Preparation method of magnesium-doped conjoined double-sphere ZnMn2-yMgyO4 material

Abstract

The invention discloses a preparation method of a magnesium element doped conjoined double-sphere ZnMn2-yMgyO4 material, and belongs to the technical field of zinc ion batteries. Zinc nitrate, manganese nitrate, urea and magnesium nitrate are added into distilled water, and a constant-temperature reaction is performed in a hydrothermal reaction kettle. And filtering the reaction product, drying the product in a drying oven, calcining in a muffle furnace, and cooling to obtain the ZnMn2-yMgyO4 material. According to the method, the electrochemical performance of the ZnMn2O4 material is improved by doping magnesium metal at a manganese site, a conjoined double-sphere form is observed in a microscopic form, wrinkles are fully distributed on the surface of the form, the specific surface area of the material can be well increased, the contact area with an electrolyte is increased, and active sites of a reaction are improved.

Description

Technical Field

[0001] The present invention discloses a preparation method of magnesium-doped conjoined double-sphere-shaped ZnMn 2-y Mg y O 4 materials, belonging to the technical field of zinc-ion batteries. Background Technique

[0002] Compared with lithium-ion batteries, aqueous zinc-ion batteries have many advantages. The biggest advantage is economic environmental protection. The electrolyte of zinc-ion batteries is an aqueous solution, which has outstanding environmental protection performance compared with the organic electrolytes used in lithium-ion batteries. During the assembly of zinc-ion batteries, it can be completed in the atmospheric environment, without relying on devices such as inert gases and glove boxes, and has good economy. Therefore, the development prospect of aqueous zinc-ion batteries is broad.

[0003] When aqueous zinc-ion batteries are developing rapidly, there are also certain problems. The zinc negative electrode has high activity in neutral electrolytes, and the hydrogen evolution reaction on the zinc surface will be stronger, resulting in the easy generation of zinc dendrites on the negative electrode of the battery and side reactions related to water / oxygen. As the most important component of zinc-ion batteries, the positive electrode material has problems such as dissolution of active substances, slow ion diffusion, and by-products, resulting in poor zinc-ion stability, which seriously hinders the practical application of aqueous zinc-ion batteries.

[0004] Therefore, it is urgent to modify the positive electrode material of aqueous zinc-ion batteries to improve the stability and specific capacity of the battery. Summary of the Invention

[0005] To solve the above problems, the present invention provides a preparation method of magnesium-doped ZnMn at the manganese site 2-y Mg y O 4 materials. Zinc nitrate, manganese nitrate, and urea are dispersed in distilled water. After sufficient stirring, magnesium nitrate is added. After the mixed solution is stirred sufficiently, it is placed in a hydrothermal reaction kettle and reacted at a constant temperature in an oven. After the reaction is completed, the reaction product is taken out and washed. After drying at a constant temperature, it is placed in a muffle furnace and calcined at a constant temperature. After cooling down with the furnace, ZnMn 2-y Mg y O 4 materials are obtained. This synthesis method is simple and low-cost, and is suitable for large-scale industrial production.

[0006] The preparation method of the conjoined double-sphere-shaped ZnMn 2-y Mg y O 4 materials of the present invention includes the following steps:

[0007] First step, disperse zinc nitrate in deionized water, add manganese nitrate and urea, and stir evenly;

[0008] In the second step, after adding magnesium nitrate, it is placed in a hydrothermal reactor and reacted at a constant temperature in an oven, and then cooled naturally;

[0009] In the third step, the product in the hydrothermal reactor is washed and filtered, and the product is placed in an oven to dry;

[0010] In the fourth step, the dried product is calcined in a muffle furnace and cooled to obtain ZnMn 2-y Mg y O 4 material.

[0011] Further, in the above technical solution, y = 0.01, 0.02, 0.03, 0.05.

[0012] Further, in the above technical solution, in the first step, the molar ratio of zinc nitrate, manganese nitrate to urea is 1:2:6.

[0013] Further, in the above technical solution, in the second step, the molar ratio of magnesium nitrate to manganese nitrate is 1:199, 2:198, 3:197, 5:195.

[0014] Further, in the above technical solution, in the second step, the constant temperature reaction temperature is 160 °C and the constant temperature reaction time is 8 hours.

[0015] Further, in the above technical solution, in the third step, the reaction product is washed and filtered with distilled water, the reaction product is placed in distilled water to form a suspension, and ultrasonic treatment is carried out in an ultrasonic cleaner for 3 minutes, and then the suspension is suction filtered, and the total washing is carried out 3 times.

[0016] Further, in the above technical solution, in the third step, the drying temperature is 80 °C and the drying time is 1 hour.

[0017] Further, in the above technical solution, in the fourth step, the calcination temperature is 400 °C, where: the heating program is set for 2 hours, cooled to below 200 °C for 2 hours, and the constant temperature calcination time is 5 hours.

[0018] The present invention also provides a conjoined double-sphere-shaped ZnMn 2-y Mg y O 4 material, where: y = 0.01, 0.02, 0.03, 0.05; the 2θ diffraction peaks are 29.286°, 36.403°, 44.785°, 51.909°, 54.44°, 59.011°, 60.808°.

[0019] The present invention also provides ZnMn 2-y Mgy O 4 Application of the material in the positive electrode sheet of an aqueous zinc-ion battery.

[0020] Advantages of the invention:

[0021] The invention provides a method for preparing Mg-doped modified ZnMn 2-y Mg y O 4 material. The synthesis method is simple and easy to operate. The raw materials used are cheap and easily available. After doping with Mg element, the electrochemical performance of the material can be well improved, and a conjoined double-sphere morphology can be observed in the microscopic morphology. This morphology is covered with wrinkles on the surface, which can well increase the specific surface area of the material, and thus increase the contact area with the electrolyte. The preparation process is also more environmentally friendly and does not pollute the environment. Brief description of the drawings

[0022] Figure 1 SEM diagram of the Mg-doped modified ZnMn 1.95 Mg 0.05 O 4 material in Example 1 of the present invention;

[0023] Figure 2 XRD diagram of the Mg-doped modified ZnMn 1.95 Mg 0.05 O 4 material in Example 1 of the present invention;

[0024] Figure 3 XPS diagram of the Mg-doped modified ZnMn 1.95 Mg 0.05 O 4 material in Example 1 of the present invention;

[0025] Figure 4 SEM diagram of the Mg-doped modified ZnMn 1.97 Mg 0.03 O 4 material in Example 2 of the present invention;

[0026] Figure 5 EDS diagram of the Mg-doped modified ZnMn 1.97 Mg 0.03 O 4 material in Example 2 of the present invention;

[0027] Wherein: a is the EDS spectrum diagram, and b is the position of the EDS test sampling point.

[0028] Figure 6 SEM diagram of the Mg-doped modified ZnMn 1.98 Mg 0.02 O 4 material in Example 3 of the present invention;

[0029] Figure 7 For the magnesium-doped modified ZnMn in Embodiment 3 of the present invention 1.98 Mg 0.02 O 4 Element distribution of the material

[0030] Figure; wherein: a is the element distribution diagram of Zn, Mn, and O, b is the element distribution diagram of Zn, c is the element distribution diagram of Mn, and d is the element distribution diagram of O.

[0031] Figure 8 For the magnesium-doped modified ZnMn in Embodiment 4 of the present invention 1.99 Mg 0.01 O 4 SEM image of the material

[0032] Figure 9 For the magnesium-doped modified ZnMn in Embodiment 5 of the present invention 2-y Mg y O 4 Galvanostatic charge-discharge graph of the material Detailed implementation manners

[0033] The present invention will be further described below through specific examples. However, these examples are merely exemplary and do not limit the protection scope of the present invention to only the embodiments.

[0034] In the following embodiments, the reagents, materials, and instruments used, unless otherwise specified, are all conventional reagents, conventional materials, and conventional instruments, which can be obtained commercially. Among them, the reagents involved can also be obtained by conventional synthesis methods.

[0035] Embodiment 1

[0036] First step, weigh 2.2728 g of zinc nitrate, disperse it in deionized water and stir, then add 4.1875 g of manganese nitrate and 4.3245 g of urea, and stir.

[0037] Second step, add 0.08904 g of magnesium nitrate to the uniformly mixed solution and stir for 2 hours; the molar ratio of magnesium nitrate to manganese nitrate is 5:195;

[0038] Third step, continuously stir the above mixed solution for 2 h, then put it into a hydrothermal reaction kettle and react at a constant temperature of 160 °C in an oven for 8 hours, and then cool down naturally.

[0039] Fourth step, take out the reaction product from the hydrothermal reaction kettle, perform a cleaning operation, wash and filter the reaction product with distilled water, place the reaction product in distilled water to form a suspension, and perform ultrasonic treatment in an ultrasonic cleaner for 3 minutes, and then filter the suspension. The total cleaning is carried out 3 times.

[0040] In the fifth step, the washed filtration product is placed in an oven and dried at 80 °C for 1 hour.

[0041] In the sixth step, the dried product is calcined in a muffle furnace. After the calcination is completed, the temperature is decreased with the furnace to obtain the ZnMn 1.95 Mg 0.05 O 4 material. The calcination temperature is 400 °C, where the heating program is set for 2 hours, the temperature is decreased to below 200 °C for 2 hours, and the constant-temperature calcination time is 5 hours.

[0042] As can be seen from Figure 1 , the synthesized material is mainly composed of small spherical particles and defective cube-shaped particles. The particles are relatively loose and there is no agglomeration phenomenon. Among them, there is a relatively unique conjoined double-sphere morphology. There are many holes in the cubic structure, and these holes mainly appear in the center position of the cube, which greatly increases the surface area of the cube, and a certain amount of electrolyte can be stored in the holes, thereby promoting the transfer of ions in the electrolyte.

[0043] As can be seen from Figure 2 , the diffraction angles corresponding to the diffraction peaks of this material are consistent with those of the tetragonal spinel phase ZnMn 2 O 4 standard card (PDF#24-1133). The sharp diffraction peaks indicate that the material has a high degree of crystallization. The diffraction peaks at 2θ of 29.286°, 36.403°, 44.785°, 51.909°, 54.44°, 59.011° and 60.808° in the figure respectively belong to the (112) crystal plane, (211) crystal plane, (220) crystal plane, (105) crystal plane, (312) crystal plane, (321) crystal plane and (224) crystal plane in the ZnMn 2 O 4 standard card library. No obvious impurity peaks are found in the figure, indicating that the synthesized material has a high purity.

[0044] As can be seen from Figure 3 is the XPS diagram of the doped and modified ZnMn 1.95 Mg 0.05 O 4 material. The binding energies of Zn2p 1 / 2 and Zn2p 3 / 2 are 1044.9 eV and 1021.83 eV respectively, indicating that Zn ions exist in the material in the divalent positive state. The two main peaks of Mn 2p, Mn 2p 3 / 2 and Mn 2p 1 / 2The electron binding energies are 642.11 eV and 653.86 eV respectively, and the peak energy interval is 11.75 eV, indicating that the valence state of the Mn element is +3. The characteristic peak of the Mn element is composed of two peaks, namely the Mn-O-Mn peak bond (529.80 eV) and the Mn-O-O bond (531.54 eV). The Mg1s binding energy was observed at 1304.45 eV. The valence states of the elements in the doped and modified material are the same as those in the ZnMn 2 O 4 material.

[0045] Example 2

[0046] First step, weigh 2.2728 g of zinc nitrate, disperse it in deionized water and stir, then add 4.2305 g of manganese nitrate and 4.3245 g of urea, and stir.

[0047] Second step, add 0.05343 g of magnesium nitrate to the uniformly mixed solution and stir for 2 hours. The molar ratio of magnesium acetate to manganese nitrate is 3:197.

[0048] Third step, continuously stir the above mixed solution for 2 h and then put it into a hydrothermal reaction kettle, react at a constant temperature of 160 °C in an oven for 8 hours, and then cool down naturally.

[0049] Fourth step, take out the reaction product from the hydrothermal reaction kettle, perform a cleaning operation, wash and filter the reaction product with distilled water, place the reaction product in distilled water to form a suspension, and perform ultrasonic treatment in an ultrasonic cleaner for 3 minutes, and then filter the suspension. Wash a total of 3 times.

[0050] Fifth step, put the washed and filtered product into an oven and dry it at 80 °C for 1 hour.

[0051] Sixth step, place the dried product in a muffle furnace for calcination. After the calcination is completed, cool it down with the furnace to obtain ZnMn 1.97 Mg 0.03 O 4 material. The calcination temperature is 400 °C, where the heating program is set for 2 hours, cooled down to below 200 °C for 2 hours, and the constant temperature calcination time is 5 hours.

[0052] It can be seen from Figure 4 that some of the surfaces of the cubic morphology are very smooth, while some are relatively rough and covered with wrinkles, and different cubic structures coexist.

[0053] It can be seen from Figure 5 the ZnMn 1.97 Mg 0.03 O 4It can be seen from the EDS map of the material that surface scanning of the material and point scanning at different morphological positions were carried out. The Au element was detected in the EDS map because the surface of the sample was sputtered with gold before the test to increase the conductivity of the sample surface. At the same time, a certain amount of carbon element was detected, mainly because the test carrier was a conductive carbon tape. Through the EDS test and analysis of the sample, the atomic ratio of Zn, Mn, O, and Mg was 1:2.9:3.4:0.05, which was close to the ratio in the molecular formula. Subsequently, EDS point scanning analysis was carried out on the representative particles in the sample. In the double-sphere morphology, the surface was mainly manganese oxide. On the surface of the cube structure, the triangular pyramid protrusion, and the sphere with more wrinkles, it was mainly zinc manganese oxide.

[0054] Example 3

[0055] First step, weigh 4.2520 g of zinc nitrate, disperse it in deionized water and stir, then add 8.4609 g of manganese nitrate and 4.3245 g of urea, and stir.

[0056] Second step, add 0.03562 g of magnesium nitrate to the uniformly mixed solution and stir for 2 hours. The molar ratio of magnesium nitrate to manganese nitrate is 2:198.

[0057] Third step, continuously stir the above mixed solution for 2 h and then put it into a hydrothermal reaction kettle, react at a constant temperature of 160 °C in an oven for 8 hours, and then naturally cool down.

[0058] Fourth step, take out the reaction product from the hydrothermal reaction kettle and carry out a cleaning operation. Wash and filter the reaction product with distilled water, place the reaction product in distilled water to form a suspension, and ultrasonicate it in an ultrasonic cleaner for 3 minutes, and then filter the suspension. Wash a total of 3 times.

[0059] Fifth step, put the washed and filtered product into an oven and dry it at 80 °C for 1 hour.

[0060] Sixth step, place the dried product in a muffle furnace for calcination. After the calcination is completed, cool it down with the furnace to obtain the ZnMn 1.98 Mg 0.02 O 4 material. The calcination temperature is 400 °C, where the heating program is set for 2 hours, cooled to below 200 °C for 2 hours, and the constant-temperature calcination time is 5 hours.

[0061] From Figure 6 it can be seen that there is a conjoined double-sphere morphology formed by two spherical particles connected together. This is not caused by particle agglomeration, but an independent special morphology. This morphology is covered with wrinkles, which can well increase the specific surface area of the material, thus increasing the contact area with the electrolyte and enhancing the active sites of the reaction.

[0062] From Figure 7 ZnMn in 1.98 Mg 0.02 O 4 the elemental distribution map of the material, it can be seen that the distributions of Zn, Mn, O, and Mg elements are relatively uniform.

[0063] Example 4

[0064] In the first step, weigh 2.2728 g of zinc nitrate, disperse it in deionized water and stir, then add 4.2734 g of manganese nitrate and 4.3245 g of urea, and stir.

[0065] In the second step, add 0.1781 g of magnesium nitrate to the uniformly mixed solution and stir for 2 hours. The molar ratio of magnesium nitrate to manganese nitrate is 1:199.

[0066] In the third step, continuously stir the above mixed solution for 2 h, then put it into a hydrothermal reaction kettle, keep it at a constant temperature of 160 °C in an oven for 8 hours, and then cool it naturally.

[0067] In the fourth step, take out the reaction product from the hydrothermal reaction kettle, perform a cleaning operation, wash and filter the reaction product with distilled water, place the reaction product in distilled water to form a suspension, and perform ultrasonic treatment in an ultrasonic cleaner for 3 minutes, and then perform suction filtration on the suspension. Wash a total of 3 times.

[0068] In the fifth step, put the washed and filtered product into an oven and dry it at 80 °C for 1 hour.

[0069] In the sixth step, calcine the dried product in a muffle furnace. After the calcination is completed, cool it with the furnace to obtain ZnMn 1.99 Mg 0.01 O 4 material. The calcination temperature is 400 °C, where the heating program is set for 2 hours, cooled to below 200 °C for 2 hours, and the constant-temperature calcination time is 5 hours.

[0070] From Figure 8 it can be seen that there are triangular prism-shaped protrusions on the cube morphology, which increases the contact surface between the material and the electrolyte.

[0071] Example 5

[0072] Prepare the ZnMn 2-y Mg y O 4 material into a positive electrode sheet of an aqueous zinc-ion battery and assemble it into a battery for testing.

[0073] In the first step, weigh 0.24 g of ZnMn 2-y Mg y O4 Materials, 0.03 g of acetylene black, were placed in an agate mortar and ground thoroughly for 40 min.

[0074] In the second step, 0.03 g of polyvinylidene fluoride and 0.7 ml of N-methylpyrrolidone were made into a binder and mixed thoroughly with the ground product.

[0075] In the third step, the mixed slurry was coated on a stainless steel foil and then placed in an oven and dried at 80 °C for 1 h.

[0076] In the fourth step, the stainless steel foil coated with the active material was punched into circular pieces with a diameter of 10 mm.

[0077] In the fifth step, a metal zinc sheet was used as the counter electrode, glass fiber as the separator, and the electrolyte was 2 mol / L ZnSO 4 solution, and the battery was assembled. After assembly, the battery was left stationary for 24 h and then waited to be tested.

[0078] From Figure 9 it can be seen that the highest initial charge-discharge capacity was for the ZnMn 1.97 Mg 0.03 O 4 material, which was 141.09 mAh / g. As the number of cycles increased, the ZnMn 1.95 Mg 0.05 O 4 material exhibited good electrochemical performance. At a current density of 50 mAh / g, after 10 cycles, the discharge capacity increased from 133.45 mAh / g to 150.94 mAh / g, and when charged and discharged at a current density of 100 mAh / g, the discharge capacity was basically stable at 127 mAh / g.

[0079] According to the disclosure of the above specification, those skilled in the art to which the present invention pertains can also make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.

Claims

1. Conjoined double ball form ZnMn 2-y Mg y The preparation method of O4 material is characterized in that: The following steps are involved: The first step is to disperse zinc nitrate in deionized water, add manganese nitrate and urea, and stir evenly; The second step is to add magnesium nitrate and stir evenly, and then put it into the hydrothermal reactor, react at a constant temperature in an oven, and then cool it down naturally; The third step is to wash and filter the product from the hydrothermal reactor and put the product into an oven for drying; The fourth step is to calcine the dried product in a muffle furnace and cool it down to obtain ZnMn 2-y Mg y O4 material.

2. According to claim 1, the conjoined double-ball ZnMn 2-y Mg y The preparation method of O4 material is characterized by: y＝0.01，0.02，0.03，0.05。 3. According to claim 1, the conjoined double-ball ZnMn 2-y Mg y The preparation method of O4 material is characterized by: In the first step, the molar ratio of zinc nitrate, manganese nitrate and urea is 1:2:

6.

4. According to claim 1, the conjoined double-ball ZnMn 2-y Mg y The preparation method of O4 material is characterized by: In the second step, the molar ratio of magnesium nitrate to manganese nitrate is 1:199, 2:198, 3:197, and 5:

195.

5. According to claim 1, the conjoined double-ball ZnMn 2-y Mg y The preparation method of O4 material is characterized by: In the second step, the isothermal reaction temperature is 160° C. and the isothermal reaction time is 8 hours.

6. According to claim 1, the conjoined double-ball ZnMn 2-y Mg y The preparation method of O4 material is characterized by: In the third step, the reaction product was washed and filtered with distilled water. The reaction product was placed in distilled water to form a suspension, and ultrasonicated for 3 minutes in an ultrasonic cleaner. The suspension was then filtered and washed 3 times in total.

7. According to claim 1, the conjoined double-ball ZnMn 2-y Mg y The preparation method of O4 material is characterized by: In the third step, the drying temperature is 80° C. and the drying time is 1 hour.

8. According to claim 1, the conjoined double-ball ZnMn 2-y Mg y The preparation method of O4 material is characterized by: In the fourth step, the calcination temperature is 400° C., wherein: the temperature rise program is set to 2 hours, the temperature is lowered to below 200° C. for 2 hours, and the constant temperature calcination time is 5 hours.

9. ZnMn in the form of conjoined double balls obtained by any one of the preparation methods of claims 1 to 8 2-y Mg y O4 material, characterized by: The ZnMn 2-y Mg y O4 material, y=0.01, 0.02, 0.03, 0.05; 2θ diffraction peaks are 29.286°, 36.403°, 44.785°, 51.909°, 54.44°, 59.011°, 60.808°.

10. ZnMn as claimed in claim 9 2-y Mg y Application of O4 materials in positive electrode of aqueous zinc-ion batteries.

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