Battery cell, battery and electric device

Abstract

The application relates to an electric core, a battery and an electric device, and relates to the technical field of power batteries. The electric core comprises a positive pole piece, a negative pole piece and a diaphragm. The positive pole piece and the negative pole piece are laminated and wound to form a winding core structure. The diaphragm is arranged between the positive pole piece and the negative pole piece and is wound with the positive pole piece and the negative pole piece to form the winding core structure. The diaphragm comprises a base film and a coating layer, the coating layer comprises a first coating layer and a second coating layer, the first coating layer is coated on the middle region of the base film along a first direction, the second coating layer is coated on the two end regions of the base film along the first direction, and the porosity of the first coating layer is greater than that of the second coating layer. The electric core provided by the application can improve the wetting speed of the middle position of the electric core, improve the problem of insufficient wetting of the middle position of the electric core, and further solve the problems of lithium precipitation and shortened cycle life caused by insufficient wetting of the middle position of the electric core.

Description

Technical Field

[0001] This application relates to the field of power battery technology, specifically to a battery cell, a battery, and an electrical device. Background Technology

[0002] As the application of power batteries becomes more widespread, the performance requirements for them are also increasing. In particular, in fields such as new energy vehicles, the demand for battery capacity is rising due to the increasing range requirements of vehicles and the increasing weight of vehicles such as trucks.

[0003] In existing technologies, increasing battery capacity is typically achieved by increasing the size of the battery and the cell. However, as the cell size increases, the problem of insufficient electrolyte wetting in the middle of the cell becomes increasingly prominent. After electrolyte injection, due to the obstruction of structures such as the separator, the amount of electrolyte penetrating closer to the center of the cell is less. This results in a significant difference in the wetting rate and degree between the center and the periphery of the cell, leading to increased internal side reactions, lithium plating, and shortened cycle life during cell use, severely impacting cell quality.

[0004] Therefore, there is an urgent need to provide a cell structure that can improve the wetting speed in the middle of the cell, improve the problem of insufficient wetting in the middle of the cell, and thus solve the problems of lithium plating and shortened cycle life caused by insufficient wetting in the middle of the cell. Utility Model Content

[0005] The purpose of this application is to provide a battery cell, battery, and electrical device that can improve the wetting speed in the middle of the battery cell, improve the problem of insufficient wetting in the middle of the battery cell, and thus solve the problems of lithium plating and shortened cycle life caused by insufficient wetting in the middle of the battery cell.

[0006] To achieve the above objectives, in a first aspect, this application provides a battery cell comprising a positive electrode, a negative electrode, and a separator. The positive and negative electrode sheets are stacked and wound to form a wound core structure. The separator is disposed between the positive and negative electrode sheets and is wound along with the positive and negative electrode sheets to form the wound core structure. The separator comprises a base film and a coating layer. The coating layer comprises a first coating layer and a second coating layer. The first coating layer is applied to the middle region of the base film along a first direction, and the second coating layer is applied to both ends of the base film along the first direction. The porosity of the first coating layer is greater than the porosity of the second coating layer.

[0007] Based on the embodiments described above, when the battery cell is used, the entire core structure needs to be immersed in the electrolyte. During the charging and discharging process of the battery cell, lithium electrons move between the positive and negative electrode plates using the electrolyte as a medium to form a current circuit. In the battery cell manufacturing process, the positive electrode plate, separator, and negative electrode plate need to be stacked sequentially and then formed into a core structure by winding. At this time, along the radial direction of the core structure, the closer to the center of the core, the more difficult it is for the electrolyte to penetrate, resulting in a large difference in the degree of wetting between the center and the ends of the battery cell, affecting the capacity and service life of the battery cell.

[0008] In this application, a coating is applied to the diaphragm, specifically divided into a first coating layer and a second coating layer. The first coating layer is located in the middle region of the base film along a first direction, which corresponds to the direction perpendicular to the winding direction of the core, i.e., the axial direction of the cylindrical or elliptical cylindrical structure formed by winding. The high porosity of the first coating layer creates a transmission channel in the middle region of the core structure, allowing the electrolyte to pass through quickly. This rapidly delivers the electrolyte to the middle region of the core structure, increasing the wetting rate and mitigating the problem of significant differences in wetting between the middle and edge regions of the core structure.

[0009] Meanwhile, at both ends of the diaphragm along the first direction, since the winding itself is located at both ends of the core structure, the electrolyte can quickly penetrate into this area. Therefore, a second coating layer with lower porosity and lower cost compared to the first coating layer is applied to this area. By using differentiated coating, wetting efficiency at all locations of the core structure can be guaranteed while reducing overall cost.

[0010] In summary, this application utilizes a coating layer on the base film to create a transport channel in the middle region of the core structure, leveraging the high porosity of the first coating layer. This channel allows for rapid electrolyte passage, improving the wetting efficiency in the middle region and mitigating the significant difference in wetting levels between the middle and edge regions. Simultaneously, a second coating layer with lower porosity is applied at both ends. This differentiated approach ensures efficient wetting at all locations within the core structure while reducing overall cost.

[0011] In some embodiments, a coating is formed on at least one side of the base film along the thickness direction.

[0012] Based on the above embodiments of this application, by setting a coating on the base film, particularly a first coating layer in the middle region of the base film, the high porosity of the first coating layer allows the electrolyte to pass through quickly, thereby improving the electrolyte wetting degree in the middle region of the core structure. In actual production, the coating can be set on both sides of the base film thickness direction. In this case, the overall thickness of the coating in the core structure is relatively large, resulting in better electrolyte flow within the core structure and facilitating wetting of the middle region. Alternatively, if the wetting rate requirements are met, the coating can be set on only one side of the base film thickness direction, which reduces production costs compared to setting coatings on both sides of the base film.

[0013] In some embodiments, second coating layers are symmetrically arranged on both sides of the first coating layer along the first direction.

[0014] Based on the above embodiments of this application, by symmetrically setting the second coating layers on both sides of the first coating layer, the conductivity of each region to the electrolyte is more balanced, thereby making the wetting degree of each position more balanced and improving problems such as lithium plating caused by the large difference in the wetting degree of each position of the core structure.

[0015] In some embodiments, along the first direction, the width ratio of the second coating layer coated at both ends of the base film to the width ratio of the first coating layer coated in the middle region of the base film is 1:2:1.

[0016] Based on the embodiments described above, the aforementioned limitations ensure that the second coating layers on both sides of the first coating layer are symmetrical, thereby making the wetting rate of each region more balanced. Furthermore, they guarantee the area ratio of the first coating layer, ensuring an improvement in the overall wetting rate of the core structure.

[0017] In some embodiments, the thickness H1 of the first coating layer is consistent with the thickness H2 of the second coating layer.

[0018] Based on the embodiments described above, by setting the thickness of the first coating layer and the second coating layer to be the same, the thickness of the separator composed of the coating and the base film is kept consistent at all locations. This facilitates the winding process of the core structure and avoids performance differences within the battery cell caused by variations in separator thickness, thus preventing any impact on the battery cell's charging and discharging efficiency and other parameters.

[0019] In some embodiments, the thickness H1 of the first coating layer is set to 3μm≤H1≤5μm.

[0020] Based on the embodiments described above, the thickness of the first coating layer is specifically limited. When the thickness of the first coating layer and the thickness of the second coating layer are set to be the same, the thickness of the second coating layer is also limited. This avoids the problems of the first coating layer being too thick, which could affect the overall energy density of the core structure, or the first coating layer being too thin, which could result in a small increase in the wetting rate in the middle region of the core structure. In other words, by limiting the thickness of the first coating layer to a suitable range, it ensures an increase in the wetting rate in the middle region of the core structure while avoiding affecting the energy density of the battery cell.

[0021] In some embodiments, the base film material is any one of polypropylene, polyethylene, and polypropylene / polyethylene composite materials.

[0022] Based on the above embodiments of this application, the material of the base film is specifically limited, and the good mechanical strength and chemical stability of the above material are used to achieve isolation between the positive electrode and the negative electrode, so as to avoid short circuit while allowing lithium ions to pass freely.

[0023] According to a second aspect of this application, a battery is provided, the battery including a casing and the aforementioned battery cell. A receiving cavity is formed inside the casing, and a winding structure is disposed within the receiving cavity.

[0024] Based on the above embodiments of this application, the battery provided by this application includes the aforementioned battery cell. Through the above configuration, by forming a coating on the base film, the high porosity of the first coating layer creates a transport channel in the middle region of the core structure, allowing the electrolyte to pass through quickly. This improves the wetting efficiency in the middle region and alleviates the problem of significant differences in wetting levels between the middle and edge regions. Simultaneously, a second coating layer with lower porosity is provided at both ends. This differentiated configuration ensures wetting efficiency at all locations within the core structure, preventing increased side reactions and lithium plating during battery use, extending the battery's cycle life, and reducing overall cost.

[0025] In some embodiments, the battery further includes two tabs, which are respectively connected to a positive electrode and a negative electrode.

[0026] Based on the above embodiments of this application, the tabs are connected to the positive electrode and the negative electrode respectively, and then connected to the positive terminal and the negative terminal of the battery respectively, thereby realizing the connection and conduction between the core structure and the outside, and realizing the input and output of the battery.

[0027] According to a third aspect of this application, an electrical device is provided, comprising a device body and the aforementioned battery. The device body has an internal power supply chamber, and the battery is disposed within the power supply chamber.

[0028] Based on the above embodiments of this application, the electrical device provided by this application includes the above-mentioned battery, and therefore also has the above-mentioned beneficial effects. To avoid repetition, it will not be described again here.

[0029] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0030] The accompanying drawings are provided to further illustrate the present application and form part of the specification. They are used together with the following detailed description to explain the present application, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the structure of the battery cell provided in the embodiments of this application.

[0031] Figure 2 This is a cross-sectional schematic diagram of the single-layer wound core structure of the battery cell provided in the embodiments of this application.

[0032] Figure 3 This is a schematic diagram of the production and processing flow of the diaphragm provided in the embodiments of this application.

[0033] Explanation of reference numerals in the attached figures 1. Positive electrode sheet; 2. Negative electrode sheet; 3. Core structure; 4. Separator; 41. Base film; 42. First coating layer; 43. Second coating layer. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, 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, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0036] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0037] 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 further defined and explained in subsequent figures.

[0038] In the description of this application, it should be noted that, unless otherwise stated, the terms "inner," "outer," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0039] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "setup" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0040] In existing technologies, increasing battery capacity is typically achieved by increasing the size of the battery and the cell. However, as the cell size increases, the problem of insufficient electrolyte wetting in the middle of the cell becomes increasingly prominent. After electrolyte injection, due to the obstruction of structures such as the separator, the amount of electrolyte penetrating closer to the center of the cell is less. This results in a significant difference in the wetting rate and degree between the center and the periphery of the cell, leading to increased internal side reactions, lithium plating, and shortened cycle life during cell use, severely impacting cell quality.

[0041] Therefore, there is an urgent need to provide a cell structure that can improve the wetting speed in the middle of the cell, improve the problem of insufficient wetting in the middle of the cell, and thus solve the problems of lithium plating and shortened cycle life caused by insufficient wetting in the middle of the cell.

[0042] To address the aforementioned problems in the prior art, embodiments of this application provide a battery cell. (Reference) Figure 1 and Figure 2As shown, the battery cell includes a positive electrode 1, a negative electrode 2, and a separator 4. The positive electrode 1 and the negative electrode 2 are stacked and wound to form a wound core structure 3. The separator 4 is disposed between the positive electrode 1 and the negative electrode 2, and is wound with the positive electrode 1 and the negative electrode 2 to form the wound core structure 3. The separator 4 includes a base film 41 and a coating. The coating includes a first coating layer 42 and a second coating layer 43. The first coating layer 42 is coated on the middle region of the base film 41 along a first direction, and the second coating layer 43 is coated on the two end regions of the base film 41 along the first direction. The porosity of the first coating layer 42 is greater than the porosity of the second coating layer 43.

[0043] Based on the embodiments described above, when the battery cell is used, the core structure 3 needs to be completely immersed in the electrolyte. During the charging and discharging process of the battery cell, lithium electrons move between the positive electrode 1 and the negative electrode 2 using the electrolyte as a medium to form a current circuit. During the battery cell manufacturing process, the positive electrode 1, the separator 4, and the negative electrode 2 need to be stacked sequentially and then formed into the core structure 3 by winding. At this time, along the radial direction of the core structure 3, the closer to the center of the core, the more difficult it is for the electrolyte to penetrate, resulting in a large difference in the degree of wetting between the center and the end of the battery cell, which affects the capacity and service life of the battery cell.

[0044] In this application, a coating is applied to the diaphragm 4, specifically dividing the coating into a first coating layer 42 and a second coating layer 43. The first coating layer 42 is disposed in the middle region of the base film 41 along a first direction, which corresponds to the direction perpendicular to the winding direction of the core, i.e., the axial direction of the cylindrical or elliptical cylinder structure formed by winding. Figure 1 In the X direction. At this time, the high porosity of the first coating layer 42 is used to form a transmission channel in the middle region of the core structure 3, which allows the electrolyte to pass through quickly, so as to quickly transport the electrolyte to the middle region of the core structure 3, thereby improving the overall wetting rate of the core structure 3 and improving the problem of large difference in wetting degree between the middle region and the edge region of the core structure 3.

[0045] Meanwhile, at both ends of the diaphragm 4 along the first direction, since it is located at both ends of the core structure 3 after winding, the electrolyte can quickly penetrate into this area. Therefore, a second coating layer 43 with lower porosity and lower cost compared to the first coating layer 42 is provided in this area. By using differentiated coating, wetting efficiency at each position of the core structure 3 can be guaranteed, while reducing the overall cost.

[0046] In summary, this application utilizes the high porosity of the first coating layer 42 to create a transport channel in the middle region of the core structure 3, allowing the electrolyte to pass through quickly. This improves the wetting efficiency in the middle region and addresses the issue of significant differences in wetting levels between the middle and edge regions. Simultaneously, a second coating layer 43 with lower porosity is applied to both ends. This differentiated approach ensures consistent wetting efficiency at all locations within the core structure 3 while reducing overall cost.

[0047] Specifically, this application improves the electrolyte throughput by setting a first coating layer 42 with high porosity. In the actual production and processing, the first coating layer 42 and the second coating layer 43 can be selected from any suitable materials, provided that the corresponding porosity requirements are met.

[0048] For example, in this application, the first coating layer 42 can be selected from a porous ceramic material with high porosity, such as porous alumina or zeolite molecular sieve. The high porosity of these materials allows the electrolyte to pass through quickly. Furthermore, in practical applications, a hydrophilic polymeric binder, such as a fluorinated copolymer or an acrylic polymer, can be incorporated into the above materials. By mixing these materials in a certain proportion, the high porosity and good adhesion of the materials create a capillary adsorption effect for the electrolyte, ultimately forming a rapid electrolyte channel at the location of the first coating layer 42.

[0049] In contrast, the porosity requirement for the material corresponding to the second coating layer 43 is lower, and in some cases, non-porous materials can be directly selected. In specific production processes, ordinary inorganic materials can be chosen, such as ordinary alumina or boehmite, which are less expensive than porous ceramic materials. Using these materials to form the second coating layer 43 provides basic thermal stability and mechanical strength to the coated area.

[0050] Furthermore, in this application, a coating structure is provided on the diaphragm 4 to improve the wetting efficiency of the middle region of the core structure 3. As for the specific structure of the core structure 3 and the specific materials of the positive electrode 1 and the negative electrode 2, any suitable setting in the prior art can be selected.

[0051] In some embodiments of this application, the base film 41 may have a coating formed on at least one side along the thickness direction of the base film 41.

[0052] Based on the above embodiments of this application, by providing a coating on the base film 41, particularly by providing a first coating layer 42 in the middle region of the base film 41, the high porosity of the first coating layer 42 allows the electrolyte to pass through quickly, thereby improving the electrolyte wetting degree in the middle region of the core structure 3. In actual production, the coating can be provided on both sides of the base film 41 in the thickness direction. In this case, the overall thickness of the coating in the core structure 3 is relatively large, resulting in better electrolyte flow within the core structure 3 and facilitating wetting of the middle region of the core structure 3. Furthermore, if the wetting rate requirements can be met, the coating can also be provided on only one side of the base film 41 in the thickness direction, which reduces production costs compared to providing coatings on both sides of the base film 41.

[0053] Specifically, refer to Figure 2 As shown in the exemplary embodiment provided in this application, coatings can be provided on both sides of the base film 41 along the thickness direction, and the coatings on both sides are symmetrically arranged along the thickness direction of the base film 41. In this case, the overall wetting rate of the core structure 3 with the electrolyte is greatly improved, but the cost is also higher. However, when a coating is provided on only one side of the base film 41, the cost can be effectively reduced while ensuring a certain wetting rate. The specific configuration can be made according to the actual situation, and this application does not impose specific limitations on it.

[0054] refer to Figure 2 As shown in some embodiments of this application, second coating layers 43 are symmetrically arranged on both sides of the first coating layer 42 along the first direction.

[0055] Based on the above embodiments of this application, by symmetrically setting the second coating layers 43 on both sides of the first coating layer 42, the conductivity of each region to the electrolyte is more balanced, thereby making the wetting degree of each position more balanced and improving problems such as lithium plating caused by the large difference in the wetting degree of each position of the core structure 3.

[0056] Further, refer to Figure 2 As shown, in some embodiments of this application, along the first direction, the width ratio of the second coating layer 43 coated at both ends of the base film 41 to the width ratio of the first coating layer 42 coated in the middle region of the base film 41 can be 1:2:1.

[0057] Based on the embodiments described above, the aforementioned limitations ensure that the second coating layers 43 on both sides of the first coating layer 42 are symmetrical, thereby making the wetting rate of each region more balanced. Furthermore, the area ratio of the first coating layer 42 is maintained, ensuring an improvement in the overall wetting rate of the core structure 3.

[0058] Specifically, at this time, the width of the first coating layer 42 accounts for half of the overall width of the coating, that is, the area covered by the first coating layer 42 accounts for half of the area of ​​one side of the diaphragm 4, and the area covered by the first coating layer 42 is located in the middle area of ​​the core structure 3 along the first direction, away from the two ends of the core structure 3 along the first direction, that is, the area where the electrolyte is difficult to wet quickly under normal conditions. However, by setting the first coating layer 42, the passage rate of the electrolyte in this area can be increased, and the wetting effect of the middle area of ​​the core structure 3 can be improved.

[0059] refer to Figure 2 As shown, in some embodiments of this application, the thickness H1 of the first coating layer 42 may be consistent with the thickness H2 of the second coating layer 43.

[0060] Based on the above embodiments of this application, by setting the thickness of the first coating layer 42 and the second coating layer 43 to be the same, the thickness of the separator 4, which is composed of the coating and the base film 41, is kept consistent at all positions. On the one hand, this facilitates the winding process of the core structure 3, and on the other hand, it avoids performance differences within the battery cell caused by differences in the thickness of the separator 4, thus avoiding affecting various parameters such as the charging and discharging efficiency of the battery cell.

[0061] Furthermore, in some embodiments of this application, the thickness H1 of the first coating layer 42 can be set to 3μm≤H1≤5μm.

[0062] Based on the embodiments described above, the thickness of the first coating layer 42 is specifically limited. When the thickness of the first coating layer 42 and the thickness of the second coating layer 43 are the same, the thickness of the second coating layer 43 is also limited. This avoids the problem that an excessively large thickness of the first coating layer 42 would affect the overall energy density of the core structure 3, or that an excessively small thickness of the first coating layer 42 would result in a small increase in the wetting rate in the middle region of the core structure 3. In other words, by limiting the thickness of the first coating layer 42 to a suitable range, both the increase in the wetting rate in the middle region of the core structure 3 is ensured, while avoiding any impact on the energy density of the battery cell.

[0063] Specifically, in actual production and processing, the thickness of the first coating layer 42 can be set to multiple specific dimensions such as 3μm, 3.5μm, 4μm, 4.5μm, and 5μm, while the thickness of the second coating layer 43 is consistent with the thickness of the first coating layer 42. The specific settings can be determined based on factors such as wetting rate requirements, and this application does not impose specific limitations in this regard.

[0064] In some embodiments of this application, the base film 41 can be made of any one of polypropylene (PP), polyethylene (PE), and polypropylene / polyethylene composite materials.

[0065] Based on the above embodiments of this application, the material of the base film 41 is specifically limited. The good mechanical strength and chemical stability of the material are used to achieve isolation between the positive electrode 1 and the negative electrode 2, so as to avoid short circuits while allowing lithium ions to pass freely.

[0066] Based on the above settings in this application, and with reference to Figure 3 As shown, the diaphragm 4 of this application includes the following steps during production and processing: S0010 Preparation of the first coating slurry: First, porous ceramic materials such as porous alumina or zeolite molecular sieve materials, a hydrophilic polymer binder, and a thickener are dispersed in a solution. Then, the above materials are mixed evenly by high-speed stirring to obtain the first slurry.

[0067] S0011 Preparation of the second coating slurry: Non-porous or low-porosity materials such as ordinary alumina, binders and thickeners are dispersed in a solution, and then the above materials are mixed evenly by high-speed stirring to obtain the second slurry.

[0068] S0030 coating: Coating equipment such as a slot extrusion coating device is used to uniformly coat the first slurry and the second slurry onto the base film 41.

[0069] S0040 Drying and curing: The coated base film 41 is sent into an oven for segmented drying to remove the solvent. Then, through hot pressing or heat treatment, the first slurry and the second slurry are cured and firmly bonded to the base film 41, finally forming a diaphragm 4 covered with the first coating layer 42 and the second coating layer 43.

[0070] S0050 winding and slitting: The cured diaphragm 4 is wound and slitted to finally form the finished diaphragm 4.

[0071] Furthermore, in order to ensure the stable formation of the first coating layer 42 and to avoid the first slurry having excessive fluidity and affecting the formation process of the first coating layer 42, the solid content in the first slurry can be controlled at 20%-50% during preparation. Similarly, the solid content in the second slurry can be controlled at 20%-50% to ensure the stable formation of the second coating layer 43.

[0072] Furthermore, in order to improve the coating quality, in some other embodiments of this application, before the coating step, a step may be included: S0020 base film pretreatment, which improves the adsorption performance of the base film 41 surface by corona treatment or plasma treatment, so that the first slurry and the second slurry can better adhere to the base film 41.

[0073] Based on the above technical solutions, this application embodiment also provides a battery, which includes a casing and the aforementioned battery cell. A receiving cavity is formed inside the casing, and a winding core structure 3 is disposed within the receiving cavity.

[0074] Based on the above embodiments of this application, the battery provided by this application includes the aforementioned battery cell. Through the above configuration, by providing a coating on the base film 41, the high porosity of the first coating layer 42 forms a transport channel in the middle region of the core structure 3, allowing the electrolyte to pass through quickly. This improves the wetting efficiency in the middle region and alleviates the problem of significant differences in wetting levels between the middle and edge regions. Simultaneously, a second coating layer 43 with lower porosity is provided at both ends. This differentiated configuration ensures wetting efficiency at all locations of the core structure 3, avoids increased side reactions and lithium plating during battery use, extends the battery's cycle life, and reduces overall cost.

[0075] In some embodiments of this application, the battery may further include two tabs, which are respectively connected to the positive electrode 1 and the negative electrode 2.

[0076] Based on the above embodiments of this application, the tabs are connected to the positive electrode 1 and the negative electrode 2 respectively, and then connected to the positive and negative terminals of the battery respectively, thereby realizing the connection and conduction between the core structure 3 and the outside, and realizing the input and output of the battery.

[0077] Based on the above technical solutions, this application also provides an electrical device, which includes a device body and the aforementioned battery. The device body has an internal power supply cavity, and the battery is disposed within the power supply cavity.

[0078] In this application, the electrical equipment can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0079] Based on the above embodiments of this application, the electrical equipment provided by this application includes the above-mentioned battery, and therefore also has the above-mentioned beneficial effects. To avoid repetition, it will not be described again here.

[0080] The performance of the cell and battery in this application will be further compared and illustrated below through a specific embodiment and a comparative example.

[0081] Example 1 The separator 4 is prepared using the core structure 3 fabrication process disclosed in this application, and then assembled with the positive electrode 1 and the negative electrode 2 to form a lithium iron phosphate battery, specifically including: (1) To prepare the first slurry, porous alumina powder, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) binder and carboxymethylcellulose sodium (CMC-Na) thickener are dispersed in N-methylpyrrolidone (NMP) solvent in a ratio of 100:5:1. The above materials are then mixed evenly by high-speed stirring to obtain the first slurry with a solid content of 35%.

[0082] (2) To prepare the second slurry, ordinary nano alumina, polyacrylate binder and sodium carboxymethyl cellulose thickener are separated in deionized water solvent and then the above materials are mixed evenly by high-speed stirring to obtain a second slurry with a solid content of 35%.

[0083] (3) Base film treatment: a polyethylene porous base film 41 with a thickness of 9 μm was selected, and then the base film 41 was subjected to corona treatment.

[0084] (4) Coating: The second slurry, the first slurry, and the second slurry are sequentially coated on one surface of the base film 41 in the thickness direction along the first direction at a width ratio of 1:2:1, and the coating thickness is 3μm.

[0085] (5) Drying and curing: The coated base film 41 is dried in three ovens at 90°C, 110°C and 130°C, and then hot-pressed and leveled at 50°C and 0.5 MPa.

[0086] (6) Winding and slitting: The cured diaphragm 4 is wound and slitted to finally form the finished diaphragm 4.

[0087] Comparative Example The comparative example and Example 1 have basically the same processing steps, except that: in the comparative example, ordinary nano alumina is used as the main raw material to prepare a third slurry with the same composition as the second slurry in Example 1. Then, the third slurry is uniformly coated on the entire surface of the base film 41 in the thickness direction to form a third coating layer with a thickness of 3 μm.

[0088] Subsequently, the separators 4 prepared in Example 1 and the comparative example were stacked and wound with the positive electrode 1 and the negative electrode 2 to obtain the core structure 3, and assembled to form a lithium iron phosphate battery. The performance of the lithium iron phosphate battery was then tested as follows, and the following results were obtained: (1) Electrolyte wetting rate tests were conducted on the lithium iron phosphate batteries obtained in Example 1 and the comparative example. The full wetting time of the lithium iron phosphate battery separator 4 in Example 1 was 15s, and the full wetting time of the lithium iron phosphate battery separator 4 in the comparative example was 15s. The full wetting time of the lithium iron phosphate battery refers to the time required from the start of wetting until the entire core structure 3 is fully wetted.

[0089] (2) The interface impedance of the lithium iron phosphate batteries obtained in Example 1 and the comparative example was tested. The interface impedance of the lithium iron phosphate battery in Example 1 was 25mΩ and the interface impedance of the lithium iron phosphate battery in the comparative example was 35mΩ.

[0090] (3) Fast charge cycle life tests were conducted on the lithium iron phosphate batteries obtained in Example 1 and the comparative example. The capacity retention rate of the lithium iron phosphate battery in Example 1 after 1000 charge-discharge cycles was 85%, and the capacity retention rate of the lithium iron phosphate battery in the comparative example after 1000 charge-discharge cycles was 78%. Among them, the capacity retention rate refers to the percentage of the battery's current maximum usable capacity to its initial rated capacity after a certain number of charge-discharge cycles or a period of use.

[0091] As can be seen from the above test structure, the above-described settings of this application can significantly improve the electrolyte wetting rate of the core structure 3 and alleviate the problem of large differences in wetting degree between the middle area and the edge of the core structure 3. Simultaneously, it can also reduce the cross-sectional impedance of the battery and improve the cycle life of the battery.

[0092] The preferred embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this application, various simple modifications can be made to the technical solution of this application, and these simple modifications all fall within the protection scope of this application.

[0093] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this application will not describe the various possible combinations separately.

[0094] Furthermore, various different implementations of this application can be combined in any way, as long as they do not violate the spirit of this application, they should also be regarded as the content disclosed in this application.

Claims

1. A battery cell, characterized in that, The battery cell includes: Positive electrode sheet and negative electrode sheet, wherein the positive electrode sheet and negative electrode sheet are stacked and wound to form a core structure; A diaphragm is disposed between the positive electrode and the negative electrode, and is wound with the positive electrode and the negative electrode to form the core structure; The membrane includes a base membrane and a coating. The coating includes a first coating layer and a second coating layer. The first coating layer is applied to the middle region of the base membrane along a first direction, and the second coating layer is applied to the two end regions of the base membrane along the first direction. The porosity of the first coating layer is greater than that of the second coating layer.

2. The battery cell according to claim 1, characterized in that, Along the thickness direction of the base film, the coating is formed on at least one side of the base film.

3. The battery cell according to claim 1, characterized in that, Along the first direction, the second coating layers are symmetrically arranged on both sides of the first coating layer.

4. The battery cell according to claim 3, characterized in that, Along the first direction, the width ratio of the second coating layer coated at both ends of the base film to the width ratio of the first coating layer coated in the middle region of the base film is 1:2:

1.

5. The battery cell according to any one of claims 1-4, characterized in that, The thickness H1 of the first coating layer is consistent with the thickness H2 of the second coating layer.

6. The battery cell according to claim 5, characterized in that, The thickness H1 of the first coating layer is set to 3μm≤H1≤5μm.

7. The battery cell according to claim 1, characterized in that, The base film material is any one of polypropylene, polyethylene, and polypropylene / polyethylene composite materials.

8. A battery, characterized in that, The battery includes: The shell has an internal cavity; and, The battery cell according to any one of claims 1-7, wherein the winding structure is disposed within the receiving cavity.

9. The battery according to claim 8, characterized in that, The battery also includes two tabs, which are respectively connected to the positive electrode and the negative electrode.

10. An electrical appliance, characterized in that, The electrical equipment includes: The main body of the equipment contains an internal power supply chamber; and, The battery as described in claim 8 or 9, wherein the battery is disposed within the power supply cavity.

Images