Co-NiO / CNT composite layer modified lithium-sulfur battery diaphragm and preparation method thereof
By using Co-NiO/CNT composite layer modification on the lithium-sulfur battery separator, the problems of low Coulomb efficiency, capacity attenuation and poor conductivity of lithium-sulfur batteries are solved, and higher discharge specific capacity and cycling stability are achieved.
Patent Information
- Application Number
- CN202510199288.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-24
- Publication Date
- 2025-05-16
AI Technical Summary
The low Coulombic efficiency, rapid capacity attenuation, poor conductivity and volume expansion problems caused by polysulfide conversion of lithium-sulfur batteries limit their performance improvement and commercial development.
The lithium-sulfur battery separator modified with Co-NiO/CNT composite layer is used to form porous single-crystal nanosheets through self-assembly of cobalt-doped nickel oxide and carbon nanotubes, increasing the reactive area and conductivity, and inhibiting the shuttle effect and volume expansion of polysulfides.
It significantly improves the discharge specific capacity and cycle stability of lithium-sulfur batteries, improves the rate performance and sulfur utilization rate of the battery, and extends the service life of the battery.
Smart Images
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of lithium-sulfur battery materials, and specifically relates to a lithium-sulfur battery separator modified with a Co-NiO / CNT composite layer and a preparation method thereof. Background Art
[0002] With the continuous advancement of science and technology, electric vehicles and mobile electronic devices have put forward higher requirements for the storage capacity of secondary batteries, and there is an urgent need to find energy storage devices with high discharge capacity and long cycle life. The theoretical specific capacity of lithium-sulfur batteries is as high as 1675mAh / g, and the theoretical discharge capacity is as high as 2600Wh / kg. It is one of the most promising new secondary battery candidates; and the advantages of lithium-sulfur batteries such as abundant reserves of elemental sulfur, low cost, and environmental friendliness have gradually attracted the attention of many scholars. However, the performance improvement and commercial development of lithium-sulfur batteries are also restricted by a series of problems. For example, the shuttle effect of the reaction intermediate lithium polysulfide easily leads to low Coulomb efficiency and rapid capacity decay; the poor conductivity of elemental sulfur and insoluble Li2S / Li2S2 is not conducive to electron transfer in the cathode, resulting in reduced sulfur utilization, slower sulfur conversion kinetics, and poor battery rate performance; the conversion between polysulfides easily produces volume expansion, destroys the electrode structure, and causes the pole piece to shed powder or even fall off.
[0003] In response to the significant problems exposed by lithium-sulfur batteries, most researchers have tried to start from the perspective of the separator. Traditional commercial separators have a large number of micron or nanopores that allow lithium ions to pass through, but polysulfides can also pass from the pores to the lithium negative electrode to cause side reactions; in addition, the conductivity of commercial separators is insufficient, and the ion transmission rate will slow down, resulting in a decrease in battery capacity or an increase in internal resistance, affecting the service life of the battery. Although certain research progress has been made in the specific capacity and discharge specific capacity of lithium-sulfur batteries, there is still a significant gap compared with the theoretical value. Therefore, it is necessary to explore ideal materials to modify commercial separators to achieve efficient adsorption and kinetic conversion of polysulfides.
[0004] Recent studies have shown that adsorption of polysulfides through sulfur catalysts is an important way to improve the reaction kinetics of lithium-sulfur batteries. Transition metal compounds, including transition metal oxides (TMOs), sulfides and nitrides, are generally considered to be effective catalyst options due to their strong affinity for lithium polysulfides (LiPSs). Upon retrieval, the invention patent CN118702166A discloses a method for preparing a neodymium-doped nickel oxide hollow metal oxide modified positive electrode sheet. The method synthesizes a neodymium-doped nickel oxide (Nd-dop NiO) composite material with a nano-microsphere morphology composed of hollow metal oxide nanoparticles through a sol-gel method, including dissolution, curing, and carbonization steps. The method is cumbersome, the preparation process is complex, and the conductivity is poor, resulting in a rapid decay of the battery capacity. Summary of the invention
[0005] The purpose of the present invention is to provide a lithium-sulfur battery separator modified with a Co-NiO / CNT composite layer, and a preparation method and application thereof. Co-NiO helps to expose more active sites, strengthen the adsorption of soluble polysulfides, effectively inhibit the shuttle effect, and improve the efficiency of redox reactions; CNT forms an interwoven conductive network, shortens the transmission path of electrons, improves the utilization rate of the sulfur positive electrode, and improves the interface impedance. The present invention is achieved through the following technical solutions:
[0006] The invention discloses a Co-NiO / CNT composite layer modified lithium-sulfur battery separator. The lithium-sulfur battery separator uses a polypropylene separator as a substrate and a composite film formed by self-assembly of porous cobalt-doped nickel oxide and carbon nanotubes as a modified layer.
[0007] Furthermore, the thickness of the modified layer of the lithium-sulfur battery separator is 5-15 μm.
[0008] Furthermore, the cobalt-doped nickel oxide / carbon nanotubes are porous single-crystalline nanosheets, showing a typical hexagonal single-crystalline structure.
[0009] The present invention also discloses a method for preparing the Co-NiO / CNT composite layer modified lithium-sulfur battery separator, comprising the following steps:
[0010] Step 1, preparing a cobalt-doped nickel oxide / carbon nanotube composite material;
[0011] (a) dissolving nickel salt, cobalt salt and carbon nanotubes in deionized water, and stirring to obtain a mixed solution;
[0012] (b) adding ammonia water to the mixed solution and adjusting the pH to alkaline to obtain a precursor solution; subjecting the precursor solution to a hydrothermal reaction at a reaction temperature of 100 to 200° C. and a reaction time of 8 to 12 hours;
[0013] (c) centrifuging, washing and drying the obtained precipitate to obtain a precursor composite material;
[0014] (d) placing the composite material in a tube furnace for calcining to obtain a porous cobalt-doped nickel oxide / carbon nanotube composite material;
[0015] Step 2: Prepare uniform slurry
[0016] The binder is dissolved in N-methylpyrrolidone, and then the porous structure cobalt-doped nickel oxide / carbon nanotubes are added and mixed for several hours to obtain a uniform slurry;
[0017] Step 3: Load the mixed slurry on the substrate by a doctor blade coating method, and vacuum dry it to obtain a lithium-sulfur battery separator modified with a Co-NiO / CNT composite layer.
[0018] Furthermore, the nickel salt is at least one of nickel chloride, nickel nitrate or nickel sulfate; the cobalt salt is at least one of cobalt chloride, cobalt nitrate or cobalt sulfate.
[0019] Furthermore, the molar ratio of the cobalt salt to the nickel salt is 1:4 to 1:10.
[0020] Furthermore, the heating rate of the tubular furnace is 2 to 10°C / min; the protective atmosphere is one or more of argon, nitrogen, and helium; the insulation temperature is 200 to 500°C; and the insulation time is 2 to 5h.
[0021] The present invention also discloses the use of the Co-NiO / CNT composite layer modified lithium-sulfur battery separator in the preparation of button batteries. The prepared lithium-sulfur battery has a specific capacity of up to 1327.09 mAh g at 0.2C discharge. -1 After 500 cycles at 1C, the discharge capacity can be maintained at 613.5 mAh g -1 .
[0022] Compared with the prior art, the present invention has the following beneficial technical effects:
[0023] The present invention provides a lithium-sulfur battery separator modified by a Co-NiO / CNT composite layer. The Co-NiO / CNT composite material is a porous single crystal nanosheet, exhibiting a typical hexagonal single crystal structure, and has a low cost and a simple and efficient synthesis method. Among them, cobalt-doped nickel oxide has a smaller pore size and a porous structure, which increases the reactive area, thereby providing more reactive sites. The conductive layer formed by self-assembly of carbon nanotubes can promote the transmission of ions and electrons in the battery due to its advantages such as excellent chemical stability, thermal stability, high conductivity and large specific surface area; in addition, it also has a rich pore structure, has an adsorption effect on lithium polysulfide in the electrolyte, can alleviate the "shuttle effect", and improve the performance of the lithium-sulfur battery; the above characteristics of the modified separator give the lithium-sulfur battery excellent discharge specific capacity and cycle stability.
[0024] Cobalt-doped nickel oxide and carbon nanotubes synergistically modify the lithium-sulfur battery separator, showing rapid lithium ion conduction and efficient adsorption and catalytic conversion of polysulfides. The prepared battery has excellent rate performance and cycle stability. Cobalt-doped nickel oxide (Co-NiO) has a synergistic effect of adsorption and catalysis on polysulfides. It is compounded with carbon nanotubes and used as a separator modification layer for lithium-sulfur batteries. The introduction of porous cobalt-doped nickel oxide in the separator provides more adsorption and catalytic sites for polysulfides, preventing them from diffusing to the anode, improving the utilization rate of sulfur, and solving the problem that the discharge specific capacity of existing lithium-sulfur batteries is still low. Carbon nanotubes can not only make up for the lack of conductivity of oxides and improve the electronic conduction of lithium sulfide, but also the high specific surface area can adsorb polysulfides. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 This is the X-ray diffraction (XRD) spectrum of Co-NiO / CNT prepared in Example 1;
[0026] Figure 2 This is a scanning electron microscope (SEM) image of Co-NiO / CNT prepared in Example 1;
[0027] Figure 3 This is a BET graph obtained by nitrogen adsorption test of Co-NiO / CNT prepared in Example 1;
[0028] Figure 4 This is the pore size distribution diagram obtained by the nitrogen adsorption test of Co-NiO / CNT prepared in Example 1;
[0029] Figure 5 This is a cross-sectional SEM image of the diaphragm modified with the Co-NiO / CNT composite material prepared in Example 1;
[0030] Figure 6 The cycle performance of the Co-NiO / CNT composite modified diaphragm and the polypropylene diaphragm prepared in Example 1 at 0.2C in a lithium-sulfur battery;
[0031] Figure 7 The long cycle performance of the Co-NiO / CNT composite modified diaphragm and the polypropylene diaphragm prepared in Example 1 at 1C in a lithium-sulfur battery. DETAILED DESCRIPTION
[0032] In order to make the purpose, technical solution and advantages of the present invention more clear, the following is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, not all embodiments.
[0033] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.
[0034] Example 1
[0035] The present invention discloses a lithium-sulfur battery separator modified with a Co-NiO / CNT composite layer and a preparation method thereof, comprising the following steps:
[0036] Co(NO3)2·6H2O and Ni(NO3)2·6H2O were dissolved in 60 mL of deionized water at a molar ratio of 1:99, and 0.1 g of CNT was added, and stirred at a speed of 600 r / min for 1 h to obtain a uniform mixed solution.
[0037] Ammonia water was added to the mixed solution, the pH value was adjusted to 10, and the mixture was stirred at a speed of 600 r / min for 1 hour to obtain a uniform mixed solution; the precursor solution was subjected to a hydrothermal reaction at a reaction temperature of 200° C. and a reaction time of 8 hours.
[0038] The reaction solution was washed with ethanol and deionized water, and dried in an oven at 60° C. for 12 h to obtain a precursor composite material;
[0039] The composite material was placed in a tube furnace with a heating rate of 10°C / min and calcined at 200°C for 4h in a N2 atmosphere to obtain a porous cobalt-doped nickel oxide / carbon nanotube composite material;
[0040] Co-NiO / CNT and PVDF were added into N-methylpyrrolidone at a mass ratio of 9:1, and mixed evenly to obtain a membrane modification material;
[0041] The membrane modification material was evenly coated on the surface of the polypropylene membrane by a scraping method, and the composite membrane was obtained by vacuum drying at 60°C for 12 hours.
[0042] The XRD pattern of Co-NiO / CNT in Example 1 is as follows Figure 1 As shown, there are obvious characteristic peaks corresponding to NiO in the diffraction pattern of Co-NiO / CNT material.
[0043] The Co-NiO / CNT material prepared in Example 1 was subjected to SEM analysis. Figure 2 As shown, it can be observed that the NCO@CNT material presents a hexagonal single crystal structure.
[0044] The specific surface area and pore size distribution of Co-NiO / CNT in Example 1 are as follows: Figure 3 and Figure 4 As shown, it can be seen that the material has a large specific surface area and rich pore structure.
[0045] The cross section of Co-NiO / CNT / PP in Example 1 is as follows: Figure 5 As shown, the thickness of the modified layer is 6.5 μm.
[0046] The assembled battery was subjected to a cycle stability test. Figure 6 The battery with the composite separator has a high specific capacity of 1327.09 mAh g at 0.2C discharge. -1 , the Coulombic efficiency remains at 99.8%.
[0047] Depend on Figure 7 The long cycle stability test results of the battery containing the composite separator show that the battery still has 613.5 mAh g after 500 cycles at 1C. -1The battery performance of the composite diaphragm is significantly improved compared with that of the pure polypropylene diaphragm.
[0048] Example 2
[0049] This embodiment provides a Co-NiO / CNT composite layer modified lithium-sulfur battery separator and a preparation method thereof:
[0050] Co(NO3)2·6H2O and Ni(NO3)2·6H2O were dissolved in 60 mL of deionized water at a molar ratio of 1:49, and 0.1 g of CNT was added, and stirred at a speed of 600 r / min for 3 h to obtain a uniform mixed solution.
[0051] Ammonia water was added to the mixed solution, the pH value was adjusted to 12, and the mixture was stirred at a speed of 600 r / min for 1 hour to obtain a uniform mixed solution; the precursor solution was subjected to a hydrothermal reaction at a reaction temperature of 150° C. and a reaction time of 10 hours.
[0052] The reaction solution was washed with ethanol and deionized water, and dried in an oven at 60° C. for 12 h to obtain a precursor composite material;
[0053] The composite material was placed in a tube furnace with a heating rate of 10°C / min and calcined at 500°C for 2h in an Ar atmosphere to obtain a porous cobalt-doped nickel oxide / carbon nanotube composite material;
[0054] Co-NiO / CNT and PVDF were added into N-methylpyrrolidone at a mass ratio of 9:1, and mixed evenly to obtain a membrane modification material;
[0055] The membrane modification material was evenly coated on the surface of the polypropylene membrane by a scraping method, and the composite membrane was obtained by vacuum drying at 60°C for 12 hours.
[0056] Example 3
[0057] This embodiment provides a Co-NiO / CNT composite layer modified lithium-sulfur battery separator and a preparation method thereof:
[0058] Co(NO3)2·6H2O and Ni(NO3)2·6H2O were dissolved in 60 mL of deionized water at a molar ratio of 1:4, and 0.1 g of CNT was added, and stirred at a speed of 600 r / min for 3 h to obtain a uniform mixed solution.
[0059] Ammonia water was added to the mixed solution, the pH was adjusted to 12, and the mixture was stirred at a speed of 600 r / min for 1 hour to obtain a uniform mixed solution; the precursor solution was subjected to a hydrothermal reaction at a reaction temperature of 180° C. and a reaction time of 10 hours.
[0060] The reaction solution was washed with ethanol and deionized water, and dried in an oven at 60° C. for 12 h to obtain a precursor composite material;
[0061] The composite material was placed in a tube furnace with a heating rate of 5°C / min and calcined at 400°C for 2h in an Ar atmosphere to obtain a porous cobalt-doped nickel oxide / carbon nanotube composite material;
[0062] Co-NiO / CNT and PVDF were added into N-methylpyrrolidone at a mass ratio of 9:1, and mixed evenly to obtain a membrane modification material;
[0063] The membrane modification material was evenly coated on the surface of the polypropylene membrane by a scraping method, and the composite membrane was obtained by vacuum drying at 60°C for 12 hours.
[0064] Example 4
[0065] This embodiment provides a Co-NiO / CNT composite layer modified lithium-sulfur battery separator and a preparation method thereof:
[0066] Co(NO3)2·6H2O and Ni(NO3)2·6H2O were dissolved in 60 mL of deionized water at a molar ratio of 1:9, and 0.1 g of CNT was added, and stirred at a speed of 600 r / min for 3 h to obtain a uniform mixed solution.
[0067] Ammonia water was added to the mixed solution, the pH value was adjusted to 12, and the mixture was stirred at a speed of 600 r / min for 1 hour to obtain a uniform mixed solution; the precursor solution was subjected to a hydrothermal reaction at a reaction temperature of 150° C. and a reaction time of 12 hours.
[0068] The reaction solution was washed with ethanol and deionized water, and dried in an oven at 60° C. for 12 h to obtain a precursor composite material;
[0069] The composite material was placed in a tube furnace with a heating rate of 10°C / min and calcined at 400°C for 3h in a N2 atmosphere to obtain a porous cobalt-doped nickel oxide / carbon nanotube composite material.
[0070] Co-NiO / CNT and PVDF were added into N-methylpyrrolidone at a mass ratio of 9:1, and mixed evenly to obtain a membrane modification material;
[0071] The membrane modification material was evenly coated on the surface of the polypropylene membrane by a scraping method, and the composite membrane was obtained by vacuum drying at 60°C for 12 hours.
[0072] Example 5
[0073] This embodiment provides a Co-NiO / CNT composite layer modified lithium-sulfur battery separator and a preparation method thereof:
[0074] Co(NO3)2·6H2O and Ni(NO3)2·6H2O were dissolved in 60 mL of deionized water at a molar ratio of 1:49, and 0.1 g of CNT was added, and stirred at a speed of 600 r / min for 3 h to obtain a uniform mixed solution.
[0075] Ammonia water was added to the mixed solution, the pH was adjusted to 12, and the mixture was stirred at a speed of 600 r / min for 1 hour to obtain a uniform mixed solution; the precursor solution was subjected to a hydrothermal reaction at a reaction temperature of 180° C. and a reaction time of 12 hours.
[0076] The reaction solution was washed with ethanol and deionized water, and dried in an oven at 60° C. for 12 h to obtain a precursor composite material;
[0077] The composite material was placed in a tube furnace with a heating rate of 10°C / min and calcined at 400°C for 3h in an Ar atmosphere to obtain a porous cobalt-doped nickel oxide / carbon nanotube composite material.
[0078] Co-NiO / CNT and PVDF were added into N-methylpyrrolidone at a mass ratio of 9:1, and mixed evenly to obtain a membrane modification material;
[0079] The membrane modification material was evenly coated on the surface of the polypropylene membrane by a scraping method, and the composite membrane was obtained by vacuum drying at 60°C for 12 hours.
[0080] Example 6
[0081] This embodiment provides a Co-NiO / CNT composite layer modified lithium-sulfur battery separator and a preparation method thereof:
[0082] Co(NO3)2·6H2O and Ni(NO3)2·6H2O were dissolved in 60 mL of deionized water at a molar ratio of 1:99, and 0.1 g of CNT was added, and stirred at a speed of 600 r / min for 3 h to obtain a uniform mixed solution.
[0083] Ammonia water was added to the mixed solution, the pH value was adjusted to 12, and the mixture was stirred at a speed of 600 r / min for 1 hour to obtain a uniform mixed solution; the precursor solution was subjected to a hydrothermal reaction at a reaction temperature of 180° C. and a reaction time of 12 hours.
[0084] The reaction solution was washed with ethanol and deionized water, and dried in an oven at 60° C. for 12 h to obtain a precursor composite material;
[0085] The composite material was placed in a tube furnace with a heating rate of 2°C / min and calcined at 300°C for 5h in an Ar atmosphere to obtain a porous cobalt-doped nickel oxide / carbon nanotube composite material.
[0086] Co-NiO / CNT and PVDF were added into N-methylpyrrolidone at a mass ratio of 9:1, and mixed evenly to obtain a membrane modification material;
[0087] The membrane modification material was evenly coated on the surface of the polypropylene membrane by a scraping method, and the composite membrane was obtained by vacuum drying at 60°C for 12 hours.
[0088] Example 7
[0089] This embodiment provides a Co-NiO / CNT composite layer modified lithium-sulfur battery separator and a preparation method thereof:
[0090] Co(NO3)2·6H2O and Ni(NO3)2·6H2O were dissolved in 60 mL of deionized water at a molar ratio of 1:9, and 0.1 g of CNT was added, and stirred at a speed of 600 r / min for 1 h to obtain a uniform mixed solution.
[0091] Ammonia water was added to the mixed solution, the pH value was adjusted to 10, and the mixture was stirred at a speed of 600 r / min for 1 hour to obtain a uniform mixed solution; the precursor solution was subjected to a hydrothermal reaction at a reaction temperature of 150° C. and a reaction time of 10 hours.
[0092] The reaction solution was washed with ethanol and deionized water, and dried in an oven at 60° C. for 12 h to obtain a precursor composite material;
[0093] The composite material was placed in a tube furnace with a heating rate of 2°C / min and calcined at 300°C for 4h in an Ar atmosphere to obtain a porous cobalt-doped nickel oxide / carbon nanotube composite material.
[0094] Co-NiO / CNT and PVDF were added into N-methylpyrrolidone at a mass ratio of 9:1, and mixed evenly to obtain a membrane modification material;
[0095] The membrane modification material was evenly coated on the surface of the polypropylene membrane by a scraping method, and the composite membrane was obtained by vacuum drying at 60°C for 12 hours.
[0096] Example 8
[0097] This embodiment provides a Co-NiO / CNT composite layer modified lithium-sulfur battery separator and a preparation method thereof:
[0098] Co(NO3)2·6H2O and Ni(NO3)2·6H2O were dissolved in 60 mL of deionized water at a molar ratio of 1:49, and 0.1 g of CNT was added, and stirred at a speed of 600 r / min for 1 h to obtain a uniform mixed solution.
[0099] Ammonia water was added to the mixed solution, the pH value was adjusted to 12, and the mixture was stirred at a speed of 600 r / min for 1 hour to obtain a uniform mixed solution; the precursor solution was subjected to a hydrothermal reaction at a reaction temperature of 150° C. and a reaction time of 12 hours.
[0100] The reaction solution was washed with ethanol and deionized water, and dried in an oven at 60° C. for 12 h to obtain a precursor composite material;
[0101] The composite material was placed in a tube furnace with a heating rate of 10°C / min and calcined at 350°C for 4h in an Ar atmosphere to obtain a porous cobalt-doped nickel oxide / carbon nanotube composite material;
[0102] Co-NiO / CNT and PVDF were added into N-methylpyrrolidone at a mass ratio of 9:1, and mixed evenly to obtain a membrane modification material;
[0103] The membrane modification material was evenly coated on the surface of the polypropylene membrane by a scraping method, and the composite membrane was obtained by vacuum drying at 60°C for 12 hours.
[0104] Example 9
[0105] This embodiment provides a Co-NiO / CNT composite layer modified lithium-sulfur battery separator and a preparation method thereof:
[0106] Co(NO3)2·6H2O and Ni(NO3)2·6H2O were dissolved in 60 mL of deionized water at a molar ratio of 1:9, and 0.1 g of CNT was added, and stirred at a speed of 600 r / min for 3 h to obtain a uniform mixed solution.
[0107] Ammonia water was added to the mixed solution, the pH value was adjusted to 10, and the mixture was stirred at a speed of 600 r / min for 1 hour to obtain a uniform mixed solution; the precursor solution was subjected to a hydrothermal reaction at a reaction temperature of 200° C. and a reaction time of 8 hours.
[0108] The reaction solution was washed with ethanol and deionized water, and dried in an oven at 60° C. for 12 h to obtain a precursor composite material;
[0109] The composite material was placed in a tube furnace with a heating rate of 5°C / min and calcined at 300°C for 4h in a N2 atmosphere to obtain a porous cobalt-doped nickel oxide / carbon nanotube composite material;
[0110] Co-NiO / CNT and PVDF were added into N-methylpyrrolidone at a mass ratio of 9:1, and mixed evenly to obtain a membrane modification material;
[0111] The membrane modification material was evenly coated on the surface of the polypropylene membrane by a scraping method, and the composite membrane was obtained by vacuum drying at 60°C for 12 hours.
[0112] Example 10
[0113] This embodiment provides a Co-NiO / CNT composite layer modified lithium-sulfur battery separator and a preparation method thereof:
[0114] Co(NO3)2·6H2O and Ni(NO3)2·6H2O were dissolved in 60 mL of deionized water at a molar ratio of 1:4, and 0.1 g of CNT was added, and stirred at a speed of 600 r / min for 3 h to obtain a uniform mixed solution.
[0115] Ammonia water was added to the mixed solution, the pH value was adjusted to 12, and the mixture was stirred at a speed of 600 r / min for 1 hour to obtain a uniform mixed solution; the precursor solution was subjected to a hydrothermal reaction at a reaction temperature of 180° C. and a reaction time of 12 hours.
[0116] The reaction solution was washed with ethanol and deionized water, and dried in an oven at 60° C. for 12 h to obtain a precursor composite material;
[0117] The composite material was placed in a tube furnace with a heating rate of 2°C / min and calcined at 300°C for 2h in an Ar atmosphere to obtain a porous cobalt-doped nickel oxide / carbon nanotube composite material;
[0118] Co-NiO / CNT and PVDF were added into N-methylpyrrolidone at a mass ratio of 9:1, and mixed evenly to obtain a membrane modification material;
[0119] The membrane modification material was evenly coated on the surface of the polypropylene membrane by a scraping method, and the composite membrane was obtained by vacuum drying at 60°C for 12 hours.
[0120] The present invention provides a lithium-sulfur battery diaphragm modified with a Co-NiO / CNT composite layer with a simple process. A porous single-crystal Co-NiO / CNT nanosheet is synthesized by a one-step hydrothermal method and annealing treatment under a protective atmosphere. The doping of Co atoms has a strong chemical adsorption effect on polysulfides, effectively inhibiting the shuttle effect of polysulfides. In addition, the CNT skeleton structure not only effectively limits the shuttle effect, but also has good lithium affinity and electrolyte wettability, which is conducive to the rapid conduction of electrons and ions. The composite material is used for the diaphragm modification of lithium-sulfur batteries to greatly improve the capacity and cycle stability of lithium-sulfur batteries.
[0121] The above-mentioned embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.
Claims
1. A method for preparing a lithium-sulfur battery separator modified with a Co-NiO / CNT composite layer, characterized in that: The lithium-sulfur battery separator is based on a polypropylene separator and a composite membrane formed by self-assembly of porous cobalt-doped nickel oxide and carbon nanotubes is used as a modification layer.
2. The Co-NiO / CNT composite layer modified lithium-sulfur battery separator according to claim 1, characterized in that: The thickness of the lithium-sulfur battery separator modification layer is 5-15 μm.
3. The Co-NiO / CNT composite layer modified lithium-sulfur battery separator according to claim 1, characterized in that: Cobalt-doped nickel oxide / carbon nanotubes are porous single-crystalline nanosheets that exhibit a typical hexagonal single-crystalline structure.
4. The method for preparing a lithium-sulfur battery separator modified with a Co-NiO / CNT composite layer according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1, preparing a cobalt-doped nickel oxide / carbon nanotube composite material; (a) dissolving nickel salt, cobalt salt and carbon nanotubes in deionized water, and stirring to obtain a mixed solution; (b) adding aqueous ammonia to the mixed solution to adjust the pH to alkaline to obtain a precursor solution; The precursor solution is subjected to a hydrothermal reaction at a reaction temperature of 100 to 200° C. and a reaction time of 8 to 12 hours; (c) centrifuging, washing and drying the reaction solution to obtain a precursor composite material; (d) placing the composite material in a tube furnace for calcining to obtain a porous cobalt-doped nickel oxide / carbon nanotube composite material; Step 2: Prepare uniform slurry The binder is dissolved in N-methylpyrrolidone, and then the porous structure cobalt-doped nickel oxide / carbon nanotubes are added and mixed for several hours to obtain a uniform slurry; Step 3: Load the mixed slurry on the substrate by a doctor blade coating method, and vacuum dry it to obtain a lithium-sulfur battery separator modified with a Co-NiO / CNT composite layer.
5. The method for preparing the modified lithium-sulfur battery separator according to claim 4, characterized in that: In the step (a), the nickel salt is at least one of nickel chloride, nickel nitrate or nickel sulfate; the cobalt salt is at least one of cobalt chloride, cobalt nitrate or cobalt sulfate.
6. The method for preparing the modified lithium-sulfur battery separator according to claim 4, characterized in that: In the step (a), the molar ratio of the cobalt salt to the nickel salt is 1:4 to 1:
99.
7. The method for preparing the modified lithium-sulfur battery separator according to claim 4, characterized in that: In the step (d), the heating rate of the tubular furnace is 2 to 10°C / min; the protective atmosphere is one or more of argon, nitrogen, and helium; the insulation temperature is 200 to 500°C; and the insulation time is 2 to 5 hours.
8. Use of the Co-NiO / CNT composite layer modified lithium-sulfur battery separator according to any one of claims 1 to 3 in the preparation of button batteries, wherein the prepared lithium-sulfur battery has a specific capacity of up to 1327.09 mAh g at 0.2C discharge -1 After 500 cycles at 1C, the discharge capacity can be maintained at 613.5 mAh g -1 .
9. The lithium-sulfur battery with a Co-NiO / CNT composite layer modified diaphragm as claimed in claim 8, wherein the lithium-sulfur battery is composed of a S / CNT composite material as a positive electrode, a Co-NiO / CNT composite layer modified diaphragm, an ether electrolyte, and a lithium metal negative electrode.