Preparation method of beta / epsilon complex-phase manganese dioxide positive electrode material and energy storage material

Abstract

The invention discloses a preparation method of a high-performance beta / epsilon complex-phase manganese dioxide positive electrode material for multi-type energy storage application, and belongs to the field of lithium-manganese battery and aqueous zinc-manganese battery electrode materials. According to the method, industrial electrolytic manganese dioxide and soluble aluminum salt are taken as raw materials, the aluminum salt and EMD are mixed, ball-milled and dried, and a two-stage annealing process is adopted, so that the beta / epsilon complex-phase high-performance aluminum-doped manganese dioxide positive electrode material is obtained. After a CR2032HT lithium-manganese battery is assembled, the discharge capacity can reach 210 mAh under the constant resistance load of 100 DEG C and 1 kilohm, and the weight loss ratio of the material is 1t after the material is stored for 168 h and 300 h at 125 DEG C; 0.35% and lt; 0.5%; and after the material is stored at different temperatures for 1 hour, the direct-current internal resistance of the material at the high temperature of 125 DEG C is reduced, and excellent lithium-manganese battery high-temperature performance is shown. After an aqueous zinc-manganese battery is assembled, the material has a larger CV active area and a lower CV oxidation peak position at a scanning speed of 0.5 mV s <-1 >; under the current density of 1A g <-1 >, the material has higher discharge capacity (236.6 mAh / g), and has more excellent coulombic efficiency (close to 100%) and capacity retention ratio after 1200 cycles.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium-manganese batteries and aqueous zinc-manganese batteries, and particularly relates to a preparation method of a high-performance β / ε composite manganese dioxide positive electrode material and application of the material in the two types of energy storage devices. BACKGROUND

[0002] With the rapid development of portable electronic devices, electric vehicles and energy storage technologies, the requirements for micro lithium-manganese power sources are becoming higher and higher. Due to the characteristics of low cost, good safety, compact size, high mechanical strength and the like, the micro lithium-manganese power sources have become irreplaceable portable energy storage devices in the fields of consumer electronics, electronic price tags, industrial control mainboards, intelligent medical treatment, intelligent security, intelligent transportation, intelligent meters, Internet of Things and the like. However, with the wide application of the micro power sources, some special or extreme environments, such as aerospace, polar scientific exploration, deep-sea exploration, industrial kiln monitoring and the like, make the equipment and the corresponding micro power sources face the challenge of extreme temperature. In a high-temperature environment, the crystal structure stability of the material is poor, the dissolution of manganese elements is aggravated, and the side reaction between the electrolyte and the positive electrode is increased, which seriously affects the cycle life and safety of the battery. It is of great significance to develop manganese oxide positive electrode materials with high-temperature resistance for expanding the application boundary of lithium-manganese batteries and improving the performance of related equipment. In addition, the aqueous zinc-manganese battery is a low-cost and high-safety energy storage device with great application potential, but its energy storage performance depends on the breakthroughs in long cycle stability and high capacity. The manganese oxide positive electrode material is expected to have high cycle stability and high capacity. The development of manganese oxide with high stability and high capacity is also of great significance for the wide application of zinc-manganese batteries.

[0003] Due to the wide application scenarios of manganese dioxide, a large number of studies on the preparation and application of manganese dioxide have been carried out. Researchers use hydrothermal / solvothermal method, sol-gel method, electrochemical deposition method and the like to prepare manganese dioxide, with MnSO4 and KMnO4 as manganese raw materials, and explore the influence of preparation parameters such as solvent content, temperature, time, auxiliary synthesis solvent, voltage and PH value on the crystal form, morphology and specific surface area of manganese dioxide.

[0004] The synthesized manganese dioxide has zero-dimensional (nanoparticles), one-dimensional (nanorods / nanowires), two-dimensional (nanosheets / films), and three-dimensional (bulk structure) morphologies. The prepared crystal structures include α-MnO2 (tunnel structure, 2x2 channels), ε-MnO2 (layered tunnel structure, 2x2 channels), β-MnO2 (rutile type, 1x1 channels), γ-MnO2 (mixed tunnel structure, 1x4 and 2x2 channels coexist), and δ-MnO2 (layered structure). α-MnO2 is applied to the positive electrode material of sodium-ion batteries, with a reversible specific capacity of 120 mAh / g; β-MnO2 is applied to the positive electrode of lithium-manganese batteries, with an initial capacity of 180 mAh / g, but poor cycle stability (capacity retention rate of 60% after 100 cycles). γ-MnO2 is applied to catalyze CO oxidation, with a light-off temperature (T50) 50°C lower than that of β-MnO2; δ-MnO2 is applied to heavy metal adsorption (such as Pb 2+ 、Cd 2+ ) in environmental governance, with an adsorption capacity of more than 300 mg / g. In order to improve the performance of manganese dioxide in the field of energy storage, manganese dioxide is compounded with carbon materials such as graphene and activated carbon, and applied to supercapacitors, which improves the rate performance (capacity retention rate >80% at a current density of 10 A / g), and the energy density of supercapacitors reaches 15 Wh / kg. However, the above preparation process is suitable for laboratory research, and the yield of prepared manganese dioxide is not high; the wet chemical preparation method using MnSO4 and KMnO4 as manganese raw materials also has additional energy consumption or environmental disposal, increasing the preparation cost and time. Moreover, the stability of pure manganese dioxide in the field of energy storage is not good, and the structure is easy to collapse. Although there have been some studies on doping to improve the stability of manganese dioxide, its main application is in supercapacitors, and the capacity of lithium-ion batteries, sodium-ion batteries, and aqueous zinc-manganese batteries still needs to be greatly improved.

[0005] Therefore, it is urgent to explore a preparation process suitable for mass production, environmentally friendly, and low energy consumption, and to obtain high-performance manganese dioxide with high capacity and good stability, especially excellent stability at high temperatures.

[0006] The present application uses electrolytic manganese dioxide produced in large quantities as raw material, and only through annealing process, a proper amount of chemical elements is added to improve the strength of Mn-O bond, and the crystal structure of manganese dioxide is optimized, so that the crystal structure (β-MnO2) which can exist at high temperature and the crystal structure (ε-MnO2) with high ion diffusion rate are retained, thereby a large amount of manganese dioxide with high temperature structure stability and high capacity is produced. The preparation process is different from hydrothermal and solvothermal processes, and there is no environmental problem of auxiliary solvent, which is conducive to green production. In the framework of this preparation process, the influence of doping content, annealing process procedure and parameters on the crystal structure, stability and wide temperature capacity of manganese dioxide is explored, which has important significance for the development of portable electronic devices using miniature lithium manganese power supply and water-based zinc manganese battery in extreme environments. SUMMARY

[0007] The present application discloses a preparation method of high-performance β / ε complex-phase manganese dioxide cathode material for multi-type energy storage applications, which solves the problems of poor high-temperature structural stability and poor electrochemical energy storage performance of lithium manganese battery manganese dioxide cathode material, and poor cycle stability and low capacity of zinc manganese battery during charging and discharging.

[0008] Technical scheme 1. Raw material ratio Electrolytic manganese dioxide (EMD) and aluminum salt (aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum acetate) are mixed in a mass ratio of 1-60% of Al salt to EMD.

[0009] 2. Preparation steps Ball milling: the raw materials and zirconium oxide grinding balls (diameter 5 mm) are added to the ball milling tank in a ball-to-material ratio of 1:1-2:1, and ball milling is carried out at 100-400 rpm for 0.2-15 h to form a uniform precursor.

[0010] Drying: vacuum drying at 90°C for 12h to remove moisture.

[0011] Annealing: First stage: calcination at 260-380°C for 0.5-6h to decompose the aluminum salt and form a doped manganese dioxide precursor; Second stage: calcination at 425-600°C for 0.5-72h to form β / ε complex-phase manganese dioxide.

[0012] In some preferred cases, in the two-stage annealing process, the first-stage annealing temperature is 350°C, and the annealing holding time is 6h; the second-stage annealing temperature is 460°C, and the annealing holding time is 24h, and the heating rate is 5°C / min.

[0013] The two-stage annealing process ensures that the required β / ε-MnO2 is obtained, otherwise any one of the processes will produce impurities or non-target phase materials.

[0014] The β / ε-MnO2 prepared by the method contains β and ε crystal phases of manganese dioxide.

[0015] Another technical solution of the present application is the application of the doped manganese oxide cathode material in the preparation of energy storage materials including lithium manganese batteries or aqueous zinc manganese batteries.

[0016] A preparation method of a lithium manganese battery, the β / ε-MnO2 is mixed with acetylene black and PVDF to coat aluminum foil, and CR2032HT button cells are assembled.

[0017] A preparation method of an aqueous zinc manganese battery, the β / ε-MnO2 is mixed with superconducting carbon black and PVDF, and then NMP is used as a solvent to prepare a slurry to coat graphite paper, and CR2032 button cells are assembled, which are aqueous zinc manganese batteries.

[0018] Beneficial effects: Process simplification: ball milling realizes uniform mixing, annealing process is compatible with doping process, β / ε bimorph MnO2 preparation is realized, and the goal of improving the stability and high capacity of high-temperature manganese dioxide is achieved.

[0019] Industrial manganese raw materials: cheap industrial electrolytic manganese oxide is used as manganese raw material, and through annealing and doping modification, high-performance manganese dioxide for lithium manganese batteries and aqueous zinc manganese batteries is prepared. The process is cheap, green and environmentally friendly, and is suitable for batch industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 XRD of examples 1, 2, 3, 4, 5, 6, 8, 9, 10, 11.

[0021] Figure 2 SEM of the material of example 1.

[0022] Figure 3 XPS analysis of examples 1, 7 and EMD.

[0023] Figure 4 Band gap of examples 1, 7. Figure 5 Discharge capacity of example 1 at 100℃ under 1KΩ load.

[0024] Figure 6 Discharge pulse DC internal resistance of example 1 at room temperature.

[0025] Table 1 Battery performance parameters of example 1 before and after storage at 125℃ for 168h.

[0026] Table 2 Battery performance parameters of example 1 before and after storage at 125℃ for 300h.

[0027] Table 3. Change of direct current resistance of Example 1 before and after low temperature, normal temperature, high temperature storage.

[0028] Figure 7 Example 1 and Example 7 CV curves at 0.5 mV s -1

[0029] Figure 8 Example 1 and Example 7 capacity comparison chart at 1 A g -1

[0030] Figure 9 Example 1 and Example 7 long-term cycle performance and coulomb efficiency at 1 A g -1 DETAILED DESCRIPTION

[0031] The specific embodiments of the present application are described in detail below, but it should be understood that the scope of the present application is not limited to the specific embodiments. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without making creative efforts fall within the scope of the present application. The experimental methods described in the embodiments of the present application are all conventional methods unless otherwise specified.

[0032] The experimental methods and detection methods described below are all conventional methods unless otherwise specified; the reagents and raw materials described below are all commercially available unless otherwise specified.

[0033] The terms used in the present application should be understood as being used to describe specific embodiments, and should not be considered as limiting the present application. In addition, the numerical ranges described in the present application should be understood as explicitly disclosing all intermediate values between the upper and lower limits of the range. Each smaller range between any stated numerical value or numerical range of intermediate values, and any other numerical value or intermediate value within the stated range, is considered to be included within the scope of the present application. The upper and lower limits of these smaller ranges can be independently selected to be optionally included or excluded from the scope of the present application.

[0034] At the same time, unless the context clearly requires otherwise, the terms "comprise", "comprise", and the like in the entire specification and claims should be interpreted as having an inclusive meaning rather than an exclusive or exhaustive meaning; that is, as "including but not limited to".

[0035] Example 1 1. Weigh 50 g of aluminum nitrate nonahydrate and dissolve it in 150 ml of deionized water to form solution A.

[0036] 2. Weigh 100 g of electrolytic manganese dioxide (EMD) and add it to the ball mill tank.

[0037] ​​​3. Pour solution A into the ball mill jar.

[0038] 4. Ball mill for 0.5 h with zirconia milling balls (5 mm in diameter) at 250 rpm.

[0039] 5. Dry at 90 °C for 12 h to obtain the precursor solid powder.

[0040] 6. Put the solid powder into a corundum crucible and place it in a muffle furnace. First, heat it to 375 °C and calcine it for 6 h, then heat it to 460 °C and calcine it for 24 h. The heating rate for both annealing processes is 5 °C. After natural cooling, the material of Example 1 is obtained. Figure 1 The XRD pattern of the material and the XRD refinement pattern of the XRD pattern are shown in FIG. 1. The XRD is a composite phase of β-manganese dioxide and ε-manganese dioxide. Through the refinement fitting, the percentage contents of β-manganese dioxide and ε-manganese dioxide are 63.311% and 37.689%, respectively. The morphology structure (SEM) of the β / ε-MnO2 prepared by the process is shown in FIG. 2, which presents a block structure assembled by nanoparticles. Figure 2

[0041] Example 2 1. Weigh 50 g of aluminum nitrate nonahydrate and dissolve it in 150 ml of deionized water to form solution A.

[0042] 2. Weigh 100 g of electrolytic manganese dioxide (EMD) and add it to the ball mill jar.

[0043] 3. Pour solution A into the ball mill jar.

[0044] 4. Ball mill for 0.5 h with zirconia milling balls (5 mm in diameter) at 250 rpm. 5. Dry at 90 °C for 12 h to obtain the precursor solid powder.

[0045] 6. Put the solid powder into a corundum crucible and place it in a muffle furnace. First, heat it to 375 °C and calcine it for 6 h, then heat it to 460 °C and calcine it for 12 h. The heating rate for both annealing processes is 5 °C. After natural cooling, the material of Example 2 is obtained. The XRD pattern of the material is shown in FIG. 3, which has the same phase structure as the material of Example 1, except that there is a certain difference in the crystallization intensity, indicating that reducing the holding time of the second annealing process can also obtain β / ε composite phase manganese dioxide. Figure 1

[0046] Example 3 1. Weigh 50 g of aluminum nitrate nonahydrate and dissolve it in 150 ml of deionized water to form solution A.

[0047] 2. Weigh 100 g of electrolytic manganese dioxide (EMD) and add it to the ball mill jar.

[0048] ​​3. Pour solution A into the ball mill jar.

[0049] 4. Grind with zirconia grinding balls (5mm in diameter) for 15 hours at a speed of 250 rpm.

[0050] 5. Dry at 90℃ for 12 hours to obtain the precursor solid powder.

[0051] 6. The solid powder was placed in a corundum dry pan and calcined in a muffle furnace at 375°C for 6 hours, then calcined at 460°C for 24 hours. The heating rate for both annealing processes was 5°C. After natural cooling, the material of Example 3 was obtained. The XRD pattern of this material is shown below. Figure 1 As shown, its phase structure is mainly ε-phase manganese dioxide, indicating that ball milling also has an important influence on the crystal form of manganese oxide.

[0052] Example 4: 1. Weigh 50 g of aluminum nitrate nonahydrate and dissolve it in 150 ml of deionized water to form solution A.

[0053] 2. Weigh 100g of electrolytic manganese dioxide (EMD) and add it to the ball mill jar.

[0054] 3. Pour solution A into the ball mill jar.

[0055] 4. Grind with zirconia grinding balls (5mm in diameter) for 15 hours at a speed of 250 rpm.

[0056] 5. Dry at 90℃ for 12 hours to obtain the precursor solid powder.

[0057] 6. The solid powder was placed in a corundum dry pan and calcined in a muffle furnace at 375°C for 6 hours, then calcined at 440°C for 24 hours. The heating rate for both annealing processes was 5°C. After natural cooling, the material of Example 4 was obtained. The XRD pattern of this material is shown below. Figure 1 As shown, β / ε composite phase manganese dioxide can be obtained, but a heterogeneous peak appears near 22° and the degree of crystallization decreases, indicating that lowering the second annealing temperature has an important impact on the crystal transformation of manganese oxide and easily produces a small amount of heterogeneous phase.

[0058] Example 5: 1. Weigh 50 g of aluminum nitrate nonahydrate and dissolve it in 150 ml of deionized water to form solution A.

[0059] 2. Weigh 100g of electrolytic manganese dioxide (EMD) and add it to the ball mill jar.

[0060] 3. Pour solution A into the ball mill jar.

[0061] 4. Grind with zirconia grinding balls (5mm in diameter) for 0.5 hours at a speed of 250 rpm.

[0062] 5. Dry at 90°C for 12h to obtain the precursor solid powder.

[0063] 6. Put the solid powder into a corundum crucible and place it in a muffle furnace, first heat to 375°C and calcine for 6h, then heat to 500°C and calcine for 24h, the heating rate of both annealing is 5°C, after natural cooling, the material of Example 5 is obtained. The XRD pattern of the material is shown in Figure 1 , β / ε composite phase manganese dioxide can be obtained, but a miscellaneous peak appears near 18°, indicating that increasing the second stage annealing temperature has an important influence on the crystal transformation of manganese oxide.

[0064] Example 6: 1. Weigh 100 g of aluminum nitrate nonahydrate and dissolve it in 150 ml of deionized water to form solution A.

[0065] 2. Weigh 100 g of electrolytic manganese dioxide (EMD) and add it to the ball mill jar.

[0066] 3. Pour solution A into the ball mill jar.

[0067] 4. Mill with zirconia balls (diameter 5mm) at 250 rpm for 0.5h.

[0068] 5. Dry at 90°C for 12h to obtain the precursor solid powder.

[0069] 6. Put the solid powder into a corundum crucible and place it in a muffle furnace, first heat to 375°C and calcine for 6h, then heat to 460°C and calcine for 12h, the heating rate of both annealing is 5°C, after natural cooling, the material of Example 6 is obtained. The XRD pattern of the material is shown in Figure 1 , the phase of the material is the same as that of Example 1, which is also β / ε composite phase manganese dioxide, indicating that increasing the aluminum doping amount can also obtain β / ε composite phase manganese dioxide without producing other impurities.

[0070] Example 7: 1. Weigh 50 g of electrolytic manganese dioxide (EMD).

[0071] 2. Put the solid powder into a corundum crucible and place it in a muffle furnace, first heat to 375°C and calcine for 6h, then heat to 425°C and calcine for 2h, the heating rate of both annealing is 5°C, after natural cooling, the material of Example 7 is obtained. The powder absorption spectrum of the material is shown in Figure 4 , the band gap is slightly higher than that of Al-doped manganese oxide, indicating that Al doping does not reduce the conductivity of the material.

[0072] Example 8: 1. Weigh 50 g of aluminum nitrate nonahydrate and dissolve it in 150 ml of deionized water to form solution A.

[0073] 2. Weigh 100g of electrolytic manganese dioxide (EMD) and add it to the ball mill jar.

[0074] 3. Pour solution A into the ball mill jar.

[0075] 4. Grind with zirconia grinding balls (5mm in diameter) for 0.5 hours at a speed of 250 rpm.

[0076] 5. Dry at 90℃ for 12 hours to obtain the precursor solid powder.

[0077] 6. The solid powder was placed in a corundum dry pan and calcined in a muffle furnace at 460°C for 24 hours. The annealing heating rate was 5°C. After natural cooling, the material of Example 8 was obtained. The XRD pattern of this material is shown below. Figure 1 As shown, although a β / ε composite phase manganese dioxide can be obtained, compared with the phase of the material obtained by the two-stage annealing process in Example 1, an impurity peak appears near 18°, and the crystallinity of the phase is reduced. This indicates that only by adopting a suitable two-stage annealing process can a relatively pure target phase be obtained.

[0078] Example 9: 1. Weigh 50 g of aluminum nitrate nonahydrate and dissolve it in 150 ml of deionized water to form solution A.

[0079] 2. Weigh 100g of electrolytic manganese dioxide (EMD) and add it to the ball mill jar.

[0080] 3. Pour solution A into the ball mill jar.

[0081] 4. Grind with zirconia grinding balls (5mm in diameter) for 0.5 hours at a speed of 250 rpm.

[0082] 5. Dry at 90℃ for 12 hours to obtain the precursor solid powder.

[0083] 6. The solid powder was placed in a corundum dry pan and calcined in a muffle furnace at 375°C for 24 hours. The annealing heating rate was 5°C. After natural cooling, the material of Example 9 was obtained. The XRD pattern of this material is shown below. Figure 1 As shown, a double peak appears near 20°, indicating the formation of an impurity phase. This low-temperature first-stage process failed to form the ideal β / ε composite phase manganese dioxide.

[0084] Example 10: 1. Weigh 50 g of aluminum nitrate nonahydrate and dissolve it in 150 ml of deionized water to form solution A.

[0085] 2. Weigh 100g of electrolytic manganese dioxide (EMD) and add it to the ball mill jar.

[0086] 3. Pour solution A into the ball mill jar.

[0087] 4. Grind with zirconia grinding balls (5mm in diameter) for 0.5 hours at a speed of 250 rpm.

[0088] 5. Dry at 90℃ for 12 hours to obtain the precursor solid powder.

[0089] 6. Place the solid powder in a corundum dry pot, place it in a muffle furnace and heat it to 520°C for 24 hours. The annealing heating rate is 5°C. After natural cooling, the material of Example 10 is obtained.

[0090] Example 11: 1. Weigh 50 g of aluminum nitrate nonahydrate and dissolve it in 150 ml of deionized water to form solution A.

[0091] 2. Weigh 100g of electrolytic manganese dioxide (EMD) and add it to the ball mill jar.

[0092] 3. Pour solution A into the ball mill jar.

[0093] 4. Grind with zirconia grinding balls (5mm in diameter) for 0.5 hours at a speed of 250 rpm.

[0094] 5. Dry at 90℃ for 12 hours to obtain the precursor solid powder.

[0095] 6. The solid powder was placed in a corundum dry pan and calcined in a muffle furnace at 550°C for 24 hours. The annealing heating rate was 5°C. After natural cooling, the material of Example 11 was obtained. The XRD patterns of the materials prepared in Examples 10 and 11 are shown below. Figure 1 As shown, it exhibits obvious Mn2O3 phase characteristics. This indicates that a single moderate-temperature annealing (460℃) (Example 8) cannot obtain pure composite phase manganese oxide, and the degree of crystallization is low. When the temperature is increased (520℃, 550℃), a β / ε composite phase manganese dioxide with increased crystallinity and no impurities is not obtained; instead, it transforms into Mn2O3, which is not the ideal target phase material. This again demonstrates that only by adopting a suitable two-stage annealing process can a relatively pure β / ε composite phase manganese dioxide target product be obtained.

[0096] Rutile (β-MnO2) with its (1×1) tunnel structure possesses high mechanical strength and thermal stability, providing a rigid framework for composite systems and suppressing volume expansion during charging and discharging. ε-MnO2 typically exhibits a more robust layered tunnel structure with numerous defects and vacancies, allowing for the passage of protons (H⁺) and metal ions (such as Zn²⁺, Li⁻). +) high efficiency of intercalation / deintercalation, low polarization loss, but relatively poor structural stability. In order to combine the advantages of the two crystal forms, make the perfect transformation of electrolytic manganese dioxide (γ-MnO2) into β and ε bimorphous MnO2, and apply it to lithium-manganese batteries and zinc-manganese batteries, we improve the preparation and annealing process to obtain a simple, efficient, stable and high-capacity preparation method of Al-doped β / ε-MnO2.

[0097] We respectively analyzed the electrolytic manganese dioxide (EMD), the annealed electrolytic manganese dioxide (Example 7) and the two-stage annealed Al-doped manganese dioxide (Example 1) by XPS, as shown in Figure 3 The full spectrum analysis showed that the electrolytic manganese dioxide and the high-temperature annealed electrolytic manganese dioxide were mainly composed of Mn and O elements, and the Al-doped (Al-β / ε-MnO2) was mainly composed of Mn, O and Al elements. Through the analysis of Mn 2p orbit and O 1s orbit, the Mn of the high-temperature annealed electrolytic manganese dioxide moved to the low binding energy direction, which meant that the content of Mn 3+ increased. After Al doping, compared with the high-temperature annealed electrolytic manganese dioxide, Mn continued to move to the low binding energy direction, and the oxygen vacancy increased significantly, which meant that Al donated electrons to Mn, and there was obvious electron transfer between Al-Mn, which strengthened the Al-Mn bonding effect and was beneficial to improve the structural stability, and the doping of Al constructed more oxygen vacancy defects. In summary, Al doping optimized the electronic structure of manganese dioxide, Al-Mn bonding effect, and defect structure, thereby improving the material performance, which also made the β / ε-MnO2 exhibit obvious advantages in high-temperature performance. At the same time, in order to determine the influence of Al doping on the forbidden band width, we conducted solid ultraviolet test to determine the forbidden band width of β / ε-MnO2, as shown in Figure 4 After Al doping, the forbidden band width decreased slightly, indicating that Al doping would not reduce the conductivity of the material.

[0098] The β / ε-MnO2 prepared in Example 1 was used as the positive electrode material of lithium-manganese battery to assemble CR2032HT button cell, which was assembled as follows: β / ε-MnO2, acetylene black and PVDF were mixed at a ratio of 8:1:1 to prepare slurry, which was coated on aluminum foil to assemble CR2032HT button cell.

[0099] The discharge capacity under 1KΩ load at 100℃ was 210 mAh, as shown in Figure 5 The change of pulse direct current resistance during discharge of different capacity when the assembled CR2032HT button cell was used for pulse test at room temperature was as shown in Figure 6 The change of discharge resistance within 100 mAh capacity was not significant.

[0100] The materials prepared in Example 1 were stored in four batches at a high temperature of 125°C for 168 h. The weight loss rate of the materials was about 0.35% and the average weight loss rate was 0.348%. After 300 h of storage, the weight loss rate of the materials was about 0.5% and the average weight loss rate was 0.498%, as shown in Tables 1 and 2.

[0101] Table 1

[0102] Table 2

[0103] The materials prepared in Example 1 were stored in four batches at different temperatures for 1 hour. The DC internal resistance of the tested materials was compared with the DC internal resistance of the materials before testing. As shown in Table 3, under normal temperature conditions, the DC internal resistance of the materials did not change much after 1 hour of storage; after 1 hour of storage at a high temperature of 125°C, the DC internal resistance of the materials decreased significantly.

[0104] Table 3

[0105] comprehensive Figure 5 , 6 As shown in Tables 1, 2, and 3, the aluminum-doped β / ε-MnO2 prepared by this invention has a significant high-temperature advantage compared to room temperature, which gives it a certain advantage in the large-scale production of lithium manganese battery cathode materials.

[0106] The β / ε-MnO2 prepared in Example 1 was used as the positive electrode material for an aqueous zinc-manganese battery to assemble a CR2032 button cell. The assembly was as follows: β / ε-MnO2: superconducting carbon black: PVDF = 7:2:1 was mixed with NMP as a solvent to form a slurry, which was then coated onto graphite paper to assemble the CR2032 button cell.

[0107] At 0.5 mV s -1 Cyclic voltammetry (CV) tests were performed at the scan rate, such as... Figure 7 As shown, compared to pure MnO2 (Example 7), Al-doped β / ε-MnO2 has a larger CV active area and a lower oxidation peak.

[0108] In 1A g -1 The charge / discharge curves at current densities show that, as Figure 8 As shown, β / ε-MnO2 has a significantly higher discharge capacity than pure MnO2, reaching 236.6 mAh / g.

[0109] In 1 A g -1 Perform long-loop tests, such as Figure 9As shown, after 1200 cycles, the coulombic efficiency of β / ε-MnO2 is close to 100%, which can be attributed to the contribution of the dual-phase β / ε-MnO2, and its capacity is significantly higher than that of pure MnO2, and the capacity retention is greater than 100%.

[0110] In summary Figure 7 , 8 , 9, the aluminum-doped dual-phase β / ε-MnO2 prepared by the present application has obvious performance advantages, which has a certain advantage in the large-scale production of water-based zinc-manganese battery positive materials.

Claims

1. A method for preparing a β / ε multiphase manganese dioxide cathode material, characterized in that, β / ε-MnO2 is prepared by mixing Al salt and EMD with electrolytic manganese dioxide (EMD) and soluble aluminum salt, followed by ball milling, drying, and two-stage annealing.

2. The method according to claim 1, characterized in that, The aluminum salt is any one of aluminum sulfate, aluminum chloride, aluminum nitrate, or aluminum acetate.

3. The method according to claim 1, characterized in that, The mass ratio of Al salt to EMD is 1-60%.

4. The method according to claim 1, characterized in that, The ball milling speed is 250~300 rpm, and the ball milling time is 0.2 h~15 h.

5. The method according to claim 1, characterized in that, The process involves two stages of annealing. The first stage annealing temperature is 260~380℃, and the annealing holding time is 0.5~6 h. The second stage annealing temperature is 425~600℃, and the annealing holding time is 0.5~72 h. The heating rate is 1~10 ℃ / min.

6. The method according to claim 5, characterized in that, The process involves two stages of annealing. The first stage is annealing at 350℃ for 6 hours, and the second stage is annealing at 460℃ for 24 hours with a heating rate of 5℃ / min.

7. The doped manganese oxide cathode material prepared by the preparation method according to claims 1-6, characterized in that, β / ε-MnO2 contains manganese dioxide with β and ε bicrystalline phases.

8. The application of the doped manganese oxide cathode material according to claim 7 in the preparation of energy storage materials including lithium manganese batteries or aqueous zinc manganese batteries.

9. A method for preparing a lithium manganese battery, characterized in that, The β / ε-MnO2 of claim 7 is mixed with acetylene black and PVDF to form a slurry, which is then coated onto aluminum foil to assemble a CR2032HT button cell.

10. A method for preparing an aqueous zinc-manganese battery, characterized in that, After mixing the β / ε-MnO2 described in claim 7 with superconducting carbon black and PVDF, and then using NMP as a solvent, the mixture is slurried, coated onto graphite paper, and assembled to obtain a CR2032 button cell, which is an aqueous zinc-manganese battery.

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