Battery internal gas production testing tool, testing method and calculation method

Abstract

The present application relates to the technical field of battery, in particular to a kind of battery internal gas production testing tool, testing method and calculation method.Testing tool includes the gas pressure monitoring hole and temperature monitoring hole being arranged on the battery upper cover;The gas pressure monitoring hole is provided with hollow sealing nail;The sealing nail is connected with gas pressure sensor by hollow connecting pipe;The temperature monitoring hole is provided with fixed seat;Temperature sensor is arranged in the fixed seat.The battery internal gas production testing tool of the present application can realize real-time monitoring of the gas in the battery during the conventional test process, and ensure that the test process does not interfere with the performance state of the battery itself;On the other hand, its pressure-resistant design and gas collection strategy can be applied to the thermal runaway test environment, realize the internal gas pressure monitoring before the battery valve is opened, can obtain the real-time gas production of the battery at different temperature stages, and quantitatively evaluate the shell pressure-bearing capacity of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a tooling, testing method, and calculation method for testing the gas production inside a battery. Background Technology

[0002] During battery cycling and storage, electrolyte decomposition and electrode side reactions can lead to internal gas production, resulting in volume expansion, increased internal resistance, performance degradation, and even failure. Currently, most monitoring of internal battery gases relies on non-in-situ detection, requiring the gas to be removed from the battery before measurement. This method not only fails to achieve real-time dynamic monitoring and capture the gas production evolution process and early signs of failure, but also alters the battery's electrochemical and safety performance during gas extraction, affecting subsequent use and research. Furthermore, existing technologies capable of in-situ gas production monitoring suffer from limited device pressure resistance, making accurate data collection under extreme conditions such as thermal abuse difficult. This makes it impossible to accurately obtain changes in internal gas production and the casing pressure limit before thermal runaway. Therefore, how to achieve real-time dynamic monitoring of internal gas production under battery operation and even extreme conditions through in-situ, high-pressure-resistant monitoring methods, providing direct evidence for failure analysis, thermal management early warning, and battery structural safety design, is a pressing technical problem to be solved in this field. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings and defects of the prior art by providing a testing fixture, testing method, and calculation method for the gas production inside a battery.

[0004] To achieve the above objectives, this application adopts the following solution: A fixture for testing the gas production inside a battery includes a pressure monitoring hole and a temperature monitoring hole disposed on the top cover of the battery; the pressure monitoring hole is provided with a hollow sealing nail; the sealing nail is connected to a pressure sensor through a hollow connecting tube; the temperature monitoring hole is provided with a fixing base; and a temperature sensor is disposed inside the fixing base.

[0005] The pressure sensor is connected to a buffer fixture; the buffer fixture includes a base, a slide plate disposed above the base, an upper plate disposed above the slide plate, and a buffer spring disposed between the slide plate and the upper plate; the base, slide plate, and upper plate are connected by a connecting rod; the slide plate can slide on the connecting rod; the battery is disposed between the base and the slide plate; the pressure sensor is disposed above the upper plate; the hollow connecting tube passes through the slide plate and the upper plate and is connected to the pressure sensor.

[0006] There are two temperature monitoring holes, which are located between the battery explosion-proof valve and the positive electrode tab; preferably, the diameter of the temperature monitoring hole is 2mm; preferably, the temperature sensor extends into the battery to a depth of 2mm.

[0007] The mounting base and the battery cover are threadedly connected via a first adapter; preferably, a sealing filler is provided between the mounting base and the temperature sensor; preferably, 302 sealant; preferably, a sealing gasket is provided at the connection between the mounting base and the cover plate; preferably, a fluororubber sealing gasket.

[0008] The pressure monitoring hole is a liquid injection hole between the battery explosion-proof valve and the negative electrode tab; the sealing pin is threadedly connected to the battery top cover via a second adapter; sealing tape is provided between the threads; preferably, the sealing pin extends into the battery to a depth of 2mm.

[0009] For cyclic testing or storage testing, the battery is connected to a constant displacement fixture.

[0010] For the battery thermal runaway gas generation test, an aluminum alloy clamp that matches the large surface size of the battery is used for fixation, and heat insulation cotton and heating elements are sequentially placed between the battery and the clamp.

[0011] This invention also includes a method for testing the internal gas production of a battery, using the aforementioned battery internal gas production testing fixture, specifically including the following steps: using a pressure sensor to test the initial pressure P0 and time t. i pressure P i The initial temperature T0 and time t were measured using a temperature sensor. i Temperature T i .

[0012] The present invention also includes a method for calculating the amount of gas produced inside a battery, which is based on the temperature measured by the temperature sensor and the gas pressure obtained by the gas pressure sensor in the test fixture.

[0013] The calculation method described above is based on the following formula. ;in, For the increase in gas volume, From the initial state to time t i The increase in the amount of substance; n0 represents the amount of gas inside the battery in the initial state; n i Let time t i The amount of gas inside the battery.

[0014] ; Based on the initial pressure P0 and initial temperature T0 inside the battery measured by the temperature sensor and pressure sensor in the test fixture, the value at any test time t is determined. i Real-time pressure P i With real-time temperature T i ; V is the volume of the gas phase space, V = a b (1-x%) c + a b h1+ a b h2; x% is the battery thickness-to-casing ratio after battery formation, a is the length of the battery inner casing, b is the width of the inner casing, c is the height of the electrode assembly, h1 is the gap between the electrode assembly and the top cover, and h2 is the gap between the electrode assembly and the bottom of the battery inner casing.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The battery internal gas generation testing fixture of this invention, on the one hand, enables real-time monitoring of internal gas during routine testing, ensuring that the testing process does not interfere with the battery's performance; on the other hand, its pressure-resistant design and gas collection strategy are applicable to thermal runaway testing environments, enabling monitoring of internal gas pressure before the battery valve opens, obtaining real-time gas generation at different temperature stages, and quantitatively assessing the battery's casing pressure-bearing capacity. This method expands the application boundaries of battery internal gas monitoring, providing reliable technical support for in-depth research into battery failure mechanisms and improving battery structural safety. Attached Figure Description

[0016] Figure 1 This is an overall schematic diagram of the battery internal gas production testing fixture of the present invention; Figure 2 This is a schematic diagram of the buffer fixture of the battery internal gas production testing fixture of the present invention. Figure 3 This is an exploded view of the battery cover plate of the present invention; Figure 4 This is a schematic diagram of the thermal runaway test of the battery internal gas production testing fixture of the present invention. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0018] Figure 1-4 A tooling for testing the amount of gas generated inside a battery is shown, including a pressure monitoring port and a temperature monitoring port disposed on the battery cover. The pressure monitoring hole is a liquid injection hole between the battery explosion-proof valve and the negative electrode tab. An M4×6mm aluminum sealing nail 4 is installed at the pressure monitoring hole. The sealing nail has a hollow structure. The sealing nail 4 is threadedly connected to the second adapter 11 on the battery cover. Sealing tape is applied between the threads. This achieves a sealing level far exceeding the design parameters of the battery explosion-proof valve (sealing pressure resistance level of 2~3 MPa, while the battery explosion-proof valve design is below 1.2 MPa). The aluminum sealing nail is uniformly coated with insulating material and extends into the battery to a predetermined depth (denoted as 2 mm). This depth ensures that the inserted part does not touch the electrode assembly and remains in the gap, serving as insulation and preventing electro-hydraulic corrosion, thus ensuring that the signal collected by the battery is not interfered with. A pressure sensor 5 is connected to the pressure monitoring hole on the battery cover via a stainless steel hollow connecting pipe 3. One end of the hollow steel pipe 3 is connected to the sealing nail 4, and the other end is connected to the air inlet of the pressure sensor 5, thereby connecting the pressure sensor to the inside of the battery for real-time acquisition of internal pressure data.

[0019] Two temperature monitoring holes, one primary and one backup, are mutually calibrated and located between the battery explosion-proof valve and the positive electrode tab. Each temperature monitoring hole has a diameter of 2mm. A PTFE (polytetrafluoroethylene) mounting base 2 with external threads is installed at the temperature monitoring hole via a first adapter 10 threaded fastening method. The mounting base 2 is a hollow structure, with a temperature sensor penetrating through it. The probe end of the temperature sensor extends 2mm into the battery through the mounting base, achieving the same penetration depth as the air pressure monitoring hole. To ensure long-term airtightness at this hole, 302 sealant is used to fill and seal the space between the mounting base and the temperature sensor. A fluororubber gasket is used at the connection between the mounting base and the upper cover plate, forming a redundant sealing structure.

[0020] Through the above structural design, while ensuring reliable connection and signal output of pressure and temperature sensors, the overall sealing of the battery cover and the protection of sensors from electro-hydraulic corrosion are ensured, thus providing the necessary structural foundation for accurate measurement of the internal gas production of the battery under different operating conditions.

[0021] The pressure sensor is connected to a buffer fixture. The buffer fixture includes a base 9, a slide plate 7 positioned above the base, an upper plate positioned above the slide plate, and a buffer spring 6 positioned between the slide plate 7 and the upper plate. The base 9, slide plate, and upper plate are connected by a connecting rod. The slide plate 7 can slide on the connecting rod. The battery is positioned between the base and the slide plate. The pressure sensor is positioned above the upper plate. A hollow connecting tube passes through the slide plate and the upper plate and connects to the pressure sensor. The base supports and fixes the entire fixture. The upper plate is located below the pressure sensor and supports and protects the display unit of the pressure sensor, isolating it from the battery. In the event of abnormalities such as thermal runaway of the battery, the buffer spring 6 can buffer the high-speed airflow that is suddenly ejected, absorbing some of the impact energy, thereby preventing the fixture from being damaged due to instantaneous overload and protecting the pressure sensor from direct impact. Through the above structure, the pressure acquisition system can improve the safety of the testing process and the reliability of the equipment while ensuring airtightness and measurement accuracy.

[0022] The battery internal gas production test method provided by the present invention has a battery installation technical solution configured according to the test type. According to the test requirements, thermocouples are arranged in the temperature monitoring hole as temperature sensors to monitor the battery temperature.

[0023] For cyclic or storage testing, the battery is connected to a constant displacement fixture. The constant displacement fixture is set with an expansion force, which can be determined according to the actual testing requirements of the battery, but must not be less than 2 kN.

[0024] For battery thermal runaway gas generation testing, an aluminum alloy clamp matching the battery's large surface area is used for fixation. Insulation cotton and heating elements 8 are sequentially placed between the battery and the clamp, forming a stacked contact structure of "clamp-insulation cotton-heating elements-battery". The heating elements can be configured to be single-sided or double-sided adhered. When single-sided adhered, the side without heating elements forms the corresponding "clamp-insulation cotton-battery" contact structure. During installation, the minimum torque applied to the aluminum alloy clamp must not be less than 3 kN (this is to ensure the battery's internal volume remains unchanged).

[0025] The present invention also includes a method for calculating the amount of gas produced inside a battery, which is based on the temperature measured by the temperature sensor and the gas pressure obtained by the gas pressure sensor in the test fixture.

[0026] The present invention provides a method for testing the gas production inside a battery, wherein the calculation of the gas production is based on the ideal gas law (Formula 1). Formula 1 P is pressure, V is volume, R is a constant, T is temperature, and n is the amount of substance; The specific technical solution for calculating gas production is as follows: First, let the thickness-to-casing ratio of the battery under test after formation be x%, the inner casing length be a, the inner casing width be b, the electrode assembly height be c, the gap between the electrode assembly and the top cover be h1, and the gap between the electrode assembly and the bottom of the inner casing be h2. Then determine the internal gas phase space volume V of the battery, i.e., V = a. b (1-x%) c + a b h1+ a b h2.

[0027] Based on the test conditions, the battery is secured using a constant displacement fixture or clamp, and the gas phase space volume V can be set to a constant value. Using temperature and pressure sensors, the initial pressure P0 and initial temperature T0 inside the battery, as well as the pressure at any test time t, can be obtained. i Real-time pressure P i With real-time temperature T i .

[0028] Calculate the amount of gas n0 inside the battery in the initial state according to Formula 1. Formula 2 and time t i The amount of substance n of the gas inside the battery i , Formula 3 Therefore, we obtain the time from the initial state to time t. i The increase in the amount of gaseous substance, Δn. Formula 4 Finally, the increase in the amount of substance Δn is converted into the increase in gas volume ΔV under standard conditions, which is denoted as the amount of gas produced internally by the battery during this period. Formula 5 In addition to the required gas production calculation method, the time (t) can be shortened according to demand. i This allows us to obtain the relationship between the amount of gas produced inside the battery and time.

[0029] The following is a specific example.

[0030] Example 1: Cyclic performance testing was conducted using a 63.3Ah lithium iron phosphate prismatic battery as the test object. First, the battery cover was specially treated according to the methods described in the technical specifications, and the pressure sensor was installed and the temperature sensor was hermetically sealed. Then, the treated battery was placed in a constant displacement fixture, and an initial preload of 3kN was applied for tightening. Fast-charging cycle testing was then conducted under this condition. Through the above testing process, real-time data on the internal pressure and temperature of the battery were collected for subsequent calculation and analysis of gas production based on the ideal gas law.

[0031] The following example demonstrates the test results of 0-100 fast charging cycles of the battery.

[0032] The battery has a thickness-to-shell ratio of 99.5%, an inner shell length of 204 mm, an inner shell width of 32 mm, an electrode assembly height of 75 mm, a gap of 8 mm between the electrode assembly and the top cover, and no gap between the electrode assembly and the bottom of the inner shell. Before cycling begins, the battery's initial temperature T0 is 27.4℃, and the initial internal pressure P0 is 0.078 MPa. After 100 cycles, the temperature T... 100 The temperature is 30.1℃, and the pressure is P. 100 It is 0.365 MPa.

[0033] First, the internal gas volume of the battery is calculated. V=[32 204 75 (1-99.5%)+32 8 204] 10 -9 =5.47×10 -5 m 3 ; According to Formula 2, calculate the amount of substance n0 of the gas inside the battery in the initial state. According to Formula 3, calculate the amount of gas n inside the battery after 100 fast charging cycles. 100 , According to Formula 4, Δn is calculated. Finally, according to Formula 5, the amount of substance increment Δn is converted into the gas volume increment ΔV under standard conditions. Example 2: A 104.5Ah lithium iron phosphate prismatic battery was used as the test object for thermal runaway gas generation testing. First, the battery cover was specially treated according to the method described in the technical specifications, and the pressure sensor, temperature sensor, and airtight sealing were completed. This thermal runaway test used a single-sided heating element triggering method. The treated battery was placed in a clamp with the same dimensions as the battery's main surface area, and an initial preload of 3kN was applied using a torque wrench for tightening before being placed in a vacuum chamber. Figure 4 (As shown). Through the above testing process, the internal pressure and temperature data of the battery are collected in real time for subsequent calculation and analysis of gas production based on the ideal gas law.

[0034] The battery, after formation, has a full charge-to-casing ratio of 99.6%. The inner casing is 204mm long and 32mm wide, the electrode assembly is 118mm high, the gap between the electrode assembly and the top cover is 8mm, and there is no gap between the electrode assembly and the bottom outer casing. Before the thermal runaway test, the initial battery temperature T0 is 27.43℃, and the initial internal pressure P0 is 0.0196MPa. At the instant the battery valve is opened, the temperature T... 开阀 The temperature is 100.65℃, and the pressure is P. 开阀 It is 0.5288 MPa.

[0035] First, the internal gas volume of the battery is calculated. V=[32 204 118 (1-99.6%)+204 32 8] 10 -9 =5.53×10 -5 m 3 ; According to Formula 2, calculate the amount of substance n0 of the gas inside the battery in the initial state. According to Formula 3, calculate the amount of substance n of the internal gas of the battery just before the valve opens. 开阀 , According to Formula 4, Δn is calculated. Finally, Formula 5 converts the amount of substance increment Δn into the gas volume increment ΔV under standard conditions. The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of the equivalents of the claims be included within the invention.

[0036] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A fixture for testing the gas production rate inside a battery, characterized in that, It includes a pressure monitoring hole and a temperature monitoring hole set on the battery cover; the pressure monitoring hole is provided with a hollow sealing nail; the sealing nail is connected to the pressure sensor through a hollow connecting tube; the temperature monitoring hole is provided with a fixing base; the fixing base is provided with a temperature sensor.

2. The battery internal gas production testing fixture according to claim 1, characterized in that, The pressure sensor is connected to a buffer fixture; the buffer fixture includes a base, a slide plate disposed above the base, an upper plate disposed above the slide plate, and a buffer spring disposed between the slide plate and the upper plate; the base, slide plate, and upper plate are connected by a connecting rod; the slide plate is slidable on the connecting rod; the battery is disposed between the base and the slide plate; the pressure sensor is disposed above the upper plate; the hollow connecting tube passes through the slide plate and the upper plate and is connected to the pressure sensor.

3. The battery internal gas production testing fixture according to claim 1, characterized in that, There are two temperature monitoring holes, which are located between the battery explosion-proof valve and the positive electrode tab; preferably, the diameter of the temperature monitoring hole is 2mm; preferably, the temperature sensor extends into the battery to a depth of 2mm.

4. The battery internal gas production testing fixture according to claim 3, characterized in that, The mounting base and the battery cover are threadedly connected via a first adapter; preferably, a sealing filler is provided between the mounting base and the temperature sensor; preferably, 302 sealant; preferably, a sealing gasket is provided at the connection between the mounting base and the battery cover; preferably, a fluororubber sealing gasket.

5. The battery internal gas production testing fixture according to claim 1, characterized in that, The air pressure monitoring hole is a liquid injection hole between the battery explosion-proof valve and the negative electrode tab; the sealing nail is threadedly connected to the battery top cover via a second adapter; sealing tape is provided between the threads; preferably, the sealing nail extends into the battery to a depth of 2mm.

6. The battery internal gas production testing fixture according to claim 1, characterized in that, For cyclic testing or storage testing, the battery is connected to a constant displacement fixture.

7. The battery internal gas production testing fixture according to claim 1, characterized in that, For the battery thermal runaway gas generation test, an aluminum alloy clamp that matches the large surface size of the battery is used for fixation, and heat insulation cotton and heating elements are sequentially placed between the battery and the clamp.

8. A method for testing the amount of gas generated inside a battery, characterized in that, The test is performed using the battery internal gas production testing fixture according to any one of claims 1-7, specifically including the following steps: using a pressure sensor to test the initial pressure P0 and time t. i pressure P i The initial temperature T0 and time t were measured using a temperature sensor. i Temperature T i .

9. A method for calculating the gas production inside a battery, characterized in that, The temperature measured by the temperature sensor and the air pressure obtained by the air pressure sensor in the test fixture according to any one of claims 1-7 are used for calculation.

10. The calculation method according to claim 9, characterized in that, Calculate according to the following formula ;in, For the increase in gas volume, From the initial state to time t i The increase in the amount of substance; n0 represents the amount of gas inside the battery in the initial state; n i Let time t i The amount of gas inside the battery; in, ; Based on the initial pressure P0 and initial temperature T0 inside the battery measured by the temperature sensor and pressure sensor in the test fixture, the value at any test time t is determined. i Real-time pressure P i With real-time temperature T i ; V is the volume of the gas phase space, V = a b (1-x%) c + a b h1 + a b h2; x% is the battery thickness-to-casing ratio after battery formation, a is the length of the battery inner casing, b is the width of the inner casing, c is the height of the electrode assembly, h1 is the gap between the electrode assembly and the top cover, and h2 is the gap between the electrode assembly and the bottom of the battery inner casing.

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