CN217009229U

CN217009229U - Positive pole piece and cylindrical lithium ion battery comprising same

Info

Publication number: CN217009229U
Application number: CN202220599361.2U
Authority: CN
Inventors: 安敏俊; 薄晋科; 张良; 李猛; 王东; 冯建伟; 曹仕良
Original assignee: Dalian CBAK Power Battery Co Ltd
Current assignee: Dalian CBAK Power Battery Co Ltd
Priority date: 2022-03-18
Filing date: 2022-03-18
Publication date: 2022-07-19
Anticipated expiration: 2032-03-18

Abstract

The utility model provides a positive pole piece and a cylindrical lithium ion battery comprising the same. The positive pole piece comprises a current collector and more than one pole lug; the surface of the current collector is provided with an active material layer and more than one blank area; any tab comprises an upper end part which is used for being welded and fixed with the metal cover plate; the lower end part is used for being welded and fixed with the blank area of the current collector; the bottom end of the upper end part and the top end of the lower end part are fixedly connected; the upper end portion and the lower end portion are both rectangular in shape, the width of the rectangle where the upper end portion is located is L3, the width of the rectangle where the lower end portion is located is L2, and L3 is larger than L2. This positive pole piece can increase the welding area of anodal auricle and cylinder electricity core top cap, improves and increases the current capacity, prevents to generate heat and leads to educing lithium, falls the material phenomenon.

Description

Positive pole piece and cylindrical lithium ion battery comprising same

Technical Field

The utility model belongs to the technical field of positive pole pieces for cylindrical batteries, and particularly relates to a positive pole piece and a cylindrical lithium ion battery comprising the same.

Background

Various configurations of the battery include prismatic, button-shaped, and cylindrical configurations. In the cylindrical battery structure, a positive pole piece, a diaphragm and a negative pole piece are wound into a cylinder around a central pin, and the positive pole piece and the negative pole piece are electrically connected with the outside through a pole lug.

At present, a cylindrical steel shell power lithium battery is constructed with a single-pole lug and a double-pole lug which are both rectangular, the current is large when the lithium battery is subjected to power test under normal conditions, the generated heat is large, thermal reaction is generated inside a battery core, and the phenomena of material falling, lithium separation, CID turning and the like of a pole piece can occur in generated gas.

SUMMERY OF THE UTILITY MODEL

The utility model provides a positive pole piece and a cylindrical lithium ion battery comprising the same, and aims to solve the problems that the existing cylindrical lithium battery generates heat seriously to cause lithium precipitation, material falling and the like when being subjected to a high-rate test.

Specifically, the utility model provides the following technical scheme:

a positive pole piece for a cylindrical lithium ion battery comprises a current collector and more than one pole lug; the surface of the current collector is provided with an active material layer and more than one blank area;

any tab comprises an upper end part which is used for being welded and fixed with the metal cover plate; the lower end part is used for being welded and fixed with the blank area of the current collector; the bottom end of the upper end part and the top end of the lower end part are fixedly connected;

the upper end portion and the lower end portion are both rectangular in shape, the width of the rectangle where the upper end portion is located is L3, the width of the rectangle where the lower end portion is located is L2, and L3 is larger than L2.

Preferably, in the positive electrode sheet, L2 < L3 < (3 × L2). When L3 is not less than (3 × L2), the time of current overcurrent is longer when the battery cell is charged and discharged normally, and the heat productivity is increased, so that the heat dissipation of the battery cell is influenced, and the failure of the battery cell is possibly caused.

More preferably, L3 is (1.8 × L2) to (2.2 × L2). The present inventors have found that the calorific value can be significantly improved by limiting the magnitude relationship between L3 and L2 to the above range.

Preferably, in the above-mentioned positive electrode sheet, it includes along 2 utmost point ear pieces of length interval of the mass flow body, the surface of the mass flow body is equipped with along two margin regions of length interval of the mass flow body with utmost point ear piece is connected.

Preferably, in the positive electrode sheet, a width L2 of a rectangle in which a lower end of any one of the electrode tabs is located is 0.4 to 0.6% of the length of the current collector. Less than 0.4% of the length of the current collector of L2 influences the welding area between the lower end of the tab and the current collector, and more than 0.6% of the length of the current collector of L2 influences the winding formation of the current collector.

Preferably, in the positive electrode plate, any of the blank areas is rectangular, the width of the rectangle in which the blank area is located is L1, and L1 is greater than L2.

Preferably, in the above-described positive electrode sheet, the unit of L2 is mm, and the area of the rectangle in which the lower end portions of the electrode tabs are located and exposed out of the current collector is (3 × L)2)～(5×L2)mm². The lower tip of utmost point auricle exposes the part of mass flow body is the bending segment of utmost point auricle, if the area that lower tip place rectangle exposes is too little, then the battery core that rolls up can be collided with to lower left closed angle and lower right closed angle of upper end place rectangle when utmost point auricle is buckled, if the area that lower tip place rectangle exposes is too much, then can reduce utmost point auricle bending back and metal cover plate's welding area, reduces the overcurrent capacity, improves the temperature rise.

Preferably, in the positive electrode plate, the upper end of the electrode lug is fixed to the metal cover plate by ultrasonic welding; the lower end part of the pole lug plate and the white remaining area of the current collector are fixed through ultrasonic welding.

Preferably, in the positive electrode plate, the current collector is made of aluminum foil and has a thickness of 10 to 20 μm;

and/or the pole lug is made of aluminum and has a thickness of 0.1-0.5 mm;

and/or the active material layer comprises a positive electrode active material, a binder and a conductive agent; preferably, in the active material layer, the amount of the positive active material is 90-97 wt%, the amount of the binder is 0.5-3 wt%, and the amount of the conductive agent is 0-6 wt%.

The utility model also provides a cylindrical lithium ion battery which comprises the positive pole piece, the diaphragm, the electrolyte and the negative pole piece.

The utility model has the following beneficial effects:

according to the positive pole piece for the cylindrical lithium ion battery, the blank area is reserved on the surface of the current collector, the other areas are active material areas, the shape of the positive pole lug piece is that two rectangles with different sizes are combined into a whole, the small rectangle is subjected to ultrasonic welding with the blank area, and the large rectangle is subjected to ultrasonic welding with the cover plate of the cylindrical battery, so that the welding area of the positive pole lug piece and the top cover of the cylindrical battery cell can be increased, the overcurrent capacity is improved and increased, and the phenomena of lithium precipitation and material dropping caused by heating are prevented.

Drawings

Fig. 1 is a schematic structural diagram of the positive electrode sheet of example 1, wherein, 1-pole lug, 2-current collector, and 3-white area.

Fig. 2 is a temperature rise comparison of the battery cells made of the positive electrode plates provided in example 1 and comparative example 1 at different discharge rates.

Detailed Description

The following examples are intended to illustrate the utility model but are not intended to limit the scope of the utility model. The examples do not show the specific techniques or conditions, according to the technical or conditions described in the literature in the field, or according to the product specifications.

Example 1

As shown in fig. 1, example 1 provides a positive electrode sheet comprising a current collector and two electrode tabs spaced along the length of the current collector;

the current collector is made of aluminum foil, the length of the current collector is 2100mm, the height of the current collector is 58mm, and the thickness of the current collector is 15 micrometers; the surface of the current collector is provided with two blank areas which are equidistantly spaced along the length of the current collector and connected with the pole lug plate, and the other areas are active material layers;

any one of the blank areas is rectangular, the width L1 of the rectangle in which the blank area is located is 10.5mm, and the height is 58 mm;

the using amount of a positive electrode active material (the positive electrode active material is a ternary material) in the active material layer is 91 wt%, the using amount of a binder (PVDF) is 3 wt%, the using amount of a conductive agent Super-P is 4.5 wt%, and the using amount of a carbon nano tube is 1.5 wt%;

any one of the pole lug plates is made of aluminum, is 0.5mm thick and comprises an upper end part which is used for being fixed with a cover plate of the cylindrical battery through ultrasonic welding; the lower end part is used for being fixed with the blank area of the current collector in an ultrasonic welding mode;

the upper end part and the lower end part are both rectangular, the width L3 of the rectangle in which the upper end part is positioned is 16mm, the height is 27mm, the width L2 of the rectangle in which the lower end part is positioned is 8mm, and the height is 61 mm;

the rectangular area of the lower end part of the pole lug plate exposed out of the current collector is (4 xL 2) mm²。

The preparation steps are as follows: homogenizing powder materials of the positive active material, the binder and the conductive agent and a solvent (7-hour total homogenizing process), dispersing to prepare positive slurry, coating the positive slurry on the surface of a positive current collector, coating by using an interval coating method, wherein an uncoated area is a blank area, rolling and cutting after coating, and performing ultrasonic welding on a positive lug in the blank area to obtain a positive pole piece.

And assembling the obtained positive pole piece, winding the positive pole piece, the negative pole piece and the pole lug with the diaphragm after ultrasonic welding, rolling out a roll core, putting the roll core into a shell, performing bottom pointing, rolling groove, baking, injecting liquid, performing ultrasonic welding on the upper end part of the pole lug after liquid injection and a cover plate of the cylindrical battery, sealing, and preparing the battery core.

Comparative example 1

Comparative example 1 differs from example 1 only in that: the width of the upper end of the pole lug piece is 8mm, namely the width of the pole lug piece is the same as that of the lower end of the pole lug piece.

Comparative example 2

Comparative example 2 differs from example 1 only in that the rectangle in which the lower end portions of the pole tabs are located exposes the current collector with an area of 2 xl 2mm²。

Comparative example 3

Comparative example 3 differs from example 1 only in that the rectangle in which the lower end portions of the pole tabs are located exposes the current collector with an area of 6 × L2mm²。

Test examples

1. Battery cell manufacturing process

The cell processing results for example 1 and comparative examples 1-3 are shown in table 1 below. And the short-circuit rate data after winding is obtained by a short-circuit tester in a manner that two anode and cathode probes are in contact with the anode and the cathode of the winding core. And (3) measuring 50 samples in each example, specifically, after winding, firstly measuring the short circuit of each sample, recording the number of short-circuited samples, further putting the samples which are not short-circuited into a shell, dotting the bottom, rolling a groove, then measuring the short circuit, also recording the number of short-circuited samples, and calculating the short circuit rate according to the sum of the number of short-circuited samples recorded twice.

TABLE 1

	Short circuit rate after winding	Welding of pole lug with cover plate	Closing cover	Conclusion
					Example 1	0％	Weldable	Closable lid	Can produce and produce
Comparative example 1	0％	Weldable	Closable lid	Can produce and produce
					Comparative example 2	10％	Weldable	Closable lid	Can not produce
Comparative example 3	0％	Weldable	Can not be closed	Can not produce

The reason why the short circuit rate of the comparative example 2 is high is that the diaphragm of the winding core is pierced by the left lower part and the left and right sharp corners of the upper end part of the tab in the bending process of the tab, and the short circuit occurs.

The reason why the cover cannot be closed in the comparative example 3 is that the bent tab is contacted with the inside of the shell in the tab bending process, and the cover cannot be closed.

2. Cell test

The cells manufactured by the positive electrode plates of example 1 and comparative example 1 were respectively discharged at different magnifications, and the temperature rises were compared, as shown in fig. 2, where the ordinate temperature is the maximum temperature minus the minimum temperature.

As shown in the result of fig. 2, the temperature rise of example 1 is lower than that of comparative example 1, and a 10C rate test can be performed, whereas the 10C rate test cannot be performed in comparative example 1, because the heat generation is severe and the gas production is large in the test process of comparative example 1, which causes the cell structure failure (CID flip), and the cell structure failure is reduced to 0V.

Although the utility model has been described in detail hereinabove by way of general description, specific embodiments and experiments, it will be apparent to those skilled in the art that modifications and improvements can be made thereto without departing from the scope of the utility model. Accordingly, it is intended that all such modifications and alterations be included within the scope of this invention as defined in the appended claims.

Claims

1. A positive pole piece for a cylindrical lithium ion battery is characterized by comprising a current collector and more than one pole lug; the surface of the current collector is provided with an active material layer and more than one blank area;

2. The positive electrode plate for the cylindrical lithium ion battery according to claim 1, wherein L2 < L3 < (3 xL 2).

3. The positive electrode sheet for a cylindrical lithium ion battery according to claim 2, wherein L3 is (1.8 XL 2) - (2.2 XL 2).

4. The positive electrode plate for the cylindrical lithium ion battery according to claim 1, comprising 2 tab pieces spaced along the length of the current collector, wherein the surface of the current collector is provided with two blank areas spaced along the length of the current collector to connect with the tab pieces.

5. The positive electrode sheet for a cylindrical lithium ion battery according to claim 1, wherein a width L2 of a rectangle in which a lower end portion of any one of the electrode tabs is located is 0.4 to 0.6% of a length of the current collector.

6. The positive electrode plate for the cylindrical lithium ion battery according to claim 1, wherein any of the blank areas is rectangular, the width of the rectangle in which the blank area is located is L1, and L1 is greater than L2.

7. The positive electrode sheet for the cylindrical lithium ion battery according to claim 1, wherein the unit of L2 is mm, and the rectangular area where the lower end of the electrode tab is exposed out of the current collector is (3 XL 2) - (5 XL 2) mm²。

8. The positive pole piece for the cylindrical lithium ion battery according to claim 1, wherein the upper end of the pole lug is fixed to the metal cover plate by ultrasonic welding; the lower end part of the pole lug plate and the blank area of the current collector are fixed by ultrasonic welding.

9. The positive electrode plate for the cylindrical lithium ion battery according to claim 1, wherein the current collector is made of aluminum foil and has a thickness of 10-20 μm;

and/or the pole lug is made of aluminum and has a thickness of 0.1-0.5 mm;

and/or the active material layer includes a positive electrode active material, a binder, and a conductive agent.

10. A cylindrical lithium ion battery comprising the positive electrode sheet according to any one of claims 1 to 9, a separator, an electrolyte, and a negative electrode sheet.