Evaluation method of lithium battery gas production and parameter optimization method in aging process

Abstract

This invention relates to a method for evaluating the gas production of lithium batteries and a parameter optimization method in the aging process. The method uses a lithium battery gas production evaluation device to obtain the gas production of the lithium battery. The device includes, from top to bottom: a receiving chamber filled with liquid; a liquid collector located below the receiving chamber to collect overflowing liquid; and a mass meter located below the liquid collector, used to measure the total mass of the liquid collector and the liquid within it. This method can record the gas production and rate of the lithium battery under different conditions in real time, has a wide range of applications, low cost, and is easy to operate.

Description

Technical Field

[0001] This invention relates to the field of lithium battery testing technology, and in particular to a method for evaluating the gas production of lithium batteries and a method for optimizing parameters in the aging process. Background Technology

[0002] In the 1990s, lithium-ion batteries were successfully developed and applied to the market as a new type of green rechargeable battery. Their development has been rapid over the past decade or so, consistently holding the largest market share in the small rechargeable battery market. In recent years, with the rapid growth in the production of power lithium-ion batteries, the product structure of lithium-ion batteries has also undergone significant changes. The proportion of lithium-ion batteries used in electric vehicles is constantly increasing, making them the dominant force in the lithium-ion battery industry. Furthermore, with the rapid penetration of lithium-ion batteries in energy storage power stations, 5G base stations, and other fields, the market share of lithium-ion batteries for energy storage is also continuously increasing.

[0003] As the market share of lithium batteries continues to increase and their application areas expand, the requirements for their performance and safety are also becoming more stringent, leading to more in-depth research. Gas production in lithium batteries has always been a key focus for researchers, as it directly impacts battery performance and safety. Excessive gas production can result in poor adhesion between the positive and negative electrodes, incomplete charging and discharging, reduced capacity, and significantly shortened battery life. Continuous gas production during use can cause the battery to swell, deforming the casing or leading to leakage. Poor adhesion between the positive and negative electrodes can also lead to continuous lithium plating, ultimately resulting in safety incidents. Therefore, optimizing formulations and processes to reduce gas production is crucial.

[0004] Currently, there are limited methods for studying gas production in lithium batteries, primarily relying on high-end gas chromatography-mass spectrometry (GC-MS). This equipment is expensive and can only measure the amount of gas produced before and after the reaction, failing to characterize the gas production volume and rate during the reaction process in real time. Furthermore, it is extremely inconvenient for situations with large sample sizes and frequent experiments. Therefore, developing a simple and easy-to-operate device and method for characterizing gas production is particularly necessary. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the technical defects of the prior art, which is that the gas production testing equipment for lithium batteries is expensive and inconvenient for frequent testing.

[0006] To address the aforementioned technical problems, this invention provides a method for evaluating the gas production of a lithium battery. The method uses a lithium battery gas production evaluation device to obtain the gas discharge volume of the lithium battery. The lithium battery gas production evaluation device comprises, from top to bottom, the following components arranged sequentially:

[0007] A container filled with liquid;

[0008] A liquid collector is located below the receiving chamber to collect liquid that overflows from the receiving chamber;

[0009] A mass measuring device is located below the liquid collector, and the mass measuring device is used to measure the total mass of the liquid collector and the liquid in the liquid collector;

[0010] The method for evaluating the gas production of lithium batteries includes the following steps:

[0011] S1. Immerse the lithium battery in the liquid in the container;

[0012] S2. Use a mass measuring instrument to measure and obtain the initial total mass m0 of the liquid collector and the liquid in the liquid collector;

[0013] S3. Charge the lithium battery, record the reading of the mass meter at fixed intervals, and obtain a dataset M = {m1, m2, m3, ... m}. n}, where m n This represents the reading of the mass measuring instrument during the nth recording.

[0014] S4. Calculate the displacement V of the lithium battery at each time point: V = {v1, v2, v3, ... v} n}, where v n Let n be the exhaust volume corresponding to the nth time point. ρ is the density of the liquid.

[0015] Preferably, the process after S4 includes:

[0016] S5. Based on the amount of lithium battery emissions at each time point, plot a curve fitting graph of the amount of emissions changing over time.

[0017] Preferably, the container is further provided with a clamp for fixing the lithium battery, which fixes the lithium battery so that the electrodes of the lithium battery are exposed above the liquid surface.

[0018] Preferably, the electrodes and charging equipment of the lithium battery are sealed and placed in the liquid of the containment chamber.

[0019] Preferably, the mass measuring instrument is an electronic balance.

[0020] Preferably, the container is a temperature-adjustable container.

[0021] This invention discloses a parameter optimization method for lithium battery aging process, based on the above-mentioned method for evaluating the gas production of lithium batteries, including:

[0022] The variable to be optimized in the lithium battery aging process is selected as ambient temperature, which is controlled by adjusting the temperature of the liquid in the containment chamber.

[0023] The exhaust volume of lithium batteries was tested at different ambient temperatures, and the ambient temperature at which the exhaust volume reached a stable level in the shortest time was selected as the optimal aging ambient temperature.

[0024] This invention discloses a parameter optimization method for lithium battery aging process, based on the above-mentioned method for evaluating the gas production of lithium batteries, including:

[0025] The variable to be optimized in the lithium battery aging process is the battery charging amount.

[0026] The displacement of lithium batteries under different battery charge levels was tested, and the minimum battery charge level corresponding to the stable displacement was selected as the optimal battery charge level in the aging process.

[0027] This invention discloses a parameter optimization method for lithium battery aging process, based on the above-mentioned method for evaluating the gas production of lithium batteries, characterized by comprising:

[0028] The variable to be optimized in the lithium battery aging process is selected as the charging current.

[0029] The displacement of lithium batteries under different charging currents was tested, and the minimum charging current corresponding to the stable displacement was selected as the optimal charging current in the aging process.

[0030] This invention discloses a parameter optimization method for lithium battery aging process, based on the above-mentioned method for evaluating the gas production of lithium batteries, including:

[0031] The variables to be optimized in the lithium battery aging process are ambient temperature T, battery charge Q, and charging current I.

[0032] By changing the ambient temperature, battery charge, and charging current, the displacement V of the lithium battery was tested under different ambient temperatures, battery charge, and charging currents, where 10℃ < T < 60℃, 0 < Q < 100%, and 0.05C < I < 1.0C, where C is the rated capacity of the lithium battery cell.

[0033] Based on different ambient temperatures T, battery charge Q, and charging current I, a function V(T,Q,I) is constructed, and the ambient temperature T, battery charge Q, and charging current I corresponding to the maximum exhaust volume V are selected as the optimal solution.

[0034] The technical solution of the present invention has the following advantages compared with the prior art:

[0035] 1. This invention can record the amount and rate of gas production of lithium batteries under different conditions in real time.

[0036] 2. This invention has a wide range of applications. It can not only study the differences between different raw materials and evaluate the impact of different lithium battery production processes, but also be used to evaluate the safety of battery material systems.

[0037] 3. The corresponding device and method in this invention are simple to operate and have low cost.

[0038] 4. Traditional lithium battery gas generation metering methods require cutting open the battery cell to measure the gas output. This invention eliminates the need to cut open the battery cell, enabling non-destructive testing of the battery.

[0039] 5. The battery cell in this invention is completely sealed and does not come into contact with the outside world, so there is no risk of moisture entering or air leakage.

[0040] 6. The battery cell of the present invention is tightly sealed before the soft pack is sealed, and then placed in the lithium battery gas production evaluation device. In this way, as long as the cell produces gas, the amount of gas produced by the battery can be measured. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the device for evaluating gas generation in lithium batteries according to the present invention.

[0042] Figure 2 A graph showing the displacement of the battery as a function of its state of charge (SOC).

[0043] Explanation of the markings on the attached diagrams: 10, container; 20, liquid collector; 30, mass measuring instrument; 40, iron frame; 50, lithium battery. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0045] Reference Figure 1 As shown, the present invention discloses a method for evaluating the gas production of a lithium battery. The gas production of the lithium battery is obtained based on a lithium battery gas production evaluation device. The lithium battery gas production evaluation device includes a receiving chamber 10, a liquid collector 20 and a mass meter 30 arranged sequentially from top to bottom.

[0046] The container 10 is filled with liquid. The container 10 can be placed on the iron frame 40 or fixed in other ways.

[0047] The liquid collector 20 is located below the receiving chamber 10 to collect liquid overflowing from the receiving chamber 10.

[0048] The mass meter 30 is located below the liquid collector 20, and the mass meter 30 is used to measure the total mass of the liquid collector 20 and the liquid in the liquid collector 20.

[0049] The method for evaluating the gas production of lithium batteries in this invention includes the following steps:

[0050] S1. Immerse the lithium battery 50 in the liquid in the container 10.

[0051] S2. Use mass measuring instrument 30 to measure and obtain the initial total mass m0 of liquid collector 20 and the liquid in liquid collector 20.

[0052] S3. Charge the lithium battery 50, and record the reading of the mass meter 30 at fixed intervals to obtain a dataset M = {m1, m2, m3, ... m}. n}, where m n This represents the reading of the mass meter 30 during the nth recording.

[0053] S4. Calculate the displacement V of lithium battery 50 at each time point: V = {v1, v2, v3, ... v} n}, where v n Let n be the exhaust volume corresponding to the nth time point. ρ is the density of the liquid.

[0054] S5. Based on the displacement of lithium battery 50 at each time point, plot a curve fitting graph of the displacement changing over time.

[0055] It should be noted that in this invention, when the lithium battery is powered on, it generates gas, which causes the battery to swell. This swelling causes the liquid in the containment chamber to overflow into the mass measuring device. By acquiring data from the mass measuring device, the amount of gas discharged can be calculated.

[0056] In this invention, the battery cell is completely sealed and does not come into contact with the outside world, eliminating the risk of moisture ingress or gas leakage. Specifically, the battery cell is tightly sealed before being placed in the soft pack, and then placed in a lithium battery gas generation assessment device. In this way, whenever the cell generates gas, the amount of gas produced by the battery can be measured.

[0057] In one embodiment, the receiving chamber 10 of the present invention is further provided with a clamp for fixing the lithium battery 50, which fixes the lithium battery 50 so that the electrodes of the lithium battery 50 are exposed above the liquid surface. By exposing the electrodes of the lithium battery 50 above the liquid surface, it is convenient to charge the lithium battery 50. In another embodiment, the clamp may not be used, and the electrodes of the lithium battery 50 and the connection between the lithium battery electrodes and the charging device may be sealed and placed directly in the liquid of the receiving chamber 10, while the charging device is placed outside. In this way, charging can be performed directly in the liquid.

[0058] In this invention, the mass measuring device 30 is an electronic balance. The receiving chamber 10 can be a beaker. The liquid collector 20 can be a watch glass. The electronic balance can record data in real time and export the recorded data, thus facilitating the acquisition of a mass dataset that changes over time for subsequent calculations. Furthermore, a high-precision electronic balance can be selected, which has relatively high measurement accuracy.

[0059] The container 10 is a temperature-adjustable container. Specifically, a resistance heating wire and a temperature sensor are installed inside the container. The resistance heating wire heats the liquid in the container, and the temperature sensor collects the liquid temperature. When the liquid reaches a preset temperature, the resistance heating wire stops heating. By cooperating with the temperature sensor, the temperature of the liquid in the container 10 can be adjusted. Furthermore, the container 10 in this invention can also be a water bath.

[0060] In the existing lithium battery manufacturing process, the formation of lithium-ion batteries after electrolyte filling generally involves the following steps:

[0061] (1) Charge the lithium battery to form a dense and thin SE I film on the surface of the negative electrode. The SE I film is mainly used to protect the negative electrode and electrolyte from further reaction. The quality of the SE I film formation on the surface of the negative electrode is directly related to the ambient temperature, charging current and the amount of electricity charged during charging. (2) Set aside. (3) Vent the gas to remove the waste gas generated in (1) and (2). (4) Seal the lithium battery.

[0062] Therefore, in order to improve the efficiency of the aging process, it is extremely important to select appropriate ambient temperature, battery charge amount and charging current. Below, this invention discloses some parameter optimization methods in the lithium battery aging process.

[0063] This invention discloses a parameter optimization method for lithium battery aging process, based on the above-mentioned method for evaluating the gas production of lithium batteries, including:

[0064] The variable to be optimized in the lithium battery aging process is selected as ambient temperature, which is controlled by adjusting the temperature of the liquid in the containment chamber.

[0065] The exhaust volume of lithium batteries was tested at different ambient temperatures, and the ambient temperature at which the exhaust volume reached a stable level in the shortest time was selected as the optimal aging ambient temperature.

[0066] This invention discloses a parameter optimization method for lithium battery aging process, based on the above-mentioned method for evaluating the gas production of lithium batteries, including:

[0067] The variable to be optimized in the lithium battery aging process is the battery charging amount.

[0068] The displacement of lithium batteries under different battery charge levels was tested, and the minimum battery charge level corresponding to the stable displacement was selected as the optimal battery charge level in the aging process.

[0069] This invention discloses a parameter optimization method for lithium battery aging process, based on the above-mentioned method for evaluating the gas production of lithium batteries, including:

[0070] The variable to be optimized in the lithium battery aging process is selected as the charging current.

[0071] The displacement of lithium batteries under different charging currents was tested, and the minimum charging current corresponding to the stable displacement was selected as the optimal charging current in the aging process.

[0072] This invention discloses a parameter optimization method for lithium battery aging process, based on the above-mentioned lithium battery gas production evaluation method, characterized by comprising:

[0073] The variables to be optimized in the lithium battery aging process are ambient temperature T, battery charge Q, and charging current I.

[0074] The displacement V of the lithium battery was tested under different ambient temperatures, battery charge levels, and charging currents, where 0℃ < T < 60℃, 0 < Q < 100%, and 0.05C < I < 1.0C (where C is the rated capacity of the lithium battery cell).

[0075] Based on different ambient temperatures T, battery charge Q, and charging current I, a function V(T,Q,I) is constructed, and the ambient temperature T, battery charge Q, and charging current I corresponding to the maximum exhaust volume V are selected as the optimal solution.

[0076] The technical solutions of the present invention will be further described and explained below with reference to specific embodiments.

[0077] Example 1:

[0078] This embodiment uses the apparatus and method to evaluate the gas production of a battery during the formation process.

[0079] Positive electrode preparation: Using N-methylpyrrolidone (NMP) as a solvent, the positive electrode active material (LiMn2O4), conductive agent, and PVDF are mixed in a mass ratio of 97.5:1.0:1.5 to prepare a positive electrode slurry. The uniformly stirred slurry is coated onto the surface of a 15µm current collector aluminum foil, dried, and then rolled and sliced ​​to obtain the positive electrode sheet.

[0080] Negative electrode fabrication: Using NMP as a solvent, artificial graphite, conductive agent, and binder are mixed in a mass ratio of 95:1.0:4.0 to prepare a negative electrode slurry. The uniformly stirred slurry is coated onto the surface of an 8µm current collector copper foil, dried, and then rolled and sliced ​​to obtain the negative electrode sheet.

[0081] The positive electrode, negative electrode, separator, and electrolyte were assembled into a pouch cell (3g electrolyte filling). The cell was left to stand for 24 hours. Then, a clamp was used to support the cell above the beaker, ensuring the cell itself was below the electrolyte level and the aluminum-plastic film seal area was above the liquid level. Water was poured into the beaker until it overflowed and flowed into a watch glass on the balance. The cell was allowed to stand for 30 minutes, and the balance reading was recorded as 1.2608g. The battery was then charged at a constant current of 0.3A and a voltage of 4.2V, with charging data recorded every minute. The balance reading was taken every 10 minutes. The final balance reading was 10.6742g.

[0082] Throughout the process, the battery's charging capacity was 465mA, and the amount of gas produced was (10.6742-1.2608) / 1 = 9.4134mL. The gas production mainly occurred before the state of charge (SOC) reached 20%.

[0083] See Figure 2 The figure shows the displacement curve as a function of SOC during battery charging.

[0084] Example 2:

[0085] The preparation processes for the positive and negative electrodes are the same as in Example 1.

[0086] Assemble the positive electrode, negative electrode, separator, and electrolyte into a pouch cell (increase the electrolyte volume to 5g) and let it stand for 24 hours.

[0087] Place the battery in a beaker, fill it with water, and charge it. The charging conditions are the same as in Example 1.

[0088] To simplify the experimental process, only the balance readings before and after charging were recorded, which were 1.4721g and 13.1712g, respectively.

[0089] The total gas produced during the entire process was (13.1712 - 1.4721) / 1 = 11.6991 mL. This represents an increase of nearly 25% in gas production compared to Example 1. This indicates that the amount of electrolyte added has a significant impact on the gas production during the battery aging process.

[0090] Example 3:

[0091] This embodiment uses the device and method to evaluate the gas production of a battery when it is stored at high temperature.

[0092] The positive and negative electrode sheets were fabricated as in Example 1. The positive and negative electrode sheets, separator, and electrolyte were assembled into a pouch cell (3g electrolyte injection), and then subjected to aging treatment to obtain the finished pouch cell. The battery capacity was tested at 560mA, and the battery was finally fully charged.

[0093] Use clamps to support the beaker, ensuring the battery cell is below the liquid level and the aluminum-plastic film sealing area is above the liquid surface. Place the constant-temperature water bath heating rod into the beaker and pour water into it until it overflows and flows into the watch glass on the balance. Let it stand for 30 minutes and read the balance reading as 1.7614 g. Heat the water in the beaker to a constant temperature of 60°C and maintain this temperature for 24 hours. The final balance reading is 5.4182 g.

[0094] The gas produced during the process is (5.4182-1.7614) / 1=3.6568mL.

[0095] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for optimizing parameters in a lithium battery aging process based on an evaluation method for the gas production of lithium batteries, characterized by include: The method for evaluating the gas production of the lithium battery includes: obtaining the gas discharge volume of the lithium battery based on a lithium battery gas production evaluation device, wherein the lithium battery gas production evaluation device comprises, from top to bottom, the following components: A container filled with liquid; A liquid collector is located below the receiving chamber to collect liquid that overflows from the receiving chamber; A mass measuring device is located below the liquid collector, and the mass measuring device is used to measure the total mass of the liquid collector and the liquid in the liquid collector; The method for evaluating the gas production of lithium batteries includes the following steps: S1. Immerse the lithium battery in the liquid in the container; S2. Use a mass measuring instrument to measure and obtain the initial total mass m0 of the liquid collector and the liquid in the liquid collector; S3, charging operation is performed on the lithium battery, and the indication of the mass meter is recorded every fixed time to obtain a data set M={m1, m2, m3, …m n}, wherein m n n represents the indication of the mass meter recorded for the nth time. S4. Calculate the displacement V of the lithium battery at each time point: V = {v1, v2, v3, ... v} n }, where v n Let n be the exhaust volume corresponding to the nth time point. , The density of the liquid; The variables to be optimized in the lithium battery aging process are ambient temperature T, battery charge Q, and charging current I. By changing the ambient temperature, battery charge, and charging current, the displacement V of the lithium battery was tested under different ambient temperatures, battery charge, and charging currents, where 10℃ < T < 60℃, 0 < Q < 100%, and 0.05C < I < 1.0C, where C is the rated capacity of the lithium battery cell. Based on different ambient temperatures T, battery charge Q, and charging current I, a function V(T,Q,I) is constructed. The ambient temperature T, battery charge Q, and charging current I corresponding to the maximum exhaust volume V are selected as the optimal solution. The battery cells are tightly sealed before being placed in the soft pack. Then, they are placed in the lithium battery gas production evaluation device. In this way, as long as the cells produce gas, the amount of gas produced by the battery can be measured.

2. The parameter optimization method in the lithium battery aging process according to claim 1, characterized in that: The process after S4 includes: S5, plotting a curve fitting graph of the amount of exhaust gas as a function of time based on the amount of exhaust gas from the lithium battery at each time point.

3. The parameter optimization method in the lithium battery aging process according to claim 1, characterized in that: The container is also equipped with a clamp for fixing the lithium battery, which secures the lithium battery so that the electrodes of the lithium battery are exposed above the liquid surface.

4. The parameter optimization method in the lithium battery aging process according to claim 1, characterized in that: The electrodes of the lithium battery and the connection between the lithium battery electrodes and the charging device are sealed and placed in the liquid of the containment chamber.

5. The parameter optimization method in the lithium battery aging process according to claim 1, characterized in that: The mass measuring instrument is an electronic balance.

6. The parameter optimization method in the lithium battery aging process according to claim 1, characterized in that: The container is a temperature-adjustable container.

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