Battery moisture detection method and device

Abstract

The embodiment of the invention discloses a battery moisture detection method and device, a battery comprises a shell, a pole column arranged on the shell in a penetrating mode and a sealing piece arranged between the pole column and the shell, the method comprises the steps that the volume phase water permeation amount of the sealing piece is calculated, and the volume phase water permeation amount is the permeation amount of moisture entering the shell through the sealing piece; calculating the gap water permeation amount of the sealing element, wherein the gap water permeation amount is the permeation amount of water entering the interior of the shell through a contact interface between the sealing element and the pole and a contact interface between the sealing element and the shell; and based on the volume phase water permeability and the gap water permeability, determining the total permeation amount of water intruding into the battery. According to the scheme provided by the invention, the total penetration amount of the water intruding into the battery after the manufacturing is completed is obtained by comprehensively considering the water permeability of the material of the sealing element, namely the volume phase water permeability and the gap water permeability between the parts such as the pole in contact with the sealing element, so that the water intruding condition in the lithium battery can be more accurately evaluated; and a more reliable reference basis is provided for design, manufacturing and use of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery moisture detection, in particular to a battery moisture detection method and device. BACKGROUND

[0002] In the manufacturing process of lithium ion batteries, there are three very critical items that must be strictly controlled: one is dust; two is metal particles; three is moisture. If dust and metal particles are not well controlled, it will directly cause internal short circuit, fire and combustion safety accidents of the battery; and if moisture is not effectively controlled, it will also cause great harm to the performance of the battery, such as reacting with lithium salt in the electrolyte to generate hydrofluoric acid, which will corrode the battery and continue to react with lithium carbonate in the SEI film to generate lithium fluoride precipitate, thereby destroying the compactness and uniformity of the SEI film, causing the internal resistance of the battery to increase and the discharge capacity to continuously decrease, thereby shortening the cycle life of the battery. Therefore, it is very important to accurately monitor the moisture content in the battery, but currently the battery cannot be accurately monitored for water content from the manufacturing to the end of the life cycle state, and can only be disassembled at a certain stage to take the electrolyte and measure the moisture content with a Karl Fischer moisture tester. SUMMARY

[0003] In order to solve the problems of the prior art, the present application provides a battery moisture detection method and device to solve one or more technical problems existing in the prior art, which can more accurately evaluate the moisture intrusion in the lithium battery.

[0004] In a first aspect, the present application provides a battery moisture detection method, the battery comprising a shell, a pole column penetrating the shell, and a sealing element arranged between the pole column and the shell, the battery moisture detection method comprising: calculating a bulk phase water permeation amount of the sealing element, the bulk phase water permeation amount being a permeation amount of water that permeates through the sealing element into the inside of the shell; calculating a gap water permeation amount of the sealing element, the gap water permeation amount being a permeation amount of water that enters the inside of the shell through a contact interface between the sealing element and the pole column and the shell; determining a total permeation amount of water that intrudes into the inside of the battery based on the bulk phase water permeation amount and the gap water permeation amount.

[0005] Further, in the present application, the calculation of the bulk phase water permeation amount of the sealing element comprises: obtaining a bulk phase permeation coefficient of the sealing element, and calculating the bulk phase water permeation amount of the sealing element according to the bulk phase permeation coefficient, a surface area of the sealing element facing an outside space of the shell, and a permeation time, wherein the bulk phase permeation coefficient is determined by a working condition temperature of the battery and a bulk phase permeation coefficient model, and the bulk phase permeation coefficient model represents the relationship between the bulk phase permeation coefficient and the temperature.

[0006] Further, in the application, the pole post is in a columnar structure, and the sealing member is in a ring structure, and the sealing member is sleeved on the pole post; The bulk water permeation amount of the sealing member is calculated according to the bulk permeation coefficient, the surface area of the sealing member towards the outside space of the shell, and the permeation time, and the following formula is used: wherein, is the bulk water permeation amount, is the bulk permeation coefficient, is the outer diameter of the sealing member, is the inner diameter of the sealing member, is the permeation time.

[0007] Further, in the application, the calculation of the gap water permeation amount of the sealing member comprises: obtaining a gap permeation coefficient, and calculating the gap water permeation amount of the sealing member according to the gap permeation coefficient, the contact area of the sealing member with the shell and the pole post, and the permeation time.

[0008] Further, in the application, the calculation of the gap water permeation amount of the sealing member according to the gap permeation coefficient, the contact area of the sealing member with the shell and the pole post, and the permeation time uses the following formula: wherein, is the gap bulk water permeation amount, is the gap permeation coefficient, is the outer diameter of the sealing member, is the inner diameter of the sealing member, is the thickness of the sealing member after compression, is the permeation time.

[0009] Further, in the application, the obtaining of the gap permeation coefficient comprises: measuring the total water permeation amount of a sample battery based on Karl Fischer method, the sample battery being the same as the battery; calculating the bulk water permeation amount of the sealing member of the sample battery; calculating the gap water permeation amount of the sealing member of the sample battery according to the total water permeation amount of the sample battery and the bulk water permeation amount of the sealing member of the sample battery; calculating the gap permeation coefficient based on the gap water permeation amount of the sealing member of the sample battery and the contact area of the sealing member of the sample battery with the shell and the pole post.

[0010] Further, in the present application, the gap permeation coefficient is calculated based on the gap permeation amount of the sealing member of the sample battery and the contact area of the sealing member of the sample battery with the shell and the pole. A gap permeation coefficient model is constructed, which represents the relationship between the gap permeation coefficient and the growth rate of the gap permeation coefficient and the contact area. The following formula is used: wherein, is the gap permeation coefficient, is the growth rate of the gap permeation coefficient, is the contact area of the sealing member of the sample battery with the shell and the pole, is a constant.

[0011] Further, in the present application, the method further includes the process of obtaining the growth rate of the gap permeation coefficient , which includes: obtaining the gap permeation amount of the sealing member of the sample battery at a plurality of different preset temperatures; calculating the gap permeation coefficient at a plurality of different preset temperatures based on the gap permeation amount of the sealing member of the sample battery at a plurality of different preset temperatures and the contact area of the sealing member of the sample battery with the shell and the pole; calculating the growth rate of the gap permeation coefficient based on the gap permeation coefficient at a plurality of different preset temperatures and a plurality of different preset temperatures .

[0012] Further, in the present application, the growth rate of the gap permeation coefficient is calculated based on the gap permeation coefficient at a plurality of different preset temperatures and a plurality of different preset temperatures using the following formula: wherein, represents temperature, represents a parameter related to temperature.

[0013] In a second aspect, the present application provides a battery moisture detection device, the battery comprising a shell, a pole penetrating the shell, and a sealing member arranged between the pole and the shell, the device comprising: a first calculation module configured to calculate the bulk permeation amount of the sealing member, the bulk permeation amount being the amount of water penetrating into the interior of the shell through the sealing member; ​a second calculation module configured to calculate a gap water permeation amount of the sealing member, the gap water permeation amount being a permeation amount of water entering an inside of the shell through a contact interface between the sealing member and the pole and the shell; a moisture determination module configured to determine a total permeation amount of the moisture invading the inside of the battery based on the bulk water permeation amount and the gap water permeation amount.

[0014] The one or more technical solutions of the present application have at least one or more of the following advantages: In the implementation of the technical solutions of the present application, the total amount of water permeation invading the inside of the battery after being manufactured is obtained by comprehensively considering the water permeation of the sealing member itself, i.e., the bulk water permeation, and the gap water permeation between the sealing member and the pole and other components in contact with the sealing member, so that the moisture invasion in the inside of the lithium battery can be more accurately evaluated, and a more reliable reference basis is provided for the design, manufacture and use of the battery.

[0015] Additional aspects and advantages of the present application will be made apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0016] The disclosure of the present application will become more apparent from the following description in conjunction with the accompanying drawings. It is readily understood by those skilled in the art that the drawings are merely intended to illustrate the present application and are not intended to limit the scope of protection of the present application. In addition, similar numbers in the drawings are used to represent similar components, wherein: Figure 1 is a flowchart of a battery moisture detection method provided by some embodiments of the present application; Figure 2 is a flowchart of a process of obtaining a gap permeation coefficient provided by some embodiments of the present application; Figure 3 is a flowchart of a process of obtaining a growth rate of the gap permeation coefficient provided by some embodiments of the present application; Figure 4 is a sectional view of a partial structure of a battery provided by some embodiments of the present application; Figure 5 is a schematic diagram of a total moisture permeation amount of batteries of A and B types provided by some embodiments of the present application; Figure 6 is a schematic diagram of a relationship between a temperature and a gap permeation coefficient of batteries of A and B types provided by some embodiments of the present application; Figure 7 is a schematic diagram of a relationship between a gap water permeation area and a gap permeation coefficient of batteries of A and B types provided by some embodiments of the present application; Figure 8 is a structural schematic diagram of a battery moisture detection device provided by some embodiments of the present application.​ Detailed Implementation

[0017] 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.

[0018] 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.

[0019] 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.

[0020] The solution of this application will now be described in detail with reference to the accompanying drawings and various embodiments.

[0021] Example 1 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: 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; S200: calculating a gap water permeation amount of the seal, the gap water permeation amount being a permeation amount of water entering an inside of the case through a contact interface between the seal and the pole and the case; S300: determining a total water permeation amount of water invading the inside of the battery based on the bulk water permeation amount and the gap water permeation amount.

[0022] The battery water detection method provided by the embodiments of the present application focuses on two water permeation paths that may exist in the seal: one is bulk permeation in which water directly penetrates the body of the seal, and the other is gap permeation in which water penetrates through the gap of the contact interface (or assembly section) between the seal and the pole and the case. By comprehensively considering the two water permeation paths and quantitatively calculating the permeation amounts of the two types, the total amount of water invasion into the inside of the battery is accurately evaluated, which provides a basis for the design of the sealing reliability of the battery and the prediction of the service life. The present application increases the bulk water permeation amount on the basis of the gap water permeation amount and simultaneously performs quantitative calculation, so that the total water invasion amount model of the battery during the whole service life is upgraded from a "single path" to a "double path", the prediction accuracy is improved, and the total water permeation amount under an ultra-long service life can be predicted to early warn the risk.

[0023] In the calculation of the bulk water permeation amount of the seal, the permeation amount of water diffusing into the inside of the battery through the seal is quantified. Specifically, the bulk water permeation amount refers to the cumulative water mass that enters the closed space of the case under the driving action of pressure difference, concentration difference, etc. through the internal microstructure (such as the intermolecular gap, free volume, etc.) of the sealing material. This calculation can comprehensively consider the inherent permeation characteristics (such as the bulk permeation coefficient) of the sealing material, the effective area of the water in the contact environment, the thickness of the permeation path, and the action time, etc. By accurately calculating the bulk water permeation amount, the short board of the water blocking performance of the sealing material itself can be revealed, which provides quantitative basis for material selection, sealing structure optimization, and risk control of water invasion during the whole life cycle of the battery.

[0024] In the calculation of the gap water permeation amount of the seal, the permeation amount of water invading the inside of the battery through the contact interface defects between the seal and the pole and the case is quantified. The gap water permeation amount refers to the water mass that enters the inside of the case through the leakage channel formed by the micro-assembly gap or the discontinuous contact area between the contact interface between the seal and the pole and the case under the driving of pressure difference, capillary action, etc. This calculation can be based on the geometric characteristics (such as the contact area of the seal with the case and the pole, etc.) of the gap of the contact interface and other parameters, and the cumulative permeation amount is obtained by combining the action time. By accurately evaluating the gap water permeation amount, the assembly process defects, interface sealing failure risks can be effectively identified, which provides quantitative theoretical basis for optimizing the design of the sealing structure of the pole, improving the integrity of the interface contact, and inhibiting the interface leakage.

[0025] Finally, the total water permeation amount of the water invading the inside of the battery is determined by the volume water permeation amount and the gap water permeation amount invading the inside of the battery through the above two water permeation paths.

[0026] It should be noted that in the embodiments of the present application, the shape of the pole and the sealing member is not specifically limited, and can be set according to actual product requirements without departing from the inventive concept of the present application. In some specific embodiments, the pole is in a columnar structure, and the sealing member is in a ring structure, and the sealing member is sleeved on the pole.

[0027] It can be understood that the shape and size of the sealing member can be adaptively adjusted according to the structure and size of the battery (especially the pole), the sealing requirement, and the material characteristics, etc. The inner diameter and the outer diameter of the sealing member are matched with the size of the through hole formed on the pole and the shell. For a square aluminum shell battery, the outer diameter of the through hole formed on the shell is larger than other parts of the battery, and the outer diameter of the sealing member needs to be slightly larger than the inner diameter of the through hole, so that after the edge is rolled, the sealing member is compressed to achieve sealing. Therefore, the space design of the sealing member will be smaller than its actual size, and it is relatively stable in the battery. After research and design, once the compression rate is fixed, the compression thickness which greatly affects the permeation of water will not change.

[0028] The following describes the present application scheme with the pole being in a columnar structure and the sealing member being in a ring structure as examples.

[0029] In some specific embodiments, the calculating the volume water permeation amount of the sealing member comprises: obtaining the volume permeation coefficient of the sealing member, and calculating the volume water permeation amount of the sealing member according to the volume permeation coefficient, the surface area of the sealing member facing the outside space of the shell, and the permeation time, wherein the volume permeation coefficient is determined by the working temperature of the battery and a volume permeation coefficient model, and the volume permeation coefficient model represents the relationship between the volume permeation coefficient and the temperature.

[0030] In calculating the volume water permeation of the sealing member, a core material attribute parameter, the volume permeation coefficient of the sealing member, needs to be obtained first. The coefficient is an inherent physical constant that measures the water permeation capacity of a specific material under a unit thickness and a unit pressure difference, and is the basis for calculating its intrinsic water permeation. It should be noted that the volume permeation coefficient is not a constant. It depends on the working temperature of the battery and other factors. For example, for some polymer materials, the increase in temperature will intensify the thermal motion of the polymer chain segment, expand the free volume between molecules, and thus significantly accelerate the dissolution and diffusion rate of water molecules in the material. Therefore, in order to improve the accuracy of the calculation, when obtaining the volume permeation coefficient, the working temperature of the battery and the volume permeation coefficient model are used to determine the volume permeation coefficient. The variable of the volume permeation coefficient model is temperature, which represents the relationship between the volume permeation coefficient of the sealing member and the temperature. By substituting the current working temperature into the model, the accurate and effective volume permeation coefficient value at this specific temperature can be calculated.

[0031] After obtaining the volume permeation coefficient corresponding to the working temperature, the final calculation can be performed in combination with the geometric and time parameters. The geometric parameters include but are not limited to the surface area of the sealing member facing the external space of the shell. The surface area is the effective surface area of the sealing member directly exposed to the humid environment outside the battery. The surface area is the "entrance" of water permeation, and the larger the surface area, the more water permeates in the same time. The permeation time refers to the total time of the battery exposed to the working environment.

[0032] In some specific embodiments, the volume water permeation of the sealing member is calculated according to the volume permeation coefficient, the surface area of the sealing member facing the external space of the shell, and the permeation time using the following formula: wherein, is the volume water permeation of the sealing member, is the volume permeation coefficient of the sealing member, is the outer diameter of the sealing member, is the inner diameter of the sealing member, is the permeation time.

[0033] Specifically, the above formula describes the mass transfer process of water molecules permeating through a flat and dense polymer material in a steady-state diffusion manner under pressure difference driving, and its basic form is: water permeation = permeation coefficient × area × time. The volume water permeation of the sealing member is the calculation result of the formula, representing the total amount of water permeating through the sealing member material body into the shell of the battery within the permeation time t. The volume permeation coefficient of the sealing member is the core intrinsic property parameter of the sealing material, which comprehensively reflects the permeation or diffusion ability of water molecules in the material, and its value determines the strength of the intrinsic barrier performance of the material. The coefficient is determined by experiment and is strongly dependent on temperature. Considering temperature, the temperature correction of the bulk phase permeation coefficient can be used , thereby improving the applicability and accuracy of the calculation. is the surface area of the sealing member facing the outside space of the shell, which represents the effective permeation area. is the outer diameter of the sealing member, which defines the maximum boundary of the sealing member exposed to the humid environment outside the battery. is the inner diameter of the sealing member, which defines the boundary of the sealing member in contact with the pole, and this part of the area is occupied by the pole and does not participate in permeation. The calculated area of the annular shape is the effective mass transfer area of the sealing member exposed to the moisture pressure difference on both sides, and the invalid area covered by the pole can be directly excluded, and the final sealing structure of the sealing member is included in the analysis to improve the reliability of the solution. Moisture can only penetrate through the material body of this annular area. is the permeation time, i.e. the duration of the water permeation process. It can be understood that the water permeation amount is directly proportional to the time, and the longer the time, the more the total water invasion. The above formula is very suitable for calculating the bulk water permeation amount of O-rings, gaskets and other static sealing members with regular annular structure. It clearly shows that for permeation through the material body, the water amount is not determined by the volume of the sealing member, but by the exposed lateral area, thereby providing guidance for the design of the sealing member. Thinning the thickness of the sealing member will not significantly reduce the bulk permeation amount, and reducing the outer diameter R or increasing the inner diameter r (i.e. reducing the effective annular area) can directly reduce the water permeation amount, providing a basis for compact design. Through the above formula, the calculation of bulk water permeation amount is converted from empirical estimation to a quantitative index that can be calculated, verified and optimized, thereby providing guidance for battery design.

[0034] In some specific embodiments, the calculation of the gap water permeation amount of the sealing member comprises: obtaining a gap permeation coefficient, and calculating the gap water permeation amount of the sealing member according to the gap permeation coefficient, the contact area of the sealing member with the shell and the pole, and the permeation time.

[0035] 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.

[0036] 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: 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.

[0037] 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.

[0038] ReferenceFigure 2 In some specific embodiments, the obtaining the interstitial transmission coefficient comprises: S110: measuring the total moisture transmission of a sample cell based on the Karl Fischer method, the sample cell being the same as the battery; S120: calculating the bulk water transmission of the seal of the sample cell; S130: calculating the interstitial water transmission of the seal of the sample cell according to the total moisture transmission of the sample cell and the bulk water transmission of the seal of the sample cell; S140: obtaining the interstitial transmission coefficient based on the interstitial water transmission of the seal of the sample cell and the contact area of the seal of the sample cell with the shell and the pole.

[0039] It should be noted that in the embodiments of the present application, when obtaining the interstitial transmission coefficient of the battery seal, first, the total moisture transmission of a sample cell is measured by the Karl Fischer method. The sample cell selected here needs to be completely consistent with the target battery in terms of key parameters such as structure, seal specification, and assembly process, to ensure that the measurement result can truly reflect the moisture penetration characteristics of the target battery and provide accurate basic data support for subsequent calculation. Secondly, the bulk water transmission of the seal of the sample cell is calculated. The bulk water transmission here also refers to the total amount of water that penetrates through the body of the seal material into the shell of the battery within the penetration time, and the specific calculation process can refer to the foregoing description. Subsequently, the interstitial water transmission of the seal is calculated by difference according to the obtained "total moisture transmission" and "bulk water transmission". Since the total moisture transmission of the sample cell is composed of "bulk penetration" and "interstitial penetration", the water amount that penetrates only through the interstitial space between the seal and the shell and the pole can be accurately separated by subtracting the bulk water transmission from the total transmission, and this value is a key intermediate variable for calculating the interstitial transmission coefficient. Finally, based on the corresponding relationship between the interstitial water transmission and the contact area, the interstitial transmission coefficient is derived. In this way, the water transmission paths that were originally mixed together are separated, and the pure interstitial water transmission can be obtained without disassembling and checking the interstitial space, improving the test efficiency and considering the influence of assembly quality on the interstitial water transmission rate.

[0040] In some specific embodiments, the obtaining the interstitial transmission coefficient based on the interstitial water transmission of the seal of the sample cell and the contact area of the seal of the sample cell with the shell and the pole comprises: constructing an interstitial transmission coefficient model, the interstitial transmission coefficient model representing the relationship between the interstitial transmission coefficient, the growth rate of the interstitial transmission coefficient, and the contact area, and using the following formula: wherein, is the interstitial transmission coefficient, a growth rate of the gap permeation coefficient, a contact area of the sealing member of the sample battery with the shell and the pole, a constant.

[0041] Specifically, the gap permeation coefficient model can characterize the mathematical correlation between the gap permeation coefficient and the key influencing factors, break through the limitation of traditional single parameter calculation, and more comprehensively reflect the change rule of the gap permeation capacity. By binding the core index of “gap permeation coefficient” with the parameters such as “growth rate of gap permeation coefficient”, “contact area” and “constant”, a quantifiable and derivable calculation logic is formed, so that the gap permeation coefficient can be calculated by combining the gap permeation amount in the future. Moreover, by introducing the contact area factor, the reverse design of the maximum allowable contact area can be realized, thereby providing a calculation basis for the design of the sealing member.

[0042] The growth rate of the gap permeation coefficient represents the speed of the change of the gap permeation coefficient with time or other external conditions, and embodies the dynamic change characteristics of the gap permeation performance. For example, in long-term use, the aging of the sealing member may cause the gap permeation coefficient to increase, and this parameter quantifies this change trend. The contact area of the sealing member of the sample battery with the shell and the pole is a geometric parameter that has been determined in the early stage, and reflects the distribution range of the gap. The larger the contact area, the more potential paths for water penetration in theory, and the more significant the influence on the gap permeation coefficient. The constant is usually a fixed value calibrated based on experimental data or derived by theory, and its role is to correct the model error and ensure that the calculation results of the formula are consistent with the actual situation. The determination of the constant can ensure the accuracy and universality of the model by combining a large amount of sample test data.

[0043] Referring to Figure 3 , in some specific embodiments, the method further includes a process of obtaining the growth rate of the gap permeation coefficient , including: S210: obtaining the gap permeation amount of the sealing member of the sample battery at a plurality of different preset temperatures; S220: calculating the gap permeation coefficient at a plurality of different preset temperatures based on the gap permeation amount of the sealing member of the sample battery at a plurality of different preset temperatures and the contact area of the sealing member of the sample battery with the shell and the pole; S230: calculating the growth rate of the gap permeation coefficient based on the gap permeation coefficient at a plurality of different preset temperatures and a plurality of different preset temperatures.

[0044] It can be understood that in the correlation calculation of the gap transmission coefficient, the growth rate of the gap transmission coefficient is one of the key parameters of the model, which can be measured and derived from data under multiple temperature conditions. In specific implementation, since temperature can significantly affect the material properties (such as elasticity, molecular motion rate) of the sealing member and the permeability of moisture, multiple different preset temperatures need to be set. At each preset temperature, the gap water transmission amount of the sample battery sealing member at the corresponding preset temperature is measured by the method of "Karl Fischer method for measuring total water permeation amount minus body water permeation amount" to establish the corresponding relationship between temperature and gap water transmission amount, providing original data support for subsequent calculation of the gap transmission coefficient at different temperatures.

[0045] Secondly, for the gap water transmission amount measured at each preset temperature, the gap transmission coefficient corresponding to each preset temperature is calculated according to the relationship between the gap water transmission amount and the gap transmission coefficient, and the contact area of the sample battery sealing member with the shell and the pole (the contact area does not change with temperature). Through this step, the corresponding relationship between temperature and gap water transmission amount is converted into a direct correlation between temperature and gap transmission coefficient, laying a foundation for analyzing the change rule of the transmission coefficient with temperature.

[0046] Finally, based on the gap transmission coefficients at multiple different preset temperatures and the growth rates of the gap transmission coefficients derived at multiple different preset temperatures Since the gap transmission coefficient will show a certain change trend with the increase of temperature (usually the higher the temperature, the more intense the molecular motion, and the larger the transmission coefficient), in some specific embodiments, multiple preset temperature values can be taken as the abscissa, and the corresponding gap transmission coefficients can be taken as the ordinate to construct the relationship curve or data model of "temperature-gap transmission coefficient". Subsequently, the change slope or trend characteristics of the curve are analyzed by linear fitting, nonlinear regression and other mathematical methods. For example, if the gap transmission coefficient changes linearly with temperature, the slope is the growth rate; if the gap transmission coefficient changes nonlinearly with temperature, the growth rate in different temperature intervals needs to be obtained by derivative calculation or piecewise fitting. By quantifying the influence degree of temperature on the gap transmission coefficient, the "growth rate" parameter for the gap transmission coefficient model is finally obtained, ensuring that the model can adapt to the calculation requirements in different temperature environments.

[0047] In some specific embodiments, the growth rate of the gap transmission coefficient is calculated based on the gap transmission coefficients at multiple different preset temperatures and the growth rates of the gap transmission coefficients derived at multiple different preset temperatures The following formula is used: Wherein, represents temperature, represents a parameter related to temperature.

[0048] Specifically, when the growth rate is calculated based on a plurality of different preset temperatures and corresponding gap permeation coefficients, a quantitative correlation between temperature and gap permeation coefficient can be established by a specific formula to accurately derive the growth rate. In the above formula, the temperature T refers to a plurality of different preset temperatures set in the previous experiment, which cover the temperature range in the actual use scenario of the battery and are key environmental variables affecting the gap permeation coefficient. represents a parameter related to temperature, i.e., a characteristic parameter that changes with temperature, and its specific physical meaning can be determined in combination with experimental background and penetration theory. For example, it can be a molecular diffusion coefficient, an elastic modulus, etc. of the sealing material, which are strongly related to temperature, or it can be a correction coefficient of the influence of temperature on the gap structure (for example, the thermal expansion and contraction of the sealing member due to temperature rise changes the gap width, i.e., quantifies the influence of such structural changes on the permeation coefficient), which is not specifically limited here. In actual application, the value of the parameter can be determined by fitting the measured gap permeation coefficients at different temperatures, thereby establishing a quantitative relationship between temperature and the change rate of the gap permeation coefficient, providing a basis for subsequent thermodynamic behavior analysis and engineering prediction.

[0049] The scheme of the present application will be described below through some specific experimental examples.

[0050] Take two different models of lithium iron phosphate aluminum shell batteries (A and B) as examples. The inner and outer diameter parameters of the sealing members of the A and B models of batteries are different, and under the condition that other structures are well sealed, the way for water to enter the aluminum shell is the sealing member. The water permeability of the sealing member includes the water permeability of the material itself, i.e., the bulk phase water permeability, and the water permeability between the gap of the part of the sealing member in contact with the surrounding. The bulk phase water permeation amount within a certain time can be obtained according to the water permeability coefficient of the material the surface area of the sealing member facing the outside space of the shell permeation time; the gap water permeation amount can be obtained according to the gap water permeability coefficient gap area (i.e., the contact area of the sealing member with the shell and the pole) permeation time.

[0051] The relevant parameters of the sealing members of the A and B models of batteries are shown in Table 1 below: Table 1 Relevant parameters of sealing members The cross-sectional view of part of the structure of the A and B models of batteries is shown in 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. Table 2 Parameters of Battery-Related Components Test method: 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.

[0052] 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%.

[0053] 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. Table 3: Bulk Transmission Coefficient at Different Temperatures Based on the above data, the relationship between bulk transmittance and temperature is fitted, and the relationship can be expressed as follows: in, Where T is the bulk transmittance coefficient and T is the temperature.

[0054] After testing, the total water permeability of batteries of models A and B is as follows: Figure 5 As shown.

[0055] 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.

[0056] 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: Table 4 Relationship between permeable area of ​​gaps and temperature 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.

[0057] 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: 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: in, Temperature is expressed in Kelvin. This represents parameters related to temperature.

[0058] By solving the problem using known data, the model for the gap permeability coefficient, temperature, and gap permeable area is obtained as follows: Example 2 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: 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. 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. 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.

[0059] In some specific embodiments, the first computing module 10 is specifically used for: 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.

[0060] 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; 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.

[0061] In some specific embodiments, the second computing module 20 is specifically used for: 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.

[0062] 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: 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.

[0063] In some specific embodiments, the second computing module 20 is further configured to: 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.

[0064] In some specific embodiments, the second computing module 20 is further configured to: 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.

[0065] In some specific embodiments, the second calculation module 20 is also used for: 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. .

[0066] 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: in, Indicates temperature. This represents parameters related to temperature.

[0067] 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.

[0068] 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.

[0069] 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 penetrates into the battery is determined.

2. The battery moisture detection method according to claim 1, characterized in that, 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.

3. The battery moisture detection method according to claim 2, 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.

4. The battery moisture detection method according to claim 3, characterized in that, 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.

5. The battery moisture detection method according to claim 4, 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 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.

6. The battery moisture detection method according to claim 4 or 5, characterized in that, The process 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.

7. The battery moisture detection method according to claim 6, 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.

8. The battery moisture detection method according to claim 7, 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. .

9. The battery moisture detection method according to claim 8, 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.

10. 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 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. 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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