Gamma-manganese dioxide positive electrode material and preparation method and application thereof

Abstract

The invention relates to a preparation method and application of a gamma-manganese dioxide positive electrode material, and the preparation method comprises the following steps: dissolving potassium persulfate, manganese disulfide and potassium permanganate in deionized water, transferring into a hydrothermal kettle after the potassium persulfate, the manganese disulfide and the potassium permanganate are completely dissolved, putting into a drying oven, and carrying out hydrothermal synthesis at a certain temperature for a certain time to obtain gamma-manganese dioxide. And after the reaction is completed, taking out the hydrothermal kettle after cooling, washing and filtering the product for multiple times, and drying in a drying oven to obtain the finished product gamma-manganese dioxide. Manganese dioxide prepared by the method has a nano single-crystal structure and is different from a traditional material, and a sample does not contain K < + >. The problems of low specific capacity and poor cycling stability caused by low ionic conductivity and poor intercalation and deintercalation reversibility of gamma-manganese dioxide are solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrode materials, and particularly relates to a gamma-manganese dioxide positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] The rapid development of smart grids, new energy vehicles and electronic devices has made electrochemical energy storage systems widely concerned in the world. The successful development and commercialization of electrochemical energy storage systems, especially the rapid rise of lithium ion batteries, has promoted the transformation of portable electronic devices and electric vehicles.

[0003] However, the safety of commercial lithium ion batteries limits their large-scale application, while zinc-based energy storage technology is highly recognized due to its high chargeability and practical potential, combined with the rich natural resources and low cost of zinc, as well as high safety, theoretical capacity (about 820 mAhg - 1), low redox potential (-0.76 V vs. standard hydrogen electrode) and other significant advantages, which shows great application potential in safe and stable energy storage power supply fields.

[0004] So far, the development of zinc ion battery (ZIBs) positive electrode materials has made some remarkable progress, such as manganese-based or vanadium-based oxides, prussian blue analogues and redox active materials. Among these positive electrode materials, manganese dioxide is favored by researchers due to its multiple crystal structures (gamma-, gamma-, delta-, gamma-, lambda-, epsilon-, and R-MnO2). It is low in cost, low in toxicity, and easy to form composites with conductive nanofillers.

[0005] Among them, gamma-manganese dioxide has excellent thermal stability, but its narrow tunnel width [1*1] is not conducive to zinc ion intercalation and deintercalation, resulting in low specific capacity and poor cycle stability. The traditional method is to improve the ionic conductivity by adding additional metal salts to intercalate cations in the manganese dioxide structure, but this method may affect the morphology and phase of the final product. SUMMARY

[0006] In order to overcome the above problems, the application provides a gamma-manganese dioxide positive electrode material and a preparation method and application thereof, thereby solving the problems of low specific capacity and poor cycle stability of the battery prepared by the traditional method.

[0007] To achieve the above purpose, the application adopts the following technical solutions:

[0008] A preparation method of a gamma-manganese dioxide positive electrode material, characterized in that it comprises the following steps:

[0009] Step one: dissolve potassium persulfate (K2S2O8), manganese disulfide (MnS2) and potassium permanganate (KMnO4) in deionized water in sequence, magnetically stir until completely dissolved to obtain a mixed solution A;

[0010] Step two: transfer the mixed solution A obtained in step one into a hydrothermal reactor for hydrothermal reaction, and form gamma-manganese dioxide after sufficient reaction;

[0011] Step three: after cooling the product obtained in step two to room temperature, perform ultrasonic and centrifugal cleaning;

[0012] Step four: after drying and grinding the product obtained in step three, the gamma-manganese dioxide positive electrode material is obtained.

[0013] Further, the molar ratio of potassium persulfate (K2S2O8) to potassium permanganate (KMnO4) in step one is 1:1:1-1.5;

[0014] The magnetic stirring in step one is magnetic stirring at room temperature for 10-15 min.

[0015] Further, the hydrothermal reaction in step two is that the hydrothermal reactor is heated in a forced air drying oven for hydrothermal reaction, and the reaction temperature in the forced air drying oven is 110-130℃, and the holding time is 6-8h.

[0016] Further, the ultrasonic and centrifugal cleaning in step three is as follows: after washing the product obtained in step two with deionized water, ultrasonic treatment is performed at a power of 80-100w for 1-2h, and then centrifugal treatment is performed at 5000-8000r / min for 5-8min, and the above steps are repeated for 6-10 times.

[0017] Further, the drying and grinding in step four are as follows: the product obtained in step three is dried in a forced air drying oven at a drying temperature of 50-80℃ for 10-15h, and then the material is taken out after natural cooling to 30℃ and ground; the grinding is performed by a ball mill at a rotating speed of 250-300r / min for 10-20min.

[0018] The application also discloses a preparation method of the positive electrode sheet of the gamma-manganese dioxide positive electrode material.

[0019] The prepared gamma-manganese dioxide positive electrode material, conductive carbon black and PVDF solution are mechanically mixed to obtain a slurry, which is coated on a titanium foil, dried at 30-60℃ for 6-12h, and then taken out, and the titanium foil is cut into a round sheet with a diameter of 10-14mm to obtain the positive electrode sheet of the gamma-manganese dioxide positive electrode material.

[0020] Further, the mass ratio of the gamma-manganese dioxide positive electrode material, the conductive carbon black and the PVDF solution is 7:2:1; the mass concentration of the PVDF is 1-4%.

[0021] Further, the mass concentration of the PVDF is 2%.

[0022] The application further discloses a gamma-manganese dioxide positive electrode material prepared by the preparation method.

[0023] The application further discloses application of the gamma-manganese dioxide positive electrode material prepared by the preparation method in a new energy battery.

[0024] In the application, the prepared gamma-manganese dioxide positive electrode material is prepared into a positive electrode sheet, and the positive electrode sheet, a metal zinc sheet negative electrode and a glass fiber diaphragm are assembled into a button cell.

[0025] In the application, the solvent of the battery electrolyte is deionized water, and 2MZnSO4+0.2MMnSO4 is used as a solute.

[0026] In the application, in order to measure the performance of the battery, the prepared button cell is placed for 8-10 hours, and the prepared button cell is subjected to long cycle test under the condition that the rate is 5A / g.

[0027] The application has the following beneficial effects:

[0028] (1) The substance used for regulating the structure of the gamma-manganese dioxide in the application is the oxidant potassium persulfate, by controlling the addition amount of the potassium persulfate, the morphology and phase of the potassium persulfate are not changed, and the specific capacity and cycle stability of the zinc-manganese battery are improved.

[0029] (2) The manganese dioxide prepared by the method has a wider tunnel structure, which is different from the traditional cation doping to widen the tunnel, and the sample does not contain K+ in the tunnel. The application of the material in the battery solves the problems of low ion conductivity of the gamma-manganese dioxide, poor embedment and extraction reversibility, low specific capacity and poor cycle stability.

[0030] (3) The preparation method of the gamma-manganese dioxide positive electrode material is scientific and reasonable in design, simple in operation and suitable for batch production and use. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 TEM-EDS characterization diagram of the gamma-manganese dioxide prepared in example 1 of the application;

[0032] Figure 2 XRD characterization comparison diagram of the gamma-manganese dioxide prepared in example 1 of the application;

[0033] Figure 3 Coulomb efficiency and cycle performance comparison chart of zinc-manganese battery composed of γ-manganese dioxide prepared in embodiment 1 of the present application and zinc-manganese battery composed of commercial γ-manganese dioxide;

[0034] Figure 4 Charge-discharge curve chart of zinc-manganese battery composed of γ-manganese dioxide prepared in embodiment 1 of the present application. DETAILED DESCRIPTION

[0035] The present application is further described below in conjunction with the accompanying drawings and embodiments:

[0036] In the embodiment of the present application, the positive electrode of the comparative battery is commercial ordinary γ-manganese dioxide.

[0037] Embodiment 1

[0038] (1) Preparation of positive electrode material of γ-manganese dioxide

[0039] Step one: accurately weigh 4.536g of potassium persulfate (K2S2O8) and dissolve it in 160ml, accurately weigh 6.345g of potassium permanganate (KMnO4) and dissolve it in the above solution, accurately weigh 4.536g of manganese disulfide (MnS2) and dissolve it in the above solution, and magnetically stir for 12min to obtain a mixed solution.

[0040] Step two: transfer the mixed solution obtained in step one into a hydrothermal reaction kettle, and keep it in a 120℃ oven for 7h.

[0041] Step three: after cooling the product obtained in step two to room temperature, wash it with deionized water, then perform ultrasonic treatment under the condition of power 90w for 2h, and then perform centrifugation, wherein the centrifugation is performed by using a centrifuge at 6000r / min for 6min, and the process is repeated for 8 times.

[0042] Step four: place the product obtained in step three into an oven and dry it at 60℃ for 12h. Then naturally cool it to 30℃, take out the material, and grind it, wherein the grinding is performed by using a ball mill at a rotation speed of 280r / min for 15min to obtain the γ-manganese dioxide positive electrode material.

[0043] Characterize the γ-manganese dioxide positive electrode material prepared in embodiment 1:

[0044] Figure 1 SEM-EDS characterization chart of γ-manganese dioxide prepared in embodiment 1 of the present application.

[0045] From the EDS energy spectrum of Figure 1 It can be seen from the EDS energy spectrum of that the potassium element is not contained in embodiment 1.

[0046] Figure 2XRD characterization chart of the γ-manganese dioxide prepared in Example 1 of the present application.

[0047] By Figure 2 It can be seen that the manganese dioxide prepared in Example 1 of the present application has a standard crystal form, i.e. γ-manganese dioxide positive electrode material.

[0048] Preparation of γ-manganese dioxide positive electrode sheet:

[0049] The prepared γ-manganese dioxide positive electrode material, KB and a PVDF solution with a mass concentration of 2% were mechanically mixed at a mass ratio of 7:2:1 to obtain a viscous slurry, which was coated on a titanium foil and cut into 12mm round sheets as positive electrode sheets of button cells.

[0050] (2) Preparation of zinc-manganese battery

[0051] The above γ-manganese dioxide positive electrode sheet, ordinary zinc sheet negative electrode and glass fiber separator were assembled into a CR2025 type button cell, and the electrolyte was 2M ZnSO4+0.2M MnSO4. The assembled battery was left to stand for 8 hours. Similarly, a commercial ordinary γ-manganese dioxide positive electrode and an ordinary zinc sheet negative electrode and a glass fiber separator were assembled into a battery as a control.

[0052] (3) Electrochemical performance test of zinc-manganese battery

[0053] The above zinc-manganese battery was subjected to cycle performance test on a charge-discharge tester, and the test condition was 0.5A / g.

[0054] Figure 3 and Figure 4 Electrochemical performance chart of the zinc-manganese battery composed of the γ-manganese dioxide prepared in Example 1 of the present application.

Claims

1. A method for preparing a γ-manganese dioxide cathode material, characterized in that, Comprising the following steps: Step one: dissolve potassium persulfate (K2S2O8), manganese disulfide (MnS2) and potassium permanganate (KMnO4) in deionized water in turn, magnetically stir until completely dissolved, to obtain a mixed solution A; Step two: transfer the mixed solution A obtained in step one into a hydrothermal reactor for hydrothermal reaction, and form γ-manganese dioxide after sufficient reaction; Step three: cool the product obtained in step two to room temperature, and then perform ultrasonic and centrifugal cleaning; Step four: dry and grind the product obtained in step three to obtain the γ-manganese dioxide positive electrode material.

2. The method for preparing the γ-manganese dioxide cathode material according to claim 1, characterized in that, The preparation method specifically comprises the following steps: The molar ratio of potassium persulfate (K2S2O8), manganese disulfide (MnS2) and potassium permanganate (KMnO4) in step one is 1:1:1-1.5; The magnetic stirring in step one is magnetic stirring at room temperature for 10-15 min.

3. The method for preparing the γ-manganese dioxide cathode material according to claim 2, characterized in that, The hydrothermal reaction in step two is carried out by heating the hydrothermal reactor in a blast drying oven, and the reaction temperature in the blast drying oven is 110-130℃, and the holding time is 6-8h.

4. The method for preparing the γ-manganese dioxide cathode material according to claim 3, characterized in that, The ultrasonic and centrifugal cleaning in step three specifically comprises the following steps: after the product obtained in step two is cleaned with deionized water, ultrasonic treatment is performed at a power of 80-100w for 1-2h, and then centrifugal treatment is performed at 5000-8000r / min for 5-8min, and the above steps are repeated for 6-10 times.

5. The method for preparing γ-manganese dioxide cathode material according to claim 4, characterized in that, The drying in step four is carried out by drying the product obtained in step three in a blast drying oven at a drying temperature of 50-80℃ for 10-15h, and then the material is taken out after natural cooling to 30℃ and ground; the grinding is carried out by a ball mill at a rotating speed of 250-300r / min for 10-20min.

6. A method for producing a positive electrode sheet comprising the positive electrode material of claims 1 to 5, characterized by, The preparation method specifically comprises the following steps: mechanically mix the prepared γ-manganese dioxide positive electrode material, conductive carbon black and PVDF solution to obtain a slurry, coat the slurry on a titanium foil, dry the titanium foil at 30-60℃ for 6-12h, take out the titanium foil, and then cut the titanium foil into round pieces with a diameter of 10-14mm to obtain the positive electrode sheet of the γ-manganese dioxide positive electrode material.

7. The method of producing a positive electrode sheet according to claim 6, characterized by: The mass ratio of the γ-manganese dioxide positive electrode material, conductive carbon black and PVDF solution is 7:2:1; and the mass concentration of the PVDF is 1-4%.

8. The method of producing a positive electrode sheet according to claim 7, characterized by: The mass concentration of the PVDF is 2%.

9. A γ-manganese dioxide positive electrode material prepared by the preparation method of any one of claims 1-5.

10. An application of a γ-manganese dioxide positive electrode material prepared by the preparation method of any one of claims 1-5 in a new energy battery.

Images