CN113054165B - A negative pole piece of a zinc secondary battery and its preparation method and application - Google Patents

Abstract

The invention provides a negative pole piece of a zinc secondary battery and a preparation method and application thereof, wherein the negative pole piece comprises a zinc-containing metal substrate and a protective layer arranged on the surface of the zinc-containing metal substrate; the protective layer includes a hydrogel film and a zinc salt dispersed in the hydrogel film. The preparation method comprises the following steps: (1) mixing the gel polymer, zinc salt and a solvent to obtain hydrogel dispersed with the zinc salt; (2) and (3) coating the hydrogel obtained in the step (1) on a zinc-containing metal substrate, and drying to obtain the negative pole piece. The negative pole piece provided by the invention has the advantages of uniform zinc deposition, corrosion resistance, good cyclicity, high safety and the like, and is an excellent choice for the negative pole material in the zinc secondary battery.

Description

A negative pole piece of a zinc secondary battery and its preparation method and application

technical field

The invention belongs to the technical field of zinc secondary batteries, and in particular relates to a negative pole piece of a zinc secondary battery and a preparation method and application thereof.

Background technique

Among the existing energy storage technologies, electrochemical energy storage technology is considered to be the most promising energy storage technology due to its high efficiency, long life, strong flexibility and low maintenance cost. Among them, batteries have become an excellent renewable energy integrated energy storage technology due to their long cycle life, high power and energy density, simple maintenance, and high efficiency and convenience. Lithium-ion batteries that are currently the most widely promoted on the market are hindered by the fact that the organic electrolytes used in their electrolytes are usually toxic and flammable. In recent years, aqueous zinc-ion batteries (ZIBs) have been regarded as the most promising new electrochemical energy storage devices due to their low cost, high safety, simple operation, and environmental friendliness.

Zinc battery is one of the oldest batteries. Compared with lithium ion battery (LIB), zinc battery is an aqueous electrolyte, which greatly solves the problem of safety. Recently, rechargeable zinc secondary batteries have been revived as a safe and environmentally friendly electrochemical system. For decades, a great deal of research has been done on zinc-ion batteries, and the research on cathode materials including vanadium oxide, manganese oxide, Prussian blue analogs, and organic materials is quite mature. On the contrary, research on anodes is in urgent need of development. In aqueous zinc-ion secondary batteries, metal zinc is abundant in source, cheap, low redox potential (-0.76V relative to standard hydrogen electrode) and high theoretical capacity (820mAhg ^-1 ), making it an excellent candidate for negative electrode By. CN107528066A discloses an aqueous zinc ion battery based on a carbonyl compound positive electrode material and a preparation method thereof, wherein the negative electrode comprises metallic zinc and its zinc alloys. The assembled aqueous zinc-ion battery can achieve an energy density of 300 Wh/kg (based on carbonyl cathode material), providing a feasible solution for large-scale safe energy storage. CN111600081A discloses a water-rechargeable zinc ion battery with a wide temperature range and long cycle life. The positive electrode material in the battery is an organic material such as polyaniline or a transition metal compound that can reversibly deintercalate zinc ions, and the negative electrode material includes metal zinc flakes, Zinc foil, zinc powder, powdered porous zinc electrode, or zinc alloy. The water-rechargeable zinc-ion battery of the present invention can exhibit high energy density and long cycle life in a very wide temperature range of -90 to 60°C, and can be used in special occasions such as polar exploration, space exploration, deep sea exploration and large-scale storage. The energy field has broad application prospects. However, zinc metal as a negative electrode has many disadvantages, such as zinc dendrites, hydrogen evolution reaction and passivation, which adversely affect the capacity, coulombic efficiency and cycle performance of the battery. Therefore, it is also very important to study the protection of anode materials for zinc-ion batteries. CN111900388A discloses a negative electrode material for zinc ion batteries, the negative electrode material is a zinc-containing metal material with a protective layer deposited on the surface; wherein, the components of the protective layer are a mixture of MOF derivatives and transition metal carbides, the MOF derivatives It is the product of ZIF-8 calcined at 300～800℃ for not less than 2h. The anode protective layer has high specific surface area, uniform zinc deposition morphology and excellent electrical conductivity, which can reduce the polarization of the electrode and effectively inhibit the growth of zinc dendrites, and effectively improve the electrochemical performance of the zinc ion battery. The MOF derivatives in the protective layer need to be calcined under nitrogen protection, the production conditions are harsh, the cost is increased, and the negative electrode cannot be well prevented from generating hydrogen evolution reaction, and it is easily corroded.

Therefore, it is of great practical significance to develop a zinc anode with a simple and feasible preparation method, with uniform zinc deposition, corrosion resistance, and high stability.

SUMMARY OF THE INVENTION

In view of the deficiencies of the prior art, the purpose of the present invention is to provide a negative electrode pole piece of a zinc secondary battery and a preparation method and application thereof, wherein a protective layer is provided on the zinc-containing metal substrate of the negative electrode pole piece, and the protective layer includes water The gel film and the zinc salt dispersed in the hydrogel film can effectively prevent the 2D transport of zinc ions and make the zinc deposition more uniform and dense. At the same time, the protective layer has a low water permeability, which can effectively inhibit the side reactions of the zinc secondary battery during the charge-discharge cycle, including the zinc metal corrosion and HER reaction caused by the electrolyte, thereby greatly improving the cycle of the zinc secondary battery. The role of performance and security.

For this purpose, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a negative pole piece of a zinc secondary battery, the negative pole piece includes a zinc-containing metal substrate and a protective layer disposed on the surface of the zinc-containing metal substrate; the protective layer includes A hydrogel film and a zinc salt dispersed in the hydrogel film.

The negative pole piece provided by the present invention includes a zinc-containing metal substrate and a protective layer disposed on the surface of the zinc-containing metal substrate, and the protective layer includes a hydrogel film and a zinc salt dispersed in the hydrogel film, Due to the effect of the hydrogel film and zinc salts, the 2D transport of zinc ions can be effectively prevented, resulting in more uniform and dense zinc deposition and high ionic conductivity. At the same time, the protective layer has a low water permeability, which can effectively inhibit the side reaction of the zinc secondary battery during the charge-discharge cycle, thereby greatly improving the cycle performance and safety of the zinc secondary battery.

Preferably, the material of the zinc-containing metal substrate includes zinc flakes and/or zinc powder.

Preferably, the hydrogel film includes a physical hydrogel film or a chemical hydrogel film, preferably a physical hydrogel film.

Preferably, the material of the hydrogel film is selected from any one or a combination of at least two of chitosan, sodium alginate, sodium polyacrylate or agar, more preferably chitosan.

Preferably, the mass of the hydrogel film in the protective layer is based on 1 kg, and the amount of the zinc salt is 0.25-5 mol, for example, 0.3 mol, 0.5 mol, 1.0 mol, 1.5 mol, 2.0 mol, 2.5 mol. mol, 3.0mol, 3.5mol, 4.0mol or 4.5mol, as well as specific point values between the above-mentioned point values, limited by space and for the sake of simplicity, the present invention will not exhaustively list the specific point values included in the range.

Preferably, the zinc salt includes any one or a combination of at least two of zinc sulfate, zinc trifluoromethanesulfonate or zinc bis-trifluoromethanesulfonimide, more preferably bis-trifluoromethanesulfonate Zinc imide.

Among the three zinc salts, zinc bis-trifluoromethanesulfonimide has the strongest ionic conductivity and the most uniform zinc deposition.

Preferably, the thickness of the protective layer is 1-20 μm, for example, 2 μm, 4 μm, 5 μm, 8 μm, 10 μm, 12 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm or 19 μm, and specific points between the above point values Due to space limitations and for the sake of simplicity, the present invention will not exhaustively list the specific point values included in the range, and it is preferably 3 to 10 μm.

In the present invention, if the thickness of the protective layer is too small, the effect of preventing surface corrosion cannot be fully exerted; if the thickness of the protective layer is too large, it will cause difficulty in ion transmission and increase the overpotential.

In a second aspect, the present invention provides a method for preparing a negative pole piece as described in the first aspect, the preparation method comprising the following steps:

(1) mixing gel polymer, zinc salt and solvent to obtain a hydrogel dispersed with zinc salt;

(2) Coating the hydrogel obtained in step (1) on a zinc-containing metal substrate, and drying, to obtain the negative electrode plate.

Preferably, the mass concentration of the gel polymer in the hydrogel is 18-40 mg/mL, such as 19 mg/mL, 20 mg/mL, 22 mg/mL, 25 mg/mL, 30 mg/mL, 32 mg/mL, 34mg/mL, 35mg/mL, 36mg/mL, 38mg/mL or 39mg/mL, as well as the specific point values between the above-mentioned point values, limited by space and for the sake of simplicity, the present invention will not exhaustively list the ranges including: The specific point value of , preferably 20 to 30 mg/mL.

In the present invention, the concentration of the gel polymer determines the mechanical properties of the protective layer. When the concentration of the gel polymer is too low, the film cannot be formed; when the concentration of the gel polymer is too high, the viscosity of the hydrogel will be too high. If it is too large, the surface of the finally formed film is uneven and bubbles are more likely to be introduced, so that the finally formed protective layer is not uniform and dense enough.

The concentration of zinc salt in the hydrogel determines the ionic conductivity of the protective layer. If the concentration of zinc salt is too low, the transport of zinc ions is difficult, resulting in an increase in overpotential; if the concentration of zinc salt is too high, the zinc salt cannot be dissolved.

Preferably, the molar concentration of the zinc salt in the hydrogel is 0.01-0.1 mol/L, such as 0.02 mol/L, 0.03 mol/L, 0.04 mol/L, 0.05 mol/L, 0.06 mol/L, 0.07mol/L, 0.08mol/L or 0.09mol/L, as well as specific point values between the above-mentioned point values, limited by space and for the sake of simplicity, the present invention will not exhaustively list the specific point values included in the range.

Preferably, the solvent is a combination of water and an organic solvent.

Preferably, the organic solvent is a good solvent for the gel polymer.

Preferably, the gel polymer is chitosan, and the organic solvent is formic acid.

Preferably, the mass ratio of the organic solvent to water is 1:(50-500), for example, it can be 1:55, 1:60, 1:80, 1:100, 1:150, 1:200, 1:250 , 1:300, 1:350, 1:400, 1:450 or 1:480, etc.

In the present invention, the mixing method is stirring; the stirring includes magnetic stirring and/or mechanical stirring;

Preferably, the mixing time is 0.5-1h, for example, it can be 0.6h, 0.7h, 0.8h or 0.9h, and a specific point value between the above-mentioned point values. Due to space limitations and for the sake of brevity, the present invention The specific point values encompassed by the ranges are not exhaustively recited.

Preferably, the coating method is selected from spin coating, brush coating or blade coating, more preferably blade coating.

Preferably, the blade coating device is a four-sided preparation device.

Preferably, the set thickness of the four-sided preparation device is 10-500 μm, for example, it can be 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm or 480 μm, and specific point values between the above point values, Due to space limitations and for the sake of simplicity, the present invention will not exhaustively list the specific point values included in the range, and it is more preferably 75-150 μm.

Preferably, the drying temperature is 70-100°C, for example, it can be 75°C, 80°C, 85°C, 90°C, 95°C or 98°C, and the specific point values between the above-mentioned point values are limited by space and description. For the sake of brevity, the present invention will not exhaustively enumerate the specific value included in the range.

Preferably, the drying time is 4-10h, for example, it can be 5h, 6h, 7h, 8h or 9h, and the specific point value between the above-mentioned point values. Due to space limitations and for the sake of brevity, the present invention does not The specific point values included in the range are listed exhaustively.

In a third aspect, the present invention provides a zinc secondary battery, the zinc secondary battery includes a positive pole piece, the negative pole piece according to the first aspect, a separator and an electrolyte; the separator is arranged on the positive pole between the plate and the negative pole plate.

Preferably, the positive electrode sheet includes a titanium foil current collector and a positive electrode diaphragm.

Preferably, the material of the positive electrode film includes a positive electrode active material, a conductive agent and a binder.

Preferably, the positive active material includes manganese dioxide and/or vanadium pentoxide.

Preferably, the material of the separator includes any one or a combination of at least two of glass fiber, cellulose or polyvinylidene fluoride.

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

(1) In the present invention, a protective layer is provided on the zinc-containing metal substrate, and the protective layer includes a hydrogel film and a zinc salt dispersed in the hydrogel film. The protective layer can effectively prevent the 2D transport of zinc ions, so that the deposition of zinc is more uniform and dense; at the same time, the protective layer has a low water permeability, which can effectively inhibit the side reactions of zinc secondary batteries during charge-discharge cycles, including electrolysis. The zinc metal corrosion and HER reaction caused by the liquid, the dendrite-free cycle time of the negative pole piece of the zinc secondary battery provided with the protective layer can be as long as 800-1000h, thus greatly improving the cycle performance and safety of the zinc secondary battery. the role of sex. (2) The preparation method of the negative electrode pole piece provided by the present invention is simple, easy to operate and low cost.

Description of drawings

Fig. 1 is the surface SEM image of the negative pole piece provided in Example 1;

Fig. 2 is the SEM image of the cross section of the negative pole piece provided in Example 1;

Fig. 3 is the SEM image of the surface morphology of the zinc deposition on the negative pole piece after the negative pole piece described in Example 1 is circulated in the zinc sulfate electrolyte;

Fig. 4 is the SEM image of the surface morphology of the zinc deposition on the negative pole piece after the negative pole piece described in Comparative Example 1 is circulated in the zinc sulfate electrolyte;

5 is a long cycle performance curve diagram obtained in the cycle performance test of the symmetrical battery prepared by the negative pole piece described in Example 1 and Comparative Example 1;

6 is a graph showing the long-term cycle performance and the corresponding coulombic efficiency of the zinc-vanadium pentoxide full cells prepared in Example 1 and Comparative Example 1 in 2 mol/L zinc sulfate electrolyte.

Detailed ways

The technical solutions of the present invention are further described below through specific embodiments. It should be understood by those skilled in the art that the embodiments are only for helping the understanding of the present invention, and should not be regarded as a specific limitation of the present invention.

Example 1

This embodiment provides a negative electrode plate of a zinc secondary battery, the negative electrode plate includes a zinc plate and a protective layer disposed on the surface of the zinc plate; the protective layer includes a chitosan hydrogel film and a Zinc bis-trifluoromethanesulfonimide in the hydrogel film with a protective layer thickness of 7 μm.

The preparation method of the negative pole piece is as follows:

First, use an analytical balance to weigh quantitative zinc bis-trifluoromethanesulfonimide and chitosan powder, add them to a dilute solution of formic acid (volume ratio, formic acid:water=1:100), and prepare to contain 20 mg/mL Chitosan, 0.05mol/L bis-trifluoromethylsulfonimide zinc gel, placed on a magnetic stirrer and stirred for 30 minutes to promote the dissolution of chitosan to obtain a hydrogel; use a pipette to remove the hydrogel Glue on the zinc sheet, and then use a four-sided preparation device with a set thickness of 100 μm to evenly scrape the gel on the surface of the clean zinc sheet, and dry it in a vacuum drying oven at 80 °C for 6 hours to obtain a negative electrode. The dried zinc sheet was cut into small rounds with a diameter of 12 mm to obtain the negative electrode sheet of the zinc secondary battery.

Scanning electron microscope (SEM, instrument model Hitachi S-4800, Japan) was used to test the surface and cross-section of the prepared negative electrode piece. As can be seen from FIG. 2 , the thickness of the protective layer in this embodiment is 7 μm.

Example 2

This embodiment provides a negative pole piece of a zinc secondary battery, which differs from Example 1 only in that the zinc salt in the protective layer is zinc bis-trifluoromethanesulfonate; other materials, dosages and preparation methods are the same as Example 1 is the same.

Example 3

This embodiment provides a negative electrode plate of a zinc secondary battery, the negative electrode plate includes a zinc plate and a protective layer disposed on the surface of the substrate; the protective layer includes a chitosan hydrogel film and a The thickness of the protective layer of zinc bis-trifluoromethanesulfonimide in the hydrogel film is 7 μm; the difference between its preparation method and Example 1 is only that the mass concentration of chitosan in the hydrogel is 30 mg/mL .

Example 4

This embodiment provides a negative electrode plate of a zinc secondary battery, the negative electrode plate includes a zinc plate and a protective layer disposed on the surface of the zinc plate; the protective layer includes a chitosan hydrogel film and a For the zinc bis-trifluoromethylsulfonimide in the hydrogel film, the thickness of the protective layer is 7 μm; the difference between the preparation method and Example 1 is only that the zinc bis-trifluoromethylsulfonimide in the hydrogel is The concentration of 0.02mol/L.

Example 5

This embodiment provides a negative electrode plate of a zinc secondary battery, the negative electrode plate includes a zinc plate and a protective layer disposed on the surface of the zinc plate; the protective layer includes a chitosan hydrogel film and a For the zinc bis-trifluoromethylsulfonimide in the hydrogel film, the thickness of the protective layer is 7 μm; the difference between the preparation method and Example 1 is only that the zinc bis-trifluoromethylsulfonimide in the hydrogel is The concentration of 0.1mol/L.

Example 6

This embodiment provides a negative electrode plate of a zinc secondary battery, the negative electrode plate includes a zinc plate and a protective layer disposed on the surface of the zinc plate; the protective layer includes a chitosan hydrogel film and a The thickness of the protective layer of the zinc bis-trifluoromethanesulfonimide in the hydrogel film is 7 μm. The difference between the preparation method and Example 1 is only that the zinc bis-trifluoromethylsulfonimide in the hydrogel is The concentration of 0.5mol/L.

Example 7

This embodiment provides a negative electrode plate of a zinc secondary battery, the negative electrode plate includes a zinc plate and a protective layer disposed on the surface of the zinc plate; the protective layer includes a chitosan hydrogel film and a The thickness of the protective layer of the zinc bis-trifluoromethanesulfonimide in the hydrogel film is 7 μm. The difference between the preparation method and Example 1 is only that the zinc bis-trifluoromethylsulfonimide in the hydrogel is The concentration of 0.001mol/L.

Example 8

This embodiment provides a negative electrode plate of a zinc secondary battery, the negative electrode plate includes a zinc plate and a protective layer disposed on the surface of the zinc plate; the protective layer includes a chitosan hydrogel film and a The thickness of the protective layer of zinc bis-trifluoromethanesulfonimide in the hydrogel film is 1 μm; the difference between its preparation method and Example 1 is only that the mass concentration of chitosan in the hydrogel is 18 mg/mL .

Example 9

This embodiment provides a negative electrode plate of a zinc secondary battery, the negative electrode plate includes a zinc plate and a protective layer disposed on the surface of the zinc plate; the protective layer includes a chitosan hydrogel film and a The thickness of the protective layer of zinc bis-trifluoromethanesulfonimide in the hydrogel film is 20 μm; the difference between its preparation method and Example 1 is only that the mass concentration of chitosan in the hydrogel is 40 mg/mL .

Example 10

This embodiment provides a negative electrode plate of a zinc secondary battery, the negative electrode plate includes a zinc plate and a protective layer disposed on the surface of the zinc plate; the protective layer includes a chitosan hydrogel film and a The thickness of the protective layer of zinc bis-trifluoromethanesulfonimide in the hydrogel film is 7 μm; the difference between its preparation method and Example 1 is only that the concentration of chitosan in the hydrogel is 80 mg/mL.

Example 11

This embodiment provides a negative electrode plate of a zinc secondary battery, the negative electrode plate includes a zinc plate and a protective layer disposed on the surface of the zinc plate; the protective layer includes a chitosan hydrogel film and a The thickness of the protective layer of zinc bis-trifluoromethanesulfonimide in the hydrogel film is 7 μm; the difference between its preparation method and Example 1 is only that the concentration of chitosan in the hydrogel is 1 mg/mL.

Example 12

This embodiment provides a negative electrode plate of a zinc secondary battery, the negative electrode plate includes a zinc plate and a protective layer disposed on the surface of the zinc plate; the protective layer includes a chitosan hydrogel film and a For the zinc bis-trifluoromethanesulfonimide in the hydrogel film, the thickness of the protective layer is 10 μm; the preparation method of the negative electrode plate is the same as that in Example 1.

Comparative Example 1

This comparative example provides a negative pole piece of a zinc secondary battery, and the negative pole piece is a zinc piece.

The preparation method of the negative pole piece is as follows:

The surface of the zinc sheet was simply polished with sandpaper, and the zinc sheet was directly cut into small discs with a diameter of 12 mm to obtain the negative electrode piece of the zinc secondary battery.

The negative pole piece of Example 1 and the negative pole piece of Comparative Example 1 were cycled in 2mol/L zinc sulfate electrolyte for 40 weeks, using a scanning electron microscope (SEM, Hitachi S-4800, Japan; accelerating voltage 10kV) The surface morphology was characterized respectively, and the obtained SEM images were shown in Figures 3 and 4.

From the comparison between Figure 3 and Figure 4, it can be seen that after the surface of the zinc anode with the protective layer is cycled for 40 cycles, the surface of the zinc flakes is smoother and denser, which shows that the protective layer effectively improves the deposition morphology of the metal zinc anode. The generation of dendrites is suppressed, thereby greatly improving the cycle life and safety performance of the battery. Comparing the long cycle performance of the symmetrical battery, it is found that the zinc anode containing the protective layer greatly improves the cycle life of the symmetrical battery. It was observed that the cycle life of the symmetrical battery without the protective layer on the surface of the zinc negative electrode was very short, and after 40 cycles, the battery was disassembled, and it was found that the surface of the zinc flakes had serious pitting corrosion, and the zinc was deposited in flakes, and the zinc flakes were disassembled. There are many dendrites on the surface, and these dendrites will continue to grow and pierce the separator in the subsequent cycles, resulting in a short circuit of the battery, thereby affecting the cycle life of the zinc battery and causing safety hazards. It can be seen that the cycle life of the zinc anode symmetrical battery containing the protective layer is significantly improved, and the cycle overpotential is significantly lower than that of ordinary zinc flakes. This shows that the protective layer can regulate the growth of zinc dendrites, and has a great improvement on the hindered ion transport caused by surface passivation.

Comparative Example 2

This comparative example provides a negative pole piece of a zinc secondary battery. The negative pole piece includes a zinc piece and a protective layer on the surface of the zinc piece; the material of the protective layer is zinc bis-trifluoromethanesulfonimide. The thickness of the protective layer is 0.1 μm.

The preparation method of the negative pole piece is as follows:

First, use an analytical balance to weigh quantitative zinc bis-trifluoromethanesulfonimide powder, prepare a solution containing zinc bis-trifluoromethylsulfonimide with a concentration of 0.05 mol/L, and then use a pipette to pipette the solution On the zinc flakes, the solution was evenly spread on the surface of the zinc flakes with a four-sided preparation device, and the negative pole pieces were obtained after drying in a vacuum drying oven at 80 °C for 6 hours. The negative pole piece of the zinc secondary battery was obtained.

Comparative Example 3

This comparative example provides a negative pole piece of a zinc secondary battery. The negative pole piece includes a zinc piece and a protective layer on the surface of the zinc piece; the protective layer is a chitosan hydrogel film, and the thickness of the protective layer is 7 μm.

The preparation method of the negative pole piece is as follows:

First, weigh a quantitative amount of chitosan powder with an analytical balance, add it to a dilute solution of formic acid, (volume ratio, formic acid: water = 1:100) to form a gel containing 20 mg/mL chitosan, and place it under magnetic stirring. Stir on the device for 30 min to promote the dissolution of chitosan to obtain a hydrogel; then use a pipette to transfer the stirred hydrogel onto the zinc sheet, and then use a 100 μm thick four-sided preparation device to evenly coat the gel on a clean surface. The surface of the bare zinc sheet was dried in a vacuum drying oven at 80°C for 6 hours to obtain a negative electrode sheet, and the dried zinc sheet was cut into small discs with a diameter of 12 mm to obtain the negative electrode sheet of the zinc secondary battery.

Performance testing and result analysis

1. Cyclic performance test of symmetrical battery: Two identical negative pole pieces prepared in Example 1-12 and Comparative Example 1-3, 2mol/L zinc sulfate electrolyte and glass fiber separator were assembled into a zinc-zinc symmetrical battery The cycle performance test was carried out to obtain the dendrite-free cycle time (as shown in Table 1) and the long cycle performance curves of the symmetrical batteries prepared in Example 1 and Comparative Example 1 in the electrolyte (as shown in Figure 5). The test conditions are as follows: a long-term charge-discharge cycle test is performed using the Xinwei battery test system, the cycle current density is 0.5mA/cm ² , the amount of zinc metal circulated is controlled at 0.5mAh/cm ² , and the test temperature is 25°C.

Table 1

According to the data in Table 1, the dendrite-free cycle time refers to the cycle time during which no dendrites are generated during the cycle of the negative pole piece. From the data results of Example 1 and Comparative Example 1, it can be seen that the negative pole piece is not treated, and the results are compared very significantly. When the zinc piece without the protective layer is cycled to 60h, serious dendrites and pitting phenomenon occur. , resulting in a short circuit of the symmetrical battery, so it is necessary to add a protective layer.

From the comparison of the data results of Example 1 and Comparative Examples 2 and 3, it can be seen that the protective layer on the surface of the pole piece formed by only chitosan or zinc bis-trifluoromethanesulfonimide is not dense enough and cannot evenly cover the surface of the zinc negative electrode, so the During the cycling process, the unprotected part of the surface is likely to bear the brunt of the dendrite formation site, which further shortens the cycle life and reduces the Coulombic efficiency. The addition of zinc bis-trifluoromethanesulfonimide alone as a protective layer cannot prevent surface corrosion and lead to battery failure. In addition, when chitosan is added as a protective layer alone, due to the difficulty in transporting zinc ions, when the battery is cycled for more than 300 hours, serious side reactions will occur on the surface, resulting in the accumulation of the surface passivation layer, resulting in difficult ion transport and making the battery over cycle. The potential increases gradually. When the overpotential exceeds a certain range, the electrode surface becomes extremely unstable, and a short circuit occurs gradually, resulting in the failure of the protection.

From the comparison between Example 1 and Examples 6 and 7, it can be seen that when the concentration of zinc bis-trifluoromethylsulfonimide is too high, the ionic conductivity of the solution will be seriously affected by the precipitation of zinc salt, which makes the battery cycle for 600h. After that, failure occurred. However, when the molar concentration of zinc bis-trifluoromethanesulfonimide is too low, the surface protection layer formed is not dense enough and the ionic conductivity is also low, which makes the battery fail to protect after 550h of cycling. Comparing Example 1 with Examples 10 and 11, it can be seen that when the concentration of chitosan is too high, the formed protective layer is prone to bubbles, has high viscosity and is not conducive to the dissolution of zinc bis-trifluoromethanesulfonimide, resulting in The transport of zinc ions is difficult, and the protection fails after the battery is cycled for 750 h. However, when the concentration of chitosan is too low, a uniform and dense protective film cannot be formed, and the surface corrosion cannot be well prevented, resulting in the failure of the battery after 70 h of cycling.

As shown in Figure 5, from the comparison of the overpotential data of Example 1 and Comparative Example 1, it can be seen that the negative pole piece is not treated, and the result is very significant. At 60h, a serious overpotential increase occurred, indicating that a serious side reaction occurred on the electrode surface, resulting in short-circuit failure to the battery, and the zinc flakes with a protective layer had a cycle time of up to 1000h. Therefore, the existence of the protective layer can well prolong the cycle life of the negative pole piece.

2. Full battery cycle performance test: a negative electrode piece of a zinc secondary battery prepared in Example 1 and Comparative Example 1, a piece of commercial vanadium pentoxide, carbon black and a binder in a ratio of 8:1:1 The positive electrode plate prepared by sizing and coating on aluminum foil, 2mol/L zinc sulfate electrolyte and glass fiber separator were assembled into a zinc-vanadium pentoxide full battery for testing. The charging and discharging test conditions of the full battery are as follows: the Xinwei battery test system is used to conduct a long-term charging and discharging cycle test, the current density of the charging and discharging is 10A·g ^-1 , and the test temperature is controlled at 25℃. The test results are shown in Figure 6.

The stability of the negative electrode can also be tested by the full battery charge-discharge test. The cycle life and capacity retention rate of the full battery are largely affected by the stability of the negative electrode surface.

According to the data in FIG. 6 , the specific capacity is the amount of electricity generated by one discharge of the positive electrode material per unit mass, and the unit is milliamp-hours/g. The Coulomb efficiency refers to the ratio of the battery discharge capacity to the charge capacity during the same cycle, that is, the percentage of the discharge capacity to the charge capacity. From the data results of Example 1 and Comparative Example 1, it can be seen that the negative pole piece is not treated, and the result is very significant. The full battery assembled with the zinc piece without the protective layer was cycled to the 370th cycle. The serious capacity and Coulomb efficiency decay phenomenon causes the short-circuit failure of the whole cell, so it is confirmed that the addition of a protective layer is necessary.

The applicant declares that the present invention is to illustrate the negative pole piece of a zinc secondary battery of the present invention and its preparation method and application through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments, that is to say, it does not mean that the present invention must Implementation depends on the above-mentioned embodiment. Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims (35)

1. the negative pole piece of a zinc secondary battery, is characterized in that, described negative pole piece comprises zinc-containing metal substrate and the protective layer that is arranged on the surface of described zinc-containing metal substrate; Described protective layer comprises water a gel film and a zinc salt dispersed in the hydrogel film; The thickness of the protective layer is 1-20 μm; The negative pole piece is prepared by the following method, and the method includes the following steps: (1) mixing gel polymer, zinc salt and solvent to obtain a hydrogel dispersed with zinc salt; (2) coating the hydrogel obtained in step (1) on a zinc-containing metal substrate, and drying to obtain the negative electrode plate; The molar concentration of the zinc salt in the hydrogel is 0.01-0.1 mol/L. 2 . The negative pole piece according to claim 1 , wherein the material of the zinc-containing metal substrate comprises zinc flakes and/or zinc powder. 3 . 3. The negative pole piece according to claim 1 or 2, wherein the hydrogel film comprises a physical hydrogel film or a chemical hydrogel film. 4. The negative pole piece according to claim 3, wherein the hydrogel film is a physical hydrogel film. 5. negative pole piece as claimed in claim 1 is characterized in that, the material of described hydrogel film is selected from any one or at least two in chitosan, sodium alginate, sodium polyacrylate or agar combination. 6 . The negative pole piece according to claim 5 , wherein the material of the hydrogel film is chitosan. 7 . 7 . The negative pole piece according to claim 1 , wherein the mass of the hydrogel film in the protective layer is 1 kg, and the amount of the zinc salt is 0.25-5 mol. 8 . 8. The negative pole piece according to claim 1, wherein the zinc salt comprises any one or at least one of zinc sulfate, zinc trifluoromethanesulfonate or zinc bis-trifluoromethanesulfonimide combination of the two. 9 . The negative pole piece according to claim 8 , wherein the zinc salt is zinc bis-trifluoromethanesulfonimide. 10 . 10 . The negative electrode sheet according to claim 1 , wherein the protective layer has a thickness of 3-10 μm. 11 . 11. A preparation method of the negative electrode pole piece according to any one of claims 1-10, wherein the preparation method comprises the steps: (1) mixing gel polymer, zinc salt and solvent to obtain a hydrogel dispersed with zinc salt; (2) coating the hydrogel obtained in step (1) on a zinc-containing metal substrate, and drying to obtain the negative electrode plate; The molar concentration of the zinc salt in the hydrogel is 0.01-0.1 mol/L. 12 . The preparation method according to claim 11 , wherein the mass concentration of the gel polymer in the hydrogel is 18-40 mg/mL. 13 . The preparation method according to claim 12, wherein the mass concentration of the gel polymer in the hydrogel is 20-30 mg/mL. 14. The preparation method of claim 11, wherein the solvent is a combination of water and an organic solvent. 15. The preparation method of claim 14, wherein the organic solvent is a good solvent for the gel polymer. 16. The preparation method of claim 11, wherein the gel polymer is chitosan. 17. The preparation method of claim 14, wherein the organic solvent is formic acid. 18. The preparation method according to claim 14, wherein the mass ratio of the organic solvent to water is 1:(50-500). 19. The preparation method of claim 11, wherein the mixing method is stirring. 20. The preparation method of claim 19, wherein the stirring comprises magnetic stirring and/or mechanical stirring. 21. The preparation method of claim 11, wherein the mixing time is 0.5-1 h. 22. The preparation method according to claim 11, wherein the coating method is selected from any one of spin coating, brush coating or blade coating. 23. The preparation method of claim 22, wherein the coating method is blade coating. 24. The preparation method according to claim 23, wherein the blade coating apparatus is a four-sided preparation device. 25 . The preparation method according to claim 24 , wherein the setting thickness of the four-sided preparation device is 10-500 μm. 26 . 26 . The preparation method according to claim 25 , wherein the set thickness of the four-sided preparation device is 75-150 μm. 27 . 27. The preparation method according to claim 11, wherein the drying temperature is 70-100°C. 28. The preparation method of claim 11, wherein the drying time is 4-10 h. 29. A zinc secondary battery, characterized in that the zinc secondary battery comprises a positive pole piece, the negative pole piece according to any one of claims 1-10, a separator and an electrolyte; the separator is arranged on the between the positive pole piece and the negative pole piece. 30. The zinc secondary battery of claim 29, wherein the positive electrode sheet comprises a titanium foil current collector and a positive electrode diaphragm. 31. The zinc secondary battery of claim 30, wherein the material of the positive electrode membrane comprises a positive electrode active material, a conductive agent and a binder. 32. The zinc secondary battery of claim 31, wherein the positive active material comprises manganese dioxide and/or vanadium pentoxide. 33. The zinc secondary battery of claim 29, wherein the material of the separator comprises any one or a combination of at least two of glass fiber, cellulose or polyvinylidene fluoride. 34. The zinc secondary battery of claim 29, wherein the electrolytic solution is an aqueous solution of an electrolyte. 35. The zinc secondary battery of claim 34, wherein the electrolyte is selected from any one of zinc bis-trifluoromethanesulfonimide, zinc sulfate or zinc trifluoromethanesulfonate or A combination of at least two.

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