A long cycle life, high utilization rate hydrogel coated zinc negative electrode and a preparation method and application thereof, and a water-based zinc-iodine battery

Abstract

The application relates to the technical field of new energy batteries, and provides a long-cycle-life high-utilization hydrogel coating zinc negative electrode and a preparation method and application thereof and a water-based zinc-iodine battery. The zinc negative electrode coating is prepared by scraping a water dispersion liquid containing zinc oxide nanoparticles, sodium alginate and polyacrylamide on the surface of a zinc foil and then immersing the zinc foil in a zinc ion-containing aqueous solution for crosslinking, the hydrogel coating has high mechanical strength, low water content and a crosslinking network structure, can limit the diffusion of water molecules, can significantly improve the utilization rate of the zinc negative electrode, slow down the corrosion of the zinc negative electrode and inhibit zinc dendrites. When applied to the water-based zinc-iodine battery, the hydrogel coating can effectively inhibit the corrosion of iodine species on the zinc negative electrode and effectively improve the cycle life of the zinc-iodine battery. The water-based zinc-iodine battery prepared by the application has a long cycle life of more than 14000 times and has the advantages of low cost, safety, environmental protection and large-scale preparation, and has a wide application prospect in the future large-scale energy storage field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy battery, in particular to a long cycle life, high utilization rate of hydrogel coating zinc negative electrode and its preparation method and application, and aqueous zinc-iodine battery. BACKGROUND

[0002] To meet the requirements of renewable energy integration, there is a high demand for reliable and low-cost electrochemical energy storage systems. Among all available candidate materials, aqueous zinc batteries are considered as a promising electrochemical energy storage system due to the unique properties of zinc metal and aqueous electrolyte, including considerable capacity (5855 mAh mL -1

[0003] Aqueous zinc-iodine (Zn-I2) batteries have attracted extensive attention from researchers due to the abundant reserves of iodine resources, high theoretical capacity (about 211 mAh g -1 ), and about 1.38 V high voltage platform. However, aqueous Zn-I2 batteries have the problem of short cycle life. Specifically, zinc dendrite growth, hydrogen evolution reaction, and by-products lead to poor reversibility of zinc metal negative electrode. In addition, the conversion reaction of I2 positive electrode forms polyiodides, which can dissolve in aqueous electrolyte and diffuse to the zinc negative electrode, resulting in I2 positive active material loss and zinc corrosion, affecting the cycle stability of the battery. In order to solve these problems, researchers often use excess zinc to ensure the continuous supply of zinc negative electrode active material, which leads to very low utilization rate of zinc negative electrode (usually less than 10%). At the same time, the use of excess zinc increases the cost of the battery and reduces the actual energy density. Therefore, improving the stability of the zinc negative electrode and the utilization rate of zinc have become a problem to be solved in the field. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application provides a long cycle life, high utilization rate of hydrogel coating zinc negative electrode and its preparation method. A double network hydrogel coating containing zinc oxide nanoparticles, sodium alginate and polyacrylamide is prepared in situ on the surface of zinc foil, realizing fast and uniform zinc ion transmission and good mechanical stability, while blocking the diffusion of water molecules and polyiodides to the negative electrode, significantly reducing the side reactions at the zinc negative electrode and electrode electrolyte interface. To solve the problems of low zinc utilization rate and short cycle life of aqueous zinc-iodine battery, the aqueous zinc-iodine battery of the present application has long cycle life, high zinc utilization rate, and has the advantages of low cost, safety and environmental protection, and large-scale preparation.

[0005] The above technical purposes of the present application are achieved by the following technical solutions:

[0006] ​This invention provides a long cycle life and high utilization rate hydrogel-coated zinc anode, comprising zinc foil and a dual-network hydrogel coating containing zinc oxide nanoparticles, sodium alginate and polyacrylamide covering the surface of the zinc foil.

[0007] This invention also provides a method for preparing a hydrogel-coated zinc anode with long cycle life and high utilization rate, comprising the following preparation steps:

[0008] (1) Add sodium alginate and polyacrylamide to deionized water in a certain proportion and stir to dissolve;

[0009] (2) Add zinc oxide nanoparticles and continue stirring to obtain a uniform dispersion;

[0010] (3) The above dispersion is coated onto the zinc foil surface with a certain thickness and then placed in an aqueous solution containing zinc salt to crosslink and obtain a double-network hydrogel coated zinc anode.

[0011] The present invention is further configured such that: the sodium alginate in the above dispersion has a mass fraction of 1% to 5%, the polyacrylamide used has a molecular weight of 5 million to 20 million and a mass fraction of 0.5% to 3%, and the zinc oxide nanoparticles used have a particle size of 50 to 500 nanometers and a mass fraction of 0.1% to 2%;

[0012] The present invention is further configured such that: the thickness of the zinc foil used is 10–500 μm, and the thickness of the dispersion coating is 20–200 μm. The zinc salt used is one or a mixture of zinc sulfate, zinc trifluoromethanesulfonate, zinc chloride, and zinc acetate, and the concentration of the zinc salt is 0.5–3.0 mol·L⁻¹. -1 Soaking time: 0.1–12 hours.

[0013] The present invention is further configured such that the zinc salt used is one or a mixture of zinc sulfate, zinc trifluoromethanesulfonate, zinc chloride, and zinc acetate, and the zinc salt concentration is 0.5–3.0 mol·L⁻¹. -1 Soaking time is 0.1 to 12 hours.

[0014] Another object of the present invention is to provide an aqueous zinc-iodine battery, characterized in that it comprises a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode uses the above-mentioned hydrogel-coated zinc negative electrode, and preferably, the separator is a cellulose paper separator.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects:

[0016] The present application realizes high zinc utilization rate and excellent long cycle stability of aqueous zinc-iodine battery by in-situ preparing a double network hydrogel coating containing zinc oxide nanoparticles, sodium alginate and polyacrylamide on the surface of zinc foil, optimizing zinc nucleation and deposition behavior, and effectively inhibiting side reactions and growth of zinc dendrites. -2 The assembled Zn||Zn symmetric battery shows a cycle life of more than 1600 hours under the condition of a current density of 2mA·cm

[0017] The present application provides a hydrogel coated zinc negative electrode and a preparation method thereof, which is simple in process, low in cost, high in safety, and conducive to large-scale production, and the assembled aqueous zinc-iodine battery has high capacity and long cycle life, and can be widely applied in the field of electric vehicles and large-scale energy storage. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The zinc-zinc symmetric battery containing the hydrogel coated zinc negative electrode prepared in Example 10 of the present application has a current density of 2mA·cm -2 , and a zinc utilization rate of 60% under the condition of cycle performance

[0019] Figure 2 The zinc-zinc symmetric battery containing the hydrogel coated zinc negative electrode prepared in Comparative Example 1 of the present application has a current density of 2mA·cm -2 , and a zinc utilization rate of 60% under the condition of cycle performance

[0020] Figure 3 The zinc-zinc symmetric battery containing the hydrogel coated zinc negative electrode prepared in Example 10 of the present application has a current density of 4mA·cm -2 , and a zinc utilization rate of 60% under the condition of cycle performance

[0021] Figure 4 The zinc-zinc symmetric battery containing the hydrogel coated zinc negative electrode prepared in Comparative Example 1 of the present application has a current density of 4mA·cm -2 , and a zinc utilization rate of 60% under the condition of cycle performance

[0022] Figure 5 The charge-discharge curves of the zinc-iodine battery prepared in Example 11 of the present application under different rates

[0023] Figure 6 The cycle performance comparison of the zinc-iodine batteries prepared in Example 11 and Comparative Example 2 of the present application under 5C rate

[0024] Figure 7Cycle performance comparison of zinc-iodine batteries prepared for example 11 and comparative example 2 at 10C rate; DETAILED DESCRIPTION

[0025] The technical solutions in the present application are further described below in combination with the drawings and examples.

[0026] Example 1:

[0027] A composite hydrogel coating containing zinc oxide nanoparticles, the specific preparation steps are as follows:

[0028] (1) Preparation of polymer dispersion containing zinc oxide nanoparticles:

[0029] Add 4% by mass fraction of sodium alginate and 1% by mass fraction of polyacrylamide (molecular weight 14 million) in deionized water, stir and dissolve to get a transparent solution, then add 1% by mass fraction of zinc oxide nanoparticles (particle size 100 nm), continue to stir to make the zinc oxide nanoparticles uniformly dispersed.

[0030] (2) Preparation of hydrogel coating:

[0031] The above dispersion is uniformly coated on the surface of a smooth polytetrafluoroethylene plate by a doctor blade, the coating thickness is set to 200 μm, then the coated coating is immersed in a 0.5 mol·L -1 of zinc sulfate solution for 0.5 h, so that the polymer is crosslinked with zinc ions to form a polymer hydrogel coating.

[0032] Example 2:

[0033] A composite hydrogel coating containing zinc oxide nanoparticles, the specific preparation steps refer to example 1, the difference is that the mass fraction of polyacrylamide in the dispersion is 2%.

[0034] Example 3:

[0035] A composite hydrogel coating containing zinc oxide nanoparticles, the specific preparation steps refer to example 1, the difference is that the mass fraction of polyacrylamide in the dispersion is 3%.

[0036] Example 4:

[0037] A composite hydrogel coating containing zinc oxide nanoparticles, the specific preparation steps refer to example 1, the difference is that the mass fraction of polyacrylamide in the dispersion is 4%.

[0038] Example 5:

[0039] A composite hydrogel coating containing zinc oxide nanoparticles, the specific preparation steps refer to Example 1, the difference is that the mass fraction of polyacrylamide in the dispersion liquid is 2%, and the mass fraction of zinc oxide nanoparticles is 0.5%.

[0040] Example 6:

[0041] A composite hydrogel coating containing zinc oxide nanoparticles, the specific preparation steps refer to Example 1, the difference is that the mass fraction of polyacrylamide in the dispersion liquid is 2%, and the mass fraction of zinc oxide nanoparticles is 2%.

[0042] Example 7:

[0043] A composite hydrogel coating containing zinc oxide nanoparticles, the specific preparation steps refer to Example 1, the difference is that the mass fraction of polyacrylamide in the dispersion liquid is 2%, and the mass fraction of zinc oxide nanoparticles is 3%.

[0044] Example 8:

[0045] A composite hydrogel coating containing zinc oxide nanoparticles, the specific preparation steps refer to Example 1, the difference is that the mass fraction of polyacrylamide in the dispersion liquid is 2%, and the mass fraction of zinc oxide nanoparticles is 2%, and the zinc salt solution used for soaking is 0.5 mol·L -1 Zinc trifluoromethanesulfonate solution.

[0046] Example 9:

[0047] A composite hydrogel coating containing zinc oxide nanoparticles, the specific preparation steps refer to Example 1, the difference is that the mass fraction of polyacrylamide in the dispersion liquid is 2%, and the mass fraction of zinc oxide nanoparticles is 2%, and the zinc salt solution used for soaking is 0.5 mol·L -1 Zinc acetate solution.

[0048] The room temperature ionic conductivity and mechanical strength of the composite hydrogels prepared in Examples 1-9 were tested, and the results are shown in Table 1.

[0049] Table 1. Conductivity and mechanical property test results of Examples 1-9.

[0050] Number Conductivity (mS / cm) Tensile Stress (kPa) Tensile Strain (%) Example 1 4.9 36.2 71 Example 2 16.2 21.7 73 Example 3 15.5 15.6 84 Example 4 18.2 9.8 66 Example 5 11.3 19.8 80 Example 6 26.2 17.1 72 Example 7 22.4 11.4 68 Example 8 24 23.5 75 Example 9 20.6 20.6 73

[0051] As can be seen from Table 1, the composite hydrogel coatings prepared in Examples 1-9 all exhibit high ionic conductivity and mechanical strength, among which the composite hydrogel coating prepared in Example 6 has the highest ionic conductivity of 26.2 mS / cm, while maintaining good mechanical strength.

[0052] Example 10:

[0053] A long cycle life, high utilization rate of hydrogel coating zinc negative electrode, the specific preparation steps are as follows:

[0054] (1) Preparation of polymer dispersion liquid containing zinc oxide nanoparticles:

[0055] Add 4% by mass of sodium alginate and 2% by mass of polyacrylamide (molecular weight 14 million) in deionized water, stir and dissolve to obtain a transparent solution, then add 2% by mass of zinc oxide nanoparticles (particle size 100 nm), continue to stir to uniformly disperse the zinc oxide nanoparticles.

[0056] (2) Preparation of hydrogel coating zinc negative electrode:

[0057] The above dispersion liquid is uniformly coated on the surface of zinc foil with a thickness of 20 μm by doctor blade, the coating thickness is set to 100 μm, then the zinc foil coated with the above dispersion liquid is immersed in a zinc sulfate solution with a concentration of 0.5 mol·L -1 -1 for 0.5 h, so that the polymer is crosslinked with zinc ions to form a polymer hydrogel coating.

[0058] Comparative Example 1:

[0059] Bare zinc foil, i.e. bare zinc negative electrode without hydrogel coating

[0060] The hydrogel coated negative electrode prepared in Example 10 is used to assemble a zinc-zinc symmetric battery and test its cycle stability, as shown in Figure 1 , under the conditions of current density 2 mA·cm -2 , capacity 6.97 mAh·cm -2 (zinc utilization rate 60%), the assembled Zn||Zn symmetric battery shows a cycle life of more than 1600 hours, under the same conditions, the cycle life of the Zn||Zn symmetric battery assembled with bare zinc foil in Comparative Example 1 is only 130 hours Figure 2 ); as shown in Figure 3 , when the current density is increased to 4 mA·cm -2 , the Zn||Zn symmetric battery assembled in Example 10 can still be stably cycled for more than 920 hours, the cycle life is much longer than that of the zinc negative electrode without hydrogel coating in Comparative Example 1 (70 hours, Figure 4 ).

[0061] Example 11:

[0062] A water-based zinc-iodine battery, the specific preparation steps are as follows:

[0063] (1) Iodine-activated carbon positive electrode preparation:

[0064] The activated carbon, solid iodine particles (mass ratio 1:1) were ground in a mortar to mix thoroughly, then transferred to a sealed reagent bottle and heated at 60℃ for 12h, after cooling, the iodine-activated carbon, conductive carbon black (Super P), acrylonitrile multi-copolymer water dispersion (LA133) binder were mixed in a mass ratio of 8:1:1 and deionized water was added to stir to form a uniform slurry, then coated on the graphite paper, and after drying in an oven at 40℃, cut into a diameter of 12mm round pole piece.

[0065] (2) Preparation of zinc negative electrode:

[0066] The zinc negative electrode prepared in Example 10 was cut into a diameter of 14mm round pole piece to obtain a zinc negative electrode with a hydrogel coating.

[0067] (3) Preparation of electrolyte:

[0068] Zinc sulfate heptahydrate was added to deionized water and stirred to dissolve to obtain a zinc sulfate solution with a concentration of 2mol·L -1 as the electrolyte.

[0069] (3) Assembly of aqueous zinc-iodine battery:

[0070] According to the order of positive electrode shell, positive electrode piece, separator, zinc negative electrode with hydrogel coating, gasket, spring, negative electrode shell, a CR2032 type button type aqueous zinc-iodine battery was packaged using a button cell packaging machine.

[0071] Comparative Example 2:

[0072] An aqueous zinc-iodine battery, the specific preparation steps are the same as Example 11, except that bare zinc foil without a hydrogel coating is used as the negative electrode.

[0073] From the attached Figure 5 , it can be seen that the aqueous zinc-iodine battery prepared in Example 11 has high capacity and excellent rate performance, the specific capacity of the battery is as high as 191mAh·g -1 at a current density of 0.5C (1C=211mA·g -1 , and still has a specific capacity of 152mAh·g -1 at a current density of 10C.

[0074] From the attached Figure 6 and attached Figure 7 , it can be seen that the aqueous zinc-iodine battery prepared in Example 11 has an ultra-long cycle life, the capacity retention rate is as high as 90% after more than 12000 cycles at a current density of 5C, and still has a capacity retention rate of 80% after 14000 cycles at a current density of 10C. Far exceeding the aqueous zinc-iodine battery with bare zinc foil as the negative electrode in Comparative Example 2.

[0075] Finally, it is to be explained that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the purpose and scope of the present application, and all of them should be covered in the scope of the claims of the present application.

Claims

1. A zinc negative electrode characterized in that, A zinc foil and a double network hydrogel coating layer containing zinc oxide nanoparticles, sodium alginate and polyacrylamide on the surface of the zinc foil, The double network hydrogel coating layer is prepared by coating a water dispersion liquid containing zinc oxide nanoparticles, sodium alginate and polyacrylamide on the surface of the zinc foil, and then immersing it in a zinc ion-containing aqueous solution for crosslinking; the hydrogel coating layer blocks the diffusion of water molecules and polyiodide to the negative electrode; The zinc oxide nanoparticles have a particle size of 50-500 nm and a mass fraction of 0.1%-2%, the sodium alginate has a mass fraction of 1%-5%, and the polyacrylamide has a molecular weight of 5-20 million and a mass fraction of 0.5%-3%.

2. The method of claim 1, wherein the zinc negative electrode is prepared by the steps of: The preparation steps include: ​ Step (1) adding sodium alginate and polyacrylamide to deionized water in a certain proportion and stirring to dissolve; Step (2) adding zinc oxide nanoparticles and continuing to stir to obtain a uniform dispersion liquid; Step (3) coating the dispersion liquid on the surface of the zinc foil in a certain thickness, and then immersing it in a zinc salt-containing aqueous solution for crosslinking to obtain a double network hydrogel coating zinc negative electrode.

3. The preparation method according to claim 2, characterized in that, The zinc foil has a thickness of 10-500 μm, and the dispersion liquid has a coating thickness of 20-200 μm.

4. The production method according to claim 3, characterized by, The zinc salt is one or a mixture of more than one of zinc sulfate, trifluoromethane sulfonic acid zinc, zinc chloride and zinc acetate, the zinc salt concentration is 0.5-3.0 mol·L-1, and the immersion time is 0.1-12 h.

5. An aqueous zinc-iodine battery, characterized by, A zinc negative electrode prepared by the method of any one of claims 2, 3 or 4 is used as the negative electrode.

6. An aqueous zinc-iodine battery, characterized by, A zinc negative electrode prepared by the method of any one of claims 2, 3 or 4 is used as the negative electrode.

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