CN116544413A

CN116544413A - Preparation method of phosphorus-doped silicon-based composite anode material, and product and application thereof

Info

Publication number: CN116544413A
Application number: CN202310456019.6A
Authority: CN
Inventors: 杜宁; 王振; 叶天成; 孙宁; 叶翠翠
Original assignee: Zhejiang Lichen New Material Technology Co ltd
Current assignee: Zhejiang Lichen New Material Technology Co ltd
Priority date: 2023-04-25
Filing date: 2023-04-25
Publication date: 2023-08-04

Abstract

The invention discloses a preparation method of a phosphorus doped silicon-based composite anode material, which comprises the following steps: (1) Fully mixing phosphorus source gas, carbon source gas and silicon source gas at room temperature under inert atmosphere to obtain mixed gas; in the mixed gas, the total volume is 100%, the volume ratio of the phosphorus source gas is 0.1-3.0%, the volume ratio of the carbon source gas is 15-28%, and the balance is the silicon source gas; (2) Introducing the mixed gas into a deposition furnace in which a substrate material is placed, and obtaining an intermediate product after thermal deposition; (3) And (3) carrying out carbon coating treatment on the intermediate product, and then carrying out post-treatment to obtain the phosphorus doped silicon-based composite anode material. The invention discloses a preparation method of a phosphorus-doped silicon-based composite anode material, and a lithium ion battery assembled by the prepared anode material has excellent cycling stability, high reversible specific capacity and first coulombic efficiency.

Description

Preparation method of phosphorus-doped silicon-based composite anode material, and product and application thereof

Technical Field

The invention relates to the technical field of lithium battery anode materials, in particular to a preparation method of a phosphorus doped silicon-based composite anode material, a product and application thereof.

Background

Silicon is considered to be the most promising candidate for replacing graphite. It is the second most abundant element in the crust, is environment-friendly, and has an ultra-high theoretical capacity (4200 mAh/g). However, the drastic change in volume during lithium intercalation/deintercalation has serious adverse consequences, resulting in very poor cycling stability. Although the volumetric expansion of the silica material during lithium intercalation is greatly reduced compared with the simple substance of silicon, and the silica material also has higher theoretical specific capacity (> 2000 mAh/g), the first coulombic efficiency of the silica is too low (lower than 76%), which limits the application of the silica material to a wider range; compared with silicon oxide, the silicon-carbon product in the market has the characteristics of high first efficiency and high capacity, but the cycle performance of the silicon-carbon product is far less than that of the silicon oxide; therefore, the preparation of the silicon-based anode material with high capacity, high first efficiency and cycle performance is a urgent need at present.

A method for preparing a phosphorus doped porous carbon anode material with improved coulombic efficiency for the first time is disclosed in the chinese patent document with application publication number CN 107623118A. And dispersing an organic carbon source into water to form slurry, uniformly mixing the slurry with red phosphorus, drying, placing the dried slurry in a sealed tank filled with protective atmosphere, and calcining the calcined slurry in an inert atmosphere tube furnace to prepare the phosphorus doped porous carbon anode material. According to the technical scheme, phosphorus is taken as a doping element, so that the reversible specific capacity of the carbon material can be improved, and the first coulomb efficiency of the material is remarkably improved. The preparation method disclosed in the technical scheme is simple, but the uniformity of doping cannot be ensured by adopting liquid-phase and solid-phase mixing, so that the consistency of the preparation method can be influenced; and the first coulomb efficiency of the material obtained by the method is only 71%, which is insufficient to meet the market demand.

The Chinese patent document with the application publication number of CN 113809311A discloses a phosphorus-doped soft carbon coated silicon-based lithium ion anode material, and a preparation method and application thereof. Taking a phosphorus-containing gas source or a high-boiling point phosphorus-containing compound as a doping material, and carrying out gas-phase mixing reaction on vapor of the doping material and preheated vapor of a silicon source at 1200-1700 ℃ for 1-24h to obtain a phosphorus-doped silicon oxide material; the silicon source vapor is a mixed gas of silicon vapor and silicon dioxide vapor; and cooling the phosphorus doped silicon oxide material to room temperature, discharging, crushing and screening, analyzing and testing the screened material, and coating the material with the doping uniformity meeting the preset condition with carbon to obtain the phosphorus doped silicon-based lithium ion anode material. According to the technical scheme, the phosphorus-containing substance, the silicon vapor and the silicon oxide vapor are subjected to gas-phase mixing reaction, so that the reaction substances are fully contacted to obtain the lithium ion battery anode material with uniform bulk phase doping, the obtained material has higher cycling stability, and meanwhile, the consistency of the material is more excellent. However, the initial effect of the phosphorus doped silicon anode material obtained by the method is only 80.6% at maximum, and no obvious product advantage is achieved. More importantly, the energy consumption of the technical scheme is very high, the temperature required for preheating silicon and silicon dioxide to form vapor at least reaches 1350 ℃, the gas phase mixing reaction is also carried out at the high temperature of 1200-1700 ℃, and the later carbon coating is also carried out at the high temperature of 800-1000 ℃. Therefore, this technical solution is not suitable for large-scale industrial production.

Disclosure of Invention

Aiming at the problems in the prior art, the invention discloses a preparation method of a phosphorus-doped silicon-based composite anode material, and a lithium ion battery assembled by the prepared anode material has excellent cycling stability, high reversible specific capacity and first coulombic efficiency.

The specific technical scheme is as follows:

a preparation method of a phosphorus doped silicon-based composite anode material comprises the following steps:

(1) Fully mixing phosphorus source gas, carbon source gas and silicon source gas at room temperature under inert atmosphere to obtain mixed gas;

in the mixed gas, the total volume is 100%, the volume ratio of the phosphorus source gas is 0.1-3.0%, the volume ratio of the carbon source gas is 15-28%, and the balance is the silicon source gas;

(2) Introducing the mixed gas into a deposition furnace in which a substrate material is placed, and obtaining an intermediate product after thermal deposition;

(3) And (3) carrying out carbon coating treatment on the intermediate product, and then carrying out post-treatment to obtain the phosphorus-doped silicon-based composite anode material.

The invention discloses a preparation method of a phosphorus doped silicon-based composite anode material, which takes phosphine which is in a gaseous state at normal temperature as a silicon source, additionally introduces a gaseous carbon source, mixes the phosphine with the gaseous silicon source at the room temperature to obtain a mixed gas, and respectively bonds carbon and phosphorus with the silicon source material in the vapor deposition reaction process and carries out pyrolysis dehydrogenation; finally, the phosphorus doped silicon-based composite anode material is prepared through carbon coating treatment.

Experiments show that the average grain diameter of primary silicon grains can be obviously reduced by doping phosphorus atoms in the preparation method; the introduction of the gaseous carbon source can be mutually cooperated with the generation of doped phosphorus atoms, which is helpful for the cracking of phosphorus source gas and the promotion of the doping of phosphorus source, and when the phosphorus source gas and the silicon source gas are simultaneously blended, the phosphorus doped silicon-based composite anode material finally prepared through the series of processes has excellent cycle stability, reversible specific capacity and first coulombic efficiency.

It has been found through experiments that the above synergistic effect cannot be obtained by using only a combination of a phosphorus source gas and a silicon source gas, or only a combination of a carbon source gas and a silicon source gas.

Further experiments show that even if the combination of the phosphorus source gas, the carbon source gas and the silicon source gas is adopted, the lithium ion battery with excellent cycle stability, high reversible specific capacity and first coulombic efficiency cannot be prepared without the volume ratio of the three.

In step (1):

the phosphorus source gas is selected from phosphine;

the carbon source gas is selected from alkane gases which can be cracked at 400-800 ℃; preferably from ethylene, propylene, acetylene, etc.

The silicon source gas is selected from one or more of silane, dichlorosilane, trichlorosilane and silicon tetrachloride.

In the step (2):

the total flow rate of the mixed gas is 0.1-50L/min; preferably 20 to 50L/min; more preferably 25 to 30L/min.

The substrate material is selected from one or more of hard carbon, conductive carbon black, carbon nano tube and graphene; the mass of the added base material accounts for 0.1 to 20.0 weight percent of the total mass of the final product.

Preferably, the D50 of the substrate material is less than 200nm.

The temperature of the thermal deposition is 400-800 ℃.

In the step (3):

the intermediate product is crushed, graded and demagnetized and then subjected to carbon coating treatment;

preferably, the granularity concentration (SPAN value) of the intermediate product after crushing, grading and demagnetizing is less than or equal to 1.5, and the average particle size is less than or equal to 10 mu m; more preferably, the SPAN value is less than or equal to 1.2.

In the step (3):

the carbon coating treatment is one or more selected from gas-phase carbon coating, liquid-phase carbon coating and solid-phase carbon coating;

the carbon source adopted by the gas-phase carbon coating is hydrocarbon gas such as ethylene, propylene, acetylene and the like, and the specific carbon coating process adopts the conventional technical means in the field.

The carbon source adopted by the liquid-phase carbon coating is carbon-containing high molecular polymer, such as liquid epoxy resin, petroleum residual oil, liquid asphalt and the like, and the specific carbon coating process adopts the conventional technical means in the field.

The carbon source adopted by the solid-phase carbon coating is asphalt, and the specific carbon coating process adopts the conventional technical means in the field.

The temperature of the carbon coating treatment is selected from 600-1000 ℃; the adaptation is carried out according to the type of the carbon source.

In the step (3):

the post-treatment comprises breaking up and sieving, and the specific operation is a conventional technical means in the field. If the scattering mode adopts spiral scattering.

Preferably, the mesh number adopted by the screening is 100-800 mesh.

Based on the above process and raw materials, it is preferable that:

in the step (1), the volume ratio of the phosphorus source gas in the mixed gas is 0.5-3.0%, the volume ratio of the carbon source gas is 15-25%, and the balance is the silicon source gas;

further preferred is:

in the mixed gas, the volume ratio of the phosphorus source gas is 0.5-1.5%, the volume ratio of the carbon source gas is 15-25%, and the balance is the silicon source gas;

more preferably, in the mixed gas, the phosphorus source gas, the carbon source gas and the silicon source gas are sufficiently mixed at room temperature in a volume ratio of 1.5:25:73.5.

Most preferably, the silicon source is selected from the group consisting of trichlorosilane; experiments show that the lithium ion battery assembled by the phosphorus doped silicon-based composite anode material finally prepared by adopting trichlorosilane as a silicon source under the further preferred volume ratio has the best cycle stability, reversible specific capacity and first coulombic efficiency.

The invention also discloses the phosphorus doped silicon-based composite anode material prepared by the method.

The invention also discloses application of the phosphorus-doped silicon-based composite anode material prepared by the method in a lithium ion battery, and experiments show that the lithium ion battery assembled by the anode material has excellent cycling stability, high reversible specific capacity and first coulombic efficiency.

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

the invention discloses a preparation method of a phosphorus doped silicon-based composite anode material, which takes phosphorus source gas, carbon source gas and silicon source gas as raw materials, has simple and controllable preparation process and low energy consumption, and is suitable for industrial production.

The lithium ion battery assembled by the phosphorus doped silicon-based composite anode material prepared by the invention has excellent cycling stability, and the capacity retention rate after 100 times of cycling is up to more than 80%, and can be up to 88% at most; the capacity retention rate after 500 times of circulation is up to more than 70%, and the highest capacity retention rate can be up to 75.5%; and has both high reversible specific capacity (higher than 1800 mAh/g) and first coulombic efficiency (not lower than 90%).

Drawings

FIG. 1 is a Mapping image of the intermediate product prepared in example 1;

fig. 2 to 4 are distribution diagrams of Si element, C element, and P element, respectively, in the image range of fig. 1;

FIG. 5 is an SEM image of a phosphorus doped silicon-based composite anode material prepared in example 1;

fig. 6 is a TEM image of the phosphorus doped silicon based composite anode material prepared in example 1.

Detailed Description

The following examples are presented to further illustrate the invention and should not be construed as limiting the invention.

Example 1

(1) And fully mixing phosphine, ethylene and monosilane in a volume ratio of 1.5:25:73.5 at room temperature under the argon atmosphere to obtain a mixed gas.

(2) Introducing the mixed gas into a deposition furnace which is used for placing 100 g of hard carbon microspheres with the D50 of about 100nm and the temperature of 500 ℃ at the flow rate of 25L/min, continuously introducing the mixed gas until the surfaces of the hard carbon microspheres continuously form nuclei for growth, depositing to form a phosphorus-doped silicon carbon deposition layer, and keeping the aeration time at 10h.

(3) Cooling the deposition furnace, crushing and grading the materials after discharging the materials from the furnace to obtain uniform particles with D50 less than 5 mu m and SPAN value less than 1.2, and magnetically treating to obtain an intermediate product.

(4) And (3) under the argon atmosphere, putting the intermediate product into a chemical vapor deposition furnace, heating to 800 ℃ at a speed of 5 ℃/min, introducing acetylene gas at a flow speed of 1L/min to carry out vapor phase pyrolysis deposition carbon coating, controlling the carbon content of the carbon coating to be 4wt% of the total mass of the final product, cooling to room temperature after the deposition is finished, taking out the material, and scattering and screening to finally obtain the phosphorus doped silicon-based composite anode material.

Fig. 1 is a Mapping image of the intermediate product prepared in step (3) of this example, and distribution diagrams of Si element (fig. 2), C element (fig. 3) and P element (fig. 4) within the image range, and it can be found from the observation of fig. 2 to 4 that C, P elements have been successfully doped in the intermediate product prepared in this example, and that the two elements are uniformly dispersed in the intermediate product.

Fig. 5 is an SEM image of the final product prepared in this example, which is observed to show that the final product prepared in this example is in a regular spherical shape and has a relatively uniform particle size distribution.

Fig. 6 is a TEM image of the final product prepared in this example, which was observed to show that the surface of the negative electrode material prepared in this example was coated with a uniform carbon layer.

Example 2

The preparation process was essentially the same as in example 1, except that in step (1), the volume ratio of phosphine, ethylene and monosilane was replaced by 3:15:82.

Example 3

The preparation process was essentially the same as in example 1, except that in step (1), the volume ratio of phosphine, ethylene and monosilane was replaced by 0.5:25:74.5.

Comparative example 1

The preparation process was essentially the same as in example 1, except that in step (1), the volume ratio of phosphine, ethylene and monosilane was replaced by 5:25:70.

Comparative example 2

The preparation process was substantially the same as in example 1, except that in step (1), only ethylene and monosilane were added in a volume ratio of 25:75 to mix to obtain a mixed gas.

Comparative example 3

The preparation process was essentially the same as in example 1, except that in step (1), the volume ratio of phosphine, ethylene and monosilane was replaced by 2:30:68.

Comparative example 4

The preparation process was essentially the same as in example 1, except that in step (1), the volume ratio of phosphine, ethylene and monosilane was replaced by 2:13:85.

Comparative example 5

The preparation process was essentially the same as in example 1, except that in step (1), only phosphine was added in a volume ratio of 2:98 and mixed with monosilane to obtain a mixed gas.

Example 4

(1) And fully mixing phosphine, propylene and dichlorosilane in a volume ratio of 1.5:25:73.5 at room temperature under the argon atmosphere to obtain a mixed gas.

(2) Introducing the mixed gas into a deposition furnace which is used for placing 100 g of graphene microspheres with the D50 of about 100nm and the temperature of 400 ℃ at the flow rate of 30L/min, continuously introducing the mixed gas until the surfaces of the graphene microsphere particles continuously form nuclei for growth, depositing to form a phosphorus-doped silicon carbon deposition layer, and keeping the aeration time at 13h.

Steps (3) to (4) are exactly the same as in example 1.

Example 5

(1) And fully mixing phosphine, acetylene and trichlorosilane at the volume ratio of 1.5:25:73.5 at room temperature under the argon atmosphere to obtain a mixed gas.

(2) And (3) introducing the mixed gas into a deposition furnace which is used for placing 100 g of conductive carbon black microspheres with the D50 of about 100nm and the temperature of 800 ℃ at the flow rate of 30L/min, continuously introducing the mixed gas until the surfaces of the conductive carbon black microspheres continuously form nuclei for growth, depositing to form a phosphorus-doped silicon carbon deposition layer, and keeping the aeration time at 5h.

Steps (3) to (4) are exactly the same as in example 1.

Application example

The anode materials prepared in each example and each comparative example were assembled into batteries, respectively.

Fully mixing and dispersing a conductive agent SuperP, sodium carboxymethylcellulose CMC and deionized water under a nitrogen protection atmosphere, adding a negative electrode material, stirring at 2000rpm for 10min, adding an aqueous binder AONE (purchased from Shenzhen City, ind. Of new materials Co., ltd.) and stirring at 2000rpm for 10min to obtain a negative electrode slurry. Wherein, the mass ratio of the cathode material to the conductive agent SuperP to the sodium carboxymethylcellulose CMC to the binder AONE (dry weight) is 70:15:5:10, the solids content of the slurry was 15wt%.

Coating the above cathode slurry on a current collector copper foil, drying at 80deg.C under relative vacuum degree of-0.1 Mpa for 30min, and rolling at room temperature to obtain a surface density of 9.1mg/cm ² Then punching and shearing into a wafer with the diameter of 14mm to prepare the electrode plate.

The counter electrode used was lithium plate CR2016 (available from Shenzhen Yongxing industry equipment science Co., ltd.) with a diameter of 16mm.

And assembling the button cell in a glove box under the protection of argon, wherein the moisture value and the oxygen value in the glove box are less than 0.01ppm. Assembled in the order of "negative electrode case-gasket-lithium sheet-electrolyte-separator-electrolyte electrode sheet-positive electrode case", wherein the electrolyte consists of Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) (EC: EMC: DEC volume ratio=1:1:1), contains LiPF of 1.0M ₆ 。

Wherein the diameter of the electrode sheet is 14mm, the diameter of the lithium sheet is 16mm, the diameter of the separator is 19mm, and the size of the battery case (positive electrode case and negative electrode case) is 20mm. The separator was a ceramic coated separator film (available from Shanghai Enjetsche New Material technologies Co., ltd.) having a thickness of 12. Mu.m. Placing the assembled button cell in a die cavity of a hydraulic sealing machine (available from Shenzhen Kogyo Co., ltd.), locking, and pressing>500kg/cm ² And then unlocking, and taking out the button cell with the sealed mouth.

When the batteries were assembled, five button cells were prepared for each set of tests, five sets of data were tested together, and the final performance was averaged over the five sets of data.

Performance test:

the XRD-D2 PHASER of Bruce is adopted for phase analysis and detection, and the Shelle formula is adopted for calculation, so that the grain size of the primary silicon grains is tested.

Morphology testing was performed using sammer femto Phenom Generation 5.

The carbon content was measured using a German El ultra-high frequency infrared carbon sulfur analyzer.

The phosphorus content was measured using a german Ai Limeng column organic element analyzer.

The battery cycle performance is tested on a blue battery test system CT2001A device, specifically:

and detecting the charge-discharge cycle characteristics of the button cell by using the blue electricity test cabinet at 25 ℃. Firstly, discharging to 0.005V at 0.1C, then discharging to 0.001V at 0.08C, discharging to 0.001V at 0.05C, discharging to 0.001V at 0.02C, and standing for 10min; charging to 1.5V at 0.1C, standing for 10min, recording the charge-discharge capacity after the first cycle, and calculating the first coulomb efficiency; and (3) circulating for 100 times in the above way, recording the charge and discharge capacity after 100 times, calculating to obtain the capacity retention rate after 100 times of circulation, wherein the capacity retention rate after 500 times of circulation is tested in the same way as the calculation process, and the test results are shown in the table 1 below.

TABLE 1

1. The mass content of phosphorus element in the intermediate products prepared for each example or each comparative example respectively;

2. the mass content of carbon element in the intermediate product prepared for each example or each comparative example, respectively;

3. average particle diameter of silicon primary crystal grains of intermediate products prepared for each example or each comparative example, respectively.

As can be seen by comparing the variations in the phosphorus content and the carbon content in Table 1, the disclosed method allows for the controlled production of phosphorus content and carbon content in the product. As is clear from the average particle size of the primary silicon crystal grains in comparative example 1 and comparative examples 2 and 3, the incorporation of the phosphorus element can effectively reduce the average particle size of the primary silicon crystal grains.

The present invention can be well implemented according to the above-described embodiments. It should be noted that, based on the above design, even if some insubstantial modifications or color-rendering are made on the present invention, the essence of the adopted technical solution is still the same as the present invention, so it should be within the protection scope of the present invention.

Claims

1. The preparation method of the phosphorus-doped silicon-based composite anode material is characterized by comprising the following steps of:

2. The method for preparing a phosphorus-doped silicon-based composite anode material according to claim 1, wherein in step (1):

the phosphorus source gas is selected from phosphine;

the carbon source gas is selected from alkane gases which can be cracked at 400-800 ℃;

3. The method for preparing a phosphorus-doped silicon-based composite anode material according to claim 1, wherein in the step (2):

the total flow rate of the mixed gas is 0.1-50L/min;

the substrate material is selected from one or more of hard carbon, conductive carbon black, carbon nano tube and graphene;

the temperature of the thermal deposition is 400-800 ℃.

4. The method for preparing a phosphorus-doped silicon-based composite anode material according to claim 1, wherein in the step (3):

the granularity concentration of the intermediate product after crushing, grading and demagnetizing is less than or equal to 1.5, and the average grain diameter is less than or equal to 10 mu m.

5. The method for preparing a phosphorus-doped silicon-based composite anode material according to claim 1, wherein in the step (3):

the temperature of the carbon coating treatment is selected from 600-1000 ℃.

6. The method for preparing a phosphorus-doped silicon-based composite anode material according to claim 1, wherein in the step (3):

the post-treatment includes breaking up and sieving.

7. The method for preparing a phosphorus-doped silicon-based composite anode material according to any one of claims 1 to 6, characterized in that:

in the step (2), the total flow rate of the mixed gas is 20-50L/min.

8. The method for preparing the phosphorus-doped silicon-based composite anode material according to claim 7, wherein the method comprises the following steps:

in the mixed gas, the phosphorus source gas, the carbon source gas and the silicon source gas are fully mixed at room temperature in a volume ratio of 1.5:25:73.5;

the silicon source gas is selected from trichlorosilane.

9. A phosphorus doped silicon based composite anode material prepared according to the method of any one of claims 1 to 8.

10. Use of the phosphorus-doped silicon-based composite anode material according to claim 9 in a lithium ion battery.