Lithium battery thermal runaway spread blocking device and method based on end face pressure amplification

Abstract

The present invention relates to a lithium battery thermal runaway propagation blocking device and method based on end face pressure amplification, wherein the device comprises a lithium battery pack, a lower end bottom plate, an upper end cover plate connected to the lower end bottom plate by a spring support, a fixture end plate arranged between the lower end bottom plate and the upper end cover plate, and a force amplification structure; when the lithium battery pack thermally runs away and expands, the expansion force is amplified by the force amplification structure and then the fixture end plate is propped open to achieve thermal runaway propagation blocking. Compared with the prior art, the present invention has the advantages of simple structure and good stability.

Description

Technical Field

[0001] The present invention relates to the field of thermal runaway and thermal safety of lithium-ion power batteries, and particularly to a device and method for blocking the spread of thermal runaway of lithium batteries based on end-face pressure amplification. Background Technique

[0002] Lithium-ion power batteries have been widely recognized and mass-produced in transportation, consumer electronics, and energy storage systems due to their advantages in specific energy, cycle life, etc. However, with the continuous higher requirements of the market and users for battery energy density, the thermal stability of high specific energy batteries using high-nickel ternary cathode materials has decreased, greatly increasing the risk of safety accidents caused by thermal runaway. Therefore, the development needs of electric vehicles and energy storage power stations have put forward higher requirements for the early warning and protection design of the thermal safety of lithium-ion battery systems.

[0003] Currently, there are mainly three methods for protecting against the spread of thermal runaway in lithium-ion battery systems. One is the method based on heat dissipation delay of the liquid cooling system; the second is the method based on the thermal isolation of battery monomers; the third is the method based on fire extinguishing after the thermal runaway of the battery.

[0004] For the safety protection against the spread of thermal runaway in lithium-ion battery systems, most of them have the characteristics of "insufficient heat dissipation efficiency", "cost-ignoring", "lag", etc., and there is a "re-ignition" phenomenon in the battery system fire. Currently, there is no good method that can be popularized.

[0005] In addition, because the reaction mechanism in the thermal runaway process is very complex and there are large differences between batteries with different material systems, there is currently no relatively reliable universal safety protection method. Summary of the Invention

[0006] The purpose of the present invention is to provide a device and method for blocking the spread of thermal runaway of lithium batteries based on end-face pressure amplification, realizing autonomous heat dissipation during the thermal runaway process and having universality.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A device for blocking the spread of thermal runaway of lithium batteries based on end-face pressure amplification includes a lithium battery pack composed of a plurality of lithium battery monomers arranged regularly, and further includes:

[0009] A lower bottom plate, an upper cover plate supported and connected to the lower bottom plate by a spring, a fixture right end plate and a fixture left end plate arranged between the lower bottom plate and the upper cover plate, and a force amplification structure;

[0010] The force amplification structure includes a first wedge block, a second wedge block and a third wedge block, wherein the second wedge block is a cylindrical wedge block; the first side edge of the first wedge block contacts one end of the lithium battery pack, the second side edge contacts the lower end bottom plate and serves as a supporting side, so that the first wedge block is stably supported by the lower end bottom plate, and the third side edge is tangentially in contact with the second wedge block; the first side edge of the third wedge block contacts and supports the upper end cover plate, and the second side edge is in point contact with the second wedge block and is fixedly connected at the intersection;

[0011] The lithium battery pack is in contact with and supported by the lower bottom plate, and the other end of the lithium battery pack is in contact with the left end plate of the fixture;

[0012] The right end plate of the fixture is in point contact with the second wedge block and slides along the lower end bottom plate and the upper end cover plate.

[0013] The lower end bottom plate is parallel to the upper end cover plate.

[0014] The device also includes a liquid cooling system disposed in the lower end base plate, which is used to assist in blocking the spread of thermal runaway.

[0015] The device also includes a pressure sensor disposed on the surface of a single cell at one end of the lithium battery pack, which is used for early warning of lithium battery failure.

[0016] The cross section of the first wedge is trapezoidal or triangular.

[0017] The cross section of the third wedge is a right triangle, wherein the first side is a right angle side and the second side is a hypotenuse.

[0018] A method for blocking the spread of thermal runaway of a lithium battery based on end face pressure amplification is implemented based on the device as described above, and the method comprises the following steps:

[0019] Step 1) Thermal runaway of a single cell of a lithium battery pack occurs;

[0020] Step 2) During thermal runaway, the lithium battery expands and produces gas due to heat, causing the battery to squeeze and expand in all directions;

[0021] Step 3) the expansion force is amplified by the force amplification structure and acts on the end plate of the fixture;

[0022] Step 4) the amplified expansion force opens the end plates of the fixture so that the spacing between the lithium battery cells increases;

[0023] Step 5) The heat transfer between battery cells is weakened to block the spread of thermal runaway.

[0024] The thermal runaway is caused by overheating, overcharging, overdischarging, mechanical failure or internal short circuit of the lithium battery.

[0025] The amplification factor of the expansion force by the force amplification structure is:

[0026] A=cotαcotβ+1

[0027] Among them, α is the acute angle formed by the third side of the first wedge block and the lower end bottom plate, and β is the acute angle between the tangent line at the intersection of the second side of the third wedge block and the second wedge block and the vertical line.

[0028] The angles α and β are designed such that: under normal operating conditions, battery expansion will not expand and open the clamp; when the lithium battery gets out of control, the clamp can be opened in time to prevent the spread of thermal runaway.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) Simple structure: The present invention uses traditional mechanical structure design, which is easy to install and maintain;

[0031] (2) Low cost: The present invention only requires simple mechanical processing under the premise of ensuring the strength of the components. The components can adopt hollow structural characteristics and do not require precise surface treatment, making processing and assembly simple and convenient;

[0032] (3) Good mobility: The present invention can be combined with an end surface pressure sensor to provide a thermal runaway safety warning for any battery in the battery system arrangement direction;

[0033] (4) Good stability: The present invention is based on the evolution mechanism of the battery's own thermal runaway process and utilizes the characteristics of the battery failure process itself to achieve stable isolation when thermal runaway occurs.

[0034] (5) Universality: The present invention can meet the safety protection requirements of thermal runaway propagation blocking for batteries of various packaging methods, capacity sizes, and material systems, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the structure of the lithium battery thermal runaway propagation blocking device of Example 1.

[0036] Figure 2 This is a schematic diagram of the structure of the lithium battery thermal runaway propagation blocking device of Example 2.

[0037] Figure 3 This is a schematic diagram of the structure of the lithium battery thermal runaway propagation blocking device of Example 3.

[0038] Figure 4 The figure is a flow chart of the method of the present invention.

[0039] Figure 5 Schematic diagram of force analysis of the force amplification structure.

[0040] The reference numerals in the figure are: 1 - lower bottom plate, 2 - upper cover plate, 3 - right end plate of the fixture, 4 - force amplification structure, 5 - lithium battery pack, 6 - pressure sensor, 7 - left end plate of the fixture. Detailed implementation mode

[0041] The present invention will be described in detail below with reference to the drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0042] Embodiment 1: This embodiment provides a lithium battery thermal runaway propagation blocking device based on end face pressure amplification, as Figure 1 shown, including a lithium battery pack 5 composed of a regular arrangement of a plurality of lithium battery monomers, a lower bottom plate 1, an upper cover plate 2 supported and connected to the lower bottom plate 1 by a spring, a right end plate 3 of the fixture and a left end plate 7 of the fixture disposed between the lower bottom plate 1 and the upper cover plate 2, and a force amplification structure 4.

[0043] The design of the spring structure can effectively buffer and adjust the vertical displacement caused by the wedge block.

[0044] The design of the upper cover plate 2 can add an additional layer of protection to the battery system.

[0045] In this embodiment, the force amplification structure 4 includes a first wedge block, a second wedge block and a third wedge block. Among them, the second wedge block is a cylindrical wedge block. The first side of the first wedge block contacts one end of the lithium battery pack 5, the second side contacts the lower bottom plate 1 and serves as a support side, so that the first wedge block is stably supported by the lower bottom plate 1, and the third side is in tangential contact with the second wedge block. The first side of the third wedge block contacts and supports the upper cover plate 2, and the second side is in point contact with the second wedge block and is fixedly connected at the intersection point. In this embodiment, the fixed connection is in the form of welding.

[0046] The lithium battery pack 5 contacts and is supported by the lower bottom plate 1, and the other end of the lithium battery pack 5 contacts the left end plate 7 of the fixture.

[0047] The right end plate 3 of the fixture is in point contact with the second wedge block and slides along the lower bottom plate 1 and the upper cover plate 2. The left end plate 7 of the fixture can be fixed or can slide along the lower bottom plate 1 and the upper cover plate 2.

[0048] In this embodiment, the lower bottom plate 1 is parallel to the upper cover plate 2.

[0049] The blocking device may further include a liquid cooling system disposed in the lower bottom plate 1 for assisting in thermal runaway blocking and performing temperature reduction treatment.

[0050] The device further includes a pressure sensor 6 disposed on the surface of a single battery at one end of the lithium battery pack 5, so as to achieve early warning of the failure of any battery along the battery arrangement direction, and gain time for early cooling, personnel evacuation, and fire extinguishing. In another embodiment, the pressure sensor may also be a strain sensor.

[0051] In this embodiment, the cross-section of the first wedge is a right triangle. In another embodiment, the cross-section of the first wedge may also be a trapezoid.

[0052] In this embodiment, the cross-section of the third wedge is a right triangle, with the first side being the right-angled side and the second side being the hypotenuse. In Embodiment 2, as Figure 2 shown, the cross-section of the third wedge is a trapezoid. In Embodiment 3, as Figure 3 shown, the cross-section of the third wedge is a non-right triangle. However, in practice, a right triangle or trapezoid structure is usually adopted to reduce the material consumption of the structure and lower the cost.

[0053] This embodiment also provides a method for blocking the spread of lithium battery thermal runaway based on end-face pressure amplification, as Figure 4 shown, which is implemented based on the device described above, and includes the following steps:

[0054] Step 1) Thermal runaway of a single battery is triggered in the lithium battery pack due to overheating, overcharging, over-discharging, mechanical failure, or internal short circuit.

[0055] Step 2) During the thermal runaway process, the lithium battery expands and generates gas due to heat, causing the battery to squeeze and expand in all directions.

[0056] Step 3) The expansion force acts on the fixture end plate through the force amplification structure.

[0057] This embodiment takes Figure 5 as an example to deduce the amplification factor of the force amplification structure as follows:

[0058] Let the normal pressure of the roller D (the second wedge) on the object A (the first wedge) be F'4. In Figure 5 (a), there is:

[0059] F'4sinα = F

[0060] F'4 = F / sinα

[0061] Where α is the acute angle formed by the third side of the first wedge and the lower bottom plate, and β is the acute angle between the tangent line at the intersection of the second side of the third wedge and the second wedge and the vertical line.

[0062] According to the law of action and reaction, the magnitude of the normal pressure of the object A on the roller is also F'4, and the direction is opposite to F'4, as shown in Figure 5 (b), that is:

[0063] F4=F / sinα

[0064] Assume that the normal pressure of object B (the third wedge) on the roller is F3, see Figure 5 (b), then in the vertical direction:

[0065] F3sinβ=F4cosα

[0066] F3sinβ=Fcosα / sinα=Fcotα

[0067] F3=Fcotα / sinβ

[0068] In the horizontal direction:

[0069] F2=F3cosβ+F4sinα

[0070] Substituting into the above formula:

[0071] F2=(cotαcotβ+1)F

[0072] According to the law of action and reaction, the force F' exerted by the roller on object C is also equal to F2:

[0073] F'=(cotαcotβ+1)F

[0074] The effective magnification is:

[0075] A=cotαcotβ+1

[0076] The angles α and β are designed so that under normal operating conditions, the battery expansion will not expand and open the clamp. When the lithium battery gets out of control, the clamp can be opened in time to prevent the spread of thermal runaway.

[0077] Step 4) The amplified expansion force opens the end plates of the clamp, so that the spacing between the lithium battery cells increases or even the uncontrolled battery rolls over, resulting in no contact. In this embodiment, the left end plate of the clamp and the right end plate of the clamp are not fixed, so when subjected to the amplified expansion force, the two slide along the upper cover plate and the lower bottom plate at the same time, expanding the spacing between the battery cells.

[0078] Step 5) The heat transfer between battery cells is weakened to block the spread of thermal runaway.

[0079] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning, or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A lithium battery thermal runaway spread blocking device based on end face pressure amplification, comprising a lithium battery pack (5) composed of a plurality of lithium battery monomers arranged regularly, characterized in that, Also includes: A lower end bottom plate (1), an upper end cover plate (2) connected to the lower end bottom plate (1) via a spring support, a right end plate (3) of the fixture and a left end plate (7) of the fixture provided between the lower end bottom plate (1) and the upper end cover plate (2), and a force amplification structure (4); The force amplification structure (4) comprises a first wedge block, a second wedge block and a third wedge block, wherein the second wedge block is a cylindrical wedge block; a first side edge of the first wedge block contacts one end of the lithium battery pack (5), a second side edge contacts the lower end bottom plate (1) and serves as a supporting side, so that the first wedge block is stably supported by the lower end bottom plate (1), and the third side edge is in tangential contact with the second wedge block; a first side edge of the third wedge block contacts and supports the upper end cover plate (2), and a second side edge is in point contact with the second wedge block and is fixedly connected at the intersection; The lithium battery pack (5) is in contact with and supported by the lower bottom plate (1), and the other end of the lithium battery pack (5) is in contact with the left end plate (7) of the fixture; The right end plate (3) of the clamp is in point contact with the second wedge block and slides along the lower end bottom plate (1) and the upper end cover plate (2); The cross section of the first wedge is a trapezoid or a triangle; The cross section of the third wedge is a right triangle, wherein the first side is a right angle side and the second side is a hypotenuse.

2. The lithium battery thermal runaway spread blocking device based on end face pressure amplification according to claim 1, characterized in that, The lower end bottom plate (1) is parallel to the upper end cover plate (2).

3. The lithium battery thermal runaway propagation blocking device based on end face pressure amplification according to claim 1, characterized in that, The device also includes a liquid cooling system arranged in the lower end base plate (1) for assisting in blocking the spread of thermal runaway.

4. A lithium battery thermal runaway spread blocking device based on end face pressure amplification according to claim 1, characterized in that, The device further comprises a pressure sensor (6) disposed on the surface of a single cell at one end of the lithium battery pack (5) and used for early warning of lithium battery failure.

5. A method for blocking the spread of thermal runaway in lithium batteries based on end-face pressure amplification, characterized in that, Based on the device implementation according to any one of claims 1 to 4, the method comprises the following steps: Step 1) Thermal runaway of a single cell of the lithium battery pack occurs; Step 2) During thermal runaway, the lithium battery expands and produces gas due to heat, causing the battery to squeeze and expand in all directions; Step 3) the expansion force is amplified by the force amplification structure and acts on the end plate of the fixture; Step 4) The amplified expansion force opens the end plates of the fixture to increase the spacing between the lithium battery cells; Step 5) Heat transfer between battery cells is weakened, and the spread of thermal runaway is blocked.

6. The method for blocking the spread of thermal runaway of a lithium battery based on end face pressure amplification according to claim 5, characterized in that, The thermal runaway is caused by overheating, overcharging, overdischarging, mechanical failure or internal short circuit of the lithium battery.

7. A method for blocking the spread of thermal runaway of a lithium battery based on end face pressure amplification according to claim 5, characterized in that, The amplification factor of the expansion force by the force amplification structure is: ， Among them, α is the acute angle formed by the third side of the first wedge block and the lower end bottom plate, β is the acute angle between the tangent line at the intersection of the second side of the third wedge block and the second wedge block and the vertical line.

8. A method for blocking the spread of thermal runaway of a lithium battery based on end-face pressure amplification according to claim 7, characterized in that, The included angle α and β are designed such that under normal operating conditions, the battery expansion will not expand and open the fixture through amplification, and when the lithium battery gets out of control, the fixture can be opened in time to achieve the barrier of thermal runaway spread.

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