阅读说明：本技术 一种聚酰亚胺改性碳硅负极材料及其制备方法 (Polyimide modified carbon-silicon negative electrode material and preparation method thereof ) 是由 徐娟 于 2020-11-16 设计创作，主要内容包括：本发明提出了一种聚酰亚胺改性碳硅负极材料及其制备方法,该聚酰亚胺改性碳硅负极材料具有首次库仑效率高、循环性能好、电极结构稳定等优点。(The invention provides a polyimide modified carbon-silicon cathode material and a preparation method thereof.)

1. A preparation method of a polyimide modified carbon-silicon negative electrode material is characterized by comprising the following steps:

s1, performing condensation reaction on polyamide acid containing carboxyl and isocyanatopropyl triethoxysilane, adding nano silicon, uniformly mixing, and performing chemical imidization reaction to obtain precursor slurry;

and S2, uniformly mixing the precursor slurry obtained in the step S1 with graphite micro powder, spray-drying, and then carrying out heat treatment to obtain the polyimide modified carbon-silicon negative electrode material.

2. The preparation method of the polyimide modified carbon-silicon negative electrode material as claimed in claim 1, wherein the polyamic acid containing carboxyl group is prepared by performing a polycondensation reaction of a diamine monomer containing carboxyl group and a tetracarboxylic dianhydride monomer;

preferably, the carboxyl group-containing diamine monomer is at least one of 3, 5-diaminobenzoic acid or 4, 4 '-diaminobiphenyl-2, 2' -dicarboxylic acid; the tetracarboxylic dianhydride monomer is at least one of 3, 3', 4, 4' -benzophenone tetracarboxylic dianhydride, 3', 4, 4' -diphenyl sulfone tetracarboxylic dianhydride, 3', 4, 4' -diphenyl sulfide tetracarboxylic dianhydride or 4, 4' -oxydiphthalic anhydride.

3. The preparation method of the polyimide modified carbon-silicon negative electrode material as claimed in claim 2, wherein the amount of the isocyanatopropyltriethoxysilane is 1-10 mol% of the carboxyl-containing diamine monomer, and the amount of the nano-silicon is 50-200 mol% of the carboxyl-containing diamine monomer.

4. The preparation method of the polyimide modified carbon-silicon negative electrode material as claimed in any one of claims 1 to 3, wherein the average particle size of the nano-silicon is 50 to 100 nm; the average grain diameter of the graphite micro powder is 1-10 mu m; preferably, the dosage ratio of the graphite micro powder to the nano silicon is 1-10: 1.

5. The method for preparing a polyimide modified carbon-silicon negative electrode material according to any one of claims 1 to 4, wherein in step S1, a chemical imidization reaction is performed by adding a dehydrating agent and an imidizing agent; preferably, the dehydrating agent is at least one of trifluoroacetic anhydride, acetic anhydride or propionic anhydride; the imidizing agent is at least one of pyridine, p-pyrroline, lutidine, collidine or quinoline.

6. The method as claimed in any one of claims 1 to 5, wherein in step S2, the inlet temperature of the spray drying is 200 ℃ to 300 ℃, and the outlet temperature is 100 ℃ to 200 ℃.

7. The method for preparing a polyimide modified carbon-silicon anode material as claimed in any one of claims 1 to 6, wherein in step S2, the heat treatment comprises raising the temperature at a rate of 1-10 ℃/min to 500 ℃ at 300-.

8. A polyimide modified carbon-silicon negative electrode material is characterized by being prepared according to the preparation method of any one of claims 1 to 7.

9. A carbon-silicon negative electrode sheet, comprising the polyimide modified carbon-silicon negative electrode material according to claim 8.

10. The carbon-silicon negative electrode sheet as claimed in claim 9, wherein the proportion of the polyimide modified carbon-silicon negative electrode material is 70-90 wt%.

Technical Field

The invention relates to the technical field of lithium ion battery cathode materials, in particular to a polyimide modified carbon-silicon cathode material and a preparation method thereof.

Background

The silicon has the theoretical lithium intercalation capacity of up to 4200mAh/g and the lithium intercalation potential of 0.2V vs. Li/Li⁺And the silicon reserves are abundant, the cost advantage is obvious, it is the most promising negative pole material of lithium ion battery. The current bottlenecks restricting the development of silicon cathode materials mainly lie in two points:

on the one hand, a volume change of up to 300% occurs during the lithium deintercalation of silicon, which leads to a fragmentation, pulverization of the silicon particles, and thus to the exposure of new surfaces, which consume large amounts of electrolyte. At the same time, the contact with the copper foil is lost, and the loss of the contact between the silicon and the foil greatly increases the transmission distance of electrons, which leads to the great reduction of the service life of the silicon material.

On the other hand, silicon is a semiconductor material, the electronic conductivity of the silicon is relatively low, the electron transmission speed is low, and a battery prepared by adopting the silicon cathode material has high internal resistance and poor rate capability. In this regard, it is common in the academia and industry to modify silicon by both silicon nanocrystallization and carbon recombination. On one hand, the silicon nanocrystallization can reduce the volume effect of silicon; on the other hand, the composite material is prepared from the silicon material and the carbon material with good conductivity, so that the stress action of silicon in the charging and discharging process is relieved, and the electronic conductivity of the silicon material is improved.

CN103531760 discloses a method for preparing porous silicon-carbon composite microspheres with an egg yolk-shell structure, which has complicated preparation process and difficult control of hollow inner diameter, can provide a certain expansion space for silicon, but has low tap density and poor conductivity, and needs to be etched by hydrofluoric acid, thus causing serious environmental pollution. CN102769139A takes natural granular graphite as a raw material, concentrated sulfuric acid as an intercalation agent and potassium permanganate as an oxidant, then expansion treatment is carried out at high temperature to prepare micro-expanded graphite, nano-silicon is mixed with the graphite, and then carbon source coating and heat treatment are carried out to obtain the silicon-carbon composite negative electrode material. CN101244814A mixes and carbonizes asphalt solution, nanometer silicon powder and granular natural graphite to prepare silicon-carbon cathode material, and this method is difficult to disperse nanometer silicon powder evenly, and the first efficiency of the prepared material is low.

Therefore, it is difficult in the technical field to develop a lithium ion battery silicon-carbon composite negative electrode material with high capacity, high first coulombic efficiency and good cycle stability.

Disclosure of Invention

Based on the technical problems in the background art, the invention provides a polyimide modified carbon-silicon negative electrode material and a preparation method thereof.

The invention provides a preparation method of a polyimide modified carbon-silicon negative electrode material, which comprises the following steps:

s1, performing condensation reaction on polyamide acid containing carboxyl and isocyanatopropyl triethoxysilane, adding nano silicon, uniformly mixing, and performing chemical imidization reaction to obtain precursor slurry;

and S2, uniformly mixing the precursor slurry obtained in the step S1 with graphite micro powder, spray-drying, and then carrying out heat treatment to obtain the polyimide modified carbon-silicon negative electrode material.

Preferably, the carboxyl group-containing polyamic acid is prepared by subjecting a carboxyl group-containing diamine monomer and a tetracarboxylic dianhydride monomer to a polycondensation reaction;

preferably, the carboxyl group-containing diamine monomer is at least one of 3, 5-diaminobenzoic acid or 4, 4 '-diaminobiphenyl-2, 2' -dicarboxylic acid; the tetracarboxylic dianhydride monomer is at least one of 3, 3', 4, 4' -benzophenone tetracarboxylic dianhydride, 3', 4, 4' -diphenyl sulfone tetracarboxylic dianhydride, 3', 4, 4' -diphenyl sulfide tetracarboxylic dianhydride or 4, 4' -oxydiphthalic anhydride.

Preferably, the amount of the isocyanatopropyltriethoxysilane is 1-10 mol% of the carboxyl-containing diamine monomer, and the amount of the nano-silicon is 50-200 mol% of the carboxyl-containing diamine monomer.

Preferably, the average particle size of the nano silicon is 50-200 nm; the average grain diameter of the graphite micro powder is 1-10 mu m. Preferably, the dosage ratio of the graphite micro powder to the nano silicon is 1-10: 1.

Preferably, in step S1, a chemical imidization reaction is performed by adding a dehydrating agent and an imidizing agent; preferably, the dehydrating agent is at least one of trifluoroacetic anhydride, acetic anhydride or propionic anhydride; the imidizing agent is at least one of pyridine, p-pyrroline, lutidine, collidine or quinoline.

Preferably, in step S2, the inlet temperature of the spray drying is 500-700 ℃ and the outlet temperature is 100-200 ℃.

Preferably, in step S2, the heat treatment comprises raising the temperature to 500 ℃ at a rate of 1-10 ℃/min, maintaining the temperature for 30-180min, raising the temperature to 900 ℃ at a rate of 1-10 ℃/min, and maintaining the temperature for 30-240 min.

The invention also provides a polyimide modified carbon-silicon negative electrode material which is prepared by the preparation method.

The invention also provides a carbon-silicon negative electrode plate which comprises the polyimide modified carbon-silicon negative electrode material.

Preferably, in the carbon-silicon negative electrode sheet, the proportion of the polyimide modified carbon-silicon negative electrode material is 70-90 wt%.

In the invention, through condensation reaction of carboxyl-containing polyamic acid and isopropyl triethoxysilane, the polyamic acid contains a carboxyl group structure and can be bonded with isopropyl triethoxysilane to form amide, so that the polyamic acid surface is grafted with a siloxane coupling agent, the siloxane coupling agent can uniformly disperse nano silicon on the surface of a polyimide matrix, the agglomeration phenomenon of nano silicon in slurry is inhibited, and the carboxyl-containing polyimide matrix can effectively disperse graphite micropowder at the same time, so that the distribution uniformity of nano silicon particles on the graphite surface is effectively improved, and the capacitance ratio cycle performance of the obtained carbon-silicon cathode material can effectively meet the application of a lithium battery.

Detailed Description

Hereinafter, the technical solution of the present invention will be described in detail by specific examples, but these examples should be explicitly proposed for illustration, but should not be construed as limiting the scope of the present invention.

Example 1

A preparation method of a polyimide modified carbon-silicon negative electrode material comprises the following steps:

s1, under the protection of nitrogen, dissolving 152.1g (1mol) of 3, 5-diaminobenzoic acid in 1200mL of N, N-dimethylacetamide solvent, stirring until the solution is completely dissolved, adding 322.2g (1mol) of 3, 3', 4, 4' -benzophenone tetracarboxylic dianhydride, and stirring at room temperature for reaction for 3 hours to obtain a polyamic acid solution;

adding 12.3g (0.05mol) of isocyanatopropyl triethoxysilane into the polyamic acid solution, heating to 60 ℃, stirring for reaction for 1h, adding 40g of nano silicon powder (with an average particle size of 80nm), stirring at the speed of 1000rpm for 10h, carrying out vacuum defoaming treatment on the obtained solution, adding 150mL of pyridine as an imidizing agent, completely dispersing, adding 80mL of acetic anhydride as a dehydrating agent, and stirring for 2h again to obtain precursor slurry;

s2, mixing the precursor slurry obtained in the step S1 with 160g of artificial graphite (the average particle size is 15 microns), stirring at 2000rpm for 10 hours, carrying out spray drying on the obtained mixed slurry under the conditions of a feeding speed of 3Kg/h, an inlet temperature of 200 ℃ and an outlet temperature of 100 ℃ and granulating to form solid powder; and (3) heating the solid powder to 400 ℃ at room temperature at a heating rate of 3 ℃/min, preserving heat for 1h, then heating to 800 ℃ at a heating rate of 5 ℃/min, preserving heat for 3h, naturally cooling to room temperature, crushing and sieving to obtain the polyimide modified carbon-silicon negative electrode material.

Example 2

A preparation method of a polyimide modified carbon-silicon negative electrode material comprises the following steps:

s1, under the protection of nitrogen, dissolving 152.1g (1mol) of 3, 5-diaminobenzoic acid in 1200mL of N, N-dimethylacetamide solvent, stirring until the solution is completely dissolved, adding 322.2g (1mol) of 3, 3', 4, 4' -benzophenone tetracarboxylic dianhydride, and stirring at room temperature for reaction for 3 hours to obtain a polyamic acid solution;

adding 2.47g (0.01mol) of isocyanatopropyl triethoxysilane into the polyamic acid solution, heating to 60 ℃, stirring for reaction for 1h, adding 14g of nano silicon powder (with an average particle size of 80nm), stirring at the speed of 1000rpm for 10h, carrying out vacuum defoaming treatment on the obtained solution, adding 150mL of pyridine as an imidizing agent, completely dispersing, adding 80mL of acetic anhydride as a dehydrating agent, and stirring for 2h again to obtain precursor slurry;

s2, mixing the precursor slurry obtained in the step S1 with 140g of artificial graphite (the average particle size is 15 microns), stirring at 2000rpm for 10 hours, carrying out spray drying on the obtained mixed slurry under the conditions of a feeding speed of 3Kg/h, an inlet temperature of 200 ℃ and an outlet temperature of 100 ℃ and granulating to form solid powder; and (3) heating the solid powder to 300 ℃ at room temperature at the heating rate of 1 ℃/min, preserving heat for 0.5h, then heating to 600 ℃ at the heating rate of 1 ℃/min, preserving heat for 4h, naturally cooling to room temperature, crushing and sieving to obtain the polyimide modified carbon-silicon negative electrode material.

Example 3

A preparation method of a polyimide modified carbon-silicon negative electrode material comprises the following steps:

s1, under the protection of nitrogen, dissolving 152.1g (1mol) of 3, 5-diaminobenzoic acid in 1200mL of N, N-dimethylacetamide solvent, stirring until the solution is completely dissolved, adding 322.2g (1mol) of 3, 3', 4, 4' -benzophenone tetracarboxylic dianhydride, and stirring at room temperature for reaction for 3 hours to obtain a polyamic acid solution;

adding 24.7g (0.1mol) of isocyanatopropyl triethoxysilane into the polyamic acid solution, heating to 60 ℃, stirring for reaction for 1h, adding 56g of nano silicon powder (with an average particle size of 80nm), stirring at the speed of 1000rpm for 10h, carrying out vacuum defoaming treatment on the obtained solution, adding 150mL of pyridine as an imidizing agent, completely dispersing, adding 80mL of acetic anhydride as a dehydrating agent, and stirring for 2h again to obtain precursor slurry;

s2, mixing the precursor slurry obtained in the step S1 with 56g of artificial graphite (the average particle size is 15 microns), stirring at the speed of 2000rpm for 10 hours, carrying out spray drying on the obtained mixed slurry under the conditions of the feeding speed of 3Kg/h, the inlet temperature of 300 ℃ and the outlet temperature of 200 ℃ and carrying out granulation to form solid powder; and (3) heating the solid powder to 500 ℃ at the room temperature at the heating rate of 10 ℃/min, preserving the heat for 3h, then heating to 900 ℃ at the heating rate of 10 ℃/min, preserving the heat for 3h, naturally cooling to the room temperature, crushing and sieving to obtain the polyimide modified carbon-silicon negative electrode material.

Example 4

A preparation method of a polyimide modified carbon-silicon negative electrode material comprises the following steps:

s1, under the protection of nitrogen, dissolving 272.2g (1mol) of 4, 4 '-diaminobiphenyl-2, 2' -dicarboxylic acid in 1500mL of N, N-dimethylacetamide solvent, stirring until the solution is completely dissolved, adding 358.3g (1mol) of 3, 3', 4, 4' -diphenylsulfone tetracarboxylic dianhydride, and stirring at room temperature for reaction for 3 hours to obtain polyamic acid solution;

adding 12.3g (0.05mol) of isocyanatopropyl triethoxysilane into the polyamic acid solution, heating to 60 ℃, stirring for reaction for 1h, adding 40g of nano silicon powder (with an average particle size of 80nm), stirring at the speed of 1000rpm for 10h, carrying out vacuum defoaming treatment on the obtained solution, adding 150mL of pyridine as an imidizing agent, completely dispersing, adding 80mL of acetic anhydride as a dehydrating agent, and stirring for 2h again to obtain precursor slurry;

s2, mixing the precursor slurry obtained in the step S1 with 160g of artificial graphite (the average particle size is 15 microns), stirring at 2000rpm for 10 hours, carrying out spray drying on the obtained mixed slurry under the conditions of a feeding speed of 3Kg/h, an inlet temperature of 200 ℃ and an outlet temperature of 100 ℃ and granulating to form solid powder; and (3) heating the solid powder to 400 ℃ at room temperature at a heating rate of 3 ℃/min, preserving heat for 1h, then heating to 800 ℃ at a heating rate of 5 ℃/min, preserving heat for 3h, naturally cooling to room temperature, crushing and sieving to obtain the polyimide modified carbon-silicon negative electrode material.

Example 5

A preparation method of a polyimide modified carbon-silicon negative electrode material comprises the following steps:

s1, under the protection of nitrogen, dissolving 152.1g (1mol) of 3, 5-diaminobenzoic acid in 1200mL of N, N-dimethylacetamide solvent, stirring until the solution is completely dissolved, adding 310.2g (1mol) of 4, 4' -oxydiphthalic anhydride, and stirring at room temperature for reaction for 3 hours to obtain polyamic acid solution;

adding 12.3g (0.05mol) of isocyanatopropyl triethoxysilane into the polyamic acid solution, heating to 60 ℃, stirring for reaction for 1h, adding 40g of nano silicon powder (with an average particle size of 80nm), stirring at the speed of 1000rpm for 10h, carrying out vacuum defoaming treatment on the obtained solution, adding 150mL of pyridine as an imidizing agent, completely dispersing, adding 80mL of acetic anhydride as a dehydrating agent, and stirring for 2h again to obtain precursor slurry;

s2, mixing the precursor slurry obtained in the step S1 with 160g of artificial graphite (the average particle size is 15 microns), stirring at 2000rpm for 10 hours, carrying out spray drying on the obtained mixed slurry under the conditions of a feeding speed of 3Kg/h, an inlet temperature of 200 ℃ and an outlet temperature of 100 ℃ and granulating to form solid powder; and (3) heating the solid powder to 400 ℃ at room temperature at a heating rate of 3 ℃/min, preserving heat for 1h, then heating to 800 ℃ at a heating rate of 5 ℃/min, preserving heat for 3h, naturally cooling to room temperature, crushing and sieving to obtain the polyimide modified carbon-silicon negative electrode material.

Comparative example 1

A carbon-silicon negative electrode material is prepared by the following steps:

s1, under the protection of nitrogen, dissolving 152.1g (1mol) of 3, 5-diaminobenzoic acid in 1200mL of N, N-dimethylacetamide solvent, stirring until the solution is completely dissolved, adding 322.2g (1mol) of 3, 3', 4, 4' -benzophenone tetracarboxylic dianhydride, and stirring at room temperature for reaction for 3 hours to obtain a polyamic acid solution;

s2, adding 40g of nano silicon powder (with the average particle size of 80nm) into the polyamic acid solution, stirring at the speed of 1000rpm for 10 hours, performing vacuum defoaming treatment on the obtained solution, adding 150mL of pyridine as an imidizing agent, dispersing completely, adding 80mL of acetic anhydride as a dehydrating agent, and stirring for 2 hours again to obtain precursor slurry;

s2, mixing the precursor slurry obtained in the step S1 with 160g of artificial graphite (the average particle size is 15 microns), stirring at 2000rpm for 10 hours, carrying out spray drying on the obtained mixed slurry under the conditions of a feeding speed of 3Kg/h, an inlet temperature of 200 ℃ and an outlet temperature of 100 ℃ and granulating to form solid powder; and (3) heating the solid powder to 400 ℃ at room temperature at a heating rate of 3 ℃/min, preserving heat for 1h, then heating to 800 ℃ at a heating rate of 5 ℃/min, preserving heat for 3h, naturally cooling to room temperature, crushing and sieving to obtain the carbon-silicon negative electrode material.

The carbon-silicon anode materials obtained in examples 1 to 5 and comparative example 1 were subjected to performance tests as shown in the following method, and the results are shown in table 1.

The carbon-silicon negative electrode materials obtained in examples 1 to 5 and comparative example 1 were respectively ball-milled and uniformly mixed with conductive agents acetylene black and binders (CMC sodium carboxymethylcellulose and SBR in a mass ratio of 1:1) according to a mass ratio of 8:1:1, and water was used as a solvent to prepare slurryCoating the material on copper foil, and preparing the negative pole piece by vacuum baking and rolling. The mixture was assembled in a glove box to form a CR2032 type, using a pure Li plate as a counter electrode, Celgard 2400 as a separator, EC: DMC (1:1 volume ratio, 1mol/L LiPF₆) Is an electrolyte. A constant current charge and discharge test is carried out on the button cell by adopting a LAND cell test system, the button cell is charged and discharged under the current density of 100mA/g, the charge and discharge voltage range is 0.01-1.5V, and the test results are shown in Table 1.

Table 1 charge-discharge cycle test results of carbon-silicon anode materials of examples 1 to 5 and comparative example 1

The battery volume expansion rate is expressed as a change in cell thickness.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.