A negative electrode coating material for aqueous zinc ion batteries and a preparation method and application thereof

Abstract

The application belongs to the technical field of aqueous zinc ion batteries, and discloses an aqueous zinc ion battery negative electrode coating material, a preparation method and application thereof. A poly-nitrogen-oxygen-sulfur heteroatom ligand capable of coordinating with zinc ions is generated by reacting coumarin hydrazide and benzyl isothiocyanate, and further prepared into a required aqueous zinc ion battery negative electrode coating material LXB@Zn by doping with polyvinylidene fluoride. The synthesized aqueous zinc ion battery negative electrode coating material contains imino, heteroatoms S, O and N, which can inhibit the hydrogen evolution reaction, provide more active sites, inhibit dendrites and inhibit side reactions, thereby effectively improving the cycle stability of the aqueous zinc ion battery. In order to solve the problem of difficult preparation of the aqueous zinc ion battery negative electrode organic coating, the application adopts a simple method of adding a binder to prepare the aqueous zinc ion battery negative electrode organic coating.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aqueous zinc-ion batteries, and relates to an aqueous zinc-ion battery negative electrode coating material and a preparation method and application thereof. BACKGROUND

[0002] An aqueous zinc-ion battery uses water as an electrolyte, and its negative electrode material zinc is relatively abundant. Compared with other batteries, the aqueous zinc-ion battery has the advantages of high safety, good environmental protection, low cost, moderate energy density, fast charging speed and the like, and is a new type of battery with wide application prospects. However, the chemical activity of zinc makes it easy to be corroded to generate hydrogen evolution reaction, and by-products such as zinc hydroxyl sulfate are generated, which can easily cause dendrite growth. In extreme cases, zinc dendrites can penetrate the separator, causing internal short circuit, thereby greatly shortening the service life of the battery. Therefore, adjusting the uniform deposition of zinc and effectively preventing hydrogen evolution and corrosion reaction has important value for improving the electrochemical performance of the aqueous zinc-ion battery.

[0003] To improve the interface stability and cycle life of the zinc negative electrode, constructing an artificial coating on the zinc surface has become a research hotspot. At present, the coating materials of the aqueous zinc-ion battery mainly include inorganic coating materials, organic coating materials, carbonyl coating materials, polymer coatings, metal organic framework materials and the like. Compared with other materials, the organic coating material has the advantages of chemical stability, adjustability, good flexibility and mechanical properties, interface adaptability, promoting uniform deposition of zinc ions, improving electrochemical performance and the like. The organic coating material can be chemically or physically adsorbed on the surface of the zinc negative electrode, preventing direct contact between the metal zinc negative electrode and the electrolyte, thereby inhibiting the dendrite and corrosion of the metal zinc negative electrode, and improving the cycle stability and performance of the zinc battery. However, the current organic coating generally has poor ion conductivity, which limits its application in the zinc-ion battery. SUMMARY

[0004] In order to overcome the shortcomings of the prior art and solve the problems of zinc negative electrode dendrite growth and hydrogen evolution, the application provides an aqueous zinc-ion battery negative electrode coating material and a preparation method and application thereof. A polyazoxysulfur heteroatom ligand capable of coordinating with zinc ions is generated by reacting coumarin hydrazide and phenyl methyl isothiocyanate, and further doped with polyvinylidene fluoride to prepare the required aqueous zinc-ion battery negative electrode coating material LXB@Zn. The synthesized aqueous zinc-ion battery negative electrode coating material contains imino, heteroatoms S, O and N, which can inhibit the hydrogen evolution reaction and provide more active sites, thereby inhibiting dendrites and side reactions, and effectively improving the cycle stability of the aqueous zinc-ion battery. In order to solve the problem of difficult preparation of the organic coating of the aqueous zinc-ion battery negative electrode, the application adopts a simple method of adding an adhesive to prepare the organic coating of the aqueous zinc-ion battery negative electrode.

[0005] The above object of the application is achieved by the following technical solutions.

[0006] A preparation method of a water-based zinc ion battery negative electrode coating material, the specific steps are:

[0007] (1) Synthesize a new compound LXB by introducing benzyl isothiocyanate into the coumarin system.

[0008] (2) Mix compound LXB with polyvinylidene fluoride (PVDF) at a mass ratio of 5:1, then add 5-10 drops of N-methyl pyrrolidone (NMP), mix uniformly with a mortar, and uniformly coat it on the surface of zinc foil with a thickness of 5-10 nm to prepare zinc ion battery negative electrode coating material LXB@Zn.

[0009] The compound LXB has the following specific structural formula:

[0010]

[0011] The specific preparation method of the compound LXB used in the above water-based zinc ion battery negative electrode coating material LXB@Zn is:

[0012] S1: 4-diethylaminosalicylaldehyde and diethyl malonate are heated to reflux in an ethanol solution to obtain compound LX-1.

[0013] S2: Stir the synthesized compound LX-1 with hydrazine hydrate in an ethanol solution at room temperature until solid precipitates to obtain compound LX-2.

[0014] S3: Heat the synthesized compound LX-2 with benzyl isothiocyanate in an ethanol solution to reflux to obtain the target compound LXB.

[0015] The preparation reaction formula is as follows:

[0016]

[0017] Further, in step S1, the mass ratio of 4-diethylaminosalicylaldehyde to diethyl malonate is 1:1-1:3; preferably 1:1.6.

[0018] Further, in step S2, 0.5-2 grams of compound LX-1 is reacted with 1 milliliter of hydrazine hydrate.

[0019] Further, in step S3, the mass ratio of compound LX-2 to benzyl isothiocyanate is 1:0.7-1:2; preferably 1:0.74.

[0020] Further, in step S1, the refluxing temperature is 70-90℃ for 4 hours.

[0021] Further, in step S2, the normal temperature is 20-30 DEG C.

[0022] Further, in step S3, the heating temperature is 70-90 DEG C, and the refluxing time is 4 hours.

[0023] The application also claims the application of the above-mentioned aqueous zinc ion battery negative electrode coating material LXB@Zn in an aqueous zinc ion battery negative electrode. The introduction of benzyl isothiocyanate increases the imino group and the poly-nitrogen-oxygen-sulfur heteroatoms in the zinc ion battery negative electrode coating material, solves the problems of zinc negative electrode dendrite growth and hydrogen evolution in the current zinc ion battery, and significantly improves the battery performance. It is found through contact angle measurement that LXB@Zn has better hydrophilicity than bare zinc, and the number of charge-discharge cycles of the half battery prepared by using LXB@Zn can reach 560 times, which is more than five times the number of cycles of the bare zinc half battery, and the electrical impedance is also significantly lower than that of the bare zinc battery.

[0024] The application adopts a large Pi bond coumarin molecule with a push-pull electron system as an organic coating, which has an electron-withdrawing group carbonyl and an electron-donating group diethylamine, can better transmit electrons through the establishment of the push-pull electron system, and can be well coordinated with zinc ions by introducing poly-nitrogen-oxygen-sulfur heteroatoms on the coumarin, so as to inhibit zinc corrosion and induce zinc ions to uniformly deposit on the negative electrode surface, thereby inhibiting the formation of dendrites.

[0025] Compared with the prior art, the application has the following beneficial effects:

[0026] (1) The application contains an imino group in the synthetic compound LXB, which can form a coordination compound with zinc ions in the electrolyte through the lone pair of electrons, thereby inhibiting the side reaction of water and zinc to form [Zn(H2O)6]2+, and improving the transmission efficiency of zinc ions in the electrolyte, thereby effectively improving the cycle stability of the aqueous zinc ion battery. + In combination, the hydrogen evolution reaction can be inhibited, and the cycle stability of the aqueous zinc ion battery is effectively improved.

[0027] (2) The application contains heteroatoms S, O and N in the synthetic compound LXB, which can form a coordination compound with zinc ions in the electrolyte through the lone pair of electrons, thereby inhibiting the side reaction of water and zinc to form [Zn(H2O)6]2+, and improving the transmission efficiency of zinc ions in the electrolyte, thereby effectively improving the cycle stability of the aqueous zinc ion battery. 2+

[0028] (3) The application contains more active nitrogen sites in the synthetic compound LXB, which can provide more active sites for the deposition and stripping of zinc ions during the cycle charging and discharging process, prevent the excessive concentration of zinc ions, and thereby inhibit the dendrite of zinc ions. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The surface morphology of LXB prepared in Example 1 of the application under an optical microscope is shown in Figures a and b, which are 100 times (Figure a) and 200 times (Figure b), respectively.​

[0030] Figure 2 Contact angle plot of LXB@Zn (as in figure b) and comparative example 1 Bare Zn (as in figure a) prepared for example 1.

[0031] Figure 3 Impedance plot of symmetric cell of LXB@Zn and comparative example 1 Bare Zn prepared for example 1.

[0032] Figure 4 Galvanostatic charge-discharge plot of half cell of LXB@Zn and comparative example 1 Bare Zn prepared for example 1.

[0033] Figure 5 Hydrogen spectrum of LXB in deuterated dimethyl sulfoxide in example 1.

[0034] Figure 6 Carbon spectrum of LXB in deuterated dimethyl sulfoxide in example 1. DETAILED DESCRIPTION

[0035] The present application is described in detail below by specific examples, but the scope of protection of the present application is not limited. Unless otherwise specified, the experimental methods used in the present application are conventional methods, and the experimental apparatus, materials, reagents, etc. used can be obtained from commercial channels.

[0036] Example 1

[0037] A preparation method of a water-based zinc ion battery negative electrode coating material;

[0038] (1) 4-diethylaminosalicylaldehyde (10 g), diethyl malonate (16 g) and 3 ml of piperidine in 20 ml of ethanol solution were heated to reflux at 80°C for 4 hours. After the complete reaction of the raw materials was detected by thin layer chromatography analysis, it was cooled to room temperature, poured into 90 ml of ice water at 0°C, and filtered and dried to obtain compound LX-1.

[0039] (2) The synthesized compound LX-1 (4 g) was stirred with 4 ml of hydrazine hydrate in 50 ml of ethanol solution at room temperature (25°C) until a large amount of yellow solid was precipitated. The compound LX-2 was obtained by filtering and drying.

[0040] (3) The synthesized compound LX-2 (1 g) was heated to reflux with phenyl methyl isothiocyanate (0.74 g) in 30 ml of ethanol solution at 80°C for 4 hours. After the complete reaction of the raw materials was detected by thin layer chromatography analysis, the target product LXB was obtained by filtering and drying. 1H-NMR (500 MHz, DMSO-d6): δ (ppm) 10.03 (s, 1H, -NH-), 9.53 (s, 1H, -NH-), 8.72 (s, 1H, -ArH), 8.61 (s, 1H, -NH-), 7.73 (d, 1H, J = 9.05, -ArH), 7.30 (s, 4H, -ArH), 7.22 (s, 1H, -ArH), 6.83 (s, 1H, -ArH), 6.65 (s, 1H, -ArH), 4.72 (d, 2H, J = 5.75), 3.49 (q, 4H, J = 7 Hz, -NCH2CH3), 1.14 (t, 6H, J = 7 Hz, -NCH2CH3). 13 C-NMR (125 MHz, DMSO-d6): δ (ppm) 161.7, 157.9, 153.2, 148.7, 139.7, 132.3, 128.6, 127.5, 127.13, 114.4, 110.8, 108.0, 105.6, 99.5, 96.3, 47.23, 44.85, 12.79.

[0041] (4) Compound LXB was mixed with PVDF at a mass ratio of 5:1, then 2 ml of N-methyl pyrrolidone (NMP) was added dropwise to mix uniformly in a mortar, and a film coating machine was used to uniformly coat it on the surface of zinc foil with a thickness of 8 nm to prepare a zinc ion battery negative electrode coating material LXB@Zn.

[0042] Comparative Example 1

[0043] The metal zinc foil was not treated and was named Bare Zn. The thickness of the zinc foil used was 80 μm.

[0044] Application Example 1

[0045] The negative electrode material LXB@Zn of the zinc ion battery prepared in Example 1 was used as the negative electrode, and copper foil was used as the positive electrode, and the two were assembled into a half battery, and the electrolyte was a 2 mol / L zinc sulfate solution for charge-discharge cycle test.

[0046] Application Comparative Example 1

[0047] The zinc foil prepared in Comparative Example 1 was used as the negative electrode, and copper foil was used as the positive electrode, and the two were assembled into a half battery, and the electrolyte was a 2 mol / L zinc sulfate solution for charge-discharge cycle test.

[0048] Test method: The half battery was tested under the experimental conditions of a current density of 5 mA / cm 2 , a capacity cutoff of 1 mAh·cm -2 .

[0049] Test results:

[0050] As Figure 2 : LXB@Zn prepared in Example 1 has a contact angle less than Bare Zn prepared in Comparative Example 1, which is a hydrophilic material, and is beneficial to the deposition and stripping of zinc ions in the electrolyte.

[0051] As Figure 3 : LXB@Zn prepared in Example 1 has an impedance less than Bare Zn prepared in Comparative Example 1.

[0052] As Figure 4 : LXB@Zn prepared in Example 1 still has a high coulombic efficiency (CE) after 560 cycles of half-cell charge and discharge, while the efficiency of Bare Zn prepared in Comparative Example 1 deteriorates after 100 cycles.

[0053] The above-described embodiments are merely preferred embodiments of the present application and are not all the embodiments that can be implemented by the present application. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present application should be considered to be within the scope of the claims of the present application.

Claims

1. A method for preparing a negative electrode coating material for aqueous zinc-ion batteries, characterized by, The specific steps are: (1) Synthesizing a new compound LXB by introducing benzyl isothiocyanate into the coumarin system; (2) Mixing the compound LXB with polyvinylidene fluoride (PVDF) at a mass ratio of 5:1, then adding 5-10 drops of N-methyl pyrrolidone (NMP), mixing uniformly with a mortar, and uniformly coating the zinc foil surface with a film applicator to a thickness of 5-10 nm to prepare a zinc ion battery negative electrode coating material LXB@Zn; The specific structural formula of the compound LXB is as follows:

2. The preparation method of the aqueous zinc ion battery negative electrode coating material according to claim 1, characterized in that, The specific preparation method of the compound LXB used in the aqueous zinc ion battery negative electrode coating material LXB@Zn is as follows: S1: 4-diethylaminosalicylaldehyde and diethyl malonate are heated to reflux in an ethanol solution to obtain compound LX-1; S2: The synthesized compound LX-1 is stirred with hydrazine hydrate in an ethanol solution at room temperature until solid precipitates to obtain compound LX-2; S3: The synthesized compound LX-2 is heated to reflux with benzyl isothiocyanate in an ethanol solution to obtain the target compound LXB; The preparation reaction formula is as follows:

3. The method for preparing an aqueous zinc-ion battery negative electrode coating material as described in claim 2, characterized in that, In step S1, the mass ratio of 4-diethylaminosalicylaldehyde to diethyl malonate is 1:1-1:

3.

4. The method for preparing an aqueous zinc-ion battery negative electrode coating material as described in claim 2, characterized in that, In step S2, 0.5-2 grams of compound LX-1 is reacted with 1 milliliter of hydrazine hydrate.

5. The method for preparing an aqueous zinc-ion battery negative electrode coating material as described in claim 2, characterized in that, In step S3, the mass ratio of compound LX-2 to benzyl isothiocyanate is 1:0.7-1:

2.

6. The method for preparing an aqueous zinc-ion battery negative electrode coating material as described in claim 2, characterized in that, In step S1, the refluxing is carried out at a heating temperature of 70-90°C for 4 hours.

7. The method for preparing an aqueous zinc-ion battery negative electrode coating material as described in claim 2, characterized in that, In step S2, the room temperature is 20-30°C.

8. The method for preparing an aqueous zinc-ion battery negative electrode coating material as described in claim 2, characterized in that, In step S3, the refluxing is carried out at a heating temperature of 70-90°C for 4 hours.

9. The aqueous zinc ion battery negative electrode coating material LXB@Zn prepared by the preparation method of any one of claims 1-8 is applied in an aqueous zinc ion battery negative electrode.

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