Battery diaphragm and high-capacity battery
By introducing a reasonable thickness ratio and material design between the porous layer and the base film in the battery separator, the problem of poor electrolyte wetting was solved, the wettability of the thick electrode and the battery performance were improved, and the expansion force buffer during cycling was provided, resulting in a significant improvement in battery performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-06
- Publication Date
- 2026-04-03
AI Technical Summary
In existing technologies, as electrode thickness increases, the problem of poor electrolyte wetting becomes serious, which leads to obstructed ion and electron transport, reduced electronic conductivity and ionic conductivity, and affects battery performance.
A battery separator design is adopted, including a base membrane and a porous layer disposed on one or both sides of the base membrane. A thick electrode is provided on the side of the porous layer away from the base membrane. The thickness ratio between the porous layer and the base membrane is between 0.2 and 0.5. The pore size is larger than that of the base membrane. The porous layer is made of materials such as nano-alumina, forming a dedicated electrolyte channel to improve wettability and electrolyte retention.
It improves the wettability of thick electrodes and the electrical performance of the battery, increases the expansion force buffer space of the battery during cycling, and significantly improves the battery performance.
Smart Images
Figure CN224082630U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of battery technology, and in particular to a battery separator and a high-capacity battery. Background Technology
[0002] In related technologies, to improve the energy density of lithium-ion batteries, thick electrode technology can be used, that is, increasing the coating density to increase the capacity of a single cell, thereby improving the energy density of the individual cell and enhancing product competitiveness. However, as the electrode becomes thicker, the problem of poor electrolyte wetting becomes more prominent, hindering the transport of ions and electrons, reducing electronic and ionic conductivity, and seriously affecting the battery's electrical performance. Utility Model Content
[0003] To address the shortcomings of existing technologies, this application provides a battery separator and a high-capacity battery, which can solve the technical problem of poor electrolyte wetting in thick electrode technology, and at the same time provide a certain buffer space for the expansion force of the battery during cycling, thereby greatly improving battery performance.
[0004] In a first aspect, this application provides a battery separator, which includes a base membrane and a porous layer disposed on one or both sides of the base membrane, wherein a thick electrode is disposed on the side of the porous layer away from the base membrane.
[0005] Furthermore, in the battery separator provided in this application, the thickness between the porous layer and the base film satisfies: b = xa; where 0 ≤ x ≤ 1, a is the thickness of the porous layer, and b is the thickness of the base film.
[0006] Furthermore, in the battery separator provided in this application, x satisfies: 0.2≤x≤0.5.
[0007] Furthermore, in the battery separator provided in this application, the pore size of the porous layer is larger than the pore size of the base film.
[0008] Furthermore, in the battery separator provided in this application, both the positive and negative electrodes on both sides of the base film are thick electrodes, and the coating surface density ρ of the positive electrode is... m1 The coating surface density ρ of the negative electrode m2 The following conditions must be met: Where N is the ratio of positive electrode capacity to negative electrode capacity per unit area, A is the specific capacity of positive electrode active material, B is the specific capacity of negative electrode active material, w1 is the mass percentage of positive electrode active material at the positive electrode, and w2 is the mass percentage of negative electrode active material at the negative electrode.
[0009] Furthermore, in the battery separator provided in this application, a porous layer is provided on one side of the base film, and the coating surface density ρ of the positive electrode is... m1 Satisfy: ρ m1 ≤230g / m 2 .
[0010] Furthermore, in the battery separator provided in this application, porous layers are provided on both sides of the base film, and the coating surface density ρ of the positive electrode is... m1 Satisfying: 230g / m 2 ≤ρ m1 ≤320g / m 2 .
[0011] Furthermore, in the battery separator provided in this application, N satisfies: 0 <N<1。
[0012] Furthermore, in the battery separator provided in this application, an electrolyte is provided between the battery separator and the thick electrode; or / and,
[0013] Porous layers include one or more of the following: porous layers made of nano-alumina, porous layers made of boehmite, porous layers made of polyvinylidene fluoride, porous layers made of polytetrafluoroethylene, porous layers made of polyimide, porous layers made of polyacrylic acid, porous layers made of polyethylene, and porous layers made of polypropylene.
[0014] Secondly, this application also provides a high-capacity battery, which includes a thick electrode and a battery separator provided in the first aspect. The thick electrode is disposed on both sides of the battery separator, and an electrolyte is disposed between the thick electrode and the battery separator.
[0015] The battery separator provided in this application includes a base membrane and a porous layer disposed on one or both sides of the base membrane. A thick electrode is provided on the side of the porous layer away from the base membrane, thereby creating a dedicated channel for the electrolyte and increasing the electrolyte retention performance of the battery separator. This improves the wettability of the thick electrode, thereby enhancing the electrical performance of the battery and solving the technical problem of poor electrolyte wetting. In addition, the porous layer can increase the electrolyte retention of the battery and also provide a certain buffer space for the expansion force of the battery during cycling, thereby greatly improving the battery performance. Attached Figure Description
[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0017] Figure 1 This is a schematic diagram of the first structure of the battery separator provided in an embodiment of this application;
[0018] Figure 2 This is a schematic diagram of the second structure of the battery separator provided in an embodiment of this application;
[0019] Figure 3An interface diagram of a battery cell without a porous layer being converted into a fully charged negative electrode sheet, provided in an embodiment of this application;
[0020] Figure 4 An interface diagram of a cell with a porous layer forming a fully charged negative electrode sheet, provided in an embodiment of this application;
[0021] Figure 5 A cell cycle trend diagram provided for an embodiment of this application. Detailed Implementation
[0022] 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 some embodiments of this application, not all 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.
[0023] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.
[0024] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.
[0025] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.
[0026] Furthermore, in this application, unless otherwise explicitly specified or limited in the embodiments, the terms "installation," "connection," "joining," and "fixing" appearing in the embodiments should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral part; it can also be a mechanical connection, an electrical connection, etc. Of course, it can also be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication between two components, or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific implementation.
[0027] Thick electrodes are a widely used design strategy in lithium-ion batteries, referring to electrodes with significant thickness within the battery. The aim is to increase the battery's energy density by increasing the amount of active material in the electrode. A major advantage of thick electrode design is the ability to reduce the use of inactive materials, thereby increasing battery energy density and reducing costs.
[0028] However, as the electrode thickness increases, the transport paths for lithium ions and electrons become longer, leading to a decrease in the rate of ion diffusion and electron conduction within the electrode, which in turn affects the rate performance and cycle life of the battery.
[0029] To address this, this application provides a battery separator and a battery. The battery separator includes a base membrane and a porous layer disposed on one or both sides of the base membrane. A thick electrode is disposed on the side of the porous layer away from the base membrane, thereby creating a dedicated channel for the electrolyte and increasing the electrolyte retention performance of the battery separator. This improves the wettability of the thick electrode, thereby enhancing the electrical performance of the battery and solving the technical problem of poor electrolyte wetting. In addition, the porous layer can increase the electrolyte retention of the battery and also provide a certain buffer space for the expansion force of the battery during cycling, thereby greatly improving the battery performance.
[0030] Please see Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of the first structure of the battery separator provided in an embodiment of this application; Figure 2 This is a schematic diagram of the second structure of the battery separator provided in an embodiment of this application.
[0031] like Figure 1 and Figure 2 As shown, this application provides a battery separator, which includes a base film 110 and a porous layer 120 disposed on one or both sides of the base film 110, wherein a thick electrode is disposed on the side of the porous layer 120 away from the base film 110.
[0032] In this embodiment, the porous layer 120 is similar to a sponge structure. It can be disposed on one side of the base membrane 110 or on both sides of the base membrane 110. The porous layer 120 has good affinity with the electrolyte. At the same time, the porous layer 120 has capillary action to provide a dedicated channel for the electrolyte between the battery separator and the thick electrode, thereby increasing the electrolyte retention performance of the battery separator, which in turn improves the wettability of the thick electrode, improves the ion and electron transport performance, avoids the decrease in the conductivity of electrons and ions, and avoids the reduction in the electrical performance of the battery.
[0033] The base membrane 110 possesses excellent mechanical properties and chemical stability, and can be a microporous film made of polyolefin materials, such as polyethylene (PE) and polypropylene (PP). Simultaneously, the main function of the base membrane 110 is to act as a flexible support, fixing and loading ceramic powder particles and other functional materials.
[0034] The thickness of the base film 110 is generally between 3 μm and 50 μm, with a porosity of 30% to 60% and an average pore size typically between 0.01 μm and 10 μm. Furthermore, the performance characteristics of the base film 110 can be controlled through a wet biaxial stretching process to meet the needs of different applications. In addition, the base film 110 can be improved through coating techniques to enhance its thermal stability, resistance to organic solvents, and electrolyte wettability.
[0035] The battery separator provided in this application includes a base membrane 110 and a porous layer 120 disposed on one or both sides of the base membrane 110. A thick electrode is provided on the side of the porous layer 120 away from the base membrane 110, which can create a dedicated channel for the electrolyte, increase the electrolyte retention performance of the battery separator, thereby improving the wettability of the thick electrode and thus improving the electrical performance of the battery. This solves the technical problem of poor electrolyte wetting. In addition, the porous layer 120 can increase the electrolyte retention of the battery and also provide a certain buffer space for the expansion force of the battery during cycling, thereby greatly improving the battery performance.
[0036] In some embodiments, the thickness between the porous layer 120 and the base film 110 satisfies: b = xa; where 0 ≤ x ≤ 1, a is the thickness of the porous layer 120, and b is the thickness of the base film 110.
[0037] In this embodiment, the thickness between the porous layer 120 and the base film 110 satisfies: b = xa, that is, the thickness of the porous layer 120 must be less than the thickness of the base film 110. A thicker porous layer 120 can easily cause the battery's load characteristics to decrease and its energy density to drop.
[0038] Furthermore, in some embodiments, x satisfies: 0.2≤x≤0.5.
[0039] In this embodiment, under the premise of ensuring that the energy density of the battery is not reduced and improving the wettability of the thick electrode, the thickness relationship between the porous layer 120 and the base film 110 needs to satisfy 0.2≤x≤0.5, that is, the ratio between the thickness of the porous layer 120 and the base film 110 needs to be between 0.2 and 0.5.
[0040] In some embodiments, the pore size of the porous layer 120 is larger than the pore size of the base film 110.
[0041] Specifically, in order to enable the porous layer 120 to have capillary action and increase the liquid retention of the battery, the pore size of the porous layer 120 is larger than the pore size of the base film 110, thereby increasing the liquid retention performance of the battery separator, thereby improving the wettability of the thick electrode and thus improving the electrical performance of the battery.
[0042] In some embodiments, both the positive and negative electrodes on both sides of the base film are thick electrodes, and the coating surface density ρ of the positive electrode is... m1 The coating surface density ρ of the negative electrode m2 The following conditions must be met: Where N is the ratio of positive electrode capacity to negative electrode capacity per unit area, A is the specific capacity of positive electrode active material, B is the specific capacity of negative electrode active material, w1 is the mass percentage of positive electrode active material at the positive electrode, and w2 is the mass percentage of negative electrode active material at the negative electrode.
[0043] In this embodiment, the positive electrode capacity per unit area can be obtained by multiplying the coating surface density of the positive electrode, the mass ratio of the positive electrode active material, and the specific capacity of the positive electrode active material. Similarly, the negative electrode capacity per unit area can be obtained by multiplying the coating surface density of the negative electrode, the mass ratio of the negative electrode active material, and the specific capacity of the negative electrode active material. Here, N can be a constant that satisfies 0 < N < N. <N<1。
[0044] In some embodiments, a porous layer 120 is provided on one side of the base film 110, and the coating surface density ρ of the positive electrode is... m1 Satisfy: ρ m1 ≤230g / m 2 .
[0045] In this embodiment, the porous layer 120 is disposed on one side of the base film 110. Both the positive and negative electrodes on both sides of the base film 110 are thick electrodes. The porous layer 120 can be located on the side of the base film 110 closer to the negative electrode to ensure the wettability of the thick electrode.
[0046] It should be noted that when the coating surface density of the positive electrode is less than 230 g / m², 2 In this case, the porous layer 120 can also be located on the side of the base film 110 close to the positive electrode, which can also achieve the effect of ensuring the wettability of the thick electrode.
[0047] In some embodiments, porous layers 120 are provided on both sides of the base film 110, and the coating surface density ρ of the positive electrode is... m1 Satisfying: 230g / m 2 ≤ρ m1 ≤320g / m 2 .
[0048] In this embodiment, when the coating surface density ρ of the positive electrode m1 Meets 230g / m 2≤ρ m1 ≤320g / m 2 In this case, porous layers 120 need to be set on both sides of the base film 110 in order to improve the wettability of the thick electrode and thus improve the electrical performance of the battery.
[0049] It should be noted that the thick electrode mentioned in this application can be formed by coating both sides of the battery electrode.
[0050] In some embodiments, the porous layers 120 on both sides of the base film 110 are provided with thick electrodes.
[0051] In this embodiment, while the base film 110 has porous layers 120 on both sides, the porous layers 120 on both sides are provided with thick electrodes on the side away from the base film 110. That is, the positive and negative electrodes on both sides of the battery separator are thick electrodes, which can improve the wettability of the thick electrodes and increase the energy density of the battery, thereby improving the electrical performance of the battery.
[0052] It should be noted that when the coating surface density ρ of the positive electrode m1 Greater than 320g / m 2 At that time, simply setting porous layers 120 on both sides of the base film 110 could not solve the technical problem of poor electrolyte wetting in thick electrode technology.
[0053] Specifically, when the coating surface density ρ of the positive electrode m1 Satisfying ρ m1 ≤230g / m 2 At this time, a porous layer 120 can be formed on the side of the base film 110 near the negative electrode; when the coating surface density ρ of the positive electrode is... m1 Meets 230g / m 2 ≤ρ m1 ≤320g / m 2 At that time, porous layers 120 need to be provided on both sides of the base membrane 110.
[0054] In some embodiments, the porous layer 120 includes one or more of the following: a porous layer made of nano-alumina, a porous layer made of boehmite, a porous layer made of polyvinylidene fluoride, a porous layer made of polytetrafluoroethylene, a porous layer made of polyimide, a porous layer made of polyacrylic acid, a porous layer made of polyethylene, and a porous layer made of polypropylene.
[0055] In this embodiment, the porous layer 120 can be made of one or more of the following materials: nano-alumina, boehmite, polyvinylidene fluoride, polytetrafluoroethylene, polyimide, polyacrylic acid, polyethylene, polypropylene, etc., thereby forming a sponge-like porous layer 120. This ensures the affinity between the porous layer 120 and the electrolyte and provides a dedicated channel for the electrolyte between the battery separator and the thick electrode, thereby increasing the electrolyte retention performance of the battery separator. This, in turn, improves the wettability of the thick electrode, enhances the ion and electron transport performance, avoids the decrease in electron and ion conductivity, and prevents the reduction in battery electrical performance.
[0056] In some embodiments, this application also provides a high-capacity battery, which includes a thick electrode and a battery separator provided in this application. The thick electrode is disposed on both sides of the battery separator, and an electrolyte is disposed between the thick electrode and the battery separator.
[0057] In this embodiment, the high-capacity battery can be a thick-electrode battery, with thick electrodes respectively disposed on both sides of the battery separator. An electrolyte is disposed between the thick electrodes and the battery separator. The electrolyte can be composed of a solvent, lithium salt, and additives. The electrolyte plays a role in transporting lithium ions in the battery, ensuring that the battery can efficiently store and release energy. Lithium-ion battery electrolytes typically use high-purity organic solvents, which have good solubility and ion conductivity, effectively supporting lithium-ion transport. Organic solvents include carbonate compounds, such as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC).
[0058] Lithium salts are a key component of electrolytes, and commonly used lithium salts include lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), and lithium tetrafluoroborate (LiBF4). Among them, lithium hexafluorophosphate (LiPF6) is the most commonly used lithium salt due to its high conductivity, electrochemical stability, and low internal resistance, making it an irreplaceable electrolyte salt in lithium-ion batteries.
[0059] To improve electrolyte performance, functional additives are typically added, such as film-forming additives (e.g., vinylene carbonate, VC) and flame-retardant additives. These additives can improve the electrochemical stability of the electrolyte, enhance battery safety, and extend cycle life.
[0060] The beneficial effects of this application will be further illustrated below with reference to the embodiments.
[0061] Comparative Example 1:
[0062] Cell 1 can be composed of a positive electrode, a negative electrode, an electrolyte, and a battery separator. The battery separator uses a base film 110 + ordinary coated separator, without any other special structures. It is manufactured using thick electrode technology (the coating density of the positive electrode is 300 g / m²). 2Meanwhile, the nominal capacity of cell 1 is 350 amp-hours.
[0063] Example 1:
[0064] Cell 2 can be composed of a positive electrode, a negative electrode, an electrolyte, and a battery separator. The battery separator adopts a "sponge-like" porous layer 120, which can be composed of boehmite and water-based adhesive. The "sponge-like" porous layer 120 is located on both sides of the base film 110, and it is prepared according to thick electrode technology (the coating surface density of the positive electrode is 300 g / m²). 2 The nominal capacity of cell 2 is 350 amp-hours.
[0065] Test Example 1:
[0066] Cells 1 and 2 have identical positive and negative electrodes, electrolytes, and the same total separator thickness. Their fully charged interface can be found by referring to... Figure 3 and Figure 4 , Figure 3 This is a diagram showing the interface of a fully charged negative electrode for a cell 1 without a porous layer 120. Figure 4 The interface diagram of a cell 2 with a porous layer 120 being converted into a fully charged negative electrode is shown.
[0067] from Figure 3 and Figure 4 As can be seen from the data, due to poor electrolyte wetting, black spots appeared in the middle of the fully charged negative electrode interface after cell 1 was formed, while the fully charged negative electrode interface of cell 2 was good after formation.
[0068] Test Example 2:
[0069] Table 1
[0070] Serial Number Number of cycles Expansion force (kgf) Capacity retention Cell 1 1000 1800 89.3％ Cell 2 1000 430 92.5％
[0071] Cell 1 and cell 2 are each subjected to 1000 charge-discharge cycles, such as... Figure 5 As shown in Table 1, after 1000 charge-discharge cycles, the expansion force of cell 1 is 1800 kgf, and the cycle capacity retention rate is 89.3%; after 1000 charge-discharge cycles, the expansion force of cell 2, which uses a "sponge-like" porous layer 120 diaphragm, is 430 kgf, and the cycle capacity retention rate is 92.5%.
[0072] Meanwhile, the capacity of cell 1 and cell 2 is 350 Ah. Under all operating conditions throughout the entire life cycle, cell 1 has an expansion force ≤6500 kgf, and cell 2 has an expansion force ≤3500 kgf. Therefore, it can be fully demonstrated that the "sponge-like" porous layer 120 separator can effectively improve the performance of batteries with thick electrodes and provide a certain buffering effect on the expansion force during cycling.
[0073] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A battery separator, characterized by, The battery separator comprises a base film and a porous layer arranged on one side or both sides of the base film, wherein the porous layer arranged on the side away from the base film is provided with a thick electrode; The pore size of the porous layer is larger than that of the base film, and the porous layer has a sponge structure and has capillary action to provide a dedicated channel for electrolyte between the battery separator and the thick electrode; The positive electrode and the negative electrode on both sides of the base film are both the thick electrode.
2. The battery separator of claim 1, wherein, The thickness between the porous layer and the base film satisfies: b=xa; wherein 0≤x≤1, a is the thickness of the porous layer, and b is the thickness of the base film.
3. The battery separator of claim 2, wherein, x satisfies: 0.2≤x≤0.
5.
4. The battery separator of claim 1, wherein, The coating surface density p of the positive electrode m1 The coating surface density p of the negative electrode m2 satisfies: wherein N is the ratio of the positive electrode capacity to the negative electrode capacity per unit area, A is the gram capacity of the positive electrode active material, B is the gram capacity of the negative electrode active material, w1 is the mass proportion of the positive electrode active material at the positive electrode, and w2 is the mass proportion of the negative electrode active material at the negative electrode.
5. The battery separator of claim 4, wherein, The porous layer is provided on one side of the base film, and the coating surface density p of the positive electrode m1 satisfies: p m1 ≤ 230 g / m 2 .
6. The battery separator of claim 4, wherein, The porous layer is provided on both sides of the base film, and the coating surface density p of the positive electrode m1 satisfies: 230 g / m 2 ≤ p m1 ≤ 320 g / m 2 .
7. The battery separator of claim 4, wherein, N satisfies: 0<N<1.
8. The battery separator of any one of claims 1-7, wherein, The battery separator and the thick electrode are provided with electrolyte; or / and, The porous layer comprises one or more of a porous layer made of nano-aluminum oxide, a porous layer made of boehmite, a porous layer made of polyvinylidene fluoride, a porous layer made of polytetrafluoroethylene, a porous layer made of polyimide, a porous layer made of polyacrylic acid, a porous layer made of polyethylene, and a porous layer made of polypropylene.
9. A high capacity battery characterized by, The battery separator comprises a thick electrode and the battery separator according to any one of claims 1-8, wherein the thick electrode is arranged on both sides of the battery separator, and the thick electrode and the battery separator are provided with electrolyte.