CN110112376B - Preparation method and application of porous silicon oxide/carbon composite negative electrode material - Google Patents

Preparation method and application of porous silicon oxide/carbon composite negative electrode material Download PDF

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CN110112376B
CN110112376B CN201910228988.XA CN201910228988A CN110112376B CN 110112376 B CN110112376 B CN 110112376B CN 201910228988 A CN201910228988 A CN 201910228988A CN 110112376 B CN110112376 B CN 110112376B
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carbon
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禹筱元
许东辉
陈文艳
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South China Agricultural University
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    • H—ELECTRICITY
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Abstract

The invention discloses a porous silicon monoxide/carbon composite negative electrode material, which is prepared by taking a biomass material rich in silicon element as a silicon carbon source, cleaning and crushing the silicon carbon source, calcining the crushed powder in air atmosphere, adding a copper chloride solution as an activating agent, and performing activation treatment to obtain active precursor powder SiO2Adding metal powder as a reducing agent, mixing, and carrying out high-temperature reaction to obtain the catalyst; the silicon carbon source used in the invention is derived from the biomass material, other modification substances are not required to be added, the source is wide, and the cost is low; the method for preparing the porous silicon oxide/carbon composite anode material is simple to operate, and the problem of volume change of the silicon-based anode material can be well solved by utilizing the natural hierarchical porous structure of the biomass; when the porous silicon oxide/carbon composite negative electrode material obtained by the method is applied to a negative electrode plate of a lithium ion battery, the battery has large specific capacity and good cycle performance and rate capability.

Description

Preparation method and application of porous silicon oxide/carbon composite negative electrode material
Technical Field
The invention belongs to the technical field of electrochemistry and new energy materials. In particular to a preparation method and application of a porous silicon oxide/carbon composite anode material.
Background
Lithium ion batteries, which have been successfully developed in the last century, have the advantages of high capacity density, high operating voltage, no memory effect, long cycle life, no pollution and the like, and gradually replace conventional secondary batteries, and are widely applied to various fields of military and civil small-sized electrical appliances (such as mobile phones, portable computers, cameras and the like). With the development and popularization of new-generation electronic products such as fast-charging mobile phones and new energy automobiles, people have made higher requirements on power lithium ion batteries of the products: high power output, long service life and high safety and stability. However, the current commercial graphite anode material cannot meet the increasing demand of the electronic product industry due to small specific capacity and low specific energy.
The silicon-based material has the advantages of high theoretical capacity, abundant reserves, environmental friendliness and the like, and is a hot spot of domestic and foreign research for replacing the traditional graphite material. However, although the theoretical capacity of the silicon-based material is high, the lattice volume expansion rate of the silicon negative electrode is as high as 300% (the same as that of the graphite material is only 10%) after charging and discharging, so that particle pulverization, material separation from a conductive agent and a bonding agent, and repeated regeneration of an SEI film are caused, and further the cycle performance is attenuated at a very high speed and finally inactivated. The problem can be solved by the silicon-based material with special morphology or modified, particularly the biomass-derived silicon-carbon composite material has wide source, low cost and environmental protection, and reports of being used in the fields of lithium battery materials and the like through a series of treatments are common.
CN1242502C discloses a silicon-aluminum alloy/carbon composite material for a lithium ion battery cathode and a preparation method thereof, wherein a two-step sintering method is adopted firstly, aluminum and silicon alloys are prepared, then an organic polymer is cracked, graphite powder is added into the organic polymer, then the reacted aluminum and silicon alloys are added to form slurry, and finally the slurry is obtained by heating reaction in a sealed system. The silicon-aluminum alloy/carbon cathode composite material prepared by the method obviously enhances the mechanical stability of the material, improves the cycling stability of the material and improves the electronic conductivity of silicon materials. However, the organic solvent used in the method is easy to cause harm to the environment and human body, and the used raw materials are more and the operation is complex.
CN103641118B discloses a production method for producing activated carbon with high specific surface area by using a composite activator, wherein the method takes rice hulls as biomass raw materials and prepares the activated carbon by using the composite activator of zinc chloride and copper chloride. Compared with the prior method for preparing the activated carbon with high specific surface area by the strong alkali method, the method reduces the application cost of the activating agent, reduces the reaction temperature for preparing the activated carbon, reduces the corrosivity to equipment, and saves the production energy consumption and the production cost. However, this method only involves the preparation of the novel composite activator, and does not involve the preparation of a silicon/carbon composite anode material.
Part of biomass sources contain about 10-20% of ash, wherein the proportion of silicon dioxide and silicic acid is large, for example, the proportion of silicon dioxide in the ash of rice husks is as high as 98%, the silicon dioxide and carbon in biomass such as bamboo leaves are mutually surrounded and form special hierarchical mesopores and micropores, and the biomass material which is not subjected to activation treatment cannot be utilized because the silicon dioxide is coated by the carbon, so that the key for better utilizing the biomass raw material is to find a proper method for carrying out carbon activation treatment on the biomass material to expose the silicon dioxide in the material.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a preparation method of a porous silicon oxide/carbon composite negative electrode material, the method is simple to operate and strong in repeatability, the preparation process of the silicon-carbon composite material can be simplified, the preparation cost of the material can be reduced, and meanwhile, the problem of volume change of the silicon-based negative electrode material can be well relieved by utilizing the natural hierarchical porous structure of biomass; the porous silicon oxide/carbon composite anode material prepared by the method has the advantages of large specific surface area, high conductivity of a carbon layer and a special hierarchical porous structure of biomass; the lithium ion battery prepared by using the porous silicon oxide/carbon composite negative electrode material has large specific capacity and better cycle performance and rate capability.
The second purpose of the invention is to provide the application of the porous silicon oxide/carbon composite anode material.
The above purpose of the invention is realized by the following technical scheme:
a preparation method of a porous silicon oxide/carbon composite anode material is characterized in that a biomass material rich in silicon element is used as a silicon carbon source, the material is cleaned and crushed, the crushed powder is placed in an air atmosphere for calcination, then a copper chloride solution is added as an activating agent for activation treatment to obtain active precursor powder, and metal powder is added as a reducing agent for mixing and then subjected to high-temperature reaction to obtain the porous silicon oxide/carbon composite anode material.
In general, silicon dioxide and carbon in the biomass material surround each other to form a specific hierarchical mesoporous and microporous structure, and the biomass material which is not subjected to activation treatment cannot be subjected to reduction reaction well due to the fact that the silicon dioxide is coated by the carbon and a silicon carbon material is directly prepared.
The preparation method of the porous silicon monoxide/carbon composite negative electrode material is a composite material with excellent electrochemical performance, which is prepared by modifying a silicon carbon material and reducing silicon dioxide in the silicon carbon material through a calcination and metal reduction method on the basis of thinning and activating a biomass material; the method can simplify the preparation process of the silicon-carbon composite material, reduce the preparation cost of the material, and well utilize the natural hierarchical porous structure of the biomass to relieve the volume change problem of the silicon-based negative electrode material; the porous silicon oxide/carbon composite negative electrode material prepared by the method can effectively maintain the stability of the material in the charging and discharging process and relieve the problem of volume change, and when the porous silicon oxide/carbon composite negative electrode material is used for a negative electrode plate of a lithium ion battery, the battery has large specific capacity, high safety coefficient, and better cycle performance and rate capability.
Preferably, the biomass material is any one or more of bamboo, crop chaff, crustacean shells and reed catkins.
Specifically, the size of the crushed biomass material is 70-120 meshes, and the specific surface area is 50-150 m2(ii)/g; the specific surface area of the activated and carbonized active precursor powder is 800-2300 m2/g。
Preferably, the cleaning is to wash the biomass material with deionized water, then fully stir the biomass material with 400-500 mL of 2mol/L hydrochloric acid solution at 80 ℃ for 8-10 hours, and obtain the biomass material after suction filtration and drying.
More preferably, the volume ratio of the biomass material powder to the hydrochloric acid solution is 1: 8-10.
Preferably, the pulverization is ball milling pulverization.
Preferably, the material ratio of the biomass material to the agate beads is 1: 20.
Further preferably, the ball milling rotating speed is 300-700 r/min, and the ball milling time is 10-12 hours.
More preferably, the rotation speed of the ball mill is 500 r/min.
In order to obtain the silicon-carbon composite negative electrode material with good performance, the content of the silicon element in the biomass material and the mass ratio of the silicon element to the carbon element can be controlled within a certain range.
Preferably, the content of silicon element in the biomass material is 5-20%.
In the invention, the temperature and the time for calcining the biomass material are required to be within a certain range so as to adjust the silicon-carbon ratio to be within a proper range.
Preferably, the reaction temperature of the air calcination is 400-500 ℃.
Preferably, the temperature rise rate of the air calcination is 8-12 ℃/min.
More preferably, the temperature rise rate of the air calcination is 10 ℃/min.
Preferably, the calcining time is 20-30 min.
Preferably, the mass ratio of the silicon element to the carbon element in the biomass material after combustion is 1: 4-5.
In order to expose the silica as much as possible, the molar concentration of the activating agent copper chloride solution and the ratio of the biomass material to the copper chloride can be selected according to actual needs.
Preferably, the molar concentration of the copper chloride solution is 0.3-0.8 mol/L.
Preferably, the mass ratio of the biomass material to the copper chloride is 1: 2-8.
Further preferably, the mass ratio of the biomass material to the copper chloride is 1: 2-6.
More preferably, the mass ratio of the biomass material to the copper chloride is 1: 5.
The type of the metal powder capable of serving as the reducing agent and the molar ratio of the silicon dioxide to the metal powder can be selected according to actual needs so as to obtain the silicon-carbon composite negative electrode material with the biomass characteristic structure.
Preferably, the metal powder is magnesium powder and/or aluminum powder.
Specifically, the particle size of the metal powder is 200-400 meshes.
Preferably, the molar ratio of silicon dioxide to metal powder in the active precursor powder is 1: 0.85-1.25.
More preferably, the grinding and mixing time of the precursor powder and the metal powder is 0.5-1 hour.
Preferably, the high temperature reaction is carried out under a protective gas.
Further preferably, the protective gas is nitrogen or argon.
More preferably, the temperature of the high-temperature reaction is 700-900 ℃.
The invention also claims the porous silicon oxide/carbon composite negative electrode material prepared by the preparation method.
In addition, the application of the porous silicon oxide/carbon composite negative electrode material in the preparation of the lithium ion battery is also in the scope of the protection of the application.
The lithium ion battery is prepared by mixing a composite material, conductive carbon black and sodium alginate according to a mass ratio of 7:2:1, adding water, uniformly stirring, coating on an aluminum foil, and then drying in vacuum to obtain a silicon-carbon composite material electrode plate, wherein the silicon-carbon composite material is used as a battery cathode, a metal lithium plate is used as an anode, an electrolyte is a 1M LiPF6/(EC + DMC) (volume ratio of 1:1) mixed system, a diaphragm is a microporous polypropylene film (Celgard2400), and the 2025 type button cell can be assembled in a glove box filled with argon (Ar).
The porous silicon oxide/carbon composite negative electrode material prepared by the inventor through creative labor has the advantages of large specific surface area, specific hierarchical porous structure of biomass, high conductivity of a carbon layer, large specific capacity of a battery when being used as a negative electrode plate of a lithium ion battery, and excellent cycle performance and rate capability.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, the biomass is used as a raw material, the used silicon carbon source is derived from the biomass, other modifying substances are not required to be added, the source is wide, and the cost is low; the method for preparing the porous silicon monoxide/carbon composite anode material is simple to operate and strong in repeatability, can simplify the preparation process of the silicon carbon composite material, reduce the preparation cost of the material, and simultaneously well utilizes the natural hierarchical porous structure of the biomass to relieve the volume change problem of the silicon-based anode material; when the porous silicon oxide/carbon composite negative electrode material obtained by the method is applied to a negative electrode plate of a lithium ion battery, the battery has large specific capacity and good cycle performance and rate capability.
Drawings
Fig. 1 is a Scanning Electron Microscope (SEM) image of the silicon-carbon composite negative electrode material prepared from the bamboo shoot shell in example 1.
Fig. 2 is a Scanning Electron Microscope (SEM) image of the silicon-carbon composite negative electrode material prepared from the bamboo leaves of example 2.
Fig. 3 is a powder diffraction (XRD) pattern of the silicon-carbon composite negative electrode material prepared from bamboo shoot shells in example 1.
FIG. 4 shows that the silicon-carbon composite negative electrode material prepared from bamboo shoot shells is 0.01-3.0V and 200mA g in example 1-1Graph of cycling performance at current density.
FIG. 5 shows that the silicon-carbon composite negative electrode material prepared from bamboo leaves in example 2 is 0.01-3.0V at 200mA g-1Graph of cycling performance at current density.
FIG. 6 shows that the silicon-carbon composite negative electrode material prepared from reed floc in example 3 is at 0.01-3.0V and 100mA g-1Graph of cycling performance at current density.
FIG. 7 is a graph showing the rate performance of the silicon-carbon composite negative electrode material prepared from bamboo shoot shells at 0.01-3.0V in example 1, wherein the current densities are 100mA g-1、200mA g-1、300mA g-1、500mA g-1、1000mA g-1、2000m A g-1、3000m A g-1。
FIG. 8 is a graph showing the rate performance of the silicon-carbon composite negative electrode material prepared from bamboo leaves in example 2 at 0.01-3.0V, wherein the current densities are 100mA g-1、200mA g-1、300mA g-1、500mA g-1、1000mA g-1、2000mA g-1、3000mA g-1。
FIG. 9 is a cyclic voltammetry curve of the silicon-carbon composite negative electrode material prepared from bamboo shoot shells in example 1 at 0.01-3.0V and a sweep rate of 0.2 mV/s.
FIG. 10 is a cyclic voltammetry curve of the silicon-carbon composite negative electrode material prepared from bamboo leaves in example 2 at 0.01-3.0V and a sweep rate of 0.2 mV/s.
Detailed Description
The invention is further described with reference to the drawings and the following detailed description, which are not intended to limit the invention in any way. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.
Unless otherwise indicated, reagents and materials used in the following examples are commercially available.
In the examples, the SEM analysis was performed using a Japanese Electron microscopy (JEOL) JSM-6380LA Scanning Electron Microscope (SEM) for observing the microscopic morphology of the surface of the sample at an acceleration voltage of 15KV, and the sample was dispersed with absolute ethanol, dropped onto the surface of a conductive paste, and dried in air.
The apparatus used for XRD analysis was an X-ray diffractometer (XRD) of Ultima type IV, manufactured by Japan science, Inc., for characterizing the crystal phase structure of the prepared final product. The test conditions are Cu target, K alpha radiation, 40kV and 40mA, step width is 0.02o, and scanning range is 5-80 o. The sample is powder, and the sample is directly detected after being placed in a groove of a sample table and flattened during detection.
The instrument used for the charge and discharge test is a BTS51800 battery test system of New Wille electronics Limited, Shenzhen, with the model of CT-3008W, and the charge and discharge test is carried out under the current density of 100-3000 mA/g within the voltage range of 0.01-3.0V.
Example 1 preparation method of bamboo shoot shell silicon carbon Material
A preparation method of a bamboo shoot shell silicon carbon material comprises the following steps:
crushing 20 g of dried bamboo shoot shells in a crusher and sieving, wherein the content of silicon element in the dried bamboo shoot shells is 15%; weighing 10 g of 70-mesh bamboo shoot shell powder, dispersing the powder into deionized water, washing and drying, uniformly adding 2mol/L hydrochloric acid solution, stirring in a water bath at 80 ℃ for 9 hours, cooling, performing suction filtration and washing, and drying to obtain cleaned powder for later use; then weighing 10 g of pickled bamboo shoot shell powder, and carrying out uniform ball milling on the pickled bamboo shoot shell powder for 11 hours in a planetary ball mill at a rotating speed of 500r/min to obtain small-particle ball-milled bamboo shoot shell powder;
placing the small-particle bamboo shoot shell powder in an air atmosphere, raising the temperature to 450 ℃ at the speed of 10 ℃/min, calcining for 25min, taking out, taking 5g of the small-particle bamboo shoot shell powder, dispersing in 250 ml of 0.5mol/L copper chloride solution, stirring, soaking for 24 h, heating to 60 ℃, starting to concentrate, transferring to a high-temperature tube furnace in an argon atmosphere after the volume of a concentrated solution is changed to 20 ml, raising the temperature to 500 ℃ at the speed of 10 ℃/min, preserving the heat for 1.5 h, taking out a sample, washing with 4mol/L hydrochloric acid until filtrate is colorless, washing with deionized water until the pH is neutral, and drying to obtain active precursor powder;
and (2) putting 0.5g of the active precursor powder into a mortar, adding 0.2g of simple substance aluminum powder, grinding and mixing uniformly for 1 hour, putting into a high-temperature tube furnace under the protection of argon atmosphere, raising the temperature to 700 ℃ at a speed of 10 ℃/min, calcining for 3 hours, taking out, dispersing the powder into deionized water, adding 2mol/L hydrochloric acid solution, performing suction filtration and washing until the pH value is neutral, and drying to obtain the biomass source (bamboo shoot shell) silicon-carbon composite negative electrode material.
Example 2 preparation method of bamboo leaf silicon carbon material
A preparation method of a bamboo leaf silicon carbon material comprises the following steps:
crushing 20 g of dried yellow bamboo leaves in a crusher, and sieving, wherein the content of silicon element in the dried yellow bamboo leaves is 5%; weighing 10 g of 100-mesh bamboo leaf powder, dispersing the bamboo leaf powder into deionized water, washing and drying, uniformly adding 2mol/L hydrochloric acid solution, stirring in a water bath at 80 ℃ for 8 hours, cooling, performing suction filtration and washing, and drying to obtain washed powder for later use; weighing 10 g of the bamboo leaf powder after the acid washing, placing the bamboo leaf powder in a planetary ball mill, and carrying out uniform ball milling for 10 hours at a rotating speed of 300r/min to obtain small-particle bamboo leaf powder after ball milling;
placing the small-particle bamboo leaf powder in an air atmosphere, raising the temperature to 400 ℃ at the speed of 8 ℃/min, calcining for 20min, taking out, dispersing 250 ml of 0.3mol/L copper chloride solution in 5g of small-particle bamboo leaf powder, stirring, soaking for 24 hours, heating to 60 ℃, starting to concentrate, transferring the concentrated solution to a high-temperature tube furnace in the argon atmosphere after the volume of the concentrated solution is changed to 20 ml, raising the temperature to 550 ℃ at the speed of 10 ℃/min, preserving the heat for 1.5 hours, taking out a sample, washing the sample with 4mol/L hydrochloric acid until the filtrate is colorless, washing with deionized water until the pH is neutral, and drying to obtain active precursor powder;
putting 0.5g of active precursor powder into a mortar, adding 0.28g of simple substance aluminum powder, grinding and mixing uniformly for 1 hour, putting into a high-temperature tube furnace under the protection of argon atmosphere, raising the temperature to 700 ℃ at a speed of 10 ℃/min, calcining for 3 hours, taking out, dispersing the powder in deionized water, adding 2mol/L hydrochloric acid solution, carrying out suction filtration and washing until the pH value is neutral, and drying to obtain the biomass source (bamboo leaf) silicon-carbon composite negative electrode material.
Example 3 preparation method of silicon carbon material from reed batting
A preparation method of a reed floc silicon carbon material comprises the following steps:
crushing 20 g of dried reed floc in a crusher and then sieving, wherein the content of silicon element in the dried reed floc is 20%; weighing 10 g of 120-mesh reed floc powder, dispersing the powder into deionized water, washing and drying, uniformly adding a 2mol/L hydrochloric acid solution, stirring in a water bath at 80 ℃ for 10 hours, cooling, performing suction filtration and washing, and drying to obtain cleaned powder for later use; then weighing 10 g of the reed catkin powder after acid washing, and carrying out uniform ball milling for 12 hours in a planetary ball mill at the rotating speed of 700r/min to obtain small-particle reed catkin powder after ball milling;
placing the small-particle reed floc powder in an air atmosphere, raising the temperature to 500 ℃ at the speed of 12 ℃/min, calcining for 30min, taking out, taking 5g of the small-particle reed floc powder, dispersing 250 ml of 0.8mol/L copper chloride solution, stirring, soaking for 24 hours, heating to 60 ℃, starting concentration, transferring the concentrated solution to a high-temperature tube furnace in the argon atmosphere after the volume of the concentrated solution is changed to 20 ml, raising the temperature to 550 ℃ at the speed of 10 ℃/min, preserving the heat for 1.5 hours, taking out a sample, washing the sample with 4mol/L hydrochloric acid until filtrate is colorless, washing with deionized water until the pH is neutral, and drying to obtain active precursor powder;
putting 0.5g of active precursor powder into a mortar, adding 0.2g of simple substance magnesium powder, grinding and mixing uniformly for 1 hour, putting into a high-temperature tube furnace under the protection of argon atmosphere, raising the temperature to 700 ℃ at a speed of 10 ℃/min, calcining for 3 hours, taking out, dispersing the powder in deionized water, adding 2mol/L hydrochloric acid solution, carrying out suction filtration and washing until the pH value is neutral, and drying to obtain the biomass source (reed catkin) silicon-carbon composite negative electrode material.
Comparative example 1
This comparative example is substantially the same as example 1 except that the concentration of the copper chloride solution was 1.0 mol/L.
Comparative example 2
This comparative example is substantially the same as example 1 except that the concentration of the copper chloride solution was 0.2 mol/L.
Comparative example 3
This comparative example is essentially the same as example 1 except that the biomass material was not subjected to combustion in air for a period of time.
Comparative example 4
This comparative example is essentially the same as example 1, except that the molar ratio of silica to metal powder in the active precursor powder is 1: 0.5.
Comparative example 5
This comparative example is essentially the same as example 1 except that the mass of biomass material to volume ratio of copper chloride solution was 1: 10.
Performance testing
Method and device
Mixing the bamboo shoot shell silicon-carbon composite negative electrode material prepared in the example 1 with conductive carbon black and sodium alginate according to the mass ratio of 7:2:1, adding a proper amount of deionized water, uniformly stirring, coating the mixture on a copper foil, drying the copper foil in a vacuum oven at 90 ℃, and cutting the copper foil on a sheet punching machine to obtain the bamboo shoot shell silicon-carbon composite negative electrode material electrode sheet. The obtained electrode is used as a negative electrode, a metal lithium sheet is used as a positive electrode, the electrolyte is a mixed system containing 1M LiPF6/(EC-DMC) (the volume ratio is 1:1), the diaphragm is a microporous polypropylene film (Celgard2400), a 2025 type button cell is assembled in a glove box filled with argon (Ar), and a charge and discharge performance test is carried out by using a BTS51800 cell test system of New Will electronics Limited, Shenzhen.
Mixing the bamboo leaf silicon-carbon composite negative electrode material prepared in the example 2 with conductive carbon black and sodium alginate according to the mass ratio of 7:2:1, adding a proper amount of deionized water, uniformly stirring, coating the mixture on a copper foil, drying the copper foil in a vacuum oven at 90 ℃, and cutting the copper leaf silicon-carbon composite negative electrode material on a sheet punching machine to obtain the bamboo leaf silicon-carbon composite negative electrode material electrode sheet. The obtained electrode is used as a negative electrode, a metal lithium sheet is used as a positive electrode, the electrolyte is a mixed system containing 1M LiPF6/(EC-DMC) (the volume ratio is 1:1), the diaphragm is a microporous polypropylene film (Celgard2400), a 2025 type button cell is assembled in a glove box filled with argon (Ar), and a charge and discharge performance test is carried out by using a BTS51800 cell test system of New Will electronics Limited, Shenzhen.
And (2) mixing the silicon-carbon composite negative electrode material prepared from the reed floc obtained in the example 3 with conductive carbon black and sodium alginate according to the mass ratio of 7:2:1, adding a proper amount of deionized water, uniformly stirring, coating the mixture on a copper foil, drying the copper foil in a vacuum oven at 90 ℃, and cutting the copper foil on a sheet punching machine to obtain the silicon-carbon composite negative electrode material electrode sheet prepared from the reed floc. The obtained electrode is used as a negative electrode, a metal lithium sheet is used as a positive electrode, the electrolyte is a mixed system containing 1M LiPF6/(EC-DMC) (the volume ratio is 1:1), the diaphragm is a microporous polypropylene film (Celgard2400), a 2025 type button cell is assembled in a glove box filled with argon (Ar), and a charge and discharge performance test is carried out by using a BTS51800 cell test system of New Will electronics Limited, Shenzhen.
Second, result in
After the bamboo shoot shell in the embodiment 1 is combusted, the mass ratio of the silicon element to the carbon element is 1:4.5, the silicon-carbon material of the bamboo shoot shell prepared in the embodiment 1 is shown in fig. 1, the charge and discharge performance test results of the material are shown in fig. 3, fig. 4, fig. 7 and fig. 9, and it can be seen from fig. 3 and fig. 4 that the first discharge specific capacity of the material under the current density of 0.01-3.0V and 200mA/g can reach 3500mAh/g, and the first discharge specific capacity can still keep 1300mAh/g after 250 times of cyclic discharge, which indicates that the material has better electrochemical cycle performance; as can be seen from fig. 7, after the material undergoes high-rate charge-discharge cycling, the capacity of the material remains stable when the material returns to low-current charge-discharge, which indicates that the material has better rate performance; fig. 9 is a cyclic voltammogram of the material, and a characteristic peak position of the material reaction and good electrochemical cycling performance can be observed.
After the bamboo leaves in the embodiment 2 are combusted, the mass ratio of silicon element to carbon element is 1:4, the bamboo leaf silicon-carbon material prepared in the embodiment 2 is shown in fig. 2, the charge and discharge performance test results of the material are respectively shown in fig. 5, fig. 8 and fig. 10, and as can be seen from fig. 2 and fig. 5, the material has a first discharge specific capacity of 1500mAh/g under the current density of 200mA/g and 0.01-3.0V, has a discharge specific capacity of 1100mAh/g after 350 times of circulation, and has a good electrochemical circulation performance; as can be seen from fig. 8, after the material undergoes high-rate charge-discharge cycling, the capacity of the material remains stable when the material returns to low-current charge-discharge, which indicates that the material has better rate performance; fig. 10 is a cyclic voltammogram of a material, and a characteristic peak position of a material reaction and good electrochemical cycling performance can be observed.
After the reed floc in the embodiment 3 is combusted, the mass ratio of silicon element to carbon element is 1:5, the charge and discharge performance test result of the silicon-carbon material prepared in the embodiment 3 is shown in fig. 6, and it can be seen from fig. 6 that the material has a first discharge specific capacity of 1100mAh/g under the current density of 0.01-3.0V and 100mA/g, and still has a 600mAh/g specific capacity after 90 times of cyclic discharge, and has a better electrochemical cycle performance.
The bamboo shoot shell silicon carbon material obtained in the comparative example 1 has the first discharge specific capacity of 2200mAh/g under the current density of 0.01-3.0V and 200mA/g, but the specific capacity is only 500mAh/g after 100 times of cyclic discharge, which indicates that the material has poor electrochemical stability; meanwhile, after high-rate charge-discharge circulation, the capacity of the material is attenuated to 400mAh/g when the material returns to low-current charge-discharge, which shows that the material has no good rate performance; the reason for the above phenomena is mainly that the carbon layer structure inside the material collapses due to excessive copper chloride etching, the biomass silicon-carbon composite structure of the material itself is damaged, and the problem of volume expansion of silicon-based particles cannot be effectively alleviated.
The bamboo shoot shell silicon carbon material obtained in the comparative example 2 has the first discharge specific capacity of only 1400mAh/g under the current density of 0.01-3.0V and 200mA/g, and 820mAh/g is reserved after 100 times of cyclic discharge specific capacity, which indicates that the material has good electrochemical cyclicity; after high-rate charge-discharge circulation, the capacity of the material is reserved at 750mAh/g when the material returns to low-current charge-discharge, and the material has good rate performance. The reason why the phenomenon occurs is probably that the etching degree is low due to the low concentration of copper chloride, the contact surface of silicon dioxide is less in the metal reduction process, and the activation degree of a carbon layer is low, so that the prepared material has low discharge capacity.
The material obtained in the comparative example 3 has the first discharge specific capacity of only 1100mAh/g under the current density of 200mA/g and the first discharge specific capacity of only 650mAh/g after 100 times of cyclic discharge, and has the capacity of only 620mAh/g when the material returns to low-current charge and discharge after high-rate charge and discharge circulation, so that the material has good rate capability. The reason for this phenomenon is that: the material which is not calcined in the air can not expose out the silicon dioxide inside to effectively contact the metal powder, and the theoretical capacity of the material is too low due to too high carbon content.
The material obtained by the comparative example 4 has a first discharge specific capacity of only 680mAh/g under the current density of 0.01-3.0V and 200mA/g, and only 520mAh/g is reserved after 100 times of cyclic discharge specific capacity, so that the material has good stability but low capacity, and the main reason is that the metal powder has too little molar quantity, only a small part of silicon dioxide is reduced into silicon protoxide, and the silicon dioxide has low conductivity and low theoretical capacity, so that the specific capacity of the prepared material is low finally.
The first discharge specific capacity of the bamboo shoot shell silicon carbon material obtained in the comparative example 5 under the current density of 0.01-3.0V and 200mA/g reaches 3400mAh/g, but the first discharge specific capacity is only 1100mAh/g after 100 times of cyclic discharge and the capacity is continuously attenuated, and the first discharge specific capacity is only about 600mAh/g after 200 times of cyclic discharge; and after high-rate charge-discharge circulation, the capacity of the material is attenuated to 720mAh/g when the material returns to low-current charge-discharge, which shows that the material has no good rate performance and electrochemical circulation stability, and the main reasons are that the copper chloride solution has large molar quantity, the concentration of the solution is rapidly increased after concentration, the etching degree of the copper chloride is too high, the porous structure of the material and the carbon layer coating structure are damaged, and the structural stability of the material is poor.
According to the results, the porous silicon oxide/carbon composite negative electrode material prepared by the method can effectively maintain the stability of the material in the charging and discharging processes, and relieve the problem of volume change, and when the porous silicon oxide/carbon composite negative electrode material is used for a negative electrode plate of a lithium ion battery, the battery has large specific capacity, high safety coefficient, and good cycle performance and rate capability.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (5)

1. A preparation method of a porous silicon oxide/carbon composite negative electrode material is characterized in that a biomass material rich in silicon element is used as a silicon carbon source, the silicon carbon source is cleaned and crushed, the crushed powder is placed in an air atmosphere for calcination, and then a copper chloride solution is added as an activating agent for activation treatment to obtain active precursor powder SiO2Adding metal powder as a reducing agent, mixing, and carrying out high-temperature reaction to obtain the catalyst;
the biomass material is any one or more of bamboo wood, crustacean shells and reed floc;
the content of silicon element in the biomass material is 5-20%;
the reaction temperature of air calcination is 400-500 ℃; the calcining time is 20-30 min;
the mass ratio of the biomass material to the copper chloride is 1: 2-8; the molar concentration of the copper chloride solution is 0.3-0.8 mol/L;
the molar ratio of silicon dioxide to metal powder in the active precursor powder is 1: 0.85-1.25.
2. The preparation method according to claim 1, wherein the mass ratio of the silicon element to the carbon element in the biomass material after combustion is 1: 4-5.
3. The production method according to claim 1, wherein the metal powder is magnesium powder and/or aluminum powder.
4. The porous silicon oxide/carbon composite negative electrode material prepared by the preparation method of any one of claims 1 to 3.
5. Use of the porous silica/carbon composite anode material of claim 4 in the preparation of lithium ion batteries.
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