A metal oxide / mesoporous manganese dioxide / conductive polymer composite material, a preparation method and application thereof

Abstract

This invention belongs to the field of lithium battery material technology, specifically relating to a metal oxide / mesoporous manganese dioxide / conductive polymer composite material, its preparation method, and its application. The preparation method includes the following steps: 1) ball milling a commercial metal oxide; 2) mixing the metal oxide powder with an organic polymer monomer and a methyl orange solution and ultrasonically dispersing the mixture to obtain a liquid mixture; 3) adding a potassium permanganate solution to the liquid mixture and performing a high-pressure hydrothermal reaction under stirring to obtain the composite material; 4) subjecting the composite material to alkali treatment, filtering, washing with water, and drying to obtain the metal oxide / mesoporous manganese dioxide / conductive polymer composite material. This metal oxide / mesoporous manganese dioxide / conductive polymer composite material can be used to prepare lithium battery cathode materials with high specific capacity, high conductivity, and high stability in a simple, efficient, and low-cost manner. It is easy to industrialize and solves the problems of low conductivity and poor rate discharge performance of traditional metal oxide cathode materials.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery materials technology, specifically relating to a metal oxide / mesoporous manganese dioxide / conductive polymer composite material, its preparation method, and its application. Background Technology

[0002] In the selection of cathode materials for lithium primary batteries, chromium oxide (Cr8O) is a common choice. 21 High chromium oxide materials possess advantages such as high theoretical energy density (1210 Wh / kg), high discharge voltage plateau (>3.0 V), and good low-to-medium rate discharge performance. However, pure chromium oxide materials have poor conductivity, resulting in low high-rate discharge capability and a significant gap between the discharge specific capacity and the theoretical value. Therefore, improving chromium oxide materials to enhance their conductivity and rate discharge performance is an important direction for improving lithium primary batteries.

[0003] Traditional methods for improving metal oxides mostly involve mechanical mixing or simple coating. CN112968176A uses ball milling to modify chromium oxide (Cr8O) 21 The mechanical mixing of chromium oxide and carbon nanotubes to prepare composite oxide materials improved the discharge capacity and conductivity of the materials. However, simple ball milling easily leads to uneven mixing and unstable discharge performance. CN102339994A combines chromium oxide and graphene through hydrothermal coprecipitation, effectively improving the conductivity and significantly enhancing the cycle performance of the composite material. However, chromium oxide is extremely sensitive to solvents, especially in high-temperature and high-pressure environments, where it readily forms chromium anhydride (H2CrO4), making the preparation of chromium oxide / graphene composite materials using the hydrothermal coprecipitation method very difficult.

[0004] Current research on the improvement of metal oxides mainly focuses on improving the conductivity of chromium oxides. However, most improvement methods suffer from problems such as uneven doping of composite materials, harsh preparation conditions, and low yield, which limit the further application of these improved composite materials. Summary of the Invention

[0005] The purpose of this invention is to provide a metal oxide / mesoporous manganese dioxide / conductive polymer composite material to address the shortcomings of the prior art, which can solve the problems of low conductivity and low high-rate discharge performance of traditional metal oxide cathode materials.

[0006] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0007] A metal oxide / mesoporous manganese dioxide / conductive polymer composite material comprises metal oxide particles, mesoporous manganese dioxide and a conductive polymer supported on their surface; wherein the general structural formula of the conductive polymer is shown in Formula 1 below:

[0008] Formula 1

[0009] In Formula 1, the polymer monomer is lithium 3,4-thiophene dicarboxylate, the polymerization site between monomers is the 1 and 2 sites on the thiophene ring, and R1 is the alkane chain contained in the lithium carboxylate group on the thiophene ring, wherein the number of carbons in R1 is between 2 and 10.

[0010] According to the above scheme, the conductive polymer is obtained by treating the thiophene polymer with an alkali (i.e., the reaction of the thiophene polymer with lithium hydroxide) to introduce Li ions into the thiophene polymer shown in Formula 2, thereby converting the carboxyl groups on the thiophene polymer into lithium carboxylic acid groups.

[0011] Formula 2

[0012] In Formula 2, the polymer monomer is 3,4-thiophene dicarboxylic acid, and the polymerization sites between monomers are the 1 and 2 sites on the thiophene ring. R1 is the alkane chain contained in the carboxylic acid group on the thiophene ring, and the number of carbons in R1 is between 2 and 10. n is the degree of polymerization.

[0013] According to the above scheme, the mass ratio of the metal oxide, mesoporous manganese dioxide and conductive polymer is 1:(0.01~0.1):(0.01~0.1).

[0014] According to the above scheme, the metal oxide is one or more of chromium oxide, vanadium oxide, lead oxide, etc.

[0015] This invention also provides a method for preparing the above-mentioned metal oxide / mesoporous manganese dioxide / conductive polymer composite material, which mainly includes the following steps:

[0016] 1) Mix the metal oxide powder with methyl orange solution and 3,4-thiophene dicarboxylic acid monomer, and disperse the mixture using ultrasound to obtain a mixed solution;

[0017] 2) Transfer the mixed solution obtained in step 1) to a hydrothermal reactor, add potassium permanganate solution while stirring, and seal to carry out the hydrothermal reaction;

[0018] 3) After washing and filtering the solid product obtained from the hydrothermal reaction in step 2), add lithium hydroxide solution, perform alkali treatment under heating and stirring conditions, wash and dry to obtain the finished metal oxide / mesoporous manganese dioxide / conductive polymer composite material.

[0019] According to the above scheme, in step 1), the metal oxide powder is obtained by pulverizing commercial metal oxides. The pulverization method is to use a planetary ball mill to pulverize the commercial metal oxides at a speed of 200~600r / min for 1~3h, and then sieve them through an 800-mesh sieve to obtain powder with a particle size of less than 19 micrometers.

[0020] According to the above scheme, in step 1), methyl orange is added as a conductive polymer template agent. In step 1), the concentration of methyl orange as a conductive polymer template agent is 2~10 mg / ml. The concentrations of metal oxide powder and 3,4-thiophene dicarboxylic acid monomer added to the methyl orange solution are 20~200 mg / ml and 2~20 mg / ml, respectively. The mass ratio of metal oxide to 3,4-thiophene dicarboxylic acid is 1:(0.01~0.1), preferably 1:(0.02~0.5).

[0021] According to the above scheme, in step 2), the concentrations of the metal oxide and the 3,4-thiophene dicarboxylic acid monomer in the mixed solution after adding potassium permanganate solution are 10~100 mg / ml and 1~10 mg / ml, respectively.

[0022] According to the above scheme, in step 2), potassium permanganate is prepared as an aqueous solution with a concentration of 1~8 mg / ml. It is added as an oxidant and a source of manganese oxide. The amount added is such that the mass ratio of manganese dioxide to metal oxide generated by the potassium permanganate solution is (0.01~0.1):1, preferably (0.02~0.1):1.

[0023] According to the above scheme, in step 2), the temperature of the hydrothermal reaction is 100~200℃ and the hydrothermal reaction time is 1~5h.

[0024] According to the above scheme, in step 3), after the solid product obtained from the hydrothermal reaction is washed and filtered, it is not dried (to improve its dispersion). Instead, it is ultrasonically dispersed and mixed with a lithium hydroxide solution in a wet state (to further improve its dispersion) for alkali treatment, so that the lithium hydroxide can react quickly and completely with the solid product obtained from the hydrothermal reaction. The concentration of the lithium hydroxide solution is 1~5 mol / L; the reaction temperature during alkali treatment is 30~60℃, and the reaction time is 1~3 h.

[0025] The present invention also provides a lithium metal oxide battery, wherein the positive electrode material is the above-mentioned metal oxide / mesoporous manganese dioxide / conductive polymer composite material.

[0026] The metal oxide / mesoporous manganese dioxide / conductive polymer composite material of this invention comprises mesoporous manganese dioxide and a conductive polymer loaded onto the surface of metal oxide particles. The mesoporous manganese dioxide / conductive polymer is synthesized using potassium permanganate as an oxidant, methyl orange solution as a template agent, and thiophene-based organic monomers. Specifically, the pulverized metal oxide particles are ultrasonically dispersed in methyl orange solution. After adding potassium permanganate solution, a high-pressure hydrothermal reaction is performed under stirring to form a uniformly loaded mesoporous manganese dioxide / conductive polymer material on the surface of the metal oxide. Finally, the composite material is treated with lithium hydroxide solution to introduce Li ions into the conductive polymer, resulting in the metal oxide / mesoporous manganese dioxide / conductive polymer composite material.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] The metal oxide / mesoporous manganese dioxide / conductive polymer composite material provided by this invention exhibits stable properties and good electrical conductivity. The loading of mesoporous manganese dioxide and the conductive polymer effectively increases the mesoporous structure and specific surface area of ​​the composite material, improving the wettability of the electrolyte. Furthermore, the conductive polymer further enhances the electrical conductivity of the composite material, thereby increasing its electronic conductivity. Simultaneously, the introduction of lithium carboxylate onto the conductive polymer significantly enhances the lithium-ion conductivity during battery discharge, improving the ionic conductivity of the composite material. Through the synergistic effect of mesoporous manganese dioxide, the conductive polymer, and the metal oxide, both electronic and ionic conductivity of the material can be improved simultaneously, reducing the battery's internal resistance and further improving the battery's rate discharge performance. This effectively overcomes the application defects of traditional chromium oxide cathode materials. Attached Figure Description

[0029] Figure 1 The image shows a surface SEM image of the chromium oxide / manganese dioxide / conductive polymer cathode material prepared in Example 1.

[0030] Figure 2 This is a comparison of the surface pore size distribution of the cathode materials prepared in Example 1 and Comparative Example 1.

[0031] Figure 3 The adsorption-desorption curves of the cathode materials prepared in Example 1 and Comparative Example 1 are compared. Detailed Implementation

[0032] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the present invention is not limited to the following embodiments.

[0033] Example 1

[0034] A metal oxide / mesoporous manganese dioxide / conductive polymer composite material comprises chromium oxide particles and mesoporous manganese dioxide and a conductive polymer supported on their surfaces. During preparation, the mass ratio of the metal oxide, mesoporous manganese dioxide, and conductive polymer monomers is approximately 1:0.02:0.02. The conductive polymer has the following general structural formula:

[0035]

[0036] The starting monomer of the conductive polymer in this composite material is 3,4-thiophene diacetic acid. The formation process of the conductive polymer in the preparation of the composite material is basically as follows: 3,4-thiophene diacetic acid monomer polymerizes to generate thiophene polymer. The polymerization sites between monomers are the 1 and 2 sites on the thiophene ring. R1 is the alkane chain contained in the carboxylic acid group on the thiophene ring, where R1 has 2 carbons and n is the degree of polymerization. Then, through the reaction of the thiophene polymer with lithium hydroxide, Li ions are introduced into the thiophene polymer shown in Formula 2, so that the carboxyl group on the thiophene polymer is converted into a lithium carboxylic acid group, forming the conductive polymer shown in Formula 1 in the composite material.

[0037] The preparation method of the above-mentioned metal oxide / mesoporous manganese dioxide / conductive polymer composite material is as follows:

[0038] Step 1: Use a ball mill to process commercial chromium oxide (Cr8O). 21 The material was ball-milled at a speed of 500 r / min for 2 hours. After milling, it was sieved through an 800-mesh sieve to obtain powder with a particle size of less than 19 micrometers.

[0039] Step 2: Weigh 2g of ball-milled chromium oxide powder and add it to 20ml of methyl orange solution (solution concentration 5mg / ml). Mix and disperse by ultrasonication for 30min. Then add 40mg of 3,4-thiophene diacetic acid monomer and continue ultrasonic dispersion for 1h.

[0040] Step 3: After ultrasonic dispersion, transfer the resulting mixed solution to a 50ml hydrothermal reactor inner liner, add 20ml potassium permanganate solution (solution concentration 4mg / ml) while stirring, and perform hydrothermal reaction at 120℃ for 2 hours while maintaining stirring.

[0041] Step 4: After the hydrothermal reaction is complete, the material in the hydrothermal reactor is filtered and washed, and then transferred to 30 ml of potassium hydroxide solution (2 mol / L) in a wet state. The mixture is stirred and reacted at 50°C for 30 min. After the reaction is complete, the resulting composite material is filtered, washed with water, and dried in a vacuum drying oven at 60°C for 24 h to obtain the finished chromium oxide / manganese dioxide / conductive polymer composite material.

[0042] Depend on Figure 1 and Figure 2 , Figure 3 It can be seen that the surface of the finished chromium oxide / manganese dioxide / conductive polymer composite material has a porous and loose structure. The mesoporous manganese dioxide is in close contact with the metal oxide and conductive polymer material, introducing abundant mesoporous structures and increasing the specific surface area of ​​the composite material. BET results show that its average pore size is 4.3 nm and its specific surface area is 252.1 m². 2 / g; while the commodity Cr8O 21 The average pore size is 9.3 nm, and the specific surface area is 102.5 m². 2 / g, which proves that the co-loading of manganese dioxide and conductive polymer in this invention increases the mesoporous structure and specific surface area of ​​the composite material, which is more conducive to electrolyte wetting.

[0043] Application example: The metal oxide / mesoporous manganese dioxide / conductive polymer composite material (97 wt%) prepared in Example 1 was dissolved in a solvent (NMP) with a binder (PVDF, 1.4 wt%) and a conductive agent (SP001, 1.6 wt%) to prepare a slurry. The slurry was then coated onto an aluminum foil with a thickness of 12 μm. After drying, rolling, and cutting, a lithium primary battery positive electrode sheet was prepared.

[0044] The above-mentioned lithium-ion battery positive electrode sheet, separator (PP1600, single-sided aluminum oxide coating) and negative lithium sheet (150μm thickness) are wound together to form an electrode assembly. Then, tabs are welded, and the assembly is packaged with aluminum-plastic film. After liquid injection, pre-discharge and other processes, a soft-pack lithium primary battery is prepared, with the battery model CP755593.

[0045] Example 2

[0046] The preparation method of the metal oxide / mesoporous manganese dioxide / conductive polymer composite material is as follows:

[0047] The difference between this embodiment and specific embodiment 1 is that the commercial metal oxide selected in step 1 is vanadium oxide (V2O5), while the rest is the same as in specific embodiment 1.

[0048] The metal oxide / mesoporous manganese dioxide / conductive polymer composite material prepared in this embodiment was used to prepare a lithium primary battery positive electrode and a corresponding lithium primary battery according to the method in Example 1.

[0049] Example 3

[0050] The preparation method of the metal oxide / mesoporous manganese dioxide / conductive polymer composite material is as follows:

[0051] The difference between this embodiment and Specific Embodiment 1 is that the 3,4-thiophene diacetic acid monomer added in step 2 is changed to 200 mg, and the concentration of potassium permanganate solution added in step 3 is changed to 20 mg / ml. Otherwise, it is the same as Specific Embodiment 1. That is, during the preparation process, the mass ratio of the added metal oxide, mesoporous manganese dioxide, and conductive polymer monomer is approximately 1:0.1:0.02.

[0052] The metal oxide / mesoporous manganese dioxide / conductive polymer composite material prepared in this embodiment was used to prepare a lithium primary battery positive electrode and a corresponding lithium primary battery according to the method in Example 1.

[0053] Example 4

[0054] The preparation method of the metal oxide / mesoporous manganese dioxide / conductive polymer composite material 4 is as follows:

[0055] The difference between this embodiment and Specific Embodiment 1 is that the polymer monomer added in step 2 is replaced with 100 mg of 3,4-thiophene diacetic acid monomer, while the rest is the same as in Specific Embodiment 1. That is, in the preparation process, the mass ratio of the added metal oxide, mesoporous manganese dioxide and conductive polymer monomer is approximately 1:0.02:0.5.

[0056] The metal oxide / mesoporous manganese dioxide / conductive polymer composite material prepared in this embodiment was used to prepare a lithium primary battery positive electrode and a corresponding lithium primary battery according to the method in Example 1.

[0057] Example 5

[0058] The preparation method of the metal oxide / mesoporous manganese dioxide / conductive polymer composite material 5 is as follows:

[0059] The difference between this embodiment and Specific Embodiment 1 is that the amount of potassium permanganate solution added in step 3 changes to 40 mL, while the rest is the same as in Specific Embodiment 1. That is, during the preparation process, the mass ratio of the added metal oxide, mesoporous manganese dioxide, and conductive polymer monomer is approximately 1:0.04:0.02.

[0060] The metal oxide / mesoporous manganese dioxide / conductive polymer composite material prepared in this embodiment was used to prepare a lithium primary battery positive electrode and a corresponding lithium primary battery according to the method in Example 1.

[0061] Example 6

[0062] The preparation method of the metal oxide / mesoporous manganese dioxide / conductive polymer composite material 6 is as follows:

[0063] The difference between this embodiment and specific embodiment 1 is that the ball milling time in step 1 is changed to 3 hours, and the hydrothermal temperature in step 3 is changed to 200°C. The rest is the same as specific embodiment 1.

[0064] The metal oxide / mesoporous manganese dioxide / conductive polymer composite material prepared in this embodiment was used to prepare a lithium primary battery positive electrode and a corresponding lithium primary battery according to the method in Example 1.

[0065] Comparative Example 1

[0066] The preparation method of metal oxide cathode material is as follows: Commercial chromium oxide (Cr8O) is milled using a ball mill. 21 The material was ball-milled at a speed of 500 r / min for 2 hours. After milling, it was sieved through an 800-mesh sieve to obtain powder with a particle size of less than 19 micrometers.

[0067] The chromium oxide cathode material prepared in this comparative example was used to prepare lithium primary battery cathode sheets and corresponding lithium primary batteries according to the method in Example 1.

[0068] Comparative Example 2

[0069] The preparation method of metal oxide / commercial manganese dioxide composite cathode material is as follows: Commercial chromium oxide (Cr8O) is used... 21 The metal oxide and commercial battery positive electrode manganese dioxide (MnO2) were ball-milled and mixed at a mass ratio of 1:0.02. The mixture was ball-milled at a speed of 500 r / min for 2 h. The mixture was then sieved through an 800 mesh sieve to obtain powder with a particle size of less than 19 micrometers, thus obtaining the metal oxide / commercial manganese dioxide composite positive electrode material.

[0070] The chromium oxide / carbon nanotube cathode material prepared in this comparative example was used to prepare lithium primary battery cathode sheets and corresponding lithium primary batteries according to the method in Example 1.

[0071] Comparative Example 3

[0072] The preparation method of metal oxide / conductive polymer cathode material is as follows:

[0073] Step 1: Use a ball mill to process commercial chromium oxide (Cr8O). 21 The material was ball-milled at a speed of 500 r / min for 2 hours. After milling, it was sieved through an 800-mesh sieve to obtain powder with a particle size of less than 19 micrometers.

[0074] Step 2: Weigh 2g of the ball-milled chromium oxide powder and add it to 20ml of methyl orange solution (solution concentration 5mg / ml). Sonicate and disperse for 30min. Then add 0.2g of 3,4-thiophene diacetic acid monomer and continue sonication for 1h.

[0075] Step 3: After ultrasonic dispersion, transfer the mixed solution to a 50ml hydrothermal reactor inner liner, add 5ml of hydrogen peroxide solution (concentration of 30%) while stirring, and perform hydrothermal reaction at 120℃ for 2 hours while maintaining stirring.

[0076] Step 4: After the hydrothermal reaction is complete, the material in the hydrothermal reactor is filtered and washed, and then transferred to 30 ml of potassium hydroxide solution (2 mol / L) in a wet state. The mixture is stirred and reacted at 50°C for 30 min. After the reaction is complete, the composite material is filtered, washed with water, and dried in a vacuum drying oven at 60°C for 24 h to obtain the finished chromium oxide / conductive polymer material.

[0077] The chromium oxide / conductive polymer cathode material prepared in this comparative example was used to prepare lithium primary battery cathode sheets and corresponding lithium primary batteries according to the method in Example 1.

[0078] Comparative Example 4

[0079] The preparation method of metal oxide / manganese dioxide is as follows:

[0080] Step 1: Use a ball mill to process commercial chromium oxide (Cr8O). 21 The material was ball-milled at a speed of 500 r / min for 2 hours. After milling, it was sieved through an 800-mesh sieve to obtain powder with a particle size of less than 19 micrometers.

[0081] Step 2: Weigh 2g of the ball-milled chromium oxide powder, add 20ml of deionized water, and continue ultrasonic dispersion for 1 hour.

[0082] Step 3: After ultrasonic dispersion, transfer the mixed solution to a 50ml hydrothermal reactor inner liner, add 20ml of potassium permanganate solution (solution concentration 20mg / ml) while stirring, and perform hydrothermal reaction at 120℃ for 2 hours while stirring.

[0083] Step 4: After the hydrothermal reaction is complete, the material in the hydrothermal reactor is filtered and washed, and then transferred to 30 ml of potassium hydroxide solution (2 mol / L) in a wet state. The mixture is stirred and reacted at 50°C for 30 min. After the reaction is complete, the composite material is filtered, washed with water, and dried in a vacuum drying oven at 60°C for 24 h to obtain the finished chromium oxide / manganese dioxide material.

[0084] The chromium oxide / conductive polymer cathode material prepared in this comparative example was used to prepare lithium primary battery cathode sheets and corresponding lithium primary batteries according to the method in Example 1.

[0085] Comparative Example 5

[0086] The preparation method of metal oxide / mesoporous manganese dioxide / conductive polymer is as follows:

[0087] Step 1: Use a ball mill to process commercial chromium oxide (Cr8O). 21 The material was ball-milled at a speed of 500 r / min for 2 hours. After milling, it was sieved through an 800-mesh sieve to obtain powder with a particle size of less than 19 micrometers.

[0088] Step 2: Weigh 2g of the ball-milled chromium oxide powder and add it to 20ml of methyl orange solution (solution concentration 5mg / ml). Sonicate and disperse for 30min. Then add 0.2g of 3,4-thiophene diacetic acid monomer and continue sonication for 1h.

[0089] Step 3: After ultrasonic dispersion, transfer the mixed solution to a 50ml hydrothermal reactor inner liner, add 20ml of potassium permanganate solution (solution concentration 20mg / ml) while stirring, and perform hydrothermal reaction at 120℃ for 2 hours while stirring.

[0090] Step 4: After the hydrothermal reaction is completed, the material in the hydrothermal reactor is filtered and washed, and then dried in a vacuum drying oven at 60°C for 24 hours to obtain the finished chromium oxide / mesoporous manganese dioxide / conductive polymer material.

[0091] The chromium oxide / conductive polymer cathode material prepared in this comparative example was used to prepare lithium primary battery cathode sheets and corresponding lithium primary batteries according to the method in Example 1.

[0092] The positive electrode materials in all embodiments and comparative examples were prepared using the same process as in Example 1, including slurry preparation, coating, slicing, and drying to form positive electrode sheets. Lithium sheets and electrolytes of the same specifications were used, and the same type of primary lithium battery was assembled and injected. After pre-discharge, the battery internal resistance was measured using a battery internal resistance tester, and the batteries underwent 1C discharge testing using a battery discharge testing device. The test results for each group of batteries are listed in Table 1. The internal resistance of the batteries in Examples 2-6 was also lower than that in Comparative Examples 1-5, all below 5 mΩ, and their 1C discharge capacity was higher than that in Comparative Examples 1-5, exceeding 330 mAh / g.

[0093] Table 1. Cathode material composition and test results for each battery

[0094]

[0095] As shown in Table 1, the metal oxide / mesoporous manganese dioxide / conductive polymer composite material provided by this invention exhibits lower battery internal resistance and higher discharge capacity. Comparing the data from Example 1 and Comparative Example 1 reveals that, compared to untreated metal oxide, the metal oxide / mesoporous manganese dioxide / conductive polymer composite material provided by this invention has lower internal resistance and higher discharge capacity, indicating that the novel composite material provided by this invention can effectively improve the problems of low conductivity and low high-rate discharge performance of traditional metal oxide cathode materials.

[0096] Comparing the data from Example 1 and Comparative Examples 2 and 4 reveals that the commercial manganese dioxide used in Comparative Example 2 is solid granular with no pores, a small specific surface area, and poor conductivity. When mixed with chromium oxide, it leads to a deterioration in the electrochemical performance of the material. Compared to Comparative Example 1, the battery produced has increased internal resistance and decreased discharge capacity. In Comparative Example 4, the manganese dioxide prepared by the hydrothermal method can be loaded onto the surface of chromium oxide, but the manganese dioxide grains are large, lack a mesoporous structure, and have a small specific surface area, resulting in high battery internal resistance and low material discharge capacity. In contrast, the metal oxide / mesoporous manganese dioxide / conductive polymer composite material prepared in Example 1 significantly reduces battery internal resistance while increasing battery discharge capacity. This indicates that the mesoporous manganese dioxide material obtained by the method of this invention not only bonds tightly with chromium oxide and conductive polymers, but also its mesoporous structure and high specific surface area increase the contact area between the composite material and the electrolyte, reducing interfacial impedance and effectively improving the material's conductivity, thereby reducing the battery's internal resistance.

[0097] Comparing the data from Example 1 and Comparative Example 3 reveals that the absence of mesoporous manganese dioxide structure leads to a significant increase in the internal resistance of the composite material and a decrease in discharge capacity. This indicates that the porous structure and high specific surface area brought by the mesoporous manganese dioxide in the composite material of the present invention can improve the electrolyte wettability of the composite material, thereby enhancing the electronic conductivity of the material. Comparing the data from Comparative Example 1 and Comparative Example 4 reveals that, compared with organic polymers with high conductivity, manganese dioxide in the composite material, as a metal oxide, has low conductivity. The combination of two metal oxides alone is difficult to improve the conductivity of the material. At the same time, due to the lack of conductive polymer as Li ion anchors, the improvement effect of alkali treatment on the composite material is negligible. Comparing the data from Example 1 and Comparative Example 5 reveals that the subsequent potassium hydroxide alkali treatment introduces lithium carboxylic acid groups into the composite material, which can further improve the ionic conductivity of the material during discharge, reduce the internal resistance of the material, and increase the discharge capacity of the material. Therefore, it can be concluded that the synergistic effect of the mesoporous manganese dioxide in the composite material and the alkali-treated conductive polymer can improve the electronic conductivity and ionic conductivity of the material, thereby effectively improving the problems of low conductivity of metal oxides and low high-rate discharge performance of batteries.

[0098] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A metal oxide / mesoporous manganese dioxide / conductive polymer composite material, characterized in that, It comprises metal oxide particles, mesoporous manganese dioxide supported on its surface, and a conductive polymer; wherein the general structural formula of the conductive polymer is as follows: The polymer monomer is lithium 3,4-thiophene dicarboxylate, the polymerization site between monomers is the 1 and 2 sites on the thiophene ring, and R1 is the alkane chain contained in the lithium carboxylate group on the thiophene ring, wherein the number of carbons in R1 is between 2 and 10.

2. The metal oxide / mesoporous manganese dioxide / conductive polymer composite material according to claim 1, characterized in that: The mass ratio of the metal oxide, mesoporous manganese dioxide, and conductive polymer is 1:(0.01~0.1):(0.01~0.1).

3. The metal oxide / mesoporous manganese dioxide / conductive polymer composite material according to claim 1 or 2, characterized in that: The metal oxide is one or more of chromium oxide, vanadium oxide, and lead oxide.

4. The method for preparing the metal oxide / mesoporous manganese dioxide / conductive polymer composite material according to claim 1, characterized in that: The main steps include: 1) Mix the metal oxide powder with methyl orange solution and 3,4-thiophene dicarboxylic acid monomer, and disperse the mixture using ultrasound to obtain a mixed solution; 2) Transfer the mixed solution obtained in step 1) to a hydrothermal reactor, add potassium permanganate solution while stirring, and seal to carry out the hydrothermal reaction; 3) After washing and filtering the solid product obtained from the hydrothermal reaction in step 2), add lithium hydroxide solution and perform alkali treatment under heating and stirring conditions. After washing and drying, the finished metal oxide / mesoporous manganese dioxide / conductive polymer composite material is obtained.

5. The method for preparing the metal oxide / mesoporous manganese dioxide / conductive polymer composite material according to claim 4, characterized in that: The metal oxide powder is obtained by pulverizing commercial metal oxides, with a particle size not exceeding 30 micrometers.

6. The method for preparing the metal oxide / mesoporous manganese dioxide / conductive polymer composite material according to claim 4, characterized in that: In step 1), methyl orange is added as a conductive polymer template agent, and its solution concentration is 2-10 mg / ml; the mass ratio of metal oxide and 3,4-thiophene dicarboxylic acid is 1:(0.01-0.1).

7. The method for preparing the metal oxide / mesoporous manganese dioxide / conductive polymer composite material according to claim 4, characterized in that: In step 2), the concentrations of the metal oxide and the 3,4-thiophene dicarboxylic acid monomer in the mixed solution after adding potassium permanganate solution are 10–100 mg / ml and 1–10 mg / ml, respectively.

8. The method for preparing the metal oxide / mesoporous manganese dioxide / conductive polymer composite material according to claim 4, characterized in that: In step 2), potassium permanganate is added as an oxidant and a source of manganese oxide. The amount added is such that the mass ratio of manganese dioxide to metal oxide generated by the potassium permanganate solution is (0.01~0.1):1; the concentration of the potassium permanganate solution used is 1~8 mg / ml.

9. The method for preparing the metal oxide / mesoporous manganese dioxide / conductive polymer composite material according to claim 4, characterized in that: In step 2), the hydrothermal reaction temperature is 100–200℃ and the hydrothermal reaction time is 1–5 h; in step 3), after washing and filtration, the product is ultrasonically dispersed and mixed with lithium hydroxide solution in a wet state so that lithium hydroxide can react quickly and completely with the solid product obtained from the hydrothermal reaction; wherein, the concentration of lithium hydroxide solution is 1–5 mol / L.

10. A lithium metal oxide battery, characterized in that: The positive electrode material is the metal oxide / mesoporous manganese dioxide / conductive polymer composite material as described in claim 1.

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