阅读说明：本技术 一种生物发酵二氧化锰/石墨烯复合电极材料的制备方法及应用 (Preparation method and application of biological fermentation manganese dioxide/graphene composite electrode material ) 是由 宋根娣 高亚辉 王佳伟 王芳 杨桦 张震 孙新媱 周阳 鲁照帅 何乡帅 任美欣 于 2021-08-24 设计创作，主要内容包括：本发明涉及一种生物发酵二氧化锰/石墨烯复合电极材料的制备方法及应用,先从锰矿石附近土壤中分离出菌株M1,接种到LB液体培养基中,回旋振荡培养后得到活化菌液,将活化菌液、氯化锰溶液接种到Lept液体培养基中,回旋振荡发酵培养,得发酵液；将石墨烯材料接种到发酵液中,回旋振荡发酵培养后高速离心,收集沉淀物,将沉淀物真空冷冻干燥,得复合电极材料前驱体；将前驱体高温煅烧,得生物发酵二氧化锰/石墨烯复合电极材料。本发明采用生物发酵法,利用矿石土壤中分离的细菌与氯化锰和石墨烯共同发酵培养,制备条件温和；所得复合电极材料电化学性能良好,可用于制备超级电容器、电池等,填补了复合电极材料生物技术制备领域的空白。(The invention relates to a preparation method and application of a biological fermentation manganese dioxide/graphene composite electrode material, which comprises the steps of firstly separating a strain M1 from soil near manganese ore, inoculating the strain M1 into an LB liquid culture medium, carrying out rotary oscillation culture to obtain an activated bacterial liquid, inoculating the activated bacterial liquid and a manganese chloride solution into a Lept liquid culture medium, and carrying out rotary oscillation fermentation culture to obtain a fermentation liquid; inoculating the graphene material into fermentation liquor, performing rotary oscillation fermentation culture, then performing high-speed centrifugation, collecting precipitate, and performing vacuum freeze drying on the precipitate to obtain a composite electrode material precursor; and calcining the precursor at high temperature to obtain the biological fermentation manganese dioxide/graphene composite electrode material. The invention adopts a biological fermentation method, utilizes bacteria separated from ore soil to carry out fermentation culture together with manganese chloride and graphene, and has mild preparation conditions; the obtained composite electrode material has good electrochemical performance, can be used for preparing super capacitors, batteries and the like, and fills the gap in the field of biotechnological preparation of composite electrode materials.)

1. A preparation method of a biological fermentation manganese dioxide/graphene composite electrode material is characterized by comprising the following steps:

(1) activating strains: separating a strain M1 from soil near manganese ore, inoculating the strain on an LB culture medium flat plate for activation for 10-15h through aseptic operation, then selecting an activated strain M1 for inoculation into 50ml of LB liquid culture medium through aseptic operation, carrying out rotary oscillation culture for 12-18h in a full-temperature oscillation culture shaker, taking a culture bacterial liquid, centrifuging, then removing a supernatant, adding aseptic water into the obtained precipitate to obtain an activated bacterial liquid for later use;

(2) primary inoculation culture: sequentially and aseptically inoculating the activated bacterium liquid prepared in the step (1) and a manganese chloride solution into a leptin liquid culture medium, and carrying out rotary oscillation fermentation culture in a full-temperature oscillation culture shaking table to obtain a fermentation liquid;

(3) and (3) secondary inoculation culture: inoculating a graphene material into the fermentation liquor prepared in the step (2) in a sterile operation manner, carrying out rotary oscillation fermentation culture in a full-temperature oscillation culture table, then centrifuging the obtained fermentation liquor at a high speed, removing supernatant, and collecting precipitate for later use;

(4) and (3) freeze drying treatment: performing vacuum freeze drying on the precipitate collected in the step (3) to obtain a precursor of the biological fermentation manganese dioxide/graphene composite electrode material;

(5) high-temperature calcination treatment: and (4) calcining the composite electrode material precursor prepared in the step (4) at high temperature to obtain the biological fermentation manganese dioxide/graphene composite electrode material.

2. The method according to claim 1, wherein the strain M1 in step (1) is Pseudomonas sp.

3. The method according to claim 1, wherein the cultivation temperature in the step (1) is 28-30 ℃, the rotational oscillation speed is 130-; subpackaging the culture bacterial liquid into a plurality of centrifugal tubes of 1.5ml, and adding 1ml of the culture bacterial liquid into each centrifugal tube; the speed of the centrifugal operation is 3000-4000r/min, the centrifugal time is 2-4min, the supernatant is discarded after the centrifugation, and 500ul of sterile water is added into the obtained precipitate to obtain the activated bacteria liquid.

4. The method according to claim 1, wherein the inoculation amount of the activated bacteria liquid in step (2) is 5ul/ml, the inoculation amount of the manganese chloride solution is 0.2-1.4ul/ml, the temperature of the rotary shaking fermentation culture is 28-30 ℃, the speed of the rotary shaking is 130-180r/min, and the time is 36-60 h.

5. The production method according to claim 1 or 4, wherein the concentration of the manganese chloride solution in the step (2) is 1 mol/L.

6. The method according to claim 1, wherein the composition of the Lept liquid medium in the step (2) comprises: 0.5g/L yeast extract, 0.5g/L Casa mini Acids, 1g/L glucose, 10mM HEPES, 0.48mM CaC1₂，0.83mM MgSO₄，3.7μM FeCl₃。

7. The method according to claim 1, wherein the amount of the graphene inoculated in step (3) is 0-0.05mg/ml, the temperature of the rotary shaking fermentation culture is 28-30 ℃, the speed of the rotary shaking fermentation culture is 130-180r/min, and the time of the fermentation culture is 2-3 days; the high speed centrifugation speed is 8000-10000r/min, and the centrifugation time is 5-15 min.

8. The method according to claim 1, wherein the temperature of the vacuum freeze-drying in the step (4) is-70 ℃ and the time is 18 to 24 hours.

9. The preparation method according to claim 1, wherein the high-temperature calcination in the step (5) is carried out by: placing the composite electrode material precursor prepared in the step (4) into a high-temperature calcining furnace, and heating the calcining furnace to 250 ℃ at the speed of 2 ℃/min under the inert gas atmosphere; then the temperature is increased to 320 ℃ at the speed of 1 ℃/min, and the temperature is kept for 1 h; then heating to 550 ℃ at the speed of 1 ℃/min, and preserving heat for 1 h; finally, the temperature of the calcining furnace is raised to 700-900 ℃ within 180min, and then the calcining furnace is cooled along with the furnace.

10. An application of a biological fermentation manganese dioxide/graphene composite electrode material in the field of preparation of super capacitors and batteries.

Technical Field

The invention relates to the technical field of electrodes, in particular to a preparation method and application of a biological fermentation manganese dioxide/graphene composite electrode material.

Background

With the development and utilization of energy resources, a series of problems such as climate warming, resource shortage, ecological environment deterioration and the like are brought, and therefore, a matched high-efficiency energy storage device must be developed to solve the problems. At present, the high-efficiency energy storage technology is widely concerned by various countries, and for various defects of chemical secondary power supplies such as storage batteries in the actual use process, various countries are actively and deeply developing a physical energy storage secondary power supply, namely a large-capacity capacitor (also called as a super capacitor), and research on the super capacitor is mainly focused on preparation of high-performance electrode materials, so that the capacity and energy of the capacitor are improved. At present, the electrochemical capacitor electrode materials are various, such as carbon materials, metal oxide materials, conductive polymer materials, composite electrode materials and the like.

The metal manganese dioxide has low price, abundant reserves, environmental protection and good electrochemical performance, is an important electrode material, has wide application and important research prospect in the fields of battery anode materials, ion exchangers, catalysts and the like, and has great attention on how to improve the comprehensive performance of the manganese dioxide electrode material.

Carbon materials such as activated carbon, graphene, carbon black, carbon fibers, carbon aerogel, carbon nanotubes, etc. as electrode materials for electrochemical capacitors, current research is mainly focused on the preparation of porous electrode materials with large specific surface area.

In recent years, the research focus is the application of the composite electrode material in secondary power sources such as storage batteries, super capacitors and the like. The method is particularly important for the development and research of cheap metal manganese dioxide/carbon composite electrode materials, effectively overcomes the defects of a single electrode material, and improves the comprehensive performance of a secondary power supply by utilizing the synergistic effect among all components.

The preparation methods of the electrode material mainly comprise an electrochemical precipitation method, a sol-gel method and the like, and reports of preparing the composite electrode material by utilizing biological fermentation are not available. It has been shown that certain pseudomonads carry specific manganese oxide gene clusters, the enzymes encoded by which catalyze the formation of manganese oxide multimers on the cell surface. The Pseudomonas can secrete polysaccharide, protein and other substances in the growth and reproduction process, and the substances are gathered on the cell surface and can convert Mn²⁺Accumulating on cell surface to obtain Mn²⁺The reaction mass concentration is increased and manganese oxides can be formed by a plurality of enzymes encoded by pseudomonas bacteria.

Along with social development, people pay more and more attention to green energy and ecological environment, and the research of a green and environment-friendly manganese dioxide/graphene composite material is particularly important. The bacteria separated from the ore soil are utilized for biological fermentation, so that the method has the characteristics of high safety, environmental friendliness, low cost and the like, has wide application prospect in the field of green synthesis of manganese dioxide/graphene composite electrode materials, and fills the blank of the preparation method of the electrode material in the biological field.

Disclosure of Invention

The invention provides a preparation method and application of a biological fermentation manganese dioxide/graphene composite electrode material. The preparation method is mild in preparation conditions, can be used for preparing super capacitors, batteries and the like, and fills the gap in the field of biotechnological preparation of composite electrode materials.

The invention is realized by the following technical scheme, and the preparation method of the biological fermentation manganese dioxide/graphene composite electrode material provided by the invention comprises the following steps:

(1) activating strains: separating a strain M1 from soil near manganese ore, inoculating the strain on an LB culture medium flat plate for activation for 10-15h through aseptic operation, then selecting an activated strain M1 for aseptic operation and inoculating the strain into 50ml of LB liquid culture medium, carrying out rotary oscillation culture in a full-temperature oscillation culture shaker for 12-18h to obtain a culture bacterial liquid, centrifuging the culture bacterial liquid, removing supernatant, adding aseptic water into obtained precipitate to obtain activated bacterial liquid for later use;

(2) primary inoculation culture: sequentially inoculating the activated bacterium liquid and the manganese chloride solution prepared in the step (1) into a leptin liquid culture medium in a sterile operation manner, and carrying out rotary oscillation fermentation culture in a full-temperature oscillation culture table to obtain a fermentation liquid;

(3) and (3) secondary inoculation culture: inoculating a graphene material into the fermentation liquor prepared in the step (2) in a sterile operation manner, carrying out rotary oscillation fermentation culture in a full-temperature oscillation culture shaking table, centrifuging the cultured fermentation liquor at a high speed, removing supernatant, and collecting precipitate for later use;

(4) and (3) freeze drying treatment: performing vacuum freeze drying on the precipitate collected in the step (3) to obtain a precursor of the biological fermentation manganese dioxide/graphene composite electrode material;

(5) high-temperature calcination treatment: and (4) calcining the composite electrode material precursor prepared in the step (4) at high temperature to obtain the biological fermentation manganese dioxide/graphene composite electrode material.

Further, the strain M1 in the step (1) is a Pseudomonas bacterium.

Further, the culture temperature of the step (1) is 28-30 ℃, and the rotary oscillation speed is 130-; and subpackaging the culture bacteria liquid into a plurality of 1.5ml centrifuge tubes, adding 1ml of the culture bacteria liquid into each centrifuge tube for centrifugation, wherein the centrifugation speed is 3000-4000r/min, the centrifugation time is 2-4min, discarding the supernatant after centrifugation, and adding 500ul of sterile water into the obtained precipitate to obtain the activated bacteria liquid.

Further, the inoculation amount of the activated bacterium liquid in the step (2) is 5ul/ml, the inoculation amount of the manganese chloride solution is 0.2-1.4ul/ml, and the concentration of the manganese chloride solution is 1 mol/L.

Further, the temperature of the rotary shaking fermentation culture in the step (2) is 28-30 ℃, the speed of the rotary shaking is 130-180r/min, and the time is 36-60 h.

Further, the composition of the leptin liquid culture medium in the step (2) comprises: 0.5g/L yeast extract, 0.5g/L Casa amino Acids (casamino Acids), 1g/L glucose, 10mM HEPES (4-hydroxyethylpiperazine ethanesulfonic acid), 0.48mM CaC1₂，0.83mM MgSO₄，3.7μM FeCl₃。

Further, the inoculation amount of the graphene in the step (3) is 0-0.05mg/ml, and the fermentation culture time is 2-3 days; the high speed centrifugation speed is 8000-10000r/min, and the centrifugation time is 5-15 min.

Further, the temperature of vacuum freeze drying in the step (4) is-70 ℃, and the time is 18-24 h.

Further, the high-temperature calcination in the step (5) comprises the following specific operations: placing the composite electrode material precursor prepared in the step (4) into a high-temperature calcining furnace, and heating the calcining furnace to 250 ℃ at the speed of 2 ℃/min under the inert gas atmosphere; then the temperature is increased to 320 ℃ at the speed of 1 ℃/min, and the temperature is kept for 1 h; then heating to 550 ℃ at the speed of 1 ℃/min, and preserving heat for 1 h; finally, the temperature of the calcining furnace is raised to 700-900 ℃ within 180min, and then the calcining furnace is cooled along with the furnace.

The biological fermentation manganese dioxide/graphene composite electrode material prepared by the method is applied to the field of preparation of super capacitors and batteries.

Compared with the prior art, the invention has the following advantages:

(1) according to the invention, a biological fermentation method is adopted, bacteria separated from ore soil, manganese chloride and graphene are effectively utilized to carry out fermentation culture, manganese dioxide particles are stably attached to the surface of the graphene through the adhesion effect of the bacteria, the preparation condition is mild, and the distribution is uniform.

(2) The biological fermentation manganese dioxide/graphene composite electrode material prepared by the invention has clear morphological characteristics, successfully and effectively utilizes manganese element in manganese chloride by adopting a biological fermentation method, biologically synthesizes manganese dioxide, and has good electrochemical performance.

(3) The biological fermentation manganese dioxide/graphene composite electrode material prepared by the invention has good electrochemical performance, can be used for preparing super capacitors, batteries and the like, has the characteristics of high safety, environmental friendliness, simple process, convenience in operation and the like, and fills the gap in the field of biological preparation of composite electrode materials.

Drawings

Fig. 1 is an SEM image of the biomanese dioxide/graphene composite electrode material prepared in example 3;

fig. 2 is a graph of electrochemical performance of the biomanid/graphene composite electrode material prepared in example 3.

Detailed Description

For a better understanding of the contents of the invention, reference will now be made to the following examples and accompanying drawings which illustrate the invention. The present embodiment is implemented based on the technology of the present invention, and a detailed implementation manner and operation steps are given, but the scope of the present invention is not limited to the following embodiments.

Separating the strain M1 from the soil near manganese ore (the separation method is the prior art and is not described again), freezing and storing in a refrigerator, taking out the strain M1 when in use, inoculating the strain M1 on an LB culture medium plate in a sterile operation, activating for about 12h at 28-30 ℃, and then carrying out subsequent operations. The strain M1 is specifically a pseudomonas bacterium.

Example 1

(1) Activating strains: an activated soil bacterium M1 is selected from an LB medium flat plate, and is inoculated into 50ml of LB liquid medium in an aseptic operation, the activated soil bacterium M1 is cultured in a full-temperature shaking culture table at 28 ℃ under the shaking speed of 130r/min for 12h in a rotary shaking culture mode, the cultured bacterium liquid (hereinafter referred to as 'cultured bacterium liquid') is subpackaged into a plurality of centrifuge tubes of 1.5ml, 1ml of cultured bacterium liquid is added into each centrifuge tube, the centrifuge tubes are centrifuged for 2min at the speed of 3000r/min, the supernatant is discarded, and the sediment in each centrifuge tube is washed by 500ul of sterile water to obtain the activated bacterium liquid for later use.

(2) Primary inoculation culture: taking 500ul of the activated bacterium solution prepared in the step (1) and 20ul of 1mol/L manganese chloride solution, sequentially inoculating the activated bacterium solution and the 1mol/L manganese chloride solution into 100ml of a Lept liquid culture medium through aseptic operation, putting the Lept liquid culture medium into a full-temperature shaking culture table, carrying out rotary shaking culture for 36h at 28 ℃ and at a shaking speed of 130r/min to obtain fermentation liquor, and preparing 20 bottles of fermentation liquor for later use by adopting the method;

the composition of the Lept liquid culture medium comprises: 0.5g/L yeast extract, 0.5g/L Casa amino Acids (casamino Acids), 1g/L glucose, 10mM HEPES (4-hydroxyethylpiperazine ethanesulfonic acid), 0.48mM CaC1₂，0.83mM MgSO₄，3.7μM FeCl₃；

(3) Secondary inoculation: inoculating the prepared graphene material into 20 bottles of fermentation liquor prepared in the step (2) in an aseptic operation manner, inoculating 0.5mg of graphene into each bottle of fermentation liquor, putting the fermentation liquor back into a full-temperature shaking culture table at 28 ℃ and carrying out rotary shaking culture at the shaking speed of 130r/min for 2 days, centrifuging the cultured 20 bottles of fermentation liquor at a high speed of 8000r/min for 5min, removing supernatant, collecting all precipitates in a plastic beaker container, and storing the precipitates in a refrigerator at the temperature of-20 ℃ for later use;

(4) and (3) freeze drying treatment: putting the precipitate prepared in the step (3) into a vacuum freeze drying oven, freeze drying at-70 ℃ for 18h, and taking out to obtain a precursor of the biological manganese dioxide/graphene composite electrode material;

(5) and (3) calcining: placing the composite electrode material precursor prepared in the step (4) into a high-temperature calcining furnace, and heating the calcining furnace to 250 ℃ at the speed of 2 ℃/min under the atmosphere of inert gas nitrogen; then the temperature is raised to 320 ℃ at the speed of 1 ℃/min, and the temperature is kept for 1 h; then heating to 550 ℃ at the speed of 1 ℃/min, and keeping the temperature for 1 h; and finally, heating to 700 ℃ within 180min, and cooling to obtain the biological fermentation manganese dioxide/graphene composite electrode material.

Example 2

(1) Activating strains: an activated soil bacterium M1 is selected from an LB medium flat plate, and is inoculated into 50ml of LB liquid medium in an aseptic operation, the activated soil bacterium M1 is cultured in a full-temperature shaking culture table for 14h in a rotary shaking culture at 28 ℃ and the shaking speed of 150r/min, the cultured bacterium liquid (hereinafter referred to as 'cultured bacterium liquid') is subpackaged into a plurality of centrifuge tubes of 1.5ml, 1ml of cultured bacterium liquid is added into each centrifuge tube, the centrifuge tubes are centrifuged for 2min at the speed of 3500r/min, the supernatant is discarded, and the precipitate in each centrifuge tube is washed by 500ul of sterile water to obtain the activated bacterium liquid for later use.

(2) Primary inoculation culture: taking 500ul of the activated bacterium solution prepared in the step (1) and 40ul of 1mol/L manganese chloride solution, sequentially inoculating the activated bacterium solution and the 1mol/L manganese chloride solution into 100ml of a Lept liquid culture medium through aseptic operation, putting the Lept liquid culture medium into a full-temperature shaking culture table, carrying out rotary shaking culture for 48 hours at the temperature of 30 ℃ and the shaking speed of 150r/min to obtain fermentation liquor, and preparing 20 bottles of fermentation liquor for later use by adopting the method;

the composition of the Lept liquid culture medium comprises: 0.5g/L yeast extract, 0.5g/L Casa amino Acids (casamino Acids), 1g/L glucose, 10mM HEPES (4-hydroxyethylpiperazine ethanesulfonic acid), 0.48mM CaC1₂，0.83mM MgSO₄，3.7μM FeCl₃；

(3) Secondary inoculation: inoculating the prepared graphene material into 20 bottles of fermentation liquor prepared in the step (2) in an aseptic operation manner, inoculating 1mg of graphene into each bottle of fermentation liquor, putting the fermentation liquor back into a full-temperature shaking culture table at 30 ℃ and carrying out rotary shaking culture at the shaking speed of 150r/min for 2.5 days, centrifuging the cultured 20 bottles of fermentation liquor at a high speed of 8000r/min for 10min, removing supernatant, collecting all precipitates in a plastic beaker container, and storing the precipitates in a refrigerator at the temperature of-20 ℃ for later use;

(4) and (3) freeze drying treatment: putting the precipitate prepared in the step (3) into a vacuum freeze drying oven, freeze drying at-70 ℃ for 18h, and taking out to obtain a precursor of the biological manganese dioxide/graphene composite electrode material;

(5) and (3) calcining: placing the composite electrode material precursor prepared in the step (4) into a high-temperature calcining furnace, and heating the calcining furnace to 250 ℃ at the speed of 2 ℃/min under the atmosphere of inert gas nitrogen; then the temperature is raised to 320 ℃ at the speed of 1 ℃/min, and the temperature is kept for 1 h; then heating to 550 ℃ at the speed of 1 ℃/min, and keeping the temperature for 1 h; and finally, heating to 800 ℃ within 180min, and cooling to obtain the biological fermentation manganese dioxide/graphene composite electrode material.

Example 3

(1) Activating strains: an activated soil bacterium M1 is selected from an LB medium flat plate, and is inoculated into 50ml of LB liquid medium in an aseptic operation, the activated soil bacterium M1 is cultured in a full-temperature shaking culture table for 16h in a rotary shaking culture at 28 ℃ and the shaking speed of 150r/min, the cultured bacterium liquid (hereinafter referred to as 'cultured bacterium liquid') is subpackaged into a plurality of centrifuge tubes of 1.5ml, 1ml of cultured bacterium liquid is added into each centrifuge tube, the centrifuge tubes are centrifuged for 2min at the speed of 3500r/min, the supernatant is discarded, and the precipitate in each centrifuge tube is washed by 500ul of sterile water to obtain the activated bacterium liquid for later use.

(2) Primary inoculation culture: taking 500ul of the activated bacterium solution prepared in the step (1) and 100ul of 1mol/L manganese chloride solution, sequentially inoculating the activated bacterium solution and the 1mol/L manganese chloride solution into 100ml of a Lept liquid culture medium through aseptic operation, putting the Lept liquid culture medium into a full-temperature shaking culture table, carrying out rotary shaking culture for 48 hours at 28 ℃ and under the shaking speed of 150r/min to obtain fermentation liquor, and preparing 20 bottles of fermentation liquor for later use by adopting the method;

the composition of the Lept liquid culture medium comprises: 0.5g/L yeast extract, 0.5g/L Casa amino Acids (casamino Acids), 1g/L glucose, 10mM HEPES (4-hydroxyethylpiperazine ethanesulfonic acid), 0.48mM CaC1₂，0.83mM MgSO₄，3.7μM FeCl₃；

(3) Secondary inoculation: inoculating the prepared graphene material into 20 bottles of fermentation liquor prepared in the step (2) in an aseptic operation manner, inoculating 3mg of graphene into each bottle of fermentation liquor, putting the fermentation liquor back into a full-temperature shaking culture table at 28 ℃, carrying out rotary shaking culture at the shaking speed of 150r/min for 2.5 days, centrifuging the cultured 20 bottles of fermentation liquor at a high speed of 8000r/min for 10min, removing supernatant, collecting all precipitates in a plastic beaker container, and storing the precipitates in a refrigerator at the temperature of-20 ℃ for later use;

(4) and (3) freeze drying treatment: putting the precipitate prepared in the step (3) into a vacuum freeze drying oven, freeze drying at-70 ℃ for 20h, and taking out to obtain a precursor of the biological manganese dioxide/graphene composite electrode material;

(5) and (3) calcining: placing the composite electrode material precursor prepared in the step (4) into a high-temperature calcining furnace, and heating the calcining furnace to 250 ℃ at the speed of 2 ℃/min under the atmosphere of inert gas nitrogen; then the temperature is raised to 320 ℃ at the speed of 1 ℃/min, and the temperature is kept for 1 h; then heating to 550 ℃ at the speed of 1 ℃/min, and keeping the temperature for 1 h; and finally, heating to 800 ℃ within 180min, and cooling to obtain the biological fermentation manganese dioxide/graphene composite electrode material.

Fig. 1 is a scanning electron microscope image of the bio-fermented manganese dioxide/graphene composite electrode material prepared in this example, which shows that manganese dioxide particles are uniformly attached to the graphene surface of the prepared composite electrode material, and the small arrows in fig. 1 indicate the manganese dioxide particles.

Fig. 2 is a charge-discharge curve of the biological manganese dioxide/graphene composite electrode material prepared in this example at a current density of 1A/g, which shows that the prepared composite electrode material has good electrochemical properties.

Example 4

(1) Activating strains: an activated soil bacterium M1 is selected from an LB medium flat plate, and is inoculated into 50ml of LB liquid medium in an aseptic operation, the activated soil bacterium M1 is cultured in a full-temperature shaking culture table for 18h in a rotary shaking culture at 28 ℃ and the shaking speed of 150r/min, the cultured bacterium liquid (hereinafter referred to as 'cultured bacterium liquid') is subpackaged into a plurality of centrifuge tubes of 1.5ml, 1ml of cultured bacterium liquid is added into each centrifuge tube, the centrifuge tubes are centrifuged for 4min at the speed of 4000r/min, the supernatant is discarded, and the precipitate in each centrifuge tube is washed by 500ul of sterile water to obtain the activated bacterium liquid for later use.

(2) Primary inoculation culture: taking 500ul of the activated bacterium solution prepared in the step (1) and 120ul of 1mol/L manganese chloride solution, sequentially inoculating the activated bacterium solution and the 1mol/L manganese chloride solution into 100ml of a Lept liquid culture medium through aseptic operation, putting the Lept liquid culture medium into a full-temperature shaking culture table, carrying out rotary shaking culture for 48 hours at 28 ℃ and under the shaking speed of 150r/min to obtain fermentation liquor, and preparing 20 bottles of fermentation liquor for later use by adopting the method;

the composition of the Lept liquid culture medium comprises: 0.5g/L yeast extract, 0.5g/L Casa amino Acids (casamino Acids), 1g/L glucose, 10mM HEPES (4-hydroxyethylpiperazine ethanesulfonic acid), 0.48mM CaC1₂，0.83mM MgSO₄，3.7μM FeCl₃；

(3) Secondary inoculation: inoculating the prepared graphene material into 20 bottles of fermentation liquor prepared in the step (2) in a sterile operation manner, inoculating 5mg of graphene into each bottle of fermentation liquor, putting the fermentation liquor back into a full-temperature shaking culture table at 28 ℃, carrying out rotary shaking culture at the shaking speed of 150r/min for 3 days, centrifuging the cultured 20 bottles of fermentation liquor at a high speed of 10000r/min for 10min, removing supernatant, collecting all precipitates in a plastic beaker container, and storing the precipitates in a refrigerator at the temperature of-20 ℃ for later use;

(4) and (3) freeze drying treatment: putting the precipitate prepared in the step (3) into a vacuum freeze drying oven, freeze drying at-70 ℃ for 24h, and taking out to obtain a precursor of the biological manganese dioxide/graphene composite electrode material;

(5) and (3) calcining: placing the composite electrode material precursor prepared in the step (4) into a high-temperature calcining furnace, and heating the calcining furnace to 250 ℃ at the speed of 2 ℃/min under the atmosphere of inert gas nitrogen; then the temperature is raised to 320 ℃ at the speed of 1 ℃/min, and the temperature is kept for 1 h; then heating to 550 ℃ at the speed of 1 ℃/min, and keeping the temperature for 1 h; and finally, heating to 800 ℃ within 180min, and cooling to obtain the biological fermentation manganese dioxide/graphene composite electrode material.

The above description is only an embodiment of the present invention, and is not intended to limit the present invention in any way, and the present invention may also have other embodiments according to the above structures and functions, and is not listed again. Therefore, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention by those skilled in the art can be made within the technical scope of the present invention.