In-situ chemical synthesis bi-material composite positive electrode material as well as preparation method and application thereof
Through the conjugated symbiotic structure of multi-wall carbon nanotubes and lithium cobalt oxide synthesized in situ chemically, the electrochemical performance degradation caused by density differences and uneven mixing during physical mixing of battery capacitors is solved, and a high specific capacity and stable electrode structure is achieved.
Patent Information
- Application Number
- CN202510658780.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-21
- Publication Date
- 2025-07-25
AI Technical Summary
The problem of electrochemical performance degradation in the positive electrode material of traditional battery-type capacitors during physical mixing is caused by material density differences and uneven mixing.
Through in-situ chemical synthesis method, multi-walled carbon nanotubes were compounded with lithium cobalt oxide, carbon nanotubes were guided to grow by using CoNi-MOF catalyst, and a conjugated symbiotic structure between multi-walled carbon nanotubes and lithium cobalt oxide was formed by sol-gel method, solving the problems of uneven material mixing and poor interface contact.
The specific capacity and electrochemical performance of the electrode material are improved, the volume expansion and secondary agglomeration of lithium cobalt oxide particles are inhibited, and the electron transport capability and the stability of the electrode structure are enhanced.
Smart Images
Figure CN120376348A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of positive electrode materials for capacitors, and particularly relates to a dual-material composite positive electrode material prepared by in-situ chemical synthesis, a preparation method thereof, and an application thereof. Background Art
[0002] In order to further combine two different charge-discharge mechanisms of capacitive energy storage and battery energy storage, researchers combined lithium-rich battery materials and porous / nano carbon materials into a dual-material composite positive electrode, used battery negative electrode materials (such as graphite, Li4Ti5O 12 etc.) as the negative electrode, and an organic lithium-ion electrolyte as the electrolyte, and developed a battery-type capacitor (LIBC). The energy density of the battery-type capacitor mainly depends on the positive electrode composite material. Therefore, the research on the positive electrode composite material is mainly based on the positive electrode materials of lithium-ion batteries. Common ones include lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMnO2), lithium iron phosphate (LiFePO4), ternary materials (LiNi x Co y Mn 1-x-y O2), lithium vanadium phosphate (Li3V2(PO4)3), etc. The capacitive positive electrode materials added in the dual-material composite positive electrode are mainly activated carbon (AC). In addition, new carbon materials such as graphene and carbon aerogel have continuously expanded the positive electrode capacitance material system of LIBC. Professor John B. Goodenough discovered the LiCoO2 positive electrode material in 1980. Due to its high energy density, high tap density, and reliability, LiCoO2 is still widely used as the main positive electrode material for lithium-ion batteries (LIB) in the portable electronic product market. Carbon nanotubes are a kind of nanoscale tubular structure carbon material formed by convolution of single-layer or multi-layer two-dimensional graphene sheets, and have excellent mechanical and electrochemical properties.
[0003] The traditional positive electrode of the battery-type capacitor is generally prepared by physically mixing battery positive electrode materials and capacitive materials, such as mechanical grinding, mechanical stirring, etc. However, during the physical mixing preparation process, due to the large density difference between the battery materials and the capacitive materials, it is very easy to cause problems such as fragmentation of battery material particles and uneven mixing, thereby affecting the electrochemical performance of the materials. Summary of the Invention
[0004] The present invention aims to provide a dual-material composite positive electrode material prepared by in-situ chemical synthesis, a preparation method thereof, and an application thereof. By means of chemical synthesis, multi-walled carbon nanotubes (capacitive materials) are combined with lithium cobalt oxide (battery materials) to prepare a multi-walled carbon nanotube / lithium cobalt oxide dual-material positive electrode and used in battery-type capacitors to solve the problems existing in the prior art using physical mixing.
[0005] A preparation method of a dual-material composite cathode material by in-situ chemical synthesis in this solution includes the following steps:
[0006] S1. Preparation of CoNi-MOF catalyst: Hydrothermal method is used to prepare CoNi-MOF catalyst by using cobalt nitrate, nickel nitrate, and 2-methylimidazole.
[0007] S2. Preparation of multi-walled carbon nanotubes: Chemical vapor deposition method is used to prepare multi-walled carbon nanotubes by using the CoNi-MOF catalyst.
[0008] S3. Composite of dual-material cathode: Sol-gel method is used to prepare a dual-material composite cathode material with conjugated symbiosis of multi-walled carbon nanotubes and lithium cobaltate.
[0009] Further, in S1, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, and 2-methylimidazole are separately dissolved in ethanol. The Co(NO3)2·6H2O and Ni(NO3)2·6H2O solutions are mixed, then the 2-methylimidazole solution is added dropwise and stirred continuously. Finally, the mixed solution is transferred to a reaction kettle with polytetrafluoroethylene, the temperature is set at 110°C - 130°C, and after reacting for 10 - 15 h, the CoNi-MOF catalyst is formed.
[0010] Further, in S1, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, and 2-methylimidazole with a molar mass ratio of 1:1:10 - 20 are separately dissolved in 100 ml of ethanol.
[0011] Further, in S2, the CoNi-MOF catalyst is evenly spread on a quartz boat, placed in a tube furnace, an inert gas is introduced and the temperature is continuously raised to 650°C, a carbon source gas is introduced, after fully reacting, the carbon source gas is turned off, and the inert gas is continuously introduced until the temperature drops to room temperature, thus obtaining multi-walled carbon nanotubes.
[0012] Further, the inert gas is argon, and the carbon source gas is acetylene, and the flow rates are both controlled at 180 - 230 ml / min.
[0013] Further, in S3, LiNO3, Co(NO3)2·6H2O, C6H8O7, and multi-walled carbon nanotubes are respectively dissolved in deionized water. The LiNO3 solution is quickly mixed with the Co(NO3)2·6H2O solution, and the multi-walled carbon nanotube solution is added and stirred. Subsequently, the citric acid solution is slowly added to the mixed solution and continuously stirred, and then the pH of the mixed solution is adjusted to 8. The obtained sol is heated to obtain a wet gel. The wet gel is dried to obtain a dry gel, and the dry gel is ball-milled into fine powder using a ball mill. Then the fine powder is placed in a microwave heating furnace and heated for several hours and then the heating is stopped. After cooling to room temperature, a dual-material composite cathode with conjugated symbiosis of multi-walled carbon nanotubes and lithium cobaltate can be obtained.
[0014] Further, in S3, 1mol / L ammonia water is used to adjust the pH of the mixed solution.
[0015] Further, the power of the microwave heating furnace is set to 1500W, the temperature is set to 600°C, and the heating is carried out for 10h.
[0016] The cathode material of the battery-type capacitor prepared by the present invention is applied to the preparation of battery-type capacitors.
[0017] The present invention realizes the conjugated symbiotic structure of multi-walled carbon nanotubes (MWCNT) and lithium cobaltate (LiCoO2) through a chemical synthesis route, and solves the problem of the decline in electrochemical performance caused by material density difference, uneven mixing, and poor interfacial contact in the traditional physical mixing process for the preparation of the cathode of battery-type capacitors. Its working principle and effects lie in the following key links:
[0018] 1. The CoNi-MOF catalyst synthesized by the present invention has a porous structure and a high specific surface area, provides uniform active sites for the carbon source, increases the contact area of the reaction, and improves the efficiency of the catalytic reaction. During the chemical vapor deposition process, it guides the directional growth of multi-walled carbon nanotubes (MWCNT) to form a carbon tube network with a smooth surface and a high degree of graphitization.
[0019] 2. Under the synergistic catalytic effect of Co / Ni bimetals, the growth of carbon tubes can be promoted at 650°C, the doping of heteroatoms can be inhibited, and the conductivity of the carbon tubes can be ensured.
[0020] 3. Citric acid is used as a chelating agent to form a stable metal-organic complex with Li + , Co 2+ to form a stable metal-organic complex. By adjusting the pH (pH≈8), a uniform sol is formed, enabling the molecular-level uniform mixing of MWCNT and the LiCoO2 precursor, and avoiding the problem of particle fragmentation in traditional mechanical mixing.
[0021] 4. Microwave heating (600 °C) rapidly induces the crystallization of LiCoO2. At the same time, some chemical bonds (such as C–O–Co bonds) are formed between the oxygen-containing functional groups on the surface of MWCNT and the surface of LiCoO2 particles at high temperature, forming a conjugated symbiotic interface and enhancing the electron transport ability.
[0022] 5. MWCNT is embedded in the gaps between LiCoO2 particles in the form of a network skeleton, forming a continuous conductive path and significantly reducing the contact resistance (Rct) of the electrode material.
[0023] 6. MWCNT inhibits the volume expansion and secondary aggregation of LiCoO2 particles during charge and discharge through physical barrier effects, making the particle distribution more uniform, increasing the reaction activity of most lithium cobalt oxides, improving the specific capacity, and maintaining the stability of the electrode structure. Description of the Drawings
[0024] Figure 1 SEM images of the materials obtained in Example 1, Comparative Example 1, and Comparative Example 3.
[0025] Figure 2 Discharge curves of the materials obtained in Example 1, Comparative Example 1, and Comparative Example 3.
[0026] Figure 3 Graphs showing the results of the rate performance tests of the materials obtained in Example 1, Comparative Example 1, and Comparative Example 3.
[0027] Figure 4 Graphs showing the results of the rate performance tests of the soft-pack batteries obtained in Application Example 1, Application Example 2, and Application Example 3. Detailed Description of the Invention
[0028] The following is a further detailed description through specific embodiments:
[0029] Example 1, a preparation method of an in-situ chemically synthesized dual-material composite cathode material, comprising the following steps:
[0030] S1. Preparation of the CoNi-MOF catalyst:
[0031] The catalyst is prepared by a one-step hydrothermal method. Weigh 0.873 g of Co(NO3)2·6H2O, 0.870 g of Ni(NO3)2·6H2O, and 3.93 g of 2-methylimidazole, and dissolve them in 100 ml of ethanol respectively. Ultrasonic for 30 min, mix the Co(NO3)2·6H2O and Ni(NO3)2·6H2O solutions, then slowly drop the 2-methylimidazole solution into the mixture and continuously stir to make them fully blend. Finally, transfer the mixed solution to a reaction kettle with polytetrafluoroethylene, set the temperature to 120 °C, and after reacting for 12 h, the CoNi-MOF catalyst is generated;
[0032] S2. Preparation of Multi-Walled Carbon Nanotubes
[0033] The multi-walled carbon nanotubes were prepared by chemical vapor deposition. 0.5 g of CoNi-MOF catalyst was evenly spread on a quartz boat and placed in a tube furnace. Argon was introduced at a rate of 200 ml / min and the temperature was continuously raised to 650 °C. Then, acetylene, as the carbon source gas, was introduced at a rate of 200 ml / min. After reacting for 100 min, the acetylene gas was turned off, and argon was continuously introduced until the temperature dropped to room temperature. The black product was the multi-walled carbon nanotubes;
[0034] S3. Composite of Dual-Material Cathode
[0035] The dual-material composite cathode in which multi-walled carbon nanotubes and lithium cobaltate coexist conjugately was prepared by the sol-gel method. 2.07 g of lithium nitrate (LiNO3), 8.73 g of cobalt nitrate (Co(NO3)2·6H2O), 5.76 g of citric acid (C6H8O7), and 0.3 g of multi-walled carbon nanotubes were respectively dissolved in 100 ml of deionized water and ultrasonicated for 30 min. The LiNO3 solution was quickly mixed with the Co(NO3)2·6H2O solution, and the multi-walled carbon nanotube solution was added, followed by stirring for 20 min. Subsequently, the citric acid solution was slowly added to the mixed solution and continuously stirred. Then, 1 mol / L ammonia water (NH4OH) was used to adjust the pH of the mixed solution to approximately 8. The resulting sol was heated to 45 °C to obtain a wet gel, and the wet gel was dried at 120 °C to obtain a dry gel. The dry gel was ball milled into fine powder using a ball mill, and then the fine powder was placed in a microwave heating furnace with the power set to 1500 W and the temperature set to 600 °C. After heating for 10 h, the heating was stopped, and after cooling to room temperature, the dual-material composite cathode in which multi-walled carbon nanotubes and lithium cobaltate coexist conjugately, that is, the cathode material for the battery-type capacitor, was obtained.
[0036] Comparative Example 1: Preparation of Lithium Cobaltate
[0037] The lithium cobaltate material was prepared by the sol-gel method. 2.07 g of lithium nitrate (LiNO3), 8.73 g of cobalt nitrate (Co(NO3)2·6H2O), and 5.76 g of citric acid (C6H8O7) were respectively dissolved in 100 ml of deionized water and ultrasonicated for 30 min. The LiNO3 solution was quickly mixed with the Co(NO3)2·6H2O solution, followed by stirring for 20 min. Subsequently, the citric acid solution was slowly added to the mixed solution and continuously stirred. Then, 1 mol / L ammonia water (NH4OH) was used to adjust the pH of the mixed solution to approximately 8. The resulting sol was heated to 45 °C to obtain a wet gel, and the wet gel was dried at 120 °C to obtain a dry gel. The dry gel was ball milled into fine powder using a ball mill, and then the fine powder was placed in a microwave heating furnace with the power set to 1500 W and the temperature set to 600 °C. After heating for 10 h, the heating was stopped, and after cooling to room temperature, the lithium cobaltate material was obtained.
[0038] Comparative Example 2: Mechanically mixed multi-walled carbon nanotube / lithium cobalt oxide dual-material composite cathode
[0039] The multi-walled carbon nanotubes prepared in step S2 of Example 1 and the lithium cobalt oxide prepared in Comparative Example 1 were used to prepare the dual-material composite cathode material at a mass ratio of 1:9. Specifically: the multi-walled carbon nanotubes and the lithium cobalt oxide were put into a ball mill jar and ball-milled at a speed of 500 rpm / min for 6 h, and then the obtained powder was used to prepare the battery electrode sheet.
[0040] Application Example: Battery assembly
[0041] Application Example 1: The lithium cobalt oxide material, conductive carbon black (Super-P), and polyvinylidene fluoride (PVDF) in Comparative Example 1 were added in a ratio of 90:5:5, and an appropriate amount of N-methylpyrrolidone (NMP) solvent was added and stirred evenly; then the stirred slurry was scraped onto a 12-μm aluminum foil with a coater, placed in a vacuum oven and dried overnight at 120°C, and finally the dried electrode sheet was punched into a φ12-mm electrode disc.
[0042] In a glove box under an argon atmosphere (water and oxygen content < 0.2 ppm), using a CR2025-type battery case, a metal lithium sheet was used as the counter electrode and reference electrode, an electrolyte system of EC:DMC:EMC with a volume ratio of 1:1:1 containing 1 mol / L of LiPF6, and an NKK ceramic separator. A button-type half-cell was assembled in the order of the outer shell, gasket, lithium sheet, electrolyte, separator, negative electrode sheet, and outer shell. After the battery assembly was completed, the battery was quickly sealed on a hydraulic sealer. The assembled battery was left standing for 12 hours before testing to allow the electrolyte to fully penetrate. (EC, DMC, and EMC represent ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, respectively)
[0043] Application Example 2: The difference from Application Example 1 is that the dual-material composite cathode material obtained by the mechanical mixing method in Comparative Example 2 was used to prepare the electrode disc with conductive carbon black (Super-P) and polyvinylidene fluoride (PVDF).
[0044] Application Example 3: The difference from Application Example 1 is that the in-situ chemically synthesized dual-material composite cathode material prepared in Example 1 was used to prepare the electrode disc with conductive carbon black (Super-P) and polyvinylidene fluoride (PVDF).
[0045] I. Physical characterization
[0046] From Figure 1It can be seen that particles with a diameter of approximately 800 nm were formed in Comparative Example 1, and these particles aggregated together to form secondary particles with a diameter of more than 50 μm; in Comparative Example 2, carbon nanotubes were added, and these secondary particles with a diameter of more than 50 μm were adhered to each other through ball milling with the carbon nanotubes to form new particles with a larger diameter; Example 1 was an in-situ synthesized lithium cobalt oxide / carbon nanotube material, which prevented the aggregation between particles during the synthesis of lithium cobalt oxide, made the particle distribution more uniform, and formed a cathode material in which multi-walled carbon nanotubes and lithium cobalt oxide coexisted conjugately.
[0047] II. Testing of Electrochemical Performance
[0048] It can be seen from Figure 2 that the specific capacities of the materials in Comparative Example 2 and Example 1 are both lower than that in Comparative Example 1. This is because the addition of carbon nanotubes in Comparative Example 2 and Example 1 reduced their specific capacities, but the specific capacity of Example 1 is already close to that of Comparative Example 1, while there is a large difference in Comparative Example 2. This is because although the carbon nanotubes reduced the specific capacity of the composite material, the carbon nanotubes in Example 1 reduced the aggregation of secondary particles of lithium cobalt oxide and increased the reaction activity of most of the lithium cobalt oxide, so its specific capacity is higher.
[0049] III. Rate Cycling Test
[0050] It can be seen from Figure 3 that after rate cycling, the performance of Example 1 is significantly higher than that of Comparative Examples 1 and 2, with Comparative Example 1 being the lowest. This shows that the addition of carbon nanotubes helps to increase the rate performance of the composite material, and the performance of the carbon nanotube composite lithium cobalt oxide material is better after in-situ synthesis.
[0051] IV. Battery Rate Test
[0052] Using Comparative Example 1, Comparative Example 2, and Example 1 as the positive electrodes (corresponding to Application Example 1, Application Example 2, and Application Example 3 respectively), and a hard and soft carbon composite material as the negative electrode, a 1 Ah soft-pack battery-type capacitor was prepared. Through rate testing, it can be found that when discharging at a rate of 100C, the capacity retention rate of Application Example 3 is much higher than that of Application Example 1. This is because the carbon nanotubes in Application Example 3 reduced the polarization of lithium cobalt oxide and increased the ion transfer ability of the composite material.
Claims
1. A preparation method of a dual-material composite cathode material by in-situ chemical synthesis, characterized in that, It includes the following steps: S1. Preparation of CoNi-MOF catalyst: Hydrothermal method is used to prepare CoNi-MOF catalyst by using cobalt nitrate, nickel nitrate and 2-methylimidazole. S2. Preparation of multi-walled carbon nanotubes: Chemical vapor deposition method is used to prepare multi-walled carbon nanotubes by using the CoNi-MOF catalyst. S3. Composite of dual-material positive electrode: Sol-gel method is used to prepare a dual-material composite positive electrode material in which multi-walled carbon nanotubes and lithium cobaltate coexist conjugately.
2. The preparation method of a dual-material composite cathode material by in-situ chemical synthesis according to claim 1, characterized in that: In S1, Co(NO3)2·6H2O, Ni(NO3)2·6H2O and 2-methylimidazole are respectively dissolved in ethanol. The Co(NO3)2·6H2O solution and the Ni(NO3)2·6H2O solution are mixed, then the 2-methylimidazole solution is added dropwise and stirred continuously. Finally, the mixed solution is transferred to a reaction kettle with polytetrafluoroethylene. The temperature is set at 110°C to 130°C. After reacting for 10 to 15 hours, the CoNi-MOF catalyst is generated.
3. The preparation method of a dual-material composite cathode material by in-situ chemical synthesis according to claim 2, characterized in that: In S1, Co(NO3)2·6H2O, Ni(NO3)2·6H2O and 2-methylimidazole with a molar mass ratio of 1:1:10 to 20 are respectively dissolved in 100 ml of ethanol.
4. The preparation method of a dual-material composite cathode material by in-situ chemical synthesis according to claim 1, characterized in that: In S2, the CoNi-MOF catalyst is evenly spread on a quartz boat and placed in a tube furnace. An inert gas is introduced and the temperature is continuously raised to 650°C. A carbon source gas is introduced. After sufficient reaction, the carbon source gas is turned off, and the inert gas is continuously introduced until the temperature drops to room temperature, thus obtaining multi-walled carbon nanotubes.
5. The preparation method of a dual-material composite cathode material prepared by in-situ chemical synthesis according to claim 4, characterized in that: The inert gas is argon, and the carbon source gas is acetylene, and the flow rates are both controlled at 180 to 230 ml / min.
6. The preparation method of a dual-material composite cathode material by in-situ chemical synthesis according to claim 1, characterized in that: In S3, LiNO3, Co(NO3)2·6H2O, C6H8O7 and multi-walled carbon nanotubes are respectively dissolved in deionized water. The LiNO3 solution is quickly mixed with the Co(NO3)2·6H2O solution, the multi-walled carbon nanotubes solution is added, and stirred; then the citric acid solution is slowly added to the mixed solution and stirred continuously. Then the pH of the mixed solution is adjusted to 8, and the obtained sol is heated to obtain a wet gel; the wet gel is dried to obtain a dry gel, the dry gel is ball-milled to fine powder by a ball mill, and then the fine powder is put into a microwave heating furnace and heated for several hours and then the heating is stopped. After cooling to room temperature, a dual-material composite positive electrode in which multi-walled carbon nanotubes and lithium cobaltate coexist conjugately can be obtained.
7. The preparation method of a dual-material composite cathode material by in-situ chemical synthesis according to claim 6, characterized in that: In S3, 1 mol / L ammonia water is used to adjust the pH of the mixed solution.
8. The preparation method of a dual-material composite cathode material by in-situ chemical synthesis according to claim 7, characterized in that: The power of the microwave heating furnace is set at 1500 W, the temperature is set at 600°C, and heated for 10 h.
9. A dual-material composite cathode material synthesized in-situ, characterized in that Obtained by using the preparation method according to any one of claims 1 to 8.
10. A dual-material composite positive electrode material prepared by in-situ chemical synthesis according to claim 9 is applied to the preparation of a battery-type capacitor.