Interlayer-Surface Dual-Modified Layered Manganese Dioxide Cathode Active Material, Its Preparation and Application in Aqueous Zinc Secondary Batteries

Abstract

The present invention belongs to the field of aqueous zinc ion batteries, and particularly relates to an interlayer-surface dual-modified layered manganese dioxide cathode active material, its preparation, and its application in aqueous zinc secondary batteries. Among them, the preparation method of the active material is as follows: a raw material solution containing a manganese source and zinc hexafluorosilicate is subjected to a first-stage reaction to obtain interlayer-modified manganese dioxide; then the interlayer-modified manganese dioxide is subjected to a second-stage reaction in a modification solution containing a phosphoric acid source to obtain the interlayer-surface dual-modified layered manganese dioxide cathode active material. The material prepared by the method of the present invention has good zinc ion diffusion ability, active ion transport speed, structural stability, and interfacial compatibility, and can improve the capacity of zinc ion batteries and the stability under high current.

Description

Technical Field

[0001] The present invention belongs to the field of aqueous batteries, and specifically relates to the field of cathode materials for aqueous zinc secondary batteries. Background Art

[0002] With the rapid development of new energy energy storage technologies, layered manganese dioxide (MnO2) has become an ideal cathode material for energy storage systems such as zinc-ion batteries due to its high theoretical capacity and low-cost advantages. However, MnO2 still has key problems in practical applications, such as poor structural stability, serious Mn 2+ dissolution, and many interfacial side reactions, resulting in poor cycle life and rate performance.

[0003] In view of the problems existing in manganese dioxide materials, some modification schemes such as doping and coating have been reported in the prior art. For example, Chinese patent document with publication number CN113410443A discloses a preparation method and application of a highly stable copper-intercalated manganese dioxide electrode material, specifically recording a scheme of preparing copper-intercalated manganese dioxide material by hydrothermal reaction after mixing manganese sulfate, copper source, and potassium permanganate.

[0004] Chinese patent document with publication number CN114212826A discloses a Mo metal-doped MnO2 electrode material and its preparation method and application, specifically recording a preparation scheme of hydrothermal reaction using acetylene black, potassium permanganate, concentrated sulfuric acid, and sodium molybdate as raw materials.

[0005] In addition, Chinese patent document with publication number CN116768272A discloses a scheme of a manganese-based cathode material with oxygen defects introduced electrochemically in situ. Chinese patent document with publication number CN117623393A discloses an aqueous zinc-ion battery cathode material MnO2@CNT and its preparation method, specifically recording a scheme of hydrothermal preparation of MnO2@CNT nanofiber material from manganese acetate, potassium permanganate, and carbon nanotubes.

[0006] In summary, the schemes of the prior art can improve the structure or interface of manganese dioxide to a certain extent and obtain good performance in some aspects, but there is still room for improvement in stability at high capacity and high current. Summary of the Invention

[0007] Aiming at the problems of low conductivity, Mn dissolution caused by Jahn-Teller effect, and insufficient cycle life existing in the existing manganese dioxide cathode materials, the first object of the present invention is to provide a preparation method of an interlayer-surface dual-modified layered manganese dioxide cathode active material, aiming to prepare a cathode active material with special interlayer-surface synergistic modification, thereby taking into account excellent two-electron reaction effects and excellent capacity performance.

[0008] The second object of the present invention is to provide an interlayer-surface dual-modified layered manganese dioxide positive electrode active material prepared by the preparation method and its application in an aqueous zinc secondary battery.

[0009] The third object of the present invention is to provide an aqueous zinc secondary battery comprising the interlayer-surface dual-modified layered manganese dioxide positive electrode active material.

[0010] A preparation method of an interlayer-surface dual-modified layered manganese dioxide positive electrode active material, in which a raw material solution containing a manganese source and zinc hexafluorosilicate is subjected to a first-stage reaction to obtain interlayer-modified manganese dioxide; then the interlayer-modified manganese dioxide is subjected to a second-stage reaction in a modification solution containing a phosphoric acid source to obtain the interlayer-surface dual-modified layered manganese dioxide positive electrode active material.

[0011] The present invention innovatively uses zinc hexafluorosilicate to participate in the synthesis process of manganese dioxide in situ, so as to optimize the layered and interlayer structures of manganese dioxide, optimize the uniform deposition and conduction of metal ions. In addition, further combined with the subsequent surface modification of the phosphoric acid source, synergy can be achieved, which can improve the zinc ion diffusion ability, the transmission speed of active ions, the structural stability and the interfacial compatibility of the material. In addition, it can also effectively prevent the phase change and Mn 2+ dissolution during the higher-capacity two-electron reaction of manganese dioxide, thereby improving the capacity of the zinc ion battery and the stability under high current.

[0012] In the present invention, the manganese source includes permanganate and divalent manganese salt.

[0013] In the present invention, the permanganate can be, for example, potassium permanganate. The divalent manganese salt can be any water-soluble divalent manganese ion salt, for example, it can be manganese sulfate.

[0014] In the present invention, the weight ratio of permanganate to divalent manganese salt is 0.1~1:1; further, it can be 0.3~0.6:1.

[0015] In the present invention, zinc hexafluorosilicate participates in the synthesis process of manganese dioxide in situ, so as to optimize the phase and interlayer structure of manganese dioxide in situ, which is beneficial to the joint synergy with the subsequent surface modification of the phosphoric acid source and optimize the performance of the obtained manganese dioxide material.

[0016] In the present invention, the weight ratio of the manganese source to zinc hexafluorosilicate is 1:0.2~1; further, it can be 1:0.5~0.9; more preferably, it is 1:0.6~0.8.

[0017] In the present invention, in the raw material solution, a structure regulator is further included; the structure regulator includes at least one of an anionic surfactant, a cationic surfactant and a nonionic surfactant; further preferably, it is an anionic surfactant.

[0018] The research of the present invention also shows that using zinc hexafluorosilicate in combination with the said structure regulator, especially the preferably anionic surfactant, participates in the synthesis process of manganese dioxide in-situ. Thus, it is expected to further optimize the interlayer and surface structures of the prepared manganese dioxide, which helps to further synergize with the subsequent surface modification of the phosphate source and optimize the performance of the obtained manganese dioxide material.

[0019] In the present invention, the said anionic surfactant can be, for example, a hydrocarbon sulfonate of C 10 ~C 20 , or a hydrocarbon sulfate of C 10 ~C 20 . The hydrocarbon group therein can be, for example, a saturated carbon chain, a partially unsaturated carbon chain, a benzene ring, an alkyl-substituted benzene ring, etc.

[0020] In the present invention, the said cationic surfactant can be, for example, a quaternary ammonium salt with 1 to 2 long chains. The said long chain can be, for example, a saturated carbon chain of C 10 ~C 20 , a partially unsaturated carbon chain, a benzene ring, an alkyl-substituted benzene ring, etc.

[0021]

[0022] In the present invention, the said non-ionic surfactant can be, for example, fatty alcohol polyoxyethylene ether (AEO, Alcohol Ethoxylate); alkylphenol polyoxyethylene ether (APEO, Alkylphenol Ethoxylate); fatty acid polyoxyethylene ester (PEG fatty acid ester); and further can be a block copolymer (F127).

[0023] The said structure regulator is 5 to 50% of the weight of the manganese source, and further can be 10 to 20%.

[0024] In the present invention, there is no special requirement for the solvent in the said raw material solution. For example, it can be water, or a mixed solvent containing water and an organic solvent. The said organic solvent is, for example, a solvent miscible with water, and further can be an alcohol solvent such as ethanol and ethylene glycol. When using the said mixed solvent, the volume ratio of water to the organic solvent can be 1 to 10:1 to 10; and further can be 3 to 5:1.

[0024] In the present invention, the temperature of the first-stage reaction is 70 to 90 °C.

[0025] In the present invention, the first-stage reaction process is carried out under microwave assistance. The research of the present invention shows that in the in-situ participation of zinc hexafluorosilicate and further combined with the microwave reaction mode, the in-situ modification effect of manganese dioxide can be unexpectedly further enhanced, which helps to further enhance the ion transport efficiency of the prepared material, inhibit the structural distortion, optimize the desolvation energy barrier at the electrode-electrolyte interface, enhance the interfacial charge transfer ability, and further improve the electrochemical performance of the prepared material at high current.

[0026] In the present invention, the power of the microwave can be 100-700 W; preferably 200-400 W. Under the microwave assistance of the preferred power, it helps to further improve the electrochemical performance of the prepared material at high current.

[0027] In the present invention, the time of the first-stage reaction is 5-60 min; further, it can be 10-20 min.

[0028] In the present invention, after the first-stage reaction is completed, a cooling medium can be used for rapid cooling, and then solid-liquid separation is carried out to obtain the interlayer-modified manganese dioxide.

[0029] In the present invention, the interlayer-modified manganese dioxide and the solution containing a phosphoric acid source are innovatively subjected to a second-stage reaction (surface modification), so that it can cooperate synergistically with the first-stage reaction to enhance the electrochemical performance of the prepared material at high current.

[0030] In the present invention, the phosphoric acid source includes at least one of phosphoric acid, sodium phosphate, ammonium phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate; preferably at least one of ammonium dihydrogen phosphate and diammonium hydrogen phosphate. Research shows that using the preferred phosphoric acid source helps to further improve the electrochemical performance of the prepared material at high current.

[0031] In the present invention, the weight ratio of the phosphoric acid source to the interlayer-modified manganese dioxide is 0.05-0.25:1; preferably 0.1-0.15:1.

[0032] In the present invention, the temperature during the second-stage reaction process is 50-70 °C.

[0033] In the present invention, the pH during the second-stage reaction process is controlled at 2-10; preferably 6.5-7.5. Under the preferred pH, it helps to further synergistically improve the physical and chemical structure of the material and helps to further improve the long-term cycling stability of the prepared material at high current.

[0034] In the present invention, the time of the second-stage reaction is 0.5-2 h, and further, it can be 1-1.5 h.

[0035] The present invention also provides an interlayer-surface dual-modified layered manganese dioxide cathode active material prepared by the above preparation method.

[0036] The preparation method described in the present invention can endow the prepared material with special physical and chemical characteristics, and the material with such physical and chemical characteristics prepared by the preparation method can unexpectedly and effectively improve its capacity and long-term cycle stability under high current.

[0037] The present invention also provides an application of the interlayer-surface dual-modified layered manganese dioxide cathode active material prepared by the preparation method. Using it as the cathode active material, it is used to prepare an aqueous zinc secondary battery.

[0038] In the present invention, based on known processes and methods, the interlayer-surface dual-modified layered manganese dioxide cathode active material described in the present invention can be used as the cathode active material to prepare the required aqueous zinc secondary battery.

[0039] The present invention also provides an aqueous zinc secondary battery, and the positive electrode of the zinc secondary battery includes the interlayer-surface dual-modified layered manganese dioxide cathode active material prepared by the preparation method.

[0040] In the present invention, the aqueous zinc secondary battery can be an aqueous zinc ion battery.

[0041] In the battery described in the present invention, in addition to including the interlayer-surface dual-modified layered manganese dioxide cathode active material described in the present invention, other components and structural relationships can be known.

[0042] Beneficial effects: The present invention innovatively uses zinc hexafluorosilicate to participate in the synthesis process of manganese dioxide in situ, and further cooperates with the subsequent surface modification of the phosphoric acid source, which can achieve synergy, improve the zinc ion diffusion ability, the transmission speed of active ions, the structural stability and the interfacial compatibility of the material, thereby improving the capacity of the zinc ion battery and the stability under high current.

[0043] The research of the present invention also shows that innovatively using a structure regulator to participate in the first-stage reaction process, and / or cooperating with a microwave-assisted reaction method, can further strengthen the process modification effect, which helps to further improve the capacity of the prepared material and the long-cycle performance under high current. Description of the Drawings

[0044] Figure 1 XRD pattern of the material obtained in Example 1.

[0045] Figure 2 Cycling performance graph of the zinc ion battery obtained in Example 1 at 25 °C and a current density of 0.2 A / g.

[0046] Figure 3 Cycling performance graph of the zinc ion battery obtained in Example 1 at 25 °C and a current density of 2 A / g. Detailed Description of the Invention

[0047] Example 1

[0048] Step 1: Premixing:

[0049] Ultrasonically disperse a manganese source (potassium permanganate and manganese sulfate with a mass ratio of 0.3:1), zinc hexafluorosilicate, a solvent (water and ethanol with a mass ratio of 5:1), and a structure-directing agent (sodium dodecyl sulfate) with a mass ratio of 1:0.8:10:0.2 for 10 minutes to form a homogeneous mixture.

[0050] Step 2: Microwave-assisted reaction:

[0051] Transfer the mixture to a microwave reaction kettle, and set the parameters: microwave power: 300 W; reaction temperature: 80 °C (monitored in real time by infrared); reaction time: 15 minutes; after the reaction is completed, terminate the reaction with an ice-water bath at a temperature lower than 5 °C, centrifuge, wash with pre-cooled ethanol 3 times, and freeze-dry for 12 hours to obtain interlayer-modified manganese dioxide (also marked as: first-stage MnO2).

[0052] Step 3: Ammonium phosphate modification:

[0053] Disperse ammonium dihydrogen phosphate (NH4H2PO4) and first-stage MnO2 with a mass ratio of 0.1:1 in a water-methanol mixed solvent with a volume ratio of 3:1 (where the solid content of first-stage MnO2 in the solution is 0.1 - 0.15 g / mL), adjust the pH to 7.0 using ammonia water, stir at a constant temperature of 60 ± 10 °C for 1 - 1.5 hours, centrifuge, and then freeze-dry for 12 hours to obtain the final product (second-stage MnO2, XRD see Figure 1 ); the cyclic diagrams of the products are shown in Figure 2 and Figure 3 .

[0054] Example 2

[0055] Compared with Example 1, the only difference is that the structure-directing agent and its type in Step 1 are changed. The experimental groups are as follows:

[0056] Group A: The structure-directing agent is cetyltrimethylammonium bromide (CTAB);

[0057] Group B: The structure-directing agent is block copolymer (F127);

[0058] Group C: No structure-directing agent is added;

[0059] Other operations and parameters are the same as those in Example 1.

[0060] Example 3

[0061] Compared with Example 1, the difference is only that in Step 2, instead of microwave-assisted treatment, it is heated to the required temperature in an oven, and other operations and parameters are the same as those in Example 1.

[0062] Example 4

[0063] Compared with Example 1, the difference is only that in Step 1, a uniform mixture is formed by ultrasonically dispersing a manganese source (potassium permanganate and manganese sulfate with a mass ratio of 0.6:1), zinc hexafluorosilicate, a solvent (water and ethanol with a mass ratio of 3:1), and a structure-directing agent (sodium dodecyl sulfate) with a mass ratio of 1:0.7:11:0.1 for 10 minutes.

[0064] Step 2: Microwave-assisted reaction:

[0065] Transfer the mixture to a microwave reaction kettle, and set the parameters: microwave power: 200 W; reaction temperature: 70 °C (monitored in real time by infrared); reaction time: 20 minutes; after the reaction is completed, terminate the reaction with an ice-water bath at a temperature below 5 °C, perform centrifugal separation, wash 3 times with pre-cooled ethanol, and freeze-dry for 12 hours to obtain interlayer-modified manganese dioxide, and other operations and parameters are the same as those in Example 1.

[0066] Example 5

[0067] Compared with Example 1, the difference is only that the pH condition is adjusted differently in Step 3.

[0068] The experimental groups are:

[0069] Group A: Adjust the pH to 2.0 with nitric acid during the modification process;

[0070] Group B: Adjust the pH to 10.0 with ammonia water during the modification process.

[0071] Other operations and parameters are the same as those in Example 1.

[0072] Example 6

[0073] Compared with Example 1, the difference is only that the type of phosphate and the mass ratio of ammonium dihydrogen phosphate to primary MnO₂ are changed in Step 3.

[0074] The experimental groups are respectively:

[0075] Group A: The mass ratio of ammonium dihydrogen phosphate to primary MnO₂ is 0.05:1;

[0076] Group B: The mass ratio of ammonium dihydrogen phosphate to primary MnO₂ is 0.2:1;

[0077] Group C: The phosphate used is sodium dihydrogen phosphate.

[0078] Other operations and parameters are the same as those in Example 1.

[0079] Comparative Example 1

[0080] Compared with Example 1, the only difference is that the parameters in Step 1 are changed. The experimental groups are as follows:

[0081] Group A: Zinc hexafluorosilicate is not added.

[0082] Group B: Zinc trifluoromethanesulfonate is used to replace the zinc hexafluorosilicate in equal weight;

[0083] Group C: Ammonium hexafluorosilicate is used to replace the zinc hexafluorosilicate in equal weight;

[0084] Group D: Zinc sulfate is used to replace the zinc hexafluorosilicate in equal weight;

[0085] Other operations and parameters are the same as those in Example 1.

[0086] Comparative Example 2

[0087] Compared with Example 1, the only difference is that in Step 3, ammonium dihydrogen phosphate is not added. Other operations and parameters are the same as those in Example 1.

[0088] Comparative Example 3

[0089] Compared with Example 1, the only difference is that in Step 3, oxalic acid is used to replace the phosphoric acid. Other operations and parameters are the same as those in Example 1.

[0090] Full cell assembly and performance measurement:

[0091] The finally prepared MnO2 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 oven at 60 °C for 12 h to obtain a positive electrode sheet. Subsequently, a circular electrode with a diameter of about 10 mm was cut from it using a cutter, and the surface loading of the obtained positive electrode sheet was about 1.5 mg / cm 2 . A CR2025 button cell was assembled in the order of positive electrode cell case, positive electrode sheet, glass fiber separator, 0.1 mm zinc foil negative electrode, nickel foam, and negative electrode cell case, 2M ZnSO4 + 0.1M MnSO4 aqueous electrolyte was added, and finally, it was sealed using a battery encapsulation machine. At a temperature of 25 °C, the assembled aqueous zinc-ion battery was subjected to charge-discharge tests 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 test voltage range was 0.8 V - 1.8 V, and the test instrument was a BlueTec electrochemical measurement system. The results are shown in Table 1:

[0092]

[0093] From Examples 1 and Comparative Examples 1 to 3, it can be seen that innovatively adopting zinc hexafluorosilicate to participate in the synthesis process of manganese dioxide in situ, and further cooperating with the subsequent surface modification of the phosphate source, can achieve synergy, improve the zinc ion diffusion ability, the transmission speed of active ions, the structural stability and the interfacial compatibility of the material, thereby improving the capacity of the zinc ion battery and the stability under high current.

[0094] From Examples 1 and 2, it can be seen that adopting a structure regulator, especially an anionic surfactant as a structure regulator, helps to further synergize with the process and helps to further improve the performance of the prepared material.

[0095] From Examples 1 and 3, it can be seen that adopting microwave to participate in the synthesis of Step 1 helps to further cooperate synergistically with zinc hexafluorosilicate, helps to further facilitate the structural regulation of manganese dioxide, and better performance can be obtained.

Claims

1. A preparation method of an interlayer-surface dual-modified layered manganese dioxide cathode active material, characterized in that, React the raw material solution containing a manganese source and zinc hexafluorosilicate in the first-stage reaction to obtain interlayer-modified manganese dioxide; then react the interlayer-modified manganese dioxide in a modification solution containing a phosphate source in the second-stage reaction to obtain the interlayer-surface dual-modified layered manganese dioxide cathode active material; The manganese source includes permanganate and divalent manganese salt; The weight ratio of the manganese source to zinc hexafluorosilicate is 1:0.2 - 1; The temperature of the first-stage reaction is 70 - 90 °C.

2. The preparation method of the interlayer-surface dual-modified layered manganese dioxide cathode active material according to claim 1, characterized in that, The weight ratio of permanganate to divalent manganese salt is 0.1 - 1:

1.

3. The preparation method of the interlayer-surface dual-modified layered manganese dioxide cathode active material according to claim 1, characterized in that The weight ratio of the manganese source to zinc hexafluorosilicate is 1:0.5 - 0.

9.

4. The preparation method of the interlayer-surface dual-modified layered manganese dioxide cathode active material according to claim 1, characterized in that, In the raw material solution, a structure regulator is further included; the structure regulator includes at least one of an anionic surfactant, a cationic surfactant, and a nonionic surfactant; The structure regulator is 5 - 50% of the weight of the manganese source.

5. The preparation method of the interlayer-surface dual-modified layered manganese dioxide cathode active material according to claim 1, characterized in that, The time of the first-stage reaction is 5 - 60 min.

6. The preparation method of the interlayer-surface dual-modified layered manganese dioxide cathode active material according to any one of claims 1 to 5, characterized in that The first-stage reaction process is carried out under microwave assistance.

7. The preparation method of the interlayer-surface dual-modified layered manganese dioxide cathode active material according to claim 1, characterized in that, The phosphate source includes at least one of phosphoric acid, sodium phosphate, ammonium phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate; The weight ratio of the phosphate source to the interlayer-modified manganese dioxide is 0.05 - 0.25:1; The pH during the second-stage reaction is controlled at 2 - 10.

8. An interlayer-surface dual-modified layered manganese dioxide cathode active material prepared by the preparation method according to any one of claims 1 - 7.

9. Application of an interlayer-surface dual-modified layered manganese dioxide cathode active material prepared by the preparation method according to any one of claims 1 to 7, characterized in that, Use it as a cathode active material to prepare an aqueous zinc secondary battery.

10. An aqueous zinc secondary battery, characterized in that: The cathode of the aqueous zinc secondary battery includes the interlayer-surface dual-modified layered manganese dioxide cathode active material prepared by the preparation method according to any one of claims 1 - 7.

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