Three-electrode of soft package battery

Abstract

The three-electrode comprises a first aluminum plastic film, a positive plate, a second aluminum plastic film, a first diaphragm, a negative plate, a second diaphragm, a copper wire, green glue, a nickel strip, a welding point and yellow glue, a first aluminum plastic film, a positive plate, a second diaphragm, a copper wire, a first diaphragm, a negative plate and a second aluminum plastic film are sequentially assembled from top to bottom, a nickel strip is fixed to the soft package three-electrode, soldering paste is smeared on the copper wire, the copper wire is attached to the nickel strip, soldering iron is used for welding the copper wire to a welding point on the nickel strip through the soldering paste, and the soft package three-electrode is obtained. And the welding part is coated with yellow glue in a rubberizing manner. According to the utility model, the real-time point position change of the anode and the cathode can be accurately reflected, and the two copper wires are used, so that the manufacturing success rate can be well improved.

Description

Technical Field

[0001] The utility model belongs to the field of lithium batteries, and particularly relates to a three-electrode soft-pack battery. Background Art

[0002] With the rapid development of the lithium-ion battery industry, lithium batteries are widely used in the fields of electric vehicles, smart phones, laptops, etc. The research on lithium batteries is no longer limited to the whole, but needs to separately study the positive and negative electrodes, separators, electrolytes, etc. of lithium batteries. A three-electrode soft-pack has three electrodes: a working electrode (research electrode), a reference electrode, and an auxiliary electrode. There is a high input impedance in the potential difference between the reference electrode and the working electrode. The current passes between the working electrode and the auxiliary electrode, and almost no current passes through the reference electrode. Therefore, the potential change of the working electrode relative to the reference electrode can be measured more accurately. When studying the lithium intercalation situation of the fast-charging negative electrode of a lithium battery, the potential changes of the positive and negative electrodes can be monitored separately, and the potentials of the positive and negative electrodes can be separately decomposed and tested.

[0003] Compared with a two-electrode soft-pack lithium battery, the positive and negative electrodes correspond to the working electrode and the auxiliary electrode. In a common three-electrode soft-pack, a lithium sheet or a lithium strip is used as the reference electrode. Metallic lithium has a standard potential and a high exchange current density, and there will be no overpolarization in the three-electrode soft-pack. However, metallic lithium is sensitive to water and oxygen and easily reacts with them. During the charge and discharge process of the three-electrode soft-pack, metallic lithium is easily decomposed by the solvent, thus losing the function of the reference electrode. It is difficult to ensure the smooth progress of the experiment with metallic lithium as the reference electrode. Content of the Utility Model

[0004] The technical problem to be solved by the utility model is as follows: Provide a three-electrode soft-pack battery. Between the positive and negative electrodes of a traditional two-electrode soft-pack, insert two copper wires coated with a separator to remove the oxide layer as the reference electrode of the third electrode. Before the experiment, perform lithium plating on the reference electrode copper wires so that metallic lithium coats the outer side of the copper wires. For the copper wires exposed outside the three-electrode soft-pack, weld them to nickel with metallic tin. Fix the nickel strip on the three-electrode soft-pack with yellow glue. It has little influence on ion transport, can accurately reflect the real-time potential changes of the positive and negative electrodes, and improves the production success rate.

[0005] The utility model adopts the following technical solutions to solve the above technical problems:

[0006] A three-electrode soft-pack battery proposed by the utility model includes:

[0007] A first aluminum-plastic film, a positive electrode sheet, a second aluminum-plastic film, a first separator, a negative electrode sheet, a second separator, and copper wires form a three-electrode soft-pack.

[0008] Assemble the first aluminum-plastic film, the positive electrode sheet, the second separator, the copper wire, the first separator, the negative electrode sheet, and the second aluminum-plastic film in sequence from top to bottom.

[0009] Furthermore, it also includes green glue, nickel strips, welding points, and yellow glue.

[0010] Fix the nickel strip on the soft-pack three-electrode, apply soldering paste on the copper wire and attach it to the nickel strip, use a soldering iron to weld the copper wire to the welding point on the nickel strip through the soldering paste, and cover the welded part with yellow glue.

[0011] Furthermore, fix the second aluminum-plastic film on the desktop with insulating glue, weld the nickel pole ear on the negative electrode sheet, place the negative electrode sheet with the welded nickel pole ear at an appropriate position on the second aluminum-plastic film so that the pole ear heat-sealing glue is at the final heat-sealing position of the second aluminum-plastic film; lay the first separator on the negative electrode sheet with the welded nickel pole ear.

[0012] Lay the copper wire on the first separator and fix it with 1mm*5mm green glue, and then lay the second separator on the first separator to cover the copper wire.

[0013] Stack the positive electrode sheet on the second separator, pay attention to the position of the positive electrode sheet, and ensure that the positive electrode sheet must be placed within the plane of the negative electrode sheet to prevent lithium precipitation or abnormal discharge capacity during charge and discharge.

[0014] Lay the first aluminum-plastic film on the positive electrode sheet and fix it at a position corresponding to the second aluminum-plastic film with insulating glue, and finally perform heat sealing. The heat-sealing ends are the three pole ear sides, and the bottom edge is left open for subsequent electrolyte injection.

[0015] Inject the set liquid-retaining amount of electrolyte into the soft-pack three-electrode, soak for 10 minutes, heat-seal the bottom edge with a vacuum heat-sealing machine, wrap the copper wire, and perform electrochemical testing after standing for 48 hours at 45°C.

[0016] Furthermore, the first separator evenly covers the negative electrode sheet from the up, down, left, and right directions, and fixes the four edges of the first separator with insulating glue to prevent the separator from moving and causing positive and negative electrode contact short circuits.

[0017] Furthermore, weld the positive electrode ear to the positive electrode sheet through an ultrasonic welding machine, weld the negative electrode ear to the negative electrode sheet through an ultrasonic welding machine, clean the welded positive and negative electrode sheets, and cover the welded parts with insulating glue to prevent foreign matters such as dust and particles introduced during the welding process from affecting subsequent testing.

[0018] Furthermore, use a punching die with a specification of 100x40mm 2 to cut the positive electrode sheet into a set size; use a punching die with a specification of 105x45 mm 2 to cut the negative electrode sheet into a set size.

[0019] Further, use scissors to cut the first separator into a size of 120x55 mm 2 ; use scissors to cut the second separator into a size of 20x15 mm 2 to reduce the internal resistance of the soft-pack three-electrode.

[0020] Further, use scissors to cut the first aluminum-plastic film and the second aluminum-plastic film into a size of 140x70 mm 2 size.

[0021] Further, the core package includes a positive electrode sheet and a negative electrode sheet.

[0022] Further, the copper wire includes two copper wires, one of which serves as a reference electrode and the other serves as a spare electrode and is reserved by coating with small yellow glue.

[0023] The present utility model adopts the above technical solutions. Compared with the prior art, its remarkable technical effects are as follows:

[0024] In the present utility model, the size of the second separator used is relatively small, which has little influence on ion transport and also has little influence on the internal resistance of the soft-pack three-electrode, and can more accurately reflect the real-time potential changes of the positive and negative electrodes; and the use of two copper wires greatly improves the production success rate. Description of the Drawings

[0025] Figure 1 is the overall structure diagram of the present utility model.

[0026] Figure 2 is the schematic diagram of the copper wire coating of the present utility model.

[0027] Figure 3 is the schematic diagram of the copper wire welding nickel strip structure and fixation of the present utility model.

[0028] Figure 4 is the content diagram of the 0-80% SOC charging time when the negative electrode potential is 0 mv during 3C charging in the embodiment of the present utility model.

[0029] Figure 5 is the test data diagram at different temperatures in the embodiment of the present utility model. Detailed Embodiments

[0030] In order to enable technicians to better understand the method of the present utility model, the technical solutions in the embodiments of the present utility model will be described in detail below with reference to the drawings in the embodiments of the present utility model.

[0031] It should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0032] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0033] In the present invention, unless otherwise clearly defined and limited, the terms such as "mounted", "connected", "connected to", "fixed" and the like should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection or communicable with each other; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "under" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0035] To achieve the above object, the present invention provides a three - electrode soft - package battery, as Figure 1 shown, comprising:

[0036] The first aluminum-plastic film 1, the positive electrode sheet 2, the second aluminum-plastic film 3, the first separator 4, the negative electrode sheet 5, the second separator 6 and the copper wire 7. Among them, the copper wire includes two copper wires, one of which is used as a reference electrode and the other is used as a spare electrode and is coated and reserved with small yellow glue.

[0037] Before assembly, each material is processed as follows:

[0038] The treatment of the copper wire 7 is as follows: Immerse the 25-micron copper wire 7 in a 7% - 15% dilute sulfuric acid solution for 1.5 h to remove the surface oxide layer; wash it 3 - 5 times with distilled water and dry it in an oven at 80 °C. Take the positive electrode sheet 2 and the negative electrode sheet 5 as the positive electrode and the copper wire 7 as the negative electrode, and charge the positive and negative electrodes at a constant current of 30 - 50 uA for 2 h each to ensure that the surface of the copper wire is plated with metallic lithium.

[0039] Bake the first aluminum-plastic film 1, the positive electrode sheet 2, the second aluminum-plastic film 3, the first separator 4, the negative electrode sheet 5, and the second separator 6 in a vacuum drying oven at a temperature of 90 °C for 24 h.

[0040] Assemble the processed materials: Assemble the first aluminum-plastic film 1, the positive electrode sheet 2, the second separator 6, the copper wire 7, the first separator 4, the negative electrode sheet 5, and the second aluminum-plastic film 3 in order from top to bottom to form a soft-pack three-electrode. The specific connection is as follows:

[0041] Fix the second aluminum-plastic film 3 on the table with insulating glue, weld a nickel tab on the negative electrode sheet 5, and place the negative electrode sheet 5 with the welded nickel tab at an appropriate position on the second aluminum-plastic film 3 so that the tab hot melt adhesive is at the final heat-sealing position of the second aluminum-plastic film 3; lay the first separator 4 on the negative electrode sheet 5 with the welded nickel tab.

[0042] Stack the positive electrode sheet 2 on the second separator 6, pay attention to the position of the positive electrode sheet 2, and ensure that the positive electrode sheet 2 must be placed within the plane of the negative electrode sheet 5 to prevent lithium deposition or abnormal discharge capacity during charge and discharge.

[0043] Lay the first aluminum-plastic film 1 on the positive electrode sheet 2 and fix it at a position corresponding to the second aluminum-plastic film 3 with insulating glue, and finally perform heat sealing. The heat-sealing ends are the three tab edges, and the bottom edge is left open for subsequent liquid injection.

[0044] Cover the negative electrode sheet 5 evenly from top, bottom, left, and right directions with the first separator 4, and fix the four edges of the first separator 4 with insulating glue to prevent the separator from moving and causing short circuit between the positive and negative electrodes.

[0045] As Figure 2 shown, lay the two copper wires 7 on the first separator 4 respectively and fix them with a 1 mm * 5 mm green glue 8, and then lay the second separator 6 on the first separator 4 to cover the copper wires 7.

[0046] Inject the electrolyte with the set liquid retention volume into the pouch-type three-electrode, soak for 10 minutes, heat-seal the bottom edge with a vacuum heat-sealing machine, wrap the copper wire around, and let it stand for 48 hours in an environment of 45 °C before performing electrochemical tests.

[0047] As Figure 3 shown, it also includes a nickel strip 9, a welding point 10, and yellow glue 11. Fix the nickel strip 9 on the pouch-type three-electrode, apply solder paste on the copper wire 7 and attach it to the nickel strip 9, use a soldering iron to weld the copper wire 7 to the welding point 10 on the nickel strip 9 through the solder paste, and cover the welded part with yellow glue 11.

[0048] Weld the positive electrode tab and the positive electrode sheet 2 through an ultrasonic spot welder, weld the negative electrode tab and the negative electrode sheet 5 through an ultrasonic spot welder, clean the welded positive and negative electrode sheets, and cover the welded part with insulating glue to prevent foreign matters such as dust and particles introduced during the welding process from affecting subsequent tests.

[0049] Use a punching die with a specification of 100x40mm 2 to cut the positive electrode sheet 2 into a set size; use a punching die with a specification of 105x45mm 2 to cut the negative electrode sheet 5 into a set size. Use scissors to cut the first separator 4 into a size of 120x55 mm 2 ; use scissors to cut the second separator 6 into a size of 20x15 mm 2 to reduce the internal resistance of the pouch-type three-electrode. Use scissors to cut the first aluminum-plastic film 1 and the second aluminum-plastic film 3 into a size of 140x70 mm 2 .

[0050] The core package includes a positive electrode sheet 2 and a negative electrode sheet 5. The copper wire 7 includes two copper wires, one of which serves as a reference electrode and the other as a spare electrode and is covered with small yellow glue for reservation.

[0051] Select copper wire with a diameter of 25 microns, which can not affect the transmission of lithium ions between the positive and negative electrodes, effectively monitor the changes in the potential and impedance of the positive and negative electrodes during the charge and discharge process of the lithium battery, effectively monitor the potential changes of the positive and negative electrodes of the battery, and can obtain the potential of the negative electrode and the change of the lithium intercalation state more accurately.

[0052] Perform a fast charge lithium deposition potential test on the constructed lithium-ion battery pouch-type three-electrode. The specific steps are as follows:

[0053] Step 1: Let the fabricated lithium-ion battery pouch-type three-electrode stand for 5 minutes, detect the voltage stability of the electrode to ensure the stability of the electrode system.

[0054] Step 2: Verify fast charging: Charge at 3C until the potential of the negative electrode with respect to the copper wire is 0mv. At this time, the potential of the negative electrode is the same as that of metallic lithium, reaching the saturated potential of lithium deposition.

[0055] Step 3: To ensure that no lithium is deposited on the negative electrode, the 3C current is gradually decreased and charged at a constant potential.

[0056] Step 4: Intercalate lithium into the negative electrode at 0 mV until the current at the end of 1C that meets the verification requirements is reached.

[0057] Figure 4 It is a graph of the charging time content from 0 to 80% SOC when the potential of the negative electrode is 0 mV during charging at 3C. Figure 5 It is a graph of test data at different temperatures. At 25°C, 35°C, and 45°C environments, the time taken to charge to 80% gradually decreases. In addition, by monitoring the change in the potential of the copper wire with respect to the negative electrode sheet at 25°C, 35°C, and 45°C, the lithium deposition state on the surface of the negative electrode sheet during the charge and discharge process of the battery can be observed. The charging current is adjusted in real time to keep the voltage of the copper wire with respect to the negative electrode above 0 mV to achieve the fastest charging speed and design the optimal fast charging process for such materials.

[0058] The above embodiments are only used to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the present invention.

Claims

1. A three-electrode soft-pack battery, characterized in that: include: A first aluminum-plastic film (1), a positive electrode sheet (2), a second aluminum-plastic film (3), a first diaphragm (4), a negative electrode sheet (5), a second diaphragm (6) and a copper wire (7); The negative electrode sheet (5) is fixed on the second aluminum-plastic film (3), the first diaphragm (4) is fixed on the negative electrode sheet (5), the copper wire (7) is fixed on the first diaphragm (4), the second diaphragm (6) is fixed on the copper wire (7), the positive electrode sheet (2) is fixed on the second diaphragm (6), and the first aluminum-plastic film (1) is fixed on the positive electrode sheet (2), thereby forming a soft-package three-electrode.

2. The three-electrode soft-pack battery according to claim 1, characterized in that: Also includes nickel strip (9) and yellow glue (11); The nickel strip (9) is fixed on the soft-package three electrodes, the copper wire (7) is welded to the welding point (10) on the nickel strip (9), and the yellow glue (11) is wrapped around the welding position.

3. The three-electrode soft pack battery according to claim 1, characterized in that: Also includes green glue (8); The second aluminum-plastic film (3) is fixed on the desktop by means of insulating glue, a nickel electrode tab is welded on the negative electrode sheet (5), the negative electrode sheet (5) welded with the nickel electrode tab is placed on the second aluminum-plastic film (3), and the first diaphragm (4) is laid on the negative electrode sheet (5) welded with the nickel electrode tab; The copper wire (7) is fixed on the first diaphragm (4) by means of a 1 mm*5 mm green glue (8), and the second diaphragm (6) is laid on the copper wire (7); The positive electrode sheet (2) is stacked on the second diaphragm (6), the first aluminum-plastic film (1) is fixed on the positive electrode sheet (2) by means of insulating glue, and the position of the first aluminum-plastic film (1) corresponds to the position of the second aluminum-plastic film (3); The first aluminum-plastic film (1) is heat-sealed, the heat-sealed ends are three extreme ear edges, and the bottom edge is open.

4. The three-electrode soft-pack battery according to claim 1, characterized in that: The first diaphragm (4) evenly covers the negative electrode sheet (5) from top to bottom and left to right, and the four sides of the first diaphragm (4) are fixed by insulating glue.

5. The three-electrode soft-pack battery according to claim 1, characterized in that: The positive electrode tab is welded to the positive electrode sheet (2) by an ultrasonic welding machine, and the negative electrode tab is welded to the negative electrode sheet (5) by an ultrasonic welding machine, and the welding parts are coated with insulating glue.

6. The three-electrode soft pack battery according to claim 1, characterized in that: The size of the positive electrode sheet (2) is 100x40mm 2 The size of the negative electrode sheet (5) is 105x45 mm 2 .

7. The three-electrode soft-pack battery according to claim 1, characterized in that: The size of the first diaphragm (4) is 120x55 mm 2 The size of the second diaphragm (6) is 20x15 mm 2 .

8. The three-electrode soft pack battery according to claim 1, characterized in that: The size of the first aluminum-plastic film (1) and the second aluminum-plastic film (3) are both 140 mm x 70 mm. 2 .

9. The three-electrode soft-pack battery according to claim 1, characterized in that: The copper wire (7) comprises two copper wires, one of which is a reference electrode and the other is a spare electrode, and the spare electrode is coated with yellow glue.

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