A porous carbon-based metal oxide composite and a method for preparing the same
By physically adsorbing metal precursors into porous carbon materials and forming a gradient distribution using an alternating filling method, the dissolution problem of MnO2, the cathode material for zinc-ion batteries, was solved, improving conductivity and stability and achieving high-efficiency electrochemical cycling performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING INST OF TECH
- Filing Date
- 2024-06-18
- Publication Date
- 2026-05-29
Smart Images
Figure CN118645602B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrochemical energy storage secondary batteries, and specifically to a method for preparing a porous carbon-based metal oxide composite material. Background Technology
[0002] In recent years, energy issues have received increasing attention due to the continuous growth in fossil fuel consumption and the aggravation of environmental pollution. While the development of renewable energy sources such as solar, wind, and hydropower can partially address these problems, they are still constrained by factors such as timeliness, instability, regionality, and seasonality. Lithium-ion batteries, as a highly efficient energy storage system, have captured a significant share of the portable electronics market due to their high energy density and long cycle life, and are gradually expanding into new areas such as new energy vehicles and grid-scale energy storage. At the current rate of lithium consumption, limited lithium resources are insufficient to meet future strong market demand, and rising costs have attracted global attention. Therefore, the development of low-cost next-generation energy storage systems is urgently needed.
[0003] Porous carbon materials possess advantages such as high specific surface area, excellent electrical conductivity, physical and chemical stability, gas-liquid permeability, tunable pore structure, and low cost and availability, showing great promise for applications in energy storage and conversion, catalysis, and adsorption separation. Porous carbon can be classified into three types according to pore size: microporous (pore size less than 2 nm) carbon, mesoporous (pore size between 2 and 50 nm) carbon, and macroporous (pore size greater than 50 nm) carbon. The preparation method and precursor selection of porous carbon materials directly determine their performance and application range.
[0004] Metal oxides, especially MnO2, have attracted much attention among various cathode materials for zinc-ion batteries due to their high theoretical capacity and low cost. However, when MnO2 is used as a cathode material in zinc-ion batteries, it dissolves during discharge, forming MnO2. 2+ During charging, the metal oxides are oxidized again to MnO2. This dissolution-redeposition mechanism prevents the cathode material structure from maintaining its original state, leading to problems such as capacity decay and poor rate performance. Reducing the dissolution, deposition, and re-oxidation of metal oxides has become a pressing technical problem to be solved in this field. Summary of the Invention
[0005] To address the issues of capacity decay and poor rate performance caused by the dissolution of metal oxides during discharge, this invention proposes a preparation method for porous carbon-based metal oxide composite materials. The method primarily uses porous carbon as a substrate, storing metal precursors within the porous carbon channels through physical adsorption. Then, a composite material with a porous carbon channel structure filled with active materials is prepared through high-temperature treatment. Furthermore, by controlling the filling order of the carbon material and the metal precursor, a gradient distribution of metal oxides can be formed within the porous carbon, effectively reducing the dissolution of metal oxides. Moreover, by controlling the amount and number of fillings of the metal precursor, the content of active materials can be controlled.
[0006] In a first aspect, the present invention provides a method for preparing porous carbon-based metal oxide composite materials, comprising the following steps:
[0007] (1) Preparation of porous carbon materials: After grinding, deashing, activation, reduction and pulverization, carbon raw materials are obtained to obtain porous carbon materials with adjustable pore size.
[0008] The carbon-containing raw materials are selected from one or more of raw coal, coconut shell, petroleum coke, resin, and starch.
[0009] The grinding conditions are: particle size 1-100μm.
[0010] The activation refers to activation under conditions of alkali activation and / or steam activation.
[0011] In the alkali activation process, the alkali is selected from sodium hydroxide and potassium hydroxide.
[0012] The conditions for alkali activation are: alkaline environment, temperature 800-1000℃, activation time 6-10h.
[0013] The concentration of the alkali solution is 10-20 wt%, and the amount of alkali solution added is 1-2 times the mass of the carbon raw material.
[0014] The steam activation conditions are: steam activation at a temperature of 800-1000℃ for 30-60 minutes.
[0015] The reduction refers to H2 reduction, under conditions of 400-1000℃:
[0016] The term "pulverization" refers to pulverizing to a size of 0.1-20 μm.
[0017] The specific surface area of the porous carbon material ranges from 1000 to 3000 m². 2 / g.
[0018] The average pore size of the porous carbon material is 1 nm-5 nm; the pore size of BJH is 2-5 nm.
[0019] This invention optimizes the pore structure of porous carbon materials and adjusts the average pore size of porous carbon by controlling the activation and reduction steps and related parameters, so as to match the size of the subsequent metal oxide active material: if the metal oxide material to be filled into the porous carbon has poor conductivity, the average pore size of the porous carbon can be reduced; if the metal oxide material to be filled into the porous carbon has good conductivity, a porous carbon material with a large pore size can be prepared to match it.
[0020] (2) Preparation of porous carbon-based metal oxide composite materials:
[0021] 2.1 The porous carbon material obtained in step (1) is mixed with a metal salt solution, impregnated, centrifuged, dried, and calcined to obtain the first porous carbon-based metal oxide;
[0022] The metal is selected from one or more of manganese, iron, and copper.
[0023] The metal salt solution is selected from one or more of the metal nitrates, sulfates, and chlorides.
[0024] The concentration of the metal salt solution can be below the saturation dissolution level of the metal salt, and does not need to be particularly limited, such as 10-100 g / L or 0.5-2 mol / L.
[0025] The impregnation process employs ultrasonic or agitated impregnation to ensure thorough impregnation of the metal salt solution; the ultrasonic or agitated impregnation time is 30-90 minutes.
[0026] The centrifugation is performed using a centrifuge.
[0027] The drying temperature is 80-120℃, and the time is 30-100 minutes.
[0028] The roasting temperature is 600-900℃, and the time is 2-4 hours.
[0029] 2.2 Prepare an aqueous solution of graphene oxide, add a reducing agent, then add the first porous carbon-based metal oxide obtained in step 2.1, heat, centrifuge, and dry;
[0030] The concentration of the graphene oxide aqueous solution is 10-100 mg / ml.
[0031] The reducing agent is selected from one or more of hydrazine hydrate and sodium borohydride, and the amount of the reducing agent added is 1-10 wt% of graphene oxide.
[0032] After adding the reducing agent, ultrasonically disperse for 40-100 minutes.
[0033] The amount of graphene oxide used is 2-10 wt% of the porous carbon material in step (1).
[0034] The heating temperature is 80-120℃, and the time is 2-4 hours.
[0035] The drying temperature is 60-80℃, and the time is 30-60 minutes.
[0036] (3) Repeat steps 2.1 and 2.2 2-6 times in sequence until the content of metal oxide no longer changes and the porous carbon is filled with metal oxide and graphene carbon material to obtain the porous carbon-based metal oxide composite material.
[0037] Metal oxides can fill the pore structure of porous carbon, inhibiting their dissolution. The pore walls of porous carbon can form a conductive network, improving the conductivity of the active material. Compared to the commonly used method of impregnating porous carbon with metal salt solutions, this invention employs an alternating filling method. By controlling the filling order of carbon materials and metal precursors, an alternating filling of metal oxide-carbon material-metal oxide-carbon material... is formed within the porous carbon material. This results in a gradient distribution of metal oxides within the porous carbon material. Utilizing the loading effect of the porous carbon material and the high conductivity of graphene and other carbon materials, the structural damage and capacity decay caused by repeated volume changes during charge-discharge cycles of metal oxides are reduced, thus improving the conductivity of the metal oxides and reducing internal resistance. Furthermore, the alternating filling of this invention forms a "buffer layer"-like structure in the porous carbon material, providing more buffer space for metal oxide expansion and improving the structural stability of the battery material, thereby effectively improving electrochemical cycle stability.
[0038] Secondly, the present invention provides a porous carbon-based metal oxide composite material prepared by the preparation method of the first aspect.
[0039] The content of the metal oxide is 10-60% (based on the overall composite material).
[0040] The metal oxide is one or more of manganese oxide, iron oxide, and copper oxide.
[0041] Thirdly, the porous carbon-based metal oxide composite material provided by this invention has applications in the field of electrochemistry. The composite material is used as a cathode material in secondary batteries.
[0042] The beneficial effects of this invention are:
[0043] 1. This invention uses porous carbon as a substrate and stores metal oxide precursors within the porous carbon channels through physical adsorption. A composite material with a porous carbon channel structure filled with metal oxides is then prepared through high-temperature treatment. Simultaneously, the content of active substances is controlled by adjusting the amount and number of precursor filling cycles. The porous carbon structure effectively controls the size of the metal oxides, stably filling them within the porous carbon channels and inhibiting their dissolution. Furthermore, the graphene between the pore walls of the porous carbon and the metal oxide layers forms a conductive network, improving the conductivity of the metal oxides.
[0044] 2. This invention employs an alternating filling method. By controlling the filling sequence of carbon materials and metal precursors, an alternating filling of metal oxide-carbon material-metal oxide-carbon material... is formed inside the porous carbon material. The metal oxides are distributed in a gradient within the porous carbon material. Utilizing the loading effect of the porous carbon material and the occupancy effect and high conductivity of the carbon material, the exposure and dissolution of metal oxides are effectively reduced. Furthermore, the structural damage and capacity decay caused by the repeated volume changes during the charge-discharge cycle of metal oxides are reduced, thereby improving the conductivity of the metal oxides and the stability of the cathode material.
[0045] 3. The porous carbon-based metal oxide composite material prepared by this invention has a uniform and abundant pore structure, and the metal oxide can be uniformly dispersed deep inside the pores of the porous carbon material, resulting in high loading efficiency. The cathode material using the porous carbon-based metal oxide composite material of this invention still maintains a stability of up to 99% after 200 cycles in secondary battery tests. Moreover, the preparation method is simple and ingenious, making it very suitable for industrial promotion and application. Attached Figure Description
[0046] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0047] Figure 1 This is a SEM image of porous carbon from Example 1 of the present invention.
[0048] Figure 2 This is a SEM image of the porous carbon-based manganese oxide from Example 1 of the present invention. Detailed Implementation
[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.
[0050] Example 1
[0051] A method for preparing a porous carbon-based manganese oxide composite material includes the following steps:
[0052] (1) Preparation of porous carbon materials: raw coal is ground to 10 μm and deashed, activated with steam at 950 °C for 40 min, reduced at 500 °C for 2 h in H2 atmosphere, and then pulverized to 2500 mesh to obtain porous carbon materials with adjustable pore size.
[0053] The porous carbon material has the following pore size range: average pore size 1.7 nm, specific surface area 2042.9 m². 2 / g.
[0054] SEM images of porous carbon materials, as shown Figure 1 As shown, the porous carbon material has a relatively uniform pore size and a clearly visible pore structure.
[0055] (2) Preparation of porous carbon-based metal oxide composite materials:
[0056] 2.1 Mix 10g of the porous carbon material obtained in step (1) with 100mL of manganese nitrate solution with a concentration of 80g / l, sonicate for 1 hour, centrifuge, dry at 80℃ for 60min, and calcine at 300℃ for 3 hours to obtain the first porous carbon-based manganese oxide.
[0057] 2.2 Take 0.2g of graphene oxide, prepare an aqueous solution of graphene oxide with a concentration of 20mg / mL, add hydrazine hydrate as a reducing agent, sonicate for 1h, add the first porous carbon-based metal oxide obtained in step 2.1, heat at 120℃ for 3h, centrifuge after the reaction, collect the solid, and dry at 80℃ for 30min.
[0058] (3) Repeat steps 2.1 and 2.2 four times in sequence until the manganese oxide content no longer changes, the porous carbon is filled with manganese oxide and graphene carbon materials, and finally the porous carbon-based manganese oxide composite material is obtained with a manganese oxide loading of 58%.
[0059] The SEM image of the porous carbon-based manganese oxide composite material obtained in Example 1 is shown below. Figure 2 As shown, manganese oxide is uniformly filled into the porous structure of the carbon.
[0060] Example 2
[0061] A method for preparing a porous carbon-based manganese oxide composite material, wherein all other steps are the same as in Example 1, except that the concentration of manganese salt used in step 2.1 is different (60 g / L), and the manganese oxide loading in the final porous carbon-based manganese oxide composite material is 45%.
[0062] Example 3
[0063] A method for preparing a porous carbon-based iron oxide composite material: 10g of the porous carbon material obtained in step (1) is mixed with 100ml of ferric nitrate solution with a concentration of 5g / l, ultrasonically impregnated for 1 hour, centrifuged, dried at 80℃ for 60 minutes, and calcined at 400℃ for 3 hours to obtain the first porous carbon-based iron oxide.
[0064] The other steps are the same as in Example 1, and a porous carbon-based iron oxide composite material with an iron oxide loading of 22 wt% is finally obtained.
[0065] Example 4
[0066] A method for preparing a porous carbon-based manganese oxide composite material, wherein all other steps are the same as in Example 1, except that the concentration of manganese salt used in step 2.1 is different (45 g / L), and the manganese oxide loading in the final porous carbon-based manganese oxide composite material is 31%.
[0067] Example 5
[0068] A method for preparing a porous carbon-based manganese oxide composite material includes the following steps:
[0069] (1) Preparation of porous carbon materials: raw coal is ground to 10 μm and deashed, activated with steam at 950 °C for 40 min, reduced at 500 °C for 2 h in H2 atmosphere, and then pulverized to 2500 mesh to obtain porous carbon materials with adjustable pore size.
[0070] (2) Preparation of porous carbon-based metal oxide composite materials:
[0071] 2.1 Mix 10g of the porous carbon material obtained in step (1) with 100ml of manganese nitrate solution with a concentration of 60g / l, sonicate for 2 hours, centrifuge, dry at 80℃ for 60min, and calcine at 400℃ for 2 hours to obtain the first porous carbon-based manganese oxide.
[0072] 2.2 Take 0.2g of graphene oxide, prepare an aqueous solution of graphene oxide with a concentration of 20mg / mL, add hydrazine hydrate as a reducing agent, sonicate for 1h, add the first porous carbon-based metal oxide obtained in step 2.1, heat at 100℃ for 4h, centrifuge after the reaction, collect the solid, and dry at 80℃ for 30min.
[0073] (3) Repeat steps 2.1 and 2.2 three times in sequence until the manganese oxide content no longer changes, the porous carbon is filled with manganese oxide and graphene carbon materials, and finally the porous carbon-based manganese oxide composite material is obtained, wherein the manganese oxide loading is 40%.
[0074] Comparative Example 1
[0075] Step (1) is the same as in Example 1;
[0076] Step (2) Select an excess of manganese nitrate solution that is close to saturation (80 g / L), add porous carbon, sonicate for 2 h to allow the porous carbon to adsorb enough manganese nitrate solution, and then use a centrifuge to separate the excess manganese nitrate.
[0077] After drying in an oven at 80°C for 60 minutes, transfer the product to a crucible.
[0078] The crucible was placed in a muffle furnace and heated at 300°C for 3 hours to fully decompose the manganese nitrate in the porous carbon, thus obtaining the first porous carbon-based manganese oxide material.
[0079] Step (3) The porous carbon-based manganese oxide material obtained in step (2) is further adsorbed with an excess of manganese nitrate solution that is close to saturation. After ultrasonic dispersion, it is centrifuged, dried at 80°C for 60 min, and then placed in a muffle furnace for high-temperature calcination at 300°C for 3 h to obtain the second porous carbon-based manganese oxide composite material.
[0080] After repeating step (3) four times in step (4), a porous carbon-based manganese oxide composite material with a loading of 58% is finally prepared.
[0081] Comparative Example 2
[0082] Step (1) is the same as in Example 1;
[0083] Step (2) Select an excess of manganese nitrate solution that is close to saturation (100 g / L), add porous carbon, sonicate for 2 h to allow the porous carbon to adsorb enough manganese nitrate solution, and then use a centrifuge to separate the excess manganese nitrate.
[0084] After drying in an oven at 80°C for 60 minutes, transfer the product to a crucible.
[0085] The crucible was placed in a muffle furnace and heated at 300°C for 3 hours to allow the manganese nitrate in the porous carbon to fully decompose into porous carbon-based manganese oxide material, wherein the manganese oxide loading was 31%.
[0086] Test Example 1: Electrical Conductivity of Composite Materials
[0087] The resistivity of the composite materials obtained from the examples and comparative examples was measured using the ohmmeter function of a multimeter, as shown in Table 1.
[0088] Table 1
[0089] sample Powder resistivity Example 1 19.2Ω·m Example 4 21.8Ω·m Comparative Example 1 20.1Ω·m Comparative Example 2 22.7Ω·m
[0090] As can be seen from Examples 1 and 4 in Table 1, the higher the metal content, the lower the resistivity of the sample, indicating that the composite material has higher conductivity.
[0091] As can be seen from Examples 1 and 1, and Examples 4 and 2, under the same metal content, the composite material obtained by the alternating filling method of this application has a lower powder resistivity and better electrical conductivity. This is because, on the one hand, the addition of graphene oxide improves the conductivity of the composite material, and on the other hand, the metal oxides are distributed in a gradient within the porous carbon material, which is more conducive to improving the conductivity of the composite material.
[0092] Test Example 2: Electrochemical Performance Testing of Cathode Materials
[0093] The composite materials prepared in the examples and comparative examples were used as the positive electrode materials for secondary batteries. Batteries were assembled and charge-discharge tests were conducted. Specific parameters were as follows:
[0094] Electrolyte: 2M ZnSO4, positive electrode: porous carbon-supported metal oxide of the examples or comparative examples, negative electrode: zinc foil, separator: glass fiber membrane, current collector: stainless steel foil; the rate performance of the battery was tested under a current density of 0.1A / g, and the capacity retention results after 200 cycles under 0.1C conditions are shown in Table 2.
[0095] Table 2
[0096]
[0097]
[0098] As can be seen from Table 2, the composite materials prepared in Examples 1-5 have good discharge specific capacity, and the capacity retention rate can still reach more than 97% after 200 cycles under 0.1C conditions.
[0099] Data from Examples 1 and 1, and Examples 4 and 2 show that, under the same manganese oxide loading, the discharge specific capacity and cycle stability of the materials differ, especially the cycle stability data, which shows a significant difference. This indicates that the alternating filling method of the present invention can improve the stability of metal oxides and solve the technical problem of stability and rate capability differences caused by their dissolution. In particular, the composite materials of Examples 1, 2, 4, and 5 still maintain a cycle stability of up to 99% after 200 cycles. This is because the present application utilizes the alternating filling method to form a structure similar to a "buffer layer" in the porous carbon material, providing more buffer space for the expansion of metal oxides, improving the structural stability of the battery material, and thus effectively improving the electrochemical cycle stability.
Claims
1. A method for preparing a porous carbon-based metal oxide composite material, characterized in that, Includes the following steps: (1) Preparation of porous carbon materials; (2) Preparation of porous carbon-based metal oxide composite materials: 2.1 The porous carbon material obtained in step (1) is mixed and impregnated with a metal salt solution, and then centrifuged, dried and calcined to obtain the first porous carbon-based metal oxide; 2.2 Prepare an aqueous solution of graphene oxide, add a reducing agent, then add the first porous carbon-based metal oxide obtained in step 2.1, heat, centrifuge, and dry; (3) Repeat steps 2.1 and 2.2 2-6 times in sequence until the metal oxide content no longer changes and the porous carbon is filled with metal oxide and graphene carbon materials to obtain the porous carbon-based metal oxide composite material. Step (1) involves grinding, deashing, activating, reducing, and pulverizing the carbon-containing raw material to obtain a porous carbon material with adjustable pore size; the specific surface area of the porous carbon material is in the range of 1000-3000 m². 2 / g; The average pore size of the porous carbon material is 1nm-5nm; The metal is selected from one or more of manganese, iron, and copper, and the metal oxide content in the porous carbon-based metal oxide composite material is 10-60%. The amount of graphene oxide used in step 2.2 is 2-10 wt% of the porous carbon material in step (1).
2. The preparation method according to claim 1, characterized in that, The carbon-containing raw material in step (1) is selected from one or more of raw coal, coconut shell, petroleum coke, resin, and starch; the activation refers to alkali activation and / or steam activation; the reduction refers to H2 reduction at a temperature of 400-1000℃.
3. The preparation method according to claim 2, characterized in that, The alkaline activation conditions are: alkaline solution environment, temperature 800-1000℃, activation for 6-10 hours; the steam activation conditions are: steam activation at temperature 800-1000℃ for 30-60 minutes.
4. The preparation method according to claim 1, characterized in that, In step 2.1, the metal salt solution is selected from one or more of metal nitrates, sulfates, and chlorides; the drying temperature is 80-120℃ and the time is 30-100 minutes; the calcination temperature is 600-900℃ and the time is 2-4 hours.
5. The preparation method according to claim 1, characterized in that, In step 2.2, the concentration of the graphene oxide aqueous solution is 10-100 mg / ml; The reducing agent is selected from one or more of hydrazine hydrate and sodium borohydride; After adding the reducing agent, ultrasonically disperse for 40-100 minutes.
6. The preparation method according to claim 1, characterized in that, The amount of graphene oxide used in step 2.2 is 2-10 wt% of the porous carbon material in step (1); The heating temperature is 80-120℃, and the time is 2-4 hours; The drying temperature is 60-80℃, and the time is 30-60 minutes.
7. The porous carbon-based metal oxide composite material obtained by the preparation method according to any one of claims 1-6.
8. The application of the porous carbon-based metal oxide composite material according to claim 7 in the field of electrochemistry.