Polyimide porous carbon-based silicon-carbon negative electrode material as well as preparation method and application thereof

Abstract

The invention provides a polyimide porous carbon-based silicon-carbon negative electrode material as well as a preparation method and application thereof, and belongs to the technical field of lithium battery materials. The high-strength polyimide is prepared from diamine and dianhydride monomers with rigid structures, the porous carbon material prepared from the polyimide has high mechanical strength and structural stability, the structural integrity of porous carbon can be kept in the electrode manufacturing and using process, collapse or pulverization caused by stress or high temperature is reduced, and the service life of the electrode is prolonged. And the long cycle performance is improved. Polyimide is rich in nitrogen element, and nitrogen doping naturally exists in porous carbon formed after pyrolysis, so that electric contact between silicon particles and the porous carbon is enhanced, and the conductivity and rate capability of the material are improved. Therefore, the silicon-carbon negative electrode material prepared by the invention has the advantages of stable structure, good conductivity, high capacity and ultra-long cycle, and solves the problems of long preparation period, low conductivity, insufficient skeleton strength and the like of the existing porous carbon substrate.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery materials, and in particular to a polyimide porous carbon-based silicon-carbon anode material, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-ion secondary batteries are widely used in portable electronic products, electric vehicles, and energy storage due to their high mass and volume energy densities, long cycle life, and low self-discharge performance. However, the traditional graphite paired with the positive electrode far from meets the market demand. Although the existing Si has a theoretical capacity as high as 4200 mAh / g, its expansion reaches 300%, which affects the cycle performance and restricts the market promotion and application.

[0003] At present, the swelling of the Si anode is mainly alleviated by nanosizing, and silicon is made into nanospheres, nanowires, etc. However, in the conventional grinding method of nanosizing, the Si particle size can only be controlled to around 100 nm. At the same time, the excessive nanosizing process will also be accompanied by an increase in the specific surface area of the material, affecting the material processing and performance.

[0004] In order to solve the bottleneck of controlling the Si particle size by the traditional grinding method, the currently commonly used method is to use porous carbon as the matrix and obtain a silicon-carbon composite material with a Si nanosize <10 nm through silane deposition. For the silicon-carbon material prepared by this method, the characteristics of the porous carbon skeleton will have a great impact on the performance of the silicon-carbon material.

[0005] Currently commonly used porous carbons include resin-based, biomass-based, and petroleum coke-based. However, the porous carbon matrices obtained from these raw materials have problems such as long preparation cycles, low yields, low conductivity, and unstable pore structure collapse during the cycle of the porous carbon matrix. Patent CN111498827B polymerizes a diamine monomer containing a hydroxyl group and a dianhydride monomer to obtain polyamic acid, and prepares porous polyimide microspheres through the cyclization reaction of polyamic acid, and finally performs segmented heat treatment to obtain porous carbon. However, in this method, there are differences in the start time of the ring closure reaction in different regions during the cyclization reaction of polyamic acid, so there are problems such as uneven microsphere size and particle size distribution, and low carbon skeleton strength. Summary of the Invention

[0006] The purpose of the present invention is to provide a polyimide porous carbon-based silicon-carbon anode material, a preparation method thereof, and an application thereof. The silicon-carbon anode material prepared by this method has the advantages of stable structure (high skeleton strength), good conductivity, and high capacity and ultra-long cycle life, and solves the problems of long preparation cycle, low conductivity, and insufficient skeleton strength of the existing porous carbon matrix.

[0007] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a polyimide porous carbon-based silicon-carbon anode material, comprising the following steps:

[0009] Mix a diamine, an oligomer and an organic solvent to obtain a dispersed phase;

[0010] Mix liquid paraffin and a surfactant to obtain a continuous phase;

[0011] Add the dispersed phase to the continuous phase and carry out an emulsification reaction to obtain a precursor;

[0012] Mix a dianhydride with the precursor and carry out a polymerization reaction to obtain a polyimide precursor;

[0013] Mix the polyimide precursor, pyridine and acetic anhydride and carry out a ring dehydration reaction to obtain a primary imide product;

[0014] After thermally imidizing the primary imide product, carry out heat preservation decomposition to obtain porous polyimide microspheres;

[0015] Calcine the polyimide microspheres to obtain porous carbon;

[0016] Under the condition of a protective gas, introduce silane gas, carry out vapor deposition on the porous carbon, and then introduce a carbon source gas to carry out carbon coating to obtain the polyimide porous carbon-based silicon-carbon anode material.

[0017] Preferably, the molecular weight of the oligomer is 200-3000; the oligomer includes one or more of polyethylene glycol, methoxypolyethylene glycol, polyetheramine, polypropylene glycol monobutyl ether and polystyrene; the diamine includes one or more of p-phenylenediamine, m-phenylenediamine, naphthalenediamine, 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4'-aminophenoxy)benzene, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 1,4-cyclohexanediamine, 1,8-diaminonaphthalene, 1,2-phenylenediamine and tetramethyl-p-phenylenediamine;

[0018] The surfactant includes Span 85, Span 80 or Tween 80; the volume ratio of the liquid paraffin to the surfactant is (1-10):1;

[0019] The dianhydride includes one or more of pyromellitic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3’,4,4’-benzophenonetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride and 4,4’-phenylenedioxydiphthalic anhydride.

[0020] Preferably, the molar ratio of the diamine to the dianhydride is 1:(0.95 - 1.05), the mass of the oligomer is 10 - 50% of the total mass of the diamine, dianhydride and oligomer, and the volume ratio of the liquid paraffin to the organic solvent is 1:1 - 10.

[0021] Preferably, the temperature of the emulsification reaction is room temperature and the time is 1 - 15 h; the temperature of the polymerization reaction is room temperature and the time is 5 - 15 h.

[0022] Preferably, the molar ratio of the polyimide precursor to acetic anhydride is 1:1 - 1:5, and the molar ratio of acetic anhydride to pyridine is 1:1 - 5:1; the temperature of the ring dehydration reaction is room temperature and the time is 2 - 6 h.

[0023] Preferably, the pressure of the thermal imidization is 0.1 - 0.4 MPa. The thermal imidization includes: after maintaining the temperature at 100 - 120 °C for 30 - 60 min, maintaining the temperature at 200 - 220 °C for 30 - 60 min, and then maintaining the temperature at 300 - 320 °C for 30 - 60 min.

[0024] Preferably, the temperature of the heat preservation and decomposition is 250 - 270 °C and the heat preservation time is 5 - 10 h; the temperature of the calcination is 600 - 900 °C, the time is 1 - 10 h, and the heating rate to the calcination temperature is 5 - 10 °C / min.

[0025] Preferably, the protective gas includes one or more of nitrogen, argon and helium; the silane gas includes one or two of silane and disilane; the flow ratio of the silane gas to the protective gas is 1:1 - 10;

[0026] The temperature of the chemical vapor deposition is 500 - 1000 °C and the time is 1 - 12 h;

[0027] The carbon source gas includes one or more of methane, ethane, propane, acetylene and propyne, and the flow ratio of the carbon source gas to the protective gas is 1:1 - 10;

[0028] The temperature of the carbon coating is 500 - 1000 °C and the time is 1 - 12 h.

[0029] The present invention provides a polyimide porous carbon-based silicon-carbon anode material prepared by the preparation method described in the above technical solution. Based on the total mass content of silicon and carbon being 100%, the Si content is 10 - 90 wt% and the carbon content is 10 - 90 wt%.

[0030] The present invention provides an application of the polyimide porous carbon-based silicon-carbon anode material described in the above technical solution in a lithium battery.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention can prepare polyimide using diamine and dianhydride monomers with rigid structural groups, and high-strength polyimide can be obtained. The porous carbon material prepared using such polyimide has high mechanical strength and structural stability, can maintain the structural integrity of the porous carbon during the electrode manufacturing and use processes, reduce collapse or pulverization caused by stress or high temperature, and improve the long-cycle performance.

[0033] Polyimide contains abundant nitrogen elements. Nitrogen doping naturally exists in the porous carbon formed after pyrolysis, enhancing the electrical contact between silicon particles and porous carbon, contributing to improving the conductivity of the material and enhancing the rate performance.

[0034] The present invention uses polyimide as the matrix material, which is easy to regulate the molecular weight and morphology of polyimide, and can generate a high specific surface area and rich pore structure after carbonization. Moreover, by regulating the molecular weight of the oligomer for preparing polyimide, the pore distribution of the porous carbon can be made more uniform and the adjustable range can be larger, which is beneficial to the uniform deposition of silicon particles, thereby improving the lithium ion transport ability and maintaining the structural integrity of the electrode during charge and discharge.

[0035] The present invention directly prepares porous polyimide microspheres by thermal imidization of the imide product, saving the activation process of porous carbon and having a short preparation period. Description of the Drawings

[0036] Figure 1 It is a flow chart of the preparation method of the polyimide porous carbon-based silicon-carbon negative electrode material of the present invention;

[0037] Figure 2 It is a schematic diagram of the preparation process of the porous polyimide microspheres of the present invention. Detailed Embodiments

[0038] As Figures 1 to 2 shown, in the present invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well-known to those skilled in the art.

[0039] The present invention provides a preparation method of a polyimide porous carbon-based silicon-carbon negative electrode material, comprising the following steps:

[0040] Mix diamine, oligomer with an organic solvent to obtain a dispersed phase;

[0041] Mix liquid paraffin and a surfactant to obtain a continuous phase;

[0042] Add the dispersed phase to the continuous phase and carry out an emulsification reaction to obtain a precursor;

[0043] Mix dianhydride with the precursor and carry out a polymerization reaction to obtain a polyimide precursor;

[0044] Mix the polyimide precursor, pyridine and acetic anhydride, and carry out a ring dehydration reaction to obtain a primary imide product;

[0045] After subjecting the primary imide product to thermal imidization, carry out heat preservation decomposition to obtain porous polyimide microspheres;

[0046] Calcine the polyimide microspheres to obtain porous carbon;

[0047] Under the condition of a protective gas, introduce silane gas, carry out chemical vapor deposition on the porous carbon, and then introduce a carbon source gas to carry out carbon coating to obtain a polyimide porous carbon-based silicon-carbon anode material.

[0048] Preferably in the present invention, an oligomer and a diamine are added to an organic solvent and stirred for 1 to 3 h to obtain a dispersion phase Q1.

[0049] In the present invention, the molecular weight of the oligomer is preferably 200 to 3000, more preferably 400 to 2000, and further preferably 750 to 1000; the oligomer preferably includes one or more of polyethylene glycol, polyethylene glycol monomethyl ether, polyetheramine, polypropylene glycol monobutyl ether and polystyrene; when there are two or more of the above oligomers, the present invention has no special limitation on the ratio of different types of oligomers, and any ratio is acceptable.

[0050] In the present invention, the diamine preferably includes one or more of p-phenylenediamine, m-phenylenediamine, naphthalenediamine, 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4'-aminophenoxy)benzene, 2,2-bis-(3-amino-4-hydroxyphenyl)hexafluoropropane, 1,4-cyclohexanediamine, 1,8-diaminonaphthalene, 1,2-phenylenediamine and tetramethyl-p-phenylenediamine; when there are two or more of the above diamines, the present invention has no special limitation on the ratio of different types of diamines, and any ratio is acceptable.

[0051] In the present invention, the organic solvent preferably includes N,N-dimethylformamide or N-methylpyrrolidone; the present invention has no special limitation on the amount of the organic solvent used, and it can be adjusted according to actual needs to ensure uniform mixing of the materials.

[0052] Preferably in the present invention, liquid paraffin and a surfactant are stirred and mixed in a protective atmosphere for 1 to 3 h to obtain a continuous phase Q2.

[0053] In the present invention, the surfactant preferably includes Span 85, Span 80 or Tween 80; the volume ratio of the liquid paraffin to the surfactant is preferably 1 to 10:1, more preferably 3 to 6.25:1.

[0054] The present invention uses liquid paraffin as the continuous phase, enabling the dispersed phase to be uniformly dispersed therein in the form of droplets, which is helpful for the subsequent formation of polyimide porous microspheres; the surfactant can form a stable emulsion of immiscible liquid paraffin and the dispersed phase, thereby preparing porous polyimide microspheres.

[0055] The present invention preferably adds the dispersed phase to the continuous phase, and performs an emulsification reaction by stirring at room temperature under a protective atmosphere to obtain a precursor Q3.

[0056] The protective gas used in the protective atmosphere mentioned in the context of the present invention is preferably one or more of nitrogen, argon, and helium. When there are two or more of the above-mentioned protective gases, the present invention has no special limitation on the ratio of different types, and any ratio is acceptable.

[0057] In the present invention, the temperature of the emulsification reaction is preferably room temperature, and the time is preferably 1 to 15 h, more preferably 2 to 5 h.

[0058] The present invention preferably adds the dianhydride to the precursor Q3 in three batches within 1 to 2 h, and performs a polymerization reaction by stirring uniformly under a protective atmosphere to obtain a polyimide precursor Q4; the protective atmosphere is preferably a nitrogen atmosphere.

[0059] In the present invention, the dianhydride preferably includes one or more of pyromellitic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3’,4,4’-benzophenonetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, and 4,4’-p-phenylenedioxydiphthalic anhydride; when there are two or more of the above-mentioned dianhydrides, the present invention has no special limitation on the ratio of different types of dianhydrides, and any ratio is acceptable.

[0060] In the present invention, the molar ratio of the diamine to the dianhydride is preferably 1:(0.95 to 1.05), more preferably 1:(0.98 to 1.03), the mass of the oligomer is preferably 10 to 50% of the total mass of the diamine, dianhydride, and oligomer, more preferably 16 to 27%; the volume ratio of the liquid paraffin to the organic solvent is preferably 1:1 to 10, more preferably 1:1 to 5.

[0061] In the present invention, the temperature of the polymerization reaction is preferably room temperature, and the time is preferably 5 to 15 h, more preferably 5 to 10 h.

[0062] The present invention preferably adds a mixture of pyridine and acetic anhydride to the polyimide precursor Q4, stirs the reaction and then centrifuges, and washes the centrifuged product three times with petroleum ether, acetone, and ethanol respectively and then dries it to obtain a primary imide product Q5.

[0063] In the present invention, the molar ratio of the polyimide precursor to acetic anhydride is preferably 1:1 to 5, more preferably 1:1 to 2, and the molar ratio of acetic anhydride to pyridine is 1 to 5:1, more preferably 1:1.

[0064] In the present invention, the temperature of the ring dehydration reaction is preferably room temperature, and the time is preferably 2 to 6 h, more preferably 3 to 5 h.

[0065] In the present invention, the primary imide product Q5 is preferably placed in an atmosphere resistance furnace, and heat imidization is carried out by segmental heat preservation under a certain pressure in a protective atmosphere, and then the oligomer is decomposed by heat preservation to obtain porous polyimide microspheres Q6.

[0066] In the present invention, the pressure of the heat imidization is preferably 0.1 to 0.4 MPa, more preferably 0.2 to 0.3 MPa. The heat imidization preferably includes: heat preservation at 100 to 120 °C for 30 to 60 min, then heat preservation at 200 to 220 °C for 30 to 60 min, and then heat preservation at 300 to 320 °C for 30 to 60 min; the heating rate of each stage of heat preservation in the heat imidization is independently preferably 5 to 10 °C / min; the protective atmosphere is preferably a nitrogen atmosphere.

[0067] In the present invention, the temperature for heat preservation and decomposition is preferably 250 to 270 °C, more preferably 250 to 260 °C, and the heat preservation time is preferably 5 to 10 h, more preferably 5 to 8 h.

[0068] In the present invention, the porous polyimide microspheres Q6 are placed in an atmosphere resistance furnace and calcined in a protective atmosphere to obtain porous carbon Q7.

[0069] In the present invention, the temperature of the calcination is preferably 600 to 900 °C, more preferably 650 to 750 °C, the time is preferably 1 to 10 h, more preferably 2 to 4 h, and the heating rate for raising the temperature to the calcination temperature is preferably 5 to 10 °C / min, more preferably 5 to 8 °C / min; the protective atmosphere is preferably a nitrogen atmosphere.

[0070] In the present invention, the porous carbon Q7 is preferably added to a rotary furnace, and after gas phase deposition is carried out by introducing silane gas under protective gas conditions, a precursor Q8 is obtained; carbon source gas is introduced for carbon coating to obtain a negative electrode material with a controllable silicon particle size.

[0071] In the present invention, the protective gas preferably includes one or more of nitrogen, argon, and helium; the silane gas includes one or two of silane and disilane; the flow ratio of the silane gas to the protective gas is preferably 1:1 to 10, more preferably 1:1 to 2; the temperature of the gas phase deposition is preferably 500 to 1000 °C, more preferably 650 to 800 °C, and the time is preferably 1 to 12 h, more preferably 1 to 5 h.

[0072] In the present invention, the carbon source gas preferably includes one or more of methane, ethane, propane, acetylene, and propyne. The flow rate ratio of the carbon source gas to the protective gas is preferably 1:1 to 10, more preferably 1:1 to 2. The temperature for carbon coating is preferably 500 to 1000 °C, more preferably 650 to 800 °C. The time is preferably 1 to 12 h, more preferably 6 to 8 h.

[0073] The present invention has no special limitation on the flow rates of the silane gas and the carbon source gas, which can be adjusted according to actual needs. In the embodiments of the present invention, the specific flow rates of the silane gas and the carbon source gas are 5 L / min.

[0074] The present invention provides a polyimide porous carbon-based silicon-carbon anode material prepared by the preparation method described in the above technical solution. Based on 100% of the total mass content of silicon and carbon, the Si content is 10 to 90 wt%, more preferably 48 to 53 wt%, and the carbon content is 10 to 90 wt%, more preferably 47 to 52 wt%.

[0075] The present invention provides an application of the polyimide porous carbon-based silicon-carbon anode material described in the above technical solution in a lithium battery. The present invention has no special limitation on the application method, which can be applied according to the methods well-known in the art.

[0076] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0077] Example 1

[0078] S1: Polyethylene glycol monomethyl ether (0.4 g, molecular weight 200) and 4,4'-diaminodiphenyl ether (1.00 g) were added to N,N-dimethylformamide solvent (10 mL), and stirred for 3 h to mix evenly to form a dispersed phase.

[0079] S2: Liquid paraffin (50 mL) and surfactant Span 85 (8 mL) were stirred and mixed in a nitrogen atmosphere for 1 h to form a continuous phase.

[0080] S3: Under a nitrogen atmosphere, the dispersed phase was added to the continuous phase, and stirred at room temperature for 2 h to form a stable non-aqueous emulsion, i.e., precursor Q3.

[0081] S4: Pyromellitic dianhydride (1.07 g) was added to the above non-aqueous emulsion in three equal portions within 1.5 h. The molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic dianhydride was 1:0.98, and stirred at a constant speed at room temperature in a nitrogen atmosphere for 5 h to obtain polyimide precursor Q4.

[0082] S5: Add a mixture of pyridine and acetic anhydride (a total of 6 mL, with a molar ratio of pyridine to acetic anhydride of 1:1 and a molar ratio of polyimide precursor to acetic anhydride of 1:1) to the obtained polyimide precursor, stir for 3 h and then centrifuge. Wash the centrifuged product three times with petroleum ether, acetone, and ethanol respectively and then dry it to obtain the primary imide product Q5;

[0083] S6: Place the primary imide product in an atmosphere resistance furnace. Under a nitrogen atmosphere, carry out stepwise heat preservation treatment under a pressure of 0.2 MPa. Keep it at 100 °C for 30 min, at 200 °C for 30 min, and finally at 300 °C for 30 min to carry out the thermal imidization process with a heating rate of 5 °C / min. Then keep it at 250 °C for 5 h for decomposition to obtain the porous polyimide microspheres Q6;

[0084] S7: Place the obtained polyimide microspheres in an atmosphere resistance furnace, heat up and keep them calcined in a nitrogen atmosphere. The calcination temperature is 650 °C, the heat preservation time is 4 h, and the heating rate is 5 °C / min to prepare the porous carbon Q7;

[0085] S8: Add the obtained porous carbon to a rotary furnace, introduce disilane under nitrogen protection, where the flow rate of disilane gas is 5 L / min, and the ratio of disilane gas flow rate: nitrogen gas flow rate = 1:1, with a deposition temperature of 650 °C and a deposition time of 1 h; after the deposition is completed, introduce propyne under nitrogen protection, where the flow rate of propyne is 5 L / min, and the ratio of propyne gas flow rate: nitrogen gas flow rate = 1:1, carry out carbon coating at 650 °C for 6 h, and then cool it with the furnace to obtain the silicon-carbon anode material. Among them, based on the total mass content of silicon and carbon being 100%, the silicon content is 53% and the carbon content is 47%.

[0086] Example 2

[0087] The difference from Example 1 is only that: the molecular weight of polyethylene glycol monomethyl ether is 750; in the prepared silicon-carbon anode material, based on the total mass content of silicon and carbon being 100%, the silicon content is 50% and the carbon content is 50%.

[0088] Example 3

[0089] The difference from Example 1 is only that: the molecular weight of polyethylene glycol monomethyl ether is 2000; in the prepared silicon-carbon anode material, based on the total mass content of silicon and carbon being 100%, the silicon content is 51% and the carbon content is 49%.

[0090] Example 4

[0091] The difference from Example 1 is only that: the mass of polyethylene glycol monomethyl ether is 0.8 g; in the prepared silicon-carbon anode material, based on the total mass content of silicon and carbon being 100%, the silicon content is 53% and the carbon content is 47%.

[0092] Example 5

[0093] The difference from Example 1 is only that 1,8-diaminonaphthalene and 1,4,5,8-naphthalenetetracarboxylic dianhydride are used as the diamine and dianhydride monomers for synthesizing polyimide; in the prepared silicon-carbon anode material, based on the total mass content of silicon and carbon being 100%, the silicon content is 50% and the carbon content is 50%.

[0094] Example 6

[0095] The difference from Example 1 is only that a polyetheramine with a molecular weight of 400 is used as the oligomer; in the prepared silicon-carbon anode material, based on the total mass content of silicon and carbon being 100%, the silicon content is 48% and the carbon content is 52%.

[0096] Example 7

[0097] The difference from Example 1 is only that a polyetheramine with a molecular weight of 1000 is used as the oligomer; in the prepared silicon-carbon anode material, based on the total mass content of silicon and carbon being 100%, the silicon content is 51% and the carbon content is 49%.

[0098] Comparative Example 1

[0099] Put the coconut shell porous carbon material (Changzhou Chuangming) into a rotary furnace, introduce disilane under nitrogen protection, the flow rate of disilane gas is 5 L / min, the ratio of disilane gas flow rate to nitrogen flow rate is 1:1, the deposition temperature is 650 °C, and the time is 1 h; after the silane deposition is completed, introduce propyne under nitrogen protection, the flow rate of propyne is 5 L / min, where the ratio of propyne flow rate to nitrogen flow rate is 1:1; the deposition temperature is 650 °C, the deposition time is 6 h, and after the deposition is completed, it is cooled with the furnace to obtain a silicon-carbon anode material. Based on the total mass content of silicon and carbon being 100%, the silicon content is 50% and the carbon content is 50%.

[0100] Comparative Example 2

[0101] Put the resin porous carbon (Sinosteel Ma'anshan) into a rotary furnace, introduce disilane under nitrogen protection, the flow rate of disilane gas is 5 L / min, the ratio of disilane gas flow rate to nitrogen flow rate is 1:1, the deposition temperature is 650 °C, and the time is 1 h; after the silane deposition is completed, introduce propyne under nitrogen protection, the flow rate of propyne is 5 L / min, where the ratio of methane flow rate to nitrogen flow rate is 1:1; the deposition temperature is 650 °C, the deposition time is 6 h, and after the deposition is completed, it is cooled with the furnace to obtain a silicon-carbon anode material. Based on the total mass content of silicon and carbon being 100%, the silicon content is 50% and the carbon content is 50%.

[0102] Performance Test

[0103] 1) The negative electrode materials prepared in Examples 1-7 and Comparative Examples 1-2 were subjected to electrical property tests. The negative electrode materials were made into CR2032 coin cells, and the test conditions were as follows: electrolyte: JN-JW-2249; mass ratio: negative electrode material: SP: carbon nanotubes: LA132 = 94:1:1:4; counter electrode: pure lithium sheet;

[0104] Charge and discharge regime: 1) Stand still for 10 min; 2) Constant current discharge (0.1C, 0.005V); 3) Stand still for 10 min; 4) Rate discharge (0.05C, 0.005V); 5) Stand still for 10 min; 6) Rate discharge (0.02C, 0.005V);

[0105] 7) Stand still for 10 min; 8) Rate charge (0.1C, 1.5V).

[0106] The results are shown in Table 1.

[0107] Table 1 Electrical property data of the materials prepared in Examples 1-7 and Comparative Examples 1-2

[0108]

[0109]

[0110] As can be seen from Table 1, compared with Comparative Examples 1-2, the polyimide porous carbon-based silicon-carbon negative electrode material provided by the present invention has more excellent electrical properties.

[0111] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a polyimide porous carbon-based silicon-carbon anode material, characterized in that, It includes the following steps: Mix diamine, oligomer and organic solvent to obtain a dispersed phase; Mix liquid paraffin and surfactant to obtain a continuous phase; Add the dispersed phase into the continuous phase and carry out an emulsification reaction to obtain a precursor; Mix dianhydride with the precursor and carry out a polymerization reaction to obtain a polyimide precursor; Mix the polyimide precursor, pyridine and acetic anhydride and carry out a ring dehydration reaction to obtain a primary imide product; After thermally imidizing the primary imide product, carry out heat preservation and decomposition to obtain porous polyimide microspheres; Calcine the polyimide microspheres to obtain porous carbon; Under the condition of protective gas, introduce silane gas, carry out chemical vapor deposition on the porous carbon, and then introduce carbon source gas to carry out carbon coating to obtain a polyimide porous carbon-based silicon-carbon negative electrode material.

2. The preparation method according to claim 1, characterized in that, The molecular weight of the oligomer is 200-3000; the oligomer includes one or more of polyethylene glycol, monomethyl polyethylene glycol, polyetheramine, polypropylene glycol monobutyl ether and polystyrene; the diamine includes one or more of p-phenylenediamine, m-phenylenediamine, naphthalenediamine, 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4'-aminophenoxy)benzene, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 1,4-cyclohexanediamine, 1,8-diaminonaphthalene, 1,2-phenylenediamine and tetramethyl-p-phenylenediamine; The surfactant includes Span 85, Span 80 or Tween 80; the volume ratio of the liquid paraffin to the surfactant is 1-10:1; The dianhydride includes one or more of pyromellitic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3’,4,4’-benzophenonetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride and 4,4’-p-phenylenedioxydiphthalic anhydride; 3. The preparation method according to claim 2, characterized in that, The molar ratio of the diamine to the dianhydride is 1:(0.95-1.05), the mass of the oligomer is 10-50% of the total mass of the diamine, dianhydride and oligomer, and the volume ratio of the liquid paraffin to the organic solvent is 1:1-10.

4. The preparation method according to claim 3, wherein The temperature of the emulsification reaction is room temperature and the time is 1-15 h; the temperature of the polymerization reaction is room temperature and the time is 5-15 h.

5. The preparation method according to claim 1, characterized in that, The molar ratio of the polyimide precursor to acetic anhydride is 1:1-5, and the molar ratio of acetic anhydride to pyridine is 1:1-5:1; the temperature of the ring dehydration reaction is room temperature and the time is 2-6 h.

6. The preparation method according to claim 1 or 5, characterized in that, The pressure of the thermal imidization is 0.1-0.4 MPa, and the thermal imidization includes: keeping warm at 100-120 °C for 30-60 min, then keeping warm at 200-220 °C for 30-60 min, and then keeping warm at 300-320 °C for 30-60 min.

7. The preparation method according to claim 6, characterized in that, The temperature for heat preservation and decomposition is 250 - 270 °C, and the heat preservation time is 5 - 10 h; the temperature for calcination is 600 - 900 °C, the time is 1 - 10 h, and the heating rate to the calcination temperature is 5 - 10 °C / min.

8. The preparation method according to claim 1, wherein The protective gas includes one or more of nitrogen, argon and helium; the silane gas includes one or two of silane and disilane; the flow rate ratio of the silane gas to the protective gas is 1:1 - 10; The temperature for chemical vapor deposition is 500 - 1000 °C, and the time is 1 - 12 h; The carbon source gas includes one or more of methane, ethane, propane, acetylene and propyne, and the flow rate ratio of the carbon source gas to the protective gas is 1:1 - 10; The temperature for carbon coating is 500 - 1000 °C, and the time is 1 - 12 h.

9. The polyimide porous carbon-based silicon-carbon anode material prepared by the preparation method according to any one of claims 1 to 8, characterized in that, Based on the total mass content of silicon and carbon being 100%, the Si content is 10 - 90 wt%, and the carbon content is 10 - 90 wt%.

10. Use of the polyimide porous carbon-based silicon-carbon anode material according to claim 9 in a lithium battery.

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