Battery moisture detection method and device

Abstract

This application discloses a method and apparatus for detecting battery moisture. The battery includes a casing, terminals extending through the casing, and a sealing element disposed between the terminals and the casing. The method includes: calculating the bulk water permeability of the sealing element, which is the amount of water that permeates through the sealing element into the casing; calculating the gap water permeability of the sealing element, which is the amount of water that permeates through the interface between the sealing element and the terminals and the casing into the casing; and determining the total amount of water that has penetrated into the battery based on the bulk water permeability and the gap water permeability. This application's solution comprehensively considers the water permeability of the sealing element itself (i.e., bulk water permeability) and the gap water permeability between components such as the terminals that contact the sealing element to obtain the total amount of water that has penetrated into the battery after manufacturing. This allows for a more accurate assessment of the moisture intrusion situation inside the lithium battery, providing a more reliable reference for battery design, manufacturing, and use.

Description

Technical Field

[0001] This application relates to the field of battery moisture detection technology, and in particular to a battery moisture detection method and apparatus. Background Technology

[0002] In the manufacturing process of lithium-ion batteries, three critical aspects must be strictly controlled: dust, metal particles, and moisture. Failure to control dust and metal particles can directly lead to internal short circuits and fires. Similarly, uncontrolled moisture can significantly harm battery performance. For example, it can react with lithium salts in the electrolyte to form hydrofluoric acid, which corrodes the battery and further reacts with lithium carbonate, a component of the SEI film, to form lithium fluoride precipitate. This damages the density and uniformity of the SEI film, increasing internal resistance and decreasing discharge capacity, thus shortening the battery's cycle life. Therefore, accurate monitoring of the battery's moisture content is crucial. However, currently, it's impossible to accurately monitor water content throughout the entire battery's lifespan. The only method is to disassemble the battery at a certain stage and measure the moisture content using a Karl Fischer moisture analyzer. Summary of the Invention

[0003] To address the problems of the prior art, this application provides a battery moisture detection method and apparatus to solve one or more technical problems existing in the prior art, and to more accurately assess the moisture intrusion inside lithium batteries.

[0004] In a first aspect, this application provides a method for detecting battery moisture content, the battery including a casing, terminals passing through the casing, and a sealing member disposed between the terminals and the casing, the method comprising:

[0005] Calculate the bulk water permeability of the seal, where the bulk water permeability is the amount of water that permeates through the seal into the interior of the housing;

[0006] Calculate the water permeability of the seal, which is the amount of water that permeates into the interior of the housing through the contact interface between the seal, the pole, and the housing.

[0007] Based on the bulk water permeability and the gap water permeability, the total amount of water that penetrates into the battery is determined.

[0008] Furthermore, in this application, calculating the bulk water permeability of the seal includes:

[0009] The bulk permeability coefficient of the seal is obtained, and the bulk water permeability of the seal is calculated based on the bulk permeability coefficient, the surface area of ​​the seal facing the external space of the housing, and the permeation time. The bulk permeability coefficient is determined by the battery's operating temperature and a bulk permeability coefficient model, and the bulk permeability coefficient model characterizes the relationship between the bulk permeability coefficient and temperature.

[0010] Furthermore, in this application, the pole post has a columnar structure, the sealing element has a ring-shaped structure, and the sealing element is sleeved on the pole post;

[0011] The bulk water permeability of the seal is calculated using the following formula based on the bulk permeability coefficient, the surface area of ​​the seal facing the external space of the housing, and the permeation time:

[0012]

[0013] in, The volumetric water permeability, The bulk transmittance coefficient is [value missing]. The outer diameter of the seal is [missing information]. The inner diameter of the seal is [missing information]. The infiltration time is mentioned.

[0014] Furthermore, in this application, calculating the water permeability of the seal includes:

[0015] Obtain the gap permeability coefficient, and calculate the gap water permeability of the seal based on the gap permeability coefficient, the contact area between the seal and the housing and the pole, and the permeation time.

[0016] Furthermore, in this application, the calculation of the water permeability of the seal based on the gap permeability coefficient, the contact area between the seal and the housing and the pole, and the permeation time uses the following formula:

[0017]

[0018] in, The permeability of the porous phase is given by the given description. The transmittance coefficient of the slit is... The outer diameter of the seal is [missing information]. The inner diameter of the seal is [missing information]. The thickness of the seal after compression. The infiltration time is mentioned.

[0019] Furthermore, in this application, obtaining the slit transmittance coefficient includes:

[0020] The total water permeation of the sample cell was measured using the Karl Fischer method, and the sample cell was identical to the cell described above.

[0021] Calculate the bulk water permeability of the seal of the sample battery;

[0022] The permeability of the seal of the sample battery is calculated based on the total water permeation of the sample battery and the bulk water permeation of the seal of the sample battery.

[0023] The gap permeability coefficient is calculated based on the water permeability of the seal of the sample battery and the contact area between the seal and the casing and the terminal post of the sample battery.

[0024] Furthermore, in this application, the calculation of the gap permeability coefficient based on the gap water permeability of the sample battery's seal and the contact area between the sample battery's seal and the casing and terminals includes:

[0025] A gap transmission coefficient model is constructed, which characterizes the relationship between the gap transmission coefficient, its growth rate, and the contact area, using the following formula:

[0026]

[0027] in, The transmittance coefficient of the slit is... The rate of increase of the gap transmittance coefficient. The contact area between the seal and the casing and terminals of the sample battery is given. It is a constant.

[0028] Furthermore, in this application, the method also includes the growth rate of the slit transmittance coefficient. The acquisition process includes:

[0029] The water permeability of the seals of the sample batteries at multiple preset temperatures was obtained.

[0030] The gap permeability coefficient at multiple preset temperatures was calculated based on the water permeability of the seal of the sample battery at multiple different preset temperatures and the contact area between the seal of the sample battery and the casing and the terminal post.

[0031] The growth rate of the gap transmission coefficient is calculated based on the gap transmission coefficient at the multiple different preset temperatures and the multiple different preset temperatures. .

[0032] Furthermore, in this application, the growth rate of the gap transmission coefficient calculated based on the gap transmission coefficient at the plurality of different preset temperatures and the plurality of different preset temperatures is... Use the following formula:

[0033]

[0034] in, Indicates temperature. This represents parameters related to temperature.

[0035] In a second aspect, this application provides a battery moisture detection device, the battery including a housing, terminals passing through the housing, and a sealing member disposed between the terminals and the housing, the device comprising:

[0036] The first calculation module is configured to calculate the bulk water permeability of the seal, wherein the bulk water permeability is the amount of water that permeates through the seal into the interior of the housing.

[0037] The second calculation module is configured to calculate the water permeability of the seal, which is the amount of water that permeates into the interior of the housing through the contact interface between the seal, the pole, and the housing.

[0038] The moisture determination module is configured to determine the total amount of moisture that penetrates into the battery based on the bulk water permeability and the gap water permeability.

[0039] The above-described technical solutions of the present invention have at least one or more of the following beneficial effects:

[0040] In implementing the technical solution of the present invention, by comprehensively considering the water permeability of the sealing material itself (i.e., bulk water permeability) and the water permeability of gaps between components such as the terminal post that are in contact with the sealing material, the total amount of water that has penetrated into the battery after manufacturing is obtained. This allows for a more accurate assessment of the water intrusion situation inside the lithium battery, providing a more reliable reference for the design, manufacturing and use of the battery.

[0041] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0042] The disclosure of this invention will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Furthermore, similar numbers in the drawings are used to denote similar components, wherein:

[0043] Figure 1This is a flowchart of a battery moisture detection method provided in some embodiments of this application;

[0044] Figure 2 This is a flowchart illustrating the process of obtaining the slit transmission coefficient provided in some embodiments of this application;

[0045] Figure 3 The rate of increase of the slit transmittance provided in some embodiments of this application is A flowchart of the acquisition process;

[0046] Figure 4 This is a cross-sectional view of a portion of the battery structure provided in some embodiments of this application;

[0047] Figure 5 This is a schematic diagram of the total water permeation of batteries of models A and B provided in some embodiments of this application;

[0048] Figure 6 This is a schematic diagram showing the relationship between temperature and gap permeability of batteries of types A and B provided in some embodiments of this application;

[0049] Figure 7 This is a schematic diagram showing the relationship between the water permeability area and the water permeability coefficient of the gaps in batteries of models A and B provided in some embodiments of this application;

[0050] Figure 8 This is a schematic diagram of the structure of a battery moisture detection device provided in some embodiments of this application. Detailed Implementation

[0051] Some embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0052] The applicant's research revealed that controlling internal moisture in batteries typically involves two aspects: moisture infiltration during the manufacturing process and moisture infiltration due to material airtightness after manufacturing. Factors affecting battery moisture content during manufacturing primarily include the moisture content of various materials and the humidity of the production workshop. After manufacturing, the main pathway for moisture to infiltrate the battery is through the sealing rings on the terminals. The former can be mitigated or eliminated through baking and controlling workshop humidity, while the latter can be reduced by improving the dimensions of the terminals and sealing rings or by adjusting the sealing ring compression ratio. However, on the one hand, current methods for measuring internal battery moisture content only through disassembly and using the Karl Fischer method provide intermittent measurements, making continuous, non-destructive monitoring during manufacturing and subsequent use impossible, resulting in delayed and unreal-time moisture control. On the other hand, although initial moisture can be reduced during manufacturing through baking and humidity control, insufficient airtightness of the terminal sealing rings during use still presents the problem of external moisture continuously penetrating through bulk phase or interface defects. Existing technologies lack quantitative assessment and dynamic early warning methods for the amount of water infiltrating the sealing structure.

[0053] Based on one or more of the above-mentioned problems, this application proposes a battery moisture detection method and device. By comprehensively considering the water permeability of the sealing material itself (i.e., bulk water permeability) and the water permeability of gaps between components such as terminals that contact the sealing material, the total amount of moisture that has penetrated into the battery after manufacturing is obtained. This allows for a more accurate assessment of the moisture intrusion situation inside the lithium battery, providing a more reliable reference for the design, manufacturing, and use of the battery.

[0054] The solution of this application will now be described in detail with reference to the accompanying drawings and various embodiments.

[0055] Example 1

[0056] Figure 1 This is a flowchart of a battery moisture detection method provided in some embodiments of this application. The method is applicable to a typical battery structure including a casing, terminals, and seals. This structure achieves electrical connection through the terminals and seals (such as rubber rings, polymer gaskets, etc.) to achieve sealed isolation between the terminals and the casing, preventing external environmental media (especially moisture) from entering the battery. (Refer to...) Figure 1 As shown, the method includes the following steps:

[0057] S100: Calculate the bulk water permeability of the seal, where the bulk water permeability is the amount of water that permeates through the seal into the interior of the housing;

[0058] S200: Calculate the water permeability of the seal, where the water permeability is the amount of water that penetrates into the interior of the housing through the contact interface between the seal, the pole, and the housing.

[0059] S300: Based on the bulk water permeability and the gap water permeability, determine the total amount of water that has penetrated into the battery.

[0060] The battery moisture detection method provided in this application focuses on two possible moisture penetration paths for the seal: one is bulk penetration where moisture directly penetrates the seal body, and the other is penetration through gaps at the contact interface (or assembly section) between the seal and the terminal post and the casing. By comprehensively considering both penetration paths and quantifying the amount of these two types of penetration, an accurate assessment of the total amount of moisture intrusion into the battery is achieved, providing a basis for battery seal reliability design and lifespan prediction. This application adds bulk penetration to the gap penetration calculation and simultaneously quantifies it, upgrading the total moisture intrusion model over the battery's entire lifespan from a "single path" to a "dual path," improving prediction accuracy and enabling prediction of the total moisture penetration over ultra-long lifespans, thus providing early warning of risks.

[0061] In calculating the bulk water permeability of the seal, a method is used to quantify the amount of water that diffuses through the seal into the battery interior. Specifically, bulk water permeability refers to the cumulative mass of water molecules from the external environment that, driven by pressure and concentration differences, penetrate the microstructure of the seal material (such as molecular chain gaps and free volume) and ultimately enter the enclosed space of the casing. This calculation comprehensively considers parameters such as the inherent permeability characteristics of the seal material (such as the bulk permeability coefficient), the effective area in contact with ambient water, the thickness of the permeation path, and the contact time. By accurately calculating the bulk water permeability, the shortcomings of the seal material's water barrier performance can be revealed, providing a quantitative basis for material selection, seal structure optimization, and risk control of water intrusion throughout the battery's life cycle.

[0062] When calculating the water permeability of the seal, a method is used to quantify the amount of water that penetrates into the battery through defects at the contact interface between the seal and the terminal and the casing. Water permeability refers to the mass of water molecules from the external environment that, driven by pressure differences and capillary action, seeps into the casing through leakage channels formed by microscopic assembly gaps or contact discontinuities at the contact interface between the seal and the terminal and the casing. This calculation can be based on parameters such as the geometric characteristics of the contact interface gaps (e.g., the contact area between the seal and the casing and terminal) and the time of exposure to obtain the cumulative permeation. Accurate assessment of water permeability can effectively identify assembly process defects and the risk of interface seal failure, providing a quantitative theoretical basis for optimizing the terminal seal structure design, improving interface contact integrity, and suppressing interface leakage.

[0063] Finally, the total amount of water that penetrates into the battery is determined by the volumetric water permeation and the interstitial water permeation through the two water permeation paths mentioned above.

[0064] It should be noted that the shapes of the electrode post and the seal are not specifically limited in the embodiments of this application. They can be set according to actual product requirements without departing from the inventive concept of this application. In some specific embodiments, the electrode post has a columnar structure, and the seal has a ring-shaped structure, with the seal sleeved on the electrode post.

[0065] Understandably, the shape and size of the seal can be adjusted according to the battery's (especially the terminals') structure and dimensions, sealing requirements, and material properties. The inner and outer diameters of the seal are matched to the dimensions of the through-holes in the terminals and casing. For square aluminum-cased batteries, the outer diameter of the through-holes in the casing is larger than that of other parts of the battery. The outer diameter of the seal needs to be slightly larger than the inner diameter of the through-hole. This way, after the edges are rolled, the seal is compressed, thus achieving a seal. Therefore, the space design of the seal is smaller than its actual size, making it more stable within the battery. Research and design have shown that once its compression ratio is fixed, the compression thickness, which has a significant impact on moisture penetration, will remain unchanged.

[0066] The following descriptions use the example of a columnar pole and an annular seal to illustrate the solution of this application.

[0067] In some specific embodiments, calculating the bulk water permeability of the seal includes:

[0068] The bulk permeability coefficient of the seal is obtained, and the bulk water permeability of the seal is calculated based on the bulk permeability coefficient, the surface area of ​​the seal facing the external space of the housing, and the permeation time. The bulk permeability coefficient is determined by the battery's operating temperature and a bulk permeability coefficient model, and the bulk permeability coefficient model characterizes the relationship between the bulk permeability coefficient and temperature.

[0069] When calculating the bulk permeability of a seal, a core material property parameter is first required—the bulk permeability coefficient of the seal. This coefficient is an intrinsic physical constant that measures the ability of a specific material to allow water to pass through under unit thickness and unit pressure difference, and it forms the basis for calculating its intrinsic permeability. It's important to note that the bulk permeability coefficient is not a fixed constant. It depends on factors such as the battery's operating temperature. For example, for some polymer materials, increased temperature intensifies the thermal motion of polymer chains, expanding the free volume between molecules, thereby significantly accelerating the dissolution and diffusion rate of water molecules within the material. Therefore, to improve the accuracy of the calculation, the bulk permeability coefficient is determined using the battery's operating temperature and a bulk permeability coefficient model. This model uses temperature as the variable, characterizing the relationship between the seal's bulk permeability coefficient and temperature. By substituting the current operating temperature into this model, an accurate and effective bulk permeability coefficient value can be calculated for that specific temperature.

[0070] After obtaining the bulk permeability coefficient corresponding to the operating temperature, the final calculation can be performed by combining geometric and time parameters. These geometric parameters include, but are not limited to, the surface area of ​​the seal facing the external space of the casing. This surface area is the effective surface area of ​​the seal directly exposed to the humid environment outside the battery. This surface area is the "entry point" for moisture penetration; the larger the surface area, the more moisture penetrates in the same amount of time. The penetration time refers to the total time the battery is continuously exposed to this operating condition.

[0071] In some specific embodiments, the calculation of the bulk water permeability of the seal based on the bulk permeability coefficient, the surface area of ​​the seal facing the external space of the housing, and the permeation time uses the following formula:

[0072]

[0073] in, The volumetric water permeability, The bulk transmittance coefficient is [value missing]. The outer diameter of the seal is [missing information]. The inner diameter of the seal is [missing information]. The infiltration time is mentioned.

[0074] Specifically, the above formula describes the mass transfer process of water molecules through a smooth, dense polymer material via steady-state diffusion driven by a pressure difference. Its basic form is: Water permeability = Permeability coefficient × Area × Time. (Bulk phase water permeability) The result of the formula represents the total amount of moisture that permeates into the battery casing through the sealing material within a permeation time t. Bulk permeability coefficient. This is a core inherent property parameter of sealing materials, comprehensively reflecting the ability of water molecules to permeate or diffuse within the material. Its value determines the strength of the material's inherent barrier properties. This coefficient is determined experimentally and is strongly dependent on temperature. Taking temperature into account, the bulk permeability coefficient can be corrected using temperature correction. This improves the applicability and accuracy of calculations. The surface area of ​​the seal facing the external space of the housing represents the effective permeation area. The outer diameter of the seal defines the maximum boundary of the seal exposed to the humid environment outside the battery. The inner diameter of the seal defines the boundary between the seal and the electrode. This area is occupied by the electrode and does not participate in the permeation. The calculated area of ​​the annular ring represents the effective mass transfer area exposed to the moisture pressure difference on both sides of the seal. This allows for the direct elimination of ineffective areas covered by the pole, incorporating the final sealing structure of the seal into the analysis and improving the reliability of the solution. Moisture can only permeate through the material body within this annular region. The permeation time is the duration of the water permeation process. It's understandable that the permeation volume is directly proportional to time; the longer the time, the greater the total amount of water that infiltrates. This formula is highly suitable for calculating the bulk permeation volume of static seals with regular annular structures, such as O-rings and gaskets. It clearly shows that the amount of water permeating through the material body is not determined by the volume of the seal, but by its exposed lateral area. This provides guidance for seal design; reducing the seal thickness does not significantly reduce bulk permeation, while reducing the outer diameter R or increasing the inner diameter r (i.e., reducing the effective annular area) directly reduces permeation, providing a basis for compact design. Through this formula, the calculation of bulk permeation volume is transformed from empirical estimation into a calculable, verifiable, and optimizable quantitative indicator, thus providing guidance for battery design.

[0075] In some specific embodiments, calculating the water permeability of the seal includes:

[0076] Obtain the gap permeability coefficient, and calculate the gap water permeability of the seal based on the gap permeability coefficient, the contact area between the seal and the housing and the pole, and the permeation time.

[0077] When calculating the water permeability of a seal, the first step is to obtain the gap permeability coefficient. This coefficient is a key material and environmental characteristic parameter that comprehensively reflects the tightness of the seal material itself and the microscopic gap morphology characteristics at the interface between the seal and the housing and pole under specific pressure and media conditions. This coefficient is usually determined through prior standard experiments or obtained based on engineering experience databases. Next, by combining this gap permeability coefficient, the contact area between the seal and the housing and pole, and a predetermined infiltration time, the amount of water permeating through the gap between the seal and the housing and pole within the infiltration time is finally calculated using a defined formula.

[0078] In some specific embodiments, the calculation of the water permeability of the seal based on the gap permeability coefficient, the contact area between the seal and the housing and the pole, and the permeation time uses the following formula:

[0079]

[0080] in, The permeability of the porous phase is given by the given description. The transmittance coefficient of the slit is... The outer diameter of the seal is [missing information]. The inner diameter of the seal is [missing information]. The thickness of the seal after compression. The infiltration time is mentioned.

[0081] Specifically, the permeability of the porous body phase Transmission coefficient of the gap outer diameter of the seal Inner diameter of the seal Thickness of the seal after compression and infiltration time This is determined jointly. The formula is based on the actual contact area between the seal and the housing and pole (expressed as...). This method abstracts the seal as an analytical cylindrical side area, enabling macroscopic calculation of microscopic gaps. It comprehensively reflects the geometric characteristics of the permeation path and the material's permeability. Furthermore, by directly replacing the traditional initial diameter with the compressed thickness L, the formula incorporates the compression amount, allowing for assessment of the sensitivity of different compression ratios to gap permeability during the design phase. Its physical meaning is the amount of water passing through the gap direction per unit time due to pressure difference. Among these, the permeability of the gap volume phase is... This represents the total amount of water that permeates through the gaps between the seal and the shell / pole within a permeation time t. Gap permeability coefficient. This reflects the water permeability of the gap under unit conditions. The thickness of the seal after compression. It is the actual thickness of the seal after assembly, which is related to the width of the water penetration path and affects the penetration efficiency.

[0082] Reference Figure 2 As shown, in some specific embodiments, obtaining the slit transmittance coefficient includes:

[0083] S110: Measure the total water permeation of the sample cell based on the Karl Fischer method, wherein the sample cell is identical to the cell described above;

[0084] S120: Calculate the bulk water permeability of the seal of the sample battery;

[0085] S130: Calculate the gap permeability of the seal of the sample battery based on the total water permeability of the sample battery and the bulk water permeability of the seal of the sample battery.

[0086] S140: The gap permeability coefficient is calculated based on the water permeability of the seal of the sample battery and the contact area between the seal of the sample battery and the casing and the terminal post.

[0087] It should be noted that, in this embodiment, when obtaining the gap permeation coefficient of the battery seal, firstly, the total water permeation of the sample battery is measured using the Karl Fischer method. The sample battery selected here must be completely identical to the target battery in terms of key parameters such as structure, seal specifications, and assembly process to ensure that the measurement results accurately reflect the water permeation characteristics of the target battery, providing accurate basic data support for subsequent calculations. Secondly, the bulk water permeation of the sample battery seal is calculated. Here, bulk water permeation also refers to the total amount of water that permeates into the battery casing through the seal material within the permeation time; its specific calculation process can be referred to the above description. Subsequently, based on the obtained "total water permeation" and "bulk water permeation," the gap permeation of the seal is calculated by the difference. Since the total water permeation of the sample battery consists of both "bulk permeation" and "gap permeation," subtracting the bulk water permeation from the total permeation allows for the precise separation of the water that permeates only through the gap between the seal and the casing / terminal. This value is a key intermediate variable for calculating the gap permeation coefficient. Finally, based on the relationship between gap permeability and contact area, the gap permeability coefficient is derived. This separates the previously intertwined permeability paths, allowing for the determination of pure gap permeability without disassembling the package to inspect the gaps, thus improving testing efficiency. It also allows consideration of the impact of assembly quality on gap permeability.

[0088] In some specific embodiments, the gap permeability coefficient is calculated based on the gap water permeability of the sample battery's seal and the contact area between the sample battery's seal and the casing and terminals, including:

[0089] A gap transmission coefficient model is constructed, which characterizes the relationship between the gap transmission coefficient, its growth rate, and the contact area, using the following formula:

[0090]

[0091] in, The transmittance coefficient of the slit is... The rate of increase of the gap transmittance coefficient. The contact area between the seal and the casing and terminals of the sample battery is given. It is a constant.

[0092] Specifically, the gap permeability coefficient model can characterize the mathematical relationship between the gap permeability coefficient and key influencing factors, breaking through the limitations of traditional single-parameter calculations and more comprehensively reflecting the changing patterns of gap permeability. By binding the core indicator of "gap permeability coefficient" with parameters such as "gap permeability coefficient growth rate," "contact area," and "constant," a quantifiable and derivable calculation logic is formed, enabling... The transformation from static empirical values ​​to derivable functions provides a theoretical framework for calculating the gap permeability coefficient in conjunction with gap permeability. Furthermore, introducing the contact area factor enables reverse design of the maximum permissible contact area, providing a computational basis for seal design.

[0093] Among them, the growth rate of the gap transmittance coefficient This parameter represents the rate at which the gap permeability coefficient changes with time or other external conditions, reflecting the dynamic characteristics of the gap's water permeability. For example, during long-term use, aging of the seals may lead to an increase in the gap permeability coefficient, and this parameter quantifies this trend. The contact area between the sample battery's seals and the casing and terminals... These are pre-defined geometric parameters that reflect the distribution range of the gaps. The larger the contact area, the more potential pathways for water penetration there are theoretically, and the more significant the impact on the gap permeability coefficient. (Constant) These are usually fixed values ​​derived from experimental data calibration or theoretical derivation. Their purpose is to correct model errors and ensure that the calculated results match the actual situation. The determination of the model can be based on a large amount of sample test data to ensure the accuracy and universality of the model.

[0094] Reference Figure 3 As shown, in some specific embodiments, the method further includes the growth rate of the slit transmittance coefficient. The acquisition process includes:

[0095] S210: Obtain the water permeability of the seals of the sample batteries at multiple preset temperatures;

[0096] S220: The gap permeability coefficient at multiple different preset temperatures is calculated based on the gap water permeability of the sample battery seal at multiple different preset temperatures and the contact area between the sample battery seal and the casing and the terminal post.

[0097] S230: The growth rate of the gap transmission coefficient is calculated based on the gap transmission coefficient at the multiple different preset temperatures and the multiple different preset temperatures. .

[0098] Understandably, in the calculation of the gap permeability coefficient, the growth rate of the gap permeability coefficient is one of the key parameters of the model, which can be obtained through experimental measurements and data derivation under multiple temperature conditions. In practice, since temperature significantly affects the material properties of the seal (such as elasticity and molecular motion rate) and the water permeability, multiple different preset temperatures need to be set. At each preset temperature, the gap permeability of the sample battery seal at the corresponding preset temperature is measured using the aforementioned method of "Kal Fischer method to measure total water permeability - subtract bulk water permeability" to establish the correlation between temperature and gap permeability, providing original data support for subsequent calculations of the gap permeability coefficient at different temperatures.

[0099] Secondly, for the water permeability measured at each preset temperature, based on the relationship between water permeability and the permeability coefficient, and considering the contact area between the battery seal and the casing and terminals (the contact area does not change with temperature), the permeability coefficient corresponding to each preset temperature is calculated. This step transforms the correlation between temperature and water permeability into a direct relationship between temperature and the permeability coefficient, laying the foundation for analyzing the variation of the permeability coefficient with temperature.

[0100] Finally, the growth rate of the gap transmission coefficient was derived based on the gap transmission coefficient at multiple different preset temperatures and the results at multiple different preset temperatures. Because the gap transmittance coefficient exhibits a specific trend with increasing temperature (generally, the higher the temperature, the more vigorous the molecular motion, and the greater the transmittance coefficient), in some specific embodiments, multiple preset temperature values ​​can be used as the horizontal axis, and the corresponding gap transmittance coefficients as the vertical axis to construct a "temperature-gap transmittance coefficient" relationship curve or data model. Subsequently, mathematical methods such as linear fitting and nonlinear regression are used to analyze the slope or trend characteristics of this curve. For example, if the gap transmittance coefficient changes linearly with temperature, the slope is the growth rate; if the gap transmittance coefficient changes nonlinearly with temperature, the growth rate for different temperature ranges needs to be obtained through derivative calculation or piecewise fitting. By quantifying the degree of influence of temperature on the gap transmittance coefficient, the "growth rate" parameter that can be used in the gap transmittance coefficient model is finally obtained, ensuring that the model can adapt to the calculation needs under different temperature environments.

[0101] In some specific embodiments, the growth rate of the gap transmission coefficient is calculated based on the gap transmission coefficient at the multiple different preset temperatures and the multiple different preset temperatures. Use the following formula:

[0102]

[0103] in, Indicates temperature. This represents parameters related to temperature.

[0104] Specifically, when calculating the growth rate based on multiple preset temperatures and corresponding gap transmission coefficients, a specific formula can be used to establish a quantitative relationship between temperature and gap transmission coefficient, thereby accurately deriving the growth rate. In the above formula, temperature T refers to the multiple preset temperatures set in the previous experiments. These temperatures need to cover the temperature range of the actual battery usage scenario and are key environmental variables affecting the gap transmission coefficient. These represent parameters related to temperature, i.e., characteristic parameters that change with temperature. Their specific physical meaning can be determined by combining experimental background and permeation theory. For example, they could be properties of the sealing material that are strongly correlated with temperature, such as the molecular diffusion coefficient and elastic modulus. They could also be correction coefficients for the effect of temperature on the gap structure (e.g., temperature increases cause thermal expansion and contraction of the sealing material, thus changing the gap width). This refers to quantifying the impact of this structural change on the transmittance coefficient (without specific limitations). In practical applications, the parameters can be determined by fitting measured slit transmittance coefficients at different temperatures. The value of is determined to establish a quantitative relationship between temperature and the rate of change of the gap permeability coefficient, providing a basis for subsequent thermodynamic behavior analysis and engineering prediction.

[0105] The following specific experimental examples illustrate the scheme of this application.

[0106] Taking two different models of lithium iron phosphate aluminum-cased batteries (A and B) as examples, the inner and outer diameter parameters of the sealing components of models A and B are inconsistent. Under otherwise well-sealed conditions, moisture enters the aluminum casing through the sealing components. Considering the permeability of the sealing components, which includes the permeability of the material itself (bulk phase) and the permeability between the sealing components and the surrounding gaps, the amount of bulk water permeable over a certain period can be determined based on the material's permeability coefficient. Surface area of ​​the seal facing the external space of the housing The infiltration time is used to determine the permeability of the gaps; the permeability of the gaps can be determined based on the permeability coefficient of the gaps. Gap area (i.e., the contact area between the seal and the housing and pole) The infiltration time was obtained.

[0107] The relevant parameters of the seals for batteries of models A and B are shown in Table 1 below:

[0108] Table 1. Seal-related parameters

[0109]

[0110] Cross-sectional diagrams of partial structures of batteries A and B are shown below. Figure 4As shown, the battery includes a casing, terminals 1, and a seal 2. The casing includes a mating body (not shown) and a top cover 3. The body forms a receiving space for accommodating components such as battery cells. The top cover 1 covers the opening of the receiving space to seal it. A through hole is provided on the top cover 3. One end of the terminal 1 is electrically connected to the battery cell, and the other end passes through the through hole and is exposed to the outside of the casing. The seal 2 is disposed between the terminal 1 and the through hole. The parameters of the relevant components of batteries of models A and B are shown in Table 2 below.

[0111] Table 2 Parameters of Battery-Related Components

[0112]

[0113] Test method:

[0114] Empty batteries containing lithium-free electrolyte were stored at 25°C, 40°C, 60°C, 80°C, and 95% humidity. At regular intervals (e.g., 500 hours), electrolyte samples were taken, and the total water permeation of the sample batteries was measured using the Karl Fischer method. The lithium-free electrolyte was used to prevent the incoming water from reacting with lithium salts to form hydrofluoric acid, which would corrode the battery and affect the water content detection. The water content measured by the instrument is in ppm, which is converted to g in grams. The injection volume is 1,000,000, which will not be elaborated here.

[0115] It should be noted that the sealing materials used in the experimental examples of this application are all fluororubber, and the water permeability coefficient of fluororubber at room temperature is 0.132 g / (m²). 2 (24h). Based on the parameters provided above, the seal needs a certain compression ratio during use. The design of this compression ratio is closely related to the material properties of the sealing ring, the sealing effect, and the process requirements. For fluororubber, a compression ratio within the target value ± tolerance is suitable. As an example, the water permeability coefficient of the fluororubber was obtained under the condition of the lower limit of the compression ratio target value ± tolerance. This is done to ensure the maximum water permeability value under this design. If the maximum water permeability does not affect the safe use of the battery within a certain time, the infiltrated water can be considered to pose a relatively small safety risk to the battery. For example, if the target value ± tolerance can be 33% ± 8%, then the lower limit of the compression ratio can be 25%.

[0116] Furthermore, due to the increased thermal motion of molecular chains and the expansion of free volume in fluororubber seals, the number of permeation channels increases. Based on experimental test data and material permeation theory, the bulk permeability coefficient of fluororubber seals increases exponentially with increasing temperature. The permeability coefficients of fluororubber at other temperatures are given below, and the relationship between the bulk permeability coefficient and temperature is constructed based on the data, as shown in Table 3.

[0117] Table 3: Bulk Transmittance Coefficient at Different Temperatures

[0118]

[0119] Based on the above data, the relationship between bulk transmittance and temperature is fitted, and the relationship can be expressed as follows:

[0120]

[0121] in, Where T is the bulk transmittance coefficient and T is the temperature.

[0122] After testing, the total water permeability of batteries of models A and B is as follows: Figure 5 As shown.

[0123] Calculations (the calculation process is described above) show the relationship between temperature and gap permeability for batteries of models A and B as follows: Figure 6 As shown. (Refer to...) Figure 6 It can be seen that the relationship between temperature and bulk permeability of battery type B is approximately parallel to that of battery type A. We can use this relationship to obtain the gap permeability of the two batteries at other temperatures, and then calculate the gap water permeability at other temperatures.

[0124] The relationship between the water permeability area (i.e., the contact area between the seal and the casing and terminals) and temperature for batteries of models A and B, as shown in Table 4 below, is as follows:

[0125] Table 4 Relationship between permeable area of ​​gaps and temperature

[0126]

[0127] Calculations (the calculation process is described above) show the relationship between the water permeability area (i.e., the contact area between the seal and the casing and terminals) and the water permeability coefficient for batteries of models A and B as follows: Figure 7 As shown.

[0128] Combining the aforementioned local relationships between the gap permeability coefficient and temperature, and the gap permeability area, an integrated model is constructed by coupling the two. This model reveals a linear relationship between the gap permeability area and the gap permeability coefficient, which can be expressed as:

[0129]

[0130] in, Indicates the gap transmittance coefficient. It refers to the water permeability area of ​​the gaps (i.e., the contact area between the battery's seals and the casing and terminals). This represents the rate of increase in the gap transmittance coefficient, which is related to temperature. An exponential relationship is observed in the graph of the gap transmittance coefficient versus temperature. Assuming the intercepts at different temperatures differ little, they are approximated as a constant. The rate of increase of the temperature-dependent slit transmittance coefficient... It can be represented as:

[0131]

[0132] in, Temperature is expressed in Kelvin. This represents parameters related to temperature.

[0133] By solving the problem using known data, the model for the gap permeability coefficient, temperature, and gap permeable area is obtained as follows:

[0134]

[0135] Example 2

[0136] Corresponding to the first embodiment described above, this application also provides a battery moisture detection device, wherein the battery includes a casing, terminals passing through the casing, and a sealing member disposed between the terminals and the casing. (See also...) Figure 8 As shown, the device includes:

[0137] The first calculation module 10 is configured to calculate the bulk water permeability of the seal, wherein the bulk water permeability is the amount of water that permeates through the seal into the interior of the housing.

[0138] The second calculation module 20 is configured to calculate the water permeability of the seal, wherein the water permeability is the amount of water that permeates into the interior of the housing through the contact interface between the seal and the pole and the housing.

[0139] The moisture determination module 30 is configured to determine the total amount of moisture that penetrates into the battery based on the bulk water permeability and the gap water permeability.

[0140] In some specific embodiments, the first computing module 10 is specifically used for:

[0141] The bulk permeability coefficient of the seal is obtained, and the bulk water permeability of the seal is calculated based on the bulk permeability coefficient, the surface area of ​​the seal facing the external space of the housing, and the permeation time. The bulk permeability coefficient is determined by the battery's operating temperature and a bulk permeability coefficient model, and the bulk permeability coefficient model characterizes the relationship between the bulk permeability coefficient and temperature.

[0142] In some specific embodiments, the pole post has a columnar structure, the sealing element has a ring-shaped structure, and the sealing element is sleeved on the pole post;

[0143] The bulk water permeability of the seal is calculated using the following formula based on the bulk permeability coefficient, the surface area of ​​the seal facing the external space of the housing, and the permeation time:

[0144]

[0145] in, The volumetric water permeability, The bulk transmittance coefficient is [value missing]. The outer diameter of the seal is [missing information]. The inner diameter of the seal is [missing information]. The infiltration time is mentioned.

[0146] In some specific embodiments, the second computing module 20 is specifically used for:

[0147] Obtain the gap permeability coefficient, and calculate the gap water permeability of the seal based on the gap permeability coefficient, the contact area between the seal and the housing and the pole, and the permeation time.

[0148] In some specific embodiments, the calculation of the water permeability of the seal based on the gap permeability coefficient, the contact area between the seal and the housing and the pole, and the permeation time uses the following formula:

[0149]

[0150] in, The permeability of the porous phase is given by the given description. The transmittance coefficient of the slit is... The outer diameter of the seal is [missing information]. The inner diameter of the seal is [missing information]. The thickness of the seal after compression. The infiltration time is mentioned.

[0151] In some specific embodiments, the second computing module 20 is further configured to:

[0152] The total water permeation of the sample cell was measured using the Karl Fischer method, and the sample cell was identical to the cell described above.

[0153] Calculate the bulk water permeability of the seal of the sample battery;

[0154] The permeability of the seal of the sample battery is calculated based on the total water permeation of the sample battery and the bulk water permeation of the seal of the sample battery.

[0155] The gap permeability coefficient is calculated based on the water permeability of the seal of the sample battery and the contact area between the seal and the casing and the terminal post of the sample battery.

[0156] In some specific embodiments, the second computing module 20 is further configured to:

[0157] A gap transmission coefficient model is constructed, which characterizes the relationship between the gap transmission coefficient, its growth rate, and the contact area, using the following formula:

[0158]

[0159] in, The transmittance coefficient of the slit is... The rate of increase of the gap transmittance coefficient. The contact area between the seal and the casing and terminals of the sample battery is given. It is a constant.

[0160] In some specific embodiments, the second calculation module 20 is also used for:

[0161] The water permeability of the seals of the sample batteries at multiple preset temperatures was obtained.

[0162] The gap permeability coefficient at multiple preset temperatures was calculated based on the water permeability of the seal of the sample battery at multiple different preset temperatures and the contact area between the seal of the sample battery and the casing and the terminal post.

[0163] The growth rate of the gap transmission coefficient is calculated based on the gap transmission coefficient at the multiple different preset temperatures and the multiple different preset temperatures. .

[0164] In some specific embodiments, the growth rate of the gap transmission coefficient is calculated based on the gap transmission coefficient at the multiple different preset temperatures and the multiple different preset temperatures. Use the following formula:

[0165]

[0166] in, Indicates temperature. This represents parameters related to temperature.

[0167] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that the present invention can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer system (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of the present invention.

[0168] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0169] The technical solution provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for detecting moisture in a battery, the battery comprising a casing, terminals passing through the casing, and a sealing element disposed between the terminals and the casing, characterized in that, The battery moisture detection method includes: Calculate the bulk water permeability of the seal, where the bulk water permeability is the amount of water that permeates through the seal into the interior of the housing; Calculate the water permeability of the seal, which is the amount of water that permeates into the interior of the housing through the contact interface between the seal, the pole, and the housing. Based on the bulk water permeability and the gap water permeability, the total amount of water that has penetrated into the battery is determined. The calculation of the bulk water permeability of the seal includes: The bulk permeability coefficient of the seal is obtained, and the bulk water permeability of the seal is calculated based on the bulk permeability coefficient, the surface area of ​​the seal facing the external space of the housing, and the permeation time. The bulk permeability coefficient is determined by the battery's operating temperature and a bulk permeability coefficient model, and the bulk permeability coefficient model characterizes the relationship between the bulk permeability coefficient and temperature. The calculation of the water permeability of the seal includes: Obtain the gap permeability coefficient, and calculate the gap water permeability of the seal based on the gap permeability coefficient, the contact area between the seal and the housing and the pole, and the permeation time; The method of obtaining the gap transmittance coefficient includes: The total water permeation of the sample cell was measured using the Karl Fischer method, and the sample cell was identical to the cell described above. Calculate the bulk water permeability of the seal of the sample battery; The permeability of the seal of the sample battery is calculated based on the total water permeation of the sample battery and the bulk water permeation of the seal of the sample battery. The gap permeability coefficient is calculated based on the water permeability of the seal of the sample battery and the contact area between the seal and the casing and the terminal post of the sample battery.

2. The battery moisture detection method according to claim 1, characterized in that, The pole post has a columnar structure, the sealing element has a ring-shaped structure, and the sealing element is sleeved on the pole post; The bulk water permeability of the seal is calculated using the following formula based on the bulk permeability coefficient, the surface area of ​​the seal facing the external space of the housing, and the permeation time: in, The volumetric water permeability, The bulk transmittance coefficient is [value missing]. The outer diameter of the seal is [missing information]. The inner diameter of the seal is [missing information]. The infiltration time is mentioned.

3. The battery moisture detection method according to claim 1, characterized in that, The calculation of the water permeability of the seal based on the gap permeability coefficient, the contact area between the seal and the housing and the pole, and the permeation time uses the following formula: in, The water permeability of the gap, The transmittance coefficient of the slit is... The outer diameter of the seal is [missing information]. The inner diameter of the seal is [missing information]. The thickness of the seal after compression. The infiltration time is mentioned.

4. The battery moisture detection method according to claim 1, characterized in that, The gap permeability coefficient is calculated based on the water permeability of the seal of the sample battery and the contact area between the seal and the casing and the terminal post of the sample battery, including: A gap transmission coefficient model is constructed, which characterizes the relationship between the gap transmission coefficient, its growth rate, and the contact area, using the following formula: in, The transmittance coefficient of the slit is... The rate of increase of the gap transmittance coefficient. The contact area between the seal and the casing and terminals of the sample battery is given. It is a constant.

5. The battery moisture detection method according to claim 4, characterized in that, The method also includes the growth rate of the gap permeability coefficient. The acquisition process includes: The water permeability of the seals of the sample batteries at multiple preset temperatures was obtained. The gap permeability coefficient at multiple preset temperatures was calculated based on the water permeability of the seal of the sample battery at multiple different preset temperatures and the contact area between the seal of the sample battery and the casing and the terminal post. The growth rate of the gap transmission coefficient is calculated based on the gap transmission coefficient at the multiple different preset temperatures and the multiple different preset temperatures. .

6. The battery moisture detection method according to claim 5, characterized in that, The growth rate of the gap transmission coefficient is calculated based on the gap transmission coefficient at multiple different preset temperatures and the multiple different preset temperatures. Use the following formula: in, Indicates temperature. This represents parameters related to temperature.

7. A battery moisture detection device, the battery comprising a housing, terminals passing through the housing, and a sealing member disposed between the terminals and the housing, characterized in that, The device includes: The first calculation module is configured to calculate the bulk water permeability of the seal, wherein the bulk water permeability is the amount of water that permeates through the seal into the interior of the housing; the calculation of the bulk water permeability of the seal includes: obtaining the bulk permeability coefficient of the seal, and calculating the bulk water permeability of the seal based on the bulk permeability coefficient, the surface area of ​​the seal facing the external space of the housing, and the permeation time, wherein the bulk permeability coefficient is determined by the battery's operating temperature and a bulk permeability coefficient model, and the bulk permeability coefficient model characterizes the relationship between the bulk permeability coefficient and temperature; The second calculation module is configured to calculate the permeability of the seal through gaps, where permeability is the amount of water that permeates through the interface between the seal and the electrode and the housing into the interior of the housing. Calculating the permeability of the seal includes: obtaining a permeability coefficient; calculating the permeability of the seal based on the permeability coefficient, the contact area between the seal and the housing and the electrode, and the permeation time. Obtaining the permeability coefficient includes: measuring the total water permeation of the sample battery using the Karl Fischer method (the sample battery is identical to the battery); calculating the bulk permeability of the seal of the sample battery; calculating the permeability of the seal of the sample battery through gaps based on the total water permeation and the bulk permeability of the seal of the sample battery; and calculating the permeability coefficient based on the permeability of the seal of the sample battery and the contact area between the seal and the housing and the electrode. The moisture determination module is configured to determine the total amount of moisture that penetrates into the battery based on the bulk water permeability and the gap water permeability.

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