Manganese oxide-molybdenum-based material composite positive electrode and application thereof in aqueous zinc ion battery

Abstract

The invention relates to a manganese oxide-molybdenum-based material composite positive electrode and application thereof in an aqueous zinc ion battery. The composite positive electrode is prepared by mixing manganese oxide, a molybdenum-based material, a conductive carbon material and a binder. Wherein the molybdenum-based material is a molybdenum-based sulfide and / or a molybdenum-based selenium compound (MoxAy, A represents S and / or Se, x is equal to 1, y is equal to 2) or a compound of the molybdenum-based sulfide and / or the molybdenum-based selenium compound and a carbon material (such as a carbon nanotube, graphene and activated carbon), and the mass fraction of the molybdenum-based material in the composite positive electrode is 0.1-10 wt%. Wherein the molybdenum-based material serves as a redox medium and a catalyst of manganese oxide in the composite positive electrode, reversible redox of manganese ions can be promoted, the reaction dynamic characteristic is improved, and therefore the cycle stability of the water-based zinc ion battery is remarkably improved, and the service life of the water-based zinc ion battery is remarkably prolonged.

Description

Technical Field

[0001] The present invention relates to a high-performance manganese oxide-molybdenum-based material composite cathode and its application in aqueous zinc-ion batteries, belonging to the technical field of zinc-ion batteries. Background Art

[0002] In recent years, countries around the world have been accelerating the promotion of the conversion from fossil energy to clean energy such as wind energy, hydropower, and solar energy. However, renewable energy has the characteristics of intermittency and dispersity, making it difficult to carry out large-scale power generation and long-distance transmission in terms of cost. Therefore, the development of efficient energy storage / conversion devices is of great significance for the effective utilization and distribution of renewable energy. Aqueous metal-ion batteries have the advantages of high safety, low cost, and easy processing, and are expected to be used in large-scale energy storage systems. Manganese dioxide has a unique three-dimensional pore structure and excellent electrochemical zinc storage characteristics, so it has broad application prospects in the field of aqueous zinc-ion batteries.

[0003] Despite these advantages, due to the poor intrinsic conductivity of MnO2 and the significant acceleration of the dissolution of MnO2 due to the existence of the Jahn-Teller effect in the aqueous electrolyte, the capacity loss of the cathode material and irreversible crystal transformation occur. In addition, during the discharge process, the accumulation of OH- on the surface of MnO2 triggers the formation of an uncontrollable electrochemically active by-product Zn4(SO4)(OH)6·xH2O (ZSH). The inherently poor conductivity and ionic conductivity of ZSH seriously hinder the charge transfer process, leading to the deterioration of the interfacial reaction kinetics and the reduction of the utilization efficiency of active substances. To improve this deficiency, Lu et al. (Energy & Environmental Science, 2021, 14, 4418) used iodine as a redox mediator to promote the complete reaction of MnO2, fully releasing the capacity of MnO2 and significantly enhancing the MnO2 / Mn 2+Cyclic reversibility, but this method uses iodine as an electrolyte additive, which is prone to passivation and loss of activity during long cycling. Kang et al. (Journal of Colloid And Interface Science, 2024, 657, 931 - 941) introduced potassium dihydrogen phosphate as a pH buffer in the electrolyte, effectively solving the problems of severe pH fluctuations at the MnO2 interface and uncontrolled growth of ZSH, thereby improving the interfacial kinetics and cycling stability of zinc - ion batteries. However, the regulatory effect of this strategy in high - loading Zn / / MnO2 batteries under practical conditions is very limited. Liu Yu et al. (CN 110911652 A) prepared a composite material of α - MnO2 / Bi2O3 by combining Bi2O3 material with a high specific surface area and many electrochemically active sites and well - crystalline α - MnO2. This composite material can effectively improve the cycling stability of the material and achieve relatively good application effects. However, this modification requires heat treatment above 600 °C, increasing the energy consumption in the sample preparation process. In addition, the loss of reversible capacity during cycling is relatively fast, which is not suitable for commercial applications.

[0004] As can be seen from the above research results, finding a preparation method for manganese oxide positive electrodes with low requirements for preparation conditions, simple and feasible processes, and stable electrochemical performance will greatly promote the practical application of aqueous zinc / manganese oxide batteries. Summary of the Invention

[0005] The object of the present invention is to overcome the deficiencies in the prior art and provide a simple, effective, and high - performance composite positive electrode of manganese oxide - molybdenum - based material, its preparation method, and its application in aqueous zinc - ion batteries. The composite positive electrode is prepared by mixing manganese oxide, molybdenum - based material, conductive carbon material, and binder in a certain proportion. Among them, the molybdenum - based material acts as an oxidation - reduction medium for manganese oxide and a catalyst for proton reactions in the composite positive electrode, which can promote the reversible oxidation - reduction of manganese ions, improve the reaction kinetic characteristics, and finally obtain a positive electrode for aqueous zinc - ion batteries with high rate performance and high cycling stability.

[0006] To achieve the above - mentioned invention object, the present invention adopts the following technical solutions.

[0007] The first - aspect object of the present invention is to provide a molybdenum - based material (MoxAy@C, A represents S and / or Se, x = 1, y = 2), which is one or more of molybdenum - based sulfides and / or molybdenum - based selenides, or a carbon composite formed by further compounding with a carbon material, and is a nano - micro composite material. Its preparation method is hydrothermal compounding or mechanical ball - milling compounding method. The specific steps are as follows:

[0008] The hydrothermal compounding method, the specific steps are as follows:

[0009] (1) Uniformly disperse the carbon material in deionized water to obtain solution A (when there is no carbon composite, no carbon material needs to be added to the deionized water). Dissolve the molybdenum source and sulfur and / or selenium source in deionized water to obtain solution B.

[0010] (2) After uniformly mixing solutions A and B (usually equal - volume mixing), add them to a reaction kettle and maintain at 100 - 200 °C for 8 - 24 hours. Wash the obtained product thoroughly with deionized water and ethanol, and finally dry it to obtain the MoxAy@C material.

[0011] The ball - milling composite method, the specific steps are as follows: Mechanically mix commercial molybdenum sulfide powder or molybdenum selenide powder or both with the carbon material to obtain the MoxAy@C material (when there is no carbon composite, no carbon material needs to be added during the ball - milling process).

[0012] In the above - mentioned scheme, further,

[0013] The carbon material is one or more of carbon nanotubes, graphene, and activated carbon; the molybdenum source includes but is not limited to one or more of ammonium molybdate tetrahydrate, sodium molybdate, potassium molybdate, ammonium heptamolybdate; the sulfur source includes but is not limited to one or more of thiourea, sodium thiosulfate, sodium sulfide, sodium dodecylbenzenesulfonate, methionine, mercaptoacetic acid; the selenium source includes but is not limited to one or more of sodium selenide, potassium selenide, ammonium selenide, sodium selenate, potassium selenate.

[0014] In the hydrothermal composite method, the prepared molybdenum - based material is a secondary layered / nano - flower - shaped nano - micro composite structure, which is a layered or flower - shaped composite nano - micro structure (layered / flower - shaped composite product) aggregated by nano - scale flaky products (primary nano - flakes); the size of the primary nano - flakes is 10 - 100 nm, and the size of the obtained layered / flower - shaped composite product is 10 - 500 nm; in the ball - milling composite method, the prepared molybdenum - based material is a layered nano - flaky nano - micro composite structure, and the size of the obtained flaky composite product is 10 - 500 nm.

[0015] The mass fraction of MoxAy in the molybdenum - based material is 50 - 100%, and the mass fraction of the carbon material is 0 - 50%.

[0016] In a second aspect of the present invention, a method for preparing a high-performance composite cathode of manganese oxide-molybdenum-based material is provided. The specific preparation process includes but is not limited to the following steps: carbon paper, stainless steel foil, and titanium foil are used as current collectors. The active material manganese oxide contained in the cathode slurry can be one or more of crystalline or amorphous manganese dioxide, manganese sesquioxide, and their mixtures; the proportion of the active material in the composite cathode is 60-98%; the proportion of the conductive carbon material such as conductive carbon black is 0.9-20%; the proportion of the molybdenum-based material is 0.1-10%; the binder includes one or several of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), styrene-butadiene rubber (SBR), and sodium alginate (SA), and the mass ratio is 1-10%. The electrode can be prepared by the conventional industry pole piece coating process. For example, the slurry can be coated on the current collector and then dried at 50-80 °C for 1-10 hours.

[0017] In a third aspect of the present invention, an aqueous zinc-ion battery using the above composite cathode is provided, which is assembled from an electrolyte, the composite cathode, and a zinc-based anode. The selected electrolyte is preferably an aqueous solution of xM ZnSO4 + yM MnSO4, where the values of x and y range from 0.1-3, but are not limited to this electrolyte system.

[0018] The beneficial effects of the present invention are as follows: The preparation process of the present invention is very simple, and the requirements for equipment parameters are low. The molybdenum-based material described in the present invention improves the interfacial conductivity and electrochemical stability of the cathode. The process of the present invention can realize the batch synthesis of materials. The preparation method of the present invention has a low cost. Applying the composite cathode of manganese oxide-molybdenum-based material to a neutral zinc-manganese battery has excellent cycle stability and rate performance, and has broad application prospects. Description of the Drawings

[0019] Figure 1 It is the XRD pattern of molybdenum disulfide composite carbon nanotubes in Example 1.

[0020] Figure 2 It is the SEM image and EDS Mapping image of molybdenum disulfide composite carbon nanotubes in Example 1.

[0021] Figure 3 It is the SEM image and EDS Mapping image of the composite cathode of electrolytic manganese dioxide-molybdenum-based material prepared in Example 1.

[0022] Figure 4 It is the rate performance curve graph (the curve represents the discharge specific capacity) of the full battery assembled with the composite cathode of manganese oxide-molybdenum-based material as the cathode and metallic zinc as the anode material in Example 1 and Comparative Example 1.

[0023] Figure 5It is the cycle-specific capacity curve graph (the curve represents the discharge specific capacity) of the full battery assembled with the manganese oxide-molybdenum-based material composite cathode as the cathode and metallic zinc as the anode material at a 3C rate in Example 1 and Comparative Example 1. Detailed implementation mode

[0024] The present invention will be further described below in conjunction with embodiments. The description of the following embodiments is only used to help understand the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0025] There is no specific limitation on the sources of the raw materials and instruments used in the embodiments, and they can be purchased in the market or prepared according to the conventional methods well-known to those skilled in the art.

[0026] In this embodiment, the battery is assembled and tested by the following method: using the manganese oxide-molybdenum-based material composite electrode as the cathode and metallic zinc foil as the counter electrode to assemble a complete full battery, Whatman GF / B glass fiber as the separator, and an aqueous solution of 2M ZnSO4 + 0.2M MnSO4 as the electrolyte to assemble a CR2032 type button full battery. The battery test method is as follows:

[0027] Taking 308 mAh g -1 As the nominal specific capacity of the manganese oxide cathode, charge and discharge tests are carried out at different rates, and the voltage range is 0.6 - 1.8V.

[0028] Example 1 A high-performance manganese oxide-molybdenum-based material composite cathode and its application in aqueous zinc ion batteries, the specific steps are as follows:

[0029] (1) Disperse 250 mg of carbon nanotubes in 30 mL of deionized water to form a homogeneous dispersion (solution A), and then dissolve 328 mg of ammonium molybdate tetrahydrate (0.26 mmol) and 406 mg of thiourea (5.3 mmol) in 30 mL of distilled water to form solution B.

[0030] (2) Mix solution A and solution B to form a homogeneous solution. Then, transfer the mixed solution to a 100 mL stainless steel autoclave lined with Teflon and keep it at 200 °C for 24 hours. After washing and drying the obtained product, molybdenum disulfide / carbon nanotube composite (MoS2@CNT), that is, molybdenum-based material, is obtained. (3) Prepare the slurry: Weigh electrolytic manganese dioxide, Super P, MoS2@CNT, CMC, and SBR with a mass ratio of 70:15:5:5:5 in a stirring box containing deionized water, and mix them through a high-speed mixer to obtain a homogeneous electrode slurry.

[0031] (4) Coating and drying: The slurry was coated on carbon paper, dried at 50°C, and punched into 10 mm diameter disc electrodes with a loading of 1.2-1.5 mg / cm 2 .

[0032] Figure 1 This is the XRD diagram of MoS2@CNT in Example 1. The characteristic peaks of molybdenum disulfide and carbon nanotubes can be seen from the figure, proving the successful preparation of MoS2@CNT. Figure 2 The SEM results confirmed that molybdenum disulfide was evenly distributed on the surface of carbon nanotubes, among which the nanosheet-like product was the primary nanosheet of molybdenum disulfide, and its secondary product was the nanoflower-like product with a particle size range of 10-500nm. The EDS mapping test further proved the uniform distribution of Mo and S elements. The above results proved the successful preparation of MoS2@CNT with nano-micro composite structure. Figure 3 The SEM and EDS images of the electrolytic manganese dioxide-MoS2@CNT positive electrode prepared in Example 1 show that the composite material has a micron-sized particle morphology. The EDS results show that the Mn, O, Mo, and S elements are evenly distributed on the surface of the composite material, proving the successful preparation of the electrolytic manganese dioxide-MoS2@CNT positive electrode.

[0033] Figure 4 and Figure 5 The electrochemical performance diagram of the positive electrode prepared in Example 1 shows that the reversible specific capacity at 0.5C is 226 mAh g -1 , 10C can still maintain 85mAh g -1 At the same time, after cycling at a rate of 10C, it can still return to the initial capacity when it returns to 2C, showing good rate performance; in addition, after cycling at 3C for 1500 cycles, the discharge specific capacity is 139.7mAh g -1 , the capacity retention rate is 100%, showing excellent specific capacity and good long-cycle stability.

[0034] Example 2 A high-performance manganese oxide-molybdenum-based composite positive electrode and its application in an aqueous zinc ion battery, the specific steps are:

[0035] (1) 4 g of commercial nano-MoS2 powder and 2 g of carbon nanotubes were weighed and mixed thoroughly by mechanical ball milling at a rotation speed of 400 rpm for 8 hours to prepare a commercial molybdenum disulfide / carbon nanotube composite (MoS2@CNT), i.e., a molybdenum-based material.

[0036] (2) The process of preparing the positive electrode is exactly the same as steps (3) and (4) in Example 1.

[0037] The electrode sheet prepared in Example 2 was subjected to electrochemical testing, and the reversible specific capacity at a rate of 0.5C reached 214 mAh g -1, and the cycle is relatively stable.

[0038] Example 3 A high-performance manganese oxide-molybdenum-based composite cathode and its application in aqueous zinc-ion batteries. The specific steps are as follows:

[0039] (1) The preparation method of MoS2@CNT is exactly the same as that in step (1) of Example 1.

[0040] (2) Prepare the slurry: Weigh electrolytic manganese dioxide, Super P, MoS2@CNT, CMC, and SBR with a mass ratio of 80:8:2:5:5 in a stirring box containing deionized water, and mix them with a high-speed stirrer to obtain a uniform electrode slurry.

[0041] (3) The process of preparing the electrode sheet is exactly the same as that in step (4) of Example 1.

[0042] The electrode sheet prepared in Example 3 was subjected to electrochemical testing. The reversible specific capacity at a 0.5C rate reached 226.2 mAh g -1 , and the cycle is relatively stable.

[0043] Example 4 A high-performance manganese oxide-molybdenum-based composite cathode and its application in aqueous zinc-ion batteries. The specific steps are as follows:

[0044] (1) Prepare molybdenum selenide / carbon nanotube composite (MoSe2@CNT). The preparation process is the same as that in step (1) of Example 2, except that nano MoS2 is replaced with nano MoSe2.

[0045] (2) The process of preparing the positive electrode is exactly the same as that in steps (3) and (4) of Example 1.

[0046] The electrode sheet prepared in Example 4 was subjected to electrochemical testing. The reversible specific capacity at a 0.5C rate reached 251.2 mAh g -1 , and the cycle is relatively stable.

[0047] Comparative Example 1:

[0048] The difference between this comparative example and Example 1 is that no molybdenum-based material is added during the preparation of the electrode sheet. Directly weigh electrolytic manganese dioxide, Super P, CMC, and SBR with a mass ratio of 70:20:5:5 in a stirring box containing deionized water, and mix them with a high-speed stirrer to obtain a uniform electrode slurry. The electrode sheet preparation method is exactly the same as that in step (4) of Example 1.

[0049] Figure 4 and Figure 5 are the electrochemical performance diagrams of the positive electrode prepared in Comparative Example 1. The reversible specific capacity at 0.5C is 236 mAh g -1, 10C can only maintain 74.5 mAh g -1 , at the same time, after cycling at a rate of 10C and then returning to 2C, the capacity significantly decreases, and the rate performance is poor; in addition, after cycling 1500 times at 3C, the discharge specific capacity is 75.4 mAh g -1 , and the capacity retention rate is 47%, and the cycle stability is poor.

[0050] Applying the manganese oxide-molybdenum-based material composite in the present invention to the cathode material of a zinc battery, its specific capacity can reach 226 mAh g -1 , and it has excellent rate performance and cycle stability. The above are only some preferred embodiments of the present invention. The present invention is not limited to the above embodiments, nor does it limit the protection scope of the present invention. Any modifications, substitutions, improvements, etc. derived from the concept of the present invention should be included within the protection scope required by the present invention.

Claims

1. A composite positive electrode of manganese oxide-molybdenum-based material, characterized in that, The composite cathode is prepared by mixing manganese oxide, molybdenum-based material, conductive carbon material and binder.

2. The manganese oxide-molybdenum-based material composite cathode according to claim 1, characterized in that The molybdenum-based material is one or more of molybdenum-based sulfides and / or molybdenum-based selenides, or a carbon composite MoxAy@C formed by further compositing with a carbon material, where A is S and / or Se, x = 1, y = 2.

3. The manganese oxide-molybdenum-based material composite positive electrode according to claim 2, characterized in that, The molybdenum-based sulfide or molybdenum-based selenide is a nanomaterial, and the particle size range of at least one dimension thereof is 10 - 500 nm.

4. The manganese oxide-molybdenum-based material composite cathode according to claim 2, wherein, The carbon material is one or more of carbon nanotubes, graphene or activated carbon.

5. The manganese oxide-molybdenum-based material composite positive electrode according to claim 1, characterized in that, In the molybdenum-based material, the mass fraction of molybdenum-based sulfide and / or molybdenum-based selenide is 50 - 100%, preferably 50 - 80%.

6. The manganese oxide-molybdenum-based material composite positive electrode according to claim 1, characterized in that The molybdenum-based material is prepared by a hydrothermal method or a ball milling method, specifically: The hydrothermal method includes the following: (1) uniformly dispersing the carbon material in deionized water to obtain solution A, or omitting this step according to needs, and dissolving the molybdenum source and the sulfur source and / or selenium source in deionized water to obtain solution B; (2) uniformly mixing solution A and solution B, adding them into a reaction kettle, maintaining at 100 - 200 °C for 8 - 24 hours, washing the obtained product thoroughly with deionized water and ethanol respectively, and drying. The ball milling method includes the following: mechanically mixing nano molybdenum sulfide powder and / or nano molybdenum selenide powder, or further with a carbon material, to obtain the molybdenum-based material.

7. The manganese oxide-molybdenum-based material composite positive electrode according to claim 1, characterized in that, Among them, the manganese oxide is crystalline or amorphous manganese dioxide, manganese sesquioxide or a mixture thereof, preferably electrolytic manganese dioxide cathode, the primary particle size is 5 - 200 nm, and the secondary particle size is 1 - 30 μm.

8. The preparation method of the manganese oxide-molybdenum-based material composite cathode according to any one of claims 1-7, characterized in that: a) The component ratio is carried out according to the following mass ratio: the mass proportion of manganese oxide in the slurry is 60% - 98%, the mass proportion of molybdenum-based material is 0.1% - 10%, the mass proportion of conductive carbon material is 0.9% - 20%, and the mass proportion of binder is 1% - 10%; b) The electrode is prepared by using the industry-regular pole piece coating process.

9. Aqueous zinc-ion battery, characterized in that, Containing the composite cathode described in any one of claims 1 - 7 or the composite cathode prepared by the method described in claim 8.

10. The aqueous zinc-ion battery according to claim 9, wherein, The battery is assembled from an electrolyte, the composite cathode and a zinc-based anode, and the selected electrolyte is preferably an aqueous solution of xM ZnSO4 + yM MnSO4, where the value ranges of x and y are 0.1 - 3, but not limited to this electrolyte system.

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