Preparation method of sulfur-doped amorphous carbon nanosheet and application to sodium ion battery negative electrode
By preparing sulfur-doped amorphous carbon nanosheets as anode materials for sodium-ion batteries, the problems of limited reserves of precursor elements for lithium-ion batteries and difficulties in applying graphite anode materials in sodium-ion batteries have been solved, achieving high capacity, high rate performance and stable battery performance.
Patent Information
- Application Number
- CN202510256640.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-05
- Publication Date
- 2026-01-02
- Estimated Expiration
- 2045-03-05
AI Technical Summary
The limited reserves of precursor elements for lithium-ion batteries lead to high costs, and graphite anode materials are difficult to apply in sodium-ion batteries. Existing carbon materials have insufficient rate performance and stability in sodium-ion batteries.
Sulfur-doped amorphous carbon nanosheets were used as the anode material for sodium-ion batteries. The sulfur-doped carbon nanosheets were formed by pre-carbonization with sodium citrate and mixing with sublimed sulfur under a high-temperature inert atmosphere. The resulting three-dimensional porous structure was then combined with an ether electrolyte to form a stable SEI film, thereby improving the active sites and conductivity of the material.
It improves the specific capacity, fast kinetics, and high-rate performance of sodium-ion batteries, while enhancing the stability and cycle performance of electrode materials, especially exhibiting excellent electrochemical performance at high current densities.
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Figure CN119750555B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of composite materials, and relates to preparation of carbon nanosheets, in particular to a preparation method of sulfur-doped amorphous carbon nanosheets and application of the sulfur-doped amorphous carbon nanosheets to a sodium ion battery negative electrode. BACKGROUND
[0002] For many years, lithium ion batteries have been dominant in commercial energy storage devices. However, due to the limited reserves of lithium, cobalt, nickel and copper, which are required as precursor elements in the production of lithium ion batteries, the cost and output of lithium ion batteries are difficult to meet the future large-scale energy storage applications. Therefore, sodium ion batteries have attracted widespread attention due to their abundant natural resources and have become an excellent substitute for lithium ion batteries.
[0003] Due to the larger ionic radius of sodium ions compared to lithium ions, the graphite negative electrode material widely used in lithium ion batteries is difficult to follow in sodium ion batteries. So far, most researches have mainly focused on amorphous carbon materials. In principle, the specific capacity of the negative carbon material mainly comes from the surface capacitance control capacity and diffusion control capacity of the bulk phase. And heteroatom doping is a common method to improve the rate performance of various negative carbon materials of sodium ion batteries due to the expansion of interlayer spacing and the enhancement of pseudo-capacitance. Sulfur doping of carbon materials not only expands the interlayer spacing of carbon materials, facilitates the insertion and extraction of sodium ions, improves the fast kinetics of sodium ions, but also effectively improves the electrical conductivity of the material. In addition, the polysulfide generated by sulfur doping can further increase the number of active sites of the carbon material, thereby increasing the specific capacity of the sodium ion battery.
[0004] The main electrolyte types commonly used in batteries at present are ester-based electrolytes and ether-based electrolytes. Among them, the ether-based electrolyte can form a thin and dense and uniform SEI film on the surface of the negative electrode material compared with the ester-based electrolyte, which improves the interface stability of the negative electrode material. In addition, the ether-based electrolyte can also produce a special ion co-intercalation phenomenon compared with the ester-based electrolyte: during the charging and discharging of the ether-based electrolyte, the solvent molecules of the ether will be solvated with sodium ions and together deintercalate into the electrode material; causing further expansion and contraction of the electrode material, so that the active sites in the deep layer of the material are utilized, thereby increasing the reversible capacity of the battery to a certain extent. Thus, the material remains stable while the capacity gradually increases after deep charging and discharging, showing a rare self-optimization phenomenon. SUMMARY
[0005] In view of the problems existing in the prior art, a first object of the present application is to provide a preparation method of sulfur-doped amorphous carbon nanosheets.
[0006] TECHNICAL SCHEME
[0007] The preparation method of the sulfur-doped amorphous carbon nanosheets comprises the following steps:
[0008] A. Sodium citrate is taken as a carbon source, and is put into a high-temperature inert atmosphere furnace for pre-carbonization treatment to obtain carbon-coated Na2CO3 particle matrix, and the carbon-coated Na2CO3 particle matrix is pickled and dried to obtain a precursor A;
[0009] B. The precursor A is mixed with sublimed sulfur, and then is put into a high-temperature inert atmosphere furnace for high-temperature treatment, and is taken out and naturally cooled to obtain sulfur-doped carbon nanosheets.
[0010] In the step A of the preferred disclosure of the present application, the pre-carbonization treatment temperature is 400-1000 DEG C, the heat treatment time is 1-5 h, the heating rate is 5 DEG C / min, and the inert atmosphere is high-purity nitrogen with a purity of 99.999 %; preferably, the temperature is 600 DEG C, and the time is 5 h.
[0011] In the step A of the preferred disclosure of the present application, the acid pickling and drying are stirring washing with 2M hydrochloric acid solution and centrifugal washing with deionized water, and the precursor A is obtained by drying at 105 DEG C for 12 h.
[0012] In the step B of the preferred disclosure of the present application, the precursor A is mixed with sublimed sulfur at a mass ratio of 1:1-10, and is preferably mixed at a mass ratio of 1:5 by using a ball mill for sufficient mixing.
[0013] In the step B of the preferred disclosure of the present application, the high-temperature treatment temperature is 300-600 DEG C, the treatment time is 1-5 h, the heating rate is 2 DEG C / min, and the inert atmosphere is high-purity nitrogen with a purity of 99.999 %; preferably, the temperature is 400 DEG C, and the treatment time is 2 h.
[0014] The sulfur-doped amorphous carbon nanosheets prepared by the method disclosed in the present application exhibit a three-dimensional porous structure, as shown in a scanning electron microscope (SEM) image. Figure 2 As shown in the SEM image, super-thin and curved carbon sheets are obtained, which are connected to each other and integrated into a 3D foam-like structure; and as can be further seen from a transmission electron microscope (TEM) image, the material has rich support cavities in a large pore framework.
[0015] A second object of the present application is to disclose the application of the prepared sulfur-doped amorphous carbon nanosheets, i.e., the application of the prepared sulfur-doped amorphous carbon nanosheets to a negative electrode of a sodium ion battery.
[0016] A preparation method of a sulfur-doped amorphous carbon negative electrode sheet for a sodium ion battery, comprising the following steps:
[0017] S1: Sulfur-doped amorphous carbon nanosheet powder, a conductive additive and a binder are premixed, deionized water is added and stirred to obtain a negative electrode slurry, wherein the negative electrode slurry comprises 8 parts of sulfur-doped amorphous carbon nanosheet powder, 1 part of conductive additive and 1 part of binder by mass fraction;
[0018] S2: The negative electrode slurry is coated on the surface of a copper foil, and vacuum drying is performed to obtain the sulfur-doped amorphous carbon negative electrode sheet.
[0019] The third object of the present application is to disclose a sodium ion battery using the sulfur-doped amorphous carbon negative electrode sheet, comprising a positive electrode sheet, a negative electrode sheet, a battery separator and an ether electrolyte, wherein the positive electrode sheet comprises a positive electrode active material, a conductive agent and a binder, the positive electrode active material comprises any one or more of layered oxides, polyanions and prussian blue;
[0020] The battery separator is a polyethylene, polypropylene, glass fiber separator or polytetrafluoroethylene;
[0021] The ether electrolyte has one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, dioxolane, etc. as the solvent; and one or more of NaPF6, NaClO4, etc. as the salt.
[0022] Advantages
[0023] The present application discloses a sulfur-doped amorphous carbon negative electrode material and a corresponding negative electrode sheet and a preparation method of a sodium ion battery, wherein the stacking of the sulfur-doped nanometer carbon sheet presents a three-dimensional porous structure, which is expected to expand the surface area of the electrode / electrolyte for ion insertion and adsorption; and the sulfur dopant and small polysulfide aggregates enable the sulfur-doped carbon nanometer sheet to have more active sites and wider interlayer spacing, which is beneficial to the rapid storage and diffusion of ions, improves the rapid kinetics of the sodium ion battery; in addition, the sulfur-doped nanometer carbon sheet process is simple and low in cost, and can be applied as a sodium ion battery negative electrode material in the sodium ion battery, so that the sodium ion battery has high capacity, high rate performance and other excellent performances. After the material is made into a negative electrode sheet, an ether electrolyte is prepared into a sodium ion battery, and through the co-embedding effect, the stability of the solid electrolyte interface film of the sodium ion battery can be improved, and excellent cycle performance can be obtained; at the same time, the polysulfide generated by annealing of the sulfur doped in the carbon material can be further effectively activated due to the ether electrolyte, especially at high current density, thereby improving the rate performance of the material. BRIEF DESCRIPTION OF DRAWINGS
[0024] Figure 1 . Preparation method flow chart of sulfur-doped amorphous carbon nanometer sheet and its precursor A;
[0025] Figure 2 . The scanning electron microscope and transmission electron microscope images of the precursor A and the sulfur-doped amorphous carbon nanometer sheet prepared in Example 1 are compared, and the EDS element images of the sulfur-doped amorphous carbon about C, O and S are compared, and the mass percentages are 82.67%, 4.79% and 12.54% respectively;
[0026] Figure 3 . The cyclic voltammetry curves of the sulfur-doped amorphous carbon nanometer sheet prepared in Example 1 are compared under low scanning speed with ether electrolyte DME and ester electrolyte EC / PC respectively.
[0027] Figure 4 The sulfur-doped amorphous carbon nanosheet prepared in Example 1 is compared in terms of current charge-discharge at different cycles at a low current density with ether electrolyte DME and ester electrolyte EC / PC, respectively;
[0028] Figure 5 The sulfur-doped amorphous carbon nanosheet prepared in Example 1 is compared in terms of rate performance at a step current density with ether electrolyte DME and ester electrolyte EC / PC, respectively. DETAILED DESCRIPTION
[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application. In addition, in the description of the present application, the term “comprising” means “including but not limited to”.
[0030] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the described range has specifically disclosed all possible sub-ranges and single values in the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers in the described range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated in the present application, it means that any cited number (fraction or integer) in the indicated range is included.
[0031] In the present application, “and / or” describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural.
[0032] Example 1
[0033] A preparation method of a sulfur-doped amorphous carbon nanosheet, comprising the following steps:
[0034] A. Sodium citrate is used as a carbon source and placed in a high-temperature inert atmosphere furnace for pre-carbonization treatment to obtain carbon-coated Na2CO3 particle matrix. The carbon-coated Na2CO3 particle matrix is stirred and washed with 2M hydrochloric acid solution for 12 hours, then washed with deionized water and centrifuged for more than three times. The obtained sample is dried in a blast drying oven at 105°C for 12 hours to obtain precursor A; wherein the pre-carbonization temperature is 600°C, the heat treatment time is 5 hours, the heating rate is 5°C / min, and the inert atmosphere is high-purity nitrogen with a purity of 99.999%;
[0035] B. The precursor A and sublimed sulfur are mixed in a mass ratio of 1:5 using a ball mill, and the mixture is placed in a high-temperature inert atmosphere furnace with a temperature of 400°C, a heat treatment time of 2 hours, a heating rate of 2°C / min, and an inert atmosphere of high-purity nitrogen with a purity of 99.999% to obtain sulfur-doped amorphous carbon nanosheets.
[0036] In an inert atmosphere glove box with water / oxygen indicators both <0.1 ppm, the prepared sulfur-doped amorphous carbon nanosheet powder is used as a negative electrode material to prepare a sodium ion battery. Glass fiber is used as a separator, and a CR2032 button cell is assembled in the order of positive electrode shell-sulfur-doped amorphous carbon-glass fiber separator-ether-based electrolyte dimethyl ether (DME)-sodium sheet-gasket-spring sheet-negative electrode shell and subjected to electrochemical performance testing.
[0037] The sodium ion battery assembled with the above-mentioned sulfur-doped amorphous carbon negative electrode sheet with dimethyl ether (DME) as the electrolyte is subjected to low sweep rate cyclic voltammetry (CV) test at 0.2 mVs −1 , low current density charge-discharge cycle test (GCD) at 100 mAhg -1 , and rate performance test at current densities of 0.1, 0.2, 0.5, 1.0, 2.0, 5.0, 10, 20, and 50 Ag -1 . As shown in Figure 3 , the sulfur-doped amorphous carbon with dimethyl ether (DME) exhibits two pairs of redox peaks at 1.9 / 2.2 and 0.8 / 1.7 V. As shown in Figure 4 , in the low current density deep charge-discharge cycle at 100 mAhg -1 , the sulfur-doped amorphous carbon material with dimethyl ether (DME) shows a rare gradual growth trend, and the specific capacity reaches 467.2 mAh g -1 after 100 deep cycles. As shown in Figure 5 , at current densities of 0.1, 0.2, 0.5, 1.0, 2.0, 5.0, 10, 20, and 50 Ag -1The electrode in the electrolyte based on dimethyl ether of ethylene glycol (DME) can provide a reversible specific capacity of 437, 434, 414, 398, 376, 337, 305, 270 and 191 mAh g -1 .
[0038] To further illustrate the key of the present application, the following comparative examples are added for illustration.
[0039] Comparative Example 1
[0040] The preparation process of the sodium ion battery is basically the same as that of Example 1, wherein the precursor A is retained and no sulfur doping is performed.
[0041] As shown in Figure 2 , the sulfur-doped amorphous carbon material and the precursor A are compared by scanning electron microscopy and transmission electron microscopy, and it can be seen that the 3D framework structure composed of ultra-thin elastic sheets before and after sulfur doping is similar, indicating that the sulfur doping does not change the carbon layer structure.
[0042] Comparative Example 2
[0043] The preparation process of the sodium ion battery is basically the same as that of Example 1, wherein the electrolyte is replaced by ester-based electrolyte EC / PC.
[0044] As shown in Figure 3 , in the cyclic voltammetry (CV) test at a low scan rate of 0.2 mVs −1 , the sulfur-doped amorphous carbon with ester-based electrolyte EC / PC only presents a pair of redox peaks at 1.77 / 1.69 V, and it can be seen that the sulfur-doped amorphous carbon with dimethyl ether of ethylene glycol (DME) has a larger voltammetry curve area, more significant surface oxidation-reduction reaction and better electrochemical performance. As shown in Figure 4 , in the low current density deep charge-discharge cycle at 100 mAhg -1 , the sulfur-doped amorphous carbon material with ester-based electrolyte EC / PC has a specific capacity of only 331.4 mAh g -1 after 100 deep cycles. The specific capacity reaches 467.2 mAh g -1 after 100 deep cycles. As shown in Figure 5 , at a current density of 0.1, 0.2, 0.5, 1.0, 2.0, 5.0, 10, 20 and 50 A g -1 , the electrode in the electrolyte based on ester-based electrolyte EC / PC can only provide a reversible specific capacity of 444, 418, 384, 358, 328, 275, 197, 154 and 82.4 mAh g -1 . From Figure 3 , 4 and Figure 5It can be clearly seen that the electrochemical performance of the sulfur-doped amorphous carbon material in the ether electrolyte ethylene glycol dimethyl ether (DME) is significantly better than that in the ester electrolyte (EC / PC).
[0045] Example 2
[0046] A method for preparing sulfur-doped amorphous carbon nanosheets, comprising the following steps:
[0047] A. Sodium citrate is used as a carbon source and is placed in a high-temperature inert atmosphere furnace for pre-carbonization treatment to obtain a carbon-coated Na2CO3 particle matrix. The carbon-coated Na2CO3 particle matrix is stirred and washed with a 2M hydrochloric acid solution for 12h, and then washed with deionized water and centrifuged for more than three times. The obtained sample is dried in a blast drying oven at 105°C for 12h to obtain a precursor A; wherein the pre-carbonization temperature is 1000°C, the heat treatment time is 1h, the heating rate is 5°C / min, and the inert atmosphere is high-purity nitrogen with a purity of 99.999%;
[0048] B. The precursor A and sublimed sulfur are mixed in a mass ratio of 1:2 using a ball mill, and the mixture is placed in a high-temperature inert atmosphere furnace with a temperature of 300°C, a heat treatment time of 2h, a heating rate of 2°C / min, and an inert atmosphere of high-purity nitrogen with a purity of 99.999% to obtain sulfur-doped amorphous carbon nanosheets.
[0049] The obtained sulfur-doped amorphous carbon material is adapted to an ether electrolyte ethylene glycol dimethyl ether (DME) to assemble a CR2032 button cell in an inert atmosphere glove box with water / oxygen indexes both <0.1ppm. A low current density charge-discharge cycle test (GCD) is performed at 100mAh g -1 -1 .
[0050] Example 3
[0051] A method for preparing sulfur-doped amorphous carbon nanosheets, comprising the following steps:
[0052] A. Sodium citrate is used as a carbon source and is placed in a high-temperature inert atmosphere furnace for pre-carbonization treatment to obtain a carbon-coated Na2CO3 particle matrix. The carbon-coated Na2CO3 particle matrix is stirred and washed with a 2M hydrochloric acid solution for 12h, and then washed with deionized water and centrifuged for more than three times. The obtained sample is dried in a blast drying oven at 105°C for 12h to obtain a precursor A; wherein the pre-carbonization temperature is 1000°C, the heat treatment time is 1h, the heating rate is 5°C / min, and the inert atmosphere is high-purity nitrogen with a purity of 99.999%;
[0053] B. The precursor A is mixed with sublimed sulfur in a mass ratio of 1:10 by using a ball mill, and the mixture is placed in a high-temperature inert atmosphere furnace, the temperature is 600 DEG C, the heat treatment time is 2h, the heating speed is 2 DEG C / min, the inert atmosphere is pure nitrogen with a purity of 99.999%, and sulfur-doped amorphous carbon nanosheets are obtained.
[0054] The obtained sulfur-doped amorphous carbon material is assembled into a CR2032 button cell in an inert atmosphere glove box with water / oxygen indexes of <0.1 ppm by adapting an ether electrolyte ethylene glycol dimethyl ether (DME), and a 100 mAh g -1 of low current density charge-discharge cycle test (GCD) is carried out, and the specific capacity is only 446 mAh g -1 after 100 deep cycles.
[0055] The above only describes the embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation made by using the present application specification, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.
Claims
1. Use of sulfur-doped amorphous carbon nanosheets in sodium-ion batteries, characterized in that, The sodium ion battery comprises a negative electrode sheet made of sulfur-doped amorphous carbon nanosheets, a positive electrode sheet, a battery separator and an ether electrolyte, and the polysulfides generated by annealing of the sulfur doped in the sulfur-doped amorphous carbon nanosheets are effectively activated by the ether electrolyte to improve the rate performance of the material, wherein the sulfur-doped amorphous carbon nanosheets are prepared by the following steps: A. Sodium citrate is used as a carbon source and is placed in a high-temperature inert atmosphere furnace for pre-carbonization treatment to obtain a carbon-coated Na2CO3 particle matrix, and the matrix is subjected to acid washing and drying to obtain a precursor A; wherein the pre-carbonization treatment temperature is 400-1000°C, the heat treatment time is 1-5h, and the acid washing and drying are performed by stirring and washing with 2M hydrochloric acid solution for 12h, followed by centrifugal washing with deionized water and drying treatment; B. The precursor A is mixed with sublimed sulfur and then placed in a high-temperature inert atmosphere furnace for high-temperature treatment, and the sulfur-doped nanocarbon nanosheets are obtained by natural cooling; wherein the precursor A and the sublimed sulfur are mixed at a mass ratio of 1:1-10 and are fully mixed by a ball mill; the high-temperature treatment temperature is 300-600°C, and the treatment time is 1-5h.
2. Use of the sulfur-doped amorphous carbon nanosheets according to claim 1 in sodium-ion batteries, characterized in that: In step A, the inert atmosphere is high-purity nitrogen with a purity of 99.999%.
3. Use of the sulfur-doped amorphous carbon nanosheets according to claim 1 in sodium-ion batteries, characterized in that: In step A, the temperature increasing rate is 5°C / min.
4. Use of the sulfur-doped amorphous carbon nanosheets according to claim 1 in sodium-ion batteries, characterized in that: In step A, the pre-carbonization treatment temperature is 600°C, and the heat treatment time is 5h.
5. Use of the sulfur-doped amorphous carbon nanosheets according to claim 1 in sodium-ion batteries, characterized in that: In step A, the drying treatment is drying at 105°C for 12h.
6. Use of the sulfur-doped amorphous carbon nanosheets according to claim 1 in sodium-ion batteries, characterized in that: In step B, the inert atmosphere is high-purity nitrogen with a purity of 99.999%.
7. Use of the sulfur-doped amorphous carbon nanosheets according to claim 1 in sodium-ion batteries, characterized by: In step B, the temperature increasing rate is 2°C / min.
8. Use of the sulfur-doped amorphous carbon nanosheets according to claim 1 in sodium-ion batteries, characterized in that: In step B, the precursor A and the sublimed sulfur are mixed at a mass ratio of 1:
5.
9. Use of the sulfur-doped amorphous carbon nanosheets according to claim 1 in sodium-ion batteries, characterized in that: In step B, the high-temperature treatment temperature is 400°C, and the treatment time is 2h.
10. Use of the sulfur-doped amorphous carbon nanosheets according to claim 1 in a sodium-ion battery, characterized in that, The negative electrode sheet made of the sulfur-doped amorphous carbon nanosheets is prepared by the following steps: S1: The sulfur-doped amorphous carbon nanosheet micro-powder, a conductive additive and a binder are pre-mixed, deionized water is added and stirred to obtain a negative electrode slurry, wherein the negative electrode slurry comprises 8 parts of sulfur-doped amorphous carbon nanosheet micro-powder, 1 part of conductive additive and 1 part of binder by mass; S2: The negative electrode slurry is coated on the surface of a copper foil, and the negative electrode sheet is obtained after vacuum drying.
11. Use of the sulfur-doped amorphous carbon nanosheets according to claim 1 in sodium-ion batteries, characterized in that: The positive electrode sheet comprises a positive electrode active material, a conductive agent and a binder, and the positive electrode active material comprises any one or more of layered oxides, polyanion-based materials and Prussian blue-based materials.
12. Use of the sulfur-doped amorphous carbon nanosheets according to claim 1 in sodium-ion batteries, characterized by: The battery separator is a polyethylene, polypropylene, glass fiber separator or polytetrafluoroethylene.
13. Use of the sulfur-doped amorphous carbon nanosheets according to claim 1 in sodium-ion batteries, characterized by: The ether electrolyte has one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran and dioxolane as a solvent, and one or more of NaPF6 and NaClO4 as a salt.