Lithium-ion battery pack exhaust structure

Abstract

The utility model relates to the field of lithium ion battery, especially to a lithium ion battery pack exhaust structure for realizing the directional discharge of the gas generated when the battery pack thermal runaway, including the shell, including the exhaust hole structure, the exhaust hole structure sets up on the wall surface of shell, and the exhaust hole of exhaust hole structure communicates the inside of shell with the outside. The utility model is especially suitable for the lithium ion battery pack.

Description

Technical Field

[0001] This utility model relates to the field of lithium-ion batteries, and in particular to a venting structure for lithium-ion battery packs. Background Technology

[0002] Lithium-ion battery packs, with their high energy density, convert chemical energy into electrical energy and are widely used in aerospace, automotive, marine, robotics, and robotic dogs. The lithium-ion battery pack is fixed inside a casing, which primarily provides necessary protection. Under conditions of overheating, overcharging, or mechanical puncture, lithium-ion battery packs are highly likely to experience thermal runaway. In the early stages of thermal runaway, flammable gases, non-flammable gases, smoke, and even flames generated by the runaway will accumulate above the casing. If not vented promptly, this can lead to a combustion explosion, damaging not only the casing but also allowing the gases and flames to easily spread to the surrounding areas of the lithium-ion battery pack, creating even greater danger.

[0003] Currently, the main approach to thermal runaway in lithium-ion battery cells is to install pressure relief valves on the battery pack casing to release the gases generated in the initial stages of thermal runaway. However, since these valves typically only open when a certain pressure threshold is reached (usually above 10 kPa), the gas pressure generated by thermal runaway is already quite high when the valve opens. Due to the shape of the valve core, the high-pressure gas, forced open by this pressure, is suddenly ejected into the environment in a jet-like manner. Furthermore, the direction of the ejected gas, smoke, and even flames is unpredictable, sometimes causing injury to people and damage to equipment near the battery pack. Additionally, in ternary lithium-ion battery cells, the decomposition reaction is violent during thermal runaway, with flammable gases accounting for over 60% of the total gas composition. In contrast, in lithium cobalt oxide and lithium iron phosphate battery cells, the decomposition reaction is slower, and the proportion of flammable gases in the total gas composition is lower. Therefore, the different gases released during thermal runaway of different battery cells require pressure relief valves with different parameters and performance, resulting in a complex range of pressure relief valves and high subsequent maintenance costs. Utility Model Content

[0004] The technical problem to be solved by this utility model is to provide a lithium-ion battery pack exhaust structure for directional emission of gases generated during thermal runaway of the battery pack.

[0005] The technical solution adopted by this utility model to solve its technical problem is: a lithium-ion battery pack exhaust structure, including a shell and an exhaust hole structure, wherein the exhaust hole structure is disposed on the wall surface of the shell, and the exhaust hole of the exhaust hole structure connects the interior of the shell with the outside.

[0006] Furthermore, the vent is located on the side wall of the housing, and the axis of the vent is set in the horizontal direction.

[0007] Furthermore, the cross-sectional shape of the exhaust port is circular.

[0008] Furthermore, the exhaust port has a straight-through structure.

[0009] Furthermore, the vent structure includes an isolation mesh, which is disposed between the vent and the outer casing.

[0010] Furthermore, the axes of the isolation net and the exhaust vent are set perpendicular to each other.

[0011] Furthermore, the vent structure includes a mounting base, one end of the vent is mounted on the mounting base, the mounting base is mounted on the outer shell wall, and the isolation mesh is positioned between the mounting base and the outer shell wall.

[0012] Furthermore, it includes a battery pack disposed inside the casing, a chamber disposed above the battery pack, and an exhaust port of an exhaust structure connecting the chamber to the outside.

[0013] Furthermore, the battery packs include lithium cobalt oxide battery packs, ternary lithium battery packs, or lithium iron phosphate battery packs.

[0014] The beneficial effects of this utility model are: First, by incorporating vents on the casing, the internal parts of the casing are connected to the outside environment. When the battery cells generate gas due to thermal runaway, the gas can be gently released to the outside of the casing in a timely manner, preventing sudden gas ejection caused by initial pressure buildup. This effectively protects the safety of surrounding personnel and equipment, and also prevents damage to the casing from accumulated high-temperature gas. Secondly, the relatively fixed direction of the vents ensures a consistent gas discharge direction. When the vents are oriented in a safe direction, the discharged gas will be concentrated and directed towards the vent, preventing it from scattering and spraying outwards, further guaranteeing the safety of personnel and equipment.

[0015] Second, the isolation mesh prevents debris generated during thermal runaway of the battery cells from being released from the casing to the outside, thus avoiding blockage of the venting channels and preventing the danger caused by debris being ejected with the gas in extreme cases. At the same time, the isolation mesh prevents foreign objects from entering the casing through the venting ports, effectively protecting the battery pack from damage.

[0016] Third, regardless of whether the battery pack is a lithium cobalt oxide battery pack, a ternary lithium battery pack, or a lithium iron phosphate battery pack, the vent holes in this solution can be used to achieve directional venting, which greatly simplifies the related structural design and the types of components, and also reduces subsequent maintenance costs.

[0017] This invention is particularly applicable to lithium-ion battery packs. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the exhaust port and the isolation mesh of this utility model installed on the outer shell.

[0019] Figure 2 yes Figure 1 Side view.

[0020] The following are marked in the diagram: outer shell 1, vent 201, and isolation net 202. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings.

[0022] like Figure 1 and Figure 2 This is an embodiment of the venting structure for a lithium-ion battery pack. The outer casing 1 is cubic in shape, and a battery pack, which can be a lithium cobalt oxide battery pack, a ternary lithium battery pack, or a lithium iron phosphate battery pack, is housed inside the casing 1. The battery pack is fixedly installed inside the casing 1. In addition to accommodating the battery pack, the cavity inside the casing 1 also has a chamber above the battery pack. This chamber communicates with the outside through a vent 201 on the side wall of the casing 1. The chamber above the battery pack allows gases generated during battery thermal runaway to converge in the area near the top of the cavity inside the casing 1, facilitating the discharge of these gases to the outside through the vent 201.

[0023] In actual production, lithium cobalt oxide battery packs typically have cell capacities ranging from 1Ah to 10Ah, with 1-13 cells connected in series and 1-13 cells connected in parallel. Ternary lithium battery packs have cell capacities ranging from 1Ah to 62Ah, with 1-220 cells connected in series and 1-13 cells connected in parallel. Lithium iron phosphate battery packs have cell capacities ranging from 1Ah to 400Ah, with 1-250 cells connected in series and 1-13 cells connected in parallel.

[0024] The vent 201 is a straight-through vent structure with a circular shape. A mounting base is attached to one end of the vent 201 and is fixedly mounted on the outer wall of the housing 1. The mounting base has holes of the same size as the vent 201, ensuring that the vent 201 allows communication between the chamber above the battery pack and the outside. An isolation mesh 202 is fixedly installed between the mounting base and the outer wall of the housing 1. The isolation mesh 202 is pressed and fixed to the outer wall of the housing 1 by the mounting base, thus filtering out debris carried by the gas passing through the vent 201 and preventing it from being released to the outside. Both the vent 201 and the isolation mesh 202 can be made of aluminum, and their axes are perpendicular. The axis of the vent 201 is horizontal, guiding the gas generated by thermal runaway to escape horizontally. In actual operation, corresponding protective measures can be set in the direction directly opposite the outlet of the exhaust port 201 to minimize the damage caused by the gas discharged from the exhaust port 201 due to thermal runaway.

[0025] The specific diameter of the vent 201 can be adjusted according to the corresponding battery pack. For example, a relatively small vent 201 can be used for low-capacity lithium-ion battery packs, while a relatively large vent 201 can be used for high-capacity lithium-ion battery packs. The diameter of the vent 201 can be calculated using the following formula: V=σC×n s ×n p ×V1×Q1(1) Φ=0.099V (2; In equation (1): V represents the total amount of gas generated by the thermal runaway of the battery pack, expressed in liters (L). σ is the safety factor of 1.06; C represents the single-cell capacity, measured in Ah. n s This refers to the number of battery cells connected in series. n p This refers to the number of battery packs connected in parallel. V1 is the nominal voltage of a single battery cell, in volts (V). Q1 represents the gas production per unit Wh: 0.623 L / Wh for lithium cobalt oxide system, 0.442 L / Wh for lithium iron phosphate system, and 0.724 L / Wh for ternary system.

[0026] In equation (2): Φ is the diameter of the vent hole, in mm; V is the total amount of gas generated by thermal runaway of the battery pack, in L.

[0027] The following examples and comparative examples will be used to introduce the formula for calculating the diameter of the exhaust port 201.

[0028] Example 1: This embodiment provides a vent for a lithium-ion battery pack. The battery cells use a lithium cobalt oxide system, with a capacity of 4.2 Ah, 7 series connections, 7 parallel connections, a nominal voltage of 3.7V, and a capacity of 761.5 Wh. The vent 201 has a diameter of 10 mm and an area of ​​78.54 mm². 2 An external DC power supply charges the battery pack, overcharging it until thermal runaway occurs.

[0029] Example 2: This embodiment provides a vent for a lithium-ion battery pack. The battery cells use a lithium cobalt oxide system, with a capacity of 4.2 Ah, 7 series connections, 7 parallel connections, a nominal voltage of 3.7V, and a capacity of 761.5 Wh. The vent 201 has a diameter of 20 mm and an area of ​​314.16 mm². 2 An external DC power supply charges the battery pack, overcharging it until thermal runaway occurs.

[0030] Example 3: This embodiment provides a vent for a lithium-ion battery pack. The battery cells use a lithium cobalt oxide system, with a capacity of 4.2 Ah, 7 series connections, 7 parallel connections, a nominal voltage of 3.7V, and a capacity of 761.5 Wh. The vent 201 has a diameter of 30 mm and an area of ​​706.86 mm². 2 An external DC power supply charges the battery pack, overcharging it until thermal runaway occurs.

[0031] Example 4: This embodiment provides a vent for a lithium-ion battery pack. The battery cells use a lithium cobalt oxide system, with a capacity of 4.2 Ah, 7 series connections, 7 parallel connections, a nominal voltage of 3.7V, and a capacity of 761.5 Wh. The vent 201 has a diameter of 40 mm and an area of ​​1256.64 mm². 2 An external DC power supply charges the battery pack, overcharging it until thermal runaway occurs.

[0032] Example 5: This embodiment provides a vent for a lithium-ion battery pack. The battery cells use a lithium cobalt oxide system, with a capacity of 4.2 Ah, 7 series connections, 7 parallel connections, a nominal voltage of 3.7V, and a capacity of 761.5 Wh. The vent 201 has a diameter of 50 mm and an area of ​​1963.50 mm². 2An external DC power supply charges the battery pack, overcharging it until thermal runaway occurs.

[0033] Example 6: This embodiment provides a vent for a lithium-ion battery pack. The battery cells use a lithium cobalt oxide system, with a capacity of 4.2 Ah, 7 series connections, 7 parallel connections, a nominal voltage of 3.7V, and a capacity of 761.5 Wh. The vent 201 has a diameter of 60 mm and an area of ​​2827.43 mm². 2 An external DC power supply charges the battery pack, overcharging it until thermal runaway occurs.

[0034] Example 7: This embodiment provides a vent for a lithium-ion battery pack. The battery cells use a lithium cobalt oxide system, with a capacity of 8.4 Ah, 7 series connections, 7 parallel connections, a nominal voltage of 3.7V, and a capacity of 1522.92 Wh. The vent 201 has a diameter of 100 mm and an area of ​​7853.98 mm². 2 An external DC power supply charges the battery pack, overcharging it until thermal runaway occurs.

[0035] Comparative Example 1: This comparative example provides a vent for a lithium-ion battery pack. The battery cells use a lithium iron phosphate system, with a capacity of 3Ah, 8 series connections, 10 parallel connections, a nominal voltage of 3.2V, and a capacity of 768Wh. The vent 201 has a diameter of 30mm and an area of ​​706.86mm². 2 An external DC power supply charges the battery pack, overcharging it until thermal runaway occurs.

[0036] Comparative Example 2: This comparative example provides a vent for a lithium-ion battery pack. The battery cells use a ternary lithium battery system with a capacity of 10Ah, 7 series connections, 3 parallel connections, a nominal voltage of 3.65V, and a capacity of 766.5Wh. The vent 201 has a diameter of 58mm and an area of ​​2642.08mm². 2 An external DC power supply charges the battery pack, overcharging it until thermal runaway occurs.

[0037] The relevant parameters of Examples 1-7 and Comparative Examples 1-2, as well as the final exhaust port temperature, are summarized in Table 1 below.

[0038] Table 1 The experimental results from Examples 1-6 show that in Example 5, when the lithium cobalt oxide battery pack uses a 50mm hole diameter, the highest temperature of the vent hole is 351.1℃, and no cracking occurs at the weld seam of the battery pack casing. However, in the examples, the vent hole temperature is higher, and cracking occurs at the casing weld seam or the corresponding module strength is insufficient.

[0039] Meanwhile, in Comparative Example 1, the diameter of the vent hole in the lithium iron phosphate battery pack is 30mm, the highest temperature of the vent hole is 302.3℃, and there are no cracks in the outer casing welds. In Comparative Example 2, the diameter of the vent hole in the ternary lithium battery pack is 58mm, the highest temperature of the vent hole is 438.9℃, and there are no cracks in the outer casing welds. Therefore, it can be concluded that the vent hole diameter calculation for the venting structure of lithium-ion battery packs can be performed using the aforementioned vent diameter calculation formula.

Claims

1. A venting structure for a lithium-ion battery pack, comprising a casing (1), characterized in that: It includes an exhaust hole structure, which is disposed on the wall of the outer shell (1), and the exhaust hole (201) of the exhaust hole structure connects the interior of the outer shell (1) with the outside.

2. The venting structure of the lithium-ion battery pack as described in claim 1, characterized in that: The exhaust port (201) is provided on the side wall of the outer casing (1), and the axis of the exhaust port (201) is set in the horizontal direction.

3. The venting structure of the lithium-ion battery pack as described in claim 2, characterized in that: The cross-sectional shape of the exhaust port (201) is circular.

4. The venting structure of the lithium-ion battery pack as described in claim 2, characterized in that: The exhaust port (201) is a straight-through vent structure.

5. The venting structure of a lithium-ion battery pack as described in any one of claims 1 to 4, characterized in that: The vent structure includes an isolation mesh (202), which is disposed between the vent (201) and the outer shell (1).

6. The venting structure of the lithium-ion battery pack as described in claim 5, characterized in that: The axes of the isolation net (202) and the exhaust port (201) are perpendicular to each other.

7. The venting structure of the lithium-ion battery pack as described in claim 6, characterized in that: The vent structure includes a mounting base, one end of the vent (201) is set on the mounting base, the mounting base is set on the wall of the outer shell (1), and the isolation net (202) is set between the mounting base and the wall of the outer shell (1).

8. The venting structure of a lithium-ion battery pack as described in any one of claims 1 to 4, characterized in that: It includes a battery pack disposed inside the housing (1), a chamber is disposed above the battery pack, and an exhaust port (201) of an exhaust port structure connects the chamber to the outside.

9. The venting structure of the lithium-ion battery pack as described in claim 7, characterized in that: Battery packs include lithium cobalt oxide battery packs, ternary lithium battery packs, or lithium iron phosphate battery packs.

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