Elastic force testing device and method of elastic sheet for high-expansion battery pack

Abstract

The invention discloses an elastic force testing device and method of an elastic piece for a high-expansion battery pack, and relates to the field of elastic force testing, and the testing device comprises a fixed platform, a sliding platform, a pressure adapter plate, a deformation adaptation structure, an elastic piece sample piece testing installation clamp and a fixed curvature curved surface structure. The sliding platform is mounted above the fixed platform and is in sliding connection relative to the fixed platform; the pressure adapter plate is installed on the side, away from the fixed platform, of the sliding platform and used for being connected with force application equipment. The deformation adaptation structure is installed on the side, facing the fixed platform, of the sliding platform, the fixed curvature curved surface structure is installed on the side, facing the sliding platform, of the fixed platform, and the fixed curvature curved surface structure is opposite to the deformation adaptation structure; the elastic piece sample piece test installation clamp comprises two clamping pieces and an elastic piece sample piece to be tested, and the two ends of the elastic piece sample piece are respectively fixed by one clamping piece. The performance of the elastic clamping plate is directly measured, the deformation curvature of the elastic sheet is controllable, and the elastic force and the deflection of the elastic sheet can be accurately measured.

Description

Technical Field

[0001] The present invention relates to the field of elastic testing devices, specifically to an elastic force testing device for battery packs, especially applicable to testing devices and methods for carbon fiber elastic splints used in lithium metal batteries and silicon-carbon batteries. Background Art

[0002] With the gradual maturity of lithium metal secondary battery and silicon-carbon lithium ion battery technologies, these two types of batteries have great application value in the field of high specific energy. However, whether it is a lithium metal battery or a silicon-carbon battery, their charge and discharge processes are accompanied by thickness expansion and contraction. To improve their cycle performance, relatively large pressures are usually applied to the batteries currently. To apply pressure to these two types of batteries, one way is to use elastic splints to clamp the batteries. However, there is no good direct measurement method for the performance of the elastic splints.

[0003] CN106768544B, "Method for Obtaining Elastic Force of Elastic Sheet and Elastic Force Testing Device", measures the elastic force of the elastic sheet by means of planar extrusion; CN219915227U, "An Elastic Sheet Fatigue Testing Tooling", measures an elastic sheet with a straight part and an inclined part structure by using an eccentric wheel to form reciprocating motion, and neither can perform the test of the elastic force of a planar elastic sheet along a fixed curvature curved surface. Summary of the Invention

[0004] The technical problem solved by this application is as follows: Aiming at the problem that in the prior art, for high-expansion-rate batteries such as lithium metal batteries or silicon-carbon batteries, the expansion and contraction pressure changes greatly during the charge and discharge process, the elastic sheets of the elastic splints of the battery pack undergo cyclic elastic deformation, but the elastic force performance and cyclic life of the elastic splints are not easily measured accurately. A method and device for testing the elastic force of an elastic sheet for a high-expansion battery pack are provided, realizing the direct measurement of the performance of the elastic splint, controllable deformation curvature of the elastic sheet, accurate measurement of the elastic force magnitude and the deflection of the elastic sheet, and achieving the purpose of accurately measuring parameters such as the elastic force and cyclic life of the elastic sheet during the charge and discharge process of the battery pack.

[0005] The technical solution provided by this application is as follows:

[0006] A device for testing the elastic force of a shrapnel for a high-expansion battery pack, comprising a fixed platform, a sliding platform, a pressure transfer plate, a pressure sensor, a deformation adaptation structure, a shrapnel sample test installation clip, and a fixed curvature surface structure; the sliding platform is installed above the fixed platform, and the sliding platform slides up and down in the vertical direction relative to the fixed platform; the pressure transfer plate is installed on the side of the sliding platform facing away from the fixed platform, and the pressure transfer plate is used to connect the force-applying device; the pressure sensor is installed between the pressure transfer plate and the sliding platform for measuring the pressure applied by the force-applying device; the deformation adaptation structure is installed on the side of the sliding platform facing the fixed platform, the fixed curvature surface structure is installed on the side of the fixed platform facing the sliding platform, and the fixed curvature surface structure is opposite to the deformation adaptation structure; the shrapnel sample test installation clip includes two clamping members and a shrapnel sample to be tested, both ends of the shrapnel sample are fixed by one clamping member respectively, the deformation adaptation structure is provided with two sets of runway holes, each set of runway holes includes two opposite runway holes, a cylinder is connected to each of the opposite sides of each clamping member, the cylinder of each clamping member is arranged in a set of runway holes, the cylinder can slide along the length direction of the runway holes, and the cylinder can rotate in the runway holes; when the shrapnel sample is in an unloaded planar state, the cylindrical head is at the end of the two kidney-shaped holes away from each other, and when the kidney-shaped holes are deformed by force, the cylindrical head translates towards the end of the two kidney-shaped holes close to each other.

[0007] Furthermore, it further includes a set of slide bars and a set of linear sliding bearings. The set of slide bars includes multiple slide bars, the slide bars are installed on the fixed platform, the set of linear sliding bearings is installed on the sliding platform, the sliding platform is located above the fixed platform, and the slide bars pass through the corresponding set of linear sliding bearings, and the set of linear sliding bearings is slidably connected to the slide bars along the axis direction of the slide bars.

[0008] Furthermore, the deformation adaptation structure includes a body, the body is fixedly connected to the sliding platform, an installation groove is formed on the side of the body facing the fixed platform, mounting plates are formed on both sides of the installation groove of the body, the runway holes are arranged on the mounting plates, the length directions of the two sets of runway holes are coplanar, and the plane where the length directions of the two sets of runway holes are located is parallel to the fixed platform.

[0009] Furthermore, an observation groove is formed on the mounting plate, the observation groove is located between the two sets of runway holes for observing the shrapnel sample to be tested.

[0010] Further, the clamping member includes a mounting base and a mounting piece. The cylinder is connected to the opposite sides of the mounting base. There is a second blank area on one side of the mounting base, and the second blank area is located between two opposite cylinders. The shrapnel sample is clamped in the second blank area, and the diameter D1 of the cylinder ≤ the maximum width D4 of the runway hole; the distance between the two cylinders is S3, and the width of the shrapnel sample is S2, S3 > S2; both ends of the shrapnel sample are provided with shrapnel sample mounting holes, the mounting base is provided with mounting holes, and the mounting piece is mounted on the side of the shrapnel sample away from the mounting base. The bolt passes through the mounting piece, the shrapnel sample mounting hole and the mounting hole in sequence to fix the shrapnel sample.

[0011] Further, the bottom surface of the second blank area is the mounting surface, the opposite surface of the mounting base and another mounting base is the bottom surface of the first blank area, the bottom surface of the first blank area is perpendicular to the mounting surface, the bottom surface of the first blank area passes through the axis of the cylinder, and the intersection line of the bottom surface of the first blank area and the mounting surface is collinear with the axis of the cylinder.

[0012] Further, the fixed curvature curved surface structure includes a base and a curved surface member. The base is fixedly connected to the fixed platform, and the curved surface member is fixedly connected to the base. The side of the curved surface member facing the sliding platform is the deformed top arc surface, and the axis corresponding to the deformed top arc surface is parallel to the axis of the cylinder; the curved surface member is provided with two parts of inner concave side spaces, and the two parts of inner concave side spaces are respectively located at both ends of the deformed top arc surface along its circumferential direction, and the bottom of the inner concave side space is an arc surface coaxial with the deformed top arc surface.

[0013] Further, the radius corresponding to the deformed top arc surface is R1, and the radius corresponding to the bottom arc surface of the inner concave side space is R2; R1 - R2 ≥ D3 and d3 ≥ 180 - 90L1 / ΠR1, where d3 is the angle of the inner concave measurement space range, D3 is the depth of the second blank area, and L1 is the length of the exposed area of the shrapnel sample inside the two mounting posts.

[0014] Further, it further includes a laser displacement probe, and the laser displacement probe is installed on the fixed platform for measuring the distance between the fixed platform and the sliding platform.

[0015] A method for testing the elastic force of a shrapnel for a high-expansion battery pack, using the elastic force testing device for a shrapnel for a high-expansion battery pack described in any one of the above for testing, includes:

[0016] S1. Use a semi-cylindrical structure with a fixed curvature increasing from small to large to sequentially perform extrusion tests on a shrapnel until cracks appear on the shrapnel. At this time, the fixed curvature is the minimum bending radius of the shrapnel; the shrapnel is the same as the shrapnel sample to be tested;

[0017] S2. Set the radius R1 of the deformed top arc surface to be equal to the minimum bending radius of the shrapnel;

[0018] S3. Install the shrapnel sample to be tested on the clamping member;

[0019] S4. Connect the pressure transfer board to the force - applying device, and the force - applying device drives the pressure transfer board and the sliding platform to press down from the initial position. Meanwhile, detect the displacement and pressure of the sliding platform.

[0020] S5. Until reaching the pressure mutation position, stop the displacement of the sliding platform. At this time, the allowable maximum displacement deformation HM of the shrapnel sample is the displacement between the initial position and the stopped - displacement position of the sliding platform.

[0021] S6. Set the extrusion speed to HM / C 充 , the pressure - holding time is 1 - 3 h, the recovery speed is HM / C 放 , the maintenance time after recovery is 1 - 3 h, the maximum displacement is HM, where C 充 is the charging rate, and C 放 is the discharging rate.

[0022] S7. Use a new shrapnel sample as the pressing - down condition of the sliding platform according to the conditions of S6, and conduct reciprocating cyclic deformation tests according to steps S1 - S5. Then test the fatigue performance of the new shrapnel sample until the current elastic coefficient is 80% of the initial elastic coefficient and then stop the test. Among them, the initial elastic coefficient is the elastic coefficient of the new shrapnel sample measured at the set height of the sliding platform during the first cyclic deformation test, and the current elastic coefficient is the elastic coefficient of the new shrapnel sample measured at the set height of the sliding platform during the current cyclic deformation test; the elastic coefficient = pressure measured at the set height of the sliding platform / displacement.

[0023] In summary, the present application at least includes the following beneficial technical effects:

[0024] (1) The present invention can test the elastic force of the planar shrapnel, has low requirements for the sample, and can quickly evaluate the performance of the shrapnel material without bending the sample.

[0025] (2) The present invention can completely fit the test of the elastic splint of the expansion - type lithium - battery pack deforming along the fixed - curvature curved surface, and can check whether it matches the performance of the actual metal lithium - battery.

[0026] (3) The present invention adopts an adaptive rotating shaft, which can avoid generating additional deformation to affect the accuracy of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of the composition of the shrapnel elastic - force testing device of the present invention.

[0028] Figure 2 is a schematic diagram of the fixed - curvature curved - surface structure of the present invention.

[0029] Figure 3Schematic diagram of the deformation adaptation structure of the present invention.

[0030] Figure 4 Schematic diagram of the test installation clip structure for the shrapnel sample of the present invention.

[0031] Figure 5 Schematic diagram of the shrapnel sample of the present invention.

[0032] Figure 6 Schematic diagram of the mounting base of the present invention.

[0033] Figure 7 Schematic diagram of the dimensions of the test installation clip for the shrapnel sample of the present invention. Detailed implementation manners

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the following will further describe in detail the disclosed implementation manners of this application in conjunction with the accompanying drawings.

[0035] This application embodiment discloses a shrapnel elastic force test device for a battery pack, as Figure 1 shown, which includes a fixed platform 1, a sliding platform 2, a slide bar group 3, a linear sliding bearing group 4, a pressure transfer plate 5, a pressure sensor 6, a deformation adaptation structure 7, a fixed curvature surface structure 9, a shrapnel sample test installation clip 8, and a laser displacement probe 10.

[0036] The sliding platform 2 is installed above the fixed platform 1 and can slide vertically up and down relative to the fixed platform 1. The slide bar group 3 is installed on the fixed platform 1, and the linear sliding bearing group 4 is installed on the sliding platform 2. The slide bar group 3 passes through the matching linear sliding bearing group 4. The pressure transfer plate 5 is installed above the sliding platform 2 to achieve connection with the force application device. The pressure sensor 6 is installed between the pressure transfer plate 5 and the sliding platform 2 to measure the applied pressure. The deformation adaptation structure 7 is installed between the sliding platform 2 and the fixed platform 1 and fixed on the sliding platform 2. The fixed curvature surface structure 9 is installed between the deformation adaptation structure 7 and the fixed platform 1 and fixed on the fixed platform 1. The fixed curvature surface structure 9 is exactly aligned with the deformation adaptation structure 7. The four symmetric cylindrical heads of the shrapnel sample test installation clip 8 are installed in the four symmetric racetrack-shaped holes of the deformation adaptation structure 7. When the shrapnel sample expands, the left and right cylindrical heads are outside the racetrack holes. When the shrapnel sample deforms, the left and right cylindrical heads translate inward to the racetrack holes. The laser displacement probe 10 is fixedly installed on the fixed platform 1 to measure the distance between the fixed platform 1 and the sliding platform 2, and this displacement is the deflection of the shrapnel after being stressed and bent.

[0037] As Figure 2As shown, the fixed curvature surface structure 9 is symmetrically and uniformly distributed left and right, including a base 901, a deformed top arc surface 902, and an indented side space 903. The base 901 is fixedly connected to the fixed platform 1. The deformed top arc surface 902 is arranged directly above the base 901. The indented side space 903 is arranged on both sides of the base 901 and the deformed top arc surface 902 structure. The indented side space 903 should at least satisfy R1 - R2 ≥ D3 and d3 ≥ 180 - 90L1 / ΠR1. Wherein, R1 is the radius of the deformed top arc surface 902, R2 is the bottom radius of the indented side space 903, and d3 is the angle of the indented side space range; D3 is the depth of the second blank area 8025, see Figure 6 ; L1 is the length of the exposed area of the shrapnel-like part between the two cylinders 8021 on the same side, see Figure 7 . Thus, the space accommodation of the mounting seat 802 after the extreme deformation of the shrapnel is realized, and further, the free extension state of the test end of the shrapnel-like part is always maintained during the deformation process.

[0038] As Figure 3 shown, the deformation adaptation structure 7 includes a body 701, a runway hole 702, and an observation groove 703. The body 701 constitutes the main body of the deformation adaptation structure 7. There are 2 runway holes 702, which are symmetrically distributed on both sides of the body 701; the runway hole 702 is a waist-shaped hole, and the waist-shaped hole includes a long straight hole in the middle and semi-circular arcs at both ends of the long straight hole. The distance between the centers of the semi-circular arcs at the closer ends of the two runway holes 702 is L1 - 2, and it should satisfy L1 - 2 ≤ 2R3·cos(d3). The distance between the centers of the semi-circular arcs at the farther ends of the two runway holes 702 is L1 - 1, and it should satisfy L1 - 1 ≥ L1. The diameter of the semi-circular arc is D4 (that is, the maximum width of the runway hole 702 is D4). The observation groove 703 is a cut-out area, which is arranged in the middle of the two runway holes 702 to realize the observation of the elastic deformation process of the shrapnel-like part during the deformation process.

[0039] As Figure 4 shown, the shrapnel-like part test mounting clip 8 includes a tested shrapnel-like part 801, a mounting seat 802, and a mounting piece 803. Two mounting seats 802 are installed at both ends of the tested shrapnel-like part 801, and the mounting piece 803 cooperates with the mounting seat 802 to clamp the shrapnel-like part 801 in the middle.

[0040] As Figure 5 shown, the shrapnel-like part 801 includes a shrapnel-like part body 8011 and shrapnel-like part mounting holes 8012. The shrapnel-like part mounting holes 8012 are 8 holes that are symmetrically installed left and right and up and down, and there are 4 holes on each side of the shrapnel-like part body 8011.

[0041] As Figure 6As shown, the mounting base 802 includes a cylinder 8021, a mounting surface 8022, mounting holes 8023, a first blank area 8024, and a second blank area 8025. The cylinders 8021 are symmetrically distributed on the left and right sides of the mounting base 802 and are symmetrically inserted into the runway holes 702 of the two deformation adaptation structures 7 and are allowed to rotate freely. The mounting surface 8022 contacts the shrapnel sample 801. The mounting holes 8023 are evenly distributed on the mounting surface 8022 to fix the shrapnel sample 801. The mounting holes 8023, the shrapnel sample mounting holes 8012, and the mounting piece 803 are bolted together to fix the shrapnel sample 801. The first blank area 8024 is the area cut after the two cylinders 8021. The plane formed by cutting the first blank area 8024 is perpendicular to the mounting surface 8022, and the intersection line of the plane formed by cutting the first blank area 8024 and the mounting surface 8022 is nearly coincident with the axis of the cylinder 8021, so that when the cylinder 8021 is passively rotated following the deformation of the shrapnel sample 801, it will not cause lateral torsional deformation to the shrapnel sample 801. The second blank area 8025 is the installation area of the shrapnel sample and the mounting piece 803. The diameter of the cylinder 8021 is D1, and the radius of the cylinder 8021 is D2. The thickness of the mounting base 802 is equal to the diameter of the cylinder 8021, and the two surfaces in the thickness direction of the mounting base 802 are tangent to the circumferential direction of the cylinder 8021. Under this condition, the depth D3 of the second blank area 8025 = D2, ensuring that the intersection line of the bottom surface of the first blank area and the mounting surface (8022) is collinear with the axis of the cylinder (8021). D1≤D4; D2 = D1 / 2. The distance between the two cylinders 8021 is S3, and the width of the shrapnel sample is S2, S3>S2.

[0042] As Figure 7 shown, L1 is the effective test length of the sample, and L2 is the total length of the sample and the fixture. That is: after the two ends of the shrapnel sample 801 are respectively installed on the mounting base 802 and the shrapnel sample

[801] is in the natural state, the distance between the bottom surfaces of the first blank areas of the two mounting bases 802 is L1, and the distance between the far ends of the two mounting bases 802 is L2.

[0043] The steps for using this application to perform detection are as follows: install the shrapnel sample 801 on the clamping piece, connect the pressure transfer plate 5 to the force application device, and the force application device drives the pressure transfer plate 5 to press down, while detecting the displacement and pressure of the sliding platform 2; when reaching the pressure mutation position, the mounting base 802 is clamped into the sunken side space 903, and at this time, the sliding platform 2 stops displacement.

[0044] The specific test method for the shrapnel is as follows:

[0045] 1) Perform extrusion tests on semi-cylindrical structures with different fixed curvatures to check whether the sample breaks and determine the minimum bending radius of the shrapnel sample;

[0046] 2) Set the radius R1 of the fixed curvature surface structure 9 equal to the minimum bending radius of the shrapnel sample;

[0047] 3) Place the tested sample in the device;

[0048] 4) Start the device to detect the relationship between the displacement and the pressure;

[0049] 5) Detect the corresponding deformation value at the moment when the pressure of the sample undergoes a sudden change. This deformation value is the maximum allowable displacement deformation HM of the sample;

[0050] 6) Set the extrusion speed of the device to HM / C 充 , the pressure holding time is 1 - 3 h, the recovery speed is HM / C 放 , the holding time after recovery is 1 - 3 h, the maximum displacement is HM, where C 充 is the charging rate of the high expansion battery pack, and C 放 is the discharging rate of the high expansion battery pack.

[0051] 7) Use a new shrapnel sample 801 to perform a reciprocating cyclic deformation test according to step 6), and then test the fatigue performance of the sample until the current elastic coefficient is 80% of the initial elastic coefficient, and then stop the test; where the initial elastic coefficient is the elastic coefficient of the new shrapnel sample 801 measured at the set height of the sliding platform 2 during the first cyclic deformation test, and the current elastic coefficient is the elastic coefficient of the new shrapnel sample 801 measured at the set height of the sliding platform 2 during the current cyclic deformation test. The elastic coefficient = the pressure measured at the set height of the sliding platform 2 / the displacement.

[0052] The content not described in detail in the specification of this application belongs to the well - known technology in the art.

[0053] The above has described this application in detail in combination with specific implementation manners and exemplary examples. However, these descriptions should not be construed as limiting this application. Those skilled in the art understand that without departing from the spirit and scope of this application, various equivalent replacements, modifications, or improvements can be made to the technical solutions and their implementation manners of this application, and these all fall within the scope of this application. The protection scope of this application is subject to the appended claims.

Claims

1. A elastic force testing device for a shrapnel used in a high-expansion battery pack, characterized in that: It includes a fixed platform (1), a sliding platform (2), a pressure transfer plate (5), a pressure sensor (6), a deformation adaptation structure (7), a shrapnel sample test mounting clip (8), and a fixed curvature surface structure (9); The sliding platform (2) is installed above the fixed platform (1), and the sliding platform (2) slides vertically up and down relative to the fixed platform (1); The pressure transfer plate (5) is installed on the side of the sliding platform (2) facing away from the fixed platform (1), and the pressure transfer plate (5) is used to connect the force-applying device; the pressure sensor (6) is installed between the pressure transfer plate (5) and the sliding platform (2) for measuring the pressure applied by the force-applying device; The deformation adaptation structure (7) is installed on the side of the sliding platform (2) facing the fixed platform (1), and the fixed curvature surface structure (9) is installed on the side of the fixed platform (1) facing the sliding platform (2), and the fixed curvature surface structure (9) is opposite to the deformation adaptation structure (7); the shrapnel sample test mounting clip (8) includes two clamping members and a shrapnel sample (801) to be tested. The two ends of the shrapnel sample (801) are respectively fixed by a clamping member. The deformation adaptation structure (7) is provided with two sets of raceway holes (702). Each set of raceway holes includes two opposite raceway holes. A cylinder (8021) is connected to each of the opposite sides of each clamping member. The cylinder (8021) of each clamping member is arranged in a set of raceway holes. The cylinder (8021) can slide along the length direction of the raceway hole and can rotate in the raceway hole; When the shrapnel sample (801) is in an unloaded planar state, the cylindrical head is at the end of the two sets of kidney-shaped holes that are far away from each other. When the kidney-shaped holes are deformed under force, the cylindrical head translates towards the end of the two sets of kidney-shaped holes that are close to each other.

2. The elastic force testing device for the elastic piece of a high-expansion battery pack according to claim 1, characterized in that: It also includes a sliding rod group (3) and a linear sliding bearing group (4). The sliding rod group (3) includes multiple sliding rods. The sliding rods are installed on the fixed platform (1). The linear sliding bearing group (4) is installed on the sliding platform (2). The sliding platform (2) is located above the fixed platform (1), and the sliding rods pass through the corresponding linear sliding bearing group (4). The linear sliding bearing group (4) is slidably connected to the sliding rods along the axis direction of the sliding rods.

3. The elastic force testing device for the elastic piece of a high-expansion battery pack according to claim 1, wherein: The deformation adaptation structure (7) includes a body (701). The body (701) is fixedly connected to the sliding platform (2). An installation groove is formed on the side of the body (701) facing the fixed platform (1). The body (701) forms installation plates on both sides of the installation groove. The raceway holes (702) are arranged on the installation plates. The length directions of the two sets of raceway holes (702) are coplanar, and the plane where the length directions of the two sets of raceway holes (702) are located is parallel to the fixed platform (1).

4. The elastic force testing device for the shrapnel of a high-expansion battery pack according to claim 3, characterized in that: An observation groove (703) is formed on the installation plate. The observation groove (703) is located between the two sets of raceway holes (702) for observing the shrapnel sample (801) to be tested.

5. The elastic force testing device for the elastic piece of a high-expansion battery pack according to claim 1, characterized in that: The clamping member includes a mounting base (802) and a mounting piece (803). A cylinder (8021) is connected to the opposite sides of the mounting base (802). A second blank area (8025) is provided on one side of the mounting base (802). The second blank area (8025) is located between two opposite cylinders (8021). The elastic piece sample (801) is clamped in the second blank area (8025). The diameter D1 of the cylinder (8021) ≤ the maximum width D4 of the runway hole (702); the distance between the two cylinders (8021) is S3, and the width of the elastic piece sample (801) is S2, and S3 > S2; both ends of the elastic piece sample (801) are provided with elastic piece sample mounting holes (8012), the mounting base (802) is provided with a mounting hole (8023), and the mounting piece (803) is mounted on the side of the elastic piece sample (801) away from the mounting base (802). A bolt sequentially passes through the mounting piece (803), the elastic piece sample mounting hole (8012), and the mounting hole (8023) to fix the elastic piece sample (801).

6. The elastic force testing device for the elastic sheet of a high-expansion battery pack according to claim 5, characterized in that: The bottom surface of the second blank area (8025) is a mounting surface (8022). The opposite surface of one mounting base (802) and another mounting base (802) is the bottom surface of the first blank area. The bottom surface of the first blank area is perpendicular to the mounting surface (8022). The bottom surface of the first blank area passes through the axis of the cylinder (8021), and the intersecting line of the bottom surface of the first blank area and the mounting surface (8022) is collinear with the axis of the cylinder (8021).

7. A elastic force testing device for a shrapnel used in a high-expansion battery pack according to claim 5, characterized in that: The fixed curvature surface structure (9) includes a base (901) and a curved surface member. The base (901) is fixedly connected to the fixed platform (1), and the curved surface member is fixedly connected to the base (901). The side of the curved surface member facing the sliding platform (2) is a deformed top arc surface (902). The axis corresponding to the deformed top arc surface (902) is parallel to the axis of the cylinder (8021); the curved surface member is provided with two parts of recessed side spaces (903). The two parts of recessed side spaces (903) are respectively located at both ends of the deformed top arc surface (902) along its circumferential direction. The bottom of the recessed side space (903) is an arc surface coaxial with the deformed top arc surface (902).

8. The elastic force testing device for the elastic sheet of a high-expansion battery pack according to claim 7, wherein: The radius corresponding to the deformed top arc surface (902) is R1, and the radius corresponding to the bottom arc surface of the recessed side space (903) is R2; R1 - R2 ≥ D3 and d3 ≥ 180 - 90L1 / ΠR1, where d3 is the angle of the recessed side space range, D3 is the depth of the second blank area (8025), and L1 is the length of the exposed area of the elastic piece sample between the two cylinders (8021) on the same side.

9. The elastic force testing device for the elastic piece of a high-expansion battery pack according to claim 1, characterized in that: It further includes a laser displacement probe (10). The laser displacement probe (10) is mounted on the fixed platform (1) and is used to measure the distance between the fixed platform (1) and the sliding platform (2).

10. A method for testing the elastic force of an elastic sheet for a high-expansion battery pack, characterized in that, Using the elastic force testing device for the elastic piece of a high-expansion battery pack described in any one of claims 1 - 9 for testing, includes: S1. Use a semi-cylindrical structure with a fixed curvature that increases from small to large to perform extrusion tests on a shrapnel piece in sequence until cracks appear on the shrapnel piece. At this time, the fixed curvature is the minimum bending radius of the shrapnel piece; the shrapnel piece is the same as the shrapnel sample (801) to be tested. S2. Set the radius R1 of the deformation top arc surface (902) to be equal to the minimum bending radius of the shrapnel piece. S3. Install the shrapnel sample (801) to be tested on the clamping piece. S4. Connect the pressure transfer plate (5) to the force application device, and the force application device drives the pressure transfer plate (5) and the sliding platform (2) to press down from the initial position. At the same time, detect the displacement and pressure of the sliding platform (2). S5. Until reaching the pressure mutation position, stop the displacement of the sliding platform (2). At this time, the allowable maximum displacement deformation amount HM of the shrapnel sample (801) is the displacement of the sliding platform (2) from the initial position to the position where the displacement stops. S6. Set the extrusion speed to HM / C 充 , the holding pressure time is 1 - 3 h, and the recovery speed is HM / C 放 , the maintaining time after recovery is 1 - 3 h, and the maximum displacement is HM, where C 充 is the charging rate, and C 放 is the discharging rate; S7. Use a new shrapnel sample (801) as the pressing condition of the sliding platform (2) according to the conditions of S6, and perform reciprocating cyclic deformation tests according to steps S1 - S5. Then test the fatigue performance of the new shrapnel sample (801) until the current elastic coefficient is 80% of the initial elastic coefficient and then stop the test; where the initial elastic coefficient is the elastic coefficient of the new shrapnel sample (801) measured at the set height of the sliding platform (2) during the first cyclic deformation test, and the current elastic coefficient is the elastic coefficient of the new shrapnel sample (801) measured at the set height of the sliding platform (2) during the current cyclic deformation test; the elastic coefficient = pressure measured at the set height of the sliding platform (2) / displacement amount.

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