CN110550635B - Preparation method of novel carbon-coated silica negative electrode material - Google Patents
Preparation method of novel carbon-coated silica negative electrode material Download PDFInfo
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Abstract
The invention relates to a preparation method of a novel carbon-coated silica negative electrode material, which comprises the steps of crushing, crushing massive SiO into powder, preparing a mixed precursor, taking asphalt and SiO, mixing the asphalt and the SiO in proportion, performing ball milling homogenization, carbonizing and coating, placing the mixed precursor obtained in the second step into a vacuum tube furnace, preparing a composite intermediate, performing ball milling homogenization, taking out the composite intermediate obtained in the third step, performing ball milling to obtain a homogeneous composite intermediate, performing carbonization coating, placing the composite intermediate obtained in the fourth step into the vacuum tube furnace again, introducing protective gas, and keeping the temperature for a certain time to obtain the carbon-coated silica composite negative electrode material. The method adopts a mode of combining segmented mechanical fusion and a carbon coating technology, achieves a good coating effect on SiO material particles, and the coated material has the advantages of high coulomb efficiency for the first time, good cycle performance, low cost, environmental friendliness and the like.
Description
Technical Field
The invention relates to a preparation method of a novel carbon-coated silica negative electrode material.
Background
With the development of science and technology and the increasing severity of pollution caused by traditional petroleum energy, the demand of people for novel renewable energy sources is urgent. The lithium ion battery has the advantages of good cycle stability, large energy density, long cycle life, environmental friendliness and the like, and thus becomes the most promising chemical energy source in the 21 st century and has gradually developed into the main body of the secondary battery market. Among them, the electrode material is one of the key factors determining the performance of the lithium ion battery. Because the reversible specific capacity of the anode material has a small promotion space and the cathode material has a great influence on the cycling stability and capacity of the battery, the promotion of the reversible specific capacity of the cathode material is the key for improving the energy density of the lithium ion battery at present.
Graphite carbon materials are generally adopted as the anode materials of the current commercial lithium ion batteries, the volume expansion in the lithium intercalation and deintercalation process is basically below 9 percent, and the high coulombic efficiency and the excellent cycle stability performance are shown. However, the graphite electrode itself has a low theoretical lithium storage capacity (LiC) 6 ，372mAh/g)，And safety limitations that make it difficult to make breakthrough progress again. Therefore, research and development of novel negative electrode materials with high specific capacity, high charge-discharge efficiency, high cycle performance, good high-rate charge-discharge performance, high safety and low cost are urgent, become popular subjects in the field of lithium ion battery research, and have very important significance for development of lithium ion batteries.
In the research of novel non-carbon cathode materials, metals such as Si, al, mg, sn and the like capable of being alloyed with Li and alloy materials thereof are found, the reversible lithium storage amount of the metals is far higher than that of graphite cathodes, and silicon has the highest theoretical lithium storage capacity (Li) 22 Si 5 4200mAh/g, which is more than ten times of the current commercial graphite cathode), silicon also has the advantages of low de-intercalation lithium voltage platform, low electrolyte reactivity, abundant natural reserves, low price and the like, and is considered to be one of the most promising lithium ion battery cathode materials. However, the volume expansion of the silicon negative electrode material in the alloying process is up to 300%, and the silicon negative electrode material is easy to peel off from a current collector when being used alone, so that the phenomena of electrochemical corrosion, short circuit and the like caused by the exposed foil of a pole piece are caused, and the safety and the service life of the battery are influenced; meanwhile, the silicon material has huge volume expansion, so that the silicon negative electrode material cannot form a stable SEI film, the SEI film is continuously broken and established in the charging and discharging processes, the consumption of lithium ions is aggravated, and the performance of the battery is finally influenced. Therefore, when high capacity is obtained, how to improve the cycling stability of the silicon-based material and reduce the first irreversible capacity of the silicon-based material tends to commercialization and practicability becomes a research focus and difficulty of the material.
Practical solutions for silicon-based cathodes can be divided into three main flow directions, namely nano silicon-carbon composites, silicon oxide-carbon composites and amorphous silicon alloys. The silicon carbon and silicon monoxide carbon composite material has been applied to a small range, but has a larger promotion space in the aspects of first effect, circulation and the like.
SiO as a lithium ion battery cathode material has excellent electrochemical performance, and can form an inactive phase Li in the process of lithium intercalation for the first time 2 O and Li 4 SiO 4 To play a role ofThe function of relieving volume expansion is that the volume effect is obviously reduced compared with silicon material in the process of charging and discharging the battery material. Therefore, the silica material is easier to break through the limitation, and commercialization is realized early.
However, if the first irreversible capacity loss is increased due to the inert lithium oxide and lithium silicate phases generated by SiO during the first lithium intercalation, the coulombic efficiency in the first cycle is low, and Li is consumed due to the continuous generation of a Solid Electrolyte Interface (SEI) film during the subsequent charge and discharge processes, and the coulombic efficiency is lower than 100%, which results in a significant decrease in the lithium-removable capacity of the negative electrode as compared to the positive electrode in the actual battery. And the electrical conductivity of the silicon oxide itself is also low. These are the main factors that limit the achievement of long life and high rate performance of silica as the negative electrode material during charge and discharge cycles.
In patent CN201210303878.3, silicon and silicon oxide are used as initial raw materials, ball-milled, and then mixed with graphite, a conductive agent and asphalt to perform spray drying to obtain spheroidal particles, and then carbonized and sintered to obtain a silicon-carbon composite negative electrode material.
CN103474631A discloses a silica composite negative electrode material, which comprises a silica substrate, a nano silicon material uniformly deposited on the silica substrate, and a nano conductive material coating layer on the surface of the silica/nano silicon. The preparation method of the silicon monoxide composite negative electrode material comprises the steps of nano silicon chemical vapor deposition, nano conductive material coating modification, sieving and demagnetizing treatment. Although the specific capacity (> 1600m Ah/g) and the first coulombic efficiency (> 80%) of the SiO composite material are improved to a certain extent. However, the silicon monoxide composite material is prepared by artificially introducing a nano silicon material with larger volume expansion on the surface of SiO particles in a physical combination mode on the basis of the original component structure of the SiO material, the crystal grain is larger and difficult to control, the dispersibility is poor, the problem of huge volume expansion caused by the Si material cannot be effectively buffered and cannot be avoided, and the cycle performance is poor.
In order to solve the above problems of SiO, the main solution is the nanocrystallization of SiO and the compounding with other materials, and at present, the compounding with carbon materials, such as amorphous carbon, graphite, graphene, carbon nanotubes, etc., is the most studied.
In view of the above, the present invention provides a method for simply preparing a carbon-coated doped silicon monoxide for preparing a lithium ion battery negative electrode material, which is simple in preparation process and high in yield, and can effectively solve the problems of low coulombic efficiency, short cycle life and low rate performance of the existing silicon monoxide as a negative electrode material in the charge-discharge cycle process.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a novel preparation method of a carbon-coated silica negative electrode material, and the silica negative electrode prepared by the method has the advantages of simple steps, low cost, high yield, high coulombic efficiency and good cycle performance.
In order to realize the above and other related objects, the invention provides a preparation method of a novel carbon-coated silica negative electrode material, which comprises the following steps of firstly, crushing a SiO massive body, crushing the massive SiO into powder by a crusher, screening the powder with proper granularity by a sample separation sieve, placing the powder in a ball milling tank, controlling the ball milling speed to be 300-600rpm, selecting balls with the diameter of 6-10mm and controlling the ball-to-material ratio to be 4-10, and carrying out wet ball milling for 2-8h; secondly, preparing a mixed precursor, taking pitch and SiO, controlling the ratio of SiO to pitch to be 1:0.1-1, after mixing, controlling the ball milling rotation speed to be 250-600rpm, selecting balls with the diameter of 6-10mm and the ball-material ratio to be 4-10, and carrying out wet ball milling for 2-6h to obtain the mixed precursor; thirdly, performing carbonization coating, namely placing the mixed precursor in the second step into a corundum square boat, then placing the corundum square boat into a vacuum tube furnace, introducing protective gas, heating to 800-1100 ℃ at the speed of 3-8 ℃/min, preserving heat for 1-4h, cooling to room temperature, performing ball milling granulation on the compound subjected to high-temperature carbonization, controlling the ball milling speed to be 250-400rpm, selecting balls with the diameter of 6-10mm and the ball-to-material ratio to be 4-10, and performing wet ball milling for 1-4h to obtain the carbon-coated silicon oxide composite negative electrode material; and fourthly, preparing an electrode, namely taking the powdery silicon monoxide composite negative electrode material, uniformly mixing the powdery silicon monoxide composite negative electrode material with a mixture of conductive carbon black and carbon nano tubes and styrene butadiene rubber according to a mass ratio of 90.
Preferably, in the third step, the method comprises primary coating, ball milling homogenization, secondary coating carbonization and primary coating, wherein the mixed precursor in the second step is placed in a corundum ark, then the corundum ark is placed in a vacuum tube furnace, protective gas is introduced, the temperature is raised to the softening point of asphalt at the speed of 3-8 ℃/min, the temperature is kept for 1-4 hours, and then the mixture is naturally cooled to room temperature to obtain a composite intermediate; ball-milling and homogenizing, taking out the composite intermediate obtained by primary coating, placing the composite intermediate in a ball-milling tank, controlling the ball-milling rotation speed to be 250-400rpm, selecting balls with the diameter of 6-10mm, and controlling the ball-material ratio to be 4-10, and carrying out wet ball-milling for 1-4h to obtain the homogenized composite intermediate; and (2) secondary coating carbonization, placing the composite intermediate after ball milling homogenization in a corundum ark again, placing the corundum ark in a vacuum tube furnace, introducing protective gas, heating to 900-1100 ℃, keeping the temperature for 1-4h, cooling to room temperature, carrying out ball milling granulation on the cooled composite, controlling the ball milling speed to be 250-400rpm, selecting balls with the diameter of 6-10mm, and controlling the ball-to-material ratio to be 4-10, and carrying out wet ball milling for 1-4h to obtain the carbon-coated silicon oxide composite negative electrode material.
Preferably, the milling medium is deionized water or alcohol in a wet ball milling process.
Preferably, in the first step, when the median diameter D50 of SiO is 0.1-1 μm, the preparation process of the second step is carried out.
Preferably, the molar ratio of O to Si in the bulk SiO is 0.85-1.15.
Preferably, the bitumen in the second step has a softening point of 200-300 ℃ and an ash content of less than 0.05%.
Preferably, the vacuum drying temperature in the fourth step is 80 ℃.
Preferably, the protective gas is nitrogen or an inert gas.
In summary, the preparation method of the novel carbon-coated silica negative electrode material has the following beneficial effects: the method successfully realizes the good coating effect of the asphalt on the surface of silica material particles by adopting a mode of combining the segmented mechanical fusion and the carbonization coating technology, the temperature is firstly raised to the softening point of the asphalt, the asphalt is subjected to homogenization treatment after being softened and then is heated for carbonization coating, so that the asphalt is uniformly coated on the surface of the silica oxide, the bonding strength of the asphalt and the silica oxide is high, and the first coulombic efficiency and the cycle performance of the material are greatly improved; the coated material has high coulombic efficiency for the first time, breaks through the SiO theoretical efficiency and reaches 90 percent; low expansion rate, long service life, environmental protection, no pollution, low cost and easy large-scale production.
Drawings
Fig. 1 is a scanning electron microscope image of 500 times magnification of the silica powder prepared by the method, which shows the overall distribution form of the silica negative electrode material powder.
Fig. 2 is a scanning electron microscope image of 10000 times magnification of the silica powder prepared by the method, and shows the surface morphology of a single particle of the silica negative electrode material.
FIG. 3 is a first charge-discharge curve of the composite material prepared by the method, the first discharge (lithium intercalation) specific capacity of the material is 1679.6mAh/g, the charge (lithium deintercalation) specific capacity is 1527.3mAh/g, and the first charge-discharge efficiency reaches 90.1%.
FIG. 4 is a charge-discharge cycle efficiency curve of the SiOx composite material prepared by the method, wherein the reversible capacity retention rate reaches 81% after constant-current charge and discharge for 60 weeks at 0.1C under normal temperature, the black curve in the graph shows the reversible capacity retention rate of each cycle, and the calculation method is that the charging specific capacity of the cycle is divided by the charging specific capacity of the first cycle; the black discontinuity indicates the coulombic efficiency per cycle, and the calculation method is the charge specific capacity divided by the discharge specific capacity per cycle.
Detailed Description
Referring to fig. 1 to 4, the following embodiments are only described to help understand the method and the core idea of the present invention. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, it is possible to make various improvements and modifications to the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The following description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The present invention will be described in further detail below with reference to specific embodiments and drawings.
Example 1
Weighing powdered silicon monoxide (D50 is 0.1-1 μm) and asphalt (D50 is 0.4-1.3 μm) in a ball milling tank, controlling the mass ratio of the powdered silicon monoxide to the asphalt to be 1. And ball-milling and refining to obtain mixed precursor slurry.
Placing the refined mixed precursor slurry into a corundum ark, placing the corundum ark into a vacuum tube furnace, introducing protective gas, heating to 290 ℃ at the speed of 3 ℃/min, preserving heat for 2 hours, and naturally cooling to room temperature to obtain a composite intermediate. Taking out the composite intermediate, performing ball milling and refining, controlling the ball-material ratio to be 4.
Placing the homogenized composite intermediate into a corundum ark again, placing the corundum ark into a vacuum tube furnace, introducing protective gas, heating to 900 ℃, preserving heat for 2 hours, naturally cooling to room temperature, placing the cooled composite into a ball milling tank, and controlling the ball-to-material ratio to be 4, the ball milling speed to be 300rpm and the ball milling time to be 1.5 hours to obtain the carbon-coated silicon oxide composite negative electrode material.
The preparation method comprises the following steps of taking a powdery silicon monoxide composite negative electrode material, uniformly mixing the powdery silicon monoxide composite negative electrode material with a mixture of conductive carbon black and carbon nano tubes (the ratio of the conductive carbon black to the carbon nano tubes is 70). The positive plate is a metal lithium plate and is assembled into the button cell. The charging and discharging test of the button cell is carried out on a LAND cell test system of Wuhanjinuo electronics company Limited, and the charging and discharging are carried out at constant current of 0.1C under the condition of normal temperature, and the voltage range of a half cell is 2V-5mV.
Example 2
Weighing powdered silicon monoxide (D50 is 0.1-1 μm) and asphalt (D50 is 0.4-1.3 μm) in a ball milling tank, controlling the mass ratio of the two to be 1. And ball milling and refining to obtain mixed precursor slurry.
Placing the refined mixed precursor slurry into a corundum square boat, placing the corundum square boat into a vacuum tube furnace, introducing protective gas, heating to 300 ℃ at the speed of 5 ℃/min, preserving heat for 2 hours, and naturally cooling to room temperature to obtain a composite intermediate. Taking out the composite intermediate, performing ball milling and refining, controlling the ball-to-material ratio to be 6.
Placing the homogenized composite intermediate into a corundum ark again, placing the corundum ark into a vacuum tube furnace, introducing protective gas, heating to 1000 ℃, preserving heat for 1h, naturally cooling to room temperature, placing the cooled composite into a ball milling tank, and controlling the ball-material ratio to be 6.
The preparation method comprises the following steps of taking a powdery silicon monoxide composite negative electrode material, uniformly mixing the powdery silicon monoxide composite negative electrode material with a mixture of conductive carbon black and carbon nanotubes (the ratio of the conductive carbon black to the carbon nanotubes is 50. The positive plate is a metal lithium plate and is assembled into the button cell. The charging and discharging test of the button cell is carried out on a LAND cell test system of Wuhanjinuo electronic Co., ltd,
under the condition of normal temperature, the constant current charging and discharging is carried out at 0.1C, and the voltage range of the half cell is 2V-5mV.
Example 3
Weighing powdered silicon monoxide (D50 is 0.1-1 μm) and asphalt (D50 is 0.4-1.3 μm) in a ball milling tank, controlling the mass ratio of the powdered silicon monoxide to the asphalt to be 1. And ball milling and refining to obtain mixed precursor slurry.
Placing the refined mixed precursor slurry into a corundum ark, placing the corundum ark into a vacuum tube furnace, introducing protective gas, heating to 350 ℃ at the speed of 7 ℃/min, preserving heat for 3h, and naturally cooling to room temperature to obtain a composite intermediate. Taking out the composite intermediate, performing ball milling and refining, controlling the ball-material ratio to be 5.
Placing the homogenized composite intermediate into a corundum ark again, placing the corundum ark into a vacuum tube furnace, introducing protective gas, heating to 1100 ℃, preserving heat for 1h, naturally cooling to room temperature, placing the cooled composite into a ball milling tank, and controlling the ball-to-material ratio to be 5, the ball milling speed to be 350rpm and the ball milling time to be 3h to obtain the carbon-coated silicon oxide composite negative electrode material.
Taking a powdery silicon monoxide composite negative electrode material, uniformly mixing the powdery silicon monoxide composite negative electrode material with a mixture of conductive carbon black and carbon nanotubes (the ratio of the conductive carbon black to the carbon nanotubes is 60). The positive plate is a metal lithium plate and is assembled into the button cell. The charging and discharging test of the button cell is carried out on a LAND cell test system of Wuhanjinuo electronics company Limited, and the charging and discharging are carried out at constant current of 0.1C under the condition of normal temperature, and the voltage range of a half cell is 2V-5mV.
Example 4
Weighing powdered silicon monoxide (D50 is 0.1-1 μm) and asphalt (D50 is 0.4-1.3 μm) in a ball milling tank, controlling the mass ratio of the powdered silicon monoxide to the asphalt to be 1. And ball-milling and refining to obtain mixed precursor slurry.
Placing the refined mixed precursor slurry into a corundum ark, placing the corundum ark into a vacuum tube furnace, introducing protective gas, heating to 300 ℃ at the speed of 6 ℃/min, preserving heat for 2 hours, and naturally cooling to room temperature to obtain a composite intermediate. Taking out the composite intermediate, performing ball milling and refining, controlling the ball-material ratio to be 4.
Placing the homogenized composite intermediate into a corundum ark again, placing the corundum ark into a vacuum tube furnace, introducing protective gas, heating to 800 ℃, keeping the temperature for 4 hours, naturally cooling to room temperature, placing the cooled composite into a ball milling tank, and controlling the ball-to-material ratio to be 4.
The preparation method comprises the following steps of taking a powdery silicon monoxide composite negative electrode material, uniformly mixing the powdery silicon monoxide composite negative electrode material with a mixture of conductive carbon black and carbon nanotubes (the ratio of the conductive carbon black to the carbon nanotubes is 80. The positive plate is a metal lithium plate and is assembled into the button cell. The charge and discharge test of the button cell is carried out on a LAND cell test system of Wuhanjinnuo electronic Co., ltd, the constant current charge and discharge are carried out at 0.1C under the normal temperature condition, and the voltage range of a half cell is 2V-5mV.
Example 5
Weighing powdered silicon monoxide (D50 is 0.1-1 μm) and asphalt (D50 is 0.4-1.3 μm) in a ball milling tank, controlling the mass ratio of the two to be 1. And ball milling and refining to obtain mixed precursor slurry.
Placing the refined mixed precursor slurry into a corundum square boat, placing the corundum square boat into a vacuum tube furnace, introducing protective gas, heating to 350 ℃ at the speed of 8 ℃/min, preserving heat for 1h, and naturally cooling to room temperature to obtain a composite intermediate. Taking out the composite intermediate, performing ball milling and refining, controlling the ball-material ratio to be 4.
Placing the homogenized composite intermediate into a corundum ark again, placing the corundum ark into a vacuum tube furnace, introducing protective gas, heating to 1100 ℃, preserving heat for 2 hours, naturally cooling to room temperature, placing the cooled composite into a ball milling tank, and controlling the ball-material ratio to be 4.
The preparation method comprises the following steps of taking a powdery silicon monoxide composite negative electrode material, uniformly mixing the powdery silicon monoxide composite negative electrode material with a mixture of conductive carbon black and carbon nanotubes (the ratio of the conductive carbon black to the carbon nanotubes is 80. The positive plate is a metal lithium plate and is assembled into the button cell. The charge and discharge test of the button cell is carried out on a LAND cell test system of Wuhanjinnuo electronic Co., ltd, the constant current charge and discharge are carried out at 0.1C under the normal temperature condition, and the voltage range of a half cell is 2V-5mV.
Example 6
Weighing powdered silicon monoxide (D50 is 0.1-1 μm) and asphalt (D50 is 0.4-1.3 μm) in a ball milling tank, controlling the mass ratio of the powdered silicon monoxide to the asphalt to be 1. And ball milling and refining to obtain mixed precursor slurry.
Placing the refined mixed precursor slurry into a corundum square boat, placing the corundum square boat into a vacuum tube furnace, introducing protective gas, heating to 350 ℃ at the speed of 6 ℃/min, preserving heat for 2 hours, and naturally cooling to room temperature to obtain a composite intermediate. Taking out the composite intermediate, performing ball milling and refining, controlling the ball-material ratio to be 9.
Placing the homogenized composite intermediate into a corundum ark again, placing the corundum ark into a vacuum tube furnace, introducing protective gas, heating to 1100 ℃, preserving heat for 2 hours, naturally cooling to room temperature, placing the cooled composite into a ball milling tank, and controlling the ball-material ratio to be 9.
Taking a powdery silicon monoxide composite negative electrode material, uniformly mixing the powdery silicon monoxide composite negative electrode material with a mixture of conductive carbon black and carbon nanotubes (the ratio of the conductive carbon black to the carbon nanotubes is 50. The positive plate is a metal lithium plate and is assembled into the button cell. The charge and discharge test of the button cell is carried out on a LAND cell test system of Wuhanjinnuo electronic Co., ltd, the constant current charge and discharge are carried out at 0.1C under the normal temperature condition, and the voltage range of a half cell is 2V-5mV.
Example 7
Weighing powdery silica (D50 is 0.1-1 μm) and asphalt (D50 is 0.4-1.3 μm) in a ball milling tank, wherein the mass ratio of the powdery silica to the asphalt is 1. And ball milling and refining to obtain a mixed precursor.
Placing the refined mixed precursor into a corundum ark, placing the corundum ark into a vacuum tube furnace, introducing protective gas, heating to 900 ℃ at the speed of 5 ℃/min, preserving heat for 4 hours, naturally cooling to room temperature, placing the cooled compound into a ball milling tank, and controlling the ball-material ratio to be 8, the ball milling speed to be 380rpm and the ball milling time to be 1 hour to obtain the carbon-coated silicon oxide composite negative electrode material.
Taking a powdery silicon monoxide composite negative electrode material, uniformly mixing the powdery silicon monoxide composite negative electrode material with a mixture of a conductive agent SP (conductive carbon black) and CNTS (carbon nano tube) (the ratio of the conductive carbon black to the carbon nano tube is 70). The positive plate is a metal lithium plate and is assembled into the button cell. The charge and discharge test of the button cell is carried out on a LAND cell test system of Wuhanjinnuo electronic Co., ltd, the constant current charge and discharge are carried out at 0.1C under the normal temperature condition, and the voltage range of a half cell is 2V-5mV.
Example 8
Weighing powdery silicon oxide (D50 is 0.1-1 μm) and asphalt (D50 is 0.4-1.3 μm) in a ball milling tank, wherein the mass ratio of the powdery silicon oxide to the asphalt is 1. And ball milling and refining to obtain mixed precursor slurry.
Placing the refined mixed precursor slurry into a corundum square boat, placing the corundum square boat into a vacuum tube furnace, introducing protective gas, heating to 290 ℃ at a speed of 4 ℃/min, keeping the temperature for 2h, then continuing heating to 900 ℃, keeping the temperature for 2h, naturally cooling to room temperature, placing the cooled compound into a ball-milling tank, and controlling the ball-milling rotation speed to be 280rpm and the ball-milling time to be 2h to obtain the carbon-coated silicon monoxide composite negative electrode material.
Taking a powdery silicon monoxide composite negative electrode material, uniformly mixing the powdery silicon monoxide composite negative electrode material with a mixture of a conductive agent SP (conductive carbon black) and CNTS (carbon nano tube) (the ratio of the conductive carbon black to the carbon nano tube is 70). The positive plate is a metal lithium plate and is assembled into the button cell. The charge and discharge test of the button cell is carried out on a LAND cell test system of Wuhanjinnuo electronic Co., ltd, the constant current charge and discharge are carried out at 0.1C under the normal temperature condition, and the voltage range of a half cell is 2V-5mV.
Finally, the detection data of the silicon-oxygen composite negative electrode materials in the embodiments 1 to 8 are collected in the following table, wherein the yield is calculated by dividing the mass of the finally obtained negative electrode material by the total mass of the mixed dry materials before the first ball milling.
Table 1 shows values of respective parameters of the prepared anode materials
It can be seen that the first charge capacity of the partial composite negative electrode material prepared by the method reaches 1500mAh/g, the first coulombic efficiency reaches 90%, and after 50 weeks of circulation, the charge capacity retention rate is still about 80%. After the prepared carbon-coated silicon monoxide and graphite are compounded until the reversible capacity is 450mAh/g, a button cell is assembled and tested, and the capacity retention rate exceeds 80% after part of materials are circulated for 500 circles; meanwhile, the composite negative electrode material prepared by the method has the advantages of low expansion rate, long service life, low preparation cost, no pollution and the like, and is beneficial to large-scale production. Therefore, the invention overcomes various defects of the prior art and has high industrial utilization value and practical value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which may be made by those skilled in the art without departing from the spirit and scope of the present invention as defined in the appended claims.
Claims (7)
1. A preparation method of a carbon-coated silica negative electrode material is characterized by comprising the following steps:
firstly, crushing SiO blocky bodies, crushing the blocky SiO into powder by using a crusher, screening the powder with proper granularity by using a sample separation sieve, placing the powder into a ball milling tank, controlling the ball milling speed to be 300-600rpm, selecting balls with the diameter of 6-10mm, and controlling the ball-material ratio to be 4-10 to perform wet ball milling for 2-8h;
secondly, preparing a mixed precursor, taking pitch and SiO, controlling the ratio of SiO to pitch to be 1;
step three, carbonization coating, including primary coating, ball milling homogenization and secondary coating carbonization: placing the mixed precursor in the second step into a corundum ark, then placing the corundum ark into a vacuum tube furnace, introducing protective gas, heating to 800-1100 ℃ at the speed of 3-8 ℃/min, preserving heat for 1-4h, and cooling to room temperature to obtain a composite intermediate; ball milling and homogenizing: taking out the composite intermediate obtained by primary coating, placing the composite intermediate in a ball milling tank, controlling the ball milling rotation speed to be 250-400rpm, selecting balls with the diameter of 6-10mm and the ball-material ratio to be 4-10, and performing wet ball milling for 1-4h to obtain the homogeneous composite intermediate; secondary coating carbonization, placing the composite intermediate after ball milling homogenization in a corundum ark again, placing the corundum ark in a vacuum tube furnace, introducing protective gas, heating to 800-1100 ℃, keeping the temperature for 1-4h, cooling to room temperature, ball milling and granulating the compound after high-temperature carbonization, controlling the ball milling rotation speed to be 250-400rpm, selecting balls with the diameter of 6-10mm and controlling the ball-to-material ratio to be 4-10, and performing wet ball milling for 1-4h to obtain the carbon-coated silicon oxide composite negative electrode material;
and fourthly, preparing an electrode, namely taking a powdery silicon oxide composite negative electrode material, uniformly mixing the powdery silicon oxide composite negative electrode material with a mixture of conductive carbon black and carbon nano tubes and styrene butadiene rubber according to a mass ratio of 90.
2. The method for preparing the carbon-coated silica negative electrode material according to claim 1, wherein the method comprises the following steps: in the wet ball milling process, the ball milling medium is deionized water or alcohol.
3. The method for preparing the carbon-coated silica negative electrode material according to claim 1, wherein the method comprises the following steps: in the first step, when the median diameter D50 of SiO is 0.1-1 μm, the preparation process of the second step is carried out.
4. The method for preparing the carbon-coated silica negative electrode material according to claim 1, wherein the method comprises the following steps: the molar ratio of O to Si in the bulk SiO is 0.85-1.15.
5. The preparation method of the carbon-coated silicon-oxygen negative electrode material according to claim 1, characterized in that: the softening point of the asphalt in the second step is 200-300 ℃, and the ash content is less than 0.05%.
6. The method for preparing the carbon-coated silica negative electrode material according to claim 1, wherein the method comprises the following steps:
in the fourth step, the vacuum drying temperature is 80 ℃.
7. The method for preparing the carbon-coated silica negative electrode material according to claim 1, wherein the method comprises the following steps: the protective gas is nitrogen or inert gas.
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| CN113948683B (en) * | 2020-07-17 | 2023-03-03 | 河南省氟基新材料科技有限公司 | Silicon monoxide composite negative electrode material and preparation method and application thereof |
| CN113140714B (en) * | 2021-03-30 | 2022-04-15 | 苏州优源动力科技有限公司 | Method for producing silicon-oxygen cathode material by liquid phase coating and two-stage calcining method |
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