Thermal runaway protection pad for battery pack and battery pack

Abstract

The utility model discloses a thermal runaway protective pad for a battery pack and the battery pack, the thermal runaway protective pad comprises a sealing bag and a temperature-sensitive hydrogel block sealed in the sealing bag, and the temperature-sensitive hydrogel block has a conformation change point adapted to the working range of a battery cell; when the temperature of the battery cell reaches a conformation change point, the temperature-sensitive hydrogel block releases water, and at least part of the water is changed into water vapor, so that the air pressure in the sealing bag is increased; the sealing bag is configured to break when the internal air pressure reaches the preset pressure so as to release the water vapor. Therefore, the temperature-sensitive hydrogel block releases water when the temperature rises to a conformation change point, the water is heated and rapidly vaporized to form a layer of gas film with poor heat conduction, and the gas film separates heat conduction between the battery cells and delays high temperature spreading. And moreover, the generated water vapor enables the internal air pressure of the sealing bag to rise to burst the sealing bag, and the water vapor escapes from the sealing bag to take away heat, so that the heat dissipation effect is realized, and the safety of the battery is guaranteed.

Description

Technical Field

[0001] The utility model relates to the field of battery protection, in particular to a thermal runaway protection pad and a battery pack for a battery pack. Background Art

[0002] During the use of a battery, due to reasons such as overcharging, over-discharging, internal short circuit or external damage, the battery cell may undergo a thermal runaway phenomenon, that is, the temperature of the battery cell rises rapidly, and even causes a fire or explosion, posing a serious threat to the safety of users. At present, in order to prevent the chain reaction caused by the thermal runaway of the battery cell, the mainstream technology is to add an aerogel thermal insulation pad with extremely low thermal conductivity between the battery cells. The aerogel material has a dispersed nanoporous structure. The dispersion effect of its nanoparticles on gas flow and the scattering effect on thermal carriers make its thermal conductivity comparable to or even lower than that of gas. Therefore, aerogel can effectively isolate the heat conduction between battery cells, delay the spread of high temperature, and gain precious time to deal with thermal runaway events.

[0003] However, the aerogel thermal insulation pad can only insulate heat and cannot effectively dissipate heat. When the battery suddenly releases chemical energy in the form of heat energy, although the aerogel thermal insulation pad can temporarily prevent the temperature from spreading, it cannot fundamentally eliminate the accumulated heat, so it cannot completely guarantee the safety of the battery. Summary of the Utility Model

[0004] Embodiments of the utility model provide a thermal runaway protection pad and a battery pack for a battery pack to solve the problem that the existing heat insulation measures cannot dissipate heat, and achieve the effect of both heat insulation and heat dissipation and ensuring the safety of the battery.

[0005] Specifically, the utility model provides a thermal runaway protection pad for a battery pack, which includes a sealed bag and a temperature-sensitive hydrogel block sealed in the sealed bag. The temperature-sensitive hydrogel block has a conformational change point adapted to the working range of the battery cell. When the temperature of the battery cell reaches the conformational change point, the temperature-sensitive hydrogel block releases water, and at least part of the water turns into water vapor, so that the air pressure in the sealed bag increases. The sealed bag is configured to expand and rupture when the internal air pressure reaches a preset pressure to release the water vapor.

[0006] Optionally, the preset pressure is 2.0 MPa to 2.8 MPa.

[0007] Optionally, the thickness of the temperature-sensitive hydrogel block is 0.1 mm to 10 mm.

[0008] Optionally, the water content of the temperature-sensitive hydrogel block is ≥80%.

[0009] Optionally, the thermal runaway protection pad further includes a buffer layer, and the buffer layer is arranged on one side of the sealed bag.

[0010] Optionally, the number of the seal bags is two, and the buffer layer is arranged between the two seal bags.

[0011] Optionally, the buffer layer is adhered to the seal bag.

[0012] Optionally, the thickness of the buffer layer is 0.1 mm to 2 mm.

[0013] Optionally, the buffer layer is a foam with a thermal conductivity of 0.02 W / mK to 0.05 W / mK.

[0014] Optionally, the seal bag is an aluminum-plastic film or a waterproof plastic film.

[0015] The present utility model further provides a battery pack, which includes the thermal runaway protection pad as described in any one of the above and at least two battery cells. The thermal runaway protection pad is arranged between two adjacent battery cells, and the seal bag abuts against the battery cell.

[0016] The beneficial effects of the present utility model are as follows:

[0017] In the thermal runaway protection pad and the battery pack provided by the present utility model, under normal conditions, the thermosensitive hydrogel block can retain a large amount of water. When the external temperature rises to the conformational change point of the thermosensitive hydrogel block, the thermosensitive hydrogel block releases water, and the water is quickly vaporized by heat to form a gas film with very poor thermal conductivity. The gas film cuts off the heat conduction between the battery cells, delays the spread of high temperature, and plays a heat insulation role. Moreover, the generated water vapor causes the internal pressure of the seal bag to rise. When the internal pressure rises to a preset pressure, the seal bag expands and ruptures, and the water vapor escapes from the seal bag, taking away the heat, achieving a heat dissipation effect and ensuring the safety of the battery. Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the following will briefly introduce the drawings required to be used in the description of the embodiments of the present utility model. Obviously, the drawings in the following description are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a schematic structural diagram of a thermal runaway protection pad in an embodiment of the present utility model;

[0020] Figure 2 It is a schematic structural diagram of a battery pack in an embodiment of the present utility model;

[0021] Figure 3 It is a schematic principle diagram of a battery pack during thermal runaway in an embodiment of the present utility model;

[0022] Figure 4 It is the temperature trend diagram of the battery pack in an embodiment of the present utility model;

[0023] Figure 5 It is the temperature trend diagram of the battery pack in the prior art.

[0024] In the figure: 100, sealing bag; 200, temperature-sensitive hydrogel block; 300, buffer layer; 400, battery cell; 500, double-sided tape. Specific embodiments

[0025] In order to make the technical problems, technical solutions and beneficial effects solved by the present utility model clearer and more understandable, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present utility model and are not used to limit the present utility model.

[0026] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "radial", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present utility model. In the description of the present utility model, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0027] In the description of the present utility model, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific situations.

[0028] Figure 1 It is the schematic structural diagram of the thermal runaway protection pad in an embodiment of the present utility model, as Figure 1 shown, and with reference to Figures 2 to 3, an embodiment of the present utility model provides a thermal runaway protection pad for a battery pack, which includes a sealed bag 100 and a temperature-sensitive hydrogel block 200 sealed in the sealed bag 100. The temperature-sensitive hydrogel block 200 has a conformational change point adapted to the operating range of the battery cell. When the temperature of the battery cell reaches the conformational change point, the temperature-sensitive hydrogel block 200 releases moisture, and at least part of the moisture turns into water vapor, so as to increase the air pressure in the sealed bag 100. The sealed bag 100 is configured to expand and rupture when the internal air pressure reaches a preset pressure, so as to release the water vapor.

[0029] In the embodiment of the present utility model, in the normal state, the temperature-sensitive hydrogel block 200 can retain a large amount of moisture. When the external temperature rises to the conformational change point of the temperature-sensitive hydrogel block 200, the temperature-sensitive hydrogel block 200 releases moisture, and the moisture quickly vaporizes when heated, forming a gas film with very poor thermal conductivity. The gas film cuts off the heat conduction between the battery cells 400, delays the spread of high temperature, and plays a heat insulation role. Moreover, the generated water vapor causes the internal air pressure of the sealed bag 100 to rise. When the internal air pressure rises to the preset pressure, the sealed bag 100 expands and ruptures, and escapes from the sealed bag 100, taking away the heat, achieving a heat dissipation effect, and ensuring the safety of the battery.

[0030] During application, as Figure 3 shown, the thermal runaway protection pad is arranged between the battery cells 400. When a certain battery cell 400 has a thermal runaway, the temperature-sensitive hydrogel block 200 can quickly release moisture, and the Leidenfrost phenomenon occurs: the water vapor flows along the arrow towards the thermally runaway battery cell 400 and forms a gas film with very poor thermal conductivity. The gas film reduces the influence of sudden high temperature on the adjacent battery cells 400; moreover, when there is enough water vapor, it breaks through the sealed bag 100 at both ends and breaks through the air release valve of the battery pack, taking away the heat, and realizing the safety protection of the entire battery pack.

[0031] Specifically, the preset pressure is 2.0 MPa to 2.8 MPa. If the preset pressure value is too low, the sealed bag 100 will burst soon after the water vapor is generated, it is difficult to form a gas film or the existence time of the gas film is short, and the heat insulation effect cannot be guaranteed; if the preset pressure value is too high, it is difficult for the generated water vapor to burst the sealed bag 100, and the heat dissipation effect cannot be guaranteed.

[0032] In an embodiment of the present utility model, the thickness of the temperature-sensitive hydrogel block 200 is 0.1 mm to 10 mm. Specifically, the thickness of the temperature-sensitive hydrogel block 200 can be 0.1 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm or any value between the two values. If the thickness of the temperature-sensitive hydrogel block 200 is relatively small, resulting in less water content in the temperature-sensitive hydrogel block 200 with the same length and width, a good protection function cannot be achieved; if the thickness of the temperature-sensitive hydrogel block 200 is relatively large, it is not conducive to the full utilization of the temperature-sensitive hydrogel block 200.

[0033] In an embodiment of the present utility model, the water content of the temperature-sensitive hydrogel block 200 ≥ 80%. The temperature-sensitive hydrogel block 200 has a three-dimensional network of water-soluble or hydrophilic polymers. Therefore, it can absorb and retain a large amount of water at the normal working temperature of the battery pack (-40°C to 60°C), and can quickly release water and take away heat when encountering a sudden high temperature (100°C to 150°C). The temperature-sensitive hydrogel block 200 is generally a high polymer such as polysaccharides, polypeptides or acrylic acid and its derivatives, with a water content of more than 80%. The more the water content, the more heat can be taken away by the material of the same volume.

[0034] In an embodiment of the present utility model, the thermal runaway protection pad further includes a buffer layer 300, and the buffer layer 300 is disposed on one side of the sealed bag 100. Further, the buffer layer 300 is a foam with a thermal conductivity of 0.02 W / mK to 0.05 W / mK, which can further delay the heat transfer between the battery cells; and has good compressibility to reduce the stress caused by the expansion and contraction of the battery cell 400 during charging and discharging. The thickness needs to be designed according to the expansion and reliability requirements of the battery cell 400, and can be 0.1 mm, 0.2 mm, 0.5 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm or any value between the two values.

[0035] In an embodiment of the present utility model, the number of the sealed bags 100 is two, and the buffer layer 300 is disposed between the two sealed bags 100. With this setting, both sides of the thermal runaway protection pad are sealed bags 100, so as to protect the battery cells 400 on both sides.

[0036] Further, the buffer layer 300 is adhered to the sealed bag 100 by double-sided tape, which is convenient for rapid preparation.

[0037] In an embodiment of the present utility model, the sealing bag 100 is an aluminum-plastic film or a waterproof plastic film, which has a certain strength and can isolate water vapor to prevent the thermosensitive hydrogel block 200 from being extruded out of the sealing bag 100 during the charging and discharging process along with the expansion and contraction of the battery.

[0038] As Figure 3 shown, the present utility model also provides a battery pack, which includes a battery cell 400 and a thermal runaway protection pad in any of the above embodiments to have all the effects of the thermal runaway protection pad; the thermal runaway protection pad is disposed on one side of the battery cell 400, and the sealing bag 100 abuts against the battery cell 400.

[0039] In an embodiment of the present utility model, the number of battery cells 400 is two, and the thermal runaway protection pad is disposed between the two battery cells 400. Further, the number of battery cells 400 is n (n>2), and the number of thermal runaway protection pads is n - 1, and one thermal runaway protection pad is disposed between every two adjacent battery cells 400.

[0040] The present utility model is further described below through experimental examples to verify the heat insulation and heat dissipation effects of the thermal runaway protection pad.

[0041] Experimental Example 1

[0042] For a battery pack composed of three battery cells (No. 1# - 3#), one thermal runaway protection pad provided by the embodiment of the present utility model is inserted between every two adjacent battery cells. A ceramic heating sheet is inserted at the battery cell 3#, and the battery cell 3# is first overcharged and then thermally runaway is induced by heating. The temperatures of the battery cells 1#, 2#, 3# and the ceramic heating sheet are monitored in real time, and a temperature trend graph as Figure 4 shown is drawn. In the figure, 1# is the temperature trend line of the battery cell 1#, 2# is the temperature trend line of the battery cell 2#, 3# is the temperature trend line of the battery cell 3#, and 0# is the temperature trend line of the ceramic heating sheet.

[0043] Experimental Example 2

[0044] For a battery pack composed of three battery cells (No. 1# - 3#), one aerogel heat insulation pad in the prior art is inserted between every two adjacent battery cells. A ceramic heating sheet is inserted at the battery cell 3#, and the battery cell 3# is first overcharged and then thermally runaway is induced by heating. The temperatures of the battery cells 1#, 2#, 3# and the ceramic heating sheet are monitored in real time, and a temperature trend graph as Figure 5 shown is drawn. In the figure, 1# is the temperature trend line of the battery cell 1#, 2# is the temperature trend line of the battery cell 2#, 3# is the temperature trend line of the battery cell 3#, and 0# is the temperature trend line of the ceramic heating sheet.

[0045] Consisting of Figure 4 、 Figure 5It can be seen that when using the aerogel heat insulation pad in the prior art, as the ceramic heating sheet heats the battery cell 3# to trigger thermal runaway, after the battery cell 3# explodes, after a certain delay time, the battery cells 2# and 1# are successively detonated and thermal runaway occurs. This shows that the aerogel heat insulation pad in the prior art can only delay the spread of high temperature and buy precious time to deal with thermal runaway events, but cannot fundamentally eliminate heat and cannot completely ensure the safety of the battery.

[0046] When using the thermal runaway protection pad provided by the embodiment of the present invention, after the battery cell 3# has a thermal runaway, first, the maximum temperature that the battery cell 3# can reach is reduced by about 200 °C compared with Experimental Example 2. More importantly, although the temperatures of the battery cells 2# and 1# have increased, no thermal runaway occurs within the observation time range. Thus, it can be seen that the thermal runaway protection pad provided by the present invention can, while delaying the spread of high temperature, take away heat through water vapor, achieve a heat dissipation effect, and ensure the safety of the battery.

[0047] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention and should all be included in the protection scope of the present invention.

Claims

1. A thermal runaway protection pad for a battery pack, characterized in that, It includes a sealed bag and a temperature-sensitive hydrogel block sealed in the sealed bag. The temperature-sensitive hydrogel block has a conformational change point adapted to the operating range of the battery cell. When the temperature of the battery cell reaches the conformational change point, the temperature-sensitive hydrogel block releases moisture, and at least part of the moisture turns into water vapor, so as to increase the air pressure in the sealed bag. The sealed bag is configured to expand and rupture when the internal air pressure reaches a preset pressure to release the water vapor.

2. The thermal runaway protection pad according to claim 1, wherein the preset pressure is 2.0 MPa to 2.8 MPa.

3. The thermal runaway protection pad according to claim 1, wherein the thickness of the temperature-sensitive hydrogel block is 0.1 mm to 10 mm.

4. The thermal runaway protection pad according to claim 1, wherein the water content of the temperature-sensitive hydrogel block is ≥ 80%.

5. The thermal runaway protection pad according to claim 1, wherein the thermal runaway protection pad further includes a buffer layer, and the buffer layer is arranged on one side of the sealed bag and adhered to the sealed bag.

6. The thermal runaway protection pad according to claim 5, wherein the number of the sealed bags is two, and the buffer layer is arranged between the two sealed bags.

7. The thermal runaway protection pad according to claim 5, wherein the thickness of the buffer layer is 0.1 mm to 2 mm.

8. The thermal runaway protection pad according to claim 5, wherein the buffer layer is a foam with a thermal conductivity of 0.02 W / mK to 0.05 W / mK.

9. The thermal runaway protection pad according to claim 1, wherein the sealed bag is an aluminum-plastic film or a waterproof plastic film.

10. A battery pack, characterized in that, It includes the thermal runaway protection pad according to any one of claims 1 to 9 and at least two battery cells. The thermal runaway protection pad is arranged between two adjacent battery cells, and the sealed bag abuts against the battery cell.

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