Composite film, battery, and power-using device

Abstract

The application provides a composite film and a battery, wherein the battery comprises: a composite film, comprising: a lithium supplement layer; a first base film, which is arranged on one side of the lithium supplement layer and is configured to be suitable for bearing the lithium supplement layer; and a second base film, which is arranged on the side of the first base film away from the lithium supplement layer and is configured to isolate a positive electrode sheet and a negative electrode sheet. The composite film of the application comprises two base films and one lithium supplement layer, the first base film is used to bear the lithium supplement layer, the lithium supplement layer can be previously arranged on the composite film, and then the composite film is combined with the positive electrode sheet and the negative electrode sheet, so that the safety of the lithium supplement process of the battery is improved, and the problem of serious heating and poor stability when the lithium metal is directly rolled with the negative electrode sheet is avoided. Therefore, the battery made of the composite film of the embodiment can have higher coulomb efficiency, higher energy density and longer cycle life.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and more specifically, to a composite film, a battery, and an electrical device. Background Technology

[0002] In related technologies, during the fabrication of lithium batteries, lithium can be added to the negative electrode to form a pre-lithiated negative electrode, thereby improving the initial efficiency, energy density, and battery charge-discharge cycle performance of the negative electrode. In existing technologies, lithium addition to the negative electrode is typically achieved by pressing lithium powder or lithium foil with the negative electrode; however, the negative electrode material suffers from severe heat generation and poor stability during contact with lithium metal. Summary of the Invention

[0003] One objective of this application is to provide a new technology solution for composite films that can at least solve the problems of severe heat generation and poor stability during lithium replenishment at the negative electrode in the prior art.

[0004] Another object of this application is to provide a battery comprising the aforementioned composite film.

[0005] Another object of this application is to provide an electrical device including the aforementioned battery.

[0006] According to a first aspect of this application, a composite film is provided, comprising: a lithium replenishment layer; a first base film disposed on one side of the lithium replenishment layer, the first base film being configured to support the lithium replenishment layer; and a second base film disposed on the side of the first base film away from the lithium replenishment layer, the second base film being configured to isolate a positive electrode and a negative electrode.

[0007] Optionally, the air permeability of the first base film is greater than that of the second base film.

[0008] Optionally, the air permeability of the first base membrane is ≤250s / 100ml.

[0009] Optionally, the air permeability of the second base membrane is 100s / 100ml to 500s / 100ml.

[0010] Optionally, the ionic conductivity of the first base film is greater than that of the second base film.

[0011] Optionally, the ionic conductivity of the first base film is ≥6*10 -4 s / cm.

[0012] Optionally, the ionic conductivity of the second base film is 1*10⁻⁶. -4 s / cm~1*10 -2 s / cm.

[0013] Optionally, the material of the first base film includes at least one of polypropylene, polyethylene, polyester film, polyimide, polyetherimide, polyvinyl alcohol, polyacrylic acid, polyvinylidene fluoride, and polytetrafluoroethylene.

[0014] Optionally, the lithium replenishment layer satisfies at least one of the following conditions: the thickness of the lithium replenishment layer is 1 μm to 15 μm; the areal density of the lithium replenishment layer is 1 g / m³. 2 ~8g / m 2 .

[0015] Optionally, the first base film has an ablation layer on the side away from the lithium replenishment layer, and the ablation layer is configured to chemically react with lithium.

[0016] Optionally, the ablation layer satisfies at least one of the following conditions: the ablation layer is configured to undergo an intercalation reaction with lithium at 0.5V to 4V; the electronic conductivity of the ablation layer is less than 10. -7 s / cm; the thickness of the ablation layer is 0.5μm to 10μm; the areal density of the ablation layer is 1g / m³. 2 ~12g / m 2 .

[0017] Optionally, the ablation layer is made of at least one of titanium oxyfluoride, lithium titanate, lithium aluminum titanium phosphate, lithium lanthanum titanate, titanium dioxide, tungsten oxide, zinc oxide, and silicon suboxide.

[0018] Optionally, a solid electrolyte layer is provided between the first base film and the lithium replenishment layer.

[0019] Optionally, the material of the solid electrolyte layer includes at least one of lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium lanthanum zirconium oxide, lithium phosphate, and their doped products.

[0020] According to a second aspect of this application, a battery is provided, including a positive electrode, a negative electrode, and a composite film, wherein the composite film is any of the composite films described in the above embodiments.

[0021] According to a third aspect of this application, an electrical device is provided, including any of the batteries described in the above embodiments.

[0022] The composite film according to this application includes two base films and one lithium replenishment layer. The lithium replenishment layer is carried by the first base film, allowing it to be pre-set onto the composite film. The second base film serves as a conventional separator between the positive and negative electrode sheets. Further bonding the composite film with the positive and negative electrode sheets improves the safety of the battery lithium replenishment process, avoiding the problems of severe heat generation and poor stability when lithium metal is directly rolled with the negative electrode sheet. Therefore, the battery made with the composite film of this embodiment can have higher coulombic efficiency, higher energy density, and longer cycle life. Furthermore, the pre-lithiation of the composite film with the positive and negative electrode sheets in this embodiment does not require rolling, thus pre-lithiation can be completed under a sealed vacuum, solving the problems of active lithium consumption during negative electrode lithium replenishment and safety issues during storage.

[0023] Other features and advantages of this application will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the present application and, together with their description, serve to explain the principles of the present application.

[0025] Figure 1 This is a schematic diagram of the structure of a battery according to the first embodiment of this application;

[0026] Figure 2 This is a schematic diagram of the structure of a battery according to the second embodiment of this application;

[0027] Figure 3 This is a schematic diagram of the structure of a battery according to the third embodiment of this application;

[0028] Figure 4 This is a schematic diagram of the structure of a battery according to the fourth embodiment of this application;

[0029] Figure 5 This is a schematic diagram of the structure of the first diaphragm in the composite membrane according to the fourth embodiment of this application;

[0030] Figure 6 This is a schematic diagram of the structure of the second diaphragm in the composite membrane according to the fourth embodiment of this application;

[0031] Figure 7 This is a process flow diagram of the preparation of the first diaphragm according to the fourth embodiment of this application.

[0032] Figure Labels

[0033] Composite membrane 100; Lithium replenishment layer 11; Solid electrolyte layer 12; First base membrane 13; Ablation layer 21; Second base membrane 22;

[0034] Positive electrode 200;

[0035] Negative electrode 300. Detailed Implementation

[0036] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0037] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0038] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0039] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0040] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0041] The composite membrane 100 according to an embodiment of this application will now be described in detail with reference to the accompanying drawings.

[0042] like Figures 1 to 3 As shown, the composite film 100 according to an embodiment of this application includes: a first base film 13, a second base film 22, and a lithium replenishment layer 11.

[0043] Specifically, a first base film 13 is disposed on one side of the lithium replenishment layer 11, and the first base film 13 is configured to support the lithium replenishment layer 11. A second base film 22 is disposed on the side of the first base film 13 away from the lithium replenishment layer 11, and the second base film 22 is configured to isolate the positive electrode 200 and the negative electrode 300.

[0044] In other words, the composite film 100 according to the embodiments of this application mainly consists of a first base film 13, a second base film 22, and a lithium replenishment layer 11. The composite film 100 may include the lithium replenishment layer 11, the first base film 13, and the second base film 22 arranged sequentially. When the composite film 100 is combined with the positive electrode 200 and the negative electrode 300, the lithium replenishment layer 11 in the composite film 100 can be attached to the surface of the negative electrode to achieve lithium replenishment to the negative electrode.

[0045] Specifically, the lithium replenishment layer 11 can be disposed on the surface of the first base film 13. Optionally, the lithium replenishment layer 11 can be lithium foil or lithium powder. The lithium foil or lithium powder can be coated on one side of the surface of the first base film 13. The coating method can include, but is not limited to, wet coating, dry calendering, and 3D printing. For example, inert lithium powder can be uniformly coated on one side of the surface of the first base film 13 by wet coating to form the lithium replenishment layer 11 on that side surface.

[0046] A first base film 13 with a lithium replenishment layer 11 formed on its surface can be combined with a second base film 22 to form a composite film 100. Thus, the battery prepared by the composite film 100 includes a negative electrode 300, a lithium replenishment layer 11, a first base film 13, a second base film 22, and a positive electrode 200, which are stacked in sequence.

[0047] The first base film 13 can serve as a carrier to support the lithium replenishment layer 11 in the composite film 100. That is, the first base film 13 mainly plays the role of supporting the lithium replenishment layer 11. Therefore, the first base film 13 can be made of any material suitable for supporting the lithium replenishment layer 11. For example, the first base film 13 can be made of a non-insulating material.

[0048] The second base membrane 22 can serve as an insulating layer in the composite membrane 100 to isolate ions. Therefore, the second base membrane 22 can be any commonly used insulating membrane in the prior art to isolate the positive electrode 200 and the negative electrode 300.

[0049] In the battery manufacturing process, a lithium replenishment layer 11 can be formed first on the surface of the first base film 13, and then the first base film 13, the second base film 22, the positive electrode 200, and the negative electrode 300 with the lithium replenishment layer 11 formed on their surfaces can be alternately stacked to form a battery. Alternatively, the first base film 13 and the second base film 22 with the lithium replenishment layer 11 formed on their surfaces can be combined to form a composite film 100, and then the composite film 100 can be alternately stacked with the positive electrode 200 and the negative electrode 300 to form a battery. Figure 1 The battery shown.

[0050] Therefore, the composite film 100 according to this embodiment includes two base films and one lithium replenishment layer 11. The lithium replenishment layer 11 is supported by the first base film 13, allowing it to be pre-set onto the composite film 100. The second base film 22 serves to conventionally isolate the positive electrode 200 and the negative electrode 300. Combining the composite film 100 with the positive electrode 200 and the negative electrode 300 improves the safety of the battery lithium replenishment process, avoiding the problem of severe heat generation and poor stability when lithium metal is directly rolled with the negative electrode 300. Therefore, the battery made with the composite film 100 of this embodiment can have higher coulombic efficiency, higher energy density, and longer cycle life. Furthermore, the pre-lithiation of the composite film 100 with the positive electrode 200 and the negative electrode 300 in this embodiment does not require rolling; pre-lithiation can be completed under a sealed vacuum, solving the problems of active lithium consumption during the lithium replenishment process of the negative electrode 300 and safety issues during storage.

[0051] According to one embodiment of this application, the air permeability value of the first base membrane 13 is less than that of the second base membrane 22. Air permeability value refers to the ability of 100 ml of oxygen to pass through 1 inch of water at a pressure of 1.22 kPa. 2 The time taken for the membrane to be in place. The lower the permeability value, the better the membrane's permeability. Since the permeability value of the first base membrane 13 is lower than that of the second base membrane 22, the pore size of the pore structure on the first base membrane 13 is larger, which is more conducive to the migration of lithium ions, while the pore size of the pore structure on the second base membrane 22 is smaller.

[0052] In conventional technology, the lithium replenishment layer 11 is directly placed on the base film. The conventional base film is equivalent to the second base film 22 in this embodiment. Since the adhesion between the lithium replenishment layer 11 and the conventional base film is poor, it is not conducive to composite. If the two are strongly composited, the force on the conventional base film will increase, resulting in an increase in the air permeability of the conventional base film, which in turn affects the ionic conductivity of the conventional base film.

[0053] In this embodiment, since the air permeability of the first base film 13 is smaller than that of the second base film 22, that is, the second base film 22 has a lower air permeability than the traditional base film, there are more types of first base film 13 that can be selected. After the lithium replenishment layer 11 comes into contact with the negative electrode 300, lithium can be separated from the first base film 13, ensuring the air permeability of the first base film 13 and not affecting ion diffusion.

[0054] It should be noted that the air permeability values ​​of the first base film 13 and the second base film 22 can be the air permeability values ​​of the base film raw materials before preparation, i.e., the air permeability values ​​before lamination. During the preparation of the composite film 100 of this embodiment, the air permeability values ​​of the first base film 13 and the second base film 22 may increase slightly after being pressed, but they can still satisfy the requirement that the air permeability value of the first base film 13 is less than that of the second base film 22.

[0055] The air permeability value of the base membrane can be tested using either the first base membrane 13 or the second base membrane 22, with a side length of 20cm, in a Wang Yan-style air permeability tester.

[0056] According to a preferred embodiment of this application, the air permeability of the first base film 13 is ≤250s / 100ml. For example, 50s / 100ml, 100s / 100ml, 150s / 100ml, 180s / 100ml, 210s / 100ml, 250s / 100ml.

[0057] Specifically, when the air permeability of the first base film 13 is greater than 250s / 100ml, the first base film 13 can still play the role of supporting the lithium replenishment layer 11, improving the safety of the battery lithium replenishment process and making the battery have a longer cycle life. However, the air permeability of the first base film 13 will decrease, and the coulombic efficiency will be less different from that of traditional batteries.

[0058] When the air permeability of the first base film 13 is ≤250s / 100ml, the air permeability of the first base film 13 is good, which not only helps to improve the safety of the battery lithium replenishment process, but also helps to maintain the battery resistance at a low value, reduce the influence of the first base film 13 on lithium ion migration, and significantly improve the cycle life and coulombic efficiency of the battery.

[0059] In some optional embodiments of this application, the air permeability of the second base membrane 22 is 100s / 100ml to 500s / 100ml.

[0060] Specifically, when the air permeability of the second base membrane 22 is >500s / 100ml, the air permeability of the second base membrane 22 is poor, which affects ion diffusion and reduces the ionic conductivity of the second base membrane 22.

[0061] When the air permeability of the second base film 22 is <100s / 100ml, the air permeability of the second base film 22 is too good, the area of ​​the second base film 22 will decrease, and thus have an adverse effect on the performance of the battery.

[0062] When the air permeability of the second base membrane 22 is between 100s / 100ml and 500s / 100ml, the second base membrane 22 has good air permeability, which can separate the positive electrode 200 and the negative electrode 300 to prevent short circuits from occurring between the two electrodes, and can also form a channel for ion movement and migration.

[0063] In some alternative embodiments, the ionic conductivity of the first base film 13 is greater than that of the second base film 22. As a result, the first base film 13 is more conducive to the migration of lithium ions and improves the overall performance of the battery. Meanwhile, the second base film 22 can meet the requirements of separating the positive electrode 200 and the negative electrode 300.

[0064] According to other embodiments of this application, the ionic conductivity of the first base film 13 is ≥6*10⁻⁶. -4 s / cm. For example, 6*10 -4 s / cm, 7*10 -4 s / cm, 1*10 -3 s / cm, 9*10 -3 s / cm, 1*10 -2 s / cm, 1*10 -1 s / cm. It should be noted that the above ionic conductivity can be the ionic conductivity measured by the first base film 13 when it is immersed in the electrolyte.

[0065] Specifically, when the ionic conductivity of the first base film 13 is less than 6*10 -4 At a conductivity of s / cm, the first base film 13 can still function as a support for the lithium replenishment layer 11, improving the safety of the battery lithium replenishment process. When the ionic conductivity of the first base film 13 is ≥6*10 -4 At a speed of s / cm, lithium ions migrate more readily, thus improving battery performance.

[0066] In some specific embodiments, during the production process of the composite membrane 100, the first base membrane 13 can be pressed at 15 MPa for 600 seconds. After pressing, the air permeability of the first base membrane 13 is ≤250s / 100ml, and the lithium-ion conductivity after immersion in electrolyte is ≥6*10. -4 s / cm.

[0067] In some optional embodiments of this application, the ionic conductivity of the second base film 22 is 1*10⁻⁶. -4 s / cm~1*10 -2 With a density of s / cm, the second base film 22 can meet the requirements of separating the positive electrode 200 and the negative electrode 300, and the second base film 22 can be made from a wider range of materials.

[0068] In some specific embodiments of this application, the material of the first base film 13 includes at least one of polypropylene (PP), polyethylene (PE), polyester film (PET), polyimide (PI), polyetherimide (PEI), polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE).

[0069] In other words, the first base film 13 can be mainly made of one or more of the above-mentioned materials. These materials have excellent air permeability and ionic conductivity, which can facilitate the migration of lithium ions while supporting the lithium replenishment layer 11, thereby improving the overall performance of the battery.

[0070] According to some optional embodiments of this application, the thickness of the lithium replenishment layer 11 is 1 μm to 15 μm. For example, the thickness of the lithium replenishment layer 11 can be 1 μm, 2 μm, 3 μm, 5 μm, 10 μm, or 15 μm. Setting the thickness of the lithium replenishment layer 11 to 1 μm to 15 μm allows the lithium replenishment layer 11 to have sufficient thickness to compensate for the lithium source consumed in the formation of the SEI film (solid electrolyte interface film) during the first charge, thereby improving the battery's initial efficiency, energy density, and charge-discharge cycle life.

[0071] According to some other embodiments of this application, the areal density of the lithium replenishment layer 11 is 1 g / m³. 2 ~8g / m 2 For example, the areal density of the lithium replenishment layer 11 can be 1 g / m³. 2 2g / m 2 4g / m 2 6g / m 2 8g / m 2 The areal density of the lithium replenishment layer 11 is set to be ≥1 g / m³. 2 This allows for sufficient lithium replenishment of the negative electrode 300, improving the battery's initial efficiency, energy density, and charge-discharge cycle life. The areal density of the lithium replenishment layer 11 is set to ≤8 g / m². 2 This can reduce the lithium demand in the composite membrane 100 while fully replenishing lithium in the negative electrode 300, thereby reducing the production cost of the composite membrane 100.

[0072] In some specific embodiments of this application, the first base film 13 is provided with an ablation layer 21 on the side away from the lithium replenishment layer 11, and the ablation layer 21 is configured to be able to chemically react with lithium.

[0073] Specifically, the location of the ablation layer 21 may include, but is not limited to, the following situations.

[0074] Case 1: The ablation layer 21 is disposed between the first base film 13 and the second base film 22.

[0075] Case 2: The ablation layer 21 is disposed on the side of the second base film 22 away from the first base film 13.

[0076] The ablation layer 21 can be made of any material that can chemically react with lithium. Thus, after lithium metal pierces the first base film 13, it can chemically react with the ablation layer 21, thereby blocking the lithium metal by the barrier formed by the ablation layer 21 and the second base film 22. This prevents the lithium metal from passing through the barrier formed by the ablation layer 21 and the second base film 22 to reach the positive electrode 200 and cause an internal short circuit in the battery. In particular, it avoids the safety problems caused by high-capacity lithium metal or lithium alloy negative electrodes, thereby improving the safety of the battery.

[0077] In some specific embodiments, the material of the ablation layer 21 can be configured into a stable and uniform slurry, and then the slurry can be coated onto the surface of the second base film 22 by a coating method, including but not limited to gravure roller coating and spraying. The second base film 22 coated with the ablation layer 21 can be composited with the first base film 13 coated with the lithium replenishment layer 11, the positive electrode 200, and the negative electrode 300 to form a composite material. Figure 2 The battery shown.

[0078] According to some optional embodiments of this application, the ablation layer 21 is configured to undergo an intercalation reaction with lithium at 0.5V to 4V. Specifically, the intercalation reaction is a solid-phase reversible chemical reaction in which metallic lithium can reversibly insert into the ablation layer 21 at 0.5V to 4V. During this process, the structure of the material of the ablation layer 21 can remain unchanged, which is beneficial to improving the safety and stability of the battery.

[0079] According to other embodiments of this application, the electronic conductivity of the ablation layer 21 is less than 10. -7 At s / cm, this is conducive to the intercalation reaction between the ablation layer 21 and the lithium metal, effectively preventing the lithium metal from passing through the second base film 22 to reach the positive electrode 200 and causing an internal short circuit in the battery.

[0080] In some specific embodiments of this application, the ablation layer 21 is made of titanium oxyfluoride (TiOF2) or lithium titanate (Li4Ti5O). 12 It includes at least one of lithium aluminum titanium phosphate (LATP), lithium lanthanum titanate (LLTO), titanium dioxide (TiO2), tungsten oxide (WO3), zinc oxide (ZnO), and silicon suboxide (SiO).

[0081] In other words, the ablative layer 21 can be mainly made of one or more of the above-mentioned materials. These materials have low electronic conductivity and can undergo an intercalation reaction with metallic lithium at 0.5V to 4V, effectively preventing metallic lithium from passing through the second base film 22 to the positive electrode 200 and causing an internal short circuit in the battery, thus improving battery safety.

[0082] It should be noted that when the ablation layer 21 is connected to the second base film 22 by coating, one or more of the above materials can be added to an adhesive to form a slurry to be coated.

[0083] According to some optional embodiments of this application, the thickness of the ablation layer 21 is 0.5 μm to 10 μm. For example, the thickness of the ablation layer 21 can be 0.5 μm, 1 μm, 2 μm, 3 μm, 5 μm, or 10 μm.

[0084] When the thickness of the ablation layer 21 is 0.5μm to 10μm, the ablation layer 21 has sufficient thickness to block the ablation of metallic lithium, while avoiding the ablation layer 21 being too thick and affecting the energy density of the battery.

[0085] According to other embodiments of this application, the areal density of the ablation layer 21 is 1 g / m³. 2 ~12g / m 2 For example, the areal density of the ablation layer 21 can be 1 g / m³. 2 2g / m 2 3g / m 2 5g / m 2 10g / m 2 12g / m 2 .

[0086] When the areal density of the ablation layer 21 is 1 g / m 2 ~12g / m 2 At the same time, the ablation layer 21 can have sufficient density to block the ablation of metallic lithium, preventing metallic lithium from passing through the ablation layer 21 and the second base layer, and can also avoid excessive manufacturing cost of the ablation layer 21, which is conducive to reducing the production cost of the composite film 100.

[0087] In some specific embodiments of this application, a solid electrolyte layer 12 is provided between the first base film 13 and the lithium replenishment layer 11.

[0088] Specifically, the solid electrolyte layer 12 can be made of a material that can form a solid electrolyte. For example, the solid electrolyte layer 12 can be made of an inorganic solid electrolyte. The inorganic solid electrolyte can be configured into a stable and uniform slurry, and then the slurry is coated onto the surface of the first base film 13 by coating. The coating method can include, but is not limited to, gravure roller coating and spraying.

[0089] A solid electrolyte layer 12 is provided between the first base film 13 and the lithium replenishment layer 11. This can prevent the metal lithium from blocking the pores of the first base film 13 when it passes through them, thus affecting the air permeability of the first base film 13. At the same time, the solid electrolyte layer 12 in the composite film 100 can also act as a solid electrolyte interface film formed during the first charging process of the battery, which is beneficial to improving the negative electrode interface.

[0090] In some specific implementations, such as Figure 3As shown, the composite membrane 100 may include a lithium replenishment layer 11, a solid electrolyte layer 12, a first base film 13, and a second base film 22, which are stacked sequentially. During the preparation of the composite membrane 100, a solid electrolyte can first be coated onto one side of the first base film 13. After drying, a solid electrolyte layer 12 can be formed on the surface of the first base film 13. Then, metallic lithium is coated onto the side of the solid electrolyte layer 12 away from the first base film 13 to form a first separator. That is, the first separator includes the lithium replenishment layer 11, the solid electrolyte layer 12, and the first base film 13. Then, during battery fabrication, the negative electrode 300, the first separator, the second base film 22, and the positive electrode 200 are composited.

[0091] In some alternative embodiments, such as Figure 4 As shown, the composite membrane 100 may include a lithium replenishment layer 11, a solid electrolyte layer 12, a first base membrane 13, an ablation layer 21, and a second base membrane 22, which are stacked sequentially. During the preparation of the composite membrane 100, a solid electrolyte is first coated onto one side of the first base membrane 13. After drying, a solid electrolyte layer 12 is formed on the surface of the first base membrane 13. Then, metallic lithium is coated onto the side of the solid electrolyte layer 12 away from the first base membrane 13 to form a first separator. The material constituting the ablation layer 21 is coated onto one side of the second base membrane 22 to form a second separator. Then, during battery fabrication, the negative electrode 300, the first separator, the second separator, and the positive electrode 200 are composited.

[0092] In some other alternative embodiments, the first separator and the second separator can be combined to form a composite membrane 100, and then the composite membrane 100 can be combined with the positive electrode 200 and the negative electrode 300 to form a battery.

[0093] According to some optional embodiments of this application, the material of the solid electrolyte layer 12 includes at least one of lithium aluminum titanium phosphate (LATP), lithium lanthanum titanate (LLTO), lithium lanthanum zirconium oxide (LLZO), lithium phosphate (Li3PO4), and their doped products.

[0094] In other words, the solid electrolyte layer 12 can be mainly made of one or more of the above-mentioned materials, or made of products doped with one or more of the above-mentioned materials. The above-mentioned materials do not require a desolvation process, have a relatively high ion transference number, and have an ionic conductivity much greater than that of the solid electrolyte interface film rich in Li2O and Li2CO3 components naturally formed during the first charge of the battery, which is beneficial to improving the battery's initial efficiency and energy density.

[0095] It should be noted that when the solid electrolyte layer 12 is connected to the first base film 13 by coating, one or more of the above materials can be added to a binder to form a slurry to be coated.

[0096] This application also provides a battery comprising a positive electrode 200, a negative electrode 300, and a composite film 100. The composite film 100 is the composite film 100 according to any of the above embodiments. A lithium supplement layer 11 is located between the negative electrode 300 and the first base film 13.

[0097] Since the composite film 100 according to the embodiments of the present invention has the above-mentioned technical effects, the battery according to the embodiments of the present application also has the corresponding technical effects, namely, it is beneficial to improve the safety of the battery lithium replenishment process, avoid the problem of severe heat generation and poor stability when lithium metal is directly rolled with the negative electrode 300, and enable the battery to have higher coulombic efficiency, higher energy density and longer cycle life.

[0098] In some optional embodiments, the positive electrode 200 includes a positive current collector and a positive active material, which can be a conventional positive active material in the art. For example, the positive active material may include at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, nickel-cobalt-aluminum ternary materials (NCA) and nickel-cobalt-manganese ternary materials (NMC), lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, and lithium manganese silicate.

[0099] The negative electrode 300 may include a negative electrode current collector and a negative electrode active material, which may be a conventional negative electrode active material. For example, the negative electrode active material may include at least one of silicon-carbon, silicon-oxygen, tin, graphite, and hard carbon.

[0100] The battery and its composite film 100 of this application will be described in detail below with reference to specific embodiments and comparative examples.

[0101] Comparative Example 1

[0102] S1. Fabrication of the positive electrode

[0103] 960g of positive electrode active material ternary 622 (96%), 30g of binder PVDF (3%), 5g of acetylene black (0.5%), and 5g of conductive agent carbon fiber (HV) (0.5%) were added to 2000g of solvent NMP (nitromethylpyrrolidone) and then stirred in a vacuum mixer to form a stable and uniform positive electrode slurry.

[0104] The positive electrode slurry was uniformly and intermittently coated on both sides of an aluminum foil (aluminum foil size: width 160mm, thickness 16μm) using a slit coating equipment; then dried at 393K, and pressed into a sheet by a roller press to obtain positive electrode sheet 200.

[0105] Cut the positive electrode sheet 200 into a rectangular sheet with dimensions of 48mm*56mm, and spot weld the tabs in the width direction.

[0106] S2, Fabrication of the negative electrode

[0107] Add 1000g of silica powder to 2000g of water, then add 50g of polyacrylic acid (PAA) and stir vigorously to form a uniform and stable negative electrode slurry.

[0108] The negative electrode slurry was uniformly and intermittently coated on both sides of a copper foil (copper foil size: width 160mm, thickness 8μm) using a slit coating equipment; then dried at 393K, and after being pressed by a roller press, a negative electrode sheet 300 was obtained.

[0109] S3. The negative electrode 300 is placed in a drying room with a dew point of -50°C. The negative electrode 300 is rolled with a 6μm lithium foil (attached to a 100μm thick PET release film) to form a lithium-replenishing negative electrode. After rolling, the PET release film is peeled off from the surface of the negative electrode, and the negative electrode and the lithium-replenishing layer 11 are wound together.

[0110] S4, Battery Manufacturing

[0111] A battery is fabricated by alternately stacking the positive electrode 200 obtained in step S1, the lithium-filled negative electrode obtained in step S3, and the first base film 13. The positive electrode 200 and the lithium-filled negative electrode are alternately separated by a separator composed of the first base film 13 and the second base film 22, resulting in a dry cell. The first base film 13 is made of PET nonwoven fabric, with dimensions of 1200 mm width and 6 μm thickness. The second base film 22 is made of PP film, with dimensions of 1200 mm width and 8 μm thickness.

[0112] The prepared dry cell was placed in an aluminum-plastic film outer packaging, electrolyte was injected, and then vacuum sealed. It was then placed at 60℃ for 48 hours, pressure-formed at 45℃, re-encapsulated, vented, and capacity-tested to obtain a lithium battery. The first base film 13 had a permeability of 240s / 100ml and an ionic conductivity of 9.9*10⁻⁶. -3 S / cm; the second base membrane 22 has an air permeability of 260s / 100ml and an ionic conductivity of 1.09*10. -3 S / cm.

[0113] Comparative Example 2

[0114] The positive electrode 200 is obtained by using the same steps as Comparative Example 1, S1, and the negative electrode 300 is obtained by using steps S2.

[0115] Inert lithium powder is uniformly sprayed onto the surface of the first base film 13 using an electrostatic powder spraying device. After rolling, a first base film 13 containing a lithium replenishment layer 11 is obtained, wherein the lithium replenishment layer 11 has a thickness of 6μm. The first base film 13 is made of PE material and has a thickness of 12μm.

[0116] A battery is prepared by alternately stacking a positive electrode 200, a first base film 13 containing a lithium replenishment layer 11, and a negative electrode 300, wherein the positive electrode 200 and the negative electrode 300 are alternately isolated by the first base film 13 to obtain a dry cell.

[0117] The prepared dry cell was placed in an aluminum-plastic film outer packaging, electrolyte was injected, and then vacuum sealed. It was then placed at 60℃ for 48 hours, pressure-formed at 45℃, re-encapsulated, vented, and capacity-tested to obtain a lithium battery. The first base film 13 had a permeability of 240s / 100ml and an ionic conductivity of 9.9*10⁻⁶. -3 S / cm.

[0118] Comparative Example 3

[0119] The positive electrode 200 is obtained by using the same steps as Comparative Example 1, S1, and the negative electrode 300 is obtained by using steps S2.

[0120] Inert lithium powder is uniformly sprayed onto the surface of the second base film 22 using an electrostatic powder spraying device. After rolling, a second base film 22 containing a lithium replenishment layer 11 is obtained, wherein the thickness of the lithium replenishment layer 11 is 6μm. The second base film 22 is made of PP material and has a thickness of 12μm.

[0121] A battery is prepared by alternately stacking a positive electrode 200, a second base film 22 containing a lithium replenishment layer 11, and a negative electrode 300, wherein the positive electrode 200 and the negative electrode 300 are alternately isolated by the second base film 22 to obtain a dry cell.

[0122] The prepared dry cell was placed in an aluminum-plastic film outer packaging, electrolyte was injected, and then vacuum sealed. It was then placed at 60℃ for 48 hours, pressure-formed at 45℃, re-encapsulated, vented, and capacity-tested to obtain a lithium battery. The second base film 22 has a permeability of 260s / 100ml and an ionic conductivity of 1.58*10⁻⁶. -3 S / cm.

[0123] Example 1

[0124] The positive electrode 200 is obtained by using the same steps as Comparative Example 1, S1, and the negative electrode 300 is obtained by using steps S2.

[0125] The first base film 13 is placed in a drying room, and inert lithium powder is evenly sprayed onto the surface of the first base film 13 using an electrostatic powder spraying device. After rolling, a first base film 13 containing a lithium replenishment layer 11 is obtained, wherein the lithium replenishment layer 11 has a thickness of 4μm. The first base film 13 is made of PE material and has a thickness of 6μm.

[0126] A battery is fabricated by alternately stacking a positive electrode 200, a first base film 13 containing a lithium replenishment layer 11, a second base film 22, and a negative electrode 300, using a stacking method. The first base film 13 and the second base film 22 containing the lithium replenishment layer 11 are formed as shown in the figure. Figure 1 The composite film 100 shown alternately separates the positive electrode 200 and the negative electrode 300 to obtain a dry cell. The second base film 22 has a thickness of 4 μm and is made of PP. During battery fabrication, the lithium replenishment layer 11 on the surface of the first base film 13 is close to the negative electrode 300.

[0127] The prepared dry cell is placed in an aluminum-plastic film outer packaging, electrolyte is injected, and then it is vacuum sealed. After being placed at 60°C for 48 hours, it is pressurized at 45°C for formation, secondary packaging, degassing, and capacity testing to obtain a lithium battery.

[0128] The first base membrane 13 has an air permeability of 240s / 100ml and an ionic conductivity of 9.9*10. -3 S / cm; the second base membrane 22 has an air permeability of 260s / 100ml and an ionic conductivity of 9.9*10. -4 S / cm.

[0129] Example 2

[0130] The positive electrode 200 is obtained by using the same steps as Comparative Example 1, S1, and the negative electrode 300 is obtained by using steps S2.

[0131] The first base film 13 is placed in a drying room, and inert lithium powder is evenly sprayed onto the surface of the first base film 13 using an electrostatic powder spraying device. After rolling, a first base film 13 containing a lithium replenishment layer 11 is obtained, wherein the lithium replenishment layer 11 has a thickness of 4μm. The first base film 13 is made of PE material and has a thickness of 9μm.

[0132] 5000g of titanium oxyfluoride powder was added to 20000g of water, followed by 500g of polyacrylic acid (PAA) and vigorous stirring to form a uniform and stable titanium oxyfluoride slurry. The titanium oxyfluoride slurry was then uniformly coated onto a single surface of the second base film 22 using a gravure roller coating machine, with a coating thickness of 3μm. The film was then dried at 383K to obtain the second base film 22 coated with the ablation layer 21. The second base film 22 is made of PP material and has a thickness of 4μm.

[0133] A battery is fabricated by alternately stacking a positive electrode 200, a first base film 13 containing a lithium replenishment layer 11, a second base film 22 coated with a dissolution layer 21, and a negative electrode 300. The first base film 13 containing the lithium replenishment layer 11 and the second base film 22 coated with the dissolution layer 21 are formed as follows: Figure 3The composite film 100 shown is used to alternately isolate the positive electrode 200 and the negative electrode 300 to obtain a dry cell. During the battery manufacturing process, the lithium replenishment layer 11 on the surface of the first base film 13 is close to the negative electrode 300, and the ablation layer 21 on the surface of the second base film 22 is close to the first base film 13.

[0134] The prepared dry cell was placed in an aluminum-plastic film outer packaging, electrolyte was injected, and then vacuum sealed. It was then placed at 60℃ for 48 hours, pressure-formed at 45℃, re-encapsulated, vented, and capacity-tested to obtain a lithium battery. The first base film 13 had a permeability of 220s / 100ml and an ionic conductivity of 9.1*10⁻⁶. -3 S / cm; the second base membrane 22 has an air permeability of 260s / 100ml and an ionic conductivity of 9.9*10. -4 S / cm.

[0135] Example 3

[0136] The positive electrode 200 is obtained by using the same steps as Comparative Example 1, S1, and the negative electrode 300 is obtained by using steps S2.

[0137] The first base film 13 is placed in a drying room, and inert lithium powder is evenly sprayed onto the surface of the first base film 13 using an electrostatic powder spraying device. After rolling, a first base film 13 containing a lithium replenishment layer 11 is obtained, wherein the lithium replenishment layer 11 has a thickness of 4μm. The first base film 13 is made of PI nonwoven fabric with a thickness of 8μm.

[0138] 5000g of titanium oxyfluoride powder was added to 20000g of water, followed by 500g of polyacrylic acid (PAA) and vigorous stirring to form a uniform and stable titanium oxyfluoride slurry. The titanium oxyfluoride slurry was then uniformly coated onto a single surface of the second base film 22 using a gravure roller coating machine, with a coating thickness of 2μm. The film was then dried at 383K to obtain the second base film 22 coated with the ablation layer 21. The second base film 22 is made of PP material and has a thickness of 4μm.

[0139] A battery is fabricated by alternately stacking a positive electrode 200, a first base film 13 containing a lithium replenishment layer 11, a second base film 22 coated with an ablation layer 21, and a negative electrode 300. The first base film 13 containing the lithium replenishment layer 11 and the second base film 22 coated with the ablation layer 21 form a composite film 100, which alternately isolates the positive electrode 200 and the negative electrode 300, resulting in a dry cell. During battery fabrication, the lithium replenishment layer 11 on the surface of the first base film 13 is close to the negative electrode 300, and the ablation layer 21 on the surface of the second base film 22 is close to the positive electrode 200.

[0140] The prepared dry cell was placed in an aluminum-plastic film outer packaging, electrolyte was injected, and then vacuum sealed. It was then placed at 60℃ for 48 hours, pressure-formed at 45℃, re-encapsulated, vented, and capacity-tested to obtain a lithium battery. The first base film 13 had a permeability of 180s / 100ml and an ionic conductivity of 10.6*10⁻⁶. -3 S / cm; the second base membrane 22 has an air permeability of 260s / 100ml and an ionic conductivity of 9.9*10. -4 S / cm.

[0141] Example 4

[0142] The positive electrode 200 is obtained by using the same steps as Comparative Example 1, S1, and the negative electrode 300 is obtained by using steps S2.

[0143] The first base film 13 is placed in a drying room, and inert lithium powder is evenly sprayed onto the surface of the first base film 13 using an electrostatic powder spraying device. After rolling, a first base film 13 containing a lithium replenishment layer 11 is obtained, wherein the lithium replenishment layer 11 has a thickness of 4μm. The first base film 13 is made of PEI (polyetherimide) material and has a thickness of 10μm.

[0144] 5000g of titanium oxyfluoride powder was added to 20000g of water, followed by 500g of polyacrylic acid (PAA) and vigorous stirring to form a uniform and stable titanium oxyfluoride slurry. The titanium oxyfluoride slurry was then uniformly coated onto a single surface of the second base film 22 using a gravure roller coating machine, with a coating thickness of 2μm. The film was then dried at 383K to obtain the second base film 22 coated with the ablation layer 21. The second base film 22 is made of PP material and has a thickness of 4μm.

[0145] A battery is fabricated by alternately stacking a positive electrode 200, a first base film 13 containing a lithium replenishment layer 11, a second base film 22 coated with an ablation layer 21, and a negative electrode 300. The first base film 13 containing the lithium replenishment layer 11 and the second base film 22 coated with the ablation layer 21 form a composite film 100, which alternately isolates the positive electrode 200 and the negative electrode 300, resulting in a dry cell. During battery fabrication, the lithium replenishment layer 11 on the surface of the first base film 13 is close to the negative electrode 300, and the ablation layer 21 on the surface of the second base film 22 is close to the first base film 13.

[0146] The prepared dry cell was placed in an aluminum-plastic film outer packaging, electrolyte was injected, and then vacuum sealed. It was then placed at 60℃ for 48 hours, pressure-formed at 45℃, re-encapsulated, vented, and capacity-tested to obtain a lithium battery. The first base film 13 had a permeability of 150s / 100ml and an ionic conductivity of 9.4*10⁻⁶. -2 S / cm; the second base membrane 22 has an air permeability of 260s / 100ml and an ionic conductivity of 9.9*10. -4 S / cm.

[0147] Example 5

[0148] The positive electrode 200 is obtained by using the same steps as Comparative Example 1, S1, and the negative electrode 300 is obtained by using steps S2.

[0149] 5000g of lithium aluminum titanium phosphate powder was added to 15000g of water, followed by 200g of polyacrylic acid (PAA), and vigorously stirred to form a uniform and stable solid electrolyte slurry. The solid electrolyte slurry was then uniformly coated onto a single side of a first base film 13 using a gravure roller coating machine. The first base film 13 was made of PET material with a thickness of 6μm, and the coating layer thickness was 2μm. The film was then dried at 383K to obtain the first base film 13 coated with the solid electrolyte.

[0150] The first base film 13 coated with solid electrolyte is placed in a drying room, and inert lithium powder is uniformly sprayed onto the surface of the first base film 13 using an electrostatic powder spraying device. After rolling, the first base film 13 containing a lithium replenishment layer 11 is obtained, wherein the thickness of the lithium replenishment layer 11 is 6μm.

[0151] A battery is fabricated by alternately stacking a positive electrode 200, a first base film 13 containing a lithium replenishment layer 11 and a solid electrolyte layer 12, and a second base film 22 with a negative electrode 300, using a stacking method. The first base film 13 and the second base film 22 containing the lithium replenishment layer 11 and the solid electrolyte layer 12 are formed as shown in the figure. Figure 2 The composite membrane 100 shown is used to alternately separate the positive electrode 200 and the negative electrode 300, thus obtaining a dry cell. The first base film 13 has a thickness of 4 μm and is made of PP. During the battery fabrication process, the lithium replenishment layer 11 on the surface of the first base film 13 is close to the negative electrode 300.

[0152] The prepared dry cell was placed in an aluminum-plastic film outer packaging, electrolyte was injected, and then vacuum sealed. It was then placed at 60℃ for 48 hours, pressure-formed at 45℃, re-encapsulated, vented, and capacity-balanced to obtain a lithium battery. The first base film 13 had a permeability of 130s / 100ml and an ionic conductivity of 10.2*10⁻⁶. -3 S / cm; the second base membrane 22 has an air permeability of 260s / 100ml and an ionic conductivity of 9.9*10. -4 S / cm.

[0153] Example 6

[0154] The positive electrode 200 is obtained by using the same steps as Comparative Example 1, S1, and the negative electrode 300 is obtained by using steps S2.

[0155] like Figure 7As shown, 5000g of lithium aluminum titanium phosphate powder was added to 15000g of water, followed by 200g of polyacrylic acid (PAA), and vigorously stirred to form a uniform and stable solid electrolyte slurry. The solid electrolyte slurry was then uniformly coated onto a single side of a first base film 13 using a gravure roller coating machine. The first base film 13 was made of PET material with a thickness of 6μm, and the coating layer thickness was 2μm. The film was then dried at 383K to obtain the first base film 13 coated with the solid electrolyte; this first base film 13 is SP1.

[0156] The first base film 13 coated with solid electrolyte is placed in a drying room, and inert lithium powder is uniformly sprayed onto the surface of the first base film 13 coated with solid electrolyte using an electrostatic powder spraying device. After rolling, a first base film 13 containing a lithium replenishment layer 11 is obtained. The first base film 13 is SP2, wherein the thickness of the lithium replenishment layer 11 is 6μm.

[0157] 5000g of titanium oxyfluoride powder was added to 20000g of water, followed by 500g of polyacrylic acid (PAA) and vigorous stirring to form a homogeneous and stable titanium oxyfluoride slurry. The titanium oxyfluoride slurry was then uniformly coated onto a single surface of the second base film 22 using a gravure roller coating machine, with a coating thickness of 3μm. The film was then dried at 383K to obtain the second base film 22 coated with the ablation layer 21. This second base film 22 is made of TP1. The second base film 22 is made of PP material and has a thickness of 8μm.

[0158] A battery is fabricated by alternately stacking a positive electrode 200, a first base film 13 containing a lithium replenishment layer 11 and a solid electrolyte layer 12, a second base film 22 coated with an ablation layer 21, and a negative electrode 300. The lithium replenishment layer 11, the solid electrolyte layer 12, the first base film 13, the ablation layer 21, and the second base film 22 are formed as follows: Figure 4 The composite membrane 100 shown is used to alternately separate the positive electrode 200 and the negative electrode 300, thus obtaining a dry cell. The first base film 13 has a thickness of 4 μm and is made of PP. During the battery fabrication process, the lithium replenishment layer 11 on the surface of the first base film 13 is close to the negative electrode 300.

[0159] The prepared dry cell was placed in an aluminum-plastic film outer packaging, electrolyte was injected, and then vacuum sealed. It was then placed at 60℃ for 48 hours, pressure-formed at 45℃, re-encapsulated, vented, and capacity-tested to obtain a lithium battery. The first base film 13 had a permeability of 100s / 100ml and an ionic conductivity of 10.2*10⁻⁶. -2 S / cm; the second base membrane 22 has an air permeability of 260s / 100ml and an ionic conductivity of 9.9*10. -4 S / cm.

[0160] Example 7

[0161] The positive electrode 200 is obtained by using the same steps as Comparative Example 1, S1, and the negative electrode 300 is obtained by using steps S2.

[0162] The first base film 13 is placed in a drying room, and inert lithium powder is evenly sprayed onto the surface of the first base film 13 using an electrostatic powder spraying device. After rolling, a first base film 13 containing a lithium replenishment layer 11 is obtained, wherein the lithium replenishment layer 11 has a thickness of 4μm. The first base film 13 is made of PE material, with a thickness of 12μm, and is a high-porosity membrane.

[0163] A battery is fabricated by alternately stacking a positive electrode 200, a first base film 13 containing a lithium replenishment layer 11, a second base film 22, and a negative electrode 300, using a stacking method. The first base film 13 and the second base film 22 containing the lithium replenishment layer 11 are formed as shown in the figure. Figure 1 The composite membrane 100 shown is used to alternately separate the positive electrode 200 and the negative electrode 300, resulting in a dry cell. The first base membrane 13 has a thickness of 12 μm, is made of PE, and is a low-porosity separator. During battery fabrication, the lithium replenishment layer 11 on the surface of the first base membrane 13 is close to the negative electrode 300.

[0164] The prepared dry cell was placed in an aluminum-plastic film outer packaging, electrolyte was injected, and then vacuum sealed. It was then placed at 60℃ for 48 hours, pressure-formed at 45℃, re-encapsulated, vented, and capacity-balanced to obtain a lithium battery. The first base film 13 had a permeability of 280s / 100ml and an ionic conductivity of 8.8*10⁻⁶. -3 S / cm; the second base membrane 22 has an air permeability of 260s / 100ml and an ionic conductivity of 9.9*10. -4 S / cm.

[0165] Example 8

[0166] The positive electrode 200 is obtained by using the same steps as Comparative Example 1, S1, and the negative electrode 300 is obtained by using steps S2.

[0167] The first base film 13 is placed in a drying room, and inert lithium powder is evenly sprayed onto the surface of the first base film 13 using an electrostatic powder spraying device. After rolling, a first base film 13 containing a lithium replenishment layer 11 is obtained, wherein the lithium replenishment layer 11 has a thickness of 4μm. The first base film 13 is made of PE material and has a thickness of 12μm.

[0168] A battery is fabricated by alternately stacking a positive electrode 200, a first base film 13 containing a lithium replenishment layer 11, a second base film 22, and a negative electrode 300, using a stacking method. The first base film 13 and the second base film 22 containing the lithium replenishment layer 11 are formed as shown in the figure. Figure 1The composite membrane 100 shown is used to alternately separate the positive electrode 200 and the negative electrode 300, thus obtaining a dry cell. The first base film 13 has a thickness of 12 μm and is made of PE. During the battery fabrication process, the lithium replenishment layer 11 on the surface of the first base film 13 is close to the negative electrode 300.

[0169] The prepared dry cell was placed in an aluminum-plastic film outer packaging, electrolyte was injected, and then vacuum sealed. It was then placed at 60℃ for 48 hours, pressure-formed at 45℃, re-encapsulated, vented, and capacity-tested to obtain a lithium battery. The first base film 13 had a permeability of 250s / 100ml and an ionic conductivity of 7.0*10⁻⁶. -4 S / cm; the second base membrane 22 has an air permeability of 250s / 100ml and an ionic conductivity of 5.5*10. -4 S / cm.

[0170] For ease of comparison, the material composition and structure of the composite membrane 100 in the batteries of Comparative Examples 1 to 3 and Examples 1 to 8 are listed in Table 1 below. The air permeability and ionic conductivity of the first base membrane 13 and the second base membrane 22 for preparing each composite membrane 100 are listed in Table 2 below.

[0171] Table 1 Material composition and structure of composite membranes

[0172]

[0173] Table 2 shows the performance of the first base film 13 and the second base film 22 used to prepare the composite film 100.

[0174]

[0175] The batteries of Comparative Examples 1 to 3 and Examples 1 to 8 were tested below.

[0176] Five batteries from each of the comparative examples and embodiments were taken and subjected to coulombic efficiency and charge-discharge cycle tests at 0.2C using a LAND CT 2001C secondary battery performance testing device at 25±1℃. The steps are as follows:

[0177] Let it sit for 10 minutes;

[0178] Constant voltage charging until 4.2V / 0.05C cutoff;

[0179] Let it sit for 10 minutes;

[0180] One cycle is completed by constant current discharge to 3.0V.

[0181] The ratio of the first discharge capacity to the first charge capacity is the initial coulombic efficiency. Repeat the above steps. During the cycle, the cycle ends when the battery capacity falls below 80% of the initial discharge capacity. The number of cycles is the battery's cycle life, and the average value of each group is taken. After the cycle life is completed, test the battery dimensions and calculate the battery expansion rate by comparing them with the dimensions before cycling. The test results are shown in Table 3 below.

[0182] Table 3 Performance Comparison

[0183] label Loop count Capacity retention Coulomb efficiency Comparative Example 1 252 80％ 99.93％ Comparative Example 2 736 80％ 99.95％ Comparative Example 3 426 80％ 99.91％ Example 1 1765 80％ 99.96％ Example 2 2033 80％ 99.98％ Example 3 2176 80％ 99.98％ Example 4 1987 80％ 99.97％ Example 5 1839 80％ 99.97％ Example 6 2250 80％ 99.98％ Example 7 1400 80％ 99.95％ Example 8 1670 80％ 99.96％

[0184] As shown in Table 2, Comparative Example 1 uses a conventional rolling process to roll lithium metal and the negative electrode 300 together. Although a first base film 13 and a second base film 22 are provided between the positive electrode 200 and the negative electrode 300, the cycle life and coulombic efficiency of the battery are both at a low level. Comparative Examples 2 and 3 coat lithium metal onto the first base film 13 and the second base film 22 respectively, with only one base film between each group of positive electrode 200 and negative electrode 300. In this case, the cycle life and coulombic efficiency of the battery are still at a low level.

[0185] In Example 1, lithium metal is coated onto a first base film 13, and two base films are disposed between the positive electrode 200 and the negative electrode 300. The first base film 13 carries the lithium metal, and the two base films are then composited with the positive electrode 200 and the negative electrode 300. The battery achieves 1765 cycles, which is a limited improvement compared to Comparative Examples 1 and 2. Furthermore, the coulombic efficiency of 99.96% in this example is superior to any of the comparative examples. Therefore, the composite film 100 composed of the lithium replenishment layer 11 and two base films in this embodiment can significantly improve the coulombic efficiency and cycle life of the battery.

[0186] In Examples 2 to 4, the composite membrane 100 comprises a lithium replenishment layer 11, a first base membrane 13, an ablation layer 21, and a second base membrane 22. In Example 2, the ablation layer 21 is located between the first base membrane 13 and the second base membrane 22. In Examples 3 and 4, the ablation layer 21 is located on the side of the second base membrane 22 furthest from the first base membrane 13. As can be seen from Table 2, after adding the ablation layer 21 to the composite membrane 100, the cycle life and coulombic efficiency of the battery are both greater than those of the battery in Example 1. Therefore, adding the ablation layer 21 to the composite membrane 100 is beneficial for further improving the coulombic efficiency and cycle life of the battery.

[0187] In Example 5, the composite membrane 100 consists of a lithium replenishment layer 11, a solid electrolyte layer 12, a first base membrane 13, and a second base membrane 22. As shown in Table 2, after adding the solid electrolyte layer 12 to the composite membrane 100, the battery cycle life increased from 1765 cycles in Example 1 to 1839 cycles, and the coulombic efficiency also increased from 99.96% to 99.97%. Therefore, adding the solid electrolyte layer 12 to the composite membrane 100 is beneficial for further improving the battery's coulombic efficiency and cycle life.

[0188] In Example 6, the composite membrane 100 consists of a lithium replenishment layer 11, a solid electrolyte layer 12, a first base membrane 13, an ablation layer 21, and a second base membrane 22. As shown in Table 2, the battery of Example 6 has the highest cycle life of all examples, at 2250 cycles, and the highest coulombic efficiency, at 99.98%. Therefore, simultaneously adding the solid electrolyte layer 12 and the ablation layer 21 to the composite membrane 100 can further improve the battery's coulombic efficiency and cycle life.

[0189] In Example 7, the permeability of the first base membrane 13 is 280 s / 100 ml, which is higher than 250 s / 100 ml, and the permeability of the first base membrane 13 is greater than that of the second base membrane 22. The corresponding battery cycle life is 1400, and the coulombic efficiency is 99.95%. Compared with the three comparative examples, Example 7 shows a significantly better cycle life. Although the coulombic efficiency is not improved compared to Comparative Example 2, it can be seen that the composite membrane 100 in Example 7 still helps to improve the battery cycle life. Comparing Example 7 with Examples 1 to 6, it can be seen that using a first base membrane 13 with a permeability of less than 250 s / 100 ml is beneficial for improving the battery coulombic efficiency.

[0190] In Example 8, two base films of the same material and thickness were used, so that the air permeability of the first base film 13 and the second base film 22 were equal, both being 250s / 100ml. The corresponding battery cycle count was 1670, which is a significant improvement compared to the three comparative examples. Its coulombic efficiency was 99.96%, which is greater than any of the comparative examples, but the improvement was small. Compared with Examples 2 to 6, it can be seen that when the air permeability of the first base film 13 is greater than that of the second base film 22, the coulombic efficiency of the battery can be improved more significantly.

[0191] It should be noted that, according to experiments, the material and thickness of the first base film 13 and the second base film 22 have little impact on the coulombic efficiency and cycle life of the battery.

[0192] In summary, the composite film 100 according to the embodiments of the present invention includes at least two base films and one lithium replenishment layer 11. By using the first base film 13 to support the lithium replenishment layer 11, the lithium replenishment layer 11 can be pre-set on the composite film 100. Then, the composite film 100 is combined with the positive electrode 200 and the negative electrode 300, which helps to improve the safety of the battery lithium replenishment process and avoids the problem of severe heat generation and poor stability when lithium metal is directly rolled with the negative electrode 300. Therefore, the battery made of the composite film 100 of this embodiment can have higher coulombic efficiency, higher energy density and longer cycle life.

[0193] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. A composite membrane, characterized in that, include: Lithium replenishment layer; A first base film is disposed on one side of the lithium replenishment layer, and the first base film is configured to support the lithium replenishment layer. The second base film is disposed on the side of the first base film away from the lithium replenishment layer, and the second base film is configured to isolate the positive electrode and the negative electrode; the air permeability of the first base film is less than that of the second base film.

2. The composite membrane according to claim 1, characterized in that, The air permeability of the first base membrane is ≤250s / 100ml.

3. The composite membrane according to claim 1, characterized in that, The air permeability of the second base membrane is 100s / 100ml to 500s / 100ml.

4. The composite membrane according to claim 1, characterized in that, The ionic conductivity of the first base film is greater than that of the second base film.

5. The composite membrane according to claim 1, characterized in that, The ionic conductivity of the first base film is ≥6*10 -4 s / cm.

6. The composite membrane according to claim 1, characterized in that, The ionic conductivity of the second base film is 1*10 -4 s / cm~1*10 -2 s / cm.

7. The composite membrane according to claim 1, characterized in that, The material of the first base film includes at least one of polypropylene, polyethylene, polyester film, polyimide, polyetherimide, polyvinyl alcohol, polyacrylic acid, polyvinylidene fluoride, and polytetrafluoroethylene.

8. The composite membrane according to claim 1, characterized in that, The lithium replenishment layer satisfies at least one of the following conditions: The thickness of the lithium replenishment layer is 1μm to 15μm; The areal density of the lithium replenishment layer is 1 g / m³. 2 ~8g / m 2 .

9. The composite membrane according to claim 1, characterized in that, The first base film has an ablation layer on the side away from the lithium replenishment layer, and the ablation layer is configured to chemically react with lithium.

10. The composite membrane according to claim 9, characterized in that, The ablation layer satisfies at least one of the following conditions: The ablation layer is configured to undergo an intercalation reaction with lithium at 0.5V to 4V; The electronic conductivity of the ablation layer is less than 10. -7 s / cm; The thickness of the ablation layer is 0.5 μm to 10 μm; The areal density of the ablation layer is 1 g / m³. 2 ~12g / m 2 .

11. The composite membrane according to claim 9, characterized in that, The ablation layer is made of at least one of the following materials: titanium oxyfluoride, lithium titanate, lithium aluminum titanium phosphate, lithium lanthanum titanate, titanium dioxide, tungsten oxide, zinc oxide, and silicon suboxide.

12. The composite membrane according to any one of claims 1-11, characterized in that, A solid electrolyte layer is provided between the first base film and the lithium replenishment layer.

13. The composite membrane according to claim 12, characterized in that, The solid electrolyte layer is made of at least one of lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium lanthanum zirconium oxide, lithium phosphate, and their doped products.

14. A battery, characterized in that, It includes a positive electrode, a negative electrode, and a composite film, wherein the composite film is the composite film according to any one of claims 1-13, and the lithium replenishment layer is located between the negative electrode and the first base film.

15. An electrical appliance, characterized in that, Includes the battery as described in claim 14.

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