A battery and electronic device

Abstract

The application provides a battery and an electronic device. The battery comprises a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode active layer on at least one surface of the positive electrode current collector; the positive electrode current collector comprising a polymer layer and a conductive layer on at least one surface of the polymer layer, the conductive layer comprising a conductive region; the positive electrode active layer is at least partially on the surface of the conductive layer away from the polymer layer; the battery satisfies: A*N*q*10 ‑5 ≤10; in formula 1, A is the surface area of the conductive region, mm 2 ; q is the area density of the positive electrode active layer, mAh / cm 2 ; N is the number of the positive electrode sheets in the battery. The battery has excellent capacity and safety performance.

Description

Technical Field

[0001] This invention relates to a battery and electronic device, belonging to the field of new energy technology. Background Technology

[0002] Currently commonly used current collectors include metal foil current collectors (e.g., aluminum foil, aluminum alloy foil, copper foil, or copper alloy foil), porous metal foil current collectors (e.g., aluminum mesh, copper mesh), and conductive layer-polymer layer-conductive layer composite current collectors (the conductive layer can be aluminum foil or copper foil). Among these, metal foil current collectors have the drawback of not being able to be further thinned and reduced in weight when applied to batteries. Furthermore, metal foil current collectors have low safety performance when matched with high-capacity positive electrode active materials or high-capacity negative electrode materials. Porous metal foil current collectors can only be weight-reduced when they are thick enough. When the thickness of the porous foil current collector is too thin, it is easy for the porous foil current collector to be unusable due to insufficient strength. In addition, due to the hollow structure of the porous foil current collector, it is easy for the positive electrode slurry or negative electrode slurry to be leaked when coated on the surface of the porous foil current collector, making the coating difficult. When the metal layer in the conductive layer-polymer layer-conductive layer composite current collector is copper foil, this composite current collector has almost no significant improvement effect on the needle penetration safety of the battery when applied to batteries. When the metal layer is aluminum foil, it has almost no significant improvement effect on the needle penetration safety performance of high state of charge (SOC) batteries. Summary of the Invention

[0003] This invention provides a battery that combines excellent capacity and safety performance.

[0004] The present invention provides an electronic device including the battery described above. The battery is the driving source or energy storage source of the electronic device, thus the electronic device has excellent battery life and longevity, and has broad market application prospects.

[0005] The present invention provides a battery comprising a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active layer located on at least one surface of the positive current collector;

[0006] The positive electrode current collector includes a polymer layer and a conductive layer located on at least one surface of the polymer layer, the conductive layer including conductive regions; the positive electrode active layer is at least partially located on the surface of the conductive layer away from the polymer layer;

[0007] The battery satisfies: A*N*q*10 -5 ≤10;

[0008] In Equation 1, A is the surface area of ​​the conductive region, in mm. 2 ;

[0009] q is the areal density of the positive electrode active layer, in mAh / cm³.2 ;

[0010] N is the number of positive electrode plates in the battery.

[0011] The battery described above, wherein A*N*q*10 -5 ≤6.

[0012] In the battery described above, the conductive layer includes a first conductive layer and a second conductive layer, wherein the first conductive layer is located on one surface of the polymer layer, and the second conductive layer is located on the surface of the polymer layer away from the first conductive layer;

[0013] The first conductive layer includes a first conductive region, the area of ​​the first conductive region on the polymer layer is S1, the cross-sectional area of ​​the polymer layer is S2, 1% ≤ S1 / S2 ≤ 95%; and / or;

[0014] The second conductive layer includes a second conductive region, the area of ​​the second conductive region on the polymer layer is S3, the cross-sectional area of ​​the polymer layer is S2, and 1% ≤ S3 / S2 ≤ 95%.

[0015] The battery as described above, wherein 10% ≤ S1 / S2 ≤ 50%; and / or; 10% ≤ S3 / S2 ≤ 50%.

[0016] In the battery described above, the first conductive region includes a plurality of first conductive sub-regions, wherein the plurality of first conductive sub-regions are arranged at intervals or at least two of the plurality of first conductive sub-regions are connected to each other; and / or,

[0017] The second conductive region includes a plurality of second conductive sub-regions, which are arranged at intervals or at least two of the plurality of second conductive sub-regions are connected to each other.

[0018] In the battery described above, the first conductive layer and / or the second conductive layer are mesh structures.

[0019] The battery as described above, wherein 10mm 2 ≤A≤250000mm 2 .

[0020] The battery described above has a capacity of 4 mAh / cm³. 2 ≤q≤14mAh / cm 2 .

[0021] The battery as described above, wherein 1 ≤ N ≤ 60.

[0022] In the battery described above, the thickness of the polymer layer is 0.5-20 μm.

[0023] In the battery described above, the thickness of the conductive layer is 0.1-5 μm.

[0024] The battery as described above further includes a negative electrode sheet, which includes a negative current collector, and the negative current collector and the positive electrode sheet are stacked together.

[0025] The present invention provides a battery pack, wherein the battery pack includes the battery as described above.

[0026] This invention provides an electronic device, wherein the driving source or energy storage source of the electronic device is a battery as described above; or,

[0027] The driving source or energy storage source of the electronic device is the battery pack as described above.

[0028] This invention improves the needle penetration safety performance of batteries, especially high SOC (30%-100% SOC) batteries, by ensuring that the surface area of ​​the conductive region of the positive electrode current collector, the areal density of the positive electrode active layer, and the number of positive electrode sheets satisfy a specific relationship.

[0029] The present invention provides an electronic device including the battery described above. The battery is the driving source or energy storage source of the electronic device, thus the electronic device has excellent battery life and longevity, and has broad market application prospects. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the accompanying drawings used in the description of the embodiments of the present invention or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the cross-sectional structure of the current collector in some embodiments of the present invention;

[0032] Figure 2 This is a schematic diagram of the surface structure of the current collector in some embodiments of the present invention;

[0033] Figure 3 This is a schematic diagram of the surface structure of the positive electrode sheet in some embodiments of the present invention.

[0034] Explanation of reference numerals in the attached figures:

[0035] 1: Polymer layer;

[0036] 2: Conductive layer;

[0037] 3: Electrode;

[0038] 4: Positive electrode active layer;

[0039] 21: Blank area;

[0040] 231: Part One;

[0041] 232: Part Two. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0043] Figure 1 This is a schematic diagram of the cross-sectional structure of the current collector in some embodiments of the present invention; Figure 2 This is a schematic diagram of the surface structure of the current collector in some embodiments of the present invention; Figure 3 This is a schematic diagram of the surface structure of the positive electrode sheet in some embodiments of the present invention. For example... Figure 1-3 As shown, a first aspect of the present invention provides a battery including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive active layer located on at least one surface of the positive current collector;

[0044] The positive electrode current collector includes a polymer layer and a conductive layer located on at least one surface of the polymer layer, the conductive layer including a conductive region; the positive electrode active layer is at least partially located on the surface of the conductive layer away from the polymer layer;

[0045] The battery satisfies: A*N*q*10 -5 ≤10 formula 1;

[0046] In Equation 1, A is the surface area of ​​the conductive region, in mm. 2 ;

[0047] q is the areal density of the positive electrode active layer, mAh / cm³. 2 ;

[0048] N is the number of positive electrode plates in the battery.

[0049] In Equation 1, 10 represents the total safe threshold capacity released by N positive electrode plates, in Ah. When the surface area of ​​the positive electrode current collector conductive region, the areal density of the positive electrode active layer, and the number of positive electrode plates in the battery satisfy the relationship in Equation 1, the battery's needle penetration safety performance and internal short circuit performance can be increased while ensuring the battery's capacity.

[0050] Furthermore, when A*N*q*10-5 When the value is ≤6, the internal short-circuit safety performance and needle penetration safety performance of the battery can be further improved while ensuring the battery capacity.

[0051] In this invention, the surfaces of the positive current collector refer to the two surfaces with the largest area that are arranged opposite each other in the positive current collector. In the positive electrode sheet of this invention, the positive active layer can be located on one surface of the positive current collector or on both surfaces of the positive current collector.

[0052] In this invention, the surfaces of the polymer layer refer to the two surfaces of the polymer layer that have the largest area and are arranged opposite each other. In the positive current collector of this invention, the conductive layer can be located on one surface of the polymer layer or on both surfaces of the polymer layer. When the conductive layer is located on only one surface of the polymer layer, the area of ​​the conductive region refers to the area of ​​the conductive region in that conductive layer; when the conductive layer is located on both surfaces of the polymer layer, the area of ​​the conductive region refers to the average area of ​​the conductive regions in the two conductive layers.

[0053] In some embodiments of the present invention, the conductive layer includes a first conductive layer and a second conductive layer, wherein the first conductive layer is located on one surface of the polymer layer and the second conductive layer is located on the surface of the polymer layer away from the first conductive layer;

[0054] The first conductive layer includes a first conductive region, the area of ​​the first conductive region projected onto the polymer layer by a first orthogonal projection of the first conductive region is S1, the cross-sectional area of ​​the polymer layer is S2, 1% ≤ S1 / S2 ≤ 95%; and / or;

[0055] The second conductive layer includes a second conductive region, the area of ​​which is S3 as a second orthogonal projection onto the polymer layer, and the cross-sectional area of ​​the polymer layer is S2, where 1% ≤ S3 / S2 ≤ 95%.

[0056] It is understood that the positive current collector of the present invention includes a first conductive layer, a polymer layer, and a second conductive layer stacked together. The first conductive layer includes a first conductive region and a first blank region that are interconnected, and / or, the second conductive layer includes a second conductive region and a second blank region that are interconnected.

[0057] In this invention, the first orthographic projection refers to the shape formed on the polymer layer when incident light irradiates the first conductive area in a direction perpendicular to the polymer layer. The second orthographic projection refers to the shape formed on the polymer layer when incident light irradiates the second conductive area in a direction perpendicular to the polymer layer.

[0058] Due to the presence of the first blank area and / or the second blank area, when the positive electrode sheet including the positive current collector is applied to a battery, the contact area between the positive electrode sheet and the negative electrode sheet is small. This reduces the probability of direct contact between the positive current collector and the negative current collector or between the positive current collector and the negative electrode active layer, thus improving the battery's safety performance. Furthermore, when the battery is punctured or experiences an internal short circuit, the battery generates heat at a high rate, resulting in an extremely large instantaneous current. The conductive layer 2 with blank areas 21 (the first blank area and / or the second blank area) in the positive current collector will melt under high current, creating a localized circuit break that acts as a "fuse," further enhancing the battery's safety performance. Therefore, the battery including this invention exhibits excellent safety performance, especially when the battery is a high-SOC battery. Furthermore, when the area of ​​the first orthogonal projection and / or the second orthogonal projection satisfies the aforementioned relationship with the area of ​​the polymer layer, it is beneficial to the performance of the positive current collector, further improving the battery's performance.

[0059] Furthermore, when 10% ≤ S1 / S2 ≤ 50%; and / or 10% ≤ S3 / S2 ≤ 50%, the overall performance of the battery can be further improved.

[0060] It is worth mentioning that in the positive current collector of the present invention, the conductive layer 2 with the blank area 21 structure is located on the surface of the polymer layer 1. When used to prepare the positive electrode sheet, the positive current collector can be further thinned or its weight reduced, and it is not easy for material leakage to occur during the coating process, making coating convenient.

[0061] The polymer layer 1 of the present invention can be made of polymers commonly used in the art. Exemplarily, the polymer layer 1 can be made of at least one of polyethylene terephthalate, polyimide, polyethylene, polypropylene, polyetheretherketone, and polymethyl methacrylate. The present invention does not impose any particular limitation on the molecular weight of the above polymers.

[0062] The material of the conductive region of the present invention can be a metal material commonly used in the art. For example, the metal material can be at least one of aluminum, nickel, and aluminum alloy.

[0063] In this invention, the blank area and the conductive area together form a conductive layer. This invention does not impose any particular limitation on the number or shape of the conductive areas. Exemplarily, the first conductive area includes a plurality of first conductive sub-regions, which are spaced apart or at least two of the plurality of first conductive sub-regions are interconnected; and / or,

[0064] The second conductive region includes a plurality of second conductive electron regions, which are arranged at intervals or at least two of them are connected to each other.

[0065] In some embodiments of the present invention, any two adjacent conductive regions are interconnected among the multiple conductive regions, and the conductive regions and blank regions together form a mesh structure conductive layer, that is, the first conductive layer and / or the second conductive layer is a mesh structure.

[0066] The present invention does not impose any particular limitation on the cross-sectional shape of the blank area 21. The cross-sectional shape of the blank area 21 can be circular, square, rectangular, triangular, or irregular. In particular, when the cross-sectional area of ​​the blank area 21 is quadrilateral, it is more conducive to improving battery performance and battery processing and manufacturing.

[0067] like Figure 3 As shown, in the positive electrode sheet of the present invention, the positive current collector includes an active layer region, and a positive active layer 4 is disposed thereon in the active layer region; the positive electrode sheet also includes a tab 3, which is connected to the active layer region and extends away from the positive current collector. In some embodiments, the tab 3 can be obtained by die-cutting the positive current collector or by welding it to the active layer region.

[0068] In Formula 1, the area of ​​the conductive region refers to the area of ​​the conductive region where the positive electrode active layer 4 is disposed. In this invention, the areal density of the positive electrode active layer can be obtained by assembling a half-cell with a unit area of ​​positive electrode sheet and lithium foil.

[0069] like Figure 2 As shown, in some embodiments of the present invention, the blank area 21 is rectangular, and the conductive area includes a first portion 231 extending in the second direction of the positive current collector, and / or a second portion 232 extending in the first direction of the positive current collector. The first portion 231 and the second portion 232 have an overlapping area, and the first direction and the second direction are perpendicular to each other.

[0070] A satisfies equation 2;

[0071] A=n1*d1*L2+n2*d2*L1-n1*n2*d1*d2 Formula 2;

[0072] In Equation 2, d1 is the extension dimension of the first part 231 in the first direction, in mm;

[0073] n1 is the number of first parts 231, and the n1 first parts 231 have the same extension dimension in the first direction;

[0074] L1 is the extension dimension of the positive electrode active layer 4 in the first direction, in mm;

[0075] d2 is the extension dimension of the second part 232 in the second direction, in mm;

[0076] n2 is the number of second parts 232, and the n2 second parts 232 have the same extension dimension in the second direction;

[0077] L2 is the extension dimension of the positive electrode active layer 4 in the second direction, in mm;

[0078] d1>0, d2>0; n1≥0, n2≥0, and n1 and n2 are not both 0; L1>0, L2>0.

[0079] The present invention does not particularly limit the first direction and the second direction of the positive electrode current collector. For example, the first direction can be the length direction (x direction) of the positive electrode current collector, and the second direction can be the width direction (y direction) of the positive electrode current collector.

[0080] The inventors also discovered in their research that when 10mm 2 ≤A≤250000mm 2 ; and / or, 4mAh / cm 2 ≤q≤10mAh / cm 2 When 2≤N≤60, the obtained battery has better safety performance and relatively higher capacity and energy density.

[0081] In some embodiments of the present invention, when the thickness of the polymer layer 1 is 0.5-20 μm, the mechanical properties of the battery can be improved while ensuring the energy density of the battery.

[0082] In some embodiments of the present invention, when the thickness of the conductive layer 2 is 0.1-5 μm, the discharge performance of the battery can be improved while ensuring the energy density and safety performance of the battery.

[0083] In some implementations, the positive current collector can be prepared by a method including the following steps:

[0084] 1) A polymer film with through holes is laminated onto at least one surface of the metal foil-polymer layer-metal foil composite current collector;

[0085] 2) After removing the metal foil that is not attached to the polymer film in the metal foil-polymer layer-metal foil composite current collector by means of chemical etching or laser etching through through holes, the polymer film is peeled off to obtain a positive current collector including a conductive layer with interconnected conductive areas and blank areas;

[0086] The polymer film with through holes can be formed by metal die-cutting or laser etching; the chemical etching can be acid etching or alkali etching; the peel force between the polymer film and the surface of the metal foil-polymer layer-metal foil composite current collector is 0.02-0.1 N / m;

[0087] Laser etching can be femtosecond laser etching. In femtosecond laser etching, the wavelength can be 150nm to 350nm, the power can be 10mW to 50mW, and the time can be 10fs to 60fs. The specific process parameters can be adjusted according to the actual situation.

[0088] The battery of the present invention can be a stacked battery, and the battery further includes a negative electrode and a separator, wherein the separator is located between the positive electrode and the negative electrode. The number N of positive electrode plates in the battery of the present invention is at least 1. In some embodiments, when the number of positive electrode plates is N, the number of negative electrode plates can be N+1, and the number of separators can be 2(N+1).

[0089] In some embodiments of the present invention, the negative electrode sheet includes a negative current collector, and the negative current collector and the positive electrode sheet are stacked together. That is, the battery of the present invention can be a battery without a negative electrode active layer, which has a higher energy density and is easy to use. It should be noted that when the battery is a battery without a negative electrode active layer, before the battery is first formed and charged for activation, the negative electrode current collector contains an inductive film layer, but the negative electrode current collector does not contain negative electrode active material. After the battery is formed and activated, the negative electrode current collector contains negative electrode active material.

[0090] A second aspect of the present invention provides a battery pack comprising the battery of the first aspect.

[0091] It is understood that the battery pack of the present invention may include other batteries commonly used in the art, in addition to the battery of the first aspect. Because the battery pack of the present invention includes the battery of the first aspect, it has excellent capacity and needle penetration safety performance.

[0092] A third aspect of the present invention provides an electronic device, wherein the driving source or energy storage source of the electronic device is a battery as described in the first aspect; or,

[0093] The power source or energy storage source for the electronic device is the battery pack in the second aspect.

[0094] In some implementations, the electronic device can be any device that uses a secondary battery as a power source or energy storage source, such as a mobile phone, a navigator, a drone, or an electric vehicle.

[0095] Since the driving source or energy storage source of the electronic device of the present invention is a battery of the first aspect or a battery pack of the second aspect, the electronic device has excellent safety performance and battery life, and has a wide market application prospect.

[0096] The present invention will now be described in detail through specific embodiments.

[0097] Example 1

[0098] The battery in this embodiment is prepared by a method including the following steps:

[0099] 1) Preparation of positive electrode current collector

[0100] a. A 9μm polypropylene (PP) film is bonded to the two surfaces of the aluminum layer-polymer layer-aluminum layer composite current collector (the polymer layer 1 has a thickness of 8μm and is made of polyethylene terephthalate, and the aluminum layer has a thickness of 1μm). The peel force between the polypropylene film and the surface of the aluminum layer-polymer layer-aluminum layer composite current collector is 0.05N / m. The PP film is pre-cut with 30*30mm through holes by laser cutting.

[0101] b. A femtosecond laser was used to etch the aluminum layer on both surfaces of the aluminum-polymer-aluminum composite current collector that was not protected by the PP film through a through hole. The femtosecond laser wavelength was 200nm, the power was 30mW, and the time was 40fs.

[0102] c. After the etching process is completed, the PP film is peeled off from the surface of the aluminum layer-polymer layer-aluminum layer composite current collector to obtain a positive electrode current collector including a conductive layer with blank areas and conductive areas connected to each other (the conductive layer has a mesh structure, and the blank areas of the mesh structure are rectangular).

[0103] 2) Preparation of positive electrode sheet

[0104] The positive electrode active material (LiNi) was prepared using a vacuum stirrer. 0.70 Co 0.10 Mn 0.20 48.5g of O2, 0.5g of conductive agent - acetylene black, 0.5g of conductive agent - carbon nanotubes and 0.5g of binder (polyvinylidene fluoride) were mixed evenly in N-methylpyrrolidone (NMP) to form a stable and uniform positive electrode slurry. The stirring speed of the vacuum mixer was 1000 rpm and the stirring time was 12h.

[0105] Then, the positive electrode slurry is coated onto the surface of the aluminum layer of the positive electrode current collector, controlling the areal density of both sides to be 395 g / m². 2 (Surface capacity q=7mAh / cm²) 2 Then it is dried at 80℃ and rolled by a roller press (compacted density 3.40 g / cm³). 3 The positive electrode sheet is obtained by welding the tabs and the tab rollers.

[0106] 3) Preparation of negative electrode sheet

[0107] Pure copper foil with a thickness of 8μm was used as the standard negative electrode.

[0108] 4) Battery manufacturing

[0109] The positive electrode sheet is die-cut to obtain a positive electrode sheet with an active layer region size of 266×72mm (L1=266mm, L2=72mm); the negative electrode sheet is die-cut to obtain a negative electrode sheet with an active layer region size of 270×74mm.

[0110] The die-cut positive electrode, separator (15μm thick) and die-cut negative electrode sheet are stacked in a Z-shape, hot-pressed, and then the electrode tabs are welded to obtain the electrode assembly. The electrode assembly is placed in an aluminum-plastic film, injected with 2.2mL / Ah electrolyte, and sealed with a formation welding cover to obtain the battery.

[0111] The number of positive electrode plates is 30, the number of negative electrode plates is 31, the number of separator layers is 62, the hot pressing temperature is 80℃, the holding time is 3 minutes, and the pressure is 2 tons.

[0112] The electrolyte was obtained by dissolving 1 wt% LiNO3 in a 4 M LiFSI solution in dimethyl glycol ether (DME).

[0113] Other parameters are detailed in Table 1.

[0114] Example 2

[0115] The battery preparation method in this embodiment is basically the same as that in embodiment 1, except that in step 4), the number of positive electrode plates is 50, the number of negative electrode plates is 51, and the number of separator layers is 102.

[0116] Example 3

[0117] The battery preparation method in this embodiment is basically the same as that in Example 1, except that in step 4), the number of positive electrode plates is 10, the number of negative electrode plates is 11, and the number of separator layers is 22.

[0118] Example 4

[0119] The battery preparation method in this embodiment is basically the same as that in Example 1, except that:

[0120] In step 1), the area of ​​the conductive region differs from that in Example 1;

[0121] In step 4), there are 13 positive electrode plates, 14 negative electrode plates, and 28 layers of separator.

[0122] Example 5

[0123] The battery preparation method in this embodiment is basically the same as that in Example 1, except that:

[0124] In step 2), the double-sided areal density of the positive electrode is 598 g / cm³. 2 (Area capacity q=10.6mAh / cm²)2 );

[0125] In step 4), there are 33 positive electrode plates, 34 negative electrode plates, and 68 layers of separator.

[0126] Example 6

[0127] The battery preparation method in this embodiment is basically the same as that in Example 1, except that in step 2), the double-sided areal density of the positive electrode sheet is 197.5 g / m². 2 (Surface capacity q=3.5mAh / cm²) 2 ).

[0128] Example 7

[0129] The battery preparation method in this embodiment is basically the same as that in Example 4, except that the blank area of ​​the mesh structure is circular.

[0130] Comparative Example 1

[0131] The preparation method of the battery in this comparative example is basically the same as that in Example 1, except that: in step 1), the positive electrode current collector is an aluminum layer-polymer layer-aluminum layer composite current collector (the thickness of polymer layer 1 is 8μm, the material is polyethylene terephthalate, and the thickness of aluminum layer is 1μm), and the metal layer of the composite current collector is not etched.

[0132] Comparative Example 2

[0133] The preparation method of the battery in this comparative example is basically the same as that in Example 1, except that in step 4), the number of positive electrode plates is changed to 65, the number of negative electrode plates is 66, and the number of separator layers is 132.

[0134] Performance testing

[0135] The following performance tests were performed on the batteries in the examples and comparative examples, and the test results are shown in Table 1 and Table 2, respectively.

[0136] 1. Needle prick safety test

[0137] Five batteries were taken from each battery and subjected to a charge-discharge cycle test at 0.2C under 25°C conditions using a secondary battery performance testing device. The steps were as follows: rest for 10 minutes; charge at a constant current of 0.2C to 4.3V, then charge at a constant voltage to 4.3V / 0.05C cutoff; rest for 10 minutes; discharge at 0.5C to 3.6V, which constitutes one cycle. After repeating this step twice, the batteries were fully charged according to the same charging steps and then subjected to a nail penetration test.

[0138] After photographing the voltage, weight, and appearance of the fully charged battery to be tested, it was fixed onto the needle; [The following is a description of the method used]. A high-temperature resistant steel needle was inserted completely into the center of the battery cell at a speed of 25±5 mm / s and held in place until the cell temperature cooled to room temperature, penetrating through the geometric center of the punctured surface. During the puncture, the needle was inserted perpendicularly to the battery plates, remaining inside the battery. The battery was observed for 1 hour, and the puncture test results were recorded.

[0139] 2. Capacity and volumetric energy density

[0140] Two batteries were used for each test. Using a secondary battery performance testing device, the batteries were subjected to charge-discharge cycles at 25°C to calibrate the cell capacity. The steps were as follows: rest for 10 minutes; charge at a constant current of 0.2C to 4.3V, then charge at a constant voltage to 4.3V / 0.05C cutoff; rest for 10 minutes; discharge at 0.5C to 2.8V, which constitutes one cycle. This process was repeated three times, and the final discharge capacity was taken as the calibrated discharge capacity.

[0141] Volumetric energy density can be calculated from the cell capacity and cell volume (excluding structural components such as aluminum-plastic film and tabs). Volumetric energy density = Capacitance × Average discharge voltage / Cell volume. In this example, the positive electrode material is LiNi. 0.70 Co 0.10 Mn 0.20 O2 has an average discharge voltage of 3.78V, and the cell volume is determined based on the actual cell design (the cell volume before formation and charging).

[0142] Table 1

[0143]

[0144] Table 2

[0145] Cell capacity (Ah) Cell volume (L) Volumetric energy density (Wh / L) Example 1 40.22 0.10 1532.10 Example 2 67.03 0.16 1536.61 Example 3 13.41 0.03 1509.95 Example 4 17.43 0.04 1517.54 Example 5 66.99 0.15 1697.28 Example 6 20.11 0.06 1192.05 Example 7 17.05 0.04 1501.86 Comparative Example 1 60.33 0.15 1535.85 Comparative Example 2 87.14 0.21 1538.17

[0146] Based on the experimental results in Tables 1 and 2, it can be seen that this patented solution not only has high volumetric energy density, but also greatly ensures the needle penetration safety performance of the battery cell.

[0147] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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; and 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 the present invention.

Claims

1. A battery, characterized in that, It includes a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive active layer located on at least one surface of the positive current collector; The positive electrode current collector includes a polymer layer and a conductive layer located on at least one surface of the polymer layer, the conductive layer including conductive regions; the positive electrode active layer is at least partially located on the surface of the conductive layer away from the polymer layer; The battery satisfies: A*N*q*10 -5 ≤10; In Equation 1, A is the surface area of ​​the conductive region, in mm. 2 ; q is the areal density of the positive electrode active layer, in mAh / cm³. 2 ; N is the number of positive electrode plates in the battery.

2. The battery according to claim 1, characterized in that, A*N*q*10 -5 ≤6。 3. The battery according to claim 1 or 2, characterized in that, The conductive layer includes a first conductive layer and a second conductive layer, wherein the first conductive layer is located on one surface of the polymer layer, and the second conductive layer is located on the surface of the polymer layer away from the first conductive layer; The first conductive layer includes a first conductive region, the area of ​​the first conductive region on the polymer layer is S1, the cross-sectional area of ​​the polymer layer is S2, 1% ≤ S1 / S2 ≤ 95%; and / or; The second conductive layer includes a second conductive region, the area of ​​the second conductive region on the polymer layer is S3, the cross-sectional area of ​​the polymer layer is S2, and 1% ≤ S3 / S2 ≤ 95%.

4. The battery according to claim 3, characterized in that, 10% ≤ S1 / S2 ≤ 50%; and / or; 10% ≤ S3 / S2 ≤ 50%.

5. The battery according to claim 3 or 4, characterized in that, The first conductive region includes a plurality of first conductive sub-regions, wherein the plurality of first conductive sub-regions are arranged at intervals or at least two of the plurality of first conductive sub-regions are connected to each other; and / or, The second conductive region includes a plurality of second conductive sub-regions, which are arranged at intervals or at least two of the plurality of second conductive sub-regions are connected to each other.

6. The battery according to claim 5, characterized in that, The first conductive layer and / or the second conductive layer are mesh structures.

7. The battery according to any one of claims 1-6, characterized in that, 10mm 2 ≤A≤250000mm 2 ; and / or, 4mAh / cm 2 ≤q≤14mAh / cm 2 ; and / or, 1≤N≤60。 8. The battery according to any one of claims 1-6, characterized in that, The thickness of the polymer layer is 0.5-20 μm; and / or, The thickness of the conductive layer is 0.1-5 μm.

9. The battery according to any one of claims 1-8, characterized in that, It also includes a negative electrode sheet, which includes a negative current collector, and the negative current collector and the positive electrode sheet are stacked together.

10. A battery pack, characterized in that, The battery pack includes the battery as described in any one of claims 1-9.

11. An electronic device, characterized in that, The driving source or energy storage source of the electronic device is the battery according to any one of claims 1-9; or, The driving source or energy storage source of the electronic device is the battery pack as described in claim 10.

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