substrate, wherein the composite coating comprises a ceramic base layer and a plurality of bonding particles dispersed in the ceramic base layer, and the particle size of a single bonding particle is greater than the thickness of the ceramic base layer.

[0022] 1A , an embodiment of the present disclosure provides a battery separator 100 , including a base layer 1 and adhesive particles 2 dispersed in the base layer 1 , wherein the adhesive particles 2 are exposed on at least one side of the base layer 1 in the thickness direction.

[0023] In the disclosed embodiment, the above-mentioned bonding particles are further referred to as organic bonding particles. In the above-mentioned diaphragm, the bonding particles used to bond the electrode and the diaphragm are directly dispersed in the base layer, and the bonding particles have an exposed portion on at least one side of the outer surface relative to the thickness direction of the base layer, so that when it is used in a battery, good contact between the bonding particles and the electrode can be achieved. During the hot pressing process of the battery cell manufacturing process, the bonding particles are soft and will not damage the electrode and can fully exert their bonding effect, thereby enhancing the bonding force between the diaphragm and the electrode, improving the structural stability of the battery cell, and avoiding the battery from sliding and dislocating due to external forces (for example, shaking) during transportation and assembly. It can also avoid the influence of vibration during the use of the finished battery, and at the same time improve the shrinkage of the diaphragm substrate after the electrolyte. More importantly, the bonding particles protrude relative to the base layer, and even after hot pressing, a gap can be left between the electrode plate and the ceramic base layer, reserving an exhaust channel for the gas generated during battery formation (specifically, a rapid exhaust channel between the diaphragm and the electrode plate, and the gas can be quickly discharged along the gap formed between the exposed parts of the multiple bonding particles), avoiding the phenomenon of bubbling and deterioration of the interface leading to lithium precipitation (for lithium-ion batteries) or sodium precipitation (for sodium-ion batteries). More importantly, the above-mentioned base layer can be obtained directly by one coating, which saves the process, greatly improves the production efficiency and reduces the production cost. In the present disclosure, the base layer can be provided on one side surface of the diaphragm, or the base layer can be provided on both sides of the opposite surfaces of the diaphragm in the thickness direction.

[0024] In the present disclosure, the bonding particles can be spherical or quasi-spherical. When the bonding particles are spherical, the particle size of the bonding particles refers to the diameter of the bonding particles; when the bonding particles are quasi-spherical, the particle size of the bonding particles refers to the size of the bonding particles perpendicular to the thickness of the separator (i.e., perpendicular to the stacking direction of the substrate and composite coating). In some embodiments of the present disclosure, the sphericity (Ψ) of the bonding particles is in the range of 0.75 to 1.

[0025] In some embodiments of the present disclosure, referring to FIG1B , the base layer 1 includes a substrate 10 and a composite coating 20 disposed on at least one surface of the substrate 10 in the thickness direction. The composite coating 20 includes a ceramic base layer 21 and a plurality of bonding particles 2 dispersed in the ceramic base layer 21, with the bonding particles 2 exposed on the outer surface of the ceramic base layer 21. In this way, the bonding particles are surrounded by the ceramic material to a certain depth (the lower part of the bonding particles) in the direction from the substrate side to the composite coating layer, so the bonding particles have good adhesion to the substrate and the ceramic base layer; at the same time, the other part (top) of the bonding particles is exposed relative to the ceramic base layer. At the same time, compared with the prior art (the average thickness of the organic material bonding layer is generally 3 μm), the thickness of the composite coating of the present disclosure can be relatively smaller while achieving the same effect, thereby facilitating an improvement in the volume energy density of the battery.

[0026] In some embodiments of the present disclosure, the ceramic substrate includes ceramic particles. The ceramic substrate is primarily composed of ceramic particles, with gaps between the particles. This provides numerous gas channels within the ceramic substrate, providing more exhaust channels for gases generated during battery formation. This further prevents bubbling and deterioration of the interfaces between the diaphragm substrate and the ceramic substrate, and between the diaphragm and the electrode pads, thereby improving battery performance.

[0027] In some embodiments of the present disclosure, the particle size D50 of the ceramic particles is in the range of 0.1μm to 1.5μm. For example, the particle size of the ceramic particles can be 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, etc. By controlling the particle size of the ceramic particles within the above range, the porosity of the ceramic substrate can be controlled within a suitable range, so that the gas generated during battery formation can be discharged from the composite coating in a timely manner. In the embodiment of the present disclosure, the particle size D50 of the ceramic particles is the particle size corresponding to the cumulative volume percentage of the ceramic particles reaching 50%, which can be measured using a laser particle size analyzer. Specifically, the material of the ceramic substrate is taken and pretreated to remove substances such as binders that may be present therein, and then its particle size D50 is measured using a laser particle size analyzer.

[0028] In some embodiments of the present disclosure, the material of the ceramic particles includes but is not limited to at least one of alumina, boehmite, silicon dioxide, silicon carbide, and silicon nitride.

[0029] In some embodiments of the present disclosure, the thickness of the ceramic substrate is x μm, and the particle size D50 of the bonding particles is in the range of (x+0.4 μm) to (x+2.0 μm). For example, the particle size D50 of the bonding particles may be x+0.4 μm, x+0.5 μm, x+0.6 μm, x+0.7 μm, x+0.8 μm, x+0.9 μm, x+1.0 μm, x+1.1 μm, x+1.2 μm, x+1.3 μm, x+1.4 μm, x+1.5 μm, x+1.6 μm, x+1.7 μm, x+1.8 μm, x+1.9 μm, etc. It is understandable that, considering that ceramic particles may exist between the bonding particles and the substrate in some cases, when the particle size of the bonding particles is x+aμm, the thickness of the bonding particles protruding relative to the ceramic base layer is greater than or equal to aμm; furthermore, the bonding particles are solid structures, and active ions are difficult to pass through. Excessively large particles will lead to increased local impedance and affect the polarization consistency of the battery; therefore, the particle size of the bonding particles is controlled within the above range, so that the diaphragm can take into account both the adhesion with the electrode plates and the ionic conductivity of the diaphragm, thereby making the structural stability inside the battery cell higher, the battery consistency good, and the battery rate and cycle performance better.

[0030] In some specific embodiments of the present disclosure, the thickness of the ceramic base layer is x μm, and the particle size D50 of the bonding particles is in the range of (x+0.8 μm) to (x+1.5 μm). For example, the particle size D50 of the bonding particles can be x+0.8 μm, x+0.9 μm, x+1.0 μm, x+1.1 μm, x+1.2 μm, x+1.3 μm, x+1.4 μm, x+1.5 μm, etc. The particle size D50 of the bonding particles is further controlled within the above range, and the height of the bonding particles protruding relative to the ceramic base layer can be basically controlled to be 0.8 μm to 1.5 μm. Such a height is conducive to the bonding between the diaphragm and the electrode pole piece, further improving the interfacial bonding force between the diaphragm and the electrode pole piece, improving the structural stability inside the battery cell, and enhancing the long-term stability of the battery cell during transportation and multiple charge and discharge cycles. At the same time, it will not affect the conduction of ions in the composite coating, so that the battery has good consistency and the best overall performance. In the embodiment of the present disclosure, when testing the particle size D50 of the bonding particles in the battery separator, the separator is sampled and tested under a scanning electron microscope (SEM). The particle size (diameter) of all the bonding particles is calculated within an area of ​​100*100 μm of the optional separator, and the particle sizes of these bonding particles are sorted from small to large. At this time, the median particle size is the D50 particle size of the bonding particles.

[0031] The particle size distribution of the bonding particles can be D10>(D50-1μm), D90<(D50+1μm). By controlling the particle size distribution of the bonding particles within the above range, it can be achieved that the proportion of invalid colloid particles with a particle size smaller than the thickness xμm of the ceramic substrate is less than 10%, and the proportion of large colloid particles with a particle size greater than (D50+1μm) that affect ion transmission is less than 10%. At the same time, the size distribution of the bonding particles exposed relative to the ceramic substrate can be basically controlled within 0-2.5μm. The PVDF spray glue solution used in traditional battery diaphragms generally has a protruding height difference of 0-20μm. In other words, the composite coating has a high flatness, and the bonding particles can achieve better bonding with the electrode plates, which can not only enhance the bonding force between the diaphragm and the electrode plates, but also help to further optimize the battery interface. In the embodiment of the present disclosure, the D10 of the above-mentioned bonding particles refers to the particle size corresponding to when the cumulative volume percentage of the bonding particles reaches 10%, and D90 is the particle size corresponding to when the cumulative volume percentage of the bonding particles reaches 90%. When testing the particle size D10 and D90 of the bonding particles in the battery separator, the separator is sampled and tested under a scanning electron microscope (SEM). The particle size (diameter) of all bonding particles is calculated within an area of ​​100*100μm of the optional separator, and the particle size of these bonding particles is sorted from small to large. At this time, D10 refers to the particle size when the particle size ranks 10%; D90 refers to the particle size when the particle size ranks 90%.

[0032] In some embodiments of the present disclosure, the relative deviation of the plurality of bonding particles exposed from the ceramic substrate is less than or equal to 2.5 μm. Specifically, it refers to 2500 μm. 2 Within this range, the maximum exposed dimension of the bonding particles relative to the ceramic substrate is b = 2.5 μm, the minimum exposed dimension of the bonding particles relative to the ceramic substrate is a = 0 μm, and ba ≤ 2.5 μm. This optimizes the smoothness of the composite coating, ensuring that each bonding particle achieves good adhesion to the electrode sheet, further improving the structural stability of the battery cell.

[0033] In some embodiments of the present disclosure, x is in the range of 0.5 to 4. That is, the thickness of the ceramic substrate is in the range of 0.5 μm to 4 μm. For example, the thickness of the ceramic substrate can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3.0 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4.0 μm, 4.2 μm, 4.5 μm, 4.8 μm, etc. When the thickness of the ceramic substrate is controlled within the above range, the thermal stability and mechanical properties of the diaphragm can be improved, and the ionic conductivity and thinness of the diaphragm can be better.

[0034] In some embodiments of the present disclosure, the surface density of the plurality of bonding particles in the composite coating is 0.125 g / m 2 ~0.625g / m 2 (The corresponding coverage area is about 5% to 25%). For example, in the composite coating, the surface density of the bonding particles can be 0.125 g / m 2 , 0.175g / m 2 , 0.225g / m 2 , 0.275g / m 2 , 0.325g / m 2 , 0.375g / m 2 , 0.425g / m 2 , 0.475g / m 2 , 0.525g / m 2 , 0.575g / m 2 , 0.625g / m 2 In some specific embodiments of the present disclosure, the surface density of the plurality of bonding particles in the composite coating is 0.25 g / m 2 ~0.4g / m 2 For example, in the composite coating, the surface density of the bonding particles can be 0.25 g / m 2 , 0.3g / m 2 , 0.35g / m 2 , 0.4g / m 2 Etc. By controlling the coating amount of the bonding particles within the above range, there are sufficient bonding particles to bond with the electrode plates, while taking into account the active ion transmission of the diaphragm, and controlling the battery impedance at a relatively low level, which is conducive to the full performance of the battery. Furthermore, when the total content of the bonding particles is within the above range, it is possible to better control costs while achieving better bonding performance. Furthermore, in combination with the recommended particle size range of the bonding particles, controlling the content of the bonding particles within the above range means controlling the number of bonding particles in the composite coating within a suitable range, so that the bonding particles are evenly distributed in the composite coating and the density is relatively suitable, taking into account the stability of the battery cell structure and the rate performance of the battery. In the embodiment of the present disclosure, the test method of the surface density of the bonding particles includes: taking a unit area of ​​the diaphragm and weighing its mass m1, the unit is g, and then using a reagent to clean the coating (composite coating) on ​​the substrate to obtain the mass m2 of the substrate, the mass of the composite coating per unit area m3 = m1-m2, the unit is g, the washed composite coating (including ceramics and bonding particles) is separated by high-speed centrifugation, and the total mass m4 of the ceramic particles is weighed, the unit is g, and the surface density of the bonding particles = (m3-m4) / unit area, the unit is g / m 2 .

[0035] In some embodiments of the present disclosure, the material of the bonding particles includes an amorphous polymer and / or a crystalline polymer. In some specific embodiments, the glass transition temperature (Tg) of the amorphous polymer is in the range of 70°C to 100°C. For example, the Tg of the amorphous polymer can be 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, etc. In some specific embodiments, the melting point Tm of the crystalline polymer is in the range of 110°C to 125°C. For example, the Tm of the crystalline polymer can be 110°C, 115°C, 120°C, 125°C, etc. The Tg or Tm of the material of the bonding particles is controlled within the above range, and the bonding particles are solid at room temperature. In the preparation process of the composite coating slurry, there is no need to deliberately control the temperature, which reduces production costs and is also conducive to obtaining a composite coating slurry with suitable viscosity. At the same time, the Tg or Tm of the above bonding particles is adapted to the temperature of the hot pressing treatment of the battery cell assembly. During the hot pressing treatment of the electrode sheets and diaphragms, the electrode sheets and diaphragms are further in contact, and the bonding particles soften to fully exert their bonding effect without causing large deformation (for example, melting, etc.) to cause deformation of the bonding particles or even blockage of the substrate. Specifically, the above hot pressing treatment includes: in the battery cell manufacturing process, after the negative electrode sheets, diaphragms and positive electrode sheet groups are stacked or wound, they are placed in a hot pressing device, heated to a certain temperature (generally 75-100°C) and maintained for a certain period of time to improve the tightness inside the battery cell.

[0036] In the embodiments of the present disclosure, when the material of the above-mentioned bonding particles includes an amorphous polymer and a crystalline polymer, it may include one or both of the following two situations: (1) the same composite coating includes bonding particles made of an amorphous polymer and bonding particles made of a crystalline polymer; (2) the material of the same bonding particle is a mixture of an amorphous polymer and a crystalline polymer.

[0037] In some specific embodiments of the present disclosure, the material of the bonding particles includes a crystalline polymer and an amorphous polymer. The glass transition temperature (Tg) of the bonding particles of the amorphous polymer is in the range of 70°C to 100°C, and the Tg of the crystalline polymer is in the range of 100°C to 100°C. m In the range of 110°C to 125°C. For example, the glass transition temperature of the amorphous polymer can be 70°C, 75°C, 80°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 98°C, 100°C, etc. For example, the Tg of the bonding particle material can be 100°C, ... m It can be 110°C, 115°C, 120°C, 125°C, etc. At this time, the Tg of the amorphous polymer or the Tg of the crystalline polymer is controlled. mWithin the above range, the bonding particles basically maintain their original shape during the long-term baking of the battery cell (baking at 90°C for more than 10 hours), reducing the risk of the bonding particles melting and blocking the pores of the substrate, which is more conducive to the preparation of the battery cell.

[0038] In some embodiments of the present disclosure, the crystalline polymer (i.e., the material of the crystalline bonding particles) includes polyethylene (PE), modified polypropylene (PP), and low-melting-point polyethylene terephthalate (PET). In some embodiments of the present disclosure, the amorphous polymer includes, but is not limited to, at least one of modified polyvinyl chloride (PVC), polystyrene (PS), polyacrylonitrile, polyacrylate (PMMA), styrene-acrylonitrile copolymer (ANS), styrene-acrylate copolymer, acrylonitrile-acrylate copolymer, and styrene-acrylonitrile-acrylate copolymer. Crystalline polymers include, but are not limited to, at least one of polyethylene, polypropylene, and low-melting-point polyethylene terephthalate (PET). Among them, polyacrylate polymers include copolymers of at least one of propyl methacrylate, ethylene glycol methacrylate, and diacetone acrylamide with methyl methacrylate. The thermal stability (glass transition temperature or melting point) and swelling characteristics of the above-mentioned materials are relatively suitable. The swelling rate of the bonding particles composed of the above-mentioned materials in the electrolyte is low, and a high cohesive force can still be maintained during long-term storage of the battery and battery cycling, so its bonding ability is relatively stable; the risk of clogging the pores of the diaphragm substrate due to swelling of the bonding particles is also greatly reduced, lithium ions can flow continuously, the internal resistance of the battery is small, and the consistency of the direct current internal resistance (DCIR) at various locations inside the battery is good, and the battery performance can be fully utilized. In addition, the price of the above-mentioned materials is low, which can further reduce the cost of the diaphragm. In particular, the present disclosure adds a cross-linking monomer (at least one of propyl methacrylate, ethylene glycol methacrylate, and diacetone acrylamide) to PMMA, which increases the cross-linking degree of the PMMA polymer and increases the molecular weight of PMMA, thereby enhancing the interaction between PMMA molecular chain segments and reducing swelling.

[0039] In addition, compared with the commonly used binder PVDF in related technologies, the above-mentioned amorphous polymers and crystalline polymers do not contain fluorine, are more environmentally friendly, and have low cost, and are therefore more conducive to the production and application of battery separators.

[0040] In the present disclosure, the substrate in the separator can be any material known in the art. In some specific embodiments, the substrate can be a polyolefin material, including but not limited to polyethylene microporous substrates and polypropylene microporous substrates. The porosity of the substrate can be selected by a person skilled in the art based on production needs. For example, it can be in the range of 25% to 80%, and this disclosure does not impose any limitation on this value.

[0041] The present disclosure also provides a battery. As shown in FIG6 , the battery 60 includes a positive electrode sheet 61 , a negative electrode sheet 63 , and a battery separator 100 provided in the present disclosure, the separator being disposed between the positive electrode sheet and the negative electrode sheet.

[0042] The above-mentioned diaphragm has good thermal stability and mechanical stability, and the diaphragm has good adhesion to the positive and negative electrode sheets. Therefore, the above-mentioned diaphragm is not easy to be dislocated during the storage and circulation of the battery; it can also provide a good exhaust channel for the gas generated during the battery formation process, improve the problem of diaphragm and electrode stratification, and the internal structure stability of the battery is good, which is conducive to the long-term and stable performance of the battery.

[0043] In the present disclosure, the battery may be a liquid battery using an electrolyte, wherein the electrolyte used may be any electrolyte known in the art.

[0044] In the present disclosure, the above-mentioned positive electrode plate can be any positive electrode plate known in the art; the above-mentioned negative electrode plate can be any negative electrode plate known in the art.

[0045] The present disclosure also provides an electric device 70. As shown in FIG7 , the electric device 70 includes a battery 60 provided in the present disclosure. Since the battery provided in the present disclosure is used for power supply, the electric device has stable power supply and high market competitiveness.

[0046] In some embodiments of the present disclosure, the above-mentioned electrical equipment includes but is not limited to 3C electronic equipment, new energy vehicles, electric bicycles, etc.

[0047] The technical solution of the present disclosure is further illustrated below with multiple embodiments.

[0048] Example 1

[0049] A composite coating slurry (specifically comprising boehmite particles with a D50 particle size of 0.7 μm and polyethylene bonding particles) was applied by roller coating on opposite sides of a microporous polypropylene substrate having a thickness of 12 μm and a porosity of 40%, dried at 85°C, and cut to obtain a diaphragm. The diaphragm comprised a substrate and a composite coating disposed on one surface of the substrate. The composite coating comprised a ceramic base layer having a thickness of 2.0 μm, in which bonding particles with a particle size of D50 = 2.4 μm were dispersed. The bonding particles had a melting point (Tm) of 120°C. In the composite coating, the coating amount of the bonding particles was 0.325 g / m 2 .

[0050] Example 2

[0051] The difference from Example 1 is that the composite coating includes a ceramic base layer with a thickness of 2.0 μm, and bonding particles with a particle size D50 of 2.7 μm are dispersed in the ceramic base layer.

[0052] Example 3

[0053] The difference from Example 1 is that the composite coating includes a ceramic base layer with a thickness of 2.0 μm, and bonding particles with a particle size D50 of 3.3 μm are dispersed in the ceramic base layer.

[0054] Example 4

[0055] The difference from Example 1 is that the composite coating includes a ceramic base layer with a thickness of 2.0 μm, and bonding particles with a particle size D50 of 3.7 μm are dispersed in the ceramic base layer.

[0056] Example 5

[0057] The difference from Example 1 is that the composite coating includes a ceramic base layer with a thickness of 2.0 μm, and bonding particles with a particle size D50 of 4.0 μm are dispersed in the ceramic base layer.

[0058] Example 6

[0059] The difference from Example 1 is that the composite coating includes a ceramic base layer with a thickness of 2.0 μm, and bonding particles with a particle size D50 of 4.3 μm are dispersed in the ceramic base layer.

[0060] Example 7

[0061] The difference from Example 1 is that the particle size D50 of the bonding particles dispersed in the ceramic substrate is 3.3 μm; the surface density of the bonding particles in the composite coating is 0.1 g / m 2 .

[0062] Example 8

[0063] The difference from Example 1 is that the particle size D50 of the bonding particles dispersed in the ceramic substrate is 3.3 μm; the surface density of the bonding particles in the composite coating is 0.125 g / m 2 .

[0064] Example 9

[0065] The difference from Example 1 is that the particle size D50 of the bonding particles dispersed in the ceramic substrate is 3.3 μm; the surface density of the bonding particles in the composite coating is 0.28 g / m 2 .

[0066] Example 10

[0067] The difference from Example 1 is that the particle size D50 of the bonding particles dispersed in the ceramic substrate is 3.3 μm; the surface density of the bonding particles in the composite coating is 0.48 g / m 2 .

[0068] Example 11

[0069] The difference from Example 1 is that the particle size D50 of the bonding particles dispersed in the ceramic substrate is 3.3 μm; the surface density of the bonding particles in the composite coating is 0.625 g / m 2 .

[0070] Example 12

[0071] The difference from Example 1 is that the particle size D50 of the bonding particles dispersed in the ceramic substrate is 3.3 μm, ie, x+1.3 μm; the bonding particles are polyacrylate polymers (PMMA); and the Tg of the bonding particles is 90°C.

[0072] Example 13

[0073] The difference from Example 1 is that the thickness of the ceramic base layer in the diaphragm is 3 μm, the particle size D50 of the bonding particles dispersed in the ceramic base layer is 4.3 μm, the bonding particles are polyacrylate polymer (PMMA), and the Tg of the bonding particles is 90°C.

[0074] Example 14

[0075] The difference from Example 1 is that the thickness of the ceramic substrate in the diaphragm is 0.5 μm, the particle size D50 of the boehmite particles in the ceramic substrate is 0.4 μm, the particle size D50 of the bonding particles dispersed in the ceramic substrate is 1 μm; the bonding particles are modified polyethylene polymer (PE); the T m is 120℃.

[0076] In order to highlight the beneficial effects of the embodiments of the present disclosure, the following comparative examples are provided.

[0077] Comparative Example 1

[0078] A battery separator comprises a microporous polypropylene substrate with a thickness of 12 μm and a porosity of 40%, with ceramic particle layers and organic adhesive layers laminated on opposite sides. The ceramic particle layer is 2.0 μm thick and comprises boehmite particles with a D50 particle size of 0.7 μm, and is applied by roller coating. The organic adhesive layer has an average thickness of 3 μm and is made of polyvinylidene fluoride (PVDF), with an areal density of 0.25 g / m 2 The coating method is water-based spraying.

[0079] Performance Testing

[0080] (1) Morphology test: The morphology of the battery separators of each embodiment was observed by scanning electron microscopy (SEM), and the SEM photos of the battery separators of some embodiments are summarized in Figures 2A to 5. It can be seen that the battery separators provided by the embodiments of the present disclosure have not undergone significant changes in the morphology of the bonding particles and the interface morphology of the separator itself after hot pressing. In particular, in view of the fact that in the process of SEM sample preparation, in order to expose the cross section of the battery separator, ion cutting is used for sample preparation, and the exposed part of the bonding particles at the cross section is worn under the bombardment of high-energy ions (Figures 2B and 3B), and the bonding particles are marked with white circles in Figure 2C. Figure 5 is a surface SEM photo of the battery pole piece disassembled after the normal temperature cycle test of Example 4. This is because the bonding between the bonding particles and the electrode pole piece is relatively strong. When the pole core is disassembled after the cycle, the bonding particles stick to the surface of the pole piece, which fully demonstrates that the battery separator provided by the embodiments of the present disclosure can be stably bonded to the electrode pole piece.

[0081] (2) Bonding strength test: The battery separator and the electrode plate of each embodiment were laminated and then hot pressed under the conditions of temperature 95°C, pressure 2 MPa and time 60 s. The peel strength between the separator and the electrode plate was then tested to obtain the bonding strength between the coating and the electrode plate.

[0082] (3) Battery performance test

[0083] ① Prepare test cells containing separators for batteries of the embodiment and the comparative example respectively: prepare positive electrode sheets and negative electrode sheets, wherein the positive electrode sheet includes a positive electrode current collector (specifically aluminum foil) and a positive electrode active material layer, and the positive electrode active material includes a positive electrode active material (specifically lithium iron phosphate, LiFePO4), a conductive agent (specifically Super P), and a binder (specifically polyvinylidene fluoride, PVDF) in a mass ratio of 95:2.6:2.4; the negative electrode sheet includes a negative electrode current collector (specifically copper foil) and a negative electrode active material including a negative electrode active material (specifically graphite) in a mass ratio of 96.00:1.40:2.60, a conductive agent (specifically Super P), and a binder (specifically CMC+SBR=1+1.6);

[0084] Separators from each example and comparative example were placed between the positive and negative electrodes to separate them. Seven positive electrode layers, eight negative electrode layers, and 16 separator layers were stacked to obtain dry cells. The dry cells were then hot-pressed at 95°C and 2 MPa for 60 seconds. Each dry cell was placed in an aluminum-plastic film outer package and dried under vacuum at 95°C for 12 hours. After cooling, the electrolyte was injected and the cells were vacuum-sealed. After allowing to soak at 50°C for 48 hours, the cells were pressurized at 25°C, aged at 45°C, repackaged, vented, and capacity-separated to obtain Example batteries S1-S14 and Comparative Example battery DS1.

[0085] ② Battery discharge impedance DCIR test: the battery is discharged at 50% SOC at a temperature of 25°C at a current density of 1.5C for 30 seconds;

[0086] ③ Normal temperature cycle test:

[0087] The battery was tested for charge and discharge cycles at 1.0C charge and 1.0C discharge at 25±1°C. The steps were as follows: 10 minutes of rest; 1.0C constant current charging to 3.8V, constant voltage charging to 0.05C cutoff; 10 minutes of rest; 1.0 constant current discharge to 2.0V (one cycle). This step was repeated for 1000 cycles to measure the battery's capacity retention. The test was continued, and the number of cycles at which the battery's capacity retention reached 85% was recorded as the battery's cycle life. The results are summarized in Table 1. Five batteries were sampled from each group, and the average value was calculated.

[0088] Table 1

[0089] The data in Table 1 demonstrates that the battery separators provided by the embodiments of the present disclosure exhibit strong adhesion to the electrode plates, maintaining structural stability within the battery cell during both manufacturing and cycling. Furthermore, the bonding strength of the battery separators provided by the embodiments of the present disclosure is comparable to that of the PVDF organic adhesive layers commonly used in related art. Furthermore, the bonding strength between the embodiment separators and the comparative example separators and the electrode plates is comparable, and their electrochemical performance is also comparable. In other words, the battery separators provided by the embodiments of the present disclosure achieve comparable performance to existing technologies while significantly reducing process steps and production costs.

[0090] Furthermore, by comparing the data between Examples 1-6, it can be found that when the relationship between the D50 of the bonding particles and the thickness of the ceramic substrate is adjusted within the range suggested in the present disclosure (Examples 2-5), the electrochemical performance of the final battery can be optimized, especially when the relationship between the D50 of the bonding particles and the thickness of the ceramic substrate is controlled within the range further suggested in the present disclosure (Example 3), the electrochemical performance of the battery is better; by comparing Examples 7-11, when the surface density of the bonding particles is adjusted within the range further suggested in the present disclosure (Example 9), the bonding strength between the diaphragm and the electrode plate can be controlled within a more appropriate range, thereby improving the electrochemical performance of the final battery.

[0091] The above is an exemplary embodiment of the present disclosure. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made thereto without departing from the principles of the present disclosure. These improvements and modifications are also considered to be within the scope of protection of the present disclosure.

Claims

1. A separator (100) for a battery, characterized in that, Comprising: A substrate layer (1), the substrate layer (1) comprising a base material (10) and bonding particles (2), and in the thickness direction of the separator, the bonding particles (2) are exposed on at least one outer surface of the base material (10).

2. The separator (100) for a battery according to claim 1, wherein, The substrate layer (1) comprises: A composite coating (20), the composite coating (20) being provided on at least one surface in the thickness direction of the base material (10), the composite coating (20) comprising a ceramic base layer (21) and a plurality of the bonding particles (2) dispersed in the ceramic base layer (21), and the bonding particles (2) are exposed on the outer surface of the ceramic base layer (21).

3. The separator (100) for a battery according to claim 2, characterized in that, The particle size D50 of the bonding particles (2) is greater than or equal to the thickness of the ceramic base layer (21).

4. The battery separator (100) according to claim 3, characterized in that, The thickness of the ceramic base layer (21) is x μm, and the particle size D50 of the bonding particles (2) is in the range of (x μm + 0.4 μm) to (x μm + 2.0 μm).

5. The diaphragm according to claim 4, characterized in that, The particle size D50 of the bonding particles (2) is in the range of (x μm + 0.8 μm) to (x μm + 1.5 μm).

6. The separator (100) for a battery according to claim 4 or 5, characterized in that, The x is in the range of 0.5 to 4.

7. The separator (100) for a battery according to any one of claims 2-6, characterized in that, The ceramic base layer (21) comprises ceramic particles; the particle size D50 of the ceramic particles is in the range of 0.1 μm to 1.5 μm.

8. The separator (100) for a battery according to any one of claims 1-7, characterized in that, The areal density of the bonding particles (2) is 0.125 g / m 2 ~0.625 g / m 2 .

9. The separator (100) for a battery according to claim 8, characterized in that, The areal density of the bonding particles (2) is 0.25 g / m 2 ~0.4 g / m 2 .

10. The separator (100) for a battery according to any one of claims 1-9, characterized in that, The bonding particles (2) comprise an amorphous polymer and / or a crystalline polymer.

11. The separator (100) for a battery according to claim 10, characterized in that, The bonding particles (2) comprise an amorphous polymer, and the glass transition temperature of the amorphous polymer is in the range of 70°C to 100°C.

12. The separator (100) for a battery according to claim 10 or 11, characterized in that, The bonding particles comprise a crystalline polymer, and the melting point of the crystalline polymer is in the range of 110°C to 125°C.

13. The separator (100) for a battery according to any one of claims 10 to 12, characterized in that, The bonding particles comprise an amorphous polymer, and the amorphous polymer comprises at least one of modified polyvinyl chloride, polystyrene, polyacrylonitrile, polyacrylate (PMMA), styrene-acrylonitrile copolymer, styrene-acrylate copolymer, acrylonitrile-acrylate copolymer, and styrene-acrylonitrile-acrylate copolymer.

14. The separator (100) for a battery according to any one of claims 10 to 13, characterized in that, The bonding particles comprise a crystalline polymer, and the crystalline polymer comprises at least one of polyethylene, polypropylene, and polyethylene terephthalate.

15. A battery (60), characterized in that, The battery comprises a positive electrode plate (61), a negative electrode plate (63), and a battery separator (100) according to any one of claims 1-14, and the separator (100) is disposed between the positive electrode plate (61) and the negative electrode plate (63).

16. An electrical device (70), characterized in that, The electrical device (70) comprises the battery (60) according to claim 15.

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