Battery cell and lithium ion battery

Abstract

The utility model discloses a kind of battery cell and lithium ion battery, battery cell includes first pole piece and second pole piece, first pole piece and second pole piece are alternately laminated along first direction;First diaphragm is located between adjacent first pole piece and second pole piece, first diaphragm includes first base film and first adhesive layer arranged in at least one side of first base film, first diaphragm and first pole piece, second pole piece form laminated structure;Second diaphragm is located in the outermost side of laminated structure in first direction, second diaphragm includes second base film and second adhesive layer, breakdown resistance layer arranged in at least one side of second base film, breakdown resistance layer is located between second base film and second adhesive layer.The first diaphragm and second diaphragm in the application synergistic effect, both improve battery cell cycle stability, and enhance the security of mechanical abuse time, effectively prolong the service life of lithium ion battery and reduce security risk.

Description

Technical Field

[0001] This utility model relates to the field of lithium-ion battery technology, and in particular to a battery cell and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries are lithium-ion batteries that contain lithium (including metallic lithium, lithium alloys, lithium ions, and lithium polymers) in their electrochemical system. In recent years, lithium-ion batteries have been widely used in digital products, electric vehicles, and energy storage systems due to their many advantages such as long cycle life, good safety performance, and fast charging and discharging.

[0003] In the current field of lithium-ion battery technology, the expansion of cells during cycling and the safety hazards under mechanical abuse conditions severely restrict the performance and lifespan of lithium-ion batteries. Traditional separators, when dealing with changes in the volume of electrode materials, suffer from insufficient adhesion, making it difficult to effectively limit the relative displacement between the electrode and the separator, leading to increased cell expansion. Under mechanical abuse conditions such as needle penetration and compression, separators frequently fail due to electrical breakdown and high-temperature shrinkage, greatly affecting the safety performance of lithium-ion batteries. Utility Model Content

[0004] The main purpose of this utility model is to propose a battery cell and a lithium-ion battery, which aims to solve the technical problems in existing lithium-ion battery technology, such as the increased cycle expansion caused by insufficient bonding performance of traditional separators, poor resistance to electrical breakdown and high-temperature shrinkage, which leads to safety hazards caused by mechanical abuse.

[0005] To achieve the above objectives, this utility model proposes a battery cell, comprising:

[0006] The first electrode and the second electrode are alternately stacked along a first direction;

[0007] A first diaphragm is located between adjacent first and second electrodes. The first diaphragm includes a first base film and a first adhesive layer disposed on at least one side of the first base film. The first diaphragm forms a laminated structure with the first electrode and the second electrode.

[0008] The second diaphragm is located on the outermost side of the laminated structure in the first direction. The second diaphragm includes a second base film and a breakdown-resistant layer and a second adhesive layer disposed on at least one side of the second base film. The breakdown-resistant layer is located between the second base film and the second adhesive layer.

[0009] In some embodiments, the second base film is provided with the puncture-resistant layer and the second adhesive layer on both sides.

[0010] In some embodiments, there are two second diaphragms, respectively disposed on both sides of the laminated structure in the first direction.

[0011] In some embodiments, the first adhesive layer is provided on both sides of the first base film.

[0012] In some embodiments, the first electrode or the second electrode located on the outermost side of the stacked structure is a positive electrode.

[0013] In some embodiments, the first adhesive layer is composed of a plurality of particles, the average particle size of which is 0.2 μm-2 μm.

[0014] In some embodiments, the thickness of the breakdown-resistant layer is 0.5 μm-2.5 μm.

[0015] In some embodiments, the material of the puncture-resistant layer is an inorganic filler and / or an organic filler; the inorganic filler includes at least one of alumina, alumina hydrate, gibbsite, silicon dioxide, magnesium oxide, magnesium hydroxide, titanium dioxide, BaTiO2, ZrO, alumina-silica composite oxide, aluminum nitride, boron nitride, organosilicon, diamond, barium sulfate, calcium fluoride, barium fluoride, talc, or montmorillonite; the organic filler is an aromatic polyamide.

[0016] In some embodiments, the material of the first adhesive layer and / or the second adhesive layer is selected from at least one of ethylene, propylene, vinylidene fluoride, acrylic acid, and acrylate.

[0017] This utility model also provides a lithium-ion battery, including a battery cell.

[0018] The battery cell provided in this application has an inner first separator that is firmly bonded to the first and second electrodes via a first adhesive layer. This effectively limits the relative displacement of the first and second electrodes caused by volume changes during charging and discharging, significantly suppressing cell expansion. The outer second separator integrates a breakdown-resistant layer and a second adhesive layer. The breakdown-resistant layer can withstand mechanical forces such as needle punctures and compression, preventing the separator from rupturing and causing a short circuit. The second adhesive layer ensures the breakdown-resistant layer is firmly attached, preventing the separator from shrinking and detaching at high temperatures, further enhancing the overall safety of the battery cell. The synergistic effect of the first and second separators in this application improves both the cycle stability of the battery cell and the safety under mechanical abuse, effectively extending the lifespan of the lithium-ion battery and reducing safety risks. Attached Figure Description

[0019] FIG. 1 This is a schematic diagram of the structure of a battery cell according to an embodiment of the present invention;

[0020] FIG. 2 This is a schematic diagram of the structure of an embodiment of the first diaphragm of this utility model;

[0021] FIG. 3This is a schematic diagram of the structure of an embodiment of the second diaphragm of this utility model.

[0022] Explanation of icon numbers:

[0023] 100 Battery cell 10 First electrode tab 20 Second electrode tab 30 First separator 31 First base film 32 First adhesive layer 40 Second separator 41 Second base film 42 Breakdown resistance layer 43 Second adhesive layer

[0024] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0025] The solutions in the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0026] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0027] It should also be noted that when a component is described as "fixed to" or "set on" another component, it can be directly on the other component or there may be an intervening component present. When a component is described as "connected to" another component, it can be directly connected to the other component or there may be an intervening component present.

[0028] Furthermore, the use of terms such as "first" and "second" in this utility model is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this utility model.

[0029] Please refer to FIGS. 1 to 3This application provides a battery cell 100, including a first electrode 10, a second electrode 20, a first separator 30, and a second separator 40. The first electrode 10 and the second electrode 20 are alternately stacked along a first direction; the first separator 30 is located between adjacent first electrodes 10 and second electrodes 20, and the first separator 30 includes a first base film 31 and a first adhesive layer 32 disposed on at least one side of the first base film 31. The first separator 30 forms a stacked structure with the first electrode 10 and the second electrode 20; the second separator 40 is located on the outermost side of the stacked structure in the first direction, and the second separator 40 includes a second base film 41 and a breakdown-resistant layer 42 and a second adhesive layer 43 disposed on at least one side of the second base film 41. The breakdown-resistant layer 42 is located between the second base film 41 and the second adhesive layer 43.

[0030] Among them, the first electrode 10 and the second electrode 20 are the core electrochemical reaction components of the battery cell 100, respectively undertaking the functions of lithium ion insertion and extraction. During charging and discharging, lithium ions migrate back and forth between the two electrodes, realizing the conversion of electrical energy and chemical energy, and providing energy output for the battery cell 100.

[0031] The first base film 31 serves as the basic support structure, possessing excellent chemical stability and ion conductivity, allowing lithium ions to pass through while physically isolating the first electrode 10 and the second electrode 20 to prevent direct contact and short circuits between the positive and negative electrodes. The first adhesive layer 32 is disposed on at least one side of the first base film 31. Through its adhesive properties, it tightly adheres to the first electrode 10 and the second electrode 20, limiting the relative displacement of the first electrode 10 and the second electrode 20 during cycling, effectively mitigating the expansion problem of the cell 100 caused by changes in the volume of the electrode materials.

[0032] The second base membrane 41 provides basic ion conduction and physical isolation functions, ensuring the normal electrochemical operation of the cell 100. The breakdown-resistant layer 42, located outside the second membrane 40, is made of high-strength, high-temperature-resistant material. When the cell 100 encounters mechanical abuse conditions such as needle puncture or compression, the breakdown-resistant layer 42 can resist external puncture, preventing electrical breakdown caused by membrane damage, while maintaining structural stability at high temperatures to avoid thermal shrinkage failure. The second adhesive layer 43, situated between the laminated structure and the breakdown-resistant layer 42, firmly connects the second membrane 40 to the outside of the laminated structure, enhancing the overall structural strength of the cell 100 and ensuring that the breakdown-resistant layer 42 effectively provides protection during mechanical abuse.

[0033] The battery cell 100 in this embodiment adopts a layered structure design. By dividing the functions of different separators, it solves the problems of expansion and mechanical abuse safety hazards existing in traditional battery cells 100. Specifically, the first separator 30 of the inner layer of the battery cell 100 provided in this application is firmly bonded to the first electrode 10 and the second electrode 20 by the first adhesive layer 32, which can effectively limit the relative displacement of the first electrode 10 and the second electrode 20 caused by volume changes during charging and discharging, and significantly suppress the expansion of the battery cell 100. The second separator 40 of the outer layer integrates the breakdown-resistant layer 42 and the second adhesive layer 43. The breakdown-resistant layer 42 can resist mechanical external forces such as needle puncture and extrusion, preventing the separator from rupturing and causing short circuits. The second adhesive layer 43 ensures that the breakdown-resistant layer 42 is firmly attached, avoiding the separator shrinkage and detachment at high temperatures, and further enhancing the overall safety of the battery cell 100. The first separator 30 and the second separator 40 in this application work together to improve the cycle stability of the battery cell 100 and enhance the safety during mechanical abuse, effectively extending the service life of lithium-ion batteries and reducing safety risks.

[0034] In some embodiments, the second base film 41 is provided with a breakdown-resistant layer 42 and a second adhesive layer 43 on both sides.

[0035] Among them, the second base film 41, as the core carrier for load bearing and ion transport, has a double-sided structure that gives it stronger resistance to bending and tearing. Under the internal stress or external mechanical pressure generated by the charging and discharging of the battery cell 100, the second base film 41 maintains its flat shape by means of the symmetrical external structure constraint, ensuring unobstructed ion channels and avoiding battery performance degradation caused by deformation of the second base film 41.

[0036] The double-sided puncture-resistant layers 42 can adopt a gradient composite design. The outer layer is a high-hardness puncture-resistant layer (such as a nano-ceramic particle reinforced coating), which can directly resist the puncture of sharp objects; the inner layer is a high-toughness impact layer (such as an elastic polymer modified layer), which absorbs impact energy and prevents crack propagation. When both sides are subjected to force simultaneously, the puncture-resistant layers 42 achieve a dual protective effect of hard blocking and soft buffering through the complementary properties of the inner and outer layer materials.

[0037] In this embodiment, the second diaphragm 40 is designed with a double-sided breakdown-resistant layer 42 and a second adhesive layer 43. By symmetrically arranging the breakdown-resistant layer 42, the battery cell 100 can simultaneously disperse stress on both sides when subjected to external force, avoiding stress concentration that could cause local damage. The double-sided second adhesive layer 43 not only strengthens the connection between the diaphragm and the internal electrode and the external shell, but also assists the breakdown-resistant layer 42 in forming a prestressed structure. This structure can actively offset some of the deformation energy during mechanical impact. At the same time, the flexible buffer of the adhesive layer can reduce the risk of interlayer separation caused by the difference in the thermal expansion coefficient of the materials in high-temperature environments, thereby achieving a synergistic improvement in safety performance and structural stability.

[0038] In some embodiments, there are two second diaphragms 40, which are respectively disposed on both sides of the laminated structure in the first direction.

[0039] In this embodiment, two second diaphragms 40 are located on both sides of the laminated structure, forming a symmetrical mechanical support and safety barrier. In cases of mechanical abuse, the two second diaphragms 40 can independently disperse external forces, preventing concentrated impact on the laminated structure. During the cycling process of the cell 100, they work together to limit electrode expansion, maintaining internal structural stability through dual-sided constraint. Compared to a single-diaphragm structure, this more evenly disperses internal stress, preventing localized deformation of the cell 100, extending its lifespan, and improving cycle stability. Furthermore, the dual-diaphragm design allows the cell 100 to maintain basic protection even if one diaphragm fails partially, significantly improving overall reliability.

[0040] It should be understood that in actual production, the materials and structure of the second diaphragm 40 on both sides can be flexibly adjusted according to different application requirements (such as using high-hardness, puncture-resistant materials for the outer layer and emphasizing flexibility for the inner layer) to achieve precise matching of protective performance.

[0041] In some embodiments, a first adhesive layer 32 is provided on both sides of the first base film 31.

[0042] During charging and discharging, the electrode material undergoes volume changes, causing relative displacement between the electrode and the separator, which in turn causes the cell 100 to expand. In this embodiment, the double-sided first adhesive layer 32 is tightly bonded to the first electrode 10 and the second electrode 20 on both sides. When the electrode material expands or contracts, the double-sided first adhesive layer 32 simultaneously provides a reverse binding force to counteract the electrode displacement trend, thereby suppressing the internal structural disorder of the cell 100 and maintaining the morphological stability and long-term performance of the cell 100.

[0043] Compared to a single-sided adhesive layer, the double-sided design provides double the fixing force, which can more accurately and evenly offset the displacement caused by changes in electrode volume, significantly reducing the expansion rate of cell 100. Furthermore, the double-sided first adhesive layer 32 increases the contact area and bonding strength between the electrode and the separator, reducing friction and wear caused by relative sliding at the interface, lowering interface impedance, and improving the charge and discharge efficiency of cell 100. Simultaneously, the stable interface structure helps suppress the shedding of active material, maintaining the capacity retention rate of cell 100 during long-term cycling.

[0044] In some embodiments, the first electrode 10 or the second electrode 20 located on the outermost side of the stacked structure is a positive electrode.

[0045] The outer positive electrode plate serves as the outer protective layer and core of the electrochemical reaction in the cell 100, performing a dual function. First, thanks to the highly stable positive electrode material (such as lithium iron phosphate or ternary materials), it directly withstands external mechanical stress, using the material's inherent hardness and toughness to buffer impacts. Second, during charging and discharging, it efficiently enables the insertion and extraction of lithium ions. Its outer position allows lithium ions to enter the electrolyte more quickly, accelerating ion conduction efficiency and improving the charging and discharging rate of the cell 100.

[0046] The inner electrode (negative electrode or another positive electrode) forms a stable stacked structure with the first separator 30, working together with the outer positive electrode to complete the electrochemical reaction. The first separator 30 acts as a physical barrier and ion conductor between the inner and outer electrodes, while the inner electrode receives lithium ions transmitted from the outer positive electrode, continuously promoting the redox reaction and ensuring that the cell 100 outputs electrical energy stably.

[0047] In this embodiment, the positive electrode is placed on the outermost side of the stacked structure. From an electrical perspective, the positive electrode, as the starting point for lithium-ion insertion and extraction, can shorten the ion transport path and optimize the electric field distribution inside the cell 100 by placing it on the outside, thus reducing the polarization effect. From a safety perspective, the positive electrode material usually has higher thermal stability and mechanical strength. Placing it on the outside can serve as the first line of defense against external mechanical impacts and thermal hazards, while avoiding direct exposure of the negative electrode lithium metal, reducing the risk of short circuits, and achieving a balance between performance and safety.

[0048] In some embodiments, the first adhesive layer 32 is composed of a plurality of particles with an average particle size of 0.2 μm-2 μm.

[0049] In this embodiment, the first adhesive layer 32 is constructed using particles with a diameter of 0.2μm-2μm. When the particles come into contact with the electrode, the smaller particles (0.2μm-1μm) can penetrate deep into the electrode pores, enhancing the mechanical interlocking force; while the larger particles (1μm-2μm) form support points on the surface of the first separator 30, optimizing the interfacial stress distribution. This graded particle size design ensures both adhesive strength and reserves channels for lithium-ion transport, achieving a balance between physical fixation and electrochemical performance.

[0050] Compared to continuous film adhesive layers, granular structures maintain high adhesive strength while exhibiting better flexibility.

[0051] In some embodiments, the thickness of the breakdown layer 42 is 0.5 μm to 2.5 μm.

[0052] In this embodiment, the 0.5μm-2.5μm thickness design of the breakdown-resistant layer 42 serves several purposes. From a mechanical protection perspective, the thinner thickness (0.5μm-1μm) ensures the material responds quickly to external impacts, rapidly dispersing stress due to its high modulus properties; while the thicker thickness (1μm-2.5μm) enhances puncture resistance through a multi-layered composite structure. From an electrochemical perspective, this thickness range maintains sufficient physical barrier properties while keeping the overall impedance of the second separator 40 at a low level, ensuring efficient lithium-ion transport and achieving a synergistic improvement in both protective performance and battery performance.

[0053] In some embodiments, the material of the puncture-resistant layer 42 is an inorganic filler and / or an organic filler; the inorganic filler includes at least one of alumina, alumina hydrate, gibbsite, silicon dioxide, magnesium oxide, magnesium hydroxide, titanium dioxide, BaTiO2, ZrO, alumina-silica composite oxide, aluminum nitride, boron nitride, organosilicon, diamond, barium sulfate, calcium fluoride, barium fluoride, talc, or montmorillonite; the organic filler is an aromatic polyamide.

[0054] Among them, inorganic fillers such as alumina and silicon oxide have high melting points and excellent electrical insulation properties, which can significantly improve the thermal stability and breakdown voltage of the second separator 40. In the event of thermal runaway in a lithium-ion battery, their high-temperature resistance can effectively prevent the separator from shrinking and short-circuiting; their high dielectric constant can disperse the electric field and reduce the risk of partial discharge. Furthermore, the polar inorganic surface can enhance the wettability of the electrolyte and optimize ion conductivity, while the nanoscale inorganic particles can improve the puncture resistance of the second separator 40 and resist electrode burrs.

[0055] Aromatic polyamides, as organic fillers, possess highly regular molecular chains and contain numerous benzene ring structures, endowing the material with extremely high mechanical strength and thermal stability. Strong intermolecular hydrogen bonds form a dense network, effectively resisting external punctures and high-temperature attack. When the thickness is controlled between 0.5 μm and 2.5 μm, the aromatic polyamide layer can achieve efficient stress dispersion due to its molecular properties while maintaining low ion transport impedance, thus achieving a balance between protective and electrochemical performance.

[0056] Compared to traditional polyolefin separator materials, aromatic polyamides have significant advantages. While polyolefin materials are lower in cost, they are prone to softening and shrinking at high temperatures and lack mechanical strength. Aromatic polyamides, on the other hand, maintain dimensional stability at high temperatures (200°C) due to strong hydrogen bonding and rigid molecular chains. Furthermore, their nanoscale porous structure facilitates rapid lithium-ion conduction, ensuring 100% cell safety while improving charge and discharge efficiency.

[0057] Inorganic and organic fillers can be used in combination to achieve complementary performance. This retains the high insulation properties of inorganic materials while incorporating the flexibility of organic materials, allowing the second diaphragm 40 to maintain good electrical properties and mechanical strength at high temperatures. Simultaneously, the composite filler can regulate the pore structure of the second diaphragm 40, optimize electrolyte retention and ion conduction, and reduce costs while ensuring performance, thus improving cost-effectiveness.

[0058] In some embodiments, the material of the first adhesive layer 32 and / or the second adhesive layer 43 is selected from at least one of ethylene, propylene, vinylidene fluoride, acrylic acid, and acrylate.

[0059] The first adhesive layer 32 and / or the second adhesive layer 43 are made of at least one of ethylene, propylene, vinylidene fluoride, acrylic acid, and acrylate, based on a precise match between their molecular structure characteristics and the interface requirements of the battery cell 100. Ethylene and propylene polymers have good flexibility and chemical stability, which can provide a buffer when the electrode material undergoes volume changes, preventing the adhesive layer from breaking; the fluorine-containing structure of vinylidene fluoride gives the material excellent chemical corrosion resistance, which can resist long-term erosion by the electrolyte and maintain interface stability; acrylic acid and acrylate substances, with their abundant polar groups (such as carboxyl groups and ester groups), form strong hydrogen bonds or chemical bonds with the electrode surface, which greatly improves the bonding strength.

[0060] This embodiment utilizes a combination of multiple materials to improve the interfacial stress distribution by leveraging the flexibility of ethylene and propylene, enhance chemical durability with the help of vinylidene fluoride, and achieve high adhesion by relying on acrylic substances. This allows the first adhesive layer 32 and the second adhesive layer 43 to effectively suppress the cyclic expansion of the cell 100, reduce interfacial impedance, and improve the long-term cycle performance and reliability of the cell 100 while ensuring a firm bond between the electrode and the separator.

[0061] This application also provides a lithium-ion battery, including the cell 100 described above. This lithium-ion battery can possess all the technical features and corresponding beneficial effects of the cell 100 described above, which will not be repeated here.

[0062] The above embodiments of this utility model are merely examples for clearly illustrating the present utility model, and are not intended to limit the implementation of the present utility model. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this utility model are still within the protection scope of this utility model.

Claims

1. A battery cell, characterized in that, include: The first electrode and the second electrode are alternately stacked along a first direction; A first diaphragm is located between adjacent first and second electrodes. The first diaphragm includes a first base film and a first adhesive layer disposed on at least one side of the first base film. The first diaphragm forms a laminated structure with the first electrode and the second electrode. The second diaphragm is located on the outermost side of the laminated structure in the first direction. The second diaphragm includes a second base film and a breakdown-resistant layer and a second adhesive layer disposed on at least one side of the second base film. The breakdown-resistant layer is located between the second base film and the second adhesive layer.

2. The battery cell according to claim 1, characterized in that, The second base film has the puncture-resistant layer and the second adhesive layer on both sides.

3. The battery cell according to claim 1, characterized in that, The second diaphragm is provided in two parts, respectively located on both sides of the laminated structure in the first direction.

4. The battery cell according to claim 1, characterized in that, The first adhesive layer is provided on both sides of the first base film.

5. The battery cell according to claim 1, characterized in that, The first or second electrode located on the outermost side of the stacked structure is a positive electrode.

6. The battery cell according to claim 1, characterized in that, The first adhesive layer is composed of multiple particles with an average particle size of 0.2 μm-2 μm.

7. The battery cell according to claim 1, characterized in that, The thickness of the puncture-resistant layer is 0.5μm-2.5μm.

8. A lithium-ion battery, characterized in that, Includes the battery cell as described in any one of claims 1 to 7.

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