Stoichiometric manganese oxide electrode material and synthesis method thereof

Abstract

The invention relates to a stoichiometric manganese oxide electrode material and a synthesis method thereof, through doping of at least five cations such as trivalent active cations, pentavalent and hexavalent cations, the valence state of manganese is between + 3.1 and + 3.9, and the valence state of manganese is still above + 3 after discharge, the trivalent active cations can provide a small part of capacity, and thus, the stoichiometric manganese oxide electrode material is obtained. The pentavalent and hexavalent cations play roles in stabilizing the structure and inhibiting manganese dissolution, and multiple ions play a synergistic effect, so that the long cycle stability of the manganese oxide positive electrode is improved; oxygen vacancy and compensation are realized through sulfur doping, so that the internal conductivity of the manganese oxide positive electrode made of the manganese oxide electrode material with the stoichiometric ratio to protons, Zn < 2 + > and Na < + > ions is improved; and a coating layer is formed on the surface of the manganese oxide positive electrode through PO4 < 3-> ions, so that manganese dissolution is further inhibited.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical energy storage materials, and in particular relates to a stoichiometric manganese oxide electrode material and a synthesis method. Background Art

[0002] In recent years, batteries, as important energy storage devices, have experienced rapid development. Lithium-ion batteries are relatively mature secondary battery energy storage systems, but they still have flammable safety issues, and the shortage of lithium ore resources has caused their prices to continue to rise. In order to meet the requirements of energy storage and application, it is very promising to promote the application of low-cost, high-safety new aqueous and organic secondary batteries in the field of energy storage. In the field of positive electrode materials for energy storage batteries, compared with positive electrode materials such as Prussian blue, vanadium compounds, organic matter and polyanion skeletons, manganese dioxide positive electrode materials have higher specific capacity and working voltage, better cycle stability, and are environmentally friendly and low-priced, which makes manganese dioxide materials a very promising positive electrode material.

[0003] However, due to the Jahn-Teller distortion, Mn 3+ The ions are converted into divalent manganese and dissolved into the electrolyte, and the manganese dioxide positive electrode undergoes irreversible phase change during repeated cycles, resulting in capacity decay of the battery during long cycles. In addition, the intrinsic conductivity of Mn-based materials is low, and the oxygen atoms in the manganese-based positive electrode materials react with protons and Zn 2+ 、Na + The electrostatic interaction between ions hinders the diffusion of ions in the solid state, resulting in poor rate performance of the manganese dioxide cathode.

[0004] Patent CN117976894A, a manganese dioxide high entropy material and its preparation method and application, zinc ion battery positive electrode and zinc ion battery, proposes that the conductivity of manganese dioxide materials can be increased by doping with multiple metal ions and the structural stability can be increased by inhibiting the Jan-Taylor effect; at the same time, multi-ion doped manganese dioxide with a similar high entropy configuration can simultaneously improve the long-cycle stability and reaction kinetics of manganese dioxide materials through the synergistic effect between different ions, and by adding iodine ion additives to the electrolyte, additional I - / I 0 The redox circuit can promote the improvement of the specific capacity, kinetics and cycle life of the multi-ion-doped manganese dioxide positive electrode; however, the iodide ion additive in the electrolyte will corrode the commonly used metal current collector. The battery capacity is relatively low in the electrolyte without iodine ions, and its preparation plan remains at the laboratory level, with weak industrialization potential.

[0005] Patent CN116062807A, high entropy doped manganese-based layered oxide and its preparation method, sodium ion battery positive electrode material and battery, proposes to use more than five low-content metal elements in Nax The technical solution of forming high entropy doping in MnO2 lattice can increase the Na x Due to the stability of the MnO2 lattice, it exhibits excellent cycle stability and rate characteristics as a positive electrode material for sodium-ion batteries; however, the preparation scheme has high energy consumption, the uniformity of the solid-solid reaction is poor, and the cycle stability needs to be improved.

[0006] Patent CN113936925B, a sulfur anion doped manganese dioxide material and its preparation and use, and a zinc ion battery containing the same, proposes to obtain a manganese dioxide material with a molecular formula of MnO by sulfur anion doping X S Y The manganese dioxide material has excellent electrochemical properties as a positive electrode material for zinc-ion batteries; however, the preparation method has high energy consumption, doping only occurs on the surface of the material, and the uniformity of doping needs to be improved.

[0007] Based on the above problems, the present invention proposes a method for synthesizing a stoichiometric manganese oxide electrode material, which realizes that the manganese oxide positive electrode mainly undergoes an insertion / extraction reaction, and uses it as the positive electrode of an aqueous zinc ion battery and an organic sodium ion battery, which has excellent rate performance and cycle stability. Summary of the invention

[0008] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a stoichiometric manganese oxide electrode material and a synthesis method.

[0009] This stoichiometric manganese oxide electrode material has the general chemical formula: X MnO 2-y-z S y (PO4) z , where A includes trivalent metal ions, pentavalent metal ions and hexavalent metal ions, the types of doping elements are greater than or equal to 5, and X is the atomic content parameter of element A, 0.01≤x≤0.2;

[0010] y is the atomic content parameter of sulfur element, 0.01≤y≤0.15; z is the ion content parameter of phosphate ion, 0.01≤z≤0.1; and the valence state of Mn is +3.1 to +3.9.

[0011] Preferably, the trivalent metal ions include one or more of indium, bismuth, lanthanum, cobalt, iron, chromium and aluminum; the pentavalent metal ions include one or more of niobium and tantalum; and the hexavalent metal ions include one or more of molybdenum, tungsten and selenium.

[0012] The method for synthesizing the stoichiometric manganese oxide electrode material comprises the following steps:

[0013] Step 1: preparing a mixed solution of manganese salt and a plurality of high-valent ion salts, and adding a conductive additive and a dispersant;

[0014] Step 2: prepare an alkaline solution and add a surfactant;

[0015] Step 3: Add the alkaline solution in step 2 dropwise to the solution in step 1 to obtain a slurry through reaction, transfer the slurry to an aging kettle, add a sulfiding agent and a phosphate for aging, and then obtain a stoichiometric manganese oxide electrode material after filtering, washing and drying.

[0016] Preferably, in step one, the dispersant includes sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate or polyacrylamide; and the conductive additive includes carbon fiber, graphene, carbon nanotube or acetylene black.

[0017] Preferably, in step 2, the alkaline solution includes aqueous ammonia, quaternary ammonium base, alkaline solution of lithium, alkaline solution of sodium or alkaline solution of potassium; and the surfactant is sodium dodecyl sulfate, sodium dodecylbenzene sulfonate or octadecyltrimethylammonium chloride.

[0018] Preferably, in step three, the vulcanizing agent includes one or more of thioacetamide, thiourea, sodium thiosulfate and sodium sulfide; the phosphate includes one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate and sodium monohydrogen phosphate.

[0019] Preferably, in step three, the reaction and aging are carried out in an oxidizing atmosphere or a solution containing an oxidant.

[0020] The application of this stoichiometric manganese oxide electrode material is to compound the stoichiometric manganese oxide electrode material onto a metal current collector to prepare a manganese oxide positive electrode for an aqueous or organic secondary battery.

[0021] The beneficial effects of the present invention are:

[0022] 1) The stoichiometric manganese oxide electrode material prepared by the present invention has good cycle stability and rate performance. By doping at least five kinds of cations such as trivalent active cations, pentavalent and hexavalent cations, the valence state of manganese is between +3.1 and +3.9, and is still above +3 after discharge. The trivalent active cations provide a small part of the capacity, and the pentavalent and hexavalent cations stabilize the structure and inhibit the dissolution of manganese. Multiple ions play a synergistic role, thereby improving the long-term cycle stability of the manganese oxide positive electrode.

[0023] 2) The present invention realizes oxygen vacancies and compensation by sulfur doping, thereby improving the internal resistance of protons and Zn in the manganese oxide positive electrode made of this stoichiometric manganese oxide electrode material. 2+ 、Na + Ionic conductivity; through PO4 3- The ions form a coating on the surface of the manganese oxide positive electrode, further inhibiting the dissolution of manganese.

[0024] 3) The present invention can prepare a manganese oxide positive electrode for an aqueous or organic secondary battery by compounding the stoichiometric manganese oxide electrode material onto a conventional weldable metal current collector without causing corrosion to the metal current collector. Thus, the use of carbon cloth or titanium-based current collectors that are difficult to industrialize or have high costs can be avoided, and the invention has better prospects for commercial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Cycle curves of aqueous zinc ion batteries assembled with the positive electrode materials of Examples 2 to 4 and Comparative Example 1;

[0026] Figure 2 The rate diagram of the aqueous zinc ion battery assembled with the positive electrode materials of Examples 2 to 4 and Comparative Example 1;

[0027] Figure 3 The specific capacity-voltage curve of the organic sodium battery assembled with the positive electrode materials of Examples 2 to 4 and Comparative Example 1;

[0028] Figure 4 The rate diagram of the organic sodium battery assembled with the positive electrode materials of Examples 2 to 4 and Comparative Example 1;

[0029] Figure 5 2 is an electron microscope image of the manganese oxide synthesized in Examples 2 to 4 and Comparative Example 1. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with embodiments. The description of the following embodiments is only used to help understand the present invention. It should be noted that for ordinary persons in the art, without departing from the principle of the present invention, the present invention can also be modified in some ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0031] Embodiment 1

[0032] As an embodiment, the stoichiometric manganese oxide electrode material has a chemical formula of: x MnO 2-y-z S y (PO4) z , wherein A contains at least 5 doping elements of trivalent / pentavalent / hexavalent ions, and the trivalent / pentavalent / hexavalent ions contain at least 1 each, and the atomic content parameter of the A element is 0.01≤x≤0.2.

[0033] The valence state of Mn in the above-mentioned stoichiometric manganese oxide material is +3.1 to +3.9. And after discharge, it is still above +3, which fundamentally suppresses the problem of positive electrode manganese dissolution and irreversible phase change caused by the Jan-Taylor effect. Trivalent active cations provide a small amount of capacity, while pentavalent and hexavalent metal ions do not participate in the battery reaction, which supports the layered structure well, stabilizes the structure, and inhibits manganese dissolution. Multiple ions play a synergistic role, which improves the long-cycle stability of the manganese oxide positive electrode.

[0034] The S element that replaces the O element has an atomic content parameter of 0.01≤y≤0.15. The oxygen vacancies and compensation are realized by S doping, which improves the internal resistance of the manganese oxide positive electrode to protons and Zn 2+ 、Na + Ionic conductivity.

[0035] Via PO4 3- The ions form manganese phosphate compounds with part of the low-valent manganese, forming a coating layer on the surface of the manganese oxide positive electrode, further inhibiting the dissolution of manganese, making the stoichiometric manganese oxide electrode material have better stability, and the ion content parameter of the phosphate ion is 0.01≤z≤0.1.

[0036] Embodiment 2

[0037] As another embodiment, this embodiment 2 proposes, based on the embodiment 1, a method for synthesizing and applying a stoichiometric manganese oxide electrode material, specifically comprising the following steps:

[0038] Step 1. Add 1L of water to a reactor, pour 336g of manganese sulfate, 24.7g of bismuth salt, 6.5g of lanthanum nitrate, 4g of ammonium niobium oxalate, 3.9g of ammonium molybdate, and 5.5g of selenium sulfate into the water in a molar ratio of 2:0.05:0.02:0.02:0.02:0.02:0.02, stir to dissolve, then add 2g of carbon nanotubes and 0.1% of sodium tripolyphosphate, and let in air.

[0039] Step 2: Dissolve 200 grams of sodium hydroxide in a deionized water solution, then add ammonia water as a complexing agent, with a content of 5%, and sodium dodecyl sulfate, with a content of 0.1%, and stir to dissolve into a uniform solution.

[0040] Step 3: Add the solution in step 2 dropwise to the reactor in step 1 at a rate of 1 L / h under a stirring speed of 30 Hz. After all the solution has been added, continue stirring for 2 hours.

[0041] Step 4: Transfer the product obtained in step 3 to an aging kettle, add 7.5 g of thioacetamide and 11.5 g of ammonium dihydrogen phosphate, continue stirring for 1 hour, then filter and wash with water, then dry the material in an oven at 80°C and sieve to obtain a product with the chemical formula (Bi 0.02La 0.01 Nb 0.01 Mo 0.01 Se 0.01 )Mn 0.94 O 1.9 S 0.05 (PO4) 0.05 The layered manganese oxide has an average valence of +3.73 because of the interlayer insertion of sodium, ammonium and a small amount of high-valent metal ions.

[0042] Bi 0.02 La 0.01 Nb 0.01 Mo 0.01 Se 0.01 )Mn 0.94 O 1.9 S 0.05 (PO4) 0.05 The positive electrode material is mixed evenly with acetylene black, PTFE emulsion and isopropyl alcohol in a set proportion and rolled into a sheet of a certain thickness; the sheet is dried in an oven and compounded onto a stainless steel foil current collector through a conductive adhesive to prepare a positive electrode sheet.

[0043] The negative electrode is pure zinc foil, the electrolyte is 2M ZnSO4+1.5M Na2SO4 aqueous solution, and sodium hydroxide is used to adjust the pH value to neutral to assemble an aqueous zinc secondary battery.

[0044] The negative electrode is a sodium sheet, the electrolyte is a 1M NaClO4 solution, the solvent is propylene carbonate (PC) and 2% by volume of fluoroethylene carbonate (FEC), and an organic sodium ion battery is assembled.

[0045] Embodiment 3

[0046] As another example, this Example 3 proposes a method for synthesizing and applying a stoichiometric manganese oxide electrode material based on Example 2, replacing 3.9g of ammonium molybdate with 5.4g of ammonium tungstate, and the other parameters and conditions are exactly the same as those in Example 2. The chemical formula is (Bi 0.02 La 0.01 Nb 0.01 W 0.01 Se 0.01 )Mn 0.94 O 1.9 S 0.05 (PO4) 0.05 The layered manganese oxide has an average valence of +3.62 because of the interlayer insertion of sodium, ammonium and a small amount of high-valent metal ions.

[0047] It should be noted that the parts in this embodiment that are the same or similar to those in the second embodiment can be referenced to each other and will not be described in detail in this application.

[0048] Embodiment 4

[0049] As another embodiment, this embodiment 4 proposes, on the basis of the embodiment 2, a method for synthesizing and applying a stoichiometric ratio manganese oxide electrode material, in which the amount of high-valent metal ions added is doubled, that is, the corresponding metal ion salt is added according to a molar ratio of 2:0.1:0.04:0.04:0.04:0.04:0.04, and the other parameters and conditions are exactly the same as those in the embodiment 2. The chemical formula is (Bi 0.04 La 0.02 Nb 0.02 Mo 0.02 Se 0.02 )Mn 0.88 O 1.9 S 0.05 (PO4) 0.05 The layered manganese oxide has an average valence of +3.58 because of the interlayer insertion of sodium, ammonium and a small amount of high-valent metal ions.

[0050] It should be noted that the parts in this embodiment that are the same or similar to those in the second embodiment can be referenced to each other and will not be described in detail in this application.

[0051] Comparative Example 1

[0052] As a comparative example, based on Example 1, no high-valent metal ion salt is added to the reaction kettle in step 1, no sulfiding agent and phosphate are added to the aging kettle in step 4, and other parameters and conditions are exactly the same as those in Example 2. MnO2 positive electrode material can be obtained, and the average valence of manganese is +3.84.

[0053] It should be noted that the parts in this embodiment that are the same or similar to those in the second embodiment can be referenced to each other and will not be described in detail in this application.

[0054] The positive electrode sheets obtained by the methods of Example 2 to Example 4 and Comparative Example 1 have the cycle and rate performance of the aqueous zinc secondary battery obtained by assembling the positive electrode sheets. Figure 1 and Figure 2 As shown, it can be seen that the battery assembled using the positive electrode of comparative example 1 decays very quickly. After 3600 cycles, the battery capacity retention rate is less than 60%. The reason is that there is no high-valent metal ion support layer structure between the layers, which causes the MnO2 layered structure to collapse after the cycle and the battery capacity decays rapidly.

[0055] In the second embodiment of the present invention, (Bi 0.02 La 0.01 Nb 0.01 Mo 0.01 Se 0.01 )Mn 0.94 O 1.9 S 0.05 (PO4)0.05 The battery assembled with the positive electrode material has no capacity decay after 4000 cycles at a rate of 2C; 0.02 La 0.01 Nb 0.01 W 0.01 Se 0.01 )Mn 0.94 O 1.9 S 0.05 (PO4) 0.05 The initial cycle trend of the battery assembled with the positive electrode material is comparable to that of the battery in Example 2, and the capacity retention rate after 4000 cycles is 92%. 0.04 La 0.02 Nb 0.02 W 0.02 Se 0.02 )Mn 0.88 O 1.9 S 0.05 (PO4) 0.05 The capacity retention rate of the positive electrode material after 4000 cycles is as high as 89%, which proves that the stoichiometric manganese oxide synthesized by the present invention has excellent cycle stability.

[0056] In addition, if Figure 2 As shown, compared with the battery assembled with the positive electrode of the control group, the battery assembled with the positive electrode materials synthesized in Examples 2 to 4 has better rate performance. This is because sulfur replaces part of the oxygen position in the manganese oxide, which improves the internal proton and Zn of the manganese oxide positive electrode. 2+ 、Na + Ionic conductivity.

[0057] The charge-discharge curves and rate diagrams of the organic sodium ion batteries obtained in Examples 2 to 4 and Comparative Example 1 are shown in Figure 3 and Figure 4 As shown, the present invention is through Bi 3+ ,La 3+ , Nb 5+ 、Mo 6+ / W 6+ 、Se 6+ The doping of the layered manganese oxide with metal ions and S ions and the coating with phosphate inhibited the dissolution of manganese, stabilized the layered structure, and improved the ionic conductivity of the material. In Examples 2 to 4, stoichiometric layered manganese oxides with high discharge specific capacity and good rate performance were obtained.

[0058] The stoichiometric layered manganese oxide structures obtained in Examples 2 to 4 and Comparative Example 1 are as follows Figure 5 As shown, the synthesized stoichiometric layered manganese oxide positive electrode is spherical particles with a size of 5-10 microns, while Figure 5The electron microscope images of Example 2 and Example 3 show that compared with Bi 3+ ,La 3+ , Nb 5+、 Mo 6+ 、Se 6+ Doped manganese oxide materials, Bi 3+ ,La 3+ , Nb 5+ , W 6 + 、Se 6+ Doping makes the crystallite size on the spherical particles more narrow and elongated, while the surface of the MnO2 positive electrode material in comparative example 1 is more loose and porous.

[0059] It should be noted that the parts in this embodiment that are the same or similar to those in the first embodiment can be referenced to each other and will not be described in detail in this application.

[0060] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

Claims

1. A stoichiometric manganese oxide electrode material, characterized in that: The general chemical formula is: A X MnO 2-y-z S y (PO4) z , where A includes trivalent metal ions, pentavalent metal ions and hexavalent metal ions, the types of doping elements are greater than or equal to 5, and X is the atomic content parameter of element A, 0.01≤x≤0.2; y is the atomic content parameter of sulfur element, 0.01≤y≤0.15; z is the ion content parameter of phosphate ion, 0.01≤z≤0.1; and the valence state of Mn is +3.1 to +3.

9.

2. The stoichiometric manganese oxide electrode material according to claim 1, characterized in that: The trivalent metal ions include one or more of indium, bismuth, lanthanum, cobalt, iron, chromium and aluminum; the pentavalent metal ions include one or more of niobium and tantalum; and the hexavalent metal ions include one or more of molybdenum, tungsten and selenium.

3. The method for synthesizing a stoichiometric manganese oxide electrode material according to any one of claims 1 to 2, characterized in that: The following steps are involved: Step 1: preparing a mixed solution of manganese salt and a plurality of high-valent ion salts, and adding a conductive additive and a dispersant; Step 2: prepare an alkaline solution and add a surfactant; Step 3: Add the alkaline solution in step 2 dropwise to the solution in step 1 to obtain a slurry through reaction, transfer the slurry to an aging kettle, add a sulfiding agent and a phosphate for aging, and then obtain a stoichiometric manganese oxide electrode material after filtering, washing and drying.

4. The method for synthesizing a stoichiometric manganese oxide electrode material according to claim 3, characterized in that: In step 1, the dispersant includes sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate or polyacrylamide; the conductive additive includes carbon fiber, graphene, carbon nanotube or acetylene black.

5. The method for synthesizing the stoichiometric manganese oxide electrode material according to claim 3, characterized in that: In step 2, the alkaline solution includes ammonia water, quaternary ammonium base, lithium alkaline solution, sodium alkaline solution or potassium alkaline solution; the surfactant is sodium dodecyl sulfate, sodium dodecylbenzene sulfonate or octadecyltrimethylammonium chloride.

6. The method for synthesizing a stoichiometric manganese oxide electrode material according to claim 3, characterized in that: In step three, the vulcanizing agent includes one or more of thioacetamide, thiourea, sodium thiosulfate and sodium sulfide; the phosphate includes one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate and sodium monohydrogen phosphate.

7. The method for synthesizing a stoichiometric manganese oxide electrode material according to claim 3, characterized in that: In step three, the reaction and aging are carried out in an oxidizing atmosphere or a solution containing an oxidant.

8. The use of the stoichiometric manganese oxide electrode material according to claim 1, characterized in that: The stoichiometric manganese oxide electrode material is compounded onto a metal current collector to prepare a manganese oxide positive electrode for an aqueous or organic secondary battery.

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