A method, apparatus, and system for testing the weight loss rate of batteries.

Abstract

This invention relates to a method, apparatus, and system for testing the weight loss rate of batteries. The testing method includes: opening a hole in a glove box or a weight loss testing device within a glove box, in an argon gas protective atmosphere where the moisture and oxygen content are both below 0.01 ppm; performing initial weight calibration in the weight loss testing device under room temperature and atmospheric pressure conditions to obtain the initial weight M1 of the battery sample; subjecting the battery sample to isothermal vacuum treatment under sealed conditions, and monitoring the rate of sample weight change over time in real time; the isothermal vacuum treatment includes a heating stage and an isothermal stage; when the rate of sample weight change per unit time under the isothermal stage is lower than a preset threshold and remains below it for a preset time, the isothermal vacuum treatment is considered to be over; after returning to room temperature and atmospheric pressure, performing final weight calibration on the battery sample to obtain the final weight M2 of the battery sample; and calculating the weight loss rate k of the battery sample, k = (M1 - M2) / M1.

Description

Technical Field

[0001] This invention relates to the field of battery performance testing technology, and in particular to a method, apparatus and system for testing the weight loss rate of batteries. Background Technology

[0002] As the new energy industry continues to demand higher energy density and safety from lithium batteries, solid-liquid hybrid lithium batteries, with their advantages of high safety from solid electrolytes and high ionic conductivity from liquid electrolytes, have become a key technological route bridging traditional liquid lithium batteries and all-solid-state lithium batteries. However, the content of liquid components in solid-liquid hybrid lithium batteries directly affects the battery's cycle stability, safety performance, and energy storage efficiency. Quantitative detection of these components has become a core requirement for industry technology control, and weight loss rate, as a key indicator of the liquid content within the battery, is a core basis for battery type definition and performance evaluation. In recent years, industry standards have increasingly clarified the requirements for testing battery weight loss rate. For example, the draft for comments on the national solid-state battery standard has set a weight loss rate of ≤0.5% as the core criterion for solid-state batteries. The weight loss rate of solid-liquid hybrid lithium batteries is usually distributed in the range of 1.68%-10.33%, and the testing methods need to balance accuracy and specificity. Especially for solid-liquid hybrid batteries, there are interactions between liquid components and solid electrolytes, such as adsorption, binding, or capillary retention, which makes the volatilization behavior of liquid components exhibit obvious staged and nonlinear characteristics.

[0003] Existing methods for testing weight loss rate mainly include traditional drying weight loss methods and thermogravimetric analysis (TG) methods, but these methods have significant drawbacks for testing solid-liquid hybrid lithium batteries: The drying loss method typically involves heating the sample at a fixed temperature, vacuum level, and processing time, and then calculating the weight loss rate based on the difference in mass before and after treatment. Traditional drying methods are mostly applicable to pure liquid or pure solid-state batteries. In solid-liquid mixed systems, the interaction between the solid electrolyte and liquid components can easily lead to incomplete evaporation of liquid substances, and it is impossible to distinguish between electrolyte decomposition weight loss and liquid component evaporation weight loss, resulting in large detection errors. Thermogravimetric analysis (TG) records the mass change of a sample with temperature in real time through a programmed temperature rise method, providing relatively complete information on the weight loss process. However, TG tests are typically based on preset heating rates and atmospheric conditions, with test parameters determined before the experiment begins, making dynamic adjustment based on the actual weight loss rate of the sample during the test difficult. For solid-liquid hybrid batteries, due to the different distribution states of liquid components in the pores of the solid electrolyte, the volatilization rates of different samples vary significantly. Under uniform programmed temperature rise and atmospheric conditions, the volatilization process of some samples may be unstable or the weight loss rate may fluctuate greatly, thus affecting the consistency of test results between different samples.

[0004] Therefore, the unique structure of solid-liquid hybrid lithium batteries makes it impossible for traditional testing devices to achieve efficient desorption and accurate measurement of liquid components. There is an urgent need to develop a dedicated testing device and method that is adapted to the characteristics of solid-liquid hybrid systems and takes into account both testing accuracy and ease of operation, so as to meet the industry's needs for quality control and technological research and development of this type of battery. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a method, apparatus, and system for testing the weight loss rate of batteries. By real-time monitoring of the weight loss process of battery samples and using the rate of sample weight change as the basis for process control and endpoint determination, combined with isothermal vacuum treatment and dynamic vacuum adjustment, stable control of the battery weight loss process is achieved, effectively improving the accuracy and repeatability of the weight loss rate test results.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for testing the weight loss rate of a battery, comprising: The battery sample to be tested is perforated in a glove box with an argon gas protective atmosphere where the moisture and oxygen content are both below 0.01 ppm, or in a weight loss rate testing device in the glove box. In the weight loss rate testing device, the initial weight was calibrated under room temperature and normal pressure conditions to obtain the initial weight M1 of the battery sample; In the weight loss rate testing device, the battery sample is subjected to isothermal vacuum treatment under sealed conditions, and the rate of change of sample weight over time is monitored in real time during the treatment process; wherein, the isothermal vacuum treatment includes a heating stage and an isothermal stage. When the rate of change of sample weight per unit time is lower than the preset threshold and continues for a preset time during the isothermal stage, the isothermal vacuum treatment is determined to be over. After the weight loss rate testing device is restored to room temperature and normal pressure, the final weight of the battery sample is calibrated to obtain the final weight M2 of the battery sample. Calculate the weight loss rate k of the battery sample, k = (M1 - M2) / M1.

[0007] Preferably, during the isothermal vacuum treatment, the heating rate of the battery sample in the heating stage and the isothermal temperature in the isothermal stage are controlled according to the liquid components in the battery sample, so that the weight change rate of the battery sample in the heating stage changes continuously rather than abruptly with the temperature rise, and reaches the isothermal temperature at which the liquid components can effectively volatilize when entering the isothermal stage.

[0008] Preferably, in the constant temperature vacuum treatment process, a first vacuum degree is used in the heating stage, and a second vacuum degree lower than the first vacuum degree is used in the constant temperature stage.

[0009] Preferably, the preset threshold is 0.01 wt% / min; the preset time is not less than 10 min; During the heating stage, the heating rate is 0.5–5 °C / min, preferably 1–3 °C / min; 10 -3 Pa ≤ Vacuum degree ≤ 10 0 Pa; During the isothermal stage, the isothermal temperature is 80-150℃, and the vacuum degree is ≤10. -3 Pa, the duration of the isothermal phase is ≥6 hours.

[0010] Preferably, during the isothermal stage, the vacuum level is dynamically adjusted according to the real-time monitored rate of sample weight change, so that the rate of sample weight change remains within a preset stable range during the isothermal stage. Specifically, when the rate of change of the sample weight is higher than the upper limit of the preset stability range, the vacuum level of the weight loss rate testing device is reduced to slow down the evaporation rate; when the rate of change of the sample weight is lower than the lower limit of the preset stability range, the vacuum level of the weight loss rate testing device is increased to accelerate the evaporation rate. The preset stability range is 0.01-0.05 wt% / min.

[0011] Preferably, the test method is applied to the weight loss rate test of solid-liquid hybrid battery systems, liquid battery systems, or solid-state battery systems; more preferably, it is applied to the weight loss rate test of solid-liquid hybrid battery systems.

[0012] Secondly, embodiments of the present invention provide a device for testing the weight loss rate of batteries, the device comprising: A sealed chamber for holding the battery sample to be tested; A vacuum pump, connected to the sealed chamber, is used to control the vacuum level inside the sealed chamber; A heating clamp, located inside the sealed chamber, is used to fix the battery sample and control the heating rate and constant temperature during the isothermal vacuum treatment stage. A balance is positioned below the heating clamp to monitor the weight of the battery sample in real time and output real-time weight data. A temperature detector is used to monitor the temperature of the battery sample in real time and output real-time temperature data; A vacuum detector is used to monitor the vacuum level inside the sealed chamber in real time and output real-time vacuum level data. The processor is configured to invoke a weight loss rate test preset program according to input instructions, control the vacuum pump and heating fixture according to the weight loss rate test preset program to perform isothermal vacuum treatment on the battery sample, and acquire real-time weight data, real-time temperature data and real-time vacuum degree data in real time; monitor the sample weight change rate over time according to the real-time weight data; determine that the isothermal vacuum treatment ends when the sample weight change rate per unit time is lower than a preset threshold and continues for a preset time; calculate and output the weight loss rate k of the battery sample, k = (M1 - M2) / M1, based on the initial weight M1 and final weight M2 of the battery sample before and after executing the weight loss rate test preset program.

[0013] Preferably, the sealed chamber is also equipped with an explosion-proof valve, which is used to automatically open and release pressure when the pressure inside the sealed chamber reaches the safe pressure relief threshold of the explosion-proof valve.

[0014] Thirdly, embodiments of the present invention provide a weight loss rate testing system for batteries, including the weight loss rate testing device described in the second aspect above.

[0015] Preferably, the weight loss rate testing system further includes a glove box and an opening treatment device; The glove box is used to provide an argon gas protective atmosphere with both moisture and oxygen content below 0.01 ppm; the weight loss rate testing device is placed inside the glove box; The hole-opening processing device includes a manual hole-opening processing device or an automatic hole-opening processing device, used to open holes in the battery sample to be tested, so that the liquid components in the battery sample can evaporate.

[0016] The weight loss rate testing method, apparatus, and system for batteries provided in this invention achieve stable, controllable, and reliable endpoint determination of the battery weight loss process by performing pore treatment on battery samples under a controlled inert atmosphere and implementing segmented isothermal vacuum treatment under sealed conditions, combined with real-time monitoring of the rate of change of sample weight over time. In particular, compared to traditional weight loss rate testing methods that use fixed temperature, fixed vacuum, and fixed treatment time, this invention no longer relies on a preset time as the test endpoint. Instead, it uses the actual weight loss behavior of the sample, with the rate of change of sample weight falling below a preset threshold for a preset time as the termination criterion, effectively avoiding test errors introduced by insufficient evaporation or overtreatment.

[0017] Furthermore, this invention implements segmented control of the heating and isothermal stages during the isothermal vacuum treatment process. Based on the volatilization characteristics of the liquid components in the battery sample, the heating rate, isothermal temperature, and vacuum level are synergistically regulated. This ensures that the sample exhibits continuous rather than abrupt weight loss behavior during the heating stage and remains within the effective volatilization temperature range of the liquid components upon entering the isothermal stage, thereby improving the stability of the liquid component volatilization process. During the isothermal stage, the vacuum level is dynamically adjusted based on the real-time monitored rate of sample weight change, maintaining the sample weight loss rate within a preset stable range. This reduces fluctuations in volatilization rates caused by differences in structure and liquid component content among different samples, significantly improving the reproducibility of weight loss rate test results across different samples, batches, and test conditions.

[0018] Furthermore, by placing the entire weight loss rate testing device inside an argon-protected glove box with low water and oxygen content, this invention effectively avoids interference from moisture and oxygen on the electrolyte and liquid components in the battery sample, ensuring the stability of the testing process and the reliability of the results. The device integrates real-time weighing, temperature monitoring, vacuum monitoring, and process parameter adjustment and control functions, and is equipped with safety structures such as explosion-proof valves, ensuring both testing accuracy and operational safety.

[0019] The weight loss rate testing method for batteries proposed in this invention is applicable not only to solid-liquid hybrid battery systems, but also to liquid battery systems and solid battery systems. It has the advantages of strong adaptability, clear operation process, and stable and reliable test results, and can provide accurate and reliable data support for battery performance evaluation and process optimization. Attached Figure Description

[0020] Figure 1 A flowchart of a battery weight loss rate testing method provided in an embodiment of the present invention; Figure 2 A schematic diagram of a battery weight loss rate testing system provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of a battery weight loss rate testing device provided in an embodiment of the present invention. Detailed Implementation

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0022] This invention provides a method, apparatus, and system for testing the weight loss rate of batteries, which can quantitatively analyze the weight loss rate of battery samples under controlled conditions to meet the testing needs of different battery systems.

[0023] Figure 1 This is a flowchart of a method for testing the weight loss rate of a battery according to an embodiment of the present invention. The following will first refer to... Figure 1 The technical solution of the present invention will be described below.

[0024] The main method execution steps of this invention include: Step 110: In a glove box with an argon gas protective atmosphere where the moisture and oxygen content are both below 0.01 ppm, or in a weight loss rate testing device in the glove box, the battery sample to be tested is perforated.

[0025] Specifically, the opening process can be performed manually or automatically. Manual opening can be carried out inside the glove box or in the weight loss rate testing device, while automatic opening can be performed directly in the weight loss rate testing device.

[0026] Operating within a glove box under an argon gas protective atmosphere with moisture and oxygen content both below 0.01 ppm can effectively prevent side reactions between battery samples and moisture or oxygen in the air during the opening process. In particular, it prevents the electrolyte from absorbing moisture, decomposing, or reacting with metallic lithium, thereby introducing additional mass changes unrelated to subsequent weight loss testing. This ensures that the weight loss mainly comes from the actual volatilization of the original liquid components inside the battery.

[0027] Step 120: In the weight loss rate testing device, the initial weight is calibrated under room temperature and normal pressure conditions to obtain the initial weight M1 of the battery sample.

[0028] The initial weight M1 at this point includes the mass of the battery sample itself and the mass of all liquid components inside the battery that have not yet undergone significant volatilization, thus providing a reliable initial benchmark for subsequent weight loss rate determination.

[0029] Step 130: In the weight loss rate testing device, under sealed conditions, the battery sample is subjected to constant temperature vacuum treatment, and the rate of change of sample weight over time is monitored in real time during the treatment process. The constant temperature vacuum treatment includes a heating stage and a constant temperature stage.

[0030] During the isothermal vacuum treatment process, the heating rate of the battery sample during the heating stage and the isothermal temperature during the isothermal stage are controlled according to the liquid components in the battery sample. This ensures that the weight change rate of the battery sample during the heating stage changes continuously rather than abruptly with the temperature increase. For example, the weight change rate during the heating stage is less than 0.02 wt% / min, and the isothermal temperature at which the liquid components can effectively volatilize is reached when entering the isothermal stage.

[0031] For battery samples undergoing weight loss testing, their liquid components are known. Therefore, based on the boiling point range, saturated vapor pressure variation characteristics with temperature, and volatilization behavior under vacuum conditions of the liquid components, the volatilization sensitivity corresponding to each temperature range during the heating stage can be determined in advance, and the corresponding heating rate can be matched accordingly, so that the driving force for volatilization of the liquid components gradually increases with temperature, rather than being released suddenly within a certain temperature range.

[0032] The purpose of this control is to avoid excessively rapid heating within a certain temperature range, which could lead to violent boiling or splashing volatilization of liquid components in a short period of time, causing an abnormally large instantaneous weight loss rate, making the weight loss process uncontrollable, damaging the sample structure, or causing large measurement errors. By controlling the heating rate, the weight change rate can be made to decrease continuously with the increase of temperature, ensuring that the volatilization process is mainly controlled by temperature and vacuum conditions, rather than being dominated by random factors. This is beneficial for the consistency of cross-sectional comparison of test results between different samples.

[0033] Specifically, a relatively low heating rate is used in the range where the vapor pressure of the liquid component rises rapidly with temperature; while a relatively high heating rate is allowed in the range where the volatilization behavior is relatively slow. This allows the rate of weight change per unit time to be controlled within a preset range throughout the entire heating phase, so that the weight loss process exhibits a continuous and controllable trend.

[0034] For commonly used liquid components, based on their physical properties and the vacuum range and temperature control accuracy achievable by the weight loss rate testing device proposed in this invention, the effective volatilization temperature range and corresponding recommended heating rate range for the liquid component under different vacuum conditions can be pre-established experimentally, thereby forming a matching heating control curve. The heating control curve includes the target heating rate for each temperature range, the target temperature for entering the isothermal stage, and the corresponding vacuum parameters. Each commonly used liquid component can have its corresponding heating control curve obtained using the above method and written into the corresponding liquid component's weight loss rate test preset program, forming a liquid component-preset program database. When the liquid component contained in the battery sample to be tested belongs to the data recorded in the established database, the corresponding preset program can be directly called for testing. When the liquid component contained in the sample to be tested is not in the established database, the relationship between the liquid component and the preset program can be established experimentally and added to the database. Alternatively, liquid components with similar physical properties and their corresponding preset programs can be found based on the liquid component in the sample to be tested. Based on computer simulation, a preset program suitable for the sample to be tested can be generated through parameter correction.

[0035] When entering the isothermal stage, the set isothermal temperature is not lower than the effective volatilization temperature range of the liquid component under the corresponding vacuum conditions, so as to ensure that the liquid component can continue to volatilize fully in the isothermal stage until it tends to stabilize.

[0036] Furthermore, different vacuum levels can be used during the isothermal vacuum treatment process, specifically during the heating and isothermal stages. For example, a first vacuum level can be used during the heating stage, while a second vacuum level lower than the first can be used during the isothermal stage. This setup allows for the suppression of premature and rapid evaporation of liquid components during the heating stage by using relatively high ambient pressure, ensuring that the weight loss behavior is primarily temperature-controlled. Conversely, during the isothermal stage, increasing the vacuum level enhances the mass transfer driving force of the liquid components, enabling them to fully and stably evaporate within the target temperature range. This shortens the time to reach a steady weightless state and improves testing efficiency.

[0037] Preferably, during the heating phase, the heating rate is 0.5–5 °C / min, more preferably 1–3 °C / min; 10 -3 Pa ≤ Vacuum degree ≤ 10 0 Pa; within this heating rate range, both testing efficiency and controllability of the weight loss process can be balanced, avoiding thermal shock. During the isothermal stage, the isothermal temperature is 80-150℃, and the vacuum degree is ≤10. -3 Pa. The isothermal temperature range is set to cover the effective volatilization temperature range of electrolyte solvents or plasticizers in common battery systems, while being below the temperature threshold at which electrolytes, binders, or electrode materials undergo significant thermal decomposition, thus ensuring that weight loss mainly comes from the volatilization of liquid components.

[0038] Furthermore, during the isothermal phase, the vacuum level can be dynamically adjusted based on the real-time monitored rate of sample weight change, ensuring that the rate of sample weight change remains within a preset stable range (e.g., 0.01-0.05 wt% / min). The allowable vacuum level adjustment is fine-tuning, with a range of ±10%.

[0039] Specifically, when the rate of sample weight change exceeds the upper limit of the preset stability range, the vacuum level of the weight loss rate testing device is reduced to slow down the evaporation rate; when the rate of sample weight change falls below the lower limit of the preset stability range, the vacuum level of the weight loss rate testing device is increased to accelerate the evaporation rate. This ensures that when testing battery samples with different structures, different liquid component contents, or different internal diffusion paths, relatively consistent weight loss kinetics conditions can be maintained during the isothermal phase, thereby reducing fluctuations in the evaporation rate caused by sample differences and significantly improving the reproducibility of weight loss rate test results and the comparability of test results between different samples.

[0040] Step 140: When the rate of change of sample weight per unit time is lower than the preset threshold and continues for a preset time during the isothermal stage, the isothermal vacuum treatment is determined to be over.

[0041] In a specific example, the preset threshold is 0.01 wt% / min; the preset time is not less than 10 min.

[0042] When the rate of weight change is consistently below the preset threshold, it indicates that the volatile liquid components in the battery sample have been basically completely evaporated. Extending the processing time further will have minimal impact on the weight loss results. Therefore, this state can be used as an objective endpoint criterion for the weight loss process, thereby avoiding errors caused by relying on fixed time or human experience to determine the endpoint.

[0043] Typically, considering the diffusion time required for the liquid components inside the battery to migrate outward from porous electrodes, separators, or composite interfaces, the evaporation process remains relatively slow even under high vacuum conditions. Therefore, it is preferable to set the isothermal stage time to be ≥6 hours. Based on meeting the 6-hour requirement, the endpoint is determined using the aforementioned method of sample weight change rate per unit time. If the isothermal stage time obtained by determining the endpoint using the sample weight change rate per unit time is less than 6 hours, then 6 hours is taken as the endpoint, and the isothermal stage ends.

[0044] Step 150: After restoring the weight loss rate testing device to room temperature and normal pressure, perform final weight calibration on the battery sample to obtain the final weight M2 of the battery sample. Step 160: Calculate the weight loss rate k of the battery sample, k = (M1 - M2) / M1.

[0045] The weight loss rate testing method for batteries proposed in this invention can be applied to the weight loss rate testing of solid-liquid hybrid battery systems, liquid battery systems, or solid-state battery systems; preferably, it is applied to the weight loss rate testing of solid-liquid hybrid battery systems. This method can effectively solve the problems of low liquid component content, complex volatilization behavior, and the inability of traditional fixed-condition testing methods to accurately reflect the true weight loss characteristics in solid-liquid hybrid batteries. It not only provides accurate and objective weight loss rate test results, but is also suitable for comparative analysis of weight loss rates of solid-liquid hybrid battery samples with different formulations and structures.

[0046] The weight loss rate testing method for batteries proposed above in this invention can be used... Figure 2 The weightlessness rate testing system shown implements this. The weightlessness rate testing system includes... Figure 3 The illustrated embodiment of the present invention provides a battery weight loss rate testing device. The following is in conjunction with... Figure 2 , Figure 3 Further explanation is needed.

[0047] exist Figure 2 and Figure 3 In the diagram, the symbols are as follows: 1. Glove box; 2. Pipeline; 3. Vacuum pump; 4. Sealed chamber; 5. Opening treatment device; 6. Heating fixture; 7. Balance; 8. Explosion-proof valve; 9. Battery sample; 10. Weight loss rate testing device.

[0048] The weight loss rate testing device 10 is installed inside the glove box 1. The hole-opening device 5 can be an automatic hole-opening device or a manual hole-opening device. When making holes in the casing of the battery sample 9, the hole-opening device 5 is pre-installed in the glove box 1.

[0049] Weight loss rate testing device 10 Figure 3 ,include: Sealed chamber 4 is used to hold the battery sample 9 to be tested; Vacuum pump 3 is connected to the interior of sealed chamber 4 through pipe 2 and is used to control the vacuum level inside sealed chamber 4; Heating clamp 6 is set in the sealed chamber to fix the battery sample 9 and to control the heating rate and constant temperature during the isothermal vacuum treatment stage; Balance 7, located below heating clamp 6, is used to monitor the weight of battery sample 9 in real time and output real-time weight data; A temperature detector (not shown in the figure) is used to monitor the temperature of battery sample 9 in real time and output real-time temperature data. A vacuum detector (not shown in the figure) is used to monitor the vacuum level inside the sealed chamber 4 in real time and output real-time vacuum level data. The processor (not shown in the figure) is used to call the weight loss rate test preset program according to the input command, control the vacuum pump 4 and the heating fixture 6 to perform isothermal vacuum treatment on the battery sample 9 according to the weight loss rate test preset program, and acquire real-time weight data, real-time temperature data and real-time vacuum degree data in real time; monitor the sample weight change rate over time according to the real-time weight data; determine that the isothermal vacuum treatment ends when the sample weight change rate per unit time is lower than the preset threshold and continues for a preset time; calculate and output the weight loss rate k of the battery sample, k = (M1 - M2) / M1, based on the initial weight M1 and the final weight M2 of the battery sample before and after executing the weight loss rate test preset program.

[0050] When using the above-mentioned device and system to test the battery weight loss rate, in an argon-protected glove box 1, under a protective atmosphere where the moisture and oxygen content are both below 0.01 ppm, a fully automatic or manual opening device 5 is used to open holes at preset positions on the battery casing within the glove box 1 or the weight loss rate testing device 10. This ensures unobstructed evaporation channels for the liquid components inside the battery and prevents side reactions between air, moisture, and the battery sample. The battery sample 9 is then transferred to the sealed chamber 4 and sealed to ensure that the protective atmosphere inside the device is not disturbed. Before sealing, the balance 7 performs initial weight calibration on the battery sample 9 under normal temperature and pressure to obtain the initial sample weight M1, and records the data to the processor.

[0051] After the sealed chamber 4 is sealed, the processor calls and executes the corresponding weightlessness rate test program according to the received external instructions. The processor sends control commands according to the test program to start the vacuum pump 3, evacuating the sealed chamber 4 to quickly establish the required vacuum level, while simultaneously monitoring the vacuum level inside the sealed chamber 4 in real time. When the vacuum level reaches the program-set trigger value, the heating fixture 6 starts the heating program, and the test program enters the isothermal vacuum treatment stage.

[0052] Heating fixture 6 heats battery sample 9, while vacuum pump 3 continues to evacuate the sealed chamber 4, executing the heating phase according to the set temperature rise and vacuum degree curves. After the heating phase ends, the temperature reaches a constant temperature. At this point, vacuum pump 3 and sealed chamber 4 together form and maintain a temperature not lower than 10°C. -3 A high vacuum environment of Pa is used to accelerate the desorption and volatilization of liquid components.

[0053] During the isothermal phase, the processor acquires sample weight data from the balance 7, temperature data from the temperature detector, and vacuum data from the vacuum detector in real time. It monitors the sample weight change rate and dynamically adjusts the vacuum level according to a preset stable range to ensure that the sample weight change rate remains within a stable range during the isothermal phase. Once the weight change rate falls below a preset threshold (e.g., 0.01 wt% / min) and remains below it for a preset time (e.g., 10 min), the isothermal vacuum treatment is considered complete. Subsequently, the device naturally returns to room temperature and atmospheric pressure. The sealed chamber 4 is opened, and in the inert environment of the glove box 1, the battery sample 9 is finally calibrated using the balance 7 to obtain the final weight M2. The processor calculates the battery sample weight loss rate k using the formula k=(M1-M2) / M1, and the result directly reflects the content of volatile liquid components inside the battery.

[0054] Preferably, the device is also equipped with an explosion-proof valve 8, which is a preferred feature to improve safety. The explosion-proof valve 8 is installed on the sealed chamber 4 of the weight loss rate testing device and is used to automatically release pressure in case of overpressure during the constant temperature vacuum treatment process. When the battery sample 9 experiences rapid evaporation of liquid components or local gas release under heating conditions (heating fixture 6 and high vacuum), causing an abnormal increase in pressure inside the sealed chamber 4, the explosion-proof valve 8 can open in time to release excess pressure, preventing damage to the sealed chamber 4 and its internal components, and avoiding safety hazards to the external environment from the volatile components. The explosion-proof valve 8 automatically closes after the pressure returns to a safe range, ensuring that the protective atmosphere and vacuum level of the sealed chamber 4 remain stable, thereby ensuring that the weight loss rate test of the battery sample 9 is conducted under safe and controllable conditions.

[0055] It is understood that the parameters or ranges such as temperature, heating rate, vacuum degree, and time defined or exemplified in the embodiments of the present invention are merely settings or descriptions in specific embodiments of the present invention. Those skilled in the art can, in practical applications, appropriately adjust or set each parameter according to the specific type and content of the liquid components in the battery sample to be tested, as well as the battery structural characteristics, combined with the temperature control accuracy and vacuum regulation capability achievable by the device, to achieve sufficient evaporation of the liquid components and accurate determination of the weight loss rate. Different parameter settings based on the technical solution of the present invention will not depart from the protection scope of the present invention.

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to a specific embodiment. Based on this embodiment, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0057] Example 1 In this embodiment, the test object is a pouch lithium-ion battery with a capacity of approximately 2Ah, and the positive electrode of the battery is LiNi. 0.8 Co 0.1 Mn 0.1 The active material is O2 (NCM811), the negative electrode is graphite, the separator is a polyethylene / polypropylene composite separator, and the electrolyte is 1M LiPF6 dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (volume ratio 1:1).

[0058] First, high-purity argon gas is continuously introduced into the argon-protected glove box 1 to control the moisture and oxygen content in the glove box 1 to below 0.01 ppm, so as to ensure that the battery will not react with air, moisture or oxygen during the opening and subsequent processing.

[0059] The battery sample is placed inside the sealed chamber 4 and secured using the heated clamp 6. Based on the battery casing design, a fully automated perforation device 5 is used to create a hole at the top of the pouch battery, ensuring unobstructed electrolyte evaporation. The perforation process is completed within the sealed chamber 4, which is located inside the glove box 1, to prevent moisture in the air from contacting the electrolyte.

[0060] Balance 7 measures the initial weight of the sample after the hole is opened. Balance M1 measures 48g and records the data to the processor.

[0061] The sealed chamber 4 is sealed. Based on externally input instructions, the processor invokes the corresponding preset program for weightlessness testing and, according to this program, controls the vacuum pump 3 to start evacuating the chamber, reducing the pressure inside the sealed chamber 4 to 0.8 × 10⁻⁶. -3Pa, simultaneously controlling the start of heating fixture 6 to heat battery sample 9 to 110℃ at a heating rate of 2℃ / min. During the heating phase, balance 7 collects sample weight in real time, and the processor calculates and monitors that the weight change rate is always less than 0.02wt% / min to ensure that there is no localized rapid boiling or splashing of liquid components throughout the process.

[0062] After the temperature is raised to 110℃, the program enters the constant temperature stage. The constant temperature time is set to be no less than 6 hours. At the same time, the processor dynamically monitors the weight change rate and makes appropriate fine adjustments to the vacuum degree based on real-time data. The fine adjustment range is ±10% to keep the weight change rate within the balance range of 0.01–0.05wt% / min during the constant temperature stage.

[0063] When the vacuum degree has been finely adjusted to 10%, at 8 hours and 15 minutes of the isothermal stage, the sample weight change rate was found to be lower than the preset threshold of 0.01wt% / min. This state was then maintained for 10 minutes. At 8 hours and 25 minutes of the isothermal stage, the processor determined that the isothermal vacuum treatment had reached a stable state and that the volatile liquid components had basically evaporated. The isothermal stage ended and the process entered the room temperature and pressure recovery stage.

[0064] The processor controls the shutdown of the heating clamp 6 and the vacuum module 3, and controls the opening of the one-way air inlet valve (not shown in the figure) set on the sealed chamber 4. After the temperature and pressure inside the sealed chamber 4 naturally return to room temperature and normal pressure, the sealed chamber 4 is opened, and the final weight of the battery sample is measured by the balance 7. The balance M2 balance is 45.2g.

[0065] The weight loss rate of the battery sample was calculated using the formula k=(M1-M2) / M1, which is approximately 5.8% (48g-45.2g) / 48g. This data reflects the content of volatile liquid components inside the pouch battery.

[0066] As can be seen from this embodiment, the isothermal vacuum treatment method and weight loss rate testing device described in this invention can accurately determine the weight loss rate of liquid components in soft-pack lithium batteries under safe and controllable conditions.

[0067] The weight loss rate testing method, apparatus, and system for batteries provided in this invention achieve stable, controllable, and reliable endpoint determination of the battery weight loss process by performing pore treatment on battery samples under a controlled inert atmosphere and implementing segmented isothermal vacuum treatment under sealed conditions, combined with real-time monitoring of the rate of change of sample weight over time. In particular, compared to traditional weight loss rate testing methods that use fixed temperature, fixed vacuum, and fixed treatment time, this invention no longer relies on a preset time as the test endpoint. Instead, it uses the actual weight loss behavior of the sample, with the rate of change of sample weight falling below a preset threshold for a preset time as the termination criterion, effectively avoiding test errors introduced by insufficient evaporation or overtreatment.

[0068] Furthermore, this invention implements segmented control of the heating and isothermal stages during the isothermal vacuum treatment process. Based on the volatilization characteristics of the liquid components in the battery sample, the heating rate, isothermal temperature, and vacuum level are synergistically regulated. This ensures that the sample exhibits continuous rather than abrupt weight loss behavior during the heating stage and remains within the effective volatilization temperature range of the liquid components upon entering the isothermal stage, thereby improving the stability of the liquid component volatilization process. During the isothermal stage, the vacuum level is dynamically adjusted based on the real-time monitored rate of sample weight change, maintaining the sample weight loss rate within a preset stable range. This reduces fluctuations in volatilization rates caused by differences in structure and liquid component content among different samples, significantly improving the reproducibility of weight loss rate test results across different samples, batches, and test conditions.

[0069] Furthermore, by placing the entire weight loss rate testing device inside an argon-protected glove box with low water and oxygen content, this invention effectively avoids interference from moisture and oxygen on the electrolyte and liquid components in the battery sample, ensuring the stability of the testing process and the reliability of the results. The device integrates real-time weighing, temperature monitoring, vacuum monitoring, and process parameter adjustment and control functions, and is equipped with safety structures such as explosion-proof valves, ensuring both testing accuracy and operational safety.

[0070] The weight loss rate testing method for batteries proposed in this invention is applicable not only to solid-liquid hybrid battery systems, but also to liquid battery systems and solid battery systems. It has the advantages of strong adaptability, clear operation process, and stable and reliable test results, and can provide accurate and reliable data support for battery performance evaluation and process optimization.

[0071] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0072] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented in hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0073] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for testing the weight loss rate of batteries, characterized in that, The testing method includes: The battery sample to be tested is perforated in a glove box with an argon gas protective atmosphere where the moisture and oxygen content are both below 0.01 ppm, or in a weight loss rate testing device in the glove box. In the weight loss rate testing device, the initial weight was calibrated under room temperature and normal pressure conditions to obtain the initial weight M1 of the battery sample; In the weight loss rate testing device, the battery sample is subjected to isothermal vacuum treatment under sealed conditions, and the rate of change of sample weight over time is monitored in real time during the treatment process; wherein, the isothermal vacuum treatment includes a heating stage and an isothermal stage. When the rate of change of sample weight per unit time is lower than the preset threshold and continues for a preset time during the isothermal stage, the isothermal vacuum treatment is determined to be over. After the weight loss rate testing device is restored to room temperature and normal pressure, the final weight of the battery sample is calibrated to obtain the final weight M2 of the battery sample. Calculate the weight loss rate k of the battery sample, k = (M1 - M2) / M1.

2. The method for testing the weight loss rate of a battery according to claim 1, characterized in that, During the isothermal vacuum treatment, the heating rate of the battery sample during the heating stage and the isothermal temperature during the isothermal stage are controlled according to the liquid components in the battery sample. This ensures that the weight change rate of the battery sample during the heating stage changes continuously rather than abruptly with the temperature increase, and reaches the isothermal temperature at which the liquid components can effectively volatilize when entering the isothermal stage.

3. The method for testing the weight loss rate of a battery according to claim 1, characterized in that, During the constant temperature vacuum treatment process, a first vacuum degree is used during the heating stage, and a second vacuum degree lower than the first vacuum degree is used during the constant temperature stage.

4. The method for testing the weight loss rate of a battery according to claim 1, characterized in that, The preset threshold is 0.01 wt% / min; the preset time is not less than 10 min; During the heating stage, the heating rate is 0.5–5 °C / min, preferably 1–3 °C / min; 10 -3 Pa ≤ Vacuum degree ≤ 10 0 Pa; During the isothermal stage, the isothermal temperature is 80-150℃, and the vacuum degree is ≤10. -3 Pa, the duration of the isothermal phase is ≥6 hours.

5. The method for testing the weight loss rate of a battery according to claim 1, characterized in that, During the isothermal phase, the vacuum level is dynamically adjusted based on the real-time monitored rate of sample weight change, so that the rate of sample weight change remains within a preset stable range during the isothermal phase. Specifically, when the rate of change of the sample weight is higher than the upper limit of the preset stability range, the vacuum level of the weight loss rate testing device is reduced to slow down the evaporation rate; when the rate of change of the sample weight is lower than the lower limit of the preset stability range, the vacuum level of the weight loss rate testing device is increased to accelerate the evaporation rate. The preset stability range is 0.01-0.05 wt% / min.

6. The method for testing the weight loss rate of a battery according to claim 1, characterized in that, The test method is applied to the weight loss rate test of solid-liquid hybrid battery systems, liquid battery systems, or solid-state battery systems; preferably, it is applied to the weight loss rate test of solid-liquid hybrid battery systems.

7. A device for testing the weight loss rate of batteries, characterized in that, The device includes: A sealed chamber for holding the battery sample to be tested; A vacuum pump, connected to the sealed chamber, is used to control the vacuum level inside the sealed chamber; A heating clamp, located inside the sealed chamber, is used to fix the battery sample and control the heating rate and constant temperature during the isothermal vacuum treatment stage. A balance is positioned below the heating clamp to monitor the weight of the battery sample in real time and output real-time weight data. A temperature detector is used to monitor the temperature of the battery sample in real time and output real-time temperature data; A vacuum detector is used to monitor the vacuum level inside the sealed chamber in real time and output real-time vacuum level data. The processor is configured to invoke a weight loss rate test preset program according to input instructions, control the vacuum pump and heating fixture according to the weight loss rate test preset program to perform isothermal vacuum treatment on the battery sample, and acquire real-time weight data, real-time temperature data and real-time vacuum degree data in real time; monitor the sample weight change rate over time according to the real-time weight data; determine that the isothermal vacuum treatment ends when the sample weight change rate per unit time is lower than a preset threshold and continues for a preset time; calculate and output the weight loss rate k of the battery sample, k = (M1 - M2) / M1, based on the initial weight M1 and final weight M2 of the battery sample before and after executing the weight loss rate test preset program.

8. The weight loss rate testing device for batteries according to claim 7, characterized in that, The sealed chamber is also equipped with an explosion-proof valve, which is used to automatically open and release pressure when the pressure inside the sealed chamber reaches the safe pressure relief threshold of the explosion-proof valve.

9. A weight loss rate testing system for batteries, characterized in that, The weightlessness rate testing system includes the weightlessness rate testing device as described in claim 7 or 8.

10. The weightlessness rate testing system according to claim 9, characterized in that, The weightlessness rate testing system also includes a glove box and an opening treatment device; The glove box is used to provide an argon gas protective atmosphere with both moisture and oxygen content below 0.01 ppm; the weight loss rate testing device is placed inside the glove box; The hole-opening processing device includes a manual hole-opening processing device or an automatic hole-opening processing device, used to open holes in the battery sample to be tested, so that the liquid components in the battery sample can evaporate.

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