Lithium ion battery composite diaphragm

Abstract

The utility model discloses a lithium ion battery composite diaphragm which comprises a base diaphragm, and additional diaphragms cover the upper surface and the lower surface of the base diaphragm; the additional film comprises a heat insulation layer close to the base film and a reinforcing layer far away from the base film, and limiting holes are uniformly distributed in the heat insulation layer; ceramic particles are arranged in the limiting holes, and the two opposite tangent planes of the ceramic particles abut against the base film and the reinforcing layer respectively. The additional membranes are arranged on the two sides of the base membrane, and the ceramic particles are additionally arranged between the additional membranes and the base membrane, so that when the composite membrane is extruded by external force, the reinforcing layer made of the polyvinylidene fluoride layer material at the outermost side is firstly stressed, and in the force transmission process, the stress points of the base membrane are dispersed through the plurality of ceramic particles, so that the composite membrane is formed. Damage of the base film caused by concentrated stress can be avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium ion battery diaphragms, in particular to a lithium ion battery composite diaphragm. Background Art

[0002] A lithium-ion battery composite separator is a type of membrane material used within the battery. Its primary function is to isolate the positive and negative electrodes from direct contact, preventing short circuits, while allowing lithium ions to move freely between the two electrodes. Composite separators are typically made of multiple layers of different materials to improve their performance and stability. Composite separators can enhance battery safety and cycle life, reduce internal resistance, and increase energy and power density.

[0003] The patent application "A Lithium-ion Battery Composite Separator," with publication number CN116799430A, proposes a lithium-ion battery composite separator comprising a base membrane, a micro-ceramic coating, and a nano-ceramic coating. The micro-ceramic coating and the nano-ceramic coating are sequentially applied to the upper and / or lower surfaces of the base membrane. The separator is susceptible to damage when subjected to relatively small stress points in the battery. Utility Model Content

[0004] The purpose of the utility model is to provide a composite diaphragm for a lithium ion battery.

[0005] To achieve the above objectives, the present invention provides the following technical solutions:

[0006] A lithium-ion battery composite diaphragm comprises a base membrane, the upper and lower surfaces of which are covered with additional membranes; the additional membrane comprises a heat-insulating layer close to the base membrane and a reinforcing layer away from the base membrane, the heat-insulating layer being evenly distributed with limiting holes; ceramic particles are disposed in the limiting holes, and two opposing tangent surfaces of the ceramic particles respectively abut against the base membrane and the reinforcing layer.

[0007] A further solution: the base membrane includes a porous polymer membrane, a transition interface membrane provided on the upper and lower surfaces of the porous polymer membrane, and a gelled microporous polymer membrane provided on the outside of the transition interface membrane.

[0008] A further solution is that the outer periphery of the ceramic particles is fixedly connected to the limiting hole.

[0009] A further solution: the limiting holes are distributed in an array.

[0010] A further solution: the material of the reinforcement layer is polyvinylidene fluoride.

[0011] A further solution: the thermal insulation layer is made of ceramic fiber.

[0012] A further solution: the particle size of the ceramic particles is 25 μm-50 μm; the pore size of the limiting holes is 25 μm-50 μm.

[0013] A further solution: the thickness of the base film is 45-60 μm.

[0014] A further solution: the thickness of the additional film is 20-30 μm.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] The utility model arranges additional films on both sides of the base membrane and adds ceramic particles between the additional film and the base membrane. When the composite diaphragm is squeezed by external force, the reinforcement layer made of the outermost polyvinylidene fluoride layer is first subjected to the force. During the force transmission process, the force points of the base membrane are dispersed by a number of ceramic particles, thereby avoiding damage to the base membrane caused by concentrated force.

[0017] The ceramic particles placed between the base membrane and the additional membrane create a certain gap between the two. The ceramic particles can reduce the contact area with the base membrane during heat transfer from external heat, thereby reducing the heating efficiency of the diaphragm body. The presence of the thermal insulation layer made of ceramic fiber material further enhances the thermal insulation effect of the composite diaphragm. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural diagram of an embodiment;

[0019] Figure 2 Schematic diagram of the structure of the basement membrane in the embodiment;

[0020] Figure 3 Schematic diagram of the structure of the additional membrane in the embodiment;

[0021] In the figure: 1-base film, 11-porous polymer film, 12-transition interface film, 13-gelled microporous polymer film, 2-additional film, 21-thermal insulation layer, 211-limiting hole, 22-reinforcement layer. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are the directions or positional relationships in which the product of the present invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as a limitation on the present invention.

[0024] See also Figures 1 to 3 In this embodiment, a lithium-ion battery composite separator comprises a base film 1, with an additional film 2 covering the upper and lower surfaces of the base film 1. The additional film 2 comprises a thermal insulation layer 21, a reinforcement layer 22, and uniformly distributed ceramic particles (not shown) disposed between the thermal insulation layer 21 and the reinforcement layer 22. The reinforcement layer 22 is adhered to the base film 1. Opposite cut surfaces of the ceramic particles rest against the base film 1 and the reinforcement layer 22, respectively. The ceramic particles create a gap between the base film 1 and the additional film 2, reducing the contact surface with the base film 1 during external heat transfer and lowering the thermal efficiency of the base film 1. The thermal insulation layer 21 further enhances the thermal insulation effect.

[0025] Furthermore, the thermal insulation layer 21 is evenly distributed with an array of retaining holes 211. Ceramic particles are positioned within these retaining holes 211, and their outer peripheries are fixedly connected to the retaining holes 211, facilitating the installation of the ceramic particles and the thermal insulation layer 21. The specific method for this fixed connection is to first apply a thin layer of glue to the surface of the thermal insulation layer 21; then, evenly sprinkle the micron-sized ceramic particles onto the glue, allowing them to naturally fall into the retaining holes 211, and wait for the glue to dry and solidify, forming a fixed bond.

[0026] Furthermore, the base film 1 includes a porous polymer film 11, a transitional interface film 12 disposed on the upper and lower surfaces of the porous polymer film 11, and a gelled microporous polymer film 13 disposed outside the transitional interface film 12. The porous polymer film 11, the transitional interface film 12, and the gelled microporous polymer film 13 are tightly bonded together, and the transitional interface film 12 has the functions of protecting the negative electrode, preventing further decomposition of the electrolyte, and reducing battery self-discharge.

[0027] Furthermore, two opposite cut surfaces of the ceramic particles rest against the gelled microporous polymer membrane 13 and the reinforcement layer 22 respectively.

[0028] Furthermore, the reinforcing layer 22 is made of polyvinylidene fluoride (PVDF). The PVDF layer can enhance the chemical corrosion resistance, electrochemical stability, and thermal stability of the diaphragm, thereby preventing short circuits and safety issues within the battery. At the same time, the PVDF coating can also improve the porosity and puncture resistance of the diaphragm, enabling the diaphragm to better maintain the stability and fluidity of the electrolyte, thereby improving the overall performance of the battery. The PVDF layer also allows the diaphragm to be tightly bonded to the electrodes, reducing electrode impedance and battery polarization, thereby improving battery performance.

[0029] Furthermore, the material of the heat insulation layer 21 is ceramic fiber. Ceramic fiber has a low thermal conductivity and can effectively slow down the transfer of heat. In an environment with drastic temperature changes, ceramic fiber can maintain stable thermal insulation performance to ensure the safety of the insulated object.

[0030] Furthermore, the particle size of the ceramic particles is 25 μm-50 μm, and the aperture of the limiting hole is approximately the same as the particle size of the ceramic particles.

[0031] Furthermore, the thickness of the base film is 45-60 μm.

[0032] Furthermore, the thickness of the additional film is 20-30 μm.

[0033] When the present invention is in use, the diaphragm can be combined with the corresponding lithium-ion battery in a conventional installation method. During the operation of the battery, if the battery is subjected to pressure, the pressure first contacts the additional membrane 2, specifically, first contacts the outermost polyvinylidene fluoride reinforcement layer 22. During the force transmission process, the force is decomposed into several force points through several ceramic particles and transmitted to the base membrane 1, thereby avoiding reducing the damage of the base membrane 1 caused by excessive single-point pressure. At the same time, due to the gaps generated by the ceramic particles between the gelled microporous polymer membrane 13 and the reinforcement layer 22, the external heat transfer efficiency is reduced, and the thermal insulation effect is excellent.

[0034] Although this specification is described according to implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0035] Therefore, the above description is only a preferred embodiment of the present application and is not intended to limit the scope of implementation of the present application; that is, all equivalent modifications made according to the scope of the claims of the present application are within the scope of protection of the claims of the present application.

Claims

1. A lithium-ion battery composite diaphragm, comprising a base film (1), characterized in that: The upper and lower surfaces of the base film (1) are covered with an additional film (2); the additional film (2) comprises a heat-insulating layer (21) close to the base film (1) and a reinforcing layer (22) away from the base film (1); limiting holes (211) are evenly distributed on the heat-insulating layer (21); ceramic particles are provided in the limiting holes (211), and two opposite cut surfaces of the ceramic particles respectively abut against the base film (1) and the reinforcing layer (22).

2. The lithium-ion battery composite separator according to claim 1, characterized in that The base film (1) comprises a porous polymer film (11), a transition interface film (12) provided on the upper and lower surfaces of the porous polymer film (11), and a gelled microporous polymer film (13) provided on the outside of the transition interface film (12).

3. The lithium-ion battery composite separator according to claim 1, characterized in that The outer periphery of the ceramic particles is fixedly connected to the limiting hole (211).

4. The lithium-ion battery composite separator according to claim 1, characterized in that The limiting holes (211) are distributed in an array.

5. The lithium-ion battery composite separator according to claim 1, characterized in that The material of the reinforcement layer (22) is polyvinylidene fluoride.

6. The lithium-ion battery composite separator according to claim 1, characterized in that The material of the heat insulation layer (21) is ceramic fiber.

7. The lithium-ion battery composite separator according to claim 2, characterized in that The particle size of the ceramic particles is 25 μm-50 μm; the pore size of the limiting holes is 25 μm-50 μm.

8. The lithium-ion battery composite separator according to claim 1, characterized in that The thickness of the base film (1) is 45-60 μm.

9. The lithium-ion battery composite separator according to claim 1, characterized in that The thickness of the additional film (2) is 20-30 μm.

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