WO2023019741A1

WO2023019741A1 - Current collector preparation method and pole piece

Info

Publication number: WO2023019741A1
Application number: PCT/CN2021/128165
Authority: WO
Inventors: 青勇
Original assignee: 深圳市西盟特电子有限公司
Priority date: 2021-08-19
Filing date: 2021-11-02
Publication date: 2023-02-23
Also published as: CN113764676A

Abstract

In order to overcome the problem that the existing lithium battery current collectors are prone to breakage during preparation, the present invention provides a current collector preparation method, comprising the following steps: S1: preconfiguring a plurality of microporous regions and a plurality of unperforated regions on a metal foil, the plurality of microporous regions being arranged side by side, wherein two adjacent microporous regions are spaced apart by a single unperforated region, a plurality of micropores passing through the metal foil are formed in the microporous regions, and no micropores are formed in the unperforated regions; and S2, cutting the perforated metal foil in the non-perforated regions along the extension directions thereof to obtain a plurality of current collectors. By forming micropores passing through a current collector in the current collector, the bonding area between an active material and a foil is increased, the infiltration efficiency and moisture drying efficiency of the electrolyte of a lithium-ion battery are improved, and the charge-discharge rate and productivity of the battery are improved; and cutting along the unperforated regions in which no micropores are formed avoids the problem of breakage easily caused by directly cutting a microporous structure, thereby improving the product quality and the production efficiency.

Description

A kind of preparation method of current collector and pole piece

technical field

The invention belongs to the technical field of lithium ion batteries, and in particular relates to a method for preparing a current collector and a pole piece.

Background technique

In the past ten years, lithium-ion batteries have been widely used in portable devices and power batteries due to their superior electrochemical performance, but the energy density and power density of existing lithium-ion batteries cannot meet people's needs for electric vehicles and hybrid electric vehicles. Require. At present, the current collectors of positive and negative electrodes generally use copper and aluminum foil. The main function of the current collector is to gather the current generated by the active material of the battery to form a larger current output. Therefore, the current collector should be in full contact with the active material, and the internal resistance should be as low as possible. Maybe small is better. The traditional method of making electrode pole pieces is to directly attach the active material to the current collector through a certain amount of binder. The combination of the active material and the current collector is a simple mechanical combination, and the effective contact area of the active material is limited, thereby increasing the The contact internal resistance between the active material and the current collector.

Therefore, in order to increase the energy density of the battery, it has become a popular method to increase the energy density of the battery by making microporous copper foil and aluminum foil in the prior art. Under the same specification of the foil material, the weight of the foil material is reduced, and the The energy density of the battery, and at the same time, through the "I"-shaped occlusion formed between the pores, the adhesion between the copper foil, aluminum foil and the surface active material layer is improved. During the research process, the applicant found that the existing common current collector preparation method is generally to form a microporous structure on the surface of the entire metal foil, and then slice it according to the size of the pole piece to be used to obtain a current collector with a preset width, and then The current collector is coated with active slurry, dried and other processes to obtain the pole piece. However, when this method is used for slicing, it is easy to pass through the micro-holes on the pole piece, and it is easy to form tears at the micro-holes, resulting in uneven outer edges of the pole piece, resulting in defects such as broken belts caused by force in subsequent operations such as rolling. Phenomenon.

Contents of the invention

Aiming at the problem that the existing lithium battery current collector is prone to band breakage during the preparation, the present invention provides a preparation method of the current collector and a pole piece.

The technical solution adopted by the present invention to solve the problems of the technologies described above is as follows:

The invention provides a method for preparing a current collector, comprising the following steps:

S1: preset a plurality of microporous areas and a plurality of unperforated areas on the metal foil, and a plurality of said microporous areas are arranged side by side, wherein a single said unperforated area is arranged between two adjacent microporous areas The hole areas are arranged at intervals, and a number of micro holes through the metal foil are opened on the micro hole area, and no micro holes are opened in the non-perforated area;

S2: cutting the perforated metal foil in the unperforated area along its extending direction to obtain multiple current collectors.

Optionally, the width of the non-perforated area is 1-30 mm.

Optionally, the diameter of the micropores is 10-200 μm.

Optionally, the pitch of the microholes is 1-5mm.

Optionally, the porosity of the current collector is 0.0003%-3.5%.

Optionally, the current collector is aluminum foil or copper foil; the thickness of the current collector is 2-100 μm.

Optionally, the "opening a number of micropores through the metal foil on the micropore area of the metal foil" includes:

Micropores distributed in a regular matrix throughout the metal foil are opened in the micropore area of the metal foil by mechanical drilling.

The present invention also provides a pole piece, comprising the current collector prepared by the above preparation method and an active material layer on the surface of the current collector.

Beneficial effects of the present invention:

(1) The present invention ensures that the positive and negative electrode slurry can be evenly coated on the microporous current collector by opening micropores through the current collector, and the coating does not leak, the pole piece has good flexibility, and the use of the microporous current collector On the basis of the foil material of the same specification, it can reduce the weight of the foil material and increase the energy density of the battery cell. The setting of micropores can increase the bonding area between the active material and the foil material, and effectively improve the infiltration efficiency of the lithium-ion battery electrolyte and moisture drying efficiency, while reducing the internal resistance of the foil, increasing the charge and discharge rate and production capacity of the battery.

(2) A non-perforated area is set between two adjacent micro-hole areas, and the subsequent cutting is carried out along the un-perforated area without micro-holes, which effectively ensures the flatness of the edge of the pole piece and avoids direct cutting of the micro-porous structure The problem of broken belts caused by the belt further improves product quality and production efficiency.

Description of drawings

Fig. 1 is a schematic structural view of a metal foil provided by an embodiment of the present invention;

Fig. 2 is a schematic structural diagram of a metal foil provided by another embodiment of the present invention;

3 is a schematic structural view of a current collector provided by an embodiment of the present invention;

Fig. 4 is a schematic structural view of a current collector provided by another embodiment of the present invention;

5 is a schematic diagram of a cross-sectional structure of a pole piece along the width direction provided by an embodiment of the present invention;

The reference signs in the accompanying drawings of the description are as follows:

1. Metal foil; 101, microporous area; 102, non-perforated area; 103, micropore; 2, current collector; 3, pole piece; 4, active material layer.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

It should be noted that all directional indications (such as top, both sides, surface...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement between the various structures in a certain posture (as shown in the accompanying drawings) Situations, etc., if the specific posture changes, the directional indication also changes accordingly.

Please refer to FIG. 1-FIG. 4. On the one hand, an embodiment of the present invention provides a method for preparing a current collector, which includes the following steps:

S1: preset a plurality of microporous areas 101 and a plurality of non-perforated areas 102 on the metal foil 1, and a plurality of the microporous areas 101 are arranged side by side, wherein two adjacent microporous areas 101 are separated by The single unperforated area 102 is arranged at intervals, and a number of micropores 103 penetrating the metal foil are opened on the microporous area 101, and no micropores are opened in the unperforated area 102;

S2: cutting the perforated metal foil 1 in the unperforated area 102 along its extending direction to obtain a plurality of current collectors 2 .

In the present invention, by setting the microporous area 101 on the metal foil 1, it is ensured that the positive and negative electrode slurry can be evenly coated on the microporous current collector, and the coating does not leak, the pole piece has good flexibility, and the use of the microporous current collector On the basis of the foil material of the same specification, the weight of the foil material can be reduced, and the energy density of the battery cell can be increased. The setting of the micropore 103 can increase the bonding area between the active material and the metal foil 1, and effectively improve the electrolyte strength of the lithium-ion battery. The wetting efficiency and moisture drying efficiency improve the adhesion between the active material and the current collector, reduce the interface resistance, thereby reducing the internal resistance of the battery, and improving the charge and discharge rate and production capacity of the battery.

Set an unperforated area 102 between two adjacent microporous areas 101, and cut along the unperforated area 102 without micropores during subsequent cutting, so as to avoid the problem of broken bands caused by direct cutting of the microporous structure, and further improve Product quality and production efficiency.

Please refer to Figures 2-4, in some preferred embodiments, the metal foil 1 is provided with non-perforated areas 102 at the edges of both sides along the length direction of the microporous area 101, to further ensure that each piece of current collector obtained by cutting Both sides of the current collector 2 contain unperforated regions 102, which avoids the occurrence of broken bands in the subsequent radiation pressure process due to the microporous structure at the edge of the current collector 2.

In some embodiments, the width of the unperforated area 102 is 1-30 mm.

When the width of the unperforated area 102 is less than 1 mm, since the width of the unperforated area 102 is too small, and the blade of the cutting device has a certain width, it is easy to cause the subsequent cutting of the metal foil 1 to accidentally cut into the microporous area 101, thereby causing problems such as broken bands. If the width of the unperforated area 102 is greater than 30mm, due to the increase in the area of the unperforated area 102, on the one hand, the area of the microporous area 101 will decrease, and the area of the microporous area 101 will be too large. Small, so that the number of micropores 103 is reduced, so that the bonding area between the active material layer and the current collector cannot be significantly increased, so the infiltration efficiency and moisture drying efficiency of the lithium-ion battery electrolyte cannot be effectively improved. On the other hand, the setting is too wide The unperforated area 102 will cause waste of raw materials and increase the production cost, so the width of the unperforated area 102 is preferably 1-30 mm.

In some embodiments, the diameter of the micropores 103 is 10-200 μm.

When the pore diameter of the micropores 103 is less than 10 μm, it is not conducive to the coating of the active material layer, and the bonding area between the active material layer and the current collector cannot be effectively increased, which may easily cause blockage of the active material material and affect the ion conduction of the current collector 2. / Conductivity, thereby affecting the function of the battery cell. If the pore size of the micropore 103 is greater than 200 μm, the too large pore size will easily reduce the mechanical properties of the current collector and reduce the stability and safety of the pole piece.

In some embodiments, the pitch of the microholes 103 is 1-5 mm.

The hole spacing within the above range is conducive to maintaining high mechanical strength of the current collector, further improving the safety and stability of the pole piece.

In some embodiments, the porosity of the current collector 2 is 0.0003%-3.5%.

When the porosity of the current collector 2 is greater than 3.5%, it is not conducive to the improvement of the energy density of the battery, and at the same time, the current collector is prone to broken belts during the subsequent high-strength tension stretching and rolling process, resulting in low production and processing efficiency; the current collector When the porosity of 2 is less than 0.0003%, the lithium ion diffusion path is few, the transmission is limited, and the charge and discharge rate of the battery, the infiltration efficiency of the electrolyte and the volatilization efficiency of water cannot be improved.

In some embodiments, the current collector 2 is aluminum foil or copper foil; the thickness of the current collector is 2-100 μm.

Generally, the positive electrode sheet of lithium-ion battery uses aluminum foil as the current collector, and the negative electrode sheet uses copper foil as the current collector. The current collector 2 within the above thickness range can not only maintain a high mechanical strength, but also ensure that the active material layer smoothly penetrates the micropores 103, and increase the bonding area with the current collector 2, which is conducive to improving the electrolyte of lithium-ion batteries. Wetting efficiency and water evaporation efficiency improve the charge and discharge rate and production capacity of the battery.

In some embodiments, the "opening a number of micropores 103 penetrating through the metal foil 1 on the micropore region 101 of the metal foil 1" includes:

A number of micropores 103 distributed in a regular matrix throughout the metal foil 1 are opened in the micropore area 101 of the metal foil 1 by means of mechanical drilling.

The microholes 103 are formed by mechanical drilling, which keeps the original physical and chemical properties of the metal foil 1 unchanged, and at the same time maintains high elongation and tensile strength. Preferably, the micropores 103 are arranged in a regular matrix distribution, which can ensure the uniformity of the hole spacing, thereby ensuring the uniformity of the positive and negative slurry coating, and improving the charging and discharging performance of the battery.

It should be noted that the width of the microporous region 101 is designed according to the size of the current collector 2 required for actual production, and there is no special limitation on the width of the microporous region 101 here.

Referring to FIG. 5 , the present invention also provides a pole piece 3 , including the above-mentioned current collector 2 and an active material layer 4 on the surface of the current collector 2 .

Further, the active material layer 4 generally includes active material materials, conductive agents, binders, etc. The specific materials of the active material layer are commonly used materials in the field, which can be added according to actual needs, and are not particularly limited here. 2. The active material layers on the two surfaces are connected by micropores 103, showing an "I"-shaped occlusal structure, which significantly increases the bonding area between the current collector 2 and the active material layer 4. The micropores 103 provide electrolyte and ion migration. The channels are opened to further improve the electrolyte infiltration efficiency and moisture drying efficiency, as well as the battery charge and discharge rate and production capacity.

It should be noted that the surface of the current collector in the non-perforated area 102 can be coated with an active material layer or not coated with an active material layer. Whether the surface of the current collector in the non-perforated area 102 needs to be coated with an active material Layers are determined according to actual needs, and are not specifically limited here.

The present invention will be further described below by specific embodiment:

Example 1

This example is used to illustrate the preparation method of the current collector disclosed in the present invention, which includes the following steps:

S1: Take an aluminum foil with a thickness of 50 μm, set a micro-hole area and an un-perforated area on the aluminum foil at intervals as shown in Figure 1, wherein the width of the un-perforated area is 15 mm, and use a punching device to drill holes mechanically In the micropore area, a number of micropores distributed in a regular matrix through the aluminum foil are opened, wherein the pore diameter is 80 μm, the pore spacing is 2 mm, and the porosity is 2.0%;

S2: Cut the perforated aluminum foil along the length direction of the unperforated area using a cutting device to obtain several sheets of current collectors A.

Example 2

S1: Take a copper foil with a thickness of 30 μm, set a micro-hole area and an unperforated area on the copper foil at intervals as shown in Figure 2, wherein the width of the un-perforated area is 20mm, use a punching device, and drill through a machine In the micropore area, a number of micropores distributed in a regular matrix through the copper foil are opened in the micropore area, wherein the pore diameter is 100 μm, the hole spacing is 4mm, and the porosity is 0.0008%;

S2: Cut the perforated copper foil along the length direction of the unperforated area using a cutting device to obtain several sheets of current collectors B.

Example 3

This embodiment is used to illustrate the pole piece disclosed by the present invention:

The current collector A is taken, the positive electrode slurry is coated on the microporous area of the current collector A, and the electrode sheet A is obtained by drying and rolling.

Example 4

The current collector B is taken, the negative electrode slurry is coated on the microporous area of the current collector B, and the electrode sheet B is obtained by drying and rolling.

Comparative example 1

This comparative example is used to compare and illustrate the preparation method of the current collector disclosed by the present invention and the pole piece, including the following steps:

S1: Take an aluminum foil with a thickness of 50 μm, use a punching device, and open a number of micro-holes in a regular matrix that run through the aluminum foil in all areas of the aluminum foil surface by mechanical drilling. 2.0%;

S2: Cut the perforated aluminum foil according to the preset size to obtain several sheets of current collectors C.

S3: Take the current collector C, coat the positive electrode slurry on the entire surface of the current collector C, and obtain the pole piece C after drying and rolling.

Comparative example 2

S1: Take a copper foil with a thickness of 30 μm, use a punching device, and open a number of micro-holes distributed in a regular matrix through the copper foil in all areas of the copper foil surface by mechanical drilling, wherein the hole diameter is 100 μm, and the hole spacing is 4mm, porosity 0.0008%;

S2: Cut the punched copper foil according to the preset size to obtain several current collectors D.

S3: Take the current collector D, apply the negative electrode slurry on the entire surface of the current collector D, and obtain the pole piece D after drying and rolling.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims

A method for preparing a current collector, comprising the following steps:

S1: preset a plurality of microporous areas and a plurality of unperforated areas on the metal foil, and a plurality of said microporous areas are arranged side by side, wherein a single said unperforated area is arranged between two adjacent microporous areas The hole areas are arranged at intervals, and a number of micro holes through the metal foil are opened on the micro hole area, and no micro holes are opened in the non-perforated area;

S2: cutting the perforated metal foil in the unperforated area along its extending direction to obtain multiple current collectors.
The method for preparing a current collector according to claim 1, wherein the width of the non-perforated area is 1-30 mm.
The method for preparing a current collector according to claim 1, characterized in that the diameter of the micropores is 10-200 μm.
The method for preparing a current collector according to claim 1, characterized in that the spacing of the micropores is 1-5 mm.
The method for preparing a current collector according to claim 1, characterized in that the porosity of the current collector is 0.0003%-3.5%.
The method for preparing a current collector according to claim 1, wherein the current collector is aluminum foil or copper foil; and the thickness of the current collector is 2-100 μm.
The method for preparing a current collector according to claim 1, wherein said "opening a number of micropores penetrating through the metal foil on the microporous area of the metal foil" includes:

A number of micropores distributed in a regular matrix throughout the metal foil are opened in the micropore area of the metal foil by means of mechanical drilling.
A pole piece, characterized in that it comprises a current collector prepared by the preparation method according to any one of claims 1-7 and an active material layer on the surface of the current collector.