An amorphous CoSe2 / C anode material, its preparation method and application

Abstract

The application discloses an amorphous CoSe2 / C negative electrode material and a preparation method and application thereof, and belongs to the technical field of negative electrode materials. Co(NO3)2 6H2O and polyacrylonitrile are used as raw materials to prepare a precursor solution and perform electrostatic spinning to form a fiber membrane; subsequently, the fiber membrane is sequentially subjected to pre-oxidation and high-temperature carbonization treatment to obtain a Co / C composite material; the Co / C composite material is subjected to selenization treatment with Se powder to obtain a CoSe2 / C composite material; and the CoSe2 / C is subjected to heating reaction to obtain the amorphous CoSe2 / C negative electrode material. The amorphous CoSe2 / C composite material is used as a negative electrode of a potassium ion battery, reaction kinetics is improved, volume strain can be effectively buffered, particle rupture and electrode pulverization can be prevented, amorphization treatment is performed in the preparation steps, more defects and active sites are provided through a disordered structure, and the structural stability is enhanced.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, and in particular to an amorphous CoSe2 / C anode material, its preparation method, and its application. Background Technology

[0002] With the continuous growth of global energy demand and the increasing severity of environmental problems, the development of efficient and clean energy storage technologies has become one of the important directions of current scientific research. Lithium-ion batteries (LIBs) are widely used in portable electronic devices, electric vehicles, and smart grids due to their high energy density, long cycle life, and environmental friendliness. However, the limited availability and uneven geographical distribution of lithium resources have led to a continuous rise in their price, limiting the large-scale application of lithium-ion batteries. Therefore, finding low-cost, high-abundance alternative energy storage systems has become a research hotspot.

[0003] Among numerous candidate energy storage technologies, potassium-ion batteries (PIBs) have attracted considerable attention due to their high natural abundance and near-lithium standard electrode potential. However, because the radius of potassium ions is significantly larger than that of lithium ions, their insertion / extraction kinetics in electrode materials are slow and prone to causing material structure collapse, resulting in problems such as rapid capacity decay and poor rate performance.

[0004] Currently, the most studied potassium-ion battery anode materials mainly include carbon-based materials (such as graphite, hard carbon, and soft carbon), alloy materials (such as Sn, Sb, and Bi), and metal compounds (such as metal oxides, sulfides, and selenides). However, all of them have some drawbacks. For example, graphite, as a classic anode material for lithium-ion batteries, performs poorly in potassium-ion batteries because its interlayer spacing is insufficient to accommodate large-sized K+ atoms. + This results in low reversible capacity and poor cycling stability. While hard carbon and soft carbon materials can improve K by increasing the interlayer spacing, this leads to low reversible capacity and poor cycling stability. + While potassium-ion batteries offer good storage performance, their capacity and rate capability still fall short of practical requirements. Alloy materials (such as Sb) have high theoretical capacity, but their drastic volume changes during charge and discharge lead to electrode pulverization and a sharp decline in cycle life. Therefore, developing novel high-performance anode materials is crucial for the practical application of potassium-ion batteries.

[0005] In recent years, transition metal selenides (TMSs, such as CoSe2, FeSe2, and NiSe2) have shown great promise in potassium-ion batteries due to their high theoretical capacity, good electronic conductivity, and unique layered structure. CoSe2, in particular, exhibits a favorable open framework formed by Se-Se dimers in its crystal structure, which is conducive to K+ ion exchange. + Co exhibits rapid diffusion, and its metallic properties can further enhance the conductivity of the material. However, CoSe2 still suffers from volume expansion and structural pulverization during charge and discharge, leading to poor cycle stability. Furthermore, its semiconductor properties limit electron transport efficiency.

[0006] To address the aforementioned issues, this paper provides an amorphous CoSe2 / C anode material and its preparation method to solve the problems existing in potassium-ion batteries. Summary of the Invention

[0007] The purpose of this invention is to provide an amorphous CoSe2 / C anode material, its preparation method, and its application, in order to solve the problems in the background art.

[0008] To achieve the above objectives, the present invention provides a method for preparing an amorphous CoSe2 / C anode material, comprising the following steps:

[0009] S1, Co(NO3)2 6H2O and polyacrylonitrile were added to N,N-dimethylformamide and stirred to obtain a precursor solution;

[0010] S2. The precursor solution is electrospinned to form a fiber membrane.

[0011] S3. The fiber membrane is pre-oxidized in air and then placed in a tube furnace for high-temperature carbonization under a protective atmosphere to obtain a Co / C composite material.

[0012] S4. Place the Co / C composite material and Se powder in a tube furnace and perform selenization treatment under a protective atmosphere to obtain the CoSe2 / C composite material.

[0013] S5. Place the CoSe2 / C composite material in a reactor and carry out a closed heating reaction under a reducing atmosphere. Cool to room temperature to obtain an amorphous CoSe2 / C anode material.

[0014] Preferably, in S1, Co(NO3)2 The concentration of 6H2O is 0.1~0.5mol / L, and the concentration of polyacrylonitrile is 8~15wt%; the stirring temperature is 25~60℃, and the stirring time is 8~24h.

[0015] Preferably, during the electrospinning process of S2, the solution propulsion speed is 0.5~1.5mL / h, the spinning voltage is 12~20kV, the receiving distance is 15~20cm, the temperature is 20~40℃, and the humidity is 30~60%.

[0016] Preferably, in step S3, the pre-oxidation temperature is 200~280℃, the heating rate is 1~5℃ / min, and the holding time is 1~6h;

[0017] The high-temperature carbonization temperature is 600~800℃, the heating rate is 1~5℃ / min, and the holding time is 2~6h.

[0018] Preferably, in step S4, the mass ratio of Co / C composite material to Se powder is 1:0.2~5.0; the selenization temperature is 450~550℃, the heating rate is 1~5℃ / min, and the holding time is 2~4h.

[0019] Preferably, in both S3 and S4, the protective atmosphere is argon.

[0020] Preferably, in step S5, the reducing atmosphere is an Ar / H2 mixed atmosphere, and the volume percentage of H2 is 5% to 25%.

[0021] Preferably, in step S5, the heating reaction temperature is 250~320℃, the heating rate is 1~5℃ / min, and the reaction time is 8~24h.

[0022] The present invention also provides a CoSe2 / C anode material, which is prepared by the above preparation method.

[0023] This invention also provides an application of the CoSe2 / C anode material, in which the prepared CoSe2 / C anode material is used as a negative electrode in a potassium-ion battery.

[0024] Preferably, in the potassium-ion battery, metallic potassium is used as the counter electrode and a potassium salt solution is used as the electrolyte.

[0025] Preferably, the potassium-ion battery assembly process is as follows: the negative electrode material is cut into a 12mm diameter circular piece as the negative electrode sheet, a 10mm diameter metallic potassium is used as the counter electrode, a Whatman GF-A glass fiber separator is used, and 1~5mol / L potassium salt is dissolved in a solvent as the electrolyte, and the battery is assembled under the protection of argon gas.

[0026] Preferably, the potassium salt is one of potassium bis(trifluoromethylsulfonyl)imide, potassium hexafluorophosphate, and potassium bis(trifluoromethylsulfonyl)imide; the solvent of the potassium salt solution is one or more of methyl ethyl carbonate, dimethyl carbonate, ethylene glycol dimethyl ether, diethyl carbonate, and ethylene carbonate.

[0027] Therefore, this invention provides an amorphous CoSe2 / C anode material, its preparation method, and its application. The amorphous CoSe2 / C composite material is used as the anode of a potassium-ion battery. The introduction of carbon material not only improves the reaction kinetics but also effectively buffers volumetric strain, preventing particle breakage and electrode pulverization. The amorphization process in the preparation step provides more defects and active sites through the disordered structure, while enhancing structural stability.

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0029] Figure 1 This is a SEM image of Embodiment 1 of the present invention;

[0030] Figure 2 This is the XRD pattern of Embodiment 1 of the present invention;

[0031] Figure 3 This is a cyclic performance diagram of an application embodiment of the present invention;

[0032] Figure 4 The circuit performance diagram is a comparative example of the application of this invention. Detailed Implementation

[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0035] Example 1

[0036] This embodiment prepares an amorphous CoSe2 / C anode material, and the specific steps are as follows:

[0037] S1, 2 mmol of Co(NO3)2 6H2O and 1.0 g of polyacrylonitrile (PAN) were added to 10 mL of N,N-dimethylformamide (DMF) and stirred at 60 °C for 12 h to obtain a precursor solution.

[0038] S2. The precursor solution is electrospinned to form a fiber membrane. The electrospinning parameters are controlled as follows: solution volume is 10 mL, feed speed is 0.8 mL / h, spinning voltage is 13 kV, and receiving distance is 15 cm. Spinning is carried out at a temperature of 30℃ and a humidity of 40% to obtain the fiber membrane.

[0039] S3. The fiber membrane is placed in a muffle furnace and pre-oxidized in air, heated to 260°C at a heating rate of 2°C / min and held for 2 hours. Then it is transferred to a tube furnace for high-temperature carbonization in an argon atmosphere, heated to 700°C at a heating rate of 5°C / min and held for 4 hours to obtain a crystalline Co / C composite material.

[0040] S4. Place 1g of Se powder and 1g of Co / C composite material into the upstream and downstream sides of a ceramic boat, respectively. Place the ceramic boat into a tube furnace and heat it to 480℃ at a heating rate of 2℃ / min under an argon atmosphere for selenization treatment. Hold the temperature for 3 hours and cool to obtain crystalline CoSe2 / C composite material.

[0041] S5. The crystalline CoSe2 / C composite material is added to a reactor filled with Ar / H2 (volume ratio of 95:5) mixed gas, heated to 260℃ at a heating rate of 5℃ / min, held for 24h, and cooled to room temperature to obtain the amorphous CoSe2 / C anode material.

[0042] The prepared amorphous CoSe2 / C anode material was examined by scanning electron microscopy, and the results are as follows: Figure 1 As shown, CoSe2 nanoparticles are uniformly dispersed on carbon fibers. X-ray diffraction was used to analyze the material, and the results are as follows. Figure 2 As shown, no crystal diffraction peaks were observed, indicating the successful preparation of amorphous CoSe2 / C.

[0043] Example 2

[0044] This embodiment provides a method for preparing an amorphous CoSe2 / C anode material, as detailed below:

[0045] S1, 1 mmol of Co(NO3)2 6H2O and 0.85g of polyacrylonitrile (PAN) were added to 10mL of N,N-dimethylformamide (DMF) and stirred at room temperature (25℃) for 8h to obtain a precursor solution.

[0046] S2. The precursor solution is electrospinned to form a fiber membrane. The electrospinning parameters are controlled as follows: solution volume is 10 mL, feed speed is 1 mL / h, spinning voltage is 12 kV, and receiving distance is 18 cm. Spinning is carried out at a temperature of 35℃ and a humidity of 50% to obtain the fiber membrane.

[0047] S3. The fiber membrane is placed in a muffle furnace and pre-oxidized in air, heated to 280°C at a heating rate of 5°C / min, and held for 1 hour. Then it is transferred to a tube furnace for high-temperature carbonization in an argon atmosphere, heated to 800°C at a heating rate of 3°C / min, and held for 2 hours to obtain a crystalline Co / C composite material.

[0048] S4. Place 2g of Se powder and 1.5g of Co / C composite material into the upstream and downstream sides of a ceramic boat, respectively. Place the ceramic boat into a tube furnace and heat it to 500℃ at a heating rate of 3℃ / min under an argon atmosphere for selenization treatment. Hold the temperature for 4 hours and cool to obtain crystalline CoSe2 / C composite material.

[0049] S5. The crystalline CoSe2 / C composite material is added to a reactor filled with Ar / H2 (volume ratio of 90:10) mixed gas, heated to 300℃ at a heating rate of 1℃ / min, held for 12h, and cooled to room temperature to obtain the amorphous CoSe2 / C anode material.

[0050] Example 3

[0051] This embodiment provides a method for preparing an amorphous CoSe2 / C anode material, as detailed below:

[0052] S1, 6 mmol of Co(NO3)2 6H2O and 1.8g of polyacrylonitrile (PAN) were added to 15mL of N,N-dimethylformamide (DMF) and stirred at 30℃ for 16h to obtain a precursor solution.

[0053] S2. The precursor solution is electrospinned to form a fiber membrane. The electrospinning parameters are controlled as follows: solution volume is 15 mL, feed speed is 1.5 mL / h, spinning voltage is 20 kV, and receiving distance is 20 cm. Spinning is carried out at a temperature of 40℃ and a humidity of 30% to obtain the fiber membrane.

[0054] S3. The fiber membrane is placed in a muffle furnace and pre-oxidized in air, heated to 220°C at a heating rate of 1°C / min, and held for 6 hours. Then it is transferred to a tube furnace for high-temperature carbonization in an argon atmosphere, heated to 600°C at a heating rate of 1°C / min, and held for 6 hours to obtain a crystalline Co / C composite material.

[0055] S4. Place 7.5g of Se powder and 1.5g of Co / C composite material into the upstream and downstream sides of a ceramic boat, respectively. Place the ceramic boat into a tube furnace and heat it to 550℃ at a heating rate of 5℃ / min under an argon atmosphere for selenization treatment. Hold the temperature for 3.5h and cool to obtain crystalline CoSe2 / C composite material.

[0056] S5. The crystalline CoSe2 / C composite material is added to a reactor filled with Ar / H2 (volume ratio of 85:15) mixed gas, heated to 280℃ at a heating rate of 2℃ / min, held for 20h, and cooled to room temperature to obtain the amorphous CoSe2 / C anode material.

[0057] Example 4

[0058] This embodiment provides a method for preparing an amorphous CoSe2 / C anode material, as detailed below:

[0059] S1, 2.5 mmol of Co(NO3)2 6H2O and 0.95g of polyacrylonitrile (PAN) were added to 5mL of N,N-dimethylformamide (DMF) and stirred at 40℃ for 20h to obtain a precursor solution.

[0060] S2. The precursor solution is electrospinned to form a fiber membrane. The electrospinning parameters are controlled as follows: solution volume is 5 mL, feed speed is 0.5 mL / h, spinning voltage is 15 kV, and receiving distance is 15 cm. Spinning is carried out at a temperature of 25℃ and a humidity of 45% to obtain the fiber membrane.

[0061] S3. The fiber membrane is placed in a muffle furnace and pre-oxidized in air, heated to 250°C at a heating rate of 3°C / min and held for 4 hours. Then it is transferred to a tube furnace for high-temperature carbonization in an argon atmosphere, heated to 650°C at a heating rate of 2°C / min and held for 3 hours to obtain a crystalline Co / C composite material.

[0062] S4. Place 4g of Se powder and 2g of Co / C composite material into the upstream and downstream sides of a ceramic boat, respectively. Place the ceramic boat into a tube furnace and heat it to 450℃ at a heating rate of 1℃ / min under an argon atmosphere for selenization treatment. Hold the temperature for 2.5h and cool to obtain crystalline CoSe2 / C composite material.

[0063] S5. The crystalline CoSe2 / C composite material is added to a reactor filled with Ar / H2 (volume ratio of 80:20) mixed gas, heated to 250℃ at a heating rate of 3℃ / min, held for 16h, and cooled to room temperature to obtain the amorphous CoSe2 / C anode material.

[0064] Example 5

[0065] This embodiment provides a method for preparing an amorphous CoSe2 / C anode material, as detailed below:

[0066] S1, 3 mmol of Co(NO3)2 6H2O and 1.5g of polyacrylonitrile (PAN) were added to 10mL of N,N-dimethylformamide (DMF) and stirred at 50℃ for 24h to obtain a precursor solution.

[0067] S2. The precursor solution is electrospinned to form a fiber membrane. The electrospinning parameters are controlled as follows: solution volume is 10 mL, feed speed is 1.2 mL / h, spinning voltage is 18 kV, and receiving distance is 16 cm. Spinning is carried out at a temperature of 20℃ and a humidity of 60% to obtain the fiber membrane.

[0068] S3. The fiber membrane is placed in a muffle furnace and pre-oxidized in air, heated to 200°C at a heating rate of 4°C / min, and held for 5 hours. Then it is transferred to a tube furnace for high-temperature carbonization in an argon atmosphere, heated to 750°C at a heating rate of 4°C / min, and held for 5 hours to obtain a crystalline Co / C composite material.

[0069] S4. Place 0.4g of Se powder and 2g of Co / C composite material into the upstream and downstream sides of a ceramic boat, respectively. Place the ceramic boat into a tube furnace and heat it to 520℃ at a heating rate of 4℃ / min under an argon atmosphere for selenization treatment. Hold the temperature for 2 hours and cool to obtain crystalline CoSe2 / C composite material.

[0070] S5. The crystalline CoSe2 / C composite material is added to a reactor filled with Ar / H2 (volume ratio of 75:25) mixed gas, heated to 320℃ at a heating rate of 4℃ / min, held for 8h, and cooled to room temperature to obtain the amorphous CoSe2 / C anode material.

[0071] Comparative Example 1

[0072] This comparative example follows the same steps as in Example 1, except that step S1 is modified to involve adding 6 mmol of Co(NO3)2. 6H2O and 1.0 g of polyacrylonitrile (PAN) were added to 10 mL of N,N-dimethylformamide (DMF) and stirred at 60 °C for 12 h to obtain a precursor solution.

[0073] The increased salt concentration in the precursor solution leads to instability in the spinning jet, a wider fiber diameter distribution, and even beading and fiber breakage. After pre-oxidation and carbonization, larger and unevenly distributed Co particles are formed. In the subsequent selenization process, the large Co particles are difficult to completely selenize, resulting in crystalline Co@CoSe2 / C composite material. After treatment in a reactor, amorphous Co@CoSe2 / C anode material is finally obtained.

[0074] Comparative Example 2

[0075] The steps in this comparative example are the same as those in Example 2, except that in step S2, the spinning voltage is changed to 10kV.

[0076] The reduction in spinning voltage leads to a significant decrease in electric field strength, resulting in difficulty in jet initiation. The electric field force is insufficient to continuously and stably overcome surface tension and pull the jet out of the needle, causing the jet to be intermittent and dripping, and the solution failing to be fully stretched into fibers. Ultimately, amorphous CoSe2 / C anode materials cannot be obtained.

[0077] Comparative Example 3

[0078] The steps in this comparative example are the same as those in Example 3, except that in step S5, the heating rate during the sealing and heating treatment of the reactor is modified to 8°C / min.

[0079] Due to the increased heating rate, when the material reaches the 280℃ holding point, it still retains a higher concentration of non-equilibrium defects and higher internal energy. The entire system is in a metastable state further away from equilibrium, ultimately yielding a crystalline CoSe2 / C anode material.

[0080] Comparative Example 4

[0081] The steps in this comparative example are the same as those in Example 4, except that in step S5, the heat preservation time during the sealing and heating treatment of the reactor is modified to 6 hours.

[0082] The reduced holding time resulted in insufficient amorphous relaxation, ultimately leading to the formation of crystalline CoSe2 / C anode material.

[0083] Comparative Example 5

[0084] The steps in this comparative example are the same as those in Example 5, except that in step S5, the filling atmosphere in the reactor is changed to pure Ar.

[0085] The presence of H2 inhibits the volatilization and oxidation of Se at high temperatures. Without the inhibition of H2, the atoms in the material are more likely to migrate and rearrange under thermal drive, thus crystallizing and finally obtaining crystalline CoSe2 / C anode material.

[0086] Application Examples

[0087] The amorphous CoSe2 / C anode material prepared in Example 1 was used to assemble a potassium-ion battery. The specific assembly method is as follows:

[0088] The negative electrode material was cut into 12mm diameter discs as negative electrode plates, and 10mm diameter metallic potassium was used as the counter electrode. The glass fiber separator electrolyte of whatmanGF-A was 1mol / L potassium hexafluorophosphate dissolved in dimethyl carbonate. The cells were assembled into button cells in a glove box (water and oxygen content were both below 0.01ppm).

[0089] In 25 Its cycle performance was measured at 1℃ with an operating voltage of 0.01~3V. The cycle performance of the CoSe2 / C‖K half-cell was tested as follows: Figure 3 As shown, the current density is 500 mAg -1 The material can be stably cycled 500 times with a capacity retention rate of 91.6%, indicating that the prepared material has excellent cycle stability.

[0090] Application of comparative examples

[0091] The crystalline CoSe2 / C anode material prepared in Comparative Example 5 was used to assemble a potassium-ion battery using the assembly method described in the application examples.

[0092] Cyclic performance tests were conducted on the potassium-ion batteries used in the comparative application, and the results are as follows: Figure 4 As shown, compared to the amorphous CoSe2 / C anode material used in the application examples, the crystalline CoSe2 / C anode material used in this comparative example exhibits a lower 500 mAg performance. -1 After 100 cycles at a current density, the capacity retention was only 63%, exhibiting poor cycling stability. This demonstrates that the amorphous CoSe2 / C anode material prepared by the method protected in this invention improves reaction kinetics, effectively buffers volumetric strain, and prevents particle breakage and electrode pulverization.

[0093] Therefore, this invention provides an amorphous CoSe2 / C anode material, its preparation method, and its application. The prepared amorphous CoSe2 / C anode can effectively alleviate volume changes during cycling and improve cycle stability. It has great guiding significance for the application of potassium-ion battery anodes, and this method is conducive to the large-scale application of high-performance potassium-ion battery anodes.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an amorphous CoSe2 / C anode material, characterized in that, Includes the following steps: S1, Co(NO3)2 6H2O and polyacrylonitrile were added to N,N-dimethylformamide and stirred to obtain a precursor solution; S2. The precursor solution is electrospinned to form a fiber membrane. S3. The fiber membrane is pre-oxidized in air and then placed in a tube furnace for high-temperature carbonization under a protective atmosphere to obtain a Co / C composite material. S4. Place the Co / C composite material and Se powder in a tube furnace and perform selenization treatment under a protective atmosphere to obtain crystalline CoSe2 / C composite material; S5. Place the crystalline CoSe2 / C composite material in a reactor and carry out a closed heating reaction under a reducing atmosphere. The reducing atmosphere is an Ar / H2 mixed atmosphere, with H2 accounting for 5%~25% of the volume. The heating reaction temperature is 250~320℃, the heating rate is 1~5℃ / min, and the reaction time is 8~24h. Cool to room temperature to obtain the amorphous CoSe2 / C anode material.

2. The method for preparing an amorphous CoSe2 / C anode material according to claim 1, characterized in that: In S1, Co(NO3)2 The concentration of 6H2O is 0.1~0.5mol / L, and the concentration of polyacrylonitrile is 8~15wt%; the stirring temperature is 25~60℃, and the stirring time is 8~24h.

3. The method for preparing an amorphous CoSe2 / C anode material according to claim 1, characterized in that: During the electrospinning process of S2, the solution propulsion speed is 0.5~1.5mL / h, the spinning voltage is 12~20kV, the receiving distance is 15~20cm, the temperature is 20~40℃, and the humidity is 30~60%.

4. The method for preparing an amorphous CoSe2 / C anode material according to claim 1, characterized in that: In S3, the pre-oxidation temperature is 200~280℃, the heating rate is 1~5℃ / min, and the holding time is 1~6h; The high-temperature carbonization temperature is 600~800℃, the heating rate is 1~5℃ / min, and the holding time is 2~6h.

5. The method for preparing an amorphous CoSe2 / C anode material according to claim 1, characterized in that: In S4, the mass ratio of Co / C composite material to Se powder is 1:0.2~5.0; the selenization temperature is 450~550℃, the heating rate is 1~5℃ / min, and the holding time is 2~4h.

6. The method for preparing an amorphous CoSe2 / C anode material according to claim 1, characterized in that: In both S3 and S4, the protective atmosphere is argon.

7. An amorphous CoSe2 / C anode material, characterized in that: The amorphous CoSe2 / C anode material is prepared by the preparation method described in any one of claims 1-6.

8. An application of an amorphous CoSe2 / C anode material, characterized in that: The amorphous CoSe2 / C anode material prepared in claim 7 is used as an anode sheet in potassium-ion batteries.

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