阅读说明：本技术 用于锂电池的负极集流体和锂电池 (Negative current collector for lithium battery and lithium battery ) 是由 何里烈 于 2019-09-29 设计创作，主要内容包括：本发明公开了用于锂电池的负极集流体和具有该负极集流体的锂电池。该负极集流体包括：集流体箔片,所述集流体箔片正面的至少部分表面分布设有多个正面凹孔,所述集流体箔片背面的至少部分表面分布设有多个背面凹孔；彼此邻近的所述正面凹孔和所述背面凹孔中,所述正面凹孔沿所述集流体箔片厚度方向在水平面上的投影与所述背面凹孔沿所述集流体箔片厚度方向在水平面上的投影至少部分重合。该负极集流体中箔片的两面均具有凹孔,具有比表面积大,对电极浆料粘连性力、负载量大等优点。(The invention discloses a negative electrode current collector for a lithium battery and a lithium battery having the same. The negative electrode current collector includes: the current collector comprises a current collector foil, wherein a plurality of front concave holes are distributed on at least part of the surface of the front side of the current collector foil, and a plurality of back concave holes are distributed on at least part of the surface of the back side of the current collector foil; in the front concave hole and the back concave hole which are adjacent to each other, the projection of the front concave hole on the horizontal plane along the thickness direction of the current collector foil is at least partially overlapped with the projection of the back concave hole on the horizontal plane along the thickness direction of the current collector foil. The two sides of the foil in the negative current collector are provided with concave holes, and the negative current collector has the advantages of large specific surface area, high adhesion force to electrode slurry, large loading capacity and the like.)

1. A negative current collector for a lithium battery, comprising:

the current collector comprises a current collector foil, wherein a plurality of front concave holes are distributed on at least part of the surface of the front side of the current collector foil, and a plurality of back concave holes are distributed on at least part of the surface of the back side of the current collector foil; in the front concave hole and the back concave hole which are adjacent to each other, the projection of the front concave hole on the horizontal plane along the thickness direction of the current collector foil is at least partially overlapped with the projection of the back concave hole on the horizontal plane along the thickness direction of the current collector foil.

2. The negative electrode current collector of claim 1, wherein the front recesses and the back recesses have a circular or quasi-circular projection in the thickness direction of the current collector foil.

3. The negative electrode current collector of claim 1, wherein the average thickness of the current collector foil is 10 to 20 μm.

4. The battery negative electrode current collector of claim 1, wherein the pore size of the front recesses and the back recesses is each independently 60-70% of the average thickness of the current collector foil.

5. The current collector of claim 1, wherein a pitch of at least two adjacent positive recesses is 20-30% of a pore diameter of the positive recesses.

6. The battery negative electrode current collector of claim 1, wherein a pitch of at least two adjacent back recesses is 20-30% of a pore diameter of the back recesses.

7. The negative electrode current collector of claim 1, wherein the current collector foil has a density of 30 to 60g/m²。

8. The negative electrode current collector of claim 1, wherein the tensile strength of the current collector foil is 500 to 700 MPa.

9. A lithium battery, comprising: a positive electrode, a negative electrode, a separator and an electrolyte; wherein the content of the first and second substances,

the positive electrode includes: a positive current collector and a positive electrode material supported on the positive current collector, the positive electrode material comprising: a positive electrode active material, a positive electrode conductive agent and a positive electrode binder;

the negative electrode includes: the negative electrode current collector of any one of claims 1 to 8, and a negative electrode material supported on the negative electrode current collector, the negative electrode material comprising: a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.

10. The lithium battery according to claim 9, wherein a mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is (94-96): (2-4.5): (1.5-2);

optionally, the mass ratio of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder is (94-96): (1.5-2): 2-4.5.

Technical Field

The invention relates to the technical field of lithium batteries, in particular to a negative electrode current collector for a lithium battery and the lithium battery.

Background

At present, under the continuously high requirement of the electric automobile on the endurance mileage, the lithium ion battery for improving the energy density of the lithium ion battery is the most mainstream solution development direction. The traditional solution to the energy density of lithium ion batteries has the following directions: (1) under the condition that the energy of the battery cell is not changed, the light weight of the battery cell structural part is reduced; (2) in the aspect of electric core system design, the contents of a conductive agent and a binder are reduced, the coating amount of active substances is increased, and the compaction of a pole piece is increased; (3) reduce the lightweight of the structure of electricity core module. At present, the improvement of the copper foil of the negative current collector is developed towards the direction of thickness reduction, but the reduction of the thickness of the copper foil brings many performance and process risks, for example, the width of a tab of the negative copper foil is constant, and the thinner the thickness is, the worse the overcurrent capacity of the battery is; the copper foil of the negative electrode is too thin, and the coating and rolling processes are easy to break; the cathode copper foil is too thin, the lower the tensile strength of the foil is, and the more serious the wrinkle of the rolled pole piece is.

It can be seen that there remains a need for improvements in current negative electrode current collectors for lithium batteries.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. To this end, an object of the present invention is to propose a negative electrode current collector for a lithium battery and a lithium battery. The two sides of the foil in the negative current collector are provided with concave holes, and the negative current collector has the advantages of large specific surface area, strong binding power to electrode slurry, large loading capacity and the like.

In one aspect of the present invention, a negative current collector for a lithium battery is provided. According to an embodiment of the present invention, the negative electrode current collector includes: the current collector comprises a current collector foil, wherein a plurality of front concave holes are distributed on at least part of the surface of the front side of the current collector foil, and a plurality of back concave holes are distributed on at least part of the surface of the back side of the current collector foil; in the front concave hole and the back concave hole which are adjacent to each other, the projection of the front concave hole on the horizontal plane along the thickness direction of the current collector foil is at least partially overlapped with the projection of the back concave hole on the horizontal plane along the thickness direction of the current collector foil.

According to the negative current collector for the lithium battery, provided by the embodiment of the invention, the two sides of the foil are provided with the concave holes, and the specific surface area of the foil can be obviously improved by combining the structural characteristic that the projections of the concave holes on the front side and the concave holes on the back side along the thickness direction of the current collector foil are at least partially overlapped, so that the loading capacity of electrode slurry can be effectively improved, the binding force and the conductivity of the foil to the electrode slurry can be effectively improved, the consumption of a binder in the electrode slurry can be reduced, and the internal resistance of a pole piece can be reduced. In addition, the structure characteristic of having the shrinkage pool of two sides can reduce the compaction density of electrode thick liquids to a certain extent, improves electric core multiplying power performance. On the other hand, the preparation method of the negative current collector is simple, the concave holes on the surface of the negative current collector can be obtained through a mature etching mode (such as laser double-sided etching), and the existing production line process and equipment are not changed.

In addition, the negative electrode current collector for a lithium battery according to the above embodiment of the present invention may further have the following additional technical features:

in some embodiments of the invention, projections of the front recesses and the back recesses in a thickness direction of the current collector foil are circular or circular-like.

In some embodiments of the present invention, the current collector foil has an average thickness of 10 to 20 μm.

In some embodiments of the invention, the aperture of each of the front recesses and the back recesses is independently 60-70% of the average thickness of the current collector foil.

In some embodiments of the invention, the distance between at least two adjacent front concave holes is 20-30% of the aperture of the front concave hole.

In some embodiments of the present invention, a distance between at least two adjacent back recesses is 20 to 30% of an aperture of the back recess.

In some embodiments of the invention, the density of the current collector foil is 30-60 g/m²。

In some embodiments of the invention, the tensile strength of the current collector foil is 500-700 MPa.

In another aspect of the present invention, a lithium battery is provided. According to an embodiment of the present invention, the lithium battery includes: a positive electrode, a negative electrode, a separator and an electrolyte; wherein the positive electrode includes: a positive current collector and a positive electrode material supported on the positive current collector, the positive electrode material comprising: a positive electrode active material, a positive electrode conductive agent and a positive electrode binder; the negative electrode includes: the negative electrode current collector and the negative electrode material supported on the negative electrode current collector of the above embodiments include: a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.

The lithium battery according to the embodiment of the present invention has all the features and advantages described above for the negative electrode current collector by using the negative electrode current collector of the above embodiment, and details are not repeated herein. In general, the lithium battery has excellent electrochemical properties such as energy density, rate capability, cycle performance and the like.

In addition, the lithium battery according to the above embodiment of the present invention may further have the following additional technical features:

in some embodiments of the invention, the mass ratio of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder is (94-96): (2-4.5): 1.5-2.

In some embodiments of the present invention, the mass ratio of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder is (94-96): (1.5-2): 2-4.5).

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 is a schematic structural view of a negative electrode current collector according to one embodiment of the present invention;

fig. 2 is a schematic view of the structure of a negative electrode current collector according to still another embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In one aspect of the present invention, a negative current collector for a lithium battery is provided. According to an embodiment of the present invention, referring to fig. 1, the negative electrode current collector includes: a current collector foil 100, a front pocket 110, and a back pocket 120. Specifically, a plurality of front recesses 110 are distributed on at least part of the front surface of the current collector foil 100, and a plurality of back recesses 120 are distributed on at least part of the back surface of the current collector foil 100; of the front recesses 110 and the back recesses 120 that are adjacent to each other, a projection of the front recesses 110 in the thickness direction of the current collector foil 100 at least partially coincides with a projection of the back recesses 120 in the thickness direction of the current collector foil 1000.

According to the negative current collector for the lithium battery, provided by the embodiment of the invention, the two sides of the foil are provided with the concave holes, and the specific surface area of the foil can be obviously improved by combining the structural characteristic that the projections of the concave holes on the front side and the concave holes on the back side along the thickness direction of the current collector foil are at least partially overlapped, so that the loading capacity of electrode slurry can be effectively improved, the binding force and the conductivity of the foil to the electrode slurry can be effectively improved, the consumption of a binder in the electrode slurry can be reduced, and the internal resistance of a pole piece can be reduced. In addition, the structure characteristic of having the shrinkage pool of two sides can reduce the compaction density of electrode thick liquids to a certain extent, improves electric core multiplying power performance. On the other hand, the preparation method of the negative current collector is simple, the concave holes on the surface of the negative current collector can be obtained through a mature etching mode (such as laser double-sided etching), and the existing production line process and equipment are not changed.

The negative electrode current collector for a lithium battery according to an embodiment of the present invention is further described in detail below.

According to some embodiments of the invention, the current collector foil is a copper foil. When the current collector foil adopts copper foil, the negative current collector provided by the invention is also called porous copper foil.

According to some embodiments of the invention, the front recesses and the back recesses have a circular or circular-like projection in the thickness direction of the current collector foil. Specifically, the quasi-circular shape may be an elliptical shape or the like. Therefore, by adopting the front concave hole and the back concave hole in the shapes, the specific surface area of the current collector foil can be further improved, so that the coating amount of the negative electrode material on the current collector foil and the bonding performance between the negative electrode material and the current collector foil are further improved.

According to some embodiments of the invention, the average thickness of the current collector foil may be 10 to 20 μm, such as 10 μm, 12 μm, 15 μm, 18 μm, or 20 μm. If the thickness of the current collector foil is too small, the current capacity and tensile strength of the battery can be reduced, and the problems of belt breakage, pole piece folding during the coating and rolling process are easy to occur.

According to some embodiments of the invention, the aperture diameter of each of the front recess and the back recess is independently 60 to 70% of the average thickness of the current collector foil, such as 60%, 62%, 65%, 68%, or 70%. Therefore, the specific surface area of the current collector foil can be further increased, so that the coating amount of the negative electrode material on the current collector foil and the bonding performance between the negative electrode material and the current collector foil are further improved. On the other hand, the tensile strength of the foil can be further improved by controlling the front surface concave holes and the back surface concave holes within the above range.

According to some embodiments of the present invention, the distance between at least two adjacent front recesses may be 20 to 30% of the aperture of the front recess, such as 20%, 22%, 25%, 28%, or 30%. Therefore, the specific surface area of the foil can be further improved, and the foil is ensured to have higher tensile strength. If the hole pitch of the concave hole on the front surface is too large, the specific surface area of the foil is correspondingly reduced, and the technical effects of obviously improving the binding power, the loading capacity and the like of the negative electrode material cannot be achieved; if the pitch of the positive recesses is too small and the positive recesses are too dense, the tensile strength of the foil is adversely affected.

According to some embodiments of the present invention, the distance between at least two adjacent back recesses may be 20 to 30% of the aperture of the back recess, for example, 20%, 22%, 25%, 28%, or 30%. Therefore, the specific surface area of the foil can be further improved, and the foil is ensured to have higher tensile strength. If the hole pitch of the concave hole on the back is too large, the specific surface area of the foil is correspondingly reduced, and the technical effects of obviously improving the binding power, the loading capacity and the like of the negative electrode material cannot be achieved; if the pitch of the holes in the back is too small and the holes in the back are too dense, the tensile strength of the foil is adversely affected.

According to some embodiments of the invention, the current collector foil is a foilHas a density of 30 to 60g/m²E.g. 30g/m²、35g/m²、40g/m²、45g/m²、50g/m²、55g/m²Or 60g/m²And the like.

According to some embodiments of the invention, the collector foil has a tensile strength of 500 to 700MPa, such as 500MPa, 550MPa, 600MPa, 650MPa, 700MPa, or the like.

In addition, it should be noted that an electrode tab area is reserved on the current collector foil, and no front concave hole or back concave hole is arranged in the foil electrode tab area.

In another aspect of the present invention, a lithium battery is provided. According to an embodiment of the present invention, the lithium battery includes: a positive electrode, a negative electrode, a separator and an electrolyte; wherein the positive electrode includes: a positive current collector and a positive electrode material supported on the positive current collector, the positive electrode material comprising: a positive electrode active material, a positive electrode conductive agent and a positive electrode binder; the negative electrode includes: the negative electrode current collector and the negative electrode material supported on the negative electrode current collector of the above embodiments include: a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.

According to some embodiments of the present invention, the positive electrode material includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder; the mass ratio of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder can be (94-96): (2-4.5): 1.5-2. The specific types of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder are not particularly limited, and the positive electrode active material can be at least one of common positive electrode active materials selected from lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium titanate, lithium manganese oxide and the like; the positive electrode conductive agent can be at least one of common positive electrode binders such as conductive carbon black SP or ECP, carbon nano tubes (CNT or WCNT), graphene and the like; the positive electrode binder may be at least one of common positive electrode binders such as polyvinylidene fluoride (PVDF), sodium carboxymethylcellulose (CMC), Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), and the like. The positive electrode material may further include a common solvent (e.g., NMP) for mixing the positive electrode material, and the ratio of the solvent to the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is not particularly limited, and may be selected by those skilled in the art according to actual needs.

According to some embodiments of the present invention, the negative electrode material includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder; the mass ratio of the negative electrode active material, the negative electrode conductive agent, the negative electrode binder and the thickening stabilizer can be (94-96): (1.5-2): 2-4.5). The specific types of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder are not particularly limited, and the negative electrode active material can be at least one of common negative electrode active materials selected from natural graphite, artificial graphite, mesophase microspheres, soft carbon, hard carbon and the like; the negative electrode conductive agent can be at least one of conductive carbon black SP or ECP, carbon nano tube (CNT or WCNT), graphene and other common negative electrode conductive agents; the negative electrode binder may be at least one of common negative electrode binders such as polyvinylidene fluoride (PVDF), sodium carboxymethylcellulose (CMC), Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), and the like. In addition, the negative electrode material may further include a common solvent (e.g., NMP, deionized water, etc.) for mixing the negative electrode material, and the solvent is not particularly limited and may be selected by those skilled in the art according to actual needs.

According to some embodiments of the present invention, the negative electrode material may include 94 to 96 parts by weight of a negative electrode active material, 1.5 to 2 parts by weight of a negative electrode conductive agent, and 2 to 4.5 parts by weight of a negative electrode binder. Specifically, the content of the negative electrode binder may be 2.0 parts by weight, 2.1 parts by weight, 2.2 parts by weight, 2.5 parts by weight, 3.0 parts by weight, 3.5 parts by weight, 4.0 parts by weight, 4.5 parts by weight, or the like. By adopting the negative electrode current collector of the embodiment, the bonding performance between the negative electrode material and the negative electrode current collector is obviously improved, so that the negative electrode binder with lower consumption can be adopted.

The lithium battery according to the embodiment of the present invention has all the features and advantages described above for the negative electrode current collector by using the negative electrode current collector of the above embodiment, and details are not repeated herein. In general, the lithium battery has excellent electrochemical properties such as energy density, rate capability, cycle performance and the like.

The invention will now be described with reference to specific examples, which are intended to be illustrative only and not to be limiting in any way.

General procedure

(1) The negative electrode slurry was prepared as follows:

mixing all the negative electrode binders in the negative electrode slurry formula with water, and stirring for 2-3 hours to obtain negative electrode binder slurry;

mixing and stirring all negative active materials in the negative slurry formula with a negative conductive agent, adding the obtained mixture into 40 wt% of negative binder slurry, and stirring at a low speed for 1-2 hours; then adding 30 wt% of negative electrode binder slurry, and stirring at medium speed for 1-2 h; adding 30 wt% of negative electrode binder slurry, and stirring at a high speed for 2-3 h to obtain negative electrode slurry;

(2) coating the negative electrode slurry on copper foil, rolling, slitting, forming a tab, and cutting to obtain a negative electrode sheet;

(3) the positive electrode slurry was prepared as follows:

mixing all positive binders in the positive slurry formula with NMP, and stirring for 2-3 h to obtain positive binder slurry;

mixing all positive electrode conductive agents in the positive electrode slurry formula with positive electrode binder slurry, stirring at a high speed for 1-2 h, adding all positive electrode active materials in the positive electrode slurry formula, stirring at a low speed for 1h, and stirring at a high speed for 1h to obtain positive electrode slurry;

(4) coating the anode slurry on an aluminum foil, then rolling, slitting, forming a tab and cutting to obtain an anode plate;

(5) and (4) taking the negative plate and the positive plate obtained in the steps (2) and (4), and sequentially carrying out the working procedures of lamination, assembly, liquid injection, formation and capacity grading to obtain a finished lithium battery.