Preparation method for improving cycle performance of lithium negative electrode material

Abstract

The invention discloses a preparation method for improving the cycle performance of a lithium negative electrode material, and relates to the technical field of lithium negative electrode materials. Lithium powder, Ti3C2Tx and polysiloxane are mixed and calcined to prepare the modified lithium metal material, Ti3C2Tx has a layered structure and provides a stable conductive frame, and the formation of the frame can provide electronic conductivity and effectively inhibit local current density in the charge-discharge process, so that deposition of lithium is limited in the structure, the defects of lithium dendrites are overcome, and the performance of the lithium metal material is improved. The functional group on the surface of the Ti3C2Tx has high binding energy with lithium metal, volume change of the pole piece in the long-time charging and discharging process can be reduced, due to introduction of polysiloxane, the surface energy of Li ion diffusion can be reduced through the Si-O functional group of polysiloxane, Li < + > is evenly distributed, the risk of SEI film breakage is reduced, and therefore the cycle performance of the battery end is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium negative electrode materials, and in particular to a preparation method for improving the cycle performance of lithium negative electrode materials. Background Art

[0002] At present, the energy crisis is a major obstacle to the development of today's society. The fundamental solution to this problem is to use clean energy on a large scale. Clean energy mainly comes from lithium batteries. How to improve the performance of lithium batteries has become a difficult problem now.

[0003] Lithium anode materials are ideal for next-generation, high-energy-density batteries. However, lithium's high reactivity leads to defects such as unstable SEI (solid electrolyte interface) films and dendrite growth, limiting its application in lithium battery anodes. Therefore, addressing the capacity decay of metallic lithium after prolonged charge and discharge cycles has become a pressing issue.

[0004] Therefore, we propose a preparation method to improve the cycle performance of lithium negative electrode materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method for improving the cycle performance of lithium negative electrode materials, so as to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solution: a preparation method for improving the cycle performance of lithium negative electrode materials, comprising the following steps: Step 1: Lithium powder, Ti3C2T x Mixing with polysiloxane and calcining to obtain a modified lithium metal material; Step 2: Mix the modified lithium metal material, the binder and the conductive agent, stir evenly to obtain a negative electrode slurry, evenly coat the negative electrode slurry on a copper foil, and vacuum dry to obtain a negative electrode material.

[0007] Furthermore, in step 1, the lithium powder and Ti3C2T x The mass ratio is (12~75):1; In step 1, the mass ratio of the lithium powder to the polysiloxane is (50-70):1; In step 2, the mass ratio of the modified lithium metal material, the binder and the conductive agent is (5-8):1:1.

[0008] Furthermore, in step 1, the calcination process conditions are: temperature 200°C~250°C, time 15h~20h, heating rate 5°C / min~10°C / min, and annealing rate 15°C / min~25°C / min.

[0009] Furthermore, in step 2, the process conditions for vacuum drying are: temperature 100° C. to 120° C., and time 8 h to 12 h.

[0010] Furthermore, in step 1, the thickness of the copper foil is 10 μm; The coating thickness of the negative electrode slurry is 20 μm to 40 μm.

[0011] Furthermore, the binder is polyvinylidene fluoride; The conductive agent is Li400.

[0012] Furthermore, the polysiloxane is a mixture of one or more of polydimethylsiloxane, polymethylphenylsiloxane, and polydiethylsiloxane.

[0013] In the above technical solution, lithium powder, Ti3C2T x Mixed with polysiloxane, the modified lithium metal material Ti3C2T was obtained by calcination. x It has a layered structure and provides a stable conductive framework. The formation of the framework can provide electronic conductivity, effectively suppressing the local current density during charge and discharge, so that the deposition of lithium is limited to the interior of the structure, thereby improving the defects of lithium dendrites. x The functional groups on the surface have a high binding energy with lithium metal, which will also reduce the volume change of the electrode during long-term charging and discharging; In addition, the introduction of polysiloxane can reduce the surface energy of Li ion diffusion through its own Si-O functional groups, making Li + Even distribution reduces the risk of SEI film rupture, thereby improving the cycle performance of the battery.

[0014] Furthermore, the surface of the modified lithium metal material is coated with polypyrrole, and the specific process is as follows: S1: mixing citric acid and NaOH solution with the modified lithium metal material, stirring evenly, ultrasonically dispersing, heating for reaction, cooling, washing, and drying to obtain a lithium oxide-rich metal material; S2: Mix the lithium oxide-rich metal material with polyvinyl pyrrolidone, stir in an ice bath for 0.5h~1.5h, add pyrrole, stir for 5min~15min, add FeCl3, react for 3h~5h, precipitate, centrifuge, and dry to obtain a polypyrrole-coated modified lithium metal material.

[0015] Furthermore, in S1, the ratio of citric acid, NaOH solution and modified lithium metal material is (0.5~1.5) g: (40~80) mL: (20~60) g.

[0016] Furthermore, in S1, the process conditions of ultrasonic dispersion are: frequency 300kHz~500kHz, time 5min~15min; The process conditions of the heating reaction are: temperature 120℃~160℃, time 15~25h.

[0017] Furthermore, in S2, the ratio of lithium oxide-rich metal material, polyvinyl pyrrolidone, pyrrole and FeCl3 is: (0.1~1) g: (50~250) mL: (0.1~1.5) mL: (50~250) mL.

[0018] Furthermore, in S1, the concentration of the NaOH solution is 0.1 mol / L; In S2, the pyrrole is added in the form of an aqueous solution with a concentration of 0.1 mol / L; In S2, the FeCl3 is added in the form of an aqueous solution with a concentration of 0.2 mol / L.

[0019] Furthermore, in S2, the centrifugal process conditions are: rotation speed 1000 rpm~2000 rpm, time 5 min~15 min; The drying process conditions are: temperature 40℃~60℃, time 8h~12h.

[0020] Furthermore, the negative electrode material is used to prepare a button battery, and the specific process is as follows: The positive electrode slurry is evenly coated on aluminum foil and vacuum dried to obtain a positive electrode material; and the positive electrode material is assembled according to the assembly sequence to obtain a button battery.

[0021] Furthermore, the thickness of the aluminum foil is 15 μm; The coating thickness of the positive electrode slurry is 10 μm to 20 μm.

[0022] Furthermore, the assembly sequence is: take the battery shell, place the negative electrode material, add the electrolyte, place the separator, add the electrolyte, place the positive electrode material, place the gasket spring, and assemble the battery shell.

[0023] Furthermore, the battery case is CR2032 model; The diaphragm is selected from one of polypropylene diaphragm, polyethylene diaphragm and polyvinylidene fluoride diaphragm; The thickness of the separator is 20 μm.

[0024] Furthermore, the process conditions of the vacuum drying are: temperature 100°C to 120°C, time 8h to 12h.

[0025] Furthermore, the positive electrode slurry is prepared by the following process: Lithium cobalt oxide, a binder, and a conductive agent are mixed in a mass ratio of (5-8):1:1, and stirred evenly to obtain a positive electrode slurry.

[0026] In the above technical solution, the surface of the modified lithium metal material is first subjected to an oxidation-enriched treatment to increase the oxygen functional groups on its surface and increase the reactive sites. x The interlayer spacing of Ti3C2T becomes larger and more uniform, and the oxygen functional groups can also x The layers play a supporting role, maintaining a large specific surface area, which is beneficial to the migration and diffusion of electrolyte ions and improves the cycle stability of the battery; Surface coating with polypyrrole can prevent direct contact between lithium powder and electrolyte, reduce side reactions, stabilize the SEI film, and improve the battery's charge and discharge efficiency and cycle stability. In addition, polypyrrole has a certain elasticity, which can alleviate the volume expansion and contraction of lithium negative electrode materials during the charge and discharge process, alleviate stress concentration inside the negative electrode material, reduce the possibility of cracking, and extend the battery's cycle life.

[0027] Compared with the prior art, the present invention has the following beneficial effects: 1. Lithium powder, Ti3C2T x Mixed with polysiloxane, the modified lithium metal material Ti3C2T was obtained by calcination. x It has a layered structure and provides a stable conductive framework. The formation of the framework can provide electronic conductivity, effectively suppressing the local current density during charge and discharge, so that the deposition of lithium is limited to the interior of the structure, thereby improving the defects of lithium dendrites. x The surface functional groups have a high binding energy with lithium metal, which will also reduce the volume change of the electrode during long-term charge and discharge. The introduction of polysiloxane can reduce the surface energy of Li ion diffusion through its own Si-O functional groups, making Li + Even distribution reduces the risk of SEI film rupture, thereby improving the cycle performance of the battery.

[0028] 2. The surface of the modified lithium metal material is subjected to an oxidation treatment to increase the oxygen functional groups on its surface and the reactive sites. x The interlayer spacing of Ti3C2T becomes larger and more uniform, and the oxygen functional groups can also x The layers play a supporting role, maintaining a large specific surface area, which is beneficial to the migration and diffusion of electrolyte ions and improves the cycle stability of the battery.

[0029] 3. Surface coating of polypyrrole can prevent direct contact between lithium powder and electrolyte, reduce side reactions, stabilize the SEI film, and improve the battery's charge and discharge efficiency and cycle stability. In addition, polypyrrole has a certain elasticity, which can alleviate the volume expansion and contraction of lithium negative electrode materials during the charge and discharge process, alleviate stress concentration inside the negative electrode material, reduce the possibility of cracking, and extend the battery's cycle life.

[0030] 4. Polypyrrole has positive charge and can electrostatically adsorb with oxygen functional groups, thus enhancing the bonding between polypyrrole and Ti3C2T x The binding force. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0032] In the following specific embodiments, Battery case, model CR2032; Copper foil, thickness 10 μm; Aluminum foil, thickness 15 μm; Polypropylene diaphragm, thickness 20 μm; Li400, specific surface area 9m 2 / g; Lithium powder, 10μm~20μm; Ti3C2T x , 2μm~10μm; Polyvinylidene fluoride, model: Solvay 5130; Pyrrole solution, concentration 0.1 mol / L; FeCl3 solution, concentration 0.2 mol / L; NaOH solution, concentration 0.1 mol / L; Example 1: A preparation method for improving the cycle performance of a lithium negative electrode material, comprising the following steps: Step 1: Preparation of modified lithium metal material: Lithium powder, Ti3C2T x and polydimethylsiloxane, and calcined to obtain modified lithium metal material; lithium powder and Ti3C2T x The mass ratio of lithium powder to polydimethylsiloxane is 18:1; the mass ratio of lithium powder to polydimethylsiloxane is 65:1; the calcination process conditions are: temperature 250℃, time 20h, heating rate 10℃ / min, annealing rate 25℃ / min; Step 2: Preparation of negative electrode materials: The modified lithium metal material, polyvinylidene fluoride and Li400 are mixed in a mass ratio of 8:1:1 and stirred evenly to obtain a negative electrode slurry; The negative electrode slurry was evenly coated on a 10 μm thick copper foil and vacuum dried to obtain a negative electrode material; the vacuum drying process conditions were: temperature 120° C., time 12 h.

[0033] The negative electrode material obtained by the above process can be used to prepare a button battery, which includes the following steps: (1) Preparation of positive electrode slurry: Lithium cobalt oxide, polyvinylidene fluoride and Li400 were mixed in a mass ratio of 8:1:1 and stirred evenly to obtain a positive electrode slurry; (2) Preparation of button batteries: Step 1. Evenly coat the positive electrode slurry on a 15 μm thick aluminum foil and vacuum dry it to obtain the positive electrode material; Step 2. Take the battery shell, place the negative electrode material, add the electrolyte, place a 20 μm thick polypropylene separator, add the electrolyte, place the positive electrode material, place the gasket spring, assemble the battery shell, and obtain a button battery; the coating thickness of the negative electrode slurry is 40 μm; the coating thickness of the positive electrode slurry is 20 μm; in step 1, the process conditions for vacuum drying are: temperature 120°C, time 12 hours.

[0034] Example 2: Compared with Example 1, lithium powder and Ti3C2T x The mass ratio was adjusted to 12:1, and the other conditions remained unchanged.

[0035] Example 3: Compared with Example 1, lithium powder and Ti3C2T x The mass ratio was adjusted to 16:1, and the other conditions remained unchanged.

[0036] Example 4: Compared with Example 1, lithium powder and Ti3C2T x The mass ratio was adjusted to 20:1, and the other conditions remained unchanged.

[0037] Example 5: Compared with Example 1, lithium powder and Ti3C2T x The mass ratio was adjusted to 22:1, and the other conditions remained unchanged.

[0038] Example 6: Compared with Example 1, the mass ratio of lithium powder to polydimethylsiloxane is adjusted to 50:1, and the other conditions remain unchanged.

[0039] Example 7: Compared with Example 1, the mass ratio of lithium powder to polydimethylsiloxane is adjusted to 60:1, and the other conditions remain unchanged.

[0040] Example 8: Compared with Example 1, the mass ratio of lithium powder to polydimethylsiloxane is adjusted to 70:1, and the other conditions remain unchanged.

[0041] Example 9: Compared with Example 1, the mass ratio of lithium powder to polydimethylsiloxane is adjusted to 75:1, and the other conditions remain unchanged.

[0042] Example 10: Compared with Example 1, lithium powder and Ti3C2T xThe mass ratio of lithium powder to polydimethylsiloxane remains unchanged, and the mass ratio of lithium powder to polydimethylsiloxane remains unchanged. The process conditions are adjusted. The specific steps are as follows: Step 1: Preparation of modified lithium metal material: Lithium powder, Ti3C2T x and polydimethylsiloxane, and calcined to obtain modified lithium metal material; lithium powder and Ti3C2T x The mass ratio of lithium powder to polydimethylsiloxane is 18:1; the mass ratio of lithium powder to polydimethylsiloxane is 65:1; the calcination process conditions are: temperature 230℃, time 18h, heating rate 8℃ / min, annealing rate 20℃ / min; Step 2: Preparation of negative electrode materials: The modified lithium metal material, polyvinylidene fluoride and Li400 are mixed in a mass ratio of 6:1:1 and stirred evenly to obtain a negative electrode slurry; The negative electrode slurry was evenly coated on a 10 μm thick copper foil and vacuum dried to obtain a negative electrode material; the vacuum drying process conditions were: temperature 110° C., time 10 h.

[0043] The negative electrode material obtained by the above process can be used to prepare a button battery, which includes the following steps: (1) Preparation of positive electrode slurry: Lithium cobalt oxide, polyvinylidene fluoride and Li400 were mixed in a mass ratio of 6:1:1 and stirred evenly to obtain a positive electrode slurry; (2) Preparation of button batteries: Step 1. Evenly coat the positive electrode slurry on a 15 μm thick aluminum foil and vacuum dry it to obtain the positive electrode material. Step 2. Take the battery shell, place the negative electrode material, add the electrolyte, place a 20 μm thick polypropylene separator, add the electrolyte, place the positive electrode material, place the gasket shrapnel, assemble the battery shell, and obtain a button battery. The coating thickness of the negative electrode slurry is 30 μm; the coating thickness of the positive electrode slurry is 15 μm. In step 1, the process conditions for vacuum drying are: temperature 110°C, time 10 hours.

[0044] Example 11: Compared with Example 1, lithium powder and Ti3C2T x The mass ratio of lithium powder to polydimethylsiloxane remains unchanged, and the mass ratio of lithium powder to polydimethylsiloxane remains unchanged. The process conditions are adjusted. The specific steps are as follows: Step 1: Preparation of modified lithium metal material: Lithium powder, Ti3C2T x and polydimethylsiloxane, and calcined to obtain modified lithium metal material; lithium powder and Ti3C2T xThe mass ratio of lithium powder to polydimethylsiloxane is 18:1; the mass ratio of lithium powder to polydimethylsiloxane is 65:1; the calcination process conditions are: temperature 200℃, time 15h, heating rate 5℃ / min, annealing rate 15℃ / min; Step 2: Preparation of negative electrode materials: The modified lithium metal material, polyvinylidene fluoride and Li400 are mixed in a mass ratio of 5:1:1 and stirred evenly to obtain a negative electrode slurry; The negative electrode slurry was evenly coated on a 10 μm thick copper foil and vacuum dried to obtain a negative electrode material; the process conditions of the vacuum drying were: temperature 100° C., time 8 h.

[0045] The negative electrode material obtained by the above process can be used to prepare a button battery, which includes the following steps: (1) Preparation of positive electrode slurry: Lithium cobalt oxide, polyvinylidene fluoride and Li400 were mixed in a mass ratio of 5:1:1 and stirred evenly to obtain a positive electrode slurry; (2) Preparation of button batteries: Step 1. Evenly coat the positive electrode slurry on a 15 μm thick aluminum foil and vacuum dry it to obtain the positive electrode material; Step 2. Take the battery shell, place the negative electrode material, add the electrolyte, place a 20 μm thick polypropylene separator, add the electrolyte, place the positive electrode material, place the gasket shrapnel, assemble the battery shell, and obtain a button battery; the coating thickness of the negative electrode slurry is 20 μm; the coating thickness of the positive electrode slurry is 10 μm; in step 1, the process conditions for vacuum drying are: temperature 100°C, time 8 hours.

[0046] Example 12: Compared with Example 1, polypyrrole is coated on the surface of the modified lithium metal material, and other conditions remain unchanged. The specific process is as follows: Step 1: Preparation of modified lithium metal material: Lithium powder, Ti3C2T x and polydimethylsiloxane, and calcined to obtain modified lithium metal material; lithium powder and Ti3C2T x The mass ratio of lithium powder to polydimethylsiloxane is 18:1; the mass ratio of lithium powder to polydimethylsiloxane is 65:1; the calcination process conditions are: temperature 250℃, time 20h, heating rate 10℃ / min, annealing rate 25℃ / min; Step 2: Preparation of polypyrrole-coated modified lithium metal material: S1: Mix citric acid, NaOH solution and modified lithium metal material in a ratio of 1.5g:80mL:60g, stir evenly, ultrasonically disperse, heat to react, cool, wash and dry to obtain lithium oxide-rich metal material; S2: Mix the lithium oxide-rich metal material with polyvinyl pyrrolidone, stir in an ice bath for 1.5h, add pyrrole solution, stir for 15min, add FeCl3 solution, react for 5h, precipitate, centrifuge and dry to obtain polypyrrole-coated modified lithium metal material; in S1, the process conditions for ultrasonic dispersion are: frequency 500kHz, time 15min; the process conditions for heating reaction are: temperature 160℃, time 25h; in S2, the ratio of lithium oxide-rich metal material, polyvinyl pyrrolidone, pyrrole solution and FeCl3 solution is: 1g:250mL:1.5mL:250mL; in S2, the process conditions for centrifugation are: speed 2000rpm, time 15min; the process conditions for drying are: temperature 60℃, time 12h; Step 3: Preparation of negative electrode materials: The polypyrrole-coated modified lithium metal material, polyvinylidene fluoride and Li400 were mixed in a mass ratio of 8:1:1 and stirred evenly to obtain a negative electrode slurry; The negative electrode slurry was evenly coated on a 10 μm thick copper foil and vacuum dried to obtain a negative electrode material; the vacuum drying process conditions were: temperature 120° C., time 12 h.

[0047] The negative electrode material obtained by the above process can be used to prepare a button battery, which includes the following steps: (1) Preparation of positive electrode slurry: Lithium cobalt oxide, polyvinylidene fluoride and Li400 were mixed in a mass ratio of 8:1:1 and stirred evenly to obtain a positive electrode slurry; (2) Preparation of button batteries: Step 1. Evenly coat the positive electrode slurry on a 15 μm thick aluminum foil and vacuum dry it to obtain the positive electrode material; Step 2. Take the battery shell, place the negative electrode material, add the electrolyte, place a 20 μm thick polypropylene separator, add the electrolyte, place the positive electrode material, place the gasket spring, assemble the battery shell, and obtain a button battery; the coating thickness of the negative electrode slurry is 40 μm; the coating thickness of the positive electrode slurry is 20 μm; in step 1, the process conditions for vacuum drying are: temperature 120°C, time 12 hours.

[0048] Example 13: Compared with Example 12, the process conditions were adjusted, and the other conditions remained unchanged. The specific process is as follows: Step 1: Preparation of modified lithium metal material: Lithium powder, Ti3C2T x and polydimethylsiloxane, and calcined to obtain modified lithium metal material; lithium powder and Ti3C2T xThe mass ratio of lithium powder to polydimethylsiloxane is 18:1; the mass ratio of lithium powder to polydimethylsiloxane is 65:1; the calcination process conditions are: temperature 230℃, time 18h, heating rate 8℃ / min, annealing rate 20℃ / min; Step 2: Polypyrrole-coated modified lithium metal material S1: Mix citric acid, NaOH solution and modified lithium metal material in a ratio of 1.0g:60mL:40g, stir evenly, ultrasonically disperse, heat to react, cool, wash and dry to obtain lithium oxide-rich metal material; S2: Mix the lithium oxide-rich metal material with polyvinyl pyrrolidone, stir in an ice bath for 1.0h, add pyrrole solution, stir for 10min, add FeCl3 solution, react for 4h, precipitate, centrifuge and dry to obtain polypyrrole-coated modified lithium metal material; in S1, the process conditions for ultrasonic dispersion are: frequency 400kHz, time 10min; the process conditions for heating reaction are: temperature 140℃, time 20h; in S2, the ratio of lithium oxide-rich metal material, polyvinyl pyrrolidone, pyrrole solution and FeCl3 solution is: 0.5g:150mL:1.0mL:150mL; in S2, the process conditions for centrifugation are: speed 1500rpm, time 10min; the process conditions for drying are: temperature 50℃, time 10h; Step 3: Preparation of negative electrode materials: The modified lithium metal material, polyvinylidene fluoride and Li400 are mixed in a mass ratio of 7:1:1 and stirred evenly to obtain a negative electrode slurry; The negative electrode slurry was evenly coated on a 10 μm thick copper foil and vacuum dried to obtain a negative electrode material; the vacuum drying process conditions were: temperature 110° C., time 10 h.

[0049] The negative electrode material obtained by the above process can be used to prepare a button battery, which includes the following steps: (1) Preparation of positive electrode slurry: Lithium cobalt oxide, polyvinylidene fluoride and Li400 were mixed in a mass ratio of 7:1:1 and stirred evenly to obtain a positive electrode slurry; (2) Preparation of button batteries: Step 1. Evenly coat the positive electrode slurry on a 15 μm thick aluminum foil and vacuum dry it to obtain the positive electrode material. Step 2. Take the battery shell, place the negative electrode material, add the electrolyte, place a 20 μm thick polypropylene separator, add the electrolyte, place the positive electrode material, place the gasket shrapnel, assemble the battery shell, and obtain a button battery. The coating thickness of the negative electrode slurry is 30 μm; the coating thickness of the positive electrode slurry is 15 μm. In step 1, the process conditions for vacuum drying are: temperature 110°C, time 10 hours.

[0050] Example 14: Compared with Example 12, the process conditions were adjusted, and the other conditions remained unchanged. The specific process is as follows: Step 1: Preparation of modified lithium metal material: Lithium powder, Ti3C2T x and polydimethylsiloxane, and calcined to obtain modified lithium metal material; lithium powder and Ti3C2T x The mass ratio of lithium powder to polydimethylsiloxane is 18:1; the mass ratio of lithium powder to polydimethylsiloxane is 65:1; the calcination process conditions are: temperature 200℃, time 15h, heating rate 5℃ / min, annealing rate 15℃ / min; Step 2: Polypyrrole-coated modified lithium metal material S1: Mix citric acid, NaOH solution and modified lithium metal material in a ratio of 0.5g:40mL:20g, stir evenly, ultrasonically disperse, heat to react, cool, wash and dry to obtain lithium oxide-rich metal material; S2: Mix the lithium oxide-rich metal material with polyvinyl pyrrolidone, stir in an ice bath for 0.5h, add pyrrole solution, stir for 5min, add FeCl3 solution, react for 3h, precipitate, centrifuge and dry to obtain polypyrrole-coated modified lithium metal material; in S1, the process conditions for ultrasonic dispersion are: frequency 300kHz, time 5min; the process conditions for heating reaction are: temperature 120℃, time 15h; in S2, the ratio of lithium oxide-rich metal material, polyvinyl pyrrolidone, pyrrole solution and FeCl3 solution is: 0.1g:50mL:0.1mL:50mL; in S2, the process conditions for centrifugation are: speed 1000rpm, time 5min; the process conditions for drying are: temperature 40℃, time 8h; Step 3: Preparation of negative electrode materials: The modified lithium metal material, polyvinylidene fluoride and Li400 are mixed in a mass ratio of 5:1:1 and stirred evenly to obtain a negative electrode slurry; The negative electrode slurry was evenly coated on a 10 μm thick copper foil and vacuum dried to obtain a negative electrode material; the process conditions of the vacuum drying were: temperature 100° C., time 8 h.

[0051] The negative electrode material obtained by the above process can be used to prepare a button battery, which includes the following steps: (1) Preparation of positive electrode slurry: Lithium cobalt oxide, polyvinylidene fluoride and Li400 were mixed in a mass ratio of 5:1:1 and stirred evenly to obtain a positive electrode slurry; (2) Preparation of button batteries: Step 1. Evenly coat the positive electrode slurry on a 15 μm thick aluminum foil and vacuum dry it to obtain the positive electrode material; Step 2. Take the battery shell, place the negative electrode material, add the electrolyte, place a 20 μm thick polypropylene separator, add the electrolyte, place the positive electrode material, place the gasket shrapnel, assemble the battery shell, and obtain a button battery; the coating thickness of the negative electrode slurry is 20 μm; the coating thickness of the positive electrode slurry is 10 μm; in step 1, the process conditions for vacuum drying are: temperature 100°C, time 8 hours.

[0052] Comparative Example 1: Compared with Example 1, Ti3C2T was not added during the preparation of the modified lithium metal material. x , the other conditions remain unchanged.

[0053] Comparative Example 2: Compared with Example 1, polydimethylsiloxane was not added during the preparation of the modified lithium metal material, and other conditions remained unchanged.

[0054] Comparative Example 3: Compared with Example 1, traditional Li material is used as the negative electrode material, and other conditions remain unchanged.

[0055] Comparative Example 4: Compared with Example 12, the modified lithium metal material is not subjected to the enriched oxidation treatment, and the other conditions remain unchanged.

[0056] Comparative Example 5: Compared with Example 12, the modified lithium metal material is subjected to an enriched oxidation treatment, but is not subjected to polypyrrole coating, and the other conditions remain unchanged.

[0057] experiment: The batteries obtained in the examples and comparative examples were tested using a button battery charge and discharge tester. The button batteries were charged and discharged at 0.5 mA / cm2 for 50 cycles, 100 cycles, and 200 cycles, with a voltage range of 4.2 V. The following table shows the performance test results of the obtained battery;

[0058] Based on the data in the above table, we can draw the following conclusions: Compared with Example 1, the battery cycle performance obtained in Comparative Examples 1 to 3 gradually decreased. It can be seen that the lithium metal, Ti3C2T x Mixing with polydimethylsiloxane and then calcining can improve the cycle performance of the battery; Compared with Example 1, the battery cycle performance obtained in Comparative Example 12 is better because the rich oxidation treatment increases the oxygen functional groups on the surface of the modified lithium metal material, increases the reactive sites, and the Ti3C2T in the modified lithium metal material x The interlayer spacing of Ti3C2T becomes larger and more uniform, and the oxygen functional groups can also xThe layers play a supporting role, maintaining a large specific surface area, which is conducive to the migration and diffusion of electrolyte ions and improves the cycle stability of the battery; the polypyrrole coating can prevent direct contact between lithium powder and electrolyte, reduce the occurrence of side reactions, stabilize the SEI film, and improve the battery's charge and discharge efficiency and cycle stability; Compared with Example 12, the battery cycle performance obtained in Comparative Examples 4 and 5 gradually decreased. It can be seen that the setting of the materials used and the process conditions in this application can improve the cycle performance of the obtained batteries.

[0059] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A preparation method for improving the cycle performance of lithium negative electrode materials, characterized in that: The following steps are involved: Step 1: Lithium powder, Ti3C2T x Mixing with polysiloxane and calcining to obtain a modified lithium metal material; Step 2: Mix the modified lithium metal material, the binder and the conductive agent, stir evenly to obtain a negative electrode slurry, evenly coat the negative electrode slurry on a copper foil, and vacuum dry to obtain a negative electrode material.

2. The method for improving the cycle performance of a lithium negative electrode material according to claim 1, wherein: In step 1, the lithium powder and Ti3C2T x The mass ratio is (12~75):

1.

3. The method for preparing a lithium negative electrode material for improving cycle performance according to claim 1, wherein: In step 1, the mass ratio of the lithium powder to the polysiloxane is (50-70):

1.

4. The method for improving the cycle performance of a lithium negative electrode material according to claim 1, wherein: In step 2, the mass ratio of the modified lithium metal material, the binder and the conductive agent is (5-8):1:

1.

5. The method for improving the cycle performance of a lithium negative electrode material according to claim 1, wherein: In step 1, the calcination process conditions are: temperature 200°C~250°C, time 15h~20h, heating rate 5°C / min~10°C / min, and annealing rate 15°C / min~25°C / min.

6. The method for improving the cycle performance of a lithium negative electrode material according to claim 1, wherein: In step 2, the process conditions for vacuum drying are: temperature 100° C. to 120° C., and time 8 h to 12 h.

7. The method for improving the cycle performance of a lithium negative electrode material according to claim 1, wherein: The surface of the modified lithium metal material is coated with polypyrrole, and the specific process is as follows: S1: mixing citric acid and NaOH solution with the modified lithium metal material, stirring evenly, ultrasonically dispersing, heating for reaction, cooling, washing, and drying to obtain a lithium oxide-rich metal material; S2: Mix the lithium oxide-rich metal material with polyvinyl pyrrolidone, stir in an ice bath for 0.5h~1.5h, add pyrrole, stir for 5min~15min, add FeCl3, react for 3h~5h, precipitate, centrifuge, and dry to obtain a polypyrrole-coated modified lithium metal material.

8. The method for improving the cycle performance of a lithium negative electrode material according to claim 4, wherein: In S1, the ratio of citric acid, NaOH solution and modified lithium metal material is (0.5~1.5) g: (40~80) mL: (20~60) g; In S2, the ratio of lithium oxide-rich metal material, polyvinyl pyrrolidone, pyrrole and FeCl3 is: (0.1~1) g: (50~250) mL: (0.1~1.5) mL: (50~250) mL.

9. The negative electrode material obtained by the method for improving the cycle performance of a lithium negative electrode material according to any one of claims 1 to 8, characterized in that: Application in the negative electrode of button batteries.

Images