CN113193306A

CN113193306A - Diaphragm with temperature sensing function

Info

Publication number: CN113193306A
Application number: CN202110319231.9A
Authority: CN
Inventors: 苏岳锋; 闫康; 陈来; 蒋晓平; 吴锋
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2021-03-25
Filing date: 2021-03-25
Publication date: 2021-07-30

Abstract

The invention relates to a diaphragm with a temperature sensing function, and belongs to the technical field of lithium ion batteries. The diaphragm is of a multilayer composite structure and comprises a lower polymer layer, a middle thermocouple layer and an upper polymer layer, wherein the polymer is a polypropylene film or a polyethylene film, and the thermocouple is a copper-constantan thermocouple. The thermocouple has high sensitivity and small size, and the monitoring range is wide, so that the working temperature of the battery can be fully covered. The thermocouple is compounded into the diaphragm material, so that the internal temperature of the battery can be sensed in real time, and the internal temperature change of the battery can be monitored; when the internal temperature of the battery exceeds the warning threshold value, the internal temperature can be timely fed back to the control system through the thermocouple sensor, and the battery is correspondingly regulated and controlled. The selection of the copper-constantan thermocouple can reduce the cost of the thermocouple while ensuring the sensitivity, accuracy and temperature monitoring window of the thermocouple.

Description

Diaphragm with temperature sensing function

Technical Field

The invention relates to a diaphragm with a temperature sensing function, and belongs to the technical field of lithium ion batteries.

Background

The lithium ion battery has the advantages of high working voltage, high specific capacity, long cycle life and the like, and is widely applied to a power system of an electric automobile. With the prosperous development of the electric automobile industry, consumers have increasingly strict requirements on the safety of electric automobiles as well as the endurance mileage of electric automobiles. In order to improve the endurance mileage of the electric automobile, the number of lithium ion batteries in the battery power system is more and the arrangement is more dense. In the cycle process of the lithium ion battery, a large amount of heat can be released by chemical reaction, the performance and safety of the battery can be influenced by the heat, and serious thermal runaway can be caused if the heat is not dissipated in time. The internal temperature of lithium ions in the electric automobile is monitored in real time, the working condition of the battery can be effectively judged, and the abnormal change of the temperature can be early warned in advance, so that the occurrence of thermal runaway is avoided. In the existing battery internal temperature monitoring technology, an invasive external temperature sensing device is required, so that the battery performance is influenced, and a larger error problem also exists.

The diaphragm with the temperature sensing function can accurately sense the internal temperature of the battery in real time, has the minimum influence on the performance of the battery, and is urgently needed for improving the safety performance of the electric automobile.

Disclosure of Invention

In view of the above, the present invention provides a diaphragm with a temperature sensing function.

In order to achieve the purpose, the technical scheme of the invention is as follows:

the diaphragm with the temperature sensing function is of a multilayer composite structure and comprises a lower polymer layer, a middle thermocouple layer and an upper polymer layer, wherein the polymer is a polypropylene film or a polyethylene film, and the thermocouple is a copper-constantan thermocouple. The thermocouple has high sensitivity and small size, and the monitoring range is wide, so that the working temperature of the battery can be fully covered. The thermocouple is compounded into the diaphragm material, so that the internal temperature of the battery can be sensed in real time, and the internal temperature change of the battery can be monitored; when the internal temperature of the battery exceeds the warning threshold value, the internal temperature can be timely fed back to the control system through the thermocouple sensor, and the battery is correspondingly regulated and controlled. The selection of the copper-constantan thermocouple can reduce the cost of the thermocouple while ensuring the sensitivity, accuracy and temperature monitoring window of the thermocouple.

Preferably, the polymer has a porous three-dimensional structure, the aperture is 0.01-10 microns, and the porosity is 10-90%; the thicknesses of the upper polymer layer and the lower polymer layer are respectively 1-100 micrometers. The polymer can ensure effective transmission of lithium ions without increasing the quality of the separator.

Preferably, the copper-constantan thermocouple is formed by welding a copper conductor and a constantan conductor.

Preferably, the copper conductor and the constantan conductor in the copper-constantan thermocouple are welded through a connecting conductor.

Preferably, the connecting conductor is a copper conductor or a constantan conductor.

Preferably, the copper conductor in the copper-constantan thermocouple is a copper foil or a copper wire, and the constantan conductor is a constantan foil or a constantan wire.

Preferably, the copper foil has a thickness of 1-100 microns, a width of 0.05-50 mm and a length of 1-500 mm.

Preferably, the constantan foil has a thickness of 1-100 microns, a width of 0.05-50 mm and a length of 1-500 mm.

Preferably, the diameter of the copper wire is 1-100 micrometers, and the length of the copper wire is 1-500 millimeters.

Preferably, the diameter of the constantan wire is 1-100 micrometers, and the length of the constantan wire is 1-500 millimeters.

Advantageous effects

The diaphragm structure can effectively sense the internal temperature of the battery and realize the real-time monitoring of the working temperature of the battery, thereby timely feeding back the abnormal condition of the temperature of the battery and preventing the thermal runaway of the battery. Meanwhile, the separator with the sandwich structure can well transmit lithium ions, and the influence on the performance of the battery is minimized. Furthermore, the thickness or diameter size of the copper-constantan thermocouple conductor is controlled in a micrometer range, so that the influence of the thermocouple on lithium ion transmission is reduced while the normal work of the thermocouple is ensured, and the influence of the quality of the thermocouple on the battery specific energy is reduced.

Drawings

FIGS. 1-2 are schematic structural views of a separator according to example 1 of the present invention;

FIG. 3 is a schematic structural view of a separator according to embodiment 2 of the present invention;

wherein, 1-lower polymer layer, 2-upper polymer layer, 3-copper conductor, 4-constantan conductor, 5-welding point, 6-connecting conductor.

Detailed Description

The present invention will be described in further detail with reference to specific examples.

Comparative example 1

The single-layer 30-micron-thickness polypropylene diaphragm with the mass of 54mg is used in a soft package battery with the capacity of 76mAh, the mass of a positive electrode material, namely nickel-cobalt-manganese ternary positive electrode material NCM811, is 400mg, the mass of a positive electrode current collector aluminum foil is 84mg, the mass of a negative electrode material, namely graphite is 224mg, and the mass of a negative electrode current collector copper foil is 146 mg. The total mass of the soft package battery is 908 mg.

Example 1

As shown in fig. 1-2, a diaphragm with temperature sensing function is a multi-layer composite structure, and comprises a lower polymer layer 1, an intermediate thermocouple layer and an upper polymer layer 2, wherein the polymer is a polypropylene film, and the thermocouple is a copper-constantan thermocouple. The copper-constantan thermocouple is formed by welding a copper conductor 3 and a constantan conductor 4.

The thicknesses of the lower polymer layer 1 and the upper polymer layer 2 were 15 μm, respectively, and the total mass of the lower polymer layer 1 and the upper polymer layer 2 was 54 mg.

The copper conductor 3 in the copper-constantan thermocouple is a copper foil, the length is 30mm, the width is 5mm, and the thickness is 8 μm; the constantan conductor 4 is a constantan foil, the length is 30mm, the width is 5mm, and the thickness is 8 μm.

The total mass of the copper-constantan thermocouple was 21.9 mg.

When the separator described in the example was used in a pouch cell having a capacity of 76mAh in place of the single-layer separator described in comparative example 1, the total weight of the cell was increased by only 2.4%.

The performance of the cell was not significantly different from that of the cell of comparative example 1.

Example 2

As shown in fig. 3, the diaphragm with the temperature sensing function is a multilayer composite structure and comprises a lower polymer layer 1, a middle thermocouple layer and an upper polymer layer 2, wherein the polymer is a polypropylene film, and the thermocouple is a copper-constantan thermocouple. The copper-constantan thermocouple is formed by welding a copper conductor 3 and a constantan conductor 4 through a connecting conductor 6.

The thicknesses of the lower polymer layer 1 and the upper polymer layer 2 were 10 μm, respectively, and the total mass of the lower polymer layer 1 and the upper polymer layer 2 was 36 mg.

The copper conductor in the copper-constantan thermocouple is a copper foil, the length is 30mm, the width is 5mm, and the thickness is 8 μm; the constantan conductor is constantan foil, the length is 30mm, the width is 5mm, and the thickness is 8 μm. The connecting conductor 6 is a copper foil with the length of 15mm, the width of 5mm and the thickness of 8 μm.

The total mass of the copper-constantan thermocouple is 27.375 mg.

When the separator described in the example is used in a soft package battery with the capacity of 76mAh instead of the single-layer separator described in comparative example 1, the total weight of the battery is increased by only 1.03%.

In summary, the invention includes but is not limited to the above embodiments, and any equivalent replacement or local modification made under the spirit and principle of the invention should be considered as being within the protection scope of the invention.

Claims

1. A diaphragm having a temperature sensing function, characterized in that: the diaphragm is of a multilayer composite structure and comprises a lower polymer layer, a middle thermocouple layer and an upper polymer layer, wherein the polymer is a polypropylene film or a polyethylene film, and the thermocouple is a copper-constantan thermocouple.

2. A diaphragm having a temperature sensing function according to claim 1, wherein: the polymer has a porous three-dimensional structure, the aperture is 0.01-10 microns, and the porosity is 10-90%; the thicknesses of the upper polymer layer and the lower polymer layer are respectively 1-100 micrometers.

3. A diaphragm having a temperature sensing function according to claim 1, wherein: the copper-constantan thermocouple is formed by welding a copper conductor and a constantan conductor.

4. A diaphragm having a temperature sensing function according to claim 1, wherein: and the copper conductor and the constantan conductor in the copper-constantan thermocouple are welded through a connecting conductor.

5. A diaphragm having a temperature sensing function according to claim 4, wherein: the connecting conductor is a copper conductor or a constantan conductor.

6. A diaphragm having a temperature sensing function according to claim 3 or 4, wherein: the copper conductor in the copper-constantan thermocouple is a copper foil or a copper wire, and the constantan conductor is a constantan foil or a constantan wire.

7. A diaphragm having a temperature sensing function according to claim 6, wherein: the copper foil has a thickness of 1-100 micrometers, a width of 0.05-50 mm, and a length of 1-500 mm.

8. A diaphragm having a temperature sensing function according to claim 6, wherein: the constantan foil has a thickness of 1-100 microns, a width of 0.05-50 mm, and a length of 1-500 mm.

9. A diaphragm having a temperature sensing function according to claim 6, wherein: the diameter of the copper wire is 1-100 microns, and the length of the copper wire is 1-500 millimeters.

10. A diaphragm having a temperature sensing function according to claim 6, wherein: the constantan wire has a diameter of 1-100 micrometers and a length of 1-500 millimeters.