Lithium ion battery silicon-based negative electrode material, preparation method thereof and battery

Abstract

The invention provides a lithium ion battery silicon-based negative electrode material, a preparation method thereof and a battery, and belongs to the technical field of new energy battery electrode materials. The preparation method of the silicon-based negative electrode material of the lithium ion battery comprises the following steps: oxidizing carbon nanofiber acid, and then carrying out silicon loading to obtain a CNF / Si composite material; the preparation method comprises the following steps: adding an aniline monomer into a xanthan gum solution, and then adding an ammonium persulfate solution until a polymerization reaction is performed to form a dark green gel product A; adding graphene quantum dots into the gel product A, then adding a ferric chloride solution, and stirring for reaction to obtain a gel product B; and adding a CNF / Si composite material into the gel product B, heating and stirring, dropwise adding a borax solution for reaction, and annealing to obtain the silicon-based negative electrode material of the lithium ion battery. The lithium ion battery silicon-based negative electrode material and the battery provided by the invention have the advantages of high cycling stability, high specific capacity and wide application range.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy battery electrode materials, and in particular to a lithium ion battery silicon-based negative electrode material and a preparation method thereof and a battery. Background Art

[0002] Lithium-ion batteries are widely used in electronic products, portable power tools, electric vehicles and other fields. With the rapid development of electronic technology and the growing market of new energy vehicles, the market demand for lithium-ion batteries with higher energy density is becoming more urgent. However, the negative electrode used in commercial lithium-ion batteries is graphite negative electrode, and its theoretical specific capacity is only 372mAh / g, which cannot meet the requirements of high energy density batteries.

[0003] Silicon is considered to be an ideal choice for the next generation of lithium-ion battery negative electrode materials due to its relatively high specific capacity (4200mAh / g) and low lithium desorption platform. However, the volume expansion and contraction rate of silicon negative electrode during lithium desorption is greater than 300%, which makes its cycle performance in lithium batteries poor; in addition, silicon has low electronic conductivity and ionic conductivity, which makes its rate performance poor. Therefore, the optimization and modification research of silicon-based negative electrode materials is needed by the market. Summary of the invention

[0004] In order to solve the problems mentioned in the background technology, the present invention provides a lithium-ion battery silicon-based negative electrode material, which has high cycle stability, high specific capacity and a wide range of applications.

[0005] Specifically: A method for preparing a silicon-based negative electrode material for a lithium-ion battery comprises the following steps: Step 1, adding carbon nanofibers to nitric acid solution, ultrasonically dispersing, then refluxing at 80-85°C for 3-4h, and drying for later use; Step 2, adding porous silicon nanoparticles to anhydrous ethanol, ultrasonically dispersing, then adding the carbon nanofibers treated in step 1, continuing ultrasonic dispersion, transferring the mixture to a vacuum filtration device, and collecting CNF / Si wet material; Step 3: Spread the CNF / Si wet material in a quartz boat and place it in a fume hood to dry naturally. Then put the quartz boat into the middle of the quartz tube of the tube furnace, connect the vacuum pump and the nitrogen system, and evacuate to 0.9-1×10 -2 Pa, then fill with nitrogen to restore to normal pressure, vacuum-fill with nitrogen for 2-4 cycles, then heat to 400-410 °C, keep warm for 2-3 h, then cool naturally, collect CNF / Si composites, and seal and store in a nitrogen-filled glove box; Step 4, adding aniline monomer to the xanthan gum solution, stirring evenly, and then adding ammonium persulfate solution dropwise until a polymerization reaction forms a dark green gel product A; Step 5, adding graphene quantum dots to the gel product A obtained in step 4, ultrasonically dispersing, then adding ferric chloride solution, stirring and reacting for 1-2 hours, to obtain a gel product B; Step 6: Add the CNF / Si composite material obtained in step 3 to the gel product B obtained in step 5, heat to 60-65°C, stir for 1-2h, then add borax solution dropwise, reduce to 50-55°C, adjust pH = 9-9.5, react for 0.5-1h, vacuum filter, dry, then transfer to a reactor and anneal at 60-65°C in a nitrogen atmosphere for 2-3h, and obtain a lithium-ion battery silicon-based negative electrode material after cooling.

[0006] When implementing the above embodiment, preferably, the nitric acid solution in step 1 is 65% nitric acid; and the addition ratio of the carbon nanofibers to the nitric acid solution is 1 g: 20-25 mL.

[0007] When implementing the above embodiment, preferably, in step 2, the particle size of the porous silicon nanoparticles is 80-100 nm, and the porosity is 50%-60%.

[0008] When implementing the above embodiment, preferably, in step 2, the addition ratio of porous silicon nanoparticles to anhydrous ethanol is 1 g:100-120 mL; the addition mass ratio of porous silicon nanoparticles to carbon nanofibers is 1:1.5-2.

[0009] When implementing the above embodiment, preferably, in step 3, the CNF / Si wet material paving thickness is ≤5 mm; the nitrogen flow rate is 45-50 sccm; and the heating rate is 4-5 °C / min.

[0010] When implementing the above embodiment, preferably, in step 4, the added volume ratio of aniline monomer to xanthan gum solution is 4.5-5:100, the mass fraction of xanthan gum solution is 2%-3%; the concentration of ammonium persulfate solution is 4-5M, and the dropping rate is 1-2mL / min.

[0011] When implementing the above embodiment, preferably, in step 5, the addition ratio of graphene quantum dots to gel product A is 2-2.5 g:1000 mL; the concentration of ferric chloride solution is 0.15-0.2 M, and the addition volume ratio of ferric chloride solution to gel product A is 20:1.

[0012] When implementing the above embodiment, preferably, in step 6, the addition ratio of CNF / Si composite material to gel product B is 1 g:100-110 mL; the mass fraction of borax solution is 0.5%-0.7%, and the volume ratio of borax solution to gel product B is 1:5.

[0013] When implementing the above embodiment, preferably, in step 6, the drying temperature is 80-85° C.; and the annealing heating rate is 3-5° C. / min.

[0014] In addition, the present invention also provides a lithium ion battery silicon-based negative electrode material, which is prepared by the above-mentioned preparation method.

[0015] In addition, the present invention also provides a battery, the negative electrode material of which is prepared by the above-mentioned preparation method.

[0016] Compared with the prior art, the present invention has the following beneficial features: 1. The lithium-ion battery silicon-based negative electrode material of the present invention uses linear carbon nanofibers (CNF) as a conductive skeleton, and loads silicon material on the surface of the carbon nanofibers to improve the specific capacity of the negative electrode material; in addition, aniline monomer reacts with xanthan gum and ammonium persulfate to generate polyaniline (PANI), and graphene quantum dots (GQDs) are added to construct a xanthan gum-PANI-GQDs gel network; the CNF / Si composite material is mixed with the xanthan gum-PANI-GQDs gel network, and borax is added to cross-link the CNF and the xanthan gum. Moreover, since the linear structure of the CNF can be entangled with the xanthan gum-PANI-GQDs gel network through mechanical interlocking to form a stable structure, the xanthan gum-PANI-GQDs gel network is reorganized through dynamic hydrogen bonds and borate bonds to buffer the volume expansion stress of silicon.

[0017] 2. The lithium-ion battery silicon-based negative electrode material of the present invention, wherein the xanthan gum-PANI-GQDs gel network constructed therein is introduced during preparation , xanthan gum and The coordination forms a rigid region, inhibits crack propagation, and improves the stability of the structure. In addition, the xanthan gum-PANI-GQDs gel network has a dual conductive path, which combines with CNF through the π-π stacking of PANI conjugated chains to provide an electron transmission channel; GQDs are embedded in the gel network, and the electron transition efficiency is improved through the quantum confinement effect. In addition, the xanthan gum The group (sulfate group) promotes the migration of lithium ions and can improve the fast charging effect. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0019] In order to facilitate those skilled in the art to implement the present invention, some of the reagents used in the embodiments and comparative examples are now described: Carbon nanofiber: Jiangsu Xianfeng Nanomaterial Technology; Porous silicon nanoparticles: The particle size of porous silicon nanoparticles is 80nm, and the porosity is 60%, Beijing Zhongke Keyou Technology; Aniline monomer: Jinan Quansheng Chemical; Xanthan gum: Anhui Xinsheng Biotechnology; Ammonium persulfate: Shandong Hairui New Materials; Graphene quantum dots: Suzhou Kaifa New Materials Technology; Ferric chloride: Jinan Xinnuo Chemical; Borax: Shandong Youwei Chemical.

[0020] Example 1

[0021] A lithium-ion battery silicon-based negative electrode material, the preparation steps of which are as follows: Step 1, adding carbon nanofibers to 65% nitric acid solution at a solid-liquid ratio of 1g:20-25mL, ultrasonically dispersing, then refluxing at 80-85°C for 3-4h, and drying for later use; Step 2, adding porous silicon nanoparticles to anhydrous ethanol at a solid-liquid ratio of 1g:100-120mL, ultrasonically dispersing, and then adding the carbon nanofibers treated in step 1, the added mass ratio of porous silicon nanoparticles to carbon nanofibers is 1:1.5-2, and ultrasonic dispersion is continued for 1h, and the mixture is transferred to a vacuum filtration device, filtered with a 0.22 μm nylon membrane, and CNF / Si wet material is collected; Step 3: Spread the CNF / Si wet material in a quartz boat with a thickness of ≤5 mm, place it in a fume hood and dry it naturally. Then put the quartz boat into the middle of the quartz tube of the tube furnace, connect the vacuum pump and the nitrogen system, and evacuate to 0.9-1×10 -2 Pa, close the vacuum valve, then fill with nitrogen to restore normal pressure, repeat the vacuum-nitrogen filling cycle 2-4 times, then keep the nitrogen flow rate at 45-50sccm throughout the process, raise the temperature to 400-410℃ at 4-5℃ / min, keep it at that temperature for 2-3h, then cool naturally, collect the CNF / Si composite material, and seal it in a nitrogen-filled glove box; Step 4, adding aniline monomer to 2%-3% xanthan gum solution at a volume ratio of 4.5-5:100, stirring evenly, and then adding 4-5M ammonium persulfate solution dropwise at 1-2 mL / min until a dark green gel product A is formed by polymerization reaction; Step 5, adding graphene quantum dots to the gel product A obtained in step 4 at a solid-liquid ratio of 2-2.5 g:1000 mL, ultrasonically dispersing, then adding 0.15-0.2 M ferric chloride solution to the gel product A at a volume ratio of 20:1, stirring and reacting for 1-2 hours to obtain a gel product B; Step 6. Add the CNF / Si composite material obtained in step 3 to the gel product B obtained in step 5 at a solid-liquid ratio of 1g:100-110mL, heat to 60-65°C, stir for 1-2h, then drop 0.5%-0.7% borax solution, the volume ratio of borax solution to gel product B is 1:5, reduce to 50-55°C, adjust pH=9-9.5 (adjust with NaOH), react for 0.5-1h, vacuum filter, dry at 80°C for 2h, then transfer to a reactor and anneal at 60-65°C in a nitrogen atmosphere for 2-3h, and obtain a lithium-ion battery silicon-based negative electrode material after cooling.

[0022] Example 2

[0023] A lithium-ion battery silicon-based negative electrode material, the preparation steps of which are as follows: Step 1, adding carbon nanofibers to 65% nitric acid solution at a solid-liquid ratio of 1g:20-25mL, ultrasonically dispersing, then refluxing at 80-85°C for 3-4h, and drying for later use; Step 2, adding porous silicon nanoparticles to anhydrous ethanol at a solid-liquid ratio of 1g:100-120mL, ultrasonically dispersing, and then adding the carbon nanofibers treated in step 1, the added mass ratio of porous silicon nanoparticles to carbon nanofibers is 1:1.5-2, and ultrasonic dispersion is continued for 1h, and the mixture is transferred to a vacuum filtration device, filtered with a 0.22 μm nylon membrane, and CNF / Si wet material is collected; Step 3: Spread the CNF / Si wet material in a quartz boat with a thickness of ≤5 mm, place it in a fume hood and dry it naturally. Then put the quartz boat into the middle of the quartz tube of the tube furnace, connect the vacuum pump and the nitrogen system, and evacuate to 0.9-1×10 -2 Pa, close the vacuum valve, then fill with nitrogen to restore normal pressure, repeat the vacuum-nitrogen filling cycle 2-4 times, then keep the nitrogen flow rate at 45-50sccm throughout the process, raise the temperature to 400-410℃ at 4-5℃ / min, keep it at that temperature for 2-3h, then cool naturally, collect the CNF / Si composite material, and seal it in a nitrogen-filled glove box; Step 4, adding aniline monomer to 2%-3% xanthan gum solution at a volume ratio of 4.5-5:100, stirring evenly, and then adding 4-5M ammonium persulfate solution dropwise at 1-2 mL / min until a dark green gel product A is formed by polymerization reaction; Step 5, adding graphene quantum dots to the gel product A obtained in step 4 at a solid-liquid ratio of 2-2.5 g:1000 mL, ultrasonically dispersing, then adding 0.15-0.2 M ferric chloride solution to the gel product A at a volume ratio of 20:1, stirring and reacting for 1-2 hours to obtain a gel product B; Step 6. Add the CNF / Si composite material obtained in step 3 to the gel product B obtained in step 5 at a solid-liquid ratio of 1g:100-110mL, heat to 60-65°C, stir for 1-2h, then drop 0.5%-0.7% borax solution, the volume ratio of borax solution to gel product B is 1:5, reduce to 50-55°C, adjust pH=9-9.5 (adjust with NaOH), react for 0.5-1h, vacuum filter, dry at 80°C for 2h, then transfer to a reactor and anneal at 60-65°C in a nitrogen atmosphere for 2-3h, and obtain a lithium-ion battery silicon-based negative electrode material after cooling.

[0024] Example 3

[0025] A lithium-ion battery silicon-based negative electrode material, the preparation steps of which are as follows: Step 1, adding carbon nanofibers to 65% nitric acid solution at a solid-liquid ratio of 1g:20-25mL, ultrasonically dispersing, then refluxing at 80-85°C for 3-4h, and drying for later use; Step 2, adding porous silicon nanoparticles to anhydrous ethanol at a solid-liquid ratio of 1g:100-120mL, ultrasonically dispersing, and then adding the carbon nanofibers treated in step 1, the added mass ratio of porous silicon nanoparticles to carbon nanofibers is 1:1.5-2, and ultrasonic dispersion is continued for 1h, and the mixture is transferred to a vacuum filtration device, filtered with a 0.22 μm nylon membrane, and CNF / Si wet material is collected; Step 3: Spread the CNF / Si wet material in a quartz boat with a thickness of ≤5 mm, place it in a fume hood and dry it naturally. Then put the quartz boat into the middle of the quartz tube of the tube furnace, connect the vacuum pump and the nitrogen system, and evacuate to 0.9-1×10 -2 Pa, close the vacuum valve, then fill with nitrogen to restore normal pressure, repeat the vacuum-nitrogen filling cycle 2-4 times, then keep the nitrogen flow rate at 45-50sccm throughout the process, raise the temperature to 400-410℃ at 4-5℃ / min, keep it at that temperature for 2-3h, then cool naturally, collect the CNF / Si composite material, and seal it in a nitrogen-filled glove box; Step 4, adding aniline monomer to 2%-3% xanthan gum solution at a volume ratio of 4.5-5:100, stirring evenly, and then adding 4-5M ammonium persulfate solution dropwise at 1-2 mL / min until a dark green gel product A is formed by polymerization reaction; Step 5, adding graphene quantum dots to the gel product A obtained in step 4 at a solid-liquid ratio of 2-2.5 g:1000 mL, ultrasonically dispersing, then adding 0.15-0.2 M ferric chloride solution to the gel product A at a volume ratio of 20:1, stirring and reacting for 1-2 hours to obtain a gel product B; Step 6. Add the CNF / Si composite material obtained in step 3 to the gel product B obtained in step 5 at a solid-liquid ratio of 1g:100-110mL, heat to 60-65°C, stir for 1-2h, then drop 0.5%-0.7% borax solution, the volume ratio of borax solution to gel product B is 1:5, reduce to 50-55°C, adjust pH=9-9.5 (adjust with NaOH), react for 0.5-1h, vacuum filter, dry at 80°C for 2h, then transfer to a reactor and anneal at 60-65°C in a nitrogen atmosphere for 2-3h, and obtain a lithium-ion battery silicon-based negative electrode material after cooling.

[0026] Comparative Example 1

[0027] A lithium-ion battery silicon-based negative electrode material, the preparation steps of which are as follows: Step 1, adding carbon nanofibers to 65% nitric acid solution at a solid-liquid ratio of 1g:20-25mL, ultrasonically dispersing, then refluxing at 80-85°C for 3-4h, and drying for later use; Step 2, adding porous silicon nanoparticles to anhydrous ethanol at a solid-liquid ratio of 1g:100-120mL, ultrasonically dispersing, and then adding the carbon nanofibers treated in step 1, the added mass ratio of porous silicon nanoparticles to carbon nanofibers is 1:1.5-2, and ultrasonic dispersion is continued for 1h, and the mixture is transferred to a vacuum filtration device, filtered with a 0.22 μm nylon membrane, and CNF / Si wet material is collected; Step 3: Spread the CNF / Si wet material in a quartz boat with a thickness of ≤5 mm, place it in a fume hood and dry it naturally. Then put the quartz boat into the middle of the quartz tube of the tube furnace, connect the vacuum pump and the nitrogen system, and evacuate to 0.9-1×10 -2 Pa, close the vacuum valve, then fill with nitrogen to restore normal pressure, repeat the vacuum-nitrogen filling cycle 2-4 times, then maintain the nitrogen flow rate at 45-50sccm throughout the process, heat to 400-410℃ at 4-5℃ / min, keep warm for 2-3h, then cool naturally, and obtain the silicon-based negative electrode material for lithium-ion batteries after ball milling.

[0028] The lithium-ion battery silicon-based negative electrode materials obtained in Examples 1-3 and Comparative Example 1 were assembled into batteries for experimental verification.

[0029] Battery assembly process: According to the mass ratio of 95:1.5:1.5:2, the negative electrode material, conductive agent (SP), CMC and SBR are mixed and coated on copper foil to obtain the negative electrode sheet. According to the mass ratio of 96.5:2:1.5, the positive electrode active material lithium cobalt oxide, conductive agent (SP) and PVDF are mixed evenly and coated on aluminum foil to obtain the positive electrode sheet. The electrolyte is 1mol / L LiPF6+EC+EMC, and the separator is a polyethylene / propylene composite microporous membrane. Assemble them into a battery.

[0030] The first discharge capacity was tested at 0.1C; then a 200-cycle test was performed, with charge and discharge at 1C, a discharge cut-off voltage of 0.01 V, and a charge cut-off voltage of 1.5 V; the capacity retention rate after 50 weeks, 100 weeks, and 200 weeks was recorded, and the test results are as follows: 0.1C first discharge capacity (mAh / g) Capacity retention rate after 50 cycles of 1C charge and discharge (%) Capacity retention rate after 100 cycles of 1C charge and discharge (%) Capacity retention rate after 200 cycles of 1C charge and discharge (%) Example 1 3159 95.3 90.6 84.7 Example 2 3207 94.2 88.5 83.8 Example 3 3186 94.4 89.4 84.1 Comparative Example 1 2869 56.3 37.5 25.8 The above test results show that the capacity of Examples 1-3 is higher than that of carbon-based batteries, and they can still maintain a relatively high capacity after 200 cycles, which shows that they have high cycle stability. Comparative Example 1 simulates a common carbon / silicon negative electrode material battery, which also has a high capacity, but its capacity retention rate after 200 cycles is low and its stability is poor.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a silicon-based negative electrode material for a lithium-ion battery, characterized in that: The steps include: Step 1, adding carbon nanofibers to nitric acid solution, ultrasonically dispersing, then refluxing at 80-85°C for 3-4h, and drying for later use; Step 2, adding porous silicon nanoparticles to anhydrous ethanol, ultrasonically dispersing, then adding the carbon nanofibers treated in step 1, continuing ultrasonic dispersion, transferring the mixture to a vacuum filtration device, and collecting CNF / Si wet material; Step 3: Spread the CNF / Si wet material in a quartz boat and place it in a fume hood to dry naturally. Then put the quartz boat into the middle of the quartz tube of the tube furnace, connect the vacuum pump and the nitrogen system, and evacuate to 0.9-1×10 -2 Pa, then fill with nitrogen to restore to normal pressure, vacuum-fill with nitrogen for 2-4 cycles, then heat to 400-410 °C, keep warm for 2-3 h, then cool naturally, collect CNF / Si composites, and seal and store in a nitrogen-filled glove box; Step 4, adding aniline monomer to the xanthan gum solution, stirring evenly, and then adding ammonium persulfate solution dropwise until a polymerization reaction forms a dark green gel product A; Step 5, adding graphene quantum dots to the gel product A obtained in step 4, ultrasonically dispersing, then adding ferric chloride solution, stirring and reacting for 1-2 hours, to obtain a gel product B; Step 6: Add the CNF / Si composite material obtained in step 3 to the gel product B obtained in step 5, heat to 60-65°C, stir for 1-2h, then add borax solution dropwise, reduce to 50-55°C, adjust pH = 9-9.5, react for 0.5-1h, vacuum filter, dry, then transfer to a reactor and anneal at 60-65°C in a nitrogen atmosphere for 2-3h, and obtain a lithium-ion battery silicon-based negative electrode material after cooling.

2. The preparation method according to claim 1, characterized in that: The nitric acid solution in step 1 is 65% nitric acid; the addition ratio of carbon nanofibers to nitric acid solution is 1g:20-25mL.

3. The preparation method according to claim 1, characterized in that: In step 2, the particle size of the porous silicon nanoparticles is 80-100 nm, and the porosity is 50%-60%.

4. The preparation method according to claim 1, characterized in that: In step 2, the addition ratio of porous silicon nanoparticles to anhydrous ethanol is 1 g:100-120 mL; the addition mass ratio of porous silicon nanoparticles to carbon nanofibers is 1:1.5-2.

5. The preparation method according to claim 1, characterized in that: In step 3, the CNF / Si wet material paving thickness is ≤5 mm; the nitrogen flow rate is 45-50 sccm; and the heating rate is 4-5 ℃ / min.

6. The preparation method according to claim 1, characterized in that: In step 4, the added volume ratio of aniline monomer to xanthan gum solution is 4.5-5:100, the mass fraction of xanthan gum solution is 2%-3%; the concentration of ammonium persulfate solution is 4-5M, and the dropping rate is 1-2mL / min.

7. The preparation method according to claim 1, characterized in that: In step 5, the addition ratio of graphene quantum dots to gel product A is 2-2.5 g:1000 mL; the concentration of ferric chloride solution is 0.15-0.2 M, and the addition volume ratio of ferric chloride solution to gel product A is 20:

1.

8. The preparation method according to claim 1, characterized in that: In step 6, the addition ratio of CNF / Si composite material to gel product B is 1 g:100-110 mL; the mass fraction of borax solution is 0.5%-0.7%, and the volume ratio of borax solution to gel product B is 1:

5.

9. A lithium-ion battery silicon-based negative electrode material, characterized in that: The method is prepared by any one of claims 1 to 8.

10. A battery, characterized in that: The negative electrode material is prepared by the preparation method described in any one of claims 1 to 8.