Zinc-cobalt alloy in eutectic ionic liquid as well as preparation method and application of zinc-cobalt alloy

Abstract

The invention discloses a zinc-cobalt alloy in eutectic ionic liquid as well as a preparation method and application of the zinc-cobalt alloy, and belongs to the field of zinc ion batteries. The preparation method comprises the following steps: adding a cobalt salt precursor into a eutectic ionic liquid, fully stirring to obtain an ionic liquid-cobalt salt composite solution, controlling the temperature, carrying out replacement deposition, washing a replacement product with absolute ethyl alcohol and deionized water, and drying to obtain the cobalt-cobalt-ion-liquid composite material. The invention not only provides a simple and efficient synthesis method for the zinc-cobalt alloy, but also can effectively solve the common problems of zinc dendrite growth and the like of the zinc ion battery when the zinc-cobalt alloy provided by the invention is used as the anode of the zinc ion battery.

Description

TECHNICAL FIELD

[0001] The application relates to a zinc-cobalt alloy in a eutectic ionic liquid and a preparation method and application thereof, and belongs to the field of zinc ion batteries. BACKGROUND

[0002] Aqueous zinc ion batteries have become a promising energy storage technology due to their low cost, high biological safety and relatively stable physical and chemical properties. The metal zinc (Zn) anode is an attractive candidate for ion batteries due to its high theoretical capacity, suitable redox potential and natural abundance. However, the zinc metal anode is susceptible to dendrite growth and side reactions, resulting in low coulombic efficiency and rapid performance degradation of the battery. It is of great practical significance and wide application value to construct a suitable interface layer to cope with these challenges and achieve high-performance zinc ion batteries. Cobalt (Co) is a transition metal known for its excellent biocompatibility and electrical conductivity, making it very suitable for energy storage devices. Zinc-cobalt (ZnCo) alloy has a theoretical capacity of up to 1014mA h g -1 , is corrosion resistant, can improve structural stability, effectively suppress zinc ion battery dendrite growth, and significantly improve the application potential of zinc ion batteries.

[0003] Traditional methods for preparing zinc-cobalt alloy mainly include solvothermal method, hydrothermal method, liquid phase method and electrodeposition method. These methods often have the disadvantages of high temperature, high energy consumption, difficult controllability, high environmental damage, high equipment and technology requirements, difficult performance control, and no obvious improvement in coulombic efficiency of the prepared zinc-cobalt alloy. The application proposes a method for preparing zinc-cobalt alloy by displacement deposition in a eutectic ionic liquid as an anode material for zinc ion batteries, which has the characteristics of mild conditions, simple operation and easy control. The prepared zinc-cobalt alloy material has good performance in suppressing zinc dendrite growth and stabilizing battery charging and discharging in the assembled zinc battery. SUMMARY

[0004] In order to overcome the problems in the background art, the purpose of the application is to provide a zinc-cobalt alloy in a eutectic ionic liquid and a preparation method and application thereof.

[0005] In order to achieve the above-mentioned purpose, the application is realized by the following technical scheme:

[0006] A preparation method of a zinc-cobalt alloy in a eutectic ionic liquid, comprising the following steps:

[0007] (1) adding cobalt salt into a eutectic ionic liquid and heating and stirring to obtain an ionic liquid-cobalt salt composite solution;

[0008] (2) soaking zinc sheet in anhydrous ethanol, repeatedly washing with water, polishing with sandpaper and polishing with nano-sized aluminum oxide to obtain a clean treated zinc sheet;

[0009] (3) The cleaned zinc sheet is used as a substrate, and is placed in a constant-temperature ion liquid-cobalt salt composite solution for displacement deposition. After the displacement deposition, the substrate is washed with anhydrous ethanol and water, and dried, so that a zinc-cobalt alloy film is obtained on the surface of the substrate.

[0010] More preferably, the cobalt salt is cobalt chloride hexahydrate, cobalt nitrate hexahydrate or cobalt sulfate heptahydrate; and the eutectic ionic liquid is choline chloride-ethylene glycol ionic liquid, choline chloride-urea ionic liquid, betaine hydrochloride-ethylene glycol ionic liquid, betaine hydrochloride-urea ionic liquid, choline chloride-betaine hydrochloride-ethylene glycol ionic liquid or choline chloride-betaine hydrochloride-urea ionic liquid.

[0011] More preferably, the solid-liquid ratio of the cobalt salt to the eutectic ionic liquid is 0.1-1.0 mol / L, and the concentration of the cobalt salt in the ion liquid-cobalt salt composite solution is 0.1-2 mol / L.

[0012] More preferably, the preparation method of the eutectic ionic liquid comprises:

[0013] The preparation method of the choline chloride-ethylene glycol ionic liquid comprises: drying choline chloride and ethylene glycol respectively, mixing them, and heating and stirring until the white solid powder becomes a colorless transparent solution, so that the choline chloride-ethylene glycol ionic liquid is obtained; the molar ratio of the choline chloride to the ethylene glycol is 1:(1-4).

[0014] The preparation method of the choline chloride-urea ionic liquid comprises: drying choline chloride and urea respectively, mixing them, and heating and stirring until the white solid powder becomes a colorless transparent solution, so that the choline chloride-urea ionic liquid is obtained; the molar ratio of the choline chloride to the urea is 1:(1-4).

[0015] The preparation method of the betaine hydrochloride-ethylene glycol ionic liquid comprises: drying betaine hydrochloride and ethylene glycol respectively, mixing them, and heating and stirring until the white solid powder becomes a colorless transparent solution, so that the betaine hydrochloride-ethylene glycol ionic liquid is obtained; the molar ratio of the betaine hydrochloride to the ethylene glycol is 1:(1-4).

[0016] The preparation method of the betaine hydrochloride-urea ionic liquid comprises: drying betaine hydrochloride and urea respectively, mixing them, and heating and stirring until the white solid powder becomes a colorless transparent solution, so that the betaine hydrochloride-urea ionic liquid is obtained; the molar ratio of the betaine hydrochloride to the urea is 1:(1-4).

[0017] The preparation method of the choline chloride-betaine hydrochloride-ethylene glycol ionic liquid comprises the following steps: drying choline chloride, betaine hydrochloride and ethylene glycol respectively, then mixing them, and then placing them in a conical flask and heating and stirring in an oil bath until the solid powder is completely dissolved into a colorless transparent solution, so as to obtain the choline chloride-betaine hydrochloride-ethylene glycol ionic liquid; the molar ratio of the choline chloride, the betaine hydrochloride and the ethylene glycol is 1:(0.5-1):(1-4).

[0018] The preparation method of the choline chloride-betaine hydrochloride-urea ionic liquid comprises the following steps: drying choline chloride, betaine hydrochloride and urea respectively, then mixing them, and then placing them in a conical flask and heating and stirring in an oil bath until the solid powder is completely dissolved into a colorless transparent solution, so as to obtain the choline chloride-betaine hydrochloride-urea ionic liquid; the molar ratio of the choline chloride, the betaine hydrochloride and the urea is 1:(0.5-1):(1-4).

[0019] More preferably, the temperature of the isothermal displacement deposition is 298K-373K, and the time is 2-240min.

[0020] More preferably, in the step (1), water or anhydrous ethanol is added into the ionic liquid-cobalt salt composite solution; the volume ratio of the water or the anhydrous ethanol to the eutectic ionic liquid is 1:10.

[0021] The application also claims to protect the zinc-cobalt alloy electrode prepared by the preparation method of the zinc-cobalt alloy in the eutectic ionic liquid.

[0022] The application also claims to protect a zinc ion battery comprising the zinc-cobalt alloy electrode as an anode in the zinc ion battery.

[0023] The zinc-cobalt alloy electrode prepared by the eutectic ionic liquid displacement deposition can expose more zinc (002) crystal surface deposition sites in the charging and discharging process. The zinc-cobalt alloy can be preferentially adsorbed on the surface of the zinc sheet, increase the interface migration energy barrier, inhibit the growth of dendrites, and thus improve the corrosion resistance. At the same time, the zinc (002) crystal surface has smooth atomic arrangement and low surface energy, which is beneficial to the uniform deposition of Zn 2+ and better corrosion resistance. The eutectic ionic liquid can change the surface growth of the zinc electrode, and thus significantly improve the charging and discharging reversibility and the cycle stability of the battery. Most importantly, the eutectic ionic liquid can reconstruct the Zn 2+ solvation structure, reduce the water content in the first solvation shell, reduce the reaction activity of free water, inhibit the hydrogen evolution reaction, and thus stabilize the zinc ion battery. The eutectic ionic liquid can be in-situ polymerized on the surface of the zinc negative electrode to form a Zn 2+ protective layer, reduce the side reaction between zinc and electrolyte, control the deposition of Zn 2+ on the surface of the zinc foil, and promote a more stable stripping / plating process.

[0024] The present application has the advantages that the zinc-cobalt alloy electrode obtained by the constant temperature replacement of the eutectic ionic liquid has high safety, high stability and strong corrosion resistance, and has the advantage of low cost, and the zinc-cobalt alloy electrode is assembled into a zinc ion battery as an anode, and after long cycle 1000 hours of stability charge and discharge, shows high reversibility and inhibits the growth of zinc dendrites. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The physical map of the zinc-cobalt alloy electrode material prepared in Example 1, Example 3, Example 5, Example 6, (a) is the physical map of the zinc-cobalt alloy electrode material prepared in Example 1; (b) is the physical map of the zinc-cobalt alloy electrode material prepared in Example 3; (c) is the physical map of the zinc-cobalt alloy electrode material prepared in Example 5; (d) is the physical map of the zinc-cobalt alloy electrode material prepared in Example 6.

[0026] Figure 2 The battery stability test chart of the zinc ion battery assembled by the zinc-cobalt alloy electrode material prepared in Example 1.

[0027] Figure 3 The scanning electron microscope chart of the zinc-cobalt alloy electrode material prepared in Example 1.

[0028] Figure 4 The X-ray fluorescence spectrum chart of the zinc-cobalt alloy electrode material prepared in Example 1.

[0029] Figure 5 The battery stability test chart of the zinc ion battery assembled by the zinc-cobalt alloy electrode material prepared in Example 2.

[0030] Figure 6 The battery stability test chart of the zinc ion battery assembled by the zinc-cobalt alloy electrode material prepared in Example 3.

[0031] Figure 7 The battery stability test chart of the zinc ion battery assembled by the zinc-cobalt alloy electrode material prepared in Example 4.

[0032] Figure 8 The battery stability test chart of the zinc ion battery assembled by the zinc-cobalt alloy electrode material prepared in Example 5.

[0033] Figure 9 The battery stability test chart of the zinc ion battery assembled by the zinc-cobalt alloy electrode material prepared in Example 7.

[0034] Figure 10The battery stability test chart of the zinc ion battery assembled with the zinc-cobalt alloy electrode material prepared in Example 8. DETAILED DESCRIPTION

[0035] The application will be further described in connection with the specific embodiments. However, the scope of the application is not limited thereto.

[0036] A preparation method of a zinc-cobalt alloy electrode material, comprising the following steps:

[0037] (1) adding a cobalt salt into a eutectic ionic liquid to obtain an ionic liquid-cobalt salt composite solution through heating and stirring.

[0038] Preparation of the eutectic ionic liquid:

[0039] a. Preparation of choline chloride-ethylene glycol ionic liquid: choline chloride and ethylene glycol are dried and sealed for standby, mixed according to a certain amount of molar ratio, then placed in an Erlenmeyer flask and heated and stirred in an oil bath until the white solid powder becomes a colorless transparent solution, i.e. choline chloride-ethylene glycol ionic liquid is obtained; the molar ratio of choline chloride and ethylene glycol is 1:(1-4); the heating and stirring conditions can be selected at a temperature of 30-100℃ and a time of 2-40min, as a typical but non-limiting example, in the following examples of the application, the heating can be performed for the purpose of dissolving the solid, and the specific heating temperature and heating time can be adjusted according to the actual situation, which will not affect the product performance.

[0040] b. Preparation of choline chloride-urea ionic liquid: choline chloride and urea are dried and sealed for standby, mixed according to a certain amount of molar ratio, then placed in an Erlenmeyer flask and heated and stirred in an oil bath until the white solid powder becomes a colorless transparent solution, i.e. choline chloride-urea ionic liquid is obtained; the molar ratio of choline chloride and urea is 1:(1-4); the heating and stirring conditions can be selected at a temperature of 70-100℃ and a time of 2-40h, as a typical but non-limiting example, in the following examples of the application, the heating can be performed for the purpose of dissolving the solid, and the specific heating temperature and heating time can be adjusted according to the actual situation, which will not affect the product performance.

[0041] c. Preparation of betaine hydrochloride-ethylene glycol ionic liquid: betaine hydrochloride and ethylene glycol are dried and sealed respectively, mixed according to a certain amount of molar ratio, then placed in a conical flask and heated and stirred in an oil bath until the white solid powder becomes a colorless transparent solution, i.e. betaine hydrochloride-ethylene glycol ionic liquid is obtained; the molar ratio of betaine hydrochloride and ethylene glycol is 1:(1-4); the heating and stirring conditions can be selected at a temperature of 60-100℃ for 2-40h, as a typical but non-limiting example, in the following examples of the present application, the heating can be carried out for the purpose of achieving solid dissolution, and the specific heating temperature and heating time can be adjusted according to the actual situation, which will not affect the product performance.

[0042] d. The preparation steps of the betaine hydrochloride-urea ionic liquid include: mixing betaine hydrochloride and urea after drying, heating and stirring until the white solid powder becomes a colorless transparent solution, i.e. betaine hydrochloride-urea ionic liquid is obtained; the molar ratio of betaine hydrochloride and urea is 1:(1-4); the heating and stirring conditions can be selected at a temperature of 70-100℃ for 2-10h, as a typical but non-limiting example, in the following examples of the present application, the heating can be carried out for the purpose of achieving solid dissolution, and the specific heating temperature and heating time can be adjusted according to the actual situation, which will not affect the product performance.

[0043] e. The preparation steps of the choline chloride-betaine hydrochloride-ethylene glycol ionic liquid include: mixing choline chloride, betaine hydrochloride and ethylene glycol after drying, heating and stirring until the white solid powder becomes a colorless transparent solution, i.e. choline chloride-betaine hydrochloride-ethylene glycol ionic liquid is obtained; the molar ratio of choline chloride, betaine hydrochloride and ethylene glycol is 1:(0.5-1):(1-4). The heating and stirring conditions can be selected at a temperature of 70-100℃ for 2-10h, as a typical but non-limiting example, in the following examples of the present application, the heating can be carried out for the purpose of achieving solid dissolution, and the specific heating temperature and heating time can be adjusted according to the actual situation, which will not affect the product performance.

[0044] f.The preparation steps of the choline chloride-betaine hydrochloride-urea ionic liquid include: drying choline chloride, betaine hydrochloride and urea respectively, then mixing them according to the molar ratio of 1:(0.5-1):(1-4), then placing them in a conical flask and heating and stirring in an oil bath until the solid powder is completely dissolved into a colorless transparent solution, thereby obtaining the choline chloride-betaine hydrochloride-urea ionic liquid; the heating and stirring conditions can be selected at a temperature of 70-100℃ for 2-20h, as a typical but non-limiting example, in the following examples of the present application, the heating can be performed as long as the purpose of solid dissolution is achieved, and the specific heating temperature and heating time can be adjusted according to the actual situation, which will not affect the performance of the product.

[0045] (2) Surface treatment of the substrate: zinc sheet (1.0 cm x 1.0 cm x 0.1 cm) was used as the substrate, and the surface of the zinc sheet was treated by soaking in anhydrous ethanol (concentration of 95%, soaking for 10 min), rinsing with deionized water, and polishing with nano-alumina.

[0046] (3) Constant temperature displacement deposition: under the condition of a temperature of 298-373K, the substrate with surface pretreatment in step (2) was used as the working substrate, and was placed in the ionic liquid-cobalt salt composite solution prepared in step (1) for displacement deposition for 0.1-10h. The substrate after displacement deposition was rinsed with anhydrous ethanol and deionized water, and was dried to obtain a zinc-cobalt alloy thin film on the surface of the substrate.

[0047] In some embodiments, the cobalt salt in step (2) is cobalt chloride hexahydrate, cobalt nitrate hexahydrate, or cobalt sulfate heptahydrate.

[0048] In some embodiments, the concentration of the cobalt salt in the ionic liquid-cobalt salt composite solution in step (2) is 0.1-2mol / L. For example, in the following examples of the present application, the concentration of the cobalt salt in the ionic liquid-cobalt salt composite solution can be selected as 1mol / L.

[0049] The zinc-cobalt alloy electrode material can be obtained by the above method, and the zinc-cobalt alloy electrode material can be assembled into a zinc ion battery as a negative electrode, such as a Zn||Zn symmetric battery, a Zn||Cu symmetric battery, and a Zn||MnO2 full battery. The specific assembly method of the battery can be performed by using conventional operations in the art.

[0050] For example: the zinc-cobalt alloy electrode material is used as the negative electrode of the zinc ion battery, and is assembled into a zinc ion battery button cell according to the negative electrode shell-elastic sheet-gasket-zinc-cobalt alloy material-separator (dropping 2M zinc sulfate aqueous solution)-zinc sheet-positive electrode shell.

[0051] Example 1

[0052] A method for preparing zinc-cobalt alloy in a eutectic ionic liquid, comprising the following steps:

[0053] (1) Preparation of eutectic ionic liquid: choline chloride and ethylene glycol were dried respectively, then mixed according to the molar ratio of 1:3, then placed in a conical flask and heated and stirred in an 80℃ oil bath for 30min until the solid powder completely dissolved into a colorless transparent solution, i.e. choline chloride-ethylene glycol ionic liquid was obtained.

[0054] (2) 11.91g of cobalt chloride hexahydrate was added to a narrow-mouth bottle containing 50mL of choline chloride-ethylene glycol ionic liquid, and heated and stirred to obtain a cobalt salt composite electrolyte.

[0055] (3) Surface treatment of the substrate: zinc sheet (1.0cm×1.0cm×0.1cm) was used as the substrate, and the surface of the substrate was treated by soaking in anhydrous ethanol (concentration of 95%, soaking time of 10min), rinsing with deionized water, and polishing with nano-alumina.

[0056] (4) Constant temperature displacement deposition: under the condition of a temperature of 298K, the substrate with surface pretreatment in step (3) was used as the working substrate, and was placed in the cobalt salt composite electrolyte prepared in step (2) for displacement deposition for 10min, and then the sample after displacement deposition was rinsed with anhydrous ethanol and deionized water, and dried to obtain a zinc-cobalt alloy thin film on the surface of the substrate.

[0057] The specific morphology of the zinc-cobalt alloy electrode material prepared is a uniform and dense zinc-cobalt alloy thin film on the surface of the zinc sheet ( Figure 1 ), as can be seen from the scanning electron microscope image that the zinc-cobalt alloy coating grows uniformly on the surface of the zinc sheet ( Figure 3 ), and the energy dispersive X-ray spectrum further shows that the zinc-cobalt alloy obtained by displacement is uniformly distributed on the surface of the zinc sheet substrate ( Figure 4 ).

[0058] The battery stability test of the zinc ion battery assembled with the zinc-cobalt alloy electrode material as the negative electrode showed that the battery could still show a relatively regular curve shape after 500 hours of charge-discharge cycling at a current density of 5mA / cm 2 , indicating good battery stability ( Figure 2 ).

[0059] Example 2

[0060] A method for preparing zinc-cobalt alloy in a eutectic ionic liquid and its application, comprising the following steps:

[0061] (1) Preparation of the eutectic ionic liquid: After drying betaine hydrochloride and ethylene glycol respectively, mix them according to the molar ratio of 1:2, then place them in a conical flask and heat and stir in a 60℃ oil bath for 10h until the solid powder completely dissolves into a colorless transparent solution, which is the betaine hydrochloride and ethylene glycol ionic liquid.

[0062] (2) Take 14.55g of cobalt nitrate hexahydrate and add it to a narrow-mouth bottle containing 50mL of betaine hydrochloride and ethylene glycol ionic liquid, heat and stir to obtain a 1mol / L cobalt salt composite electrolyte.

[0063] (3) Surface treatment of the substrate: take zinc sheet (1.0cm x 1.0cm x 0.1cm) as the substrate, soak the zinc sheet in anhydrous ethanol (concentration of 95%, soak for 10min), rinse with deionized water, and polish the surface of the substrate with nano-level aluminum oxide.

[0064] (4) Constant temperature displacement deposition: under the condition of a temperature of 353K, take the surface pretreated substrate of step (3) as the working substrate, and place it in the cobalt salt composite electrolyte prepared in step (2) for displacement deposition for 10min, rinse the sample after displacement deposition with anhydrous ethanol and deionized water, and dry it to obtain a zinc-cobalt alloy thin film on the surface of the substrate. As a negative electrode, the zinc-cobalt alloy electrode material is assembled into a zinc ion battery, which still shows a relatively regular curve shape after 100 hours of charge-discharge cycling at a current density of 5mA / cm 2 , showing good battery stability Figure 5 .

[0065] Example 3

[0066] A method for preparing a zinc-cobalt alloy in a eutectic ionic liquid and its application, comprising the following steps:

[0067] (1) Preparation of the eutectic ionic liquid: After drying choline chloride and ethylene glycol respectively, mix them according to the molar ratio of 1:4, then place them in a conical flask and heat and stir in a 100℃ oil bath for 2min until the solid powder completely dissolves into a colorless transparent solution, which is the choline chloride-ethylene glycol ionic liquid.

[0068] (2) Take 14.05g of cobalt sulfate heptahydrate and add it to a narrow-mouth bottle containing 50mL of choline chloride-ethylene glycol ionic liquid, heat and stir to obtain a 1mol / L cobalt salt composite electrolyte.

[0069] (3) Surface treatment of the substrate: take zinc sheet (1.0cm x 1.0cm x 0.1cm) as the substrate, soak the zinc sheet in anhydrous ethanol (concentration of 95%, soak for 10min), rinse with deionized water, and polish the surface of the substrate with nano-level aluminum oxide.

[0070] (4) Constant temperature displacement deposition: under the condition of 298K, the surface pretreated substrate of step (3) is used as the working substrate, and is placed in the blue solution of 1 mol / L cobalt nitrate hexahydrate prepared in step (2) for displacement deposition for 10 min. The sample after displacement deposition is washed with anhydrous ethanol and deionized water, and dried to obtain a zinc-cobalt alloy thin film on the surface of the substrate.

[0071] The actual photo of the zinc-cobalt alloy electrode material prepared on the surface of the zinc sheet through displacement reaction is shown in FIG. 2. Figure 1 The zinc-cobalt alloy electrode material is assembled into a zinc ion battery as a negative electrode. Under the current density of 5 mA / cm 2 , the charge-discharge cycle of 250 hours still shows a relatively regular curve shape, showing good battery stability. Figure 6

[0072] Example 4

[0073] A method for preparing a zinc-cobalt alloy in a eutectic ionic liquid and application thereof, comprising the following steps:

[0074] (1) Preparation of a eutectic ionic liquid: choline chloride and urea are dried respectively, then mixed according to the molar ratio of 1:3, then placed in a conical flask and heated and stirred in a 70℃ oil bath for 20 h until the solid powder is completely dissolved into a colorless transparent solution, i.e. choline chloride-urea ionic liquid is obtained.

[0075] (2) 11.91 g of cobalt chloride hexahydrate is added to a narrow-mouth bottle containing 50 mL of choline chloride-urea ionic liquid, heated and stirred to obtain a 1 mol / L cobalt salt composite electrolyte.

[0076] (3) Surface treatment of the substrate: zinc sheet (1.0 cm x 1.0 cm x 0.1 cm) is used as the substrate, and the substrate surface is treated by soaking in anhydrous ethanol (concentration of 95%, soaking for 10 min), washing with deionized water, and polishing with nano-sized alumina.

[0077] (4) Constant temperature displacement deposition: under the condition of 373K, the surface pretreated substrate of step (3) is used as the working substrate, and is placed in the 1 mol / L cobalt salt-ionic liquid solution prepared in step (2) for displacement deposition for 20 min. The sample after displacement deposition is washed with anhydrous ethanol and deionized water, and dried to obtain a zinc-cobalt alloy thin film on the surface of the substrate.

[0078] The zinc-cobalt alloy electrode material is assembled into a zinc ion battery as a negative electrode. Under the current density of 5 mA / cm 2 , the charge-discharge cycle of 300 hours still shows a relatively regular curve shape, showing good battery stability. Figure 7

[0079] ​​Example 5

[0080] A method for preparing zinc-cobalt alloy in a eutectic ionic liquid and its application, comprising the following steps:

[0081] (1) Preparation of eutectic ionic liquid: dry choline chloride and urea respectively, then mix them according to the molar ratio of 1:2, then place them in a conical flask and heat and stir in a 100℃ oil bath for 40h until the solid powder completely dissolves into a colorless transparent solution, which is choline chloride-urea ionic liquid.

[0082] (2) Take 11.91g of cobalt chloride hexahydrate and add it to a narrow-mouth bottle containing 50mL of choline chloride-urea ionic liquid, heat and stir to obtain a 1mol / L cobalt salt composite electrolyte.

[0083] (3) Surface treatment of the substrate: take zinc sheet (1.0cm x 1.0cm x 0.1cm) as the substrate, soak the zinc sheet in anhydrous ethanol (concentration of 95%, soaking time of 10min), rinse with deionized water, and polish the substrate surface with nano-alumina.

[0084] (4) Constant temperature displacement deposition: under the condition of a temperature of 333K, take the surface pretreated substrate of step (3) as the working substrate, and place it in the 1mol / L cobalt salt-ionic liquid solution prepared in step (2) for displacement deposition for 2min, then rinse the sample after displacement deposition with anhydrous ethanol and deionized water, and dry it to obtain a zinc-cobalt alloy thin film on the surface of the substrate.

[0085] The actual photo of the zinc-cobalt alloy electrode material prepared on the surface of the zinc sheet through displacement reaction is shown in Figure 1 . The zinc-cobalt alloy electrode material is assembled into a zinc ion battery as a negative electrode, which still shows a relatively regular curve shape after 800 hours of charge and discharge cycling under a current density of 5mA / cm 2 , showing good battery stability Figure 8 .

[0086] Example 6

[0087] A method for preparing zinc-cobalt alloy in a eutectic ionic liquid and its application, comprising the following steps:

[0088] (1) Preparation of eutectic ionic liquid: dry choline chloride, betaine hydrochloride and urea respectively, then mix them according to the molar ratio of 1:1:3, then place them in a conical flask and heat and stir in a 70℃ oil bath for 2h until the solid powder completely dissolves into a colorless transparent solution, which is choline chloride-betaine hydrochloride-urea ionic liquid.

[0089] (2) Take 11.91 g of cobalt chloride hexahydrate and add it to a narrow-mouth bottle containing 50 mL of choline chloride-betaine hydrochloride-urea ionic liquid, heat and stir to obtain a 1 mol / L cobalt salt composite electrolyte.

[0090] (3) Surface treatment of the substrate: zinc pieces (1.0 cm x 1.0 cm x 0.1 cm) are used as the substrate, and the zinc pieces are immersed in anhydrous ethanol (95% concentration, 10 min), rinsed with deionized water, and polished with nano-alumina to treat the surface of the substrate.

[0091] (4) Constant temperature displacement deposition: under the condition of a temperature of 333 K, the surface pretreated substrate of step (3) is used as the working substrate, and is placed in the 1 mol / L cobalt salt-ionic liquid solution prepared in step (2) for displacement deposition for 240 min. The sample after displacement deposition is rinsed with anhydrous ethanol and deionized water, and dried to obtain a zinc-cobalt alloy thin film on the surface of the substrate.

[0092] A photograph of the actual zinc-cobalt alloy electrode material prepared on the surface of the zinc piece through displacement reaction is shown in FIG. 1. Figure 1

[0093] Example 7

[0094] A method for preparing a zinc-cobalt alloy in a eutectic ionic liquid and applications thereof, comprising the following steps:

[0095] (1) Preparation of a eutectic ionic liquid: choline chloride, betaine hydrochloride, and urea are dried separately, then mixed in a molar ratio of 1:1:3, placed in a conical flask, and heated and stirred in a 100°C oil bath for 20 h until the solid powder completely dissolves into a colorless transparent solution, i.e., a choline chloride-betaine hydrochloride-urea ionic liquid is obtained.

[0096] (2) Take 11.91 g of cobalt chloride hexahydrate and add it to a narrow-mouth bottle containing 50 mL of choline chloride-betaine hydrochloride-urea ionic liquid, heat and stir to obtain a 1 mol / L cobalt salt composite electrolyte.

[0097] (3) Surface treatment of the substrate: zinc pieces (1.0 cm x 1.0 cm x 0.1 cm) are used as the substrate, and the zinc pieces are immersed in anhydrous ethanol (95% concentration, 10 min), rinsed with deionized water, and polished with nano-alumina to treat the surface of the substrate.

[0098] (4) Constant temperature displacement deposition: under the condition of a temperature of 333 K, the surface pretreated substrate of step (3) is used as the working substrate, and is placed in the 1 mol / L cobalt salt-ionic liquid solution prepared in step (2) for displacement deposition for 240 min. The sample after displacement deposition is rinsed with anhydrous ethanol and deionized water, and dried to obtain a zinc-cobalt alloy thin film on the surface of the substrate. ​

[0099] Zinc-cobalt alloy electrode material as negative electrode assembled into zinc ion battery, at a current density of 5mA / cm 2 , still shows a relatively regular curve shape after 300 hours of charge-discharge cycle, showing good battery stability Figure 9 ).

[0100] Example 8

[0101] A method for preparing zinc-cobalt alloy in a eutectic ionic liquid and its application, comprising the following steps:

[0102] (1) Preparation of eutectic ionic liquid: dry choline chloride-betaine hydrochloride-ethylene glycol respectively, then mix according to the molar ratio of 1:(0.5-1):(1-4), then place in a conical flask and heat and stir in a 70℃ oil bath for 10h until the solid powder completely dissolves into a colorless transparent solution, i.e. choline chloride-betaine hydrochloride-urea ionic liquid is obtained.

[0103] (2) Take 14.55g of cobalt nitrate hexahydrate and add it to a narrow-mouth bottle containing 50mL of choline chloride-betaine hydrochloride-ethylene glycol ionic liquid, heat and stir to obtain a 1mol / L cobalt salt composite electrolyte.

[0104] (3) Surface treatment of the substrate: take zinc sheet (1.0cm x 1.0cm x 0.1cm) as the substrate, soak the zinc sheet in anhydrous ethanol (concentration of 95%, soak for 10min), rinse with deionized water, and polish the surface of the substrate with nano-sized aluminum oxide.

[0105] (4) Constant temperature displacement deposition: under the condition of a temperature of 333K, take the surface pretreated substrate of step (3) as the working substrate, and place it in the 1mol / L cobalt salt-ionic liquid solution prepared in step (2) for displacement deposition for 30min, rinse the sample after displacement deposition with anhydrous ethanol and deionized water, and dry to obtain a zinc-cobalt alloy thin film on the surface of the substrate.

[0106] Zinc-cobalt alloy electrode material as negative electrode assembled into zinc ion battery, at a current density of 5mA / cm 2 , still shows a relatively regular curve shape after 600 hours of charge-discharge cycle, showing good battery stability Figure 10 ).

[0107] Finally, it should be pointed out that the above preferred embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present application.

Claims

1. A method for producing a zinc-cobalt alloy in a deep eutectic solvent, characterized by: The method comprises the following steps: (1) adding a cobalt salt into a eutectic ionic liquid and heating and stirring to obtain an ionic liquid-cobalt salt composite solution; (2) soaking zinc sheets in anhydrous ethanol, repeatedly washing with water, polishing with sandpaper and polishing with nano-alumina to obtain clean zinc sheets; (3) taking the clean zinc sheets as a substrate, placing the substrate in the ionic liquid-cobalt salt composite solution for constant temperature displacement deposition, washing the substrate after displacement deposition with anhydrous ethanol and water, and drying to obtain a zinc-cobalt alloy film on the surface of the substrate.

2. The method for preparing zinc-cobalt alloy in a eutectic ionic liquid according to claim 1, characterized in that: The cobalt salt is cobalt chloride hexahydrate, cobalt nitrate hexahydrate or cobalt sulfate heptahydrate; the eutectic ionic liquid is choline chloride-glycol ionic liquid, choline chloride-urea ionic liquid, betaine hydrochloride-glycol ionic liquid, betaine hydrochloride-urea ionic liquid, choline chloride-betaine hydrochloride-glycol ionic liquid or choline chloride-betaine hydrochloride-urea ionic liquid.

3. The method for preparing zinc-cobalt alloy in a eutectic ionic liquid according to claim 1, characterized in that: The molar concentration of the cobalt salt in the ionic liquid-cobalt salt composite solution is 0.1-2.0 mol / L.

4. The method for preparing zinc-cobalt alloy in a eutectic ionic liquid according to claim 1, characterized in that: The preparation method of the eutectic ionic liquid comprises: The preparation method of the choline chloride-glycol ionic liquid comprises: drying choline chloride and glycol separately, mixing them, heating and stirring until the white solid powder turns into a colorless transparent solution, and then obtaining the choline chloride-glycol ionic liquid; the molar ratio of the choline chloride to the glycol is 1:(1-4); The preparation method of the choline chloride-urea ionic liquid comprises: drying choline chloride and urea separately, mixing them, heating and stirring until the white solid powder turns into a colorless transparent solution, and then obtaining the choline chloride-urea ionic liquid; the molar ratio of the choline chloride to the urea is 1:(1-4); The preparation method of the betaine hydrochloride-glycol ionic liquid comprises: drying betaine hydrochloride and glycol separately, mixing them, heating and stirring until the white solid powder turns into a colorless transparent solution, and then obtaining the betaine hydrochloride-glycol ionic liquid; the molar ratio of the betaine hydrochloride to the glycol is 1:(1-4); The preparation method of the betaine hydrochloride-urea ionic liquid comprises: drying betaine hydrochloride and urea separately, mixing them, heating and stirring until the white solid powder turns into a colorless transparent solution, and then obtaining the betaine hydrochloride-urea ionic liquid; the molar ratio of the betaine hydrochloride to the urea is 1:(1-4); The preparation method of the choline chloride-betaine hydrochloride-glycol ionic liquid comprises: drying choline chloride, betaine hydrochloride and glycol separately, mixing them, placing them in an Erlenmeyer flask and heating and stirring in an oil bath until the solid powder completely dissolves into a colorless transparent solution, and then obtaining the choline chloride-betaine hydrochloride-glycol ionic liquid; the molar ratio of the choline chloride to the betaine hydrochloride to the glycol is 1:(0.5-1):(1-4). The preparation method of the choline chloride-betaine hydrochloride-urea ionic liquid comprises the following steps: drying choline chloride, betaine hydrochloride and urea respectively, then mixing them, placing them in a conical flask and heating and stirring in an oil bath until the solid powder is completely dissolved into a colorless transparent solution, thereby obtaining the choline chloride-betaine hydrochloride-urea ionic liquid; the molar ratio of the choline chloride, the betaine hydrochloride and the urea is 1:(0.5-1):(1-4).

5. The method for preparing zinc-cobalt alloy in a eutectic ionic liquid according to claim 1, characterized in that: The temperature of the constant-temperature displacement deposition is 298K-373K, and the time is 2-240min.

6. The method for preparing zinc-cobalt alloy in a eutectic ionic liquid according to claim 1, characterized in that: In the step (1), water or anhydrous ethanol is added into the ionic liquid-cobalt salt composite solution; the volume ratio of the water or the anhydrous ethanol to the eutectic ionic liquid is 1:

10.

7. A zinc-cobalt alloy electrode prepared by the method according to any one of claims 1-6.

8. A zinc-ion battery, characterized by: A zinc ion battery comprising the zinc-cobalt alloy electrode according to claim 7 as an anode.

Images