CN111725569B

CN111725569B - Roll up core and battery

Info

Publication number: CN111725569B
Application number: CN202010590495.3A
Authority: CN
Inventors: 刘春洋; 李素丽; 李俊义
Original assignee: Zhuhai Cosmx Battery Co Ltd
Current assignee: Zhuhai Cosmx Battery Co Ltd
Priority date: 2020-06-24
Filing date: 2020-06-24
Publication date: 2022-05-13
Anticipated expiration: 2040-06-24
Also published as: CN111725569A

Abstract

The invention provides a winding core and a battery, wherein the winding core comprises: positive plate, negative pole piece and be located positive plate with the book layer of formation is convoluteed by the diaphragm between the negative pole piece, be connected with positive tab on the positive plate, be connected with the negative pole ear on the negative pole piece, the coating has the coating on the diaphragm, the coating is the insulating layer, just the coating has pore structure. In the roll core, the positive plate and the negative plate are separated by the diaphragm, the coating is coated on the diaphragm, a pore structure in the coating can contain electrolyte, the content of the electrolyte in the roll core can be increased, the cycle performance of the battery is improved, the coating has certain strength and can enhance the strength of the diaphragm, and the lithium ion battery is not easy to deform or damage when being extruded or collided from the outside, so that the safety performance of the battery is improved.

Description

Roll up core and battery

Technical Field

The invention relates to the technical field of batteries, in particular to a winding core and a battery.

Background

Along with the continuous improvement of the energy density of the lithium ion battery, the thickness of the ceramic diaphragm is continuously reduced, so that the remaining amount of electrolyte of the lithium ion battery is reduced, the cycle performance of the battery is poor, and the lithium ion battery is easy to deform or damage when being extruded or collided by the outside, so that the safety performance of the battery is reduced.

Disclosure of Invention

In view of this, the invention provides a winding core and a battery, which are used to solve the problems that the lithium ion battery has low electrolyte retention amount, poor battery cycle performance, and low battery safety performance caused by easy deformation or damage of the lithium ion battery when being extruded or collided by the outside.

In order to solve the technical problems, the invention adopts the following technical scheme:

in a first aspect, a winding core according to an embodiment of the invention comprises:

positive plate, negative pole piece and be located positive plate with the book layer of formation is convoluteed by the diaphragm between the negative pole piece, be connected with positive tab on the positive plate, be connected with the negative pole ear on the negative pole piece, the coating has the coating on the diaphragm, the coating is the insulating layer, just the coating has pore structure.

The diaphragm is provided with two layers, the negative pole piece is arranged on the outer side of the outer-layer diaphragm, the positive pole piece is arranged between the two layers of the diaphragm, and the coating is arranged on the inner side of the inner-layer diaphragm.

The winding layer comprises a plurality of winding sections, a first winding section is arranged at the center of the winding core, the first winding section sequentially comprises a second winding section, a third winding section, … and an Nth winding section along the direction extending towards the periphery, at least part of the negative electrode sheet is arranged at the first winding section, the positive electrode sheet extends towards the periphery from the third winding section, and N is an integer greater than 3.

Wherein the coating extends from the second folded section to the third folded section.

Wherein the coating layer has a width in the axial direction of the winding core equal to the width of the separator in the axial direction of the winding core.

Wherein, the coating is a high polymer material layer filled with ceramic particles.

Wherein the coating is formed from a mixture of alumina, an acrylate, and carboxymethyl cellulose.

The positive pole piece is provided with a positive pole current collector, the positive pole lug is connected to the positive pole current collector, the negative pole piece is provided with a negative pole current collector, and the negative pole lug is connected to the negative pole current collector.

Wherein, the thickness of the coating is 3um-15 um.

In a second aspect, a battery according to an embodiment of the present invention includes a jelly roll as described in the above embodiments.

The technical scheme of the invention has the following beneficial effects:

a winding core according to an embodiment of the invention comprises: positive plate, negative pole piece and be located positive plate with the book layer of formation is convoluteed by the diaphragm between the negative pole piece, be connected with positive tab on the positive plate, be connected with the negative pole ear on the negative pole piece, the coating has the coating on the diaphragm, the coating is the insulating layer, just the coating has pore structure. In the roll core, the positive plate and the negative plate are separated by the diaphragm, the coating is coated on the diaphragm, a pore structure in the coating can contain electrolyte, the content of the electrolyte in the roll core can be increased, the cycle performance of the battery is improved, the coating has certain strength and can enhance the strength of the diaphragm, and the lithium ion battery is not easy to deform or damage when being extruded or collided from the outside, so that the safety performance of the battery is improved.

Drawings

Fig. 1 is a schematic structural view of a winding core according to an embodiment of the present invention.

Reference numerals

A positive plate 10; a positive tab 11; a positive electrode current collector 12;

a negative electrode tab 20; a negative electrode tab 21; a negative current collector 22;

a diaphragm 30; a first folding section 31; a second folded section 32; a third folded section 33;

and (6) coating 40.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention, are within the scope of the invention.

A winding core according to an embodiment of the invention is described in detail below.

As shown in fig. 1, the winding core according to the embodiment of the present invention includes a positive electrode sheet 10, a negative electrode sheet 20, and a winding layer formed by winding a separator 30 and located between the positive electrode sheet 10 and the negative electrode sheet 20, the positive electrode tab 11 is connected to the positive electrode sheet 10, the negative electrode tab 21 is connected to the negative electrode sheet 20, a coating layer 40 is coated on the separator 30, the coating layer 40 is an insulating layer, and the coating layer 40 has a pore structure.

That is, the winding core is mainly composed of the positive electrode sheet 10, the negative electrode sheet 20, and a winding layer, wherein the winding layer is located between the positive electrode sheet 10 and the negative electrode sheet 20, and the winding layer is formed by winding the separator 30, and the winding layer formed by winding the separator 30 separates the positive electrode sheet 10 from the negative electrode sheet 20. Be connected with anodal ear 11 on positive plate 10, be connected with negative pole ear 21 on negative plate 20, can coat on diaphragm 30 and have coating 40, and coating 40 can extend along the direction that the diaphragm was convoluteed, and coating 40 is the insulating layer, and coating 40 has pore structure, can store electrolyte through pore structure, increases the content of electrolyte in the book core. In the roll core, the positive plate 10 and the negative plate 20 are separated by the diaphragm 30, the coating 40 is coated on the diaphragm 30, a pore structure in the coating 40 can contain electrolyte, the content of the electrolyte in the roll core can be increased, the cycle performance of the battery is improved, the coating has certain strength and can enhance the strength of the diaphragm, and the lithium ion battery is not easy to deform or damage when being extruded or collided by the outside, so that the safety performance of the battery is improved. In addition, coating 40 can have certain elasticity, and when the external world extrudeed or collided the core, coating 40 had the cushioning effect, can extrude coating 40 when the core takes place the inflation, can absorb the inflation that the core produced through coating 40, was applied to the battery with rolling up the core, can keep the integrality and the stability of battery.

In some embodiments of the present invention, the separator 30 may have two layers, the negative electrode sheet 20 may be disposed on the outer side of the outer layer separator, the positive electrode sheet 10 may be disposed between the two layers of separators 30 to prevent the positive electrode sheet 10 from contacting the negative electrode sheet 20, and the coating layer 40 may be disposed on the inner side of the inner layer separator.

In an embodiment of the present invention, the winding layer may include a plurality of winding sections, where a first winding section 31 is located at the center of the winding core, a second winding section 32, a third winding section 33, … and an nth winding section are sequentially located from the first winding section 31 along a direction extending toward the outer periphery, the negative electrode sheet 20 is at least partially located at the first winding section 31, the positive electrode sheet 10 extends from the third winding section 33 toward the outer periphery, N is an integer greater than 3, and two adjacent winding sections may form a circle, for example, the first winding section 31 and the second winding section 32 may form a circle, and the circle may be in an elliptical shape.

In some embodiments, the coating 40 extends from the second folded section 32 to the third folded section 33, and the coating 40 has insulation property, so that an insulating tape does not need to be attached to the positions from the second folded section 32 to the third folded section 33, which is beneficial to improving the flatness of the battery.

Alternatively, the width of the coating layer 40 in the axial direction of the winding core and the width of the separator 30 in the axial direction of the winding core may be equal, so that the coating layer 40 covers the separator 30 in the axial direction of the winding core, increasing the amount of stored electrolyte and enhancing the strength of the separator.

The coating 40 may contain inorganic matter and organic matter, the inorganic matter and the organic matter may be insulating materials, the inorganic matter may be ceramic materials, the organic matter may be high molecular materials such as rubber, resin and the like, for example, the inorganic matter may be at least one of silicon nitride, silicon dioxide, aluminum oxide or aluminum nitride, the inorganic matter may be a nano material, the organic matter may be polypropylene or polyurethane, the weight proportion of the inorganic matter in the coating 40 may be not less than 80%, the strength of the coating may be enhanced by the inorganic matter, and the flexibility of the coating may be improved by the high molecular materials. The porosity of the coating 40 can be selected according to actual needs, and the porosity of the coating 40 can be 20% to 50%, for example, the porosity of the coating 40 can be 20%.

According to some embodiments, the coating 40 may be a layer of polymer material filled with ceramic particles, such as acrylic resin filled with nano-alumina.

Alternatively, the ceramic particles may include at least one of silica, alumina, zirconia, magnesium hydroxide, boehmite, barium sulfate, fluorophlogopite, fluoroapatite, mullite, cordierite, aluminum titanate, titania, copper oxide, zinc oxide, boron nitride, aluminum nitride, magnesium nitride, attapulgite. For example, the ceramic particles may be silica or alumina. The high polymer material may include at least one of polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene naphthalate, polyimide, polyamide, polyurethane, and aramid.

Optionally, the coating 40 may have a good thermal conductivity, which is beneficial to heat transfer along the coating 40 in the axial direction of the winding core, and is beneficial to heat dissipation of the winding core, thereby preventing the temperature of the winding core from being too high. For example, coating 40 is favorable to rolling up the heat at core center and losing when section 33 is rolled up to the third from second book section 32, prevents to roll up the high temperature at core center, avoids lithium ion battery to roll up the inside diaphragm of core and the current collector contact department temperature of core higher at charge-discharge in-process, avoids taking place the short circuit and leads to the battery security performance to reduce.

In some embodiments, the coating 40 may be formed from a mixture of alumina, acrylate and carboxymethyl cellulose, the proportions of alumina, acrylate and carboxymethyl cellulose being selected as desired, for example the weight ratio of alumina, acrylate and carboxymethyl cellulose may be 80:10:10 or 70:15: 15. Can strengthen the intensity of coating through aluminium oxide, acrylic ester and carboxymethyl cellulose can form gradually the layer, and carboxymethyl cellulose can take place the swelling in electrolyte, and carboxymethyl cellulose after the swelling makes coating 40 have certain elasticity, when external extrusion or collision roll core, coating 40 has the cushioning effect, in addition, is applied to the battery with rolling up the core, can extrude coating 40 when rolling up the core and taking place the inflation, can absorb the inflation that rolls up the core production through coating 40.

Alternatively, the positive electrode sheet 10 may be provided with a positive electrode current collector 12, the positive electrode tab 11 is connected to the positive electrode current collector 12, the negative electrode sheet 20 is provided with a negative electrode current collector 22, and the negative electrode tab 21 is connected to the negative electrode current collector 22. The positive electrode current collector 12 may be an aluminum foil, the negative electrode current collector 22 may be a copper foil, the negative electrode current collector 22 may be partially located in the center of the winding core, and the negative electrode tab 21 may be located in the center of the winding core; the positive electrode collector 12 may extend from the second folded section 32 to the third folded section 33, the positive electrode tab 11 may be located at a position adjacent to the second folded section 32, the coating 40 may be U-shaped, the coating 40 added to the separator at the second folded section 32 to the third folded section 33 may improve the strength of the separator, and the insulating tapes at the tab positions of the positive electrode tab 10 and the negative electrode tab 20 may be removed, which is beneficial to improving the flatness of the battery.

Alternatively, the thickness of the coating 40 may be 3um to 15um, for example, the thickness of the coating 40 may be 3um, 10um or 15um, and the specific thickness may be selected according to actual situations.

The embodiment of the invention provides a battery, which comprises the winding core in the embodiment. The battery with the roll core in the embodiment of the invention can increase the content of electrolyte in the battery, improve the recycling performance of the battery, ensure that the lithium ion battery is not easy to deform or damage when being extruded or collided by the outside and improve the safety performance of the battery. In addition, the coating has certain elasticity, and the coating has buffer action, and the roll core is applied to the battery, can extrude the coating when the battery expands, can absorb the expansion that the battery produced through the coating, can keep battery's integrality and stability.

The jelly roll and the battery in the embodiments of the present invention can be prepared by various methods, and the present invention will be further described with reference to some specific examples.

Example 1

Preparing a positive plate: mixing a positive electrode active material lithium cobaltate, a conductive agent acetylene black and a binder polyvinylidene fluoride (PVDF) according to a mass ratio of 97: 2: 1, uniformly mixing, and adding the mixture into a solvent N-methyl-2-pyrrolidone (NMP) to prepare positive electrode slurry with certain viscosity; uniformly coating the positive electrode slurry on an aluminum foil of a positive electrode current collector, drying at 90 ℃, cold pressing and splitting to prepare a battery positive plate, welding an aluminum tab at the head position of the positive electrode current collector, and not sticking an insulating tape at the tab position;

preparing a negative plate: mixing negative active material graphite, conductive agent acetylene black, thickening agent sodium carboxymethylcellulose (NaCMC) and binder Styrene Butadiene Rubber (SBR) according to a mass ratio of 97: 1: 1: 1, uniformly mixing to prepare battery negative electrode slurry; uniformly coating the negative electrode slurry on a copper foil of a negative current collector, drying at 85 ℃, cold pressing and splitting to prepare a battery negative plate, welding a nickel electrode at the head position of the negative current collector, and not sticking an insulating tape at the tab position;

preparing coating slurry: mixing alumina, acrylic ester and carboxymethyl cellulose with deionized water according to the weight ratio of 80:10:10 to prepare slurry with the solid content of 50%;

coating a diaphragm: coating slurry on positions, corresponding to a second folding section and a third folding section of a winding core, of a ceramic diaphragm of a PE (polyethylene) base material, wherein the thickness of the coating slurry is 5 mu m, and then drying the ceramic diaphragm;

preparing a roll core: and rolling the positive plate, the coated diaphragm, the negative plate and the diaphragm containing the coating slurry into a roll core corresponding to the second roll-folding section to the third roll-folding section.

And packaging the prepared roll core by using an aluminum plastic film, injecting liquid and sealing. Then, the obtained cell was tested.

Example 2

preparing coating slurry: mixing alumina, acrylic ester and carboxymethyl cellulose with deionized water according to the weight ratio of 70:15:15 to prepare slurry with the solid content of 50%;

coating a diaphragm: coating slurry on positions, corresponding to a second winding section to a third winding section, of a winding core of a ceramic diaphragm of a PE (polyethylene) base material, wherein the thickness of the coating slurry is 3 mu m, and then drying;

Example 3

coating a diaphragm: coating slurry on the positions, corresponding to the second folding section and the third folding section of the winding core, of the ceramic diaphragm of the PE substrate, wherein the thickness of the coating slurry is 10 mu m, and then drying the ceramic diaphragm;

Example 4

coating a diaphragm: coating slurry on positions, corresponding to a second folding section and a third folding section of the winding core, of the ceramic diaphragm of the PE substrate, wherein the thickness of the coating slurry is 15 micrometers, and then drying the ceramic diaphragm;

Comparative example 1

Preparing a positive plate: mixing a positive electrode active material lithium cobaltate, a conductive agent acetylene black and a binder polyvinylidene fluoride (PVDF) according to a mass ratio of 97: 2: 1, uniformly mixing, and adding the mixture into a solvent N-methyl-2-pyrrolidone (NMP) to prepare positive electrode slurry with certain viscosity; uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil, drying at 90 ℃, cold pressing, splitting to prepare a battery positive plate, welding an aluminum tab at the head position, and pasting an insulating adhesive tape at the tab position;

preparing a negative plate: mixing negative active material graphite, conductive agent acetylene black, thickening agent sodium carboxymethylcellulose (NaCMC) and binder Styrene Butadiene Rubber (SBR) according to a mass ratio of 97: 1: 1: 1, uniformly mixing to prepare battery negative electrode slurry; and uniformly coating the negative electrode slurry on a copper foil of a negative current collector, drying at 85 ℃, cold pressing, splitting to prepare a battery negative plate, welding a nickel electrode at the head position, and pasting an insulating adhesive tape at the tab position.

A diaphragm: taking a ceramic diaphragm of a PE substrate;

and rolling the positive plate, the diaphragm and the negative plate into a roll core.

Comparative example 2

a diaphragm: taking a ceramic diaphragm of a PE substrate;

The structures of the cores prepared in examples 1 to 4 can be specifically referred to as shown in fig. 1.

The cells of the above examples 1 to 4 and comparative examples were made into batteries and tested, and the test results are shown in table 1 below.

TABLE 1 Battery test results for different cells

Name(s)	Electrolyte retention amount	Baking at 130 deg.C	Baking at 150 DEG C	Frontal extrusion
					Example 1	5.85g	No combustion and no leakage	Without combustion	Without combustion
Example 2	5.77g	No combustion and no leakage	Without combustion	Without combustion
					Example 3	6.09g	No combustion and no leakage	Without combustion	Without combustion
Example 4	6.54g	No combustion and no leakage	Without combustion	Without combustion
					Comparative example 1	5.28g	Burning of	Burning of	Burning of
Comparative example 2	5.26g	Combustion and leakage liquid	Burning of	Burning of

The test results in table 1 show that the electrolyte retention in the batteries of the cells with the coatings added in examples 1 to 4 is improved, the electrolyte amount is gradually increased along with the thickening of the coatings, the batteries with the coatings added are baked at 130 ℃ without combustion or leakage, the batteries with the coatings added can pass the baking test at 150 ℃, and the same effect as that of the batteries with the coatings added without the head insulating tape can be achieved.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships are changed accordingly.

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A winding core, comprising:

the battery comprises a positive plate, a negative plate and a coil layer which is positioned between the positive plate and the negative plate and is formed by winding a diaphragm, wherein the positive plate is connected with a positive tab, the negative plate is connected with a negative tab, the diaphragm is coated with a coating, the coating is an insulating layer and has a pore structure, and the coating has elasticity;

the diaphragm is provided with two layers, the negative plate is arranged on the outer side of the outer-layer diaphragm, the positive plate is arranged between the two layers of diaphragms, and the coating is arranged on the inner side of the inner-layer diaphragm;

the winding layer comprises a plurality of winding sections, wherein a first winding section is positioned at the center of a winding core, a second winding section, a third winding section, … and an Nth winding section are sequentially arranged from the first winding section along the direction extending to the periphery, the negative electrode sheet is at least partially positioned at the first winding section, the positive electrode sheet extends from the third winding section to the periphery, and N is an integer greater than 3;

the coating extends from the second folded section to the third folded section.

2. The winding core of claim 1, wherein the coating layer has a width in the axial direction of the winding core equal to the width of the separator in the axial direction of the winding core.

3. The winding core of claim 1, wherein the coating is a layer of polymer material filled with ceramic particles.

4. The winding core of claim 3, wherein the coating is formed from a mixture of alumina, acrylate, and carboxymethyl cellulose.

5. The winding core according to claim 1, wherein a positive electrode current collector is arranged on the positive electrode sheet, the positive electrode tab is connected to the positive electrode current collector, a negative electrode current collector is arranged on the negative electrode sheet, and the negative electrode tab is connected to the negative electrode current collector.

6. The winding core of claim 1, wherein the coating has a thickness of 3um to 15 um.

7. A battery, characterized in that it comprises a jellyroll according to any one of claims 1 to 6.