Diaphragm and battery

Abstract

The utility model relates to the technical field of batteries, in particular to a diaphragm, which comprises a base membrane and a ceramic layer coated on at least one surface of the base membrane, the ceramic layer is provided with a groove, and the material of the ceramic layer comprises aluminum nitride. The ceramic layer is arranged in the diaphragm, the ceramic layer is made of the aluminum nitride material with excellent heat conduction capability, the heat conduction performance of the diaphragm can be remarkably improved, the groove is formed in the diaphragm, a channel for electrolyte infiltration is provided, the electrolyte can rapidly flow along the electrolyte infiltration channel, the lithium ion concentration of the electrolyte at the diaphragm is balanced, and the service life of the diaphragm is prolonged. And moreover, convective heat exchange is realized in the moving process of the electrolyte, and the heat-conducting property of the diaphragm is improved.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and more specifically, to a separator. Background Technology

[0002] In the field of lithium battery technology, the electrical performance and safety of batteries have always been key research areas. Among these, temperature control is one of the critical factors affecting battery performance. Excessively high or low temperatures can affect the battery's charging and discharging efficiency and lifespan, and may even lead to safety accidents.

[0003] The separator is a key component that prevents short circuits caused by direct contact between the positive and negative electrodes. However, traditional separator materials have poor thermal conductivity, making it difficult to effectively transfer and dissipate the heat generated by the battery during operation, thus affecting the battery's electrical performance and safety.

[0004] Currently, although the positive and negative electrodes have strong conductivity and corresponding thermal conductivity, the thermal conductivity bottleneck of the separator has not yet been effectively solved.

[0005] (1) In the existing cell temperature control methods, although the thermal conductivity of ceramic materials is relatively high, they still cannot effectively transfer heat, especially when the cell temperature is high. This affects the charging and discharging efficiency and lifespan of the battery, and may even cause safety accidents.

[0006] (2) Existing ceramic materials have poor thermal expansion coefficient and mechanical properties, and are prone to cracking or deformation in high temperature environment, which affects the electrical performance and safety of the battery.

[0007] Therefore, there is an urgent need for a new type of separator technology to improve the thermal conductivity of batteries.

[0008] Therefore, there is an urgent need to invent a separator and a battery. Utility Model Content

[0009] One of the objectives of this invention is to provide a separator that can improve the thermal conductivity of a battery, addressing the shortcomings of existing technologies.

[0010] To solve the above-mentioned technical problems, this application adopts the following technical solution:

[0011] A diaphragm is provided, comprising a base film and a ceramic layer coated on at least one surface of the base film in the thickness direction, the ceramic layer having grooves, the ceramic layer being made of aluminum nitride.

[0012] Furthermore, it also includes an adhesive layer, which is disposed opposite to the two outermost surfaces in the thickness direction of the diaphragm.

[0013] Furthermore, the grooves are configured as multiple parallel elongated strips.

[0014] Furthermore, the width of the groove is 0.1mm to 2mm.

[0015] Furthermore, the material of the adhesive layer is PMMA or PVDF.

[0016] Furthermore, the particle size of the adhesive layer material is 1μm to 15μm with a Dv50.

[0017] Furthermore, the depth of the groove is 10% to 100% of the thickness of the ceramic layer.

[0018] Furthermore, the thermal conductivity of the aluminum nitride is between 100 W / m·K and 320 W / m·K.

[0019] The beneficial effects of this invention are as follows: By setting a ceramic layer in the separator, and the ceramic layer material being aluminum nitride with excellent thermal conductivity, the thermal conductivity of the separator can be significantly improved. Furthermore, grooves are provided on the separator to provide channels for electrolyte wetting, allowing the electrolyte to flow rapidly along these channels. This ensures a balanced lithium-ion concentration at the separator and prevents lithium-ion imbalance caused by changes in the relative areas of the positive and negative electrodes after corner formation, thus improving corner lithium deposition. Because of the formed electrolyte wetting channels, convective heat transfer is achieved during electrolyte movement, further enhancing the thermal conductivity of the separator.

[0020] The second objective of this invention is to provide a battery that includes the aforementioned separator.

[0021] Furthermore, the separator may have a ceramic layer on one side near the positive electrode, or it may have a ceramic layer on both sides near the positive and negative electrodes. Attached Figure Description

[0022] The accompanying drawings, which are included to provide a further understanding of the present invention and constitute a part of this invention, illustrate exemplary embodiments of the present invention and are used to explain the present invention, but do not constitute an undue limitation of the present invention. In the drawings:

[0023] Figure 1 This is one of the structural schematic diagrams of this utility model;

[0024] Figure 2 This is the second structural schematic diagram of the present invention;

[0025] Figure 3 This is a top view of the groove of this utility model;

[0026] Figure 4 This is a scanning electron microscope image of the groove of this utility model.

[0027] Wherein: 1-base film; 2-ceramic layer; 21-groove; 3-coating layer. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terminology used in the specification of this application is for the purpose of describing specific embodiments only and is not intended to limit this application.

[0029] In the description of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0030] Although this application discloses preferred embodiments as described above, it is not intended to limit the claims. Any person skilled in the art can make several possible changes and modifications without departing from the concept of this application. Therefore, the scope of protection of this application should be determined by the scope defined in the claims of this application.

[0031] With the rapid development of lithium-ion batteries, battery safety performance has received increasing attention. Improving the performance of the separator is one of the most important methods to enhance battery safety. The separator's primary function in a battery is to prevent short circuits between the positive and negative electrodes, allowing lithium ions to move freely within it. Improving the separator's safety performance plays a crucial role in ensuring battery safety. Traditional separators, due to their poor thermal conductivity, easily accumulate heat on their surface, leading to short circuits between the positive and negative electrodes and resulting in poor battery safety.

[0032] In existing technologies, a ceramic layer is coated on the surface of the separator. Because the ceramic layer has good thermal conductivity and heat resistance, it can reduce the maximum temperature of the separator surface, thus improving battery safety. However, while this method improves the thermal conductivity of the separator, the sheet-like structure results in low heat conduction efficiency through a thinner separator, while a thicker ceramic layer would reduce the battery's energy density.

[0033] This application provides an electrolyte flow channel within the diaphragm, allowing heat to be exchanged through the flow of the electrolyte within the diaphragm. This results in a wide heat exchange radiation area and high heat exchange efficiency.

[0034] like Figure 1-4 As shown, this embodiment provides a separator, including a base film 1 and a ceramic layer 2 coated on at least one surface of the base film 1 in the thickness direction. The ceramic layer 2 is provided with grooves 21, and the material of the ceramic layer 2 includes aluminum nitride. Due to the grooves 21, when the battery undergoes pressurized formation, the presence of the grooves 21 causes the positive and negative electrode plates and the battery separator to adhere, forming a space to accommodate the electrolyte. The electrolyte can flow along the grooves 21. When hot spots appear in the separator (hot spots refer to locations with higher temperatures), the heat from the hot spots can be transferred to the electrolyte, and the heat transfer is achieved through the flow of the electrolyte. This method of heat transfer through electrolyte flow results in high heat transfer efficiency. Furthermore, because the grooves 21 provide channels for electrolyte flow, lithium ions can also diffuse along these channels, improving the efficiency of lithium ion diffusion and reducing problems such as lithium plating at battery corners.

[0035] Because the ceramic layer 2 prepared by Al2O3 and boehmite ceramics used in the present invention may crack or break after long-term use, especially when the battery undergoes frequent charge and discharge cycles, this may lead to a decline in the performance of the separator and affect the safety and life of the battery.

[0036] In this application, the material of the ceramic layer 2 includes aluminum nitride. Aluminum nitride has high thermal conductivity and good mechanical properties, which can form a good heat conduction path, reduce the maximum temperature of the battery, and has high flexural strength, effectively reducing the possibility of separator damage.

[0037] Preferably, the groove 21 is designed to connect the diaphragm at different locations. By connecting different locations, heat exchange at different locations can be achieved. A reasonable arrangement of the groove 21 can improve the heat transfer efficiency of the diaphragm.

[0038] Preferably, the battery also includes an adhesive layer 3, which is disposed opposite to the two outermost surfaces in the thickness direction of the separator. During hot pressing, the contact between the positive and negative electrode sheets and the separator is not completely tight, with gaps and air layers remaining. This can lead to significant thermal resistance during heat transfer. The adhesive layer 3 fills these gaps, allowing heat to be transferred more smoothly between the positive and negative electrode sheets and the separator, thereby reducing contact thermal resistance. The adhesive layer 3 enables a tight fit between the positive and negative electrode sheets, reduces contact thermal resistance between the positive and negative electrode sheets and the separator, and improves the safety performance of the battery.

[0039] In some embodiments, the grooves 21 are configured as multiple parallel elongated strips. This shape of the grooves 21 allows for communication between different membrane positions at the greatest distance with fewer grooves, which is beneficial for flow heat exchange. These parallel elongated grooves 21 increase the porosity of the membrane surface, allowing substances such as air and electrolyte to flow more easily along the grooves 21, thereby improving the overall permeability of the membrane. This ensures gas exchange inside the battery and good wetting of the electrolyte in the membrane, which helps the normal chemical reaction inside the battery to proceed. Furthermore, the manufacturing process of the elongated grooves 21 is simpler and can improve the efficiency of membrane manufacturing.

[0040] Preferably, the width of the groove 21 is 0.1mm to 2mm. Within this width range, the groove 21 can effectively exert the capillary effect. When the electrolyte comes into contact with the separator, due to the surface tension of the liquid, the electrolyte will form a meniscus within the groove 21. The appropriate width of the groove 21 ensures that the capillary force experienced by the electrolyte within the groove 21 is just right, allowing it to quickly and fully fill the groove 21, achieving good wetting of the electrolyte and separator, providing more channels for lithium-ion transport. Good electrolyte wetting makes the transport of lithium ions within the separator smoother. The appropriately wide groove 21 provides a channel for the directional transport of lithium ions, reduces the resistance to lithium-ion diffusion within the separator, accelerates the migration speed of lithium ions between the positive and negative electrodes, thereby improving the charge and discharge efficiency of the battery, enabling the battery to complete the charge and discharge process in a shorter time, and improving the overall performance of the battery.

[0041] Preferably, the material of the coating layer 3 is PMMA or PVDF, and the particle size of the material of the coating layer 3 is Dv50 of 1μm to 15μm. Choosing PMMA or PVDF as the material of the coating layer 3 provides a certain degree of elasticity, which can make the contact between the separator and the positive and negative electrode plates of the battery tighter during the battery thermal formation process, reduce the contact thermal resistance between the positive and negative electrode plates and the separator, and provide a certain compression space, which can not only reduce the thickness, but also provide more storage space for electrolyte and improve the corner lithium plating. Controlling the particle size of the material of the coating layer 3 to Dv50 of 1μm to 15μm can make lithium ions easily pass through the coating layer 3, which is beneficial to the conductivity of lithium ions.

[0042] Preferably, the depth of the groove 21 is 10% to 100% of the thickness of the ceramic layer 2. If the groove 21 is too shallow, it may not be able to fully exert its function of guiding and storing the electrolyte. When the depth of the groove 21 reaches 10% to 100% of the thickness of the ceramic layer 2, the mechanical strength of the ceramic layer 2 will not be excessively weakened, so that the separator can still maintain good structural integrity in the complex environment inside the battery, resist certain external impacts and deformations, and reduce the risk of battery short circuits caused by damage to the ceramic layer 2.

[0043] Preferably, the thermal conductivity of aluminum nitride is between 100 W / m·K and 320 W / m·K, which helps to achieve a uniform temperature distribution inside the battery.

[0044] Another aspect of this application is to provide a battery including the above-mentioned separator. The battery of this application is not particularly limited as long as it meets the requirement of being able to be configured with the separator of this application.

[0045] like Figure 1 As shown, preferably, the separator has a ceramic layer 2 only on the side closest to the positive electrode. Due to the good thermal conductivity of the ceramic layer 2, a single layer is sufficient to maintain a uniform temperature for the separator. The separator is positioned on the side closest to the positive electrode because lithium deposition is prone to occur at the corners of the negative electrode. Therefore, by placing the ceramic layer 2 on the positive electrode, the distribution of lithium ions entering the negative electrode is more uniform, reducing lithium ion deposition. Placing the ceramic layer 2 on only one side, compared to two sides, reduces the number of process steps, simplifies operation, reduces the difficulty of process control and potential quality problems, and improves production efficiency and product yield.

[0046] like Figure 2 As shown, ceramic layers 2 can also be provided on both sides near the positive and negative electrode plates. When ceramic layers 2 are provided on both sides, they can provide all-round protection for the separator, have better thermal conductivity, and the heat-generating points cannot directly contact the base film 1, thus providing thermal insulation for the easily meltable base film 1.

[0047] The foregoing description illustrates and describes several preferred embodiments of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the present invention's conception through the foregoing teachings or related technical or knowledge. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be protected within the scope of the appended claims.

Claims

1. A diaphragm characterized by: The diaphragm comprises a base film (1) and a ceramic layer (2) coated on at least one surface of the base film (1) in the thickness direction, the ceramic layer (2) is provided with grooves (21), and the material of the ceramic layer (2) comprises aluminum nitride.

2. The separator of claim 1, wherein: The diaphragm further comprises a rubber coating layer (3) oppositely arranged on the two outermost surfaces in the thickness direction of the diaphragm.

3. The septum of claim 1, wherein: The grooves (21) are arranged in the form of multiple parallel strips.

4. The diaphragm of claim 3, wherein: The width of the grooves (21) is 0.1mm-2mm.

5. The diaphragm of claim 2, wherein: The material of the rubber coating layer (3) is PMMA or PVDF.

6. The diaphragm of claim 5, wherein: The particle size Dv50 of the material of the rubber coating layer (3) is 1-15μm.

7. The septum of claim 4, wherein: The depth of the grooves (21) is 10%-100% of the thickness of the ceramic layer (2).

8. The septum of claim 1, wherein: The thermal conductivity of the aluminum nitride is 100-320W / m·K.

9. A battery, characterized by The diaphragm comprises the diaphragm according to any one of claims 1-8.

10. The battery of claim 9, wherein, The diaphragm can be provided with a ceramic layer (2) on one side close to the positive electrode sheet, or can be provided with ceramic layers (2) on both sides close to the positive electrode sheet and the negative electrode sheet.

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