Preparation method of molybdenum trioxide-zinc metal battery stable in acidic system

Abstract

The invention relates to a new energy technology, belongs to the technical field of preparation of novel aqueous batteries, and particularly relates to a preparation method of a stable molybdenum trioxide-zinc metal battery in an acidic system. Molybdenum trioxide is used as a positive electrode active material, a mixed solution of aluminum salt and zinc salt is used as an electrolyte, zinc metal is used as a negative electrode, the existence of the aluminum salt can maintain the pH stability of the electrolyte, molybdenum trioxide is used as a positive electrode under an acidic condition, a large amount of protons are provided, and then reversible proton exchange of molybdenum trioxide is ensured. And meanwhile, the influence on zinc negative electrode corrosion under the acidic condition is relieved. Molybdenum trioxide is used as an electrochemical reaction of a battery positive electrode, an electrochemical oxidation-reduction reaction can be rapidly carried out in an environment in which aluminum salt exists, and meanwhile, the existence of the aluminum salt is beneficial to uniform deposition of zinc ions. Furthermore, the molybdenum trioxide-zinc battery is higher in specific capacity, higher in energy density, better in rate capability and longer in service life.

Description

Technical Field

[0001] The invention relates to new energy technology and belongs to the technical field of novel aqueous battery preparation, and in particular to a method for preparing a stable molybdenum trioxide-zinc metal battery in an acidic system. Background Art

[0002] Molybdenum trioxide (MoO3) is a promising cathode material for aqueous zinc-ion batteries due to its high theoretical capacity. The open tunnel structure and confined fluid provide selective ion channels for the non-diffusive Grotthuss transport of protons, significantly improving the ionic conductivity and reducing the migration energy barrier. However, in aqueous batteries, molybdenum trioxide (MoO3) as a cathode material has the problems of instability and severe capacity decay. Taking aqueous zinc-ion batteries as an example, the increase in interfacial pH caused by the proton consumption of the hydrogen evolution reaction of the zinc metal anode causes the precipitation of byproduct alkaline zinc salts, which inevitably consumes water and electrolyte salts, and ultimately leads to battery failure.

[0003] At the same time, the accumulation of basic zinc salts will increase the charge transfer resistance of the interface, thereby slowing down the transfer of zinc ions at the electrode / electrolyte interface and hindering the kinetics, making it difficult to achieve high power density and long cycle zinc metal batteries.

[0004] In view of the above problems, the present invention proposes a metal cation additive, which maintains the pH stability of the interface and thus ensures the structural stability of molybdenum trioxide, thereby ultimately improving the overall electrochemical performance of the zinc ion battery. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a stable aqueous electrolyte molybdenum trioxide-zinc metal battery, by adding a certain amount of aluminum salt to the zinc salt to maintain the pH in the electrolyte in a stable state, while providing stable conditions for the proton / zinc storage of molybdenum trioxide under acidic conditions, thereby ensuring that the zinc metal battery with molybdenum trioxide as the positive electrode has high stability, while the rate performance and energy density are greatly improved.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing a stable molybdenum trioxide-zinc metal battery in an acidic system comprises the following steps:

[0008] 1) Molybdenum trioxide, a conductive agent and a binder are fully mixed and ground for 30 minutes to obtain a positive electrode material mixture;

[0009] 2) adding the positive electrode material mixture obtained in step 1) into N-methylpyrrolidone, stirring thoroughly, and continuing grinding to obtain a mixed slurry;

[0010] 3) Take a cut titanium foil of 1*1 cm, and use a needle scraping method to evenly coat the mixed slurry prepared in step 2) on the titanium foil with a needle, and vacuum dry overnight to obtain a positive electrode material;

[0011] 4) The positive electrode material obtained in step 3) is used as the positive electrode, and the cut 1*1 cm zinc foil is used as the negative electrode. The positive electrode, the separator and the negative electrode are assembled in sequence, and an electrolyte is added to finally obtain a stable aqueous molybdenum trioxide-zinc metal battery.

[0012] Furthermore, in the above preparation method, in step 1), the conductive agent is any one of single-walled carbon nanotubes, acetylene black and SUPER P.

[0013] Furthermore, in the above preparation method, in step 1), the binder is polyvinylidene fluoride.

[0014] Furthermore, in the above-mentioned preparation method, in step 1), the mass ratio of molybdenum trioxide, conductive agent and binder is 7:2:1 or 8:2:1.

[0015] Furthermore, in the above preparation method, in step 2), the positive electrode material mixture is added to N-methylpyrrolidone at a ratio of 15 wt %.

[0016] Furthermore, in the above preparation method, in step 3), the coating amount of the mixed slurry on the titanium foil is 1.2 mg / cm 2 .

[0017] Furthermore, in the above preparation method, in step 3), the vacuum drying temperature is 60-80°C.

[0018] Furthermore, in the above preparation method, in step 4), the electrolyte is a mixed salt solution of zinc salt and aluminum salt.

[0019] Furthermore, in the above preparation method, in step 4), the concentration of the zinc salt is 2 mol / L.

[0020] Furthermore, in the above preparation method, in step 4), the concentration of the aluminum salt is 0 to 0.6 mol / L.

[0021] Furthermore, in the above preparation method, in step 4), the zinc salt is any one of zinc sulfate, zinc chloride and zinc trifluoromethanesulfonate.

[0022] Furthermore, in the above preparation method, in step 4), the aluminum salt is aluminum chloride or aluminum sulfate.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention uses molybdenum trioxide as the positive electrode active material, a mixed solution of aluminum salt and zinc salt as the electrolyte, and zinc foil as the negative electrode. The presence of aluminum salt can maintain the pH stability of the electrolyte, and molybdenum trioxide is used as the positive electrode under acidic conditions to provide a large number of protons, thereby ensuring that molybdenum trioxide undergoes reversible proton exchange. At the same time, the effect of acidic conditions on the corrosion of the zinc negative electrode is mitigated. The electrochemical reaction of molybdenum trioxide as the positive electrode of the battery can quickly carry out electrochemical redox reactions in the presence of aluminum salts, and the presence of aluminum salts is conducive to the uniform deposition of zinc ions. This makes the battery specific capacity of the molybdenum trioxide-zinc metal battery higher, the energy density greater, the rate performance better, and the battery life longer.

[0025] 2. The molybdenum trioxide-zinc metal battery provided by the present invention has a remaining capacity of about 90.48% after 100 charge and discharge cycles under the charge and discharge condition of 1C.

[0026] 3. The molybdenum trioxide-zinc metal battery provided by the present invention has excellent electrochemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the XRD diagram of molybdenum trioxide in Example 1 of the present invention.

[0028] Figure 2 This is the SEM image of molybdenum trioxide in Example 1 of the present invention.

[0029] Figure 3 This is a graph showing the charge and discharge capacity test results of the molybdenum trioxide-zinc metal battery of Example 1 of the present invention.

[0030] Figure 4 This is a graph showing the cycle life test results of the molybdenum trioxide-zinc metal battery of Example 1 of the present invention.

[0031] Figure 5 It is a comparison chart of the charge and discharge curves of the molybdenum trioxide-zinc metal battery of Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0032] Example 1

[0033] 1) Preparation of positive electrode material mixture: Commercial molybdenum trioxide, conductive agent (acetylene black), and binder (PVDF) powders were fully mixed and ground at a mass ratio of 7:2:1 for 30 minutes to obtain a positive electrode material mixture;

[0034] 2) taking a positive electrode material mixture at a ratio of 15 wt %, adding it to N-methylpyrrolidone (NMP), stirring it thoroughly, and continuing to grind it to prepare a mixed slurry;

[0035] 3) Take the cut 1*1cm titanium foil and use the needle scraping method to spread the mixed slurry at a rate of 1.2mg / cm 2The coating amount is evenly coated on the titanium foil with a needle, and then placed in a vacuum oven and dried overnight at 60-80°C to obtain the positive electrode material.

[0036] 4) Battery assembly: The positive electrode material obtained in step 3) is used as the positive electrode, and the cut 1*1 cm zinc foil is used as the negative electrode. The positive electrode, the separator and the negative electrode are sequentially loaded into a Swagelok battery device, and an electrolyte is added. The electrolyte is a mixed salt solution of aluminum sulfate (0.6 mol / L) and zinc sulfate (2 mol / L), and an aqueous molybdenum trioxide-zinc metal battery is obtained.

[0037] Example 2

[0038] 1) Preparation of positive electrode material mixture: Molybdenum trioxide, conductive agent (acetylene black), and binder (PVDF) powders were fully mixed and ground at a mass ratio of 7:2:1 for 30 minutes to obtain a positive electrode material mixture;

[0039] 2) taking a positive electrode material mixture at a ratio of 15 wt %, adding it to N-methylpyrrolidone (NMP), stirring it thoroughly, and continuing to grind it to prepare a mixed slurry;

[0040] 3) Take the cut 1*1cm titanium foil and use the needle scraping method to spread the mixed slurry at a rate of 1.2mg / cm 2 The coating amount is evenly coated on the titanium foil with a needle, and then placed in a vacuum oven and dried overnight at 60-80°C to obtain the positive electrode material.

[0041] 4) Battery assembly: The positive electrode material obtained in step 3) is used as the positive electrode, and the cut 1*1 cm zinc foil is used as the negative electrode. The positive electrode, the separator and the negative electrode are sequentially loaded into a Swagelok battery device, and an electrolyte is added. The electrolyte is a mixed salt solution of aluminum sulfate (0.2 mol / L) and zinc sulfate (2 mol / L), and an aqueous molybdenum trioxide-zinc metal battery is obtained.

[0042] Example 3

[0043] 1) Preparation of positive electrode material mixture: Molybdenum trioxide, conductive agent (acetylene black), and binder (PVDF) powders were fully mixed and ground at a mass ratio of 7:2:1 for 30 minutes to obtain a positive electrode material mixture;

[0044] 2) taking a positive electrode material mixture at a ratio of 15 wt %, adding it to N-methylpyrrolidone (NMP), stirring it thoroughly, and continuing to grind it to prepare a mixed slurry;

[0045] 3) Take the cut 1*1cm titanium foil and use the needle scraping method to spread the mixed slurry at a rate of 1.2mg / cm 2 The coating amount is evenly coated on the titanium foil with a needle, and then placed in a vacuum oven and dried overnight at 60-80°C to obtain the positive electrode material.

[0046] 4) Battery assembly: The positive electrode material obtained in step 3) is used as the positive electrode, and the cut 1*1 cm zinc foil is used as the negative electrode. The positive electrode, the separator and the negative electrode are sequentially loaded into the Swagelok battery device, and an electrolyte is added. The electrolyte is a mixed salt solution of aluminum sulfate (0.4 mol / L) and zinc sulfate (2 mol / L), and an aqueous molybdenum trioxide-zinc metal battery is obtained.

[0047] from Figure 1 and Figure 2 The structure and morphology of molybdenum trioxide can be determined.

[0048] from Figure 3 It can be seen that Example 1 has excellent rate capability. Similarly, at a current density of 1 A / g, after 100 cycles, it has an excellent capacity retention rate of 90.48% ( Figure 4 ).from Figure 5 It can be seen that Example 1 has a better coulombic efficiency than Comparative Example 1. This proves that Example 1 after modification has outstanding electrochemical performance compared to other cases.

[0049] Comparative Example 1

[0050] 1) Preparation of positive electrode material mixture: Molybdenum trioxide, conductive agent (acetylene black), and binder (PVDF) powders were fully mixed and ground at a mass ratio of 7:2:1 for 30 minutes to obtain a positive electrode material mixture;

[0051] 2) taking a positive electrode material mixture at a ratio of 15 wt %, adding it to N-methylpyrrolidone (NMP), stirring it thoroughly, and continuing to grind it to prepare a mixed slurry;

[0052] 3) Take the cut 1*1cm titanium foil and use the needle scraping method to spread the mixed slurry at a rate of 1.2-2mg / cm 2 The coating amount is evenly coated on the titanium foil with a needle, and then placed in a vacuum oven and dried overnight at 60-80°C to obtain the positive electrode material.

[0053] 4) Battery assembly: The positive electrode material obtained in step 3) is used as the positive electrode, and the cut 1*1 cm zinc foil is used as the negative electrode. The positive electrode, the separator and the negative electrode are sequentially loaded into a Swagelok battery device, and an electrolyte is added. The electrolyte is a zinc sulfate solution (2 mol / L), and an aqueous molybdenum trioxide-zinc metal battery is obtained.

[0054] Battery performance test

[0055] Charge and discharge capacity test:

[0056] Taking the mass of the positive electrode of the battery as a reference, the molybdenum trioxide-zinc metal batteries prepared in Examples 1 to 3 and Comparative Example 1 were respectively subjected to constant current charge and discharge tests using 5 different current densities of 500 mA / g, 1 A / g, 2 A / g, 3 A / g, and 5 A / g. The charge and discharge voltage range was 0.3 to 1.1 V. The test results are shown in Table 1 below:

[0057] Table 1 Discharge capacity at different current densities

[0058]

[0059] It can be seen from Table 1 that Example 1 with an added concentration of 0.6 mol / L aluminum sulfate has excellent rate performance compared with Examples 2 and 3 and Comparative Example 1.

Claims

1. A method for preparing a stable molybdenum trioxide-zinc metal battery in an acidic system, characterized in that: The steps include: 1) Molybdenum trioxide, a conductive agent and a binder are fully mixed and ground for 30 minutes to obtain a positive electrode material mixture; 2) adding the positive electrode material mixture obtained in step 1) into N-methylpyrrolidone, stirring thoroughly, and continuing grinding to obtain a mixed slurry; 3) Take a cut titanium foil of 1*1 cm, and use a needle scraping method to evenly coat the mixed slurry prepared in step 2) on the titanium foil with a needle, and vacuum dry overnight to obtain a positive electrode material; 4) The positive electrode material obtained in step 3) is used as the positive electrode, and the cut 1*1 cm zinc foil is used as the negative electrode. The positive electrode, the separator and the negative electrode are assembled in sequence, and an electrolyte is added to finally obtain a stable aqueous molybdenum trioxide-zinc metal battery.

2. The preparation method according to claim 1, characterized in that: In step 1), the conductive agent is any one of single-walled carbon nanotubes, acetylene black and SUPER P.

3. The preparation method according to claim 1, characterized in that: In step 1), the binder is polyvinylidene fluoride.

4. The preparation method according to claim 1, characterized in that: In step 1), the mass ratio of molybdenum trioxide, conductive agent and binder is 7:2:1 or 8:2:

1.

5. The preparation method according to claim 1, characterized in that: In step 2), the positive electrode material mixture is added into N-methylpyrrolidone at a ratio of 15 wt %.

6. The preparation method according to claim 1, characterized in that: In step 3), the coating amount of the mixed slurry on the titanium foil is 1.2 mg / cm 2 .

7. The preparation method according to claim 1, characterized in that: In step 3), the vacuum drying temperature is 60-80°C.

8. The preparation method according to claim 1, characterized in that: In step 4), the electrolyte is a mixed salt solution of zinc salt and aluminum salt.

9. The preparation method according to claim 8, characterized in that: In step 4), the concentration of the zinc salt is 2 mol / L; the concentration of the aluminum salt is 0-0.6 mol / L.

10. The preparation method according to claim 8, characterized in that: In step 4), the zinc salt is any one of zinc sulfate, zinc chloride and zinc trifluoromethanesulfonate; and the aluminum salt is aluminum chloride or aluminum sulfate.

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