Preparation method and application of SnO2 / carbon nanotube lithium-sulfur battery interlayer
By using vacuum deposition of SnO2/carbon nanotube composite intermediate layer in lithium sulfur batteries, the problem of polysulfide diffusion is solved, the electrochemical performance and cycle life of lithium sulfur batteries are improved, and the preparation process is simplified to avoid pollution.
Patent Information
- Application Number
- CN202510500345.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-21
- Publication Date
- 2025-07-25
AI Technical Summary
The free diffusion of polysulfides in existing lithium-sulfur batteries leads to a reduction in positive electrode active sulfur and damage to the negative electrode SEI membrane structure, affecting the battery circulation performance and service life. The traditional intermediate layer preparation process is complex, low efficiency and serious pollution.
SnO2 is rapidly deposited on the carbon nanotube film by vacuum evaporation technology to form a SnO2/carbon nanotube composite intermediate layer. Using the chemisorption capacity of SnO2 and the conductivity of carbon nanotubes, the polysulfide shuttle effect is suppressed and ion conduction is accelerated.
It significantly weakens the shuttle effect of the battery, improves electrochemical performance, extends battery life and improves charging and discharging efficiency. The preparation process is simple, fast and without obvious pollution.
Smart Images
Figure CN120376643A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of lithium-sulfur batteries, and in particular, to a preparation method and application of an SnO2 / carbon nanotube intermediate layer for lithium-sulfur batteries. Background Art
[0002] Lithium batteries have been fully integrated into all aspects of human life. From portable electronic devices to emerging industries such as new energy vehicles and drones, they all show strong application potential. At the same time, people are also looking for alternatives with lower prices and higher specific energy of the batteries. Therefore, lithium-sulfur batteries have attracted extensive research in the scientific research field. Due to reasons such as their high theoretical specific capacity and theoretical specific energy, and the low price of the positive electrode sulfur, they have attracted the interest of more and more research scholars, and lithium-sulfur batteries have developed rapidly in recent years.
[0003] However, with the continuous in-depth research, researchers have found that lithium-sulfur batteries also have some deficiencies. For example, during the charge and discharge process of the battery, the free diffusion of polysulfides will cause two key problems: First, the active sulfur in the positive electrode continuously decreases due to participating in the polysulfide formation reaction, resulting in a continuous decrease in the true discharge capacity of the battery; Second, the polysulfides migrating to the negative electrode region will chemically react with the negative electrode metal lithium, leading to the destruction of the solid electrolyte interface film (SEI film) structure on the negative electrode surface, which will irreversibly affect the cycle performance and service life of the battery. In recent years, research scholars have proposed the concept of "intermediate layer", and the intermediate layer of lithium-sulfur batteries has thus been widely studied. The reasons are as follows: First, the intermediate layer can load some metal oxides, which can play a role in sulfur fixation, inhibit the shuttle effect, increase the charge and discharge capacity of the battery, and extend the cycle life of the battery; Second, considering the conductivity of the battery, a carbon-based intermediate layer with unique electrochemical properties can be selected, which can significantly increase the ion conduction and electron migration rates, and accelerate the electrode reaction process, improving the battery performance; Third, some carbon materials have good flexibility and deformability, which can greatly solve the volume change problem during the charge and discharge of lithium-sulfur batteries. The existing intermediate layers include the following several types: carbon material intermediate layer, metal oxide / carbon-based intermediate layer, metal carbide / carbon-based intermediate layer, metal carbide / carbon-based intermediate layer, etc. The above several intermediate layers can all improve the cycle life and discharge capacity of the battery to a certain extent by inhibiting the shuttle effect. However, the preparation processes of many intermediate layers have the following disadvantages: complex preparation process, slow speed, low efficiency, and pollution of waste materials, etc. Summary of the Invention
[0004] To solve the technical problems mentioned in the background art, the present invention provides a preparation method for the intermediate layer of a SnO2 / carbon nanotube lithium-sulfur battery and applies it to the lithium-sulfur battery. During the evaporation coating process of the present invention, SnO2 is rapidly evaporated by Joule heat and deposited onto the carbon nanotube thin film. This entire evaporation coating process only needs to last for several seconds, and compared with the traditional preparation of the intermediate layer, the efficiency is greatly improved, and the entire preparation process has simple steps, high speed, and no obvious pollution. When it is applied to the lithium-sulfur battery, it can be found that SnO2 can chemically adsorb polysulfides, inhibit the shuttle effect of polysulfides, and at the same time provide reactive sites. The carbon nanotube material can accelerate ion conduction and electron migration and act as a physical barrier to intercept some polysulfides, weakening the shuttle effect. Therefore, using the SnO2-CNT thin film as the intermediate layer material, compared with the traditional lithium-sulfur battery without an intermediate layer, the lithium-sulfur battery can maintain good cycling performance during use, extend its service life, and improve its charge and discharge efficiency.
[0005] The object of the present invention can be achieved by the following technical solutions:
[0006] A preparation method for the intermediate layer of a SnO2 / carbon nanotube lithium-sulfur battery. After cutting the carbon nanotube thin film, prepare a SnO2 dispersion solution, filter SnO2 onto the carbon nanotube thin film, and then use the vacuum evaporation coating technology to uniformly load SnO2 onto a new carbon nanotube thin film to form a composite intermediate layer material with both the ability to chemically adsorb polysulfides and good electrical conductivity.
[0007] Specifically, it includes the following steps:
[0008] (1) Cut the carbon nanotube thin film;
[0009] (2) Place the SnO2 powder and absolute ethanol in an ultrasonic cleaner and use ultrasonic waves to disperse to obtain a SnO2 dispersion solution;
[0010] (3) Use the internal and external air pressure difference formed by a vacuum water pump to uniformly filter SnO2 from the dispersion solution onto the surface of the carbon nanotube thin film;
[0011] (4) Use the high vacuum and high temperature environment of a vacuum Joule heat evaporation coater to rapidly evaporate SnO2 from the original carbon nanotube thin film, control the evaporation coating time, and make it uniformly deposit on the surface of the new carbon nanotube thin film to obtain the intermediate layer of the SnO2 / carbon nanotube lithium-sulfur battery.
[0012] Further, in step (2), 0.01 - 0.1 g of SnO2 powder is mixed with 25 - 40 mL of absolute ethanol, preferably 0.01 g of SnO2 powder is mixed with 25 mL of absolute ethanol, and after mixing, it is ultrasonically dispersed for 20 - 30 min, preferably 25 min.
[0013] Further, during the evaporation coating in step (4), the evaporation coating temperature is 1050 °C, the evaporation coating time is 0.5 - 3 s, preferably 2 s; the substrate material is a carbon nanotube film, the filtered carbon nanotube film is placed in the lower layer, the new carbon nanotube film is placed in the upper layer, and the distance between the two is 0.5 cm.
[0014] The thickness of the SnO₂ / carbon nanotube lithium-sulfur battery intermediate layer obtained through the above preparation process is 10 μm. The tubular structures of the carbon nanotubes are irregular and interlaced to form a two-dimensional network structure. There are gaps between individual carbon nanotubes, and spherical SnO₂ particles are attached to the outer walls of the tubular structures of the carbon nanotubes. As the evaporation coating time increases, the number of SnO₂ particles attached to the carbon nanotubes increases, the particle size becomes larger, the distribution becomes more uniform, and the tubular structures of the carbon nanotubes are gradually covered by SnO₂ particles.
[0015] Another object of the present invention is to provide the application of the SnO₂ / carbon nanotube lithium-sulfur battery intermediate layer in a lithium-sulfur battery.
[0016] Specifically, the preparation method of the lithium-sulfur battery is as follows:
[0017] The active material of the battery cathode is a carbon-sulfur composite cathode material (HCS / CNT-S). The cathode active material is mixed with conductive carbon and a binder to prepare a cathode sheet. The anode uses a lithium metal sheet, and the intermediate layer is the SnO₂ / carbon nanotube lithium-sulfur battery intermediate layer; the electrolyte is a lithium salt electrolyte, and the separator is a PP separator; assemble in the order of the positive electrode case, the positive electrode sheet, 15 μL of electrolyte, the intermediate layer, 10 μL of electrolyte, the PP separator, 15 μL of electrolyte, the lithium sheet, the gasket, the spring sheet, and the negative electrode case to obtain the required lithium-sulfur battery.
[0018] Advantages of the present invention:
[0019] During the evaporation coating process of the present invention, Joule heat is used to quickly evaporate SnO₂ so that it is deposited on the carbon nanotube film. This entire evaporation coating process only needs to last for several seconds. Compared with the traditional preparation of the intermediate layer, the efficiency is greatly improved, and the entire preparation process has simple steps, high speed, and no obvious pollution; when it is applied to a lithium-sulfur battery, compared with a traditional lithium-sulfur battery without an intermediate layer, the shuttle effect of the battery is significantly weakened, and the electrochemical performance of the battery is improved. Description of the Drawings
[0020] The present invention will be further described below with reference to the drawings.
[0021] Figure 1 It is a process schematic diagram of the preparation method of the present invention;
[0022] Figure 2 It is an assembly schematic diagram of the lithium-sulfur battery;
[0023] Figure 3 SEM images of the surface morphologies of the SnO2-CNT films prepared in a) Example 1, b) Example 2, c) Example 3, and d) Example 4;
[0024] Figure 4 a) TEM photograph, b) high-resolution image of SnO2, c) elemental distribution map of C, d) elemental distribution map of Sn, and e) elemental distribution map of O of the SnO2-CNT film in Example 4;
[0025] Figure 5 a) XPS total energy spectrum, b) high-resolution image of Sn 3d, c) high-resolution image of C1s, and d) high-resolution image of O 1s of the SnO2-carbon nanotube film in Example 4;
[0026] Figure 6 a) Cyclic voltammetry analysis and b) electrochemical impedance comparison analysis diagram with no intermediate layer (PP) of the lithium-sulfur battery based on Example 4;
[0027] Figure 7 Charge-discharge diagram of the lithium-sulfur battery based on Example 4 under 1C condition;
[0028] Figure 8 Long cycle performance diagram of the lithium-sulfur battery based on Example 4 at 1C discharge rate. Detailed implementation manners
[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.
[0030] Example 1:
[0031] As Figure 1As shown in the process, after cutting the carbon nanotube film to an appropriate size, 0.01 g of SnO2 powder was mixed with 25 mL of absolute ethanol, placed in an ultrasonic machine and dispersed for 20 min. Then, at the upper edge of the suction flask, 10 mL of SnO2-absolute ethanol solution was added dropwise with a dropper, and the residual solution was rinsed with absolute ethanol to obtain the carbon nanotube film (with a thickness of 20 μm) after suction filtration. Then, evaporation coating was carried out. The suction-filtered carbon nanotube film was placed on the lower layer, and a new carbon nanotube film (with a thickness of 10 μm) was placed on the upper layer. The SnO2 on the lower-layer carbon nanotube film was evaporated onto the upper-layer carbon nanotube film (the evaporation coating conditions were 1050 °C, 0.5 s, and the distance between the upper and lower carbon nanotube films was 0.5 cm), so that the upper-layer carbon nanotube film was loaded with a layer of SnO2, and the SnO2-CNT intermediate layer film was prepared.
[0032] Example 2:
[0033] After cutting the carbon nanotube film to an appropriate size, 0.01 g of SnO2 powder was mixed with 25 mL of absolute ethanol, placed in an ultrasonic machine and dispersed for 20 min. Then, at the upper edge of the suction flask, 10 mL of SnO2-absolute ethanol solution was added dropwise with a dropper, and the residual solution was rinsed with absolute ethanol to obtain the carbon nanotube film (with a thickness of 20 μm) after suction filtration. Then, evaporation coating was carried out. The suction-filtered carbon nanotube film was placed on the lower layer, and a new carbon nanotube film (with a thickness of 10 μm) was placed on the upper layer. The SnO2 on the lower-layer carbon nanotube film was evaporated onto the upper-layer carbon nanotube film (the evaporation coating conditions were 1050 °C, 1 s, and the distance between the upper and lower carbon nanotube films was 0.5 cm), so that the upper-layer carbon nanotube film was loaded with a layer of SnO2, and the SnO2-CNT intermediate layer film was prepared.
[0034] Example 3:
[0035] After cutting the carbon nanotube film to an appropriate size, 0.01 g of SnO2 powder was mixed with 25 mL of absolute ethanol, placed in an ultrasonic machine and dispersed for 20 min. Then, at the upper edge of the suction flask, 10 mL of SnO2-absolute ethanol solution was added dropwise with a dropper, and the residual solution was rinsed with absolute ethanol to obtain the carbon nanotube film (with a thickness of 20 μm) after suction filtration. Then, evaporation coating was carried out. The suction-filtered carbon nanotube film was placed on the lower layer, and a new carbon nanotube film (with a thickness of 10 μm) was placed on the upper layer. The SnO2 on the lower-layer carbon nanotube film was evaporated onto the upper-layer carbon nanotube film (the evaporation coating conditions were 1050 °C, 2 s, and the distance between the upper and lower carbon nanotube films was 0.5 cm), so that the upper-layer carbon nanotube film was loaded with a layer of SnO2, and the SnO2-CNT intermediate layer film was prepared.
[0036] Example 4:
[0037] After cutting the carbon nanotube film to an appropriate size, 0.01 g of SnO2 powder was mixed with 25 mL of absolute ethanol, placed in an ultrasonic machine and dispersed for 20 min. Then, at the upper edge of the suction flask, 10 mL of SnO2-absolute ethanol solution was added dropwise with a dropper, and the residual solution was rinsed with absolute ethanol to obtain a suction-filtered carbon nanotube film (thickness 20 μm). Then, evaporation coating was carried out. The suction-filtered carbon nanotube film was placed on the lower layer, and a new carbon nanotube film (thickness 10 μm) was placed on the upper layer. The SnO2 on the lower-layer carbon nanotube film was evaporated onto the upper-layer carbon nanotube film (the evaporation coating conditions were 1050 °C, 3 s, and the distance between the upper and lower carbon nanotube films was 0.5 cm), so that the upper-layer carbon nanotube film was loaded with a layer of SnO2, and the SnO2-CNT intermediate layer film was prepared; the characterization of the SnO2-CNT intermediate layer film prepared in this example is as Figure 4 and Figure 5 shown.
[0038] The SEM images of the SnO2-CNT intermediate layer films prepared in Examples 1 to 4 are as Figure 3 shown. With the increase of the evaporation coating time, the particle size of SnO2 attached to the carbon nanotubes increases, the amount of particles increases, and SnO2 is tightly combined with the tubular structure of CNT, which is beneficial to the rapid transmission of charges. Since SnO2 can provide reactive sites, it can chemically adsorb polysulfides and promote the electrochemical conversion process of lithium-sulfur batteries. The increase of nano-SnO2 particles helps to enhance the ability of the SnO2-CNT film to adsorb polysulfides, can more effectively inhibit the shuttle effect of polysulfides, and improve the charge-discharge performance of lithium-sulfur batteries. As can be seen from the attached drawings, within the evaporation coating time of 2 s, the nucleation and growth of SnO2 particles on CNT are very uniform; when the time is extended to 3 s, the particle diffusion time increases, the particle size of some particles on the surface layer of the CNT film increases significantly, the specific surface area decreases, and the catalytically active sites decrease. Therefore, 2 s is preferably used as the preparation condition for the intermediate layer composite film.
[0039] Example 5:
[0040] The pre-prepared positive electrode slurry was evenly coated on the aluminum foil. After drying in the air, it was transferred to an oven and dried for 12 h. After taking out, it was cut into positive electrode sheets with a diameter of 12 mm, and an intermediate layer with a diameter of 16 mm was cut on the SnO2-CNT film prepared in Example 4 using a cutting machine. Then, the glove box was adjusted, and the materials were put into the glove box. Assemble in the order from bottom to top: positive electrode case, positive electrode sheet, 15 μL of electrolyte, intermediate layer, 10 μL of electrolyte, PP separator, 15 μL of electrolyte, lithium sheet, gasket, spring sheet, negative electrode case (as Figure 2As shown). After assembly, the battery is compacted and left standing for one day. The battery prepared by the above method is tested using a battery tester and an electrochemical workstation. Its cyclic voltammetry curve, charge-discharge capacity, battery cycle life, and capacity decay are measured, as Figures 6 - 8 shown. After loading the intermediate layer, the battery exhibits excellent sulfur fixation performance in cyclic voltammetry tests. Electrochemical impedance spectroscopy tests show that after adding the intermediate layer, the charge transfer impedance of the battery decreases, and the charge transport performance is greatly improved. Cyclic performance tests show that under the condition of 1C, the initial discharge capacity of the battery is as high as 1223 mAh / g. After about 10 cycles of activation, the battery capacity remains at 885 mAh / g. In subsequent long-term cyclic tests, the retained amounts of the battery discharge capacity at 500, 1000, 1500, and 2000 cycles are 626, 421, 355, and 318 mAh / g, respectively. Correspondingly, in the subsequent 2000-cycle cyclic test, the loss of the battery capacity per cycle is only about 0.28 mAh / g. And after long-term cyclic tests, the Coulomb efficiency of the battery still remains at 100%, indicating that the battery still has good capacity retention and cyclic stability under high-current discharge conditions. Therefore, the addition of the intermediate layer can significantly improve the electrochemical performance of lithium-sulfur batteries.
[0041] The above specific implementation part specifically introduces the analysis method involved in the present invention. It should be noted that the above introduction is only to help those skilled in the art better understand the method and idea of the present invention, rather than a limitation on the relevant content. Without departing from the principle of the present invention, those skilled in the art can also make appropriate adjustments or modifications to the present invention, and the above adjustments and modifications should also fall within the protection scope of the present invention.
Claims
1. A preparation method of an intermediate layer for a SnO2 / carbon nanotube lithium-sulfur battery, characterized in that, After cutting the carbon nanotube film, prepare the SnO₂ dispersion liquid, and filter the SnO₂ onto the carbon nanotube film by suction filtration. Subsequently, use the vacuum evaporation technology to uniformly load the SnO₂ onto the new carbon nanotube film, obtaining the SnO₂ / carbon nanotube intermediate layer for the lithium-sulfur battery.
2. The preparation method of an intermediate layer of a SnO2 / carbon nanotube lithium-sulfur battery according to claim 1, characterized in that Specifically, it includes the following steps: (1) Cut the carbon nanotube film; (2) Place the SnO₂ powder and absolute ethanol in an ultrasonic cleaner, and use ultrasonic waves to disperse to obtain the SnO₂ dispersion liquid; (3) Utilize the internal and external air pressure difference formed by a vacuum water pump to uniformly filter the SnO₂ from the dispersion liquid onto the surface of the carbon nanotube film; (4) Use a vacuum Joule heat evaporation instrument to quickly evaporate the SnO₂ from the original carbon nanotube film, and control the evaporation time to uniformly deposit it on the surface of the new carbon nanotube film, obtaining the SnO₂ / carbon nanotube intermediate layer for the lithium-sulfur battery.
3. The preparation method of an intermediate layer of a SnO2 / carbon nanotube lithium-sulfur battery according to claim 2, wherein, In step (2), 0.01 - 0.1 g of SnO₂ powder is mixed with 25 - 40 mL of absolute ethanol, and after mixing, it is ultrasonically dispersed for 20 - 30 min.
4. The preparation method of an intermediate layer of a SnO2 / carbon nanotube lithium-sulfur battery according to claim 3, characterized in that, 0.01 g of SnO₂ powder is mixed with 25 mL of absolute ethanol, and after mixing, it is ultrasonically dispersed for 25 min.
5. The preparation method of an intermediate layer of a SnO2 / carbon nanotube lithium-sulfur battery according to claim 2, characterized in that, In step (4) during evaporation, the evaporation temperature is 1050 °C, and the evaporation time is 0.5 - 3 s.
6. The preparation method of an SnO2 / carbon nanotube lithium-sulfur battery intermediate layer according to claim 5, characterized in that, The evaporation time is 2 s.
7. The preparation method of an intermediate layer of a SnO2 / carbon nanotube lithium-sulfur battery according to claim 2, characterized in that In step (4), the substrate material is a carbon nanotube film. The suction-filtered carbon nanotube film is placed on the lower layer, and the new carbon nanotube film is placed on the upper layer, with a distance of 0.5 cm between them.
8. Application of the SnO₂ / carbon nanotube intermediate layer for the lithium-sulfur battery prepared by the preparation method according to any one of claims 1 - 7 in the lithium-sulfur battery.