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WO2022021933A1 - 非水电解质二次电池用负极材料及其制备方法 - Google Patents

非水电解质二次电池用负极材料及其制备方法 Download PDF

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WO2022021933A1
WO2022021933A1 PCT/CN2021/086364 CN2021086364W WO2022021933A1 WO 2022021933 A1 WO2022021933 A1 WO 2022021933A1 CN 2021086364 W CN2021086364 W CN 2021086364W WO 2022021933 A1 WO2022021933 A1 WO 2022021933A1
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negative electrode
silicon
electrode material
carbon
particles
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English (en)
French (fr)
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刘江平
陈青华
贺劲鑫
姚林林
房冰
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兰溪致德新能源材料有限公司
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the invention relates to the field of lithium ion battery materials, in particular to a negative electrode material for a non-aqueous electrolyte secondary battery and a preparation method thereof.
  • the present invention provides a negative electrode material for a non-aqueous electrolyte secondary battery, so as to solve the problems of the large expansion effect of the silicon-based negative electrode material and the instability of the solid electrolyte interface (SEI) film in the prior art, thereby improving the performance of the material. Cycle, rate performance.
  • SEI solid electrolyte interface
  • the present invention provides a negative electrode material for a non-aqueous electrolyte secondary battery, comprising porous secondary particles and a sealing layer on the surface of the secondary particles, wherein the secondary particles are aggregated by primary particles of a silicon-based material It is characterized in that the primary particles are supported on a three-dimensional network body, and the primary particles are connected by a three-dimensional network body; and the three-dimensional network body is formed of carbon nanomaterials whose surfaces are coated with fast ion conductors.
  • the present invention also provides a method for preparing the above-mentioned negative electrode material, comprising the following steps:
  • S1 The binder, carbon nanomaterials, silicon-based materials, and fast ion conductor materials are uniformly dispersed in a solvent to make a slurry;
  • step S3 sintering the product of step S2 in a protective atmosphere, and then performing vapor-phase infiltration deposition to obtain pyrolytic carbon-enhanced porous secondary particles;
  • step S4 The product of step S3 is surface-coated to obtain a negative electrode material.
  • the silicon carbon negative electrode material for a secondary lithium battery and the preparation method thereof provided by the present invention have the following beneficial effects:
  • the negative electrode material provided by the present invention uses fast ion conductors to coat carbon nanomaterials and forms a three-dimensional network structure, so that the primary particles of silicon-based materials are connected in the same way, and the conductive and ion-conducting performance can be more effectively improved.
  • the present invention realizes vapor-phase infiltration deposition by controlling the deposition temperature and gas flow rate, so that the pyrolytic carbon enhances the combination of silicon particles and conductive materials, greatly improves the interface bonding strength, and effectively relieves the volume expansion of silicon materials;
  • the preparation method provided by the present invention can effectively control the generation and distribution of micropores by adjusting the gas flow rate, thereby making the product pores uniform and controllable in size.
  • Fig. 1 is the schematic flow chart of the preparation method of negative electrode material according to the present invention.
  • Fig. 2 is the SEM image of the material that has not been coated with the polymer layer in Example 1 of the present invention
  • Example 3 is a SEM image of the negative electrode material coated with a polymer layer in Example 1 of the present invention.
  • the porosity of the porous secondary particles in the examples can be measured by mercury porosimeter and BET specific surface area test method.
  • the present invention provides a negative electrode material for a non-aqueous electrolyte secondary battery, comprising porous secondary particles and a sealing layer on the surface of the secondary particles, wherein the secondary particles are aggregated from primary particles of a silicon-based material, and characterized in that , the primary particles are supported on a three-dimensional network body, and the primary particles are connected by a three-dimensional network body; the three-dimensional network body is formed by a carbon nanomaterial whose surface is coated with a fast ion conductor.
  • the structure of the secondary particles can effectively buffer the volume expansion of the material during the charging and discharging process.
  • the relative particle size of the primary particles is small, which can shorten the diffusion distance of lithium ions and improve the diffusion efficiency, thereby improving the rate performance of the material.
  • the conductive and ion-conducting three-dimensional network composed of fast ion conductors and carbon nanomaterials connects the primary particles, which can ensure high conductivity and high ion conductivity, and the network structure can further buffer the volume expansion of silicon particles.
  • the negative electrode material further includes pyrolytic carbon, and the pyrolytic carbon is deposited on the surfaces of the primary particles and the three-dimensional network to enhance the interface bonding between the silicon-based material and the three-dimensional network.
  • the fully charged expansion rate B of the primary particle refers to the growth rate of the volume after the primary particle is filled with lithium compared to the volume before the lithium insertion, and the expansion rate is related to the type of the selected silicon-based material, which can be tested by the following method : Mix the selected silicon material: SP (carbon black): PAA (polyacrylic acid) in a mass ratio of 80:10:10, add an appropriate amount of deionized water as a solvent, and continuously stir with a magnetic stirrer for 8 hours to a paste.
  • SP carbon black
  • PAA polyacrylic acid
  • the stirred slurry was poured on copper foil with a thickness of 9 ⁇ m, coated with an experimental coater, and dried under vacuum (-0.1 MPa) at 85 °C for 6 h to obtain a negative electrode sheet, which was observed by FEI Inspect S50 scanning electron microscope.
  • the average particle size of the silicon material before lithium intercalation is obtained as D1 ⁇ m.
  • the electrode sheet was rolled to 100 ⁇ m on a manual roll-to-roll machine, and then a round sheet with a diameter of 12 mm was obtained by a punching machine, which was dried at 85° C. under vacuum (-0.1 MPa) for 8 hours.
  • the silicon-based material includes metal silicon, pure silicon, silicon alloys (Si-M, such as Si-Sn), silicon composites (Si-X, such as Si-C), silicon compounds (eg Si 3 N 4 , SiC), silicon oxide SiO x (wherein, 0 ⁇ x ⁇ 2), at least one of silicon oxide modified by doping element doping (doping element such as Li, Mg)
  • the sealing layer includes organic polymers, including but not limited to polyvinylidene fluoride and its derivatives, carboxymethyl cellulose and its derivatives, sodium carboxymethyl cellulose and its derivatives, polyvinyl pyrrolidone and its derivatives, polyacrylic acid and its derivatives, polyacrylamide, polyimide, polyamideimide, polybutylene styrene At least one of the rubbers, the organic polymer has a good sealing effect, and at the same time can effectively reduce the specific surface area and reduce side reactions
  • the mass ratio of the primary particles of the silicon-based material is 75-85% by weight, preferably 78-82%; The ratio is 1-10wt%, preferably 3-8%, more preferably 4-6%; the mass proportion of the fast ion conductor layer is 1-10wt%, preferably 3-8%, more preferably 4-6%; the mass ratio of the sealing layer is 0.5-20%, preferably 1-15%, more preferably 2-10%.
  • the mass ratio of each substance is in the above range, the material exhibits excellent electrical properties.
  • the negative electrode material further includes a binder, and the mass ratio of the binder is less than 0.5% based on the mass of the negative electrode material being 100%, and the content of the binder is less. It is beneficial to the formation of through-holes in the material, so that the cracked carbon gas can smoothly pass through the pores for infiltration deposition.
  • the binder here is not the raw material binder added during the preparation process, but the binder in the negative electrode material product formed after the preparation process, which can also be understood as the sintering residue of the binder. thing. The sintering process is described in detail below.
  • the specific surface area of the negative electrode material is 0.3-20 m 2 /g, preferably 2-10 m 2 /g, more preferably 2-5 m 2 /g, when the specific surface area is here In the range, the adhesion when applied to the electrode is better, and the battery capacity is higher;
  • the particle size D50 is 1-50 ⁇ m, preferably 5-20 ⁇ m, more preferably 6-15 ⁇ m.
  • the preparation method of the negative electrode material is described, and the negative electrode material is prepared as follows:
  • S1 The binder, carbon nanomaterials, silicon-based materials, and fast ion conductor materials are uniformly dispersed in a solvent to make a slurry;
  • step S3 sintering the product of step S2 in a protective atmosphere, and then performing vapor-phase infiltration deposition to obtain pyrolytic carbon-enhanced porous secondary particles;
  • step S4 The product of step S3 is surface-coated to obtain a negative electrode material.
  • the mass percentage of each substance in the slurry is: binder 0.5-3%, carbon nanomaterial 1-10%, silicon-based material 80-90%, fast ion conductor 1-10% 10%; the addition of the various substances is not limited in a specific order, preferably, the carbon nanomaterials are added to the solvent first, then the fast ion conductors are added, and finally the silicon-based materials are added. In this way, it can be ensured that the fast ion conductor is covered on the conductive material to the greatest extent, and the silicon material is supported on the surface of the fast ion conductor in the form of particles. At this time, the negative electrode material can make a fast-charging secondary battery.
  • the solid content of the slurry is not particularly limited, but is preferably 1 to 50%.
  • the air inlet temperature and air outlet temperature of spray granulation are not specifically limited, preferably: the air inlet temperature is 200 to 400°C, and the air outlet temperature is 80 to 150°C.
  • the particle size and specific surface area of the secondary particle embryos can be controlled.
  • the porosity of the secondary particle embryo can be controlled by adjusting the air inlet temperature, the air outlet temperature and the spray rate.
  • the sintering conditions of the secondary particle body are not specifically limited.
  • the sintering temperature is controlled to be 600-950°C
  • the heating rate is controlled to be 3-8°C/min
  • the sintering time is controlled to be 0.5-3h.
  • the gas phase infiltration deposition refers to controlling the flow rate of the carrier and the carbon source gas, so that the carbon source gas is deposited on the surface of the primary particle through the pores of the secondary particle body, preferably, the carrier gas is hydrogen, nitrogen , at least one of helium gas, the introduction of carbon source gas is at least one of methane, ethane, propane, propylene, acetylene, the introduction volume ratio of carrier gas and carbon source gas is 3 ⁇ 20:1, deposition The temperature is 600 ⁇ 900°C, and the deposition time is 1 ⁇ 12h.
  • the binder includes one or more of PVP, PVA, epoxy resin, phenolic resin, asphalt, emulsified asphalt, white sugar, and glucose;
  • the solvent includes one or more of ethanol, pure water, toluene, and xylene. or more.
  • the coating method of the surface coating is not specifically limited, and specifically, it may be at least one of liquid phase coating, solid phase coating, gas deposition coating, and mechanical coating.
  • Disperse 60 g of carbon nanotubes in water with a solid content of 2% add 230 g of HF aqueous solution with a concentration of 10% and 290 g of a LiOH aqueous solution with a concentration of 10%, and disperse LiF on the surface of the carbon nanotubes; Then add 1kg of SiO powder to it (the expansion ratio of SiO in the fully charged state is 135% tested by the above method), and finally add 20g of phenolic resin and stir to make a slurry with a solid content of about 25%.
  • the air inlet temperature is 250 degrees
  • the air outlet temperature is 90 degrees to obtain granulated secondary particle blanks.
  • the granulated secondary particle body was sintered at 900°C, and the heating rate was 5°C/min. After sintering, 6L/min hydrogen-nitrogen mixture and 0.6L/min acetylene were continuously introduced, and deposited at 900°C for 3 hours to make the gas After entering the pores of the secondary particle body, pyrolytic carbon is generated, and after natural cooling, gas-phase pyrolytic carbon-enhanced porous secondary particles are obtained. .
  • Fig. 1 is the preparation process and product schematic diagram of Example 1. It can be seen that LiF and carbon nanotubes form a three-dimensional network structure 1 after spray granulation, and primary particles 2 of silicon active particles are embedded in the network structure to form porous spherical secondary particles. (As shown in Figure 1a, which is a schematic diagram of the structure of the granulated secondary particle body), then by vapor infiltration deposition, the pyrolytic carbon 3 penetrates into the interior of the secondary particle through the pores and is deposited on the primary particle 2 and the three-dimensional network body 3.
  • Figure 1b which is a schematic structural diagram of the secondary particle reinforced inside the gas-phase pyrolytic carbon
  • Figure 1c it is a secondary particle with a surface sealed pores, that is, a schematic diagram of the structure of the negative electrode material).
  • FIG. 1 is the SEM image of the material that has not been coated with the polymer layer, showing the three-dimensional network structure and pores.
  • FIG. 3 is a SEM image of a negative electrode material coated with a polymer layer, the negative electrode material is spherical, and the coating layer seals the pores.
  • Example 2 The other steps are the same as in Example 1, the difference is that the SiO in Example 1 is replaced with Li-doped SiO powder, and the expansion rate of Li-doped SiO powder in the fully charged state is measured to be 105%, and the spray granulation is adjusted. The porosity of the secondary particles was measured to be 58% at the same temperature and spray rate.
  • Example 2 The other steps are the same as in Example 1, the difference is that the porosity of the secondary particles is measured to be 80% by adjusting the process parameters such as spray drying temperature.
  • Example 2 The other steps are the same as in Example 1, the difference is that the SiO in Example 1 is replaced with Li-doped SiO powder, and the expansion rate of Li-doped SiO powder in the fully charged state is measured to be 105%. Temperature and other process parameters, the measured porosity of the secondary particles is 48%.
  • Example 2 The other steps are the same as in Example 1, except that "230 g of 10% HF aqueous solution and 290 g of 10% 10% LiOH aqueous solution" in Example 1 are changed to "220 g of 10% Al(H 2 PO) 4 ) 3 aqueous solution and 160 g of LiOH aqueous solution with a concentration of 10%", that is, replace the fast ion conductor with Al(H 2 PO 4 ) 3 .
  • Example 2 Other steps are the same as in Example 1, except that the porosity of the secondary particles is measured to be 55% by adjusting the spray drying temperature and other process parameters, that is, the porosity/expansion ratio ⁇ 0.45.
  • Example 2 Other steps are the same as in Example 1, except that by adjusting the process parameters such as spray drying temperature, the porosity of the secondary particles is measured to be 85%, that is, the porosity/expansion ratio>0.6.
  • Example 1 The other steps are the same as in Example 1, the difference is that "58 g of 40% HF aqueous solution and 290 g of 10% LiOH aqueous solution to disperse LiF on the surface of carbon nanotubes" in Example 1 are removed, that is, it is not Carbon nanotubes are coated with fast ion conductors.
  • Example 2 Continue to feed 6L/min hydrogen-nitrogen mixture and 0.6L/min acetylene after sintering in Example 1, and deposit at 900°C for 3h, so that the gas enters the pores of the secondary particle body to generate pyrolytic carbon, and the temperature is naturally cooled. Then the porous secondary particles reinforced by gas-phase pyrolytic carbon are obtained and removed, that is, the sintered secondary ions are not enhanced by gas-phase pyrolytic carbon, and the surface of the pitch cracked carbon is directly sealed.
  • Example 1 The other steps are the same as in Example 1, the difference is that in Example 1, 1kg of porous secondary particles were dispersed in 2kg, 1% concentration of sodium carboxymethyl cellulose aqueous solution, first dried with a spray dryer, and then in Heating in an oven at 120°C for 2h and curing for 2h” was changed to “1kg of porous secondary particles at 900°C, with 3L/min nitrogen and 0.3L/min acetylene, vapor deposition for 3h, and the secondary The surface of the particles is coated with gas-phase pyrolytic carbon, and the surface is sealed.” That is, the conductive carbon layer is used to seal the surface.
  • the negative electrode materials prepared in each example and comparative example were conventionally prepared for CR2032 type button batteries and their electrical properties were tested. Charge and discharge the battery with the LAND battery test system. After standing for 6 hours, discharge at 0.05C to 0.005V, and then discharge at 0.01C to 0.005V; after standing for 5 minutes, charge at 0.05C constant current to 1.5 V; after standing for 5min, repeat the above steps twice; then discharge to 0.005V at 0.25C; after standing for 5min, charge at 0.25C constant current to 1.5V, and cycle 100 times.
  • the specific charging capacity of the first cycle is the specific capacity of the pole piece, the specific charging capacity of the 50th cycle / the charging capacity of the first cycle ⁇ 100%, and the capacity retention rate is calculated.
  • the expansion ratio of the material was tested by the following method: discharge the 0.25C of the above-mentioned cycled charge to 0.005V, then disassemble the charge in the glove box, clean the pole piece with DEC and measure the thickness of the pole piece.
  • the calculation method of expansion ratio is: (thickness of fully charged pole piece after cycle - thickness of fresh pole piece)/thickness of fresh pole piece ⁇ 100%.
  • the rate performance of the material was tested by the following method: the prepared CR2032 button battery was allowed to stand at room temperature for 12 hours, and then the constant current charge and discharge test was performed on the blue electricity test system. C current was charged and discharged, and the cycle was repeated 3 times. Then charge and discharge at 1C current, and cycle 3 times. Finally, charge and discharge at 2C current and cycle 3 times.
  • the capacity retention rate was calculated by calculating the charging capacity of the ninth cycle/the charging capacity of the first cycle ⁇ 100%, and the higher the value was, the better the rate performance was.
  • Table 1 shows the test results of the electrochemical performance of the negative electrode materials obtained in each example and the comparative example. It can be seen from the table that the negative electrode materials provided by the examples 1 to 5 of the present invention have a low expansion rate and excellent cycle and rate performance.
  • the comparative example 1 to 2 indicate that the prepared material has good electrochemical performance only when the material porosity and the expansion rate of the silicon material satisfy a certain relationship.
  • Comparative example 3 shows that the coating of fast ion conductors is beneficial to improve the rate capability of the material
  • comparative example 4 shows that the infiltration-deposited cracked carbon can strengthen the combination of silicon-based materials and the three-dimensional network, otherwise the silicon-based materials are easy to be damaged during the charge-discharge cycle. Falling off, resulting in poor cycle performance
  • Comparative Example 5 shows that the sealing effect of organic polymers is better, and the volume expansion can be suppressed to a certain extent.

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Abstract

本发明公开了一种非水电解质二次电池用负极材料及其制备方法，所述负极材料包括多孔二次粒子及二次粒子表面的封孔层，所述二次粒子由硅基材料的一次粒子聚集而成，其特征在于，所述一次粒子负载在三维网络体上，所述一次颗粒通过三维网络体连接；所述三维网络体由表面包覆有快离子导体的碳纳米材料形成。本发明提供的负极材料表现出极低的膨胀率以及较高的导电导离子性能，当所述负极材料用于二次电池时，电池具有优异的倍率性能及循环性能。本发明制备方法简单易行、成本低，适用于大规模生产。

Description

非水电解质二次电池用负极材料及其制备方法 技术领域
本发明涉及锂离子电池材料领域，具体涉及一种非水电解质二次电池用负极材料及其制备方法。
背景技术
近年来，硅基负极材料因其高的比容量成为下一代锂离子电池负极研究的重点，但要实现大规模应用还存在以下关键问题：①脱嵌锂带来的巨大的体积膨胀和收缩而导致的颗粒破碎粉化及电极结构破坏，造成电化学性能失效；②由于膨胀收缩带来的SEI膜不断破坏重组，持续消耗电解液和可逆锂源导致电极容量衰减加速，充放电效率急剧降低。
发明内容
针对以上问题，本发明提供了一种非水电解质二次电池用负极材料，以解决现有技术中硅基负极材料膨胀效应大、固体电解质界面(SEI)膜不稳定等问题，从而提高材料的循环、倍率性能。
在一个实施例中，本发明提供了一种非水电解质二次电池用负极材料，包括多孔二次粒子及二次粒子表面的封孔层，所述二次粒子由硅基材料的一次粒子聚集而成，其特征在于，所述一次粒子负载在三维网络体上，所述一次颗粒通过三维网络体连接；所述三维网络体由表面包覆有快离子导体的碳纳米材料形成。
在另一个实施例中，本发明还提供了上述负极材料的制备方法，包括以下步骤：
S1：将粘结剂、碳纳米材料、硅基材料、快离子导体材料均匀分散在溶剂中，制成浆料；
S2：将上述浆料进行喷雾造粒，得到由包覆着快离子导体层的碳纳米材料连接和隔离硅颗粒的二次粒子坯体；
S3：将步骤S2的产物在保护气氛下烧结，然后进行气相渗透沉积，得到热解炭增强的多孔二次粒子；
S4：将步骤S3的产物进行表面包覆，得到负极材料。
与现有技术相比，本发明提供的二次锂电池用硅碳负极材料及其制备方法具有以下有益效果：
(1)本发明提供的负极材料，采用快离子导体包覆碳纳米材料并形成三维网络结构，使得硅基材料一次粒子连接相同，更有效地提高导电导离子性能，可制备出高倍率且循环优异的非水电解质二次电池；
(2)本发明通过控制沉积温度及气体流量，实现气相渗透沉积，使热解炭增强硅颗粒与导电材料的结合，大大提高界面结合强度，有效缓解硅材料的体积膨胀；
(3)本发明所提供的制备方法，通过调节气体流量、可有效控制微孔的生成及分布，从而使产品孔隙均匀、大小可控。
本申请实施例的额外层面及优点将部分地在后续说明中描述和显示，或是经由本申请实施例的实施而阐释。
附图说明
构成本申请的一部分的说明书附图用来提供对本发明的进一步理解，本发明的示意性实施例及其说明用于解释本发明，并不构成对本发明的不当限定。在附图中：
图1为本发明所述负极材料制备方法的流程示意图；
图2为本发明实施例1还未包覆聚合物层的材料SEM图；
图3为本发明实施例1已包覆聚合物层的负极材料SEM图。
具体实施方式
本申请的实施例将会被详细的描述在下文中。本申请的实施例不应该被解释为对被申请的限制。
实施例中多孔二次粒子的孔隙率可通过压汞仪、BET比表面积测试法测得。
本发明提供了一种非水电解质二次电池用负极材料，包括多孔二次粒子及二次粒子表面的封孔层，所述二次粒子由硅基材料的一次粒子聚集而成，其特征在于，所述一次粒子负载在三维网络体上，所述一次颗粒通过三维网络体连接；所述三维网络体由表面包覆有快离子导体的碳纳米材料形成。二次粒子的结构可有效缓冲材料在充放电过程中体积膨胀，同时一次粒子相对粒径较小，可缩短锂离子的扩散距离，提高扩散效率，从而提高材料的倍率性能。由快离子导体及碳纳米材料组成的导电导离子三维网络体，使一次粒子连接相通，可保证高导电性及高导离子性能，同时网络结构可进一步缓冲硅颗粒的体积膨胀。
在一较佳的实施方式中，所述负极材料中还包括热解炭，所述热解炭沉积在一次粒子和三维网络体表面，用来增强硅基材料与三维网络体的界面结合。
在一较佳的实施方式中，所述二次粒子的孔隙率A与所述一次粒子满电态膨胀率B的比值满足：0.45＜A/B＜0.6，优选地为0.5≤A/B＜0.6，更优选地为A/B＝0.5；如果比例小于0.45，则表明二次粒子内部没有足够的空间容纳膨胀，可能导致二次粒子结构崩坍从而性能变差；如果比例＞0.6则会导致二次粒子整体密度太低，从而导致颗粒和最终极片体积比容量偏低。所述一次粒子满电态膨胀率B是指一次粒子嵌满锂后的体积相比于嵌锂之前的体积的增长率，其膨胀率与所选硅基材料的种类有关，可通过以下方法测试：按质量比80:10:10将选择的硅 材料:SP(碳黑):PAA(聚丙烯酸)混合，加入适量去离子水作溶剂，用磁力搅拌机连续搅拌8h至糊状。将搅拌好的浆料倒在厚度9μm的铜箔上，用实验型涂布机涂布后在85℃真空(-0.1MPa)条件下干燥6h，得到负极电极片，采用FEI Inspect S50扫描电镜观察极片，根据相应的比例尺得到硅材料嵌锂前的平均粒径为D1μm。在手动对辊机上将电极片轧至100μm，再用冲片机制得直径12mm的圆片，在85℃真空(-0.1MPa)条件下干燥8h。在手套箱中组装CR2032型扣式电池，以金属锂片为对电极，聚丙烯微孔膜为隔膜，1mol/L LiPF6 in EC(碳酸乙酯):DEC(碳酸二乙酯)＝1:1为电解液。用蓝电(LAND)电池测试系统对电池进行充放电测试，静置6h后，以0.05C放电至0.005V，再以0.01C放电至0.005V，然后拆解扣电，用DEC清洗极片，并采用FEI Inspect S50扫描电镜观察极片，根据相应的比例尺得到硅材料嵌锂后的平均粒径为D2，将硅材料颗粒看作为类球形结构，则可通过式(Ⅰ)计算得到膨胀率B：
膨胀率
Figure PCTCN2021086364-appb-000001
在一较佳的实施方式中，所述硅基材料包括金属硅、纯硅、硅合金(Si-M，如Si-Sn)、硅复合物(Si-X，如Si-C)、硅化合物(如Si 3N 4，SiC)、氧化硅SiO x(其中，0＜x＜2)中，由掺杂元素掺杂改性的硅氧化物(掺杂元素如：Li、Mg)的至少一种；所述硅活性颗粒的粒径D50优选为0.01～2μm；所述封孔层包括有机聚合物，所述有机聚合物包括但不限于聚偏氟乙烯及其衍生物、羧甲基纤维素及其衍生物、羧甲基纤维素钠及其衍生物、聚乙烯基吡咯烷酮及其衍生物、聚丙烯酸及其衍生物、聚丙烯酰胺、聚酰亚胺、聚酰胺酰亚胺、聚丁苯橡胶中的至少一种，有机聚合物具有较好的封孔效果，同时可有效降低比表面积，减少副反应，此外有机聚合物具有一定的弹性，可在一定程度缓冲体积膨胀；所述快离子导体包括氧化铝、二氧化钛、氧化锆、氧化钒、氧化锌、氧化钴、氧化磷、氧化硼、氧化硅、偏磷酸铝、偏磷酸锂、偏磷酸钴、氟化锂、氟化铝、氟化铁中的至少一种，快离子导体还具有SEI膜功能，可稳定SEI的生成，降低锂离子的损耗，从而提高可逆容量；所述碳纳米材料包括碳纤维、炭黑、碳纳米管、石墨烯中的至少一种，所述碳纳米材料可以形成三维网络结构。
在一较佳的实施方式中，以负极材料质量为100％计，所述硅基材料一次粒子的质量占比为75～85wt％，优选地为78～82％；所述碳纳米材料质量占比为1～10wt％，优选地为3～8％，更优选地为4～6％；所述快离子导体层质量占比为1～10wt％选地为3～8％，更优选地为4～6％；，所述封孔层质量占比为0.5～20％，优选地为1～15％，更优选地为2～10％。当各物质质量比例在以上范围时，材料表现出优异的电学性能。
在一较佳实施方式中，所述负极材料中还包括粘结剂，以所述负极材料质量为100％计，所述粘结剂的质量比小于0.5％，较少的粘结剂含量，有利于材料通孔的形成，从而使裂解碳气体顺利通过孔隙进行渗透式沉积。需说明的是，此处的粘结剂并非是制备过程中加入的原料粘结剂，而是在制备过程后形成的负极材料产品中的粘结剂，也可理解为粘结剂的烧结残留物。关于烧结过程下文详细介绍。
在一较佳的实施方式中，所述负极材料的比表面积为0.3～20m 2/g，优选地为2～10m 2/g，更优选地为2～5m 2/g，当比表面积在此范围时，涂布于电极时的粘结性较好，同时电池容量更高；粒径D50为1～50μm，优选地为5～20μm，更优选地为6～15μm。
接下来描述负极材料的制备方法，负极材料是这样制备的：
S1：将粘结剂、碳纳米材料、硅基材料、快离子导体材料均匀分散在溶剂中，制成浆料；
S2：将上述浆料进行喷雾造粒，得到由包覆着快离子导体层的碳纳米材料连接和隔离硅颗粒的二次粒子坯体；
S3：将步骤S2的产物在保护气氛下烧结，然后进行气相渗透沉积，得到热解炭增强的多孔二次粒子；
S4：将步骤S3的产物进行表面包覆，得到负极材料。
在一较佳实施方式中，所述浆料中各物质的质量百分比为：粘结剂0.5～3％、碳纳米材料1～10％、硅基材料80％～90％、快离子导体1～10％；所述各物质的加入没有特定的顺序限定，优选地，先将碳纳米材料加入溶剂中，然后加入快离子导体，最后加入硅基材料。这样，可确保快离子导体最大程度地包覆在导电材料上，并且硅材料以颗粒的形式负载在快离子导体表面，此时负极材料可以制作一种快充型的二次电池。不具体限定浆料的固含量，优选的是1～50％。
不具体限定喷雾造粒的进风温度和出风温度，优选地为：进风温度200～400℃，出风温度80～150℃，此时可控制二次粒子胚体的粒径和比表面积在合适的范围内，同时可通过调节进风温度、出风温度及喷雾速率来控制二次粒子胚体的孔隙率。
不具体限定二次粒子坯体的烧结条件，为了效率和经济起见，优选的是，烧结温度控制为600～950℃，升温速率控制为3～8℃/min，烧结时间控制为0.5～3h。
所述气相渗透沉积，是指通过控制通入载体和碳源气体的流量速率，使碳源气体通过二次粒子坯体的孔隙沉积在一次粒子表面，优选地，通入载气为氢气、氮气、氦气中的至少一种，通入碳源气体为甲烷、乙烷、丙烷、丙烯、乙炔中的至少一种，载气和碳源气体的通入体积比例为3～20：1，沉积温度为600～900℃，沉积时间为1～12h。
所述粘结剂包括PVP、PVA、环氧树脂、酚醛树脂、沥青、乳化沥青、白糖、葡萄糖中的一种或多种；所述溶剂包括乙醇、纯水、甲苯、二甲苯中的一种或多种。
不具体限定表面包覆的包覆方式，具体的可以是液相包覆、固相包覆、气体沉积包覆、机械包覆中的至少一种方式。
以下，示出实施例和比较例，更具体说明本发明，但本发明不限于此。
实施例1
将60g碳纳米管分散在水中，固含量为2％，加入230g浓度为10％的HF水溶液和290g浓度为10％的LiOH水溶液，将LiF分散包覆在碳纳米管表面；充分搅拌均匀后，然后向其中加入1kg SiO粉体(通过以上方法测试SiO满电态的膨胀率为135％)，最后加入20g酚醛树脂搅拌均匀制成浆料，固含量约为25％。
采用喷雾造粒设备造粒，进风温度250度，出风温度90度，得到造粒的二次粒子坯体。
将造粒后的二次粒子坯体900℃烧结，升温速率为5℃/min，烧结后继续通入6L/min氢氮混合气和0.6L/min乙炔，在900℃下沉积3h，使气体进入二次粒子坯体的孔隙内生成热解碳，自然降温后得到气相热解碳增强的多孔二次粒子，采用压汞仪、BET比表面积测试法测得二次粒子的孔隙率为70％。
将1kg多孔二次粒子分散在2kg、1％浓度的羧甲基纤维素钠水溶液中，先使用喷雾干燥机干燥后，然后在烘箱内加热120℃固化2h，进行表面封孔。
图1为实施例1的制备流程及产品示意图，可见喷雾造粒后LiF与碳纳米管形成三维网体1结构，硅活性颗粒一次粒子2嵌入在网状结构中，形成多孔球状的二次粒子(如图1a所示，其为造粒的二次粒子坯体的结构示意图)，随后通过气相渗透沉积，热解炭3通过孔隙渗入二次粒子内部沉积在一次粒子2及三维网络体3上，增强硅活性物质与导电导离子体的结合(如图1b所示，其为气相热解碳内部增强的二次粒子的结构示意图)，最后在二次粒子表面包覆有机聚合物层4(如图1c所述，其为表面封孔的二次粒子，也即负极材料的结构示意图)。
用扫描电镜(SEM，电子扫描电镜FEI Inspect S50)分析材料的形貌，图2为还未包覆聚合物层的材料SEM图，可见三维网络结构及孔隙。图3为包覆聚合物层的负极材料SEM图，该负极材料为类球形，包覆层将孔隙封住。
实施例2
其他步骤与实施例1相同，区别在于将实施例1中的SiO换为Li掺杂的SiO粉体，测得Li掺杂的SiO粉体满电态的膨胀率为105％，调节喷雾造粒的温度及喷雾速率，测得二次粒子的孔隙率为58％。
实施例3
其他步骤与实施例1相同，区别在于通过调节喷雾干燥温度等工艺参数，测得二次粒子的孔隙率为80％。
实施例4
其他步骤与实施例1相同，区别在于将实施例1中的SiO换为Li掺杂的SiO粉体，测得Li掺杂的SiO粉体满电态的膨胀率为105％，通过调节喷雾干燥温度等工艺参数，测得二次粒子的孔隙率为48％。
实施例5
其他步骤与实施例1相同，区别在于将实施例1中的“230g浓度为10％的HF水溶液和290g浓度为10％的LiOH水溶液”，改为“220g浓度为10％的Al(H 2PO 4) 3水溶液和160g浓度为10％的LiOH水溶液”，即将快离子导体更换为Al(H 2PO 4) 3。
对比例1
其他步骤与实施例1相同，区别在于通过调节喷雾干燥温度等工艺参数，测得二次粒子的孔隙率为55％，即孔隙率/膨胀率＜0.45。
对比例2
其他步骤与实施例1相同，区别在于通过调节喷雾干燥温度等工艺参数，测得二次粒子的孔隙率为85％，即孔隙率/膨胀率＞0.6。
对比例3
其他步骤与实施例1相同，区别在于将实施例1中的“58g浓度为40％的HF水溶液和290g浓度为10％的LiOH水溶液，将LiF分散包覆在碳纳米管表面”去掉，即不在碳纳米管表面包覆快离子导体。
对比例4
将实施例1中“烧结后继续通入6L/min氢氮混合气和0.6L/min乙炔，在900℃下沉积3h，使气体进入二次粒子坯体的孔隙内生成热解碳，自然降温后得到气相热解碳增强的多孔二次粒子”去掉，即将烧结后的二次离子不进行气相热解碳增强，直接进行沥青裂解碳表面封孔。
对比例5
其他步骤与实施例1相同，区别在于将实施例1中“1将1kg多孔二次粒子分散在2kg、1％浓度的羧甲基纤维素钠水溶液中，先使用喷雾干燥机干燥后，然后在烘箱内加热120℃固化2h”表面封孔的方式，改为“将1kg多孔二次粒子在900℃下，通入气体为3L/min氮气和0.3L/min乙炔，气相沉积3h，在二次粒子表面包覆气相热解碳，进行表面封孔”，即采用导电碳层进行表面封孔。
将各实施例及对比例所制得的负极材料采用常规制备CR2032型扣式电池并进行电学性能测试。用蓝电(LAND)电池测试系统对电池进行充放电测试，静置6h后，以0.05C放电至0.005V，再以0.01C放电至0.005V；静置5min后，0.05C恒流充电至1.5V；静置5min后，重复两次上述步骤；然后采用0.25C放电至0.005V；静置5min后，0.25C恒流充电至1.5V，循环100次。首次循环的充电比容量即为极片比容量，第50圈的充电比容量/第1圈的充电容量×100％，计算得到容量保持率。
采用以下方法测试材料的膨胀率：将上述循环后的扣电0.25C放电至0.005V，然后在手套箱中拆解扣电，用DEC清洗极片并测量极片的厚度。膨胀率计算方式为：(循环后满电态极片厚度-新鲜极片厚度)/新鲜极片厚度×100％。
采用以下方法测试材料的倍率性能：将制得的CR2032型扣式电池在室温下静置12h，再在蓝电测试系统上恒流充放电测试，充放电截止电压0.005-1.5V，先以0.25C电流进行充放电，循环3次。再以1C电流进行充放电，循环3次。最后以2C电流进行充放电，循环3次。将第9圈的充电容量/第1圈的充电容量×100％，计算得到容量保持率，数值越高被认为倍率性能越好。
表1各实施例和对比例所得负极材料的电化学性能测试结果
Figure PCTCN2021086364-appb-000002
表1为各实施例和对比例所得负极材料的电化学性能测试结果，由表可知，本发明实施例1～5提供的负极材料具有较低的膨胀率以及优异的循环和倍率性能，对比例1～2表明只有材料孔隙率与硅材料的膨胀率满足一定关系时，所制备的材料才具有较好的电化学性能。对比例3表明快离子导体的包覆有利于提高材料的倍率性能，对比例4表明渗透沉积的裂解碳可加强硅基材料与三维网络体的结合，否则硅基材料在充放电循环过程中易脱落，导致循环性能差，对比例5表明有机聚合物的封孔效果更好，且可一定程度抑制体积膨胀。
为使本发明实施例的目的、技术方案和优点更加清楚，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本发明一部分实施例，而不是全部的实施例。 基于本发明中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。

Claims (10)

  1. 一种非水电解质二次电池用负极材料，包括多孔二次粒子及二次粒子表面的封孔层，所述二次粒子由硅基材料的一次粒子聚集而成，其特征在于，所述一次粒子负载在三维网络体上，所述一次颗粒通过三维网络体连接；所述三维网络体由表面包覆有快离子导体的碳纳米材料形成。
  2. 如权利要求1所述的负极材料，其特征在于，所述负极材料中还包括热解炭，所述热解炭沉积在一次粒子和三维网络体表面，用来增强一次粒子与三维网络体的界面结合。
  3. 如权利要求1所述的负极材料，其特征在于，所述二次粒子的孔隙率A与所述一次粒子满电态膨胀率B的比值满足：0.45＜A/B＜0.6。
  4. 如权利要求1所述的负极材料，其特征在于，所述硅基材料包括金属硅、纯硅、硅合金、硅复合物、硅化合物、氧化硅SiO x、由掺杂元素掺杂改性的硅氧化物中的至少一种，其中所述氧化硅SiO x中0＜x＜2；所述封孔层包括有机聚合物，优选所述有机聚合物包括聚偏氟乙烯及其衍生物、羧甲基纤维素及其衍生物、羧甲基纤维素钠及其衍生物、聚乙烯基吡咯烷酮及其衍生物、聚丙烯酸及其衍生物、聚丙烯酰胺、聚酰亚胺、聚酰胺酰亚胺、聚丁苯橡胶中的至少一种；所述快离子导体包括氧化铝、二氧化钛、氧化锆、氧化钒、氧化锌、氧化钴、氧化磷、氧化硼、氧化硅、偏磷酸铝、偏磷酸锂、偏磷酸钴、氟化锂、氟化铝、氟化铁中的至少一种；所述碳纳米材料包括碳纤维、炭黑、碳纳米管、石墨烯中的至少一种。
  5. 如权利要求1所述的负极材料，其特征在于，以所述负极材料质量为100％计，所述硅基材料一次粒子的质量占比为75～85wt％，所述碳纳米材料的质量占比为1～10wt％，所述快离子导体层质量占比为1～10wt％，所述封孔层的质量占比为0.5～20％；优选地，所述负极材料中还包括粘结剂的烧结残留物，以所述负极材料质量为100％计，所述粘结剂的烧结残留物的质量比小于0.5％。
  6. 如权利要求1所述的负极材料，其特征在于，所述负极材料的比表面积为0.3～20m 2/g；粒径D50为1～50μm。
  7. 一种用于制备权利要求1～6任一项所述的负极材料的方法，其特征在于，包括以下步骤：
    S1：将粘结剂、碳纳米材料、硅基材料、快离子导体材料分散在溶剂中，制成浆料；
    S2：将上述浆料进行喷雾造粒，得到由包覆着快离子导体层的碳纳米材料连接和隔离硅颗粒的二次粒子坯体；
    S3：将步骤S2的产物在保护气氛下烧结，得到多孔二次粒子；
    S4：将步骤S3的产物进行表面包覆，得到负极材料。
  8. 如权利要求7所述的方法，其特征在于，所述方法包括以下步骤：
    S1：将所述粘结剂、所述碳纳米材料、所述硅基材料、所述快离子导体材料分散在所述溶剂中，制成所述浆料；
    S2：将所述浆料进行喷雾造粒，得到所述由包覆着快离子导体层的碳纳米材料连接和隔离硅颗粒的二次粒子坯体；
    S3：将所述步骤S2的产物在保护气氛下烧结，然后进行气相渗透沉积，得到热解炭增强的所述多孔二次粒子；
    S4：将所述步骤S3的产物进行表面包覆，得到所述负极材料；
    优选地，所述步骤S1包括：先将所述碳纳米材料加入所述溶剂中，然后加入所述快离子导体，其次加入所述硅基材料，最后加入所述粘结剂，形成所述浆料；
    优选地，所述喷雾造粒过程中，进风温度为200～400℃，出风温度为80～150℃；
    优选地，所述烧结过程中，烧结温度为600～950℃，升温速率为3～8℃/min，烧结时间为0.5～3h；
    优选地，所述气相渗透沉积的过程包括：将载体和碳源气体通过所述烧结后的所述二次粒子坯体的孔隙并沉积形成热解碳；更优选所述载体为氢气、氮气、氦气中的至少一种，所述碳源气体为甲烷、乙烷、丙烷、丙烯、乙炔中的至少一种，且所述载体和所述碳源气体的体积比例为3～20：1；更优选所述气相渗透沉积的过程中的沉积温度为600～900℃，沉积时间为1～12h；
    优选地，所述表面包覆过程包括：将封孔层材料以液相包覆、固相包覆、气体沉积包覆或机械包覆的方式包覆在所述步骤S3的产物表面，形成所述负极材料。
  9. 如权利要求7或8所述的方法，其特征在于，所述步骤S1中各物质的质量百分比为：所述粘结剂0.5～3％、所述碳纳米材料1～10％、所述硅基材料80％～90％、所述快离子导体材料1～10％。
  10. 如权利要求9所述的方法，其特征在于，所述粘结剂包括PVP、PVA、环氧树脂、酚醛树脂、沥青、乳化沥青、白糖、葡萄糖中的一种或多种；所述溶剂包括乙醇、纯水、甲苯、二甲苯中的一种或多种。
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