Pressure-controllable battery charging and discharging thickness measuring system and method

Abstract

The invention relates to a pressure-controllable battery charge and discharge thickness measurement system and method. A first mobile platform and a second mobile platform are in sliding connection with a sliding rod group and can slide up and down along the sliding rod group; the spring group is compressed when the first moving platform moves downwards; the battery fixing clamp is installed between the first mobile platform and the second mobile platform, and a tested battery is installed in the battery fixing clamp. The second moving platform is pushed by pressure to slide downwards to contact and push the battery fixing clamp to downwards extrude the first moving platform, and the first moving platform downwards extrudes the spring set to enable the spring set to deform; the first range finder is used for measuring the compression displacement of the spring; and the second range finder measures the distance variation between the two mobile platforms in the process from the contact of the second mobile platform with the battery fixing clamp to the stop of downward sliding, namely the expansion amplitude of the battery thickness in the charging and discharging process. According to the invention, the purpose of quantitative measurement from qualitative evaluation to pressure, thickness and other parameters in the charging and discharging process of the high-expansion-rate battery is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery charge and discharge thickness testing systems, and relates to a battery charge and discharge thickness measurement system and method with controllable pressure, which is applicable to the thickness measurement of metal lithium batteries and silicon-carbon batteries during charge and discharge under specified pressure conditions. Background Art

[0002] With the gradual maturity of metal lithium secondary battery technology, metal lithium secondary batteries can also achieve charge and discharge within a certain period, and their specific energy is as high as over 530 Wh / kg, having great application value in the field of high specific energy. However, compared with traditional graphite anode materials, metal lithium secondary batteries lack the space for lithium ion insertion, so obvious volume expansion will occur during the charging process. Especially for square soft-packaged metal lithium batteries, the thickness expansion at the end of their life can even reach up to 40%. Lithium ion batteries with silicon as the anode also have extremely high specific energy. However, the reaction of silicon combined with lithium also leads to a sharp increase in the monomer thickness.

[0003] Currently, conventional metal lithium battery tests are carried out by clamping with splints or simple springs. The initial pressure is generally between 1000 N and 2000 N. However, the pressure after a single full charge can reach 20000 N, or even as high as over 200000 N, and the pressure change rate reaches 10 to 100 times. Therefore, the method of clamping with a splint or a simple spring structure cannot effectively evaluate the law of the influence of the applied pressure on the charge and discharge cycle performance of metal lithium batteries.

[0004] CN 110212209A "A Constant Temperature and Constant Pressure Type Thermal Battery Electrical Performance Test System and Its Test Method" involves a pressure of only 30 - 300 N, which is much smaller than the pressure value range after a single full charge; this invention does not involve the first rangefinder and the second rangefinder of the present invention, resulting in the inability to precisely control the pressure during the thermal battery test and the inability to measure the expansion amount of the battery. CN209069247U "A Battery Thickness Measuring Device after Formation" is a measuring device for the total thickness of the battery, only involving a thickness measuring instrument, and does not involve the test of the expansion thickness during the charge and discharge process of the battery under controllable pressure conditions. CN112433158A "A Lithium Ion Battery Expansion Rate" test method has a pressure of 100 - 5000 N, which is much smaller than the pressure value after a single full charge. In its test method, when the pressure is constant, no measures are taken to keep the pressure constant with a spring, only the initial pressure is kept constant, and the pressure during the expansion process cannot be kept constant. CN 212205953 U "A Core Expansion Measuring Device" measures the thickness expansion of the core within a limited space. The pressure of the core causes the spring to compress due to the thickness change, and the pressure can only change passively, without involving the method of actively and precisely controlling the pressure in real time by measuring the spring compression amount in real time and adjusting it at any time. Summary of the Invention

[0005] The technical problem solved by the present invention is as follows: Aiming at the problems in the prior art that for high expansion rate batteries such as metal lithium batteries or silicon-carbon batteries, the pressure change amplitude during charge and discharge is large, the thickness is inconvenient to measure, and the influence of pressure on the battery cycle life cannot be effectively evaluated, a battery charge and discharge thickness measurement system and method with controllable pressure are proposed. By using an appropriate spring design and a method of dynamically controlling the spring compression amount to control the battery pressure, the pressure accuracy can be controlled within 5%, achieving the purpose of quantitatively measuring parameters such as pressure, thickness, and cycle life of high expansion rate batteries during charge and discharge from qualitative judgment; by measuring the distance change amount between two moving platforms, the deformation amount of the volume change of the battery during charge and discharge can be accurately, effectively and real-time measured.

[0006] The solution of the present invention to solve the technical problem is: A battery charge and discharge thickness measurement system with controllable pressure, including a first fixed platform, a first moving platform, a slide bar group, a spring group, a second moving platform, a battery fixing fixture, a second fixed platform, a lift, a first distance measuring instrument and a second distance measuring instrument;

[0007] The first fixed platform is at the bottom, the first moving platform is above the first fixed platform, the lower end of the slide bar group is fixedly connected to the first fixed platform, the first moving platform is slidably connected to the slide bar group and can slide up and down along the slide bar group; the spring group is installed between the first fixed platform and the first moving platform, and the first moving platform compresses the spring group when moving downward; the second moving platform is above the first moving platform, the second moving platform is slidably connected to the slide bar group and can move up and down along the slide bar group; the second fixed platform is above the second moving platform, and the top of the slide bar group is fixedly connected to the second fixed platform; the battery fixing fixture is installed between the first moving platform and the second moving platform, and the battery to be tested is installed inside the battery fixing fixture;

[0008] The lift is installed on the second fixed platform, controls the up and down displacement of the internal screw rod, the lower end of the screw rod is fixedly connected to the second moving platform, and the second moving platform moves up and down under the action of the lift;

[0009] The second moving platform slides downward under the push of pressure, contacts and pushes the battery fixing fixture to squeeze the first moving platform downward, and the first moving platform squeezes the spring group downward to cause the spring group to deform;

[0010] The first distance measuring instrument is installed on the first fixed platform or the first moving platform, and is used to measure the spring compression displacement amount L(t); the second distance measuring instrument is fixedly installed on the first moving platform or the second moving platform, and measures the distance change amount between the first moving platform and the second moving platform during the process from the second moving platform contacting the battery fixing fixture to stopping sliding downward. During the charge and discharge test process, the expansion amplitude Δh of the battery thickness is equal to the distance change amount between the first moving platform and the second moving platform.

[0011] Further, it also includes a motor and a speed reducer;

[0012] The motor and the speed reducer are installed on the second fixed platform, and the transmission shaft of the motor is connected to the transmission shaft of the elevator after being decelerated by the speed reducer.

[0013] Further, the motor is a stepping motor, which realizes the controllable and dynamic adjustment of the value of L(t).

[0014] Further, it also includes a first linear bearing and a second linear bearing;

[0015] The first linear bearing is fixedly installed on the first moving platform, and the first moving platform is in direct contact with and slides on the slide bar group through the balls inside the first linear bearing;

[0016] The second linear bearing is fixedly installed on the second moving platform, and the second moving platform is in direct contact with and slides on the slide bar group through the balls inside the second linear bearing.

[0017] Further, it also includes a collision prevention plate and rollers;

[0018] The collision prevention plate is fixedly installed on the side of the second moving platform and extends downward beyond the lower surface of the second moving platform. The height of the extended part structure is less than the total thickness of the battery fixing fixture, forming a support space after the battery fixing fixture is taken out to prevent the first moving platform and the second moving platform from directly contacting;

[0019] The collision prevention plate is provided with a connection interface with the first moving platform, connecting the second moving platform and the first moving platform as a whole to realize the rapid replacement of the spring group;

[0020] The rollers are installed at the bottom of the first moving platform.

[0021] Further, it also includes an adapter plate;

[0022] The adapter plate is fixedly installed on the upper surface of the first moving platform, including an upper surface, a linear bearing mounting hole, and a positioning slideway; the linear bearing mounting hole is used for installing the first linear bearing, and the upper surface is recessed to form a positioning slideway matching the battery fixing fixture, so that after the battery fixing fixture is placed in the positioning slideway, the battery inside the battery fixing fixture is at the center position of pressure transmission.

[0023] Further, the battery fixing fixture includes a lower clamping plate, an upper clamping plate, a positioning frame, and positioning pins;

[0024] A positioning frame is installed between the lower clamping plate and the upper clamping plate. A battery is installed in the hollow position in the middle of the positioning frame. The thickness of the positioning frame is less than the minimum thickness of a single battery. The positioning pins are fixedly installed on the upper surface of the lower clamping plate, and the positioning pins pass through the positioning holes of the positioning frame and the upper clamping plate to achieve positioning alignment.

[0025] Further, the spring group internally includes a plurality of rectangular springs, and the plurality of rectangular springs are symmetrically distributed. The ultimate deformation amount ΔL 极限 is greater than 100 mm. By adjusting the number and type of springs, the ultimate elastic force F 极限 is between 1000 N and 200000 N.

[0026] A method for measuring the thickness of a battery during charging and discharging with controllable pressure includes the following steps:

[0027] Assume that at time t during system operation, the pressure of the single battery is P(t), the displacement control amount of the motor is J(t), the displacement amount of the spring compression measured by the first rangefinder is L(t), and in the uncompressed state L(t) =, and Δh(t) is the change amount of the thickness of the single battery under test;

[0028] According to the maximum expanded thickness of the test battery, adjust the elastic coefficient of the spring group to match the test battery. Obtain the displacement control amount J(t) of the motor according to P(t), and calibrate the displacement control amount J(t) of the motor through the spring compression displacement amount L(t);

[0029] Place the test battery into the measurement system according to the assembly relationship and connect the charging and discharging equipment;

[0030] Turn on the first rangefinder, and the first rangefinder measures the displacement amount L(t) of the spring compression;

[0031] Start the motor, let the screw of the elevator press down the second moving platform, the second moving platform presses down the battery fixing clamp with the battery, the battery fixing clamp presses down the first moving platform, and the first moving platform compresses the spring group;

[0032] When the moment of detecting L(t)>0 is detected, the displacement control amount J(t) of the motor is synchronously set to zero, and J(t) of the motor gradually increases from 0 to the specified J0, where J0 is the set maximum displacement control amount;

[0033] Turn on the second rangefinder, and the second rangefinder starts to record the change amount Δh(t) of the battery thickness;

[0034] Start the charging and discharging program, and the motor performs real-time dynamic adjustment according to J(t) = L(t) - Δh(t) to continuously control the pressure, realizing the high-precision control function of the pressure;

[0035] The second rangefinder records the change amount Δh(t) of the battery thickness over time t in real time, realizing the thickness measurement function.

[0036] Further, the adjustment of the elastic coefficient of the spring group to match the test battery is specifically as follows:

[0037] Let the maximum expansion amplitude of the battery thickness during charge and discharge be Δh 最大 , and the ultimate deformation amount of the spring group be L 极限 , the maximum displacement of the first moving platform relative to the first fixed platform be L max , the elastic coefficient of the spring group be k, and the maximum allowable pressure of the single battery under test be P max , the pressure-receiving area of the single battery under test be S, and the measurement system should satisfy:

[0038]

[0039] where a is the safety distance and a > 0

[0040] The beneficial effects of the present invention compared with the prior art are as follows:

[0041] (1) By passively providing a constant pressure through the deformation of the spring, the present invention can achieve that the pressure change rate during the expansion and contraction process of battery charge and discharge is not greater than 10% without the need for external real-time voltage stabilization adjustment. The battery cycle charge and discharge test generally takes from 1 month to several years. By this method, energy consumption can be effectively saved

[0042] (2) The present invention adopts a large-amplitude spring deformation design, combines a double displacement measuring instrument to feedback the change of the battery thickness during the charge and discharge process, and dynamically adjusts the pressure conditions in real time through measuring and feedback values to study the influence of complex pressure conditions on the battery cycle life

[0043] (3) The present invention controls the displacement of the elevator through a stepping motor, and combines the measurement data of the first rangefinder during the charge and discharge process of the single battery to dynamically adjust the stepping motor in real time, so that the measurement data of the rangefinder fully meets the required set value, thereby realizing real-time and high-precision control of the pressure and achieving the purpose of controllable pressure

[0044] (4) The second tester of the present invention measures the change amount of the distance between two moving clamping plates, can accurately and indirectly measure the thickness deformation amount during the charge and discharge process of the battery in real time, can effectively study the change of the battery volume during the charge and discharge cycle process, and can solve the problem that ordinary equipment cannot measure the thickness and cycle life under controllable pressure conditions

[0045] (5) The present invention adopts the method of vertical sliding rods cooperating with linear bearings for directional sliding, and at the same time uses pins to fix the relative positions of the upper and lower clamping plates of the battery fixing fixture, which can ensure that the single battery does not deform or slip to cause battery damage under the pressure conditions of 1000N to 200000N Brief Description of the Drawings

[0046] Figure 1 is a schematic diagram of the composition of the charge and discharge thickness measurement system with controllable pressure of the present invention

[0047] Figure 2 Schematic diagram of the battery fixing fixture of the present invention;

[0048] Figure 3 Schematic diagram of the structure of the adapter plate of the present invention. Detailed implementation manners

[0049] The present invention will be further described below with reference to the accompanying drawings.

[0050] As Figure 1 shown, a pressure-controllable battery charge and discharge thickness measurement system proposed by the present invention includes: a first fixed platform 1, a first moving platform 2, a slide bar group 3, a spring group 4, a first linear bearing 5, an adapter plate 6, a second moving platform 7, a second linear bearing 8, a battery fixing fixture 9, a second fixed platform 10, a lift 11, a motor 13, a reducer 14, a first distance measuring instrument 15, a collision prevention plate 16, a roller 17, and a second distance measuring instrument 18.

[0051] The first fixed platform 1 is at the bottom, the first moving platform 2 is above the first fixed platform 1, the slide bar group 3 can be multiple, the lower end of the slide bar group 3 is fixedly connected to the first fixed platform 1, and the first moving platform 2 is slidably connected to the slide bar group 3 and can slide up and down along the slide bar group 3; the spring group 4 is installed between the first fixed platform 1 and the first moving platform 2, and the spring group 4 is compressed when the first moving platform 2 moves downward; the second moving platform 7 is above the first moving platform 2, the second moving platform 7 is slidably connected to the slide bar group 3 and can move up and down along the slide bar group 3; the second fixed platform 10 is above the second moving platform 7, and the top of the slide bar group 3 is fixedly connected to the second fixed platform 10; the battery fixing fixture 9 is installed between the first moving platform 2 and the second moving platform 7, and the battery to be tested is installed inside the battery fixing fixture 9.

[0052] The lift 11 is installed on the second fixed platform 10, the lift 11 can control the up and down displacement of the internal screw 12, and the lower end of the screw 12 is fixedly connected to the second moving platform 7; the second moving platform 7 moves up and down under the action of the lift 11.

[0053] The motor 13 and the reducer 14 are installed on the second fixed platform 10, and the transmission shaft of the motor 13 is connected to the transmission shaft of the lift 11 after being decelerated by the reducer 14. The motor 13 is preferably a stepping motor to achieve controllable and dynamic adjustment of the value of L(t).

[0054] The second moving platform 7 slides downward under the push of pressure, contacts and pushes the battery fixing fixture 9 to squeeze the first moving platform 2 downward, and the first moving platform 2 squeezes the spring group 4 downward to deform the spring group 4.

[0055] The first distance measuring instrument 15 is installed on the first fixed platform 1 or the first moving platform 2 for measuring the spring compression displacement L(t); the second distance measuring instrument 18 is fixedly installed on the first moving platform 2 or the second moving platform 7 to measure the distance change between the first moving platform 2 and the second moving platform 7 during the process from the second moving platform 7 contacting the battery fixing fixture 9 to stopping sliding downwards. During the charge and discharge test process, the expansion amplitude Δh of the battery thickness is equal to the distance change between the first moving platform 2 and the second moving platform 7.

[0056] The first linear bearing 5 is fixedly installed on the first moving platform 2, and the first moving platform 2 is in direct contact with and slides along the slide bar group 3 through the balls inside the first linear bearing 5.

[0057] The second linear bearing 8 is fixedly installed on the second moving platform 7, and the second moving platform 7 is in direct contact with and slides along the slide bar group 3 through the balls inside the second linear bearing 8.

[0058] The anti-collision plate 16 is fixedly installed on the side of the second moving platform 7 and extends downward beyond the lower surface of the second moving platform 7. The height of the extended part structure is less than the total thickness of the battery fixing fixture 9, forming a support space after the battery fixing fixture 9 is taken out to prevent the first moving platform 2 and the second moving platform 7 from directly contacting; the anti-collision plate 16 is provided with a connection interface with the first moving platform 2 to connect the second moving platform 7 and the first moving platform 2 into one body. The second moving platform 7 drives the first moving platform 2 to rise, so that the limiting structure below the first moving platform 2 is separated from the spring group 4, realizing the disassembly of the upper limiting structure of the spring group 4 and the rapid replacement of the spring group 4.

[0059] The adapter plate 6 is fixedly installed on the upper surface of the first moving platform 2. As Figure 3 shown, the adapter plate 6 includes an upper surface 601, a linear bearing mounting hole 602, and a positioning slideway 603; the linear bearing mounting hole 602 is used for installing the first linear bearing 5, and the upper surface 601 is recessed to form a positioning slideway 603 matching the battery fixing fixture 9, so that after the battery fixing fixture 9 is placed in the positioning slideway 603, the battery inside the battery fixing fixture 9 is at the exact center position of pressure transmission.

[0060] The roller 17 is installed at the bottom of the first moving platform 2.

[0061] As Figure 2As shown in the figure, the battery fixing fixture 9 includes a lower clamping plate 901, an upper clamping plate 902, a positioning frame 904 and a positioning pin 905. The positioning frame 904 is installed between the lower clamping plate 901 and the upper clamping plate 902. The battery 903 is installed at the hollow position in the middle of the positioning frame 904. The thickness of the positioning frame 904 is less than the minimum thickness of the single battery. The positioning pin 905 is fixedly installed on the upper surface of the lower clamping plate 901. The positioning pin 905 passes through the positioning holes of the positioning frame 904 and the upper clamping plate 902 to achieve positioning and alignment, and at the same time protect the single battery under test from misalignment of the lower clamping plate 901 and the upper clamping plate 902 during the dynamic pressure test. Otherwise, the single battery is prone to diaphragm breakage and damage, or even fire and explosion.

[0062] The spring group 4 internally includes a plurality of rectangular springs, and the plurality of rectangular springs are symmetrically distributed, with the ultimate deformation amount ΔL 极限 greater than 100 mm. By adjusting the number and type of springs, the ultimate elastic force F 极限 is between 1000 N and 200000 N.

[0063] The measurement accuracy of the first distance measuring instrument 15 is not less than 5 μm, and the measurement accuracy of the second distance measuring instrument 18 is not less than 0.2 mm. The first distance measuring instrument 15 and the second distance measuring instrument 18 are preferably laser distance measuring instruments, and the laser distance measuring instrument can report and transmit the measured distance through voltage analog quantity, current analog quantity or communication data.

[0064] Let the elastic coefficient of the spring group 4 be k, the pressure-bearing area of the test battery be S, the time be t, and the required pressure be P(t). Then the spring compression displacement L(t) is equal to the displacement of the first moving platform 2 and satisfies

[0065] Let the maximum expansion amplitude of the battery thickness during charge and discharge be Δh 最大 , the ultimate deformation amount of the spring group 4 be L 极限 , the maximum displacement of the first moving platform 2 relative to the first fixed platform 1 be L max , the elastic coefficient of the spring group 4 be k, and P max be the maximum allowable pressure of the single battery under test, and S be the pressure-bearing area of the single battery under test. The measurement system should satisfy and L max ≤L 极限 -Δh 最大 -a, where a is the safety distance and a > 0.

[0066] At time t when the system is running, the pressure of the single cell is P(t), the displacement control amount of the stepper motor is J(t), the displacement amount of the spring compression measured by the first rangefinder 15 is L(t), and in the uncompressed state L(t)=0. Δh(t) is the change amount of the thickness of the single cell under test. Based on the battery charge and discharge thickness measurement system of the present invention, the battery charge and discharge process pressure control and thickness measurement method includes the following steps:

[0067] Step 1: According to the maximum expansion thickness of the test battery, adjust the spring force coefficient of the spring group to match the test battery. Obtain the displacement control amount J(t) of the stepper motor according to P(t), and calibrate the displacement control amount J(t) of the stepper motor through the spring compression displacement amount L(t);

[0068] Step 2: Place the test battery into the measurement system according to the assembly relationship and connect the charge and discharge equipment;

[0069] Step 3: Turn on the first rangefinder, and the first rangefinder measures the spring compression displacement amount L(t);

[0070] Step 4: Start the stepper motor, let the screw of the elevator press down the second moving platform, the second moving platform presses down the battery fixing fixture equipped with the battery, and the battery fixing fixture presses down the first moving platform, and the first moving platform compresses the spring group;

[0071] Step 5: When the moment of detecting L(t)>0 is detected, the displacement control amount J(t) of the stepper motor is synchronously set to zero; J(t) of the stepper motor gradually increases from 0 to the specified J0, where J0 is the set maximum displacement control amount;

[0072] Step 6: Turn on the second rangefinder, and the second rangefinder starts to record the battery thickness change amount Δh(t);

[0073] Step 7: Start the charge and discharge program, and the stepper motor performs real-time dynamic adjustment according to J(t)=L(t)-Δh(t) to continuously control the pressure, realizing the high-precision pressure control function;

[0074] Step 8: The second rangefinder records the expansion amount Δh(t) of the battery thickness in real time with respect to time t, realizing the thickness measurement function.

[0075] Although the present invention has been disclosed above with preferred embodiments, it is not used to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention without departing from the spirit and scope of the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the technical solution of the present invention all belong to the protection scope of the technical solution of the present invention.

[0076] The content not detailed in the description of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. A pressure-controllable battery charge and discharge thickness measurement system, characterized in that: It comprises a first fixed platform (1), a first movable platform (2), a sliding rod group (3), a spring group (4), a second movable platform (7), a battery fixing fixture (9), a second fixed platform (10), an elevator (11), a first rangefinder (15) and a second rangefinder (18); The first fixed platform (1) is at the bottom, the first movable platform (2) is above the first fixed platform (1), the lower end of the slide bar group (3) is fixedly connected to the first fixed platform (1), the first movable platform (2) is slidably connected to the slide bar group (3) and can slide up and down along the slide bar group (3); the spring group (4) is installed between the first fixed platform (1) and the first movable platform (2), and the spring group (4) is compressed when the first movable platform (2) moves downward; the second movable platform (7) is above the first movable platform (2), the second movable platform (7) is slidably connected to the slide bar group (3) and can move up and down along the slide bar group (3); the second fixed platform (10) is above the second movable platform (7), the top of the slide bar group (3) is fixedly connected to the second fixed platform (10); the battery fixing fixture (9) is installed between the first movable platform (2) and the second movable platform (7), and the battery to be tested is installed inside the battery fixing fixture (9); The lift (11) is installed on the second fixed platform (10) to control the internal screw (12) to move up and down. The lower end of the screw (12) is fixedly connected to the second movable platform (7). The second movable platform (7) moves up and down under the action of the lift (11); The second mobile platform (7) slides downward under the pressure, contacts and pushes the battery fixing fixture (9) to press the first mobile platform (2) downward, and the first mobile platform (2) presses the spring group (4) downward to cause the spring group (4) to deform; The first distance meter (15) is mounted on the first fixed platform (1) or the first mobile platform (2) and is used to measure the spring compression displacement L(t); the second distance meter (18) is fixedly mounted on the first mobile platform (2) or the second mobile platform (7) and is used to measure the distance change between the first mobile platform (2) and the second mobile platform (7) from the time when the second mobile platform (7) contacts the battery fixing fixture (9) to the time when the second mobile platform (7) stops sliding downward; during the charge and discharge test process, the expansion amplitude Δh of the battery thickness is equal to the distance change between the first mobile platform (2) and the second mobile platform (7).

2. A pressure-controllable battery charge and discharge thickness measurement system according to claim 1, characterized in that: It also includes a motor (13) and a reducer (14); The motor (13) and the reducer (14) are installed on the second fixed platform (10), and the transmission shaft of the motor (13) is connected to the transmission shaft of the elevator (11) after being reduced in speed by the reducer (14).

3. A pressure-controllable battery charge and discharge thickness measurement system according to claim 2, characterized in that: The motor (13) is a stepping motor, which enables controllable and dynamic adjustment of the value of L(t).

4. A pressure-controllable battery charge and discharge thickness measurement system according to claim 1, characterized in that: It also includes a first linear bearing (5) and a second linear bearing (8); The first linear bearing (5) is fixedly mounted on the first movable platform (2), and the first movable platform (2) directly contacts and slides with the slide bar group (3) via the balls inside the first linear bearing (5); The second linear bearing (8) is fixedly mounted on the second movable platform (7), and the second movable platform (7) directly contacts and slides with the slide bar group (3) via the balls inside the second linear bearing (8).

5. The pressure-controllable battery charge and discharge thickness measurement system according to claim 1, characterized in that: It also includes an anti-collision plate (16) and a roller (17); The anti-collision plate (16) is fixedly mounted on the side of the second mobile platform (7) and extends downwardly from the lower surface of the second mobile platform (7); the height of the extended portion structure is less than the total thickness of the battery fixing fixture (9); a support space is formed after the battery fixing fixture (9) is removed, thereby preventing the first mobile platform (2) and the second mobile platform (7) from direct contact; The anti-collision plate (16) is provided with a connection interface with the first mobile platform (2), so that the second mobile platform (7) and the first mobile platform (2) are connected as a whole, thereby realizing rapid replacement of the spring group (4); The roller (17) is installed at the bottom of the first mobile platform (2).

6. A pressure-controllable battery charge and discharge thickness measurement system according to claim 4, characterized in that: Also includes an adapter plate (6); The adapter plate (6) is fixedly mounted on the upper surface of the first mobile platform (2), and comprises an upper surface (601), a linear bearing mounting hole (602) and a positioning slideway (603); the linear bearing mounting hole (602) is used to mount the first linear bearing (5), and the upper surface (601) is concave to form a positioning slideway (603) matched with the battery fixing fixture (9), so that after the battery fixing fixture (9) is placed in the positioning slideway (603), the battery inside the battery fixing fixture (9) is in the exact center position for pressure transmission.

7. A pressure-controllable battery charge and discharge thickness measurement system according to claim 1, characterized in that: The battery fixing fixture (9) comprises a lower clamping plate (901), an upper clamping plate (902), a positioning frame (904) and a positioning pin (905); A positioning frame (904) is installed between the lower clamping plate (901) and the upper clamping plate (902), and a battery (903) is installed in the hollow position in the middle of the positioning frame (904). The thickness of the positioning frame (904) is less than the minimum thickness of a single battery. A positioning pin (905) is fixedly installed on the upper surface of the lower clamping plate (901), and the positioning pin (905) passes through the positioning holes of the positioning frame (904) and the upper clamping plate (902) to achieve positioning and alignment.

8. The pressure-controllable battery charge and discharge thickness measurement system according to claim 1, characterized in that: The spring group (4) comprises a plurality of rectangular springs, the plurality of rectangular springs are symmetrically distributed, and the limit deformation ΔL 极限 If the spring length is greater than 100 mm, the limit spring force F can be achieved by adjusting the number and type of springs. 极限 Between 1000N and 200000N.

9. A pressure-controllable battery charge and discharge thickness measurement method based on the system according to any one of claims 2 to 8, characterized in that: The following steps are involved: Assume that at time t when the system is running, the pressure of the single battery is P(t), the displacement control amount of the motor (13) is J(t), the displacement amount of the spring compression measured by the first rangefinder (15) is L(t), the uncompressed state L(t)=0, and Δh(t) is the change in thickness of the single battery under test; According to the maximum expansion thickness of the test battery, the elastic coefficient of the spring group (4) is adjusted to match the test battery, the displacement control amount J(t) of the motor (13) is obtained according to P(t), and the displacement control amount J(t) of the motor (13) is calibrated by the spring compression displacement amount L(t); Place the test battery into the measurement system according to the assembly relationship and connect the charging and discharging equipment; Turning on the first distance meter (15), the first distance meter (15) measures the spring compression displacement L(t); The motor (13) is started, so that the screw rod of the lift (11) presses down the second mobile platform (7), the second mobile platform (7) presses down the battery fixing fixture equipped with the battery, the battery fixing fixture presses down the first mobile platform (2), and the first mobile platform (2) compresses the spring group (4); When L(t)>0 is detected, the displacement control amount J(t) of the motor (13) is synchronously set to zero, and the J(t) of the motor (13) gradually increases from 0 to a specified J0, where J0 is the set maximum displacement control amount; Turning on the second distance meter (18), so that the second distance meter (18) starts to record the battery thickness change Δh(t); When the charging and discharging procedure is started, the motor (13) performs real-time dynamic adjustment according to J(t)=L(t)-Δh(t) to continuously control the pressure, thereby realizing a high-precision pressure control function; The second distance meter (18) records in real time the change Δh(t) of the battery thickness over time t, thereby realizing a thickness measurement function.

10. A pressure-controlled battery charge and discharge thickness measurement method according to claim 9, characterized in that: The elastic coefficient of the regulating spring group (4) is kept matching with the test battery, specifically: Assume that the maximum expansion amplitude of the battery thickness during the charge and discharge process is Δh 最大 , the limit deformation of the spring group (4) is L 极限 , the maximum displacement of the first mobile platform (2) relative to the first fixed platform (1) is L max The elastic coefficient of the spring group (4) is k, and the maximum allowable pressure of the tested single battery is P max , the pressure area of ​​the tested single cell is S, and the measurement system should meet the following requirements: and L max ≤ L 极限 -Δh 最大 -a Where a is the safety distance, a>0.

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