Reference electrode and battery

Abstract

The utility model provides a reference electrode and a battery, the reference electrode comprises a current collector, one end of the current collector is provided with a connecting part used for connecting a test instrument; and the electrode material layer is arranged on the surface of one side of the other end of the current collector. According to the utility model, the electrode material layer is arranged on the surface of one side of the current collector, so that compared with the mode that the electrode material layers are arranged on the two sides of the current collector, errors caused by difference between the distances between the electrode material layers on the two sides of the current collector and the positive electrode and between the electrode material layers on the two sides of the current collector and the negative electrode can be reduced, and the potential measurement precision of the measured electrode is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of battery, specifically relates to a reference electrode and battery. BACKGROUND

[0002] In the application of lithium ion battery, the battery management system can only measure the voltage difference of the positive electrode and the negative electrode in the whole battery, cannot reflect the real voltage state of the pole piece inside the battery, and with the increase of the charging current, the negative electrode voltage will gradually decrease, and even be lower than the lithium precipitation voltage, which will be accompanied by the abnormal phenomenon of lithium precipitation on the negative electrode surface. Lithium precipitation phenomenon will lead to battery capacity loss on the one hand, reduce the service life of the battery, on the other hand, the lithium metal formed by precipitation forms lithium dendrite, which is easy to pierce the diaphragm, and then causes the short circuit of the positive and negative electrodes, and induces serious safety problems. By constructing a reference electrode in the battery to form a three-electrode system, the voltage change of the positive and negative electrodes in the charging and discharging process can be clearly reflected, so as to obtain the lithium precipitation boundary of the battery and construct a reasonable charging and discharging strategy.

[0003] Common reference electrode materials include copper, lithium and alloy materials, but all have the problem of insufficient test precision. CONTENT OF THE UTILITY MODEL

[0004] The embodiment of the utility model provides a kind of reference electrode and battery, can improve the technical problem of insufficient reference electrode measurement precision.

[0005] First, the embodiment of the utility model provides a kind of reference electrode, comprising: current collector, one end of the current collector has the connecting part for connecting test instrument;

[0006] Electrode material layer is arranged on the surface of another end of the current collector.

[0007] In an embodiment, the current collector has a first surface and a second surface, the first surface is provided with the electrode material layer, and the second surface is a foil area.

[0008] In an embodiment, the reference electrode is long strip, the width of the reference electrode is 0.2mm~1mm;And / or

[0009] The thickness of the reference electrode is 35 μm~100 μm.

[0010] In an embodiment, the thickness of the electrode material layer is 25 μm~90 μm;And / or

[0011] The length of the electrode material layer is 5mm~20mm.

[0012] In an embodiment, the current collector is aluminum foil, and the electrode material layer is lithium iron phosphate material layer.

[0013] In an embodiment, an insulating layer is sleeved on the current collector between the electrode material layer and the connecting portion.

[0014] In an embodiment, the thickness of the insulating layer is 0.1mm-0.3mm.

[0015] In the second aspect, the embodiments of the utility model provide a kind of battery, including electrode assembly and above-mentioned reference electrode, the electrode assembly includes positive plate, negative plate and diaphragm, the positive plate and the negative plate are laminatedly arranged, and the diaphragm is arranged between adjacent positive plate and negative plate, one end of the electrode material layer of the reference electrode is arranged between adjacent positive plate and negative plate, and the diaphragm is arranged between the reference electrode and the positive plate and the negative plate on its two sides.

[0016] In an embodiment, the electrode material layer is located between the current collector and the negative plate.

[0017] In an embodiment, the positive plate is provided with a positive tab, the negative plate is provided with a negative tab, and the reference electrode is spaced apart from the positive tab and the negative tab.

[0018] In an embodiment, the electrode assembly is a roll core, and the positive tab and the negative tab are arranged at one axial end of the roll core, and the reference electrode is arranged at the other axial end of the roll core.

[0019] In an embodiment, the battery further includes a cover plate and a shell that are latched together, the electrode assembly is arranged in the shell, the cover plate is provided with a reference electrode lead-out hole, in the case that the insulating layer is sleeved on the current collector and located between the electrode material layer and the connecting portion, the insulating layer is located in the reference electrode lead-out hole, and the connecting portion is located outside the shell.

[0020] In an embodiment, the minimum distance between the hole wall of the reference electrode lead-out hole and the edge of the cover plate is 1mm-5mm; and / or

[0021] A sealing adhesive layer is arranged between the insulating layer and the hole wall of the reference electrode lead-out hole.

[0022] The embodiments of the utility model have the beneficial effects that:

[0023] In the embodiments of the utility model, by arranging the electrode material layer on one side surface of the current collector, compared with arranging the electrode material layer on both sides of the current collector, the error caused by the distance difference between the electrode material layers on both sides of the current collector and the positive plate and the negative plate can be reduced, so as to improve the potential measurement accuracy of the measured electrode. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical scheme in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0025] Figure 1 is a structural schematic view of a reference electrode provided by the embodiments of the present application;

[0026] Figure 2 is a structural schematic view of a battery provided by the embodiments of the present application;

[0027] Figure 3 is an exploded schematic view of a battery provided by the embodiments of the present application (without showing the shell);

[0028] Figure 4 is a potential curve diagram of a reference electrode of the present application;

[0029] Figure 5 is a cycle curve diagram of a copper wire electrode;

[0030] Figure 6 is a cycle curve diagram of a reference electrode of the present application;

[0031] Figure 7 is a comparison curve diagram of a fitting voltage of a reference electrode and a voltage of a full battery of the present application;

[0032] Figure 8 is a comparison curve diagram of a voltage of a reference electrode and a voltage of a copper wire electrode of the present application;

[0033] Figure 9 is a comparison curve diagram of a voltage of a single-layer reference electrode and a double-layer reference electrode;

[0034] Figure 10 and Figure 11 is a disassembled negative electrode sheet diagram of a battery full of electricity composed of reference electrodes with different widths of the present application.

[0035] Mark explanation: reference electrode-1; current collector-11; connecting part-112; electrode material layer-12; insulating layer-13; electrode assembly-2; positive electrode sheet-21; negative electrode sheet-22; diaphragm-23; positive electrode lug-24; negative electrode lug-25; cover plate-3; reference electrode leading hole-31; shell-4; sealing adhesive layer-5. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of the present application. In addition, it should be understood that the specific implementation described herein is only used to illustrate and explain the present application, and is not used to limit the present application. In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower directions of the device in the actual use or working state, and specifically refer to the drawing direction in the drawings. The "inner" and "outer" refer to the outline of the device.

[0037] The amount of lithium plated on the surface of the copper reference electrode is continuously consumed during the cycle process, which affects the test precision. The lithium reference electrode is easy to induce side reactions, disturb the reference signal, and affect the test precision, and the manufacturing process is complex. The amount of lithium plated in the alloy material will affect the test precision, and the alloy material is easy to expand, powder and other phenomena.

[0038] Please refer to Figures 1-3 , in a first aspect, the embodiments of the present application provide a reference electrode 1, which comprises: a current collector 11, one end of the current collector 11 has a connecting part 112 for connecting a test instrument;

[0039] An electrode material layer 12 is arranged on one side surface of the other end of the current collector 11.

[0040] It can be understood that by arranging the electrode material layer 12 on the current collector 11, the electrode material layer 12 has good interface stability and high reactivity, and has good adaptability with the positive electrode plate and the negative electrode plate in the three-electrode battery, thereby improving the cycle stability and good reproducibility of the reference electrode 1 in the use process, so that it can play an excellent monitoring effect in the long cycle process of the three-electrode battery, and further improve the potential measurement precision of the measured electrode; at the same time, by arranging the electrode material layer 12 on one side surface of the current collector 11, that is, arranging the electrode material layer 12 on one side of the current collector 11, compared with arranging the electrode material layer 12 on both sides of the current collector 11, the error caused by the distance difference between the electrode material layer 12 on both sides of the current collector 11 and the positive electrode and the negative electrode (the positive electrode is a high-voltage area, and the negative electrode is a low-voltage area) can be reduced, thereby improving the potential measurement precision of the measured electrode. The current collector 11 is made of conductive material.

[0041] It can be understood that the reference electrode 1 is an electrode used as a reference for comparison when measuring the electrode potential of a battery. A battery is formed by connecting the electrode to be measured with the reference electrode 1 having a precisely known electrode potential value, and the electrode potential of the battery is measured to calculate the electrode potential of the electrode to be measured. The testing instrument (as an example, a multi-channel voltage recorder) can be an instrument for testing the potential of the reference electrode 1, and is electrically connected to the connection part 112 of the reference electrode 1.

[0042] As an example, the active material in the electrode material layer 12 can include one or more of lithium cobaltate, lithium titanate, and lithium iron phosphate. The current collector 11 is in the form of a sheet. The material of the electrode material layer 12 can be provided on one side surface of one end of the current collector 11, i.e., single-sided coating.

[0043] As an example, the reference electrode 1 in the present application can be obtained by the following method: forming an electrode material layer 12 by providing electrode material on one side surface of one end of the current collector 11 to obtain a reference electrode 1 preform, assembling the reference electrode 1 preform into a lithium battery, then performing a discharge charging operation on the lithium battery, adjusting the state of charge of the lithium battery to 30% SOC 70% SOC, disassembling the lithium battery, taking out the reference electrode 1 preform after the state of charge adjustment and cutting and cleaning to obtain the reference electrode 1. The reference electrode 1 after the state of charge adjustment can maintain a stable potential and can more accurately reflect the positive and negative electrode voltages inside the battery.

[0044] In an embodiment, the current collector 11 has a first surface and a second surface, the first surface is provided with the electrode material layer 12, and the second surface is an empty foil area.

[0045] It can be understood that the current collector 11 is in the form of a sheet and has opposite first and second surfaces, the electrode material layer 12 is provided only on the first surface, and the second surface is an empty foil area.

[0046] In an embodiment, the reference electrode 1 is in the form of a strip, and the width of the reference electrode 1 is 0.2mm-1mm, for example, it can be 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, etc.

[0047] In an embodiment, the thickness of the reference electrode 1 is 35μm-100μm, for example, it can be 35μm, 45μm, 55μm, 65μm, 75μm, 85μm, 95μm, 100μm, etc.

[0048] It can be understood that during the operation of the battery, the ion migration rate is very fast, and the presence of the reference electrode 1 will affect the migration of ions in the battery, affecting the migration of ions, thereby producing a shadow effect (such as Figure 10 and Figure 11The shadow effect will further affect the potential measurement accuracy of the measured electrode. By controlling the width and thickness of the reference electrode 1, the influence of the reference electrode 1 on the battery system can be reduced, the generation of the shadow effect can be reduced, and the potential measurement accuracy of the measured electrode can be improved.

[0049] In an embodiment, the thickness of the electrode material layer 12 is 25 μm to 90 μm, for example, can be 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, etc.

[0050] In an embodiment, the length of the electrode material layer 12 is 5 mm to 20 mm, for example, can be 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, etc.

[0051] It can be understood that by controlling the thickness and length of the electrode material layer 12, the average potential of the electrode material layer 12 can be regulated to have a stable potential, thereby improving the potential measurement accuracy of the measured electrode, and at the same time, the electrode material layer 12 can be easily processed.

[0052] In an embodiment, the current collector 11 is an aluminum foil, and the electrode material layer 12 is a lithium iron phosphate material layer.

[0053] It can be understood that the lithium iron phosphate material has a stable potential and can provide a stable reference electrode 1 potential, thereby improving the potential measurement accuracy of the measured electrode. An oxide layer can be formed on the surface of the aluminum foil, so that the reference electrode 1 can stably exist in the electrolyte, thereby improving the stability of the reference electrode 1. The above-mentioned reference electrode 1 has the advantages of stable potential, high accuracy, and long service life.

[0054] As an example, the material of the electrode material layer 12 of the reference electrode 1 is a material layer containing lithium iron phosphate (LFP), and the electrode material layer 12 further contains a binder and a conductive agent, wherein the binder is polyvinylidene fluoride (PVDF), the conductive agent is at least one of acetylene black, conductive carbon black, carbon nanotubes, and graphene, and the carbon nanotubes are one of multi-walled carbon nanotubes and single-walled carbon nanotubes. In the electrode material layer 12, the mass percentage of lithium iron phosphate is 70% to 95%, the mass percentage of the binder is 2% to 10%, and the mass percentage of the conductive agent is 2% to 20%.

[0055] In an embodiment, an insulating layer 13 is sleeved on the current collector 11 between the electrode material layer 12 and the connecting portion 112.

[0056] It can be understood that by sleeving the insulating layer 13 on the current collector 11, the insulating layer 13 can be penetrated on the cover plate 3 of the battery when the reference electrode 1 is installed in the battery, thereby reducing the probability of short circuit caused by the contact between the reference electrode 1 and the cover plate 3.

[0057] As an example, the insulating layer is an insulating tape, so as to be bonded with the current collector 11.

[0058] In an embodiment, the thickness of the insulating layer 13 is 0.1mm-0.3mm, for example, can be 0.1mm, 0.12mm, 0.14mm, 0.16mm, 0.18mm, 0.20mm, 0.22mm, 0.24mm, 0.26mm, 0.28mm, 0.30mm, etc.

[0059] It can be understood that the insulating layer 13 can be arranged adjacent to the electrode material layer 12, or can be arranged spaced apart from the electrode material layer 12. Since the space in the shell 4 of the battery is limited, the insulating layer 13 is arranged adjacent to the electrode material layer 12, at this time, since the electrode material layer 12 of the reference electrode 1 is located between the positive plate 21 and the negative plate 22 when the reference electrode 1 is used, by controlling the thickness of the insulating layer 13, the probability of the gap between the positive plate 21 and the negative plate 22 caused by the insulating layer 13 can be reduced, thereby facilitating the installation of the reference electrode 1, while ensuring the insulation effect of the insulating layer 13.

[0060] In a second aspect, the embodiments of the utility model provide a battery, including electrode assembly 2 and above-mentioned reference electrode 1, electrode assembly 2 includes positive plate 21, negative plate 22 and diaphragm 23, positive plate 21 and negative plate 22 are arranged in layers, and diaphragm 23 is arranged between adjacent positive plate 21 and negative plate 22, one end of reference electrode 1 with electrode material layer 12 is arranged between adjacent positive plate 21 and negative plate 22, and diaphragm 23 is arranged between reference electrode 1 and the positive plate 21 and the negative plate 22 on both sides of it.

[0061] It can be understood that the diaphragm 23 is arranged between the reference electrode 1 and the positive plate 21 on one side of the reference electrode 1, and the diaphragm 23 can separate the reference electrode 1 and the positive plate 21, and the diaphragm 23 is arranged between the reference electrode 1 and the negative plate 22 on the other side of the reference electrode 1, and the diaphragm 23 can separate the reference electrode 1 and the negative plate 22, thereby reducing the probability of short circuit of the reference electrode 1 and the positive plate 21 and the negative plate 22 on both sides thereof due to contact. The electrode assembly 2 can be a winding cell or a laminated cell. The reference electrode 1 can be used to measure the potential of the positive plate 21, or can be used to measure the potential of the negative plate 22.

[0062] It can be understood that the three-electrode system battery can reflect the positive and negative electrode voltage state in real time, so as to control the positive and negative electrode voltage within the safe range. The three-electrode system battery can observe the change of the positive and negative electrode voltage caused by the change of the state of charge (SOC), the battery, the temperature, etc. in real time, and then be used to support the establishment of the fast charging strategy of the battery.

[0063] As an example, when the reference electrode 1 is installed, one side surface of the reference electrode 1 can be first attached to the separator 23. For example, when the battery cell is a wound battery cell, the reference electrode 1 and the separator 23 on the surface of the reference electrode 1 can be inserted between the positive electrode sheet 21 and the negative electrode sheet 22 during the stacking of the positive electrode sheet 21, the separator 23 and the negative electrode sheet 22, and the separator 23 is arranged on both side surfaces of the reference electrode 1. For example, when the battery cell is a stacked battery cell, the reference electrode 1 and the separator 23 on the surface of the reference electrode 1 can be inserted between the positive electrode sheet 21 and the negative electrode sheet 22 during the stacking of the positive electrode sheet 21, the separator 23 and the negative electrode sheet 22 in sequence, and the separator 23 is arranged on both side surfaces of the reference electrode 1. Thus, the installation of the reference electrode 1 is completed.

[0064] In an embodiment, the electrode material layer 12 is located between the current collector 11 and the negative electrode sheet 22.

[0065] It can be understood that, during the charging of the battery, the negative electrode voltage will continuously decrease, and under large current charging, the negative electrode voltage will approach or even be lower than 0V, which will easily form lithium dendrites and even pierce the separator 23 to cause positive and negative short circuit and trigger safety problems. Therefore, in the test of the electrode potential, the negative electrode potential will be focused on. By arranging the electrode material layer 12 towards the negative electrode sheet 22, the electrode material layer 12 can be close to the negative electrode sheet 22, so as to improve the test accuracy of the negative electrode potential.

[0066] In an embodiment, the positive electrode sheet 21 is provided with a positive electrode tab 24, and the negative electrode sheet 22 is provided with a negative electrode tab 25. The reference electrode 1 is spaced apart from the positive electrode tab 24 and the negative electrode tab 25.

[0067] It can be understood that, by spacing the reference electrode 1 from the positive electrode tab 24 and the negative electrode tab 25, the interference of the reference electrode 1 on the positive electrode tab 24 and the negative electrode tab 25 can be reduced, and the connection operation of the positive electrode tab 24 and the negative electrode tab 25 with the positive electrode sheet 21 and the negative electrode sheet 22, respectively, can be facilitated.

[0068] In an embodiment, the electrode assembly 2 is a winding core, the positive electrode tab 24 and the negative electrode tab 25 are arranged at one axial end of the winding core, and the reference electrode 1 is arranged at the other axial end of the winding core.

[0069] It can be understood that by arranging the positive tab 24 and the negative tab 25 at one axial end of the winding core and arranging the reference electrode 1 at the other axial end of the winding core, the interference of the reference electrode 1 with the positive tab 24 and the negative tab 25 can be effectively reduced, and the connection of the positive tab 24 and the negative tab 25 with the positive plate 21 and the negative plate 22 can be facilitated.

[0070] In an embodiment, the reference electrode 1 is arranged between the outermost positive plate 21 and the outermost negative plate 22 at the other axial end of the winding core.

[0071] In an embodiment, the battery further comprises a cover plate 3 and a shell 4, the electrode assembly 2 is arranged in the shell 4, the cover plate 3 is provided with a reference electrode lead-out hole 31, and in the case that the insulating layer 13 is sleeved on the current collector 11 and located between the electrode material layer 12 and the connecting portion 112, the insulating layer 13 is located in the reference electrode lead-out hole 31, and the connecting portion 112 is located outside the shell 4.

[0072] It can be understood that by arranging the insulating layer 13 in the reference electrode lead-out hole 31, the reference electrode 1 can be separated from the cover plate 3, so as to reduce the probability of short circuit caused by the contact between the reference electrode 1 and the cover plate 3. The height of the insulating layer 13 can be the same as or greater than the thickness of the cover plate 3.

[0073] In an embodiment, the minimum distance between the hole wall of the reference electrode lead-out hole 31 and the edge of the cover plate 3 is 1 mm to 5 mm, for example, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, etc.

[0074] It can be understood that the distance between the reference electrode lead-out hole 31 and the edge of the cover plate 3 can facilitate the processing of the reference electrode lead-out hole 31, and the reference electrode lead-out hole 31 can be further processed without changing the original processing line of the battery cover plate 3. The size of the reference electrode lead-out hole 31 can be arranged according to the size of the reference electrode 1, as long as the reference electrode 1 can be easily led out from the reference electrode lead-out hole 31.

[0075] As an example, the position of the reference electrode lead-out hole 31 corresponds to the position of the reference electrode 1, so as to reduce the interference of the reference electrode 1 with the positive tab 24 and the negative tab 25, facilitate the connection of the positive tab 24 and the negative tab 25 with the positive plate 21 and the negative plate 22, and facilitate the leading out of the connecting portion 112 of the reference electrode 1 to the outside of the battery through the reference electrode lead-out hole 31. The reference electrode lead-out hole 31 can be a circular hole, so as to facilitate the processing.

[0076] In an embodiment, the cover plate 3 is provided with a liquid injection hole.

[0077] It can be understood that, by arranging the injection hole and the reference electrode lead-out hole 31 on the cover plate 3, the battery processing can be facilitated, and the battery can be placed vertically (the injection hole and the reference electrode lead-out hole 31 are located at the top). By arranging the injection hole and the reference electrode lead-out hole 31 at intervals, the interference with the original injection process can be reduced.

[0078] In an embodiment, a sealing glue layer 5 is arranged between the insulating layer 13 and the hole wall of the reference electrode lead-out hole 31.

[0079] It can be understood that the sealing glue layer 5 can effectively seal the reference electrode lead-out hole 31.

[0080] As an example, the installation process of the reference electrode 1 includes: inserting one end of the reference electrode 1 with the electrode material layer 12 between the positive plate 21 and the negative plate 22 of the electrode assembly 2, then wrapping the insulating layer 13 on the reference electrode 1, then leading out the reference electrode 1 from the reference electrode lead-out hole 31 so that the connecting part 112 is located outside the shell 4, and finally sealing the reference electrode lead-out hole 31 with sealing glue. The sealing glue is epoxy resin type glue.

[0081] Test Example

[0082] First reference electrode: the current collector is an aluminum foil with a thickness of 12 μm and a width of 0.6 mm, one side surface of the current collector is provided with an electrode material layer 12, the thickness of the electrode material layer 12 is 50 μm, and the length is 15 mm, the mass content of lithium iron phosphate in the electrode material layer 12 is 80%, the mass content of polyvinylidene fluoride is 10%, the mass content of conductive carbon black is 9%, and the mass content of carbon nanotubes is 1%.

[0083] Second reference electrode: the difference from the first reference electrode is that the width of the current collector is 1.3 mm.

[0084] Copper wire electrode: a copper wire with a diameter of 50 μm, the surface is plated with lithium, and the length of the active material lithium is 15 mm.

[0085] Double-layer electrode: the difference from the first reference electrode is that the two surfaces of the current collector are both provided with an electrode material layer 12.

[0086] The first reference electrode is used as the positive electrode of the battery, and the lithium metal element is used as the negative electrode of the battery to make a button cell, and then the button cell is charged and discharged between 2.7-3.7 V, the positive electrode is adjusted to 50% SOC, then it is left for 12 h, the potential during the standing is taken, and the lithium iron phosphate potential curve is obtained, as shown in Figure 4 .

[0087] The first reference electrode, the graphite negative electrode, and the lithium iron phosphate positive electrode are combined to form a full cell, which is charged and discharged at 0.33 C for 2 cycles and at 1 C for 50 cycles, and the reference electrode cycle life curve is obtained, as shown in Figure 6As shown. The positive and negative electrode voltages of the full battery are tested during the cycling process to obtain the full battery voltage, as shown. Figure 7 As shown. During the test cycle, the voltage between the first reference electrode and the positive electrode is obtained, and the voltage between the first reference electrode and the negative electrode is obtained, yielding the negative electrode voltage. The positive and negative electrode fitting voltages are then derived from the positive and negative electrode voltages, as shown below. Figure 7 As shown, the fitted voltage change in the second cycle is as follows: Figure 8 and Figure 9 As shown.

[0088] A full cell was constructed using a copper wire electrode as a reference electrode, along with a graphite anode and a lithium iron phosphate cathode. The cell underwent two charge-discharge cycles at 0.33C and 50 charge-discharge cycles at 1C. The cycle life curve of the copper wire electrode was obtained, as shown below. Figure 5 As shown. During the test cycle, the voltage between the copper wire electrode and the positive electrode is obtained to get the positive electrode voltage. The voltage between the copper wire electrode and the negative electrode is tested to obtain the negative electrode voltage. The positive and negative electrode fitting voltages are then obtained from the positive and negative electrode voltages. The change of the fitting voltage in the second cycle is shown in the figure. Figure 8 As shown.

[0089] A full cell was constructed using a bilayer electrode, a graphite anode, and a lithium iron phosphate cathode. The cell underwent two charge-discharge cycles at 0.33C and 50 cycles at 1C. The voltage between the bilayer electrode and the cathode was measured during these cycles to obtain the positive electrode voltage. The voltage between the bilayer electrode and the anode was also measured to obtain the negative electrode voltage. Fitted voltages were derived from these positive and negative electrode voltages. The change in the fitted voltage during the second cycle is shown below. Figure 9 As shown.

[0090] The aforementioned first reference electrode, graphite negative electrode, and lithium iron phosphate positive electrode are used to assemble a full battery. After fully charging, the reference electrode and negative electrode are disassembled, as follows: Figure 10 As shown.

[0091] A full battery is constructed by combining the second reference electrode, the graphite negative electrode, and the lithium iron phosphate positive electrode. After fully charging, the lithium iron phosphate reference electrode 3 and the negative electrode are disassembled, as follows: Figure 11 As shown.

[0092] from Figure 4 It can be seen that the first reference electrode 1 has a stable potential. From Figure 5 and Figure 6 It can be seen that the first reference electrode exhibits higher potential stability during cycling than the copper wire electrode. From Figure 7 It can be seen that the battery voltage obtained by fitting with the first reference electrode is close to the actual full cell voltage, which can improve the testing accuracy of the lithium iron phosphate reference electrode in this application. From Figure 8 It can be seen that the battery voltage obtained by fitting with the first reference electrode is more stable than the battery voltage obtained by fitting with the copper wire electrode. From Figure 9It can be seen that there is a difference between the battery voltage obtained by fitting with the first reference electrode and the battery voltage obtained by fitting with the double-layer electrode. From Figure 10 and Figure 11 It can be seen that black shadows (such as...) are formed on the negative electrode obtained from the disassembly of the second reference electrode. Figure 11 At point A in the middle, Figure 11 Point B is the second reference electrode. No black shadows are visible on the negative electrode obtained after disassembling the first reference electrode (e.g., ...). Figure 10 At point A in the middle, Figure 10 (Point B is the first reference electrode). This is because the increased width of the reference electrode results in a black shadow on the negative electrode (shadowing effect). The negative electrode is gold when fully charged and black when de-charged. It can be seen that the shadowing effect can be effectively reduced by controlling the width of the reference electrode.

[0093] The embodiments of this utility model have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this utility model. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this utility model. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this utility model. Therefore, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. A reference electrode, characterized in that, include: A current collector, one end of which has a connection portion for connecting to a test instrument; An electrode material layer is disposed on one side surface of the other end of the current collector.

2. The reference electrode according to claim 1, characterized in that, The current collector has a first surface and a second surface, the first surface being provided with the electrode material layer, and the second surface being an empty foil area.

3. The reference electrode according to claim 1, characterized in that, The reference electrode is elongated and has a width of 0.2 mm to 1 mm; and / or The thickness of the reference electrode is 35 μm to 100 μm.

4. The reference electrode according to claim 1, characterized in that, The thickness of the electrode material layer is 25 μm to 90 μm; and / or The length of the electrode material layer is 5mm to 20mm.

5. The reference electrode according to claim 1, characterized in that, The current collector is aluminum foil, and the electrode material layer is a lithium iron phosphate material layer.

6. The reference electrode according to claim 1, characterized in that, An insulating layer is provided on the current collector between the electrode material layer and the connection portion.

7. The reference electrode according to claim 6, characterized in that, The thickness of the insulating layer is 0.1 mm to 0.3 mm.

8. A battery, characterized in that, The device includes an electrode assembly and a reference electrode as described in any one of claims 1-7. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The positive electrode and the negative electrode are stacked, and the separator is disposed between adjacent positive and negative electrode sheets. The reference electrode has one end with the electrode material layer disposed between adjacent positive and negative electrode sheets, and the separator is disposed between the reference electrode and the positive and negative electrode sheets on both sides thereof.

9. The battery according to claim 8, characterized in that, The electrode material layer is located between the current collector and the negative electrode sheet.

10. The battery according to claim 8, characterized in that, The positive electrode plate is provided with a positive electrode tab, the negative electrode plate is provided with a negative electrode tab, and the reference electrode is provided at intervals with the positive electrode tab and the negative electrode tab.

11. The battery according to claim 10, characterized in that, The electrode assembly is a winding core, with the positive electrode tab and the negative electrode tab both disposed at one axial end of the winding core, and the reference electrode disposed at the other axial end of the winding core.

12. The battery according to claim 8, characterized in that, The battery also includes a cover plate and a housing that fit together. The electrode assembly is disposed inside the housing. A reference electrode lead-out hole is provided on the cover plate. When the insulating layer is sleeved on the current collector and located between the electrode material layer and the connecting part, the insulating layer is located inside the reference electrode lead-out hole, and the connecting part is located outside the housing.

13. The battery according to claim 12, characterized in that, The minimum distance between the wall of the reference electrode lead-out hole and the edge of the cover plate is 1mm to 5mm; and / or A sealant layer is provided between the insulating layer and the hole wall of the reference electrode lead-out hole.

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