CN117894919A

CN117894919A - Reference electrode based on flexible substrate and preparation method and application thereof

Info

Publication number: CN117894919A
Application number: CN202410065710.6A
Authority: CN
Inventors: 杨恒昭; 王鹏宇
Original assignee: ShanghaiTech University
Current assignee: ShanghaiTech University
Priority date: 2024-01-16
Filing date: 2024-01-16
Publication date: 2024-04-16

Abstract

The invention provides a reference electrode based on a flexible substrate, a preparation method and application thereof, and particularly relates to the technical field of reference electrodes. The reference electrode includes: a flexible substrate, a conductive current collector, and an active reference substance layer, wherein the conductive current collector is disposed on the flexible substrate; the active reference material layer is disposed on the conductive current collector, the active reference material layer including lithium titanate. According to the invention, the flexible substrate is combined with the conductive current collector, and the lithium titanate with better stability is used as a reference substance, so that the reference electrode with stability and long-acting property can be obtained, and the reference electrode is light, thin, flexible and wide in application range.

Description

Reference electrode based on flexible substrate and preparation method and application thereof

Technical Field

The invention relates to the technical field of reference electrodes, in particular to a reference electrode based on a flexible substrate, and a preparation method and application thereof.

Background

As a most common and widely used rechargeable battery, a lithium ion battery has advantages of high energy density, long life, low self-discharge rate, light weight, and the like. Currently, lithium ion batteries are widely used and dominant in the fields of consumer electronics, electric vehicles, energy storage systems, and the like. However, since lithium ion batteries have a sharp conversion of various forms of energy within a limited volume, the generated heat risks deformation or temperature runaway. Therefore, the implanted potential sensor technology capable of in-situ monitoring the internal environment of the battery is an effective means for predicting and avoiding unsafe behaviors such as cracking, burning, explosion and the like of the lithium ion battery.

The reference electrode is a commonly used potential sensor in an electrochemical energy storage system, and the potential of each electrode in the battery is measured by forming the battery with the electrode to be measured and measuring the voltage difference, so that the physicochemical process in the battery is analyzed. At present, the reference electrode mainly uses metal lithium as an active substance, the metal lithium has strong chemical activity, is easy to react with electrolyte and anode and cathode electrode materials, is not easy to store and transport, can negatively influence the service life and potential stability of the lithium reference electrode, and even introduces other safety risks.

Therefore, there is a need to provide a long-life, high-stability reference electrode to solve the above-mentioned problems.

Disclosure of Invention

In view of the shortcomings of the prior art, the invention provides a reference electrode based on a flexible substrate, a preparation method and application thereof, the stability of the reference electrode is improved, and the service life is prolonged.

To achieve the above and other related objects, the present invention provides a reference electrode based on a flexible substrate, the reference electrode comprising a flexible substrate, a conductive current collector, and an active reference substance layer, wherein the conductive current collector is disposed on the flexible substrate; the active reference material layer is disposed on the conductive current collector, the active reference material layer including lithium titanate.

In one example of the invention, the flexible substrate is selected from polyimide or mylar; and/or the conductive current collector is selected from copper foil or gold-plated copper foil.

In an example of the present invention, the mass ratio of the lithium titanate in the active reference substance layer is 85% to 95%, the active reference substance layer further includes a conductive agent and a binder, and the mass ratio of the conductive agent to the binder is (0.8 to 1.2): 1.

in one example of the invention, the active reference substance layer has a thickness of 5 to 10 μm.

In one example of the invention, the reference electrode further comprises a protective layer, wherein the protective layer is a parylene coating, and the thickness of the protective layer is 3-5 μm.

In an example of the present invention, the conductive agent is at least one selected from conductive carbon black, conductive graphite, acetylene black, ketjen black, carbon nanotubes, carbon fibers, and graphene; the binder is at least one selected from polytetrafluoroethylene, polyvinylidene fluoride and polyvinylidene fluoride.

In an example of the present invention, the conductive agent is a composition of conductive carbon black and graphite KS-6, the mass of the conductive carbon black being 1.5 to 2.5 times the mass of the graphite KS-6.

In another aspect, the invention provides a method for preparing a reference electrode, comprising at least the steps of:

fixing a conductive current collector on a flexible substrate to prepare a flexible current collector;

dispersing lithium titanate, a conductive agent and a binder in a solvent to prepare electrode slurry;

and coating the electrode slurry on the flexible current collector, and drying to obtain the reference electrode.

In one example of the invention, the coated area of the flexible current collector is determined and the masking tape is covered in the uncoated area prior to coating the electrode slurry.

The invention also provides the use of a reference electrode based on a flexible substrate for use in a battery.

The reference electrode of the invention takes lithium titanate as an active reference substance, has good stability in a wider temperature range, can keep stable potential for a long time, and further realizes long-time performance monitoring of the lithium ion battery; the flexible current collector combined by the flexible substrate and the conductive current collector is light, thin and flexible, can meet the device requirements of different sizes and shapes, has a wide application range, can ensure the long-term performance stability of the reference electrode, and has good application prospect.

In addition, the lithium titanate can exist stably in the air, so that the production of a reference electrode and a reference electrode in a glove box is avoided, complicated experimental steps are eliminated, and the lithium titanate is easy to manufacture; meanwhile, through the use of the reference electrode, the state change of the positive electrode and the negative electrode can be directly monitored, the effective distinction of the electrochemical behaviors of the positive electrode and the negative electrode is realized, and the lithium ion battery is not required to be disassembled, so that the nondestructive analysis of the life decay mechanism of the lithium ion battery is realized.

Drawings

In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of a flexible substrate-based reference electrode according to one embodiment of the present invention;

FIG. 2 is an exploded view of a flexible substrate-based reference electrode of the present invention in one embodiment;

fig. 3 is a flow chart of a method of preparing a reference electrode based on a flexible substrate according to an embodiment of the invention.

Reference numerals

10. A reference electrode; 11. a flexible substrate; 12. a conductive current collector; 13. an active reference material layer.

Detailed Description

Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.

Unless otherwise indicated or contradicted, terms or phrases used herein have the following meanings:

herein, reference is made to "plural", "multiple", etc., as without particular limitation, to an index greater than or equal to 2 in number. For example, "one or more" means one kind or two or more kinds.

Herein, "preferred", "better" are merely embodiments or examples that describe better results, and it should be understood that they do not limit the scope of the invention. If there are multiple "preferences" in a solution, if there is no particular description and there is no conflict or constraint, then each "preference" is independent of the others.

Herein, "further," "still further," "particularly," and the like are used for descriptive purposes and are not to be construed as limiting the scope of the invention.

Reference herein to a range of values is to be construed as continuous and includes two endpoints (i.e., a minimum value and a maximum value) of the range of values and each value between the two endpoints of the range of values unless otherwise indicated. When multiple numerical ranges are provided to describe a feature or characteristic, the numerical ranges may be combined.

The reference electrode is an electrode that serves as a reference for comparison when measuring various electrode potentials. The electrode potential of the electrode to be measured can be calculated by forming a battery by the electrode to be measured and a reference electrode with a potential value which is precisely known. The existing reference electrode is generally formed by directly packaging a lithium metal sheet into a battery core, or by introducing a metal wire into the battery core and then performing low-current electroplating, so that a layer of lithium metal is formed on the surface of a copper wire. The metal lithium continuously reacts with the electrolyte in the circulation process, so that the metal lithium of the reference electrode is continuously consumed, and byproducts generated by the reaction of the metal lithium and the electrolyte are deposited on the surface of the reference electrode, so that the monitoring accuracy of the reference potential is affected; the diameter of the used metal wire is only a few micrometers, the mechanical property is poor, the metal wire is extremely easy to break or damage in the preparation or use process, the stability of a cell provided with a reference electrode is poor, and the cell is difficult to stably test for a long time. Based on the reference electrode, the invention provides a reference electrode based on a flexible substrate, a preparation method of the reference electrode and application of the reference electrode.

Referring to fig. 1 and 2, a first aspect of the present invention provides a reference electrode based on a flexible substrate, the reference electrode 10 comprising a flexible substrate 11, a conductive current collector 12 and an active reference substance layer 13. Wherein, the flexible substrate 11 is more flexible and changeable as a substrate material, and can adapt to the device requirements of different sizes and shapes; the conductive current collector 12 is used as a current collector and is arranged on the flexible substrate 11, and the conductive current collector and the flexible substrate form a flexible current collector; the active reference substance layer 13 is disposed on the conductive current collector 12, and the active reference substance layer 13 includes lithium titanate as an active reference substance, which can maintain stable potential for a long time to ensure working quality. The reference electrode prepared by combining the flexible current collector and the lithium titanate active material has the advantages of better stability, flexibility, variability and wide application range.

In some embodiments, the flexible substrate 11 may be selected from flexible materials, such as polyimide or mylar, etc., and further, the flexible substrate 11 is a polyimide substrate. The conductive current collector 12 may be made of a metal material having good electrochemical stability, such as copper, nickel, gold, platinum, silver, or the like; alternatively, the conductive current collector 12 is copper foil or gold-plated copper foil. Preferably, the conductive current collector 12 is gold-plated copper foil, so that certain measurement accuracy can be ensured, and cost can be saved. The flexible current collector 12 may be formed by fixing the flexible current collector 12 to the flexible substrate 11, and the fixing manner of the two is not limited herein, for example, the flexible substrate 11 and the conductive current collector 12 are bonded together by an adhesive, or the like.

The shape and size of each component of the reference electrode 10 are not limited in the present application, and can be adjusted according to the lithium ion battery requirements of different sizes and different packaging forms. It should be noted that the size of the flexible substrate 11 needs to be larger than the size of the conductive current collector 12 to provide support for the conductive current collector 12.

Referring to fig. 1 and 2, in some embodiments, the active reference material layer 13 comprises lithium titanate as the active reference material in an amount of 85% to 95% by mass. Alternatively, the mass ratio of lithium titanate in the active reference substance layer 13 may be 85%, 90%, or 95%, or the like.

In some embodiments, active reference substance layer 13 further comprises a conductive agent and a binder, the conductive agent can increase electron conductivity, and act to collect micro-current between the active reference substances, between the active reference substances and the current collector, to reduce contact resistance; the binder is used to bind the active reference substance and the conductive agent and to provide a certain binding force to the active reference substance layer 13 so that it is bound to the conductive current collector 12.

The conductive agent and binder may be selected from the class of materials conventional in the art. As an example, the conductive agent includes at least one of conductive carbon black (SP), conductive graphite, acetylene black, ketjen black, carbon nanotubes, carbon fibers, and graphene. Optionally, the conductive agent is conductive carbon black; alternatively, a combination of carbon fibers and conductive carbon black; or a combination of carbon nanotubes and graphene, and the like. Further, the conductive agent is a combination of conductive carbon black and graphite KS-6, and the mass of the conductive carbon black is 1.5 to 2.5 times that of the graphite KS-6, alternatively, the mass of the conductive carbon black is 1.5 times, 2.0 times or 2.5 times that of the graphite KS-6.

As an example, the binder includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, for example, the binder is polytetrafluoroethylene, or vinylidene fluoride, or the like. Furthermore, the adhesive adopts polyvinylidene fluoride, so that the reference electrode is tightly attached to the diaphragm in the battery, and meanwhile, the conditions of material stripping, material falling from the conductive current collector and the like cannot be caused by the influence of stress between pole pieces.

Further, the mass ratio of the conductive agent to the binder in the active reference substance layer is (0.8-1.2): 1, further, the mass ratio of the conductive agent to the binder is 1:1.

the active reference substance layer 13 is prepared by preparing lithium titanate, a conductive agent and a binder into an active slurry, coating the active slurry on the conductive current collector 12, and drying.

Referring to fig. 1, in an embodiment, the reference electrode 10 further includes a protective layer (not shown in the figure), which can protect the reference electrode from corrosion, greatly improve the service life of the reference electrode, realize electrode potential monitoring for long-term testing of the lithium ion battery, and ensure the use safety. In this embodiment, the protective layer is a parylene coating, the thickness of the protective layer is 3 to 5 μm, alternatively, the thickness of the protective layer is 3 μm, 4 μm or 5 μm, and so on. In other embodiments, other materials having corrosion protection may be selected for the protective layer.

Referring to fig. 2 and 3, a second aspect of the present invention provides a method for preparing a reference electrode based on a flexible substrate, the method at least comprising the following steps:

s1, fixing a conductive current collector 12 on a flexible substrate 11 to prepare a flexible current collector;

s2, dispersing lithium titanate, a conductive agent and a binder in a solvent to prepare electrode slurry;

and S3, coating the electrode slurry on a flexible current collector, and drying to obtain the reference electrode 10.

Specifically, the flexible substrate 11 in step S1 may be made of a flexible material, for example, polyimide or mylar, etc., and further, the flexible substrate 11 is polyimide. The conductive current collector 12 may be made of a metal material having good electrochemical stability, such as copper, nickel, gold, platinum, silver, or the like; optionally, the conductive current collector 12 is copper foil or gold-plated copper foil, preferably, gold-plated copper foil is selected for the conductive current collector 12, so that certain measurement accuracy can be ensured, and cost can be saved. The conductive current collector 12 and the flexible substrate 11 are fixed in this step, for example, by gluing, that is, by an adhesive.

In other embodiments, the flexible current collector in this step may also be directly selected from flexible printed circuit boards (Flexible Printed Circuit, FPC; a printed circuit with polyimide as a base plate and copper foil attached to its surface as a conductor), which may be purchased by conventional commercial means or may be self-prepared.

And S2, dispersing the lithium titanate, the conductive agent and the binder into a solvent according to a required proportion, and uniformly stirring to obtain the electrode slurry. Wherein, the mass of the lithium titanate accounts for 85-95% of the total mass of the solid materials (lithium titanate, conductive agent and binder), and the mass ratio of the conductive agent to the binder is (0.8-1.2): 1, preferably 1:1. It should be noted that, specific materials of the conductive agent and the binder are described in detail above, and will not be described herein.

The solvent in this step may be an organic solvent which does not chemically react with the above substances, such as N-methylpyrrolidone (NMP), and is added in such an amount that lithium titanate, a conductive agent and a binder are completely dissolved.

And step S3, uniformly coating the electrode slurry prepared in the step S2 on the conductive current collector 12, and drying to prepare the reference electrode. The coating amount of the electrode slurry should be such that the thickness of the active reference substance layer 13 obtained after drying is 5 to 10 μm, for example, 5 μm, 7 μm or 10 μm, etc., and the thickness of the active reference substance layer 13 is adjusted according to actual use requirements, and the coating thickness is generally controlled to be as small as possible without affecting the performance of the reference electrode 10, so as to avoid affecting the battery performance. The drying mode of this step may be selected from those conventional in the art, for example, drying in an oven at 70℃to 100℃for 8 hours to 16 hours.

It should be noted that, before step S3 is performed, it is necessary to determine the coating area of the flexible current collector, then cover the shielding tape in the non-coating area to serve as the tab of the reference electrode, and remove the shielding tape after coating is completed.

The lithium titanate is used as an active reference substance, is easy to manufacture, has good stability in a wider temperature range, can keep the electric potential stable for a long time, ensures the working quality, and can realize the long-time performance monitoring of the lithium ion battery; the flexible current collector combined by the flexible substrate and the conductive current collector is light, thin and flexible, can meet the device requirements of different sizes and shapes, has a wide application range, can ensure the long-term performance stability of the reference electrode, has good application prospect, and realizes the long service life and the performance stability of the lithium battery implanted potential sensor based on the reference electrode.

A third aspect of the invention provides the use of a flexible substrate based reference electrode for use in a cell to monitor electrode potential.

The battery can be a lithium ion battery, a sodium ion battery and the like according to a chemical system; the lithium ion battery comprises a positive electrode material which is lithium iron phosphate, lithium cobalt oxide, lithium manganate, lithium nickelate, lithium-rich manganese base, nickel cobalt manganese ternary or nickel cobalt aluminum ternary, and a negative electrode material which is graphite, metal lithium or alloy battery. The sodium ion battery comprises a positive electrode material which is a layered oxide (Na _x TMO ₂ (x is less than or equal to 1, TM is one or more of 3d transition metals such as Ni, mn, fe, co, cu), polyanion compound (Na _x M _y [(XO _m ) _n –] _z Wherein M is an electroactive transition metal, X is a nonmetallic element such as P, S, si) or Prussian blue cathode material (A _x M[Fe(CN) ₆ ] _y ·zH ₂ O (x is more than 0 and less than 2, y is more than 0 and less than 1, A is alkali metal element such as Li, na and K, M is transition metal element such as Fe, mn, co, ni, cu), and the cathode material is graphite, titanium-based oxide and alloy battery.

The above-described batteries can be classified into liquid batteries (liquid electrolytes), all-solid batteries (solid electrolytes), and semi-solid batteries (liquid electrolytes+solid electrolytes) according to the type of electrolyte.

The above-mentioned batteries can be classified into soft pack batteries, hard case square batteries, hard case cylindrical batteries, etc. according to the type of package.

As an example, reference electrodes are used in lithium ion batteries for monitoring the electrode potential of the battery. The lithium ion battery comprises a positive pole piece, a negative pole piece, a diaphragm and a reference electrode 10, wherein the diaphragm is arranged between the positive pole piece and the negative pole piece, the reference electrode 10 is arranged between the diaphragm and the positive pole piece, and/or the reference electrode 10 is arranged between the diaphragm and the negative pole piece. In order to prevent electrical contact, a separator is additionally provided on the side of the positive or negative electrode sheet opposite to the reference electrode 10, and the size of the additional separator is as small as possible so as to reduce the internal resistance of the battery, if electrical contact can be prevented.

The lithium ion battery of the invention firstly makes a battery core according to a conventional process known by a person skilled in the art, the reference electrode and the auxiliary diaphragm made according to the invention are implanted between the positive pole piece and the negative pole piece of the middle layer of the bare battery core, then the other end of the current collector which is not covered with the active reference substance layer is led out of the battery shell, and then the battery core is packaged, so that the lithium ion battery with the stable reference electrode is obtained.

The technical solutions of the present invention will be described in detail below by means of several specific examples and comparative examples, and unless otherwise indicated, the raw materials and reagents used in the following examples are commercially available or can be prepared by conventional methods in the art, and the instruments used in the examples are commercially available.

Example 1

The embodiment provides a reference electrode comprising a polyimide substrate, a gold-plated copper current collector and an active reference substance layer, wherein the gold-plated copper current collector is fixed on the polyimide substrate, and the active reference substance layer is coated on the gold-plated copper current collector. The thickness of the active reference substance layer is 5 mu m, and the composition of the active reference substance layer and the mass ratio of each component are as follows: lithium titanate: conductive agent (SP: KS-6=2.5:1.2): binder polyvinylidene fluoride=92.5:3.7:3.8.

The preparation method of the reference electrode is as follows:

(1) Bonding a gold-plated copper current collector on a polyimide substrate to prepare a flexible current collector;

(2) Uniformly mixing lithium titanate, a conductive agent (SP: KS-6) and polyvinylidene fluoride according to a mass ratio of 92.5:3.7:3.8, adding a solvent N-methylpyrrolidone (NMP), mixing and stirring until the mixture is completely dissolved, and preparing electrode slurry;

(3) Determining a coating area on the gold-plated copper current collector, covering a layer of shielding tape on the non-coating area, and then coating the electrode slurry prepared in the step (2) on the gold-plated copper current collector; drying in an oven at 80 ℃ for 12 hours to obtain a reference electrode, wherein the coating amount of the electrode slurry is ensured to ensure that the thickness of the dried coating is 8 mu m.

Example 2

This embodiment differs from embodiment 1 in that: and after the step S3 is finished, a layer of parylene coating with the thickness of 5 mu m is deposited on the surface of the active reference substance layer.

Example 3

This embodiment differs from embodiment 1 in that: the mass ratio of each component in the active reference substance layer is as follows: lithium titanate: conductive agent (SP: KS-6=1.5:1): binder polyvinylidene fluoride=85:7.5:7.5, the thickness of the active reference substance layer was 10 μm.

Example 4

This embodiment differs from embodiment 1 in that: the mass ratio of each component in the active reference substance layer is as follows: lithium titanate: conductive agent (SP: KS-6=2.5:1): binder polyvinylidene fluoride=95:2.7:2.3, the thickness of the active reference substance layer was 5 μm.

Example 5

This embodiment differs from embodiment 2 in that: the thickness of the parylene coating was 4 μm.

Example 6

This embodiment differs from embodiment 2 in that: the thickness of the parylene coating was 3. Mu.m

Comparative example 1

This comparative example uses a conventional lithium metal sheet as a reference electrode.

The reference electrodes prepared in examples 1 to 6 and comparative example 1 above were applied to lithium ion batteries, and the preparation process of the lithium ion batteries was as follows:

(1) Preparing a positive electrode plate: according to the mass ratio NCM811 (Nickel: cobalt lithium manganate composite material, wherein nickel: cobalt: manganese=0.8:0.1:0.1): conductive agent conductive carbon black (SP): mixing a binder polyvinylidene fluoride (PVDF) =90:5:5, adding a solvent N-methyl pyrrolidone (NMP), and uniformly stirring to prepare positive electrode slurry; uniformly coating the anode slurry on an anode current collector aluminum foil, drying, and rolling and cutting to obtain an anode plate;

(2) Preparing a negative electrode plate: the artificial graphite comprises the following components in percentage by mass: SP: SBR (styrene butadiene rubber): mixing CMC (sodium carboxymethyl cellulose) =94.5:1.7:2:1.8, adding deionized water as solvent, and stirring uniformly to obtain negative electrode slurry; uniformly coating the negative electrode slurry on a negative electrode current collector copper foil, drying, and rolling and cutting to obtain a negative electrode plate;

(3) A diaphragm: selecting a polypropylene (PP) porous polymer film with the thickness of 12 mu m;

(4) Preparing an electrolyte: at the water content<In a 10ppm argon atmosphere glove box, the volume ratio of EC, DEC and PC was 1:1: mixing at a ratio of 1 to obtain an organic solvent, and drying thoroughly the lithium salt (LiPF ₆ ) Dissolving in organic solvent, mixing to obtain electrolyte, wherein LiPF ₆ The concentration of (C) was 1mol/L.

(5) And (3) battery assembly: in a glove box, sequentially stacking or winding the prepared positive electrode plate, the membrane and the negative electrode plate to prepare an electric core; the reference electrodes prepared in the above examples and comparative examples were inserted into the cells, respectively, the cells with the reference electrodes inserted therein were packaged with a case, and electrolyte was injected to obtain lithium ion batteries.

The potential of the positive electrode and the negative electrode is continuously monitored by using the reference electrode in the battery for 30 days, the potential fluctuation of the reference electrodes in the examples 1 to 6 is small and negligible in the monitoring process, and the potential fluctuation of the reference electrode in the comparative example 1 is large, so that the accuracy of electrode potential measurement is affected. The reference electrode prepared by the method has better stability and longer service life, is lighter, thinner and more flexible due to the adoption of the flexible current collector, can meet the requirements of equipment with different sizes and shapes, and has wide application range. Therefore, the invention effectively overcomes some practical problems in the prior art, thereby having high utilization value and use significance.

The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.

Claims

1. A reference electrode based on a flexible substrate, comprising:

a flexible substrate;

a conductive current collector disposed on the flexible substrate; and

An active reference material layer disposed on the conductive current collector, the active reference material layer comprising lithium titanate.

2. The flexible substrate-based reference electrode according to claim 1, wherein the flexible substrate is selected from any one of polyimide, mylar; and/or the conductive current collector is selected from copper or gold-plated copper foil.

3. The flexible substrate-based reference electrode of claim 1, wherein the mass ratio of the lithium titanate in the active reference substance layer is 85% to 95%; the active reference substance layer further comprises a conductive agent and a binder, wherein the mass ratio of the conductive agent to the binder is (0.8-1.2): 1.

4. the flexible substrate-based reference electrode according to claim 1, wherein the active reference substance layer has a thickness of 5-10 μm.

5. The flexible substrate-based reference electrode of claim 1, further comprising a protective layer, the protective layer being a parylene coating, the protective layer having a thickness of 3-5 μm.

6. The flexible substrate-based reference electrode of claim 3, wherein the conductive agent is selected from at least one of conductive carbon black, graphite, acetylene black, ketjen black, carbon nanotubes, carbon fibers, and graphene; the binder is at least one selected from polytetrafluoroethylene, polyvinylidene fluoride and polyvinylidene fluoride.

7. The flexible substrate-based reference electrode according to claim 6, wherein the conductive agent is a combination of conductive carbon black and graphite KS-6, the mass of the conductive carbon black being 1.5 to 2.5 times the mass of the graphite KS-6.

8. A method of preparing a flexible substrate-based reference electrode according to any one of claims 1 to 7, comprising at least the steps of:

9. The method of manufacturing according to claim 7, wherein the electrode paste is applied to the flexible current collector before the flexible current collector is coated, a coated area of the flexible current collector is determined, and a masking tape is covered in a non-coated area.

10. Use of a flexible substrate-based reference electrode according to any of claims 1 to 7 in a battery.