Preparation method of carbon nanotube-polypyrrole-Prussian white composite material for lithium ion battery
By preparing carbon nanotube-polypyrrole-Prussian white composite material, the problem of poor conductivity of Prussian white was solved, the high-speed performance and cycle stability of lithium-ion batteries were improved, and high reversible capacity and structural stability were achieved.
Patent Information
- Application Number
- CN202511022006.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-24
- Publication Date
- 2025-11-18
AI Technical Summary
The poor conductivity of Prussian white materials used in existing lithium-ion batteries leads to insufficient structural stability and electrochemical activity during lithium-ion insertion/extraction.
A carbon nanotube-polypyrrole-Prussian white composite material was used, with carbon nanotubes as a conductive scaffold and polypyrrole as a connecting medium, to improve the crystallinity and electron transport channels of Prussian white, forming a composite material with high conductivity and structural stability.
It improves the high-speed performance and cycle stability of lithium-ion batteries, ensures the structural stability and electrochemical activity during lithium-ion insertion/extraction, and achieves high reversible capacity and long-term cycle performance.
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Figure CN120978032A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of lithium ion batteries, and particularly relates to a preparation method of a carbon nanotube-poly pyrrole-prussian white composite material for lithium ion batteries. BACKGROUND
[0002] Lithium ion batteries have attracted wide attention due to their economic and efficient advantages. Compared with lithium batteries and sodium batteries, lithium batteries show unique advantages in cost and rate, such as high lithium reserves (about 500 times of lithium) and the use of aluminum foil negative current collector which is expected to greatly reduce the cost; compared with lithium and sodium, LI+ has the smallest Stokes radius (in PC solvent), indicating that LI+ has the highest ionic conductivity and ion transference rate (three times of Li+), and theoretically, lithium batteries can improve the rate capability without sacrificing specific capacity; in addition, lithium batteries can operate at a higher voltage in a wider voltage range, and low-melting-point lithium metal (only 63.4℃) can melt lithium dendrites to cut off the short circuit before the battery is seriously out of control, so high energy density and high safety can be achieved. Although the theoretical performance of lithium batteries is excellent, the technology is now in its infancy, and existing lithium battery electrode materials are not suitable for lithium batteries, so electrode materials need to be designed and developed for lithium batteries to manufacture functional lithium ion batteries.
[0003] In the prior art, prussian white is usually prepared by chemical co-precipitation growth, but the prussian white crystals generated in this way contain a large amount of coordinated water and vacancies, and have low crystallinity, resulting in poor structural stability and poor electrochemical activity during lithium ion intercalation / deintercalation. SUMMARY
[0004] The present application provides a preparation method of a carbon nanotube-poly pyrrole-prussian white composite material for lithium ion batteries to solve the technical problem of poor conductivity of prussian white.
[0005] According to a first aspect of the embodiment of the present application, a carbon nanotube-poly pyrrole-prussian white composite material for lithium ion batteries is provided, which mainly consists of carbon nanotubes, prussian white attached to the surface of the carbon nanotubes, and poly pyrrole connecting the prussian white to each other, wherein the prussian white is a sheet structure with a size of 20-100 nm, the carbon nanotube is a multi-walled carbon nanotube with a diameter of 10-50 nm, and the poly pyrrole is a sheet structure with a thickness of 100-200 nm and a size of 500 nm-1 μm.
[0006] According to a second aspect of the embodiment of the present application, a preparation method of a carbon nanotube-poly pyrrole-prussian white composite material for lithium ion batteries is provided, which comprises the following steps:
[0007] (1) a preparation process of reaction liquid A: dissolving a soluble divalent manganese salt and lithium citrate in deionized water, then adding N-methyl pyrrolidone and polypyrrole to form reaction liquid A;
[0008] (2) a preparation process of reaction liquid B: adding methanol and N,N-dimethylacetamide solution of carbon nanotubes into aqueous lithium ferrocyanide solution to form reaction liquid B;
[0009] (3) a co-deposition process: mixing reaction liquid B with reaction liquid A and heating to perform co-deposition to generate carbon nanotube-polypyrrole-prussian white composite material.
[0010] Preferably, in the preparation process of reaction liquid A, the concentration of lithium citrate is 0.1-0.3 mmol / mL, the soluble divalent manganese salt is MnCl2, the molar ratio of MnCl2 to N-methyl pyrrolidone is 0.1-0.5:10, and the total concentration of added polypyrrole is 1.0-5.0 mg / mL.
[0011] Preferably, in the preparation process of reaction liquid B, the concentration of lithium ferrocyanide in aqueous lithium ferrocyanide solution is 0.10-0.50 mmol / mL, the volume ratio of added methanol to aqueous lithium ferrocyanide solution is 1:1-2, the mass ratio of carbon nanotubes to lithium ferrocyanide is 0.5-5:1000, and the concentration of carbon nanotubes in N,N-dimethylacetamide solution of carbon nanotubes is 0.1-0.5 mg / mL.
[0012] Preferably, in the co-deposition process, the reaction temperature is 80-90°C, and the volume ratio of reaction liquid A to reaction liquid B is 1-4:1.
[0013] One embodiment of the present specification can achieve at least the following beneficial effects: the carbon nanotube-polypyrrole-prussian white composite material provided by the present application uses high-conductivity carbon nanotubes as a support, and by adding polypyrrole, it provides nucleation active sites for carbon nanotube-prussian white co-deposition to improve the crystallinity of prussian white, improves the mutual connection between prussian white crystals, provides a channel for electron transmission, further combines carbon nanotubes to improve the conductivity and structural stability of PW, improves the structural stability and electrochemical activity during Li+ insertion / extraction on the basis of maintaining the structure framework of prussian white, and when used as a positive electrode material of a lithium ion electrode, it is beneficial to realize high-rate performance and cycle stability. BRIEF DESCRIPTION OF DRAWINGS
[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present specification or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.
[0015] Figure 1 is a scanning electron microscope image of the carbon nanotube-polyazole-prussian white composite material prepared in Embodiment 1 of the present application;
[0016] Figure 2 is a charge-discharge voltage-capacity graph of the half battery prepared in Embodiment 1 of the present application;
[0017] Figure 3 is a capacity curve graph of the half battery prepared in Embodiment 1 of the present application, which is cycled at 0.2C, 0.5C, 1C, 2C, and 0.2C for 100 times of charge and discharge, respectively;
[0018] Figure 4 is a scanning electron microscope image of the carbon nanotube-polyazole-prussian white composite material prepared in Embodiment 2 of the present application;
[0019] Figure 5 is a charge-discharge voltage-capacity graph of the half battery prepared in Embodiment 2 of the present application;
[0020] Figure 6 is a capacity curve graph of the half battery prepared in Embodiment 2 of the present application, which is cycled at 0.2C, 0.5C, 1C, 2C, and 0.2C for 100 times of charge and discharge, respectively;
[0021] Figure 7 is a scanning electron microscope image of the carbon nanotube-polyazole-prussian white composite material prepared in Embodiment 3 of the present application;
[0022] Figure 8 is a charge-discharge voltage-capacity graph of the half battery prepared in Embodiment 3 of the present application;
[0023] Figure 9 is a capacity curve graph of the half battery prepared in Embodiment 3 of the present application, which is cycled at 0.2C, 0.5C, 1C, 2C, and 0.2C for 100 times of charge and discharge, respectively. DETAILED DESCRIPTION
[0024] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those ordinarily skilled in the art without creative work fall within the scope of the present application. Unless otherwise defined, the technical terms or scientific terms used herein should be understood as the common meanings by those having ordinary skills in the art to which the present application belongs. The "comprising" and similar words used herein mean that the elements or objects before the words encompass the elements or objects listed after the words and their equivalents, without excluding other elements or objects.
[0025] The preferred embodiments of the present application will be described in more detail below. Although the preferred embodiments of the present application are described below, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. If no specific technology or condition is specified in the embodiments, the technology or condition described in the literature in the art or according to the product manual is used. If no manufacturer of the reagent or instrument is specified, it is a conventional product that can be obtained commercially. In the following examples, unless otherwise specified, "%" means weight percent.
[0026] The structure of the carbon nanotube-poly pyrrole-prussian white composite material provided by the present application will be introduced first below. The composite material mainly consists of carbon nanotubes, prussian white attached to the surface of the carbon nanotubes, and poly pyrrole connecting the prussian white to each other. The prussian white is a flaky structure with a size of 20-100 nm, the carbon nanotube is a multi-walled carbon nanotube with a diameter of 10-50 nm, and the poly pyrrole is a flaky structure with a thickness of 100-200 nm and a size of 500 nm-1 μm.
[0027] In the composite material, the carbon nanotubes can be used as the "branches and trunks" for conducting electricity and supporting structure. Specifically, the carbon nanotubes are multi-walled carbon nanotubes with a diameter of 10-50 nm. The multi-walled carbon nanotubes have excellent electrical conductivity, and the tubular structure can form a continuous three-dimensional network, which can be used as the "skeleton" of the whole composite material. The diameter of 10-50 nm can avoid the self-winding and agglomeration of the carbon nanotubes, and can provide sufficient and uniform surface for the attachment of Prussian white, so that the Prussian white can be dispersedly grown on the surface, and the problem of agglomeration of Prussian white caused by aggregation during traditional carbon material doping can be avoided. At the same time, the mechanical strength of the carbon nanotubes can enhance the overall structural stability of the composite material, and resist the volume expansion stress during the lithium ion insertion / desorption process. Prussian white is the "active core" for storing lithium ions. Specifically, the Prussian white has a flaky structure with a size of 20-100 nm, which is induced to grow from the nucleation active points provided by the polypyrrole. Compared with the Prussian white prepared by the traditional chemical co-precipitation method (containing a large amount of coordination water and vacancies, and low crystallinity), the flaky structure of the Prussian white has higher crystallinity and fewer crystal defects, which can reduce the risk of structural collapse during lithium ion intercalation / deintercalation. In addition, the size of 20-100 nm can make the Prussian white have a larger specific surface area, increase the contact sites with the electrolyte, and the short-range diffusion path of the flaky structure can accelerate the lithium ion migration, and lay the foundation for high rate performance. At the same time, the polypyrrole in the composite material can be used as the "bridge" for electron transmission and structural connection. Specifically, the polypyrrole has a sheet structure with a thickness of 100-200 nm and a size of 500 nm-1 μm, which can connect the Prussian white to each other. In the traditional method, the bonding strength between the carbon nanotubes and the Prussian white is low, which can only improve the electrical conductivity of the Prussian white near the carbon nanotubes, and the part far away from the carbon nanotubes still exists in isolation, which causes the electron transmission to be blocked. The sheet structure of the polypyrrole can be used as the "conductive bridge" to connect the multiple Prussian white flaky crystals dispersed on the surface of the carbon nanotubes to each other, form an electron transmission channel through the whole composite material, ensure that all Prussian white particles can participate in efficient electron conduction, and solve the problem of local poor conductivity. At the same time, the thickness of 100-200 nm and the size of 500 nm-1 μm make the polypyrrole can wrap the surface of the Prussian white, enhance the bonding strength between the Prussian white and the carbon nanotubes, and avoid the performance degradation caused by interface peeling during the cycle process.
[0028] The embodiment of the present application also provides a preparation method of the carbon nanotube-polypyrrole-Prussian white composite material for lithium ion batteries.
[0029] Step S1: configuring a reaction liquid A, including: dissolving a soluble divalent manganese salt and lithium citrate in deionized water, and then adding N-methyl pyrrolidone and polypyrrole to disperse uniformly to form the reaction liquid A.
[0030] In this step, soluble divalent manganese salt and lithium citrate are first dissolved in deionized water. The soluble divalent manganese salt serves as a manganese source, providing the necessary metal ions for the formation of Prussian white and is an important component of Prussian white crystals. Lithium citrate acts as a ligand, forming a weak coordination with the metal ions in the soluble divalent manganese salt, stabilizing the state of the metal ions and preventing them from reacting prematurely before being mixed with other reaction solutions. At the same time, the lithium element it contains can also participate in the structural construction of Prussian white, helping to improve the lithium-ion storage performance of the composite material. Next, N-methylpyrrolidone and polypyrrole are added to the above solution. N-methylpyrrolidone, as a solvent, can improve the dispersibility of polypyrrole in the system because polypyrrole itself has poor solubility in water. With the help of N-methylpyrrolidone, it can be more uniformly dispersed in the reaction solution. Polypyrrole can provide nucleation sites for the co-deposition of Prussian white in the subsequent co-deposition process, which is beneficial to improving the crystallinity of Prussian white. At the same time, it can also act as a connecting medium to connect Prussian white crystals to each other, creating channels for electron transport. Finally, the above components are uniformly mixed through dispersion to form reaction solution A. This uniform dispersion state can avoid problems such as poor crystallization state of Prussian white due to uneven concentration of local components.
[0031] Step S2: Prepare reaction solution B: Add methanol and N,N-dimethylacetamide solution of carbon nanotubes to lithium ferrocyanide aqueous solution and disperse evenly to form reaction solution B.
[0032] This step begins with an aqueous solution of lithium ferrocyanide, which serves as the core raw material, providing the necessary cyanide ligands and lithium source for the formation of Prussian white. Next, methanol is added to this aqueous solution. Methanol adjusts the polarity and dispersibility of the solution, helping to improve the dispersion of subsequently added carbon nanotubes in the system, while also helping to maintain the stability of the solution. Then, an N,N-dimethylacetamide solution of carbon nanotubes is added. N,N-dimethylacetamide, as a solvent, effectively disperses the carbon nanotubes, preventing them from agglomerating due to their inherent tendency to cluster. This ensures that the carbon nanotubes are uniformly distributed in the reaction solution. As the conductive framework and structural support of the composite material, the carbon nanotubes can form a continuous conductive network, improving the conductivity and structural stability of the composite material. Finally, a dispersion process is performed to uniformly mix all the above components to form reaction solution B. This uniform dispersion ensures that when mixed with reaction solution A for co-deposition, the carbon nanotubes can uniformly carry the Prussian white, and all components can fully react, avoiding performance degradation of the composite material due to carbon nanotube agglomeration or uneven raw material distribution.
[0033] S3. Co-deposition process: The reaction solution B and the reaction solution A are mixed and heated to perform co-deposition, generating carbon nanotube-polypyrrole-Prussian white composite material.
[0034] The purpose of this step is to promote the chemical reaction of the key components in the two reaction solutions through the mixing and heating of reaction solution A and reaction solution B, and to orderly assemble them into the target composite material. Specifically, the prepared reaction solution B is mixed with reaction solution A. Manganese ions from reaction solution A react with ferrocyanide ions from reaction solution B after mixing, gradually forming Prussian white crystals. Simultaneously, polypyrrole in reaction solution A provides nucleation sites for the co-deposition of Prussian white, guiding the crystals to grow at suitable locations, increasing their crystallinity, and subsequently connecting the generated Prussian white crystals. Carbon nanotubes in reaction solution B act as a framework, providing a supporting surface for the adhesion of Prussian white crystals, allowing them to adhere uniformly and preventing agglomeration. Heating promotes the reaction, accelerates the reaction rate, and helps improve the crystal quality of Prussian white and the bonding stability between the components. Throughout the process, the components work synergistically, ultimately forming a carbon nanotube-polypyrrole-Prussian white composite material, consisting of carbon nanotubes, Prussian white attached to the surface of the carbon nanotubes, and polypyrrole connecting the Prussian white crystals.
[0035] The principle of this invention is as follows: The components in the composite material provided by this invention work synergistically to achieve high electrochemical activity and reversible capacity, good cycling stability, and excellent high-rate performance. Specifically, the continuous conductive network of carbon nanotubes provides the main channel for electron transport, the connecting effect of polypyrrole ensures that electrons can reach each Prussian white particle, and the highly crystalline lamellar Prussian white provides stable lithium-ion storage sites, while the large specific surface area increases the chance of reaction contact. The synergy of these three factors gives the composite material a high reversible capacity, higher than that of traditional Prussian white materials (which have lower capacity due to low crystallinity and poor conductivity). Experiments have shown that the composite material can still maintain a high reversible capacity at high rates. This is because the electron channels formed by the polypyrrole connections shorten the electron transport distance, avoiding electron accumulation; at the same time, the short-range diffusion path of the lamellar Prussian white allows lithium ions to be rapidly inserted / extracted, reducing concentration polarization at high rates; moreover, the high conductivity of carbon nanotubes reduces the overall resistance. These three factors together solve the problem of the rapid capacity drop of traditional Prussian white at high rates. Meanwhile, the high crystallinity of Prussian white reduces structural defects and lowers the risk of lattice collapse during cycling; the carbon nanotube framework resists volume expansion, preventing the overall structure of the composite material from breaking; and the interfacial encapsulation of polypyrrole enhances the bonding strength between the components, preventing the Prussian white from delaminating from the carbon nanotubes during cycling. This synergistic effect allows the composite material to maintain a high capacity even after long-term cycling, significantly outperforming traditional Prussian white materials.
[0036] In a preferred embodiment of the present invention, in the preparation step of reaction solution A, the concentration of lithium citrate is 0.1-0.3 mmol / mL, the soluble divalent manganese salt is MnCl2, the molar ratio of MnCl2 to N-methylpyrrolidone is 0.1-0.5:10, and the total concentration of added polypyrrole is 1.0-5.0 mg / mL.
[0037] In a preferred embodiment of the present invention, in the preparation step of reaction solution B, the concentration of lithium ferrocyanide in the lithium ferrocyanide aqueous solution is 0.10-0.50 mmol / mL, the volume ratio of methanol to lithium ferrocyanide aqueous solution is 1:1-2, the mass ratio of carbon nanotubes to lithium ferrocyanide is 0.5-5:1000, and the concentration of carbon nanotubes in the N,N-dimethylacetamide solution is 0.1-0.5 mg / mL.
[0038] In a preferred embodiment of the present invention, in the co-deposition process, the reaction temperature is 80-90°C, and the volume ratio of the reaction solution A to the reaction solution B is 1-4:1.
[0039] The carbon nanotube-polypyrrole-Prussian white composite material provided by this invention uses highly conductive carbon nanotubes as a scaffold, and adds polypyrrole to provide nucleation sites for carbon nanotube-Prussian white co-deposition to improve the crystallinity of Prussian white, enhance the interconnection between Prussian white crystals, provide channels for electron transport, and further combine carbon nanotubes to improve the conductivity and structural stability of PW. While maintaining the structural framework of Prussian white, it improves the structural stability and electrochemical activity during Li+ insertion / extraction. When used as a positive electrode material for lithium-ion electrodes, it is beneficial to achieve high-rate performance and cycle stability.
[0040] All raw materials used in the embodiments of this invention were obtained through commercial purchase.
[0041] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.
[0042] In some embodiments, the positive electrode material for lithium-ion batteries comprises the aforementioned carbon nanotube-polypyrrole-Prussian white composite material, or a material prepared according to the aforementioned method for preparing the carbon nanotube-polypyrrole-Prussian white composite material.
[0043] In some embodiments, the positive electrode material for lithium-ion batteries may include the aforementioned carbon nanotube-polypyrrole-Prussian white composite material and a substrate serving as a current collector, wherein the aforementioned carbon nanotube-polypyrrole-Prussian white composite material is attached to the surface of the aforementioned current collector substrate. The aforementioned substrate is not particularly limited and may be, for example, aluminum foil, carbon-coated aluminum foil, etc. Depending on the material used for the aforementioned substrate, if a flexible material is used as the substrate, the aforementioned electrode may be a flexible electrode.
[0044] The aforementioned carbon nanotube-polypyrrole-Prussian white composite material can be coated onto the surface of the aforementioned substrate by means of coating or other methods to form a thin film or other coating. Furthermore, as a material coated onto the aforementioned substrate, in addition to the carbon nanotube-polypyrrole-Prussian white composite material, it may further contain other components, such as adhesives such as polyvinylidene fluoride (PVDF) and sodium carboxymethyl cellulose (CMC) / styrene-butadiene rubber (SBR), conductive additives such as Super P carbon black, acetylene black, Ketjen black, and conductive graphite, and solvents such as N-methylpyrrolidone (NMP), N-dimethylamide (DMF), and dimethyl sulfoxide (DMSO).
[0045] The aforementioned carbon nanotube-polypyrrole-Prussian white composite material, or the carbon nanotube-polypyrrole-Prussian white composite material prepared by the aforementioned method, can be used as a positive electrode active material to prepare positive electrode materials for lithium-ion batteries. The positive electrode materials for lithium-ion batteries using such composite materials have high capacitance and charge transport performance.
[0046] The technical solution of the present invention will be further illustrated by the following embodiments.
[0047] Example 1: Carbon nanotube-polypyrrole-Prussian white composite material (reaction solution A / B volume ratio 1:1)
[0048] Composite material preparation
[0049] (1) Preparation of reaction solution A: Dissolve 0.1 mmol / mL MnCl2 and 0.2 mmol / mL lithium citrate in 35 mL of deionized water and stir magnetically for 30 minutes until a colorless and transparent mixture is formed; add 0.035 mol N-methylpyrrolidone to the mixture, followed by 2.0 mg / mL polypyrrole, and continue stirring for 12 hours until evenly dispersed to obtain reaction solution A.
[0050] (2) Preparation of reaction solution B: Under magnetic stirring, lithium ferrocyanide was dissolved in 35 mL of deionized water to form a solution with a concentration of 0.2 mmol / mL; 35 mL of methanol was added to the solution and stirred to form a mixture; 2.0 mL of N,N-dimethylacetamide solution containing 0.5 mg / mL multi-walled carbon nanotubes (total mass of carbon nanotubes 1.0 mg) was added and stirred for 1 hour until it was evenly dispersed to obtain reaction solution B.
[0051] (3) Co-deposition process: Heat reaction solution A and reaction solution B to 85°C respectively; while stirring at 500 rpm, slowly add reaction solution B (volume ratio 1:1) to reaction solution A, and continue stirring for 1 hour after the addition is completed.
[0052] (4) Modification and post-treatment: 0.125 g / mL of 5-sulfosalicylic acid dihydrate was added to the co-deposited product, and the mixture was stirred in an ice bath (around 0°C) for 6 hours; it was washed three times with deionized water, centrifuged, and dried at 60°C for 24 hours to obtain composite material 1. The scanning electron microscope image of composite material 1 is shown below. Figure 1 As shown. From Figure 1 It can be seen that composite material 1 has an overall sheet-like structure.
[0053] 2. Electrode preparation
[0054] Eight parts by mass of composite material 1 and one part by mass of conductive carbon black were dispersed in a solution of one part by mass of polyvinylidene fluoride dissolved in 17 parts by mass of N-methylpyrrolidone. The mixture was stirred for 3 hours until a uniform slurry was formed. The slurry was coated on the surface of an aluminum foil (20 μm thick) and dried at 120 °C for 24 hours to obtain electrode 1.
[0055] 3. Performance Testing
[0056] A coin cell was assembled using a lithium sheet as the counter electrode and a 1 mol / L lithium hexafluorophosphate (KPF6) solution of ethylene carbonate (EC) / diethyl carbonate (DMC) (volume ratio 1:1) as the electrolyte. The performance of the prepared electrode 1 was tested according to Appendix F of GB / T30835-2014, and the results are shown below. Figure 2 , Figure 3 .from Figure 2 It can be seen that the initial charging capacity of electrode 1 at 0.5C reaches 129mAh / g, and the initial discharge capacity at a discharge rate of 0.5C is as high as 118mAh / g, indicating that the electrode material has high storage performance. Figure 3 Capacity plots are shown for 100 cycles at discharge rates of 0.2C, 0.5C, 1C, and 2C. From... Figure 3It can be seen that electrode 1 has excellent high-speed performance and cycle stability. After 100 cycles at 0.2C, 0.5C and 1C respectively, and a total of 300 charge-discharge cycles, the capacity is still maintained at 108mAh / g at a high rate of 2C. After 100 cycles at 0.2C, 0.5C, 1C and 2C respectively, and a total of 400 cycles, and then 100 charge-discharge cycles at 0.2C, and a total of 500 cycles, the capacity retention rate is still 88.7% compared to the initial 0.2C, showing excellent stability.
[0057] Example 2: Carbon nanotube-polypyrrole-Prussian white composite material (reaction solution A / B volume ratio 2:1)
[0058] Composite material preparation
[0059] (1) Preparation of reaction solution A: Dissolve 0.15 mmol / mL MnCl2 and 0.3 mmol / mL lithium citrate in 40 mL of deionized water and stir magnetically for 30 minutes until a colorless and transparent mixture is formed; add 0.3 mol N-methylpyrrolidone to the mixture, followed by 3.0 mg / mL polypyrrole, and continue stirring for 12 hours until evenly dispersed to obtain reaction solution A.
[0060] (2) Preparation of reaction solution B: Under magnetic stirring, lithium ferrocyanide was dissolved in 20 mL of deionized water to form a solution with a concentration of 0.3 mmol / mL; 20 mL of methanol was added to the solution and stirred to form a mixture; 1.8 mL of N,N-dimethylacetamide solution containing 0.5 mg / mL multi-walled carbon nanotubes (total mass of carbon nanotubes 0.9 mg) was added and stirred for 1 hour until it was evenly dispersed to obtain reaction solution B.
[0061] (3) Co-deposition process: Heat reaction solution A and reaction solution B to 80°C respectively; while stirring at 500 rpm, slowly add reaction solution B (volume ratio 2:1) to reaction solution A, and continue stirring for 1.5 hours after the addition is completed.
[0062] (4) Modification and post-treatment: 0.2 g / mL of 5-sulfosalicylic acid dihydrate was added to the co-deposited product, and the mixture was stirred in an ice bath (around 0°C) for 6 hours; it was washed three times with deionized water, centrifuged, and then dried at 60°C for 24 hours to obtain composite material 2. Figure 4 As shown, from Figure 4 It can be seen that composite material 2 has an overall sheet-like structure.
[0063] 2. Electrode preparation (same as in Example 1)
[0064] 3. Performance Testing
[0065] A coin half-cell was assembled using a lithium sheet as the counter electrode and a 1 mol / L lithium hexafluorophosphate (KPF6) solution of ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio 1:1) as the electrolyte. The performance of the prepared electrode was tested according to Appendix F of GB / T 30835-2014, and the results are shown below. Figure 5 , Figure 6 ,from Figure 5 It can be seen that the electrode has an initial charge capacity of 135 mAh / g at 0.5C and an initial discharge capacity of 122 mAh / g at a discharge rate of 0.5C, indicating that the electrode material has excellent initial charge and discharge performance. Figure 6 The figures show the capacity change curves after 100 cycles at discharge rates of 0.2C, 0.5C, 1C, and 2C. (From...) Figure 3 As can be seen, the electrode exhibits excellent high-rate performance and cycle stability: after 100 cycles at 0.2C, 0.5C and 1C respectively (300 cycles in total), the capacity is still maintained at 108mAh / g at a high rate of 2C; after completing 100 cycles each at 0.2C, 0.5C, 1C and 2C (400 cycles in total), it is recharged and discharged at 0.2C for 100 cycles (500 cycles in total), and the capacity retention rate reaches 90.2%, showing outstanding long-term cycle stability.
[0066] Example 3: Carbon nanotube-polypyrrole-Prussian white composite material (reaction temperature 90℃)
[0067] 1. Preparation of composite materials
[0068] (1) Preparation of reaction solution A: Dissolve 0.08 mmol / mL MnCl2 and 0.1 mmol / mL lithium citrate in 30 mL of deionized water and stir magnetically for 30 minutes until a colorless and transparent mixture is formed; add 0.2 mol N-methylpyrrolidone to the mixture, followed by 1.5 mg / mL polypyrrole, and continue stirring for 12 hours until evenly dispersed to obtain reaction solution A.
[0069] (2) Preparation of reaction solution B: Under magnetic stirring, lithium ferrocyanide was dissolved in 40 mL of deionized water to form a solution with a concentration of 0.15 mmol / mL; 40 mL of methanol was added to the solution and stirred to form a mixture; 2.0 mL of N,N-dimethylacetamide solution containing 0.5 mg / mL multi-walled carbon nanotubes (total mass of carbon nanotubes 1.0 mg) was added and stirred for 1 hour until it was evenly dispersed to obtain reaction solution B.
[0070] (3) Co-deposition process: Heat reaction solution A and reaction solution B to 90°C respectively; while stirring at 500 rpm, slowly add reaction solution B (volume ratio 3:1) to reaction solution A, and continue stirring for 1 hour after the addition is completed.
[0071] (4) Modification and post-treatment: 0.1 g / mL of 5-sulfosalicylic acid dihydrate was added to the co-deposited product, and the mixture was stirred in an ice bath (around 0°C) for 6 hours; it was washed three times with deionized water, centrifuged, and dried at 60°C for 24 hours to obtain composite material 3. Figure 7 As shown.
[0072] 2. Electrode preparation (same as in Example 1)
[0073] 3. Performance Testing
[0074] Using lithium foil as the counter electrode, and 1 mol / L lithium hexafluorophosphate (KPF6) dissolved in ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio 1:1) solution as the electrolyte, a button half-cell was assembled. The performance of the aforementioned electrode was tested according to Appendix F of GB / T30835-2014, and the results are shown in... Figure 8 , Figure 9 .from Figure 8 It can be seen that the electrode has an initial charge capacity of 125 mAh / g at 0.5C and an initial discharge capacity of 115 mAh / g at a discharge rate of 0.5C, indicating that the electrode material has good initial charge and discharge performance. Figure 9 The figures show the capacity change curves after 100 cycles at discharge rates of 0.2C, 0.5C, 1C, and 2C. (From...) Figure 9 As can be seen, the electrode exhibits excellent high-rate performance and cycle stability: after 100 cycles at 0.2C, 0.5C and 1C respectively (300 cycles in total), the capacity is still maintained at 108mAh / g at a high rate of 2C; after completing 100 cycles each at 0.2C, 0.5C, 1C and 2C (400 cycles in total), it is recharged and discharged at 0.2C for 100 cycles (500 cycles in total), and the capacity retention rate at 2C is 87.3%, showing good long-term cycle stability.
[0075] Comparative Example 1: Composite material lacking polypyrrole (verifying the role of polypyrrole)
[0076] Composite material preparation
[0077] (1) Preparation of reaction solution A: Dissolve 0.1 mmol / mL MnCl2 and 0.2 mmol / mL lithium citrate in 35 mL of deionized water and stir magnetically for 30 minutes until a colorless and transparent mixture is formed; add 0.035 mol N-methylpyrrolidone (without adding polypyrrole) to the mixture and stir continuously for 12 hours until it is evenly dispersed to obtain reaction solution A.
[0078] (2) Preparation of reaction solution B: Same as the steps in the modified Example 1 (containing 0.5 mg / mL carbon nanotube solution).
[0079] (3) Co-deposition process: Same as in Example 1 (85°C, volume ratio 1:1).
[0080] (4) Modification and post-treatment: Same as in Example 1, to obtain composite material D1.
[0081] 2. Electrode preparation (same as in Example 1)
[0082] 3. Performance Testing
[0083] 0.2C reversible capacity is 92mAh / g, and 2C reversible capacity is 45mAh / g;
[0084] After 100 cycles of 2C, the capacity retention rate is 42%.
[0085] Comparative Example 2: Composite material lacking carbon nanotubes (verifying the role of carbon nanotubes)
[0086] Composite material preparation
[0087] (1) Preparation of reaction solution A: Same as in Example 1 (containing 2.0 mg / mL polypyrrole).
[0088] (2) Preparation of reaction solution B: Dissolve lithium ferrocyanide in 35 mL of deionized water (0.2 mmol / mL);
[0089] Add 35 mL of methanol (without adding carbon nanotube solution), stir for 1 hour, and obtain reaction solution B.
[0090] (3) Co-deposition process: Same as in Example 1 (85°C, volume ratio 1:1).
[0091] (4) Modification and post-treatment: Same as in Example 1, to obtain composite material D2.
[0092] 2. Electrode preparation (same as in Example 1)
[0093] 3. Performance Testing
[0094] 0.2C reversible capacity is 105mAh / g, and 2C reversible capacity is 58mAh / g;
[0095] After 100 cycles of 2C, the capacity retention rate is 51%.
[0096] Comparative Example 3: Pure Prussian white prepared by conventional methods
[0097] 1. Preparation of pure Prussian white, comprising: mixing 35 mL of 0.1 mmol / mL MnCl2 solution with 35 mL of 0.2 mmol / mL lithium ferrocyanide solution (volume ratio 1:1), stirring magnetically for 1 hour; washing the product three times with deionized water, centrifuging and drying at 60℃ for 24 hours to obtain pure Prussian white D3.
[0098] 2. Electrode preparation, including: dispersing 8 parts by mass of pure Prussian white D3 and 1 part by mass of conductive carbon black into a solution of 1 part by mass of polyvinylidene fluoride dissolved in 17 parts by mass of N-methylpyrrolidone, stirring for 3 hours to form a uniform slurry; coating the slurry onto the surface of aluminum foil (thickness 20 μm), drying at 120℃ for 24 hours to obtain electrode D3.
[0099] 3 Performance Tests
[0100] The test conditions are the same as in Example 1:
[0101] 0.2C reversible capacity is 85mAh / g, and 2C reversible capacity is 30mAh / g;
[0102] After 50 cycles of 2C, the capacity retention rate is 35%.
[0103] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0104] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.
Claims
1. A carbon nanotube-polypyrrole-Prussian white composite material for lithium-ion batteries, characterized in that, The composite material mainly consists of carbon nanotubes, Prussian white attached to the surface of the carbon nanotubes, and polypyrrole connecting the Prussian white to each other. The Prussian white is a sheet-like structure with a size between 20 and 100 nm, the carbon nanotubes are multi-walled carbon nanotubes with a diameter between 10 and 50 nm, and the polypyrrole is a sheet-like structure with a thickness between 100 and 200 nm and a size between 500 nm and 1 μm.
2. A method for preparing a carbon nanotube-polypyrrole-Prussian white composite material for lithium-ion batteries, characterized in that, The method includes the following steps: S1. Prepare reaction solution A, including: dissolving soluble divalent manganese salt and lithium citrate in deionized water, then adding N-methylpyrrolidone and polypyrrole, and dispersing them evenly to form reaction solution A; S2. Prepare reaction solution B: Add methanol and N,N-dimethylacetamide solution of carbon nanotubes to lithium ferrocyanide aqueous solution and disperse evenly to form reaction solution B; S3. Co-deposition process: The reaction solution B and the reaction solution A are mixed and heated to perform co-deposition, generating carbon nanotube-polypyrrole-Prussian white composite material.
3. The method for preparing carbon nanotube-polypyrrole-Prussian white composite material for lithium-ion batteries according to claim 2, characterized in that, In the preparation of reaction solution A, the concentration of lithium citrate is 0.1–0.3 mmol / mL, the soluble divalent manganese salt is MnCl2, the molar ratio of MnCl2 to N-methylpyrrolidone is 0.1–0.5:10, and the total concentration of added polypyrrole is 1.0–5.0 mg / mL.
4. The method for preparing carbon nanotube-polypyrrole-Prussian white composite material for lithium-ion batteries according to claim 2 or 3, characterized in that, In the preparation step of reaction solution B, the concentration of lithium ferrocyanide in the lithium ferrocyanide aqueous solution is 0.10-0.50 mmol / mL, the volume ratio of methanol to lithium ferrocyanide aqueous solution is 1:1-2, the mass ratio of carbon nanotubes to lithium ferrocyanide is 0.5-5:1000, and the concentration of carbon nanotubes in the N,N-dimethylacetamide solution is 0.1-0.5 mg / mL.
5. The method for preparing carbon nanotube-polypyrrole-Prussian white composite material for lithium-ion batteries according to claim 2 or 3, characterized in that, In the co-deposition process, the reaction temperature is 80-90°C, and the volume ratio of reaction solution A to reaction solution B is 1-4:
1.
6. A positive electrode material for lithium-ion batteries, comprising the preparation method of the carbon nanotube-polypyrrole-Prussian white composite material for lithium-ion batteries as described in claim 1, or the carbon nanotube-polypyrrole-Prussian white composite material obtained by the preparation method of the carbon nanotube-polypyrrole-Prussian white composite material for lithium-ion batteries as described in any one of claims 2 to 5.