CN202495522U - Square lithium ion battery with winding structure and positive pole piece thereof - Google Patents

Abstract

The utility model belongs to the technical field of lithium ion batteries, more specifically, the utility model relates to a positive electrode piece of a square lithium ion battery with a winding structure, including a positive electrode collector and a positive electrode diaphragm coated on both sides of the positive electrode collector , grooves are arranged on the positive electrode diaphragm. Compared with the prior art, the utility model has a groove on the positive electrode sheet of the square lithium-ion battery with a winding structure. In particular, the groove is located at the turning point after the positive electrode sheet is wound, and the opposite negative electrode material is always in the In the unsaturated state of charge, compared with the negative electrode materials in other regions, the volume expansion of the negative electrode sheet at the turning point is small, and the corresponding expansion stress is small and easy to release, so there will be no winding square shape caused by excessive stress or concentration. Distortion of Li-ion cells. In addition, the utility model also discloses a winding structure square lithium ion battery comprising the positive electrode sheet.

Description

A winding structure square lithium-ion battery and its positive electrode sheet

technical field

The utility model belongs to the technical field of lithium ion batteries, more specifically, the utility model relates to a square lithium ion battery with a winding structure and a positive electrode sheet thereof.

Background technique

With the trend of miniaturization and personalization of consumer portable electronic products, prismatic lithium-ion batteries, especially soft-packed prismatic lithium-ion batteries, have become the first choice or even the only power source for smartphones. As the core component of lithium-ion batteries, the assembly of batteries is usually done in two ways: lamination and winding. Relatively speaking, the winding method has been adopted by many lithium-ion battery manufacturers because of its simple process, high assembly efficiency and ease of automation.

As we all know, the electrode active materials of commercialized lithium-ion batteries are in different delithiation or lithium intercalation states, due to the change of lattice parameters, the macroscopic manifestation is the volume change of the active material. Taking graphite material as an example, from a completely delithiated state to a fully intercalated lithium state, its volume will expand by more than 10%. The expansion of the material will inevitably lead to internal stress between the layers of the wound lithium-ion battery. For the wound square lithium-ion cell, it is concluded through force analysis that the internal stress is mainly concentrated at the winding corner and is not easy to release. The macroscopic performance is along the width direction of the square lithium-ion cell, from both sides to the middle Squeeze effect. The more the material expands, the greater the internal stress and the more obvious the extrusion effect. When it reaches a certain level, it will cause the distortion and deformation of the wound square lithium-ion battery, and even cause the frustration of the interlayer pole pieces. This deformation or setback not only directly affects the mechanical dimensions of lithium-ion cells, but also affects their service life and even their safety performance.

In view of this, it is indeed necessary to provide a square lithium-ion battery with a wound structure and a positive electrode sheet thereof that can prevent twisting and deformation of the square lithium-ion cell with a wound structure.

Utility model content

One of the objectives of the present utility model is to provide a positive electrode sheet capable of preventing twisting and deformation of a winding square lithium-ion cell.

In order to achieve the above object, the utility model adopts the following technical solutions:

A positive electrode sheet of a winding structure square lithium ion battery, comprising a positive electrode collector and a positive electrode membrane coated on both surfaces of the positive electrode collector, grooves are arranged on the positive electrode membrane.

As an improvement of the positive electrode sheet of the square lithium-ion battery with winding structure of the present invention, the groove is located at the turning point of the positive electrode sheet after winding.

As an improvement of the positive electrode sheet of the square lithium ion battery with winding structure of the utility model, the depth of the groove is 5-90% of the thickness of the positive electrode film on one side. If the depth of the groove is too small, it will have little effect on inhibiting the expansion of the battery; if the depth of the groove is too large, the energy density of the battery will be greatly affected.

As an improvement of the positive electrode sheet of the square lithium ion battery with winding structure of the utility model, the depth of the groove is 20-70% of the thickness of the positive electrode film on one side.

As an improvement of the positive electrode sheet of the square lithium-ion battery with winding structure of the utility model, the depth of the groove is 30% of the thickness of the positive electrode film on one side.

As an improvement of the positive electrode sheet of the square lithium-ion battery with winding structure of the present invention, the total area of the groove accounts for 5-30% of the total area of the single-sided positive electrode film. If the total area of the groove is too large, it will have a great impact on the energy density of the battery; if the total area of the groove is too small, it cannot ensure that the groove completely covers the turning of the positive plate.

As an improvement of the positive electrode sheet of the square lithium-ion battery with winding structure of the present invention, the shape of the groove is rectangular, semicircular or semielliptical.

Compared with the prior art, there is a groove on the positive plate of the square lithium-ion battery with the winding structure of the utility model. In particular, the groove is located at the turning point after the positive plate is wound, and the opposite negative electrode material is always in the position when charging. In the unsaturated state of charge, compared with the negative electrode materials in other regions, the volume expansion of the negative electrode sheet at the turning point is small, and the corresponding expansion stress is small and easy to release, so there will be no winding square shape caused by excessive stress or concentration. Distortion of Li-ion cells.

Another object of the present utility model is to provide a winding structure square lithium-ion battery, comprising a positive electrode sheet, a negative electrode sheet, a diaphragm spaced between the positive electrode sheet and the negative electrode sheet, a packaging bag, and an electrolyte, the positive electrode sheet A sheet, a separator and a negative electrode sheet are wound to form a cell, and the positive electrode sheet is the positive electrode sheet of a square lithium-ion battery with a winding structure as described in the above paragraph.

As an improvement of the winding structure square lithium-ion battery of the present invention, after the positive electrode sheet, separator and negative electrode sheet are wound around the cell, the groove is located at the turning point of the positive electrode sheet.

Compared with the prior art, the square lithium-ion battery with winding structure of the utility model has grooves on the positive electrode sheet, thereby greatly reducing the battery deformation caused by the expansion of the negative electrode, and preventing the short circuit of the battery caused by the frustration of the electrode sheet And the safety accidents caused by it, and at the same time prevent the electrolyte leakage accident caused by the damage of the packaging bag caused by excessive expansion, thereby improving the safety performance and cycle life of the lithium-ion battery.

Description of drawings

Fig. 1 is the schematic diagram of the structure of the positive plate of the utility model embodiment 1;

Fig. 2 is a schematic structural diagram of the positive electrode sheet of Embodiment 2 of the present utility model;

Fig. 3 is a schematic diagram of the structure of the positive electrode sheet in Embodiment 3 of the present utility model;

Fig. 4 is a structural schematic diagram of a winding structure square lithium-ion battery of the present invention.

Detailed ways

In the following, the winding structure square lithium-ion battery and its positive electrode sheet of the present invention will be described in detail in combination with the accompanying drawings and specific implementation methods.

Specific implementation mode 1

As shown in Figure 1 , a positive electrode piece of a square lithium-ion battery with a winding structure of the utility model includes a positive electrode current collector 1 and a positive electrode diaphragm 2 coated on both sides of the positive electrode current collector 1, and the positive electrode diaphragm 2 Groove 3 is arranged on it.

Wherein, the groove 3 is located at the turn of the positive electrode sheet after being wound.

The depth of the groove 3 is 5-90% of the thickness of the single-sided positive electrode membrane 2, preferably 20-70%, more preferably 30%.

The total area of the groove 3 accounts for 5-30% of the total area of the single-sided positive electrode membrane 2 .

The shape of the groove 3 is rectangle, semicircle or semiellipse.

In this specific embodiment, the grooves 3 are arranged on both sides of the positive electrode current collector 1 and the grooves 3 are distributed symmetrically (the axis of symmetry is the positive electrode current collector 1) (as shown in FIG. 1 ); the grooves 3 The number of winding circles can be selected according to the number of winding turns, generally not less than the number of winding turns, preferably symmetrically arranged on two corners of the same circle.

As shown in Fig. 4, a kind of winding structure square lithium ion battery of the present utility model comprises positive electrode sheet 4, negative electrode sheet 5, the diaphragm 6 that is spaced between described positive electrode sheet 4 and negative electrode sheet 5, packaging bag 7, and Electrolyte, the positive electrode sheet 4 , separator 6 and negative electrode sheet 5 are wound to form a cell 8 , and the positive electrode sheet 4 is the positive electrode sheet of a square lithium-ion battery with a winding structure as described in the above paragraph. Wherein, after the positive electrode sheet 4 , the separator 6 and the negative electrode sheet 5 are wound around the cell 8 , the groove 3 is located at the turning point of the positive electrode sheet 4 .

Specific implementation mode 2

The difference from the specific embodiment 1 is that the groove 3 of this specific embodiment is provided on one of the positive electrode membranes 2 located on both sides of the positive electrode current collector 1 (as shown in FIG. 2 ). Certainly, the groove 3 should be at the turning point after the positive electrode sheet is wound. The rest are the same as the specific implementation mode 1, and will not be repeated here.

Specific implementation mode 3

The difference from Embodiment 1 is that the grooves 3 of this embodiment are provided on both sides of the positive electrode diaphragm 2 located on both sides of the positive electrode current collector 1, but the grooves 3 are not axisymmetric. distribution (as shown in Figure 3). Certainly, the groove 3 should be at the turning point after the positive electrode sheet is wound.

The rest are the same as the specific implementation mode 1, and will not be repeated here.

In order to test the technical effect of the positive plate of the utility model winding structure square lithium ion battery, the utility model takes the flexible package winding structure square lithium ion battery of model 103450 (50mm in length, 34mm in width and 10mm in thickness) as the evaluation object .

Respectively assemble 103450 electric cores with the same assembly machine and process parameters with the positive electrode sheet in the prior art (that is, no groove is provided on the positive electrode sheet) and the positive electrode sheet, negative electrode sheet and diaphragm of the present invention, and adopt the same process flow And the process parameters are finally made into qualified flexible packaging 103450 winding square lithium ion batteries. Randomly select qualified batteries from each group for comparative testing. The test content includes: storing and cycling the batteries under different SOC (state of charge) and different temperature conditions (specifically including: half-charged state (50% SOC) Storage test for three months at room temperature, storage test for half-charged state (50% SOC) at 45°C for three months, full charge state (100% SOC) for three months at room temperature, full charge state (100% SOC) storage test at 45°C for three months, storage test at full charge (100% SOC) at 60°C for one month, and cycle test at 45°C 1C cycle 500 times), count the distortion of each group of cells ratio, and the results are shown in Table 1.

Table 1: Battery storage test and cycle test results

It can be seen from Table 1 that, compared with the prior art, the lithium-ion battery applied with the positive plate of the square lithium-ion battery with the winding structure of the present invention will hardly be distorted and deformed when used under various conditions. This is because, the utility model winding structure square lithium ion battery is provided with a groove on the positive electrode sheet, and this groove is located at the turning point after the positive electrode sheet is wound, and the negative electrode material facing it is always in the unsaturated state of charge when charging. Compared with the negative electrode materials in other areas, the volume expansion of the negative electrode sheet at the turning point is small, and the corresponding expansion stress is small and easy to release, so there will be no damage to the wound square lithium-ion battery caused by excessive stress or concentration. of distortion.

It can be understood that this description only gives some implementations of the present utility model.

It should be noted that the opening method of the groove 3 in the utility model can be: first calculate the position of the turning point after the positive electrode sheet is wound, and then cut the positive electrode sheet at the calculated position with a cutting knife after the positive electrode sheet is cold pressed. , When cutting, the depth, area and shape of the groove 3 can be controlled according to actual needs.

According to the above principles, the utility model can also make appropriate changes and modifications to the above specific implementation methods. Therefore, the utility model is not limited to the specific implementation manners disclosed and described above, and some modifications and changes to the utility model should also fall within the scope of protection of the claims of the utility model. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present utility model.

Claims (9)

1. a winding-structure rectangular lithium ion battery positive plate comprises plus plate current-collecting body and is coated in the anodal diaphragm on the said plus plate current-collecting body two sides, and it is characterized in that: said anodal diaphragm is provided with groove.

2. winding-structure rectangular lithium ion battery positive plate according to claim 1 is characterized in that: said groove is positioned at the turning after said positive plate is reeled.

3. winding-structure rectangular lithium ion battery positive plate according to claim 1 is characterized in that: the degree of depth of said groove is the 5-90% of the anodal diaphragm thickness of single face.

4. winding-structure rectangular lithium ion battery positive plate according to claim 3 is characterized in that: the degree of depth of said groove is the 20-70% of the anodal diaphragm thickness of single face.

5. winding-structure rectangular lithium ion battery positive plate according to claim 4 is characterized in that: the degree of depth of said groove is 30% of the anodal diaphragm thickness of single face.

6. winding-structure rectangular lithium ion battery positive plate according to claim 1 is characterized in that: the gross area of said groove accounts for the 5-30% of the anodal diaphragm gross area of single face.

7. winding-structure rectangular lithium ion battery positive plate according to claim 1 is characterized in that: said groove be shaped as rectangle, semicircle or half elliptic.

8. winding-structure rectangular lithium ion battery; Comprise positive plate, negative plate, be interval in barrier film, packaging bag between said positive plate and the negative plate; And electrolyte; Said positive plate, barrier film and negative plate are reeled and are formed electric core, and it is characterized in that: said positive plate is each described winding-structure rectangular lithium ion battery positive plate of claim 1 to 7.

9. winding-structure rectangular lithium ion battery according to claim 8 is characterized in that: positive plate, barrier film and negative plate are reeled behind the electric core, and said groove is positioned at the turning of said positive plate.

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