Modified layered manganese dioxide cathode active material, its preparation and application in aqueous zinc-ion batteries

Abstract

The present invention belongs to the field of zinc-ion batteries, and particularly relates to a modified layered manganese dioxide cathode active material, its preparation, and its application in aqueous zinc-ion batteries. Among them, the preparation steps of the active material are as follows: A mixed solution A containing a manganese source, an additive of formula 1 (#imgabs0#), and an alcohol-water solvent is subjected to solvothermal modification treatment to obtain a first-stage modified MnO2 with grafting modification between layers; then the first-stage modified MnO2 is dispersed in a solution B containing an elastic precursor compound and an oxidant for a second-stage modification to obtain the modified layered manganese dioxide cathode active material; the elastic precursor compound includes at least one of formula A (#imgabs1#), formula B (#imgabs2#), formula C (#imgabs3#), and formula D (#imgabs4#). The material prepared by the method of the present invention helps to induce the deposition of zinc, improve the wetting of the electrolyte, and helps to improve the capacity utilization rate of the material in zinc batteries and its performance at high rates.

Description

Technical Field

[0001] The present invention belongs to the field of aqueous zinc ion batteries, and particularly relates to the field of manganese dioxide cathode materials for zinc ion batteries. Background Art

[0002] Due to their high safety, low cost, and environmental friendliness, zinc ion batteries (ZIBs) have become important candidates for the next-generation energy storage systems. As a cathode material for zinc ion batteries, layered manganese dioxide (MnO2) has attracted much attention due to its high theoretical capacity and rich resources. However, MnO2 faces problems such as slow zinc ion diffusion kinetics, poor structural stability, and high interfacial reaction impedance in practical applications, which severely limit its electrochemical performance.

[0003] In view of the problems existing in the manganese dioxide cathode active material, some modification ideas such as element doping, surface modification, and nanostructure design have been proposed in the prior art. For example, the patent document with the publication number CN119706948A discloses a preparation method of a cerium-copper co-doped δ-MnO2 microsphere aqueous zinc ion battery cathode material. The patent document with the publication number CN119390126A discloses a preparation method of a cobalt-doped manganese dioxide material using Co3[Co(CN)6]2 as a hard template. The patent document with the publication number CN114212826A discloses a Mo metal-doped MnO2 electrode material and its preparation method. The patent document with the publication number CN114899389A discloses a preparation method of Ga-modified MnO2 nanorods. The patent document with the publication number CN117747820A discloses an aqueous zinc ion battery cathode material of Al-doped α-MnO2. The patent document with the publication number CN116199264A discloses a non-metal B-doped β-phase MnO2 electrode material. Again, the patent document with the publication number CN118888721A discloses a C-coated δ-MnO2 cathode material containing O vacancies, its preparation method, and application. The patent document with the publication number CN117623393A discloses an aqueous zinc ion battery cathode material MnO2@CNT and its preparation method.

[0004] In summary, although the prior art discloses many doping or coating modification schemes, the existing methods often can only improve certain aspects of performance singly and are difficult to simultaneously solve problems such as low conductivity, large Mn dissolution loss, unsatisfactory material capacity utilization rate, long cycle life, and rate performance. Summary of the Invention

[0005] Aiming at the problems existing in the existing manganese dioxide positive electrode active material, such as low conductivity, Mn dissolution caused by the Jahn-Teller effect, and insufficient cycle life, the first object of the present invention is to provide a preparation method of a modified layered manganese dioxide positive electrode active material, aiming to prepare a positive electrode active material with double modification of interlayer and surface and excellent electrochemical performance.

[0006] The second object of the present invention is to provide a modified layered manganese dioxide positive electrode active material prepared by the above preparation method.

[0007] The third object of the present invention is to provide the application of the modified layered manganese dioxide positive electrode active material in the preparation of an aqueous zinc ion battery.

[0008] The fourth object of the present invention is to provide an aqueous zinc ion battery containing the modified layered manganese dioxide positive electrode active material.

[0009] A preparation method of a modified layered manganese dioxide positive electrode active material, in which a mixed solution A containing a manganese source, an auxiliary agent of formula 1, and an alcohol-water solvent is subjected to solvothermal modification treatment to obtain a first-stage modified MnO2 with graft modification between layers; then the first-stage modified MnO2 is dispersed in a solution B containing an elastic precursor compound and an oxidant for the second-stage modification to obtain the modified layered manganese dioxide positive electrode active material;

[0010]

[0011] Formula 1

[0012] In formula 1, R1 and R2 are each independently H, an alkyl group with 1 to 4 carbon atoms, or an alkoxy group with 1 to 4 carbon atoms; alternatively, R1 and R2 cyclize to form an aromatic ring;

[0013] The elastic precursor compound includes at least one of formula A, formula B, formula C, and formula D;

[0014] Formula A;

[0015] Formula B;

[0016] Formula C;

[0017] Formula D;

[0018] R3 is an alkyl group with 1 to 4 carbon atoms;

[0019] R4 is H or an alkyl group with 1 to 4 carbon atoms.

[0020] Innovatively, the present invention conducts solvothermal treatment on a manganese source and an additive of Formula 1 in an alcohol-water solvent, thereby synthesizing layered manganese dioxide and selectively in-situ modifying a reaction modification material of manganese dioxide and Formula 1 between the layers of manganese dioxide, which is conducive to constructing a better zinc deposition space and optimizing the zinc deposition uniformity. In addition, an elastic precursor compound and an oxidizing agent are further used for the second-stage modification, which is conducive to constructing an electrolyte-philic elastic modification interface on the surface of manganese dioxide. The research of the present invention shows that the combination of interlayer modification assisted by the alcohol-water solvent of Formula 1 and surface modification participated by the elastic precursor compound can achieve synergy, contribute to inducing zinc deposition, improving the wetting of the electrolyte, and contribute to improving the capacity utilization rate of the material in a zinc battery and its performance at high rates.

[0021] In the present invention, the manganese source includes at least one of MnSO4, Mn(CH3COO)2, and KMnO4; preferably, it is potassium permanganate and manganese sulfate with a mass ratio of 0.2 to 1.2:1, and further can be 0.6 to 0.8:1.

[0022] In the present invention, the manganese source is subjected to solvothermal modification in a system containing an additive of Formula 1 and an alcohol-water solvent, so that layered manganese dioxide can be successfully prepared. Moreover, it is also conducive to grafting zincophilic and hydrophobic modification materials between the layers of the layered manganese dioxide, which is conducive to the combined synergy with the subsequent second-stage modification to improve the capacity and high-rate performance of the material.

[0023] In Formula 1 of the present invention, R1 and R2 can be independent substituents or can cyclize with each other to form an aromatic ring, and the aromatic ring can be, for example, a benzene ring.

[0024] Furthermore, the additive of Formula 1 includes at least one of Formula 1A and Formula 1B;

[0025] Formula 1A

[0026] Formula 1B.

[0027] The research of the present invention shows that using Formula 1B as the additive of Formula 1 can further improve the process synergy, contribute to further improving the interlayer modification effect of manganese dioxide, and contribute to further improving the performance of the prepared material.

[0028] The weight ratio of the additive of Formula 1 to the manganese source is 0.5 to 1.5:1; further can be 0.6 to 1:1; and even further is 0.7 to 0.8:1.

[0029] In the present invention, the use of the alcohol-water solvent helps to form layered manganese dioxide. Moreover, it is also conducive to combining with the additive of Formula 1 to in-situ induce zincophilic and hydrophobic modification structures between the layers of the layered manganese dioxide.

[0030] In the present invention, the alcohol in the alcohol-water solvent is a C1-C4 unit alcohol, diol or triol. For example, it can be at least one of methanol, ethanol, isopropanol, etc.

[0031] In the alcohol-water solvent described above, the volume ratio of water to alcohol is 2-6:1; more preferably, it can be 3-5:1.

[0032] In the mixed solution A, the weight ratio of the manganese source to the alcohol-water solvent can be 1:1-20; considering the processing scale and cost, it can be further 1:3-10.

[0033] In the present invention, the temperature of the solvothermal modification treatment is 100-200 °C, and it can be further 120-180 °C; more preferably, it is 120-150 °C. In the present invention, under the preferred solvothermal temperature, the modification effect of the additive of Formula 1 can be further enhanced, which is helpful for further improving the long cycle performance of the prepared material at high current.

[0034] In the present invention, the time of the solvothermal modification treatment is 8-20 h, and it can be further 10-12 h.

[0035] In the present invention, innovatively, the first-stage modified MnO2 is dispersed in the solution B containing an elastic precursor compound and an oxidant. Based on the combination of the surface characteristics of the elastic precursor compound, the oxidant and the first-stage modified MnO2, it is beneficial to construct a liquid-philic modification interface on its surface, which is conducive to combining with the first-stage modification (solvothermal modification) to synergistically enhance the performance of the material.

[0036] In the present invention, the solvent in the solution B is at least one of water and an organic solvent; wherein, the organic solvent includes at least one of C1-C4 alcohols, acetonitrile, and acetone.

[0037] Preferably, the solvent in the solution B contains a water-organic solvent mixed solvent with a mass ratio of 5-15:1. The research of the present invention shows that using the preferred solvent to assist the modification treatment of the elastic precursor compound is helpful for further combining with the additive of Formula 1 to enhance the modification effect of the interlayer and surface of manganese dioxide, and is helpful for further improving the stability of the prepared material, especially for improving its long cycle stability at high current.

[0038] In the present invention, the elastic precursor compound is preferably Formula B. Research shows that using Formula B as the elastic precursor compound, compared with other components, it can be further combined and synergistic with the process of the present invention, which is helpful for further improving the long cycle stability of the assembled battery at high current.

[0039] In the present invention, in the solution B, the weight ratio of the elastic precursor compound to the first-stage modified MnO2 is 0.2-3:1; more preferably, it is 0.5-0.8:1.

[0040] In the present invention, the oxidant is persulfate, such as at least one of sodium persulfate and ammonium persulfate.

[0041] In the present invention, the oxidant is 0.002 to 0.01 times the weight of the first-stage modified MnO₂, and further can be 0.003 to 0.005 times.

[0042] In the present invention, in solvent B, the mass concentration of the first-stage modified MnO₂ can be 5 to 30%; further can be 10 to 20%.

[0043] In the present invention, the temperature of the second-stage modification process is 25 to 50 °C, and the time is 2 to 10 h.

[0044] In the present invention, after the second-stage modification, if necessary, a third-stage modification treatment in the presence of an alkali solution can be selectively carried out.

[0045] The alkali solution is a sodium hydroxide solution with a concentration of 0.5 to 2 M.

[0046] The weight ratio of the basic solute in the alkali solution to the product of the second-stage modification can be 0.1 to 1 times, and further can be 0.4 to 0.6 times.

[0047] The present invention also provides a modified layered manganese dioxide positive electrode active material prepared by the above preparation method.

[0048] The preparation method of the present invention can endow the prepared material with special physical and chemical characteristics. For example, layered manganese dioxide can be obtained, and a conversion modification layer of formula 1 can be constructed between its layers, as well as a surface layer converted from an elastic precursor compound. Moreover, the material with special physical and chemical characteristics prepared by the preparation method of the present invention can improve the deposition of zinc, improve the wettability, and the ion and electron conduction pathways, which helps to significantly improve its performance.

[0049] The present invention also provides an application of the modified layered manganese dioxide positive electrode active material prepared by the above preparation method. Using it as the positive electrode active material to prepare an aqueous zinc-ion battery.

[0050] The present invention also provides an aqueous zinc-ion battery. The positive electrode of the aqueous zinc-ion battery contains the modified layered manganese dioxide positive electrode active material prepared by the above preparation method.

[0051] For the aqueous zinc-ion battery of the present invention, except for containing the modified layered manganese dioxide positive electrode active material of the present invention, other components and structures can be well-known.

[0052] Beneficial effects

[0053] The present invention innovatively synthesizes layered manganese dioxide with the assistance of an additive of formula 1 and an alcohol-water solvent, and in-situ constructs a zincophilic and hydrophobic modified structure on the layered manganese dioxide. Further, a second modification involving an elastic precursor compound and an oxidant is carried out to construct a liquid-philic structure on the surface of the manganese dioxide. The research of the present invention shows that the material with special physical and chemical characteristics prepared by the preparation method helps to induce the deposition of zinc, improve the wetting of the electrolyte, and contribute to improving the capacity utilization rate of the material in zinc batteries and its performance at high rates. Description of the Drawings

[0054] Figure 1 It is a cyclic performance diagram of the zinc-ion battery obtained in Example 1 at 25 °C and a current density of 0.2 A / g;

[0055] Figure 2 It is a cyclic performance diagram of the zinc-ion battery obtained in Example 1 at 25 °C and a current density of 2 A / g. Detailed Embodiments

[0056] In the present invention, as an exemplary embodiment, the elastic precursor material may be the components of formula B and formula C. Among them, as a specific alternative, the formula B may be exemplified by formula B1, which is a compound of formula B with R3 being methyl. In the present invention, after the second modification treatment is carried out using this component, optionally, an alkali solution treatment is continued to obtain the final product. The alkali solution for the alkali solution treatment may be a sodium hydroxide solution with a concentration of 0.5 - 2 M. The weight ratio of the alkali in the alkali solution to formula B1 may be 0.4 - 0.8:1. The time for the alkali solution treatment may be 1 - 5 h.

[0057] In the present invention, formula C is typically represented by formula C1, which is specifically formula C with R4 being H.

[0058] Example 1

[0059] Step 1: Premixing:

[0060] An additive of formula 1 (formula 1B in this case), a manganese source (the manganese source is potassium permanganate and manganese sulfate with a mass ratio of 0.7:1), and solvent A (a mixed solution of water and ethanol with a volume ratio of 3:1) with a mass ratio of 0.8:1:4 are fully mixed.

[0061] Step 2: First modification

[0062] The mixture prepared in Step 1 is transferred to a polytetrafluoroethylene solvent thermal reactor (pressure-resistant reactor), and a solvent thermal reaction is carried out at 130 °C for 12 hours while maintaining the pressure, and then suction filtration and washing are carried out to obtain a modified manganese dioxide material (labeled as Z-MnO2).

[0063] Step 3: Second modification

[0064] Stir and modify solvent B (a mixed solution of water and methanol with a mass ratio of 12:1), an elastic precursor compound (in this case, formula B1 where R3 is methyl), Z-MnO2, and potassium persulfate with a mass ratio of 9:0.6:1:0.005 at 30 °C for 5 hours; then stir and modify with 1M NaOH (the solvent is methanol; where the sodium hydroxide is 0.5 - 0.6 times the weight of formula B1) at 30 °C for 3 hours, and then perform suction filtration and washing to obtain HZ-MnO2.

[0065] Example 2

[0066] Compared with Example 1, the difference is only that the formula 1 auxiliary agent in step 1 is changed to formula 1A, and other operations and parameters are the same as those in Example 1.

[0067] Example 3

[0068] Compared with Example 1, the difference is only that in step 1, the weight ratio of the formula 1 auxiliary agent (in this case, formula 1B), the manganese source (the manganese source is a mixture of potassium permanganate and manganese sulfate with a mass ratio of 0.6:1), and solvent A (a mixed solution of water and ethanol with a volume ratio of 5:1) is 0.7:1:8; the temperature in step 2 is 160 °C and the time is 10 h.

[0069] Other operations and parameters are the same as those in Example 1.

[0070] Example 4

[0071] Compared with Example 1, the difference is only that the conditions in step 3 are changed, and the experimental groups are respectively:

[0072] Group A: Solvent B is water;

[0073] Group B: Solvent B is methanol;

[0074] Other operations and parameters are the same as those in Example 1.

[0075] Example 5

[0076] Compared with Example 1, the difference is only that the conditions in step 3 are changed, and the experimental groups are respectively:

[0077] Group A: The elastic precursor compound is formula C1; after the modification in step 3, no subsequent treatment with sodium hydroxide is required;

[0078] Group B: Solvent B is a mixed solution of water and ethanol with a mass ratio of 10:1, and the weight ratio of solvent B, the elastic precursor compound, Z-MnO2, and ammonium persulfate is 8:0.7:1.5:0.004, the reaction temperature is 45 °C, and the reaction time is 3 hours.

[0079] Other operations and parameters are the same as those in Example 1.

[0080] Comparative Example 1

[0081] Compared with Example 1, the difference is only that in Step 1, the additive of Formula 1 is not added, and other operations and parameters are the same as those in Example 1.

[0082] Comparative Example 2

[0083] Compared with Example 1, the difference is only that in Step 1, the same weight of is used to replace the additive of Formula 1, and other operations and parameters are the same as those in Example 1.

[0084] Comparative Example 3

[0085] Compared with Example 1, the difference is only that in Step 1, the same weight of is used to replace the additive of Formula 1, and other operations and parameters are the same as those in Example 1.

[0086] Comparative Example 4

[0087] Compared with Example 1, the difference is only that in Step 1, Solvent A is water, and the dosage of Solvent A and other operations and parameters are the same as those in Example 1.

[0088] Comparative Example 5

[0089] Compared with Example 1, the difference is only that in Step 1, Solvent A is methanol, and the dosage of Solvent A and other operations and parameters are the same as those in Example 1.

[0090] Comparative Example 6

[0091] Compared with Example 1, the difference is only that in Step 3, the elastic precursor compound is not added, and other operations and parameters are the same as those in Example 1.

[0092] Comparative Example 7

[0093] Compared with Example 1, the difference is only that the elastic precursor compound in Solution B is added to Solvent A in Step 1, and the additive of Formula 1 in Solvent A is added to Solution B, and other operations and parameters are the same as those in Example 1.

[0094] Full cell assembly and performance measurement

[0095] The finally prepared manganese dioxide active material, conductive carbon black, and polyvinylidene fluoride in each case were mixed evenly at a mass ratio of 7:2:1, and an appropriate amount of NMP was added as a dispersant to make a uniform slurry. Subsequently, the slurry was coated on the surface of a stainless steel mesh current collector and transferred to a vacuum drying at 60 °C for 12 h to obtain a positive electrode sheet. Subsequently, a cutting machine was used to cut it into circular electrodes with a diameter of about 10 mm, and the areal loading of the obtained positive electrode sheet was about 1.5 mg / cm 2。Assemble the CR2025 button battery in the order of the positive electrode battery case, the positive electrode plate, the glass fiber separator, the 0.1 mm zinc foil negative electrode, the nickel foam, and the negative electrode battery case. Add the 2M ZnSO4 + 0.1M MnSO4 aqueous electrolyte, and finally seal it with a battery encapsulation machine. At a temperature of 25 °C, perform charge and discharge tests on the assembled aqueous zinc ion battery using a small current of 0.2 A / g and a large current of 2 A / g respectively to explore the electrochemical performance of the material. The voltage range of the test is 0.8 V - 1.8 V, and the test instrument is the BlueTEC electrochemical measurement system. The results are shown in Table 1:

[0096]

[0097] It can be seen from Example 1 and Comparative Examples 1 - 7 that by first synthesizing layered manganese dioxide with the aid of the formula 1 assistant and the alcohol-water solvent in the structure of the present invention, and then performing the second-stage modification with the participation of the elastic precursor compound, a lyophilic structure can be constructed on the surface of manganese dioxide, which helps to improve the capacity utilization rate of the material in zinc batteries and its performance at high rates.

[0098] In addition, it can be seen from Example 1 and Example 2 that using formula 1B as the formula 1 assistant can obtain better process synergy. It can be seen from Example 1 and Example 4 that by innovatively performing the second-stage modification assisted by the elastic precursor compound in the alcohol-water mixed solvent, better process synergy can be obtained. It can be seen from Example 1 and Example 5 that using formula B of the present invention as the elastic precursor compound can obtain better process modification effects.

Claims

1. A preparation method of a modified layered manganese dioxide cathode active material, characterized in that, The mixed solution A containing a manganese source, an additive of Formula 1, and an alcohol-water solvent is subjected to solvothermal modification treatment to obtain a first-stage modified MnO2 with interlayer graft modification; then the first-stage modified MnO2 is dispersed in solution B dissolved with an elastic precursor compound and an oxidant for a second-stage modification to obtain the modified layered manganese dioxide cathode active material described above. ； Formula 1 In Formula 1, R1 and R2 are each independently H, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms; or, R1 and R2 cyclize to form an aromatic ring. The elastic precursor compound includes at least one of Formula A, Formula B, Formula C, and Formula D. Formula A; Formula B; Formula C; Formula D; R3 is an alkyl group having 1 to 4 carbon atoms. R4 is H or an alkyl group having 1 to 4 carbon atoms.

2. The preparation method of the modified layered manganese dioxide cathode active material according to claim 1, characterized in that, The manganese source includes at least one of MnSO4, Mn(CH3COO)2, and KMnO4. The additive of Formula 1 includes at least one of Formula 1A and Formula 1B. Formula 1A; Formula 1B; The weight ratio of the additive of Formula 1 to the manganese source is 0.5 to 1.5:

1.

3. The preparation method of the modified layered manganese dioxide cathode active material according to claim 1, characterized in that, The alcohol in the alcohol-water solvent is a monohydric alcohol, dihydric alcohol, or trihydric alcohol having 1 to 4 carbon atoms. In the alcohol-water solvent, the volume ratio of water to alcohol is 2 to 6:

1. In the mixed solution A, the weight ratio of the manganese source to the alcohol-water solvent is 1:1 to 20.

4. The preparation method of the modified layered manganese dioxide cathode active material according to any one of claims 1 to 3, characterized in that, The temperature of the solvothermal modification treatment is 100 to 200 °C, and the time is 8 to 20 h.

5. The preparation method of the modified layered manganese dioxide cathode active material according to claim 1, characterized in that, The solvent in solution B is at least one of water and an organic solvent; wherein, the organic solvent includes at least one of an alcohol having 1 to 4 carbon atoms, acetonitrile, and acetone.

6. The preparation method of the modified layered manganese dioxide cathode active material according to claim 5, characterized in that, In solution B, the solvent contains a water-organic solvent mixed solvent with a mass ratio of 5 to 15:

1.

7. The preparation method of the modified layered manganese dioxide cathode active material according to claim 1, 5 or 6, characterized in that, The oxidant is a persulfate. The oxidant is 0.002 to 0.01 times the weight of the first-stage modified MnO2. The weight ratio of the elastic precursor compound to the first-stage modified MnO2 is 0.2 to 3:

1. In solution B, the mass concentration of the first-stage modified MnO2 is 5 to 30%. The temperature of the second-stage modification process is 25 to 50 °C, and the time is 2 to 10 h.

8. A modified layered manganese dioxide cathode active material prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the modified layered manganese dioxide positive electrode active material prepared by the preparation method according to any one of claims 1 to 7, characterized in that, Using it as a cathode active material for preparing an aqueous zinc-ion battery.

10. An aqueous zinc ion battery, characterized in that: The cathode of the aqueous zinc-ion battery described above contains the modified layered manganese dioxide cathode active material prepared by the preparation method according to any one of claims 1 to 7.

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