An in-situ stress gage expansion testing device and method

Abstract

This disclosure relates to an online in-situ stress electrode expansion testing device and method, including a clamping mechanism, a sealing test unit, and a pressure sensor. The sealing test unit includes a fixed part and a movable force transmission part. A sealed test cavity is formed within the fixed part to accommodate the electrode assembly under test and the electrolyte. A rolling guide assembly is provided between the movable force transmission part and the fixed part. The rolling guide assembly includes multiple rolling elements distributed circumferentially along the movable force transmission part, and each rolling element makes rolling contact with the fixed part and the movable force transmission part respectively. The expansion force is transmitted to the pressure sensor through the sealing test unit in conjunction with the movable force transmission part, realizing online in-situ detection of electrode expansion stress during charging and discharging. At the same time, the rolling elements can reduce the frictional resistance generated by ordinary sliding fit. The roller and the upper electrode mold are almost completely sealed, preventing electrolyte leakage. This allows the pressure change obtained by the pressure sensor to more accurately reflect the actual expansion stress of the electrode assembly under test.

Description

Technical Field

[0001] This disclosure relates to the field of battery testing technology, and more specifically, to an online in-situ stress electrode expansion testing device and method. Background Technology

[0002] During the charging and discharging process of lithium-ion batteries, lithium ions repeatedly insert and extract within the positive and negative electrode materials, causing the electrodes to expand and contract along their thickness, generating corresponding expansion stress. This expansion behavior is particularly problematic for silicon-carbon anodes, graphite anodes, and some high-capacity cathode materials. It affects the interlayer contact, the stress state of the separator, and the stability of the battery's internal structure. Long-term accumulation can lead to electrode powder shedding, interface failure, cell bulging, and decreased cycle performance. Therefore, online in-situ detection of electrode expansion stress under electrolyte wetting and charge / discharge conditions is crucial for electrode material selection, formulation optimization, battery structure design, and cycle life evaluation.

[0003] Existing online in-situ expansion stress detection technologies typically assemble the electrode under test, diaphragm, and mating electrodes into a test chamber capable of containing electrolyte. This chamber is connected to an external charging / discharging device via conductive terminals. A clamping mechanism applies a predetermined clamping action to the test chamber, allowing the thickness-direction expansion force generated during electrode charging and discharging to be transmitted to the pressure detection device via a clamping or force-transmitting component. To limit the movement direction of the force-transmitting component and maintain the relative position of the test components, existing devices generally use guide holes, guide sleeves, or mutually fitting rigid surfaces for sliding contact. When the expansion force generated by the electrode is small, this force must first overcome the static frictional resistance of the sliding contact area, resulting in only a portion of the force being transmitted to the pressure detection device. Furthermore, assembly gaps, component misalignment, surface wear, and changes in clamping conditions can cause fluctuations in frictional resistance, easily leading to data lag, distortion, or decreased repeatability. Therefore, existing technologies struggle to reduce frictional losses during the transmission of electrode expansion force, and the pressure detection results cannot accurately reflect the actual expansion stress of the electrode during charging and discharging.

[0004] Therefore, improvements are needed to the existing technology to solve the technical problem that the force transmission loss caused by sliding friction when the electrode expansion force is transmitted to the pressure sensor during the testing process leads to distortion of the expansion stress detection results. Summary of the Invention

[0005] The purpose of this disclosure is to provide an online in-situ stress electrode expansion testing device and method to solve the above-mentioned technical problems.

[0006] Other features and advantages of this disclosure will become apparent from the following detailed description, or may be learned in part from practice of this disclosure.

[0007] According to one aspect of this disclosure, an online in-situ stress electrode expansion testing device is provided, including a clamping mechanism, a sealed testing unit disposed within the clamping mechanism and capable of charging and discharging, and a pressure sensor; The sealing test unit includes a fixed part and a movable force transmission part. The fixed part forms a sealed test cavity that accommodates the electrode assembly to be tested and the electrolyte. The movable force transmission part is movably sealed and fitted with the fixed part along the thickness direction of the electrode assembly to be tested. One end of the movable force transmission part abuts against the electrode assembly to be tested, and the other end abuts against the pressure sensor. A rolling guide assembly is provided between the movable force transmission part and the fixed part. The rolling guide assembly includes a plurality of rolling elements distributed circumferentially along the movable force transmission part, and each rolling element makes rolling contact with the fixed part and the movable force transmission part respectively.

[0008] Optionally, the rolling guide assembly further includes an annular retainer, which is sleeved on the outer periphery of the movable force transmission part and located inside the fixed part, and the annular retainer is provided with a plurality of retaining holes spaced apart along its circumference; Multiple rolling elements are disposed in multiple retaining holes in a corresponding manner. Each rolling element protrudes partially from the inner and outer circumferential surfaces of the annular retaining element and makes rolling contact with the outer circumferential surface of the movable force transmission part and the inner circumferential surface of the fixed part, respectively.

[0009] Optionally, a first annular seal is provided between the fixed part and the movable force transmission part. The first annular seal is arranged around the movable force transmission part and makes sealing contact with the inner peripheral surface of the fixed part and the outer peripheral surface of the movable force transmission part, respectively. Along the moving direction of the active force transmission part, the first annular seal is located between the sealing test cavity and the rolling guide assembly, so as to isolate the rolling guide assembly from the sealing test cavity.

[0010] Optionally, the inner peripheral surface of the fixed part is provided with a plurality of first guide grooves, and the outer peripheral surface of the movable force transmission part is provided with a plurality of second guide grooves corresponding one-to-one with the plurality of first guide grooves. Both the first guide grooves and the second guide grooves extend along the moving direction of the movable force transmission part. The corresponding first guide groove and the second guide groove together form a rolling channel, and each of the rolling elements passes through the corresponding retaining hole and is disposed in the corresponding rolling channel.

[0011] Optionally, the electrode assembly under test includes a first electrode sheet, a diaphragm, and a second electrode sheet stacked sequentially along its thickness direction; The movable force transmission part is made of conductive material and abuts against the first electrode sheet. The fixing part includes a conductive support part disposed on the side of the second electrode sheet away from the diaphragm, and the conductive support part abuts against the second electrode sheet. The movable force transmission part and the conductive support part are respectively provided with a first wiring part and a second wiring part extending to the outside of the sealed test chamber.

[0012] Optionally, the fixing part further includes a test housing and a threaded locking member. The test housing has a first port and a second port that are disposed opposite to each other along the thickness direction of the electrode assembly under test. The movable force transmission part passes through the first port, and the conductive support part is installed at the second port. A first annular seal is provided between the movable force transmission part and the first port. The threaded locking part is sleeved on the movable force transmission part and threadedly connected to the test housing. The first annular seal is sandwiched between the threaded locking part and the test housing. The conductive support is threadedly connected to the second port, and a second annular seal is sandwiched between the conductive support and the test housing. The test housing, the movable force transmission part, and the conductive support together enclose the sealed test cavity.

[0013] Optionally, the clamping mechanism includes a first clamping member, a second clamping member, at least two support columns, and adjusting nuts corresponding to the support columns. The first clamping member and the second clamping member are arranged opposite to each other along the thickness direction of the electrode assembly to be tested, and at least two support columns are spaced apart on the outer periphery of the sealing test unit. One end of the support column is fixedly connected to the second clamping member, the first clamping member is slidably sleeved on the support column, and the adjusting nut is threadedly connected to the support column and abuts against the side of the first clamping member away from the second clamping member.

[0014] Optionally, the sealing test unit is supported on the side of the second clamping member facing the first clamping member, the pressure sensor is installed on the first clamping member, and the detection end of the pressure sensor and the movable force transmission part are arranged opposite to each other along the thickness direction of the electrode assembly under test.

[0015] This invention also provides an online in-situ stress electrode expansion testing method, implemented using the online in-situ stress electrode expansion testing device described above. The testing method includes the following steps: S1, Place the electrode assembly to be tested into a sealed test chamber, add electrolyte into the sealed test chamber and seal it, so that the electrode assembly to be tested is electrically connected to an external charging and discharging device; S2, install the sealing test unit on the clamping mechanism, so that the movable force transmission part abuts against the pressure sensor, adjust the clamping mechanism to apply an initial load to the sealing test unit, and obtain the initial pressure value after the pressure value of the pressure sensor stabilizes. S3, the test electrode assembly is charged and discharged by the external charging and discharging device. The test electrode assembly expands along its thickness direction and pushes the movable force transmission part to move. The rolling guide assembly rolls and guides the movable force transmission part during its movement. The detection pressure value during the charging and discharging process is obtained by the pressure sensor. S4. Determine the change in expansion stress of the electrode assembly under test based on the difference between the detected pressure value and the initial pressure value.

[0016] Optionally, step S2 includes the following steps: S21, the sealed test unit is left to stand for a preset immersion time after sealing is completed, so that the electrolyte wets the electrode assembly to be tested. S22, the sealing test unit is carried in the clamping mechanism, the clamping mechanism is adjusted so that the movable force transmission part is in contact with the pressure sensor, and the pressure value of the pressure sensor reaches the preset initial pressure range; S23, continuously acquire the pressure value of the pressure sensor according to the preset sampling interval. When the difference between two consecutive acquired pressure values ​​is not greater than the preset pressure stability threshold, determine the currently acquired pressure value as the initial pressure value and determine the corresponding time as the test start time.

[0017] As can be seen from the above technical solutions, the exemplary embodiments disclosed herein possess at least the following advantages and positive effects: In some embodiments of the present disclosure, the following technical solutions are provided: During testing, a sealed test unit containing the electrode assembly to be tested and the electrolyte is installed in a clamping mechanism, such that one end of the movable force transmission part abuts against the electrode assembly to be tested, and the other end abuts against a pressure sensor; the electrode assembly to be tested is charged and discharged within the sealed test chamber, and expands or contracts along the thickness direction during lithium insertion or delithiation; when the electrode assembly to be tested expands, it applies a force to the movable force transmission part, pushing the movable force transmission part to move relative to the fixed part along the thickness direction of the electrode assembly to be tested; during the movement of the movable force transmission part, multiple rolling elements distributed circumferentially thereon make rolling contact with the fixed part and the movable force transmission part respectively, so as to guide the movement of the movable force transmission part and reduce the motion resistance it experiences; The dynamic force transmission unit then transmits the expansion force generated by the electrode assembly under test to the pressure sensor, which in turn acquires the expansion stress change of the electrode assembly under test during charging and discharging. This solution uses a sealed test unit combined with the dynamic force transmission unit to transmit the expansion force to the pressure sensor, realizing online in-situ detection of electrode expansion stress during charging and discharging. At the same time, by setting multiple circumferentially distributed rolling elements between the dynamic force transmission unit and the fixed part, the dynamic force transmission unit obtains rolling guidance when moving under force, which can reduce the frictional resistance and force transmission loss caused by ordinary sliding fit, and reduce the influence of the deviation of the dynamic force transmission unit on the detection results, so that the pressure change acquired by the pressure sensor more accurately reflects the actual expansion stress of the electrode assembly under test.

[0018] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings: Figure 1 This is a schematic diagram of the overall structure of the online in-situ stress electrode expansion testing device in this embodiment.

[0020] Figure 2 This is an axial sectional view of the sealing test unit in the online in-situ stress electrode expansion test device of this embodiment.

[0021] Figure 3 This is a cross-sectional view of the rolling guide assembly in the online in-situ stress electrode expansion testing device of this embodiment.

[0022] Figure 4This is a partial axial cross-sectional view of the rolling guide assembly and the first annular seal in the online in-situ stress electrode expansion testing device of this embodiment.

[0023] Illustrations: 10. Clamping mechanism; 11. First clamping element; 12. Second clamping element; 13. Support column; 14. Adjusting nut; 20. Sealing test unit; 21. Fixing part; 22. Test housing; 221. First port; 222. Second port; 223. Threaded locking part; 224. Conductive support part; 225. Second wiring part; 23. Sealed test chamber; 24. Movable force transmission part; 241. First wiring part; 25. Electrode assembly to be tested; 251. First electrode plate; 252. Diaphragm; 253. Second electrode plate; 254. Electrolyte; 30. Pressure sensor; 31. Detection end; 40. Rolling guide assembly; 41. Annular retainer; 42. Retaining hole; 43. Rolling element; 44. First annular seal; 45. Second annular seal; 46. First guide groove; 47. Second guide groove; 48. Rolling channel. Detailed Implementation

[0024] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be more thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art.

[0025] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., may be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0026] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0027] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0028] Example 1: Figure 1 This is a schematic diagram of the overall structure of the online in-situ stress electrode expansion testing device in this embodiment. It shows the overall arrangement of the clamping mechanism, the sealing test unit and the pressure sensor, as well as the positional relationship between the detection end of the pressure sensor and the movable force transmission part.

[0029] Figure 2 This is an axial sectional view of the sealing test unit in the online in-situ stress electrode expansion testing device of this embodiment, which shows the assembly relationship of the fixed part, the movable force transmission part, the sealing test chamber, the electrode assembly under test, the rolling guide assembly, and the sealing structure along the thickness direction of the electrode assembly under test.

[0030] Figure 3 This is a transverse cross-sectional view of the rolling guide assembly in the online in-situ stress electrode expansion testing device of this embodiment. It shows that the annular retainer is sleeved on the outer periphery of the active force transmission part, multiple rolling elements are distributed along the circumference of the active force transmission part, and the structure in which the first guide groove and the second guide groove together form a rolling channel.

[0031] Figure 4 This is a partial axial cross-sectional view of the rolling guide assembly and the first annular seal in the online in-situ stress electrode expansion testing device of this embodiment. It shows the rolling contact relationship between the rolling element and the fixed part and the movable force transmission part, as well as the positional relationship of the first annular seal between the sealing test cavity and the rolling guide assembly.

[0032] like Figures 1 to 4 As shown, an online in-situ stress electrode expansion testing device is provided, including a clamping mechanism 10, a sealed testing unit 20 disposed in the clamping mechanism 10 and capable of charging and discharging, and a pressure sensor 30.

[0033] The sealing test unit 20 includes a fixed part 21 and a movable force transmission part 24. The fixed part 21 forms a sealed test cavity 23 that accommodates the electrode assembly 25 to be tested and the electrolyte 254. The movable force transmission part 24 is movably sealed and fitted with the fixed part 21 along the thickness direction of the electrode assembly 25 to be tested. One end of the movable force transmission part 24 abuts against the electrode assembly 25 to be tested, and the other end abuts against the pressure sensor 30.

[0034] It should be noted that the sealed test unit 20 for charging and discharging in this solution does not involve placing the finished battery that has already been packaged into the device for testing. Instead, it places the electrode assembly 25 to be tested in a sealed environment and brings it into contact with the liquid electrolyte 254, thereby forming a test system capable of electrochemical charging and discharging.

[0035] Depending on the testing objective, the electrode assembly 25 under test can be made of silicon-carbon anode, graphite anode, or cathode material. It can also be a half-cell system composed of the electrode under test and lithium metal, or a full-cell system composed of a cathode and anode. During the test, the sealed test unit 20 can be connected to an external electrochemical workstation or charge / discharge equipment. Without disassembling the electrode assembly 25 under test or damaging its electrolyte 254 wetting environment, charge / discharge tests and expansion stress detection can be performed simultaneously, thereby obtaining pressure change data of the same electrode assembly 25 under test at different stages such as static wetting, charging lithium insertion, and discharging lithium extraction.

[0036] Specifically, the sealed test chamber 23 provides the electrode assembly under test 25 with an electrolyte 254 immersion environment isolated from the external air. The fixed part 21 serves as a fixed reference when the movable force transmission part 24 moves. The movable force transmission part 24 can respond to the small expansion displacement of the electrode assembly under test 25 along the thickness direction. Before the test begins, the electrode assembly under test 25 can be left to stand and immerse in the electrolyte 254. After the detection value of the pressure sensor 30 tends to stabilize, the pressure value in the stable state is used as the initial pressure value. During the charging process, the electrode assembly under test 25 undergoes a lithium intercalation reaction and expands along the thickness direction, thereby pushing the movable force transmission part 24 toward the pressure sensor 30. The force generated by the expansion is transmitted along the path of "electrode assembly under test 25 - movable force transmission part 24 - pressure sensor 30". During the discharging process, as the electrode assembly under test 25 delithiates and contracts, the force applied to the movable force transmission part 24 decreases accordingly, and the detection value of the pressure sensor 30 changes accordingly. Therefore, the pressure change obtained by the pressure sensor 30 can continuously reflect the expansion stress change of the electrode assembly under test 25 during the charging and discharging process.

[0037] A rolling guide assembly 40 is provided between the movable force transmission part 24 and the fixed part 21. The rolling guide assembly 40 includes a plurality of rolling elements 43 distributed circumferentially along the movable force transmission part 24. Each rolling element 43 makes rolling contact with the fixed part 21 and the movable force transmission part 24 respectively.

[0038] Preferably, the multiple rolling elements 43 are evenly distributed circumferentially along the movable force transmission part 24, and roll synchronously between the fixed part 21 and the movable force transmission part 24 as the movable force transmission part 24 moves along the thickness direction of the electrode assembly under test 25. The multiple rolling elements 43 mainly undertake the rolling guidance and circumferential straightening functions of the movable force transmission part 24. The expansion force is still directly transmitted from the electrode assembly under test 25 to the pressure sensor 30 through the movable force transmission part 24. This can convert the sliding friction between the movable force transmission part 24 and the fixed part 21 into rolling friction, reduce the friction loss of the small expansion force during the transmission process, and reduce the possibility of the movable force transmission part 24 becoming misaligned or stuck.

[0039] Let the initial pressure value be P0 when the static soaking is completed and the pressure value is stable, and the detection pressure value at any test moment during the charge and discharge process be P. t Then it can be calculated according to η = (P t The relative expansion characterization value is obtained by dividing P0 by P0 × 100%. For example, P0 is 108.4000, P t When the value is 125.3000, η ​​is approximately 15.59%. Where P0 and P... t Using the same detection unit, η is used to characterize the degree of expansion stress change of the electrode assembly 25 under test relative to the initial state; after further establishing the calibration relationship between pressure change and electrode thickness change or volume change, the corresponding geometric expansion rate can also be determined accordingly.

[0040] The working principle of this invention is as follows: During testing, a sealed test unit 20 containing the electrode assembly 25 to be tested and the electrolyte 254 is installed in the clamping mechanism 10, so that one end of the movable force transmission part 24 abuts against the electrode assembly 25 to be tested, and the other end abuts against the pressure sensor 30; the electrode assembly 25 to be tested is charged and discharged in the sealed test chamber 23, and expands or contracts along the thickness direction during lithium insertion or delithiation; when the electrode assembly 25 to be tested expands, it applies a force to the movable force transmission part 24, pushing the movable force transmission part 24 to move relative to the fixed part 21 along the thickness direction of the electrode assembly 25 to be tested; during the movement of the movable force transmission part 24, a plurality of rolling elements 43 distributed circumferentially thereon make rolling contact with the fixed part 21 and the movable force transmission part 24 respectively, so as to guide the movement of the movable force transmission part 24 and reduce the motion resistance it experiences; The force transmission unit 24 then transmits the expansion force generated by the electrode assembly under test 25 to the pressure sensor 30, and the pressure sensor 30 obtains the expansion stress change of the electrode assembly under test 25 during the charging and discharging process. This scheme uses the sealed test unit 20 in conjunction with the movable force transmission unit 24 to transmit the expansion force to the pressure sensor 30, realizing online in-situ detection of the electrode expansion stress during the charging and discharging process. At the same time, by setting multiple circumferentially distributed rolling elements 43 between the movable force transmission unit 24 and the fixed part 21, the movable force transmission unit 24 obtains rolling guidance when it moves under force, which can reduce the frictional resistance generated by ordinary sliding fit and the resulting force transmission loss, and reduce the influence of the deviation of the movable force transmission unit 24 on the detection results, so that the pressure change obtained by the pressure sensor 30 more accurately reflects the actual expansion stress of the electrode assembly under test 25.

[0041] In this embodiment, the rolling guide assembly 40 further includes an annular retainer 41, which is sleeved on the outer periphery of the movable force transmission part 24 and located inside the fixed part 21. The annular retainer 41 is provided with a plurality of retaining holes 42 at intervals along its circumference. A plurality of rolling elements 43 are correspondingly disposed in the plurality of retaining holes 42. Each rolling element 43 protrudes partially from the inner and outer circumferential surfaces of the annular retainer 41 and rolls in contact with the outer circumferential surface of the movable force transmission part 24 and the inner circumferential surface of the fixed part 21, respectively.

[0042] Specifically, the annular retainer 41 mainly constrains the circumferential spacing and relative position of each rolling element 43, enabling multiple rolling elements 43 to form a stable multi-point rolling support around the movable force transmission part 24. Assembly gaps can be maintained between the annular retainer 41 and the movable force transmission part 24 and the fixed part 21, respectively, so that the load is mainly transmitted through the rolling elements 43, avoiding direct friction between the annular retainer 41 and the movable force transmission part 24 or the fixed part 21. When the movable force transmission part 24 moves along the thickness direction of the electrode assembly 25 under test, each rolling element 43 rolls between two opposing surfaces, and the annular retainer 41 adapts to the rolling elements 43, thereby maintaining the distribution state of each rolling element 43. The rolling elements 43 can be balls or rollers, preferably zirconia ceramic balls with high hardness, corrosion resistance, and good electrical insulation properties, to improve the stability of the rolling guide assembly 40 under long-term reciprocating micro-displacement conditions.

[0043] In this embodiment, a first annular seal 44 is provided between the fixed part 21 and the movable force transmission part 24. The first annular seal 44 is arranged around the movable force transmission part 24 and makes sealing contact with the inner peripheral surface of the fixed part 21 and the outer peripheral surface of the movable force transmission part 24, respectively. Along the moving direction of the movable force transmission part 24, the first annular seal 44 is located between the sealing test cavity 23 and the rolling guide assembly 40, so as to isolate the rolling guide assembly 40 from the sealing test cavity 23.

[0044] Preferably, the first annular seal 44 is made of fluororubber material resistant to electrolyte 254 corrosion. It forms a sealing boundary between the sealed test chamber 23 and the rolling guide assembly 40, so that the electrode assembly under test 25 and the electrolyte 254 are located on one side of the sealing boundary, while the rolling guide assembly 40 is located on the other side. This prevents electrolyte 254 from entering the contact area between the rolling element 43 and the movable force transmission part 24 and the fixed part 21, reducing the impact of electrolyte 254 evaporation, crystallization, or corrosion on the rolling state, and preventing side reactions between the material of the rolling element 43 and the electrolyte 254 that could contaminate the electrode assembly under test 25. The compression of the first annular seal 44 can be appropriately reduced while meeting the sealing requirements to reduce its resistance to the movement of the movable force transmission part 24, so that the movable force transmission part 24 can maintain a sealed fit and sensitively respond to the small expansion force generated by the electrode assembly under test 25.

[0045] In this embodiment, it is further explained that the inner peripheral surface of the fixing part 21 is provided with a plurality of first guide grooves 46, and the outer peripheral surface of the movable force transmission part 24 is provided with a plurality of second guide grooves 47 corresponding one-to-one with the plurality of first guide grooves 46. The first guide grooves 46 and the second guide grooves 47 both extend along the moving direction of the movable force transmission part 24. The corresponding first guide grooves 46 and the second guide grooves 47 together enclose a rolling channel 48, and each rolling element 43 passes through the corresponding retaining hole 42 and is disposed in the corresponding rolling channel 48.

[0046] It should be noted that the first guide groove 46 and the second guide groove 47 define the rolling trajectory of each rolling element 43 along the moving direction of the movable force transmission part 24. Their cross-sectional profile can be adapted to the outer profile of the rolling element 43, and a fitting clearance that meets the rolling requirements is maintained. When the electrode assembly under test 25 expands or contracts and drives the movable force transmission part 24 to reciprocate, each rolling element 43 rolls along the corresponding rolling channel 48, avoiding circumferential movement, mutual aggregation, or separation from the predetermined position of the rolling elements 43. The multiple rolling channels 48 distributed circumferentially restrict the radial offset and circumferential rotation of the movable force transmission part 24, thereby reducing the possibility of the movable force transmission part 24 deflection, jamming, and increased local friction.

[0047] The rolling element 43 mainly serves as a guide and straightener. The axial expansion force generated by the electrode assembly under test 25 is still directly transmitted to the pressure sensor 30 through the movable force transmission part 24, which helps to maintain the continuity of the expansion stress transmission path and the repeatability of the test results.

[0048] In this embodiment, the electrode assembly under test 25 includes a first electrode sheet 251, a diaphragm 252, and a second electrode sheet 253 stacked sequentially along its thickness direction; the movable force transmission part 24 is made of conductive material and abuts against the first electrode sheet 251; the fixing part 21 includes a conductive support part 224 disposed on the side of the second electrode sheet 253 away from the diaphragm 252, and the conductive support part 224 abuts against the second electrode sheet 253; the movable force transmission part 24 and the conductive support part 224 are respectively provided with a first wiring part 241 and a second wiring part 225 extending to the outside of the sealed test chamber 23.

[0049] Specifically, the names of the first electrode 251 and the second electrode 253 are mainly used to distinguish their relative positions within the sealed test chamber 23, and do not constitute a limitation on the electrode polarity. When testing negative electrode materials, one of the electrode sheets can be a silicon-carbon negative electrode sheet or a graphite negative electrode sheet, and the other electrode sheet can be a lithium metal sheet or a matching positive electrode sheet; when testing positive electrode materials or full cells, the material combination of the two electrode sheets can also be adjusted accordingly.

[0050] The movable force transmission part 24 and the conductive support part 224, while supporting the electrode assembly under test 25, respectively form conductive paths on both sides. The first wiring part 241 and the second wiring part 225 can be connected to an external electrochemical workstation or charge-discharge equipment, thereby completing constant current charge-discharge, cyclic charge-discharge, or cyclic voltammetry tests in a sealed state. To avoid mutual interference between the detection circuit and the charge-discharge circuit, the pressure sensor 30 and the clamping mechanism 10 can maintain electrical isolation from the charge-discharge circuit where the first wiring part 241 and the second wiring part 225 are located.

[0051] In this embodiment, the fixing part 21 further includes a test housing 22 and a threaded locking member 223. The test housing 22 has a first port 221 and a second port 222 that are arranged opposite to each other along the thickness direction of the electrode assembly 25 to be tested. The movable force transmission part 24 passes through the first port 221, and the conductive support part 224 is installed at the second port 222. A first annular seal 44 is provided between the movable force transmission part 24 and the first port 221. The threaded locking member 223 is sleeved on the movable force transmission part 24 and threadedly connected to the test housing 22. The first annular seal 44 is sandwiched between the threaded locking member 223 and the test housing 22.

[0052] The conductive support 224 is threadedly connected to the second port 222, and a second annular seal 45 is sandwiched between the conductive support 224 and the test housing 22. The test housing 22, the movable force transmission part 24 and the conductive support 224 together form a sealed test cavity 23.

[0053] Preferably, the test housing 22 is made of an insulating material resistant to electrolyte 254 corrosion, so as to maintain electrical insulation between the movable force transmission part 24 and the conductive support part 224; the first annular seal 44 and the second annular seal 45 can be made of fluororubber material resistant to electrolyte 254. During assembly, the electrode assembly to be tested 25 can be placed in the test housing 22 and electrolyte 254 can be added. Then, the second port 222 is closed by the conductive support part 224, and the first annular seal 44 is pressed by the threaded locking part 223, so that the two ports are sealed respectively.

[0054] The threaded connection facilitates adjustment of the compression of the annular seal 44. The compression of the first annular seal 44 is preferably sufficient to prevent leakage of the electrolyte 254 without hindering the slight axial movement of the movable force transmission part 24. This structure can be assembled in a controlled environment such as a glove box and reduces the ingress of external moisture and the evaporation or leakage of the electrolyte 254 during testing, making it suitable for long-duration cyclic charge-discharge tests.

[0055] In this embodiment, the clamping mechanism 10 includes a first clamping member 11, a second clamping member 12, at least two support columns 13, and adjusting nuts 14 corresponding to the support columns 13. The first clamping member 11 and the second clamping member 12 are arranged opposite to each other along the thickness direction of the electrode assembly 25 to be tested. The at least two support columns 13 are spaced apart on the outer periphery of the sealing test unit 20. One end of the support column 13 is fixedly connected to the second clamping member 12. The first clamping member 11 is slidably sleeved on the support column 13. The adjusting nut 14 is threadedly connected to the support column 13 and abuts against the side of the first clamping member 11 away from the second clamping member 12.

[0056] It should be noted that at least two support columns 13 form a rigid limiting frame around the outer periphery of the sealing test unit 20, enabling the first clamping member 11 to maintain a relatively stable parallel state relative to the second clamping member 12. Preferably, three support columns 13 are provided and are distributed at intervals around the sealing test unit 20 to improve the clamping mechanism 10's ability to resist off-center loading and tilting.

[0057] During clamping, the adjusting nuts 14 can be turned sequentially or simultaneously to allow the first clamping member 11 to move smoothly along the support column 13 and gradually apply an initial load to the sealing test unit 20. By adjusting the position of each adjusting nut 14, the distance between the first clamping member 11 and the second clamping member 12, as well as the initial test pressure, can be changed. The support column 13 can also be provided with scale markings arranged along its axial direction to assist in observing the positional changes of the first clamping member 11 and verifying the consistency of the clamping state.

[0058] In this embodiment, the sealing test unit 20 is supported on the side of the second clamping member 12 facing the first clamping member 11, the pressure sensor 30 is installed on the first clamping member 11, and the detection end 31 of the pressure sensor 30 and the movable force transmission part 24 are arranged opposite to each other along the thickness direction of the electrode assembly 25 to be tested.

[0059] The sealing test unit 20 is stably supported by the second clamping member 12, while the pressure sensor 30 is held on the moving path of the movable force transmission part 24 by the first clamping member 11, so that the electrode assembly under test 25, the movable force transmission part 24 and the pressure sensor 30 form a continuous force transmission path extending along the thickness direction. During installation, the detection end 31 of the pressure sensor 30 can be kept in contact with the movable force transmission part 24 by adjusting the clamping mechanism 10, and the pressure sensor 30 can generate an appropriate initial pressure reading; after the initial pressure reading stabilizes, the charge and discharge test is then performed.

[0060] The expansion force generated by the electrode assembly under test 25 is transmitted to the pressure sensor 30 via the movable force transmission part 24, thereby reducing the influence of eccentric load and lateral component force on the detection results. The pressure sensor 30 can be connected to an external display or data acquisition device to synchronously record the detection pressure values ​​at each charging and discharging stage; when the pressure sensor 30 outputs a force, the nominal expansion stress of the electrode assembly under test 25 can also be determined by combining it with the effective force-bearing area of ​​the movable force transmission part 24.

[0061] Example 2: An online in-situ stress electrode expansion testing method, characterized by employing an online in-situ stress electrode expansion testing device as described in Example 1, and the testing method comprising the following steps: S1, place the electrode assembly under test 25 into the sealed test chamber 23, add electrolyte 254 into the sealed test chamber 23 and seal it, so that the electrode assembly under test 25 is electrically connected to the external charging and discharging equipment. Specifically, the electrode assembly 25 under test can be configured as a half-cell system or a full-cell system depending on the testing objective. For example, a half-cell system can be composed of a silicon-carbon anode sheet or a graphite anode sheet and a lithium metal sheet, or a full-cell system can be composed of a positive electrode sheet and a negative electrode sheet. For electrode materials and electrolyte 254 that are sensitive to moisture, the assembly, electrolyte filling, and sealing of the electrode assembly 255 under test can be completed in an inert atmosphere. The amount of electrolyte 254 added should be sufficient to fully wet the electrode sheet and the separator 252 without hindering the movement of the movable force transmission part 24. After sealing, the electrical connection relationship on both sides of the electrode assembly 25 under test is checked to avoid short circuits or poor contact, thereby providing stable testing conditions for subsequent simultaneous electrochemical testing and expansion stress detection.

[0062] S2, install the sealing test unit 20 on the clamping mechanism 10, so that the movable force transmission part 24 abuts against the pressure sensor 30, adjust the clamping mechanism 10 to apply an initial load to the sealing test unit 20, and obtain the initial pressure value after the pressure value of the pressure sensor 30 stabilizes. During installation, the force direction of the sealing test unit 20, the movement direction of the movable force transmission part 24, and the detection direction of the pressure sensor 30 should be basically consistent. The clamping mechanism 10 should be gradually adjusted to apply the initial load to avoid damage to the electrode assembly 25 under test or the pressure sensor 30 exceeding its range due to excessive instantaneous loading.

[0063] The initial load ensures stable contact between the layers of the electrode assembly under test 25, while eliminating assembly gaps between the sealing test unit 20 and the clamping mechanism 10. Since the immersion process after liquid injection, stress relaxation of the seals, and contact adjustments within the electrode assembly under test 25 can all cause pressure changes, the initial pressure value should be determined after the pressure value stabilizes, so that it can serve as a benchmark for the stress state of the electrode assembly under test 25 before charging and discharging.

[0064] S3, the test electrode assembly 25 is charged and discharged by an external charging and discharging device. The test electrode assembly 25 expands along its thickness direction and pushes the movable force transmission part 24 to move. The rolling guide assembly 40 rolls and guides the movable force transmission part 24 during its movement. The detection pressure value during the charging and discharging process is obtained by the pressure sensor 30. During charging and discharging, external charging and discharging equipment drives the electrode assembly under test 25 to undergo lithium insertion and delithiation reactions according to preset current, voltage, and cutoff conditions. The thickness change of the electrode assembly under test 25 is converted into a thrust on the movable force transmission part 24. The movable force transmission part 24 moves along the thickness direction under the constraint of the rolling guide assembly 40 and transmits the expansion force to the pressure sensor 30. The rolling guide assembly 40 can reduce the frictional resistance and deflection of the movable force transmission part 24 during movement, making the detection value of the pressure sensor 30 closer to the actual expansion force generated by the electrode assembly under test 25. The pressure value can be recorded synchronously with the test time, charge / discharge capacity, voltage, or number of cycles, thereby distinguishing the expansion stress changes in different stages such as static immersion, charging lithium insertion, discharging lithium delithiation, and cycle decay.

[0065] S4. Determine the change in expansion stress of the electrode assembly 25 under test based on the difference between the detected pressure value and the initial pressure value.

[0066] Let the initial pressure value be P0, and the detected pressure value at any test moment be P. t Then the pressure change ΔP at that test moment t This can be represented as ΔP t =P t -P0; when ΔP t When ΔP is positive, it indicates that the electrode assembly 25 under test has expanded relative to its initial state, causing an increase in expansion stress. t A negative value indicates that the electrode assembly 25 under test has contracted or its expansion stress has decreased. Further, this can be calculated according to η = (P... t The relative expansion stress change rate is determined by P0 / P0×100%. If the pressure sensor 30 outputs a force, the force change can be converted into a nominal expansion stress change by combining the effective force-bearing area of ​​the movable force transmission part 24. After establishing the calibration relationship between pressure change and electrode thickness change or volume change in advance, the geometric expansion rate of the electrode assembly 25 under test can be further determined.

[0067] In this embodiment, step S2 specifically includes the following steps: S21, the sealed test unit 20 is left to stand for a preset immersion time to allow the electrolyte 254 to immerse the electrode assembly 25 under test; Specifically, the preset immersion time can be determined based on the pore structure of the electrode material under test, the electrode thickness, the viscosity of the electrolyte 254, and the liquid absorption performance of the diaphragm 252. For example, it can be set to 2–24 hours. During the static immersion period, the electrode assembly 25 under test is not charged or discharged, allowing the electrolyte 254 to gradually penetrate into the electrode sheet and the diaphragm 252 under conditions where there is no lithium insertion or delithiation reaction, thereby reducing additional pressure changes caused by insufficient immersion during subsequent testing. The temperature of the static environment should be kept relatively stable to avoid volume changes in the electrolyte 254 and the sealed test unit 20 due to temperature fluctuations, which could affect the determination of the initial pressure value.

[0068] S22, the sealing test unit 20 is carried in the clamping mechanism 10, the clamping mechanism 10 is adjusted so that the movable force transmission part 24 is in contact with the pressure sensor 30, and the pressure value of the pressure sensor 30 reaches the preset initial pressure range. When adjusting the clamping mechanism 10, the moving direction of the movable force transmission part 24 should be substantially aligned with the detection direction of the pressure sensor 30. The initial load applied to the sealing test unit 20 should be gradually increased to eliminate assembly gaps inside the electrode assembly 25 under test and between the sealing test unit 20 and the clamping mechanism 10. The preset initial pressure range can be determined based on the area of ​​the electrode assembly 25 under test, the allowable degree of compression, and the range of the pressure sensor 30. It should be within the linear detection range of the pressure sensor 30, while avoiding excessive initial load that could pre-compact or damage the electrode assembly 25 under test. Preferably, the initial pressure value should be between 5% and 20% of the full scale of the pressure sensor 30, thereby providing sufficient detection margin for subsequent expansion stress.

[0069] S23. The pressure value of the pressure sensor 30 is continuously acquired according to the preset sampling interval. When the difference between two consecutive pressure values ​​is not greater than the preset pressure stability threshold, the current pressure value is determined as the initial pressure value, and the corresponding time is determined as the test start time.

[0070] It should be noted that after the initial loading is completed, the stress relaxation of the seal, the contact adjustment between the layers of the electrode assembly 25 under test, and the slight deformation of the clamping mechanism 10 may all cause the pressure value to change in a short period of time. Therefore, it is necessary to continuously collect the pressure value to determine whether the test system has reached a stable state.

[0071] The preset sampling interval can be set to 1–60 seconds, and the preset pressure stabilization threshold can be determined based on the resolution of the pressure sensor 30 and the expected test accuracy, for example, set to 0.1%–1% of the preset initial pressure value. When the difference between two consecutive pressure values ​​meets the stabilization condition, it indicates that the pressure fluctuations caused by assembly and resting have been reduced to within the allowable range. The initial pressure value determined at this time can serve as a comparison benchmark for changes in expansion stress during subsequent charging and discharging processes. The corresponding time is used as the test start time, and it also ensures that the pressure detection data is consistent with the time, voltage, current, and capacity data recorded by the external charging and discharging equipment.

[0072] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

[0073] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. An online in-situ stress electrode expansion testing device, characterized in that, It includes a clamping mechanism, a sealing test unit disposed within the clamping mechanism and capable of charging and discharging, and a pressure sensor; The sealing test unit includes a fixed part and a movable force transmission part. The fixed part forms a sealed test cavity that accommodates the electrode assembly to be tested and the electrolyte. The movable force transmission part is movably sealed and fitted with the fixed part along the thickness direction of the electrode assembly to be tested. One end of the movable force transmission part abuts against the electrode assembly to be tested, and the other end abuts against the pressure sensor. A rolling guide assembly is provided between the movable force transmission part and the fixed part. The rolling guide assembly includes a plurality of rolling elements distributed circumferentially along the movable force transmission part, and each rolling element makes rolling contact with the fixed part and the movable force transmission part respectively.

2. The online in-situ stress electrode expansion testing device according to claim 1, characterized in that, The rolling guide assembly further includes an annular retainer, which is sleeved on the outer periphery of the movable force transmission part and located inside the fixed part. The annular retainer has a plurality of retaining holes spaced apart along its circumference. Multiple rolling elements are disposed in multiple retaining holes in a corresponding manner. Each rolling element protrudes partially from the inner and outer circumferential surfaces of the annular retaining element and makes rolling contact with the outer circumferential surface of the movable force transmission part and the inner circumferential surface of the fixed part, respectively.

3. The online in-situ stress electrode expansion testing device according to claim 2, characterized in that, A first annular seal is provided between the fixed part and the movable force transmission part. The first annular seal is arranged around the movable force transmission part and makes sealing contact with the inner circumferential surface of the fixed part and the outer circumferential surface of the movable force transmission part, respectively. Along the moving direction of the active force transmission part, the first annular seal is located between the sealing test cavity and the rolling guide assembly, so as to isolate the rolling guide assembly from the sealing test cavity.

4. The online in-situ stress electrode expansion testing device according to claim 3, characterized in that, The inner peripheral surface of the fixed part is provided with a plurality of first guide grooves, and the outer peripheral surface of the movable force transmission part is provided with a plurality of second guide grooves corresponding one-to-one with the plurality of first guide grooves. Both the first guide grooves and the second guide grooves extend along the moving direction of the movable force transmission part. The corresponding first guide groove and the second guide groove together form a rolling channel, and each of the rolling elements passes through the corresponding retaining hole and is disposed in the corresponding rolling channel.

5. The online in-situ stress electrode expansion testing device according to claim 1, characterized in that, The electrode assembly to be tested includes a first electrode sheet, a diaphragm, and a second electrode sheet stacked sequentially along its thickness direction; The movable force transmission part is made of conductive material and abuts against the first electrode sheet. The fixing part includes a conductive support part disposed on the side of the second electrode sheet away from the diaphragm, and the conductive support part abuts against the second electrode sheet. The movable force transmission part and the conductive support part are respectively provided with a first wiring part and a second wiring part extending to the outside of the sealed test chamber.

6. The online in-situ stress electrode expansion testing device according to claim 5, characterized in that, The fixing part further includes a test housing and a threaded locking member. The test housing has a first port and a second port that are arranged opposite to each other along the thickness direction of the electrode assembly under test. The movable force transmission part passes through the first port, and the conductive support part is installed at the second port. A first annular seal is provided between the movable force transmission part and the first port. The threaded locking part is sleeved on the movable force transmission part and threadedly connected to the test housing. The first annular seal is sandwiched between the threaded locking part and the test housing. The conductive support is threadedly connected to the second port, and a second annular seal is sandwiched between the conductive support and the test housing. The test housing, the movable force transmission part, and the conductive support together enclose the sealed test cavity.

7. The online in-situ stress electrode expansion testing device according to claim 1, characterized in that, The clamping mechanism includes a first clamping member, a second clamping member, at least two support columns, and adjusting nuts corresponding to each of the support columns. The first clamping member and the second clamping member are arranged opposite to each other along the thickness direction of the electrode assembly to be tested, and at least two support columns are spaced apart on the outer periphery of the sealing test unit. One end of the support column is fixedly connected to the second clamping member, the first clamping member is slidably sleeved on the support column, and the adjusting nut is threadedly connected to the support column and abuts against the side of the first clamping member away from the second clamping member.

8. The online in-situ stress electrode expansion testing device according to claim 7, characterized in that, The sealing test unit is supported on the side of the second clamping member facing the first clamping member. The pressure sensor is installed on the first clamping member, and the detection end of the pressure sensor and the movable force transmission part are arranged opposite to each other along the thickness direction of the electrode assembly under test.

9. A method for online in-situ stress electrode expansion testing, characterized in that, The online in-situ stress electrode expansion testing device as described in any one of claims 1 to 8 is used, and the testing method includes the following steps: S1, Place the electrode assembly to be tested into a sealed test chamber, add electrolyte into the sealed test chamber and seal it, so that the electrode assembly to be tested is electrically connected to an external charging and discharging device; S2, install the sealing test unit on the clamping mechanism, so that the movable force transmission part abuts against the pressure sensor, adjust the clamping mechanism to apply an initial load to the sealing test unit, and obtain the initial pressure value after the pressure value of the pressure sensor stabilizes. S3, the test electrode assembly is charged and discharged by the external charging and discharging device. The test electrode assembly expands along its thickness direction and pushes the movable force transmission part to move. The rolling guide assembly rolls and guides the movable force transmission part during its movement. The detection pressure value during the charging and discharging process is obtained by the pressure sensor. S4. Determine the change in expansion stress of the electrode assembly under test based on the difference between the detected pressure value and the initial pressure value.

10. The online in-situ stress electrode expansion testing method according to claim 9, characterized in that, Step S2 includes the following steps: S21, the sealed test unit is left to stand for a preset immersion time after sealing is completed, so that the electrolyte wets the electrode assembly to be tested. S22, the sealing test unit is carried in the clamping mechanism, the clamping mechanism is adjusted so that the movable force transmission part is in contact with the pressure sensor, and the pressure value of the pressure sensor reaches the preset initial pressure range; S23, continuously acquire the pressure value of the pressure sensor according to the preset sampling interval. When the difference between two consecutive acquired pressure values ​​is not greater than the preset pressure stability threshold, determine the currently acquired pressure value as the initial pressure value and determine the corresponding time as the test start time.

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