WO2024051291A1

WO2024051291A1 - Electrode sheet and battery

Info

Publication number: WO2024051291A1
Application number: PCT/CN2023/102848
Authority: WO
Inventors: 张健; 彭冲
Original assignee: 珠海冠宇电池股份有限公司
Priority date: 2022-09-08
Filing date: 2023-06-27
Publication date: 2024-03-14
Also published as: CN115295757A

Abstract

The present disclosure relates to the technical field of batteries, and in particular to an electrode sheet and a battery comprising the electrode sheet. The electrode sheet comprises a current collector, an active material layer located on one side or two sides of the current collector, and a base coating layer arranged between the current collector and the active material layer, wherein the base coating layer has a pattern structure, and the pattern structure divides the base coating layer into a continuous coating region and several dispersed exposed foil regions; and the active material layer fills the exposed foil regions and covers the surface of the coating region. The active material layer and the current collector in the electrode sheet of the present disclosure have excellent adhesion and have relatively high energy density.

Description

A pole piece and battery

Technical field

The present disclosure relates to the field of battery technology, and in particular to a pole piece and a battery including the pole piece.

Background technique

Batteries are currently widely used in consumer electronics, electric vehicles, energy storage and other fields. The core component of a battery is a pole piece and a separator. The pole piece is usually formed by coating an active material on a current collector. However, the adhesion between the active material layer and the current collector is usually low.

Therefore, it is very important to develop a pole piece that enhances the adhesion between the active material layer and the current collector while maintaining performance.

Contents of the invention

The purpose of the present disclosure is to overcome the above-mentioned problems existing in the prior art and provide a pole piece and a battery including the pole piece. The active material layer in the pole piece of the present disclosure has good adhesion with the current collector and has high energy density.

A first aspect of the present disclosure provides a pole piece, including a current collector, an active material layer located on one side or both sides of the current collector, and an undercoat layer disposed between the current collector and the active material layer. , wherein the undercoat layer has a pattern structure, which divides the undercoat layer into a continuous coating area and a number of scattered exposed foil areas; the active material layer fills the exposed foil area and covers the surface of the coating area.

A second aspect of the disclosure provides a battery, the negative electrode piece and/or the positive electrode piece of the battery are the electrode pieces described in the first aspect of the disclosure.

Through the above technical solutions, the present disclosure has at least the following advantages compared with the prior art:

(1) The active material layer of the pole piece of the present disclosure has good adhesion with the current collector;

(2) The battery of the present disclosure has higher energy density.

Other features and advantages of the present disclosure will be described in detail in the detailed description that follows.

Description of the drawings

Figure 1 shows a top view of a primer smear according to an example of the present disclosure.

Figure 2 shows a side view of the base smear shown in Figure 1 of this disclosure.

Figure 3 shows a side view of a pole piece according to an example of the present disclosure.

Detailed ways

The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only some of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of this disclosure.

A first aspect of the present disclosure provides a pole piece, which includes a current collector, an active material layer located on one side or both sides of the current collector, and a primer disposed between the current collector and the active material layer. layer, wherein the undercoat layer has a pattern structure that divides the undercoat layer into a continuous coating area and a number of scattered exposed foil areas; the active material layer fills the exposed foil area and covers all the surface of the coating area.

A specific implementation of the pole piece is shown in Figures 1, 2 and 3. Figure 1 is a top view of a primer smear provided in an example, Figure 2 is a side view of the primer smear shown in Figure 1, and Figure 3 shows a The example provides a side view of the pole piece. As shown in Figures 1, 2 and 3, the pole piece 05 includes: a current collector 00; the surface of the current collector 00 is coated with an undercoat 01, wherein the undercoat 01 has a pattern structure, and the pattern structure The base coating 01 is divided into a continuous coating area and several scattered exposed foil areas 02; the surface of the base coating 01 is covered with an active material layer, and the active material layer fills the exposed foil area 02 and covers all the exposed foil areas 02. On the surface of the coating area, the active material layer includes granular active material 03 and conductive agent 04.

In order to increase the adhesion between the current collector and the active material layer, a base coat can be coated on the current collector (completely covering the current collector), and the adhesive content of the base coat should be higher than that of the active material layer. agent content, so the adhesive force between the active material layer and the current collector is strong, thereby enhancing the adhesive force between the active material layer and the current collector. However, the inventors of the present disclosure discovered that in this manner, the undercoat layer affects the energy density of the battery. Therefore, the inventor of the present disclosure proposes a method of arranging an exposed foil area on the undercoat layer, so that most of the exposed foil area can be embedded with active material particles, thereby effectively utilizing the space of the undercoat layer and improving the adhesion between the active material and the current collector. The relay also takes into account the energy density.

The exposed foil area 02 is the area where the undercoat layer does not cover the current collector 00 (exposing the current collector so that it can contact the active material).

In the present disclosure, by filling the exposed foil area 02 with the active material layer and covering the surface of the coating area so that the active material layer and the current collector 00 are in direct contact, it has been possible to make the battery pole piece Achieve higher energy density with unchanged adhesion compared to solutions with primer.

The undercoat layer and the active material layer may be located on one side of the current collector 00 or on both sides of the current collector 00 .

According to a specific implementation, the undercoat layer 01 can first cover the current collector 00 , and then the active material layer is covered on the undercoat layer 01 to form the pole piece of the present disclosure.

In one example, the area of the undercoat layer 01 that does not cover the current collector is a foil-exposed area. There are several exposed foil areas, which are (preferably as evenly distributed as possible) dispersed in the undercoat layer. The other areas are coating area. When the coverage ratio of the coating area of the undercoat layer 01 on the current collector 00 is within a certain range, it can not only ensure that the pole piece 05 has a certain adhesive force, but also enable the battery to have a higher energy density. .

According to a specific embodiment, the coverage rate of the coating area of the primer layer 01 on the current collector 00 is 30-80% (for example, 30%, 40%, 50%, 60%, 70%, 80% % and the range consisting of any two points).

Preferably, the coverage rate of the coating area of the undercoat layer 01 on the current collector 00 is 50-70%.

According to a specific implementation, the exposed foil areas 02 are each independently circular, square, strip-shaped, polygonal, patterned or irregular, as well as other arbitrary shapes.

In one example, the minimum distance of the exposed foil area is d, and the minimum distance of the exposed foil area exceeding 80% is d80, and d80>D90 of the active material in the active material layer.

The minimum distance of the exposed foil area 02 is represented by d, which refers to the distance between the two nearest points of the uncoated primer area in the exposed foil area. For example, when the exposed foil area is circular, d is the diameter; when the exposed foil area is irregular, d is the shortest distance between any two points; when the exposed foil area is strip-shaped (such as As shown in Figure 1), the shortest distance is the distance in the width direction (as shown in Figure 2).

The parameter "dn" is set for the exposed foil area, which is used to represent the d value of the exposed foil area exceeding n%. For example, d80<80% of the d value of the exposed foil area, and >20% of the d value of the exposed foil area.

In an example, the d80 of the exposed foil area is 30 μm-500 μm (for example, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm).

In one example, the d80 of the exposed foil area is 40 μm-200 μm.

The active material in the active material layer is in the form of granules, as shown by mark 03 in Figure 3 . live The parameter "Dm" is set for the specific substance. Dm refers to the particle size that reaches the cumulative volume m% from the small particle size side in the volume-based particle size distribution. D90 refers to the particle size that reaches 90% of the cumulative volume from the small particle size side in the volume-based particle size distribution. For example, D90 = 30 μm, then the sum of the volumes of particles ≤ 30 μm accounts for 90% of the total volume.

In one example, the D90 of the active material is 15 μm-50 μm.

According to a specific implementation, the d80 of the exposed foil area is greater than the D90 of the active material. Most of the active material particles 03 that meet the above size conditions can be embedded in most of the exposed foil areas 02 and can have good contact with the current collector 00 .

The term "dn of the exposed foil area is greater than Dm of the active material" includes various possible size relationships that can achieve this condition, that is, it is not limited to the n and m numbers themselves. For example, "the d80 of the exposed foil area is greater than the D90 of the active material" must at least meet the requirement that 90% of the active material can be embedded in 80% of the exposed foil area, which also includes "all active materials can be embedded in at least 80% of the exposed foil area" The situation of "exposed foil areas" also includes (for example, when all the pores in the exposed foil areas are the same) the situation of "at least 90% of the active material can be embedded in all exposed foil areas", and so on.

The formation method of the foil-exposed area is not particularly limited. In one example, the foil-exposed area is formed by coating the undercoat slurry on the current collector through gravure printing. In another example, the foil-exposed area is achieved by laser drilling on the base coat layer without exposing the foil.

According to a specific implementation, the base coating includes a first adhesive, a first conductive agent and a first thickener, wherein based on the total weight of the base coating 01, the first adhesive The content of the first conductive agent is 20-40% by weight (such as 20%, 25%, 30%, 35%, 40%), and the content of the first conductive agent is 30-60% by weight (such as 30%, 35%, 40%). %, 45%, 50%, 55%, 60%), the components and content of the base coating are the components and content in the coating area, and the content of the first thickener is 20-40 % by weight (eg 20%, 25%, 30%, 35%, 40%).

According to a specific embodiment, the active material layer includes an active material, a second adhesive, a second conductive agent and a second thickener, wherein based on the total weight of the active material layer, the active material The content of the second adhesive is 94-98% by weight (such as 94%, 95%, 96%, 97%, 98%), and the content of the second adhesive is 1-2.5% by weight (such as 1%, 1.5%, 2 %, 2.5%), the content of the second conductive agent is 0.5-1.5% by weight (such as 0.5%, 1%, 1.5%), and the content of the second thickening agent is 0.5-2% by weight (such as 0.5 %, 1%, 1.5%, 2%).

In one example, the first thickener and the second thickener may be the same or different, and are each independently selected from the group consisting of sodium carboxymethylcellulose, polyvinyl alcohol, polyethylene glycol and polyvinylpyrrolidone. One kind and many kinds.

According to a specific embodiment, the first adhesive and the second adhesive may be the same or different, and are each independently selected from adhesives containing carboxyl groups and/or ester groups.

In one example, the first adhesive and the second adhesive are each independently selected from one of polyacrylates, acrylic-modified styrene-butadiene rubber, and acrylic-modified vinylidene fluoride. Kind or variety.

According to a specific embodiment, the thickness of the primer layer is 0.2 μm-2 μm (for example, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm) .

According to a specific implementation, the thickness of the primer layer is 0.4 μm-0.8 μm.

According to a specific implementation, the thickness of the active material layer is 30 μm-70 μm (thickness of one side of the current collector).

In one example, the first conductive agent and the second conductive agent are one or more of carbon black, carbon tube, graphene, metal conductive powder, carbon fiber, acetylene black and Ketjen black. For example, the second conductive agent in the active material layer can be obtained by mixing graphene and carbon black according to a certain mass percentage, or can be obtained by mixing carbon black and metal conductive powder according to a certain mass percentage, or Carbon black, graphene or metal conductive powder may be used alone as the conductive agent in the active material layer, and this disclosure does not limit it.

In one example, the specific surface areas of the first conductive agent and the second conductive agent are each independently 10 m ² /g to 1000 m ² /g.

The undercoat layer of the present disclosure can be applied to both positive and negative electrode sheets.

When the undercoat of the present disclosure is used for a negative electrode sheet: the undercoat 01 uses an adhesive containing carboxyl or ester groups to produce chemical bonding with the copper foil to improve the adhesive force.

In one example, the active material is a negative active material.

In one example, the negative active material includes one or more of hard carbon, artificial graphite, natural graphite, silicon oxide, silicon carbon compound, and lithium titanate. For example, the negative active material in the active material layer can be obtained by mixing artificial graphite and natural graphite in a certain mass percentage, or it can be obtained by mixing artificial graphite and silicon oxide in a certain mass percentage, or it can be Artificial graphite, natural graphite or silicon oxide alone is used as the conductive agent in the active material layer, which is not specifically limited in this disclosure.

When the undercoating of the present disclosure is used for the positive electrode sheet:

In one example, the active material is a positive active material.

The positive electrode current collector can be aluminum foil commonly used in this field.

The positive active material is selected from the group consisting of lithium cobalt oxide, lithium manganate, lithium nickel oxide, lithium nickel cobalt manganate, lithium iron phosphate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium-rich manganese-based materials, lithium nickel cobalt aluminate and One or more types of lithium titanate. For example, the positive active material in the active material layer can be obtained by mixing lithium cobalt oxide and lithium manganate according to a certain mass percentage, or can be obtained by mixing lithium cobalt oxide and lithium nickelate according to a certain mass percentage. , it is also possible to use lithium cobalt oxide, lithium manganate or lithium nickel oxide alone as the conductive agent in the active material layer, which is not specifically limited in this disclosure.

A second aspect of the disclosure provides a battery, the negative electrode piece and/or the positive electrode piece of the battery are the electrode pieces described in the second aspect of the disclosure.

The selection of other components in the battery of the present disclosure (such as separators, electrolytes, etc.) and the assembly of the battery can be performed in a conventional manner in the art, and will not be described again here.

Compared with the conventional method of having an undercoat layer, the active material layer and current collector of the pole piece of the present disclosure maintains good adhesion between the active material layer and the current collector, and at the same time can reduce the thickness and significantly improve the Energy Density.

The terms "first", "second", etc. in this disclosure are used to distinguish similar objects and are not used to describe a specific order or sequence.

The present disclosure will be described in detail through examples below. The embodiments described in this disclosure are only some of the embodiments of this disclosure, but not all of the embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this disclosure.

The following embodiments only provide the undercoat layer on the negative electrode sheet. This arrangement is only an implementation manner and does not limit the present disclosure. It is understood that significant effects can also be achieved when used in positive electrode sheets.

Example 1

(1) Prepare negative electrode undercoat slurry: mix 30% by weight of acrylic modified styrene-butadiene rubber, 20% by weight of carbon black, 20% by weight of carbon nanotubes, and 30% by weight of sodium carboxymethylcellulose , add deionized water, adjust the solid content of the slurry to 30% by weight, and stir to prepare a negative electrode undercoat slurry;

(2) Prepare the negative active material layer slurry: 96% by weight of artificial graphite (active material, D90 is 28 μm), 1% by weight of carbon black, 1.5% by weight of acrylic modified styrene-butadiene rubber, 1.5% by weight Mix % sodium carboxymethylcellulose by weight, add deionized water, adjust the solid content of the slurry to 40% by weight, and prepare a negative active material layer slurry after stirring;

(3) Prepare the negative electrode sheet: Coat the negative electrode undercoat slurry on the copper foil, dry it to obtain the undercoat layer, and then perform laser drilling on the undercoat layer to obtain the exposed foil area (so that the exposed foil area is Round, d80 as shown in Table 1) Coat the negative electrode slurry in step 3 on the bottom smear through the extrusion coating process; roll, cut, weld the tabs and affix protective tape to obtain the negative electrode Pole piece; the measured thickness of the base coating is 0.8 μm, the thickness of the active material layer is 50 μm, and the coverage rate of the base coating is shown in Table 1;

(4) Prepare the positive electrode sheet: Mix 96% by weight of lithium cobalt oxide, 1% by weight of carbon black, 1% by weight of carbon nanotubes, and 2% by weight of PVDF, add a certain amount of NMP, and adjust the solid content of the slurry to 70% by weight, stir and prepare the cathode slurry; coat the cathode slurry on the cathode current collector and dry to obtain the cathode sheet; roll, cut, weld the tabs and affix protective tape to obtain the cathode piece.

(5) Place the separator between the positive and negative electrode sheets, wind or laminate them, assemble the battery, and obtain a qualified battery product.

Example 2 Group

This set of examples is used to illustrate the impact on performance when the basecoat coverage is changed.

The process was carried out according to Example 1, except that different laser drilling conditions were used to change the coverage of the primer layer (keeping the size distribution and d80 of the exposed foil area unchanged), as shown in Table 1.

Example 3 group

This set of examples is used to illustrate the impact on the effect when the exposed foil area d80 is changed.

The process was carried out according to Example 1, except that different gravure plates were used for coating to change the d80 of the exposed foil area (keeping the coverage of the base coating unchanged), as shown in Table 1.

Comparative example 1

There is no exposed foil area on the undercoat layer, and the entire undercoat layer is covered with the slurry; other steps are carried out according to Example 1.

Comparative example 2

The process is carried out according to Embodiment 1, except that step (1) is omitted, that is, the undercoat layer is no longer provided, and the negative active material is directly coated on the negative current collector.

test case

(1) Energy density test

The test method includes: charging the batteries obtained in the Examples and Comparative Examples with a current of 0.5C to the cut-off voltage, and charging with a constant voltage to a cut-off voltage of 0.02C; after leaving it alone for 10 minutes, the battery is discharged to 3.0V with a current of 0.2C; the discharge energy is For the energy of the battery, calculate the energy density = energy/(battery length*width*height), the unit is Wh/L, and record the results in Table 1.

(2) Peeling strength test of negative electrode sheet

The test method includes: cutting the negative electrode sheets obtained in the examples and comparative examples into small pieces of negative electrode sheets with a length of 240mm and a width of 30mm, using NITTO No. 5000NS tape, and cutting the tape into small pieces of tape according to the specifications of a length of 200mm and a width of 24mm. Stick one side of the tape piece on the steel plate (260mm*50mm), stick the negative electrode piece on the other side of the tape piece, ensure that the negative electrode piece completely covers the tape piece, use a hand-held roller (diameter 95mm, width 45mm, weight 2kg ) Roll back and forth 3 times to bond the negative electrode piece and the tape piece together, and then use a tensile machine (tensile machine model Dongguan Kejian KJ-1065 series) to test (180-degree peeling), and the test equipment automatically Dynamically record the tensile force value that changes with the peeling displacement, and draw a curve of the tensile force value changing with the peeling displacement. The abscissa is the peeling displacement, and the ordinate is the tensile force value. The tensile force value when the curve is flat and the peeling displacement is greater than 5mm is the peeling force. , the peeling force represents the peeling strength, the unit is N/m, the results are recorded in Table 1.

Table 1

As can be seen from Table 1, the data of the Example proves that the way of setting the exposed foil area on the undercoat layer allows most of the exposed foil area to embed active material particles, which can make the active material layer and the current collector have good Adhesion, the battery also has a higher energy density.

The above are only preferred embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present disclosure shall be included in the scope of protection of the present disclosure. within.

Claims

A pole piece, characterized by comprising a current collector, an active material layer located on one side or both sides of the current collector, and an undercoat layer disposed between the current collector and the active material layer, wherein the The base coating has a pattern structure, which divides the base coating into a continuous coating area and a number of scattered exposed foil areas; the active material layer fills the exposed foil area and covers the coating area s surface.
The pole piece according to claim 1, wherein the coverage rate of the coating area of the undercoat layer on the current collector is 30-80%, preferably 50-70%.
The pole piece according to claim 1 or 2, wherein the minimum distance of the exposed foil area is d, and the minimum distance of the exposed foil area exceeding 80% is d80, d80> in the active material layer D90 of active substance.
The pole piece according to claim 3, wherein the d80 of the exposed foil area is 30 μm-500 μm, preferably 40 μm-200 μm.
The pole piece according to claim 3, wherein the D90 of the active material is 15 μm-50 μm.
The pole piece according to any one of claims 1 to 5, wherein the exposed foil areas are each independently in a circular, square, strip, polygonal, patterned or irregular shape.
The pole piece according to any one of claims 1 to 6, wherein the undercoat layer includes a first adhesive, a first conductive agent and a first thickener, wherein the total weight of the undercoat layer As a benchmark, the content of the first adhesive is 20-40% by weight, the content of the first conductive agent is 30-60% by weight, and the content of the first thickener is 20-40% by weight.
The pole piece according to any one of claims 1 to 7, wherein the active material layer includes an active material, a second adhesive, a second conductive agent and a second thickener, wherein the active material layer Based on the total weight of The content of the second thickener is 0.5-2% by weight.
The pole piece according to claim 7 or 8, wherein the first adhesive and the second adhesive are each independently selected from adhesives containing carboxyl groups and/or ester groups;

Preferably, the first adhesive and the second adhesive are each independently selected from one of polyacrylates, acrylic-modified styrene-butadiene rubber, and acrylic-modified vinylidene fluoride, or Various.
The pole piece according to claim 7 or 8, wherein the first thickener and the second thickener are the same or different;

And/or, the first thickener and the second thickener are each independently selected from one or more types of sodium carboxymethylcellulose, polyvinyl alcohol, polyethylene glycol and polyvinylpyrrolidone.
The pole piece according to any one of claims 7-10, wherein the first conductive agent and The second conductive agent is one or more of carbon black, carbon tube, graphene, metal conductive powder, carbon fiber, acetylene black and Ketjen black.
The pole piece according to any one of claims 1 to 11, wherein the thickness of the undercoat layer is 0.2 μm-2 μm, preferably 0.4 μm-0.8 μm.
The pole piece according to any one of claims 1-12, wherein the thickness of the active material layer is 30 μm-70 μm.
The pole piece according to claim 11, wherein the first conductive agent and the second conductive agent have specific surface areas each independently ranging from 10 m 2 /g to 1000 m 2 /g.
A battery, characterized in that the battery includes the pole piece according to any one of claims 1-14; the pole piece is a positive pole piece and/or a negative pole piece.