A nitrogen-doped manganese dioxide / alpha-manganese sulfide composite material, a preparation method thereof and application of the composite material in a zinc ion battery
Patent Information
- Application Number
- CN202611149225.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-31
- Publication Date
- 2026-09-29
AI Technical Summary
b class="d_n">[0005]针对现有水系锌离子电池用二氧化锰正极本征导电性差、循环过程锰离子溶出严重、晶格易发生不可逆坍塌，以及传统硫脲气相掺杂工艺仅能实现晶格单一N、S阴离子掺杂、无法生成硫化物异质相、性能提升存在明显瓶颈等缺陷，本发明提供一种氮掺杂二氧化锰/立方岩盐相α-硫化锰复合材料及其制备方法与水系锌离子电池应用
[0024]相较于现有的锰基水系锌离子电池正极材料，本发明具有如下优点和进步性：
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Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of electrode materials for aqueous zinc-ion batteries. Specifically, it relates to a nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material, its preparation method, and its application. Background Technology
[0002] Manganese dioxide is the mainstream cathode material for aqueous zinc-ion batteries. However, pure manganese dioxide has poor intrinsic conductivity, and lattice collapse easily occurs during zinc ion insertion and extraction. Simultaneously, manganese ions continuously dissolve into the electrolyte, causing rapid capacity decay and short cycle life, making it difficult to meet practical energy storage requirements. Existing modification methods mostly focus on morphology control, cation doping, and oxygen vacancy construction, which can only simply optimize the manganese dioxide matrix structure. They do not simultaneously carry out gas-phase sulfidation modification, thus failing to form heterogeneous composite structures and cannot fundamentally alleviate the problems of manganese dissolution and structural damage.
[0003] The closest existing technology is the paper by LIANG JR et al. on the dual-temperature-zone calcination modification of δ-MnO2 with thiourea: upstream, thiourea is decomposed at 250℃ to produce ammonia and hydrogen sulfide, while downstream, manganese dioxide is treated at 170℃. This method can only dope N and S into the MnO2 lattice in anionic form, slightly improving conductivity through Mn-N and Mn-S bonds. The product is still pure-phase manganese dioxide, without the formation of an independent manganese sulfide crystalline phase (LIANG JR, et al. Dual Anions Doping Enhanced Conductivity and Stability of Layered δ-MnO2 Cathode for Aqueous Zinc-Ion Battery. Adv. Funct. Mater., 2025, 35, 2501135). This approach relies solely on single-lattice doping modification, lacking the synergistic effect of the two-phase heterogeneous interface. Its effect on buffering lattice distortion and inhibiting manganese dissolution is limited, resulting in a significant bottleneck in improving rate capability and long-cycle performance. By searching and analyzing existing technologies, it was found that they have multiple defects. First, the modification mechanism is singular and there is no synergistic effect of heterogeneous phases. Second, the thiourea pyrolysis temperature is high, and it is difficult to accurately control the degree of sulfidation over a wide temperature range, making it impossible to directionally generate cubic rock salt phase α-MnS. Third, there is a lack of synergistic quantitative control of manganese source, nitrogen and sulfur source and calcination temperature, making it difficult to simultaneously achieve uniform nitrogen doping and controllable in-situ sulfidation.
[0004] To address the aforementioned technological gaps, this invention provides a low-temperature, precise, partitioned calcination process. Through coordinated control of proportions and temperature, it simultaneously achieves the in-situ precipitation of manganese dioxide lattice nitrogen doping and cubic rock salt α-MnS heterogeneous phase. Relying on the dual synergistic effect of doping defects and heterogeneous interfaces, it simultaneously optimizes ion dynamics and structural stability. The process is simple and controllable, and has significant application value for the industrialization of high-performance aqueous zinc-ion batteries. Summary of the Invention
[0005] To address the shortcomings of existing manganese dioxide cathodes used in aqueous zinc-ion batteries, such as poor intrinsic conductivity, severe manganese ion dissolution during cycling, irreversible lattice collapse, and the limitations of traditional thiourea vapor-phase doping processes which can only achieve single N and S anion doping and cannot generate sulfide heterophases, resulting in significant bottlenecks in performance improvement, this invention provides a nitrogen-doped manganese dioxide / cubic rock salt phase α-manganese sulfide composite material, its preparation method, and its application in aqueous zinc-ion batteries.
[0006] This invention aims to simultaneously achieve in-situ controllable precipitation of nitrogen doping in the manganese dioxide lattice and α-MnS heterocrystalline phase by segmented low-temperature calcination in a dual-temperature zone and precise control of the sulfur-manganese atomic ratio. The entire preparation process is simple to operate, the process parameters are controllable, and the energy consumption is lower, making it suitable for large-scale batch preparation. The resulting composite electrode has both excellent ion transport kinetics and long-term structural stability, effectively balancing high rate capacity and ultra-long cycle life, thus solving the core performance shortcomings of traditional manganese-based cathode materials.
[0007] Specifically, the technical objective of this invention is achieved as follows: a method for preparing a nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material, the method comprising the following steps:
[0008] (1) Dissolve a soluble divalent manganese salt in N,N-dimethylformamide solvent and stir at 40~70℃ to obtain a homogeneous solution; add potassium permanganate solution to the solution and react at 40~70℃ for 30~60 min; after the reaction is completed, centrifuge to collect the solid precipitate, wash and dry to obtain manganese dioxide precursor; wherein, the molar ratio of divalent manganese ions in the divalent manganese salt to permanganate ions in the potassium permanganate is (1.4~1.6):1; more preferably, the molar ratio is 1.5:1;
[0009] (2) Take nitrogen and sulfur sources and place them in the upstream temperature zone of the tube furnace. Place the manganese dioxide precursor obtained in step (1) in the downstream temperature zone of the tube furnace and calcine it in stages under an inert carrier gas atmosphere. The upstream temperature zone temperature is 140~200℃, the downstream temperature zone temperature is 180~220℃, the heating rate is 3~8℃ / min, and the temperature is held for 1~4 h. After calcination, it is naturally cooled to room temperature to obtain nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material.
[0010] Wherein, the nitrogen and sulfur sources are single organic compounds containing both nitrogen and sulfur elements, or solid mixtures composed of nitrogen-containing compounds and sulfur-containing compounds; the mass ratio of the manganese dioxide precursor to the nitrogen and sulfur sources is 2:(3~5), corresponding to a sulfur-manganese atomic ratio of 1.7~2.9.
[0011] More preferably, in the preparation method of nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material as described above, the divalent manganese salt in step (1) is selected from one or more of the following mixtures: manganese sulfate monohydrate, manganese acetate tetrahydrate, manganese nitrate hexahydrate, and manganese chloride tetrahydrate.
[0012] More preferably, in the preparation method of nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material as described above, the reaction temperature in step (1) is 58~62℃ and the reaction time is 35~45 min.
[0013] More preferably, in the preparation method of nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material as described above, the washing in step (1) is alternating washing with deionized water and anhydrous ethanol; the drying is vacuum drying, the drying temperature is 50~80℃, and the drying time is 6~12 h.
[0014] More preferably, in the preparation method of nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material as described above, the mass ratio of the manganese dioxide precursor to the nitrogen and sulfur sources in step (2) is 2:3.5, corresponding to a sulfur-manganese atomic ratio of 2.0.
[0015] More preferably, in the preparation method of nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material as described above, in step (2), when the nitrogen and sulfur sources are single organic compounds containing both nitrogen and sulfur elements, the organic compound is thioacetamide or thiourea;
[0016] When the nitrogen and sulfur sources are solid mixtures composed of nitrogen-containing compounds and sulfur-containing compounds, the nitrogen-containing compound is urea and the sulfur-containing compound is elemental sulfur powder.
[0017] More preferably, in the preparation method of nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material as described above, the inert carrier gas in step (2) is nitrogen or argon.
[0018] More preferably, in the preparation method of the nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material as described above, the upstream temperature of the thioacetamide is 140~170℃, the heating rate is 3~8℃ / min, and the holding time is 2~4 h;
[0019] The upstream temperature zone of the thiourea is 170~200℃, the heating rate is 3~8℃ / min, and the holding time is 1~3 h.
[0020] It should be noted that the upstream and downstream of the tubular furnace in step (2) are independent temperature control zones. The upstream nitrogen and sulfur sources undergo low-temperature pyrolysis to produce nitrogen- and sulfur-containing gaseous active components, which migrate downstream with the carrier gas and undergo gas-solid reaction with the manganese dioxide precursor, simultaneously realizing nitrogen doping and in-situ sulfidation of manganese dioxide, and finally forming an N-MnO2 / α-MnS heterocomposite structure.
[0021] In addition, the present invention also provides a nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material, which is prepared by the above preparation method. The composite material is a heterogeneous composite structure of nitrogen-doped manganese dioxide and cubic rock salt phase α-manganese sulfide, wherein nitrogen doping enters the manganese dioxide lattice and α-manganese sulfide precipitates in situ as an independent crystal phase.
[0022] The present invention also provides an aqueous zinc-ion battery cathode, which comprises the above-mentioned nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material as the cathode active material.
[0023] The present invention also provides an aqueous zinc-ion battery comprising the above-described positive electrode.
[0024] Compared with existing manganese-based aqueous zinc-ion battery cathode materials, this invention has the following advantages and advancements:
[0025] (1) Existing thiourea double-temperature calcination can only prepare single-phase N and S co-doped manganese dioxide; This invention achieves in-situ generation of cubic rock salt phase α-MnS while realizing nitrogen doping of MnO2 lattice by precisely controlling the sulfur-manganese atomic ratio. Relying on the synergistic modification of lattice defects and heterogeneous interfaces, it breaks through the performance limit of traditional single-doped materials.
[0026] (2) The N-MnO2 and α-MnS two-phase interface form a built-in electric field, which reduces the charge transport barrier and weakens the Zn 2+ Electrostatic interactions with the manganese dioxide matrix enhance electron-to-Zn exchange. 2+ The diffusion rate and rate performance of the material are superior to those of pure MnO2.
[0027] (3) The flexible α-MnS phase can buffer the lattice distortion caused by the charging and discharging process and suppress the collapse of the sheet; the two-phase interface can anchor the manganese element, effectively alleviate the problem of manganese ion dissolution during the cycle, and significantly improve the long cycle capacity retention rate of the electrode.
[0028] (4) The present invention preferably uses thioacetamide as the nitrogen and sulfur source, and can stably generate NH3 and H2S reaction gases at a low temperature of 150℃, without the need for high-temperature cracking at 250℃ in the prior art, thus consuming less energy; at the same time, by limiting the S / Mn ratio, the degree of sulfidation is precisely controlled to prevent excessive sulfidation from damaging the active matrix of manganese dioxide, and the process has excellent reproducibility.
[0029] (5) The manganese dioxide precursor is synthesized by low temperature liquid phase method. Only one step of dual temperature zone calcination is needed to simultaneously complete nitrogen doping and in-situ sulfidation, without complicated post-processing steps. There are many types of nitrogen and sulfur raw materials available, and the cost is low. It is suitable for large-scale production and can be widely used in water-based energy storage zinc-ion batteries. Attached Figure Description
[0030] Figure 1 The image shows the XRD pattern of a nitrogen-doped manganese dioxide / α-manganese sulfide composite material and a manganese dioxide precursor prepared in Example 1 of this invention.
[0031] Figure 2 This is a SEM image of a nitrogen-doped manganese dioxide / α-manganese sulfide composite material prepared in Example 1 of this invention.
[0032] Figure 3 This is a TEM image of a nitrogen-doped manganese dioxide / α-manganese sulfide composite material prepared in Example 1 of this invention;
[0033] Figure 4 This is an HRTEM image of a nitrogen-doped manganese dioxide / α-manganese sulfide composite material prepared in Example 1 of this invention.
[0034] Figure 5 This is a rate performance diagram of a nitrogen-doped manganese dioxide / α-manganese sulfide composite material prepared in Example 1 of this invention.
[0035] Figure 6 This is a nitrogen-doped manganese dioxide / α-manganese sulfide composite material prepared in Example 1 of the present invention at 1 A g –1 Cyclic performance at current density.
[0036] Figure 7 This is a nitrogen-doped manganese dioxide / α-manganese sulfide composite material prepared in Example 1 of the present invention at 3 A g –1 Cyclic performance at current density.
[0037] Figure 8 This is the XRD pattern of the nitrogen-doped manganese dioxide cathode material prepared in Comparative Example 1 of this invention.
[0038] Figure 9 This is the XRD pattern of the manganese dioxide / α-manganese sulfide composite cathode material prepared in Comparative Example 2 of this invention. Detailed Implementation
[0039] This invention employs a low-temperature liquid-phase synthesis combined with a dual-temperature segmented heat treatment process to prepare nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode materials for use in aqueous zinc-ion batteries. By precisely controlling the precursor ratio, dual-temperature calcination temperature, and sulfur / manganese atomic ratio, this invention simultaneously achieves in-situ precipitation of nitrogen doping in the manganese dioxide lattice and the cubic rock salt phase α-MnS heterogeneous phase. Through the synergistic regulation of doping defects and the heterogeneous interface, the electronic conductivity, zinc ion transport kinetics, and crystal structure stability of the material are optimized, significantly improving the electrode rate performance and cycle life. The preparation method of this invention is described in detail below with reference to specific embodiments, but the scope of protection of this invention is not limited to the following embodiments.
[0040] Example 1:
[0041] A nitrogen-doped manganese dioxide / α-manganese sulfide composite material and its preparation method are disclosed, specifically following these steps:
[0042] Step 1: Dissolve 0.272 g (0.95 mmol) manganese nitrate hexahydrate in 60 mL of N,N-dimethylformamide solvent and stir thoroughly at 60 °C to obtain a homogeneous solution; add 0.02 g (0.63 mmol) potassium permanganate solution to the solution and react at 60 °C for 40 min; after the reaction is complete, centrifuge to collect the solid precipitate, wash alternately with deionized water and anhydrous ethanol, and dry under vacuum at 60 °C for 10 h to obtain the manganese dioxide precursor;
[0043] Step 2: A dual-temperature zone tubular furnace calcination process was adopted. 350 mg (4.6 mmol) of thioacetamide was placed in the upstream temperature zone of the tubular furnace, and 200 mg (2.3 mmol) of manganese dioxide precursor was placed in the downstream temperature zone of the tubular furnace, controlling the S / Mn atomic ratio to be 2.0. Segmented heating calcination was carried out under an argon atmosphere. The upstream temperature was controlled at 150℃, the downstream temperature was controlled at 200℃, the heating rate was 5℃ / min, and the holding time was 2 h. After calcination, the material was naturally cooled to room temperature to obtain nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material for zinc-ion batteries.
[0044] Example 2:
[0045] A nitrogen-doped manganese dioxide / α-manganese sulfide composite material and its preparation method are disclosed, specifically following these steps:
[0046] Step 1: Dissolve 0.272 g (0.95 mmol) manganese nitrate hexahydrate in 60 mL of N,N-dimethylformamide solvent and stir thoroughly at 60 °C to obtain a homogeneous solution; add 0.02 g (0.63 mmol) potassium permanganate solution to the solution and react at 60 °C for 40 min; after the reaction is complete, centrifuge to collect the solid precipitate, wash alternately with deionized water and anhydrous ethanol, and dry under vacuum at 60 °C for 10 h to obtain the manganese dioxide precursor;
[0047] Step 2: A dual-temperature zone tubular furnace calcination process is adopted. 440 mg (5.8 mmol) thiourea is placed in the upstream temperature zone of the tubular furnace, and 200 mg (2.3 mmol) manganese dioxide precursor is placed in the downstream temperature zone of the tubular furnace, controlling the S / Mn atomic ratio to be 2.5. Segmented heating calcination is carried out under an argon atmosphere. The upstream temperature is controlled at 180℃, the downstream temperature is controlled at 200℃, the heating rate is 5℃ / min, and the holding time is 1.5 h. After calcination, the material is naturally cooled to room temperature to obtain nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material for zinc-ion batteries.
[0048] Example 3:
[0049] A nitrogen-doped manganese dioxide / α-manganese sulfide composite material and its preparation method are disclosed, specifically following these steps:
[0050] Step 1: Dissolve 0.245 g (1.0 mmol) manganese acetate tetrahydrate in 60 mL of N,N-dimethylformamide solvent and stir thoroughly at 60 °C to obtain a homogeneous solution; add 0.105 g (0.67 mol) potassium permanganate solution to the solution and react at 60 °C for 40 min; after the reaction is complete, centrifuge to collect the solid precipitate, wash alternately with deionized water and anhydrous ethanol, and dry under vacuum at 60 °C for 10 h to obtain the manganese dioxide precursor;
[0051] Step 2: A dual-temperature zone tubular furnace calcination process is adopted. 480 mg (6.4 mmol) of thioacetamide is placed in the upstream temperature zone of the tubular furnace, and 200 mg (2.3 mmol) of manganese dioxide precursor is placed in the downstream temperature zone of the tubular furnace, controlling the S / Mn atomic ratio to be 2.8. Segmented heating calcination is carried out under a nitrogen carrier gas atmosphere. The upstream temperature is controlled at 150℃, the downstream temperature is controlled at 200℃, the heating rate is 5℃ / min, and the holding time is 2 h. After calcination, the material is naturally cooled to room temperature to obtain nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material for zinc-ion batteries.
[0052] Comparative Example 1:
[0053] Step 1: Dissolve 0.272 g (0.95 mmol) manganese nitrate hexahydrate in 60 mL of N,N-dimethylformamide solvent and stir thoroughly at 60 °C to obtain a homogeneous solution; add 0.02 g (0.63 mmol) potassium permanganate solution to the solution and react at 60 °C for 40 min; after the reaction is complete, centrifuge to collect the solid precipitate, wash alternately with deionized water and anhydrous ethanol, and dry under vacuum at 60 °C for 10 h to obtain the manganese dioxide precursor;
[0054] Step 2: A dual-temperature zone tubular furnace calcination process was adopted. 280 mg (4.6 mmol) of urea was placed in the upstream temperature zone of the tubular furnace, and 200 mg (2.3 mmol) of manganese dioxide precursor was placed in the downstream temperature zone of the tubular furnace, with the nitrogen content controlled to be the same as in Example 1. Segmented heating calcination was carried out under an argon atmosphere. The upstream temperature was controlled at 180°C, the downstream temperature was controlled at 200°C, the heating rate was 5°C / min, and the holding time was 2 h. After calcination, the material was naturally cooled to room temperature to obtain nitrogen-doped manganese dioxide cathode material for zinc-ion batteries.
[0055] Comparative Example 2:
[0056] Step 1: Dissolve 0.272 g (0.95 mmol) manganese nitrate hexahydrate in 60 mL of N,N-dimethylformamide solvent and stir thoroughly at 60 °C to obtain a homogeneous solution; add 0.02 g (0.63 mmol) potassium permanganate solution to the solution and react at 60 °C for 40 min; after the reaction is complete, centrifuge to collect the solid precipitate, wash alternately with deionized water and anhydrous ethanol, and dry under vacuum at 60 °C for 10 h to obtain the manganese dioxide precursor;
[0057] Step 2: A dual-temperature zone tubular furnace calcination process is adopted. 207 mg (0.805 mmol) of sulfur powder is placed in the upstream temperature zone of the tubular furnace, and 200 mg (2.3 mmol) of manganese dioxide precursor is placed in the downstream temperature zone of the tubular furnace, controlling the S / Mn atomic ratio to be 2.8. Segmented heating calcination is carried out under an argon atmosphere. The upstream temperature is controlled at 180℃, the downstream temperature is controlled at 200℃, the heating rate is 5℃ / min, and the holding time is 2 h. After calcination, the material is naturally cooled to room temperature to obtain manganese dioxide / α-manganese sulfide composite cathode material for zinc-ion batteries.
[0058] like Figure 1The image shows the XRD patterns of a nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material and a manganese dioxide precursor prepared in Example 1 of this invention. It can be seen that the N-MnO2 / α-MnS composite material prepared by nitriding and sulfidation modification still retains the characteristic diffraction peaks of MnO2, indicating that the main crystalline phase of manganese dioxide is maintained. New diffraction peaks appear at 29.6° and 34.3°, which are consistent with the α-MnS (JCPDS No. 06-0518) standard card, proving the successful construction of the N-MnO2 / α-MnS heterocomposite structure. Simultaneously, the diffraction peak at 12° of the composite material shifts to a lower angle. According to the Bragg equation, this change corresponds to an increase in interplanar spacing, originating from the entry of N dopant with a larger ionic radius into the manganese dioxide lattice, replacing some lattice oxygen and widening the interplanar spacing, confirming the effective introduction of nitrogen doping.
[0059] like Figure 2 As shown, it is a SEM image of a nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material prepared in Example 1 of the present invention. It can be seen that the N-MnO2 / α-MnS composite material synthesized in the present invention is formed by the self-assembly of nanosheets into micron-sized spherical clusters, exhibiting a loose and porous hierarchical flower-shaped structure. This porous structure is beneficial to electrolyte wetting and ion transport.
[0060] like Figure 3 The image shown is a TEM image of a nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material prepared in Example 1 of this invention. It can be seen that the N-MnO2 / α-MnS composite material synthesized in this invention consists of interwoven ultrathin sheets forming a floral pattern, and the pores between the sheets can shorten the ion solid-phase diffusion distance.
[0061] like Figure 4 As shown, this is an HRTEM image of a nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material prepared in Example 1 of the present invention. Two different lattice stripe regions can be observed. 0.72 nm corresponds to the (001) crystal plane of manganese oxide, and 0.26 nm corresponds to the (200) crystal plane of α-MnS. The two phase lattice regions are adjacent and form a clear heterogeneous interface, which directly confirms that α-MnS and N-MnO2 have successfully constructed a closely contacted heterogeneous composite structure.
[0062] like Figure 5 The figure shows the rate performance of an N-MnO2 / α-manganese sulfide composite cathode material prepared in Example 1 of this invention. The rate performance is shown at 0.1, 0.3, 0.5, 1, 2, and 3 A g. –1 At different current densities, the specific capacities of N-MnO2 / α-MnS were 381, 386, 372, 243, 146, and 117 mAh g, respectively. –1 The specific capacities of MnO2 were 436, 414, 325, 197, 121, and 93 mAh g, respectively.–1 The current density reversed and decreased to 3 A g. –1 At that time, the specific capacity of N-MnO2 / α-MnS (411 mAh g) –1 The concentration was significantly higher than that of pure MnO2 (363 mAh g). –1 It can be seen that at 0.1 and 0.3 Ag... –1 At the specified current density, the capacity of N-MnO2 / α-MnS is slightly lower than that of pure MnO2, due to the introduction of α-MnS reducing the effective proportion of active material. With increasing current density, the specific capacity of N-MnO2 / α-MnS is significantly higher than that of pure MnO2, and the decay is slower. This is attributed to the synergistic effect of nitrogen doping and the heterostructure interface, which improves ion transport kinetics and enhances structural stability, resulting in improved high-rate performance.
[0063] like Figure 6 As shown, it is a nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material prepared in Example 1 of the present invention at 1 A g. –1 Cycling performance at current density shows that N-MnO2 / α-MnS exhibits a more gradual degradation, with a specific capacity of 204 mAh g⁻¹ after 600 cycles. –1 After 500 cycles, the specific capacity of MnO2 is only 168 mAh g. –1 This indicates that nitrogen doping and the heterostructure work synergistically to stabilize the manganese dioxide lattice structure and optimize cycle stability.
[0064] like Figure 7 As shown, it is a nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material prepared in Example 1 of the present invention at 3 A g. –1 The cycling performance diagram at current density shows that N-MnO2 / α-MnS has a higher initial capacity and a smoother capacity decay trend, exhibiting excellent high-current cycling stability.
[0065] like Figure 8 The figure shows the XRD pattern of the nitrogen-doped manganese dioxide cathode material prepared in Comparative Example 1 of this invention. The results show that single nitrogen doping only achieves elemental doping modification, and manganese dioxide still maintains its original layered crystal structure. No new α-MnS phase is formed in the system.
[0066] like Figure 9 The image shows the XRD pattern of the manganese dioxide / α-manganese sulfide composite cathode material prepared in Comparative Example 2 of this invention. It can be seen that the layered main structure of manganese dioxide is still retained after sulfidation treatment, and weak α-MnS characteristic diffraction peaks appear in the spectrum, confirming the formation of a small amount of α-MnS phase.
Claims
1. A method for preparing a nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material, characterized in that, Includes the following steps: (1) Dissolve a soluble divalent manganese salt in N,N-dimethylformamide solvent and stir at 40~70℃ to obtain a homogeneous solution; add potassium permanganate solution to the solution and react at 40~70℃ for 30~60 min; after the reaction is completed, centrifuge to collect the solid precipitate, wash and dry to obtain manganese dioxide precursor; wherein, the molar ratio of divalent manganese ions in the divalent manganese salt to permanganate ions in the potassium permanganate is (1.4~1.6):1; (2) Take nitrogen and sulfur sources and place them in the upstream temperature zone of the tube furnace. Place the manganese dioxide precursor obtained in step (1) in the downstream temperature zone of the tube furnace and calcine it in stages under an inert carrier gas atmosphere. The upstream temperature zone temperature is 140~200℃, the downstream temperature zone temperature is 180~220℃, the heating rate is 3~8℃ / min, and the temperature is held for 1~4 h. After calcination, it is naturally cooled to room temperature to obtain nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material. Wherein, the nitrogen and sulfur sources are single organic compounds containing both nitrogen and sulfur elements, or solid mixtures composed of nitrogen-containing compounds and sulfur-containing compounds; the mass ratio of the manganese dioxide precursor to the nitrogen and sulfur sources is 2:(3~5), corresponding to a sulfur-manganese atomic ratio of 1.7~2.
9.
2. The preparation method of the nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material according to claim 1, characterized in that, The divalent manganese salt mentioned in step (1) is selected from one or more of the following mixtures: manganese sulfate monohydrate, manganese acetate tetrahydrate, manganese nitrate hexahydrate, and manganese chloride tetrahydrate.
3. The method for preparing the nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material according to claim 1, characterized in that, In step (1), the reaction temperature is 58~62℃ and the reaction time is 35~45 min.
4. The preparation method of the nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material according to claim 1, characterized in that, The washing in step (1) is alternating between deionized water and anhydrous ethanol; the drying is vacuum drying at a temperature of 50~80℃ for 6~12 h.
5. The method for preparing the nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material according to claim 1, characterized in that, In step (2), the mass ratio of the manganese dioxide precursor to the nitrogen and sulfur sources is 2:3.5, corresponding to a sulfur-manganese atomic ratio of 2.
0.
6. The method for preparing the nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material according to claim 1, characterized in that, In step (2), when the nitrogen and sulfur source is a single organic compound containing both nitrogen and sulfur elements, the organic compound is thioacetamide or thiourea; When the nitrogen and sulfur sources are solid mixtures composed of nitrogen-containing compounds and sulfur-containing compounds, the nitrogen-containing compound is urea and the sulfur-containing compound is elemental sulfur powder.
7. The method for preparing the nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material according to claim 6, characterized in that, The upstream temperature range of the thioacetamide is 140~170℃, the heating rate is 3~8℃ / min, and the holding time is 2~4 h. The upstream temperature zone of the thiourea is 170~200℃, the heating rate is 3~8℃ / min, and the holding time is 1~3 h.
8. A nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material, characterized in that, The composite material is prepared by the preparation method according to any one of claims 1 to 7. The composite material is a heterogeneous composite structure of nitrogen-doped manganese dioxide and cubic rock salt phase α-manganese sulfide, wherein nitrogen doping is incorporated into the manganese dioxide lattice and α-manganese sulfide is precipitated in situ as an independent crystalline phase.
9. A positive electrode for an aqueous zinc-ion battery, characterized in that, The cathode material includes the nitrogen-doped manganese dioxide / α-manganese sulfide composite cathode material as described in claim 8 as the cathode active material.
10. An aqueous zinc-ion battery, characterized in that, It includes the positive electrode as described in claim 9.