Composite current collector, pole piece, battery cell and lithium battery

Abstract

The utility model discloses a composite current collector, pole piece, cell and lithium battery, relates to lithium battery technical field, wherein the composite current collector includes current collector main part, temperature control layer and grid frame, the temperature control layer covers the surface of current collector main part, the grid frame is embedded in the temperature control layer, the temperature control layer covers the surface of current collector main part, and the grid frame is embedded in the temperature control layer. The thickness of the grid frame is smaller than that of the temperature control layer. The pole piece disclosed by the utility model comprises the composite current collector. The battery cell disclosed by the utility model comprises the pole piece. The lithium battery disclosed by the utility model comprises the battery cell. According to the lithium battery, the temperature control layer is arranged on the surface of the current collector main body, and the grid frame is embedded in the temperature control layer, so that the problems that an existing lithium battery is easy to generate internal short circuit and thermal runaway are solved.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium batteries, and specifically, mainly relates to a composite current collector, a pole piece, a battery core and a lithium battery. Background Art

[0002] Lithium-ion batteries are widely used in electronic products, electric vehicles, energy storage systems and other fields due to their superior performance such as high specific energy and long cycle life. However, in the complex charging and discharging conditions of lithium-ion batteries in actual operation, special situations such as overcharging, overdischarging, and overheating may occur, causing rapid degradation of battery performance. In severe cases, they may cause safety problems such as short circuits, thermal runaway, and fires in the battery.

[0003] Under existing technology, ceramic diaphragms can be used to minimize the risk of short circuits, or a grid frame composed of PTC materials can be coated on the electrodes to suppress thermal runaway caused by short circuits. The grid holes of the grid frame will also be plated with a metal temperature control film made of Al or Cu. When a short circuit occurs, a large amount of heat is generated inside the battery. Since the PTC material is a thermistor with a positive temperature coefficient, the large amount of heat generated can increase the resistance of the PTC layer to reduce the short circuit current, thereby suppressing the occurrence of thermal runaway.

[0004] However, this method is relatively complicated and time-consuming. At the same time, the metal temperature-control film plated on the grid frame may produce burrs that pierce the isolation membrane and cause internal short circuits. Secondly, the thickness of the metal film is smaller than the thickness of the grid frame, and the edge of the grid frame is relatively sharp, which may also cause the isolation membrane to be scratched and cause internal short circuits. Therefore, the existing methods to reduce internal short circuits and thermal runaway of batteries are not reliable.

[0005] In view of this, it is necessary to improve the structure of existing lithium batteries. Utility Model Content

[0006] In view of the deficiencies in the prior art, the utility model provides a composite current collector, a pole piece, a battery cell and a lithium battery to solve the problems of internal short circuit and thermal runaway that the prior lithium batteries are prone to.

[0007] The utility model discloses a composite current collector, comprising a current collector body, a temperature control layer and a grid frame, wherein the temperature control layer is covered on the surface of the current collector body, the grid frame is embedded in the temperature control layer, and the thickness of the grid frame is less than the thickness of the temperature control layer.

[0008] Preferably, the grid frame has a thickness of 10-15 um.

[0009] Preferably, the current collector body is a long strip structure, and the number of grids in the grid frame is n≥ab / 2, wherein a is the length of the current collector body, b is the width of the current collector body, and the units of a and b are both centimeters.

[0010] Preferably, the area size of the grid frame ranges from 0.5 square centimeters to 8 square centimeters.

[0011] Preferably, the temperature control layer is made of one of carbon fiber, graphene and artificial graphite.

[0012] Preferably, the grid frame comprises a PTC thermistor and a metal material.

[0013] Preferably, the metal material is aluminum or copper.

[0014] The utility model discloses a pole piece, comprising any one of the above-mentioned composite current collectors.

[0015] The utility model discloses an electric core, which comprises the above-mentioned pole piece.

[0016] The utility model discloses a lithium battery, comprising the above-mentioned battery core.

[0017] The beneficial effects of the utility model are:

[0018] The pole piece, battery cell and lithium battery made of the composite current collector of the utility model can absorb the heat generated by the battery by the temperature control layer during the cycle process, reduce the abnormal heating phenomenon of the battery, and improve the cycle life of the battery. In addition, the grid frame improves the conductivity of the current collector body on the one hand, and can significantly increase the resistance and cut off the circuit inside the battery when the temperature of the battery rises abnormally on the other hand, thereby improving the safety performance of the battery and effectively avoiding safety accidents caused by internal short circuits of the battery. In addition, the thickness of the grid frame is less than the temperature control layer, and the grid frame is embedded in the temperature control layer, which greatly reduces the risk of the sharp part of the grid frame scratching the diaphragm and causing internal short circuits of the battery. The viscosity of the temperature control layer can also increase the firmness of the grid frame to avoid safety problems such as its falling off and causing short circuits. It can be seen that the utility model solves the problem that existing lithium batteries are prone to internal short circuits and thermal runaway. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0020] Figure 1 is a cross-sectional view of the composite current collector of the utility model;

[0021] Figure 2It is a structural schematic diagram of the current collector body and the grid frame in the composite current collector of the utility model.

[0022] Explanation of the accompanying drawings: 1. current collector body; 2. temperature control layer; 3. grid frame. DETAILED DESCRIPTION

[0023] The following will disclose multiple embodiments of the present invention with drawings. For the purpose of clear description, many practical details will be described together in the following description. However, it should be understood that these practical details should not be used to limit the present invention. In other words, in some embodiments of the present invention, these practical details are not necessary. In addition, in order to simplify the drawings, some conventional structures and parts will be depicted in a simple schematic manner in the drawings.

[0024] It should be noted that all directional indications such as up, down, left, right, front, back... in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture as shown in the accompanying drawings. If the specific posture changes, the directional indication will also change accordingly.

[0025] In addition, in the present utility model, the descriptions of "first", "second", etc. are only used for descriptive purposes, and do not specifically refer to the order or sequence, nor are they used to limit the present utility model. They are only used to distinguish between parts or operations described with the same technical terms, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0026] In order to further understand the content, features and effects of the utility model, the following embodiments are given as examples and described in detail with reference to the accompanying drawings:

[0027] Reference Figure 1 and Figure 2, is a composite current collector disclosed in the utility model, comprising a current collector body 1, a temperature control layer 2 and a grid frame 3, wherein the current collector body 1 is made of metal foil, the temperature control layer 2 covers the two side surfaces of the current collector body 1, the temperature control layer 2 is made of non-metallic temperature control material, preferably one of carbon fiber, graphene and artificial graphite, the temperature control layer 2 is evenly distributed on the surface of the current collector body 1 in the form of slurry coating, a layer of grid frame 3 is embedded in the temperature control layer 2 on each side, the grid frame 3 is fixedly connected to the current collector body 1, the grid frame 3 is a PTC thermistor and metal composite material, the metal of which can be aluminum or copper, to enhance the conductivity of the grid frame 3. Preferably, the thickness of the grid frame 3 is less than the thickness of the temperature control layer 2, and the thickness of the temperature control layer 2 is less than the thickness of the current collector body 1.

[0028] Reference Figure 1 and Figure 2 Preferably, the current collector body 1 is a long strip structure, the grid frame 3 is formed by a 3D printing method, the thickness of the grid frame 3 is 10 to 15 um, the number of grids in the grid frame 3 is n≥ab / 2, wherein a is the length of the current collector body 1, b is the width of the current collector body 1, the units of a and b are both centimeters, and the area size of the grid ranges from 0.5 square centimeters to 8 square centimeters.

[0029] When preparing the above-mentioned composite current collector, the grid frame 3 is fixed on the current collector body 1 by laser spot welding on the upper and lower surfaces of the current collector body 1. Then, the non-metallic temperature control material is coated on the grid frame 3 by coating, and then rolled by a roller press to make its surface flat.

[0030] Example 1

[0031] A preferred method for preparing the above composite current collector is as follows:

[0032] S1: Select ceramic PTC thermistor material and use 3D printing to prepare a grid frame 3, wherein the grid in the grid frame 3 is preferably a square with a grid side length of 3 cm; the preparation material of the ceramic PTC thermistor includes Nb, Ce, and Mn doped BaTiO3, wherein the Nb content is 0-0.8%, the Ce content is 0-0.5%, and the Mn content is 0-0.5%.

[0033] S2: Pressurizing the prepared grid frame 3 to make its surface smooth and its thickness 12 um;

[0034] S3: Fixing the grid frame 3 on the current collector body 1 by laser spot welding;

[0035] S4: using paraffin wax and graphite as raw materials, preparing graphene materials through the existing redox method;

[0036] S5: mixing and stirring the graphene and the binder to obtain a non-metallic temperature control material;

[0037] S6: Use a coating machine to coat the non-metallic temperature control material on the grid frame 3, with a thickness of 22um;

[0038] S7: putting the coated product in S6 on a roller press to roll it to ensure its flatness. After rolling, the thickness of the non-metallic temperature control material is 18 um, and the composite current collector of the utility model is obtained.

[0039] Ternary nickel cobalt manganese oxide (NCM622) was used as the positive electrode material, and graphite was used as the negative electrode material. The positive electrode material and the negative electrode material were respectively coated on the composite current collector prepared as described above to make a 45Ah soft-pack battery. The battery was injected and formed, and subjected to simulated charge and discharge temperature distribution, external short circuit, and needle puncture tests.

[0040] Embodiment 2:

[0041] The positive electrode material is ternary nickel cobalt manganese oxide (NCM622), and the negative electrode is graphite material. The positive and negative electrode materials are respectively coated on traditional battery collectors to make 45Ah soft-pack batteries, and the battery is subjected to simulated charge and discharge temperature distribution, external short circuit, acupuncture and other tests.

[0042] The results of the temperature distribution simulation test, external short circuit test and needle puncture test of the soft-pack batteries of the above-mentioned embodiments and comparative examples are shown in Table 1:

[0043] Table 1 Test results of Example 1 and Example 2

[0044]

[0045] As can be seen from the table above, in the tests of Example 1 and Example 2, the battery made of the composite current collector with a grid frame structure can maintain a normal state and low temperature in the external short circuit and needle puncture tests; while the battery made of the traditional current collector swells or catches fire and explodes in the external short circuit and needle puncture tests, and the temperature is higher. This shows that the composite current collector with a grid frame structure can reduce the heat generation phenomenon and better avoid the occurrence of short circuit or thermal runaway.

[0046] Further:

[0047] The utility model discloses a pole piece, comprising the composite current collector.

[0048] The utility model discloses an electric core, comprising the above-mentioned pole piece.

[0049] The utility model discloses a lithium battery, comprising the above-mentioned battery core.

[0050] The implementation principle and beneficial effects of the utility model are as follows: the pole piece, battery cell and lithium battery made of the composite current collector of the utility model are provided with a grid frame of PTC thermistor material and a temperature control material, so that during the cycle, the heat generated by the battery can be absorbed by the temperature control layer 2, so that the abnormal heating phenomenon of the battery can be reduced in the test and the cycle life of the battery can be improved; the grid frame 3 improves the conductivity of the current collector body 1 on the one hand, and on the other hand, when the temperature of the battery rises abnormally, it can significantly increase the resistance and cut off the circuit inside the battery, thereby improving the safety performance of the battery and effectively avoiding safety accidents caused by internal short circuit of the battery;

[0051] In addition, the thickness of the grid frame 3 is smaller than the temperature control layer 2, and the grid frame 3 is embedded in the temperature control layer 2, which greatly reduces the risk of the sharp part of the grid frame scratching the diaphragm and causing an internal short circuit in the battery. The viscosity of the temperature control layer 2 can also increase the firmness of the grid frame 3 to avoid safety problems such as its falling off and causing a short circuit. It can be seen that the utility model solves the problem that existing lithium batteries are prone to internal short circuits and thermal runaway.

[0052] The above is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A composite current collector, characterized in that: The invention comprises a current collector body (1), a temperature control layer (2) and a grid frame (3), wherein the temperature control layer (2) covers the surface of the current collector body (1), the grid frame (3) is embedded in the temperature control layer (2), and the thickness of the grid frame (3) is less than the thickness of the temperature control layer (2).

2. The composite current collector according to claim 1, characterized in that: The thickness of the grid frame (3) is 10 to 15 um.

3. The composite current collector according to claim 1, characterized in that: The current collector body (1) is a long strip structure, and the number of grids in the grid frame (3) is n≥ab / 2, where a is the length of the current collector body (1), b is the width of the current collector body (1), and the units of a and b are both centimeters.

4. The composite current collector according to claim 3, characterized in that: The area size of the grid frame (3) ranges from 0.5 square centimeters to 8 square centimeters.

5. The composite current collector according to claim 1, characterized in that: The temperature control layer (2) is made of one of carbon fiber, graphene and artificial graphite.

6. The composite current collector according to claim 1, characterized in that: The grid frame (3) comprises a PTC thermistor and a metal material.

7. The composite current collector according to claim 6, characterized in that: The metal material is aluminum or copper.

8. A pole piece, characterized in that: Comprising the composite current collector described in any one of claims 1-7.

9. A battery cell, characterized in that: Including the pole piece as claimed in claim 8.

10. A lithium battery, characterized in that: Comprising the battery cell as claimed in claim 9.

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