Pole piece structure, roll core and lithium ion battery

Abstract

The utility model provides a pole piece structure, a roll core and a lithium ion battery, and relates to the technical field of lithium ion batteries, the pole piece structure comprises a diaphragm, a positive plate and a first coating, and the diaphragm is provided with a positive binding surface; the positive plate is arranged on the diaphragm, and the positive binding surface faces the positive plate; the first coating is arranged on the positive electrode binding surface of the diaphragm and is in contact with the positive plate, and the first coating is a thin film formed by an adhesive. According to the lithium ion battery, the first coating is arranged between the diaphragm and the positive plate, so that a certain adhesive force is formed between the positive plate and the diaphragm, the stress on the positive plate can be slowly released by the first coating and the diaphragm, the risk of wrinkling caused by stress extrusion in the winding process is reduced, the thickness of the battery cell is reduced, and the service life of the battery cell is prolonged. The overall quality and the cycle performance of the battery are improved, and the energy efficiency of the battery can also be improved for reducing wrinkles.

Description

Technical Field

[0001] This utility model relates to the field of lithium-ion battery technology, and in particular to an electrode structure, a winding core, and a lithium-ion battery. Background Technology

[0002] With the global goal of carbon neutrality and the domestic push to reduce reliance on fossil fuels, the development of industrial and commercial energy storage and large-scale outdoor energy storage has been particularly significant globally, especially in China. Energy storage power stations can store excess electricity at night, which can be used to regulate the uneven electricity consumption between day and night. The energy storage field has developed rapidly in recent years. As development accelerates, the cost requirements for energy storage systems are becoming increasingly stringent, leading to higher demands on the energy efficiency of energy storage batteries. Currently, energy efficiency is as important as cycle life and safety, because improved energy efficiency increases the conversion efficiency of electrical energy, thereby reducing the cost of the entire energy storage system. The energy efficiency of lithium-ion batteries specifically refers to the energy conversion efficiency of the battery during the charging and discharging process. The calculation formula is lithium-ion battery energy efficiency = discharge energy / charging energy, usually expressed as a percentage. The higher the energy efficiency, the higher the efficiency of converting electrical energy into the chemical energy of lithium-ion batteries. This can regulate the uneven electricity consumption between day and night, fully store excess electricity at night for daytime use, reduce the electricity costs of enterprises, and at the same time, help achieve the goal of carbon neutrality as soon as possible, as well as reduce reliance on non-renewable energy. The methods to improve the energy efficiency of lithium-ion batteries usually involve improvements to the electrolyte and positive and negative electrode plates. For example, the preparation method of lithium-ion batteries with announcement number CN119108659B improves the energy efficiency performance of lithium-ion batteries by using an electrolyte prepared with fluoroethylene carbonate.

[0003] In existing technologies, when the positive electrode sheet is wound to form a core, the accumulation of stress in the inner ring will cause wrinkles to form on the positive electrode sheet. These wrinkles will not only increase the thickness of the battery, but also affect the quality of the battery pack and can directly have an adverse effect on the cycle performance of the battery. Utility Model Content

[0004] In view of this, the present invention proposes an electrode structure, a winding core, and a lithium-ion battery. By setting a first coating between the separator and the positive electrode, a certain adhesive force can be formed between the positive electrode and the separator. This allows the stress on the positive electrode to be slowly released through the first coating and the separator, reducing the risk of wrinkles caused by stress compression during the winding process. This reduces the cell thickness, improves the overall quality and cycle performance of the battery, and also increases the energy efficiency of the battery due to the reduction of wrinkles.

[0005] The technical solution of this utility model is implemented as follows:

[0006] On the one hand, this utility model provides an electrode structure, including a separator, a positive electrode, and a first coating, wherein,

[0007] The diaphragm is provided with a positive electrode bonding surface;

[0008] The positive electrode sheet is disposed on the separator, and the positive electrode bonding surface faces the positive electrode sheet;

[0009] The first coating is disposed on the positive electrode bonding surface of the separator and contacts the positive electrode sheet. The first coating is a thin film formed by an adhesive.

[0010] Based on the above technical solutions, preferably, it also includes a negative electrode sheet, which is disposed on the side of the separator away from the positive electrode bonding surface.

[0011] Further preferably, the membrane also includes a second coating, wherein the membrane has a negative electrode contact surface facing the negative electrode sheet, the second coating is disposed on the negative electrode contact surface of the membrane and contacts the negative electrode sheet, and the second coating is a thin film formed by an adhesive.

[0012] More preferably, the adhesive used in the second coating is either PVDF or PMMA.

[0013] Based on the above technical solutions, preferably, the adhesive used in the first coating is either PVDF or PMMA.

[0014] Based on the above technical solutions, preferably, the thickness of the first coating is 0.5-3 μm.

[0015] Based on the above technical solutions, preferably, the positive electrode sheet is provided with embossing.

[0016] More preferably, the embossing depth on the positive electrode sheet is 0.5-25 μm.

[0017] On the other hand, this utility model proposes a core, which is formed by winding the above-mentioned electrode structure.

[0018] On the other hand, this utility model proposes a lithium-ion battery, including the aforementioned winding core.

[0019] The electrode structure, winding core, and lithium-ion battery of this invention have the following advantages over the prior art:

[0020] (1) By setting a first coating between the separator and the positive electrode, a certain adhesive force can be formed between the positive electrode and the separator, so that the stress on the positive electrode can be slowly released through the first coating and the separator, reducing the risk of wrinkles caused by stress compression during the winding process, thereby reducing the cell thickness, improving the overall quality and cycle performance of the battery, and also increasing the energy efficiency of the battery by reducing wrinkles.

[0021] (2) The embossed structure can improve the contact effect between the first coating and the positive electrode. At the same time, since lithium ions will cause the electrode to expand when they are embedded in the positive electrode, the embossed structure can provide the positive electrode with a certain expansion space, further reducing the probability of wrinkles during use and improving the overall performance of the battery. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the electrode structure of this utility model. Detailed Implementation

[0024] The technical solutions of this utility model will be clearly and completely described below with reference to the embodiments of this utility model. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0025] like Figure 1 As shown, the electrode structure of this utility model includes a separator 1, a positive electrode 2, and a first coating 3.

[0026] The diaphragm 1 is provided with a positive electrode bonding surface 101. The main material of the diaphragm 1 can be either polyethylene (PE) or polypropylene (PP), or a composite material. Since the diaphragm 1 is a membrane structure, it has two sides, one of which is provided with the positive electrode bonding surface 101.

[0027] The positive electrode 2 is disposed on the separator 1, and the positive electrode bonding surface 101 faces the positive electrode 2. The positive electrode 2 is made of lithium iron phosphate or ternary materials, etc. That is to say, the separator 1 is disposed on the outside of the positive electrode 2, and the positive electrode bonding surface 101 is located between the positive electrode 2 and the separator 1.

[0028] The first coating 3 is disposed on the positive electrode bonding surface 101 of the separator 1 and contacts the positive electrode sheet 2. The first coating 3 is a thin film formed by adhesive.

[0029] By setting a first coating 3 between the separator 1 and the positive electrode 2, a certain adhesive force can be formed between the positive electrode 2 and the separator 1, thereby allowing the stress on the positive electrode 2 to be slowly released through the first coating 3 and the separator 1. This reduces the risk of wrinkles caused by stress compression during the winding process, thereby reducing the cell thickness and improving the overall quality and cycle performance of the battery. In addition, during the winding process, the pressure deformation of the first coating 3 can also alleviate some of the pressure.

[0030] It should be noted that, considering cost and effect, if the coating is set to a single layer, the effect of setting the coating towards the negative electrode 4 is less than that of setting the coating towards the positive electrode 2. This is because the negative electrode is made of graphite, and the coating will adsorb graphite powder during the winding process. The effect of the coating contacting the negative electrode 4 is not as good as the effect of the coating contacting the positive electrode 2. Therefore, in this embodiment, the first coating 3 is used to contact the positive electrode 2.

[0031] In some embodiments, a negative electrode 4 is also provided, which is disposed on the side of the separator 1 away from the positive electrode bonding surface 101. The positive electrode 2, the negative electrode 4 and the separator 1 form a complete stacked structure for subsequent winding to form a core.

[0032] In some embodiments, a second coating 5 is also provided. The separator 1 has a negative electrode bonding surface 102 facing the negative electrode sheet 4. The second coating 5 is provided on the negative electrode bonding surface 102 of the separator 1 and contacts the negative electrode sheet 4. The second coating 5 is a thin film formed by adhesive. The second coating 5 has the same effect as the first coating 3, which can further prevent wrinkles from forming between the positive electrode sheet 2 and the negative electrode sheet 4.

[0033] Specifically, the adhesive used in the second coating 5 is either PVDF or PMMA. PVDF has excellent electrochemical stability and high adhesion, which can effectively improve the bonding strength between the separator and the positive and negative electrodes, reduce the interface separation between the electrodes and the separator caused by mechanical stress or thermal expansion, thereby reducing the battery internal resistance and improving cycle life. PMMA is a non-fluorinated material that complies with environmental regulations such as the ban on fluorine in the EU and other regions, and its raw material cost is lower than that of PVDF.

[0034] Accordingly, the first coating 3 can be made of the same material as the second coating 5, that is, the adhesive used in the first coating 3 is also one of PVDF and PMMA.

[0035] In some embodiments, the thickness of the first coating 3 is 0.5-3 μm, and the thickness of the second coating 5 can be the same as that of the first coating 3. It should be noted that if the coating thickness is low, its effect is not significant, and if the thickness is large, it will increase the core thickness after stacking.

[0036] In some embodiments, the positive electrode 2 is further provided with embossing. The embossed structure can improve the contact effect between the first coating 3 and the positive electrode 2. At the same time, since lithium ions will cause the electrode to expand when embedded in the positive electrode 2, the embossed structure can provide the positive electrode 2 with a certain expansion space, further reducing the probability of wrinkles during use and improving the overall performance of the battery.

[0037] Specifically, the embossing structure can be selected as an array of point-pressed structures. The embossing depth on the positive electrode 2 is 0.5-25um. When the embossing depth is small, the expansion space left for the positive electrode 2 will be insufficient, and there is still a high probability of wrinkles forming. When the embossing depth is set to a large value, it may cause the positive electrode 2 to deform too much, occupying additional internal space of the cell.

[0038] The core of this invention is formed by winding the aforementioned electrode structure.

[0039] In the specific preparation process, the winding machine opens the P roller to emboss the positive electrode sheet 2 to prepare the core, then preheats and bakes the core, then hot-presses the baked core, and finally assembles it into the shell.

[0040] The winding machine P-roller pressure is 0.1-0.35 MPa, the core preheating and baking temperature is 75-105℃, the baking time is 5-30 min, the core hot pressing temperature is 75-105℃, the hot pressing time is 30-150 s, and the hot pressing pressure is 2T-15T. It should be noted that in the actual core, the number of diaphragms 1 is set on both sides and is spaced apart from the positive electrode 2 and the negative electrode 4.

[0041] The lithium-ion battery of this utility model includes the above-mentioned winding core, and after the winding core is inserted into the casing, an electrolyte is injected to obtain the lithium-ion battery of this embodiment.

[0042] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A pole piece structure, characterized by: It includes a separator (1), a positive electrode (2), and a first coating (3), wherein, A positive electrode bonding surface (101) is provided on the diaphragm (1); The positive electrode (2) is disposed on the separator (1), and the positive electrode bonding surface (101) faces the positive electrode (2); The first coating (3) is disposed on the positive electrode bonding surface (101) of the separator (1) and contacts the positive electrode sheet (2). The first coating (3) is a thin film formed by adhesive.

2. The pole piece structure of claim 1, wherein: It also includes a negative electrode (4), which is disposed on the side of the diaphragm (1) away from the positive electrode bonding surface (101).

3. The pole piece structure of claim 2, wherein: It also includes a second coating (5), on which a negative electrode bonding surface (102) facing the negative electrode sheet (4) is provided. The second coating (5) is provided on the negative electrode bonding surface (102) of the separator (1) and contacts the negative electrode sheet (4). The second coating (5) is a thin film formed by adhesive.

4. The pole piece structure of claim 3, wherein: The adhesive used in the second coating (5) is either PVDF or PMMA.

5. The pole piece structure of claim 1, wherein: The adhesive used in the first coating (3) is either PVDF or PMMA.

6. The pole piece structure of claim 1, wherein: The thickness of the first coating (3) is 0.5-3 μm.

7. The pole piece structure of claim 1, wherein: Embossing is provided on the positive electrode sheet (2).

8. The pole piece structure of claim 7, wherein: The embossing depth on the positive electrode (2) is 0.5-25 μm.

9. A core, characterized by: It is formed by winding the electrode structure according to any one of claims 1-8.

10. A lithium-ion battery, characterized by: Includes the core as described in claim 9.

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