Cylindrical battery testing method

Abstract

The invention relates to the technical field of batteries, in particular to a cylindrical battery testing method. The cylindrical battery test method mainly comprises the following steps: connecting a test element with a battery roll core; putting the battery roll core and the test element into a steel shell together; welding the cap assembly on a tab of the battery roll core; the steel shell is placed on a balance, and electrolyte with the preset weight is injected within the preset time; the cap assembly covers the opening of the steel shell; manufacturing a first mold and a second mold; the top of the steel shell is sleeved with a first mold, the pole of the cap assembly is sleeved with a second mold, and a containing space is formed between the first mold and the second mold; injecting a resin solution into the accommodating space, and standing for a preset time to solidify the resin; and putting the cylindrical battery into a test cabinet for testing. According to the cylindrical battery testing method, the electrical property parameter change in the battery can be captured in real time, so that safety evaluation and thermal runaway early warning on the battery are facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a method for testing cylindrical batteries. Background Art

[0002] With the wide application of lithium-ion batteries in the fields of new energy vehicles, energy storage systems, etc., cylindrical batteries have become one of the mainstream technical routes due to their structural stability and high energy density characteristics. However, there are significant technical bottlenecks in the existing battery testing technologies for monitoring the dynamic performance and refined diagnosis of cylindrical batteries. The existing technologies can only detect the electrical performance parameters on the surface of the battery, and cannot obtain the electrical performance data inside the battery, and thus cannot reconstruct the distribution of the electrical performance parameter field inside the battery, thereby affecting the safety assessment of the battery and the timeliness of thermal runaway warning.

[0003] Therefore, it is urgent to design a method for testing cylindrical batteries to solve the above technical problems. Summary of the Invention

[0004] The purpose of the present invention is to propose a method for testing cylindrical batteries, which can capture the changes in the electrical performance parameters inside the battery in real time, and thus is beneficial to the safety assessment and thermal runaway warning of the battery.

[0005] To achieve this purpose, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for testing cylindrical batteries, including:

[0007] Connect the test element to the battery core;

[0008] Put the battery core and the test element together into the steel shell;

[0009] Weld the cap assembly to the tab of the battery core;

[0010] Place the steel shell on a balance and inject a preset weight of electrolyte within a preset time;

[0011] Cover the cap assembly on the opening of the steel shell;

[0012] Fabricate a first mold and a second mold, and the size of the first mold is larger than that of the second mold; sleeve the first mold on the top of the steel shell, and sleeve the second mold on the pole column of the cap assembly, and a accommodating space is formed between the first mold and the second mold;

[0013] Inject the resin solution into the accommodating space and let it stand for a preset time to solidify the resin;

[0014] Put the battery into a test cabinet for testing.

[0015] As an alternative technical solution of a cylindrical battery testing method, when the test element is a temperature sensor; the step of connecting the test element to the battery core includes:

[0016] Use high-temperature tape to paste the temperature sensor on the separator or the positive electrode sheet of the battery core.

[0017] As an alternative technical solution of a cylindrical battery testing method, when the test element is a reference electrode; the step of connecting the test element to the battery core includes:

[0018] Cut a separator of a preset size, use double-sided tape to paste the cut separator on the positive electrode sheet, and then use high-temperature tape to paste the reference electrode on the cut separator.

[0019] As an alternative technical solution of a cylindrical battery testing method, when the test element is a pressure sensor; the step of connecting the test element to the battery core includes:

[0020] Use high-temperature tape to paste the pressure sensor on the separator or the positive electrode sheet of the battery core; or,

[0021] Paste high-temperature tape on the connection wire of the pressure sensor and expose the detection probe of the pressure sensor, insert the detection probe of the pressure sensor along the inner wall of the steel shell and make the bottom of the high-temperature tape flush with the top of the battery core.

[0022] As an alternative technical solution of a cylindrical battery testing method, the step of placing the steel shell on a balance and injecting a preset weight of electrolyte within a preset time includes:

[0023] Place the steel shell on a balance and inject the electrolyte in several times within 0.5 hours - 1.5 hours, and the total injection amount of the electrolyte is 5g - 9g.

[0024] As an alternative technical solution of a cylindrical battery testing method, after the step of placing the steel shell on a balance and injecting a preset weight of electrolyte within a preset time, it further includes:

[0025] Use high-temperature tape to wrap the tabs on the battery core.

[0026] As an alternative technical solution of a cylindrical battery testing method, the step of making the first mold and the second mold includes:

[0027] Use A4 paper to make the first mold and the second mold, and use tape to bond the joints of the first mold and the joints of the second mold.

[0028] As an alternative technical solution of a cylindrical battery testing method, the first mold is frustum-shaped and the second mold is cylindrical.

[0029] As an alternative technical solution of a cylindrical battery testing method, the step of injecting a resin solution into the accommodating space and standing for a preset time to solidify the resin includes:

[0030] Prepare a resin solution with an SP value of 1.7 - 2.0, apply a pressure towards the pole column to the second mold; inject the resin solution into the accommodating space and stand for 10 minutes - 30 minutes to solidify the resin.

[0031] As an alternative technical solution of a cylindrical battery testing method, there is a preset gap between the solidified resin and the pole column, and the width of the preset gap is set to be between 2 mm and 5 mm.

[0032] The beneficial effects of the present invention at least include:

[0033] The present invention provides a cylindrical battery testing method, which mainly includes the following steps: connecting a test element to a battery core; loading the battery core and the test element into a steel shell together; welding a cap assembly to the tab of the battery core; placing the steel shell on a balance and injecting a preset weight of electrolyte within a preset time; covering the cap assembly on the opening of the steel shell; manufacturing a first mold and a second mold, and the size of the first mold is larger than that of the second mold; sleeving the first mold on the top of the steel shell, sleeving the second mold on the pole column of the cap assembly, and an accommodating space is formed between the first mold and the second mold; injecting a resin solution into the accommodating space and standing for a preset time to solidify the resin; putting the battery into a test cabinet for testing.

[0034] Compared with the prior art, the present invention connects a test element to a battery core, and then loads the battery core and the test element into a steel shell together, so that the test element can be implanted inside the battery core. The first mold and the second mold are used to define the accommodating space to be sealed, and the accommodating space is injected with a resin solution for solidification and sealing. Finally, the battery is charged and discharged and the change of the electrical performance parameters inside the battery is detected. This cylindrical battery testing method can capture the relationship between the electrical performance parameters inside the battery and the battery charge and discharge time in real time, which is conducive to the safety assessment and thermal runaway warning of the battery, and improves the safety performance of the battery. Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the content of the embodiments of the present invention and these drawings.

[0036] Figure 1It is a flowchart of the cylindrical battery testing method provided by the embodiments of the present invention;

[0037] Figure 2 It is a test curve graph of implanting a temperature sensor inside the battery core;

[0038] Figure 3 It is a test curve graph of implanting a pressure sensor inside the battery core. Detailed implementation manners

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, rather than all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0040] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0041] It should be noted that: like reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0042] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the present invention is usually placed when in use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive distinction and cannot be construed as indicating or implying relative importance. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0043] In the description of the present invention, it should also be noted that, unless otherwise clearly defined and limited, the terms "arrangement" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] In the present invention, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature. The first feature being "below", "under" and "beneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the first feature has a lower horizontal height than the second feature.

[0045] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0046] This embodiment provides a method for testing cylindrical batteries, which can capture in real time the changes in the electrical performance parameters inside the battery as the battery charges and discharges, and thus is conducive to the safety assessment and thermal runaway warning of the battery.

[0047] As Figure 1 described, the method for testing cylindrical batteries mainly includes the following steps:

[0048] Connect the test element to the battery core. Exemplarily, the test element in this embodiment can be set as one of a temperature sensor, a reference electrode, or a pressure sensor.

[0049] Specifically, when the test element is a temperature sensor, the step of connecting the test element to the battery core includes using a high-temperature tape to paste the temperature sensor on the separator or the positive electrode plate of the battery core. That is to say, the operator can bond the temperature sensor at any position inside the battery core according to the test requirements, and thus can detect the temperature changes at different positions in the battery core during the charging and discharging process of the battery.

[0050] When the test component is a reference electrode, the steps of connecting the test component to the battery core include cutting a separator with a preset size, pasting the cut separator on the positive electrode sheet with double-sided tape, and then pasting the reference electrode on the cut separator with high-temperature tape.

[0051] During the charge and discharge of the battery, the potentials of the positive and negative electrodes change simultaneously, and the battery voltage measured externally is the potential difference between the two electrodes. In this embodiment, after implanting the reference electrode, the potentials of the positive and negative electrodes relative to the reference electrode can be independently measured, decoupling the electrochemical behaviors of the positive and negative electrodes respectively and avoiding errors caused by mixed potentials. At the same time, it can also monitor the local reactions inside the battery. Specifically, due to the uneven distribution of current density and electrolyte concentration in different regions of the battery core. By implanting the reference electrode at specific positions (such as near the tab, central region), the local potential changes can be monitored in real time.

[0052] Under normal circumstances, the positive electrode sheet is a smooth plane. If the reference electrode is directly pasted onto the positive electrode sheet with high-temperature tape, there will be a problem of insecure pasting. Therefore, in this embodiment, a layer of separator is first pasted on the positive electrode sheet with double-sided tape, and then the reference electrode is pasted onto the separator with high-temperature tape to improve the stability of the reference electrode pasting.

[0053] When the test component is a pressure sensor, the steps of connecting the test component to the battery core include pasting the pressure sensor on the separator or the positive electrode sheet of the battery core with high-temperature tape. That is to say, the operator can bond the pressure sensor at any position inside the battery core according to the test requirements, and then can detect the pressure changes caused by expansion at different positions in the battery core during the charge and discharge of the battery.

[0054] Of course, in some alternative embodiments, the operator can also paste the high-temperature tape on the connecting wire of the pressure sensor and expose the detection probe of the pressure sensor. After the battery core is installed in the steel shell, the detection probe of the pressure sensor is inserted along the inner wall of the steel shell and the bottom of the high-temperature tape is flush with the top of the battery core. In this way, it can be ensured that most of the high-temperature tape wrapping the connecting wire is at the opening position of the steel shell. When the subsequent cap assembly is covered on the opening of the steel shell, the high-temperature tape can play a certain protective role for the connecting wire, reducing or avoiding the extrusion and friction of the cap assembly on the connecting wire and extending the service life of the pressure sensor.

[0055] Optionally, during the winding process of the battery core in this embodiment, it can be wound manually by hand or by a winding machine.

[0056] Since there is a large temperature difference between the inner wall and the outer wall of the steel shell, in order to improve the detection accuracy of the temperature sensor, in this embodiment, the temperature sensor is pre-bonded inside the battery core before the winding battery is wound, rather than being inserted along the inner wall of the steel shell. At the same time, if the reference electrode is inserted along the inner wall of the steel shell, it will cause inaccurate potential measurement.

[0057] The battery core and the test element are loaded into the steel shell together and the base is welded, and then the cap assembly is welded to the tab of the battery core. Exemplarily, laser welding can be used in this embodiment.

[0058] Place the steel shell on a balance and inject a preset weight of electrolyte within a preset time.

[0059] Specifically, place the steel shell on a balance and inject the electrolyte in several times within 0.5 hours - 1.5 hours, and the total injection amount of the electrolyte is 5g - 9g. This can enable the electrolyte to fully fill the pores between the electrode sheets (including the positive electrode sheet and the negative electrode sheet) and the separator, improve the electrolyte wetting uniformity, enhance the utilization rate of the electrode active material, reduce the interfacial impedance, and improve the battery rate performance. At the same time, the method of injecting the electrolyte in batches can enable the bubbles to be discharged dynamically, avoiding the phenomena of bubble residue and uneven electrolyte distribution. In addition, it can also slow down the SEI film formation rate, control the interfacial side reaction rate, and extend the battery service life.

[0060] Then wrap the tab on the battery core with a high-temperature tape. Avoid the phenomenon of short circuit caused by the contact between the tab and the steel shell. In this embodiment, the gasket structure in the traditional lithium battery is cancelled, and instead, the tab on the battery core is wrapped with a high-temperature tape, which can ensure the integrity of the test element implanted inside the battery core and improve the test accuracy.

[0061] Cover the cap assembly at the opening of the steel shell, and at the same time ensure that the high-temperature tape on the connection wire of the test element is located between the cap assembly and the steel shell, thereby playing a protective role for the connection wire and slowing down the extrusion of the cap assembly on the connection wire.

[0062] Make a first mold and a second mold, and the size of the first mold is larger than that of the second mold; sleeve the first mold on the top of the steel shell, and sleeve the second mold on the pole column of the cap assembly, and a accommodating space is formed between the first mold and the second mold.

[0063] Specifically, use A4 paper to make the first mold and the second mold, and use tape (ordinary tape is fine) to bond at the seam of the first mold and the seam of the second mold. When both the first mold and the second mold are sleeved on the battery, at this time, use tweezers to expand the edge space between the first mold and the second mold to provide convenience for subsequent resin solution filling.

[0064] Optionally, the first mold in this embodiment is frustum-shaped, and the second mold is cylindrical, so that the upper size of the accommodating space is larger than the lower size, that is, the accommodating space is funnel-shaped, which is convenient for subsequent pouring of the resin solution.

[0065] Inject the resin solution into the accommodating space and let it stand for a preset time to solidify the resin, so as to realize the sealing between the cap assembly and the opening of the steel shell, and prevent electrolyte leakage and external pollution during the test. At the same time, during the charge and discharge process of the battery, the insertion / extraction of lithium ions will cause volume expansion and internal pressure fluctuations. The sealing structure has a certain mechanical strength to prevent the steel shell from deforming or cracking.

[0066] The setting of the second mold can block the resin solution and ensure that the pole column can be exposed, which is convenient for subsequent electrical performance testing.

[0067] Specifically, prepare a resin solution with an SP (solubility) value of 1.7 - 2.0, apply a pressure towards the pole column to the second mold; inject the resin solution into the accommodating space and let it stand for 10 minutes - 30 minutes to solidify the resin. When the SP value of the resin solution is less than 1.7, the resin solution is too thin, and the sealing effect after resin solidification is not good. When the difference between the SP values of the resin and the solvent is greater than 2.0, the resin solution is too thick at this time, with poor fluidity and it is difficult to seal well between the cap assembly and the steel shell.

[0068] Furthermore, during the injection molding process, a rubber pressing block is used to apply a pressure towards the pole column to the second mold. For example, the rubber pressing block can be placed on the top of the cylindrical second mold, which can prevent the resin solution from flowing from the gap between the second mold and the pole column to the end face of the pole column; ensure that the pole column can be exposed, which is convenient for subsequent electrical performance testing.

[0069] In this embodiment, a resin solution is used to seal the steel shell and the cap assembly. The low-temperature process can avoid the thermal damage caused by welding; at the same time, the resin can fill irregular gaps (such as the tiny gap between the sensor lead and the steel shell) through injection molding to achieve three-dimensional sealing, which has better adaptability to the winding structure of the cylindrical battery. In addition, some resins support partial dissolution or peeling, which is convenient for replacing test components or adjusting parameters during the experimental stage, and reduces the R & D iteration cost.

[0070] Furthermore, there is a preset gap between the solidified resin and the pole column in this embodiment, and the width of the preset gap is set between 2 mm and 5 mm. This is convenient for the test head to be clamped on the pole column of the cap assembly when the battery is put into the cabinet for testing later.

[0071] Finally, put the battery into the test cabinet for testing.

[0072] Specifically, after the resin solution solidifies, the operator can remove the first mold and the second mold, and then place the battery in the test cabinet and connect the test equipment to perform electrical performance parameter testing.

[0073] Compared with the prior art, in this embodiment, the test element is connected to the battery core, and then the battery core and the test element are loaded into the steel shell together, so that the test element can be implanted inside the battery core. The first mold and the second mold are used to define the accommodation space to be sealed, and the accommodation space is injected with resin solution for solidification and sealing. Finally, the battery is charged and discharged, and the change of the electrical performance parameters inside the battery is detected. This cylindrical battery testing method can capture the relationship between the electrical performance parameters inside the battery and the battery charge and discharge time in real time, which is conducive to the safety assessment and thermal runaway warning of the battery, and improves the safety performance of the battery.

[0074] Application example:

[0075] Figure 2 The temperature change curve of a 40P cylindrical battery after being activated with a small current for one week, discharging with a current of 40A, setting the cut-off temperature to 100°C, and implanting a temperature sensor inside the battery core. The abscissa is the battery discharge time, and the ordinate is the temperature.

[0076] Figure 3 The change curve of the expansion pressure of the battery core of a 40P cylindrical battery after being activated with a small current for one week, discharging with a current of 40A, and implanting a pressure sensor inside the battery core. The abscissa is the battery discharge time, and the ordinate is the pressure.

[0077] Obviously, the above are only the preferred embodiments of the present invention and the applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments here, and various obvious changes, re-adjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

[0078] Note that in the description of this specification, the descriptions referring to the terms "some embodiments", "other embodiments", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

Claims

1. Cylindrical battery testing method, characterized in that: include: Connecting the test element to the battery coil; Put the battery core and test components into the steel case together; Welding the cap assembly to the tab of the battery coil core; The steel shell is placed on a balance and filled with a preset weight of electrolyte over a preset time; The cap assembly is placed on the opening of the steel shell; A first mold and a second mold are manufactured, wherein the size of the first mold is larger than that of the second mold; the first mold is sleeved on the top of the steel shell, and the second mold is sleeved on the pole of the cap assembly, and an accommodating space is formed between the first mold and the second mold; Injecting the resin solution into the containing space and leaving it to stand for a preset time to allow the resin to solidify; Place the battery in the test cabinet for testing.

2. The cylindrical battery testing method according to claim 1, characterized in that: When the test element is a temperature sensor, the step of connecting the test element to the battery coil core includes: Use high temperature tape to stick the temperature sensor on the separator or positive electrode of the battery core.

3. The cylindrical battery testing method according to claim 1, characterized in that: When the test element is a reference electrode, the step of connecting the test element to the battery coil core comprises: Cut the diaphragm into a preset size, stick the cut diaphragm on the positive electrode sheet with double-sided tape, and then stick the reference electrode on the cut diaphragm with high-temperature tape.

4. The cylindrical battery testing method according to claim 1, characterized in that: When the test element is a pressure sensor, the step of connecting the test element to the battery coil core includes: Use high temperature tape to stick the pressure sensor to the diaphragm or positive electrode of the battery core; or, The high-temperature tape is attached to the connecting line of the pressure sensor and the detection probe of the pressure sensor is exposed. The detection probe of the pressure sensor is inserted along the inner wall of the steel shell and the bottom of the high-temperature tape is flush with the top of the battery roll core.

5. The cylindrical battery testing method according to claim 1, characterized in that: The steps of placing the steel shell on a balance and injecting a preset weight of electrolyte within a preset time include: The steel shell was placed on a balance and the electrolyte was injected several times within 0.5 hours to 1.5 hours, and the total injection amount of the electrolyte was 5 g to 9 g.

6. The cylindrical battery testing method according to claim 1, characterized in that: After the step of placing the steel shell on a balance and injecting a preset weight of electrolyte within a preset time, the following steps are further included: Use high-temperature tape to wrap the tabs on the battery core.

7. The cylindrical battery testing method according to claim 1, characterized in that: The steps of making the first mold and the second mold include: A4 paper is used to make the first mold and the second mold, and adhesive tape is used to bond the joints of the first mold and the second mold.

8. The cylindrical battery testing method according to claim 7, characterized in that: The first mold is in a truncated cone shape, and the second mold is in a cylindrical shape.

9. The cylindrical battery testing method according to claim 1, characterized in that: The step of injecting the resin solution into the accommodating space and leaving it to stand for a preset time to allow the resin to solidify comprises: A resin solution with an SP value of 1.7-2.0 is prepared, and pressure is applied to the second mold toward the pole; the resin solution is injected into the accommodating space and left to stand for 10 minutes to 30 minutes to allow the resin to solidify.

10. The cylindrical battery testing method according to claim 9, characterized in that: There is a preset gap between the solidified resin and the pole, and the width of the preset gap is set to between 2 mm and 5 mm.

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