Negative plate, battery cell and battery

Abstract

The utility model provides a negative plate, a battery cell and a battery. The negative plate comprises a current collector, a first negative active material coating and a second negative active material coating, the current collector is provided with a central coating area and edge coating areas located on the two sides of the central coating area in the winding direction, and the first negative active material coating is formed in the central coating area in a coating mode; the second negative electrode active material coating is formed on the edge coating area in a coating manner; and a laser etching region is arranged on one surface, deviating from the current collector, of the second negative electrode active material coating. According to the negative plate, the current collector is provided with the center coating area and the edge coating areas located on the two sides of the center coating area in the winding direction, the first negative electrode active material coating is formed in the center coating area in a coating mode, and the second negative electrode active material coating is formed in the edge coating areas in a coating mode. The laser etching region is arranged on one surface, deviating from the current collector, of the second negative electrode active material coating, so that the lithium ion contact area is increased, the electrolyte storage performance is improved, namely, the wettability of an electrode liquid is improved, the current density of an edge unit surface is reduced, the fast charging capacity under high magnification is improved, and the service life of the lithium ion battery is prolonged. And compared with the traditional negative plate, the negative plate disclosed by the utility model ensures the capacity retention ratio of the battery.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and in particular to a negative electrode sheet, a battery cell and a battery. Background Art

[0002] In recent years, with the continuous iteration and update of lithium-ion batteries and their widespread popularization in equipment applications, lithium-ion batteries have gradually developed in the direction of small size, light weight, and high energy density. As the annual power consumption of equipment increases year by year, people are increasingly demanding high energy density and high-rate fast charging cells.

[0003] However, when fast charging is performed under conditions of high energy density and high rate, that is, fast charging under conditions of high surface density, the migration path of lithium ions is long and the polarization is large due to the large amount of lithium embedded. When the sum of the equilibrium potential and the overpotential is negative relative to the Li+ / Li electrode pair, the lithium precipitation side reaction, that is, the lithium deposition side reaction, is likely to occur, especially in the constant current charging stage, when the graphite negative electrode potential is more likely to reach the lithium precipitation potential. As charging continues, the positions where lithium ions can be embedded between the graphite layers gradually decrease during the charging process, and the positions where lithium ions can be embedded in the middle of the electrode gradually decrease. Under the condition that the corresponding charging current remains unchanged, lithium ions diffuse from the middle to the edge, and the edge surface current density gradually increases, resulting in more and more lithium ions accumulating at the edge of the graphite, driving lithium precipitation at the edge of the negative electrode, resulting in the tail of the battery cell curling up during the cycle, the battery cell deformation, reduced capacity retention rate, and increased battery cell safety risks.

[0004] In order to reduce the risk of lithium deposition at the edge of the negative electrode, existing technologies such as CN 216054790 U disclose a partitioned negative electrode film roll. Although the details of coating the first film area and the second film area located on both sides of the first film area along the length direction of the negative electrode current collector are disclosed, the first negative electrode slurry in the first film area contains conventional graphite, and the second negative electrode slurry in the second film area contains high-kinetic performance graphite to improve lithium deposition at the edge of the negative electrode. However, the second negative electrode slurry in the second film area contains high-kinetic performance graphite, which makes the capacity density of the battery lower, which undoubtedly reduces the capacity retention rate of the battery. Utility Model Content

[0005] The purpose of this application is to overcome the shortcomings of the existing technology and provide a negative electrode sheet, a battery cell and a battery that can reduce negative electrode polarization, reduce the risk of lithium plating and do not reduce the battery capacity retention rate.

[0006] The purpose of this application is achieved through the following technical solutions:

[0007] A negative electrode sheet comprising a current collector, a first negative electrode active material coating, and a second negative electrode active material coating, wherein the current collector has a central coating region and edge coating regions located on either side of the central coating region along a winding direction, the first negative electrode active material coating is applied and formed on the central coating region, and the second negative electrode active material coating is applied and formed on the edge coating regions;

[0008] A laser etching area is provided on a side of the second negative electrode active material coating layer that is away from the current collector.

[0009] In one embodiment, the width of the second negative electrode active material coating layer is equal to 100 micrometers to 300 micrometers.

[0010] In one embodiment, the weight of the second negative electrode active material coating corresponding to the laser etched area accounts for 0.5% to 3% of the total weight of the second negative electrode active material coating.

[0011] In one embodiment, the etching depth of the laser etching area is 5% to 30% of the thickness of the negative electrode sheet.

[0012] In one embodiment, the second negative electrode active material coating is a fast ion conductor active material coating.

[0013] In one embodiment, the surface density of the second negative electrode active material coating layer exceeds the surface density of the first negative electrode active material coating layer by 0.5% to 1%.

[0014] In one embodiment, the edge coating areas on both sides of the central coating area extend to edge regions on both sides of the central coating area respectively.

[0015] In one embodiment, the widths of the edge coating areas on both sides of the central coating area are equal.

[0016] In one embodiment, the widths of the laser-etched regions of the second negative electrode active material coating layer in the edge coating regions on both sides of the central coating region are equal.

[0017] In one embodiment, the central coating area and the edge coating area are both double-die coating molding structures.

[0018] A battery cell comprises the negative electrode sheet described in any one of the above embodiments.

[0019] A battery comprises the battery cell described in any one of the above embodiments.

[0020] Compared with the prior art, this application has at least the following advantages:

[0021] The above-mentioned negative electrode sheet has a central coating area and edge coating areas on both sides of the central coating area along the winding direction of the current collector. The first negative electrode active material coating is coated and formed on the central coating area, and the second negative electrode active material coating is coated and formed on the edge coating area. The side of the second negative electrode active material coating facing away from the current collector is provided with a laser etching area, which not only increases the lithium ion contact area, but also improves the storage performance of the electrolyte, that is, improves the wettability of the electrode liquid, thereby reducing the current density of the edge unit surface, improving the fast charging capability at high rate, and reducing the risk of lithium plating at the negative electrode edge. Compared with traditional negative electrode sheets, the above-mentioned negative electrode sheet ensures the capacity retention rate of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 Schematic diagram of a negative electrode sheet according to an embodiment. DETAILED DESCRIPTION

[0024] To facilitate understanding of the present application, a more comprehensive description of the present application will be provided below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0025] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly attached to the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are intended only to describe specific embodiments and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0027] The present application provides a negative electrode sheet, comprising a current collector, a first negative electrode active material coating, and a second negative electrode active material coating. The current collector is provided with a central coating region and edge coating regions located on both sides of the central coating region along a winding direction. The first negative electrode active material coating is coated and formed on the central coating region, and the second negative electrode active material coating is coated and formed on the edge coating regions. The second negative electrode active material coating is provided with a laser-etched region on a side facing away from the current collector. The above-mentioned negative electrode sheet comprises a central coating region and edge coating regions located on both sides of the central coating region along a winding direction. The first negative electrode active material coating is coated and formed on the central coating region, and the second negative electrode active material coating is coated and formed on the edge coating regions. The second negative electrode active material coating is provided with a laser-etched region on a side facing away from the current collector. This not only increases the lithium ion contact area, but also improves the storage performance of the electrolyte, that is, improves the wettability of the electrode liquid, thereby reducing the current density of the edge unit area, improving the fast charging capability at high rates, and reducing the risk of lithium plating at the negative electrode edge. Compared with traditional negative electrode sheets, the above-mentioned negative electrode sheet ensures the capacity retention rate of the battery.

[0028] To better understand the technical solutions and beneficial effects of the present application, the present application is further described in detail below with reference to specific embodiments:

[0029] The negative electrode sheet 10 of one embodiment includes a current collector 100, a first negative electrode active material coating 200, and a second negative electrode active material coating 300. The current collector 100 has a central coating region 110 and edge coating regions 120 located on either side of the central coating region 110 along the winding direction. The first negative electrode active material coating 200 is applied and formed on the central coating region 110, and the second negative electrode active material coating 300 is applied and formed on the edge coating regions 120. The second negative electrode active material coating 300 has a laser-etched region 302 on a side facing away from the current collector 100.

[0030] The above-mentioned negative electrode sheet 10 and the current collector 100 are provided with a central coating area 110 and edge coating areas 120 located on both sides of the central coating area 110 along the winding direction, the first negative electrode active material coating 200 is coated and formed on the central coating area 110, and the second negative electrode active material coating 300 is coated and formed on the edge coating area 120. The side of the second negative electrode active material coating 300 facing away from the current collector 100 is provided with a laser etching area 302, which not only increases the lithium ion contact area, but also improves the storage performance of the electrolyte, that is, improves the wettability of the electrode liquid, thereby reducing the current density of the edge unit surface, improving the fast charging capability at high rate, and reducing the risk of lithium plating at the negative electrode edge. Compared with the traditional negative electrode sheet 10, the above-mentioned negative electrode sheet 10 ensures the capacity retention rate of the battery.

[0031] In one embodiment, the width of the second negative electrode active material coating 300 is equal to 100 microns to 300 microns, which reduces the risk of lithium plating at the edge of the negative electrode. In this embodiment, the width of the second negative electrode active material coating 300 is equal to 180 microns.

[0032] In one embodiment, the weight of the second negative electrode active material coating 300 corresponding to the laser-etched area 302 accounts for 0.5% to 3% of the total weight of the second negative electrode active material coating 300. This not only effectively increases the lithium ion contact area, but also effectively improves the electrolyte storage performance. In this embodiment, the weight of the second negative electrode active material coating 300 corresponding to the laser-etched area 302 accounts for 2% of the total weight of the second negative electrode active material coating 300.

[0033] In one embodiment, the laser-etched region 302 has an etching depth of 5% to 30% of the thickness of the negative electrode sheet 10, which not only effectively increases the lithium ion contact area but also effectively improves the electrolyte storage performance. In this embodiment, the laser-etched region 302 has an etching depth of 12% of the thickness of the negative electrode sheet 10.

[0034] In one embodiment, the second negative electrode active material coating 300 is a fast ion conductor active material coating, which can help lithium ion transport and transmission while helping to build a three-dimensional lithium ion channel, improve material rate capability, reduce the negative electrode surface overpotential, and reduce negative electrode polarization. In this embodiment, the second negative electrode active material, the second conductive agent, the second binder, and the fast ion conductor are added to deionized water in a weight ratio of (97.0%-98%): (0.1%-2%): (0.7%-2%): (0.4%-1.0%), and stirred to prepare a slurry of the second negative electrode active material coating 300. Furthermore, the particle size of the fast ion conductor is 200nm, which better helps lithium ion transport and transmission while helping to build a three-dimensional lithium ion channel, that is, it improves the edge dynamics of the battery electrode, improves material rate capability, reduces the negative electrode surface overpotential, reduces the negative electrode polarization, and improves the long cycle capacity of the battery. Specifically, the fast ion conductor is Li 6.5 La3Zr 1.5 Ta 0.5 O 12 .

[0035] In one embodiment, the surface density of the second negative electrode active material coating layer 300 exceeds the surface density of the first negative electrode active material coating layer 200 by 0.5% to 1%.

[0036] In one embodiment, the edge coating areas 120 located on both sides of the central coating area 110 extend to the edge areas on both sides of the central coating area 110, so that the risk of lithium plating can be reduced at both sides of the edges of the negative electrode sheet 10 along the winding direction.

[0037] In one embodiment, the edge coating areas 120 on both sides of the central coating area 110 have the same width, so that the risk of lithium plating can be reduced at both sides of the negative electrode sheet 10 along the winding direction.

[0038] In one embodiment, the widths of the laser-etched areas 302 of the second negative electrode active material coating 300 in the edge coating areas 120 on both sides of the central coating area 110 are equal, which not only increases the lithium ion contact area but also improves the storage performance of the electrolyte.

[0039] In one embodiment, both the central coating area 110 and the edge coating area 120 are formed using a dual-die coating structure. In this embodiment, a dual-die coating method is used to coat the first negative electrode active material coating 200 on the central coating area 110, and the second negative electrode active material coating 300 on the edge coating area 120. Specifically, the central coating area 110 is the center area of ​​the wound core, and the edge coating area 120 is the edge area of ​​the wound core.

[0040] The present application also provides a battery cell, comprising the negative electrode sheet 10 described in any of the above embodiments. Furthermore, the negative electrode sheet 10 comprises a current collector 100, a first negative electrode active material coating 200 and a second negative electrode active material coating 300. The current collector 100 is provided with a central coating area 110 and edge coating areas 120 located on both sides of the central coating area 110 along the winding direction. The first negative electrode active material coating 200 is coated and formed on the central coating area 110, and the second negative electrode active material coating 300 is coated and formed on the edge coating area 120. A laser etching area 302 is provided on a side of the second negative electrode active material coating 300 facing away from the current collector 100. In this embodiment, the battery cell can be a soft-pack battery cell.

[0041] In the above-mentioned battery cell, the current collector 100 of the negative electrode sheet 10 of the battery cell is provided with a central coating area 110 and edge coating areas 120 located on both sides of the central coating area 110 along the winding direction, the first negative electrode active material coating 200 is coated and formed on the central coating area 110, and the second negative electrode active material coating 300 is coated and formed on the edge coating area 120. The side of the second negative electrode active material coating 300 facing away from the current collector 100 is provided with a laser etching area 302, which not only increases the lithium ion contact area, but also improves the storage performance of the electrolyte, that is, improves the wettability of the electrode liquid, thereby reducing the current density of the edge unit surface, improving the fast charging capability at high rate, and reducing the risk of lithium plating at the negative electrode edge. Compared with the traditional negative electrode sheet 10, the above-mentioned negative electrode sheet 10 ensures the capacity retention rate of the battery.

[0042] The present application also provides a battery, comprising the battery cell described in any of the above embodiments.

[0043] Compared with the prior art, this application has at least the following advantages:

[0044] The above-mentioned negative electrode sheet 10 and the current collector 100 are provided with a central coating area 110 and edge coating areas 120 located on both sides of the central coating area 110 along the winding direction, the first negative electrode active material coating 200 is coated and formed on the central coating area 110, and the second negative electrode active material coating 300 is coated and formed on the edge coating area 120. The side of the second negative electrode active material coating 300 facing away from the current collector 100 is provided with a laser etching area 302, which not only increases the lithium ion contact area, but also improves the storage performance of the electrolyte, that is, improves the wettability of the electrode liquid, thereby reducing the current density of the edge unit surface, improving the fast charging capability at high rate, and reducing the risk of lithium plating at the negative electrode edge. Compared with the traditional negative electrode sheet 10, the above-mentioned negative electrode sheet 10 ensures the capacity retention rate of the battery.

[0045] The following are some specific examples, where "%" refers to percentages by weight. It should be noted that the following examples are not exhaustive and that the materials used in the following examples are all commercially available unless otherwise specified.

[0046] Example 1

[0047] A method for preparing a negative electrode sheet 10 includes:

[0048] (1) Graphite material, carboxymethyl cellulose, styrene-butadiene rubber, and conductive carbon black are mixed in a ratio of 97.7% wt: 0.8% wt:

[0049] 1.0% wt: 0.5% wt was added to deionized water and stirred to prepare negative electrode slurry a;

[0050] (2) Graphite material, carboxymethyl cellulose, styrene-butadiene rubber, conductive carbon black, Li 6.5 La3Zr 1.5 Ta 0.5 O 12 Add 97.7% wt: 0.5% wt: 1.1% wt: 0.2% wt: 0.5% wt into deionized water and stir to prepare negative electrode slurry b;

[0051] (3) Figure 1 , using a double-die extrusion coating method, slurry a is coated on the central coating area 110 of the current collector 100, and slurry b is coated on the edge coating area 120, wherein the central coating area 110 of the electrode sheet becomes the central area of ​​the winding core after winding, and the edge coating area 120 of the electrode sheet becomes the edge area of ​​the winding core after winding, and then dried, rolled, and cut to prepare the negative electrode sheet 10;

[0052] (4) Add lithium cobalt oxide material, conductive agent and binder according to 97% wt: 1.7% wt: 1.3% wt

[0053] N-methylpyrrolidone is stirred and evenly coated on the positive electrode current collector 100, dried, rolled, and cut to prepare a positive electrode sheet;

[0054] (5) laser etching the edge coating area 120 of the negative electrode sheet 10 after preparation, wherein the weight of the laser-etched portion accounts for 0.5%-3% of the total weight of the edge coating area 120, and the etching depth accounts for 5%-30% of the thickness of the negative electrode sheet;

[0055] (6) Winding the battery into a core in the order of positive electrode sheet / diaphragm / negative electrode / diaphragm, performing liquid injection, aging, formation, and capacity separation to complete the preparation of the battery cell.

[0056] Example 2

[0057] A method for preparing a negative electrode sheet 10 includes:

[0058] (1) Graphite material, carboxymethyl cellulose, styrene-butadiene rubber, and conductive carbon black were mixed at a ratio of 97.7% wt: 0.8%

[0059] wt: .1.0% wt: 0.5% wt was added into deionized water and stirred to prepare negative electrode slurry a; (2) graphite material, carboxymethyl cellulose, styrene-butadiene rubber, conductive carbon black, Li 6.5 La3Zr 1.5 Ta 0.5 O 12 Add 97.7% wt: 0.5% wt: 0.9% wt: 0.2% wt: 0.7% wt into deionized water and stir to prepare negative electrode slurry b;

[0060] (3) Figure 1 , using a double-die extrusion coating method, slurry a is applied to the central coating area 110 of the current collector 100, and slurry b is applied to the edge coating area 120, wherein the central coating area 110 of the electrode sheet becomes the central area of ​​the winding core after winding, and the edge coating area 120 of the electrode sheet becomes the edge area of ​​the winding core after winding, and then dried, rolled, and cut to prepare the negative electrode sheet 10;

[0061] (4) adding lithium cobalt oxide material, conductive agent, and binder in a ratio of 97% wt: 1.7% wt plus 1.3% wt to N-methylpyrrolidone, stirring, and evenly coating on the positive electrode current collector 100, drying, rolling, and cutting to prepare a positive electrode sheet;

[0062] (5) The edge coating area 120 after film production is laser etched, and the weight of the laser etched part accounts for 0.5%-3% of the total weight of the edge coating area 120, and the etching depth accounts for 5%-30% of the thickness of the negative electrode sheet.

[0063] (6) Winding the battery into a core in the order of positive electrode sheet / diaphragm / negative electrode / diaphragm, performing liquid injection, aging, formation, and capacity separation to complete the preparation of the battery cell.

[0064] Comparative Example 1

[0065] A negative electrode sheet 10 and a battery preparation method include:

[0066] (1) adding graphite material, carboxymethyl cellulose, styrene-butadiene rubber, and conductive carbon black in a ratio of 97.4% wt: 0.8% wt: 1.3% wt: 0.5% wt into deionized water and stirring to prepare a negative electrode slurry a;

[0067] (2) Applying slurry a to the entire area of ​​the current collector 100 by extrusion coating, drying, rolling, and cutting to prepare the negative electrode sheet 10;

[0068] (3) adding lithium cobalt oxide material, conductive agent, and binder in a ratio of 97% wt: 1.7% wt and 1.3% wt to N-methylpyrrolidone, stirring, and evenly coating on the positive electrode current collector 100, drying, rolling, and cutting to prepare a positive electrode sheet;

[0069] (4) Winding the battery into a core in the order of positive electrode sheet / diaphragm / negative electrode / diaphragm, performing liquid injection, aging, formation, and capacity separation to complete the preparation of the battery cell.

[0070] Batteries containing the negative electrode sheets 10 of Examples 1-2 and Comparative Example 1 were tested. The test method was as follows: first, constant current and constant voltage charging was performed to 4.48V at a temperature of (25±1)°C and a charge rate of 2.0C. The charged battery was then left for 10 minutes and then discharged to 3.0V at a discharge rate of 0.7C. The capacity retention rate at the nth cycle = capacity at the nth cycle / capacity at the third cycle × 100%. The battery's capacity retention rate (1000T) and the lithium deposition status at the electrode edge were obtained as shown below.

[0071] Battery capacity retention rate 1000T and electrode edge lithium deposition status table

[0072] Case 25℃ capacity retention rate 1000T State at the edge of the negative electrode sheet 10 Comparative Example 1 82.1％ lithium deposition Example 1 84.2％ No lithium plating Example 2 84.4％ No lithium plating

[0073] According to the above table, the capacity retention rate 1000T of the batteries of Examples 1-2 is higher than that of Comparative Example 1, and the negative electrode sheets 10 of the batteries of Examples 1-2 have no lithium plating, while the negative electrode sheet 10 of the battery of Comparative Example 1 has lithium plating.

[0074] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A negative electrode sheet, comprising a current collector, a first negative electrode active material coating and a second negative electrode active material coating, wherein the current collector is provided with a central coating area and edge coating areas located on both sides of the central coating area along a winding direction, the first negative electrode active material coating is coated and formed on the central coating area, and the second negative electrode active material coating is coated and formed on the edge coating area; characterized in that: A laser etching area is provided on a side of the second negative electrode active material coating layer that is away from the current collector.

2. The negative electrode sheet according to claim 1, characterized in that: The width of the second negative electrode active material coating layer is equal to 100 micrometers to 300 micrometers.

3. The negative electrode sheet according to claim 1, characterized in that: The weight of the second negative electrode active material coating corresponding to the laser etched area accounts for 0.5% to 3% of the total weight of the second negative electrode active material coating.

4. The negative electrode sheet according to claim 1, characterized in that: The etching depth of the laser etching area is 5% to 30% of the thickness of the negative electrode sheet.

5. The negative electrode sheet according to claim 1, characterized in that: The second negative electrode active material coating is a fast ion conductor active material coating.

6. The negative electrode sheet according to claim 1, characterized in that: The surface density of the second negative electrode active material coating layer exceeds the surface density of the first negative electrode active material coating layer by 0.5% to 1%.

7. The negative electrode sheet according to claim 1, characterized in that: The edge coating areas located on both sides of the central coating area extend to the edge areas on both sides of the central coating area respectively; and / or, The widths of the edge coating areas on both sides of the central coating area are equal; and / or, The widths of the laser-etched areas of the second negative electrode active material coating layer in the edge coating areas on both sides of the central coating area are equal.

8. The negative electrode sheet according to claim 1, characterized in that: The central coating area and the edge coating area are both double-die coating molding structures.

9. A battery cell, characterized in that: A negative electrode sheet comprising any one of claims 1 to 8.

10. A battery, characterized in that: Comprising the battery cell as claimed in claim 9.

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