Ionic conductivity testing method

Abstract

The invention provides an ionic conductivity test method, which solves the problems in the prior art, can realize dual-function test of pole piece ionic resistance and diaphragm ionic conductivity test, and realizes improvement of ionic conductivity test efficiency and consistency. Specifically, a multi-channel testing device is built by itself, multiple sets of samples can be tested at a time, meanwhile, the battery assembling process is simplified, and the testing efficiency is remarkably improved. When a symmetrical battery is assembled, the reaction area of the pole piece is limited by using the confinement diaphragm, so that the reaction area of each time is fixed, and meanwhile, a soft conductive substance is additionally arranged between the pole piece and the upper pressure head to adjust the pressing planeness, so that the pole piece can be uniformly stressed, the consistency of samples can be effectively improved, and the accuracy of a test result is ensured.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery detection, and particularly relates to an ion conductivity testing method. BACKGROUND

[0002] As the core energy of modern electronic devices, electric vehicles and energy storage systems, the performance optimization of lithium ion batteries has always been a hot research topic. As important components of the battery, the microstructure of the pole piece and the diaphragm has a crucial influence on the performance of the battery. The ion resistance of the pole piece and the ion conductivity of the diaphragm are parameters for describing the complexity of the transmission path of lithium ions in the electrode pores or diaphragm pores, and directly affect the ion transmission efficiency and electrochemical performance of the battery.

[0003] From the current research on lithium ion porous electrodes, it can be found that the actual porous electrode pores are affected by the accumulation effect and filling effect of particles, and the pore size and distribution are not uniform, and the ion resistance is difficult to characterize. Among them, the electrochemical impedance spectroscopy method is simple to operate and has short testing time, and since the electronic transmission resistance of the lithium ion porous electrode is usually small, the real ion resistance of the porous electrode can be obtained through the test of the electrochemical impedance spectroscopy.

[0004] The existing technology usually tests the ion resistance of the pole piece by assembling soft package symmetrical batteries or steel shell symmetrical batteries, and has problems such as complicated operation, low efficiency and poor consistency, especially in large-scale pole piece production lines, which cannot meet the rapid and accurate testing requirements. In addition, when assembling the pole piece symmetrical battery, the selection and assembly method of the diaphragm, the uniformity of the pressure borne by the battery, etc. have a great influence on the consistency of the test results, and there is a lack of effective control means in the existing technology. SUMMARY

[0005] The main purpose of the present application is to provide an ion conductivity testing method, which solves the problems in the prior art, realizes the dual-function testing of the ion resistance of the pole piece and the ion conductivity of the diaphragm, and improves the ion conductivity testing efficiency and consistency.

[0006] In order to achieve the above purpose, the solution of the present application is: An ion conductivity testing method, comprising the following steps: Step S1. Preparation for testing A multi-channel testing device is built, each channel of the multi-channel testing device is composed of a pressure rod and an electrolyte tank, the pressure rod moves up and down relative to the electrolyte tank, and the pressure rod and the electrolyte tank are respectively connected to the positive and negative electrodes of an EIS module of the multi-channel testing device; An insulating tape is used to stick to the non-reaction area of the diaphragm, and a circular reaction area with a diameter of 10-14mm is left in the center of the diaphragm to make a limited diaphragm; Step S2. According to different test types, the test procedure of ion resistance of the electrode sheet or ion conductivity of the separator is carried out; specifically, the test procedure of ion resistance of the electrode sheet is as follows: S2a.1 The electrode sheets are cut into circular pieces with the same diameter and placed in a vacuum oven for drying at 80-120°C for 6-12h; S2a.2 The limited separator is placed in a vacuum oven for drying at 40-50°C for 4-6h; S2a.3 The sample to be tested is assembled in a drying room, and the sample is stacked from bottom to top in the electrolyte tank of each channel in the order of electrode sheet-limited separator-electrode sheet-soft conductive material; S2a.4 A predetermined amount of electrolyte is added to the electrolyte tank of each channel; S2a.5 The pressure rod is lowered to apply a predetermined value of pressure to the sample; S2a.6 When the sample is completely soaked, the electrochemical impedance spectrum of each sample is measured, and the test frequency is 100000-1Hz; The test procedure of ion conductivity of the separator is as follows: S2b.1 The separator is cut into circular pieces with the same diameter and placed in a vacuum oven for drying at 40-50°C for 4-6h; S2b.2 The sample to be tested is assembled in a drying room, and the separator is placed in the electrolyte tank of each channel in the order of 1 layer, 2 layers, 3 layers, 4 layers, and so on; S2b.3 A predetermined amount of electrolyte is added to the electrolyte tank of each channel; S2b.4 The pressure rod is lowered to apply a predetermined value of pressure to the sample; S2a.5 When the separator is completely soaked, the electrochemical impedance spectrum of each group of separators is measured, and the test frequency is 100000-1000Hz.

[0007] The material of the insulating tape is, for example, polyimide.

[0008] The multi-channel testing device comprises a sealed box, a main frame installed in the sealed box, a pressure applying assembly, a supporting assembly and a liquid injecting assembly installed on the main frame; the sealed box is provided with a sealable door and air inlet and outlet holes; the pressure applying assembly comprises a pressure plate which performs lifting movement relative to the supporting assembly; a plurality of installation holes are equidistantly arranged on the pressure plate along the horizontal direction, and a movable shaft is installed in each installation hole; a first spring is arranged between the movable shaft and the lower surface of the pressure plate; a pressure rod is oppositely arranged on the lower end surface of the movable shaft; the supporting assembly comprises a plurality of supporting plates which are installed on the main frame and oppositely arranged with the pressure rods respectively, and each supporting plate is provided with an electrolyte tank; the liquid injecting assembly is arranged on the side of the supporting plate and is used for automatically injecting electrolyte into each electrolyte tank.

[0009] Preferably, the main frame comprises a top plate, a bottom plate, a plurality of supporting columns and a back plate; the top plate is parallel to the bottom plate, and the supporting columns and the back plate are supported between the top plate and the bottom plate; the pressure applying assembly is installed below the top plate, and the supporting assembly is installed above the bottom plate.

[0010] Preferably, the ion conductivity testing method further comprises a dew point sensor and an air pressure sensor arranged in the sealed box and used for detecting the humidity and air pressure in the sealed box respectively.

[0011] Preferably, the ion conductivity testing method further comprises a driving assembly used for driving the pressure applying assembly; the driving assembly comprises a fixed support, a first motor, a first guide rod, a lifting plate, a connecting rod, a ladder nut and a ladder screw; the fixed support is installed on the upper surface of the main frame; the first guide rod is connected between the fixed support and the main frame; the lifting plate is slidingly fitted on the first guide rod; the connecting rod penetrates through the main frame and is connected with the lifting plate and the pressure plate at the upper and lower ends thereof respectively; the ladder nut is installed on the lifting plate, the ladder screw is threadedly connected with the ladder nut, and the two ends of the ladder screw are rotatably fitted with the fixed support and the main frame respectively; the first motor is in transmission connection with the ladder screw and is used for driving the ladder screw to perform rotational movement.

[0012] Preferably, the output end of the first motor is in transmission connection with a driving wheel, the peripheral surface of the ladder screw is fixedly connected with a driven wheel, and a synchronous belt is tightly wound between the driving wheel and the driven wheel; bearings for the rotational fitting of the ladder screw are arranged on the main frame and the fixed support; the main frame is provided with a guide sleeve for the penetration of the connecting rod; the connecting rod and the guide sleeve are provided with at least two pairs of guide sleeves which are equiangularly and spacedly arranged around the ladder screw.

[0013] Preferably, a plurality of press rod sleeves are arranged below the press plate, the upper surfaces of the press rod sleeves are connected with a plurality of second guide rods, the second guide rods are movably arranged in the press plate, the circumferential surfaces of the second guide rods are provided with second springs, the press rods are transmitted into the press rod sleeves from the lower surfaces of the press rod sleeves, at least one sealing ring is arranged between the circumferential surfaces of the press rods and the press rod sleeves, the lower end surfaces of the movable shafts are provided with spherical pressure heads, the press rod sleeves are provided with connection terminals, the connection terminals are electrically connected with the press rods, and the connection terminals are used for connecting EIS modules, and the upper ends of the movable shafts and the second guide rods are axially limited by the screw rods arranged above the press plate.

[0014] Preferably, the liquid injection assembly comprises a liquid injection head arranged at the side edge of the support plate, a liquid bottle, and a fluid pump connected between the liquid injection head and the liquid bottle, and the liquid injection head is movably arranged above each electrolyte tank.

[0015] Preferably, the liquid injection assembly further comprises a two-way threaded valve connected between the liquid injection head and the fluid pump, and a liquid injection head support used for mounting the liquid injection head, and the liquid injection head support is arranged on a sliding block, and the sliding block is driven by a second motor to realize horizontal movement.

[0016] After the above technical scheme is adopted, the present application has the following technical effects: Through the multi-channel testing device, a plurality of groups of samples can be tested at one time, the testing efficiency is significantly improved, and the demand for large-scale production testing is met; the reaction area and stress uniformity of the battery are effectively controlled by using the limited separation membrane and the soft conductive material for testing, so that each pole piece is ensured to be in the same condition in the testing process, and the consistency of the testing is improved; only the test sample is stacked and placed in the electrolyte tank, the press rod is automatically pressed after the liquid injection is completed, the electrochemical impedance of the symmetrical battery is tested, and the cumbersome steps of manual operation are reduced; the method is suitable for various types of pole pieces and separation membranes, is used for evaluating the consistency of the pole pieces in batch production, the difference between the pole pieces prepared by different processes, and the electrochemical performance of the pole pieces which can be preliminarily judged by the test of the pole piece ion resistance, shortens the research and development cycle, and improves the development efficiency of new materials; the structures of the multi-channel testing device and the limited separation membrane are relatively simple, the manufacturing cost is low, and the multi-channel testing device and the limited separation membrane are easy to popularize and apply. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a perspective view of a specific embodiment of the present application.

[0018] Figure 2 It is a partial structure front perspective view of a specific embodiment of the present application.

[0019] Figure 3 It is a partial structure back perspective view of a specific embodiment of the present application.

[0020] Figure 4Part structure front view of specific embodiment of the present application.

[0021] Figure 5 Part structure cross-sectional view of specific embodiment of the present application.

[0022] Figure 6 Electrochemical impedance spectrogram of graphite negative electrode sheet.

[0023] Figure 7 Electrochemical impedance spectrogram of ternary positive electrode sheet.

[0024] Figure 8 Polar sheet ion impedance and polar sheet tortuosity data table.

[0025] Figure 9 Electrochemical impedance spectrogram of different layer number separators.

[0026] Figure 10 Separator ion resistance and ion conductivity data table.

[0027] Explanation of reference numerals: 1-sealing box; 11-sealing door; 2-main body frame; 21-top plate; 22-bottom plate; 23-stanchion; 24-back plate; 241-strip-shaped hole; 25-guide sleeve; 3-pressing assembly; 31-pressing disc; 311-mounting hole; 32-moving shaft; 33-first spring; 34-pressing rod; 35-pressing rod sleeve; 36-second guide rod; 37-second spring; 38-sealing ring; 39-spherical pressure head; 310-connection terminal; 4-supporting assembly; 41-supporting disc; 42-electrolyte tank; 5-liquid injection assembly; 51-liquid injection head; 52-electrolyte bottle; 53-fluid pump; 54-two-way threaded valve; 55-liquid injection head support; 56-sliding block; 57-second motor; 571-screw rod; 6-driving assembly; 61-fixed support; 62-first motor; 63-first guide rod; 64-lifting plate; 65-connection rod; 66-ladder-shaped nut; 67-ladder-shaped screw; 68-driving wheel; 69-driven wheel; 610-synchronous belt; 620-bearing. DETAILED DESCRIPTION

[0028] In order to further explain the technical solutions of the present application, the present application will be described in detail below through specific embodiments.

[0029] The core of the present application is to simplify the assembly steps of symmetric batteries, limit the reaction area of the polar sheet, and improve the uniformity of the force of the symmetric battery by applying a multi-channel testing device, a limited separator, and a soft conductive material, thereby improving the efficiency and consistency during testing.

[0030] Specifically, the present invention discloses a method for testing ionic conductivity, comprising the following steps: Step S1. Test preparation Construction reference Figures 1 to 5 The multi-channel testing device shown (four channels in this embodiment) can be assembled at one time to test four symmetrical battery groups. Each channel can perform independent electrochemical impedance testing and independently collect data without interfering with each other. Each channel of the multi-channel testing device is composed of a pressure rod 34 and an electrolyte tank 42. The pressure rod 34 can move up and down relative to the electrolyte tank 42. The pressure rod 34 and the electrolyte tank 42 are respectively connected to the positive and negative electrodes of the EIS module (Electrochemical Impedance Spectroscopy Module) of the multi-channel testing device and conduct electricity by contacting with the electrode sheets.

[0031] Use insulating tape (such as polyimide, full name polyethylene terephthalate) to stick to the non-reactive area of ​​the diaphragm, and leave a circular reaction area with a diameter of 10~14mm in the center of the diaphragm to make a confined diaphragm. As a result, during the test, lithium ions can only pass through the circular reaction area, achieving the purpose of fixing the area involved in the reaction. Subsequently, when assembling symmetrical batteries, using a confined diaphragm for testing can effectively control the reaction area of ​​the electrode, ensuring that each symmetrical battery is under the same conditions during the test, thereby improving the consistency of the test results.

[0032] Step S2. Depending on the test type, perform the electrode ionic resistance or membrane ionic conductivity test process; specifically, the electrode ionic resistance test process is as follows: S2a.1 Cut several electrodes into discs of equal diameter and dry them in a vacuum oven at 80-120°C for 6-12 hours. The electrodes can be single-sided positive, single-sided negative, double-sided positive, or double-sided negative. Double-sided electrodes do not require scraping.

[0033] S2a.2 Place the confined diaphragm in a vacuum oven and dry it at 40-50°C for 4-6 hours.

[0034] S2a.3 Assemble the samples to be tested (the whole consisting of the electrode, confining diaphragm, and soft conductive material) in a dry room. Place the samples from bottom to top in the order of electrode - confining diaphragm - electrode - soft conductive material and place them in the electrolyte tank 42 of each channel.

[0035] S2a.4 Add a preset amount of electrolyte to the electrolyte tank 42 of each channel.

[0036] S2a.5 Lower the pressure rod 34 to apply a preset value of pressure (such as 0.5-3 MPa) to the sample.

[0037] S2a.6 When the sample is completely soaked (usually 20-60 min), measure the electrochemical impedance spectrum of each sample, and the test frequency is 100000-1 Hz.

[0038] The test procedure of the ion conductivity of the separator is as follows: S2b.1 Cut a plurality of separators into circular pieces of the same diameter, and place them in a vacuum oven to dry at 40-50°C for 4-6 h.

[0039] S2b.2 Assemble the sample to be tested in a dry room, and place the separators in the electrolyte tank 42 of each channel according to the number of layers, such as 1 layer, 2 layers, 3 layers, 4 layers, and so on.

[0040] S2b.3 Add a preset amount of electrolyte to the electrolyte tank 42 of each channel.

[0041] S2b.4 Lower the pressure rod 34 to apply a preset value of pressure (such as 0.5-3 MPa) to the sample.

[0042] S2a.5 When the sample is completely soaked (usually 20-60 min), measure the electrochemical impedance spectrum of each sample, and the test frequency is 100000-1 Hz.

[0043] The following shows the specific test results of the present application and their data analysis.

[0044] Specifically, the ion resistance data of the electrode sheet are as follows: ① The ion resistance R1 of the electrode sheet is obtained by fitting the electrochemical impedance spectrum; the specific fitting steps are to extend the low-frequency segment in the Nyquist diagram until it intersects with the X-axis, and the difference between this intersection point and 3 times the intersection point of the high-frequency segment and the X-axis is the ion resistance R1 of the electrode sheet coating.

[0045] ② The ion resistance R1 is substituted into the formula τ=(R1*A*ε*σ1) / 2d1 to calculate the tortuosity of the electrode sheet, where τ is the tortuosity of the electrode sheet, A is the reaction area of the electrode sheet (i.e. the area of the circular reaction region), ε is the porosity of the electrode sheet, σ1 is the conductivity of the electrolyte, and d1 is the thickness of the electrode sheet.

[0046] ③ Referring to the formula shown in Figure 6 , 7 , the present application respectively tests the graphite negative electrode sheet and the ternary positive electrode sheet, and the ion resistance and the tortuosity of the electrode sheet can be obtained by fitting and calculation (see Figure 8 , Examples 1 and 2 correspond to the graphite negative electrode sheet and the ternary positive electrode sheet, respectively). It can be seen that the coefficient of variation COV is less than 2%, indicating that the symmetry battery has good consistency and high accuracy.

[0047] Specifically, the ionic resistance data of the diaphragm are as follows: ① Take the EIS of each diaphragm as the baseline for linear fitting, and the intersection of the fitting line and the X-axis is R s , then the impedance of the n-layer diaphragm is R s (n). A linear fit is performed using the number of layers as the X-axis and the impedance value of each layer as the Y-axis. The slope of the linear fit equation is the ionic resistance R2 of the single-layer membrane. ② Substituting the obtained ionic resistance R2 into σ2=d2 / (R2*S) can calculate the ionic conductivity of the diaphragm, where σ2 is the ionic conductivity of the diaphragm, d2 is the thickness of the diaphragm, and S is the reaction area of ​​the diaphragm.

[0048] ③Reference Figure 9 The following table shows the electrochemical impedance spectra of the membranes with different numbers of layers. The ionic resistance and ionic conductivity of the membranes were obtained by fitting and calculation (see Figure 10 ). It can be seen that the coefficient of variation COV of the diaphragms with the same number of layers is less than 5%, and the fitting results R of 1 to 4 layers are 2 All of them are >0.99, indicating that the data repeatability and consistency are high and the experimental results are reliable.

[0049] Through the above scheme, the present invention has the following effects: (1) High testing efficiency Through the multi-channel testing device, multiple groups of samples can be tested at one time, which significantly improves the testing efficiency and meets the needs of large-scale production testing.

[0050] (2) Good test consistency Using a confined diaphragm and soft conductive materials for testing can effectively control the reaction area and force uniformity of the battery, ensuring that each electrode is under the same conditions during the test and improving the consistency of the test.

[0051] (3) Easy to operate The test samples only need to be stacked and placed in the electrolyte tank 42. After the injection is completed, the pressing rod 34 is automatically pressed down to test the electrochemical impedance of the symmetrical battery, reducing the tedious steps of manual operation.

[0052] (4) Wide range of applications This method is applicable to various types of electrodes and diaphragms. It is used to evaluate the consistency of mass-produced electrodes, the differences between electrodes prepared by different processes, and to preliminarily judge the electrochemical properties of electrodes by testing the ionic resistance of the electrodes, thereby shortening the R&D cycle and improving the development efficiency of new materials.

[0053] (5) Low cost The structures of the multi-channel testing device and the confined diaphragm are relatively simple, the manufacturing cost is low, and they are easy to promote and apply.

[0054] In addition, the present invention also introduces one embodiment of the above-mentioned multi-channel testing device, which includes a sealed box 1, a main frame 2 installed in the sealed box 1, and a pressure component 3, a supporting component 4 and a liquid injection component 5 installed on the main frame 2; the sealed box 1 is provided with a movable sealed door 11 and an air inlet and an air outlet ( Figure 1 The cam 32 is provided with a plurality of holes 311 at equal intervals along the horizontal direction on the pressure plate 31, and a movable shaft 32 is installed in the mounting hole 311; a first spring 33 is provided between the movable shaft 32 and the lower surface of the pressure plate 31 to make the movable shaft 32 have a tendency to move downward to provide a clamping force; the lower end surface of the movable shaft 32 is provided with the above-mentioned pressure rod 34; during testing, the first spring 33 with the corresponding elastic coefficient can be selected according to different test requirements; the supporting assembly 4 includes a plurality of supporting trays 41 installed on the main frame 2 and respectively opposite to each pressure rod 34, and each supporting tray 41 is provided with the above-mentioned electrolyte tank 42; the liquid injection assembly 5 is provided on the side of the supporting tray 41 for automatically injecting electrolyte into each electrolyte tank 42.

[0055] As described above, when conducting the test, it is only necessary to manually open and close the sealing door 11 to detect the status of the multi-channel testing device and set the parameters. The remaining test operations are all performed automatically by the machine, specifically: the sample to be tested is placed in the electrolyte tank 42, and the electrolyte is injected into each electrolyte tank 42 one by one along the horizontal direction by the injection component 5, and then the pressure plate 31 is pressed down so that the pressure rod 34 applies pressure to the sample to be tested in the relative electrolyte tank 42 to make it fit tightly, and the pressure rod 34 and the electrolyte tank 42 are respectively connected to the positive and negative poles of the EIS module, thereby the ionic conductivity of the electrolyte can be detected by the multi-channel testing device; at the same time, the present invention can simultaneously perform ionic conductivity tests on multiple electrolyte tanks 42, so that the present invention can greatly simplify manual operations and improve experimental test efficiency and accuracy; the design of the straight-line pressure component 3 and the support component 4 is more reasonable. Only one of the support component 4 or the injection component 5 needs to be moved horizontally to realize the single injection head 51 to inject liquid into each electrolyte tank 42, and the action performed is simpler and the positioning accuracy is higher.

[0056] Specifically, the details of the multi-channel testing device are: The main frame 2 comprises a top plate 21, a bottom plate 22, a plurality of support columns 23, and a back plate 24; the top plate 21 is parallel to the bottom plate 22, and the support columns 23 and the back plate 24 are supported between the top plate 21 and the bottom plate 22; the pressing assembly 3 is installed below the top plate 21, and the supporting assembly 4 is installed above the bottom plate 22.

[0057] The multi-channel testing device further comprises a dew point sensor and an air pressure sensor arranged in the sealed box 1 and used for detecting the humidity and the air pressure in the sealed box 1 respectively; the two sensors can be arranged on the main frame 2, i.e. above the top plate 21.

[0058] The multi-channel testing device further comprises a driving assembly 6 used for driving the pressing assembly 3; the driving assembly 6 comprises a fixed support 61, a first motor 62, a first guide rod 63, a lifting plate 64, a connecting rod 65, a ladder nut 66, and a ladder screw 67; the fixed support 61 is installed on the upper surface of the main frame 2, i.e. the upper surface of the top plate 21; the first guide rod 63 is connected between the fixed support 61 and the main frame 2; the lifting plate 64 is slidingly fitted on the first guide rod 63; the connecting rod 65 penetrates through the main frame 2 and is connected to the lifting plate 64 and the pressing plate 31 at the upper and lower ends thereof respectively; the ladder nut 66 is installed on the lifting plate 64, and the ladder screw 67 is threadedly connected to the ladder nut 66 and rotationally fitted to the fixed support 61 and the main frame 2 at the two ends thereof respectively; the first motor 62 is in transmission connection with the ladder screw 67 and used for driving the ladder screw 67 to rotate. In this way, the circular motion output by the motor can be converted into the lifting motion of the pressing plate 31, and the pressing plate 31 does not need to be driven in the upward and downward directions, so that the height space of the multi-channel testing device can be saved, the overall structure design is more compact, and the volume is smaller. In the embodiment, the first motor 62 is installed on the back surface of the back plate 24.

[0059] Further, the output end of the first motor 62 is in transmission connection with a driving wheel 68, the peripheral surface of the ladder screw 67 is fixedly connected with a driven wheel 69, and a synchronous belt 610 is tightly wound between the driving wheel 68 and the driven wheel 69. The transmission connection between the first motor 62 and the ladder screw 67 is realized through the driving wheel 68, the driven wheel 69, and the synchronous belt 610. In the embodiment, the main frame 2 and the fixed support 61 are both provided with bearings 620 for rotationally fitting the ladder screw 67.

[0060] Meanwhile, the main frame 2 is provided with guide sleeves 25 for penetrating the connecting rods 65; the connecting rods 65 and the guide sleeves 25 are provided with at least two pairs and are arranged at equal angles and intervals around the ladder screw 67, so as to ensure that the lifting motion of the pressing plate 31 is more stable.

[0061] The lower side of the pressing disc 31 is provided with a plurality of pressing rod sleeves 35, the upper surface of each pressing rod sleeve 35 is connected with a second guide rod 36, the second guide rod 36 is movably arranged in the pressing disc 31, the circumferential surface of the second guide rod 36 is provided with a second spring 37, the pressing rod 34 is transmitted into the pressing rod sleeve 35 from the lower surface of the pressing rod sleeve 35, and at least one sealing ring 38 is arranged between the circumferential surface of the pressing rod 34 and the pressing rod sleeve 35. The elasticity of the sealing ring 38 can ensure that the pressing rod 34 cannot fall out of the movable shaft 32, realize detachable connection, and also can avoid that the electrolyte enters the pressing rod sleeve 35. In the embodiment, the cross section of the pressing rod sleeve 35 is square, the second guide rod 36 is arranged at each corner of the pressing rod sleeve 35, the lower end surface of the movable shaft 32 is provided with a spherical pressure head 39, the pressing rod sleeve 35 is provided with a connecting terminal 310, the connecting terminal 310 is electrically connected with the pressing rod 34, and is used for connecting the EIS module, and the upper ends of the movable shaft 32 and the second guide rod 36 are axially limited by the screw rod arranged above the pressing disc 31, so as to prevent the movable shaft 32 and the second guide rod 36 from being separated from the pressing disc 31.

[0062] The liquid injection assembly 5 includes a liquid injection head 51 and an electrolyte bottle 52 arranged at the side of the supporting tray 41, and a fluid pump 53 connected between the liquid injection head 51 and the electrolyte bottle 52, and two through screw valves 54 can be further arranged between the fluid pump 53 and the liquid injection head 51; the liquid injection head 51 is movably arranged above each electrolyte tank 42. The opening and closing and flow of the fluid pump 53 can be controlled to automatically inject a certain amount of electrolyte into the electrolyte tank 42.

[0063] Further, the liquid injection assembly 5 further includes a liquid injection head support 55 for mounting the liquid injection head 51, the liquid injection head support 55 is arranged on a sliding block 56, the sliding block 56 is driven by a second motor 57 to realize horizontal movement. In the embodiment, the second motor 57 is a lead screw motor, the lead screw 571 of the second motor 57 is threadedly connected and arranged in the sliding block 56; the second motor 57 is arranged at the back of the back plate 24 together with the first motor 62, and the back plate 24 is provided with a strip-shaped hole 241 for movably arranging the liquid injection head support 55.

[0064] The above embodiment and drawings are not limited to the product shape and style of the present application, and any appropriate changes or modifications made by those skilled in the art shall be considered as not departing from the scope of the present application.

Claims

1. A method for testing ionic conductivity, characterized in that The following steps are involved: Step S1. Test preparation Build a multi-channel test device, where each channel of the multi-channel test device consists of a pressure rod and an electrolyte tank. The pressure rod moves up and down relative to the electrolyte tank, and the pressure rod and electrolyte tank are respectively connected to the positive and negative electrodes of the EIS module of the multi-channel test device; Use insulating tape to stick to the non-reactive area of ​​the diaphragm, and leave a circular reactive area with a diameter of 10-14 mm in the center of the diaphragm to make a confined diaphragm; Step S2. Depending on the test type, perform the electrode ionic resistance or membrane ionic conductivity test process; specifically, the electrode ionic resistance test process is as follows: S2a.1 Cut several electrodes into discs of the same diameter and dry them in a vacuum oven at 80-120°C for 6-12 hours. S2a.2 Place the confined membrane in a vacuum oven and dry at 40-50°C for 4-6 hours; S2a.3 Assemble the samples to be tested in a dry room. Place the samples in the order of electrode, confining diaphragm, electrode, and soft conductive material from bottom to top into the electrolyte tank of each channel. S2a.4 Add a preset amount of electrolyte to the electrolyte tank of each channel; S2a.5 Lower the pressure rod to apply a preset pressure to the sample; S2a.6 When the samples are fully soaked, measure the electrochemical impedance spectroscopy of each sample at a test frequency of 100,000 to 1 Hz. The test process of ion conductivity of the diaphragm is as follows: S2b.1 Cut several diaphragms into discs of equal diameter and dry them in a vacuum oven at 40-50°C for 4-6 hours. S2b.2 Assemble the samples to be tested in a dry room, placing the separators in the electrolyte tanks of each channel in layers of 1, 2, 3, 4, and so on. S2b.3 Add a preset amount of electrolyte to the electrolyte tank of each channel; S2b.4 Lower the pressure rod to apply a preset pressure to the sample; S2a.5 When the diaphragms are completely wetted, measure the electrochemical impedance spectrum of each group of diaphragms at a test frequency of 100,000 to 1,000 Hz.

2. The ionic conductivity testing method according to claim 1, wherein: The insulating tape is made of polyimide.

3. The ionic conductivity testing method according to claim 1, wherein: The multi-channel testing device includes a sealed box, a main frame installed in the sealed box, and a pressure assembly, a supporting assembly and a liquid injection assembly installed on the main frame; the sealed box is provided with a sealing door that can be opened and closed, as well as an air inlet and an air outlet; the pressure assembly includes a pressure plate that can move up and down relative to the supporting assembly; a plurality of mounting holes are provided on the pressure plate at equal intervals along the horizontal direction, and a movable shaft is installed in the mounting hole; a first spring is provided between the movable shaft and the lower surface of the pressure plate; a pressure rod is provided opposite to the lower end surface of the movable shaft; the supporting assembly includes a plurality of supporting trays installed on the main frame and respectively opposite to each pressure rod, and each supporting tray is provided with an electrolyte tank; the liquid injection assembly is provided on the side of the supporting tray, and is used to automatically inject electrolyte into each electrolyte tank.

4. The ionic conductivity testing method according to claim 3, wherein: The main frame includes a top plate, a bottom plate, several pillars, and a back plate; the top plate is parallel to the bottom plate, and the pillars and back plate are supported between the top plate and the bottom plate; the pressure assembly is installed below the top plate, and the supporting assembly is installed above the bottom plate.

5. The ionic conductivity testing method according to claim 3, wherein: It also includes a dew point sensor and an air pressure sensor arranged in the sealed box, which are used to detect the humidity and air pressure in the sealed box respectively.

6. The ionic conductivity testing method according to claim 3, wherein: It also includes a driving assembly for driving the pressure assembly; the driving assembly includes a fixed bracket, a first motor, a first guide rod, a lifting plate, a connecting rod, a trapezoidal nut and a trapezoidal screw; the fixed bracket is installed on the upper surface of the main frame; a first guide rod is connected between the fixed bracket and the main frame; the lifting plate slides on the first guide rod; the connecting rod passes through the main frame, and its upper and lower ends are respectively connected to the lifting plate and the pressure plate; a trapezoidal nut is installed on the lifting plate, and the trapezoidal screw is threadedly connected to the trapezoidal nut, and its two ends are respectively rotatably matched with the fixed bracket and the main frame; the first motor is transmission-connected to the trapezoidal screw for driving the trapezoidal screw to rotate.

7. The ionic conductivity testing method according to claim 6, wherein: The output end of the first motor is transmission-connected to a driving wheel, the circumference of the trapezoidal screw is fixedly connected to a driven wheel, and a synchronous belt is tensionedly wound around the driving wheel and the driven wheel; the main frame and the fixed bracket are both provided with bearings for the rotational cooperation of the trapezoidal screw; the main frame is provided with a guide sleeve for the connecting rod to pass through; the connecting rod and the guide sleeve are provided with at least two pairs, and are arranged at equal angles around the trapezoidal screw.

8. The ionic conductivity testing method according to claim 3, wherein: A plurality of pressure rod sleeves are provided below the pressure plate, and a plurality of second guide rods are connected to the upper surface of the pressure rod sleeve; the second guide rod is movably inserted into the pressure plate, and a second spring is provided on the circumference of the second guide rod; the pressure rod is transmitted into the pressure rod sleeve from the lower surface of the pressure rod sleeve, and at least one sealing ring is provided between the circumference of the pressure rod sleeve and the pressure rod sleeve; a spherical pressure head is provided on the lower end surface of the movable shaft; a connecting terminal is provided on the pressure rod sleeve, and the connecting terminal is electrically connected to the pressure rod for connecting to the EIS module; the upper ends of the movable shaft and the second guide rod are axially limited by a screw located above the pressure plate.

9. The ionic conductivity testing method according to claim 3, wherein: The liquid injection assembly includes a liquid injection head and an electrolyte bottle arranged on the side of the supporting tray, and a fluid pump connecting the liquid injection head and the electrolyte bottle; the liquid injection head is horizontally movably fitted above each electrolyte tank.

10. The ionic conductivity testing method according to claim 9, wherein: The injection assembly also includes a two-way threaded valve connected between the injection head and the fluid pump, and an injection head bracket for mounting the injection head; the injection head bracket is arranged on a slider, and the slider is driven by a second motor to achieve horizontal movement.

Images