CN119297234B

CN119297234B - A silicon-carbon anode material with a watermelon-like structure, its preparation method and application

Info

Publication number: CN119297234B
Application number: CN202411397941.3A
Authority: CN
Inventors: 黄国强; 康灵嘉; 张学斌; 周启豪
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2024-10-09
Filing date: 2024-10-09
Publication date: 2025-11-25
Anticipated expiration: 2044-10-09
Also published as: CN119297234A

Abstract

The invention discloses a watermelon-like silicon-carbon negative electrode material and a preparation method and application thereof, wherein the preparation method comprises the following steps of step 1, liquid phase cladding, namely adding nano silicon particles into a carbon source solution containing organic matters, uniformly stirring, filtering and drying to obtain an organic carbon source clad nano silicon material; and step 2, stirring and calcining the material obtained in the step 1 under the atmosphere of introducing protective gas, then introducing the protective gas after heating to obtain an intermediate material, and step 3, introducing carbon source gas into the intermediate material obtained in the step 2, and collecting a product after the surface of the intermediate material is deposited, wherein the product is the silicon-carbon negative electrode material imitating the watermelon structure. According to the silicon-carbon anode material, a gap is reserved between the carbon layer and silicon, so that space can be provided for volume expansion of silicon, the carbon layer and deposited carbon can buffer the volume expansion of silicon, and the volume expansion of silicon is restrained, so that a stable SEI film is formed on the outer side of the material, and consumption of lithium ions is reduced.

Description

Watermelon-structure-imitated silicon-carbon anode material and preparation method and application thereof

Technical Field

The invention relates to the technical field of lithium ion batteries, in particular to a watermelon-like structure silicon-carbon anode material and a preparation method and application thereof.

Background

The lithium ion battery is an indispensable part in modern technology due to the advantages of high energy density, low self-discharge rate, long cycle life, portability, environmental protection, no pollution and the like, and is applied to electric automobiles, smart phones and other electric tools. The lithium ion battery takes graphite as a traditional negative electrode, but because the theoretical specific capacity of the graphite is low (372 mAh/g), the lithium ion battery has a large development space in energy density and power density, and the current requirements of other electric equipment such as electric automobiles on endurance cannot be met.

Compared with a graphite electrode, the theoretical specific capacity of silicon is up to 4200mAh/g, which is 10 times of that of the graphite electrode. In addition, electrochemical lithium intercalation potential is low. Silicon is therefore considered to be the most potential negative electrode material for lithium ion batteries. However, silicon has some problems in delithiation and intercalation in that the volume of silicon material is greatly changed, repeated formation and rupture of SEI film, and continuous consumption of lithium ions results in low cycle efficiency of the battery.

Disclosure of Invention

The invention aims to provide a preparation method of a silicon-carbon negative electrode material with a watermelon-like structure, aiming at the problems that the volume change of a silicon material is huge, the repeated formation and rupture of an SEI film continuously consume lithium ions to cause low cycle efficiency of a battery in the prior art.

The second object of the invention is to provide the silicon-carbon negative electrode material with the watermelon-like structure, which is prepared by the preparation method.

The third object of the invention is to provide a negative plate based on the watermelon-like structure silicon-carbon negative electrode material.

A fourth object of the present invention is to provide a battery based on the negative electrode sheet.

The technical scheme adopted for realizing the purpose of the invention is as follows:

a preparation method of a watermelon-like structure silicon-carbon negative electrode material comprises the following steps:

step 1, liquid phase coating, namely adding nano silicon particles into a carbon source solution containing organic matters, uniformly stirring, filtering and drying to obtain an organic carbon source coated nano silicon material;

step 2, stirring and calcining the nano silicon material coated by the organic carbon source obtained in the step 1 at a first temperature for a first preset time under the atmosphere of introducing protective gas, and then heating to a second preset temperature to stop introducing the protective gas to obtain an intermediate material;

And 3, introducing carbon source gas into the intermediate material obtained in the step 2, depositing carbon on the surface of the intermediate material at a second preset temperature, stopping introducing the carbon source gas after depositing for a second preset time, preserving heat for a third preset time, and cooling to room temperature to collect a product, wherein the product is the watermelon-like structure silicon-carbon negative electrode material.

In the technical scheme, the diameter of the nano silicon particles is 5-100nm, and the specific surface area of the nano silicon particles is 50-1000m ²/g.

In the technical scheme, the stirring time in the step 1 is 2-10h;

And/or the mass fraction of the organic matters in the carbon source solution containing the organic matters is less than 15wt%.

In the above technical solution, the organic matter in the carbon source solution containing the organic matter in the step 1 is one or more of polyvinyl alcohol pyridone, glucose or carboxymethyl cellulose.

In the above technical scheme, the organic matters in the carbon source solution containing the organic matters in the step 1 are polyvinyl alcohol pyridone, glucose and carboxymethyl cellulose;

The mass fraction of the polyvinyl alcohol pyridone content is not more than 3wt%;

and/or, the mass fraction of glucose is no more than 5wt%;

And/or, the carboxymethyl cellulose content is not greater than 2.5wt%.

In the technical scheme, the protective gas in the step 2 is nitrogen, the flow rate of the nitrogen is 0.2-1L/min, the first preset temperature is 400-600 ℃, the first preset time is 2-6h, the stirring rotating speed is 2-10Hz, and the second preset temperature is 600-800 ℃;

And/or the flow rate of the carbon source gas in the step 3 is 1-2L/min, the second preset time is 6-8h, and the third preset time is 0.5-1h;

and/or the carbon source gas is one or more of methane, ethane, propane, ethylene, acetylene, benzene, naphthalene and anthracene.

In a second aspect of the invention, a watermelon-like structure silicon-carbon negative electrode material is provided, and is prepared by the preparation method.

In the technical scheme, the grain diameter of the watermelon-like structure silicon-carbon anode material is 3-35 mu m.

The third aspect of the invention provides a negative electrode plate, which comprises the silicon-carbon negative electrode material imitating the watermelon structure.

In a fourth aspect of the present invention, there is provided a battery including the negative electrode sheet.

Compared with the prior art, the invention has the beneficial effects that:

1. The invention provides a preparation method of a silicon-carbon negative electrode material imitating a watermelon structure, which comprises the steps of firstly coating a carbon layer outside nano silicon particles by a liquid phase solidification method to obtain an intermediate material, and then distributing a plurality of intermediate materials on deposited carbon by a vapor deposition method to form the silicon-carbon negative electrode material with the watermelon structure. And a gap is reserved between the carbon layer and the silicon, so that a space can be provided for the volume expansion of the silicon, and besides, the carbon layer and the deposited carbon can provide buffering for the volume expansion of the silicon and inhibit the volume expansion of the silicon. Therefore, a stable SEI film can be formed on the outer side of the material, and consumption of lithium ions is reduced.

2. The average diameter of the nano silicon particles in the silicon-carbon anode material is smaller than 100nm, which is favorable for the combination of lithium ions and silicon, and the particles are not broken due to huge strain in the processes of lithium removal and lithium intercalation, meanwhile, the sedimentation and agglomeration of the nano silicon particles are effectively prevented by adopting the aqueous solution of polyvinyl alcohol pyridone, glucose and carboxymethyl cellulose, and the carbon layer is formed by carbonizing the additives after calcination treatment and is used for coating the nano silicon particles, and can inhibit the volume change of silicon in the processes of lithium removal and lithium intercalation. In addition, during carbonization, solvent evaporation can form voids that provide room for the volumetric expansion of silicon. The deposited carbon formed in the carbon layer coating step is uniformly distributed in the intermediate products coated in the carbon layer coating step, the agglomeration phenomenon can not occur, and secondly, the deposited carbon can inhibit the volume expansion of silicon in the charge and discharge process, meanwhile, the specific surface area of the material can be reduced, the first coulomb efficiency and capacity of the battery are improved, in addition, the deposited carbon is tightly connected with a plurality of intermediate materials, a complete conductive framework is constructed, and the transfer of electrons and lithium ions is further promoted.

Drawings

FIG. 1 is a schematic structural diagram of a watermelon-like structure silicon-carbon negative electrode material provided by the invention;

FIG. 2 is an SEM image of a watermelon-like structure of a silicon-carbon negative electrode material according to example 1 of the present invention;

FIG. 3 is an EDS diagram of a silicon-carbon negative electrode material with a watermelon-like structure according to example 1 of the present invention;

FIG. 4 is a graph showing the distribution of carbon atoms in the watermelon-like structure of the silicon-carbon negative electrode material of example 1 of the present invention;

FIG. 5 is an oxygen atom distribution diagram of a watermelon-like structure silicon-carbon anode material in example 1 of the invention;

FIG. 6 is a graph showing the distribution of silicon atoms in a watermelon-like structure of a silicon-carbon negative electrode material according to example 1 of the present invention;

Fig. 7 is a graph showing the first charge and discharge of the watermelon-like structure silicon-carbon negative electrode material of example 1 of the present invention.

FIG. 8 is a chart showing coulombic efficiency performance of the watermelon-like structure silicon-carbon negative electrode material of example 1 of the present invention over multiple cycles.

Detailed Description

The present invention will be described in further detail with reference to specific examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

Example 1

A silicon-carbon negative electrode material imitating a watermelon structure is prepared by the following preparation method as shown in figure 1:

Step 1, liquid phase coating, namely pouring nano silicon particles into an aqueous solution of 3 weight percent of polyvinylpyrrolidone, 5 weight percent of glucose and 2.5 weight percent of carboxymethyl cellulose, uniformly stirring for 2 hours, filtering, and drying to obtain the nano silicon material coated with the organic carbon source.

And 2, placing the nano silicon material coated by the organic carbon source obtained in the step1 into a rotary furnace, starting the rotary furnace, introducing nitrogen at a flow rate of 0.2L/min, calcining for 4 hours at 400 ℃, keeping the rotation speed at 6Hz, heating to 700 ℃ at full power after calcining, and stopping introducing nitrogen to obtain the intermediate material.

And 3, cracking the carbon source, namely introducing acetylene at a flow rate of 1.5L/min, keeping for 8 hours, stopping introducing carbon source gas, keeping the temperature for 1 hour, cooling to room temperature, stopping the rotary kiln, and collecting the product to obtain the watermelon-like structure silicon-carbon negative electrode material.

TABLE 1 elemental content test results for the silicon carbon negative electrode material prepared in example 1

Element(s)	Line type	wt%	wt%σ	At%
					C	K-wire system	53.75	1.84	69.38
O	K-wire system	12.20	0.89	11.82
					Si	K-wire system	34.05	1.36	18.80
Total amount of		100		100

As shown in the SEM and EDS diagrams of the watermelon-like structure prepared in the embodiment as shown in FIG. 2 and FIG. 3, the preparation method and the equipment can uniformly distribute silicon in carbon to realize sufficient compounding of silicon and carbon, so as to obtain the watermelon-like structure silicon-carbon negative electrode material.

And preparing a negative plate by using a silicon-carbon negative electrode material with a watermelon-like structure, and assembling the lithium ion battery by using the negative plate for performance test. It can be seen that the first charge specific capacity of the lithium ion battery assembled by the silicon-carbon negative electrode material prepared by the embodiment is 1757.3 mAh.g ^-1, the first discharge specific capacity is 1978.1 mAh.g ^-1, the first coulomb efficiency is 88.84%, and the coulomb efficiency is maintained to be more than 99% after 250 times of circulation, so that the silicon-carbon negative electrode material with the watermelon-like structure can effectively relieve the volume expansion of silicon.

Example 2

In the embodiment, the silicon-carbon anode material with the watermelon-like structure is prepared by the following preparation method:

Step 1, liquid phase coating, namely pouring nano silicon particles into an aqueous solution of 3 weight percent of polyvinylpyrrolidone, 5 weight percent of glucose and 2.5 weight percent of carboxymethyl cellulose, uniformly stirring for 5 hours, filtering, and drying to obtain the nano silicon material coated with the organic carbon source.

And 2, placing the nano silicon material coated by the organic carbon source obtained in the step 1 into a rotary furnace, starting the rotary furnace, introducing nitrogen at a flow rate of 0.6L/min, calcining at 500 ℃ for 6 hours, maintaining the rotation speed at 8Hz, heating to 600 ℃ at full power after calcining, and stopping introducing nitrogen to obtain the intermediate material.

And 3, cracking the carbon source, namely introducing acetylene at the flow rate of 2L/min, keeping for 7h, stopping introducing the carbon source gas, keeping the temperature for 0.5h, cooling to room temperature, stopping the rotary kiln, and collecting the product to obtain the watermelon-like structure silicon-carbon negative electrode material.

Example 3

Step 1, liquid phase coating, namely pouring nano silicon particles into an aqueous solution of 3 weight percent of polyvinylpyrrolidone, 5 weight percent of glucose and 2.5 weight percent of carboxymethyl cellulose, uniformly stirring for 8 hours, filtering, and drying to obtain the nano silicon material coated with the organic carbon source.

And 2, placing the nano silicon material coated by the organic carbon source obtained in the step1 into a rotary furnace, starting the rotary furnace, introducing nitrogen at a flow rate of 0.9L/min, calcining at 600 ℃ for 12h, maintaining the rotation speed at 9Hz, heating to 700 ℃ at full power after calcining, and stopping introducing nitrogen to obtain the intermediate material.

And 3, cracking the carbon source, namely introducing acetylene at a flow rate of 1.5L/min, keeping for 7 hours, stopping introducing carbon source gas, keeping the temperature for 0.5 hour, cooling to room temperature, stopping the rotary kiln, and collecting the product to obtain the silicon-carbon negative electrode material with the watermelon-like structure.

Example 4

And 2, placing the nano silicon material coated by the organic carbon source obtained in the step 1 into a rotary furnace, starting the rotary furnace, introducing nitrogen at a flow rate of 0.7L/min, calcining for 3 hours at 450 ℃, maintaining the rotation speed at 5Hz, heating to 800 ℃ at full power after calcining, and stopping introducing nitrogen to obtain the intermediate material.

And 3, cracking the carbon source, namely introducing acetylene at the flow rate of 2L/min, keeping for 7h, stopping introducing the carbon source gas, keeping the temperature for 1h, cooling to room temperature, stopping the rotary furnace, and collecting the product to obtain the watermelon-like structure silicon-carbon negative electrode material.

Example 5

Step 1, liquid phase coating, namely pouring nano silicon particles into an aqueous solution of 3 weight percent of polyvinylpyrrolidone, 5 weight percent of glucose and 2.5 weight percent of carboxymethyl cellulose, uniformly stirring for 3 hours, filtering, and drying to obtain the nano silicon material coated with the organic carbon source.

And 2, placing the nano silicon material coated by the organic carbon source obtained in the step 1 into a rotary furnace, starting the rotary furnace, introducing nitrogen at a flow rate of 0.5L/min, calcining at 600 ℃ for 4 hours, maintaining the rotation speed at 4Hz, heating to 800 ℃ at full power after calcining, and stopping introducing nitrogen to obtain an intermediate product.

And 3, cracking the carbon source, namely introducing acetylene at a flow rate of 1.5L/min, keeping for 6 hours, stopping introducing carbon source gas, keeping the temperature for 0.5 hour, cooling to room temperature, stopping the rotary kiln, and collecting the product to obtain the silicon-carbon negative electrode material with the watermelon-like structure.

Example 6

Step 1, liquid phase coating, namely pouring nano silicon particles into an aqueous solution of 3 weight percent of polyvinylpyrrolidone, 5 weight percent of glucose and 2.5 weight percent of carboxymethyl cellulose, uniformly stirring for 6 hours, filtering, and drying to obtain the nano silicon material coated with the organic carbon source.

And 2, placing the nano silicon material coated by the organic carbon source obtained in the step 1 into a rotary furnace, starting the rotary furnace, introducing nitrogen at a flow rate of 0.2L/min, calcining for 5 hours at 500 ℃, keeping the rotary furnace at a rotation speed of 10Hz, heating to 600 ℃ at full power after calcining, and stopping introducing nitrogen to obtain an intermediate product.

And 3, cracking the carbon source, namely introducing acetylene at the flow rate of 1L/min, keeping for 6 hours, stopping introducing the carbon source gas, keeping the temperature for 1 hour, cooling to room temperature, stopping the rotary furnace, and collecting the product to obtain the watermelon-like structure silicon-carbon negative electrode material.

The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims

1. A method for preparing a silicon-carbon anode material with a watermelon-like structure, characterized by comprising the following steps:

Step 1, liquid phase coating: Add nano-silicon particles to a carbon source solution containing organic matter, stir evenly, filter, and dry to obtain nano-silicon material coated with organic carbon source. The organic matter includes polyvinylpyrrolidone, glucose, and carboxymethyl cellulose.

Step 2: The nano-silicon material coated with organic carbon source obtained in Step 1 is stirred and calcined at a first predetermined temperature for a first predetermined time under a protective gas atmosphere, and then heated to a second predetermined temperature and the protective gas is stopped to obtain an intermediate material.

Step 3: Introduce carbon source gas into the intermediate material obtained in Step 2, deposit carbon on the surface of the intermediate material at a second predetermined temperature, stop introducing carbon source gas after a second predetermined time, keep warm for a third predetermined time, and then collect the product at room temperature. The product is the silicon-carbon anode material with the watermelon-like structure. The first predetermined temperature is 400-600℃, and the second predetermined temperature is 600-800℃.

2. The method for preparing the watermelon-like silicon-carbon anode material according to claim 1, characterized in that the diameter of the nano-silicon particles is 5-100 nm, and the specific surface area of the nano-silicon particles is 50-1000 ^m² /g.

3. The method for preparing the watermelon-like silicon-carbon anode material as described in claim 1, characterized in that the stirring time in step 1 is 2-10 hours;

And/or, the mass fraction of organic matter in the carbon source solution containing organic matter is less than 15 wt%.

4. The method for preparing the watermelon-like silicon-carbon anode material as described in claim 1, characterized in that the content of organic matter in the carbon source solution containing organic matter in step 1 is;

The polyvinylpyrrolidone content is no more than 3 wt%; the glucose content is no more than 5 wt%; and the carboxymethyl cellulose content is no more than 2.5 wt%.

5. The method for preparing the watermelon-like silicon-carbon anode material according to claim 1, characterized in that, in step 2, the protective gas is nitrogen, the flow rate of nitrogen is 0.2-1 L/min, the first predetermined time is 2-6 h, the stirring speed is 2-10 Hz, and/or, in step 3, the flow rate of the carbon source gas is 1-2 L/min, the second predetermined time is 6-8 h, and the third predetermined time is 0.5-1 h;

And/or, the carbon source gas is one or more of methane, ethane, propane, ethylene, acetylene, benzene, naphthalene, and anthracene.

6. A silicon-carbon anode material with a watermelon-like structure, characterized in that it is prepared by the preparation method described in any one of claims 1-5.

7. The silicon-carbon anode material with a watermelon-like structure as described in claim 6, characterized in that the particle size of the silicon-carbon anode material with a watermelon-like structure is 3-35 μm.

8. A negative electrode sheet, characterized in that it comprises a silicon-carbon negative electrode material with a watermelon-like structure as described in any one of claims 6-7.

9. A battery, characterized in that it comprises the negative electrode sheet as described in claim 8.