Preparation method and application of N-type silicon / silicon carbide / carbon semiconductor nanocomposite material for potassium ion battery

Abstract

The present invention discloses a preparation method and application of an N-type silicon / silicon carbide / carbon semiconductor nanocomposite material for potassium ion batteries. The present invention uses a vacuum DC arc method to prepare mutually cross-linked Si / SiC nanowires. The gaps between the nanowires provide sufficient space for the volume expansion of Si. P doping converts Si into an N-type semiconductor, causing defects in the active material Si, providing sufficient ion embedding sites. The abundant electron carriers generated greatly increase the electron transfer rate. P doping also induces the reorganization of SiC nanowires, causing them to be distributed on the surface of Si, better buffering the volume expansion of Si, thereby forming a three-layer sandwich structure with an inner layer of P-doped Si, a middle layer of SiC, and an outermost layer of amorphous carbon. The present invention can effectively buffer the volume expansion of silicon, reduce the pulverization of silicon materials, and improve the conductivity of the composite material, thereby improving the electrochemical performance of potassium ion batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of potassium ion battery semiconductor nanocomposite materials, and in particular to a preparation method and application of an N-type silicon / silicon carbide / carbon semiconductor nanocomposite material for potassium ion batteries. Background Art

[0002] Potassium is an alkali metal element. Compared to lithium and sodium, potassium is abundant, inexpensive, and has a low electrochemical potential. Therefore, potassium-ion batteries developed using it offer advantages such as low cost, long life, and high energy density, meeting the needs of the energy storage field. The operating principle of potassium-ion batteries is similar to that of lithium-ion batteries, employing a "rocking chair" mechanism. However, due to the larger radius and mass of potassium ions, their volume expansion during charge and discharge is more severe than that of other alkali metal ions. This poses new challenges to the development of battery electrode and electrolyte materials. Therefore, the development of electrode materials suitable for potassium ion shuttle is extremely important.

[0003] Silicon is abundant in nature, inexpensive, and has always been considered the most promising negative electrode material due to its high theoretical specific capacity. However, due to the severe volume expansion of silicon during the electrochemical reaction, the active silicon will break and fall off from the current collector, causing the battery to short-circuit. In addition, the formation of an unstable SEI film will reduce the contact between the active material and the electrolyte, thereby affecting the electrochemical performance. Therefore, in order to fully utilize the high specific capacity of silicon, the modification of silicon has become a major hot topic. Among the current modification methods, nano-sizing and composite with carbon materials are the most widely studied. They can not only increase the reactive sites, alleviate volume expansion, but also greatly improve conductivity. The emergence of ceramic-type materials SiC can also effectively buffer the volume expansion of silicon. The strong interaction between Si-C bonds can play a good buffering role when Si undergoes volume expansion. The research on SiC has also attracted a lot of attention. Therefore, developing an electrode material suitable for potassium ion batteries has become an urgent problem to be solved. Summary of the Invention

[0004] To solve the problems existing in the prior art, the present invention provides a preparation method and application of N-type silicon / silicon carbide / carbon semiconductor nanocomposite materials for potassium ion batteries. By using a simple and low-cost experimental method, an N-type P@Si / SiC / C semiconductor nanocomposite material is prepared. This material can effectively buffer the volume expansion of silicon, reduce the pulverization of silicon materials, and improve the conductivity of the composite material, thereby improving the electrochemical performance of potassium ion batteries, solving the problems mentioned in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing an N-type silicon / silicon carbide / carbon semiconductor nanocomposite material for potassium ion batteries, comprising the following steps:

[0006] S1. Weigh micron Si powder and flake graphite, place them in a ball mill at a speed of 200-800 r / min for 1-5 hours to uniformly mix them, place the mixed product into a mold and place it in a spiral powder tablet press, and press it into a cylindrical sample block with a height of 1-5 mm and a bottom diameter of 18 mm at a pressure of 10-50 MPa;

[0007] S2. Place the cylindrical sample block in the center of the graphite crucible, then place the graphite crucible on the copper base in the vacuum DC arc device. Use a tungsten electrode grinder to grind the discharge tungsten rod for 20 minutes, with the tip of the tungsten rod facing the center of the cylindrical sample block.

[0008] S3. Place the outer glass cover of the vacuum DC arc device close to the sealing rubber ring, use a vacuum pump to evacuate the glass cover to a vacuum degree of 0.1 MPa, and fill it with a mixed gas of argon and nitrogen with a volume ratio of 1-10:1 to 5 kPa, open the exhaust valve again, and purge the reaction chamber. Repeat this operation 3-5 times to ensure that the residual air is discharged. After the purge is completed, fill it with the mixed gas to 10-50 kPa;

[0009] S4. Adjust the current range and voltage range of the vacuum DC arc device, and continuously raise the copper base by remote control until the sample block contacts the tungsten rod, thereby discharging and striking the arc. Maintain the reaction for a certain period of time. During the reaction, a bright yellow light can be observed from the glass cover.

[0010] S5. Cool the device using a liquid nitrogen condenser to form a cross-linked one-dimensional nanowire structure, then passivate the product with air for 3 to 5 hours, and then collect the Si / SiC product on the wall;

[0011] S6. Weigh NH4H2PO4 and Si / SiC in anhydrous ethanol and mix them uniformly by ultrasonication for 1 to 3 hours. Then, evaporate the ethanol at a temperature of 50°C to 90°C and freeze-dry in a vacuum freeze drying oven. Grind the dried product and calcine it in a tube furnace under an argon atmosphere to obtain P@Si / SiC.

[0012] S7. Dissolve phenolic resin in anhydrous ethanol and ultrasonically disperse it for 1-3 hours, then add P@Si / SiC and stir it with a water bath constant temperature magnetic stirrer for 2-6 hours, heat the stirrer to 50-90°C to evaporate the anhydrous ethanol, and then place the product in a vacuum freeze drying oven for freeze drying; grind the dried product into powder, and then pyrolyze it in a tubular furnace under argon atmosphere to obtain an N-type P@Si / SiC / C nanocomposite material.

[0013] Preferably, in step S1, the particle size range of the micron Si powder and the flake graphite is 50-150 mesh, and the mass ratio of the micron Si powder to the flake graphite is 1-10:1.

[0014] Preferably, in step S4, the current range is 60-120A, the voltage range is 20-60V; and the reaction time is 0.5-3h.

[0015] Preferably, in step S5, the cooling time is 5-15 minutes.

[0016] Preferably, in step S5, the specific surface area of ​​the one-dimensional nanowire structure is 200m 2 / g-400m 2 / g, high axis-to-diameter ratio of 12-20, and radial size of 20nm-40nm.

[0017] Preferably, in step S6, the mass ratio of NH4H2PO4 to Si / SiC is 1:1-10; and the calcination is carried out at a temperature of 700-1000°C for 2-6 hours.

[0018] Preferably, in step S6, the mass ratio of NH4H2PO4 to Si / SiC is 1:1-5; and the calcination is carried out at a temperature of 700-800°C for 2-4h.

[0019] Preferably, in step S7, the mass ratio of the phenolic resin to P@Si / SiC is 1-3:1; and the pyrolysis is carried out at a temperature of 400-900° C. for 4-10 hours.

[0020] Preferably, in step S7, the mass ratio of the phenolic resin to P@Si / SiC is 1-2:1; and the pyrolysis is carried out at a temperature of 400-600° C. for 4-6 hours.

[0021] Preferably, the N-type P@Si / SiC / C nanocomposite material is a three-layer sandwich structure with an inner layer of P-doped Si, a middle layer of SiC, and an outermost layer of amorphous carbon.

[0022] On the other hand, to achieve the above-mentioned purpose, the present invention also provides the following technical solution: an application of an N-type silicon / silicon carbide / carbon semiconductor nanocomposite material for potassium ion batteries in the negative electrode of a potassium ion battery, wherein the P@Si / SiC / C nanocomposite material, conductive carbon black (Super-P), sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) are stirred evenly with anhydrous ethanol to form a paste to prepare a P@Si / SiC / C negative electrode composite electrode.

[0023] Preferably, the mass ratio of the P@Si / SiC / C nanocomposite material, conductive carbon black, sodium carboxymethyl cellulose and styrene-butadiene rubber is 5:3:1:1, and the P@Si / SiC / C negative composite electrode is 0.2A·g -1After 300 cycles at a current density of 1071 mAh g -1 After fitting its impedance, its potassium ion diffusion coefficient is 8.17×10 -11 m 2 ·s -1 .

[0024] The beneficial effects of the present invention are:

[0025] 1) The present invention uses a vacuum DC arc method to synthesize cross-linked Si / SiC nanowires in one step. During the reaction, instantaneous high temperatures are generated in the device, ionizing the material into a plasma state. During the condensation process, these ions combine with each other to form a cross-linked one-dimensional nanowire structure. The one-dimensional nanowire structure has a large specific surface area, a high axial diameter ratio, and a small radial size (specific surface area of ​​200m 2 / g-400m 2 / g, a high axial-to-diameter ratio of 12-20, and a radial dimension of 20nm-40nm) can reduce the axial volume expansion of Si during cycling, avoid Si pulverization, and provide more active sites. The strong interaction between Si-C bonds in the ceramic material SiC can slow the volume expansion of Si during the reaction, thereby improving cycling performance. This method is novel and simple to prepare;

[0026] 2) The present invention prepares an N-type P@Si / SiC / C nanocomposite material by regulating the P doping content and reaction conditions. P doping converts Si into an N-type semiconductor and generates a large number of electron carriers. A large number of electron carriers can accelerate the transfer of electrons during the reaction, promote the binding of potassium ions to the anode composite material, improve the efficiency of potassium ion removal, and greatly improve the conductivity of Si. Secondly, P doping will induce the rearrangement of SiC nanowires, causing them to be distributed around Si, thereby forming a three-layer sandwich structure with P-doped Si as the inner layer, SiC in the middle, and amorphous carbon as the outermost layer, which can make SiC better buffer the volume expansion.

[0027] 3) Electrochemical performance shows that the capacity of the P@Si / SiC / C composite electrode remains at 1071 mAh g after 300 cycles. -1 , has good cycle performance and high discharge specific capacity. After fitting its impedance, its potassium ion diffusion coefficient is 8.17×10 -11 m 2 ·s -1 , indicating that the N-type semiconductor structure promotes the transport of potassium ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1is a SEM image of the nanocomposite material corresponding to Example 1 of the present invention;

[0029] Figure 2 is a long cycle performance curve of the nanocomposite material according to Example 1 of the present invention;

[0030] Figure 3 is the XRD pattern of the nanocomposite material corresponding to Example 2 of the present invention;

[0031] Figure 4 is a SEM image of the nanocomposite material corresponding to Example 2 of the present invention;

[0032] Figure 5 is an electrochemical impedance spectroscopy diagram of the nanocomposite material according to Example 2 of the present invention;

[0033] Figure 6 is a long cycle performance curve of the nanocomposite material according to Example 2 of the present invention;

[0034] Figure 7 is a SEM image of the nanocomposite material corresponding to Example 3 of the present invention;

[0035] Figure 8 is a long cycle performance curve of the nanocomposite material according to Example 3 of the present invention;

[0036] Figure 9 It is a long cycle performance curve of the nanocomposite material of Example 1 of the present invention. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] Example 1

[0039] Preparation: 2 g of micronized Si powder (50 mesh) and 2 g of flake graphite were weighed and placed in a ball mill. Mixed uniformly at 200 rpm for 1 hour, the mixture was then placed in a mold and pressed into a cylindrical sample block with a height of 1 mm and a base diameter of 18 mm using a spiral powder press at a pressure of 40 MPa. The cylindrical sample block was placed in the center of a graphite crucible. The graphite crucible was then placed on a copper base in a vacuum DC arc furnace, with the tip of a polished discharge tungsten rod facing the center of the cylindrical sample block. The vacuum DC arc furnace was sealed, and the reaction chamber was evacuated to a vacuum of 0.1 MPa and filled with a 1:1 by volume mixture of gases to 5 kPa for purge. This step was repeated three times. The mixture was then filled with a 1:1 by volume mixture of argon and nitrogen to 10 kPa. Arc discharge was initiated in a vacuum DC arc furnace set to 60A and 20V for 0.5h. Liquid nitrogen was then filled for cooling for 5min, followed by air passivation for 3h. Finally, the Si / SiC nanowires were collected. 3g of NH4H2PO4 and 3g of Si / SiC were ultrasonically dispersed in 20mL of anhydrous ethanol for 1h. The ethanol was then evaporated at 50°C and freeze-dried in a vacuum freeze-dryer. The dried product was ground and calcined at 700°C for 2h in a tube furnace under an argon atmosphere to obtain the P@Si / SiC material. 3g of phenolic resin was dissolved in 30mL of anhydrous ethanol and ultrasonically dispersed for 1h. 3g of P@Si / SiC was then added and stirred in a water bath with a thermostatic stirrer for 2h. The temperature was then raised to 50°C to evaporate the ethanol, and the product was freeze-dried in a vacuum freeze-dryer. The dried product was ground and placed in a tube furnace under argon and pyrolyzed at 400 °C for 4 h to obtain P@Si / SiC / C nanocomposite materials.

[0040] Application: P@Si / SiC / C nanocomposite material, conductive carbon black (Super P), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are mixed in a mass ratio of 5:3:1:1 with anhydrous ethanol to form a paste, and then coated on one side of a 15μm thick copper foil with a coating thickness of 0.8mm. The paste is then dried in a vacuum at 60°C for 18h to obtain a P@Si / SiC / C nanomaterial composite electrode. A 2025-type button-type potassium ion battery is assembled using metallic potassium as the positive electrode, 0.8M KPF6 EC / DEC (volume ratio of 1:1) as the electrolyte, polyethylene film PP as the separator, and the P@Si / SiC / C nanomaterial composite electrode as the negative electrode.

[0041] like Figure 1 As shown, Figure 1The scanning electron microscope image of the prepared nanocomposite material shows that the phenolic resin amorphous carbon is successfully coated around the nanowires, thereby forming irregular particles with small size. The cycle performance curve of the battery assembled according to Example 1 is shown in FIG. Figure 2 As shown, at 0.2A·g -1 After 300 cycles at a current density of 1.5 GHz, the capacity remains at 917 mAh g -1 .

[0042] Example 2

[0043] Preparation: 5 g of micronized Si powder (100 mesh) and 1 g of flake graphite were weighed and placed in a ball mill. Mixed uniformly at 600 rpm for 3 h, the mixture was then placed in a mold and pressed into a cylindrical sample block with a height of 3 mm and a base diameter of 18 mm using a spiral powder press at a pressure of 30 MPa. The cylindrical sample block was placed in the center of a graphite crucible, which was then placed on a copper base in a vacuum DC arc furnace, with the tip of a polished discharge tungsten rod facing the center of the cylindrical sample block. The vacuum DC arc furnace was sealed, and the reaction chamber was evacuated to a vacuum of 0.1 MPa and filled with a 5:1 by volume mixture of gases to 5 kPa for purge. This step was repeated four times, and then filled with a 5:1 by volume mixture of argon and nitrogen to 30 kPa. Arc discharge was initiated in a vacuum DC arc furnace set to 90A and 40V for 1 hour. Liquid nitrogen was then filled for cooling for 10 minutes, followed by air passivation for 4 hours. Finally, the Si / SiC nanowires were collected. 1g of NH4H2PO4 and 5g of Si / SiC were ultrasonically dispersed in 20mL of anhydrous ethanol for 2 hours. The ethanol was then evaporated at 70°C and freeze-dried in a vacuum freeze-dryer. The dried product was ground and calcined at 800°C for 4 hours in a tube furnace under an argon atmosphere to obtain the P@Si / SiC material. 3g of phenolic resin was dissolved in 30mL of anhydrous ethanol and ultrasonically dispersed for 2 hours. 1.5g of P@Si / SiC was added and stirred in a water bath with a thermostatic stirrer for 4 hours. The temperature was then raised to 70°C to evaporate the ethanol, and the product was freeze-dried in a vacuum freeze-dryer. The dried product was ground and placed in a tube furnace under argon and pyrolyzed at 600 °C for 6 h to obtain P@Si / SiC / C nanocomposite materials.

[0044] Application: P@Si / SiC / C nanocomposite material, conductive carbon black (Super P), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are mixed in a mass ratio of 5:3:1:1 with anhydrous ethanol to form a paste, and then coated on one side of a 15μm thick copper foil with a coating thickness of 0.8mm. The paste is then dried in a vacuum at 70°C for 20h to obtain a P@Si / SiC / C nanomaterial composite electrode. A 2025-type button-type potassium ion battery is assembled using metallic potassium as the positive electrode, 0.8M KPF6 EC / DEC (volume ratio of 1:1) as the electrolyte, polyethylene film PP as the separator, and the P@Si / SiC / C nanomaterial composite electrode as the negative electrode.

[0045] like Figure 3 As shown, Figure 3 This is the XRD diagram of the prepared nanocomposite material. From the diagram, diffraction peaks of Si, SiC and amorphous carbon can be observed, and there are no other impurities, so it has very high purity. Figure 4 This is a scanning electron microscope image. From the image, it can be observed that after pyrolysis, small irregular particles are formed, with more pores and reaction active sites, which are conducive to the transmission of ions. Figure 5 The electrochemical impedance spectroscopy diagram shows that the battery assembled according to Example 2 has a relatively small impedance, and the potassium ion diffusion coefficient is calculated to be 8.17×10 -11 m 2 ·s -1 This indicates that after P doping, Si is transformed into an N-type semiconductor, which promotes the transport of ions and the generated electron carriers accelerate the electron transfer of the composite material during the reaction process. The cycle performance curve of the battery assembled according to Example 2 is shown in FIG. Figure 6 As shown, at 0.2A·g -1 After 300 cycles at a current density of 1000, the capacity still remains at 1071 mAh g -1 , with a high discharge specific capacity, proving that P doping can effectively improve the electrochemical performance.

[0046] Example 3

[0047] Preparation: 5 g of micronized Si powder (150 mesh) and 0.5 g of flake graphite were weighed and placed in a ball mill. Mixed uniformly at 800 rpm for 5 h, the mixture was then placed in a mold and pressed into a cylindrical sample block with a height of 5 mm and a base diameter of 18 mm using a spiral powder press at a pressure of 10 MPa. The cylindrical sample block was placed in the center of a graphite crucible. The graphite crucible was then placed on a copper base in a vacuum DC arc furnace, with the tip of a polished tungsten discharge rod facing the center of the cylindrical sample block. The vacuum DC arc furnace was sealed, and the reaction chamber was evacuated to a vacuum of 0.1 MPa and filled with a 10:1 by volume mixture of argon and nitrogen to 50 kPa for purge. This step was repeated five times. The mixture was then filled with a 10:1 by volume mixture of argon and nitrogen to 50 kPa. Arc discharge was initiated in a vacuum DC arc furnace set to 120A and 60V for 3 hours. Liquid nitrogen was then filled for cooling for 15 minutes, followed by air passivation for 5 hours. Finally, the Si / SiC nanowires were collected. 0.3g of NH4H2PO4 and 3g of Si / SiC were ultrasonically dispersed in 20mL of anhydrous ethanol for 3 hours. The ethanol was then evaporated at 90°C and freeze-dried in a vacuum freeze-dryer. The dried product was ground and calcined at 1000°C for 6 hours in a tube furnace under argon atmosphere to obtain the P@Si / SiC material. 3g of phenolic resin was dissolved in 30mL of anhydrous ethanol and ultrasonically dispersed for 3 hours. 1g of P@Si / SiC was added and stirred in a water bath with a thermostatic stirrer for 6 hours. The temperature was then raised to 90°C to evaporate the ethanol, and the product was freeze-dried in a vacuum freeze-dryer. The dried product was ground and placed in a tube furnace under argon and pyrolyzed at 900 °C for 10 h to obtain P@Si / SiC / C nanocomposite materials.

[0048] Application: P@Si / SiC / C nanocomposite material, conductive carbon black (Super P), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are mixed in a mass ratio of 5:3:1:1 with anhydrous ethanol to form a paste, and then coated on one side of a 15μm thick copper foil with a coating thickness of 0.8mm. The paste is then dried in a vacuum at 80°C for 24h to obtain a P@Si / SiC / C nanomaterial composite electrode. A 2025-type button-type potassium ion battery is assembled using metallic potassium as the positive electrode, 0.8M KPF6 EC / DEC (volume ratio of 1:1) as the electrolyte, polyethylene film PP as the separator, and the P@Si / SiC / C nanomaterial composite electrode as the negative electrode.

[0049] like Figure 7 As shown, Figure 7 The scanning electron microscope image shows that a certain degree of agglomeration occurs after the phenolic resin is pyrolyzed and coated. The cycle performance curve of the battery assembled according to Example 3 is shown in FIG. Figure 8As shown, at 0.2A·g -1 After 300 cycles at a current density of 1.5 GHz, the capacity remains at 739 mAh g -1 .

[0050] Comparative Example 1

[0051] 5g of micronized Si powder (100 mesh) and 1g of flake graphite were weighed and placed in a ball mill. The mixture was uniformly mixed at 600 rpm for 3 hours. The mixed product was then placed in a mold and pressed into a cylindrical sample block with a height of 3mm and a base diameter of 18mm using a spiral powder tablet press at a pressure of 30MPa. The cylindrical sample block was placed in the center of a graphite crucible, which was then placed on a copper base in a vacuum DC arc furnace, with the tip of the polished discharge tungsten rod facing the center of the cylindrical sample block. The vacuum DC arc furnace was sealed, and the reaction chamber was then evacuated to a vacuum of 0.1MPa and filled with a mixed gas with a volume ratio of 5:1 to 5kPa for purge. This step was repeated four times, and then filled with a mixture of argon and nitrogen with a volume ratio of 5:1 to 30kPa. Arc discharge was initiated in a vacuum DC arc furnace set to 90A and 40V for 1 hour. Liquid nitrogen was then filled for cooling for 10 minutes, followed by air passivation for 4 hours. Finally, the Si / SiC nanowires were collected. 5g of NH4H2PO4 and 2.5g of Si / SiC were ultrasonically dispersed in 20mL of anhydrous ethanol for 2 hours. The ethanol was then evaporated at 70°C and freeze-dried in a vacuum freeze-dryer. The dried product was ground and calcined at 800°C for 4 hours in a tube furnace under an argon atmosphere to obtain the P@Si / SiC material. 3g of phenolic resin was dissolved in 30mL of anhydrous ethanol and ultrasonically dispersed for 2 hours. 1.5g of P@Si / SiC was added and stirred in a water bath with a thermostatic stirrer for 4 hours. The temperature was then raised to 70°C to evaporate the ethanol, and the product was freeze-dried in a vacuum freeze-dryer. The dried product was ground and pyrolyzed at 600°C in a tube furnace under argon for 6 h to obtain a P@Si / SiC / C nanocomposite. The P@Si / SiC / C nanocomposite, conductive carbon black (Super P), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were mixed with anhydrous ethanol in a mass ratio of 5:3:1:1 to form a paste. The paste was then coated on one side of a 15μm-thick copper foil to a thickness of 0.8mm. The resulting P@Si / SiC / C nanomaterial composite electrode was then vacuum-dried at 70°C for 20 h. A 2025-type button-type potassium-ion battery was assembled using potassium metal as the positive electrode, 0.8M KPF6 in EC / DEC (volume ratio 1:1) as the electrolyte, polyethylene film (PP) as the separator, and the P@Si / SiC / C nanomaterial composite electrode as the negative electrode.

[0052] like Figure 9 As shown, Figure 9 The cycle performance of the battery assembled according to Comparative Example 1 can be observed from the figure. Compared with Example 2, the discharge capacity has decreased to a certain extent. -1 After 300 cycles at a current density of 1.5, the capacity remains at 632 mAh g -1 This may be due to the excessive P doping, which destroys the structure of Si and affects the electrochemical performance.

[0053] In summary, the present invention provides an effective solution to the problems of volume expansion and poor conductivity of Si. Cross-linked Si / SiC nanowires are prepared by a vacuum DC arc method. The gaps between the nanowires provide sufficient space for Si to grow and expand. P doping converts Si into an N-type semiconductor, causing defects in the active material Si, providing sufficient ion embedding sites, and the abundant electron carriers generated greatly improve the electron transfer rate. P doping also induces the reorganization of SiC nanowires, causing them to be distributed on the surface of Si, better buffering the volume expansion of Si, thereby forming a three-layer sandwich structure with an inner layer of P-doped Si, a middle layer of SiC, and an outermost layer of amorphous carbon. Finally, the coating of phenolic resin improves the conductivity of the composite material. The nanocomposite material obtained in particular Example 2 has excellent cycle performance.

[0054] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to 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 an N-type silicon / silicon carbide / carbon semiconductor nanocomposite material for potassium ion batteries, characterized in that: The steps include: S1. Weigh micron Si powder and flake graphite, place them in a ball mill and mill them at a speed of 200-800 r / min for 1-5 hours to uniformly mix them. Place the mixed product into a mold and place it in a powder tablet press to press it into a cylindrical sample block; S2. Place the cylindrical sample block in the center of the graphite crucible, then place the graphite crucible on the copper base in the vacuum DC arc device. Use a tungsten electrode grinder to grind the discharge tungsten rod for 20 minutes, with the tip of the tungsten rod facing the center of the cylindrical sample block. S3. Place the outer glass cover of the vacuum DC arc device close to the sealing rubber ring, use a vacuum pump to evacuate the glass cover to a vacuum degree of 0.1 MPa, and fill it with a mixed gas of argon and nitrogen with a volume ratio of 1-10:1 to 5 kPa, open the exhaust valve again, and purge the reaction chamber. Repeat this operation 3-5 times to ensure that the residual air is discharged. After the purge is completed, fill it with the mixed gas to 10-50 kPa; S4. Adjust the current range and voltage range of the vacuum DC arc device, and continuously raise the copper base by remote control until the sample block contacts the tungsten rod to discharge and strike an arc, and maintain the reaction for a certain time; S5. Cool the device using a liquid nitrogen condenser to form a cross-linked one-dimensional nanowire structure, then passivate the product with air for 3 to 5 hours, and then collect the Si / SiC product on the wall; S6. Weigh NH4H2PO4 and Si / SiC in anhydrous ethanol and mix them uniformly by ultrasonication for 1 to 3 hours. Then, evaporate the ethanol at a temperature of 50°C to 90°C and freeze-dry in a vacuum freeze drying oven. Grind the dried product and calcine it in a tube furnace under an argon atmosphere to obtain P@Si / SiC. S7, dissolving phenolic resin in anhydrous ethanol and ultrasonically dispersing it for 1-3 hours, then adding P@Si / SiC and stirring with a water bath constant temperature magnetic stirrer for 2-6 hours, heating the stirrer to 50-90°C to volatilize the anhydrous ethanol, and then placing the product in a vacuum freeze drying oven for freeze drying; grinding the dried product into powder, and then pyrolyzing it in a tube furnace under an argon atmosphere to obtain an N-type silicon / silicon carbide / carbon semiconductor nanocomposite material; The mass ratio of NH4H2PO4 and Si / SiC is 1:1-10.

2. The method for preparing an N-type silicon / silicon carbide / carbon semiconductor nanocomposite material for potassium ion batteries according to claim 1, wherein: In step S1, the particle size range of the micron Si powder and the flake graphite is 50-150 mesh, and the mass ratio of the micron Si powder to the flake graphite is 1-10:

1.

3. The method for preparing an N-type silicon / silicon carbide / carbon semiconductor nanocomposite material for potassium ion batteries according to claim 1, wherein: In step S4, the current range is 60-120A, the voltage range is 20-60V; and the reaction time is 0.5-3h.

4. The method for preparing an N-type silicon / silicon carbide / carbon semiconductor nanocomposite material for potassium ion batteries according to claim 1, wherein: In step S5, the cooling time is 5-15 minutes.

5. The method for preparing an N-type silicon / silicon carbide / carbon semiconductor nanocomposite material for potassium ion batteries according to claim 1, wherein: In step S5, the specific surface area of ​​the one-dimensional nanowire structure is 200m 2 / g-400m 2 / g, high axis-to-diameter ratio of 12-20, and radial size of 20nm-40nm.

6. The method for preparing an N-type silicon / silicon carbide / carbon semiconductor nanocomposite material for potassium ion batteries according to claim 1, wherein: In step S6, the calcination is carried out at a temperature of 700-1000° C. for 2-6 hours.

7. The method for preparing an N-type silicon / silicon carbide / carbon semiconductor nanocomposite material for potassium ion batteries according to claim 1, wherein: In step S7, the mass ratio of the phenolic resin to P@Si / SiC is 1-3:1; and the pyrolysis is carried out at a temperature of 400-900° C. for 4-10 hours.

8. The method for preparing an N-type silicon / silicon carbide / carbon semiconductor nanocomposite material for potassium ion batteries according to claim 1, wherein: The N-type silicon / silicon carbide / carbon semiconductor nanocomposite material is a three-layer sandwich structure with an inner layer of P-doped Si, a middle layer of SiC, and an outermost layer of amorphous carbon.

9. Use of an N-type silicon / silicon carbide / carbon semiconductor nanocomposite material prepared by the method for preparing an N-type silicon / silicon carbide / carbon semiconductor nanocomposite material for potassium ion batteries according to any one of claims 1 to 8 in a negative electrode of a potassium ion battery, characterized in that: The N-type silicon / silicon carbide / carbon semiconductor nanocomposite material, conductive carbon black, sodium carboxymethyl cellulose and styrene-butadiene rubber were stirred evenly with anhydrous ethanol to form a paste to prepare a P@Si / SiC / C negative composite electrode.

10. The use according to claim 9, characterized in that: The mass ratio of the N-type silicon / silicon carbide / carbon semiconductor nanocomposite material, conductive carbon black, sodium carboxymethyl cellulose and styrene-butadiene rubber is 5:3:1:1, and the P@Si / SiC / C negative composite electrode is 0.2A·g -1 After 300 cycles at a current density of 1071 mAh g -1 After fitting its impedance, its potassium ion diffusion coefficient is 8.17×10 -11 m 2 ·s -1 .

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