Zinc ion battery and preparation method thereof

Abstract

The present invention discloses a zinc ion battery and its preparation method. The preparation method includes the steps of preparing a rare earth-doped metal oxide, preparing a printing ink, screen-printing an intermediate affinity layer, screen-printing a cathode and anode, and assembling a flexible micro zinc ion battery. While regulating the structure of the metal oxide, the present invention also regulates the electrode structure, effectively constructing a conductive network and facilitating ultra-high loads. The preparation method disclosed in this application can effectively address the problems of low energy density, poor rate performance, and poor cycle stability of existing zinc ion batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a zinc ion battery and a preparation method thereof. Background Art

[0002] With advances in fifth-generation mobile communications (5G) and the Internet of Things (IoT), wearable electronics are experiencing explosive growth, increasingly trending towards miniaturization and lightweighting. Simultaneously, the development of miniaturized energy storage devices with excellent electrochemical performance, high safety, and good mechanical flexibility is becoming increasingly important for powering these wearable electronic devices. Currently, lithium-ion batteries dominate the market, owing to their high energy density and long cycle life. However, the development of lithium batteries faces several challenges. The scarcity and high cost of lithium resources contribute to the high price of lithium batteries, hindering their further large-scale application. Furthermore, the high cost, toxicity, and flammability of the electrolytes used pose safety risks, limiting their application in wearable devices and some extreme applications. In recent years, aqueous zinc-ion microbatteries have garnered increasing attention due to their low redox potential (-0.76 V), high safety, non-toxicity, and low cost.

[0003] However, the development of zinc-ion microbatteries is still in its early stages of research. The biggest challenges are low active material loading and low energy density, which seriously hinder the widespread application of the batteries. Although there are many reports on optimizing the printing process, the results in terms of performance improvement are limited. For example, simply increasing the active material loading often leads to poor flexibility and slow reaction kinetics. In addition, current zinc-ion batteries also suffer from poor rate capability and insufficient cycle life. The main reasons are that current cathode materials generally have the disadvantages of low conductivity and unstable structure. To improve these shortcomings, various structural control methods (including doping, vacancies, pre-intercalation, etc.) have been reported to improve the conductivity and electrochemical performance of electrode materials. However, many reports have confirmed that a single structural control method is difficult to comprehensively improve the above-mentioned problems faced by micro zinc-ion batteries. Therefore, there is an urgent need to seek new strategies to develop high-performance zinc-ion batteries with both high energy density and excellent flexibility. Summary of the Invention

[0004] In view of the above-mentioned prior art, the present invention provides a zinc ion battery and a preparation method thereof, so as to solve the problems of low energy density, poor rate performance and poor cycle stability of the existing zinc ion batteries.

[0005] In order to achieve the above object, the technical solution adopted in the present invention is: to provide a method for preparing a zinc ion battery, comprising the following steps:

[0006] S1: dissolving a metal salt, a rare earth salt, an inorganic acid, and an oxidant in water to form a reaction base solution, and then reacting at 100-150° C. for 10-15 hours to obtain a rare earth-doped metal oxide;

[0007] S2: Dispersing hydrophobic carbon black, hydrophilic carbon nanotubes and polyvinylidene fluoride in an organic solvent to obtain a conductive ink; dispersing the rare earth-doped metal oxide prepared in S1, hydrophilic carbon nanotubes and polyvinylidene fluoride in an organic solvent to obtain a cathode ink; dispersing zinc powder, hydrophilic carbon nanotubes and polyvinylidene fluoride in an organic solvent to obtain an anode ink;

[0008] S3: Applying conductive ink to one side of the flexible substrate by screen printing and drying at 60-150° C. for 10-120 minutes; then applying cathode ink and anode ink to the pattern formed by the conductive ink and drying at 60-150° C. for 10-120 minutes, with the cathode ink and anode ink being symmetrical with each other about the center line of the conductive ink pattern as the symmetry axis;

[0009] S4: Coat the cathode and anode with electrolyte and then seal them.

[0010] On the basis of the above technical solution, the present invention can also be improved as follows.

[0011] Furthermore, the preparation method of the reaction base liquid is as follows: 2-5 mmol of metal salt, 1-3 mmol of inorganic acid and 0.1-3 mmol of rare earth salt are added to 90 mL of water, stirred until clear, and then 1-3 mmol of oxidant is added, stirred for 2 hours, and then ultrasonically treated at a power of 200-1600 W for 0.5-2 hours to obtain the result.

[0012] Furthermore, the metal salt is MnSO4, VCl3, Co(NO3)2 or NiSO4, the rare earth salt is CeCl3, LaCl3 or CsCl, the oxidant is KMnO4, and the inorganic acid is H2SO4.

[0013] Furthermore, the mass ratio of hydrophobic carbon black, hydrophilic carbon nanotubes and polyvinylidene fluoride in the conductive ink is 1-3:1-3:1; the mass ratio of rare earth-doped metal oxide, hydrophilic carbon nanotubes and polyvinylidene fluoride in the cathode ink is 6-10:1-3:1; and the mass ratio of zinc powder to hydrophilic carbon nanotubes and polyvinylidene fluoride in the anode ink is 6-10:1-3:1.

[0014] Furthermore, the organic solvent is N-methylpyrrolidone.

[0015] Furthermore, the flexible substrate is polyethylene, polypropylene, polyimide, polyethylene terephthalate, polyvinyl chloride, polyethylene oxide or polydimethylsiloxane.

[0016] Furthermore, the thickness of the flexible substrate is 50 to 200 μm.

[0017] Furthermore, the electrolyte is prepared by the following steps: 4-12 g ZnCl2, 1-3 g MnSO4 and 5 g polyvinyl alcohol are dissolved in 50 mL distilled water.

[0018] Furthermore, the packaging material used in S4 is polyimide.

[0019] The beneficial effects of the present invention are:

[0020] 1. The present invention dopes metal oxides with rare earth atoms, interspersing the interior of the metal oxides and regulating the internal structure of the metal oxides. This not only increases the capacity of the metal oxides, but also effectively enhances the structural stability of the metal oxides. The energy density and cycle stability of the resulting battery are significantly improved.

[0021] 2. In addition to regulating the internal structure of the oxide, the present invention also optimizes and adjusts the electrode structure. Introducing an amphiphilic intermediate bonding layer (conductive ink layer) between the flexible substrate and the electrode layer can play a good connecting role and increase the connection stability between the electrode and the flexible substrate. At the same time, the present invention uses screen printing to apply the conductive ink to the flexible base. The intermediate bonding layer formed has a regular concave-convex structure, which can play a good rivet role, further increasing the connection stability between the electrode and the flexible substrate.

[0022] 3. The present invention optimizes the ratio of different types of inks, selects hydrophilic carbon nanotubes as conductive fillers for conductive inks and electrodes, and adjusts the ratio with rare earth-doped metal oxides, which can effectively construct a conductive network and help achieve ultra-high load.

[0023] 4. The zinc ion battery prepared by the present invention has excellent electrochemical performance, and the active material loading capacity is up to 24 mg / cm -2 The surface capacity and surface energy density reached a record high of 7.2 mAh / cm -2 and 8.5mWh / cm -2 , which is 1-2 orders of magnitude higher than currently reported performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Figures 1 and 2 are morphological structures of the intermediate affinity layer of the electrode in the embodiment, wherein a is a SEM image of the intermediate affinity layer, and b is a laser confocal image of the intermediate affinity layer;

[0025] Figure 2 and 3 Schematic diagram of the morphological changes of different zinc electrode materials during cyclic charge and discharge. DETAILED DESCRIPTION

[0026] The specific implementation methods of the present invention are described in detail below with reference to the embodiments.

[0027] Example 1

[0028] A zinc ion battery is prepared by the following steps:

[0029] (1) Preparation of rare earth-doped metal oxides

[0030] 3 mmol MnSO4, 2 mL 0.5 M H2SO4 and 3 mmol CeCl3 were added to 90 mL deionized water at room temperature, and a clear solution was formed under magnetic stirring; then, 20 mL 0.1 M KMnO4 aqueous solution was slowly added to the above solution, and the mixture was stirred for 2 hours and then treated with ultrasound at 1000 W for 1 hour; finally, the solution was transferred to a Teflon-lined autoclave and heated at 120°C for 12 hours; it was then filtered, and the obtained solid was washed with remote water three times and then dried in air at 60°C to obtain cerium-doped MnO2.

[0031] (2) Preparation of printing ink

[0032] Conductive ink preparation: Hydrophobic carbon black, hydrophilic carbon nanotubes, and polyvinylidene fluoride were mixed in a mass ratio of 2:2:1, and the mixture was dispersed in N-methylpyrrolidone at a material-liquid ratio of 1 g:2 mL to obtain a slurry-like conductive ink.

[0033] Cathode ink preparation: Cerium-doped MnO2, hydrophilic carbon nanotubes, and polyvinylidene fluoride were mixed in a mass ratio of 7:2:1, and the mixture was dispersed in N-methylpyrrolidone at a material-liquid ratio of 1 g:2 mL to obtain a slurry cathode ink.

[0034] Anode ink preparation: Zinc powder was mixed with hydrophilic carbon nanotubes and polyvinylidene fluoride in a mass ratio of 7:2:1, and the mixture was dispersed in N-methylpyrrolidone at a material-liquid ratio of 1 g:2 mL to obtain a slurry-like anode ink.

[0035] (3) Screen printing intermediate affinity layer

[0036] The conductive ink prepared in the step was printed onto one side of a 100 μm thick polyethylene terephthalate (PET) film by screen printing and dried in a vacuum oven at 120° C. for 60 min. Figure 1 As shown, the screen-printed intermediate affinity layer has a regular concave-convex structure, which can act as a rivet for the subsequently printed active material.

[0037] (4) The cathode and anode inks prepared by screen printing technology were printed onto the pattern formed by the conductive ink and dried in a vacuum oven at 120°C for 60 min to obtain high-load microelectrodes; the cathode ink and the anode ink were symmetrical with each other with the center line of the conductive ink pattern as the symmetry axis.

[0038] (5) Assembly of flexible micro zinc ion batteries

[0039] First, a semi-solid electrolyte containing zinc salt was prepared: 10g ZnCl2, 1g MnSO4 and 5g polyvinyl alcohol were dissolved in 50mL distilled water to obtain a gel-like semi-solid electrolyte; the electrolyte was then applied to the surface of the microelectrode and encapsulated with polyimide tape to obtain a flexible zinc-ion battery.

[0040] Example 2

[0041] A zinc ion battery is prepared by the following steps:

[0042] (1) Preparation of rare earth-doped metal oxides

[0043] 2 mmol Co(NO3)2, 2 mL 0.5 M H2SO4 and 1 mmol CsCl were added to 90 mL deionized water at room temperature, and a clear solution was formed under magnetic stirring; then, 10 mL 0.1 M KMnO4 aqueous solution was slowly added to the above solution, and the mixture was stirred for 2 hours and then treated with ultrasound at 200 W for 2 hours; finally, the solution was transferred to a Teflon-lined autoclave and heated at 150°C for 10 hours; it was then filtered, and the obtained solid was washed with remote water three times and then dried in air at 60°C to obtain cesium-doped Co2O3.

[0044] (2) Preparation of printing ink

[0045] Conductive ink preparation: Hydrophobic carbon black, hydrophilic carbon nanotubes, and polyvinylidene fluoride were mixed in a mass ratio of 3:2:1, and the mixture was dispersed in N-methylpyrrolidone at a material-liquid ratio of 1 g:2 mL to obtain a slurry-like conductive ink.

[0046] Cathode ink preparation: Cesium-doped Co2O3, hydrophilic carbon nanotubes, and polyvinylidene fluoride were mixed in a mass ratio of 6:2:1, and the mixture was dispersed in N-methylpyrrolidone at a material-liquid ratio of 1 g:2 mL to obtain a slurry cathode ink.

[0047] Anode ink preparation: Zinc powder was mixed with hydrophilic carbon nanotubes and polyvinylidene fluoride in a mass ratio of 6:1:1, and the mixture was dispersed in N-methylpyrrolidone at a material-liquid ratio of 1 g:2 mL to obtain a slurry-like anode ink.

[0048] (3) Screen printing intermediate affinity layer

[0049] The conductive ink prepared in the step was printed onto one side of a polyimide film with a thickness of 200 μm by screen printing technology and dried in a vacuum oven at 150° C. for 10 min.

[0050] (4) The cathode and anode inks prepared by screen printing technology were printed onto the pattern formed by the conductive ink and dried in a vacuum oven at 150°C for 10 min to obtain high-load microelectrodes; the cathode ink and the anode ink were symmetrical with each other with the center line of the conductive ink pattern as the symmetry axis.

[0051] (5) Assembly of flexible micro zinc ion batteries

[0052] First, a semi-solid electrolyte containing zinc salt was prepared: 4g ZnCl2, 2g MnSO4 and 5g polyvinyl alcohol were dissolved in 50mL distilled water to obtain a gel-like semi-solid electrolyte; the electrolyte was then applied to the surface of the microelectrode and then encapsulated with polyimide tape to obtain a flexible zinc-ion battery.

[0053] Example 3

[0054] A zinc ion battery is prepared by the following steps:

[0055] (1) Preparation of rare earth-doped metal oxides

[0056] 5 mmol NiSO4, 6 mL 0.5 M H2SO4 and 3 mmol LaCl3 were added to 90 mL deionized water at room temperature, and a clear solution was formed under magnetic stirring; then, 30 mL 0.1 M KMnO4 aqueous solution was slowly added to the above solution, and the mixture was stirred for 2 hours and then ultrasonically treated at 1600 W for 0.5 hour; finally, the solution was transferred to a Teflon-lined autoclave and heated at 100 °C for 15 hours; it was then filtered, and the obtained solid was washed with remote water three times and then dried in air at 60 °C to obtain lanthanum-doped nickel oxide.

[0057] (2) Preparation of printing ink

[0058] Conductive ink preparation: Hydrophobic carbon black, hydrophilic carbon nanotubes, and polyvinylidene fluoride were mixed in a mass ratio of 1:3:1, and the mixture was dispersed in N-methylpyrrolidone at a material-liquid ratio of 1 g:2 mL to obtain a slurry-like conductive ink.

[0059] Cathode ink preparation: Lanthanum-doped nickel oxide, hydrophilic carbon nanotubes, and polyvinylidene fluoride were mixed in a mass ratio of 10:3:1, and the mixture was dispersed in N-methylpyrrolidone at a material-liquid ratio of 1 g:2 mL to obtain a slurry cathode ink.

[0060] Anode ink preparation: Zinc powder was mixed with hydrophilic carbon nanotubes and polyvinylidene fluoride in a mass ratio of 10:3:1, and the mixture was dispersed in N-methylpyrrolidone at a material-liquid ratio of 1 g:2 mL to obtain a slurry-like anode ink.

[0061] (3) Screen printing intermediate affinity layer

[0062] The conductive ink prepared in the step was printed onto one side of a polyimide film with a thickness of 50 μm by screen printing technology and dried in a vacuum oven at 60° C. for 120 min.

[0063] (4) The cathode and anode inks prepared by screen printing technology were printed onto the pattern formed by the conductive ink and dried in a vacuum oven at 60°C for 120 min to obtain high-load microelectrodes; the cathode ink and the anode ink were symmetrical with each other with the center line of the conductive ink pattern as the symmetry axis.

[0064] (5) Assembly of flexible micro zinc ion batteries

[0065] First, a semi-solid electrolyte containing zinc salt was prepared: 12g ZnCl2, 3g MnSO4 and 5g polyvinyl alcohol were dissolved in 50mL distilled water to obtain a gel-like semi-solid electrolyte; the electrolyte was then applied to the surface of the microelectrode and then encapsulated with polyimide tape to obtain a flexible zinc-ion battery.

[0066] Comparative Example 1

[0067] The cerium-doped MnO2 in Example 1 was replaced by ordinary MnO2, and the other conditions were exactly the same.

[0068] Comparative Example 2

[0069] The printing method of the conductive ink and the electrode ink in Example 1 was changed to a common coating method, and the other conditions were exactly the same.

[0070] Comparative Example 3

[0071] Step 3 in Example 1 (ie, not printing the intermediate affinity layer on the flexible substrate) was omitted, and the remaining conditions were exactly the same.

[0072] Result Analysis

[0073] Since the performance of the zinc ion batteries obtained in Examples 2 and 3 is substantially the same as that in Example 1, the performance of the battery will be described using the zinc ion battery in Example 1 as an example.

[0074] The microelectrodes involved in Example 1 and Comparative Examples 1 to 3 were subjected to cyclic charge and discharge tests. The test method was as follows: a blue electric test system (CT2001A) was used to perform cyclic charge and discharge tests on the prepared zinc ion batteries.

[0075] The morphological changes of different batteries during the cycle charge and discharge process are as follows Figure 2 and 3 As shown in the figure, it can be seen that at a higher loading, the electrode without the intermediate affinity layer cracks significantly (Comparative Example 3, Figure 2 A), the electrode cracking of the middle affinity layer printed by ordinary printing method (Comparative Example 2, Figure 3 ), and the intermediate affinity layer is printed by the printing method of this application, and the obtained electrode has no obvious cracks (Example 1, Figure 2 B). This shows that the intermediate affinity layer can improve the stability of the electrode structure, and the printing method of the intermediate affinity layer also affects the electrode stability. The present invention uses screen printing to form a regular concave-convex structure on the surface of the intermediate affinity layer. This structure not only increases the coating area of ​​the electrode, thereby increasing the loading capacity of the active material, but also acts as a riveting effect, making the active material loading more stable in a manner similar to building blocks. It will not crack during the cycle, and the cycling stability is significantly improved.

[0076] In addition, the areal capacity and energy density of the electrode were tested. The areal capacity and energy density of the electrode can be directly measured by the blue electric test system. The maximum areal capacity of Example 1 reached 7.5 mAh / cm 2 , much higher than that of comparative example 1 (5.2 mAh / cm 2 ), Comparative Example 2 (3.3 mAh / cm 2 ) and Comparative Example 3 (2.6 mAh / cm 2 ). At the same time, the maximum areal energy density of Example 1 reached 8.7mWh / cm 2 , which is one order of magnitude higher than the currently reported zinc-ion batteries.

[0077] Although the specific embodiments of the present invention have been described in detail in conjunction with the embodiments, this should not be construed as limiting the scope of protection of this patent. Within the scope described by the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A method for preparing a zinc ion battery, characterized in that: The following steps are involved: S1: dissolving a metal salt, a rare earth salt, an inorganic acid, and an oxidant in water to form a reaction base solution, and then reacting at 100-150° C. for 10-15 hours to obtain a rare earth-doped metal oxide; S2: Dispersing hydrophobic carbon black, hydrophilic carbon nanotubes and polyvinylidene fluoride in an organic solvent to obtain a conductive ink; dispersing the rare earth-doped metal oxide prepared in S1, hydrophilic carbon nanotubes and polyvinylidene fluoride in an organic solvent to obtain a cathode ink; dispersing zinc powder, hydrophilic carbon nanotubes and polyvinylidene fluoride in an organic solvent to obtain an anode ink; S3: Applying conductive ink to one side of the flexible substrate by screen printing and drying at 60-150° C. for 10-120 minutes; then applying cathode ink and anode ink to the pattern formed by the conductive ink and drying at 60-150° C. for 10-120 minutes, with the cathode ink and anode ink being symmetrical with each other about the center line of the conductive ink pattern as the symmetry axis; S4: Coat the cathode and anode with electrolyte and then seal them.

2. The preparation method of zinc ion battery according to claim 1, wherein The reaction base liquid is prepared by adding 2 to 5 mmol of a metal salt, 1 to 3 mmol of an inorganic acid, and 0.1 to 3 mmol of a rare earth salt to 90 mL of water, stirring until the solution is clear, then adding 1 to 3 mmol of an oxidant, stirring for 2 hours, and then ultrasonically treating the solution at a power of 200 to 1600 W for 0.5 to 2 hours.

3. the preparation method of zinc ion battery according to claim 2, is characterized in that: The metal salt is MnSO4, VCl3, Co(NO3)2 or NiSO4, the rare earth salt is CeCl3, LaCl3 or CsCl, the oxidant is KMnO4, and the inorganic acid is H2SO4.

4. the preparation method of zinc ion battery according to claim 1, is characterized in that: The mass ratio of hydrophobic carbon black, hydrophilic carbon nanotubes and polyvinylidene fluoride in the conductive ink is 1-3:1-3:1; the mass ratio of rare earth-doped metal oxide, hydrophilic carbon nanotubes and polyvinylidene fluoride in the cathode ink is 6-10:1-3:1; and the mass ratio of zinc powder to hydrophilic carbon nanotubes and polyvinylidene fluoride in the anode ink is 6-10:1-3:

1.

5. the preparation method of zinc ion battery according to claim 1, is characterized in that: The organic solvent is N-methylpyrrolidone.

6. the preparation method of zinc ion battery according to claim 1, is characterized in that: The flexible substrate is polyethylene, polypropylene, polyimide, polyethylene terephthalate, polyvinyl chloride, polyethylene oxide or polydimethylsiloxane.

7. the preparation method of zinc ion battery according to claim 6, is characterized in that: The thickness of the flexible substrate is 50 to 200 μm.

8. The preparation method of zinc ion battery according to claim 1, wherein The electrolyte is prepared by the following steps: 4-12g ZnCl2, 1-3g MnSO4 and 5g polyvinyl alcohol are dissolved in 50mL distilled water.

9. The preparation method of zinc ion battery according to claim 1, wherein The packaging material used in S4 is polyimide.

10. A zinc ion battery prepared by the preparation method according to any one of claims 1 to 9.

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