A flexible integrated negative electrode, preparation method and battery

Abstract

The present invention relates to the technical field of lithium-ion battery preparation, and particularly to a flexible integrated negative electrode, a preparation method and a battery. The method involves pretreating an iron-based flexible material and adsorbing nickel oxalate to prepare a prefabricated negative electrode, and then heat-treating the prefabricated negative electrode to obtain an integrated negative electrode comprising an iron oxide active material with a hollow structure and a current collector. Utilizing the Kirkendall effect, due to the different diffusion rates of nickel and iron, iron oxide with a hollow structure is formed on the surface of the iron-based flexible material. Combining with the integrated iron-based flexible material as the matrix ensures good mechanical bonding and electrical contact between the two, solves the problems of weak bonding between the active material and the current collector and low electronic conductivity, and at the same time eliminates the use of conductive agents and binders. This not only simplifies the manufacturing process of the battery, but also reduces the energy consumption and time cost during production, and improves production efficiency. It has very good economic benefits and development prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery preparation, and specifically to a flexible integrated negative electrode, a preparation method and a battery, in particular to a flexible integrated negative electrode with high specific capacity and high stability, a preparation method and an application thereof. Background Art

[0002] A flexible battery is a battery with flexibility and bendability. With the rapid development of economic global informatization and network technology, the information technology revolution has penetrated into all fields of social life. Information terminals are no longer limited to traditional mainframes, but are shifting towards wearable devices. In order to meet the strong demands for miniaturization, portability and wearability of information terminals, electronic devices are developing towards thinness, lightness and flexibility, making flexible batteries have great application potential in many fields such as consumer electronics, medical health, aerospace, wearable devices, etc.

[0003] Due to good electrochemical performance, lithium-ion batteries are one of the ideal choices for developing flexible energy storage devices. As an important part of lithium-ion batteries, the negative electrode material plays a decisive role in the performance of the battery to a certain extent. The most commonly used negative electrode material at present is graphite, but the theoretical capacity of graphite is relatively low (372 mAh g -1 ), which is difficult to meet the performance requirements of flexible batteries for high energy density and long battery life, and limits its application in large-capacity and high-power devices such as electric vehicles. In contrast, transition metal (iron) oxides have high theoretical specific capacity and have good application prospects as high-capacity flexible negative electrode materials. However, due to the low electronic conductivity of transition metal (iron) oxides and easy volume expansion during lithiation / delithiation; and the existing electrode preparation is to coat a mixed slurry of active material, conductive agent and binder on the current collector. Due to the low interfacial bonding strength between the active material and the current collector, the weak bonding between the two directly affects the mechanical stability and electrochemical stability of the battery under different flexible conditions, which causes a great obstacle to its practical application.

[0004] The Chinese invention patent with the authorization publication number CN111276700B discloses a flexible battery negative electrode, its preparation method, and a flexible battery. It is formed by combining at least one transition layer on one side of a substrate, and a negative electrode active material layer combined on the side of the transition layer facing away from the flexible substrate. The transition layer is a mixed material layer formed by a negative electrode active material and a conductive material that can act as a current collector. And along the direction from the flexible substrate to the negative electrode active material layer, in the transition layer, the content of the conductive material gradually decreases, and the content of the negative electrode active material gradually increases. The flexible negative electrode prepared by this method effectively alleviates the problem of expansion and pulverization of the negative electrode active material, especially alloy-based negative electrode materials, significantly improves the cycle stability, and has long cycle life, high rate performance, and good anti-bending performance. However, the negative electrode material prepared by this method cannot fundamentally solve the problems of poor mechanical stability and chemical stability caused by the volume expansion of the negative electrode material. Summary of the Invention

[0005] Aiming at the problems in the prior art that the mechanical stability and electrochemical stability of the battery are poor due to the weak combination of the current collector and the active material in the negative electrode, the present invention provides a flexible integrated negative electrode, a preparation method, and a battery.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a preparation method of a flexible integrated negative electrode, including:

[0008] Performing pretreatment on an iron-based flexible material to obtain an iron-based flexible substrate;

[0009] Adsorbing nickel oxalate on the iron-based flexible substrate to prepare a prefabricated negative electrode;

[0010] Performing heat treatment on the prefabricated negative electrode to obtain a flexible integrated negative electrode.

[0011] Optionally, the iron-based flexible material is iron foam or iron wire mesh.

[0012] Optionally, in the iron-based flexible material, the mass percentage of iron ≥ 99.5%.

[0013] Optionally, the method for performing pretreatment on the iron-based flexible material to obtain an iron-based flexible substrate is:

[0014] Soaking the iron-based flexible material in an organic solvent to remove the grease on the surface of the iron-based flexible material;

[0015] Washing and drying the iron-based flexible material with the surface grease removed to obtain an iron-based flexible substrate.

[0016] Optionally, the method for adsorbing nickel oxalate on the iron-based flexible substrate to prepare a prefabricated negative electrode is:

[0017] Immerse the iron-based flexible substrate in a mixed solution of oxalate and nickel salt, so that nickel oxalate generated by the reaction of oxalate and nickel salt is adsorbed on the surface of the iron-based flexible substrate, and then dry it to obtain a prefabricated negative electrode.

[0018] Optionally, the nickel salt includes one or more of nickel nitrate, nickel chloride and nickel sulfate; the oxalate includes one or more of sodium oxalate, ammonium oxalate and potassium oxalate.

[0019] Optionally, the molar ratio of the nickel salt to the oxalate is 1:1; the concentrations of the oxalate and the nickel salt in the mixed solution of the oxalate and the nickel salt are both 1-5 mmol / L.

[0020] Optionally, during the process of heat-treating the prefabricated negative electrode to obtain a flexible integrated negative electrode, the heat treatment temperature is 600°C to 1000°C, and the heat treatment time is 2 to 12 h.

[0021] The present invention provides a flexible integrated negative electrode prepared by using the above preparation method. At a current density of 100 μA cm -2 After 100 cycles of constant current charge and discharge, the specific capacitance retention rate reaches 81.4%.

[0022] The present invention also provides a battery including the above flexible integrated negative electrode.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention provides a method for preparing a flexible integrated negative electrode. In this method, a prefabricated negative electrode is obtained by pretreating an iron-based flexible material and adsorbing nickel oxalate. Then, the prefabricated negative electrode is heat-treated to obtain an integrated negative electrode comprising an iron oxide active material with a hollow structure and a current collector. Iron-based flexible materials generally have good electrical conductivity and flexibility, making them suitable as negative electrode materials for flexible batteries. Through pretreatment, their surface properties can be further improved, providing favorable conditions for subsequent adsorption of nickel oxalate. By adsorbing nickel oxalate on the iron-based flexible material and performing heat treatment, due to the different diffusion rates of nickel and iron, the Kirkendall effect occurs, converting the iron on the surface of the iron-based flexible material into an iron oxide active material with a hollow structure. This hollow structure not only increases the specific surface area of the material, providing more active sites for subsequent insertion and extraction of lithium ions, but also helps to improve the cycle stability and rate performance of the material. The three-dimensional structure of the matrix and the hollow structure of the active material can buffer the volume changes during charge and discharge processes. At the same time, the three-dimensional structure of the matrix can provide sufficient contact area with the electrolyte, facilitating electrolyte diffusion and contributing to the progress of electrochemical reactions. Building the active material and the current collector in the same structure ensures good mechanical bonding and electrical contact between the two, solving the problems of weak bonding between the active material and the current collector and low electronic conductivity. At the same time, the use of conductive agents and binders is eliminated, which can not only simplify the manufacturing process of the battery, avoiding the complex assembly process between the positive and negative active materials and the current collector, but also through precise control of the parameters of steps such as pretreatment, adsorption, and heat treatment, precise regulation of the structure and performance of the negative electrode material can be achieved.

[0025] The iron-based flexible material is iron foam or iron wire mesh. Iron foam or iron wire mesh has a wide source. In addition to having good electrical conductivity, their good flexibility enables them to adapt to the battery design requirements of various shapes and sizes. During the charge and discharge process of the battery, they can better adapt to volume changes, reduce internal stress, and extend the service life of the battery. At the same time, the electrode itself adopts a foam or mesh structure, which can provide sufficient contact area with the electrolyte, facilitating electrolyte diffusion and contributing to the progress of electrochemical reactions, thereby ensuring the specific capacity, rate performance, and cycle performance of the integrated electrode.

[0026] In the iron-based flexible material, the mass percentage of iron is ≥99.5%. Sufficient iron content can provide a material basis for the conversion into an iron oxide active material. At the same time, it can ensure that the iron-based flexible material has good electrical conductivity, improving the electron transfer efficiency during the charge and discharge process of the battery, reducing the internal resistance, reducing the capacity attenuation of the battery during the charge and discharge process, improving the cycle stability of the battery, and thus enhancing the overall performance of the battery.

[0027] The method for adsorbing nickel oxalate on the iron-based flexible substrate to prepare the prefabricated negative electrode is to immerse the iron-based flexible substrate in a mixed solution of oxalate and nickel salt through a simple one-step method, so that the nickel oxalate generated by the reaction of oxalate and nickel salt is adsorbed on the surface of the iron-based flexible substrate, and then dried to obtain the prefabricated negative electrode. The whole process has no complex equipment or multiple treatment steps, greatly simplifies the preparation process, reduces the energy consumption and time cost in the production process, and improves the production efficiency.

[0028] The molar ratio of the nickel salt to the oxalate is 1:1; the concentrations of the oxalate and the nickel salt in the mixed solution of oxalate and nickel salt are both 1-5 mmol / L. When the molar ratio of the nickel salt to the oxalate is 1:1, the two can react completely to generate pure nickel oxalate, which can avoid the generation of impurities caused by excessive reactants and improve the purity of the negative electrode material. Within the concentration range of 1-5 mmol / L, the reaction rate of the oxalate and the nickel salt is moderate, which helps the reaction to proceed fully. At the same time, it avoids side reactions or uneven products caused by too fast or too slow reaction rates, which is beneficial to the uniform distribution of nickel oxalate on the surface of the iron-based flexible substrate. This helps to form uniform iron oxide with a hollow structure and improve the electrochemical performance of the negative electrode material.

[0029] In the process of heat-treating the prefabricated negative electrode to obtain the flexible integrated negative electrode, the heat treatment temperature is 600 °C - 1000 °C, and the heat treatment time is 2 - 12 h, which helps iron to be oxidized into electrochemically active iron oxide, forming an interfaceless integrated negative electrode of iron oxide (active material) and iron matrix (current collector); during the heat treatment process, due to the different diffusion rates of nickel and iron elements, it is beneficial to form iron oxide with a hollow structure, relieve the volume expansion during charge and discharge, and avoid problems that cause a decline in cycle performance.

[0030] A flexible integrated negative electrode prepared by the above method, at a current density of 100 μA cm -2 After 100 cycles of constant current charge and discharge, the specific capacitance retention rate reaches 81.4%. The flexible integrated negative electrode has excellent electrochemical stability and can maintain a high energy storage capacity and power output during long-term use. The high specific capacitance retention rate and long cycle life of the flexible integrated negative electrode make it an ideal choice for high-performance batteries. It can meet the requirements of high energy density and long-life batteries in fields such as electric vehicles and energy storage systems. The successful preparation and application have promoted the innovation and development of battery technology, provided new ideas and methods for the research and development of high-performance batteries, and helped to promote the continuous progress of battery technology.

[0031] A battery includes the above-mentioned flexible integrated negative electrode. This battery has excellent electrochemical properties such as high energy density, long cycle life, and fast charge and discharge. Moreover, it has good structural flexibility, adaptability, safety, and reliability, and can be widely applied in fields such as consumer electronics, medical health, aerospace, and wearable devices. It has a wider application scenario and provides strong support for the development of related fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of a flexible integrated negative electrode of the present invention.

[0033] Figure 2 It is the charge-discharge curve diagram of the first two cycles of the flexible integrated negative electrode prepared in Example 1 of the present invention at a current density of 100 μA cm -2 -2.

[0034] Figure 3 It is the cyclic voltammetry curve diagram of the flexible integrated negative electrode prepared in Example 2 of the present invention at a scanning rate of 0.1 mV s -1 -1.

[0035] Figure 4 It is the cycling performance of the flexible integrated negative electrode prepared in Example 3 of the present invention at a current density of 100 μA cm -2 -2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

[0037] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0038] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of simplicity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0039] In this article, unless otherwise specified, the terms "comprising", "including", "containing", "having", or similar terms cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A only comprises a".

[0040] In this text, for the sake of concise description, all possible combinations of all technical features in each implementation or embodiment are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation or embodiment can be combined arbitrarily, and all possible combinations should be considered as the scope described in this specification.

[0041] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0042] In the following embodiments, conventional instruments and equipment in the art are used. For the experimental methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following embodiments. Unless otherwise stated, commercially available products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0043] The present invention will be further described in detail below in conjunction with specific embodiments, which is an explanation rather than a limitation of the present invention.

[0044] See Figure 1 , the present invention provides a flexible integrated negative electrode, wherein, preferably, the iron-based flexible material is iron foam or iron wire mesh, and in the iron-based flexible material, the mass percentage of iron ≥ 99.5%, including:

[0045] S1: Pretreat the iron-based flexible material to obtain an iron-based flexible substrate, specifically:

[0046] Immerse the iron-based flexible material in an organic solvent to remove the grease on the surface of the iron-based flexible material; the organic solvent is preferably acetone, and the immersion time is 10 - 30 min, preferably 10 - 25 min, and further preferably 15 - 20 min;

[0047] Wash and dry the iron-based flexible material with the surface grease removed to obtain an iron-based flexible substrate; among them, the washing is carried out with deionized water and ethanol, and dried at 80°C - 100°C.

[0048] S2: Adsorb nickel oxalate on the iron-based flexible substrate to prepare a prefabricated negative electrode, specifically:

[0049] Immerse the iron-based flexible substrate in a mixed solution of oxalate and nickel salt, so that nickel oxalate generated by the reaction of oxalate and nickel salt is adsorbed on the surface of the iron-based flexible substrate, and then dry it to obtain a prefabricated negative electrode; wherein, the nickel salt includes one or more of nickel nitrate, nickel chloride and nickel sulfate; the oxalate includes one or more of sodium oxalate, ammonium oxalate and potassium oxalate; the molar ratio of the nickel salt to the oxalate is 1:1; the concentrations of the oxalate and the nickel salt in the mixed solution of oxalate and nickel salt are both 1-5 mmol / L; the soaking time is 10-30 min, preferably 15-25 min, and further preferably 15-20 min;

[0050] S3: Heat-treat the prefabricated negative electrode to obtain a flexible integrated negative electrode, specifically:

[0051] Heat the prefabricated negative electrode from room temperature to 600 °C - 1000 °C at a rate of 2-8 °C / min, preferably 700 °C - 1000 °C, and further preferably 800 °C - 1000 °C. Under an air atmosphere, after heat-treating for 2-12 h, soak it in deionized water to remove residual ions, and dry it at 80 °C - 100 °C to obtain a flexible integrated negative electrode.

[0052] The present invention provides a flexible integrated negative electrode prepared by the above preparation method. At a current density of 100 μA cm -2 After 100 cycles of constant current charge and discharge, the specific capacity retention rate reaches 81.4%. This flexible integrated negative electrode has excellent electrochemical stability and can maintain a high energy storage capacity and power output during long-term use. The high specific capacity retention rate and long cycle life of this flexible integrated negative electrode make it an ideal choice for high-performance batteries. It can meet the requirements of high energy density and long-life batteries in fields such as electric vehicles and energy storage systems. The successful preparation and application have promoted the innovation and development of battery technology, provided new ideas and methods for the research and development of high-performance batteries, and helped to promote the continuous progress of battery technology.

[0053] The present invention provides a battery including the above flexible integrated negative electrode. This battery has excellent electrochemical properties such as high energy density, long cycle life and fast charge and discharge. Moreover, its structural flexibility, adaptability, safety and reliability are good, and it can be widely applied in fields such as consumer electronics, medical health, aerospace, and wearable devices, with a wider application scenario, providing strong support for the development of related fields.

[0054] Example 1

[0055] The present invention provides a preparation method of a flexible integrated negative electrode. Immerse an iron mesh with an iron content ≥ 99.5% in acetone for 10 min to remove surface grease, then rinse it with ethanol and deionized water, and dry it at 80 °C for 10 h to obtain an iron-based flexible substrate;

[0056] The iron-based flexible substrate was immersed in a mixed solution of nickel chloride and sodium oxalate with a concentration of 3 mmol / L for 20 min, and after drying at 80 °C, a prefabricated negative electrode was obtained; the prefabricated negative electrode was heated to 600 °C at a heating rate of 5 °C / min in an air atmosphere and treated for 10 h; it was soaked in deionized water to remove residual impurity (sodium, chlorine) ions and dried at 60 °C to obtain a flexible integrated electrode.

[0057] A circular electrode sheet with a diameter of 16 mm cut from the flexible integrated electrode prepared in this example was used. The counter electrode was a lithium metal sheet, and a multilayer composite PP film was used as the separator. An experimental battery was assembled in a glove box, and its electrochemical performance was tested at a voltage window of 0.01 - 3 V on a charge-discharge test platform. See Figure 2 The charge-discharge curves show that the integrated electrode exhibited a discharge specific capacity of 1308.6 μAh cm -2 and a charge specific capacity of 796 μAh cm -2 in the first cycle. The relatively low Coulombic efficiency in the first cycle was mainly attributed to the formation of the solid electrolyte interphase (SEI). In the second cycle, it exhibited a charge specific capacity of 842.7 μAh cm -2 and a discharge specific capacity of 688.6 μAh cm -2 , indicating that the integrated electrode prepared by the present invention has excellent charge-discharge performance.

[0058] Example 2

[0059] The present invention provides a method for preparing a flexible integrated negative electrode. Foamed iron with an iron content ≥ 99.5% was immersed in acetone for 20 min to remove surface grease, then rinsed clean with ethanol and deionized water, and dried at 60 °C for 12 h to obtain an iron-based flexible substrate;

[0060] The iron-based flexible substrate was immersed in a mixed solution of nickel sulfate and potassium oxalate with a concentration of 2 mmol / L for 30 min, and after drying at 80 °C, a prefabricated negative electrode was obtained; the prefabricated negative electrode was heated to 900 °C at a heating rate of 3 °C / min in an air atmosphere and treated for 6 h; it was soaked in deionized water to remove residual impurity (sulfate, potassium) ions and dried at 80 °C to obtain a flexible integrated electrode.

[0061] See Figure 3 , 0.1 mV s -1Cyclic voltammograms at the scanning rate. In the figure, the oxidation-reduction peaks at 1.66 V, 1.86 V and 0.92 V, 1.46 V respectively correspond to the oxidation-reduction of Fe during the lithium deintercalation / insertion process. The appearance of the oxidation-reduction peaks and the relatively symmetric peak shapes indicate that the oxidation-reduction reaction of Fe on the electrode is reversible. This means that during the charge-discharge process, the Fe element can reversibly convert between the oxidized state and the reduced state, thus supporting the cyclic use of the battery.

[0062] Example 3

[0063] The present invention provides a preparation method of a flexible integrated negative electrode. Foamed iron with an iron content ≥99.5% is soaked in acetone for 30 min to remove surface grease, and then rinsed clean with ethanol and deionized water and dried at 100 °C for 8 h to obtain an iron-based flexible substrate.

[0064] The iron-based flexible substrate is soaked in a mixed solution of nickel nitrate and ammonium oxalate with a concentration of 5 mmol / L for 10 min, and after drying at 80 °C, a prefabricated negative electrode is obtained; the prefabricated negative electrode is heated to 1000 °C at a heating rate of 8 °C / min in an air atmosphere and treated for 5 h; soaked in deionized water to remove residual impurity (nitrate, ammonium) ions and dried at 60 °C to obtain a flexible integrated electrode.

[0065] See Figure 4 , the cycling results show that at a current density of 100 μA cm -2 , after 100 cycles of constant current charge-discharge cycling, the specific capacity slowly decays from 940.5 μAh cm -2 to 765.7 μAh cm -2 . The capacity retention rate is about 81.4%, and the Coulomb efficiency is nearly 100%, showing excellent cycling stability. In addition, since the cycling performance data is obtained based on the test of a coin-type model battery, it is expected to further obtain the cycling performance in the flexible bending state by adopting the soft-pack battery assembly process, further demonstrating that the integrated design prepared by the present invention has excellent flexibility and long-term cycling stability.

[0066] In summary, the present invention provides a flexible integrated negative electrode, a preparation method and a battery. This method pre-treats an iron-based flexible material and adsorbs nickel oxalate to prepare a prefabricated negative electrode, and then heat-treats the prefabricated negative electrode to obtain an integrated negative electrode containing an iron oxide active material with a hollow structure and a current collector. Utilizing the Kirkendall effect, due to the different diffusion rates of nickel and iron, iron oxide with a hollow structure is formed on the surface of the iron-based flexible material. Combining the integrated iron-based flexible material as the matrix ensures good mechanical bonding and electrical contact between the two, solves the problems of weak bonding between the active material and the current collector and low electronic conductivity, and at the same time eliminates the use of conductive agents and binders. It can not only simplify the manufacturing process of the battery, but also has low cost and good economic benefits.

[0067] The above are only the preferred embodiments of the present invention and are not intended to limit the technical solutions of the present invention. Those skilled in the art should understand that without departing from the spirit and principle of the present invention, the technical solutions can be subject to several simple modifications and substitutions, and these modifications and substitutions also fall within the protection scope covered by the claims.

Claims

1. A preparation method of a flexible integrated negative electrode, characterized in that Comprising: Performing pretreatment on an iron-based flexible material to obtain an iron-based flexible substrate; in the iron-based flexible material, the mass percentage of iron ≥ 99.5%; Adsorbing nickel oxalate on the iron-based flexible substrate to prepare a prefabricated negative electrode; Performing heat treatment on the prefabricated negative electrode to obtain a flexible integrated negative electrode; the temperature of the heat treatment is 600°C to 1000°C, and the heat treatment time is 2 to 12 h.

2. The preparation method of the flexible integrated negative electrode according to claim 1, characterized in that The iron-based flexible material is foamed iron or iron wire mesh.

3. The preparation method of the flexible integrated negative electrode according to claim 1, characterized in that The method for performing pretreatment on the iron-based flexible material to obtain an iron-based flexible substrate is: Soaking the iron-based flexible material in an organic solvent to remove the grease on the surface of the iron-based flexible material; Washing and drying the iron-based flexible material with the surface grease removed to obtain an iron-based flexible substrate.

4. The preparation method of the flexible integrated negative electrode according to claim 1, characterized in that, The method for adsorbing nickel oxalate on the iron-based flexible substrate to prepare a prefabricated negative electrode is: Immersing the iron-based flexible substrate in a mixed solution of oxalate and nickel salt, so that nickel oxalate generated by the reaction of oxalate and nickel salt is adsorbed on the surface of the iron-based flexible substrate, and drying to obtain a prefabricated negative electrode.

5. The preparation method of the flexible integrated negative electrode according to claim 4, characterized in that, The nickel salt includes one or more of nickel nitrate, nickel chloride, and nickel sulfate; the oxalate includes one or more of sodium oxalate, ammonium oxalate, and potassium oxalate.

6. The preparation method of the flexible integrated negative electrode according to claim 4, wherein, The molar ratio of the nickel salt to the oxalate is 1:1; the concentrations of the oxalate and the nickel salt in the mixed solution of oxalate and nickel salt are both 1 to 5 mmol / L.

7. A flexible integrated negative electrode prepared by the preparation method according to any one of claims 1-6, characterized in that, At a current density of 100 μA cm -2 −2, after 100 cycles of galvanostatic charge-discharge, the specific capacitance retention rate reaches 81.4%.

8. A battery, characterized in that, Comprising the flexible integrated negative electrode according to claim 7.

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