CN118099402A - Spherical graphite/silicon anode material and preparation method and application thereof - Google Patents
Spherical graphite/silicon anode material and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a spherical graphite/silicon anode material, and a preparation method and application thereof, and belongs to the technical field of anode materials. Preparing silicon dioxide coated graphite microspheres through sol-gel reaction, coating graphene oxide on the surface, carrying out magnesiothermic reduction, doping Ti element to prepare Ti doped graphite/graphene/defective silicon microspheres, and then depositing carbon quantum dots on the surface to prepare the spherical graphite/silicon anode material. The spherical graphite/silicon anode material prepared by the invention has higher energy and power density, improves the conductivity of the battery, ensures higher charge and discharge efficiency of the battery, has good chemical stability and mechanical strength and better safety, and effectively resists side reactions of the electrode material, thereby improving the cycle life of the battery and having wide application prospect.
Description
Technical Field
The invention relates to the technical field of negative electrode materials, in particular to a spherical graphite/silicon negative electrode material, and a preparation method and application thereof.
Background
Lithium ion batteries are widely used in the field of 3C consumer electronics. The graphite material has good conductivity, high crystallinity and good lamellar structure, is suitable for intercalation-deintercalation of lithium, has theoretical capacity of 372 mAh g -1, has low irreversible capacity and charge-discharge efficiency of more than 90 percent, and is the anode material most widely applied to the current lithium ion battery. However, the main process of the current graphite anode material is that coke is crushed, shaped, granulated, graphitized and the like, the morphology of the final anode material is very different, the uniformity is not strong, the carbon microsphere is used as a spherical particle, the multiplying power performance is better, the isotropy is very good as a sphere, and the carbon microsphere is the best choice as the anode material. However, the manufacturing process of the carbon microsphere is complicated, and it is difficult to manufacture a good quality sample and the cost is high.
Disclosure of Invention
The invention aims to provide a spherical graphite/silicon anode material, a preparation method and application thereof, which have higher energy and power density, improve the conductivity of a battery, ensure that the battery has higher charge and discharge efficiency, good chemical stability and mechanical strength, better safety and effectively resists side reactions of the electrode material, thereby improving the cycle life of the battery and having wide application prospect
The technical scheme of the invention is realized as follows:
the invention provides a preparation method of a spherical graphite/silicon anode material, which comprises the steps of preparing silicon dioxide coated graphite microspheres through sol-gel reaction, coating graphene oxide on the surfaces, carrying out magnesiothermic reduction, doping Ti element to prepare Ti doped graphite/graphene/defective silicon microspheres, and then depositing carbon quantum dots on the surfaces to prepare the spherical graphite/silicon anode material.
As a further improvement of the invention, the method comprises the following steps:
S1, preparing silicon dioxide coated graphite microspheres: adding spherical flake graphite into water, adding alkyl orthosilicate, stirring and mixing uniformly, adding petroleum ether, adding an emulsifying agent for emulsification, adjusting the pH value, stirring for reaction, centrifuging, washing and calcining to obtain silicon dioxide coated graphite microspheres;
s2, graphene oxide coating: adding the silicon dioxide coated graphite microspheres prepared in the step S1 into graphene oxide aqueous dispersion liquid, and spray-drying to prepare coated microspheres;
S3, magnesian reduction: uniformly mixing the coated microspheres prepared in the step S2 with magnesium, heating to react under the protection of inert gas, then cooling to room temperature, adding into an acid solution to soak, centrifuging, washing and drying to prepare graphene coated defective silicon microspheres;
S4, preparing Ti-doped graphite/graphene/defective silicon microspheres: adding the graphene coated defective silicon microsphere prepared in the step S3 into water, adding glucose, tetrabutyl titanate and sodium polyacrylate, heating, stirring, reacting, and graphitizing to prepare Ti doped graphite/graphene/defective silicon microsphere;
s5, preparing a spherical graphite/silicon anode material: adding citric acid into water, heating and stirring for reaction for the first time, regulating the pH value of the solution, dialyzing, adding the Ti-doped graphite/graphene/defective silicon microsphere prepared in the step S4, heating and stirring for reaction for the second time, centrifuging, washing and drying to obtain the spherical graphite/silicon anode material.
As a further improvement of the invention, in the step S1, the mass ratio of the spherical crystalline flake graphite to the alkyl orthosilicate to the emulsifier is 10-15:7-12:1-2, the alkyl orthosilicate is methyl orthosilicate or ethyl orthosilicate, the emulsifier is at least one selected from span-20, span-40, span-60 and span-80, the pH value is adjusted to 9-10, the stirring reaction time is 5-7h, the calcining temperature is 400-600 ℃ and the calcining time is 1-3h.
As a further improvement of the invention, in the step S2, the solid-to-liquid ratio of the silicon dioxide coated graphite microspheres to the graphene oxide aqueous dispersion is 1:3-5g/mL, the concentration of the graphene oxide aqueous dispersion is 0.5-1mg/mL, the spray drying condition is that the air inlet temperature is 80-100 ℃, the air outlet temperature is 30-50 ℃, and the evaporation water quantity is 1500-2000mL/h.
As a further improvement of the invention, in the step S3, the mass ratio of the coated microsphere to the magnesium is 1:1.2-1.5, the heating rate of the heating reaction is 4-7 ℃/min, the temperature is raised to 450-550 ℃, the constant temperature reaction is carried out for 20-30min, then the temperature is raised to 650-750 ℃ at the heating rate of 5-7 ℃/min, the constant temperature reaction is carried out for 120-180min, the cooling rate of the solution to room temperature is 5-10 ℃/min, the acid solution is 5-10wt% hydrochloric acid or sulfuric acid solution, and the soaking time is 15-25min.
As a further improvement of the present invention, the mass ratio of the graphene coated defective silicon microsphere, glucose, tetrabutyl titanate and sodium polyacrylate in step S4 is 10:2-3:0.5-1:1-2, wherein the temperature of the heating and stirring reaction is 110-120 ℃, the reaction time is 10-12h, the graphitization temperature is 1100-1300 ℃, and the reaction time is 1-3h.
As a further improvement of the invention, in the step S5, the mass ratio of the citric acid to the water to the Ti-doped graphite/graphene/defective silicon microspheres is 1:20-40:4-6, the pH value of the solution is regulated to 6.9-7.1, the aperture of a dialysis bag used for dialysis is 5k-7kDa, the dialysis time is 12-15h, the temperature of the first heating and stirring reaction is 190-210 ℃ for 20-30min, the temperature of the second heating and stirring reaction is 170-190 ℃ for 100-150min.
As a further improvement of the invention, the method specifically comprises the following steps:
S1, preparing silicon dioxide coated graphite microspheres: adding 10-15 parts by weight of spherical crystalline flake graphite into 100 parts by weight of water, adding 7-12 parts by weight of methyl orthosilicate or ethyl orthosilicate, stirring and mixing uniformly, adding 200 parts by weight of petroleum ether, adding 1-2 parts by weight of emulsifying agent, emulsifying, adjusting the pH value to 9-10, stirring and reacting for 5-7 hours, centrifuging, washing, and calcining at 400-600 ℃ for 1-3 hours to obtain silicon dioxide coated graphite microspheres;
S2, graphene oxide coating: adding the silica coated graphite microsphere prepared in the step S1 into 0.5-1mg/mL graphene oxide aqueous dispersion, wherein the solid-to-liquid ratio of the silica coated graphite microsphere to the graphene oxide aqueous dispersion is 1:3-5g/mL, and spray drying to prepare the coated microsphere;
The spray drying condition is that the air inlet temperature is 80-100 ℃, the air outlet temperature is 30-50 ℃ and the evaporation water quantity is 1500-2000mL/h;
S3, magnesian reduction: uniformly mixing 10 parts by weight of the coated microsphere prepared in the step S2 with 12-15 parts by weight of magnesium, under the protection of inert gas, heating to 450-550 ℃ at a heating rate of 4-7 ℃/min, reacting at a constant temperature for 20-30min, heating to 650-750 ℃ at a heating rate of 5-7 ℃/min, reacting at a constant temperature for 120-180min, cooling to room temperature at a cooling rate of 5-10 ℃/min, adding 100 parts by weight of 5-10wt% hydrochloric acid or sulfuric acid solution, soaking for 15-25min, centrifuging, washing, and drying to obtain the graphene coated defective silicon microsphere;
S4, preparing Ti-doped graphite/graphene/defective silicon microspheres: adding 10 parts by weight of the graphene coated defect silicon microsphere prepared in the step S3 into 100 parts by weight of water, adding 2-3 parts by weight of glucose, 0.5-1 part by weight of tetrabutyl titanate and 1-2 parts by weight of sodium polyacrylate, heating to 110-120 ℃, stirring and reacting for 10-12 hours, and heating to 1100-1300 ℃ and graphitizing for 1-3 hours to prepare the Ti doped graphite/graphene/defect silicon microsphere;
S5, preparing a spherical graphite/silicon anode material: adding 10 parts by weight of citric acid into 200-400 parts by weight of water, heating to 190-210 ℃, stirring and reacting for 20-30min, adjusting the pH value of the solution to 6.9-7.1, dialyzing for 12-15h by adopting a dialysis bag with the aperture of 5k-7kDa, then adding 40-60 parts by weight of the Ti-doped graphite/graphene/defective silicon microsphere prepared in the step S4, heating to 170-190 ℃, stirring and reacting for 100-150min, centrifuging, washing and drying to prepare the spherical graphite/silicon anode material.
The invention further protects the spherical graphite/silicon anode material prepared by the preparation method.
The invention further protects application of the spherical graphite/silicon anode material in preparation of a lithium ion battery anode.
The invention has the following beneficial effects:
The natural crystalline flake graphite is widely available and low in price, and is used as a negative electrode material, so that the production cost of the battery is reduced. However, the interlayer bonding energy of natural graphite is only 16.7kJ/mol, and the graphite flakes are easily peeled off during repeated charge and discharge, resulting in poor cycle performance. In addition, the electrolyte has the defects of low specific capacity, poor compatibility with electrolyte, unsatisfactory rate performance and the like. According to the invention, the natural crystalline flake graphite microspheres are coated with silicon dioxide to form a silicon dioxide layer with compact surface, and the silicon dioxide layer is further coated with graphene oxide, so that a wrinkled graphene oxide structure is formed by spray drying, the specific surface area is greatly increased, and a larger electrochemical reaction surface area can be provided, so that higher energy and power density are realized. Through magnesian reduction, silicon dioxide is reduced into Si simple substance, so that defects are formed at the position of an original O structure, insertion and extraction of lithium ions are facilitated, a stable structure can be formed, damage of a graphite structure is prevented, the defects of natural spherical graphite are overcome, graphene oxide is reduced into graphene to form an efficient electron transfer channel, the conductivity of a battery is improved, the charge and discharge efficiency of the battery is higher, meanwhile, the battery has good chemical stability and mechanical strength, expansion and cracking are not easy to occur, side reactions of electrode materials can be effectively resisted, and the cycle life of the battery is prolonged.
After Ti is deposited by sol-gel reaction, the graphene coated defect silicon microsphere can obviously prolong the cycle life, has high structural stability, improves the charge-discharge cycle performance of the battery, ensures that lithium dendrites are difficult to generate on the surface of a negative electrode material, reduces the possibility of forming short circuits in a circuit by the lithium dendrites, and obviously improves the safety performance.
The surface of the Ti-doped graphite/graphene/defective silicon microsphere is further enriched with carbon quantum dots, the carbon quantum dots are carbon nano particles with the size smaller than 10nm, the structure of a carbon layer is changed by embedding the quantum dots, the interlayer spacing of graphite carbon is increased, the rapid migration of Li + is facilitated, the high-current discharge capacity of a battery can be obviously improved, the cycling stability of a graphite electrode is enhanced, ultra-rapid charging can be realized, the specific capacity is improved, and the adsorption and storage capacity of the whole material to lithium ions are enhanced; the mechanical stress generated by Li + in the deintercalation process is reduced, so that the structural integrity of the electrode is effectively protected and the ion diffusion distance is shortened.
The spherical graphite/silicon anode material prepared by the invention has higher energy and power density, improves the conductivity of the battery, ensures higher charge and discharge efficiency of the battery, has good chemical stability and mechanical strength and better safety, and effectively resists side reactions of the electrode material, thereby improving the cycle life of the battery and having wide application prospect.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Spherical flake graphite;
An aqueous dispersion of graphene oxide, 0.5mg/mL,
Example 1
The embodiment provides a preparation method of a spherical graphite/silicon anode material, which specifically comprises the following steps:
S1, preparing silicon dioxide coated graphite microspheres: adding 10 parts by weight of spherical crystalline flake graphite into 100 parts by weight of water, adding 7 parts by weight of methyl orthosilicate, stirring and mixing for 20min, adding 200 parts by weight of petroleum ether, adding 1 part by weight of span-20, emulsifying for 15min at 10000r/min, adjusting the pH value to 9, stirring and reacting for 5h, centrifuging, washing, and calcining at 400 ℃ for 1h to obtain silicon dioxide coated graphite microspheres;
S2, graphene oxide coating: adding the silicon dioxide coated graphite microsphere prepared in the step S1 into 0.5mg/mL graphene oxide aqueous dispersion liquid, wherein the solid-to-liquid ratio of the silicon dioxide coated graphite microsphere to the graphene oxide aqueous dispersion liquid is 1:3g/mL, and performing spray drying to obtain a coated microsphere;
The spray drying condition is that the air inlet temperature is 80 ℃, the air outlet temperature is 30 ℃ and the evaporation water quantity is 1500mL/h;
s3, magnesian reduction: uniformly mixing 10 parts by weight of the coated microsphere prepared in the step S2 with 12 parts by weight of magnesium, heating to 450 ℃ at a heating rate of 4 ℃/min under the protection of nitrogen, reacting at a constant temperature for 20min, heating to 650 ℃ at a heating rate of 5 ℃/min, reacting at a constant temperature for 120min, cooling to room temperature at a cooling rate of 5 ℃/min, adding 100 parts by weight of 5wt% sulfuric acid solution, soaking for 15min, centrifuging, washing, and drying to obtain the graphene coated defective silicon microsphere;
S4, preparing Ti-doped graphite/graphene/defective silicon microspheres: adding 10 parts by weight of the graphene coated defective silicon microsphere prepared in the step S3 into 100 parts by weight of water, adding 2 parts by weight of glucose, 0.5 part by weight of tetrabutyl titanate and 1 part by weight of sodium polyacrylate, heating to 110 ℃, stirring and reacting for 10 hours, and heating to 1100 ℃ to graphitize for 1 hour to prepare the Ti doped graphite/graphene/defective silicon microsphere;
S5, preparing a spherical graphite/silicon anode material: adding 10 parts by weight of citric acid into 200 parts by weight of water, heating to 190 ℃, stirring and reacting for 20min, adjusting the pH value of the solution to 6.9, dialyzing for 12h by adopting a dialysis bag with the aperture of 5kDa, then adding 40 parts by weight of the Ti-doped graphite/graphene/defective silicon microsphere prepared in the step S4, heating to 170 ℃, stirring and reacting for 100min, centrifuging, washing, and drying to obtain the spherical graphite/silicon anode material.
Example 2
The embodiment provides a preparation method of a spherical graphite/silicon anode material, which specifically comprises the following steps:
S1, preparing silicon dioxide coated graphite microspheres: adding 15 parts by weight of spherical crystalline flake graphite into 100 parts by weight of water, adding 12 parts by weight of ethyl orthosilicate, stirring and mixing for 20min, adding 200 parts by weight of petroleum ether, adding 2 parts by weight of span-40, emulsifying for 15min at 10000r/min, adjusting the pH value to 10, stirring and reacting for 7h, centrifuging, washing, and calcining at 600 ℃ for 3h to obtain silicon dioxide coated graphite microspheres;
S2, graphene oxide coating: adding the silicon dioxide coated graphite microsphere prepared in the step S1 into 0.5mg/mL graphene oxide aqueous dispersion liquid, wherein the solid-to-liquid ratio of the silicon dioxide coated graphite microsphere to the graphene oxide aqueous dispersion liquid is 1:5g/mL, and performing spray drying to obtain a coated microsphere;
The spray drying condition is that the air inlet temperature is 100 ℃, the air outlet temperature is 50 ℃ and the evaporation water quantity is 2000mL/h;
S3, magnesian reduction: uniformly mixing 10 parts by weight of the coated microsphere prepared in the step S2 with 15 parts by weight of magnesium, heating to 550 ℃ at a heating rate of 7 ℃/min under the protection of nitrogen, reacting at a constant temperature for 30min, heating to 750 ℃ at a heating rate of 7 ℃/min, reacting at a constant temperature for 180min, cooling to room temperature at a cooling rate of 10 ℃/min, adding 100 parts by weight of 10wt% hydrochloric acid solution, soaking for 25min, centrifuging, washing, and drying to obtain the graphene coated defective silicon microsphere;
S4, preparing Ti-doped graphite/graphene/defective silicon microspheres: adding 10 parts by weight of the graphene coated defective silicon microsphere prepared in the step S3 into 100 parts by weight of water, adding 3 parts by weight of glucose, 1 part by weight of tetrabutyl titanate and 2 parts by weight of sodium polyacrylate, heating to 120 ℃, stirring and reacting for 12 hours, and heating to 1300 ℃ to graphitize for 3 hours to prepare the Ti doped graphite/graphene/defective silicon microsphere;
S5, preparing a spherical graphite/silicon anode material: adding 10 parts by weight of citric acid into 400 parts by weight of water, heating to 210 ℃, stirring and reacting for 30min, adjusting the pH value of the solution to 7.1, dialyzing for 15h by adopting a dialysis bag with the aperture of 7kDa, then adding 60 parts by weight of the Ti-doped graphite/graphene/defective silicon microsphere prepared in the step S4, heating to 190 ℃, stirring and reacting for 150min, centrifuging, washing and drying to obtain the spherical graphite/silicon anode material.
Example 3
The embodiment provides a preparation method of a spherical graphite/silicon anode material, which specifically comprises the following steps:
S1, preparing silicon dioxide coated graphite microspheres: adding 12 parts by weight of spherical crystalline flake graphite into 100 parts by weight of water, adding 10 parts by weight of ethyl orthosilicate, stirring and mixing for 20min, adding 200 parts by weight of petroleum ether, adding 1.5 parts by weight of span-80, emulsifying for 15min at 10000r/min, adjusting the pH value to 9.5, stirring and reacting for 6h, centrifuging, washing, and calcining at 500 ℃ for 2h to obtain the silicon dioxide coated graphite microsphere;
s2, graphene oxide coating: adding the silicon dioxide coated graphite microspheres prepared in the step S1 into 0.5mg/mL graphene oxide aqueous dispersion liquid, wherein the solid-to-liquid ratio of the silicon dioxide coated graphite microspheres to the graphene oxide aqueous dispersion liquid is 1:4g/mL, and performing spray drying to obtain coated microspheres;
the spray drying condition is that the air inlet temperature is 90 ℃, the air outlet temperature is 40 ℃ and the evaporation water quantity is 1700mL/h;
S3, magnesian reduction: uniformly mixing 10 parts by weight of the coated microsphere prepared in the step S2 with 13 parts by weight of magnesium, heating to 500 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, reacting at a constant temperature for 25min, heating to 700 ℃ at a heating rate of 6 ℃/min, reacting at a constant temperature for 150min, cooling to room temperature at a cooling rate of 7 ℃/min, adding 100 parts by weight of 7wt% hydrochloric acid solution, soaking for 20min, centrifuging, washing, and drying to obtain the graphene coated defective silicon microsphere;
s4, preparing Ti-doped graphite/graphene/defective silicon microspheres: adding 10 parts by weight of the graphene coated defective silicon microsphere prepared in the step S3 into 100 parts by weight of water, adding 2.5 parts by weight of glucose, 0.7 part by weight of tetrabutyl titanate and 1.5 parts by weight of sodium polyacrylate, heating to 115 ℃, stirring and reacting for 11 hours, and heating to 1200 ℃ to graphitize for 2 hours to prepare the Ti-doped graphite/graphene/defective silicon microsphere;
S5, preparing a spherical graphite/silicon anode material: adding 10 parts by weight of citric acid into 300 parts by weight of water, heating to 200 ℃, stirring and reacting for 25min, adjusting the pH value of the solution to 7, dialyzing for 13h by adopting a dialysis bag with the aperture of 6kDa, then adding 50 parts by weight of the Ti-doped graphite/graphene/defective silicon microsphere prepared in the step S4, heating to 180 ℃, stirring and reacting for 125min, centrifuging, washing and drying to prepare the spherical graphite/silicon anode material.
Comparative example 1
In comparison with example 3, the difference is that step S1 is not performed.
The method comprises the following steps:
S1, graphene oxide coating: adding spherical crystalline flake graphite into 0.5mg/mL graphene oxide aqueous dispersion, wherein the solid-to-liquid ratio of the silicon dioxide coated graphite microspheres to the graphene oxide aqueous dispersion is 1:4g/mL, and spray drying to obtain coated microspheres;
the spray drying condition is that the air inlet temperature is 90 ℃, the air outlet temperature is 40 ℃ and the evaporation water quantity is 1700mL/h;
S2, magnesian reduction: uniformly mixing 10 parts by weight of the coated microsphere prepared in the step S1 with 13 parts by weight of magnesium, heating to 500 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, reacting at a constant temperature for 25min, heating to 700 ℃ at a heating rate of 6 ℃/min, reacting at a constant temperature for 150min, cooling to room temperature, cooling to 7 ℃/min, adding 100 parts by weight of 7wt% hydrochloric acid solution, soaking for 20min, centrifuging, washing, and drying to obtain the graphene coated defective silicon microsphere;
S3, preparing Ti-doped graphite/graphene coated microspheres: adding 10 parts by weight of the graphene coated defective silicon microsphere prepared in the step S2 into 100 parts by weight of water, adding 2.5 parts by weight of glucose, 0.7 part by weight of tetrabutyl titanate and 1.5 parts by weight of sodium polyacrylate, heating to 115 ℃, stirring and reacting for 11 hours, and heating to 1200 ℃ to graphitize for 2 hours to prepare the Ti-doped graphite/graphene coated microsphere;
S4, preparing a spherical graphite/silicon anode material: adding 10 parts by weight of citric acid into 300 parts by weight of water, heating to 200 ℃, stirring and reacting for 25min, adjusting the pH value of the solution to 7, dialyzing for 13h by adopting a dialysis bag with the aperture of 6kDa, then adding 50 parts by weight of the Ti-doped graphite/graphene coated microsphere prepared in the step S3, heating to 180 ℃, stirring and reacting for 125min, centrifuging, washing and drying to prepare the spherical graphite/silicon anode material.
Comparative example 2
In comparison with example 3, the difference is that step S2 is not performed.
The method comprises the following steps:
S1, preparing silicon dioxide coated graphite microspheres: adding 12 parts by weight of spherical crystalline flake graphite into 100 parts by weight of water, adding 10 parts by weight of ethyl orthosilicate, stirring and mixing for 20min, adding 200 parts by weight of petroleum ether, adding 1.5 parts by weight of span-80, emulsifying for 15min at 10000r/min, adjusting the pH value to 9.5, stirring and reacting for 6h, centrifuging, washing, and calcining at 500 ℃ for 2h to obtain the silicon dioxide coated graphite microsphere;
S2, magnesian reduction: uniformly mixing 10 parts by weight of the silicon dioxide coated graphite microsphere prepared in the step S1 with 13 parts by weight of magnesium, heating to 500 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, reacting at a constant temperature for 25min, heating to 700 ℃ at a heating rate of 6 ℃/min, reacting at a constant temperature for 150min, cooling to room temperature at a cooling rate of 7 ℃/min, adding 100 parts by weight of 7wt% hydrochloric acid solution, soaking for 20min, centrifuging, washing, and drying to obtain the defective silicon microsphere;
S3, preparing Ti-doped graphite/defective silicon microspheres: adding 10 parts by weight of the graphene coated defective silicon microsphere prepared in the step S3 into 100 parts by weight of water, adding 2.5 parts by weight of glucose, 0.7 part by weight of tetrabutyl titanate and 1.5 parts by weight of sodium polyacrylate, heating to 115 ℃, stirring and reacting for 11 hours, and heating to 1200 ℃ to graphitize for 2 hours to prepare the Ti-doped graphite/defective silicon microsphere;
S4, preparing a spherical graphite/silicon anode material: adding 10 parts by weight of citric acid into 300 parts by weight of water, heating to 200 ℃, stirring and reacting for 25min, adjusting the pH value of the solution to 7, dialyzing for 13h by adopting a dialysis bag with the aperture of 6kDa, then adding 50 parts by weight of the Ti-doped graphite/defective silicon microsphere prepared in the step S3, heating to 180 ℃, stirring and reacting for 125min, centrifuging, washing and drying to prepare the spherical graphite/silicon anode material.
Comparative example 3
In comparison with example 3, the difference is that step S3 is not performed.
The method comprises the following steps:
S1, preparing silicon dioxide coated graphite microspheres: adding 12 parts by weight of spherical crystalline flake graphite into 100 parts by weight of water, adding 10 parts by weight of ethyl orthosilicate, stirring and mixing for 20min, adding 200 parts by weight of petroleum ether, adding 1.5 parts by weight of span-80, emulsifying for 15min at 10000r/min, adjusting the pH value to 9.5, stirring and reacting for 6h, centrifuging, washing, and calcining at 500 ℃ for 2h to obtain the silicon dioxide coated graphite microsphere;
s2, graphene oxide coating: adding the silicon dioxide coated graphite microspheres prepared in the step S1 into 0.5mg/mL graphene oxide aqueous dispersion liquid, wherein the solid-to-liquid ratio of the silicon dioxide coated graphite microspheres to the graphene oxide aqueous dispersion liquid is 1:4g/mL, and performing spray drying to obtain coated microspheres;
the spray drying condition is that the air inlet temperature is 90 ℃, the air outlet temperature is 40 ℃ and the evaporation water quantity is 1700mL/h;
S3, preparing Ti-doped graphite/graphene/defective silicon microspheres: adding 10 parts by weight of the coated microsphere prepared in the step S2 into 100 parts by weight of water, adding 2.5 parts by weight of glucose, 0.7 part by weight of tetrabutyl titanate and 1.5 parts by weight of sodium polyacrylate, heating to 115 ℃, stirring and reacting for 11 hours, and heating to 1200 ℃ to graphitize for 2 hours to prepare the Ti-doped coated microsphere;
S4, preparing a spherical graphite/silicon anode material: adding 10 parts by weight of citric acid into 300 parts by weight of water, heating to 200 ℃, stirring and reacting for 25min, adjusting the pH value of the solution to 7, dialyzing for 13h by adopting a dialysis bag with the aperture of 6kDa, then adding 50 parts by weight of the Ti-doped coated microsphere prepared in the step S3, heating to 180 ℃, stirring and reacting for 125min, centrifuging, washing and drying to obtain the spherical graphite/silicon anode material.
Comparative example 4
In comparison with example 3, the difference is that step S4 is not performed.
The method comprises the following steps:
S1, preparing silicon dioxide coated graphite microspheres: adding 12 parts by weight of spherical crystalline flake graphite into 100 parts by weight of water, adding 10 parts by weight of ethyl orthosilicate, stirring and mixing for 20min, adding 200 parts by weight of petroleum ether, adding 1.5 parts by weight of span-80, emulsifying for 15min at 10000r/min, adjusting the pH value to 9.5, stirring and reacting for 6h, centrifuging, washing, and calcining at 500 ℃ for 2h to obtain the silicon dioxide coated graphite microsphere;
s2, graphene oxide coating: adding the silicon dioxide coated graphite microspheres prepared in the step S1 into 0.5mg/mL graphene oxide aqueous dispersion liquid, wherein the solid-to-liquid ratio of the silicon dioxide coated graphite microspheres to the graphene oxide aqueous dispersion liquid is 1:4g/mL, and performing spray drying to obtain coated microspheres;
the spray drying condition is that the air inlet temperature is 90 ℃, the air outlet temperature is 40 ℃ and the evaporation water quantity is 1700mL/h;
S3, magnesian reduction: uniformly mixing 10 parts by weight of the coated microsphere prepared in the step S2 with 13 parts by weight of magnesium, heating to 500 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, reacting at a constant temperature for 25min, heating to 700 ℃ at a heating rate of 6 ℃/min, reacting at a constant temperature for 150min, cooling to room temperature at a cooling rate of 7 ℃/min, adding 100 parts by weight of 7wt% hydrochloric acid solution, soaking for 20min, centrifuging, washing, and drying to obtain the graphene coated defective silicon microsphere;
S4, preparing a spherical graphite/silicon anode material: adding 10 parts by weight of citric acid into 300 parts by weight of water, heating to 200 ℃, stirring and reacting for 25min, adjusting the pH value of the solution to 7, dialyzing for 13h by adopting a dialysis bag with the aperture of 6kDa, then adding 50 parts by weight of the graphene coated defect silicon microsphere prepared in the step S3, heating to 180 ℃, stirring and reacting for 125min, centrifuging, washing and drying to obtain the spherical graphite/silicon anode material.
Comparative example 5
In comparison with example 3, the difference is that step S5 is not performed.
The method comprises the following steps:
S1, preparing silicon dioxide coated graphite microspheres: adding 12 parts by weight of spherical crystalline flake graphite into 100 parts by weight of water, adding 10 parts by weight of ethyl orthosilicate, stirring and mixing for 20min, adding 200 parts by weight of petroleum ether, adding 1.5 parts by weight of span-80, emulsifying for 15min at 10000r/min, adjusting the pH value to 9.5, stirring and reacting for 6h, centrifuging, washing, and calcining at 500 ℃ for 2h to obtain the silicon dioxide coated graphite microsphere;
s2, graphene oxide coating: adding the silicon dioxide coated graphite microspheres prepared in the step S1 into 0.5mg/mL graphene oxide aqueous dispersion liquid, wherein the solid-to-liquid ratio of the silicon dioxide coated graphite microspheres to the graphene oxide aqueous dispersion liquid is 1:4g/mL, and performing spray drying to obtain coated microspheres;
the spray drying condition is that the air inlet temperature is 90 ℃, the air outlet temperature is 40 ℃ and the evaporation water quantity is 1700mL/h;
S3, magnesian reduction: uniformly mixing 10 parts by weight of the coated microsphere prepared in the step S2 with 13 parts by weight of magnesium, heating to 500 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, reacting at a constant temperature for 25min, heating to 700 ℃ at a heating rate of 6 ℃/min, reacting at a constant temperature for 150min, cooling to room temperature at a cooling rate of 7 ℃/min, adding 100 parts by weight of 7wt% hydrochloric acid solution, soaking for 20min, centrifuging, washing, and drying to obtain the graphene coated defective silicon microsphere;
S4, preparing Ti-doped graphite/graphene/defective silicon microspheres: adding 10 parts by weight of the graphene coated defective silicon microsphere prepared in the step S3 into 100 parts by weight of water, adding 2.5 parts by weight of glucose, 0.7 part by weight of tetrabutyl titanate and 1.5 parts by weight of sodium polyacrylate, heating to 115 ℃, stirring and reacting for 11 hours, heating to 1200 ℃ and graphitizing for 2 hours, thus obtaining the Ti doped graphite/graphene/defective silicon microsphere, namely the spherical graphite/silicon anode material.
Test example 1
The spherical graphite/silicon anode materials prepared in examples 1 to 3 and comparative examples 1 to 5 of the present invention were measured for specific surface area using ASAP2460 type full-automatic specific surface area and porosity analyzer manufactured by Micromeritics instruments Co., USA. The results are shown in Table 1.
TABLE 1
| Group of | Specific surface area (m 2/g) |
| Example 1 | 115.4 |
| Example 2 | 115.1 |
| Example 3 | 116.2 |
| Comparative example 1 | 102.4 |
| Comparative example 2 | 90.2 |
| Comparative example 3 | 95.7 |
| Comparative example 4 | 109.6 |
| Comparative example 5 | 92.7 |
As can be seen from the above table, the spherical graphite/silicon anode materials prepared in examples 1-3 of the present invention have a large specific surface area.
Test example 2
The lithium sheet is used as a counter electrode, the polypropylene porous membrane is used as a diaphragm, and a solution prepared by fully mixing ethylene carbonate, dimethyl carbonate and ethylmethyl carbonate with LIPF 6 according to the mass ratio of 1:1:1 is used as electrolyte. The spherical graphite/silicon anode materials prepared in the examples 1-3 and the comparative examples 1-5, the adhesive sodium carboxymethylcellulose and styrene-butadiene rubber, and the conductive agent acetylene black are fully mixed in water according to the mass ratio of 94:1.5:2.5:2, uniformly coated on the surface of a copper foil, dried in an oven at 130 ℃, and roll-formed to be used as a working electrode. After assembling a counter electrode, a diaphragm, an electrolyte and a working electrode into a CR2032 type button cell at room temperature of 25 ℃, a CT2001A type LAND cell test system is used for testing the charge and discharge performance of the assembled button cell, the charge and discharge current density is 0.1C, the current magnitude is 36mA, and the cut-off voltages of charge and discharge are 3.0V and 0.001V respectively. The results are shown in Table 2.
TABLE 2
| Group of | Charging capacity (mAh/g) | Discharge capacity (mAh/g) | Irreversible capacity (mAh/g) | First coulombic efficiency (%) | Capacity retention after 200 cycles (%) |
| Example 1 | 922.1 | 901.2 | 20.9 | 98.1 | 96.12 |
| Example 2 | 919.5 | 900.7 | 18.8 | 98.4 | 96.31 |
| Example 3 | 924.2 | 906.3 | 17.9 | 98.9 | 96.75 |
| Comparative example 1 | 900.5 | 867.4 | 33.1 | 94.2 | 93.56 |
| Comparative example 2 | 904.7 | 873.6 | 31.1 | 92.1 | 90.58 |
| Comparative example 3 | 885.6 | 823.1 | 62.5 | 89.5 | 88.46 |
| Comparative example 4 | 910.2 | 876.9 | 33.3 | 86.7 | 89.19 |
| Comparative example 5 | 894.7 | 846.3 | 48.4 | 85.3 | 83.75 |
As can be seen from the above table, the spherical graphite/silicon anode materials prepared in examples 1-3 of the present invention have good electrochemical properties.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (10)
1. A preparation method of a spherical graphite/silicon anode material is characterized by preparing silicon dioxide coated graphite microspheres through sol-gel reaction, coating graphene oxide on the surfaces, performing magnesian reduction, doping Ti element to prepare Ti doped graphite/graphene/defective silicon microspheres, and then depositing carbon quantum dots on the surfaces to prepare the spherical graphite/silicon anode material.
2. The method of manufacturing according to claim 1, comprising the steps of:
S1, preparing silicon dioxide coated graphite microspheres: adding spherical flake graphite into water, adding alkyl orthosilicate, stirring and mixing uniformly, adding petroleum ether, adding an emulsifying agent for emulsification, adjusting the pH value, stirring for reaction, centrifuging, washing and calcining to obtain silicon dioxide coated graphite microspheres;
s2, graphene oxide coating: adding the silicon dioxide coated graphite microspheres prepared in the step S1 into graphene oxide aqueous dispersion liquid, and spray-drying to prepare coated microspheres;
S3, magnesian reduction: uniformly mixing the coated microspheres prepared in the step S2 with magnesium, heating to react under the protection of inert gas, then cooling to room temperature, adding into an acid solution to soak, centrifuging, washing and drying to prepare graphene coated defective silicon microspheres;
S4, preparing Ti-doped graphite/graphene/defective silicon microspheres: adding the graphene coated defective silicon microsphere prepared in the step S3 into water, adding glucose, tetrabutyl titanate and sodium polyacrylate, heating, stirring, reacting, and graphitizing to prepare Ti doped graphite/graphene/defective silicon microsphere;
s5, preparing a spherical graphite/silicon anode material: adding citric acid into water, heating and stirring for reaction for the first time, regulating the pH value of the solution, dialyzing, adding the Ti-doped graphite/graphene/defective silicon microsphere prepared in the step S4, heating and stirring for reaction for the second time, centrifuging, washing and drying to obtain the spherical graphite/silicon anode material.
3. The preparation method according to claim 2, wherein in the step S1, the mass ratio of the spherical crystalline flake graphite, the alkyl orthosilicate and the emulsifier is 10-15:7-12:1-2, the alkyl orthosilicate is methyl orthosilicate or ethyl orthosilicate, the emulsifier is at least one selected from span-20, span-40, span-60 and span-80, the pH value is adjusted to 9-10, the stirring reaction time is 5-7h, the calcination temperature is 400-600 ℃ and the time is 1-3h.
4. The preparation method according to claim 2, wherein in the step S2, the solid-to-liquid ratio of the silica-coated graphite microsphere to the graphene oxide aqueous dispersion is 1:3-5g/mL, the concentration of the graphene oxide aqueous dispersion is 0.5-1mg/mL, the spray drying condition is that the air inlet temperature is 80-100 ℃, the air outlet temperature is 30-50 ℃, and the evaporation water amount is 1500-2000mL/h.
5. The preparation method according to claim 2, wherein in the step S3, the mass ratio of the coated microsphere to the magnesium is 1:1.2-1.5, the heating rate of the heating reaction is 4-7 ℃/min, the temperature is raised to 450-550 ℃, the constant temperature is reacted for 20-30min, then the temperature is raised to 650-750 ℃ at the heating rate of 5-7 ℃/min, the constant temperature is reacted for 120-180min, the cooling rate to room temperature is 5-10 ℃/min, the acid solution is 5-10wt% hydrochloric acid or sulfuric acid solution, and the soaking time is 15-25min.
6. The preparation method according to claim 2, wherein the mass ratio of the graphene-coated defective silicon microsphere, glucose, tetrabutyl titanate and sodium polyacrylate in step S4 is 10:2-3:0.5-1:1-2, wherein the temperature of the heating and stirring reaction is 110-120 ℃, the reaction time is 10-12h, the graphitization temperature is 1100-1300 ℃, and the reaction time is 1-3h.
7. The preparation method according to claim 2, wherein in the step S5, the mass ratio of the citric acid, the water and the Ti-doped graphite/graphene/defective silicon microspheres is 1:20-40:4-6, the pH value of the solution is adjusted to 6.9-7.1, the pore diameter of a dialysis bag used in the dialysis is 5k-7kDa, the dialysis time is 12-15h, the temperature of the first heating and stirring reaction is 190-210 ℃ for 20-30min, the temperature of the second heating and stirring reaction is 170-190 ℃ for 100-150min.
8. The preparation method according to claim 2, characterized by comprising the following steps:
S1, preparing silicon dioxide coated graphite microspheres: adding 10-15 parts by weight of spherical crystalline flake graphite into 100 parts by weight of water, adding 7-12 parts by weight of methyl orthosilicate or ethyl orthosilicate, stirring and mixing uniformly, adding 200 parts by weight of petroleum ether, adding 1-2 parts by weight of emulsifying agent, emulsifying, adjusting the pH value to 9-10, stirring and reacting for 5-7 hours, centrifuging, washing, and calcining at 400-600 ℃ for 1-3 hours to obtain silicon dioxide coated graphite microspheres;
S2, graphene oxide coating: adding the silica coated graphite microsphere prepared in the step S1 into 0.5-1mg/mL graphene oxide aqueous dispersion, wherein the solid-to-liquid ratio of the silica coated graphite microsphere to the graphene oxide aqueous dispersion is 1:3-5g/mL, and spray drying to prepare the coated microsphere;
The spray drying condition is that the air inlet temperature is 80-100 ℃, the air outlet temperature is 30-50 ℃ and the evaporation water quantity is 1500-2000mL/h;
S3, magnesian reduction: uniformly mixing 10 parts by weight of the coated microsphere prepared in the step S2 with 12-15 parts by weight of magnesium, under the protection of inert gas, heating to 450-550 ℃ at a heating rate of 4-7 ℃/min, reacting at a constant temperature for 20-30min, heating to 650-750 ℃ at a heating rate of 5-7 ℃/min, reacting at a constant temperature for 120-180min, cooling to room temperature at a cooling rate of 5-10 ℃/min, adding 100 parts by weight of 5-10wt% hydrochloric acid or sulfuric acid solution, soaking for 15-25min, centrifuging, washing, and drying to obtain the graphene coated defective silicon microsphere;
S4, preparing Ti-doped graphite/graphene/defective silicon microspheres: adding 10 parts by weight of the graphene coated defect silicon microsphere prepared in the step S3 into 100 parts by weight of water, adding 2-3 parts by weight of glucose, 0.5-1 part by weight of tetrabutyl titanate and 1-2 parts by weight of sodium polyacrylate, heating to 110-120 ℃, stirring and reacting for 10-12 hours, and heating to 1100-1300 ℃ and graphitizing for 1-3 hours to prepare the Ti doped graphite/graphene/defect silicon microsphere;
S5, preparing a spherical graphite/silicon anode material: adding 10 parts by weight of citric acid into 200-400 parts by weight of water, heating to 190-210 ℃, stirring and reacting for 20-30min, adjusting the pH value of the solution to 6.9-7.1, dialyzing for 12-15h by adopting a dialysis bag with the aperture of 5k-7kDa, then adding 40-60 parts by weight of the Ti-doped graphite/graphene/defective silicon microsphere prepared in the step S4, heating to 170-190 ℃, stirring and reacting for 100-150min, centrifuging, washing and drying to prepare the spherical graphite/silicon anode material.
9. A spherical graphite/silicon anode material produced by the production method according to any one of claims 1 to 8.
10. Use of the spherical graphite/silicon negative electrode material according to claim 9 for preparing a negative electrode of a lithium ion battery.
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