Battery cell, battery device, and electric device

Abstract

The application discloses a battery monomer, a battery device and a power utilization device. The battery monomer comprises a positive electrode sheet, a negative electrode sheet and a separation film arranged between the positive electrode sheet and the negative electrode sheet; the positive electrode sheet comprises a positive electrode current collector, and the positive electrode current collector is an aluminum-based current collector; at least a negative electrode sheet edge region is provided with a first insulating layer along a first direction and / or a second direction, the edge region of the negative electrode sheet is adjacent to a side edge of the negative electrode sheet, at least part of the side edge of the positive electrode sheet is located in a positive projection of the negative electrode sheet falling into a region where the first insulating layer is located; the separation film comprises a base film and a ceramic layer located on at least one side surface of the base film, a bonding layer is arranged on a side surface of the ceramic layer away from the base film, and the thickness of the ceramic layer is 1-6 microns. The battery monomer provided by the application has high safety performance.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to battery cells, battery devices, and electrical devices. Background Technology

[0002] Batteries are not only used in energy storage systems for hydropower, thermal power, wind power, and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. However, current battery cells still have many problems in practical applications, such as the need for further improvement in their safety performance.

[0003] It should be noted that the above statements are only used to provide background information related to this application and do not necessarily constitute prior art. Utility Model Content

[0004] The first aspect of this application provides a battery cell, which includes a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes. The positive electrode includes a positive current collector, which is an aluminum-based current collector. A first insulating layer is disposed at least in the edge region of the negative electrode along a first direction and / or a second direction. The edge region of the negative electrode is adjacent to the side of the negative electrode. At least a portion of the side of the positive electrode falls within the region of the first insulating layer in the orthogonal projection of the negative electrode. The separator includes a base film and a ceramic layer located on at least one side surface of the base film. An adhesive layer is disposed on the side surface of the ceramic layer away from the base film. The thickness of the ceramic layer is 1 μm-6 μm.

[0005] This application improves the structure of the negative electrode by setting a first insulating layer at least in the edge region of the negative electrode, which protects the negative electrode. When the battery cell is subjected to abuse or abuse testing, it allows metal beads and metal debris to preferentially contact the location of the first insulating layer. The first insulating layer acts as a barrier to the metal beads and metal debris, which helps to improve the problem of short circuits and chemical reactions caused by further contact between metal materials such as metal beads and metal debris from the positive electrode and the negative electrode film layer. In this way, it improves the problem of thermal runaway and fire in the battery cell, reduces the intensity of thermal runaway, and improves the safety performance of the battery cell.

[0006] In some implementations, the battery cell satisfies at least one of the following:

[0007] (a) Along the first direction and / or the second direction, the side of the separator extends beyond the side of the negative electrode sheet by 0-6 mm; optionally, it is 2 mm-6 mm.

[0008] (b) Along the first direction and / or the second direction, the side of the negative electrode extends beyond the side of the positive electrode by 0-4 mm; optionally, it is 1 mm-4 mm.

[0009] In some embodiments, a second insulating layer is further provided in the edge region of the positive electrode sheet, the second insulating layer is located on the surface of the positive current collector, and the edge region of the positive electrode sheet is adjacent to the side of the positive electrode sheet.

[0010] In some embodiments, along the first direction and / or the second direction, the dimension of the side of the positive electrode extending beyond the edge of the first insulating layer opposite to the side of the negative electrode is 0-6 nm; optionally 1 mm-3 mm.

[0011] In some embodiments, along the first direction and / or the second direction, the side of the separator extends beyond the edge of the first insulating layer opposite to the side of the negative electrode sheet by a dimension greater than 0; it can be selected as 2mm-10mm.

[0012] In some embodiments, the battery cell further includes a housing containing a positive electrode, a separator, and a negative electrode; the housing also includes a pressure relief structure located in a first direction, and a first insulating layer is provided at least on the edge region of the negative electrode near the pressure relief structure.

[0013] In some embodiments, the aluminum-based current collector is any one of aluminum current collector, aluminum alloy current collector, or aluminum composite current collector.

[0014] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one side surface of the negative current collector, and satisfies at least one of the following (i) and (ii):

[0015] (i) The first insulating layer is located on the surface of the negative electrode current collector;

[0016] (ii) The first insulating layer is located on the surface of the negative electrode film.

[0017] In some embodiments, a first insulating layer is provided over the entire surface area of ​​the negative electrode sheet.

[0018] In some embodiments, the first insulating layer satisfies at least one of the following (A) to (D):

[0019] (A) The thickness of the first insulating layer is 0.5μm-10μm, and can be selected as 5μm-10μm;

[0020] (B) The porosity of the first insulating layer is 20%-50%, and can be selected as 20%-35%;

[0021] (C) The aperture of the first insulating layer is 10nm-3000nm, and can be selected as 50nm-1000nm;

[0022] (D) The first insulating layer contains an insulating material, which is any one of alumina, titanium oxide, zirconium oxide, silicon oxide, silicon nitride, boron nitride, silicon carbide, boron carbide, aluminosilicate ceramics, mica, mullite, cordierite, polyimide, silicone resin, and ceramic-resin composite materials.

[0023] In some embodiments, the separator includes a base film and a ceramic layer located on at least one surface of the base film, wherein an adhesive layer is disposed on the surface of the ceramic layer away from the base film, and the separator satisfies at least one of the following:

[0024] (i) The thickness of the ceramic layer is 1μm-6μm;

[0025] (ii) The ceramic layer contains ceramic material; optionally, the ceramic material is the same as the insulating material in the first insulating layer.

[0026] In some implementations, the negative electrode sheet satisfies at least one of the following (I) to (IV):

[0027] (I) The compaction density of the negative electrode sheet is 1.2 g / cm³. 3 -2.5g / cm 3 1.5g / cm³ is an optional value. 3 -1.8g / cm 3 ;

[0028] (II) The tortuosity of the negative electrode sheet is 1-4, and can be selected as 1.5-3.0;

[0029] (III) The porosity of the negative electrode sheet is 20%-60%, and can be selected as 30%-45%;

[0030] (IV) The single-sided coating weight of the negative electrode sheet is 50 mg / 1540.25 mm. 2 -500mg / 1540.25mm 2 Available in 180mg / 1540.25mm 2 -400mg / 1540.25mm 2 .

[0031] In some embodiments, the positive electrode, the separator, and the negative electrode form a wound structure or a stacked structure; a wound structure may be selected.

[0032] The second aspect of this application provides a battery device including the battery cell provided in the first aspect. The battery device includes one or more of the following: battery module, battery pack, and energy storage device.

[0033] A third aspect of this application provides an electrical device, including a single battery cell provided in the first aspect, or a battery device provided in the second aspect.

[0034] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0035] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0036] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0037] Figure 2 This is a schematic diagram of a first insulating layer disposed on one edge region of the surface of the negative electrode film layer according to an embodiment of this application.

[0038] Figure 3 This is a schematic diagram of a first insulating layer disposed on both sides of the edge region of the negative electrode film layer according to an embodiment of this application.

[0039] Figure 4 This is a schematic diagram of a first insulating layer disposed on one edge region of the surface of the negative electrode current collector according to an embodiment of this application.

[0040] Figure 5 This is a schematic diagram of a first insulating layer disposed on both sides of the edge region of the negative electrode current collector surface according to an embodiment of this application.

[0041] Figure 6 This is a schematic diagram of a first insulating layer disposed over the entire surface area of ​​the negative electrode film layer according to an embodiment of this application.

[0042] Figure 7 This is a schematic diagram of a first insulating layer disposed on one side edge region of the surface of the negative electrode film layer according to an embodiment of this application; wherein, L1 represents the dimension of the side edge of the separator extending beyond the edge line of the first insulating layer opposite to the side edge of the negative electrode sheet, L2 represents the dimension of the side edge of the second insulating layer extending beyond the edge line of the first insulating layer opposite to the side edge of the negative electrode sheet, L3 represents the dimension of the side edge of the negative electrode sheet extending beyond the side edge of the positive electrode sheet, and L4 represents the dimension of the side edge of the separator extending beyond the side edge of the negative electrode sheet.

[0043] Figure 8This is a schematic diagram of a first insulating layer disposed on both sides of the negative electrode film surface according to an embodiment of this application; wherein, L1 represents the dimension by which the side of the separator extends beyond the edge line of the first insulating layer opposite to the side of the negative electrode sheet, L2 represents the dimension by which the side of the second insulating layer extends beyond the edge line of the first insulating layer opposite to the side of the negative electrode sheet, L3 represents the dimension by which the side of the negative electrode sheet extends beyond the side of the positive electrode sheet, and L4 represents the dimension by which the side of the separator extends beyond the side of the negative electrode sheet.

[0044] Figure 9 This is a schematic diagram of a first insulating layer disposed on one side edge region of the surface of the negative electrode current collector according to an embodiment of this application; wherein, L1 represents the dimension of the side of the separator extending beyond the edge line of the first insulating layer opposite to the side of the negative electrode sheet, L2 represents the dimension of the side of the second insulating layer extending beyond the edge line of the first insulating layer opposite to the side of the negative electrode sheet, L3 represents the dimension of the side of the negative electrode sheet extending beyond the side of the positive electrode sheet, and L4 represents the dimension of the side of the separator extending beyond the side of the negative electrode sheet.

[0045] Figure 10 This is a schematic diagram of a first insulating layer disposed on the entire surface area of ​​a negative electrode film layer according to an embodiment of this application; wherein, L1 represents the dimension by which the side of the separator extends beyond the edge line of the first insulating layer opposite to the side of the negative electrode sheet, L2 represents the dimension by which the side of the second insulating layer extends beyond the edge line of the first insulating layer opposite to the side of the negative electrode sheet, L3 represents the dimension by which the side of the negative electrode sheet extends beyond the side of the positive electrode sheet, and L4 represents the dimension by which the side of the separator extends beyond the side of the negative electrode sheet.

[0046] Figure 11 yes Figure 1 An exploded view of a battery according to one embodiment of this application is shown.

[0047] Figure 12 This is a schematic diagram of a battery module according to one embodiment of this application.

[0048] Figure 13 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0049] Figure 14 yes Figure 13 An exploded view of a battery pack according to one embodiment of this application is shown.

[0050] Figure 15 This is a schematic diagram of an electrical device in which a battery is used as a power source according to one embodiment of this application.

[0051] Figure 16 This is a schematic diagram of the unfolded negative electrode sheet according to an embodiment of this application, showing the coverage area of ​​the first insulating layer; L represents the dimension of the first insulating layer extending inward from the side of the negative electrode sheet.

[0052] Explanation of reference numerals in the attached figures:

[0053] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate; 6 Positive electrode sheet; 601 Positive current collector; 602 First positive electrode film layer; 603 Second positive electrode film layer; 604 Second insulating layer; 7 Separator; 8 Negative electrode sheet; 801 Negative current collector; 802 First negative electrode film layer; 803 Second negative electrode film layer; 804 First insulating layer. Detailed Implementation

[0054] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0055] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0056] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0057] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0058] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0059] Currently, judging from market trends, battery applications are becoming increasingly widespread. Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of battery applications, market demand is constantly increasing, and battery safety performance also needs continuous improvement.

[0060] A single battery cell typically includes a positive electrode and a negative electrode. The negative electrode is responsible for the reaction that attracts or lithiates lithium ions during charging and releases or delithiates lithium during discharging. The positive electrode is responsible for the reaction that releases or delithiates lithium ions during charging and attracts or lithiates lithium during discharging. A separator is placed between the positive and negative electrodes, primarily to prevent short circuits between the positive and negative electrodes while allowing ions to pass through.

[0061] Thermal runaway refers to an uncontrollable, self-generated heating process within a single battery cell, a vicious cycle of "heating → rising temperature → more intense heating" caused by internal factors, and is an irreversible process. During this process, chemical reactions within the battery release heat and flammable gases, causing a rapid increase in internal pressure (up to MPa levels). Targeted pressure relief can effectively delay thermal runaway, inhibit heat propagation, and improve the overall safety of the battery system.

[0062] Currently, battery cells generate a large amount of heat under conditions such as abuse and abuse testing. The shrinkage of the internal separator can lead to severe thermal runaway in the battery cell, such as thermal runaway fire. In existing technologies, fire-retardant coatings can be prepared on the separator, but this cannot effectively cover the surface of the cell. The shrinkage of the separator still causes the coating structure on the surface of the separator to collapse and shrink, which cannot effectively prevent short circuits between the positive and negative electrodes. Especially for separators with poor heat resistance, after the rapid temperature rise inside the battery cell, they cannot effectively cover the surfaces of the positive and negative electrodes. Therefore, the improvement in preventing thermal runaway fire needs to be further enhanced.

[0063] Therefore, a first aspect of the embodiments of this application provides a battery cell including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; the positive electrode includes a positive current collector, which is an aluminum-based current collector; a first insulating layer is disposed at least in the edge region of the negative electrode along a first direction and / or a second direction, the edge region of the negative electrode is adjacent to the side of the negative electrode, and at least a portion of the side of the positive electrode falls within the region where the first insulating layer is located in the orthogonal projection of the negative electrode; the separator includes a base film and a ceramic layer located on at least one side surface of the base film, an adhesive layer is disposed on the side surface of the ceramic layer away from the base film, and the thickness of the ceramic layer is 1μm-6μm.

[0064] The positive current collector, as known in the art, is the substrate and conductive framework that carries the positive electrode film in the positive electrode sheet. As a conductive framework, the positive current collector has the functions of current collection and current conduction.

[0065] The first insulating layer, as is known in the art, exhibits superior electrical insulation properties. For example, the volume resistivity of the first insulating layer may be greater than or equal to 10⁻⁶. 14Ω·cm. Volume resistivity refers to the resistance of a unit cubic sample when a voltage is applied to its two opposite surfaces. For example, the volume resistivity of the first insulating layer is 1 × 10⁻⁶ Ω·cm. 14 Ω·cm, 3×10 14 Ω·cm, 5×10 14 Ω·cm, 7×10 14 Ω·cm, 9×10 14 Ω·cm, 1×10 15 Ω·cm, 3×10 15 Ω·cm, 5×10 15 Ω·cm, 7×10 15 Ω·cm, 9×10 15 Ω·cm, 1×10 16 Ω·cm, 3×10 16 Ω·cm, 5×10 16 Ω·cm, 7×10 16 Ω·cm, 9×10 16 Ω·cm, 1×10 17 Ω·cm or any range between the two.

[0066] In this embodiment, the positive electrode current collector uses an aluminum-based current collector, which has a low melting point. After thermal runaway occurs, it will heat up and melt, resulting in the generation of metal fragments and molten metal beads. The melting point of the aluminum-based current collector is less than or equal to 700°C. As an example, the melting point of the aluminum-based current collector can be 700°C, 690°C, 680°C, 670°C, 660°C, 650°C, 640°C, 630°C, 620°C, 610°C, 600°C, 590°C, 580°C, 570°C, 560°C, 550°C, or any range between the two.

[0067] During abuse tests on individual battery cells, such as thermal runaway tests, it was observed that the degree of danger varied depending on the location of contact between the positive and negative electrode plates. The positive current collector was more likely to ignite when in contact with the lithium-rich negative electrode plate. This is illustrated using an example where the negative electrode plate includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector, and the positive electrode plate includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector, with the positive current collector being a pure aluminum current collector. Details are shown in Table 1.

[0068] Table 1

[0069]

[0070] As shown in Table 1, among the four contact methods mentioned above, a short circuit between the positive current collector and the negative electrode film layer is more likely to cause a fire. Specifically, during the overcharge test, the internal temperature of the battery cell rises rapidly. If the metal material in the positive current collector has a low melting point, it will melt, resulting in the generation of metal debris and molten metal beads (such as aluminum debris and molten aluminum beads). At the same time, the violent gas generation can carry out the aluminum debris and molten aluminum beads from the positive electrode side, and even splash them. When the aluminum debris and molten aluminum beads come into contact with the negative electrode film layer (i.e., the negative electrode sheet in a lithium-rich state) in a fully charged or nearly fully charged state, chemical short circuits and forced delithiation will occur, which will then generate sparks in the air, cause violent fire, or even immediate explosion, resulting in a high risk of heat spread and posing a significant safety hazard.

[0071] This application's implementation improves the negative electrode structure by providing a first insulating layer at least in the edge region of the negative electrode, thus protecting the negative electrode. During abuse or abuse testing of the battery cell, metal beads and metal debris can preferentially contact the location of the first insulating layer. The first insulating layer acts as a barrier to metal beads and metal debris, which helps to improve the problem of short circuits and chemical reactions caused by further contact between metal materials such as metal beads and metal debris from the positive electrode and the negative electrode film layer. This, in turn, improves the problem of thermal runaway and fire in the battery cell, reduces the intensity of thermal runaway, and improves the safety performance of the battery cell.

[0072] During thermal runaway, the separator shrinks due to high temperature, starting from the side edges and moving towards the center. This causes short circuits to occur first at the edges of the positive and negative electrodes. In addition, the hot gas flow generated by thermal runaway carries metal beads, metal fragments, and other metal materials from the positive electrode, which are ejected from the side and also first come into contact with the edge of the negative electrode. Therefore, by setting a first insulating layer at least at the edge of the negative electrode, the protection effect on the negative electrode is improved, thus enhancing the safety performance of the battery cell.

[0073] The first insulating layer is a protective layer formed on a partial or complete area of ​​the surface of the negative electrode sheet. On the one hand, it has an insulating effect, which helps to prevent short circuits caused by contact between metal debris, molten metal beads, and other metal materials from the positive electrode side. On the other hand, it has a physical barrier effect, which helps to prevent metal debris, molten metal beads, and other metal materials from the positive electrode side from directly contacting the negative electrode film layer and igniting.

[0074] As an example, the base film can be either polyethylene (PE) or polypropylene (PP).

[0075] As an example, the thickness of the ceramic layer is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, or any range between the two.

[0076] In this embodiment, by setting a ceramic layer on the surface of the base film, the heat resistance and mechanical properties of the separator are improved. Furthermore, under the influence of high-temperature heat during thermal runaway, the base film shrinks, and the ceramic layer increases the resistance to this shrinkage. As the base film gradually shrinks, cracks appear in the ceramic layer, which is then distributed in a scattered pattern on the base film surface, further contributing to the separation of the positive and negative electrode plates. In summary, this method can better reduce the intensity of thermal runaway and improve the safety performance of the battery cell.

[0077] In this embodiment, the adhesive layer can enhance the interfacial bonding strength between the separator and the electrodes (negative electrode and positive electrode), thereby improving interfacial contact. Furthermore, during thermal runaway, the base film gradually shrinks or even melts upon heating, and even after the ceramic layer develops cracks or fragments, it can still be fixed to the electrode surface by the adhesive layer. This can improve the short-circuit problem between the positive and negative electrodes and reduce the severity of thermal runaway.

[0078] In this embodiment, the thickness of the ceramic layer meets the above conditions, which helps to better improve the heat resistance and structural stability of the separator, better reduce the intensity of thermal runaway, and improve the safety performance of the battery cell.

[0079] In a single battery cell, the planes of the positive electrode, separator, and negative electrode extend in a first direction and a second direction, respectively. For example, they can extend along the length and width directions to form a planar structure. In the first direction, there can be directions extending in one direction or two opposite directions. For instance, one direction in the first direction is considered the positive direction, and the other direction is considered the opposite direction. Similarly, in the second direction, there can be directions extending in one direction or two opposite directions. For instance, one direction in the second direction is considered the positive direction, and the other direction is considered the opposite direction. Correspondingly, the positive and negative electrode plates each have several sides. For example, a first insulating layer can be provided on the surface of any one or several edge regions corresponding to the sides of the negative electrode plate. Furthermore, based on protection requirements, this layer can extend further inward to more areas, thereby improving the effectiveness of preventing short-circuit fires and enhancing the safety performance of the battery cell.

[0080] As an example, such as Figure 2 , Figure 3 , Figure 4 ,and Figure 5 As shown, the positive electrode 6, the separator 7, and the negative electrode 8 are stacked sequentially in a third direction; a first insulating layer 804 may be provided on one or both sides of the negative electrode 8.

[0081] In some embodiments of this application, the battery cell satisfies at least one of the following:

[0082] (a) Along the first direction and / or the second direction, the side of the separator extends beyond the side of the negative electrode sheet by 0-6 mm; optionally, it is 2 mm-6 mm.

[0083] (b) Along the first direction and / or the second direction, the side of the negative electrode extends beyond the side of the positive electrode by 0-4 mm; optionally, it is 1 mm-4 mm.

[0084] In this embodiment, in any direction of the first direction, the side of the separator extends beyond the side of the negative electrode sheet; that is, the length of the separator is greater than or equal to the length of the negative electrode sheet. This extension of the separator length beyond the negative electrode sheet in the edge region facilitates the effective coating of the separator, preventing direct contact and short circuits between the positive and negative electrodes. Furthermore, the longer length of the separator extends the shrinkage path and time during thermal runaway, delaying the occurrence of short circuits and providing more time for directional pressure relief. Similarly, in any direction of the second direction, the side of the separator extends beyond the side of the negative electrode sheet.

[0085] like Figures 7-10 As shown, the side of the separator 7 extends beyond the side of the negative electrode plate 8 by a dimension of L4, where L4 is 0-6mm.

[0086] In the embodiments of this application, the length of the negative electrode sheet is greater than the length of the positive electrode sheet. Thus, at the edge, the length of the negative electrode sheet exceeds the length of the positive electrode sheet, which is beneficial for forming a negative electrode coating, thereby increasing the reaction area (increasing the lithium receiving area) and improving problems such as edge electrochemical lithium deposition.

[0087] like Figures 7-10 As shown, the side of the negative electrode 8 extends beyond the side of the positive electrode 6 by a dimension of L3, where L3 is 0-4mm.

[0088] In some embodiments of this application, a second insulating layer is further provided in the edge region of the positive electrode sheet. The second insulating layer is located on the surface of the positive current collector, and the edge region of the positive electrode sheet is adjacent to the side of the positive electrode sheet.

[0089] In this embodiment, by providing a second insulating layer on one or more of the edge regions of the positive electrode current collector, it can, on the one hand, cover the uneven areas (such as burrs) on the edge of the positive electrode current collector, reducing the risk of the separator being punctured; on the other hand, it also helps to prevent short circuits between the positive and negative electrodes. In summary, this is beneficial for further improving thermal runaway and enhancing the safety performance of the battery cell.

[0090] In some embodiments of this application, along the first direction and / or the second direction, the dimension of the side of the positive electrode extending beyond the edge of the first insulating layer opposite to the side of the negative electrode is 0-6 nm; optionally, it is 1 mm-3 mm.

[0091] In this embodiment, the dimension of the positive electrode side extending beyond the edge of the first insulating layer opposite to the side of the negative electrode is 0, which allows the positive electrode side to be projected onto the edge of the region of the first insulating layer when projected onto the negative electrode. The dimension of the positive electrode side extending beyond the edge of the first insulating layer opposite to the side of the negative electrode is greater than 0, which allows the positive electrode side to be projected onto the region of the first insulating layer when projected onto the negative electrode. Satisfying the above conditions helps to better improve the safety performance of the battery cell and also takes into account the energy density of the battery cell.

[0092] like Figures 7-9 As shown, the dimension of the positive electrode's side edge extending beyond the edge of the first insulating layer opposite to the negative electrode's side edge is L2, where L2 is 0-6 nm.

[0093] In some embodiments of this application, along the first direction and / or the second direction, the side of the separator extends beyond the edge of the first insulating layer opposite to the side of the negative electrode sheet by 0-6 mm; optionally, it is 2 mm-6 mm.

[0094] Taking the first direction as an example, a first insulating layer is disposed on the edge region of one side of the negative electrode sheet. The first side of the first insulating layer coincides with the side of the negative electrode sheet, and the second side of the first insulating layer is opposite to the first side. This second side is the edge line of the first insulating layer away from the side of the negative electrode sheet. Therefore, the distance between the first side and the second side of the first insulating layer is the extension dimension of the first insulating layer itself, and the dimension by which the side of the separator extends beyond the second side is the aforementioned "the dimension by which the side of the separator extends beyond the edge line of the first insulating layer opposite to the side of the negative electrode sheet".

[0095] In this embodiment, the dimension of the side of the separator extending beyond the edge of the first insulating layer opposite to the side of the negative electrode sheet satisfies the above conditions, which helps to better prevent short circuits between the positive and negative electrodes, further improves the safety performance of the battery cell, and also takes into account the energy density of the battery cell.

[0096] like Figures 7-9 As shown, the side of the separator extends beyond the edge of the first insulating layer opposite to the side of the negative electrode by a dimension L1, where L1 is greater than 0; it can be selected as 2-10 nm.

[0097] In some embodiments of this application, the battery cell further includes a housing, which contains a positive electrode, a separator, and a negative electrode; the housing also has a pressure relief structure located in a first direction, and a first insulating layer is provided at least on the edge region of the negative electrode near the pressure relief structure.

[0098] During thermal runaway, high-temperature, high-pressure airflow is generated in a short period of time. This high-temperature, high-pressure airflow may accumulate in the gaps inside the casing, causing the pressure relief structure to open directionally. The high-temperature, high-pressure airflow will flow towards the pressure relief structure, and high-temperature airflow will continue to form from within. This airflow will carry metal debris, molten metal beads, and other metallic materials from the positive electrode side towards the pressure relief structure. In addition, at the pressure relief structure location, which is in contact with the outside, the oxygen content is relatively more abundant, making it easier for metal debris, molten metal beads, and other metallic materials to short-circuit and ignite with the negative electrode film. Therefore, placing a first insulating layer on the surface of the negative electrode near the pressure relief structure can better prevent metal debris, molten metal beads, and other metallic materials from short-circuiting and igniting with the negative electrode film, thus improving the safety performance of the battery cell.

[0099] In some embodiments of this application, the aluminum-based current collector is any one of aluminum current collector, aluminum alloy current collector, and aluminum composite current collector.

[0100] Aluminum current collectors refer to aluminum foil known in the art, using aluminum of the required purity.

[0101] Aluminum current collector refers to an aluminum alloy known in the art. As an example, an aluminum alloy current collector can be any of an aluminum-iron alloy or an aluminum-manganese alloy.

[0102] An aluminum composite current collector refers to an organic material layer and a metal layer formed on at least one surface of the organic material layer, as known in the art; wherein the metal layer contains aluminum. Further, the metal layer may contain aluminum metal or an aluminum alloy. As an example, the organic material layer has a polymer substrate, which may be any one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0103] These aluminum-based current collectors have a low melting point and are more likely to melt after thermal runaway, forming aluminum debris, molten beads, and other substances that can ignite with the lithium-rich negative electrode. The embodiments of this application provide a first insulating layer on the negative electrode sheet, which helps to provide insulation and barrier, thereby improving the problem of short-circuit ignition.

[0104] In some embodiments of this application, the negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one side surface of the negative current collector, and satisfies at least one of the following (i) and (ii):

[0105] (i) The first insulating layer is located on the surface of the negative electrode current collector;

[0106] (ii) The first insulating layer is located on the surface of the negative electrode film.

[0107] In this embodiment, the first insulating layer can be disposed on the surface of the negative electrode sheet, or it can be formed directly on the surface of the negative electrode current collector, or it can be formed on the surface of the negative electrode film layer.

[0108] As an example, such as Figure 2 As shown, the positive electrode 6, the separator 7, and the negative electrode 8 are stacked sequentially in a third direction. The positive electrode 6 includes a positive current collector 601 and positive electrode film layers located on both sides of the positive current collector 601, which can be named the first positive electrode film layer 602 and the second positive electrode film layer 603, respectively. The negative electrode 8 includes a negative current collector 801 and negative electrode film layers located on both sides of the negative current collector 801, which can be named the first negative electrode film layer 802 and the second negative electrode film layer 803, respectively. A first insulating layer 804 is provided on one edge region of the surface of the negative electrode film layers (the first negative electrode film layer 802 and the second negative electrode film layer 803). Figure 3 As shown, a first insulating layer 804 is provided on the edge regions of opposite sides of the surface of the negative electrode film layer (first negative electrode film layer 802 and second negative electrode film layer 803).

[0109] As an example, such as Figure 4 As shown, the positive electrode 6, the separator 7, and the negative electrode 8 are stacked sequentially. The positive electrode 6 includes a positive current collector 601 and positive electrode film layers located on both sides of the positive current collector 601, which can be named the first positive electrode film layer 602 and the second positive electrode film layer 603, respectively. The negative electrode 8 includes a negative current collector 801 and negative electrode film layers located on both sides of the negative current collector 801, which can be named the first negative electrode film layer 802 and the second negative electrode film layer 803, respectively. A first insulating layer 804 is provided on one edge region of the negative current collector 801. Figure 5 As shown, a first insulating layer 804 is provided on both sides of the negative electrode current collector 801.

[0110] In some embodiments of this application, a first insulating layer is provided on the entire surface area of ​​the negative electrode sheet.

[0111] In this embodiment, the first insulating layer can be disposed at the edge region of the negative electrode sheet, which improves battery safety performance and reduces shading of the negative electrode film layer, thus reducing the impact on the energy density of the battery cell. Furthermore, an insulating layer can be provided over the entire surface area of ​​the negative electrode sheet to improve the safety performance of the battery cell. For example, after thermal runaway occurs, the separator may be damaged, weakening its isolation effect between the negative and positive electrode sheets. The lithium-rich surface of the negative electrode sheet is prone to contact with aluminum debris and molten beads, leading to short circuits and fires. By providing a first insulating layer over the entire surface area of ​​the negative electrode sheet, a barrier effect is achieved, better mitigating the problem of short circuits and fires. When the first insulating layer is provided over the entire surface area of ​​the negative electrode sheet, it can be formed directly on the surface of the negative electrode film layer.

[0112] As an example, such as Figure 6 As shown, the positive electrode 6, the separator 7, and the negative electrode 8 are stacked sequentially. The positive electrode 6 includes a positive current collector 601 and positive electrode film layers located on both sides of the positive current collector 601, which can be named the first positive electrode film layer 602 and the second positive electrode film layer 603, respectively. The negative electrode 8 includes a negative current collector 801 and negative electrode film layers located on both sides of the negative current collector 801, which can be named the first negative electrode film layer 802 and the second negative electrode film layer 803, respectively. A first insulating layer 804 is provided on the entire surface area of ​​the negative electrode film layers (the first negative electrode film layer 802 and the second negative electrode film layer 803).

[0113] In some embodiments of this application, the first insulating layer satisfies at least one of the following (A) to (D):

[0114] (A) The thickness of the first insulating layer is 0.5μm-10μm, and can be selected as 5μm-10μm;

[0115] (B) The porosity of the first insulating layer is 20%-50%, and can be selected as 20%-35%;

[0116] (C) The aperture of the first insulating layer is 10nm-3000nm, and can be selected as 50nm-1000nm;

[0117] (D) The first insulating layer contains an insulating material, which is any one of alumina, titanium oxide, zirconium oxide, silicon oxide, silicon nitride, boron nitride, silicon carbide, boron carbide, aluminosilicate ceramics, mica, mullite, cordierite, polyimide, silicone resin, and ceramic-resin composite materials.

[0118] As an example, if the negative electrode sheet covers the negative current collector and the negative electrode film layer located on at least one side of the negative current collector, then there are two situations: (1) when the first insulating layer is located on the surface of the negative electrode film layer, the thickness of the first insulating layer is 0.5μm-10μm; (2) when the first insulating layer is located on the surface of the negative current collector, the thickness of the first insulating layer is the same as the thickness of the negative electrode film layer.

[0119] As an example, the thickness of the first insulating layer is 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or any range between the two.

[0120] As an example, the thickness of the first insulating layer can be measured using a micrometer or an online high-precision thickness gauge.

[0121] In this embodiment, the thickness of the first insulating layer meets the above conditions, which helps to achieve good insulation and barrier effects, improve the problem of thermal runaway fire, and better improve the safety performance of the battery cell.

[0122] Furthermore, the thickness of the first insulating layer is 5μm-10μm to improve the safety performance of the battery and also to better achieve a lower energy density of the battery cells.

[0123] As an example, the porosity of the first insulating layer is 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, or any range between the two.

[0124] As an example, the porosity of the first insulating layer can be detected by methods such as microscopic analysis, gas adsorption method (BET method), and density method (theoretical density comparison method). Taking the gas adsorption method (BET method) as an example, the total pore volume and specific surface area can be calculated by measuring the amount of gas (such as nitrogen) adsorbed on the material surface, and then the porosity can be estimated.

[0125] In this embodiment, the porosity of the first insulating layer satisfies the above conditions. On the one hand, it can achieve good barrier effect and high temperature resistance; on the other hand, it can achieve ion conduction (such as lithium ions), reduce the resistance to ion conduction, promote ion migration, and take into account the charge and discharge energy efficiency of the battery cell.

[0126] In addition, the first insulating layer has a porosity within the aforementioned range, which helps to increase the surface roughness of the first insulating layer. This allows the first insulating layer to have a certain adhesive effect on the molten metal beads and metal debris from the positive electrode side after they come into contact with each other. This helps to prevent the molten metal beads and metal debris from the positive electrode side from continuing to flow to the surface of other negative electrode sheets without insulating layers, thus preventing short circuits and fires.

[0127] Furthermore, the porosity of the first insulating layer is 20%-35%. This allows for a better balance between barrier function and ion migration performance, thereby further improving the safety performance and charge / discharge energy efficiency of the battery cells.

[0128] In some embodiments of this application, the aperture of the first insulating layer is 10nm-3000nm, and can be selected as 50nm-1000nm.

[0129] As an example, the aperture of the first insulating layer is 10nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 1000nm, 1500nm, 2500nm, 2500nm, 3000nm, or any range between the two.

[0130] As an example, the pore size of the first insulating layer can be detected by methods such as microscopic analysis, such as observing the cross-section of the material through a microscope and calculating the pore size.

[0131] In this embodiment, the pore size of the first insulating layer meets the above conditions. While achieving the barrier function of the insulating layer, it also helps to promote ion migration and improve the charging and discharging energy efficiency of the battery cell.

[0132] In addition, the first insulating layer with the above-mentioned aperture plays a certain role in sticking, which helps to prevent molten metal beads and metal debris from the positive electrode side from continuing to flow to the surface of other negative electrode sheets without insulating layers, thus preventing short circuits and fires.

[0133] Furthermore, the pore size of the first insulating layer is 50nm-1000nm. This better balances barrier function and ion migration performance, thereby better ensuring the safety performance and charge / discharge energy efficiency of the battery cell.

[0134] In this embodiment, the insulating material can be any of the electronic insulating and high-temperature resistant materials known in the art. For example, it can be any one of alumina, titanium dioxide, zirconium oxide, silicon oxide, silicon nitride, boron nitride, silicon carbide, boron carbide, aluminosilicate ceramics, mica, mullite, cordierite, polyimide, silicone resin, or ceramic-resin composite materials. Exemplarily, the silicone resin can be epoxy-modified silicone resin or amino-modified silicone resin; the ceramic-resin composite material can be any one of alumina / epoxy resin composite material or silicon carbide / polyimide composite material.

[0135] These materials exhibit good high-temperature resistance, such as a high thermal decomposition temperature. Thermal decomposition temperature refers to the temperature at which a insulating material begins to undergo significant and irreversible chemical structural damage, leading to permanent changes in its quality, physical, or chemical properties. The insulating materials also possess good high-temperature thermal stability, maintaining structural stability even under high-temperature airflow. This ensures a stable, integrated insulating layer structure, providing insulation and barrier functions. This helps mitigate the problem of short-circuiting and ignition issues between the negative electrode film and molten metal beads or debris, thus improving the safety performance of individual battery cells.

[0136] As an example, the thermal decomposition temperature of the first insulating layer can be greater than or equal to 500°C. For example, the thermal decomposition temperature of the insulating layer can be 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1450°C, 1500°C, or any range between the two.

[0137] In some embodiments of this application, the ceramic layer contains a ceramic material; alternatively, the ceramic material is the same as the insulating material in the first insulating layer.

[0138] In this application, the ceramic material may be any ceramic material known in the art. For example, it may be any one of alumina ceramic (Al2O3), silica ceramic (SiO2), lithium metatitanate (Li2TiO3), or boehmite.

[0139] Furthermore, the ceramic material of the ceramic layer can be the same as the insulating material contained in the insulating layer, both of which have good insulation properties and high temperature resistance. Choosing the same material helps to improve the interface stability between the insulating layer and the ceramic layer.

[0140] In some embodiments of this application, the negative electrode sheet satisfies at least one of the following (I) to (IV):

[0141] (I) The compaction density of the negative electrode sheet is 1.2 g / cm³. 3-2.5g / cm 3 1.5g / cm³ is an optional value. 3 -1.8g / cm 3 ;

[0142] (II) The tortuosity of the negative electrode sheet is 1-4, and can be selected as 1.5-3.0;

[0143] (III) The porosity of the negative electrode sheet is 20%-60%, and can be selected as 30%-45%;

[0144] (IV) The single-sided coating weight of the negative electrode sheet is 50 mg / 1540.25 mm. 2 -500mg / 1540.25mm 2 Available in 180mg / 1540.25mm 2 -400mg / 1540.25mm 2 .

[0145] As an example, the compaction density of the negative electrode sheet is 1.2 g / cm³. 3 1.4g / cm 3 1.6g / cm 3 1.8g / cm 3 2.0g / cm 3 2.2g / cm 3 2.4g / cm 3 2.5g / cm 3 Or any range between the two.

[0146] As an example, the compaction density of the negative electrode sheet can be tested by measuring its mass and volume, and then calculating it; compaction density (g / cm³) 3 = Electrode mass (g) / Electrode volume (cm³) 3 ).

[0147] As an example, the porosity of the negative electrode sheet is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any range between two of these.

[0148] As an example, the porosity of the negative electrode sheet can be detected by the following method: refer to the method for detecting the porosity of the first insulating layer described above.

[0149] As an example, the single-sided coating weight of the negative electrode sheet is 50 mg / 1540.25 mm. 2 60mg / 1540.25mm 2 70mg / 1540.25mm 2 80mg / 1540.25mm 290mg / 1540.25mm 2 100mg / 1540.25mm 2 150mg / 1540.25mm 2 200mg / 1540.25mm 2 250mg / 1540.25mm 2 300mg / 1540.25mm 2 350mg / 1540.25mm 2 400mg / 1540.25mm 2 450mg / 1540.25mm 2 500mg / 1540.25mm 2 Or any range between the two.

[0150] The single-sided coating weight of the negative electrode refers to the amount of negative electrode film coated on one side of the surface of the negative electrode current collector. As an example, the single-sided coating weight of the negative electrode can be measured by weighing to obtain the weight per unit area.

[0151] In this embodiment, a first insulating layer can be provided on the surface of the negative electrode film. Compared with a negative electrode film without a first insulating layer, the ion migration resistance will increase. By further optimizing the design of relevant characteristic parameters of the negative electrode sheet (such as any one or more of the above-mentioned compaction density, porosity, and single-sided coating weight), ions can achieve better migration effect on the negative electrode sheet, improve the electrolyte wetting effect, and thus improve the electrical performance of the battery cell, such as improving the charge and discharge energy efficiency of the battery cell.

[0152] In some embodiments of this application, the positive electrode, the separator, and the negative electrode form a wound structure or a stacked structure; a wound structure may be selected.

[0153] In this embodiment, the positive electrode, separator, and negative electrode can be stacked to form a stacked cell or wound cell.

[0154] As an example, let's take a square battery as an example:

[0155] For a laminated structure, a positive electrode, a separator, and a negative electrode are stacked along a third direction to form a square-shaped battery cell. Within a planar region extending along a first direction and a second direction, the positive electrode, separator, and negative electrode have two opposing sides along the first direction and two opposing sides along the second direction. A first insulating layer may be provided at the edge region adjacent to any one or more sides on the surface of the negative electrode.

[0156] For the wound structure, the battery cell includes a flat section and a corner section. In the flat section, the positive electrode, separator, and negative electrode are stacked along a third direction. Within a planar region extending along a first direction, the positive electrode, separator, and negative electrode have two opposing sides along that first direction. A first insulating layer can be provided at the edge region of any one or more of these adjacent sides on the surface of the negative electrode. The positive electrode, separator, and negative electrode have sides at their wound ends, and a first insulating layer can be provided in the region adjacent to these sides on the surface of the negative electrode.

[0157] Furthermore, for wound-structured cells, the internal stress distribution is relatively concentrated, especially at the corners where bending stress is concentrated. During thermal runaway, heat dissipation in the corner areas is relatively poor, making it easier for heat to accumulate. Therefore, the separator at these locations is more prone to failure, leading to short circuits between the positive and negative electrodes and subsequent fires. The embodiments of this application, by providing a first insulating layer in at least a portion of the negative electrode sheet, effectively mitigate the problem of short circuits and fires in wound-structured cells, thereby improving the safety performance of individual battery cells.

[0158] In one embodiment of this application, a battery cell is provided.

[0159] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0160] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 The example shown is a square-structured battery cell 5.

[0161] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0162] The second aspect of the embodiments of this application provides a battery device including the battery cell provided in the first aspect above. The battery device includes one or more of the following: battery module, battery pack, and energy storage device.

[0163] In this embodiment of the application, the battery device includes the battery cell provided in the first aspect, and has the beneficial effects of the battery cell, which will not be repeated here.

[0164] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0165] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0166] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0167] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0168] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0169] The third aspect of this application provides an electrical device that includes a single battery cell provided in the first aspect, or a battery device provided in the second aspect.

[0170] In this embodiment of the application, the electrical device includes the battery cell provided in the first aspect, and has the beneficial effects of the battery cell, which will not be repeated here.

[0171] This application also provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack provided in this application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0172] As electrical equipment, battery cells, battery modules, or battery packs can be selected according to their usage requirements.

[0173] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density batteries, a battery pack or battery module can be used.

[0174] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can be powered by a battery.

[0175] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. 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.

[0176] [Performance Testing]

[0177] 1. Thermal runaway test:

[0178] The test can be conducted in accordance with the reference standard GB / T36276-2023.

[0179] Thermal runaway experimental setup: battery cell, heating plate.

[0180] Thermal runaway test procedure: After fully charging the battery cell, overcharge the battery cell and simultaneously turn on the heating plate to heat one side of the battery cell until thermal runaway occurs; the passing standard is no fire and no explosion.

[0181] Detect thermal runaway parameters: (1) Detect the outlet temperature of the explosion-proof valve (high temperature after ignition, low temperature before ignition); observe whether there is an open flame.

[0182] 2. Internal resistance test of individual battery cells:

[0183] The DC discharge method is used. Specifically, the battery cells are adjusted to different SOCs, such as 90%, 70%, 50%, 30%, and 10%, and the voltage U1 is recorded after standing for 2 hours. The battery cells are discharged or charged with a certain current I (such as 0.5C) for a certain period of time (such as 30s), and the terminal voltage U2 is recorded. The DC internal resistance is |U2-U1| / I.

[0184] 3. Testing the energy efficiency of individual battery cells:

[0185] The testing method involves performing an initial charge and discharge cycle on the battery, dividing the discharge energy of a complete charge and discharge cycle by the charging energy. Refer to GB / T36276-2023 standard for details.

[0186] (1) Set the ambient temperature to 25℃ and let it stand for 5 hours at (25±2)℃;

[0187] (2) Charge the battery cell at constant power until the charging cutoff condition is met, let it stand for 10 minutes, and record the power, time, voltage, temperature and charging energy; then discharge the battery cell at constant power until the charging cutoff condition is met, let it stand for 10 minutes, and record the power, time, voltage, temperature and discharging energy.

[0188] (3) Charge the battery cell at constant power until the charging cutoff condition is met, let it stand for 10 minutes, and record the power, time, voltage, temperature and charging energy; then discharge the battery cell at constant power until the charging cutoff condition is met, let it stand for 10 minutes, and record the power, time, voltage, temperature and discharging energy.

[0189] The energy efficiency of a single battery cell is: discharge energy / charging energy in step (3) × 100%.

[0190] [Preparation of battery cells]

[0191] Example 1

[0192] (1) Preparation of positive electrode sheet:

[0193] Lithium iron phosphate (LiFePO4, abbreviated as LFP), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) binder are mixed in a mass ratio of 97%:2%:1% and added to the solvent N-methylpyrrolidone (NMP) to form a positive electrode slurry with a solid content of 60%. The prepared positive electrode slurry is coated onto a 15μm thick aluminum foil for the positive electrode current collector using a coating machine, dried, and then rolled. A second insulating layer is set in the empty foil area at the edge of the aluminum foil to obtain the positive electrode sheet.

[0194] The step of forming the second insulating layer includes: applying ceramic powder (Al2O3) to the substrate. 3 / The alumina, zirconium oxide, and binder are mixed and a solvent (water) is used to prepare a uniform slurry (solid content of 50%) using a high-speed disperser, thus obtaining the second insulating layer slurry; wherein the mass ratio of alumina, zirconium oxide, and binder is 80%:15%:5%. The second insulating layer slurry is then coated and dried to obtain the second insulating layer.

[0195] (2) Preparation of negative electrode sheet:

[0196] Preparation of negative electrode film: The negative electrode active material graphite, conductive agent conductive carbon black, binder styrene-butadiene rubber (SBR), and dispersant sodium carboxymethyl cellulose (CMC-Na) are mixed in a mass ratio of 96%:2%:1%:1% and added to the solvent deionized water. After stirring, a negative electrode slurry with a solid content of 50% is formed. The prepared negative electrode slurry is coated onto the negative electrode current collector copper foil through a coating machine, dried, and then rolled to form a negative electrode film.

[0197] Preparation of the first insulating layer: Alumina (Al2O3) as insulating material, polyvinylidene fluoride (PVDF) as binder, and N-methylpyrrolidone (NMP) as solvent are mixed in a mass ratio of 60%:12%:28% and dispersed under the assistance of an ultrasonic cleaner (40 kHz, 30 minutes) to form a first insulating layer slurry. The first insulating layer slurry is then coated onto the surface of the negative electrode film layer in the edge area of ​​the negative electrode sheet using a coating machine. The coating thickness is controlled by adjusting the doctor blade gap. After hot air drying, the first insulating layer is formed, and the negative electrode sheet is finally obtained.

[0198] The first insulating layer coverage area: On the side near the negative electrode tab where the negative electrode plate is located, the area extending inwards from the side of the negative electrode film layer; the specific coating area is as follows... Figure 16 The figure shown is a schematic diagram of the unfolded plane of the negative electrode sheet, with L=6mm.

[0199] (3) Separating membrane:

[0200] A 12μm polypropylene (PP) base film is used. A ceramic layer and an adhesive layer are sequentially formed on both sides of the base film. The ceramic layer is composed of alumina (95wt%) and PVDF (5wt%) as adhesive, with a thickness of 2μm; the adhesive layer is composed of PVDF and has a thickness of 2μm.

[0201] (4) Preparation of electrolyte:

[0202] Solvent mixing: Mix EC (ethylene carbonate) and DMC (dimethyl carbonate) at a mass ratio of 1:1 and stir until homogeneous; slowly add LiPF6 and stir magnetically until completely dissolved; add ethylene ethylene carbonate (VC) as needed, continue stirring, filter to remove insoluble impurities, and seal and store in a glove box. In the electrolyte, the concentration of lithium salt LiPF6 is 1 mol / L, and the mass percentage of additive VC is 2%.

[0203] (5) Assembly of individual battery cells:

[0204] The aforementioned positive electrode sheet, separator, and negative electrode sheet are wound together and wrapped in an aluminum casing. Then, a prepared electrolyte is injected, and the mixture undergoes formation and aging processes to obtain a single battery cell. Furthermore, the positive electrode sheet is connected to the positive electrode tab, and the negative electrode sheet is connected to the negative electrode tab, with the positive and negative electrode tabs on the same side. An end cap and a base plate are positioned opposite each other along the height of the aluminum casing. An explosion-proof valve (i.e., a pressure relief structure) is installed on the end cap of the aluminum casing, and it is on the same side as the electrode tab. The positional and length relationships of the positive electrode sheet, separator, and negative electrode sheet along the height of the casing are as follows: Figure 7 As shown, L1=8mm, L2=2mm, L3=2mm, and L4=4mm.

[0205] Example 2

[0206] The battery cell was prepared using the method of Example 1, the difference being that in the preparation step of the negative electrode sheet, a first insulating layer was set in the empty foil area at the edge of the copper foil of the negative electrode current collector, such as... Figure 9 As shown.

[0207] Example 3

[0208] The battery cell was prepared using the method of Example 1, the difference being that, in the preparation step of the negative electrode sheet, a first insulating layer was formed over the entire surface of the negative electrode film layer of the negative electrode sheet, such as... Figure 10 As shown.

[0209] Comparative Example 1

[0210] The battery cell was prepared using the method of Example 1, the difference being that the steps for preparing the negative electrode sheet were different, and a first insulating layer was not provided. Specifically:

[0211] The negative electrode active material graphite, conductive agent conductive carbon black, binder styrene-butadiene rubber (SBR), and dispersant sodium carboxymethyl cellulose (CMC-Na) are mixed in a mass ratio of 96%:2%:1%:1% and added to the solvent deionized water. After stirring, a negative electrode slurry with a solid content of 50% is formed. The prepared negative electrode slurry is coated onto the negative electrode current collector copper foil using a coating machine, dried, and then rolled to form a negative electrode sheet.

[0212] The features and performance test results of Examples 1-3 and Comparative Example 1 are shown in Table 2.

[0213] Table 2

[0214]

[0215] As shown in Table 2, in Comparative Example 1, the negative electrode sheet lacked an insulating layer. During the thermal runaway test, the outlet temperature of the explosion-proof valve was high, and an open flame was present, resulting in a significant thermal runaway intensity and thus a substantial hazard or safety risk. In contrast, Example 1 of this application provides a first insulating layer at the edge region of the negative electrode film layer of the negative electrode sheet. During the thermal runaway process, there is no open flame, the outlet temperature of the explosion-proof valve is significantly reduced, the thermal runaway intensity is reduced, and the battery internal resistance remains essentially unchanged, with minimal sacrifice in charge-discharge energy efficiency. In Example 2, the first insulating layer is provided at the edge region of the negative electrode current collector of the negative electrode sheet, which can further reduce the thermal runaway intensity, while the battery internal resistance and charge-discharge energy efficiency remain essentially unchanged. In Example 3, the first insulating layer is provided across the entire surface of the negative electrode film layer of the negative electrode sheet, which can better reduce the thermal runaway intensity while simultaneously minimizing the increase in battery internal resistance and the sacrifice in charge-discharge energy efficiency.

[0216] Example 4-Example 5

[0217] Examples 4 and 5 were prepared using the method of Example 1, with the difference being that the thickness and porosity of the first insulating layer were different. The characteristics and performance test results of Examples 1, 4, and 5 are shown in Table 3.

[0218] Table 3

[0219]

[0220] As shown in Table 3, the increased thickness of the first insulating layer located at the edge of the negative electrode film layer helps to further reduce the outlet temperature of the explosion-proof valve, while having no negative impact on the battery's internal resistance and charge / discharge efficiency.

[0221] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized in that, The battery cell includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; The positive electrode includes a positive current collector, which is an aluminum-based current collector. Along a first direction and / or a second direction, at least the edge region of the negative electrode sheet is provided with a first insulating layer, the edge region of the negative electrode sheet is adjacent to the side of the negative electrode sheet, and at least a portion of the side of the positive electrode sheet falls within the region where the orthogonal projection of the negative electrode sheet is located. The isolation membrane includes a base membrane and a ceramic layer located on at least one side surface of the base membrane. An adhesive layer is disposed on the side surface of the ceramic layer away from the base membrane. The thickness of the ceramic layer is 1μm-6μm.

2. The battery cell according to claim 1, characterized in that, Meet at least one of the following: (a) Along the first direction and / or the second direction, the side of the separator extends beyond the side of the negative electrode sheet by 0-6 mm; (b) Along the first direction and / or the second direction, the side of the negative electrode extends beyond the side of the positive electrode by 0-4 mm.

3. The battery cell according to claim 1, characterized in that, Meet at least one of the following: (a) Along the first direction and / or the second direction, the side of the separator extends 2mm-6mm beyond the side of the negative electrode sheet; (b) Along the first direction and / or the second direction, the side of the negative electrode extends beyond the side of the positive electrode by 1 mm to 4 mm.

4. The battery cell according to claim 1 or 2, characterized in that, A second insulating layer is also provided in the edge region of the positive electrode sheet. The second insulating layer is located on the surface of the positive current collector, and the edge region of the positive electrode sheet is adjacent to the side of the positive electrode sheet.

5. The battery cell according to claim 4, characterized in that, Meet at least one of the following: Along the first direction and / or the second direction, the dimension of the side of the positive electrode sheet extending beyond the edge of the first insulating layer opposite to the side of the negative electrode sheet is 0-6 nm; Along the first direction and / or the second direction, the dimension of the side of the separator extending beyond the edge of the first insulating layer opposite to the side of the negative electrode sheet is greater than 0.

6. The battery cell according to claim 4, characterized in that, Meet at least one of the following: Along the first direction and / or the second direction, the side of the positive electrode sheet extends beyond the edge of the first insulating layer opposite to the side of the negative electrode sheet by 1mm-3mm. Along the first direction and / or the second direction, the side of the separator extends 2mm-10mm beyond the edge of the first insulating layer opposite to the side of the negative electrode sheet.

7. The battery cell according to claim 1 or 2, characterized in that, The battery cell further includes a housing, which contains the positive electrode, the separator, and the negative electrode; the housing also has a pressure relief structure located in the first direction, and the first insulating layer is provided at least in the edge region of the negative electrode near the pressure relief structure.

8. The battery cell according to claim 1 or 2, characterized in that, The aluminum-based current collector can be any one of aluminum current collector, aluminum alloy current collector, or aluminum composite current collector.

9. The battery cell according to claim 1, characterized in that, The negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one side surface of the negative current collector, and satisfies at least one of the following (i) and (ii): (i) The first insulating layer is located on the surface of the negative electrode current collector; (ii) The first insulating layer is located on the surface of the negative electrode film.

10. The battery cell according to claim 1 or 2, characterized in that, The first insulating layer is disposed on the entire surface area of ​​the negative electrode sheet.

11. The battery cell according to claim 1 or 2, characterized in that, The first insulating layer satisfies at least one of the following (A) to (D): (A) The thickness of the first insulating layer is 0.5μm-10μm; (B) The porosity of the first insulating layer is 20%-50%; (C) The pore size of the first insulating layer is 10nm-3000nm; (D) The first insulating layer contains an insulating material, which is any one of alumina, titanium oxide, zirconium oxide, silicon oxide, silicon nitride, boron nitride, silicon carbide, boron carbide, aluminosilicate ceramics, mica, mullite, cordierite, polyimide, silicone resin, and ceramic-resin composite materials.

12. The battery cell according to claim 1 or 2, characterized in that, The first insulating layer satisfies at least one of the following (A) to (D): (A) The thickness of the first insulating layer is 5μm-10μm; (B) The porosity of the first insulating layer is 20%-35%; (C) The pore size of the first insulating layer is 50nm-1000nm; (D) The first insulating layer contains an insulating material, which is any one of alumina, titanium oxide, zirconium oxide, silicon oxide, silicon nitride, boron nitride, silicon carbide, boron carbide, aluminosilicate ceramics, mica, mullite, cordierite, polyimide, silicone resin, and ceramic-resin composite materials.

13. The battery cell according to claim 1 or 2, characterized in that, The ceramic layer contains ceramic material.

14. The battery cell according to claim 13, characterized in that, The ceramic material is the same as the insulating material in the first insulating layer.

15. The battery cell according to claim 9, characterized in that, The negative electrode sheet satisfies at least one of the following (I) to (IV): (I) The compaction density of the negative electrode sheet is 1.2 g / cm³. 3 -2.5g / cm 3 ; (II) The tortuosity of the negative electrode sheet is 1-4; (III) The porosity of the negative electrode sheet is 20%-60%; (IV) The single-sided coating weight of the negative electrode sheet is 50 mg / 1540.25 mm. 2 -500mg / 1540.25mm 2 .

16. The battery cell according to claim 9, characterized in that, The negative electrode sheet satisfies at least one of the following (I) to (IV): (I) The compaction density of the negative electrode sheet is 1.5 g / cm³. 3 -1.8g / cm 3 ; (II) The tortuosity of the negative electrode sheet is 1.5-3.0; (III) The porosity of the negative electrode sheet is 30%-45%; (IV) The single-sided coating weight of the negative electrode sheet is 180 mg / 1540.25 mm. 2 -400mg / 1540.25mm 2 .

17. The battery cell according to claim 1 or 2, characterized in that, The positive electrode, the separator, and the negative electrode form a wound structure or a stacked structure.

18. A battery device, characterized in that, The battery device includes the battery cell described in any one of claims 1 to 17, and the battery device includes one or more of the following: battery module, battery pack, and energy storage device.

19. An electrical appliance, characterized in that, It includes the battery cell as described in any one of claims 1 to 17, or the battery device as described in claim 18.

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