The present application claims priority to Chinese Patent Application No. 2021103353838, entitled “COMPOSITE NEGATIVE ELECTRODE MATERIAL AND PREPARATION METHOD THEREFOR, AND LITHIUM ION BATTERY” and filed with the Chinese Patent Office on Mar. 29, 2021, the entire contents of which are hereby incorporated by reference for all purposes.
The present disclosure relates to the technical field of anode materials, and in particular, to a composite anode material, a method for preparing the composite anode material, and a lithium-ion battery.
A silicon-carbon composite anode material is a new-type lithium battery anode material with a high capacity and a long cycle, which has a capacity much higher than that of graphite and a cycle better than that of metal silicon, and is an important next-generation lithium battery anode material today. Carbon in the silicon-carbon composite anode material may enhance conductivity and stabilize a structure of the material for a silicon-oxygen material system, making it have better cycling expansion performance. However, a structure of a carbon coating layer in an existing silicon-carbon composite material is not dense enough, and there are certain pores inside the silicon-carbon composite material, which leads to a limited improvement in conductivity of a silicon active material by the carbon coating layer, being not conducive to improving the capacity and first efficiency of the material. Moreover, material particles may be pulverized during lithium deintercalation and intercalation of active silicon, resulting in poor stability and poor cycling performance.
In view of this, the present disclosure proposes a composite anode material, a method for preparing the composite anode material, and a lithium-ion battery, which can improve cycling stability of the material.
In a first aspect, the present disclosure provides a composite anode material, in which the composite anode material includes a silicon-oxygen material and a carbon coating layer on a surface of the silicon-oxygen material. A physical adsorption-desorption isotherm of the composite anode material is of a type II or type III, and a physical adsorption-desorption isotherm of the silicon-oxygen material is of a type IV or type V.
In the composite anode material provided in the present disclosure, the physical adsorption-desorption isotherm of the silicon-oxygen material is of the type IV or type V, so that the silicon-oxygen material and the carbon coating layer can be bonded more closely, which is conducive to electron conduction and ion conduction during lithium intercalation and deintercalation and is conducive to improving first efficiency, capacity, and cycling stability of the material. The physical adsorption-desorption isotherm of the composite anode material is of the type II or type III, so that the composite anode material has a dense structure, and the carbon coating layer has certain mechanical strength and a stable structure, which can ensure integrity of particles during lithium deintercalation and intercalation of active silicon, inhibit pulverization of the particles, improve stability of the silicon-oxygen material, and further improve cycling performance of the material as a whole.
In the present disclosure, classification of types of physical adsorption-desorption isotherms is based on a classification method for physical adsorption-desorption isotherms proposed by International Union of Pure and Applied Chemistry (IUPAC).
In a feasible embodiment, in a Raman spectrum, the composite anode material has a carbon characteristic peak D, a carbon characteristic peak G, and a silicon characteristic peak A, a ratio ID/IG of peak intensity ID of the carbon characteristic peak D to peak intensity IG of the carbon characteristic peak G ranges from 0.5 to 2, and a ratio of peak intensity IA of the silicon characteristic peak A to (ID+IG) ranges from 0.1 to 10.
In a feasible embodiment, the composite anode material satisfies at least one of the following conditions a to e:
In a feasible embodiment, the composite anode material satisfies at least one of the following conditions a to e:
In a second aspect, the present disclosure provides a method for preparing a composite anode material, in which the method includes the following steps:
In the above solution, by preheating, the aliphatic hydrocarbon gas can be adsorbed in pores of particles of the silicon-oxygen material whose physical adsorption-desorption isotherm is of the type IV or type V, thereby filling pores of the silicon-oxygen material. The aliphatic hydrocarbon gas is fed by intermittent pulsing, which does not lead to excessive local deposition of carbon sources. The aliphatic hydrocarbon gas is decomposed into zero-dimensional single carbon atom radicals or one-dimensional shorter carbon chains during cracking, and mutual stacking may be denser, which is more conducive to formation of the dense structure and spherical or quasi-spherical particles of the composite anode material, is conducive to integrity of a conductive network and stability of the structure of the anode material, and is conducive to improving cycling stability of the composite anode material.
In a feasible embodiment, the preparation method satisfies at least one of the following conditions a to f:
In a feasible embodiment, the preparation method satisfies at least one of the following conditions a to d:
In a feasible embodiment, the preparation method satisfies at least one of the following conditions a to e:
In a feasible embodiment, the method further includes:
In a third aspect, the present disclosure provides a lithium-ion battery, in which the lithium-ion battery includes the composite anode material as described in the first aspect or the composite anode material obtained by a preparation method as described in the second aspect.
The technical solution of the present disclosure has at least the following beneficial effects.
Preferred embodiments of the present disclosure are described below. It should be pointed out that, for those of ordinary skill in the art, some improvements and modifications can be made without departing from the principle of embodiments of the present disclosure. These improvements and modifications are also regarded as the protection scope of the embodiments of the present disclosure.
In a first aspect, the present disclosure provides a composite anode material. The composite anode material includes a silicon-oxygen material and a carbon coating layer on a surface of the silicon-oxygen material. A physical adsorption-desorption isotherm of the composite anode material is of a type II or type III, and a physical adsorption-desorption isotherm of the silicon-oxygen material is of a type IV or type V.
In the present disclosure, classification of types of physical adsorption-desorption isotherms is based on a classification method for physical adsorption-desorption isotherms proposed by IUPAC.
In the above solution, according to the composite anode material provided in the present disclosure, the physical adsorption-desorption isotherm of the silicon-oxygen material is of the type IV or type V, so that the silicon-oxygen material and the carbon coating layer can be bonded more closely, which is conducive to electron conduction and ion conduction during lithium intercalation and deintercalation and is conducive to improving first efficiency, capacity, and cycling stability of the material. The physical adsorption-desorption isotherm of the composite anode material is of the type II or type III, so that the composite anode material has a dense structure, and the carbon coating layer has certain mechanical strength and a stable structure, which can ensure integrity of particles during lithium deintercalation and intercalation of the active silicon, inhibit pulverization of the particles, improve stability of the silicon-oxygen material, and further improve cycling performance of the material as a whole.
The following are preferred technical solutions of the present disclosure, but are not used as limitations on the technical solutions provided in the present disclosure. Through the following preferred technical solutions, technical objectives and beneficial effects of the present disclosure can be better implemented and achieved.
In some embodiments, the silicon-oxygen material includes SiOx, where 0<x<2. SiOx may be, for example, SiO0.5, SiO0.8, SiO0.9, SiO, SiO1.1, SiO1.2, SiO1.5, or the like. Preferably, the silicon-oxygen material is SiO. It can be understood that composition of SiOx is relatively complex, which may be understood as being formed by nano silicon uniformly dispersed in SiO2.
In some embodiments, the silicon-oxygen material further includes a composite material of SiOx, and the composite material of SiOx includes at least one of a SiOx composite with SiOy, a SiOx composite with SiO2, a SiOx composite with LimSiOn, a SiOx composite with NamSiOn, a SiOx composite with KmSiOn, a SiOx composite with MgmSiOn, a SiOx composite with CamSiOn, a SiOx composite with AlmSiOn, a SiOx composite with amorphous carbon, a SiOx composite with graphite, a SiOx composite with graphene, a SiOx composite with carbon nanotube, and a SiOx composite with a polymer material, where 0<y<2 and x≠y, m≥1, and n≥1.
In some embodiments, a silicon grain size in the silicon-oxygen material ranges from 1 nm to 100 nm, which may be, for example, 1 nm, 10 nm, 20 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 100 nm, or the like, but is not merely limited to the values listed. Other values not listed in this value range can also be used. It can be understood that the silicon grain size of the silicon-oxygen material is controlled within the above range, which is conducive to improving structural stability, thermal stability, and long-term cycling stability of the anode material. It is to be noted that the silicon grain size in the silicon-oxygen material is a half-peak width of a 28.6° Si(111) peak measured by an XRD spectrum, and calculated using a Scherrer formula.
In some embodiments, a mass percentage of oxygen in the silicon-oxygen material ranges from 0.1% to 50%, which may be, for example, 0.1%, 1%, 10%, 20%, 25%, 30%, 35%, 40%, 50%, or the like, but is not merely limited to the values listed. Other values not listed in this value range can also be used. When the content of oxygen in the silicon-oxygen material is excessively high, the capacity of the material decreases, first Coulombic efficiency decreases. When the content of oxygen in the silicon-oxygen material is excessively low, i.e., the content of silicon increases, it is easy to cause the material to expand easily during cycling, resulting in serious pulverization of the material.
In some embodiments, a specific surface area of the silicon-oxygen material is smaller than 100 m2/g, which may be, for example, 1.50 m2/g, 2.50 m2/g, 3.50 m2/g, 5.00 m2/g, 10 m2/g, 50 m2/g, 90 m2/g, or the like, but is not merely limited to the values listed. Other values not listed in this value range can be used. A specific surface area of the composite anode material is within the above range, which ensures processing performance of the material, is conducive to improving first efficiency of a lithium battery made of the anode material, and is conducive to improving cycling performance of the anode material.
In some embodiments, a porosity φa of the silicon-oxygen material is smaller than 10%, which may be, for example, 1%, 2%, 3%, 5%, 6%, 8%, 9%, or the like, but is not merely limited to the values listed. Other values not listed in this value range can also be used. When the porosity of the silicon-oxygen material is excessively high, it is not conducive to forming a composite material with a dense structure, and it is not conducive to improving cycling stability of the material. Preferably, the porosity of the silicon-oxygen material is 1%<φa<10%.
In some embodiments, the composite anode material is spherical or quasi-spherical, and a Wadell's sphericity factor thereof is greater than 0.01, which may be, for example, 0.02, 0.04, 0.08, 0.1, 0.15, 0.2, 0.25, 0.3, 0.5, 0.6, 0.8, 0.9, 0.95, 0.99, or the like, but is not merely limited to the values listed. Other values not listed in this value range can also be used. For example, the Wadell's sphericity factor of the composite anode material ranges from 0.1 to 0.3. When the Wadell's sphericity factor of the composite anode material is excessively low, the particles have poor stability, are easily pulverized during the cycle, and have an increased cycling expansion rate.
In some embodiments, a specific surface area of the composite anode material ranges from 1 m2/g to 50 m2/g, which may be, for example, 1 m2/g, 10 m2/g, 15 m2/g, 20 m2/g, 25 m2/g, 30 m2/g, 35 m2/g, 40 m2/g, 45 m2/g, 50 m2/g, or the like, but is not merely limited to the values listed. Other values not listed in this value range can also be used. A specific surface area of the composite anode material is within the above range, which ensures processing performance of the material, is conducive to improving first efficiency of a lithium battery made of the anode material, and is conducive to improving cycling performance of the anode material.
In some embodiments, an average particle size of the composite anode material ranges from 1.0 μm to 50 μm, which may be, for example, 1.0 μm, 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 10 μm, 15 μm, 20 μm, 30 μm, 50 μm, or the like. The average particle size of the composite anode material is controlled within the above range, which is conducive to improvement of the cycling performance of the anode material. Preferably, the average particle size of the composite anode material ranges from 1.0 μm to 10 μm. If the average particle size of the composite anode material is excessively large, the cycling performance of the material decreases, rate performance decreases, and first efficiency of the battery is reduced.
In some embodiments, a porosity of the composite anode material is smaller than 10%, which may be, for example, 0.5%, 1.0%, 2.0%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 9.9%, or the like, but is not merely limited to the values listed. Other values not listed in this value range can also be used. The porosity of the composite anode material is controlled within the above range, enabling the material to have good rate performance.
In some embodiments, a mass percentage of carbon in the composite anode material ranges from 0.1% to 50%, which may be, for example, 0.1%, 3.0%, 5.0%, 10.0%, 15.5%, 20%, 30%, 50%, or the like, but is not merely limited to the values listed. Other values not listed in this value range can also be used. If the content of carbon is excessively high, transmission efficiency of lithium ions may be reduced, which is not conducive to high-rate charge and discharge of the material and degrades overall performance of the anode material. If the content of carbon is excessively low, it is not conducive to improving conductivity of the anode material and volume expansion inhibition performance of the material is relatively poor, resulting in poor long-cycling performance. Preferably, the mass percentage of carbon in the composite anode material ranges from 1% to 10%.
In some embodiments, in a Raman spectrum, the composite anode material has a carbon characteristic peak D, a carbon characteristic peak G, and a silicon characteristic peak A, and a ratio ID/IG of peak intensity ID of the carbon characteristic peak D to peak intensity IG of the carbon characteristic peak G ranges from 0.5 to 2, which may be, for example, 0.5, 0.8, 1.0, 1.2, 1.5, 1.8, 2.0, or the like. When the ratio ID/IG is excessively large, the first efficiency of the composite anode material is reduced. When the ratio ID/IG is excessively small, the rate performance of the composite anode material decreases. When the value of ID/IG is within this range, it indicates that a carbon layer is formed by cracking a carbon chain, and it is not easy to generate a graphite sheet layer.
In some embodiments, a ratio of peak intensity IA of the silicon characteristic peak A to (ID+IG) ranges from 0.1 to 10, which may be, for example, 0.1, 0.2, 0.3, 0.5, 0.6, 0.8, 1.0, or the like. When the ratio IA/(ID+IG) is excessively large, the cycling performance of the composite anode material decreases. When the ratio IA/(ID+IG) is excessively small, a discharge specific capacity of the composite anode material is reduced, which is not conducive to improving energy density of the battery. When the value of IA/(ID+IG) is within this range, the carbon coating layer is dense, and silicon is not easily exposed outside the carbon layer.
In a second aspect, as shown in
In step S100, a first aliphatic hydrocarbon gas is fed in a protective atmosphere, and a silicon-oxygen material and the first aliphatic hydrocarbon gas are preheated, in which a physical adsorption-desorption isotherm of the silicon-oxygen material is of a type IV or type V.
In step S200, a second aliphatic hydrocarbon gas is fed by intermittent pulsing, and the second aliphatic hydrocarbon gas is caused to undergo chemical vapor deposition on the preheated product, to obtain the composite anode material.
In the above solution, by preheating, the first aliphatic hydrocarbon gas can be adsorbed in pores of particles of the silicon-oxygen material whose physical adsorption-desorption isotherm is of the type IV or type V, thereby filling pores of the silicon-oxygen material. The physical adsorption-desorption isotherm of the silicon-oxygen material is of the type IV or type V, which is more conducive to deposition of the first aliphatic hydrocarbon gas in the pores. The second aliphatic hydrocarbon gas is fed by intermittent pulsing, which may not lead to excessive local deposition of carbon sources. The second aliphatic hydrocarbon gas is decomposed into zero-dimensional single carbon atom radicals or one-dimensional shorter carbon chains during cracking, and mutual stacking may be denser, which is more conducive to formation of the dense structure and spherical or quasi-spherical particles of the composite anode material, is conducive to integrity of a conductive network and stability of the structure of the anode material, and is conducive to improving cycling stability of the composite anode material.
The preparation method provided in the solution is described in detail below.
In step S100, a first aliphatic hydrocarbon gas is fed in a protective atmosphere, and a silicon-oxygen material and the first aliphatic hydrocarbon gas are preheated.
In some embodiments, the silicon-oxygen material includes SiOx, where 0<x<2. SiOx may be, for example, SiO0.5, SiO0.8, SiO0.9, SiO, SiO1.1, SiO1.2, SiO1.5, or the like. Preferably, the silicon-oxygen material is SiO. It can be understood that composition of SiOx is relatively complex, which may be understood as being formed by nano silicon uniformly dispersed in SiO2.
In some embodiments, the silicon-oxygen material further includes a composite material of SiOx, and the composite material of SiOx includes at least one of a SiOx composite with SiOy, a SiOx composite with SiO2, a SiOx composite with LimSiOn, a SiOx composite with NamSiOn, a SiOx composite with KmSiOn, a SiOx composite with MgmSiOn, a SiOx composite with CamSiOn, a SiOx composite with AlmSiOn, a SiOx composite with amorphous carbon, a SiOx composite with graphite, a SiOx composite with graphene, a SiOx composite with carbon nanotube, and a SiOx composite with a polymer material, where 0<y<2 and x≠y, m≥1, and n≥1.
In some embodiments, a silicon grain size in the silicon-oxygen material ranges from 1 nm to 100 nm, which may be, for example, 1 nm, 10 nm, 20 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 100 nm, or the like, but is not merely limited to the values listed. Other values not listed in this value range can also be used. It can be understood that the silicon grain size of the silicon-oxygen material is controlled within the above range, which is conducive to improving structural stability, thermal stability, and long-term cycling stability of the anode material. It is to be noted that the silicon grain size in the silicon-oxygen material is a half-peak width of a 28.6° Si(111) peak measured by an XRD spectrum, and calculated using a Scherrer formula.
In some embodiments, a mass percentage of oxygen in the silicon-oxygen material ranges from 0.1% to 50%, which may be, for example, 0.1%, 1%, 10%, 20%, 25%, 30%, 35%, 40%, 50%, or the like, but is not merely limited to the values listed. Other values not listed in this value range can also be used. When the content of oxygen in the silicon-oxygen material is excessively high, the capacity of the material decreases, first Coulombic efficiency decreases. When the content of oxygen in the silicon-oxygen material is excessively low, i.e., the content of silicon increases, it is easy to cause the material to expand easily during a cycle, resulting in serious pulverization of the material.
In some embodiments, a specific surface area of the silicon-oxygen material is smaller than 100 m2/g, which may be, for example, 1.50 m2/g, 2.50 m2/g, 3.50 m2/g, 5.00 m2/g, 10 m2/g, 50 m2/g, 100 m2/g, or the like, but is not merely limited to the values listed. Other values not listed in this value range can also be used. A specific surface area of the composite anode material is within the above range, which ensures processing performance of the material, is conducive to improving first efficiency of a lithium battery made of the anode material, and is conducive to improving cycling performance of the anode material.
In some embodiments, a porosity pa of the silicon-oxygen material is smaller than 10%, which may be, for example, 1%, 2%, 3%, 5%, 6%, 8%, 10%, or the like, but is not merely limited to the values listed. Other values not listed in this value range can also be used. When the porosity of the silicon-oxygen material is excessively high, it is not conducive to forming a composite material with a dense structure, and it is not conducive to improving cycling stability of the material.
In some embodiments the protective atmosphere includes at least one of nitrogen, helium, neon, argon, krypton, and xenon. Heat treatment in the protective atmosphere can improve safety of a reaction.
In some embodiments, the first aliphatic hydrocarbon gas includes at least one of acetylene, ethylene, propyne, ethane, and propylene.
In some embodiments, a gas flow rate of the first aliphatic hydrocarbon gas ranges from 0.1 L/min to 5 L/min, which may be, for example, 0.1 L/min, 0.5 L/min, 1 L/min, 1.5 L/min, 2 L/min, 2.5 L/min, 3 L/min, 3.5 L/min, 5 L/min, or the like, but is not merely limited to the values listed. Other values not listed in this value range can also be used.
In some embodiments, a preheating temperature ranges from 100° C. to 600° C., which may be, for example, 100° C., 200° C., 300° C., 350° C., 400° C., 450° C., 500° C., 550° C., 600° C., or the like, but is not merely limited to the values listed. Other values not listed in this value range can also be used. A preheating time ranges from 0.5 h to 24 h, which may be, for example, 0.5 h, 1.0 h, 1.5 h, 3 h, 5 h, 6 h, 8 h, 12 h, 15 h, 18 h, 24 h, or the like. It can be understood that, by sufficient preheating, the first aliphatic hydrocarbon gas can be adsorbed into the pores of the silicon-oxygen material and onto a surface thereof, which is conducive to formation of a dense carbon coating layer. Preferably, the preheating temperature ranges from 400° C. to 600° C., and the preheating time ranges from 1 h to 5 h.
In step S200, a second aliphatic hydrocarbon gas is fed by intermittent pulsing, and the second aliphatic hydrocarbon gas is caused to undergo chemical vapor deposition on the preheated product, to obtain the composite anode material.
The second aliphatic hydrocarbon gas is decomposed into zero-dimensional single carbon atom radicals or one-dimensional shorter carbon chains during cracking, and mutual stacking may be denser, which is more conducive to formation of the composite anode material with a dense structure, is conducive to integrity of a conductive network and stability of the structure of the anode material, and is conducive to improving cycling stability of the composite anode material. A conventional solid-phase carbon source, such as an organic matter containing aromatic rings or higher aliphatic hydrocarbons with a boiling point generally higher than a decomposition point, is decomposed into two-dimensional carbon rings or long carbon chains during cracking, and mutual stacking is not as dense as zero-dimensional single carbon atom radicals or one-dimensional shorter carbon chains, and a physical adsorption-desorption isotherm obtained by pore-size analysis has a hysteresis loop. An aromatic hydrocarbon gas, such as benzene vapor, becomes two-dimensional carbon rings after cracking, stacking thereof is not as dense as one-dimensional short carbon chains or zero-dimensional carbon atoms, and a physical adsorption-desorption isotherm obtained by pore-size analysis has a hysteresis loop, which is not conducive to maintaining cycling stability of the anode material.
In some embodiments, a weight ratio A of the second aliphatic hydrocarbon gas to the silicon-oxygen material satisfies the following relation: 1.5φa/(1−φa)≤A≤15φa/(1−φa), where φa denotes a porosity of the silicon-oxygen material. An appropriate amount of the second aliphatic hydrocarbon gas is fed, which is conducive to deposition and formation of a uniform carbon coating layer on a surface of the silicon-oxygen material and enables the silicon-oxygen material wrapped by the carbon coating layer to form a dense structure and reduce the porosity of the silicon-oxygen material.
In some embodiments, the second aliphatic hydrocarbon gas includes at least one of acetylene, ethylene, propyne, ethane, and propylene.
In some embodiments, a gas flow rate of the second aliphatic hydrocarbon gas ranges from 0.1 L/min to 5 L/min, which may be, for example, 0.1 L/min, 0.5 L/min, 1 L/min, 1.5 L/min, 2 L/min, 2.5 L/min, 3 L/min, 3.5 L/min, 5 L/min, or the like, but is not merely limited to the values listed. Other values not listed in this value range can also be used.
In some embodiments, a reaction temperature of the chemical vapor deposition ranges from 600° C. to 1050° C., which may be, for example, 600° C., 700° C., 800° C., 850° C., 900° C., 950° C., 1000° C., 1050° C., or the like, but is not merely limited to the values listed. Other values not listed in this value range can also be used. It can be understood that, by the chemical vapor deposition, the second aliphatic hydrocarbon gas is decomposed into zero-dimensional single carbon atom radicals or one-dimensional shorter carbon chains during cracking, and mutual stacking may be denser, which is more conducive to formation of the composite anode material with a dense structure, is conducive to integrity of a conductive network and stability of the structure of the anode material, and is conducive to improving cycling stability of the composite anode material. Preferably, the reaction temperature of the chemical vapor deposition ranges from 800° C. to 1000° C.
In some embodiments, during the chemical vapor deposition, the aliphatic hydrocarbon gas is continuously fed by intermittent pulsing, and an interval of the intermittent pulsing is 8 s to 12 s.
In some embodiments, the intermittent pulsing has a pulse duration of 8 s to 1 min. The pulse duration can be that the aliphatic hydrocarbon gas is fed for 10 s every 10 s by pulsing. The carbon source gas (the second aliphatic hydrocarbon gas) is fed by the intermittent pulsing, which is not easy to cause excessive local deposition of the carbon source on the surface of the silicon-oxygen material, is conducive to improving uniformity of the carbon coating layer on the surface of the silicon-oxygen material, and is conducive to formation of a uniform and dense carbon coating layer. If the second aliphatic hydrocarbon gas is continuously fed, it is not conducive to formation of a structure in which the physical adsorption-desorption isotherm of the composite anode material is of a type II or type III, and is not conducive to improving the cycling stability of the anode material.
In some embodiments, subsequent to step S200, the method further includes:
In some embodiments, the sieving includes at least one of crushing, ball milling, screening, or classification.
In a third aspect, the present disclosure provides a lithium-ion battery, in which the lithium-ion battery includes the composite anode material as described in the first aspect or the composite anode material obtained by a preparation method as described in the second aspect.
The embodiments of the present disclosure are further described below with some Examples. The Examples of the present disclosure are not limited to the following specific Examples, and can be properly modified for implementation within the protection scope.
A method for preparing a composite anode material includes the following steps:
The composite anode material S1 prepared in this Example includes a silicon-oxygen material and a carbon coating layer on a surface of the silicon-oxygen material. A physical adsorption-desorption isotherm of the composite anode material is as shown in
A method for preparing a composite anode material includes the following steps:
The composite anode material S2 prepared in this Example includes a silicon-oxygen material and a carbon coating layer on a surface of the silicon-oxygen material.
A method for preparing a composite anode material includes the following steps:
The composite anode material S3 prepared in this Example includes a silicon-oxygen material and a carbon coating layer on a surface of the silicon-oxygen material.
A method for preparing a composite anode material includes the following steps:
The composite anode material S4 prepared in this Example includes a silicon-oxygen material and a carbon coating layer on a surface of the silicon-oxygen material.
A method for preparing a composite anode material includes the following steps:
The composite anode material S5 prepared in this Example includes a silicon-oxygen material and a carbon coating layer on a surface of the silicon-oxygen material.
A method for preparing a composite anode material includes the following steps:
The composite anode material S6 prepared in this Example includes a silicon-oxygen material and a carbon coating layer on a surface of the silicon-oxygen material.
A method for preparing a composite anode material includes the following steps:
The composite anode material S7 prepared in this Example includes a silicon-oxygen material and a carbon coating layer on a surface of the silicon-oxygen material.
A method for preparing a composite anode material includes the following steps:
The composite anode material S8 prepared in this Example includes a silicon-oxygen material and a carbon coating layer on a surface of the silicon-oxygen material.
A method for preparing a composite anode material includes the following steps:
The composite anode material S9 prepared in this Example includes a silicon-oxygen material and a carbon coating layer on a surface of the silicon-oxygen material.
A method for preparing a composite anode material includes the following steps:
The composite anode material S10 prepared in this Example includes a silicon-oxygen material and a carbon coating layer on a surface of the silicon-oxygen material.
A method for preparing a composite anode material includes the following steps:
The composite anode material D1 prepared in this Comparative Example includes a silicon-oxygen material and a carbon coating layer on a surface of the silicon-oxygen material. A physical adsorption-desorption isotherm of the composite anode material is as shown in
A method for preparing a composite anode material includes the following steps:
The composite anode material D2 prepared in this Comparative Example includes a silicon-oxygen material and a carbon coating layer on a surface of the silicon-oxygen material. A physical adsorption-desorption isotherm of the composite anode material D2 is of a type IV.
Further, the anode materials prepared in Examples 1 to 10 and Comparative Examples 1 to 2, conductive carbon black, and PAA glue are made into an anode slurry at a mass ratio of 75:15:10, applied to a copper foil, and dried to prepare an anode sheet. A lithium metal sheet is used as a counter electrode and assembled into a button cell in a glove box filled with argon. Under the current density of 0.1 C, the charge and discharge test is carried out according to a charge and discharge interval of 0.01 V to 1.5 V. A first reversible specific capacity, first efficiency, and a capacity retention rate after 50 cycles of the battery are obtained from the test.
Capacity retention rate after 50 cycles at 0.2 C=discharge capacity of the 50th cycle/discharge capacity of the first cycle*100%. The results are shown in Table 2.
As can be seen from Tables 1 to 2 above, in Examples 1 to 8, by preheating, the first aliphatic hydrocarbon gas can be adsorbed in pores of particles of the silicon-oxygen material, thereby filling pores of the silicon-oxygen material. The second aliphatic hydrocarbon gas is fed by intermittent pulsing, which may not lead to excessive local deposition of carbon sources. The second aliphatic hydrocarbon gas is decomposed into zero-dimensional single carbon atom radicals or one-dimensional shorter carbon chains during cracking, and mutual stacking may be denser. As shown in
The second aliphatic hydrocarbon gas in Example 6 is excessively fed, and a weight ratio A of the second aliphatic hydrocarbon gas to the silicon-oxygen material is greater than 0.79, that is, 15φa/(1−φa)=0.79, indicating that the excessive second aliphatic hydrocarbon gas may lead to excessive local deposition of carbon sources in the silicon-oxygen material, a mass ratio of the anode active material (silicon-oxygen material) may decrease, and the first discharge specific capacity and the first Coulombic efficiency of the anode material may decrease significantly.
The second aliphatic hydrocarbon gas in Example 9 is less fed, and a weight ratio A of the second aliphatic hydrocarbon gas to the silicon-oxygen material is equal to 0.079, that is, 15φa/(1−φa)=0.079. As a result, fewer carbon sources are deposited on the surface of the silicon-oxygen material, conductivity of the anode material decreases, and the first discharge specific capacity, the first Coulombic efficiency, and the cycle retention rate are all lower compared to those in Example 1.
Main differences between Comparative Example 1 and Example 1 are as follows. The second aliphatic hydrocarbon gas fed during chemical vapor deposition is benzene vapor, and benzene vapor (C6H6) is cracked to form two-dimensional carbon rings, whose stacking is not as dense as one-dimensional short carbon chains or zero-dimensional carbon atoms formed by cracking of ethylene, a physical adsorption-desorption isotherm of the coated composite anode material after pore size analysis has a hysteresis loop, as shown in
Main differences between Comparative Example 2 and Example 1 are as follows. The second aliphatic hydrocarbon gas is fed continuously but not fed by intermittent pulsing, leading to excessive local deposition of the carbon source on the surface of the silicon-oxygen material, which is not conducive to improving uniformity of the carbon coating layer on the surface of the silicon-oxygen material, a physical adsorption-desorption isotherm of the coated composite anode material prepared is of a type IV, and the cycling capacity retention rate in Comparative Example 2 is lower than that in Example 1, which is not conducive to improving cycling stability of the anode material.
Based on the above, the method for preparing a composite anode material provided in the present disclosure is simple and easy to operate, and a preparation process is safe and efficient; the manufacturing cost is effectively reduced, and is suitable for mass production. A prepared product is used as a battery pole piece, which is conducive to electron conduction and ion conduction during lithium intercalation and deintercalation and is conducive to improving cycling stability of the battery.
Although the present disclosure is disclosed as above with preferred Examples, the Examples are not intended to limit the claims. Any person skilled in the art can make some possible changes and modifications without departing from the concept of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the scope defined by the claims of the present disclosure.
Number | Date | Country | Kind |
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202110335383.8 | Mar 2021 | CN | national |
Filing Document | Filing Date | Country | Kind |
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PCT/CN2021/128547 | 11/4/2021 | WO |