A symmetrical battery and testing tool

Abstract

The utility model proposes a symmetrical battery and a test fixture, which relates to the technical field of lithium batteries, including two pole pieces with the same polarity, a diaphragm and an aluminum foil bag, the two pole pieces are stacked in the aluminum foil bag, at least one layer of diaphragm is stacked between the two pole pieces, the pole pieces have pole ears at the top, the pole ears extend out of the aluminum foil bag, and the side of the pole piece away from the diaphragm is covered with a separator to prevent the coating on the side of the pole piece away from the diaphragm from contacting the electrolyte in the aluminum foil bag. During the manufacturing process of the pole piece of the symmetrical battery of the utility model, it is only necessary to stick a separator on the side of the pole piece away from the diaphragm, the process is simple, the separator has a certain support and shaping effect on the pole piece, and prevents the pole piece from warping during battery assembly. At the same time, the separator can prevent the electrolyte from contacting the coating on the side of the pole piece away from the diaphragm, thereby preventing lithium ions from migrating through the electrolyte to the coating on the side of the pole piece away from the diaphragm, causing deviations in the diaphragm resistance test.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium batteries, in particular to a symmetrical battery and a testing tool. Background Art

[0002] At present, the new energy industry is developing rapidly, and the technical requirements for lithium-ion batteries are constantly increasing. As one of the key indicators of battery performance, battery internal resistance has received special attention. As one of the four main materials that make up lithium batteries, the ionic resistivity of the diaphragm affects the internal resistance of the battery. At present, there is no special equipment to test the ionic resistivity of the diaphragm in the wet state, so the diaphragm resistivity can be analyzed and confirmed by setting up a symmetrical battery.

[0003] When the battery is charged and discharged, lithium ions migrate between the positive and negative electrodes through the pores of the diaphragm. Electrons participate in the entire process. When a symmetrical battery is used to test the diaphragm impedance and ion impedance, the charge and discharge process is not involved. Without the participation of electrons, the diaphragm does not undergo a Faraday reaction. Therefore, a symmetrical battery test with the same pole piece composition is used to fit the above process. Using an electrochemical workstation, electrochemical impedance tests are performed on symmetrical batteries with different numbers of diaphragm layers, and then the number of diaphragm layers is fitted with the test results. The slope k is the resistance of the diaphragm.

[0004] In the existing symmetrical battery manufacturing, the double-sided coated pole piece needs to be processed into a single-sided coated pole piece by using a solvent wet wiping method, and then assembled into a symmetrical battery by stacking. The purpose of this is to prevent the lithium ions from migrating through the electrolyte to the coating on the side of the pole piece away from the diaphragm in the untreated state, causing deviations in the diaphragm resistance test. In the prior art, the solvent wet wiping method is usually used, which can easily cause the pole piece to curl or bend, causing damage to the pole piece; when the curled pole piece is assembled into a symmetrical battery, it is easy to cause the diaphragm to wrinkle, or even the pole piece to bend, resulting in failure of battery assembly and inaccurate subsequent testing. Utility Model Content

[0005] In view of this, the utility model proposes a symmetrical battery and a testing tool to solve the problems of complicated electrode processing procedures and easy damage of the electrode in the existing symmetrical battery manufacturing process.

[0006] The technical solution of the utility model is achieved in this way:

[0007] In the first aspect, the utility model provides a symmetrical battery, comprising two pole pieces with the same polarity, a diaphragm and an aluminum foil bag, wherein the two pole pieces are stacked in the aluminum foil bag, and at least one layer of diaphragm is stacked between the two pole pieces. The pole pieces have pole ears at the tops thereof, and the pole ears extend out of the aluminum foil bag. The side of the pole piece away from the diaphragm is covered with an isolation sheet for preventing the coating on the side of the pole piece away from the diaphragm from contacting the electrolyte in the aluminum foil bag.

[0008] On the basis of the above technical solution, preferably, the isolation sheet has a size and shape matching that of the pole piece.

[0009] Further, preferably, the length dimension of the isolation sheet is 0.5mm to 2mm larger than the length dimension of the pole piece, the width dimension of the isolation sheet is 0.5mm to 2mm larger than the width dimension of the pole piece, and the outer edge of the isolation sheet is wrapped around the side of the pole piece facing the diaphragm.

[0010] As an implementation mode, the isolation sheet is a non-conductive tape.

[0011] As another embodiment, the isolation sheet is a single-sided conductive tape or a double-sided conductive tape.

[0012] On the basis of the above technical solution, preferably, the isolation sheet is a copper foil tape or an aluminum foil tape, and when the electrode is a positive electrode, the isolation sheet is configured as an aluminum foil tape, and when the electrode is a negative electrode, the isolation sheet is configured as a copper foil tape.

[0013] On the basis of the above technical solution, preferably, the pole ears at the top ends of the two pole pieces are staggered with each other in the horizontal direction.

[0014] In the second aspect, the utility model further discloses a testing tool, including a testing frame, on which a placing platform is provided, the placing platform is used to place the symmetrical battery described in the first aspect, and an electrical connection structure is provided on the placing platform, the electrical connection structure is used to be detachably electrically connected to the tab.

[0015] On the basis of the above technical solution, preferably, the electrical connection structure is arranged with two intervals in the horizontal direction, including a conductive frame and a locking bolt. The conductive frame is slidably arranged on the placement platform, and a conductive connector is fixedly arranged at one end of the conductive frame for connecting to the test power supply. The locking bolt is vertically arranged at the other end of the conductive frame for pressing and connecting the pole ear.

[0016] Compared with the prior art, the utility model has the following beneficial effects:

[0017] (1) The symmetrical battery disclosed in the utility model directly covers the side of the electrode away from the diaphragm with a separator. In this way, when the symmetrical battery is manufactured, the separator can prevent the electrolyte from contacting the coating on the side of the electrode away from the diaphragm, thereby preventing lithium ions from migrating through the electrolyte to the coating on the side of the electrode away from the diaphragm, causing deviations in the diaphragm resistance test. At the same time, during the manufacturing process of the electrode of the entire symmetrical battery, it is only necessary to paste the separator on the side of the electrode away from the diaphragm. The process is simple, and the separator has a certain supporting and shaping effect on the electrode, ensuring the uniformity of the electrode, avoiding the warping of the electrode during battery assembly, and will not affect the electrode contact and cause interface wrinkles.

[0018] (2) By setting up the test fixture, when the symmetrical battery is manufactured, it is placed flat on the placement platform, and one end of the electrical connection structure is connected to the pole ear, and the other end of the electrical connection structure is connected to the power supply, so that the diaphragm impedance and ion impedance tests can be carried out conveniently and quickly in the electrochemical workstation. After the test is completed, the electrical connection structure and the pole ear can be separated to facilitate the symmetrical battery to participate in other electrical tests. This process does not require welding of the pole ear and the power harness, and the operation process is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a schematic diagram of the explosion structure of the symmetrical battery disclosed in the utility model;

[0021] Figure 2 It is a schematic diagram of the planar structure of the symmetrical battery disclosed in the utility model;

[0022] Figure 3 for Figure 2 Plane section view at AA in the middle;

[0023] Figure 4 for Figure 3 A partial enlarged view of point B in the middle;

[0024] Figure 5 It is a schematic diagram of the assembly structure of the symmetrical battery and the test tooling disclosed in the utility model;

[0025] Figure 6 This is a diagram of the impedance fitting results of the symmetrical battery test diaphragm disclosed in the utility model;

[0026] Figure 7 This is a schematic diagram of the ionic impedance test results of the symmetrical battery disclosed in the utility model;

[0027] Reference numerals:

[0028] 1. Symmetrical battery; 11. Pole piece; 111. Pole ear; 21. Diaphragm; 31. Aluminum foil bag; 41. Isolation sheet; 2. Test tooling; 20. Test rack; 22. Placement platform; 23. Electrical connection structure; 231. Conductive rack; 232. Locking bolt; 233. Conductive joint. DETAILED DESCRIPTION

[0029] The following will be combined with the implementation of the utility model to clearly and completely describe the technical solutions in the implementation of the utility model. Obviously, the described implementation is only a part of the implementation of the utility model, not all of the implementations. Based on the implementation of the utility model, all other implementations obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0030] like Figure 1 As shown, combined Figure 2-4 The embodiment of the utility model provides a symmetrical battery 1 for testing and analyzing the resistivity of a diaphragm 21. The symmetrical battery 1 comprises two pole pieces 11 with the same polarity, a diaphragm 21 and an aluminum foil bag 31.

[0031] Two electrode sheets 11 are stacked in an aluminum foil bag 31, and at least one layer of diaphragm 21 is stacked between the two electrode sheets 11. Different numbers of diaphragms 21 can be selected according to different experimental conditions. The electrode sheets 11 have pole ears 111 at the top, and the pole ears 111 extend out of the aluminum foil bag 31. The electrode sheets 11 disclosed in this embodiment can be taken from the electrode sheets 11 in the battery cell at 50% SOC state, or from the electrode sheets 11 in the battery cell at an empty state, and of course, can also be taken from the produced electrode sheets 11.

[0032] Since the pole piece 11 is taken out of the battery cell or taken from the produced pole piece 11, both surfaces of the pole piece 11 are coated. The double-sided coated pole piece 11 needs to be processed into a single-sided coated pole piece 11 by a solvent wetting and wiping method, and then assembled into a symmetrical battery 1 by stacking. The purpose of this is to prevent lithium ions from migrating to the coating on the side of the pole piece 11 away from the diaphragm 21 through the electrolyte in the untreated state, causing deviations in the resistance test of the diaphragm 21. In the prior art, the solvent wetting and wiping method is usually used, which is easy to cause the pole piece 11 to curl or bend, causing damage to the pole piece 11; when the curled pole piece 11 is assembled into a symmetrical battery 1, it is easy to cause the diaphragm 21 to wrinkle, or even bend the pole piece 11, resulting in failure of battery assembly and inaccurate subsequent testing.

[0033] To this end, the method adopted in this embodiment is to directly cover the isolation sheet 41 on the side of the pole piece 11 away from the diaphragm 21. In this way, when the symmetrical battery 1 is manufactured, the isolation sheet 41 can prevent the electrolyte from contacting the coating on the side of the pole piece 11 away from the diaphragm 21, thereby preventing lithium ions from migrating through the electrolyte to the coating on the side of the pole piece 11 away from the diaphragm 21, causing deviations in the resistance test of the diaphragm 21. At the same time, during the manufacturing process of the pole piece 11 of the entire symmetrical battery 1, it is only necessary to paste the isolation sheet 41 on the side of the pole piece 11 away from the diaphragm 21. The process is simple, and the isolation sheet 41 has a certain supporting and shaping effect on the pole piece 11, ensuring the uniformity of the pole piece 11, preventing the pole piece 11 from warping during battery assembly, and will not affect the electrode contact and cause interface wrinkles.

[0034] As an embodiment, the isolation sheet 41 has a size and shape that matches the electrode 11. With this configuration, the isolation sheet 41 can completely cover the surface of the electrode 11 on the side away from the diaphragm 21. In the actual production process, the isolation sheet 41 can be cut into a shape consistent with the size of the electrode 11, and can be fixed to the surface of the electrode 11 on the side away from the diaphragm 21 by gluing. In this way, after the lithium ions in the coating on which the electrode 11 contacts the diaphragm 21 pass through the diaphragm 21 and are freed into the electrolyte, under the action of the isolation sheet 41, the lithium ions will not enter the coating on the side of the electrode 11 away from the diaphragm 21, so that the data is accurate when the resistance of the diaphragm 21 is tested.

[0035] As another embodiment, the length dimension of the isolating sheet 41 is 0.5 mm to 2 mm larger than the length dimension of the pole piece 11, the width dimension of the isolating sheet 41 is 0.5 mm to 2 mm larger than the width dimension of the pole piece 11, and the outer edge of the isolating sheet 41 is wrapped around the side of the pole piece 11 facing the diaphragm 21. Thus, the size of the isolating sheet 41 is larger than the size of the pole piece 11, ensuring that the isolating sheet 41 completely covers the pole piece 11 and wraps the edge of the pole piece 11, thereby effectively preventing the electrolyte from penetrating into the coating from the gap between the pole piece 11 and the isolating sheet 41, and ensuring the reliability and accuracy of the resistance test result of the diaphragm 21.

[0036] In some embodiments, the isolation sheet 41 is a non-conductive tape. In actual operation, it is only necessary to stick the non-conductive tape to the side of the electrode 11 away from the diaphragm 21. Preferably, the non-conductive tape covers the electrode 11 and wraps the edge of the electrode 11 to ensure that the electrode is flat. The non-conductive tape prevents the risk of the electrolyte contacting some coatings of the electrode 11 away from the diaphragm 21. In actual use, the symmetrical battery is not charged or discharged, and the non-conductive tape does not generate overcurrent with the electrode 11, which can more truly reflect the test results.

[0037] As another embodiment, the separator 41 is a double-sided conductive tape. The double-sided conductive tape allows current to pass through and provides better electrode connection. In this way, a symmetrical battery needs to be used for charging and discharging, and the double-sided conductive tape is used to facilitate conduction.

[0038] As some preferred embodiments, the separator 41 is a copper foil tape or an aluminum foil tape. When the electrode 11 is a positive electrode 11, the separator 41 is configured as an aluminum foil tape, and when the electrode 11 is a negative electrode, the separator 41 is configured as a copper foil tape. The separator 41 using aluminum foil tape as the positive electrode can maintain conductivity, and the separator 41 using copper foil tape as the negative electrode 11 also has good conductivity and isolation. Such a design optimizes the structure of the symmetrical battery and improves its performance and stability.

[0039] In this embodiment, the tabs 111 at the top of the two pole pieces 11 are staggered in the horizontal direction. In the specific manufacturing process, the position setting of the tabs 111 can be achieved through a cutting process. By staggering the tabs 111 of the two pole pieces 11 in the horizontal direction, after the symmetrical battery 1 is manufactured, subsequent experiments can be carried out conveniently, that is, the connection of the tabs 111 to the test equipment can be facilitated.

[0040] In some prior arts, after the symmetrical battery 1 is manufactured, a welding process is usually used to connect the pole ear 111 of the symmetrical battery 1 to the power line in an electrochemical workstation. This operation is rather troublesome, and the pole ear 111 is usually thin. After welding is completed, it is inconvenient to disassemble and the pole ear 111 is easily damaged, which makes it inconvenient to electrically connect the power supply during other electrical testing experiments.

[0041] To this end, the utility model also discloses a test fixture 2, which is used to clamp the symmetrical battery 1, so as to facilitate the placement of the battery in the electrochemical test workstation for performance testing. Figure 5 As shown, the test fixture 2 includes a test frame 20, on which a placement platform 22 is provided. The placement platform 22 is used to place the symmetrical battery 1 disclosed in the above embodiment. The placement platform 22 is provided with an electrical connection structure 23, which is used for detachable electrical connection with the tab 111.

[0042] By adopting the above technical solution, when the symmetrical battery 1 is manufactured, it is placed flat on the placement platform 22, and one end of the electrical connection structure 23 is connected to the pole ear 111, and the other end of the electrical connection structure 23 is connected to the power supply, so that the impedance test and the ion impedance test can be conveniently and quickly performed in the electrochemical workstation. After the test is completed, the electrical connection structure 23 and the pole ear 111 can be separated to facilitate the symmetrical battery 1 to participate in other electrical tests. This process does not require the pole ear 111 to be welded with the power harness, and the operation process is simple.

[0043] In order to adapt to the test of symmetrical batteries 1 of different sizes, the solution adopted in this embodiment is to set two electrical connection structures 23 at intervals in the horizontal direction. The electrical connection structure 23 includes a conductive frame 231 and a locking bolt 232. The conductive frame 231 is slidably set on the placement platform 22. The conductive frame 231 slides horizontally relative to the placement platform 22 through a slide rail. The two connection structures can adjust the distance between them through relative sliding, so that the two electrical connection structures 23 correspond to the pole ears 111 of the symmetrical battery 1 respectively, thereby adapting to the test of symmetrical batteries 1 of different sizes. A conductive connector 233 is fixedly set at one end of the conductive frame 231 for connecting to the test power supply, and a locking bolt 232 is vertically set at the other end of the conductive frame 231 for pressing and connecting the pole ears 111.

[0044] By adopting the above technical solution, after the manufactured symmetrical battery 1 is placed flat on the placement platform 22, the electrical connection structure 23 is moved horizontally to adjust the distance between the two electrical connection structures 23 so that the distance between the two and the distance between the pole lugs 111 are adapted, and then the locking bolt 232 is rotated to move the locking bolt 232 downward relative to the conductive frame 231, thereby pressing the pole lug 111. Before testing, the test power line can be connected to the conductive connector 233, thereby achieving a certain test current passing through the symmetrical battery 1.

[0045] It is worth noting that the entire test frame 20 and the conductive frame 231 are electrically isolated.

[0046] The utility model shows an example of a manufacturing method and a testing method of a symmetrical battery 1, which are as follows:

[0047] 1. Take the negative electrode sheet 11 of the battery cell at 50% SOC and cut it to obtain two electrode sheets 11 of the same size.

[0048] 2. Paste the cut isolation sheet 41 onto one side of the two pole pieces 11 .

[0049] 3. The electrode piece 11, a plurality of separators 21, and the electrode piece 11 are stacked in sequence and placed in an aluminum foil bag 31. A certain amount of electrolyte is injected into the aluminum foil bag 31, and the aluminum foil bag 31 is heat-sealed to complete the manufacture of the symmetrical battery 1.

[0050] 4. The prepared symmetrical battery 1 is allowed to stand at 25° C. for 12 to 36 hours.

[0051] 6. Furthermore, the prepared symmetrical battery 1 is subjected to pressurization treatment using a fixture, and the pressure is 0.08-0.12 MPa.

[0052] 7. Install the symmetrical battery 1 on the test fixture 2 and place it on the electrochemical workstation for testing. The frequency of the disturbing alternating current applied is 0.01 to 10E6 Hz and the amplitude is 5 to 10 mV.

[0053] 8. Perform data processing based on the results of the AC impedance test, take the resistance value at the intersection of the curve of different batteries and the real axis, and make an "impedance-number of diaphragm layers" graph. The slope k is the diaphragm impedance.

[0054] 9. Perform data processing based on the results of the AC impedance test. Subtract the intersection of the real axis and the intersection of the low-frequency extension line and the real axis, and then multiply by three to obtain the ionic impedance.

[0055] The symmetrical battery disclosed in the utility model has a simple structure and a simple manufacturing process, which solves assembly problems such as easy bending of the pole piece and easy wrinkling of the diaphragm. In addition, the symmetrical battery disclosed in this embodiment can be applied to different systems of positive and negative electrode materials and electrolyte compositions, and has strong universality. This embodiment tests the prepared symmetrical battery to evaluate the diaphragm impedance at different stages and states, which can be used as a data reference for safety and storage tests. In addition, the ionic impedance at different stages and states can also be evaluated, which can be used as a data reference for health assessment and storage tests.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A symmetrical battery, comprising two pole pieces (11) with the same polarity, a diaphragm (21) and an aluminum foil bag (31), characterized in that: The two pole pieces (11) are stacked in an aluminum foil bag (31), at least one layer of diaphragm (21) is stacked between the two pole pieces (11), the pole piece (11) has a pole ear (111) at the top, and the pole ear (111) extends out of the aluminum foil bag (31), and the side of the pole piece (11) away from the diaphragm (21) is covered with an isolation sheet (41) for preventing the coating on the side of the pole piece (11) away from the diaphragm (21) from contacting the electrolyte in the aluminum foil bag (31).

2. The symmetrical battery according to claim 1, characterized in that: The isolation sheet (41) has a size and a shape that matches the pole sheet (11).

3. The symmetrical battery according to claim 1 or 2, characterized in that: The length dimension of the isolation sheet (41) is 0.5 mm to 2 mm larger than the length dimension of the pole piece (11), the width dimension of the isolation sheet (41) is 0.5 mm to 2 mm larger than the width dimension of the pole piece (11), and the outer edge of the isolation sheet (41) is wrapped around the side of the pole piece (11) facing the diaphragm (21).

4. The symmetrical battery according to claim 3, characterized in that: The isolation sheet (41) is a non-conductive tape.

5. The symmetrical battery according to claim 3, characterized in that: The isolation sheet (41) is a double-sided conductive tape.

6. The symmetrical battery according to claim 5, characterized in that: The isolation sheet (41) is a copper foil tape or an aluminum foil tape. When the electrode sheet (11) is a positive electrode sheet, the isolation sheet (41) is configured as an aluminum foil tape. When the electrode sheet (11) is a negative electrode sheet, the isolation sheet (41) is configured as a copper foil tape.

7. The symmetrical battery according to claim 1, characterized in that: The pole ears (111) at the top ends of the two pole pieces (11) are staggered with each other in the horizontal direction.

8. A test tool, characterized in that: The test frame (20) comprises a placement platform (22) provided on the test frame (20), the placement platform (22) being used to place the symmetrical battery (1) according to any one of claims 1 to 7, and an electrical connection structure (23) being provided on the placement platform (22), the electrical connection structure (23) being used to be detachably electrically connected to the tab (111).

9. The test tool as claimed in claim 8, characterized in that: The electrical connection structure (23) is provided with two conductive frames (231) and locking bolts (232) at intervals in the horizontal direction. The conductive frame (231) is slidably provided on the placement platform (22). A conductive connector (233) is fixedly provided at one end of the conductive frame (231) for connection with a test power source. The locking bolt (232) is vertically provided at the other end of the conductive frame (231) for pressing and connecting the pole ear (111).

Images