Lithium plating method for battery reference electrode, reference electrode and application of reference electrode

Abstract

The invention relates to the field of batteries, and discloses a lithium plating method for a battery reference electrode, the reference electrode and application of the reference electrode. The method comprises the following steps: (1) performing pulse electroplating on a reference electrode base material to obtain an intermediate base material I; the pulse electroplating method comprises the following steps: introducing the reference electrode base material into a battery cell, connecting a positive electrode of a pulse power supply with a negative electrode or positive electrode of the battery cell, and connecting a negative electrode of the pulse power supply with a tab led out of the reference electrode base material; the pulse current density Im satisfies Im = I0 * (D / 50) 2 * (L / 5), and I0 is 40-300 [mu] A; (2) carrying out direct current electroplating on the intermediate base material I to obtain a reference electrode; the direct current density Iz satisfies Iz = I1 * (D / 50) 2 * (L / 5), and I1 is 13-160 [mu] A. According to the technical scheme, the defects that in the prior art, the lithium plating period of a reference electrode is long, and the potential of the reference electrode is unstable are overcome.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to a lithium plating method of a battery reference electrode, a reference electrode and application thereof. BACKGROUND

[0002] The three-electrode soft package battery is a new type of lithium ion battery electrolyte. By introducing a third electrode material, the electrochemical reaction range is expanded, thereby improving the energy density and cycle life of the battery, and enhancing the safety performance of the battery. At present, the three-electrode soft package battery has the problems of long lithium plating time, long production and test cycle, short service life of the reference electrode, and the reference electrode cannot be stable for a long time, and the reference electrode is damaged before the end of the application test.

[0003] CN118263550A discloses a preparation method of a lithium ion battery reference electrode, comprising the following steps: a, removing the surface paint layer of the reference electrode substrate; b, chemically polishing the substrate treated in step a; c, placing the substrate treated by chemical polishing in step b in a bare cell and leading out with a lead wire, and welding a tab at the lead wire outside the bare cell; d, plating lithium on the substrate of step c by pulse plating. However, the lithium plating time of this scheme is not less than 1 hour, the stable life of the Li plating layer is 24-36h, the time cost is high, and the stability of the reference electrode is insufficient.

[0004] CN117712289A discloses a stable three-electrode battery, comprising a cell, a positive electrode, a negative electrode, a separator, an electrolyte and a copper wire, the copper wire is arranged between the positive electrode and the negative electrode, and part of the copper wire is exposed outside the cell, the surface of the copper wire inside the cell is sequentially provided with a lithium layer and a chromium metal plating layer with uniform thickness, and a hole is formed on the chromium metal plating layer. However, the prepared reference electrode has poor mechanical strength and the preparation process is complicated. SUMMARY

[0005] The purpose of the present application is to overcome the defects of long plating lithium cycle and unstable reference electrode potential of the prior art.

[0006] In order to achieve the above purpose, the first aspect of the present application provides a lithium plating method of a battery reference electrode, which comprises: (1) pulse plating the reference electrode substrate to obtain an intermediate substrate I; The method of pulse plating comprises: introducing the reference electrode substrate into a cell, connecting the positive electrode of the pulse power supply with the negative electrode or the positive electrode of the cell, and connecting the negative electrode of the pulse power supply with the tab led out by the reference electrode substrate; The conditions of pulse plating include: pulse current density I msatisfying a relationship shown in formula (I), the pulse time is 1-20 min, and the pulse duty cycle is 10%-80%; Formula (I): I m =I0×(D / 50) 2 ×(L / 5); wherein I0 is 40-300 μA, I m is in units of μA; (2) performing direct current plating on the intermediate substrate I to obtain a reference electrode; The conditions of the direct current plating include: a direct current density I z satisfying a relationship shown in formula (II), the time is 20-480 min; Formula (II): I z =I1×(D / 50) 2 ×(L / 5); wherein I1 is 13-160 μA, I z is in units of μA; In formula (I) and formula (II), D is the diameter of the reference electrode substrate, in units of μm, and L is the length of the reference electrode substrate entering the battery cell, in units of cm.

[0007] The second aspect of the present application provides a reference electrode prepared by the method of the first aspect.

[0008] The third aspect of the present application provides an application of the reference electrode of the second aspect in a lithium ion battery.

[0009] The present application has at least the following advantages: (1) The lithium plating method of the battery reference electrode provided by the present application has the advantage of short plating period; (2) The reference electrode prepared by the lithium plating method provided by the present application has excellent potential stability.

[0010] (3) In the lithium plating method provided by the present application, specific pulse plating conditions and direct current plating conditions are used to obtain a dense and high-adhesion plating layer, avoiding the appearance of a spiral or dendritic lithium plating layer with poor density. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 The potential-time relationship curve between the negative electrode and the reference electrode in the lithium plating process of Example 1.

[0012] Figure 2 The potential-time relationship curve between the positive electrode and the reference electrode, the potential-time relationship curve between the negative electrode and the reference electrode, and the full battery potential-time relationship curve after the three electrodes of Example 1 after lithium plating are sequentially charged and discharged at 0.05 / 0.1 / 0.33 / 0.5 / 1 / 1.5C rate.

[0013] Figure 3 The potential-capacity relationship curve between the negative electrode and the reference electrode of the lithium-plated three-electrode of Example 1 after charging and discharging at 0.05C / 0.1C / 0.33C / 0.5C / 1C and / 1.5C rates.

[0014] Figure 4 The potential-time relationship curve between the positive electrode and the reference electrode of the lithium-plated three-electrode of Example 2 during the charging at 0.33C rate and the standing period. DETAILED DESCRIPTION

[0015] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and the values are approximations that are understood to encompass values near the endpoints and the individual points within the ranges. For ranges, the endpoints are included within the range unless expressly stated otherwise. For numerical values, the endpoints are included within the range unless expressly stated otherwise.

[0016] The SOC in the present application refers to the remaining capacity of the battery.

[0017] The pulse current density in the present application refers to the peak current density.

[0018] As described previously, the first aspect of the present application provides a method for plating lithium on a battery reference electrode, which comprises: (1) performing pulse plating on a reference electrode substrate to obtain an intermediate substrate I; The method for pulse plating comprises: introducing the reference electrode substrate into an electric cell, connecting the positive electrode of a pulse power supply with the negative electrode or the positive electrode of the electric cell, and connecting the negative electrode of the pulse power supply with the tab led out by the reference electrode substrate; The conditions for pulse plating comprise: pulse current density I m satisfying the relationship shown in formula (I), pulse time being 1-20 min, and pulse duty cycle being 10-80%; Formula (I): I m =I0×(D / 50) 2 ×(L / 5); wherein I0 is 40-300 μA, I m is in units of μA; (2) performing direct current plating on the intermediate substrate I to obtain a reference electrode; The conditions for direct current plating comprise: direct current density I z satisfying the relationship shown in formula (II), and time being 20-480 min; Formula (II): I z =I1×(D / 50)2 ×(L / 5); where I1 is 13-160μA, I z The unit is μA; In formulas (I) and (II), D is the diameter of the reference electrode substrate in μm, and L is the length of the reference electrode substrate inside the battery cell in cm.

[0019] In the technical solution of this invention, pulse electroplating is first used for pre-plating, which can effectively reduce the overall lithium plating time. Then, direct electroplating is used to improve the lithium plating density on the surface of the reference electrode substrate. Based on this, with the specific electroplating parameters in this solution, the lithium plating cycle of the reference electrode can be effectively shortened, and the prepared reference electrode has excellent potential stability.

[0020] In particular, the inventors of this invention have discovered that during pulse electroplating and DC electroplating, there is a specific proportional relationship between the size of the reference electrode substrate and the electroplating current density. If the above relationship is not met, the lithium plating layer will not be dense and the specific surface area will increase, causing the reference electrode to react with the electrolyte and consume lithium, thus accelerating the failure rate of the reference electrode. At the same time, lithium dendrites may also form, which may puncture the diaphragm during application.

[0021] Preferably, the pulse electroplating is performed for 0.01-20 seconds after each 0.01-60 seconds interval, and this cycle is repeated. More preferably, the pulse electroplating is performed for 1-5 seconds after each 1-5 seconds interval, and this cycle is repeated.

[0022] Further preferably, in order to improve the uniformity of lithium plating and thus enhance the stability of the reference electrode, the present invention provides another preferred embodiment in which the pulse electroplating is performed using a double-sided lithium plating method, the double-sided lithium plating method comprising: S1: The reference electrode substrate is introduced into the battery cell, the positive terminal of the pulse power supply is connected to the negative terminal of the battery cell, and the negative terminal of the pulse power supply is connected to the tabs led out from the reference electrode substrate. The first pulse electroplating is performed to obtain the intermediate substrate I-1. S2: Connect the positive terminal of the pulse power supply to the positive terminal of the battery cell, and connect the negative terminal of the pulse power supply to the tabs led out from the intermediate substrate I-1, and perform a second pulse electroplating to obtain the intermediate substrate I.

[0023] According to a preferred embodiment, the DC electroplating method includes: Connect the positive terminal of the DC power supply to the negative terminal of the battery cell, and connect the negative terminal of the DC power supply to the tabs led out from the intermediate substrate I to perform the first DC electroplating to obtain the intermediate substrate II; The positive pole of the direct current power supply is connected with the positive pole of the electric core, and the negative pole of the direct current power supply is connected with the pole lug led out by the intermediate substrate II to carry out the second direct current plating to obtain the reference electrode. The inventor of the present application finds that the reference electrode prepared by using the double-sided lithium plating direct current plating mode has more excellent potential stability.

[0024] Further preferably, the time of the first direct current plating is 10-240 min, preferably 20-120 min, and more preferably 20-40 min.

[0025] In the preferred case, the time of the first direct current plating is the same as the time of the second direct current plating.

[0026] According to a preferred embodiment, in step (1), the electric core introduced into the reference electrode substrate is subjected to a heating treatment before the pulse plating is carried out; the heating treatment conditions include that the temperature is 40-80℃ and the time is ≥30 min. The inventor of the present application finds that the heating treatment of the electric core can effectively shorten the lithium plating time, and the reference electrode prepared has more excellent potential stability.

[0027] Preferably, the SOC of the electric core is 1-99%, and more preferably 10-90%.

[0028] Preferably, I0 is 80-160 μA.

[0029] More preferably, I1 is 40-80 μA.

[0030] Preferably, the reference electrode substrate includes any one of copper wire, silver wire and gold wire. More preferably, the reference electrode substrate is copper wire.

[0031] According to a preferred embodiment, the reference electrode substrate is immersed in an acid solution for pretreatment before step (1) is carried out.

[0032] More preferably, the acidic substance in the acid solution is selected from at least one of sulfuric acid, hydrochloric acid and nitric acid.

[0033] The acid solution in the present application refers to a mixed solution of acidic substance and water, and the present application does not have a particular limitation on the content of the acidic substance in the acid solution, as long as the cleaning of the surface oxide layer of the reference electrode can be achieved. Exemplarily, the content of sulfuric acid in the acid solution is <70 wt%; the content of nitric acid in the acid solution is <65 wt%; and the present application does not have a particular limitation on the content of hydrochloric acid in the acid solution, and any concentration of hydrochloric acid acid solution known in the art can be used.

[0034] As described above, the second aspect of the present application provides the reference electrode prepared by the method of the first aspect.

[0035] As described above, the third aspect of the present application provides the use of the reference electrode prepared by the second aspect in a lithium ion battery.

[0036] In the following examples, the raw materials are all ordinary commercially available products unless otherwise specified.

[0037] Copper wire A: diameter (D) is 50 μm, length is 7 cm; Copper wire B: diameter (D) is 80 μm, length is 7 cm; Battery core: the rate is 0.33C, and the SOC is 60%.

[0038] Preparation Example 1 After the copper wire A is ultrasonically pickled with a 10% mass fraction of sulfuric acid aqueous solution for 30 min, the pickled copper wire is rinsed with ultrapure water and dried to obtain copper wire 1, which is used for standby.

[0039] Preparation Example 2 After the copper wire B is ultrasonically pickled with a 10% mass fraction of sulfuric acid aqueous solution for 30 min, the pickled copper wire is rinsed with ultrapure water and dried to obtain copper wire 2, which is used for standby.

[0040] Example 1 (1) The copper wire 1 is introduced into a 3 Ah soft package lithium battery core (the length of the copper wire 1 introduced into the core is 5 cm, i.e. L is 5 cm), and the core with the introduced copper wire 1 is placed in an oven for heating and holding treatment (the holding temperature is 50°C, and the time is 30 min); (2) The positive electrode of the pulse power is connected with the negative electrode of the core after the heating and holding treatment, and the negative electrode of the pulse power is connected with the tab of the copper wire 1 introduced into the core, to carry out first pulse electroplating for 5 min to obtain copper wire I (intermediate substrate I); The pulse electroplating is carried out in the mode of electroplating for 1 s, interval 1 s, and then electroplating for 1 s again, and the cycle is repeated for a total of 5 min; wherein the electroplating conditions are: I0 is 160 μA, i.e. the first pulse electroplating current density I m is 160 μA, and the pulse duty cycle is 50%; (3) The positive electrode of the direct current power is connected with the negative electrode of the core, and the negative electrode of the direct current power is connected with the tab of the copper wire I introduced into the core, to carry out first direct current electroplating for 25 min (I1 is 80 μA, i.e. the first direct current electroplating current density I z is 80 μA), to obtain copper wire II (intermediate substrate II); The positive pole of the direct current power supply is connected with the positive pole of the battery cell, and the negative pole of the direct current power supply is connected with the tab led out by the copper wire II in the battery cell, and second direct current plating is carried out for 25 min (I1 is 80 μA, that is, the second direct current plating current density I z is 80 μA), to obtain the reference electrode.

[0041] Example 2 (1) The copper wire 1 is introduced into the 3 Ah soft package lithium battery cell (the length of the copper wire 1 entering the battery cell is 5 cm, that is, L is 5 cm), the positive pole of the pulse power supply is connected with the negative pole of the battery cell, and the negative pole of the pulse power supply is connected with the tab led out by the copper wire 1 in the battery cell, and first pulse plating is carried out for 5 min (the pulse plating adopts the mode that plating is carried out for 1 s, then interval 1 s, and plating is carried out again for 1 s, and the cycle is repeated for a total of 5 min; I0 is 80 μA, that is, the first pulse plating current density I m is 80 μA, and the pulse duty cycle is 50%), to obtain the copper wire I-1 (intermediate base material I-1); The positive pole of the pulse power supply is connected with the positive pole of the battery cell, and the negative pole of the pulse power supply is connected with the tab led out by the copper wire I-1 in the battery cell, and second pulse plating is carried out for 5 min (the pulse plating adopts the mode that plating is carried out for 1 s, then interval 1 s, and plating is carried out again for 1 s, and the cycle is repeated for a total of 5 min; I0 is 80 μA, that is, the second pulse plating current density I m is 80 μA, and the pulse duty cycle is 50%), to obtain the copper wire I (intermediate base material I); (2) The positive pole of the direct current power supply is connected with the negative pole of the battery cell, and the negative pole of the direct current power supply is connected with the tab led out by the copper wire I in the battery cell, and first direct current plating is carried out for 25 min (I1 is 40 μA, that is, the first direct current plating current density I z is 40 μA), to obtain the copper wire II (intermediate base material II); The positive pole of the direct current power supply is connected with the positive pole of the battery cell, and the negative pole of the direct current power supply is connected with the tab led out by the copper wire II in the battery cell, and second direct current plating is carried out for 25 min (I1 is 40 μA, that is, the second direct current plating current density I z is 40 μA), to obtain the reference electrode.

[0042] Example 3 The same process as example 1 is adopted, and the difference lies in that the process parameters are different, and the specific parameters are shown in Table 1.

[0043] Example 4 The similar process as example 1 is adopted, and the difference lies in that the second direct current plating is not carried out, and specifically: (1) Introduce copper wire 1 into 3AH soft pack lithium battery cell (the length of copper wire 1 entering the cell is 5 cm, that is, L is 5 cm), and place the cell with introduced copper wire 1 in an oven for heating and holding treatment (the holding temperature is 50 DEG C, and the time is 30 min); (2) Connect the positive electrode of the pulse power supply with the negative electrode of the cell after the heating and holding treatment, connect the negative electrode of the pulse power supply with the tab led out by copper wire 1 in the cell, carry out first pulse electroplating for 5 min, and obtain copper wire I (intermediate base material I); The pulse electroplating adopts the mode of electroplating for 1 s, interval 1 s, electroplating for 1 s again, and the total cycle is 5 min; wherein, the electroplating condition is: I0 is 160 mu A, that is, the first pulse electroplating current density I m is 160 mu A, and the pulse duty cycle is 50%; (3) Connect the positive electrode of the direct current power supply with the negative electrode of the cell, connect the negative electrode of the direct current power supply with the tab led out by copper wire I in the cell, carry out first direct current electroplating for 25 min (I1 is 80 mu A, that is, the first direct current electroplating current density I z is 80 mu A), and obtain the reference electrode.

[0044] Example 5 The similar process as in Example 1 is adopted, and the difference is that no heating and holding treatment is carried out, specifically: (1) Introduce copper wire 1 into 3AH soft pack lithium battery cell (the length of copper wire 1 entering the cell is 5 cm, that is, L is 5 cm), connect the positive electrode of the pulse power supply with the negative electrode of the cell, connect the negative electrode of the pulse power supply with the tab led out by copper wire 1 in the cell, carry out first pulse electroplating for 5 min, and obtain copper wire I (intermediate base material I); The pulse electroplating adopts the mode of electroplating for 1 s, interval 1 s, electroplating for 1 s again, and the total cycle is 5 min; wherein, the pulse electroplating condition is: I0 is 160 mu A, that is, the first pulse electroplating current density I m is 160 mu A, and the pulse duty cycle is 50%; (2) Connect the positive electrode of the direct current power supply with the negative electrode of the cell, connect the negative electrode of the direct current power supply with the tab led out by copper wire I in the cell, carry out first direct current electroplating for 25 min (I1 is 80 mu A, that is, the first direct current electroplating current density I z is 80 mu A), and obtain copper wire II (intermediate base material II); Connect the positive electrode of the direct current power supply with the positive electrode of the cell, connect the negative electrode of the direct current power supply with the tab led out by copper wire II in the cell, carry out second direct current electroplating for 25 min (I1 is 80 mu A, that is, the second direct current electroplating current density I z is 80 mu A), and obtain the reference electrode.

[0045] Example 6 and Example 7 The same procedure as Example 1 was adopted, except that the process parameters were different, as shown in Table 1.

[0046] Comparative Example 1 The same procedure as Example 1 was adopted, except that the process parameters were different, as shown in Table 1. (1) The copper wire 1 was introduced into the 3AH soft package lithium battery cell (the length of the copper wire 1 entering the cell was 5 cm, i.e. L was 5 cm), and the cell with the introduced copper wire 1 was placed in an oven for heating and holding treatment (the holding temperature was 50°C, and the time was 30 min); (2) The positive electrode of the direct current power supply was connected to the negative electrode of the cell after the heating and holding treatment, and the negative electrode of the direct current power supply was connected to the tab of the copper wire 1 in the cell, and first direct current plating was carried out for 25 min (I1 was 80 μA, i.e. the first direct current plating current density I z was 80 μA), to obtain the copper wire I; The positive electrode of the direct current power supply was connected to the positive electrode of the cell, and the negative electrode of the direct current power supply was connected to the tab of the copper wire I in the cell, and second direct current plating was carried out for 25 min (I1 was 80 μA, i.e. the second direct current plating current density I z was 80 μA), to obtain the reference electrode.

[0047] Comparative Example 2 and Comparative Example 3 The same procedure as Example 1 was adopted, except that the process parameters were different, as shown in Table 1.

[0048] Table 1

[0049] Continued Table 1

[0050] Test Example The reference electrode stability test was carried out on the reference electrodes prepared in the examples and comparative examples, and the test results are shown in Table 2, The specific test method is as follows: (1) The 3Ah soft package three-electrode battery after plating Li was adjusted to 20% SOC, and the potential between the negative electrode and the reference electrode was tested. (2) It was successively subjected to charge and discharge tests at 0.05 / 0.1 / 0.33 / 0.5 / 1 / 1.5C rates, wherein the charge rate was equal to the discharge rate.

[0051] (3) The 3Ah soft package battery was adjusted to 20% SOC, and the potential between the negative electrode and the reference electrode was tested.

[0052] Table 2

[0053] Table 2

[0054] It can be known from the above results that the reference electrode prepared by the method for plating lithium of the reference electrode of the application has excellent potential stability, and the plating lithium time is reduced, and the manufacturing and testing cycle of the reference electrode is shortened.

[0055] In the table 2, it can be known that the reference electrode prepared by plating lithium on the reference electrode substrate by the method of the application is very stable.

[0056] Figure 1 The potential and time curves between the negative electrode and the reference electrode in the plating lithium process of example 1 in the application are exemplarily provided; in Figure 1 In the figure, the blue line represents the standing section, the red line represents the current section of the pulse plating lithium, and the green line represents the standing section of the pulse plating lithium, and it can be seen that the plating lithium curve in the figure is smooth, and the performance is stable under the large current pulse plating.

[0057] Figure 2 The potential and time curves between the positive electrode and the reference electrode, the potential and time curves between the negative electrode and the reference electrode, and the potential and time curves of the three electrodes when the three electrodes after plating lithium of example 1 are charged and discharged in turn at the rate of 0.05 / 0.1 / 0.33 / 0.5 / 1 / 1.5C are exemplarily provided; in Figure 2 In the figure, the blue line represents the potential and time curves between the negative electrode and the reference electrode, the green line represents the full battery voltage and time curves, and the red line represents the potential and time curves between the positive electrode and the reference electrode; it can be known from the figure that the reference electrode prepared by the method of the application has good stability.

[0058] Figure 3 The potential, time and capacity curves between the negative electrode and the reference electrode when the three electrodes after plating lithium are charged and discharged at the rate of 0.05C / 0.1C / 0.33C / 0.5C / 1C and / 1.5C are exemplarily provided; it can be known from the figure that the reference electrode prepared by the method of the application has good stability.

[0059] Figure 4 The potential and time curves between the positive electrode and the reference electrode of the three electrodes after plating lithium of example 2 at the rate of 0.33C charging and standing section are exemplarily provided; it can be known from the figure that when the reference electrode prepared by the method of the application is applied in the battery, the potential of the reference electrode is still stable after the battery is standing for 50h.

[0060] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for lithium plating on a battery reference electrode, characterized in that, The method includes: (1) The reference electrode substrate is subjected to pulse electroplating to obtain intermediate substrate I; The pulse electroplating method includes: introducing the reference electrode substrate into the battery cell, connecting the positive terminal of the pulse power supply to the negative terminal or positive terminal of the battery cell, and connecting the negative terminal of the pulse power supply to the tab led out from the reference electrode substrate. The conditions for pulse electroplating include: pulse current density I m The pulse duration is 1-20 min and the pulse duty cycle is 10-80%, satisfying the relationship shown in equation (I). Formula (I): I m =I0×(D / 50) 2 ×(L / 5); where I0 is 40-300μA, I m The unit is μA; (2) The intermediate substrate I is subjected to DC electroplating to obtain a reference electrode; The conditions for the DC electroplating include: DC current density I z The relationship shown in equation (II) is satisfied in 20-480 min; Formula (II): I z =I1×(D / 50) 2 ×(L / 5); where I1 is 13-160μA, I z The unit is μA; In formulas (I) and (II), D is the diameter of the reference electrode substrate in μm, and L is the length of the reference electrode substrate inside the battery cell in cm.

2. The method according to claim 1, characterized in that, The DC electroplating method includes: connecting the positive terminal of a DC power supply to the negative terminal of the battery cell, connecting the negative terminal of the DC power supply to the tabs led out from the intermediate substrate I, and performing a first DC electroplating to obtain an intermediate substrate II; Connect the positive terminal of the DC power supply to the positive terminal of the battery cell, and connect the negative terminal of the DC power supply to the tab led out from the intermediate substrate II, and perform a second DC electroplating to obtain the reference electrode.

3. The method according to claim 2, characterized in that, The first DC electroplating time is 10-240 min.

4. The method according to claim 1 or 2, characterized in that: In step (1), before the pulse electroplating is performed, the battery cell introduced into the reference electrode substrate is first subjected to heat treatment; the conditions of the heat treatment include: temperature of 40-80℃ and time ≥30min.

5. The method according to claim 1 or 2, characterized in that, I0 is 80-160μA.

6. The method according to claim 1 or 2, characterized in that, I1 is 40-80 μA.

7. The method according to claim 1 or 2, characterized in that, The reference electrode substrate includes any one of copper wire, silver wire, and gold wire; Preferably, the reference electrode substrate is a copper wire.

8. The method according to claim 1 or 2, characterized in that, Before performing step (1), the reference electrode substrate is pretreated by immersing it in an acid solution; Preferably, the acidic substance in the acid solution is selected from at least one of hydrochloric acid, sulfuric acid, and nitric acid.

9. The reference electrode prepared by the method according to claims 1-8.

10. The application of the reference electrode prepared according to claim 9 in a lithium-ion battery.

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