Device and method for detecting expansive force of single battery

Abstract

The invention discloses a single battery expansibility detection device and method, the single battery expansibility detection device is used for single battery expansibility detection, and the single battery expansibility detection device comprises a substrate, a fixed plate, a pressing plate, a displacement sensor, a clamp and an elastic member; the substrate and the fixed plate are oppositely arranged, and the distance between the substrate and the fixed plate is invariable; the pressing plate is arranged between the base plate and the fixing plate, and a pressure sensor is arranged on the pressing plate; the displacement sensor is used for detecting the displacement of the pressing plate; the clamp is arranged between the base plate and the pressing plate and is used for clamping the single battery; the elastic piece is used for connecting the abutting plate and the fixing plate, and under the action of the elastic piece, the abutting plate abuts against the clamp. Appropriate pre-tightening force is applied to the single battery through the clamp, the applied pre-tightening force is kept constant through the elastic piece, the expansion force condition of the single battery is tested by adopting a quick charging method, and the test period is shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a device and method for detecting the expansion force of a single battery. Background Art

[0002] With the development of existing technologies, the performance of lithium-ion batteries has been revolutionized, but their service life and safety have also attracted everyone's attention. During the charging and discharging process of lithium-ion batteries, due to the chemical reactions inside the battery, the battery materials, especially the positive electrode materials, will undergo volume changes, causing the battery to generate expansion force. If this expansion force is too large, it may cause damage to the internal structure of the battery, poor contact between electrodes, and even cause safety problems such as battery rupture and fire. Therefore, it is very important to test the expansion force of lithium-ion batteries. In addition, expansion force testing can help battery manufacturers understand the stability and reliability of the battery during the charge and discharge cycle, evaluate the risks that may arise in actual use of the battery, and by controlling the battery expansion force, the battery design can be optimized and the battery service life and safety can be improved. However, many current expansion force detection devices cannot ensure the constancy of the force applied to the battery, and it takes a long time to complete a test. Summary of the Invention

[0003] Based on this, the purpose of the present invention is to provide a single cell expansion force detection device and method, which applies a suitable pre-tightening force to the single cell through a clamp, maintains the applied pre-tightening force constant through an elastic member, and uses a fast charging method to test the expansion force of the single cell, thereby shortening the test cycle.

[0004] To achieve the above object, the present invention adopts the following technical solutions: The present invention first provides a single cell expansion force detection device for detecting the expansion force of a single cell, comprising a base plate, a fixed plate, a pressure plate, a displacement sensor, a clamp, and an elastic member. The base plate and the fixed plate are arranged relative to each other with a fixed distance therebetween. The pressure plate is disposed between the base plate and the fixed plate and is provided with a pressure sensor. The displacement sensor is used to detect the displacement of the pressure plate. The clamp is disposed between the base plate and the pressure plate and is used to clamp the single cell. The elastic member is used to connect the pressure plate to the fixed plate, and under the action of the elastic member, the pressure plate and the clamp are pressed tightly.

[0005] As a further improvement of the above solution of the present invention, the pressure plate includes a pressure plate 1 and a pressure plate 2 arranged opposite to each other, and the pressure sensor is arranged between the pressure plate 1 and the pressure plate 2 and connected to the pressure plate 1 and the pressure plate 2.

[0006] As a further improvement of the above solution of the present invention, the single cell expansion force detection device further includes four rectangularly distributed guide rods, one end of each of the four guide rods is connected to the base plate, and the other end of each of the four guide rods is connected to the fixing plate.

[0007] As a further improvement of the above solution of the present invention, each guide rod slides through the first pressing plate and the second pressing plate.

[0008] As a further improvement of the above solution of the present invention, the elastic member includes a plurality of springs.

[0009] As a further improvement of the above solution of the present invention, the pre-tightening force of the clamp on the single battery is 0.05-2.1 MPa.

[0010] As a further improvement of the above solution of the present invention, a buffer pad is provided at the contact position between the clamp and the single battery, and the buffer pad includes but is not limited to foam, compression pad, etc.

[0011] As a further improvement to the above solution, the present invention employs two displacement sensors, each mounted on a substrate and located on the positive and negative sides of a single cell. The displacement sensors have an accuracy of ±0.01 mm, and the pressure sensors have an accuracy of ±0.5%. This invention utilizes pressure and displacement sensors with higher precision and stability, enabling it to record minute expansion changes in single cells, offering a higher precision advantage over existing technologies.

[0012] The present invention also provides a method for detecting the expansion force of a single battery as described above, which comprises the following steps: S1. Use a clamp to clamp the single cell to be tested to apply a preload to the single cell to be tested, place the clamp between the pressure plate and the substrate, and under the action of the elastic member, press the pressure plate against the clamp, let it stand, and record the pressure sensor and displacement sensor detection data; S2. Discharge the battery to 2.5V at 1C constant current, allow to stand, then charge it to 8% SOC at 1 / 3C constant current, then charge it to 80% SOC at a constant current rate of C / 3-2.0C, and finally charge it to 3.8V at a constant current rate of C / 3 until the current drops below 0.05C, and allow to stand. S3. Repeat step S2 multiple times, and record the capacity of the single battery to be tested every 100 cycles.

[0013] As a further improvement of the above solution of the present invention, in step S1, the single battery to be tested should be at a SOC of 10%-30% under an environment of 25°C±2°C.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention applies a suitable pre-tightening force to a single battery through a clamp, maintains the applied pre-tightening force constant through an elastic member, and adopts a fast charging method to test the expansion force of the single battery, thereby shortening the test cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic structural diagram of a single battery expansion force detection device according to an embodiment of the present invention; Figure 2 Graph showing the change in expansion force of a single battery under test at different cycle times in an embodiment of the present invention; Figure 3 Graph showing displacement changes of a single cell under test at different cycle times in an embodiment of the present invention; Figure 4 1 is a comparison chart of the capacity changes of the tested single cells at different cycle times in Example and Comparative Example 1; Figure 5 2 is a comparison chart of the capacity changes of the tested single cells at different cycle times in Example 1 and Comparative Example 2.

[0016] Figure numerals: 1, substrate; 2, fixing plate; 3, pressure plate; 31, pressure plate 1; 32, pressure plate 2; 4, displacement sensor; 5, clamp; 6, elastic member; 7, pressure sensor; 8, guide rod. DETAILED DESCRIPTION

[0017] To facilitate understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0019] Example This embodiment provides a single cell expansion force detection device for detecting the expansion force of a single cell, which includes a base plate 1 , a fixing plate 2 , a pressing plate 3 , a displacement sensor 4 , a clamp 5 , and an elastic member 6 , and may further include four guide rods 8 .

[0020] The base plate 1 and the fixed plate 2 are arranged vertically relative to each other with a fixed distance between them. In this embodiment, the base plate 1 and the fixed plate 2 are both rectangular plates. Of course, in other embodiments, the base plate 1 and the fixed plate 2 can also be plates of other shapes and structures as long as they meet the requirements of use.

[0021] The four guide rods 8 are arranged in a rectangular shape. The bottom ends of the four guide rods 8 are fixedly connected to the base plate 1, and the top ends of the four guide rods 8 are fixedly connected to the fixed plate 2. The four guide rods 8 are used to mount the base plate 1 and the fixed plate 2 to ensure that the distance between the base plate 1 and the fixed plate 2 remains constant. Of course, in other embodiments, the guide rods may be of other numbers, such as three or six.

[0022] The pressure plate 3 is positioned between the base plate and the fixed plate 2 and is equipped with a pressure sensor 7 (with an accuracy of ±0.5%). Specifically, the pressure plate 3 comprises a first pressure plate 31 and a second pressure plate 32 positioned opposite each other. The pressure sensor 7 is positioned between and connected to the first and second pressure plates 31 and 32. Guide rods 8 slide through the first and second pressure plates 31 and 32, allowing the first and second pressure plates 31 and 32 to move vertically up and down.

[0023] Displacement sensor 4 (with an accuracy of ±0.01mm) is used to detect the displacement of pressure plate 3. In this embodiment, two displacement sensors 4 are provided, each mounted on substrate 1 and located on the positive and negative sides of the battery cells, respectively. Using two displacement sensors allows for detailed visualization of changes in the positive and negative electrodes, enabling analysis of the chemical reaction mechanisms within the battery.

[0024] This embodiment uses a pressure sensor 7 and a displacement sensor 4 with higher precision and stability, which can record the expansion degree of a single battery at the micron level, and has the advantage of higher precision compared to the existing technology.

[0025] The clamp 5 is positioned between the base plate 1 and the pressure plate 3 and is used to clamp the battery cells. The clamp can apply a preload force to the battery cells under test. The clamp 5 can be a conventional eight-hole clamp, with a torque of 0.7-10 N·m and a preload force of 0.05-2.1 MPa on the battery cells under test. The eight-hole clamp is conventional and consists of two 20mm thick aluminum alloy clamps with eight holes. Threaded rods and nuts are inserted through these holes to sandwich the two clamps with the battery cells, effectively clamping the battery cells in the middle of the eight-hole clamp.

[0026] The elastic member 6 is used to connect the pressing plate and the fixing plate. Under the action of the elastic member 6, the pressing plate 3 and the clamp 5 are pressed tightly. In this embodiment, the elastic member 6 is a spring.

[0027] The detection method of the single battery expansion force detection device of this embodiment includes the following steps: Use the eight-hole fixture 5 to secure the single battery. The tightening force is 10 N·m. Add foam as a buffer material between the single battery and the fixture 5 to improve the safety performance during the battery cycle. Then install the single battery with the fixture into the expansion force detection device. The preload force is set to 0.45 MPa. The device has a spring to maintain a constant preload force. Let it stand for 24 hours before the cycle test to observe the change in preload force. If it is within the error range, the cycle test can be started. The single cell is discharged at 1C to 2.5V, and then charged at 1 / 3C to 8% of the battery capacity; then 8%-40% of the capacity is charged at a constant current rate of 2.0C, and the charging cut-off condition is that the capacity is charged to 32%, and then 1.72C constant current is used to charge the capacity to 20%; then 1.44C constant current is used to charge 20% of the capacity, and the cut-off capacity is 80%; finally, 1 / 3C constant current is used to charge to 3.8V until the current is less than 0.05C, and it is left to stand for 10 minutes. During the whole process, the data of the pressure sensor 7 and the displacement sensor 4 are recorded in real time; the above steps are cycled, the battery is always in an environment of 25°C, and the capacity of the single cell to be tested is recorded every 100 cycles.

[0028] Comparative Example 1 The difference between this comparative example and the embodiment is that the single cell expansion force detection device used in this comparative example does not include a clamp, and no pre-tightening force is applied to the single cell.

[0029] Comparative Example 2 The difference between this comparative example and the embodiment is that the single battery expansion force detection device used in this comparative example does not include a spring.

[0030] The test results of Example and Comparative Example 1-2 are as follows Figure 2-4 As shown. Figure 2-4 The results show that: From the results Figure 2 It can be seen that in the embodiment, as the number of cycles increases, the expansion force of the battery gradually increases, and the change in the expansion force is real-time; from Figure 3 It can be seen that in the embodiment, as the number of cycles increases, the expansion degree of the battery also increases. In addition, the displacement sensor has a high accuracy, which can reach 0.01mm. from Figure 4 It can be seen that in the embodiment, as the number of cycles increases to 1200, the battery capacity retention rate is still as high as 85%; while as the number of cycles increases, the battery capacity of the comparative example 1 without applying a preload force rapidly decays. It can be seen that applying an appropriate preload force can improve the cycle performance of the battery and extend the battery life; from Figure 5It can be seen that in Example 2, no spring is added, and the battery capacity retention rate drops sharply in the later period, while in Example 2, the capacity retention rate of the spring is added and decreases steadily with the increase of the number of cycles. Therefore, it is shown that adding a spring to keep the preload constant can improve the battery cycle performance.

[0031] It should be noted that when a component is referred to as being "mounted on" another component, it may be directly on the other component or there may be a central component. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be a central component. When a component is considered to be "fixed to" another component, it may be directly fixed to the other component or there may be a central component.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0034] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A single cell expansion force detection device for detecting the expansion force of a single cell, characterized in that: It includes a base plate, a fixed plate, a pressure plate, a displacement sensor, a clamp and an elastic member; the base plate and the fixed plate are arranged relative to each other and the distance between them is not changeable; the pressure plate is arranged between the base plate and the fixed plate and a pressure sensor is arranged on the pressure plate; the displacement sensor is used to detect the displacement of the pressure plate; the clamp is arranged between the base plate and the pressure plate and is used to clamp the single battery; the elastic member is used to connect the pressure plate and the fixed plate, and under the action of the elastic member, the pressure plate and the clamp are pressed tightly.

2. The single cell expansion force detection device according to claim 1, characterized in that: The pressing plate includes a pressing plate 1 and a pressing plate 2 which are arranged opposite to each other. The pressure sensor is arranged between the pressing plate 1 and the pressing plate 2 and is connected to the pressing plate 1 and the pressing plate 2.

3. The single cell expansion force detection device according to claim 2, characterized in that: The single cell expansion force detection device further includes four guide rods distributed in a rectangular shape, one end of each of the four guide rods is connected to the base plate, and the other end of each of the four guide rods is connected to the fixing plate.

4. The single cell expansion force detection device according to claim 3, characterized in that: Each guide rod slides through the first pressing plate and the second pressing plate.

5. The single cell expansion force detection device according to claim 1, characterized in that: The elastic member includes a plurality of springs.

6. The single cell expansion force detection device according to claim 1, characterized in that: The pre-tightening force of the clamp on the single battery is 0.05-2.1MPa.

7. The single cell expansion force detection device according to claim 1, characterized in that: A buffer pad is provided at the contact position between the clamp and the single battery.

8. The single cell expansion force detection device according to claim 1, characterized in that: There are two displacement sensors, both of which are arranged on the substrate and located on the positive and negative sides of the single battery respectively; the accuracy of the displacement sensor is ±0.01mm, and the accuracy of the pressure sensor is ±0.5%.

9. A method for detecting the expansion force of a single battery according to claim 1-8, characterized in that: It includes the following steps: S1. Use a clamp to clamp the single cell to be tested to apply a preload to the single cell to be tested, place the clamp between the pressure plate and the substrate, and under the action of the elastic member, press the pressure plate against the clamp, let it stand, and record the pressure sensor and displacement sensor detection data; S2. Discharge the battery to 2.5V at 1C constant current, allow to stand, then charge it to 8% SOC at 1 / 3C constant current, then charge it to 80% SOC at a constant current rate of C / 3-2.0C, and finally charge it to 3.8V at a constant current rate of C / 3 until the current drops below 0.05C, and allow to stand. S3. Repeat step S2 multiple times, and record the capacity of the single battery to be tested every 100 cycles.

10. The detection method of the single battery expansion force detection device according to claim 9, characterized in that: In step S1, the single battery to be tested should be at a SOC of 10%-30% under an environment of 25°C±2°C.

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