CN115714173B - Flexible lithium-sulfur battery positive electrode material and preparation method thereof - Google Patents
Flexible lithium-sulfur battery positive electrode material and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a flexible lithium-sulfur battery positive electrode material and a preparation method thereof, and relates to the technical field of lithium-sulfur battery positive electrode materials. Adding MXene@sulfur/CNC particles into graphene oxide dispersion liquid to perform partial hydrothermal reduction and then performing directional freezing, and then performing freeze drying after the hydrothermal reduction is completed to obtain aerogel; and tabletting the aerogel to obtain the lithium-sulfur battery positive electrode material. The lithium sulfur battery anode material takes reduced graphene oxide as a framework, and MXene@sulfur/CNC particles are loaded on the framework; the load is 3.2-3.6 mg/cm 2 . The method is simple and easy to operate. The lithium sulfur battery positive electrode material prepared by the invention has good electrochemical performance. The lithium sulfur battery prepared by taking the positive electrode material of the lithium sulfur battery as the positive electrode has good multiplying power performance and good cycling stability, and has commercial application value.
Description
Technical Field
The invention relates to the technical field of lithium-sulfur battery positive electrode materials, in particular to a flexible lithium-sulfur battery positive electrode material and a preparation method thereof.
Background
Among the many electrochemical energy storage systems, lithium sulfur batteries are uniquely advantageous in flexible, lightweight battery designs: the positive electrode active material is based on a multi-electron reaction mechanism, and has a mass energy density as high as 2600Wh/kg, which is about an order of magnitude higher than that of a commercial lithium ion battery. While considered an important front direction for flexible energy storage systems, the high flexibility and high energy density on sulfur anodes tend to pull one another, as sulfur host materials address the slow conversion kinetics and capacity fade in addition to the need to relieve electrode bending strain.
There are two preparation methods for obtaining flexible sulfur anodes in general at present: the first method is to cast or deposit an active material on a flexible substrate with a current collector; another approach involves mixing the active material with a composite material that is electrochemically stable, electrically conductive, and mechanically strong to achieve a self-supporting (Free-standing) electrode and directly serve as the electrode body. The flexible electrode of the first form, because the non-conductive binder generally does not contribute to the storage of the active material, may account for part of the mass of the electrode, thereby reducing the overall energy density of the overall cell. While self-supporting flexible electrodes have a relatively high energy density due to the lack of an adhesive and current collector.
Self-supporting anodes have been designed with various novel structures of polar body/carbon matrix composite in order to load sulfur and improve polysulfide dissolution problems. How to provide enough exposed sites and to enhance the specific surface area of the polar adsorbent is a technical difficulty in designing the matrix material. In addition, different sulfur coating methods have great influence on sulfides, sulfur distribution, sulfur particle size and the like, and further relate to electrochemical performance. Therefore, designing a reasonable adsorption structure in a self-supporting sulfur positive electrode, and reversibly desorbing polysulfide after adsorbing polysulfide is critical to the design of the matrix material. However, the existing self-supporting lithium sulfur battery positive electrode material generally has the problems of interface effect, insufficient dynamics and the like, and the electrochemical performance of the lithium sulfur battery positive electrode material still needs to be further improved.
Disclosure of Invention
Based on the above, the invention provides a flexible lithium-sulfur battery positive electrode material and a preparation method thereof, so as to improve the electrochemical performance of the lithium-sulfur battery positive electrode material.
In order to achieve the above object, the present invention provides the following solutions:
according to one of the technical schemes, the lithium-sulfur battery positive electrode material takes reduced graphene oxide as a framework, and MXene@sulfur/CNC particles are loaded on the framework; the load is 3.2-3.6 mg/cm 2 。
The sulfur content in the positive electrode material of the lithium-sulfur battery is 45-50wt%.
Further, the preparation method of the MXene@sulfur/CNC particles comprises the following steps:
na is mixed with 2 S 2 O 3 Cellulose Nanocrystals (CNC) and MXaneTi 3 C 2 Adding into water for dissolution, and then dropwise adding hydrochloric acid for reaction to obtain a dispersion liquid;
and centrifuging the dispersion liquid, cleaning the obtained precipitate, and drying to obtain the MXene@sulfur/CNC particles.
MXaneTi compared with other MXene materials 3 C 2 T x (T represents a functional group) has rich surface functional groups, is suitable for being dispersed in an rGO aqueous solution system, and simultaneously has the advantages of high Young modulus, high conductivity, large specific surface area and the like, and is also more suitable for being used as a positive electrode material of a flexible lithium sulfur battery, namely MXene Ti 3 C 2 T x Other MXene materials than those described above are not suitable for use in preparing the positive electrode material of the lithium-sulfur battery of the present invention.
Further, the diameter of the cellulose nanocrystalline is 5-20 nm, and the length is 50-300 nm.
The common one-dimensional fiber nano material has high length-diameter ratio, for example, the length-diameter ratio of the carbon nano tube is up to 1000:1, and the too high length-diameter ratio is not beneficial to the coating and dispersion of sulfur particles, so that active substance sulfur is easier to fall off in the circulation process. Therefore, the invention selects cellulose nanocrystalline, and limits the diameter to 5-20 nm and the length to 50-300 nm.
The invention combines water-soluble CNC with MXene to prepare the MXene@sulfur/CNC particle powder composite sulfur-carrying material, and the polar fiber matrix (CNC) has a unique coating structure, can provide good adsorption sites and conductive channels for active substance sulfur, and further reduces the size of sulfur particles and improves the dispersibility of the sulfur particles through an in-situ dispersing agent CNC.
Further, the Na 2 S 2 O 3 Cellulose nanocrystalline, MXaneTi 3 C 2 And hydrochloric acid in a molar ratio of 1:0.4-0.6:0.005:0.01; the drying is specifically vacuum drying at 50 ℃ for 4 hours.
Na 2 S 2 O 3 Cellulose nanocrystalline, MXaneTi 3 C 2 And a molar ratio of hydrochloric acid higher than the above range affects the conductivity of the positive electrode material to lower the charge-discharge capacity of the battery, and lower than the above range causes agglomeration of sulfur particles of the active material, and thus the present invention defines Na 2 S 2 O 3 Cellulose nanocrystalline, MXaneTi 3 C 2 And hydrochloric acid in a molar ratio of 1:0.4-0.6:0.005:0.01.
The second technical scheme of the invention is that the preparation method of the positive electrode material of the lithium-sulfur battery comprises the following steps:
adding MXene@sulfur/CNC particles into graphene oxide dispersion liquid to perform partial hydrothermal reduction, then performing directional freezing, and then performing freeze drying after the hydrothermal reduction is completed to obtain aerogel; and tabletting the aerogel to obtain the lithium-sulfur battery positive electrode material.
Further, the tabletting is specifically carried out by using a tabletting machine with the pressure of 2-5 MPa to the thickness range of 80-120 mu m.
Further, the concentration of graphene oxide in the graphene oxide dispersion liquid is 3-5 mg/mL; the mass volume ratio of the MXene@sulfur/CNC particles to the graphene oxide dispersion liquid is 6-10 mg/mL.
The lower the GO (graphene oxide) concentration in the graphene oxide solution, the higher the sulfur loading, but at the same time the lower the conductivity and dispersibility of the sulfur particles. Therefore, the concentration of 3-5mg/mL is easier to disperse sulfur particles in the liquid phase, and the conductive network is constructed by the reduced graphene oxide sheets in the cooperative reduction process.
The concentration ratio of MXene@sulfur/CNC particles to GO must be strictly controlled within 2:1, and since hydrothermal reduction of GO to form hydrogel is a necessary condition for obtaining aerogel by freeze-drying, independent self-supporting hydrogel composite materials cannot be formed more than 2:1.
Further, the partial hydrothermal reduction is specifically hydrothermal reduction at 90 ℃ for 20-30 minutes; the hydrothermal reduction is completely specific to 150 ℃.
The time of the partial hydrothermal reduction must be tightly controlled so that the directional freezing cannot be performed prematurely after the dispersion has formed a gel.
The temperature of partial hydrothermal reduction is higher than the temperature which can destabilize the gelation process, the temperature which can cause sulfur particles to be settled to the bottom of a test tube in the gelation process to affect the homogeneity of the material is lower, and the time is longer than the time which can cause GO to be completely reduced, so that the temperature of partial hydrothermal reduction is required to be limited to be 90 ℃ and the time is 20-30 minutes.
The total hydrothermal reduction temperature is higher than the positive electrode capacity (sulfur melting point 155 ℃) which causes the sublimation and condensation of sulfur on the test tube wall, the conductivity is affected too much by oxygen-containing functional groups (carbonyl, carboxyl and the like) on the surface of the graphene, the conductivity is reduced by oxidation of MXene, and the reduction of GO is incomplete due to short time, so that the total hydrothermal reduction temperature needs to be limited to 150 ℃ for 12 hours.
Further, the directional freezing is specifically performed for 6 hours at the temperature of-45 to-60 ℃; the freeze drying is specifically implemented by pre-freezing at-40 ℃ for 12 hours, and then vacuumizing and freeze drying at-2 ℃ for 24 hours.
The temperature of the directional freezing is lower than-45 ℃, and the sample cannot be frozen through due to the fact that the temperature is too high, so that the temperature of the directional freezing is required to be limited to be below-45-60 ℃; too long a time of directional freezing would result in too high a power consumption of the process steps and too short a time would result in the sample not being frozen through, thus the time of directional freezing would need to be limited to 6 hours.
The heat conducting material adopted by directional freezing is copper plate or copper foil, and aims to have high heat conductivity coefficient and quick heat conducting process, and other alloy materials such as aluminum, steel and the like commonly used in the field can lead to uneven heat conduction in the freezing process as heat conducting materials, so that the formation of temperature gradient is not facilitated.
The time of freeze drying is at least 24 hours, and too short a time of freeze drying can lead to incomplete drying of the sample water, so the invention defines that the time of freeze drying is not less than 24 hours.
In the present invention, CNC is also used as a surfactant, not only Na 2 S 2 O 3 The dispersing agent which reacts with HCl effectively prevents generated sulfur particles from agglomerating and precipitating, and simultaneously the amphipathy of the dispersing agent also provides possibility for controllable preparation of the positive electrode material of the lithium-sulfur battery. Through reasonably controlling the concentration of CNC in the solution, unique oriented pore channels can be prepared, so that the dissolution of lithium polysulfide is better inhibited, and the stability of the positive electrode material is improved.
In the process of adding MXene@sulfur/CNC particles into graphene dispersion liquid to prepare the cathode material, the assembly process and the three-dimensional structure can be regulated and controlled through hydrothermal time and temperature due to amphipathy of colloid particle CNC and partially reduced graphene oxide (PrGO) in a gel system.
According to the third technical scheme, the lithium-sulfur battery comprises the positive electrode material of the lithium-sulfur battery.
Further, the lithium sulfur battery comprises a positive electrode and a negative electrode, wherein the positive electrode is made of the positive electrode material of the lithium sulfur battery; the negative electrode is one or more of metal lithium sheet, lithium powder, lithium alloy, lithium-doped carbon and lithium-doped graphite.
The fourth technical scheme of the invention is that the lithium-sulfur battery is applied to the aerospace field, satellites, space stations, electric vehicles and electronic products.
The technical conception of the invention is as follows:
unlike lithium ion battery systems where intercalation chemistry occurs, elemental sulfur of insulating nature and discharge product Li 2 S cannot be directly used as an electrode material, and has a volume expansion effect. While the high capacity of lithium sulfur batteries is required to be achieved by the formation of soluble polysulfides, the consequent "shuttling" effect also results in more confusion of the system and rapid decay of the battery capacity. Therefore, how to realize the functions of polar adsorption and catalytic conversion through the topological properties of materials with different dimensions and to consider the establishment of a flexible framework and the maintenance of an electrochemical structure are key problems in the research of the flexible lithium-sulfur battery.
The invention uses the nanofiber as the carrier of the sulfur anode, and utilizes the nanofiber to realize stable dispersion of sulfur particles, wherein the nanofiber is easy to regulate and control and has rich nucleation sites. Meanwhile, the reduced graphene oxide (rGO) nanosheets and the MXene material also have high-activity two-dimensional surfaces, and the shuttle effect can be restrained through functional groups and metal-sulfur bonding, so that the specific energy density and the cycling stability of the flexible electrode of the lithium-sulfur battery are improved. The invention researches the adsorption mechanism between the fiber/MXene composite system and polysulfide by designing and regulating the multi-element micro-nano composite structure, and improves the sulfur battery from soluble polysulfide to solid Li in the later stage of discharge 2 Reaction kinetics of this step S. The composite structure of the positive electrode material of the lithium-sulfur battery provided by the invention can adsorb polysulfide and promote Li at the same time 2 S is deposited, so that the performance of the flexible lithium sulfur battery is fully improved.
The invention discloses the following technical effects:
the invention utilizes gel formed by pi-pi bond interaction of graphene oxide GO in a low-temperature hydrothermal environment as a three-dimensional framework, and synthesizes CNC/Ti through one-step freeze drying 3 C 2 MXene/rGO fiber aerogel. In addition, due to amphipathy of the colloidal particle CNC and the partially reduced graphene oxide (PrGO) in the gel system, the assembly process and the three-dimensional structure can be regulated and controlled through hydrothermal time and temperature. Due to existence of cellulose nanocrystalline CNC, the freezing rate, the freezing direction, the temperature and the type of solute are utilized in the directional freezing processThe morphology and the size of the self-assembled ice crystals and the fiber crystals are regulated and controlled, so that the morphology and the characteristics of the freeze-dried product are regulated and controlled, and the flexibility of the aerogel is enhanced. The final fully reduced fiber-reinforced three-dimensional MXene/rGO structure is freeze-dried to form Ti 3 C 2 And (3) carrying sulfur aerogel by MXene/rGO fibers, and directly tabletting to obtain the high-performance lithium sulfur battery anode material.
The method is simple and easy to operate.
The lithium sulfur battery positive electrode material prepared by the invention has good electrochemical performance. The lithium sulfur battery prepared by taking the positive electrode material of the lithium sulfur battery as the positive electrode has good multiplying power performance and good cycling stability, and has commercial application value.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a physical diagram of a lithium-sulfur battery prepared in example 1;
fig. 2 is a graph of the rate performance of the lithium sulfur battery prepared in example 1;
FIG. 3 is a CNC/Ti powder obtained after lyophilization in step 5 of example 1 3 C 2 MXene/rGO fiber aerogel photographs;
FIG. 4 is a graph showing the morphology of the positive electrode material of the lithium-sulfur battery prepared in example 1;
fig. 5 is a cycle performance chart of the lithium sulfur battery prepared in example 1.
Detailed Description
Various exemplary embodiments of the invention will now be described in detail, which should not be considered as limiting the invention, but rather as more detailed descriptions of certain aspects, features and embodiments of the invention.
It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In addition, for numerical ranges in this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.
It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the invention described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from consideration of the specification of the present invention. The specification and examples of the present invention are exemplary only.
As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be inclusive and mean an inclusion, but not limited to.
As used herein, the term "room temperature" means 20 to 30℃unless otherwise specified.
The raw materials used in the examples of the present invention are available from commercial sources unless otherwise specified.
The Cellulose Nanocrystalline (CNC) used in the embodiment of the invention is prepared by hydrolyzing microcrystalline cellulose MCC with strong acid; the prepared cellulose nanocrystalline CNC has a large number of hydroxyl groups on the surface, so that the cellulose nanocrystalline CNC is easy to disperse, the diameter is about 5-20 nm, and the length is about 50-300 nm. The technical object of the present invention can be also achieved by other routes such as a cellulose nanocrystalline CNC obtained by a purchase route, which has a hydroxyl group on the surface, a diameter of about 5 to 20nm, and a length of about 50 to 300nm.
MXaneTi used in the examples of the invention 3 C 2 Treatment of Ti with hydrofluoric acid aqueous solution of specific concentration 3 AlC 2 MAX powder for a certain time; centrifuging the solution treated by hydrofluoric acid, and then washing with deionized water until the pH value is close to neutral; then filtering the solution to obtain MXene with accordion structure, and further ultrasonic treating to obtain Ti with less layer 3 C 2 MXene. The method comprises the following specific steps: first, 0.2g of LiF was added to 40mL of 9mol.L -1 Is stirred for 10min. Next, 2g of Ti 3 AlC 2 The powder was slowly added to the above mixed solution and reacted at 35℃with stirring for 24 hours. The obtained suspension was then subjected to centrifugal water washing (rotation speed: 3500 r.min -1 5min each time) until the pH of the supernatant is not less than 6. Then, the precipitate obtained by centrifugation was dispersed in deionized water, and subjected to ultrasonic treatment for 1.5 hours. Next, the sonicated mixture was subjected to a reaction at 4000 rmin -1 And centrifuging the mixture downwards, and collecting dark green supernatant. Finally, the supernatant is freeze-dried to obtain MXene Ti 3 C 2 T x (wherein T represents-F, -O, -OH, etc., the number of terminal groups x is not defined), i.e., MXaneTi 3 C 2 Abbreviated as MXene. MXene Ti obtained by other routes 3 C 2 T x (wherein T represents a functional group such as-F, -O, or-OH) is also capable of achieving the technical object of the present invention.
MXeneTi 3 C 2 The main function of the medium functional group is to disperse into aqueous solution without affecting the final technical effect. If the functional group is doped in a modified manner, such as N-MXene after nitrogen doping, having a stronger polarity can have an effect on the electrochemical performance.
The GO (graphene oxide) dispersion liquid used in the embodiment of the invention obtains GO dispersion liquid with different concentrations of 3, 4 and 5mg/mL by dispersing GO powder into deionized water, and the GO dispersion liquid is named as GO-3, GO-4 and GO-5 dispersion liquid. The technical purpose of the invention can be achieved by the GO dispersion liquid of 3-5mg/mL obtained by other ways.
Example 1
Step 1, 1.58g of Na 2 S 2 O 3 5.4g cellulose nanocrystalline CNC ((C) 6 H 10 O 5 ) n, molecular weight 1080) and 639mgmXene are added into 188mL deionized water, and the mixture is continuously stirred for 10min while ultrasonic dispersion is carried out, so that cellulose nanocrystalline in the mixture is completely dissolved.
And 2, dropwise adding 12mL of 1mol/L dilute hydrochloric acid into the solution (automatically titrating by a seat type micro titration tube, adjusting the titration speed, dropwise adding 12mL of 1mol/L dilute hydrochloric acid into the solution within two hours), continuously magnetically stirring in the dropwise adding process, controlling the total dropwise adding time to be about 2 hours at the stirring speed of 300rpm, and continuously magnetically stirring the solution for 2 hours at room temperature after the dropwise adding of the hydrochloric acid is completed, so as to obtain a uniform milky dispersion.
And step 3, centrifuging the uniform milky white dispersion liquid at a rotating speed of 8000rpm for 10min, then ultrasonically dispersing the separated precipitate into a 0.01M CNC solution, and continuing centrifuging for 10min to finish the cleaning of the precipitate to obtain a pale yellow precipitate.
And 4, drying the pale yellow precipitate in a vacuum drying oven at 50 ℃ for 4 hours to obtain MXene@sulfur/CNC particle powder, wherein the sulfur content in the powder is 70wt%.
Step 5, adding the MXene@sulfur/CNC particle powder into the GO-3 dispersion liquid (the concentration of the MXene@sulfur/CNC particle powder in the GO-3 dispersion liquid is 8 mg/mL), performing partial hydrothermal reduction (25 minutes of hydrothermal reduction at 90 ℃), performing dry ice bath (the same technical effect can be achieved by freezing liquid nitrogen) for 6 hours, performing hydrothermal reduction at 150 ℃ to be complete, and performing freeze drying at-50 ℃ for 24 hours to obtain CNC/Ti 3 C 2 MXene/rGO fiber aerogel (the heat conducting material used for directional freeze drying can be copper plate or copper foil, the photo of the aerogel is shown in figure 3), and tabletting to obtain the flexible self-supporting electrode with the thickness of 100 micrometers (the sulfur content in the electrode is 50%, and the load of MXene@sulfur/CNC particle powder is 3.6 mg/cm) 2 ) Namely the positive electrode material of the lithium-sulfur battery (the internal morphological characteristics are shown in figure 4).
Step 6, preparing the quasi-Compacting the prepared flexible self-supporting electrode, cutting, taking a lithium sheet as a negative electrode, adopting a Celgard diaphragm, and selecting electrolyte with the concentration of 1 mol.L -1 1, 3-Dioxolane (DOL) -ethylene glycol dimethyl ether (DME) -based lithium bistrifluoromethane sulfonyl imide (LiTFSI), designated LiTFSI/DOL-DME (volume ratio 1:1), was added with 0.1 mol.L -1 LiNO of (C) 3 And assembling into a flexible button cell (lithium sulfur battery). The physical diagram is shown in figure 1.
And 7, testing the performance of the battery. The results are shown in FIG. 2.
As can be seen from fig. 2, the flexible lithium sulfur battery prepared in this embodiment has good rate capability, and the capacity is still approximately 710mAh/g when the rate is 1C under high-current discharge; when the multiplying power is 2C, the capacity is still approximately 530mAh/g, and the method has commercial application value. The positive electrode material prepared in the embodiment successfully and stably circulates for 50 circles at 0.2 ℃, the attenuation rate of each circle is only 0.71%, and the cycle performance chart is shown in figure 5.
Example 2
The only difference from example 1 is that the GO-3 dispersion in step 5 is replaced with a GO-4 dispersion.
Results: the flexible lithium sulfur battery prepared by the embodiment has good rate capability, and the capacity is 723mAh/g when the rate is 1C under the heavy current discharge; when the multiplying power is 2C, the capacity is 541mAh/g. Stability of cycle 0.2C successfully stabilized cycle 50 cycles with an attenuation rate of 0.69% per cycle
Example 3
The only difference from example 1 is that the GO-3 dispersion in step 5 is replaced with a GO-5 dispersion.
Results: the flexible lithium sulfur battery prepared by the embodiment has good rate capability, and the capacity is 729mAh/g when the rate is 1C under the heavy current discharge; when the multiplying power is 2C, the capacity is 552mAh/g. The successful stabilization cycle was 50 cycles at 0.2C with a decay rate of only 0.66% per cycle.
The above embodiments are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention without departing from the design spirit of the present invention.
Claims (4)
1. The lithium sulfur battery positive electrode material is characterized in that the lithium sulfur battery positive electrode material takes reduced graphene oxide as a framework, and MXene@sulfur/CNC particles are loaded on the framework; the load is 3.2-3.6 mg/cm 2 ；
The preparation method of the MXene@sulfur/CNC particles comprises the following steps:
na is mixed with 2 S 2 O 3 Cellulose nanocrystals and MXene Ti 3 C 2 Adding into water for dissolution, and then dropwise adding hydrochloric acid for reaction to obtain a dispersion liquid; centrifuging the dispersion liquid, cleaning the obtained precipitate, and drying to obtain the MXene@sulfur/CNC particles;
the Na is 2 S 2 O 3 Cellulose nanocrystalline, MXene Ti 3 C 2 And hydrochloric acid in a molar ratio of 1:0.4-0.6:0.005:0.01; the drying is specifically vacuum drying at 50 ℃ for 4 hours;
the preparation method of the lithium-sulfur battery positive electrode material comprises the following steps:
adding MXene@sulfur/CNC particles into graphene oxide dispersion liquid to perform partial hydrothermal reduction, then performing directional freezing, and then performing freeze drying after the hydrothermal reduction is completed to obtain aerogel; tabletting the aerogel to obtain the positive electrode material of the lithium-sulfur battery;
the concentration of graphene oxide in the graphene oxide dispersion liquid is 3-5 mg/mL; the mass volume ratio of the MXene@sulfur/CNC particles to the graphene oxide dispersion liquid is 6-10 mg/mL;
the partial hydrothermal reduction is specifically carried out at 90 ℃ for 20-30 minutes; the hydrothermal reduction is completely carried out at 150 ℃;
the directional freezing is specifically performed at the temperature of-45 to-60 ℃ for 6 hours; the freeze drying is specifically implemented by pre-freezing at-40 ℃ for 12 hours, and then vacuumizing and freeze drying at-2 ℃ for 24 hours.
2. A lithium-sulfur battery comprising the positive electrode material for a lithium-sulfur battery according to claim 1.
3. The lithium sulfur battery according to claim 2, wherein the lithium sulfur battery comprises a positive electrode and a negative electrode, and the positive electrode is the positive electrode material of the lithium sulfur battery according to claim 1; the negative electrode is one or more of metal lithium sheet, lithium powder, lithium alloy, lithium-doped carbon and lithium-doped graphite.
4. Use of the lithium sulfur battery of claim 2 in the aerospace field, electric vehicles and electronic products.
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| CN111599986A (en) * | 2020-05-29 | 2020-08-28 | 山东理工大学 | Preparation method and application of self-supporting positive electrode of lithium-sulfur battery with coated structure |
| CN114805942A (en) * | 2022-05-19 | 2022-07-29 | 浙江理工大学 | Preparation method of RGO/CNC/CNF composite film |
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