Three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanometer porous cage lithium ion battery negative electrode and preparation method thereof

Abstract

The invention provides a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nano-porous cage lithium ion battery electrode which is composed of carbon cloth, a metal nickel layer and cobalt sulfide, the metal nickel layer is a current collecting layer formed by wrapping the surface of the carbon cloth through electro-deposition, the carbon cloth is wrapped by the metal nickel layer, and the cobalt sulfide layer is a current collecting layer formed by wrapping the metal nickel layer on the surface of the carbon cloth. And cobalt sulfide forms a cobalt sulfide layer with a porous cage structure on the surface of the carbon cloth wrapped by the nickel layer. The invention also provides a preparation method of the three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nano porous cage lithium ion battery electrode. The production process of the negative electrode of the lithium ion battery can be simplified, the active components are prevented from falling off in the charging and discharging process of the lithium ion battery, and the first coulombic efficiency, the cycle performance and the rate capability of the negative electrode of the lithium ion battery are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the field of lithium ion battery negative electrodes and relates to a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage lithium ion battery negative electrode and a preparation method thereof. Background Art

[0002] As one of the representatives of current advanced energy storage technologies, lithium-ion batteries are widely used in various industrial products such as portable electronic devices and electric vehicles due to their high energy / power density, long cycle life, and eco-friendliness. With the rapid development of smart mobile electronics and new energy industries, higher requirements are placed on the energy / power density and reliability of LIBs. Currently, the mainstream choice for commercial lithium-ion battery anodes is still graphite-based materials, which have a limited theoretical specific capacity of only 372 mAh g -1 ). Therefore, in order to overcome the shortcomings of traditional graphite and meet the ever-increasing performance requirements, many people are working hard to find alternative non-carbon materials. In recent years, transition metal sulfides have been regarded as highly promising candidate materials for lithium-ion battery anodes. Among all transition metal sulfides, cobalt sulfide has a high capacity of 590 mAh g -1 Their high theoretical specific capacity, suitable lithium insertion potential, and good micro-nanostructure diversity have attracted widespread attention. Although transition metal sulfides have very attractive capacity advantages, directly using transition metal sulfides as negative electrode materials for lithium-ion batteries will inevitably reduce the battery's rate performance and cycle stability due to their low ion transport kinetics, low conductivity, and volume changes during charge and discharge.

[0003] Yingbin Tan et al. reported the development of a CoS / rGO nanocomposite as a high-performance lithium-ion battery anode (ACS Appl. Mater. Interfaces 2016, 8, 23, 14488–14493). A hydrothermal process forms metal hydroxides on the surface of the rGO matrix, which then react with sulfur powder to form metal sulfides, which are uniformly distributed across the rGO network. The metal sulfide nanomaterials, free of significant agglomeration, are uniformly dispersed across the rGO network, forming a flaky composite structure. The CoS / rGO nanocomposite was prepared by mixing it with carbon black and 5 wt% polyvinylidene fluoride (PVDF) to form a slurry. The slurry contained 80 wt%, 10 wt%, and 10 wt%, respectively. The slurry was coated onto copper foil and vacuum-dried for 8 hours to produce a lithium-ion battery anode.

[0004] The method and the lithium-ion battery negative electrode prepared by the method have the following deficiencies: (1) Since a binder is used in the preparation of the lithium-ion battery negative electrode to bond the CoS / rGO nanocomposite material and carbon black to the copper foil, the binder itself is not conductive and will hinder electron transmission, increase electrode polarization and impedance, and have poor rate performance; (2) During the charge and discharge process of the lithium-ion battery, the insertion and extraction of lithium ions will cause huge volume changes. The lithium-ion battery negative electrode prepared by this method does not have the structural ability to effectively buffer the volume changes during the charge and discharge process. The binding force between the active components bonded by the binder and between the active components and the copper foil is also relatively limited, which can easily cause the active components to fall off and fail during the huge volume changes during charge and discharge. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode and its preparation method, so as to simplify the production process of lithium-ion battery negative electrode, avoid the active components from falling off during the charging and discharging process of lithium-ion battery, and effectively improve the cycle performance and rate performance of lithium-ion battery negative electrode.

[0006] The three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode provided by the present invention is composed of a flexible carbon cloth, a metal nickel layer and cobalt sulfide. The metal nickel layer is a continuous metal layer deposited on the surface of the flexible carbon cloth. The metal nickel layer wraps the flexible carbon cloth, and the cobalt sulfide forms a cobalt sulfide layer with a nano hollow cage structure on the surface of the flexible carbon cloth wrapped by the metal nickel layer.

[0007] In the above-mentioned technical solution of the three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode, the preferred thickness of the metal nickel layer is 50~200 nm.

[0008] In the above-mentioned technical solution of three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode, the particle size of the cobalt-based metal organic framework ZIF-67 zeolite imidazole framework precursor is preferably 200 nm~2 μm.

[0009] In the above-mentioned technical solution of the three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode, the particle size of the cobalt sulfide hollow nanoporous cage is preferably 200 nm~2 μm.

[0010] In the above-mentioned technical solution of the three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode, the carbon cloth wrapped with the metal nickel layer serves as the current collector to improve the conductivity of the negative electrode, and cobalt sulfide serves as the lithium storage active material.

[0011] The present invention also provides a method for preparing the above-mentioned three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode, the steps of which are as follows:

[0012] (1) The carbon cloth was ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for half an hour, and then vacuum dried. The cleaned carbon cloth was then immersed in a mixed solution of concentrated nitric acid and concentrated sulfuric acid and subjected to hydrophilic treatment at 80°C for 3 hours. After removal, it was washed with anhydrous ethanol and deionized water and vacuum dried to obtain the pretreated carbon cloth.

[0013] The carbon cloth model is W0S1011, and the volume ratio of concentrated nitric acid to concentrated sulfuric acid in the mixed solution is 3:1;

[0014] (2) Immersing the pretreated carbon cloth obtained in step (1) in a mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid, using the pretreated carbon cloth as a working electrode, a platinum sheet as a counter electrode, and a saturated calomel electrode as a reference electrode in a three-electrode system at 60°C, the pretreated carbon cloth is used as a working electrode, the platinum sheet is used as a counter electrode, and the saturated calomel electrode is used as a reference electrode. Under the voltage condition of 1.8 V, a constant temperature and constant voltage electrodeposition reaction is carried out at 60°C for 60 s. During the electrodeposition reaction, a metal nickel layer grows on the surface of the carbon cloth. After the reaction is completed by stirring, a current collector is obtained.

[0015] In the above preparation method, in the mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid, the concentration of ethylenediamine dihydrochloride is 1.5-2 mol / L, the concentration of nickel chloride hexahydrate is 0.8-1.2 mol / L, and the concentration of boric acid is 0.3-0.7 mol / L.

[0016] (3) The current collector obtained in step (2) is immersed in a mixed anhydrous ethanol-deionized water solution containing 2-methylimidazole and cobalt chloride hexahydrate. In a three-electrode system, the prepared current collector is used as a working electrode, a platinum sheet is used as a counter electrode, and a saturated calomel electrode is used as a reference electrode. Under the condition of 3 V voltage, constant temperature and constant voltage deposition are carried out at 30°C for 300 s. During the deposition process, a ZIF-67 zeolite imidazole framework grows on the surface of the current collector. After the electrodeposition process is completed, a precursor is obtained.

[0017] (4) The precursor obtained in step (3) is immersed in a mixed solution of anhydrous ethanol and deionized water containing sodium sulfide nonahydrate, and subjected to a chemical sulfidation reaction at a constant temperature of 60°C for 120 min. During the reaction, the ZIF-67 zeolite imidazole framework reacts in situ to form cobalt sulfide, thereby preparing a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage.

[0018] In the above preparation method, in the mixed solution of 2-methylimidazole and cobalt chloride hexahydrate in ethanol and water, the concentration of 2-methylimidazole is 0.6-1 mol / L, and the concentration of cobalt chloride hexahydrate is 0.08-0.16 mol / L.

[0019] In step (4) of the above preparation method, the concentration of sodium sulfide nonahydrate in the mixed solution of anhydrous ethanol and deionized water is 1.5-2 mg / mL, and the preferred reaction time is 60-120 min.

[0020] In the above preparation method, the concentrations of the components in the mixed solution of 2-methylimidazole and cobalt chloride hexahydrate in ethanol and water, the time, voltage and temperature of the electrodeposition reaction in step (3) will affect the crystal structure and quantity of the cobalt-based metal organic framework grown on the surface of the carbon cloth wrapped with the metal nickel layer, and further affect the thickness and micromorphology of the cobalt sulfide layer formed in situ after the chemical sulfurization reaction in step (4).

[0021] In step (1) of the above preparation method, the vacuum drying temperature does not exceed 100°C.

[0022] In the three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode provided by the present invention, cobalt sulfide is a lithium storage active material, and the carbon cloth wrapped in a nickel layer mainly plays the role of improving the conductivity of the electrode. The negative electrode uses a carbon cloth wrapped in a nickel layer as a substrate and cobalt sulfide as a lithium storage active material. The hollow nanoporous cage structure can effectively alleviate the volume expansion effect generated by the lithium-ion battery during the charge and discharge process. The cobalt sulfide layer is formed by sulfurizing a cobalt-based metal organic framework grown on the surface of the carbon cloth wrapped in a nickel layer. The cobalt-based metal organic framework has a hollow nanoporous cage structure. The nanoporous cage structure will grow into the carbon cloth wrapped in a nickel layer, and partially overlap and intersperse with the carbon cloth wrapped in a nickel layer. Therefore, the cobalt sulfide hollow nanoporous cage and the carbon cloth wrapped in a nickel layer are stably combined without the use of a binder, which is conducive to increasing the binding force between the active substances and between the active substances and the substrate, so that the active substances and carbon are not easy to fall off from the substrate. Furthermore, the hollow nanoporous cage structure of cobalt sulfide results in a larger specific surface area for the negative electrode of a lithium-ion battery, which helps provide more active sites for the embedding of lithium ions. This also allows the electrolyte to easily penetrate the gaps in the negative electrode, allowing for more complete contact between the electrolyte and the negative electrode. The combined effect of these factors gives the negative electrode provided by the present invention a significant advantage in specific capacity over existing materials, with lower irreversible capacity, excellent cycle stability, and superior rate performance.

[0023] Compared with the prior art, the present invention produces the following beneficial technical effects:

[0024] 1. The three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode provided by the present invention is composed of carbon cloth, a metal nickel layer, and cobalt sulfide. The metal nickel layer wraps the carbon cloth, and the cobalt sulfide forms a cobalt sulfide layer with a hollow nanocage structure on the outer surface of the carbon cloth wrapped by the metal nickel layer. The hollow nanoporous cage structure in the negative electrode can effectively buffer the volume expansion generated by the lithium-ion battery during the charge and discharge process, so the cobalt sulfide layer is not easy to fall off due to the huge volume expansion during the charge and discharge process. At the same time, the cobalt sulfide layer is formed by carbonization of the cobalt-based metal organic framework grown on the surface of the carbon cloth wrapped by the metal nickel layer. The cobalt sulfide layer is stably combined with the carbon cloth wrapped by the metal nickel layer, which is conducive to increasing the binding force between the active materials and between the active materials and the substrate, making the cobalt sulfide layer not easy to fall off. The lithium-ion battery negative electrode with a nano hollow cage structure has a large specific surface area, which can provide more active sites for the embedding of lithium ions, while making it easy for the electrolyte to penetrate into the gap of the negative electrode and contact the negative electrode more fully. The above factors are all conducive to improving the cycle stability of the negative electrode.

[0025] 2. The three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode provided by the present invention does not require the use of a binder, and the components have a high bonding force and extremely low interface resistance. Compared with the existing technology using a binder, the negative electrode provided by the present invention does not hinder electron transmission, increase electrode polarization and impedance due to the presence of the binder, and has excellent cycle performance and rate performance. At the same time, the specific capacity of the negative electrode is also advantageous over existing materials, and the irreversible capacity is low.

[0026] 3. The negative electrode provided by the present invention is assembled into a lithium ion battery, and the charge and discharge current density is 1 mA / cm 2 After 240 cycles under the conditions of , the capacity shows almost no attenuation and maintains a high specific capacity. At the same time, the coulombic efficiency is stabilized at more than 95% after 10 cycles, with very excellent cycle performance and very good capacity retention at different rates. At the same time, the battery negative electrode prepared by the method of the present invention has good capacity performance.

[0027] 4. The preparation process of the three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode provided by the present invention is simpler than the existing technology, has no special requirements for production equipment and process conditions, and is easy to achieve large-scale production and popularize and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a SEM photograph of the CC / Ni current collector prepared in Example 1.

[0029] Figure 2 This is a SEM photograph of the surface of the precursor prepared in Example 1.

[0030] Figure 3is the XRD spectrum of the precursor prepared in Example 1.

[0031] Figure 4 This is a SEM photograph of the negative electrode surface prepared in Example 1.

[0032] Figure 5 This is the constant current charge and discharge cycle performance curve of the lithium ion battery prepared in Example 1.

[0033] Figure 6 This is the rate performance curve of the lithium-ion battery prepared in Example 1.

[0034] Figure 7 This is a SEM photograph of the negative electrode surface prepared in Example 2.

[0035] Figure 8 This is the constant current charge and discharge cycle performance curve of the lithium ion battery prepared in Example 2.

[0036] Figure 9 This is a SEM photograph of the negative electrode surface prepared in Example 3.

[0037] Figure 10 This is a SEM photograph of the negative electrode surface prepared in Example 4. DETAILED DESCRIPTION

[0038] The following examples further illustrate the three-dimensional flexible, self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage anode and its preparation method provided by the present invention. It is important to note that the following examples are intended only to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by persons skilled in the art based on the above disclosure and implemented in accordance with the present invention remain within the scope of protection of the present invention.

[0039] Example 1

[0040] In this embodiment, a method for preparing a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode is provided, and the steps are as follows:

[0041] (1) W0S1011 carbon cloth was ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for half an hour, followed by vacuum drying. The cleaned carbon cloth was then immersed in a mixed solution of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1 and subjected to hydrophilic treatment at 80°C for 3 hours. After removal, it was washed with anhydrous ethanol and deionized water and vacuum dried to obtain a pretreated carbon cloth.

[0042] (2) 90 mmol of ethylenediamine dihydrochloride, 50 mmol of nickel chloride hexahydrate and 25 mmol of boric acid were dissolved in 50 mL of deionized water to form a mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid. The pretreated carbon cloth obtained in step (1) was immersed in the mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid. The pretreated carbon cloth was used as a working electrode, a platinum sheet was used as a counter electrode, and a saturated calomel electrode was used as a reference electrode in a three-electrode system at 60°C. The electrodeposition reaction was carried out at a constant temperature of 60°C and a constant voltage of 1.8 V for 60 s. During the electrodeposition reaction, the metal nickel layer was wrapped around the outer surface of the carbon cloth to form a metal nickel layer-wrapped carbon cloth. After the reaction was completed, a current collector was obtained.

[0043] (3) 40 mmol of 2-methylimidazole and 5 mmol of cobalt chloride hexahydrate were dissolved in 50 ml of a mixed solution of anhydrous ethanol and deionized water in a volume ratio of 4:1 to form a mixed anhydrous ethanol-deionized water solution of 2-methylimidazole and cobalt chloride hexahydrate. The current collector obtained in step (2) was immersed in the mixed anhydrous ethanol-deionized water solution containing 2-methylimidazole and cobalt chloride hexahydrate. In a three-electrode system, the prepared current collector was used as the working electrode, the platinum sheet was used as the counter electrode, and the saturated calomel electrode was used as the reference electrode. Under the condition of 3 V voltage, constant temperature and constant voltage deposition were carried out at 30°C for 300 s. During the deposition process, a ZIF-67 zeolite imidazole framework grew on the surface of the current collector. After the electrodeposition process was completed, the precursor was obtained.

[0044] (4) 50 mg of sodium sulfide nonahydrate was dissolved in 30 ml of a mixed solution of anhydrous ethanol and deionized water with a volume ratio of 5:1 to form a mixed anhydrous ethanol-deionized water solution of sodium sulfide nonahydrate. The solution was subjected to a chemical sulfurization reaction at a constant temperature of 60°C for 120 min. At this time, the cobalt-based metal organic framework was sulfurized to form cobalt sulfide, and the cobalt sulfide layer was stacked to form a cobalt sulfide layer on the outer surface of the carbon cloth wrapped with the metal nickel layer. After rinsing with deionized water and anhydrous ethanol and drying, a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage electrode was obtained.

[0045] Figure 1 This is a SEM photo of the metal nickel layer wrapped carbon cloth prepared in step (1) of this embodiment. Figure 1 It can be seen that the metal nickel layer deposited in step (2) is continuously and evenly wrapped on the surface of the carbon cloth, and the thickness of the metal nickel layer is 100 nm. Figure 2 is a SEM photo of the precursor obtained in step (3) of this embodiment. Figure 2 The block-shaped substance in the figure is a cobalt-based metal-organic framework grown on the surface of carbon cloth wrapped with a metal nickel layer. The size of the cobalt-based metal-organic framework is about 1 μm. Figure 3 is the XRD spectrum of the precursor. Figure 4The three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage electrode is obtained after calcination in step (4) of this embodiment. Figure 4 It can be seen that after the calcination in step (4), the cobalt-based metal organic framework is sulfurized to form a cobalt sulfide layer having a hollow porous cage structure similar to a cube shape. The size of the cobalt sulfide hollow nanoporous cage is about 1 μm.

[0046] The negative electrode prepared in this example was used to make a lithium-ion battery and its performance was tested.

[0047] A lithium-ion battery was assembled in a glove box filled with argon and containing water and oxygen contents below 1 ppm, using a metal lithium sheet as the counter electrode, the negative electrode prepared in this example as the working electrode, microporous polypropylene as the separator, and a mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) containing 1 M lithium hexafluorophosphate (LiPF6) as the electrolyte. The electrolyte had a volume ratio of 1:1:1 for EC, DMC, and DEC. The battery was tested using a NEWARE BTS-610 constant current charge and discharge instrument at a current density of 1 mA / cm 2 , voltage range is 0.01~ 3 V(vs. Li / Li + ), the test temperature is room temperature. The test results are as follows Figure 5 As shown by Figure 5 It can be seen that the lithium-ion battery assembled with the lithium-ion battery negative electrode of this embodiment has a charge and discharge current density of 1 mA / cm 2 The capacity of the battery is almost unchanged after 240 cycles under the condition of 1~8 mA / cm2, and the coulombic efficiency is stable at more than 95% after 10 cycles. 2 The rate performance of the lithium ion battery prepared in Example 1 was tested by cycling 160 times within the range of Figure 6 As shown by Figure 6 It can be seen that the lithium-ion battery assembled using the negative electrode of this embodiment has a very good capacity retention rate at different current densities. Figures 5 and 6 It can also be seen that the negative electrode provided in this embodiment has a high specific capacity and reversible capacity retention rate. This shows that the three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode prepared by the method of the present invention has excellent cycle stability and rate performance.

[0048] Example 2

[0049] In this embodiment, a method for preparing a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode is provided, and the steps are as follows:

[0050] (1) W0S1011 carbon cloth was ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for half an hour, followed by vacuum drying. The cleaned carbon cloth was then immersed in a mixed solution of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1 and subjected to hydrophilic treatment at 80°C for 3 hours. After removal, it was washed with anhydrous ethanol and deionized water and vacuum dried to obtain a pretreated carbon cloth.

[0051] (2) 80 mmol of ethylenediamine dihydrochloride, 40 mmol of nickel chloride hexahydrate and 20 mmol of boric acid were dissolved in 50 mL of deionized water to form a mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid. The pretreated carbon cloth obtained in step (1) was immersed in the mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid. The pretreated carbon cloth was used as a working electrode, a platinum sheet was used as a counter electrode, and a saturated calomel electrode was used as a reference electrode in a three-electrode system at 60°C. The electrodeposition reaction was carried out at a constant temperature of 60°C and a constant voltage of 1.8 V for 60 s. During the electrodeposition reaction, the metal nickel layer was wrapped around the outer surface of the carbon cloth to form a metal nickel layer-wrapped carbon cloth. After the reaction was completed, a current collector was obtained.

[0052] (3) 30 mmol 2-methylimidazole and 7.5 mmol cobalt chloride hexahydrate were dissolved in 50 ml of a mixed solution of anhydrous ethanol and deionized water in a volume ratio of 4:1 to form a mixed anhydrous ethanol-deionized water solution of 2-methylimidazole and cobalt chloride hexahydrate. The current collector obtained in step (2) was immersed in the mixed anhydrous ethanol-deionized water solution containing 2-methylimidazole and cobalt chloride hexahydrate. In a three-electrode system, the prepared current collector was used as the working electrode, the platinum sheet was used as the counter electrode, and the saturated calomel electrode was used as the reference electrode. Under the condition of 3 V voltage, constant temperature and constant voltage deposition were carried out at 30°C for 300 s. During the deposition process, a ZIF-67 zeolite imidazole framework grew on the surface of the current collector. After the electrodeposition process was completed, the precursor was obtained.

[0053] (4) 45 mg of sodium sulfide nonahydrate was dissolved in 30 ml of a mixed solution of anhydrous ethanol and deionized water with a volume ratio of 5:1 to form a mixed anhydrous ethanol-deionized water solution of sodium sulfide nonahydrate. The solution was subjected to a chemical sulfurization reaction at a constant temperature of 60°C for 90 min. At this time, the cobalt-based metal organic framework was sulfurized to form cobalt sulfide, and the cobalt sulfide layer was stacked to form a cobalt sulfide layer on the outer surface of the carbon cloth wrapped with the metal nickel layer. After rinsing with deionized water and anhydrous ethanol and drying, a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage electrode was obtained.

[0054] In this embodiment, the thickness of the metal nickel layer is 90 nm, and the size of the square cobalt-based metal-organic framework is about 800 nm. Figure 7 is a SEM photo of the nanoporous cage cobalt sulfide prepared in step (4) of this embodiment. Figure 7It can be seen that the cobalt sulfide prepared in step (4) has a nanoporous cage structure with a size of about 800 nm.

[0055] The negative electrode prepared in this example was used to make a lithium-ion battery and its performance was tested.

[0056] A lithium-ion battery was assembled in a glove box filled with argon and containing water and oxygen contents below 1 ppm, using a metal lithium sheet as the counter electrode, the negative electrode prepared in this example as the working electrode, microporous polypropylene as the separator, and a mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) containing 1 M lithium hexafluorophosphate (LiPF6) as the electrolyte. The electrolyte had a volume ratio of 1:1:1 for EC, DMC, and DEC. The battery was tested using a NEWARE BTS-610 constant current charge and discharge instrument at a current density of 1 mA / cm 2 , voltage range is 0.01~ 3 V(vs. Li / Li + ), the test temperature is room temperature. The test results are as follows Figure 8 As shown by Figure 8 It can be seen that the lithium-ion battery assembled with the lithium-ion battery negative electrode of this embodiment has a charge and discharge current density of 1 mA / cm 2 Under the conditions of high specific capacity, the capacity shows almost no attenuation after 240 cycles and the coulombic efficiency is stable at above 95% after 10 cycles.

[0057] Example 3

[0058] In this embodiment, a method for preparing a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode is provided, and the steps are as follows:

[0059] (1) W0S1011 carbon cloth was ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for half an hour, followed by vacuum drying. The cleaned carbon cloth was then immersed in a mixed solution of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1 and subjected to hydrophilic treatment at 80°C for 3 hours. After removal, it was washed with anhydrous ethanol and deionized water and vacuum dried to obtain a pretreated carbon cloth.

[0060] (2) 75 mmol of ethylenediamine dihydrochloride, 60 mmol of nickel chloride hexahydrate and 15 mmol of boric acid were dissolved in 50 mL of deionized water to form a mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid. The pretreated carbon cloth obtained in step (1) was immersed in the mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid. The pretreated carbon cloth was used as a working electrode, a platinum sheet was used as a counter electrode, and a saturated calomel electrode was used as a reference electrode in a three-electrode system at 60°C. The electrodeposition reaction was carried out at a constant temperature of 60°C and a constant voltage of 1.8 V for 60 s. During the electrodeposition reaction, the metal nickel layer was wrapped around the outer surface of the carbon cloth to form a metal nickel layer-wrapped carbon cloth. After the reaction was completed, a current collector was obtained.

[0061] (3) 40 mmol of 2-methylimidazole and 5 mmol of cobalt chloride hexahydrate were dissolved in 50 ml of a mixed solution of anhydrous ethanol and deionized water in a volume ratio of 4:1 to form a mixed anhydrous ethanol-deionized water solution of 2-methylimidazole and cobalt chloride hexahydrate. The current collector obtained in step (2) was immersed in the mixed anhydrous ethanol-deionized water solution containing 2-methylimidazole and cobalt chloride hexahydrate. In a three-electrode system, the prepared current collector was used as the working electrode, the platinum sheet was used as the counter electrode, and the saturated calomel electrode was used as the reference electrode. Under the condition of 3 V voltage, constant temperature and constant voltage deposition were carried out at 30°C for 300 s. During the deposition process, a ZIF-67 zeolite imidazole framework grew on the surface of the current collector. After the electrodeposition process was completed, the precursor was obtained.

[0062] (4) 50 mg of sodium sulfide nonahydrate was dissolved in 30 ml of a mixed solution of anhydrous ethanol and deionized water with a volume ratio of 5:1 to form a mixed anhydrous ethanol-deionized water solution of sodium sulfide nonahydrate. The solution was subjected to a chemical sulfurization reaction at a constant temperature of 60°C for 90 min. At this time, the cobalt-based metal organic framework was sulfurized to form cobalt sulfide, and the cobalt sulfide layer was stacked to form a cobalt sulfide layer on the outer surface of the carbon cloth wrapped with the metal nickel layer. After rinsing with deionized water and anhydrous ethanol and drying, a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage electrode was obtained.

[0063] In this embodiment, the thickness of the metal nickel layer is about 50 nm, and the size of the block-shaped cobalt-based metal-organic framework is about 400 nm. Figure 9 is a SEM photo of the nanoporous cage cobalt sulfide prepared in step (4) of this embodiment. Figure 9 It can be seen that the cobalt sulfide prepared in step (4) has a nanoporous cage structure, and the size of the nanoporous cage structure is about 600 nm.

[0064] Example 4

[0065] In this embodiment, a method for preparing a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode is provided, and the steps are as follows:

[0066] (1) W0S1011 carbon cloth was ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for half an hour, followed by vacuum drying. The cleaned carbon cloth was then immersed in a mixed solution of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1 and subjected to hydrophilic treatment at 80°C for 3 hours. After removal, it was washed with anhydrous ethanol and deionized water and vacuum dried to obtain a pretreated carbon cloth.

[0067] (2) 90 mmol of ethylenediamine dihydrochloride, 60 mmol of nickel chloride hexahydrate and 35 mmol of boric acid were dissolved in 50 mL of deionized water to form a mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid. The pretreated carbon cloth obtained in step (1) was immersed in the mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid. The pretreated carbon cloth was used as a working electrode, a platinum sheet was used as a counter electrode, and a saturated calomel electrode was used as a reference electrode in a three-electrode system at 60°C. The electrodeposition reaction was carried out at a constant temperature of 60°C and a constant voltage of 1.8 V for 60 s. During the electrodeposition reaction, the metal nickel layer was wrapped around the outer surface of the carbon cloth to form a metal nickel layer-wrapped carbon cloth. After the reaction was completed, a current collector was obtained.

[0068] (3) 30 mmol 2-methylimidazole and 4 mmol cobalt chloride hexahydrate were dissolved in 50 ml of a mixed solution of anhydrous ethanol and deionized water in a volume ratio of 4:1 to form a mixed anhydrous ethanol-deionized water solution of 2-methylimidazole and cobalt chloride hexahydrate. The current collector obtained in step (2) was immersed in the mixed anhydrous ethanol-deionized water solution containing 2-methylimidazole and cobalt chloride hexahydrate. In a three-electrode system, the prepared current collector was used as the working electrode, the platinum sheet was used as the counter electrode, and the saturated calomel electrode was used as the reference electrode. Under the condition of 3 V voltage, constant temperature and constant voltage deposition were carried out at 30°C for 300 s. During the deposition process, a ZIF-67 zeolite imidazole framework grew on the surface of the current collector. After the electrodeposition process was completed, the precursor was obtained.

[0069] (4) 45 mg of sodium sulfide nonahydrate was dissolved in 30 ml of a mixed solution of anhydrous ethanol and deionized water with a volume ratio of 5:1 to form a mixed anhydrous ethanol-deionized water solution of sodium sulfide nonahydrate. The solution was subjected to a chemical sulfurization reaction at a constant temperature of 60°C for 60 min. At this time, the cobalt-based metal organic framework was sulfurized to form cobalt sulfide, and the cobalt sulfide layer was stacked to form a cobalt sulfide layer on the outer surface of the carbon cloth wrapped with the metal nickel layer. After rinsing with deionized water and anhydrous ethanol and drying, a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage electrode was obtained.

[0070] In this embodiment, the thickness of the metal nickel layer is about 150 nm, and the size of the block-shaped cobalt-based metal-organic framework is about 200 nm. Figure 10 is a SEM photo of the nanoporous cage cobalt sulfide prepared in step (4) of this embodiment. Figure 10 It can be seen that the cobalt sulfide prepared in step (4) has a nanoporous cage structure, and the size of the nanoporous cage structure is about 200 nm.

[0071] Example 5

[0072] In this embodiment, a method for preparing a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode is provided, and the steps are as follows:

[0073] (1) W0S1011 carbon cloth was ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for half an hour, followed by vacuum drying. The cleaned carbon cloth was then immersed in a mixed solution of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1 and subjected to hydrophilic treatment at 80°C for 3 hours. After removal, it was washed with anhydrous ethanol and deionized water and vacuum dried to obtain a pretreated carbon cloth.

[0074] (2) 100 mmol of ethylenediamine dihydrochloride, 50 mmol of nickel chloride hexahydrate and 20 mmol of boric acid were dissolved in 50 mL of deionized water to form a mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid. The pretreated carbon cloth obtained in step (1) was immersed in the mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid. The pretreated carbon cloth was used as a working electrode, a platinum sheet was used as a counter electrode, and a saturated calomel electrode was used as a reference electrode in a three-electrode system at 60°C. The electrodeposition reaction was carried out at a constant temperature of 60°C and a constant voltage of 1.8 V for 60 s. During the electrodeposition reaction, the metal nickel layer was wrapped around the outer surface of the carbon cloth to form a metal nickel layer-wrapped carbon cloth. After the reaction was completed, a current collector was obtained.

[0075] (3) 35 mmol of 2-methylimidazole and 5 mmol of cobalt chloride hexahydrate were dissolved in 50 ml of a mixed solution of anhydrous ethanol and deionized water in a volume ratio of 4:1 to form a mixed anhydrous ethanol-deionized water solution of 2-methylimidazole and cobalt chloride hexahydrate. The current collector obtained in step (2) was immersed in the mixed anhydrous ethanol-deionized water solution containing 2-methylimidazole and cobalt chloride hexahydrate. In a three-electrode system, the prepared current collector was used as the working electrode, the platinum sheet was used as the counter electrode, and the saturated calomel electrode was used as the reference electrode. Under the condition of 3 V voltage, constant temperature and constant voltage deposition were carried out at 30°C for 300 s. During the deposition process, a ZIF-67 zeolite imidazole framework grew on the surface of the current collector. After the electrodeposition process was completed, the precursor was obtained.

[0076] (4) 45 mg of sodium sulfide nonahydrate was dissolved in 30 ml of a mixed solution of anhydrous ethanol and deionized water with a volume ratio of 5:1 to form a mixed anhydrous ethanol-deionized water solution of sodium sulfide nonahydrate. The solution was subjected to a chemical sulfurization reaction at a constant temperature of 60°C for 120 min. At this time, the cobalt-based metal organic framework was sulfurized to form cobalt sulfide, and the cobalt sulfide layer was stacked to form a cobalt sulfide layer on the outer surface of the carbon cloth wrapped with the metal nickel layer. After rinsing with deionized water and anhydrous ethanol and drying, a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage electrode was obtained.

[0077] In this embodiment, the thickness of the nickel layer is about 100 nm, the size of the block-shaped cobalt-based metal-organic framework is about 800 nm, and the cobalt sulfide has a nanoporous cage structure with a size of about 800 nm.

[0078] Example 6

[0079] In this embodiment, a method for preparing a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage negative electrode is provided, and the steps are as follows:

[0080] (1) W0S1011 carbon cloth was ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for half an hour, followed by vacuum drying. The cleaned carbon cloth was then immersed in a mixed solution of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1 and subjected to hydrophilic treatment at 80°C for 3 hours. After removal, it was washed with anhydrous ethanol and deionized water and vacuum dried to obtain a pretreated carbon cloth.

[0081] (2) 90 mmol of ethylenediamine dihydrochloride, 60 mmol of nickel chloride hexahydrate and 30 mmol of boric acid were dissolved in 50 mL of deionized water to form a mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid. The pretreated carbon cloth obtained in step (1) was immersed in the mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid. The pretreated carbon cloth was used as a working electrode, a platinum sheet was used as a counter electrode, and a saturated calomel electrode was used as a reference electrode in a three-electrode system at 60°C. The electrodeposition reaction was carried out at a constant temperature of 60°C and a constant voltage of 1.8 V for 60 s. During the electrodeposition reaction, the metal nickel layer was wrapped around the outer surface of the carbon cloth to form a metal nickel layer-wrapped carbon cloth. After the reaction was completed, a current collector was obtained.

[0082] (3) 50 mmol of 2-methylimidazole and 7.5 mmol of cobalt chloride hexahydrate were dissolved in 50 ml of a mixed solution of anhydrous ethanol and deionized water in a volume ratio of 4:1 to form a mixed anhydrous ethanol-deionized water solution of 2-methylimidazole and cobalt chloride hexahydrate. The current collector obtained in step (2) was immersed in the mixed anhydrous ethanol-deionized water solution containing 2-methylimidazole and cobalt chloride hexahydrate. In a three-electrode system, the prepared current collector was used as the working electrode, the platinum sheet was used as the counter electrode, and the saturated calomel electrode was used as the reference electrode. Under the condition of 3 V voltage, constant temperature and constant voltage deposition were carried out at 30°C for 300 s. During the deposition process, a ZIF-67 zeolite imidazole framework grew on the surface of the current collector. After the electrodeposition process was completed, the precursor was obtained.

[0083] (4) 60 mg of sodium sulfide nonahydrate was dissolved in 30 ml of a mixed solution of anhydrous ethanol and deionized water with a volume ratio of 5:1 to form a mixed anhydrous ethanol-deionized water solution of sodium sulfide nonahydrate. The solution was subjected to a chemical sulfurization reaction at a constant temperature of 60°C for 120 min. At this time, the cobalt-based metal organic framework was sulfurized to form cobalt sulfide, and the cobalt sulfide layer was stacked to form a cobalt sulfide layer on the outer surface of the carbon cloth wrapped with the metal nickel layer. After rinsing with deionized water and anhydrous ethanol and drying, a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage electrode was obtained.

[0084] In this embodiment, the thickness of the metal nickel layer is about 200 nm, the size of the block-shaped cobalt-based metal-organic framework is about 2 μm, and the cobalt sulfide has a nanoporous cage structure, and the size of the nanoporous cage structure is about 2 μm.

Claims

1. A three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage lithium ion battery electrode, characterized in that: It consists of carbon cloth, a metal nickel layer, and cobalt sulfide. The metal nickel layer is a current collecting layer formed by electroplating on the surface of the carbon cloth. The metal nickel layer wraps the carbon cloth, and cobalt sulfide forms a cobalt sulfide layer with a porous cage structure on the surface of the carbon cloth wrapped by the nickel layer.

2. The three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage lithium-ion battery electrode according to claim 1, characterized in that: The thickness of the metal nickel layer is 50~150 nm.

3. The three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage lithium ion battery electrode according to claim 1 or 2, characterized in that: The particle size of ZIF-67 zeolite imidazole framework precursor is 500 nm~1 μm.

4. The three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage lithium ion battery electrode according to claim 1 or 2, characterized in that: The particle size of cobalt sulfide hollow nanoporous cages is 500 nm~2 μm.

5. The method for preparing the three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage lithium ion battery electrode according to any one of claims 1 to 4, characterized in that Here are the steps: (1) The carbon cloth was ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for half an hour, and then vacuum dried. The cleaned carbon cloth was then immersed in a mixed solution of concentrated nitric acid and concentrated sulfuric acid and subjected to hydrophilic treatment at 80°C for 3 hours. After being taken out, the carbon cloth was washed with anhydrous ethanol and deionized water and vacuum dried to obtain a pretreated carbon cloth. The carbon cloth model is W0S1011, and the volume ratio of concentrated nitric acid to concentrated sulfuric acid in the mixed solution is 3:1; (2) Immersing the pretreated carbon cloth obtained in step (1) in a mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid, using the pretreated carbon cloth as a working electrode, a platinum sheet as a counter electrode, and a saturated calomel electrode as a reference electrode in a three-electrode system at 60°C, the pretreated carbon cloth is used as a working electrode, the platinum sheet is used as a counter electrode, and the saturated calomel electrode is used as a reference electrode. Under the voltage condition of 1.8 V, a constant temperature and constant voltage electrodeposition reaction is carried out at 60°C for 60 s. During the electrodeposition reaction, a metal nickel layer grows on the surface of the carbon cloth. After the reaction is completed by stirring, a current collector is obtained. (3) The current collector obtained in step (2) is immersed in a mixed anhydrous ethanol-deionized water solution containing 2-methylimidazole and cobalt chloride hexahydrate. In a three-electrode system, the prepared current collector is used as a working electrode, a platinum sheet is used as a counter electrode, and a saturated calomel electrode is used as a reference electrode. Under the condition of 3 V voltage, constant temperature and constant voltage deposition are carried out at 30°C for 300 s. During the deposition process, a ZIF-67 zeolite imidazole framework grows on the surface of the current collector. After the electrodeposition process is completed, a precursor is obtained; (4) The precursor obtained in step (3) is immersed in a mixed solution of anhydrous ethanol and deionized water containing sodium sulfide nonahydrate, and subjected to a chemical sulfurization reaction at a constant temperature of 60°C for 120 min. During the reaction, the ZIF-67 zeolite imidazole framework reacts in situ to form cobalt sulfide, thereby preparing a three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage lithium ion battery electrode.

6. The method for preparing the three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage lithium ion battery electrode according to claim 5, characterized in that: The carbon cloth pretreatment time was 3 h.

7. The method for preparing the three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage lithium ion battery electrode according to any one of claim 6, characterized in that: In the mixed aqueous solution of ethylenediamine dihydrochloride-nickel chloride hexahydrate-boric acid, the concentration of ethylenediamine dihydrochloride is 1.5~2 mol / L, the concentration of nickel chloride hexahydrate is 0.8~1.2 mol / L, and the concentration of boric acid is 0.3~0.7 mol / L.

8. The method for preparing the three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage lithium ion battery electrode according to any one of claims 5 to 7, characterized in that: In the mixed anhydrous ethanol-deionized water solution of 2-methylimidazole and cobalt chloride hexahydrate in step (3), the concentration of 2-methylimidazole is 0.6~1 mol / L, the concentration of cobalt chloride hexahydrate is 0.08~0.16 mol / L, and the volume ratio of anhydrous ethanol to deionized water is 4:

1.

9. The method for preparing the three-dimensional flexible self-supporting carbon cloth-nickel-cobalt sulfide hollow nanoporous cage lithium ion battery electrode according to any one of claims 5 to 8, characterized in that: In step (4), the mixed solution of anhydrous ethanol and deionized water of sodium sulfide nonahydrate has a concentration of 1.5-2 mg / mL, a reaction time of 60-120 min, and a volume ratio of anhydrous ethanol to deionized water of 4:1.

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