阅读说明：本技术 界面修饰的金属锌负极及其制备方法 (Interface modified metal zinc cathode and preparation method thereof ) 是由 孙彬 汪盼盼 董昊 金阳 于 2021-09-09 设计创作，主要内容包括：本发明公开了一种界面修饰的金属锌负极及其制备方法,以解决水系锌离子电池电极表面生成过多锌枝晶、发生副反应的技术问题。所述金属锌负极的表面涂覆有粘结剂@氧化石墨烯@氧化锌聚合物复合膜。该界面修饰的金属锌负极的制备方法,包括以下步骤：制备金属锌负极片；将氧化石墨烯溶于分散剂中,超声分散后加入氧化锌,再次超声分散后,得溶液A；将粘结剂溶于分散剂中,搅拌后得胶状物B,将B溶于溶液A中,充分反应后得溶液C；将金属锌负极片浸入到溶液C中,取出后烘干即得。本发明在锌极片表面进行修饰,涂覆PVDF@氧化石墨烯@氧化锌聚合物复合膜,改性后的锌极片在充放电后,形成数目较少的锌枝晶,延长了电池的使用寿命。(The invention discloses an interface modified metal zinc cathode and a preparation method thereof, and aims to solve the technical problems that excessive zinc dendrites are generated on the surface of an electrode of a water-based zinc ion battery and side reactions occur. The surface of the metal zinc negative electrode is coated with a binder @ graphene oxide @ zinc oxide polymer composite film. The preparation method of the interface modified metal zinc cathode comprises the following steps: preparing a metal zinc negative plate; dissolving graphene oxide in a dispersing agent, adding zinc oxide after ultrasonic dispersion, and obtaining a solution A after ultrasonic dispersion again; dissolving a binder in a dispersing agent, stirring to obtain a jelly B, dissolving the jelly B in the solution A, and fully reacting to obtain a solution C; and (3) immersing the metal zinc negative plate into the solution C, taking out and drying to obtain the zinc negative plate. According to the invention, the surface of the zinc electrode sheet is modified, and the PVDF @ graphene oxide @ zinc oxide polymer composite film is coated, so that zinc dendrites with a small number are formed after the modified zinc electrode sheet is charged and discharged, and the service life of the battery is prolonged.)

1. The interface-modified metal zinc cathode is characterized in that a binder @ graphene oxide @ zinc oxide polymer composite film is coated on the surface of the metal zinc cathode.

2. The interface-modified metallic zinc anode of claim 1, wherein the binder is PVDF and the zinc oxide is nano zinc oxide.

3. The interface-modified metal zinc anode of claim 1, wherein the binder @ graphene oxide @ zinc oxide polymer composite film is prepared from the following raw materials in parts by weight: 5-10 parts of adhesive, 1-3 parts of graphene oxide, 1-2 parts of zinc oxide and 1100-1200 parts of dispersing agent.

4. The interface-modified metallic zinc negative electrode of claim 3, wherein the dispersant is NMP.

5. The interface-modified metal zinc negative electrode of claim 1, wherein the thickness of the binder @ graphene oxide @ zinc oxide polymer composite film is 10-15 μm.

6. The preparation method of the interface modified metal zinc cathode is characterized by comprising the following steps of:

preparing a metal zinc negative plate;

dissolving 1-3 parts of graphene oxide in 1000 parts of dispersing agent, adding 1-2 parts of zinc oxide after ultrasonic dispersion, and performing ultrasonic dispersion again to obtain a dark brown solution A;

dissolving 50 parts of binder in 1000 parts of dispersant, and fully stirring to obtain a transparent jelly B;

dissolving 100-200 parts of the jelly B in the solution A, and after full reaction, obtaining a uniform bubble-free transparent solution C;

and (3) protecting one surface of the metal zinc negative plate by using an adhesive tape, completely immersing the other surface of the metal zinc negative plate into the solution C, taking out the metal zinc negative plate and drying the metal zinc negative plate to obtain the zinc-containing negative plate.

7. The preparation method of the interface modified metal zinc negative electrode according to claim 6, wherein the binder is PVDF, the zinc oxide is nano zinc oxide, and the dispersing agent is NMP.

8. The preparation method of the interface modified metal zinc negative electrode according to claim 6, wherein in the step (1), the metal zinc negative electrode sheet is prepared by the following method: cutting a round zinc pole piece by using a zinc foil, adding ethanol to completely immerse the zinc pole piece, ultrasonically cleaning, and drying to obtain the zinc-plated electrode.

9. The preparation method of the interface-modified metal zinc negative electrode according to claim 7, wherein in the step (2), the graphene oxide accounts for 3 parts, and the nano zinc oxide accounts for 2 parts.

10. The preparation method of the interface-modified metal zinc anode of claim 6, wherein in the step (5), the drying step is: drying in an electric heating forced air drying oven for 10min, taking out, and placing in a vacuum drying oven at 100 deg.C for 24 hr.

Technical Field

The invention relates to the technical field of metal zinc cathodes of water-based zinc ion batteries, in particular to an interface-modified metal zinc cathode and a preparation method thereof.

Background

With the continuous development of society, fossil fuels face the problems of resource shortage, environmental pollution and the like, and people are promoted to continuously seek clean and replaceable novel energy sources. At present, lithium ion batteries are popularized and popularized on a large scale in the market as new energy electrochemical energy storage devices, but in the practical application process, because the storage capacity of metal lithium is insufficient and the price is high, potential safety hazards such as flammability and toxicity exist in organic electrolyte, the development of the lithium batteries in the fields of large-scale power grid energy storage systems, electric vehicles and the like is further limited.

Compared with the traditional organic electrolyte, the water-system electrolyte has the advantages of high ionic conductivity, safety, reliability, no toxicity, no harm and the like, so that people turn the research attention to the water-system ion battery. In addition, the metal zinc is unique among a plurality of metal ion battery materials by virtue of the characteristics of high theoretical capacity, high hydrogen evolution overpotential, abundant resources, low price and the like. Therefore, the water-based zinc ion battery is considered as one of the most promising water-based metal ion batteries, and is also a research hotspot in the field of energy storage nowadays.

However, when the metal zinc is used as the battery cathode, zinc dendrite is generated on the surface of the electrode in the charging and discharging processes, the coulombic efficiency of the battery and the utilization rate of the metal zinc are reduced, and the battery is likely to be short-circuited due to the fact that the diaphragm is pierced by excessive dendrite generation. In addition, the surface of the electrode can generate hydrogen evolution reaction to cause electrode corrosion passivation, and the generation of hydrogen in a closed space can cause the volume expansion and even explosion of the battery, thereby seriously influencing the cycle stability and safety of the battery.

Disclosure of Invention

The invention aims to solve the technical problem of providing an interface modified metal zinc cathode and a preparation method thereof, and aims to solve the technical problems that excessive zinc dendrites are generated on the surface of an electrode of a water-based zinc ion battery and side reactions occur.

In order to solve the technical problems, the invention adopts the following technical scheme:

an interface modified metal zinc cathode is designed, and a binder @ graphene oxide @ zinc oxide polymer composite film is coated on the surface of the metal zinc cathode.

The oxidized graphene is different from the traditional graphene, after oxidation, the characteristics of the oxidized graphene are more active than that of the graphene due to the increase of oxygen-containing functional groups, the internal structure of the oxidized graphene exceeds the scale of the traditional chemical material, and the oxidized graphene serving as a soft material in a non-traditional form has the characteristics of colloid, a thin film, amphoteric molecules and the like. In addition, as an important derivative of graphene-based materials, graphene oxide is used as a precursor and a support carrier for synthesizing the graphene-based composite material, and is easy to functionalize, high in controllability and low in conductivity. In the process of compounding with metal, metal oxide, high molecular polymer and other materials, the material can be dispersed and attached effectively in large specific surface area to avoid agglomeration.

Preferably, the binder is PVDF, and the zinc oxide is nano zinc oxide.

Polyvinylidene fluoride (PVDF), which is mainly a vinylidene fluoride homopolymer or a copolymer of vinylidene fluoride and other small amount of fluorine-containing vinyl monomers, has the excellent characteristics of strong oxidation resistance, easy dispersion, chemical corrosion resistance, high-temperature color change resistance, lyophilic property and the like, and is usually used as a binder in the field of batteries.

The nano zinc oxide presents spherical or white hexagonal system crystalline particles, and has extremely high chemical activity and excellent catalytic performance. The nano-grade zinc oxide has many chemical properties different from those of the traditional zinc oxide, and has the advantages of high chemical activity, large specific surface area, good hydrophilicity and the like.

Preferably, the binder @ graphene oxide @ zinc oxide polymer composite film is prepared from the following raw materials in parts by weight: 5-10 parts of adhesive, 1-3 parts of graphene oxide, 1-2 parts of zinc oxide and 1100-1200 parts of dispersing agent.

Preferably, the dispersant is NMP.

Preferably, the thickness of the binder @ graphene oxide @ zinc oxide polymer composite film is 10-15 microns.

The preparation method of the interface modified metal zinc cathode comprises the following steps:

(1) preparing a metal zinc negative plate;

(2) dissolving 1-3 parts of graphene oxide in 1000 parts of dispersing agent, adding 1-2 parts of zinc oxide after ultrasonic dispersion, and performing ultrasonic dispersion again to obtain a dark brown solution A;

(3) dissolving 50 parts of binder in 1000 parts of dispersant, and fully stirring to obtain a transparent jelly B;

(4) dissolving 100-200 parts of the jelly B in the solution A, and after full reaction, obtaining a uniform bubble-free transparent solution C;

(5) and (3) protecting one surface of the metal zinc negative plate by using an adhesive tape, completely immersing the other surface of the metal zinc negative plate into the solution C, taking out the metal zinc negative plate and drying the metal zinc negative plate to obtain the zinc-containing negative plate.

Preferably, the binder is PVDF, the zinc oxide is nano zinc oxide, and the dispersant is NMP.

Preferably, in the step (1), the metallic zinc negative electrode sheet is prepared by the following method: cutting a round zinc pole piece by using a zinc foil, adding ethanol to completely immerse the zinc pole piece, ultrasonically cleaning, and drying to obtain the zinc-plated electrode.

Preferably, in the step (2), the graphene oxide is 3 parts, and the nano zinc oxide is 2 parts.

Preferably, in the step (5), the drying step is: drying in an electric heating forced air drying oven for 10min, taking out, and placing in a vacuum drying oven at 100 deg.C for 24 hr.

Compared with the prior art, the invention has the beneficial technical effects that:

1. according to the invention, the surface of the zinc electrode sheet is modified, and the PVDF @ graphene oxide @ zinc oxide polymer composite film is coated, so that zinc dendrites with a small number are formed after the modified zinc electrode sheet is charged and discharged, the result of battery short circuit caused by membrane penetration is avoided, the coulombic efficiency and the cycle performance are improved, and the service life of the battery is prolonged.

2. According to the invention, graphene oxide is dispersed and dissolved in NMP (N-methyl pyrrolidone), PVDF and nano zinc oxide particles are added, the mixture is coated on the surface of metal zinc and dried to form a coating, the side reaction of metal zinc and electrolyte is inhibited by utilizing the characteristics of close adhesion of a composite membrane, low conductivity of graphene oxide, hydrophilicity of nano zinc oxide and the like, zinc ions are guided to be uniformly deposited, so that the generation of zinc dendrites is reduced, and the cycle discharge life of the water system zinc ion battery is prolonged.

Drawings

FIG. 1 is a scanning electron microscope image of the surface of metallic zinc after modification of PVDF @ graphene oxide @ zinc oxide polymer in test example 1;

FIG. 2 is a schematic diagram of the dimensions and thicknesses of the PVDF @ graphene oxide @ zinc oxide polymer composite membrane in test example 1;

FIG. 3 shows that the ratio of PVDF @ graphene oxide @ zinc oxide polymer modified zinc/zinc symmetric cell to unmodified pure zinc/zinc symmetric cell in test example 1 is 0.5A · g^-1Long cycle performance at current density is plotted;

FIG. 4 is a graph comparing the long cycle performance of the PVDF @ graphene oxide @ zinc oxide polymer modified zinc/manganese dioxide full cell and the unmodified pure zinc/manganese dioxide full cell under rate conditions in test example 1;

FIG. 5 is a scanning electron microscope image of the surface of a zinc plate after cycling of the PVDF @ graphene oxide @ zinc oxide polymer modified zinc/zinc symmetric cell in test example 1;

FIG. 6 is a scanning electron microscope image of the surface of a zinc plate after cycling of the pure zinc/zinc symmetric cell in test example 1.

Detailed Description

The following examples are intended to illustrate the present invention in detail and should not be construed as limiting the scope of the present invention in any way.

The instruments and devices referred to in the following examples are conventional instruments and devices unless otherwise specified; the related reagents and raw materials are all conventional reagents and raw materials sold in the market if not specified; the related detection, test and preparation methods are all conventional methods if no special description is provided.

Example 1: the interface-modified metal zinc cathode is a disk-shaped electrode plate with the diameter of 12mm and the thickness of 2mm, and the surface of the metal zinc cathode is coated with a PVDF @ graphene oxide @ zinc oxide polymer composite film, wherein the polymer composite film is prepared from the following raw materials: 50mg of PVDF, 10mg of graphene oxide, 10mg of nano zinc oxide and 11 mL of NMP (N-methyl pyrrolidone).

Example 2: the interface-modified metal zinc cathode is a disk-shaped electrode plate with the diameter of 12mm and the thickness of 2mm, and the surface of the metal zinc cathode is coated with a PVDF @ graphene oxide @ zinc oxide polymer composite film, wherein the polymer composite film is prepared from the following raw materials: 100mg of PVDF, 30 mg of graphene oxide, 20mg of nano zinc oxide and 12 mL of NMP (N-methylpyrrolidone). The thickness of the PVDF @ graphene oxide @ zinc oxide polymer composite film is 10.83 microns.

Example 3: a preparation method of an interface modified metal zinc cathode comprises the following steps:

(1) firstly, cutting a zinc foil into a plurality of disk-shaped electrode plates with the diameter of 12mm and the thickness of 2mm by using a button cell slicer, putting the disk-shaped electrode plates into a glass bottle, adding a proper amount of ethanol to ensure that the zinc electrode plates can be completely immersed in the disk-shaped electrode plates, putting the disk-shaped electrode plates into an ultrasonic cleaning machine for cleaning for 2 minutes, then putting the disk-shaped electrode plates into an electrothermal blowing drying box for drying, taking out the disk-shaped electrode plates after drying, and sticking an adhesive tape on one side of each electrode plate for protection for later use.

(2) 10mg of graphene oxide was weighed into a glass bottle using an analytical balance, 10 mL of NMP (N-methylpyrrolidone) was added using a dropper, graphene oxide was sufficiently dissolved in NMP by ultrasonic dispersion for half an hour, then 10mg of nano zinc oxide particles were further added by weighing and ultrasonic treatment again for half an hour, and a dark brown solution, called solution A, was obtained.

(3) 500 mg of PVDF (polyvinylidene fluoride) was weighed into a glass bottle, dissolved by adding 10 mL of NMP (N-methylpyrrolidone) to a dropper, and sufficiently stirred for 4 hours with a magnetic stirrer to form a transparent gum called solution B.

(4) Adding the solution 1g B into the solution A, fully stirring for 2 hours to mix the solution A and the solution B, and fully reacting to form a uniform bubble-free transparent solution, namely solution C.

(5) And clamping the electrode slice by using a pair of tweezers, dipping the electrode slice into the solution C, taking out the electrode slice after observing that the surface of one side which is not adhered with the adhesive tape is completely covered with liquid, and drying the electrode slice in an electric heating blowing drying oven for ten minutes. Taking out again and putting into a vacuum drying oven, setting the temperature to be 100 ℃ and the time to be 24 hours.

The surface of the zinc plate is observed to be covered with a dark brown film, which indicates that the electrode surface is modified completely.

Example 4: a preparation method of an interface modified metal zinc cathode comprises the following steps:

(1) firstly, cutting a zinc foil into a plurality of disk-shaped electrode plates with the diameter of 12mm and the thickness of 2mm by using a button cell slicer, putting the disk-shaped electrode plates into a glass bottle, adding a proper amount of ethanol to ensure that the zinc electrode plates can be completely immersed in the disk-shaped electrode plates, putting the disk-shaped electrode plates into an ultrasonic cleaning machine for cleaning for 2 minutes, then putting the disk-shaped electrode plates into an electrothermal blowing drying box for drying, taking out the disk-shaped electrode plates after drying, and sticking an adhesive tape on one side of each electrode plate for protection for later use.

(2) 30 mg of graphene oxide is weighed by an analytical balance into a glass bottle, 10 mL of NMP (N-methylpyrrolidone) is added by a dropper, the graphene oxide is fully dissolved in the NMP by ultrasonic dispersion for half an hour, and then 20mg of nano zinc oxide particles are added by weighing and ultrasonic treatment for half an hour again to obtain a dark brown solution called solution A.

(3) 500 mg of PVDF (polyvinylidene fluoride) was weighed into a glass bottle, dissolved by adding 10 mL of NMP (N-methylpyrrolidone) to a dropper, and sufficiently stirred for 4 hours with a magnetic stirrer to form a transparent gum called solution B.

(4) Adding the solution 2 g B into the solution A, fully stirring for 2 hours to mix the solution A and the solution B, and fully reacting to form a uniform bubble-free transparent solution, namely solution C.

(5) And clamping the electrode slice by using a pair of tweezers, dipping the electrode slice into the solution C, taking out the electrode slice after observing that the surface of one side which is not adhered with the adhesive tape is completely covered with liquid, and drying the electrode slice in an electric heating blowing drying oven for ten minutes. Taking out again and putting into a vacuum drying oven, setting the temperature to be 100 ℃ and the time to be 24 hours.

The surface of the zinc plate is observed to be covered with a dark brown film, which indicates that the electrode surface is modified completely.

Test example 1: the modified metal zinc cathode of the embodiment 4 is subjected to battery preparation and electrochemical performance test:

the prepared electrode plates are assembled into a CP2032 symmetric button cell, and compared with a CP2032 symmetric button cell assembled by pure zinc electrode plates, a Wuhan blue electricity CT 2001A system is used at 0.5mA cm^-2And carrying out constant current charge and discharge test under the current density. In addition, the prepared modified zinc anode and unmodified pure zinc anode flakes are respectively mixed with MnO₂And (4) assembling the positive electrode into a full battery, and performing performance test under the condition of multiplying power charge and discharge. The electrolyte is 2mol/L ZnSO₄And the diaphragm is glass fiber filter paper.

As shown in fig. 1, the microstructure of the surface-modified zinc negative electrode obtained in example 4 is shown.

As shown in fig. 2, is the modified composite film thickness dimension prepared in example 4.

As shown in fig. 3, compared with the unmodified zinc/zinc symmetric battery, the modified zinc/zinc symmetric battery obtained in example 4 has better cycle performance, lower overpotential, and significantly improved charge-discharge cycle life.

As shown in fig. 4, the modified zinc/manganese dioxide full cell obtained for example 4 has more stable cycle performance and longer life span than the unmodified zinc/manganese dioxide full cell.

As shown in figure 5, the modified symmetrical battery cathode is taken out to observe the surface appearance of the modified symmetrical battery cathode, and the surface zinc dendrite number is found to be few, and a 'flat-lying' growth mode is presented, so that the short circuit of the battery caused by piercing a diaphragm is avoided, the cycle life of the battery is greatly prolonged, and the safety is improved.

As shown in fig. 6, the cathode of the short-circuited unmodified symmetric battery is taken out and observed for the microscopic morphology, and it is found that zinc dendrites which are dense and vertically grown are generated on the surface, which may cause the short circuit due to the piercing of the separator, and seriously affect the service life of the battery.

Test example 2: the modified metal zinc cathode of the embodiment 3 is subjected to battery preparation and electrochemical performance test:

the prepared electrode plates are assembled into a CP2032 symmetric button cell, and compared with a CP2032 symmetric button cell assembled by pure zinc electrode plates, a Wuhan blue electricity CT 2001A system is used0.5mA·cm^-2And carrying out constant current charge and discharge test under the current density. In addition, the prepared modified zinc anode and unmodified pure zinc anode flakes are respectively mixed with MnO₂And (4) assembling the positive electrode into a full battery, and performing performance test under the condition of multiplying power charge and discharge. The electrolyte is 2mol/L ZnSO₄And the diaphragm is glass fiber filter paper.

The prepared zinc ion battery has better cycle performance and stronger stability, the zinc dendrite is obviously inhibited, and the service life of the water system zinc ion battery is greatly prolonged.

The invention is explained in detail above with reference to the drawings and the embodiments; however, it will be understood by those skilled in the art that various changes in the specific parameters of the embodiments described above may be made or equivalents may be substituted for elements thereof without departing from the scope of the present invention, so as to form a plurality of specific embodiments, which are all common variations of the present invention and will not be described in detail.