A honeycomb porous carbon material for lithium-sulfur battery positive electrode and preparation method thereof
By preparing honeycomb porous carbon materials and doping them with cerium nitrate, the problems of insufficient conductivity and catalytic conversion ability of existing porous carbon materials were solved, and the high efficiency and long life of lithium-sulfur batteries were achieved.
Patent Information
- Application Number
- CN202411727006.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-28
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2044-11-28
AI Technical Summary
Existing porous carbon materials have insufficient conductivity and catalytic conversion capabilities in lithium-sulfur batteries, resulting in low positive electrode conductivity, severe lithium dendrite growth and shuttle effect, which affects the performance of lithium-sulfur batteries.
Honeycomb porous carbon materials were synthesized by the template method. Sodium chloride was used as a template and porous carbon was prepared by thiourea and glucose. Combined with cerium nitrate doping, Ce atoms were formed as active centers to improve the conductivity and catalytic ability of the material.
It enhances the exposure area and polar adsorption of active centers, improves the utilization rate of active materials, inhibits the shuttle effect, and improves the electrochemical performance and cycle life of lithium-sulfur batteries.
Smart Images
Figure CN119528113B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of new energy material preparation, and particularly relates to a material for a lithium-sulfur battery positive electrode and a preparation method thereof. Background Art
[0002] Lithium-sulfur batteries, with their high theoretical energy density, high theoretical specific capacity, low price, and environmental friendliness, have become a key focus for researchers as a next-generation energy storage system. While these advantages are significant, they also have inherent drawbacks, including low cathode conductivity, lithium dendrite growth, and the shuttle effect—issues that must be overcome for commercialization.
[0003] Porous carbon materials, as supporting materials, have shown potential application in lithium-sulfur (Li-S) battery cathode materials due to their excellent conductivity, high specific surface area, adjustable pore structure, and ease of modification. These properties enable porous carbon to provide abundant active sites, improve the loading and dispersion of sulfur / lithium sulfide, and enhance the kinetics of electrochemical reactions. However, existing porous carbon materials have primarily focused on the modification of non-metallic elements such as nitrogen, sulfur, phosphorus, and boron, leaving room for improvement in their polar chemical adsorption and catalytic conversion capabilities. Summary of the Invention
[0004] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications and omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.
[0005] In view of the problems existing in the prior art, the present invention is proposed.
[0006] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art: a method for preparing a honeycomb porous carbon material for a lithium-sulfur battery positive electrode, comprising the following steps:
[0007] (1) First, sodium chloride is dissolved in deionized water, stirred vigorously, and then ultrasonically dissolved. Glucose is added and stirred continuously. The mixed solution is first frozen and then freeze-dried to obtain a white powder. The white powder is thoroughly ground and mixed with thiourea.
[0008] (2) After pre-carbonization in a tube furnace, the sodium chloride was washed away with a large amount of clean water, and then vacuum dried to obtain sulfur-doped porous carbon SPC;
[0009] (3) The dried SPC was immersed in a nitrate aqueous solution and stirred, freeze-dried, and then carbonized at high temperature to obtain the dual-doped porous carbon SPC-X;
[0010] (4) Compounding SPC-X with lithium sulfide, a conductive agent, and a binder to form a uniform slurry, which is then dried to obtain a honeycomb porous carbon positive electrode.
[0011] Furthermore, the concentration of the sodium chloride aqueous solution in step (1) is 0.05-0.2 g / mL.
[0012] Furthermore, in step (1), the stirring time is 10-30 min, the speed is 200-600 r / min, and the ultrasonic time is 5-30 min.
[0013] Furthermore, the freezing time in step (1) is 8-24 hours, the freezing temperature is -60°C to -80°C; and the freeze-drying time is 36-72 hours.
[0014] Furthermore, in step (1) and step (2), the mass ratio of sodium chloride: glucose: thiourea is 4-30:0.5-7:1.
[0015] Furthermore, the concentration of the nitrate (preferably cerium nitrate) in deionized water is 10-30 mg / mL, and the immersion time is 2-6 hours. The inventors have found that increasing the concentration of the cerium nitrate aqueous solution results in cerium metal clusters or cerium oxide crystals, which occupy the pore space of the porous carbon, reduce the space for accommodating active substances, and reduce the atomic efficiency of cerium as a catalytic center. Lower cerium nitrate concentrations result in poor catalytic effects from cerium atoms. Therefore, a concentration of 10-30 mg / mL of cerium nitrate in deionized water is optimal.
[0016] Furthermore, the nitrate is one or more of cerium nitrate Ce(NO3)3, zinc nitrate Zn(NO), lanthanum nitrate La(NO3)3, indium nitrate In(NO3)3, and iron nitrate Fe(NO3)3.
[0017] Furthermore, the carbonization temperature is 800-1000°C, the heating rate is 1-5°C / min, the calcination time is 2-4h, and the atmosphere is argon or nitrogen.
[0018] In a fourth aspect, in step (4), the mass ratio of SPC-Ce to lithium sulfide, conductive agent, and binder is 2-3:5-6:1:1.
[0019] The beneficial effects of the present invention are as follows:
[0020] (1) The present invention employs a template method to synthesize a honeycomb porous carbon material with a three-dimensional structure. The template uses inexpensive and readily available sodium chloride, which can be easily removed. By adjusting the ratio of glucose to sodium chloride, porous carbons with varying specific surface areas can be synthesized, achieving rapid and efficient synthesis of porous carbon. The porous structure can accommodate more sulfur / lithium sulfide, the active material of lithium-sulfur batteries, and also increases the exposed area of the active centers, thereby improving the utilization rate of the active centers.
[0021] (2) The Ce atom, acting as the active center in the present invention, can freely switch between +3 and +4 valences due to its unique properties, catalyzing electrochemical reactions by binding and donating electrons. Furthermore, the polarity of cerium is higher than that of commonly used transition metal elements (including Ni, Co, Mn, Fe, etc.), providing a strong polar adsorption effect, achieving a combination of adsorption and catalytic conversion, improving the utilization rate of active materials, inhibiting the shuttle effect, and enhancing the electrochemical performance and cycle life of lithium-sulfur batteries.
[0022] (3) The preparation method of the present invention is scientific, reasonable, easy to implement, and low-cost. The resulting porous carbon material has simple synthesis and easily adjustable coordination composition. Ultimately, Li2S / SPC-Ce released high specific capacities of 693, 688, and 679 mAh / g in the first cycle at 0.1C, respectively. The charge and discharge efficiencies in the first three cycles were 99.3%, 98.7%, and 99.7%, respectively. This effectively improved the utilization rate of active materials, suppressed the shuttle effect, and enhanced the electrochemical performance and cycle life of lithium-sulfur batteries, providing an important reference for the next generation of high-performance lithium sulfide-based lithium-sulfur batteries. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.
[0024] Figure 1 SEM of prepared SPC-Ce at different ratios;
[0025] Figure 2 This is the charge and discharge curve of Li2S / SPC-Ce at 0.1C. DETAILED DESCRIPTION
[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.
[0027] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.
[0028] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.
[0029] A method for preparing a honeycomb porous carbon material for a lithium-sulfur battery positive electrode comprises the following steps:
[0030] (1) First, sodium chloride is dissolved in deionized water, stirred vigorously, and then ultrasonically dissolved. Glucose is added and stirred continuously. The mixed solution is first frozen and then freeze-dried to obtain a white powder. The white powder is thoroughly ground and mixed with thiourea.
[0031] (2) After pre-carbonization in a tube furnace, the sodium chloride was washed away with a large amount of clean water, and then vacuum dried to obtain sulfur-doped porous carbon SPC;
[0032] (3) The dried SPC was immersed in a nitrate aqueous solution and stirred, freeze-dried, and then carbonized at high temperature to obtain the dual-doped porous carbon SPC-X;
[0033] (4) Compounding SPC-X with lithium sulfide, a conductive agent, and a binder to form a uniform slurry, which is then dried to obtain a honeycomb porous carbon positive electrode.
[0034] The concentration of the sodium chloride aqueous solution in step (1) is 0.05-0.2 g / mL.
[0035] In step (1), the stirring time is 10-30 min, the rotation speed is 200-600 r / min, and the ultrasonic time is 5-30 min.
[0036] The freezing time in step (1) is 8-24 hours, the freezing temperature is -60°C to -80°C; and the freeze-drying time is 36-72 hours.
[0037] The mass ratio of sodium chloride:glucose:thiourea in step (1) and step (2) is 4-30:0.5-7:1.
[0038] The nitrate (preferably cerium nitrate) is immersed in deionized water at a concentration of 10-30 mg / mL for 2-6 hours. The inventors discovered that increasing the concentration of the cerium nitrate solution results in cerium metal clusters or cerium oxide crystals, which occupy the pore space of the porous carbon, reduce the space for active substances, and reduce the atomic efficiency of cerium as a catalytic center. Lower cerium nitrate concentrations, however, result in poor catalytic performance from cerium atoms. Therefore, a cerium nitrate concentration of 10-30 mg / mL in deionized water is optimal.
[0039] The nitrate is one or more of cerium nitrate Ce(NO3)3, zinc nitrate Zn(NO), lanthanum nitrate La(NO3)3, indium nitrate In(NO3)3, and iron nitrate Fe(NO3)3.
[0040] The carbonization temperature is 800-1000°C, the heating rate is 1-5°C / min, the calcination time is 2-4h, and the atmosphere is argon or nitrogen.
[0041] In the fourth aspect, the mass ratio of SPC-Ce to lithium sulfide, conductive agent, and binder in step (4) is 2-3:5-6:1:1.
[0042] Example 1
[0043] 1. Preparation of SPC
[0044] (1) Dissolve 10 g of sodium chloride in 30 mL of deionized water, stir vigorously for 30 min, and then sonicate for 15 min to completely dissolve it.
[0045] (2) After adding 1.2 g of glucose, the mixture was stirred continuously for 2 h and then immediately placed in a freezer for freezing. Freeze for 24 h and freeze-dry for 48 h to obtain a white powder.
[0046] (3) The white powder was mixed with 0.6 g of thiourea and ground thoroughly. The mixture was heated to 500 °C under an argon atmosphere and calcined for 4 h at a heating rate of 2 °C min -1 , and obtain black powder SPC.
[0047] 2. Preparation of SPC-Ce
[0048] (1) 0.347 g of cerium nitrate was added to 100 mL of distilled water solution, and then the SPC was immersed in the cerium nitrate aqueous solution for 2 h.
[0049] (2) The mixed solution was placed in a freezer and frozen for 24 hours. The black powder obtained after freeze drying for 48 hours was carbonized at 800°C for 2 hours at a heating rate of 2°C / min in an argon atmosphere. SPC-Ce was obtained after carbonization.
[0050] Figure 1This is the SEM image of SPC-Ce obtained in Example 1. From the figure, it can be seen that SPC-Ce has rich mesoporous / macroporous morphology. The rich porous structure is conducive to the infiltration of the electrolyte and the accommodation of more active substances. It is also conducive to exposing active sites, laying the foundation for achieving good electrochemical performance.
[0051] Example 2
[0052] 1. Preparation of SPC
[0053] (1) Dissolve 20 g of sodium chloride in 30 mL of deionized water, stir vigorously for 20 min, and then sonicate for 30 min to completely dissolve it.
[0054] (2) After adding 2.4 g of glucose, the mixture was stirred continuously for 2 h and then immediately placed in a freezer for freezing. Freeze for 24 h and freeze-dry for 48 h to obtain a white powder.
[0055] (3) The white powder was mixed with 1.2 g of thiourea and ground thoroughly. The mixture was heated to 600 °C under an argon atmosphere and calcined for 2 h at a heating rate of 2 °C min -1 , and obtain black powder SPC.
[0056] 2. Preparation of Li2S / SPC-Ce
[0057] (1) 0.521 g of cerium nitrate was added to 100 mL of distilled water solution, and then the SPC was immersed in the cerium nitrate aqueous solution for 2 h.
[0058] (2) The mixed solution was placed in a freezer and frozen for 24 hours. The black powder obtained after freeze drying for 48 hours was carbonized at 900°C for 2 hours at a heating rate of 1°C / min in a nitrogen atmosphere. SPC-Ce was obtained after carbonization.
[0059] (3) After SPC-Ce and lithium sulfide were combined, they were ground and mixed with a conductive agent and a binder in a ratio of 2:6:1:1. After stirring, coating, and drying, the cut pieces were made into uniform electrode sheets and assembled into a lithium-sulfur battery. The final Li2S / SPC-Ce had a first-cycle discharge capacity of 681 mAh / g at 0.1C.
[0060] Example 3
[0061] 1. Preparation of SPC
[0062] (1) Dissolve 10 g of sodium chloride in 30 mL of deionized water, stir vigorously for 30 min, and then sonicate for 15 min to completely dissolve it.
[0063] (2) After adding 1.5 g of glucose, the mixture was stirred continuously for 2 h and then immediately placed in a freezer for freezing. Freeze for 24 h and freeze-dry for 48 h to obtain a white powder.
[0064] (3) The white powder was mixed with 0.6 g of thiourea and ground thoroughly. The mixture was heated to 400 °C under an argon atmosphere and calcined for 4 h at a heating rate of 2 °C min -1 , and obtain black powder SPC.
[0065] 2. Preparation of Li2S / SPC-Ce
[0066] (1) 0.694 g of cerium nitrate was added to 100 mL of distilled water solution, and then the SPC was immersed in the cerium nitrate aqueous solution for 2 h.
[0067] (2) The mixed solution was placed in a freezer and frozen for 24 hours. The black powder obtained after freeze drying for 48 hours was carbonized at 1000°C for 2 hours at a heating rate of 2°C / min in a nitrogen atmosphere. After carbonization, SPC-Ce was obtained.
[0068] (3) After SPC-Ce is compounded with lithium sulfide, it is ground and mixed with a conductive agent and a binder in a ratio of 3:5:1:1. After stirring, coating and drying, the cut pieces are made into uniform pole pieces, and then assembled into a lithium-sulfur battery.
[0069] Figure 2 The charge-discharge curves show that Li2S / SPC-Ce releases high specific capacities of 693, 688, and 679 mAh / g in the first three cycles at 0.1C, respectively. The charge-discharge efficiencies in the first three cycles are 99.3%, 98.7%, and 99.7%, respectively. This indicates that the addition of Ce effectively improves the utilization of active materials, inhibits the shuttle effect, and improves the electrochemical performance and cycle life of lithium-sulfur batteries. These test results provide strong evidence for the practical application of SPC-Ce materials in lithium sulfide-based lithium-sulfur batteries.
[0070] The SPC-Ce prepared according to the method of Experimental Example 3 has a Ce element content of 0.51% (atomic ratio), a C element content of 89.1% (atomic ratio), a N element content of 4.52% (atomic ratio), and a S element content of 5.87% (atomic ratio).
[0071] Comparative Example 1
[0072] Compared to Experimental Example 2, the concentration of the cerium nitrate aqueous solution in Comparative Example 1 was changed to 2 mg / mL during the preparation process, while the remaining steps remained the same. The resulting sample, SPC-Ce, had a Ce content of 0.09%, indicating a low concentration of Ce atoms, which serve as catalytic conversion centers. The first-cycle capacity at 0.1C was 648 mAh / g, a 5% decrease compared to Experimental Example 2.
[0073] Comparative Example 2
[0074] Compared to Experimental Example 3, Comparative Example 2 omitted the immersion in aqueous cerium nitrate solution during the preparation process, while the remaining steps remained the same. The resulting SPC sample was free of Ce doping and lacked catalytic centers. Its first cycle capacity at 0.1C was 643 mAh / g, a 13% decrease compared to Experimental Example 3.
[0075] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A method for preparing a honeycomb porous carbon material for a lithium-sulfur battery positive electrode, characterized in that: The following steps are involved: (1) First, sodium chloride is dissolved in deionized water, stirred vigorously, and then ultrasonically dissolved. Glucose is added and stirred continuously to obtain a mixed solution. The mixed solution is first frozen, and then freeze-dried to obtain a white powder. The white powder is thoroughly ground and mixed with thiourea; the mass ratio of sodium chloride: glucose: thiourea is 4-30:0.5-7:1; (2) After pre-carbonization in a tube furnace, the sodium chloride was washed away with a large amount of clean water, and then vacuum dried to obtain sulfur-doped porous carbon SPC; (3) The dried SPC was immersed in a nitrate aqueous solution and stirred, freeze-dried, and then carbonized at high temperature to obtain dual-doped porous carbon SPC-Ce; wherein the carbonization temperature was 800-1000 °C; the concentration of nitrate in deionized water was 10-30 mg / mL, and the immersion time was 2-6 h; the nitrate was cerium nitrate Ce(NO3)3; (4) Compounding SPC-Ce with lithium sulfide, a conductive agent, and a binder to form a uniform slurry, which is then dried to obtain a honeycomb porous carbon material.
2. The method for preparing a honeycomb porous carbon material for a lithium-sulfur battery positive electrode according to claim 1, characterized in that: The concentration of the sodium chloride aqueous solution in step (1) is 0.05-0.2 g / mL.
3. The method for preparing a honeycomb porous carbon material for a lithium-sulfur battery positive electrode according to claim 1, characterized in that: In step (1), the stirring time is 10-30 min, the rotation speed is 200-600 r / min, and the ultrasonic time is 5-30 min.
4. The method for preparing a honeycomb porous carbon material for a lithium-sulfur battery positive electrode according to claim 1, characterized in that: The freezing time in step (1) is 8-24 h, the freezing temperature range is -60°C to -80°C; the freeze-drying time is 36-72 h.
5. The method for preparing a honeycomb porous carbon material for a lithium-sulfur battery positive electrode according to claim 1, characterized in that: The carbonization heating rate is 1-5 ℃ / min, the calcination time is 2-4 h, and the atmosphere is argon or nitrogen.
6. A honeycomb porous carbon material for a lithium-sulfur battery positive electrode, obtained by the preparation method of a honeycomb porous carbon material for a lithium-sulfur battery positive electrode according to any one of claims 1 to 5.
7. The honeycomb porous carbon material for a lithium-sulfur battery positive electrode according to claim 6; characterized in that: The mass ratio of SPC-Ce to lithium sulfide, conductive agent and binder is 2-3:5-6:1:1.