Battery negative pole piece as well as preparation method and application thereof

Abstract

The invention provides a battery negative pole piece as well as a preparation method and application thereof, and relates to the technical field of secondary batteries. Specifically, the surface of the negative pole piece is loaded with a negative paste area and an insulation paste area, and the insulation paste area is arranged at the edge of the negative pole piece; wherein the negative electrode slurry area comprises a negative electrode active material, and the insulating glue area comprises a binder. The insulation paste coating area is arranged in the edge area of the pole piece, so that the edge of the positive electrode is only in contact with the insulation paste of the negative electrode under the conditions of mechanical deformation of the edge of the positive electrode and existence of hidden danger of piercing the diaphragm, thereby avoiding short circuit caused by direct contact with the edge of the negative electrode, and improving the superior product rate of the battery; in addition, the cost is low, the formula is simple, automation and batch implementation are easy to promote, and good application prospects are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary batteries, and in particular to a battery negative electrode sheet, a preparation method thereof, and applications thereof. Background Art

[0002] With the shortage of fossil fuel resources and increasingly serious environmental and ecological problems, various industries and fields are currently pursuing cleaner and more environmentally friendly energy sources. Lithium-ion batteries (LIBs) have become the dominant mobile power source due to their high energy density, long life, and low self-discharge rate. They are widely used in daily life, such as electric vehicles, portable computers, and digital cameras. As lithium-ion batteries become more popular, their safety performance has begun to attract people's attention. When a battery is operating under short-circuit conditions, it will release a large amount of heat in a short period of time, and the internal temperature will rise, causing the battery to burn or even explode. There are many reasons for short circuits, including but not limited to:

[0003] 1) The diaphragm is damaged due to lithium dendrite penetration, external extrusion, thermal shrinkage, external impact, etc., resulting in direct contact between the positive and negative electrodes of the battery and a short circuit;

[0004] 2) Overcharge or over-discharge of the battery causes the voltage to exceed the carrying range; or the accumulation of lithium metal on the electrode during overcharge or over-discharge can easily cause internal short circuit;

[0005] 3) When the battery shell is damaged or the battery seal is poor, the electrolyte leaks out and causes an internal short circuit in the battery, or foreign debris enters the battery and causes a short circuit;

[0006] 4) Short circuit of the battery caused by improper operation, long-term cumulative use, substandard raw material quality, etc.

[0007] Among the current safety hazards caused by battery short circuits, in addition to man-made and avoidable issues such as battery age or strong external physical impact, a common cause of internal short circuits between the positive and negative electrodes is puncture of the separator due to bending of the positive electrode current collector foil edge within the battery cell. Optimizing the internal battery architecture can effectively reduce the probability of short circuits.

[0008] In view of this, the present invention is proposed. Summary of the Invention

[0009] The first purpose of the present invention is to provide a battery negative electrode plate, which can effectively avoid the defect of short circuit caused by direct contact between the positive and negative electrodes when the positive electrode edge bends or pierces the diaphragm by providing a negative electrode edge insulating coating design scheme.

[0010] The second object of the present invention is to provide a method for preparing the negative electrode sheet of the battery, which is simple, easy to implement, low in cost and easy to promote.

[0011] A third object of the present invention is to provide a secondary battery.

[0012] A fourth object of the present invention is to provide an electrical device.

[0013] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0014] A battery negative electrode plate, the surface of which is loaded with a negative electrode slurry area and an insulating adhesive area, wherein the insulating adhesive area is arranged at the edge of the negative electrode plate;

[0015] The negative electrode slurry area includes a negative electrode active material, and the insulating glue area includes a binder.

[0016] A method for preparing a negative electrode sheet of a battery comprises the following steps:

[0017] A negative electrode slurry and an insulating rubber are prepared respectively, and then coated on the surface of at least one side of the negative electrode current collector, and then heat treated to obtain a battery negative electrode sheet.

[0018] A secondary battery comprises the battery negative electrode plate.

[0019] An electrical device comprises the secondary battery.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention provides a design scheme for a negative electrode plate, sets an insulating glue coating area in the edge area of ​​the plate, and provides a preferred design of the glue coating formula and the glue coating position size. Based on the concept of the present invention, in the case of mechanical deformation of the positive electrode edge and the risk of puncturing the diaphragm, the positive electrode edge is only in contact with the negative electrode insulating glue, thereby avoiding direct contact with the negative electrode edge to cause a short circuit, thereby improving the quality rate of the battery. In addition, the insulating coating material provided by the present invention is easy to obtain and has a simple formula. While improving the short circuit problem of the battery cell, it can effectively control the overall cost of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 A feasible schematic diagram of a negative electrode top view is provided;

[0023] Figure 2 Another feasible schematic diagram of a top view of the negative electrode is provided. DETAILED DESCRIPTION

[0024] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0025] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "one," "two," "1," and "2" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] A first aspect of the present invention is to provide a battery negative electrode plate; specifically, the surface of the battery negative electrode plate is loaded with a negative electrode slurry area and an insulating glue area, and the insulating glue area is arranged at the edge of the negative electrode plate; wherein, the negative electrode slurry area includes a negative electrode active material, and the insulating glue area includes a binder.

[0027] As a preferred embodiment, the negative electrode slurry area and the insulating glue area can be loaded on one side of the negative electrode plate or on both sides; in some optional embodiments, whether to load the insulating glue area is selected based on the load of the negative electrode slurry area, that is, when the negative electrode slurry area is coated on one side, the insulating glue area is also coated on one side, similarly to double-sided coating.

[0028] As a preferred embodiment, the surface area distribution diagram of the negative electrode plate is as follows: Figure 1As shown; that is: the insulating rubber area is arranged in a strip-shaped manner at the edge area of ​​the long side of the electrode piece, and the negative electrode slurry area is arranged in the middle of the two insulating rubber areas; when the quadrilateral electrode piece has a significantly longer long side, this preferred embodiment is adopted. At this time, the long side direction of the positive electrode is prone to edge bending, while the short side rarely bends, so the insulating rubber area is correspondingly arranged at the edge of the two long sides.

[0029] As a preferred embodiment, the surface area distribution diagram of the negative electrode plate is as follows: Figure 2 As shown; that is: the insulating glue area surrounds the outside of the negative electrode slurry area, and can also be regarded as the negative electrode slurry area being arranged in the internal area formed by the four strip-shaped insulating glue areas; when the quadrilateral electrode does not have obvious long sides and short sides, this preferred embodiment is adopted. At this time, there is a probability that any edge of the positive electrode will bend, so the insulating glue area is correspondingly provided at the edge of each side.

[0030] As a preferred embodiment, based on the single-side width of the negative electrode plate, the width of the insulating rubber area accounts for 1% to 5%, including but not limited to any one of 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or a ratio interval composed of any two of them.

[0031] As a more preferred embodiment, the width of the insulating glue area is 1mm to 2mm, including but not limited to any one of 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2 (mm) or a numerical range consisting of any two of them.

[0032] As a preferred embodiment, the thickness of the insulating glue area is 20μm to 100μm, including but not limited to any one of 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100 (μm) or a numerical range consisting of any two of them.

[0033] As a preferred embodiment, the present invention does not impose any restrictions on the negative electrode active material, and any adjustment of the negative electrode active component is performed according to the type of battery (such as lithium-ion battery, sodium-ion battery, etc.); at the same time, the negative electrode slurry area can also include components such as conductive agents, binders, solvents, etc., and those skilled in the art can perform any implementation according to actual battery requirements. It can be understood that the process of the insulating glue area of ​​the present invention is not affected by the components of the negative electrode slurry area.

[0034] As a preferred embodiment, the binder includes a cellulose binder and an acrylic binder; wherein the cellulose binder includes at least one of hydroxymethyl cellulose (CMC), hydroxypropyl methyl cellulose (HPMC), cellulose ether (CE), sodium methyl cellulose (MC), cross-linked sodium carboxymethyl cellulose (CC-Na) or hydroxypropyl cellulose (HPC); the acrylic binder includes polyacrylic acid and / or polyacrylate.

[0035] As a more preferred embodiment, the molecular weight of the polyacrylic acid is 30w to 200w.

[0036] As a more preferred embodiment, the polyacrylate includes at least one of polymethyl methacrylate, polyethyl methacrylate, α-cyanoacrylate, etc.; and the molecular weight of the polyacrylate is 30w to 200w.

[0037] As a preferred embodiment, the mass ratio of the cellulose binder to the acrylic binder is (2-5):(10-30).

[0038] As a preferred embodiment, the insulating glue area also includes a colorant, which includes but is not limited to boehmite, or any metal oxide, sulfide, sulfate or chromate, etc.; in some more preferred embodiments, the colorant includes but is not limited to boehmite, titanium dioxide, chromium oxide, zinc oxide, iron oxide, chrome yellow, chrome orange, etc.; in the present invention, since the glue of the binder is translucent and has no obvious color, it is not easy to distinguish it from the black negative electrode slurry when it is coated on the edge of the negative electrode plate; therefore, if a colored component is added, the coating of the insulating glue area can be made white or other colors, which is easier to distinguish from the black negative electrode slurry area, and is also convenient for the CCD visual detection equipment (or similar automated program) of the coater or dispenser to identify and run.

[0039] As a more preferred embodiment, the mass proportion of the colorant in the insulating adhesive area is 65% to 85%.

[0040] A second aspect of the present invention provides a method for preparing a battery negative electrode sheet as described in the first aspect. The method comprises the following steps: preparing a negative electrode slurry and an insulating rubber material, applying the materials to at least one side of a negative electrode current collector, and performing a heat treatment to obtain the battery negative electrode sheet.

[0041] As a preferred embodiment, the preparation method of the insulating rubber material includes: adding various raw material components and water into a container and fully dispersing them, which can be carried out by stirring, oscillating, centrifuging, ultrasonicating, etc.

[0042] As a more preferred embodiment, the preparation method of the insulating rubber material includes: adding a cellulose binder, an acrylic binder and water to a planetary agitator, and stirring and dispersing them under simultaneous revolution and rotation for 20 minutes to 40 minutes, wherein the revolution frequency is 15rpm to 35rpm, and the rotation frequency is 400rpm to 600rpm; then adding a colorant to the planetary agitator, and stirring and dispersing them under simultaneous revolution and rotation for 45 minutes to 75 minutes, wherein the revolution frequency is 25rpm to 45rpm, and the rotation frequency is 1200rpm to 1800rpm; in a further preferred embodiment, the slurry temperature in the planetary agitator is controlled to be 23°C to 30°C, and the vacuum degree is ≤-0.05MPa.

[0043] The third aspect of the present invention provides a secondary battery, comprising the negative electrode sheet as described in the first aspect. It is understood that the secondary battery should also include functional or structural components such as a positive electrode sheet, a separator, and an electrolyte, and the present invention does not impose any restrictions on the composition or size of these components. As long as the negative electrode sheet is included, any embodiment that can achieve the functions of a secondary battery can be considered an embodiment of the present invention.

[0044] A fourth aspect of the present invention provides an electrical device, comprising the secondary battery described in the third aspect. Those skilled in the art will appreciate that the electrical device includes, but is not limited to, electric vehicles, household appliances, mobile communication devices, office appliances, industrial equipment, and the like; any device comprising the secondary battery may constitute an embodiment of the present invention.

[0045] Example 1

[0046] S1: Preparation of insulation mortar:

[0047] 50 parts by weight of boehmite, 0.5 parts by weight of CMC, and 2.5 parts by weight of polyacrylic acid (molecular weight 100w) were weighed respectively; CMC, polyacrylic acid, and 47 parts by weight of water were then placed into a planetary mixer and stirred and dispersed for 30 minutes (revolution: 25 rpm, rotation: 500 rpm); boehmite was then added and stirring and dispersing was continued for 1 hour (revolution: 35 rpm, rotation: 1500 rpm); during the stirring process, the slurry temperature was controlled at 25°C and the vacuum degree was ≤-0.05 MPa.

[0048] S2: Negative electrode preparation:

[0049] The negative electrode composition is prepared as follows: 0.5% CMC + 2% PAA + 1% SBR + 2% conductive carbon black CB + 94.5% graphite; the insulating paste is first applied to the edge of the battery current collector using a gravure roller coating method. The coating method is as follows: Figure 1 As shown, the current collector is a copper foil with specifications of 1000m in length, 150mm in width and 6μm in thickness; the coating width of the two insulating slurries is 1mm and the thickness is 50μm; then the negative electrode slurry is applied to the middle of the two insulating slurries with a coating thickness of 50μm; after heat treatment, the negative electrode sheet of this embodiment is obtained.

[0050] S3: Preparation of battery pack for testing:

[0051] The positive electrode sheet adopts the following composition: 96.6% 10P + 1% Li2160 + 0.5% NP801 + 1.8% FL2032 + 0.1% D300; diaphragm: PMMA diaphragm, thickness 10μm; a total of 15 layers of negative electrodes and 14 layers of positive electrodes are connected in series, and after welding the electrode sheets and tabs, the electrolyte is injected and packaged in sequence to obtain the battery pack used in this embodiment.

[0052] Example 2

[0053] It is basically the same as Example 1, with the only difference being that the coating width of the insulating adhesive paste is 1.5 mm.

[0054] Example 3

[0055] It is basically the same as Example 1, with the only difference being that the coating width of the insulating adhesive paste is 2 mm.

[0056] Example 4

[0057] It is basically the same as Example 1, except that the coating thickness of the insulating adhesive paste is 20 μm.

[0058] Example 5

[0059] It is basically the same as Example 1, except that the coating thickness of the insulating adhesive paste is 100 μm.

[0060] Example 6

[0061] The method is basically the same as Example 1, except that CMC is replaced by CE and polyacrylic acid is replaced by polyacrylate (molecular weight 100w).

[0062] Example 7

[0063] The method is basically the same as Example 1, except that boehmite and the preparation steps related to boehmite are omitted.

[0064] Example 8

[0065] The method is basically the same as Example 1, except that: 2 parts by weight of CMC and 30 parts by weight of polyacrylic acid.

[0066] Comparative Example

[0067] The method is basically the same as Example 1, except that step S1 is omitted, and in step S2, the negative electrode slurry is coated on the entire surface of the current collector.

[0068] Test example

[0069] This test example uses a pulse-type lithium battery cell (micro) short-circuit tester to perform a battery short-circuit judgment test. The method is as follows: the battery is placed on the short-circuit tester, and the operating voltage range is set to 2V~3.65V. During the voltage rise process, the CPU collects the voltages in the three sections of charging, pulse voltage maintenance and discharge through an attenuator and displays them on the LCD in the form of a curve graph; when the product under test is stimulated by high voltage and abnormal discharge occurs due to the existence of short circuit and micro-short circuit problems, the instrument will detect the corresponding voltage change in an extremely short time (milliseconds) and make corresponding judgments and status outputs.

[0070] 200 samples of each of the above examples and comparative examples were tested, and the number of short-circuited cells under the above test method was recorded. The short-circuited cells were further disassembled, and the number of short-circuited cells due to the positive electrode edge piercing the separator was recorded. The recorded results are shown in Table 1.

[0071] Table 1

[0072] Short-circuit cell ratio Number of cells short-circuited due to positive electrode puncturing the diaphragm / Number of short-circuited cells Example 1 3 / 200 1 / 3 Example 2 0 / 200 0 / 0 Example 3 0 / 200 0 / 0 Example 4 2 / 200 1 / 2 Example 5 1 / 200 0 / 1 Example 6 1 / 200 0 / 1 Example 7 13 / 200 12 / 13 Example 8 12 / 200 10 / 12 Comparative Example 20 / 200 15 / 20

[0073] It can be seen from the results in Table 1 above that, compared with the conventional solution without insulating coating, the design of coating the negative electrode edge with insulating coating can effectively improve the short circuit problem caused by the bending of the positive electrode edge piercing the diaphragm, thereby improving the battery quality.

[0074] Although the present invention has been illustrated and described using specific embodiments, it should be appreciated that the above embodiments are merely intended to illustrate the technical solutions of the present invention rather than to limit them. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and scope of the present invention. However, these modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A battery negative electrode plate, characterized in that: The surface of the negative electrode plate is loaded with a negative electrode slurry area and an insulating adhesive area, and the insulating adhesive area is arranged at the edge of the negative electrode plate; The negative electrode slurry area includes a negative electrode active material, and the insulating glue area includes a binder.

2. The battery negative electrode according to claim 1, characterized in that: The width of the insulating rubber area accounts for 1% to 5% of the width of a single side of the negative electrode plate; Preferably, the width of the insulating adhesive area is 1 mm to 2 mm, and the thickness of the insulating adhesive area is 20 μm to 100 μm.

3. The battery negative electrode plate according to claim 1, characterized in that: The binder includes a cellulose binder and an acrylic binder; The cellulose binder includes at least one of hydroxymethyl cellulose, hydroxypropyl methyl cellulose, cellulose ether, sodium methyl cellulose, cross-linked sodium carboxymethyl cellulose or hydroxypropyl cellulose; and the acrylic binder includes at least one of polyacrylic acid and polyacrylate.

4. The battery negative electrode plate according to claim 3, characterized in that: The molecular weight of the polyacrylic acid and / or the polyacrylate is 3*10 5 ~2*10 6 .

5. The battery negative electrode plate according to claim 3, characterized in that: The mass ratio of the cellulose-based binder to the acrylic-based binder is (2-5):(10-30).

6. The battery negative electrode plate according to claim 1, characterized in that: The insulating adhesive area also includes a colorant; Preferably, the colorant accounts for 65% to 85% by mass in the insulating adhesive area.

7. The battery negative electrode plate according to claim 1, characterized in that: The insulating rubber area is arranged at the long side edge of the negative electrode plate, and the negative electrode slurry area is arranged between the two insulating rubber areas; Alternatively, the insulating adhesive region surrounds the outer side of the negative electrode slurry region.

8. The method for preparing a negative electrode sheet for a battery according to any one of claims 1 to 7, wherein: The steps include: A negative electrode slurry and an insulating rubber are prepared respectively, and then coated on the surface of at least one side of the negative electrode current collector, and then heat treated to obtain a battery negative electrode sheet.

9. A secondary battery, characterized in that: The invention comprises a battery negative electrode sheet as claimed in any one of claims 1 to 8.

10. An electrical device, characterized in that: Comprising the secondary battery as claimed in claim 9.

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