Eu / Mo co-doped Mn2O3 and Na2Mn8O16 and MnCO3 composite material and preparation method thereof

Abstract

The invention discloses an Eu / Mo co-doped Mn2O3 (at) Na2Mn8O16 (at) MnCO3 composite material and a preparation method thereof, and belongs to the field of inorganic materials. The preparation method comprises the following steps: adding europium nitrate hexahydrate, a manganese nitrate solution, urea and sodium molybdate into purified water for dissolving, and carrying out constant-temperature reaction in a hydrothermal reaction kettle; after the reaction is finished, filtering, putting a precursor into a drying oven, drying, re-dispersing the precursor into deionized water, adding urea and manganese sulfate monohydrate, uniformly dispersing, performing hydrothermal reaction again, cooling to room temperature, washing precipitate with water, calcining in a muffle furnace, and cooling to obtain the Eu / Mo co-doped Mn2O3 (at) Na2Mn8O16 (at) MnCO3 composite material. According to the preparation method, the electrochemical performance of the composite material is improved through two-step hydrothermal treatment, cubic and conjoined sphere shapes with burrs are observed microcosmically, and the structure endows the material with an interconnected conductive network, a roughened high-activity surface and a more stable overall structure.

Description

TECHNICAL FIELD

[0001] The application discloses Eu / Mo co-doped Mn2O3@Na2Mn8O 16 The application discloses an Eu / Mo co-doped Mn2O3@Na2Mn8O BACKGROUND

[0002] With the rapid growth of global demand for renewable energy, developing large-scale, safe and low-cost electrochemical energy storage systems has become the focus of current research. Among various energy storage technologies, aqueous zinc-ion batteries are widely considered as one of the most promising candidate technologies for application in smart grids and distributed energy storage fields due to their safety, environmental friendliness, abundant zinc resources and high theoretical capacity.

[0003] Among the many positive electrode materials, manganese-based oxides have attracted widespread attention due to their multi-valence characteristics, high working voltage and abundant resources. Although manganese oxides have complex structures, this characteristic affects their surface properties and corresponding electrochemical performance, but also provides a stable framework for the reversible insertion / deintercalation of zinc ions. However, the further development of this type of material still faces several key challenges. First, manganese will undergo a dissolution-redeposition behavior during the cycling process, leading to irreversible loss of active material and serious capacity decay. Second, the Jahn-Teller effect will cause distortion of the crystal structure, destroying the structural integrity of the electrode. In addition, the intrinsic electronic conductivity of manganese-based materials is low, which limits their rate performance and the full utilization of active sites.

[0004] Doping modification and compounding of manganese oxides are currently the most effective methods. Doping can form lattice defects inside the material, shortening the diffusion distance of zinc ions, and compounding can effectively inhibit the problems of volume expansion and dissolution existing in the active material, and improve the electronic conductivity of the material. The combination of doping modification and compounding can improve the application of manganese-based materials in aqueous zinc-ion batteries. SUMMARY

[0005] In order to overcome the above technical defects, the application provides an Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material and a preparation method thereof. Eu(NO3)3.6H2O, Mn(NO3)2 solution, urea and Na2MoO4 are sequentially added to pure water, and a hydrothermal reaction kettle is used for constant temperature reaction; after the reaction is completed, the precursor is dried in an oven, the precursor is dispersed in deionized water again after drying, and then urea and MnSO4. H2O are added, and the hydrothermal reaction is carried out again after uniform dispersion; after cooling to room temperature, the precipitate is washed with water three times. Then calcination is carried out in a muffle furnace, and the Eu / Mo co-doped Mn2O3@Na2Mn8O 16MnCO3 composite material. The synthesis method is simple, low in cost and suitable for large-scale industrial production.

[0006] The Eu / Mo co-doped Mn2O3@Na2Mn8O 16 The MnCO3 composite material, wherein: XRD diffraction peaks are 23.2°, 33.1°, 49.8° and 55.29°; XPS peaks are 640.79 eV, 641.91 eV, 642.5, 529.32 eV, 531.14 eV, 289.13 eV, 1071.52, 1134.73 eV, 1164.49 eV, 1125.44 eV and 1155.36 eV, Mn is coexistent in +2, +3 and +4 valences, and Eu is coexistent in +2 and +3.

[0007] The Eu / Mo co-doped Mn2O3@Na2Mn8O 16 The preparation method of the MnCO3 composite material comprises the following steps:

[0008] In the first step, the europium nitrate hexahydrate and manganese nitrate solution are dispersed in deionized water, and then urea and sodium molybdate are added in sequence and stirred uniformly;

[0009] In the second step, the uniformly stirred solution is placed in a hydrothermal reaction kettle and reacted at a constant temperature in an oven, and then naturally cooled;

[0010] In the third step, the product is taken out from the hydrothermal reaction kettle, washed and filtered, and then placed in an oven for drying;

[0011] In the fourth step, the hydrothermal reaction product is re-dispersed in deionized water, and then urea and manganese sulfate monohydrate are added in sequence and stirred uniformly;

[0012] In the fifth step, the product is placed in a hydrothermal reaction kettle and reacted at a constant temperature in an oven, and then naturally cooled;

[0013] In the sixth step, the product is taken out from the hydrothermal reaction kettle, washed and filtered, and then placed in an oven for drying;

[0014] In the seventh step, the product is calcined in a muffle furnace and cooled to obtain the Eu / Mo co-doped Mn2O3@Na2Mn8O 16 MnCO3 composite material.

[0015] Further, in the first step of the above technical solution, the molar ratio of the europium nitrate hexahydrate to the manganese nitrate is 1:9; and the molar ratio of the urea to the sodium molybdate is 5:1.

[0016] Further, in the first step of the above technical solution, the molar ratio of the manganese nitrate, the urea to the sodium molybdate is 9:25:5.

[0017] Further, in the above technical solution, in the first and fourth steps, the ratio of manganese nitrate to manganese sulfate monohydrate is 9:10.

[0018] Further, in the above technical solution, in the second and fifth steps, the constant temperature reaction temperature is 160 DEG C, and the reaction time is 8 hours.

[0019] Further, in the above technical solution, in the third and sixth steps, the reaction product is washed with pure water, the reaction product is placed in pure water to form a suspension, and ultrasonic cleaning is carried out in an ultrasonic cleaner for 3 minutes, and the suspension is then suction filtered, and the washing is carried out a total of 3 times.

[0020] Further, in the above technical solution, in the third and sixth steps, the drying temperature is 80 DEG C, and the drying time is 1 hour.

[0021] Further, in the above technical solution, in the fourth step, the molar ratio of urea to manganese sulfate monohydrate is 3:1.

[0022] Further, in the above technical solution, in the seventh step, the calcination temperature is 450 DEG C, and the constant temperature calcination time is 5 hours, wherein the temperature rising program is set to 2 hours, and the temperature is lowered to below 200 DEG C for 2 hours.

[0023] The application also provides the use of the above Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material in a water-based zinc ion battery.

[0024] Advantages of the application:

[0025] 1. The Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material is prepared, the raw materials used are inexpensive and easy to obtain, the synthesis method is simple, the preparation process is also relatively environmentally friendly, and the environmental pollution is relatively small.

[0026] 2. The method optimizes the Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material, improves the electrochemical performance of the composite material by adopting a two-step hydrothermal method, and microscopically observes the cube with burrs and the connected spherical shape, which endows the material with an interconnected conductive network, a rough high-activity surface, and a more stable overall structure. This optimization in appearance is expected to simultaneously improve the ion diffusion performance, electronic conductivity and cycle stability of the electrode, thereby comprehensively enhancing its zinc storage performance. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 For example 1, the Eu / Mo co-doped Mn2O3@Na2Mn8O 16XRD pattern of MnCO3 composite material;

[0028] Figure 2 Eu / Mo co-doped Mn2O3@Na2Mn8O 16 SEM pattern of MnCO3 composite material; wherein: a is the morphology of the cube with spikes, b is the morphology of the connected sphere;

[0029] Figure 3 Eu / Mo co-doped Mn2O3@Na2Mn8O 16 XPS pattern of MnCO3 composite material;

[0030] Figure 4 Eu / Mo co-doped Mn2O3@Na2Mn8O 16 EDS pattern of MnCO3 composite material;

[0031] Figure 5 Eu / Mo co-doped Mn2O3@Na2Mn8O 16 Element distribution pattern of the morphology of the cube with spikes in the MnCO3 composite material; wherein: a is the Na element distribution pattern, b is the Mn element distribution pattern, c is the O element distribution pattern, d is the C element distribution pattern; e is the Eu element distribution pattern; f is the Mo element distribution pattern;

[0032] Figure 6 Eu / Mo co-doped Mn2O3@Na2Mn8O 16 Element distribution pattern of the morphology of the connected sphere in the MnCO3 composite material; wherein: a is the Na element distribution pattern, b is the Mn element distribution pattern, c is the O element distribution pattern, d is the C element distribution pattern; e is the Eu element distribution pattern; f is the Mo element distribution pattern;

[0033] Figure 7 Eu / Mo co-doped Mn2O3@Na2Mn8O 16 Infrared spectrum of MnCO3 composite material;

[0034] Figure 8 Eu / Mo co-doped Mn2O3@Na2Mn8O 16 Raman spectrum of MnCO3 composite material;

[0035] Figure 9 Eu / Mo co-doped Mn2O3@Na2Mn8O 16 Cyclic charge-discharge pattern of MnCO3 composite material;

[0036] Figure 10Cyclic voltammograms of Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composites in Example 5.

[0037] Figure 11 Cyclic voltammograms of Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composites in Example 5.

[0038] Figure 12 Cyclic voltammograms of Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composites in Example 5. DETAILED DESCRIPTION

[0039] The present application is further described in the following by specific examples. However, these examples are merely exemplary and are not intended to limit the scope of the present application. The present application is not limited to the examples.

[0040] In the following examples, the reagents, materials and instruments used are conventional reagents, conventional materials and conventional instruments, which are commercially available, and the reagents involved can also be synthesized by conventional synthesis methods.

[0041] Example 1

[0042] Firstly, 0.5353 g of europium nitrate hexahydrate and 3.8654 g of manganese nitrate solution (mass fraction 50%) were dispersed in deionized water and stirred uniformly;

[0043] Secondly, 1.8018 g of urea and 1.4517 g of sodium molybdate were added to the mixed solution and stirred for 1 hour;

[0044] Thirdly, the mixed solution was placed in a hydrothermal reactor and reacted at a constant temperature of 160°C in an oven for 8 hours, and then naturally cooled down.

[0045] Fourthly, the reaction product was taken out of the hydrothermal reactor, washed and filtered, and placed in pure water to form a suspension, which was ultrasonically cleaned in an ultrasonic cleaner for 3 minutes, and then suction filtered, and the washing was repeated for a total of 3 times.

[0046] Fifthly, the dried hydrothermal reaction product was re-dispersed in 60 mL of deionized water, and 2.1622 g of urea and 2.0283 g of manganese sulfate monohydrate were added in sequence and stirred uniformly;

[0047] Sixthly, the uniformly dispersed solution was placed in a hydrothermal reactor and reacted at a constant temperature of 160°C in an oven for 8 hours, and then naturally cooled down.

[0048] Seventh step, the product was taken out from the hydrothermal reactor, the reaction product was washed and filtered using purified water, the reaction product was placed in purified water to form a suspension, and the suspension was ultrasonicated in an ultrasonic cleaner for 3 minutes. The suspension was then suction filtered, and the washing and filtering process was repeated for a total of 3 times. After washing and filtering, the product was placed in an oven for drying;

[0049] Eighth step, calcination in a muffle furnace to obtain Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material. The calcination temperature was 450°C, the temperature rising program was set for 2 hours, the temperature was lowered to below 200°C for 2 hours, and the constant temperature calcination time was 5 hours.

[0050] Figure 1 The XRD pattern of the Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material is shown. The main diffraction peak positions are in good agreement with the standard spectra of Mn2O3 (standard card PDF #04-007-0856), Na2Mn8O 16 (standard card PDF #00-029-1244) and MnCO3 (standard card PDF #04-011-3970), indicating that the composite material is mainly composed of Mn2O3, Na2Mn8O 16 and MnCO3. Through full spectrum fitting of the XRD pattern, the mass fractions of each phase were determined to be Mn2O3 50.8%, Na2Mn8O 16 29.9% and MnCO3 19.3%. Among them, the Mn2O3 phase belongs to the orthorhombic system, and the characteristic diffraction peaks are located at 33.1° and 55.29°, corresponding to the (222) and (404) crystal planes, respectively. The Na2Mn8O 16 phase belongs to the tetragonal system, and presents a strong diffraction peak at 49.8°, which belongs to the (411) crystal plane. The MnCO3 phase belongs to the rhombohedral system, and presents a strong diffraction peak at 23.2°, which belongs to the (012) crystal plane.

[0051] Figure 2 The SEM image of the Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material is shown. From the image, it can be clearly observed that there are cubes with spurs and connected spherical shapes. This structure endows the material with an interconnected conductive network, a roughened high-activity surface and a more stable overall structure. This optimization in morphology is expected to simultaneously improve the ion diffusion performance, electronic conductivity and cycle stability of the electrode, thereby comprehensively enhancing its zinc storage performance.

[0052] Figure 3 The Eu / Mo co-doped Mn2O3@Na2Mn8O16 @MnCO3 composite XPS full spectrum. From the figure can be observed Na1s, Mn2p, O1s, C1s, Eu3d, Mo3d characteristic peaks. Na 1s characteristic peak at the binding energy of 1070.75 eV, O 1s characteristic peak at 530.67 eV and 529.01 eV. Mn 2p3 / 2 peak position at 641.78 eV, Mn2p1 / 2 peak position at 653.26 eV, further peak processing of Mn 2p3 / 2 can be split into three peaks, the binding energy is 640.79 eV, 641.91 eV and 642.5 eV eV, respectively, corresponding to Mn 2+ , Mn 3+ and Mn 4+ species. O 1s fine spectrum, which can be decomposed into four peaks by fitting. The peak at 529.32 eV is attributed to metal-oxygen bond, including Mn–O and Na–O; the peak at 531.14 eV is clearly attributed to carbonate. The peak at 289.13 eV is attributed to O–C=O bond in carbonate, which is the evidence of MnCO3 related bond. Na 1s spectrum binding energy is at 1071.52 eV. Eu 3+ characteristic peak at 1134.73 eV (3d5 / 2) and 1164.49 eV (3d3 / 2). The signals at 1125.44 eV and 1155.36 eV can be respectively attributed to Eu 2+ 3d5 / 2 and 3d3 / 2 energy levels.

[0053] Figure 4 Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite EDS map, Mn, O, Na, C, Eu, Mo characteristic peaks are detected in the selected analysis area, confirming that Eu and Mo elements have been successfully introduced into the composite system.

[0054] Figure 5 Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite element distribution map with spurs, in which: O element signal intensity is the highest, and the spatial distribution is the most uniform, covering all analysis areas; Mn element signal intensity is second, and its spatial distribution is highly coincident with O element, which is consistent with the characteristics of composite oxide. In comparison, the signal intensity of Na element and Mo element is relatively low, and is in the form of discrete points, and is mainly enriched in the surface area of the particles.

[0055] Figure 6 Eu / Mo co-doped Mn2O3@Na2Mn8O 16The elemental distribution diagram of conjoined spherical particles in the @MnCO3 composite material shows that O and Mn have high signal intensities, consistent with the characteristics of composite oxides. In contrast, Eu has a relatively low signal intensity and is mainly enriched in the particle surface region.

[0056] Figure 7 Eu / Mo co-doped Mn2O3@Na2Mn8O 16 FTIR spectrum of MnCO3 composite material. Located at 611 cm⁻¹. -1 The peak belongs to MnO6 octahedron. 3+ -O stretching vibrations are found in Mn2O3 and Na2Mn8O. 16 Typical characteristics. Located at 514cm. -1 The absorption peak at this point is a composite peak, mainly originating from the Mn in the MnO6 octahedron. 4+ -O stretching vibrations, and may also include contributions from Na-O bond vibrations. Located at 665 cm⁻¹. -1 The peak at 736 cm⁻¹ belongs to the Mn-O stretching vibration of the manganese oxide framework. -1 The absorption peak at 856 cm⁻¹ corresponds to the symmetric / asymmetric bending vibration of the Mn-O-Mn bridging bond, reflecting the connection mode between [MnO₆] octahedra. -1 The peak is attributed to the bending vibration of carbonate ions.

[0057] Figure 8 Eu / Mo co-doped Mn2O3@Na2Mn8O 16 Raman spectra of MnCO3 composite materials at 635 cm⁻¹ -1 The peak at 333 cm⁻¹ is the most characteristic Raman peak of manganese oxides, corresponding to the octahedral stretching vibration of MnO₆. It is located at 333 cm⁻¹. -1 The peaks at 149 and 340 cm⁻¹ are attributed to the bending vibrations of the Mo-O-Mo bridged oxygen bonds. -1 Peaks in the low wavenumber region are typically attributed to lattice vibrational modes, including Mn-O-Mn bending vibrations and those involving Na. + The presence of these peaks is related to ion movement and lattice vibrations in Na₂Mn₈O₃. 16 The structure is consistent.

[0058] Example 2

[0059] First, disperse 0.5353g europium nitrate hexahydrate and 3.8654g manganese nitrate solution (50% by mass) in deionized water and stir until homogeneous;

[0060] The second step is to add 1.8018g of urea and 1.4517g of sodium molybdate to the well-mixed solution and stir for 1 hour.

[0061] The third step is to place the above mixed solution into a hydrothermal reactor and react it at a constant temperature of 160°C in an oven for 8 hours, followed by natural cooling.

[0062] The fourth step is to remove the reaction product from the hydrothermal reactor and perform a cleaning operation. Use pure water to clean and filter the reaction product, place the reaction product in pure water to form a suspension, and sonicate it in an ultrasonic cleaner for 3 minutes. Then filter the suspension. The process is repeated a total of 3 times.

[0063] Fifth step: redisperse the dried hydrothermal reaction product in 60mL of deionized water, add 2.1622g of urea and 2.9411g of manganese acetate tetrahydrate in sequence, and stir until homogeneous;

[0064] Step 6: Place the evenly dispersed solution in a hydrothermal reactor and react at a constant temperature of 160°C in an oven for 8 hours, then allow it to cool naturally.

[0065] Step 7: Remove the product from the hydrothermal reactor, wash and filter the reaction product with purified water, place the reaction product in purified water to form a suspension, and sonicate it in an ultrasonic cleaner for 3 minutes. Then filter the suspension by suction, washing a total of 3 times. After washing and filtering, place it in an oven to dry.

[0066] Step 8: Calcination in a muffle furnace followed by cooling to obtain Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material. The calcination temperature is 450℃, with the heating program set for 2 hours, cooling to below 200℃ for 2 hours, and the isothermal calcination time for 5 hours.

[0067] Example 3

[0068] First, disperse 0.5353g europium nitrate hexahydrate and 3.8654g manganese nitrate solution (50% by mass) in deionized water and stir until homogeneous;

[0069] The second step is to add 1.8018g of urea and 1.4517g of sodium molybdate to the well-mixed solution and stir for 1 hour.

[0070] The third step is to place the above mixed solution into a hydrothermal reactor and react it at a constant temperature of 160°C in an oven for 8 hours, followed by natural cooling.

[0071] The fourth step is to remove the reaction product from the hydrothermal reactor and perform a cleaning operation. Use pure water to clean and filter the reaction product, place the reaction product in pure water to form a suspension, and sonicate it in an ultrasonic cleaner for 3 minutes. Then filter the suspension. The process is repeated a total of 3 times.

[0072] Fifth step, the dried hydrothermal reaction product was re-dispersed in 60 mL of deionized water, 2.1622 g of urea and 1.8964 g of potassium permanganate were sequentially added, and stirred uniformly;

[0073] Sixth step, the uniformly dispersed solution was placed in a hydrothermal reactor, and reacted at a constant temperature of 160°C in an oven for 8 hours, and then naturally cooled down;

[0074] Seventh step, the product was taken out from the hydrothermal reactor, washed and filtered using purified water, the reaction product was placed in purified water to form a suspension, and was subjected to ultrasonic cleaning in an ultrasonic cleaner for 3 minutes, and then the suspension was suction filtered, and the washing was repeated for a total of 3 times. After washing and filtering, it was placed in an oven for drying;

[0075] Eighth step, calcination in a muffle furnace, and cooling down to obtain Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material. The calcination temperature was 450°C, the temperature rising program was set to 2 hours, the temperature was lowered to below 200°C for 2 hours, and the constant temperature calcination time was 5 hours.

[0076] Example 4

[0077] First step, 0.5353 g of europium nitrate hexahydrate and 3.8654 g of manganese nitrate solution (mass fraction 50%) were dispersed in deionized water, and stirred uniformly;

[0078] Second step, 1.8018 g of urea and 1.4517 g of sodium molybdate were added to the uniformly mixed solution, and stirred for 1 hour;

[0079] Third step, the above mixed solution was placed in a hydrothermal reactor, and reacted at a constant temperature of 160°C in an oven for 8 hours, and then naturally cooled down.

[0080] Fourth step, the reaction product was taken out from the hydrothermal reactor, washed and filtered using purified water, the reaction product was placed in purified water to form a suspension, and was subjected to ultrasonic cleaning in an ultrasonic cleaner for 3 minutes, and then the suspension was suction filtered, and the washing was repeated for a total of 3 times.

[0081] Fifth step, the dried hydrothermal reaction product was re-dispersed in 60 mL of deionized water, 2.1622 g of urea and 2.3750 g of manganese chloride tetrahydrate were sequentially added, and stirred uniformly;

[0082] Sixth step, the uniformly dispersed solution was placed in a hydrothermal reactor, and reacted at a constant temperature of 160°C in an oven for 8 hours, and then naturally cooled down;

[0083] Seventh step, take out the product from the hydrothermal reactor, use pure water to clean and filter the reaction product, put the reaction product in pure water to form a suspension, and ultrasonic in the ultrasonic cleaner for 3 minutes, then filter the suspension, a total of 3 times. After cleaning and filtering, put it in the oven to dry;

[0084] Eighth step, calcine in the muffle furnace, and cool down to get Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material. The calcination temperature is 450°C, the temperature rising program is set to 2 hours, and the temperature is lowered to below 200°C for 2 hours, and the constant temperature calcination time is 5 hours.

[0085] Example 5

[0086] Prepare the Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material prepared in examples 1-4 into a water-based zinc ion battery positive electrode.

[0087] First step, weigh 0.24g of Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material and 0.03g of acetylene black, and use a jade mortar to grind them thoroughly.

[0088] Second step, add 0.03g of polyvinylidene fluoride and 0.6mL of a mixture of nitrogen methyl pyrrolidone to the product after grinding to prepare the binder;

[0089] Third step, coat the mixed slurry on a stainless steel foil with a thickness of 0.01mm, and dry it at a constant temperature of 80°C for 1h.

[0090] Fourth step, after the active material is completely dried, process the stainless steel foil into a positive electrode sheet with a diameter of 10mm.

[0091] Fifth step, use a zinc metal sheet as the negative electrode, glass fiber paper as the separator, and a mixture solution of 2mol / L ZnSO4 solution and 0.2mol / L MnSO4 solution as the electrolyte, assemble a water-based zinc ion battery, and then wait for 24h before testing.

[0092] Figure 9 Use the Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material as the positive electrode of the water-based zinc ion battery to cycle the charge and discharge diagram. The charge and discharge test current is set to 50mA / g, 100mA / g, 200mA / g, 300mA / g and 500mA / g. Use the Eu / Mo co-doped Mn2O3@Na2Mn8O 16The discharge capacity of the MnCO3 composite material is up to 341.48 mAh g at a low current density of 50 mA / g -1 During the electrochemical cycling process, trace amounts of SO4 2- may participate in the formation of a more stable, ionically conductive solid electrolyte interphase film, effectively inhibiting side reactions, protecting the electrode structure, and achieving excellent rate performance and long cycle life.

[0093] Figure 10 Eu / Mo co-doped Mn2O3@Na2Mn8O 16 The cyclic voltammogram of the water-based zinc ion battery with the MnCO3 composite material as the positive electrode. The sample synthesized from manganese sulfate monohydrate shows a clear rising peak near 1.7 V, which may correspond to a more clear and faster redox reaction, which is speculated to be the Mn 3+ / Mn 4+ redox couple. This is due to the optimization of material crystallinity, Eu / Mo element distribution, and interface contact between phases by the two-step hydrothermal process, thereby providing more effective active sites.

[0094] Figure 11 Eu / Mo co-doped Mn2O3@Na2Mn8O 16 The alternating current impedance curve of the water-based zinc ion battery with the MnCO3 composite material as the positive electrode. From the figure, it can be seen that the contact resistance of the material to the current collector changes slightly after the two-step hydrothermal process, or the conductivity of the material itself is slightly adjusted, which is likely due to the generation of a more dense and stable surface passivation layer or interface by the two-step hydrothermal process. Although this slightly increases the initial energy barrier for charge transfer at the interface, this more stable interface can effectively inhibit the continuous decomposition of the electrolyte and the dissolution of manganese elements during the cycling process, thereby achieving extremely excellent long-term cycle stability.

[0095] Example 6

[0096] First, 0.5353 g of europium nitrate hexahydrate, 3.8654 g of manganese nitrate solution (50% by mass), and 2.0283 g of manganese sulfate monohydrate were dispersed in deionized water and stirred uniformly;

[0097] Second, 3.964 g of urea and 1.4517 g of sodium molybdate were added to the mixed solution and stirred for 1 hour;

[0098] Third, the above mixed solution was placed in a hydrothermal reaction kettle and reacted in an oven at a constant temperature of 160°C for 8 hours, and then naturally cooled.

[0099] Fourthly, the reaction product is taken out from the hydrothermal reactor, and is cleaned by using pure water to clean and filter the reaction product, and is placed in pure water to form a suspension, and is ultrasonically cleaned in an ultrasonic cleaner for 3 minutes, and is filtered, and is cleaned for a total of 3 times.

[0100] Fifthly, calcination in a muffle furnace, and cooling to obtain a Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material by one-step hydrothermal method. The calcination temperature is 450 DEG C, wherein: the temperature rising program is set to 2 hours, and the temperature is lowered to 200 DEG C or below for 2 hours, and the constant temperature calcination time is 5 hours.

[0101] Figure 12 The cyclic charge-discharge diagram of the Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material prepared by one-step and two-step hydrothermal methods. It can be seen from the diagram that the discharge capacity of the composite material prepared by the two-step hydrothermal method is obviously improved at the current densities of 50 mA / g and 100 mA / g.

[0102] According to the disclosure of the above description, those skilled in the art of the present application can also make appropriate changes and modifications to the above embodiments. Therefore, the present application is not limited to the specific embodiments described above, and some modifications and changes of the present application should also fall within the protection scope of the claims of the present application.

Claims

1. Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material, characterized in that: The XRD diffraction peaks were at 23.2°, 33.1°, 49.8°, and 55.29°; the XPS peaks were at 640.79 eV, 641.91 eV, 642.5 eV, 529.32 eV, 531.14 eV, 289.13 eV, 1071.52 eV, 1134.73 eV, 1164.49 eV, 1125.44 eV, and 1155.36 eV. Mn exhibited a coexistence of +2, +3, and +4 valences, while Eu exhibited a coexistence of +2 and +3 valences.

2. The Eu / Mo co-doped Mn2O3@Na2Mn8O as described in claim 1 16 The method for preparing @MnCO3 composite materials is characterized by, Includes the following steps: The first step is to disperse europium nitrate hexahydrate and manganese nitrate in deionized water, then add urea and sodium molybdate in sequence and stir until well mixed. The second step is to place the well-stirred solution into a hydrothermal reactor, react it at a constant temperature in an oven, and then allow it to cool down naturally. The third step is to remove the product from the hydrothermal reactor, wash and filter it, and then put it into an oven to dry. Fourth step: The hydrothermal reaction product is redispersed in deionized water, and urea and manganese sulfate monohydrate are added in sequence and stirred until homogeneous; The fifth step is to place it in a hydrothermal reactor and react it at a constant temperature in an oven, followed by natural cooling. Step 6: Remove the product from the hydrothermal reactor, wash and filter it, and then dry it in an oven. Step 7: Calcination in a muffle furnace followed by cooling to obtain Eu / Mo co-doped Mn2O3@Na2Mn8O 16 @MnCO3 composite material.

3. The Eu / Mo co-doped Mn2O3@Na2Mn8O3 according to claim 2 16 The method for preparing @MnCO3 composite materials is characterized by: In the first step, the molar ratio of europium nitrate hexahydrate to manganese nitrate is 1:9; the molar ratio of urea to sodium molybdate is 5:

1.

4. The Eu / Mo co-doped Mn2O3@Na2Mn8O3 according to claim 2 16 The method for preparing @MnCO3 composite materials is characterized by: In the fourth step, the molar ratio of urea to manganese sulfate monohydrate is 3:

1.

5. The Eu / Mo co-doped Mn2O3@Na2Mn8O3 according to claim 2 16 The method for preparing @MnCO3 composite materials is characterized by: In steps two and five, the constant temperature reaction temperature is 160℃, and the reaction time is 8 hours.

6. The Eu / Mo co-doped Mn2O3@Na2Mn8O3 according to claim 2 16 The method for preparing @MnCO3 composite materials is characterized by: In steps three and six, the reaction products are washed with pure water. The reaction products are placed in pure water to form a suspension, and then ultrasonicated for 3 minutes in an ultrasonic cleaner. The suspension is then filtered, and the process is repeated a total of three times.

7. The Eu / Mo co-doped Mn2O3@Na2Mn8O3 according to claim 2 16 The method for preparing @MnCO3 composite materials is characterized by: In steps three and six, the drying temperature is 80℃ and the drying time is 1 hour.

8. The Eu / Mo co-doped Mn2O3@Na2Mn8O3 according to claim 2 16 The method for preparing MnCO3 composite materials is characterized by: In step seven, the calcination temperature is 450℃ and the constant temperature calcination time is 5 hours, of which the heating program is set for 2 hours and the cooling program is set to below 200℃ for 2 hours.

9. The Eu / Mo co-doped Mn2O3@Na2Mn8O as described in claim 1 16 Application of @MnCO3 composite materials in aqueous zinc-ion batteries.

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