A mxene / silicon composite material, preparation thereof and application thereof as a negative electrode of a lithium ion battery

Abstract

The application discloses a kind of MXene / silicon composite material and its preparation and as lithium ion battery negative electrode application.The preparation method of the MXene / silicon composite material includes: (1) obtaining MXene material;(2) obtain cationic surfactant intercalated MXene material solution;(3) in cationic surfactant intercalated MXene material solution metal soluble salt is added, and metal intercalated MXene material is obtained;(4) metal intercalated MXene material is activated metal in protective atmosphere high-temperature treatment, then high-temperature is passed into gas containing silane, after heat preservation treatment, and cooling to room temperature to obtain MXene / silicon composite material.The application provides the application of the MXene / silicon composite material as lithium ion battery negative electrode material, the prepared composite material can limit silicon negative electrode volume effect, substantially improve the capacity of lithium ion battery negative electrode material, and cycle performance is better.

Description

(I) TECHNICAL FIELD

[0001] The present application relates to a MXene / silicon composite material and its preparation and application as a negative electrode of a lithium ion battery. (II) BACKGROUND

[0002] The rapid development of electric vehicles, clean energy storage and portable electronic products puts forward higher requirements for the energy density of secondary batteries. The improvement of energy density depends on the performance of electrode materials. The theoretical capacity of the currently commercial graphite negative electrode material in lithium ion batteries is only 372 mAh / g, and the energy density of the power battery constructed with graphite as the negative electrode material is difficult to exceed 300 Wh / kg. Therefore, it is urgent to research and develop new high-capacity negative electrode materials.

[0003] Silicon has attracted extensive attention due to its high theoretical capacity (4200 mAh / g). However, during the cycling process of batteries, the alloying reaction between silicon and lithium will occur, resulting in a severe volume effect and a high volume expansion of up to 300%. This will cause the continuous rupture and repeated growth of the solid electrolyte interface film (SEI) between the electrolyte and the silicon-based interface, continuously consume the electrolyte, increase the impedance of the battery, and ultimately deteriorate the electrochemical performance of the battery. Therefore, in previous studies, researchers first suppressed the volume effect of silicon particles by reducing their volume and explored different nano-preparation methods. The prepared silicon nanoparticles, silicon nanowires, silicon nanotubes, and silicon nanoporous structures all have good electrochemical performance. Secondly, by doping a small amount of silicon and graphite, the tap density of the silicon-based negative electrode is improved, the low electronic conductivity of the silicon-based negative electrode is improved, and the damage caused by the volume effect is weakened through the gap between the graphite layers. Finally, researchers use a variety of new carbon materials to composite with silicon-based materials, such as graphene, carbon nanotubes, porous carbon microspheres, MXene, etc. When combined with silicon-based materials, these new carbon materials can effectively improve the defects of the silicon negative electrode, thereby endowing the silicon-based negative electrode with excellent electrochemical performance. Among them, the most special carbon material is MXene material, which is a two-dimensional inorganic compound material composed of several atomic layers of transition metal carbide, nitride or carbonitride. The precursor MAX phase of MXene material can be obtained by using different etching methods or selecting different etchants, thereby obtaining MXene materials with different surface groups and different shapes ("accordion", flaky, layered, etc.). Therefore, MXene materials have a wide range of applications. MXene materials have good electrical conductivity and strong mechanical strength, and their unique layered structure can effectively suppress the volume effect of the silicon negative electrode. However, the current developed silicon-based and MXene composite negative electrode basically uses physical composite such as electrostatic adsorption, spray drying, or simple mixing process such as ball mill and stirrer, and the interaction and binding force between silicon and MXene are not strong, the limiting effect of MXene layered sheet is greatly weakened, resulting in that the electrochemical performance still needs to be improved.

[0004] With the research of silicon-carbon negative electrode prepared by chemical vapor deposition rising, a new direction is provided for the preparation of MXene / silicon composite material. Chemical vapor deposition (CVD) technology is usually used in the surface modification process of materials, which aims to generate a solid deposition film on the surface of the material by chemical reaction of gaseous substances at a certain temperature. Due to the activity and smallness of gas molecules, it can realize the structure regulation which cannot be realized by conventional physical compounding method. As mentioned above, the unique layered structure of MXene material with nanoscale pores can limit the volume effect of silicon negative electrode. However, the conventional compounding method cannot reach the interlayer of MXene material, and cannot make MXene material play a limiting role in silicon negative electrode. Therefore, by using gaseous silicon-based precursor, the silicon-based material can be anchored into the nanoscale pores and channels of MXene material, realizing real confinement and improving the electrochemical performance of MXene / silicon composite material. (III)SUMMARY

[0005] In view of the series of problems existing in silicon negative electrode, the present application aims to provide a MXene / silicon composite material, a preparation method thereof and application as a negative electrode material of lithium ion battery.

[0006] In order to achieve the purpose of the present application, the technical scheme of the present application is described as follows:

[0007] In the first aspect, the present application provides a preparation method of MXene / silicon composite material, which introduces metal catalyst into the interlayer of MXene, and uses CVD method to prepare MXene / silicon composite material by different metal catalytic decomposition and deposition of silane in the interlayer of MXene, and the preparation method comprises the following steps:

[0008] (1) taking MAX raw material, treating in hydrofluoric acid solution to obtain MXene material;

[0009] (2) soaking the MXene material obtained in step (1) in a solution containing cationic surfactant with a content of 0.001-20 g / mL, stirring at 20-100℃ for 0.5-72h to obtain a cationic surfactant intercalated MXene material solution;

[0010] (3) adding metal soluble salt to the cationic surfactant intercalated MXene material solution obtained in step (2), stirring at 20-100℃ for 0.5-72h, then centrifuging, washing with water and drying to obtain metal intercalated MXene material;

[0011] (4) heating the metal intercalated MXene material obtained in step (3) to 300-1000℃ at a rate of 1-10℃ / min under a protective atmosphere, holding for 0.1-12h to activate the metal and its catalytic effect, then cooling to 200-800℃, and passing a gas containing silane at a flow rate of 0.01-5L / min for 1-240min, and then holding for 0.1-12h, and finally cooling to room temperature at a rate of 1-20℃ / min to obtain a MXene / silicon composite material.

[0012] In step (1) of the present application, the MXene material can be Ti3C2, Ti2C, Ti4C3, Ti2N, Nb2C, Nb4C3, Ta2C, Ta4C3, V2C, V3C2, V2N, Cr2C, Cr3C2, Zr3C2, Hf3C2, Mo2C, Mo2N, W2N, Cr2TiC2, Mo2TiC2, Mo2Ti2C3, TiNbC or Ti3CN. Those skilled in the art can select a suitable MAX raw material according to the desired MXene material to be prepared, and prepare the MXene material by the method reported in the literature. Preferably, the specific operation of step (1) is as follows: weigh the MAX raw material, add a HF solution with a mass fraction of 10-50%, wherein the addition amount of the HF solution is 3-50mL / g based on the mass of the MAX raw material, soak at room temperature for 2-56h (more preferably 24-36h), then centrifuge, wash with water to pH=6-7, and dry to obtain a MXene powder.

[0013] In step (2) of the present application, the cationic surfactant is one or a combination of any number of octadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide, preferably with a purity of greater than 90%. The concentration of the cationic surfactant in the solution is preferably 0.001-0.5mol / L, more preferably 0.005-0.3mol / L. The feeding amount of the solution containing the cationic surfactant is 5-1000mL / g based on the mass of the MXene material, preferably 50-500mL / g. The stirring in step (2) is preferably carried out at 30-80℃, more preferably at 30-65℃, and further more preferably at 30-50℃, and the stirring time is preferably 1-36h, more preferably 3-24h, and further more preferably 10-24h.

[0014] In step (3) of the present application, the metal soluble salt is a soluble salt containing at least one of iron, cobalt, nickel, lead, copper, aluminum, antimony, manganese, tin, zinc, molybdenum, vanadium, zirconium, tungsten elements, and the soluble salt can be a chloride salt, a nitrate salt, a sulfate salt or an acetate salt of the metal; preferably the purity of the metal soluble salt is greater than 90%. The concentration of the metal soluble salt added is 0.001-1 mol / L. Further, the stirring in step (3) is preferably carried out at 20-70℃, more preferably at 20-60℃, and the stirring time is preferably 1-36h, more preferably 5-24h.

[0015] In step (4) of the present application, the silane-containing gas is a mixed gas of silane and other gases, and the other gases are a mixture of one or any combination of argon, nitrogen and hydrogen, preferably the purity of argon, nitrogen and hydrogen is greater than 90%, and the purity of silane is also greater than 90%. In the silane-containing gas, the volume ratio of silane to other gases is preferably 10-30%:90-70%, more preferably 10-20%:90-80%, and most preferably 10%:90%.

[0016] In step (4) of the present application, the metal intercalated MXene material is preferably first heated at a rate of 2-8℃ per minute to 400-1000℃ for 1-12h under a protective atmosphere to activate the metal and activate its catalytic performance, and the temperature is further preferably 400-900℃, and most preferably 500-800℃, and the holding time is preferably 1-8h, and most preferably 1-6h. Then, the temperature is lowered to 200-800℃, and the temperature is preferably 300-800℃, and most preferably 400-700℃, the flow rate of the silane-containing gas is 0.01-5L / min, preferably 0.1-3L / min, and most preferably 0.1-2L / min, the silane-containing gas is introduced for 1-240min, preferably 1-180min, and most preferably 1-120min, and then held for 0.1-12h, preferably 0.1-10h, and most preferably 0.5-6h, and finally cooled to room temperature at a rate of 1-20℃ / min, preferably at a rate of 1-15℃ / min, and most preferably at a rate of 1-10℃ / min.

[0017] The preparation method of the MXene / silicon composite material of the present application preferably comprises steps (1)-(4).

[0018] In a second aspect, the present application provides a MXene / silicon composite material prepared by the preparation method according to the first aspect.

[0019] In a third aspect, the present application provides the use of the MXene / silicon composite material as a negative electrode material for lithium ion batteries.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] (1) The preparation method of the application has high efficiency and strong feasibility. The surface of MXene material is negatively charged after etching by HF acid. The cationic surfactant is inserted into the interlayer of the MXene material through electrostatic interaction. Then, the metal is intercalated into the interlayer of the MXene material by ion exchange method. The metal in the interlayer of the MXene material is activated at high temperature, and the catalytic performance is activated, which helps the subsequent catalytic decomposition and deposition of silane in the interlayer of the MXene material.

[0022] (2) The MXene / silicon composite material prepared by the application as a negative material of lithium ion battery can effectively inhibit the volume effect of silicon in the charging and discharging process, and effectively improve the cycle stability of the silicon negative material while providing high capacity. The electrochemical performance of the MXene / silicon composite material prepared by the method is obviously better than that of the MXene / silicon composite material prepared by the conventional method. (Four) Description of Drawings

[0023] Figure 1 is the EDS graph of the MXene material after the deposition of silane in the MXene material by CVD process and Sn metal catalysis in Example 1. As shown in the picture, the inside and surface of the MXene material have rich silicon nanoclusters, and the CVD deposition effect is good.

[0024] Figure 2 is the SEM graph of the MXene material after the deposition of silane in the MXene material by CVD process and Sn metal catalysis in Example 1.

[0025] Figure 3 is the TEM graph of the MXene material after the deposition of silane in the MXene material by CVD process and Sn metal catalysis in Example 1.

[0026] Figure 4 is the lithium ion battery cycle performance graph of the MXene material after the deposition of silane in the MXene material by CVD process and Sn metal catalysis in Example 1, and the comparison graph of the lithium ion battery cycle performance of the MXene material.

[0027] Figure 5 is the lithium ion battery cycle performance graph of the MXene material after the deposition of silane in the MXene material by CVD process and Zn metal catalysis in Example 2, and the comparison graph of the lithium ion battery cycle performance of the MXene material. (Five) Specific implementation method

[0028] The technical solutions of the application will be further described below with specific examples, but the protection scope of the application is not limited thereto.

[0029] Example 1

[0030] Take 2g of Ti3AlC2 powder (MAX) into a beaker, add 80mL of HF (20%) solution, stir, and soak and etch at room temperature for 24h. Then centrifuge the etched Ti3C2 MXene powder, wash it with deionized water to a pH of 6-7, and freeze-dry it in a freeze dryer for 12h. Stir 0.1g of the dried Ti3C2 MXene powder in 40mL of an aqueous solution containing 0.005mol / L hexadecyltrimethylammonium bromide (CTAB) at 40°C for 18h. Then add 0.1mol / L tin tetrachloride and stir at 40°C for 16h, rinse with deionized water, and dry. The dried sample was placed in a CVD furnace and heated to 500°C at a rate of 5°C / minute under nitrogen. The Sn metal was activated at this temperature for 2 hours. The temperature was then lowered to 400°C and a mixture of silane and argon (10%:90% by volume) was introduced for 30 minutes at a flow rate of 0.1 liter / minute. The mixture was then held at this temperature for 1 hour. Finally, the MXene / silicon composite material was cooled to room temperature at a rate of 5°C / minute to obtain the desired product.

[0031] The MXene / silicon composite material prepared in Example 1 was used to make an electrode according to the following method.

[0032] MXene / silicon composite material: carbon black: CMC were weighed in a mass ratio of 80:10:10, ground evenly and mixed with water to prepare a slurry, which was then coated on a copper current collector to make an electrode. The metal lithium sheet was used as the counter electrode, the electrolyte was 1 mol / L LiPF6+DEC / EC (1:1)+10% FEC (vol%), and a polycarbonate film was used as a separator to assemble a simulated lithium-ion battery. Figure 4 The cyclic performance curve of the corresponding battery at a current density of 100 mA / g and a voltage range of 0.01–1.5 V indicates that the measured battery has a high capacity and good cycle performance at a current density of 100 mA / g. It can be seen that the discharge capacity of the MXene / silicon composite material prepared in Example 1 after 100 cycles at a current density of 100 mA / g is close to 600 mAh / g ( Figure 4 ), compared with the capacity of ordinary Ti3C2 MXene materials (~150mAh / g), the capacity has been greatly improved, and the cycle performance is relatively excellent.

[0033] Example 2

[0034] Take 4g Ti3AlC2 powder (MAX) into a beaker and add 60mL HF (25%)

[0035] Solution, stirring, room temperature immersion etching 36h. Then the etched Nb2C MXene powder was centrifuged out, washed with deionized water to pH = 6-7, and freeze-dried in a freeze dryer for 24h. 1g of dried Nb2C MXene powder was stirred in 50mL aqueous solution containing 0.05mol / L octadecyl trimethylammonium bromide (STAB) at 35℃ for 24h. Then 0.1mol / L nickel nitrate was added and stirred at 35℃ for 24h, washed with deionized water and dried. The dried sample was placed in a CVD furnace and heated to 700℃ at a rate of 5℃ per minute under the protection of nitrogen, then the Ni metal was activated by holding at 700℃ for 4h, then cooled to 600℃ and a mixture of silane and hydrogen gas was introduced for 120min at a flow rate of 0.5L / min with a volume ratio of 10%:90%, and then held for 3h. Finally, the temperature was cooled to room temperature at a rate of 10℃ per minute to obtain the MXene / silicon composite material. The MXene / silicon composite material was used to prepare an electrode according to the method of Example 1, and an analog lithium ion battery was assembled. The discharge capacity after 100 cycles at a current density of 100mA / g was close to 550mAh / g, which was a significant improvement over the capacity of ordinary Nb2C MXene (~150mAh / g), and the cycle performance was good.

[0036] Example 3

[0037] Solution, stirring, room temperature immersion etching 36h. Then the etched Nb2C MXene powder was centrifuged out, washed with deionized water to pH = 6-7, and freeze-dried in a freeze dryer for 24h. 1g of dried Nb2C MXene powder was stirred in 50mL aqueous solution containing 0.05mol / L octadecyl trimethylammonium bromide (STAB) at 35℃ for 24h. Then 0.1mol / L nickel nitrate was added and stirred at 35℃ for 24h, washed with deionized water and dried. The dried sample was placed in a CVD furnace and heated to 700℃ at a rate of 5℃ per minute under the protection of nitrogen, then the Ni metal was activated by holding at 700℃ for 4h, then cooled to 600℃ and a mixture of silane and hydrogen gas was introduced for 120min at a flow rate of 0.5L / min with a volume ratio of 10%:90%, and then held for 3h. Finally, the temperature was cooled to room temperature at a rate of 10℃ per minute to obtain the MXene / silicon composite material. The MXene / silicon composite material was used to prepare an electrode according to the method of Example 1, and an analog lithium ion battery was assembled. The discharge capacity after 100 cycles at a current density of 100mA / g was close to 550mAh / g, which was a significant improvement over the capacity of ordinary Nb2C MXene (~150mAh / g), and the cycle performance was good.

Claims

1. A method for preparing a MXene / silicon composite material, characterized by: The preparation method comprises the following steps: (1) taking MAX raw materials, treating in a hydrofluoric acid solution to obtain MXene materials; (2) soaking the MXene materials obtained in step (1) in a solution containing 0.001-20 g / mL of a cationic surfactant, stirring at 20-100 °C for 0.5-72 h to obtain a cationic surfactant intercalated MXene material solution; (3) adding a metal soluble salt to the cationic surfactant intercalated MXene material solution obtained in step (2), stirring at 20-100 °C for 0.5-72 h, then centrifuging, washing with water, and drying to obtain a metal intercalated MXene material; (4) heating the metal intercalated MXene material obtained in step (3) to 300-1000 °C at a rate of 1-10 °C / min under a protective atmosphere, holding for 0.1-12 h to activate the metal and its catalytic effect, then cooling to 200-800 °C, and passing a gas containing silane at a flow rate of 0.01-5 L / min for 1-240 min, then holding for 0.1-12 h, and finally cooling to room temperature at a rate of 1-20 °C / min to obtain a MXene / silicon composite material.

2. The production method according to claim 1, characterized by: In step (2), the cationic surfactant is one or a combination of any number of octadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide.

3. The production method according to claim 1 or 2, characterized by: In step (2), the stirring is performed at 30-80 °C for 1-36 h.

4. The production method according to claim 3, characterized by: In step (2), the stirring is performed at 30-65 °C for 3-24 h.

5. The production method according to claim 4, characterized by: In step (2), the stirring is performed at 30-50 °C for 10-24 h.

6. The production method according to claim 1, wherein: In step (3), the metal soluble salt is a soluble salt containing at least one of iron, cobalt, nickel, lead, copper, aluminum, antimony, manganese, tin, zinc, molybdenum, vanadium, zirconium, and tungsten, and the soluble salt is a chloride, nitrate, sulfate, or acetate of the metal.

7. The production method according to claim 1, wherein: In step (3), the stirring is performed at 20-70 °C for 1-36 h.

8. The production method according to claim 7, characterized by: In step (3), the stirring is performed at 20-60 °C for 5-24 h.

9. The production method according to claim 1, wherein: In step (4), the gas containing silane is a mixture of silane and other gases, and the other gases are a mixture of one or any number of argon, nitrogen, and hydrogen; in the gas containing silane, the volume ratio of silane to other gases is 10-30%:90-70%.

10. The production method according to claim 9, characterized by: In step (4), in the gas containing silane, the volume ratio of silane to other gases is 10-20%:90-80%.

11. The production method according to claim 1, wherein: In step (4), the metal intercalated MXene material is first heated at a rate of 2-8 ℃ per minute to 400-1000 ℃ under a protective atmosphere for 1-12 h to activate the metal and activate its catalytic properties; then cooled to 200-800 ℃, and a silane-containing gas is introduced at a flow rate of 0.01-5 L / min for 1-240 min, and then incubated for 0.1-12 h, and finally cooled to room temperature at a rate of 1-20 ℃ / min.

12. The production method according to claim 11, characterized by: In step (4), the metal intercalated MXene material is first heated at a rate of 2-8 ℃ per minute to 400-900 ℃ under a protective atmosphere for 1-8 h to activate the metal and activate its catalytic properties; then cooled to 300-800 ℃, and a silane-containing gas is introduced at a flow rate of 0.1-3 L / min for 1-180 min, and then incubated for 0.1-10 h, and finally cooled to room temperature at a rate of 1-15 ℃ / min.

13. The production method according to claim 12, characterized by: In step (4), the metal intercalated MXene material is first heated at a rate of 2-8 ℃ per minute to 500-800 ℃ under a protective atmosphere for 1-6 h to activate the metal and activate its catalytic properties; then cooled to 400-700 ℃, and a silane-containing gas is introduced at a flow rate of 0.1-2 L / min for 1-120 min, and then incubated for 0.5-6 h, and finally cooled to room temperature at a rate of 1-10 ℃ / min.

14. The production method according to claim 1, wherein: The MXene / silicon composite material preparation method comprises steps (1)-(4).

15. A MXene / silicon composite material prepared according to the preparation method of any one of claims 1-14.

16. Use of the MXene / silicon composite material of claim 15 as a negative electrode material for lithium ion batteries.

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