Preparation method of axially confined cobalt sulfide and application of axially confined cobalt sulfide in negative electrode of lithium ion battery
By using axial confinement design of carbon nanotubes and a mild hydrothermal-carbonization process, a CoS/CNT heterojunction electrode material was prepared, which solved the problems of volume expansion and polysulfide dissolution in cobalt sulfide anode materials and achieved a lithium-ion battery anode material with high energy density and high stability.
Patent Information
- Application Number
- CN202511170072.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-20
- Publication Date
- 2025-11-21
AI Technical Summary
Cobalt sulfide anode materials in lithium-ion batteries suffer from problems such as volume expansion, polysulfide dissolution, and SEI instability, which affect cycle stability and battery performance.
By employing an axial confinement design of carbon nanotubes, a CoS/CNT heterojunction electrode material was prepared through gradient thermodynamic self-assembly and a mild hydrothermal-carbonization process. This constructed a two-dimensional conductive network and a physical confinement space, which suppressed volume expansion and polysulfide dissolution, and stabilized the SEI film.
The material exhibits significantly improved cycling stability and electrochemical performance. It maintains a high reversible capacity of 461 mAh/g at a rate of 5 A/g, and its coulombic efficiency remains stable at over 98.5% after 2000 cycles. This reduces preparation costs and offers environmental advantages.
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Figure CN120987374A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the field of lithium ion battery negative electrode, and particularly relates to a cobalt sulfide quantum dot controllable self-assembly method based on carbon nanotube axial space constraint effect and application of the material in lithium ion battery. BACKGROUND
[0002] Under the background of global energy transformation and low-carbon economic development, the resource constraints and environmental problems of traditional fossil energy are increasingly prominent, and clean energy and energy storage technology have become a key breakthrough. China's "carbon peak and carbon neutral" goal has accelerated the construction of a new energy system dominated by renewable energy, and the volatility of new energy generation and the popularity of electric vehicles have further highlighted the need for efficient energy storage systems. Lithium ion batteries have become the core technology in the energy storage field due to their high energy density and cycle stability, but they still face challenges in material performance optimization and cost control, especially the innovation of positive and negative materials will determine the development direction of the next generation of energy storage technology.
[0003] Among the current research of lithium ion battery negative materials, transition metal sulfides based on multi-electron conversion reactions are considered as the next generation of lithium ion battery negative candidates due to their high theoretical capacity (nearly twice the theoretical capacity of commercial graphite negative), high voltage platform (can avoid the formation of lithium dendrites), good cycle performance, and environmental friendliness. Researchers have developed a variety of transition metal sulfide materials, such as molybdenum sulfide (MoS2, MoS3), cobalt sulfide (Co9S8, CoS, Co3S4, CoS2), nickel sulfide (NiS, NiS2, Ni3S2, Ni3S4, Ni9S8), zinc sulfide (ZnS), etc. Among them, cobalt sulfides with different stoichiometric compositions have a good application potential in energy storage and conversion systems due to their rich structures and unique electronic properties. Cobalt sulfides have shown superior performance in batteries and supercapacitors in existing research. As an important member of metal sulfides, cobalt sulfide (CoS) has a high theoretical capacity (590 mAh·g -1 ) that can significantly improve the energy density of lithium ion batteries; at the same time, excellent electrical conductivity and fast redox kinetics endow the battery with higher rate performance and cycle stability. From an environmental perspective, CoS is abundant in resources, simple to prepare, and can reduce production costs by more than 30% compared to traditional cobalt-based oxides, and through nanostructure design, it can further reduce heavy metal leaching, in line with the concept of green chemistry.
[0004] However, cobalt sulfide (CoS) anode material still has several key technical bottlenecks in the process of practicalization. The first challenge is the significant volume effect, which produces a huge volume change (-200%) during lithiation / delithiation, easily leading to electrode structure pulverization and seriously affecting the cycle stability. Although nanoization and carbon composite strategies can partially alleviate this problem, these methods often come at the expense of tap density, which restricts the improvement of the volume energy density of the battery. Secondly, the dissolution and shuttle effect of polysulfides leads to the continuous loss of active material, not only reducing the coulombic efficiency, but also causing anode pollution and electrolyte consumption. Although physical confinement and chemical adsorption methods can inhibit the shuttle effect, these modification strategies usually increase the complexity of material preparation. In addition, the interface side reaction between CoS and electrolyte will form an unstable solid-state electrolyte interface (SEI), causing continuous lithium source consumption and impedance growth, which is particularly prominent under high temperature or high rate working conditions. SUMMARY
[0005] Therefore, the technical problem to be solved by the present application is to address the volume expansion of cobalt sulfide, promote electron conduction, and stabilize the SEI film. Through structural regulation and process innovation, a negative electrode material with high energy density and high stability is prepared and applied in lithium ion batteries.
[0006] To this end, the present application provides the following technical solutions:
[0007] (1) Precursor dispersion system: Dissolve cobalt chloride hexahydrate and thiourea in ethylene glycol / deionized water under constant temperature water bath conditions, and continuously stir to form a uniform solution. Add carboxylated carbon nanotubes to the above solution, stir and ultrasonic, to form a uniform suspension.
[0008] (2) Gradient thermodynamic self-assembly: After continuously stirring the above reaction solution for a period of time, quickly transfer the system to a 80ml reaction kettle. After the reaction is completed, the mixed system is allowed to stand for a period of time, then use a suction filtration device to separate the precipitate, and wash with anhydrous ethanol to remove residual reactants. The obtained product is placed in a vacuum drying box to dry, ensuring that the moisture is completely removed.
[0009] (3) Material activation treatment: After drying, the precursor is evenly spread in a magnetic boat and placed in a tube furnace. Under an argon protective atmosphere, constant temperature for a period of time. After the activation process is completed, cool to room temperature, and finally obtain the CoS / CNT anode material.
[0010] 1. The mol ratio of cobalt chloride hexahydrate to thiourea in step (1) is (1:3); the temperature of water bath heating in step (1) is (40-80)℃, the ml ratio of ethylene glycol to deionized water is (2:1), and the carbon nanotube addition amount is 10% of the reaction product.
[0011] 2. The heating rate of the reactor in step (2) is 2-5℃ / min, and the holding time is (10-12)h; the amount of ethylene glycol used in step (2) is (30-40)ml; and the separation method of the product is centrifugation or suction filtration.
[0012] 3. The activation temperature of the tubular furnace in step (3) is 600℃, the heating rate is 2-5℃ / min, and the holding time is 2-4h.
[0013] In another aspect, the present application provides a high-energy and environmentally friendly CoS / CNT heterojunction electrode active material prepared by the above preparation method, and further provides a lithium ion battery negative material, wherein the active material is the CoS / CNT material prepared by the above application method.
[0014] The technical scheme of the present application has the following advantages:
[0015] 1. Alleviate volume expansion: Through the axial confinement design, a two-dimensional conductive network and a physical confinement space are constructed, effectively inhibiting the volume expansion of cobalt sulfide and the dissolution of polysulfide. The confinement effect of carbon nanotubes reduces the material volume expansion rate by more than 60%, significantly improving the cycle stability of the material.
[0016] 2. Strong controllability of preparation process: A mild hydrothermal reaction combined with precise temperature control carbonization process is adopted, and the axial growth size of cobalt sulfide can be precisely controlled by adjusting the precursor concentration and reaction time. The design process is completed at a relatively low temperature (<600℃), avoiding material structure damage caused by high temperature treatment, while ensuring the repeatability and scalability of the process.
[0017] 3. Outstanding electrochemical performance: The unique axial confinement structure provides an efficient lithium ion transmission channel, combined with the conductive network of the matrix, so that the material still maintains a high reversible capacity of 461mAh / g at a rate of 5A / g. After 2000 cycles, the coulombic efficiency is stable at more than 98.5%, showing excellent rate performance and cycle stability.
[0018] 4. Significant cost and environmental advantages: The use of cheap and readily available cobalt salt and sulfur source as precursor, the hydrothermal-carbonization process has low energy consumption, and does not require the use of special equipment or expensive reagents. The entire preparation process only produces water and a small amount of harmless gas, and the waste liquid treatment is simple, with significant environmental advantages and industrialization potential. BRIEF DESCRIPTION OF DRAWINGS
[0019] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.
[0020] Figure 1 is the XRD pattern of CoS / CNT in Example 1 of the present application, CoS in Comparative Example 1;
[0021] Figure 2 is the scanning electron microscope (SEM) pattern of CoS / CNT in Example 1 of the present application;
[0022] Figure 3 is the Raman spectrum pattern of CoS / CNT in Example 1 of the present application;
[0023] Figure 4 is the infrared spectrum pattern of CoS / CNT in Example 1 of the present application;
[0024] Figure 5 is the CV curve pattern of CoS / CNT in Example 1 of the present application at a scan rate of 0.1-1.0 mV / s and the pseudo-capacitance contribution rate;
[0025] Figure 6 is the specific capacity-voltage curve pattern of CoS / CNT material as a negative electrode material for lithium ion battery in Example 1 of the present application at a current density of 0.2 A / g;
[0026] Figure 7 is the cycle stability pattern of CoS / CNT in Example 1 of the present application and CoS in Comparative Example 1 as a negative electrode material for lithium ion battery at a current density of 5 A / g; DETAILED DESCRIPTION
[0027] The following examples are provided to better further understand the present application, and are not limited to the best mode, and do not constitute a limitation on the content and protection scope of the present application. Any person under the inspiration of the present application or the combination of the present application with other prior art features can obtain any product same or similar to the present application, which falls within the protection scope of the present application.
[0028] The specific experimental steps or conditions not mentioned in the examples can be carried out according to the conventional experimental steps described in the literature in the art or the operation or conditions. The reagents or instruments not mentioned by the manufacturer are conventional reagent products that can be obtained by market purchase.
[0029] Example 1
[0030] Example 1 provides a method for preparing CoS / CNT anode material. This method produces anode material with high energy density and high stability, which can be applied in lithium-ion batteries. The specific steps are as follows:
[0031] (4) Precursor dispersion system: Under constant temperature water bath conditions of 60℃, 10 mmol of cobalt chloride hexahydrate and 30 mmol of thiourea were dissolved in 60 ml of ethylene glycol / deionized water and stirred continuously for 1 h to form a homogeneous solution. 0.5 g of carboxylated carbon nanotubes were added to the above solution and stirred and sonicated for 30 min to form a homogeneous suspension.
[0032] (5) Gradient thermodynamic self-assembly: After continuous stirring and sonication of the above reaction solution for 30 min, the system was quickly transferred to an 80 ml reactor, and the temperature was increased at a rate of 5 °C / min; the system was then kept at 120 °C for 12 h. After the reaction was completed, the mixture was allowed to stand for a period of time, and then the precipitate was separated by vacuum filtration and washed with anhydrous ethanol to remove residual reactants. The obtained product was dried in a vacuum drying oven at 60 °C for 12 h to ensure complete removal of moisture.
[0033] (6) Material activation treatment: The dried precursor is evenly spread in a magnetic boat and placed in a tube furnace. Under an argon protective atmosphere, the temperature is programmed to rise to 600℃ at a heating rate of 5℃ / min and held at that temperature for 4 hours.
[0034] Finally, the material was cooled to room temperature to obtain the CoS / CNT anode material.
[0035] Figure 1 These are the XRD patterns of CoS / CNT in Embodiment 1 and CoS in Comparative Example 1 of the present invention;
[0036] Figure 2 This is a scanning electron microscope (SEM) image of CoS / CNT in Embodiment 1 of the present invention;
[0037] Figure 3 This is the Raman spectrum of CoS / CNT in Example 1 of this invention;
[0038] Figure 4 This is the infrared spectrum of CoS / CNT in Embodiment 1 of the present invention;
[0039] The electrochemical performance testing method for the CoS / CNT anode material prepared in Example 1 of this invention is as follows:
[0040] (1) The preparation of the pole piece: the negative pole piece is cut into a pole piece with a diameter of 11 mm by using a 11 mm cutter, the mass thereof is weighed by using a precision balance, and the mass of the active material CoS / CNT is calculated according to the solid raw material ratio of 7:2:1 of the active material: super P: PVDF; the pole piece is taken into an argon atmosphere glove box to assemble a half battery, a negative electrode shell, a lithium sheet with a diameter of 12 mm, a glass fiber diaphragm, 170 ml of electrolyte, an electrode, a 1 mm gasket and a spring are sequentially placed, so that the battery is assembled, the battery is compressed by using a button cell sealing machine, the battery model is CR2032 button cell, and the electrolyte is LiPF6
[0041] / EC:DEC, wherein EC is ethylene carbonate; DEC is diethyl carbonate, the battery is taken out of the glove box, and the electrochemical performance is measured after standing for 24 h.
[0042] (2) Half battery performance test: the charge capacity, the cycle efficiency and the cycle stability of the button cell after 2000 cycles are detected and analyzed on a new battery charge-discharge tester under the conditions that the charge-discharge voltage interval is 0.01-3 V and the current density is 5 A / g constant current charge-discharge. After 2000 cycles, the capacity retention rate can still reach 98.5% or above, and the cycle coulombic efficiency is close to 100%.
[0043] Figure 5 is a CV curve graph and a pseudo-capacitance contribution rate of CoS / CNT at a scanning speed of 0.1-1.0 mV / s in Example 1 of the present application;
[0044] Figure 6 is a specific capacity-voltage curve graph of the CoS / CNT material as a negative electrode material of a lithium ion battery at a current density of 0.2 A / g in Example 1 of the present application;
[0045] Figure 7 is a cycle stability graph of CoS / CNT and CoS as a negative electrode material of a lithium ion battery at a current density of 5 A / g in Example 1 of the present application and Comparative Example 1;
[0046] Example 2
[0047] Example 2 provides a preparation method of a CoS / CNT negative electrode material, the method prepares a negative electrode material with high energy density and high stability and is applied in a lithium ion battery, and the specific steps are as follows:
[0048] (1) Precursor dispersion system: 15 mmol of cobalt chloride hexahydrate and 45 mmol of thiourea are dissolved in 60 ml of ethylene glycol / deionized water under the condition of a 60℃ constant temperature water bath, and are continuously stirred for 1 h to form a uniform solution. 0.5 g of carboxylated carbon nanotubes is added to the solution, and is stirred and ultrasonically treated for 30 min to form a uniform suspension.
[0049] (2) Gradient thermodynamic self-assembly: After the above reaction solution is continuously stirred and ultrasonicated for 30 min, the system is quickly transferred to an 80 ml reaction kettle, the heating rate is 5°C / min; and the temperature is kept at 120°C for 12 h. After the reaction is completed, the mixed system is allowed to stand for a period of time, then a suction filtration device is used to separate the precipitate, and anhydrous ethanol is used for washing to remove residual reactants. The obtained product is placed in a 60°C vacuum drying box for drying for 12 h to ensure complete removal of water.
[0050] (3) Material activation treatment: The dried precursor is uniformly laid in a magnetic boat and placed in a tube furnace. Under an argon protective atmosphere, the temperature is programmed to rise to 600°C at a rate of 5°C / min, and kept constant for 4 h.
[0051] Finally, it is cooled to room temperature, and finally a CoS / CNT negative electrode material is obtained.
[0052] Example 3
[0053] Example 3 provides a preparation method of a CoS / CNT negative electrode material, which prepares a negative electrode material with high energy density and high stability and is applied in a lithium ion battery, and the specific steps are as follows:
[0054] (1) Precursor dispersion system: Under the condition of a 40°C constant temperature water bath, 10 mmol of cobalt chloride hexahydrate and 30 mmol of thiourea are dissolved in 60 ml of ethylene glycol / deionized water, and stirred for 1 h to form a uniform solution. 0.5 g of carboxylated carbon nanotubes is added to the above solution, stirred and ultrasonicated for 30 min to form a uniform suspension.
[0055] (2) Gradient thermodynamic self-assembly: After the above reaction solution is continuously stirred and ultrasonicated for 30 min, the system is quickly transferred to an 80 ml reaction kettle, the heating rate is 5°C / min; and the temperature is kept at 120°C for 12 h. After the reaction is completed, the mixed system is allowed to stand for a period of time, then a suction filtration device is used to separate the precipitate, and anhydrous ethanol is used for washing to remove residual reactants. The obtained product is placed in a 60°C vacuum drying box for drying for 12 h to ensure complete removal of water.
[0056] (3) Material activation treatment: The dried precursor is uniformly laid in a magnetic boat and placed in a tube furnace. Under an argon protective atmosphere, the temperature is programmed to rise to 600°C at a rate of 5°C / min, and kept constant for 4 h.
[0057] Finally, it is cooled to room temperature, and finally a CoS / CNT negative electrode material is obtained.
[0058] Example 4
[0059] Example 4 provides a preparation method of CoS / CNT negative electrode material, which prepares a negative electrode material with high energy density and high stability and applies it in a lithium ion battery. The specific steps are as follows:
[0060] (1) Precursor dispersion system: 10 mmol of cobalt chloride hexahydrate and 30 mmol of thiourea were dissolved in 60 ml of ethylene glycol / deionized water under the condition of a constant temperature water bath at 80°C, and stirred constantly for 1 h to form a uniform solution. 0.5 g of carboxylated carbon nanotubes was added to the above solution, stirred and ultrasonicated for 30 min to form a uniform suspension.
[0061] (2) Gradient thermodynamic self-assembly: after the above reaction solution was continuously stirred and ultrasonicated for 30 min, the system was quickly transferred to an 80 ml reaction kettle, the heating rate was 5°C / min, and the temperature was kept at 120°C for 12 h. After the reaction was completed, the mixed system was allowed to stand for a period of time, then a suction filtration device was used to separate the precipitate, and anhydrous ethanol was used for washing to remove residual reactants. The obtained product was placed in a 60°C vacuum drying oven for drying for 12 h to ensure complete removal of water.
[0062] (3) Material activation treatment: the dried precursor was evenly spread in a magnetic boat and placed in a tube furnace. Under the protection of argon atmosphere, the temperature was programmed to rise to 600°C at a rate of 5°C / min, and kept constant for 4 h.
[0063] Finally, it was cooled to room temperature, and finally the CoS / CNT negative electrode material was obtained.
[0064] Example 5
[0065] Example 5 provides a preparation method of CoS / CNT negative electrode material, which prepares a negative electrode material with high energy density and high stability and applies it in a lithium ion battery. The specific steps are as follows:
[0066] (1) Precursor dispersion system: 10 mmol of cobalt chloride hexahydrate and 30 mmol of thiourea were dissolved in 60 ml of ethylene glycol / deionized water under the condition of a constant temperature water bath at 60°C, and stirred constantly for 1 h to form a uniform solution.
[0067] 0.5 g of carboxylated carbon nanotubes was added to the above solution, stirred and ultrasonicated for 2 h to form a uniform suspension.
[0068] (3) Material activation treatment: After drying, the precursor was evenly laid in a magnetic boat and placed in a tube furnace. Under an argon protective atmosphere, the temperature was programmed to rise to 600°C at a rate of 5°C / min, and kept constant for 4h.
[0069] Finally, it was cooled to room temperature, and finally a CoS / CNT negative electrode material was obtained.
[0070] Example 6
[0071] Example 6 provides a preparation method of a CoS / CNT negative electrode material, which prepares a negative electrode material with high energy density and high stability and is applied in a lithium ion battery, and the specific steps are as follows:
[0072] (1) Precursor dispersion system: Under the condition of a 60°C constant temperature water bath, 10mmol of cobalt chloride hexahydrate and 30mmol of thiourea were dissolved in 60ml of ethylene glycol / deionized water, and stirred for 1h to form a uniform solution. 0.5g of carboxylated carbon nanotubes was added to the above solution, stirred and ultrasonicated for 30min to form a uniform suspension.
[0073] (2) Gradient thermodynamic self-assembly: After continuous stirring and ultrasonication for 30min, the system was quickly transferred to an 80ml reaction kettle, and the temperature was raised at a rate of 3°C / min; kept at 120°C for 12h. After the reaction was completed, the mixed system was allowed to stand for a period of time, then an extraction filtration device was used to separate the precipitate, and anhydrous ethanol was used for washing to remove residual reactants. The obtained product was placed in a 60°C vacuum drying oven for drying for 12h to ensure complete removal of water.
[0074] (3) Material activation treatment: After drying, the precursor was evenly laid in a magnetic boat and placed in a tube furnace. Under an argon protective atmosphere, the temperature was programmed to rise to 600°C at a rate of 5°C / min, and kept constant for 4h.
[0075] Finally, it was cooled to room temperature, and finally a CoS / CNT negative electrode material was obtained.
[0076] Example 7
[0077] Example 7 provides a preparation method of a CoS / CNT negative electrode material, which prepares a negative electrode material with high energy density and high stability and is applied in a lithium ion battery, and the specific steps are as follows:
[0078] (1) Precursor dispersion system: Under the condition of a 60°C constant temperature water bath, 10mmol of cobalt chloride hexahydrate and 30mmol of thiourea were dissolved in 60ml of ethylene glycol / deionized water, and stirred for 1h to form a uniform solution. 0.5g of carboxylated carbon nanotubes was added to the above solution, stirred and ultrasonicated for 30min to form a uniform suspension.
[0079] (2) Gradient thermodynamic self-assembly: After the above reaction solution is continuously stirred for 30 min, the system is quickly transferred to a 80 ml reaction kettle, and the temperature is raised at a rate of 5 ℃ / min; the temperature is kept at 120 ℃ for 16 h. After the reaction is completed, the mixed system is allowed to stand for a period of time, then the precipitate is separated by using a suction filtration device, and washed with anhydrous ethanol to remove residual reactants. The obtained product is placed in a 60 ℃ vacuum drying oven for 12 h to ensure complete removal of moisture.
[0080] (3) Material activation treatment: The dried precursor is uniformly laid in a magnetic boat and placed in a tube furnace. Under the protection of argon atmosphere, the temperature is programmed to rise to 600 ℃ at a rate of 5 ℃ / min, and kept constant for 4 h.
[0081] Finally, it is cooled to room temperature, and finally the CoS / CNT negative electrode material is obtained.
[0082] The example is explained:
[0083] By changing the amount of cobalt chloride hexahydrate used in step (1) of Example 2, it is found that when the ratio of reactants changes within a reasonable range, the excess precursor can increase the loading capacity, but does not significantly affect the electrochemical performance of the material. This is mainly due to the fact that excess cobalt ions form soluble complexes in the sulfidation reaction, which are efficiently removed through the stepwise alcohol washing process. At the same time, the one-dimensional confined channels of carbon nanotubes produce a steric hindrance effect, which inhibits the excessive growth of cobalt sulfide lattice, ensuring the uniformity of particle size. This dual mechanism allows the material component concentration to be strictly controlled at the thermodynamic equilibrium point.
[0084] By changing the water bath heating temperature in step (1) of Example 3 and Example 4 in the range of 40-80 ℃, it is found that temperature change has multiple effects on the reaction system: on the one hand, the increase of temperature significantly improves the solubility of the reactants in the solvent, which reduces the amount of deionized water and ethylene glycol required in the subsequent process. On the other hand, the increase of temperature effectively accelerates the reaction kinetics, which significantly shortens the reaction time. It is worth noting that the increase of temperature will lead to the agglomeration tendency of the trace amount of suspended particles formed in the solution, but under the action of continuous mechanical stirring (600 rpm), the internal convection of the solution effectively inhibits the further growth of the particles, so it does not have a significant impact on the electrochemical performance of the final product.
[0085] By changing the stirring and mixing time in step (2) of Example 5, it can be found that the extension of the stirring reaction time helps to increase the convection and reduce the occurrence of particle agglomeration, making the solution more uniformly mixed. Although the improvement of electrochemical performance is limited, it helps to improve the consistency of the product.
[0086] The material activation purposes can be achieved by changing the temperature rising rate and prolonging the constant temperature time in a certain range in step (3) of Example 6 and Example 7, the rate reduction significantly enhances the directional self-assembly effect of the precursor ions in the space limited by the carbon tube, and the highly crystalline cobalt sulfide nucleus is induced to form; and the fast temperature rising causes the transient nucleation disorder due to the thermal shock, but the crystal defect self-repair is realized through the atomic rearrangement mechanism dominated by the Brownian motion in the subsequent constant temperature stage. The dynamic balance process makes the different temperature rising paths finally tend to the same thermodynamic stable state. The research on prolonging the constant temperature time reveals that the material system has an intrinsic evolution saturation point: the 12-hour hydrothermal cycle has driven the cobalt sulfide to complete the complete dynamic process from nucleation, growth to surface energy minimization, and the continued prolongation of time only triggers the surface atom micro-oscillation, and cannot change the bulk phase lattice periodicity and the carbon tube-cobalt sulfide interface electron coupling strength. The double stable mechanisms limited by the quantum size effect and the interface chemical bond saturation ensure the constancy of the electrochemical performance parameters.
[0087] Comparative Example 1
[0088] Comparative Example 1 provides a preparation method of a CoS / CNT negative electrode material, and the specific steps are as follows:
[0089] (1) The CoS / CNT negative electrode material is placed in a 60℃ vacuum drying box for drying for 12h to ensure that the material is dry. (2) Material activation treatment: the dried precursor is uniformly laid in a magnetic boat and placed in a tube furnace.
[0090] Under the protection of an argon atmosphere, the temperature is programmed to rise to 600℃ at a rate of 5℃ / min, and the temperature is kept constant for 4h. Finally, it is cooled to room temperature, and finally the CoS / CNT negative electrode material is obtained.
[0091] Figure 1 is the XRD pattern of CoS / CNT in Example 1 and CoS in Comparative Example 1 of the present application.
[0092] Figure 7 is the cycle stability diagram of CoS / CNT in Example 1 and CoS in Comparative Example 1 as a lithium ion battery negative electrode material at a current density of 5A / g;
[0093] Comparative Example:
[0094] Comparative Example 1 used activated CoS as an anode material and found that its initial capacity was less than 600 mAh / g, and the cycle capacity at a current density of 5 A / g was only 100 mAh / g. The performance defects were due to the combined effects of three mechanisms: electronic conduction blockage - lack of a continuous conductive network between isolated CoS particles, high charge transfer impedance, leading to low active material utilization; volume expansion during charging and discharging caused the particles to crumble, blocking the lithium ion diffusion path; structural dissolution collapse - polysulfide intermediates dissolved in the electrolyte, these limiting factors together caused the rate performance and cycle stability to be significantly worse than the carbon nanotube confined composite material.
[0095] Obviously, the above examples are only examples for clearly illustrating the present application, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can also be made by those of ordinary skill in the art. Here, it is not necessary and impossible to enumerate all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.
Claims
1. A hydrothermal in-situ growth strategy was adopted to induce the axially ordered assembly of cobalt sulfide within carbon nanotubes through sulfur source pyrolysis, constructing a heterojunction composite structure with dual continuous electron-ion transport channels. The specific steps are as follows: (1) Precursor dispersion system: Under constant temperature water bath conditions, cobalt chloride hexahydrate and thiourea were dissolved in ethylene glycol / deionized water and stirred continuously to form a homogeneous solution. Carboxylated carbon nanotubes were added to the above solution and stirred and sonicated to form a homogeneous suspension. (2) Gradient thermodynamic self-assembly: After the above reaction solution was continuously stirred for a period of time, the system was quickly transferred to an 80 ml reaction vessel. After the reaction was completed, the mixture was allowed to stand for a period of time, and then the precipitate was separated by a vacuum filtration device and washed with anhydrous ethanol to remove residual reactants. The obtained product was placed in a vacuum drying oven to dry, ensuring that the moisture was completely removed. (3) Material activation treatment: The dried precursor was evenly spread in a magnetic boat and placed in a tube furnace. Under an argon protective atmosphere, it was kept at a constant temperature for a period of time. After the activation process was completed, it was cooled to room temperature to finally obtain the CoS / CNT anode material.
2. The preparation method according to claim 1, characterized in that, In step (1), the mol ratio of cobalt chloride hexahydrate to thiourea is (1:3); the water bath heating temperature in step (1) is (40-80)℃, the ml ratio of ethylene glycol to deionized water is (2:1), and the amount of carbon nanotubes added is 10% of the reaction product.
3. The preparation method according to claim 1 or 2, characterized in that, In step (2), the heating rate of the reactor is 2-5℃ / min, and the holding time is (10-12)h; the amount of ethylene glycol used in step (2) is (30-40)ml; the product is separated by centrifugation or vacuum filtration.
4. The preparation method according to claims 1-3, characterized in that, In step (3), the activation temperature of the tubular furnace is 600℃, the heating rate is 2-5℃ / min, and the holding time is 2-4h.
5. A CoS / CNT heterojunction anode material prepared by the preparation method according to any one of claims 1 to 4.
6. The application of the CoS / CNT heterojunction anode active material prepared by the preparation method according to any one of claims 1 to 4 or the CoS / CNT heterojunction anode material according to claim 5 in the anode of a lithium-ion battery.