Aqueous zinc ion battery negative electrode coating material and preparation method and application thereof

Abstract

The invention belongs to the technical field of aqueous zinc ion batteries, and discloses an aqueous zinc ion battery negative electrode coating material and a preparation method and application thereof. Coumarin hydrazide reacts with benzyl isothiocyanate to generate a multi-nitrogen-oxygen-sulfur heteroatom ligand capable of coordinating with zinc ions, and the required aqueous zinc ion battery negative electrode coating material LXB-Zn is further prepared by doping with polyvinylidene fluoride. The synthesized aqueous zinc ion battery negative electrode coating material contains imino groups and heteroatoms S, O and N, can inhibit a hydrogen evolution reaction and provides more active sites, so that dendrites and side reactions are inhibited, and the cycling stability of an aqueous zinc ion battery is effectively improved. In order to solve the problem that an organic coating of a water-based zinc ion battery negative electrode is difficult to prepare, the organic coating of the water-based zinc ion battery negative electrode is prepared by adopting a simple method of adding an adhesive.

Description

Technical Field

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

[0002] Aqueous zinc-ion batteries use water as electrolyte, and the reserves of zinc, the negative electrode material, are relatively abundant. Compared with other batteries, aqueous zinc-ion batteries have the advantages of high safety, good environmental protection, low cost, moderate energy density, and fast charging speed. They are a new type of battery with broad application prospects. However, the chemical activity of zinc makes it susceptible to corrosion and hydrogen evolution reaction, and produces passivation byproducts such as zinc hydroxysulfate, which makes it very easy to cause dendrite growth. In extreme cases, zinc dendrites may penetrate the diaphragm, causing internal short circuits, thereby greatly shortening the life of the battery. Therefore, regulating the uniform deposition of zinc and effectively preventing hydrogen evolution and corrosion reactions are of great value to improving the electrochemical performance of aqueous zinc-ion batteries.

[0003] In order to improve the interfacial stability and cycle life of zinc negative electrodes, constructing artificial coatings on the zinc surface has become a hot topic of research. At present, the coating materials of aqueous zinc-ion batteries mainly include inorganic coating materials, organic coating materials, carbonyl coating materials, polymer coatings, metal-organic framework materials, etc. Compared with other materials, organic coating materials have the advantages of chemical stability, adjustability, good flexibility and mechanical properties, interface adaptability, promoting uniform deposition of zinc ions, and improving electrochemical performance. Organic coating materials can be chemically or physically adsorbed on the surface of zinc negative electrodes to prevent direct contact between the metal zinc negative electrode and the electrolyte, thereby inhibiting the dendrites and corrosion of the metal zinc negative electrode and improving the cycle stability and performance of zinc batteries. However, organic coatings generally have poor ionic conductivity, which limits their application in zinc-ion batteries. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a water-based zinc ion battery negative electrode coating material and its preparation method and application for the growth of zinc negative electrode dendrites and hydrogen evolution. Coumarin hydrazide is reacted with benzyl isothiocyanate to generate a multi-nitrogen oxygen sulfur heteroatom ligand that can coordinate with zinc ions, and further doped with polyvinylidene fluoride to prepare the required water-based zinc ion battery negative electrode coating material LXB@Zn. The synthesized water-based zinc ion battery negative electrode coating material contains imino groups, heteroatoms S, O, and N, which can inhibit hydrogen evolution reaction and provide more active sites, thereby inhibiting dendrites and side reactions, thereby effectively improving the cycle stability of water-based zinc ion batteries. In order to solve the problem of difficulty in preparing organic coatings for negative electrodes of water-based zinc ion batteries, the present invention adopts a simple method of adding an adhesive to prepare the organic coating of water-based zinc ion negative electrodes.

[0005] The above object of the present invention is achieved through the following technical solutions:

[0006] A method for preparing a negative electrode coating material for an aqueous zinc ion battery, comprising the following specific steps:

[0007] (1) A new compound LXB was synthesized by introducing benzyl isothiocyanate into the coumarin system.

[0008] (2) The compound LXB is mixed with polyvinylidene fluoride (PVDF) in a mass ratio of 5:1, and then 5-10 drops of N-methylpyrrolidone (NMP) are added and mixed evenly in a mortar. The mixture is evenly coated on the surface of zinc foil with a coating machine to a thickness of 5-10 nm to prepare the zinc ion battery negative electrode coating material LXB@Zn.

[0009] The specific structural formula of compound LXB is as follows:

[0010]

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

[0012] S1: 4-Diethylamino salicylaldehyde and diethyl malonate were heated under reflux in ethanol solution to obtain compound LX-1.

[0013] S2: The synthesized compound LX-1 and hydrazine hydrate are stirred in an ethanol solution at room temperature until a solid is precipitated to obtain compound LX-2.

[0014] S3: The synthesized compound LX-2 and benzyl isothiocyanate are heated to reflux in an ethanol solution to obtain the target compound LXB.

[0015] The preparation reaction is as follows:

[0016]

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

[0018] Furthermore, in step S2, each milliliter of hydrazine hydrate reacts with 0.5-2 grams of compound LX-1.

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

[0020] Furthermore, in step S1, reflux is performed at a heating temperature of 70-90° C. for 4 hours.

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

[0022] Furthermore, in step S3, reflux is performed at a heating temperature of 70-90° C. for 4 hours.

[0023] The present invention also requests protection for the application of the above-mentioned aqueous zinc ion battery negative electrode coating material LXB@Zn in the negative electrode of aqueous zinc ion batteries. The introduction of benzyl isothiocyanate adds imino groups and multiple nitrogen, oxygen and sulfur heteroatoms to the negative electrode coating material of zinc ion batteries, solves the problems of zinc negative electrode dendrite growth and hydrogen evolution in current zinc ion batteries, and significantly improves battery performance. Through contact angle measurement, it is found that LXB@Zn has better hydrophilicity than bare zinc, and the half-cell charge and discharge cycle number prepared with LXB@Zn can reach 560 times, which is more than five times the cycle number of bare zinc half-cell, and its electrical impedance is also significantly lower than that of bare zinc batteries.

[0024] The present invention adopts a large π-bond coumarin molecule with a push-pull electron system as an organic coating, which has an electron-withdrawing carbonyl group and an electron-donating diethylamine group in one. The push-pull electron system can better perform electron transmission, and at the same time, multiple nitrogen, oxygen and sulfur heteroatoms are introduced into the coumarin, so that it can be well coordinated with zinc ions, thereby inhibiting zinc corrosion, and inducing zinc ions to be uniformly deposited on the surface of the negative electrode, thereby inhibiting the formation of dendrites.

[0025] The beneficial effects of the present invention compared with the prior art are:

[0026] (1) The present invention utilizes the imino group contained in the synthetic compound LXB, and the imino group can react with H in the electrolyte. + The combination can inhibit the hydrogen evolution reaction and effectively improve the cycle stability of aqueous zinc ion batteries.

[0027] (2) The present invention utilizes the heteroatoms S, O, and N in the synthetic compound LXB, and the lone pair of electrons contained therein can form a coordination compound with the zinc ions in the electrolyte, thereby inhibiting the side reaction between water and zinc to form [Zn(H2O)6] 2+ , which improves the transmission efficiency of zinc ions in the electrolyte and effectively improves the cycle stability of aqueous zinc ion batteries.

[0028] (3) The present invention utilizes the fact that the synthetic compound LXB contains more active nitrogen sites, which can provide more active sites for the deposition and stripping of zinc ions during the cyclic charge and discharge process, thereby preventing the zinc ions from being deposited too concentratedly and inhibiting the formation of zinc ion dendrites. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The surface morphology of LXB prepared in Example 1 of the present invention under an optical microscope is 100 times (as shown in Figure a) and 200 times (as shown in Figure b).

[0030] Figure 2 The contact angle diagrams are shown for LXB@Zn prepared in Example 1 (as shown in FIG. b) and Bare Zn prepared in Comparative Example 1 (as shown in FIG. a).

[0031] Figure 3 Impedance diagram of the symmetrical battery of LXB@Zn prepared in Example 1 and Bare Zn prepared in Comparative Example 1.

[0032] Figure 4 Cyclic charge and discharge diagrams of half-cells of LXB@Zn prepared in Example 1 and Bare Zn prepared in Comparative Example 1.

[0033] Figure 5 Proton 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 invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0036] Example 1

[0037] A method for preparing a negative electrode coating material for an aqueous zinc ion battery;

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

[0039] (2) The synthesized compound LX-1 (4 g) and 4 ml of hydrazine hydrate in 50 ml of ethanol solution were stirred at room temperature (25° C.) until a large amount of yellow solid precipitated, which was filtered and dried to obtain compound LX-2.

[0040] (3) The synthesized compound LX-2 (1 g) and benzyl isothiocyanate (0.74 g) were heated to reflux at 80° C. for 4 hours in 30 ml of ethanol solution. After the reaction of the raw materials was completed, the product was filtered and dried to obtain the target product LXB. 1H-NMR (500MHz, 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=7Hz,-NCH2CH3),1.14(t,6H,J=7Hz,-NCH2CH3). 13 C-NMR (125MHz, 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 and PVDF were mixed at a mass ratio of 5:1, and then 2 ml of N-methylpyrrolidone (NMP) was added dropwise and mixed evenly in a mortar. The mixture was evenly coated on the surface of zinc foil with a coating machine to 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 the copper foil was used as the positive electrode. The two were assembled into a half-cell, wherein the electrolyte was a 2 mol / L zinc sulfate solution for charge and discharge cycle testing.

[0046] Application Comparative Example 1

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

[0048] Test method: At a current density of 5 mA / cm 2 、Capacity cutoff 1mAh·cm -2 The half-cell test was carried out under experimental conditions.

[0049] Test results:

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

[0051] like Figure 3 : The impedance of LXB@Zn prepared in Example 1 is lower than that of Bare Zn prepared in Comparative Example 1.

[0052] like Figure 4 The coulombic efficiency (CE) of the LXB@Zn half-cell prepared in Example 1 remained at a relatively high efficiency after 560 charge and discharge cycles, while the efficiency of the Bare Zn half-cell prepared in Comparative Example 1 deteriorated after 100 charge and discharge cycles.

[0053] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a negative electrode coating material for an aqueous zinc ion battery, characterized in that: The specific steps are: (1) A new compound LXB was synthesized by introducing benzyl isothiocyanate into the coumarin system. (2) Compound LXB and polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 5:1, and then 5-10 drops of N-methylpyrrolidone (NMP) were added, mixed evenly with a mortar, and coated evenly on the surface of zinc foil with a coating machine to a thickness of 5-10 nm to prepare a zinc ion battery negative electrode coating material LXB@Zn; The specific structural formula of compound LXB is as follows:

2. The method for preparing a negative electrode coating material for an aqueous zinc ion battery according to claim 1, wherein: The specific preparation method of the compound LXB used in the aqueous zinc ion battery negative electrode coating material LXB@Zn is: S1: 4-diethylamino salicylaldehyde and diethyl malonate were heated under reflux in an ethanol solution to obtain compound LX-1; S2: Stir the synthesized compound LX-1 and hydrazine hydrate in an ethanol solution at room temperature until a solid precipitates to obtain a compound LX-2; S3: heating the synthesized compound LX-2 and benzyl isothiocyanate under reflux in an ethanol solution to obtain the target compound LXB; The preparation reaction is as follows:

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

3.

4. The method for preparing a negative electrode coating material for an aqueous zinc ion battery as claimed in claim 2, wherein: In step S2, 0.5-2 g of compound LX-1 is reacted with each ml of hydrazine hydrate.

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

2.

6. The method for preparing a negative electrode coating material for an aqueous zinc ion battery as claimed in claim 2, wherein: In step S1, reflux is performed at a heating temperature of 70-90°C for 4 hours.

7. The method for preparing a negative electrode coating material for an aqueous zinc ion battery as claimed in claim 2, wherein: In step S2, the normal temperature is 20-30°C.

8. A method for preparing a negative electrode coating material for an aqueous zinc ion battery as claimed in claim 2, characterized in that: In step S3, reflux is performed at a heating temperature of 70-90°C for 4 hours.

9. Application of the aqueous zinc ion battery negative electrode coating material LXB@Zn prepared by the preparation method according to any one of claims 1 to 8 in the negative electrode of an aqueous zinc ion battery.

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