CN207602732U - Inside has the lithium ion battery of thermally conductive sheet - Google Patents

Abstract

The utility model belongs to technical field of lithium ion, is related to the lithium ion battery that a kind of inside has thermally conductive sheet, thermally conductive sheet is internally provided in the battery core of battery, has the function of to assist battery core heat dissipation, selected thermally conductive sheet will insulate with battery core.By setting thermally conductive sheet in inside, using the capacity of heat transmission of the superelevation of thermally conductive sheet, a heat conduction high-speed channel is provided from inside, internal heat is exported from high-speed channel, avoiding heat, aggregation causes temperature to increase in inside.

Description

Lithium-ion battery with thermal pad inside

technical field

The utility model relates to the technical field of lithium ion batteries, in particular to a lithium ion battery with a heat conducting sheet inside.

Background technique

Lithium-ion secondary batteries have the characteristics of high specific energy, good rate performance, and long cycle life, and are more and more widely used in consumer electronics, new energy vehicles, and energy storage fields. Lithium-ion secondary batteries manufactured by existing material systems and processes are not suitable for charging and discharging at high temperatures. This is because when working at high temperature, the SEI film of the negative electrode of the lithium-ion battery is unstable, which will accelerate the growth and cause the battery to deteriorate; the side reaction between the positive electrode and the electrolyte will also accelerate, resulting in the attenuation of the gas production performance of the battery. For example, when working at a temperature of 45°C, the cycle life of the battery will be reduced by 20%.

However, with the promotion of the application of lithium-ion secondary batteries, charging and discharging are often performed at high rates, and the batteries will generate a lot of heat at this time. The lithium-ion secondary battery structure is a repeating structure of positive electrode/diaphragm/negative pole unit, in which the diaphragm is a poor conductor, and the overall lithium-ion battery has poor thermal conductivity. During high-rate operation, the heat generated by the battery will cause the battery to heat up, affecting battery performance and life.

According to the inventor's research, due to the poor thermal conductivity of the battery due to the structure and materials, the internal temperature is usually much higher than the outer shell temperature under high-rate discharge and charge. This temperature gradient will aggravate the degradation of internal performance, and the degradation of internal performance will increase the resistance of the internal pole piece, resulting in increased heat generation during operation, resulting in a vicious cycle process. In addition, the huge temperature gradient will also damage the battery structure and materials. It is for this reason that the capacity of existing lithium-ion battery cells is not very large. If it exceeds 100Ah, the internal temperature will be too high to cause structural damage during operation, and the diaphragm will be damaged to cause safety problems. Although many works and studies have focused on the external heat management of Li-ion batteries, little attention has been paid to the internal heat generation of the battery. Therefore, how to export the heat generated inside the battery is an important improvement method to improve battery performance and monomer capacity.

Patent CN201620619711.1 discloses a lithium-ion battery with a heat dissipation structure, which is characterized in that a heat conduction sheet is arranged on the negative electrode. However, when the heat conduction sheet is connected to the negative electrode, an electrochemical reaction will occur, and additional processes are required, which is a challenge to the existing production equipment and processes. Patent CN201320186144.1 discloses a high-power safe lithium-ion battery with a built-in thermal diffusion structure, which is characterized by a heat-conducting sheet in contact with the battery core, but the heat-conducting sheet needs to be fixed on the battery case, and the heat-conducting sheet is based on a heat-dissipating pipe Based on this, the purpose of adding thermal fins is to facilitate heat transfer to the heat pipe. However, adding a cooling pipe to the battery structure will greatly increase the production cost of the battery. More importantly, the cooling pipe structure will greatly reduce the energy density and power density of the battery. The overall design is not worth the candle.

Utility model content

In view of the fact that the existing lithium-ion battery adopts a multi-layer positive electrode/multi-layer negative electrode/multi-layer diaphragm to form a battery cell structure with poor heat transfer, this structure has the disadvantage that internal heat is difficult to export, and a lithium-ion battery with a heat-conducting sheet inside is proposed .

In order to achieve the above object, the present invention provides following equipment and technical scheme:

In order to overcome the poor heat transfer caused by the multi-layer positive electrode/separator film/negative electrode structure of the lithium-ion secondary battery, the internal heat cannot be transmitted out of the battery in time when the battery is discharged at a high rate and the high temperature is working, and the internal overheating problem is caused by the utility model. The problem is solved by arranging a heat conduction sheet inside the battery.

The material of the heat conduction sheet is carbon material, the preferred heat conduction sheet is a graphite heat conduction sheet with high thermal conductivity, the thermal conductivity of the heat conduction sheet is 400-1800W/m·K, the preferred thermal conductivity is 800-1800W/m·K, more The preferred thermal conductivity is 1000-1800 W/m·K. The thickness of the heat conducting sheet is <1mm, preferably 0.05mm-0.1mm.

The selected heat conduction sheet should be insulated from the battery cell, and the heat conduction sheet is separated from the positive and negative electrodes of the battery cell by a polymer material that cannot be dissolved in the electrolyte to avoid electrical connection, so that no electricity will occur during the battery cycle. Chemical redox reactions.

The length and width of the heat conducting sheet should be smaller than the length and width of the cell. The insertion position of the heat conduction sheet is different according to the structure of the cell. If the cell is a winding structure, the heat conduction sheet should be in the center of the winding core. If the cell is a laminated structure, the heat conduction sheet is inside the cell, preferably in the center of the cell. , the battery is composed of several cells, and the heat conduction sheet is between the cells. The heat conduction sheet is parallel to the winding or stacking direction of the battery pole pieces, and is arranged inside the battery, and several pieces can be arranged as required. They are not in contact with each other, which increases the heat dissipation effect inside the battery.

When the lithium-ion secondary battery is working, due to the poor heat conduction of the battery structure and materials, the closer to the center of the battery, the more difficult it is for heat to be conducted, and the higher the temperature. By setting the heat conduction sheet inside and utilizing the super high thermal conductivity of the heat conduction sheet, a high-speed heat conduction channel is provided from the inside, and the internal heat is exported from the high-speed channel to avoid heat accumulation inside and cause the temperature to rise.

According to Fourier's law of heat transfer:

J＝-k·dT/dx

Where J is the heat flux and k is the thermal conductivity. dT/dx is the temperature gradient. According to the law, the heat flux is related to the temperature gradient. The heat conduction sheet is installed inside the battery. Due to the large area of the heat conduction sheet and the high thermal conductivity, the temperature of the heat conduction sheet should be lower than the internal temperature of the cell, which creates a large temperature gradient inside the cell and increases the heat flux density. It can increase the heat export and reduce the internal temperature of the battery.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the utility model is further described.

Fig. 1 is the structural representation of the utility model embodiment one;

Fig. 2 is the structural representation of the second embodiment of the utility model;

Fig. 3 is the structural representation of the utility model embodiment three;

Fig. 4 is a schematic diagram of the structure between the negative electrode and the heat conducting sheet in Fig. 3 .

In the figure: 1. heat conduction sheet, 2. positive electrode, 3. separator, 4. negative electrode, 5. negative electrode with heat conduction sheet, 6. negative electrode current collector.

Detailed ways

Now in conjunction with accompanying drawing, the utility model is described in detail. This figure is a simplified schematic diagram, only schematically illustrating the basic structure of the utility model, so it only shows the configuration related to the utility model.

Embodiment one:

As shown in Figure 1, a lithium-ion battery with a thermally conductive sheet inside the utility model, the cell is a winding structure, a thermally conductive sheet 1 is added to the winding structure, and the thermally conductive sheet 1 is on the innermost side of the winding core of the battery. Core center. The figure does not limit the specific structure of the thermally conductive sheet 1 , but is only used to describe the position of the thermally conductive sheet 1 in the winding mechanism. The length and width of the heat conduction sheet 1 should be smaller than the length and width of the battery core, and the heat conduction sheet 1 is separated from the positive and negative electrodes 2 and 4 of the battery core by the isolation film 3 of a high molecular polymer material that cannot be dissolved in the electrolyte to avoid electric shock. Connected so that no electrochemical redox reaction occurs during battery cycling.

The heat conduction sheet 1 is made of carbon material, and the preferred heat conduction sheet 1 is a graphite heat conduction sheet 1 with high thermal conductivity, and its thermal conductivity is 400-1800W/m·K, preferably 800-1800W/m·K, A more preferable thermal conductivity is 1000 to 1800 W/m·K. The thickness of the heat conducting sheet 1 is <1 mm, preferably 0.05 mm to 0.1 mm.

Embodiment two:

As shown in FIG. 2 , a lithium-ion battery of the present invention has a heat-conducting sheet inside. The battery cell is a winding structure and includes two core rolls, and the heat-conducting sheet 1 is arranged between the two winding cores. The figure does not limit the specific structure of the thermally conductive sheet 1 , but is only used to describe the position of the thermally conductive sheet 1 in the winding mechanism.

The length and width of the heat conduction sheet 1 should be smaller than the length and width of the battery core, and the heat conduction sheet 1 is separated from the positive and negative electrodes 2 and 4 of the battery core by the isolation film 3 of a high molecular polymer material that cannot be dissolved in the electrolyte to avoid electric shock. Connected so that no electrochemical redox reaction occurs during battery cycling.

The heat conduction sheet 1 is made of carbon material, and the preferred heat conduction sheet 1 is a graphite heat conduction sheet 1 with high thermal conductivity, and its thermal conductivity is 400-1800W/m·K, preferably 800-1800W/m·K, A more preferable thermal conductivity is 1000 to 1800 W/m·K. The thickness of the heat conducting sheet 1 is <1 mm, preferably 0.05 mm to 0.1 mm.

Embodiment three:

As shown in Figure 3 and Figure 4, a lithium-ion battery with a heat-conducting sheet inside the utility model, the battery cell is a laminated structure, the separator 3 is folded in an S shape, and lateral openings are formed on both sides of the separator 3 A plurality of U-shaped grooves, the positive electrode 2 is located in the groove on one side of the separator 3, the negative electrode 4 is located in the groove on the other side of the separator 3, and a negative electrode 5 with a heat conduction sheet is arranged in the center of the battery cell, that is, heat conduction The sheet 1 is arranged inside the negative electrode 4, and the negative electrode 5 with a thermal conductive sheet includes a thermal conductive sheet 1 arranged in the center of the battery cell. The length and width of the thermal conductive sheet 1 are smaller than the length and width of the battery cell. On the inner side, between the thermal conductive sheet 1 and the negative electrode 4, a separator 3 of a high molecular polymer material that cannot be dissolved in the electrolyte is used to separate the positive and negative electrodes 2 and 4 of the battery cell, so as to avoid electrical connection, so that it can be used during the battery cycle. , no electrochemical oxidation-reduction reaction occurs, and the negative electrode current collector 6 is also provided inside the negative electrode 4 .

The heat conduction sheet 1 is made of carbon material, and the preferred heat conduction sheet 1 is a graphite heat conduction sheet 1 with high thermal conductivity, and its thermal conductivity is 400-1800W/m·K, preferably 800-1800W/m·K, A more preferable thermal conductivity is 1000 to 1800 W/m·K. The thickness of the heat conducting sheet 1 is <1 mm, preferably 0.05 mm to 0.1 mm.

Inspired by the above-mentioned ideal embodiment according to the present utility model, through the above-mentioned description content, relevant staff can make various changes and modifications without departing from the scope of the present utility model. The technical scope of this utility model is not limited to the contents in the description, and its technical scope must be determined according to the scope of the claims.

Claims (9)

1. a kind of inside has the lithium ion battery of thermally conductive sheet, it is characterised in that：Thermally conductive sheet is internally provided in the battery core of battery （1）, and the thermally conductive sheet（1）With the anode and negative insulation of battery core；The thermally conductive sheet（1）Length and width dimensions be respectively smaller than battery core Length and width dimensions.

2. the internal lithium ion battery with thermally conductive sheet as described in claim 1, it is characterised in that：The thermally conductive sheet（1）'s Thermal conductivity factor is 400 ~ 1800W/m K.

3. the internal lithium ion battery with thermally conductive sheet as claimed in claim 2, it is characterised in that：The thermally conductive sheet（1）'s Thermal conductivity factor is 800 ~ 1800W/m K.

4. the internal lithium ion battery with thermally conductive sheet as claimed in claim 3, it is characterised in that：The thermally conductive sheet（1）'s Thermal conductivity factor is 1000 ~ 1800W/m K.

5. the internal lithium ion battery with thermally conductive sheet as described in claim 1, it is characterised in that：The thermally conductive sheet（1）'s Material is carbon material.

6. the internal lithium ion battery with thermally conductive sheet as claimed in claim 5, it is characterised in that：The thermally conductive sheet（1）For Graphite heat-conducting fin with high thermal conductivity（1）.

7. the internal lithium ion battery with thermally conductive sheet as described in claim 1, it is characterised in that：The thermally conductive sheet（1）It is thick Spend ＜ 1mm.

8. the internal lithium ion battery with thermally conductive sheet as claimed in claim 7, it is characterised in that：The thermally conductive sheet（1）It is thick It spends for 0.05mm ~ 0.1mm.

9. the internal lithium ion battery with thermally conductive sheet as described in claim 1, it is characterised in that：The thermally conductive sheet（1）It adopts With the anode for the macromolecule polymer material and battery core that cannot be dissolved in electrolyte（2）And cathode（4）It separates.