Preparation method and application of amorphous silicon and lithium ion battery
The preparation of amorphous silicon by supercritical preparation method solves the problem of volume expansion and contraction of crystalline silicon during lithiation, and improves the first charge and discharge efficiency and cycle stability of lithium-ion batteries.
Patent Information
- Application Number
- CN202411810563.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-10
- Publication Date
- 2025-03-07
AI Technical Summary
The volume expansion and contraction of crystalline silicon during lithiation leads to irreversible capacity loss, which seriously hinders its large-scale application in lithium-ion batteries.
The supercritical preparation method is adopted, by adding silane gas and linear saturated hydrocarbon solvent to the reactor, heating and pressurization, so that it reaches the supercritical state, and the amorphous silicon obtained is collected after a certain period of time.
It realizes efficient and low-energy consumption amorphous silicon preparation, reduces volume expansion and contraction, and improves the first charge and discharge efficiency and cycle stability of lithium-ion batteries.
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Figure CN119569062A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a preparation method and application of amorphous silicon and a lithium ion battery. Background Art
[0002] Most of the current research on lithium-ion batteries is focused on high energy density materials for applications such as electric and hybrid vehicles. Graphite anodes have been successfully commercialized due to their stable cycling characteristics, but are still limited by their limited specific capacity (372 mAh / g). Si can alloy with lithium at room temperature to form Li 3.75 Si, corresponding to 3579 mAh / g, has a specific capacity close to 10 times that of graphite. However, crystalline Si undergoes a 400% volume expansion during the lithiation process. Because volume expansion and contraction can cause Si to pulverize and lose electrical contact with the current collector and conductive agent, a large irreversible capacity loss is observed during the lithiation / delithiation process, which seriously hinders the large-scale application of silicon anodes in lithium-ion batteries.
[0003] Since the electrochemical lithiation / delithiation of crystalline Si will transform into amorphous state in only a few cycles, amorphous silicon (a-Si) shows more advantages for LIB applications. a-Si has many potential advantages over crystalline Si, including smaller volume expansion and smaller charge transfer resistance, and nano-sized a-Si has better cycle performance during volume expansion / contraction.
[0004] Therefore, it is necessary to provide a new method for preparing amorphous silicon. Summary of the invention
[0005] In order to solve the above technical problems, the present invention provides a method for preparing amorphous silicon. The method adopts supercritical fluid to prepare amorphous silicon, which can improve the initial charge and discharge efficiency of lithium batteries and the cycle stability in the battery.
[0006] The invention also provides application of amorphous silicon as carbon negative electrode material.
[0007] The present invention also provides a lithium ion battery comprising the amorphous silicon prepared by the preparation method.
[0008] In order to achieve the above object, the present invention adopts the following technical scheme:
[0009] A method for preparing amorphous silicon comprises the following steps:
[0010] S1: adding a certain volume ratio of silane gas and straight-chain saturated hydrocarbon solvent into the reactor;
[0011] S2: heating and pressurizing the reactor to reach a supercritical state;
[0012] S3: After maintaining the supercritical state for a certain period of time, amorphous silicon can be obtained by collection.
[0013] Wherein, step S1 and step S3 are performed in an inert gas atmosphere.
[0014] Wherein, the silane gas is
[0015] And / or, the straight-chain saturated hydrocarbon solvent is at least one of n-pentane, n-hexane, n-heptane and n-octane.
[0016] Wherein, the supercritical state is maintained for 5 minutes to 30 minutes.
[0017] Wherein, the volume ratio of the silane gas to the straight-chain saturated hydrocarbon solvent is 1:(10-500).
[0018] Wherein, the volume ratio of the silane gas to the straight-chain saturated hydrocarbon solvent is 1:(20-200).
[0019] Wherein, the temperature of the supercritical state is 200°C to 600°C, and the pressure is 5MPa to 50MPa.
[0020] Wherein, the temperature of the supercritical state is 300°C to 500°C, and the pressure is 20MPa to 40MPa.
[0021] The above-mentioned amorphous silicon is used as the negative electrode material of lithium-ion batteries.
[0022] A lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a diaphragm, wherein the negative electrode sheet comprises amorphous silicon obtained by the above-mentioned preparation method of amorphous silicon.
[0023] The beneficial effects of the present invention are as follows:
[0024] (1) The present invention prepares amorphous silicon by thermally decomposing silane in a supercritical state, thereby achieving a high-efficiency, low-energy consumption preparation technology.
[0025] (2) The amorphous silicon of the present invention exhibits smaller volume expansion and contraction during the process of lithium insertion and extraction, and the material particle size is optimized; this is reflected in higher initial efficiency and longer cycle performance in lithium batteries. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 This is a comparison of XRD patterns of materials prepared in Example 1 and Comparative Example 1;
[0027] Figure 2 It is a comparison chart of the room temperature cycle performance of button-type half-cells using the materials prepared in Example 1 and Comparative Example 1 as negative electrode materials. DETAILED DESCRIPTION
[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0029] A method for preparing amorphous silicon comprises the following steps:
[0030] S1: Add a certain volume ratio of silane gas and straight-chain saturated hydrocarbon solvent into the reactor; the reactor is required to be sealed and able to meet the pressure required for subsequent preparation;
[0031] S2: heating and pressurizing the reactor to reach a supercritical state; a supercritical state is a state in which the pressure and temperature of a substance simultaneously exceed its critical pressure (Pc) and critical temperature (Tc), or in other words, a state in which the relative pressure (P / Pc) and relative temperature (T / Tc) of a substance are simultaneously greater than 1 is called a supercritical state of the substance; the pressure and temperature required for the supercritical state in the present invention are the pressure and temperature of the supercritical state of a straight-chain saturated hydrocarbon solvent;
[0032] S3: After maintaining the supercritical state for a certain period of time, amorphous silicon can be obtained by collection.
[0033] The silane in the present invention is the raw material of amorphous silicon, and the straight-chain saturated hydrocarbon solvent is used as the solvent. The silane gas can be used to prepare amorphous silicon at low temperature and quickly in the state of supercritical solvent. The particle size of the amorphous silicon prepared by the present invention is 0.1-1um, and the hydrogen content is 1%-3wt%.
[0034] Preferably, step S1 and step S3 are performed in an inert gas atmosphere. That is, the addition of silane gas and solvent is performed in an inert gas atmosphere; the collection of amorphous silicon is also performed in an inert gas atmosphere. The inert gas atmosphere is one of argon and helium.
[0035] Preferably, the silane gas is Trisilane is preferred.
[0036] Preferably, the straight-chain saturated hydrocarbon solvent is at least one of n-pentane, n-hexane, n-heptane and n-octane; preferably n-hexane.
[0037] Preferably, the supercritical state is maintained for 5 min to 30 min, and more preferably for 10 min to 20 min.
[0038] Preferably, the volume ratio of the silane gas to the straight-chain saturated hydrocarbon solvent is 1:(10-500).
[0039] More preferably, the volume ratio of the silane gas to the straight-chain saturated hydrocarbon solvent is 1:(20-200).
[0040] Preferably, the temperature of the supercritical state is 200° C. to 600° C., and the pressure is 5 MPa to 50 MPa.
[0041] More preferably, the temperature of the supercritical state is 300° C. to 500° C., and the pressure is 20 MPa to 40 MPa.
[0042] A lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a diaphragm, wherein the negative electrode sheet comprises the above-mentioned silicon negative electrode material.
[0043] The experimental methods used in the following specific examples are all conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples are all commercially available unless otherwise specified.
[0044] Example 1
[0045] The method for preparing amorphous silicon in this embodiment comprises the following steps:
[0046] S1: In an argon glove box, inject 25 μL of trisilane and 5 mL of n-hexane into the reactor at a volume ratio of 1:200, take out the reactor from the argon glove box and put it into a heating device;
[0047] S2: Raise the temperature to 400°C and the pressure to 35MPa to reach a supercritical state;
[0048] S3: Maintain the above temperature and pressure for 10 minutes. Thermal decomposition occurs during this process. After the temperature reaches room temperature, the reactor is transferred to an argon glove box to collect the amorphous silicon obtained by thermal decomposition.
[0049] Example 2
[0050] The method for preparing amorphous silicon in this embodiment comprises the following steps:
[0051] S1. In an argon glove box, inject 125 μL of trisilane and 1.25 mL of n-hexane into the reactor at a volume ratio of 1:10, then take out the reactor and put it into a heating and pressurizing device;
[0052] S2, raise the temperature to 400°C and the pressure to 35MPa;
[0053] S3: Maintain the above temperature and pressure for 10 minutes, and after the temperature reaches room temperature, transfer to an argon glove box to collect the amorphous silicon.
[0054] Example 3
[0055] The method for preparing amorphous silicon in this embodiment comprises the following steps:
[0056] S1: In an argon glove box, 10 μL of trisilane and 5 mL of n-hexane were injected into the reactor at a volume ratio of 1:500, and the reactor was taken out of the argon glove box and placed in a heating device;
[0057] S2: Raise the temperature to 400°C and the pressure to 35MPa to reach a supercritical state;
[0058] S3: Maintain the above temperature and pressure for 10 minutes. Thermal decomposition occurs during this process. After the temperature reaches room temperature, the reactor is transferred to an argon glove box to collect the amorphous silicon obtained by thermal decomposition.
[0059] Example 4
[0060] The method for preparing amorphous silicon in this embodiment comprises the following steps:
[0061] S1: In an argon glove box, 25 μL of trisilane and 5 mL of n-hexane were injected into the reactor at a volume ratio of 1:200, and then the reactor was taken out and placed in a heating device;
[0062] S2: Raise the temperature to 200°C and the pressure to 35MPa;
[0063] S3: Maintain the above temperature and pressure for 10 minutes, and after the temperature reaches room temperature, transfer to an argon glove box to collect the amorphous silicon.
[0064] Example 5
[0065] The method for preparing amorphous silicon in this embodiment comprises the following steps:
[0066] S1: In an argon glove box, 25 μL of trisilane and 5 mL of n-hexane were injected into the reactor at a volume ratio of 1:200, and then taken out and placed in a heating device;
[0067] S2: The reactor reaches a supercritical state, i.e. the temperature is raised to 400°C and the pressure is 35MPa;
[0068] S3: Maintain the temperature box pressure for 30 minutes, and after the temperature reaches room temperature, transfer to an argon glove box to collect amorphous silicon.
[0069] Example 6
[0070] The method for preparing amorphous silicon in this embodiment comprises the following steps:
[0071] S1: In an argon glove box, 25 μL of trisilane and 5 mL of n-hexane were injected into the reactor at a volume ratio of 1:200, and then taken out and placed in a heating device;
[0072] S2: The reactor reaches a supercritical state, i.e. the temperature is raised to 400°C and the pressure is 35MPa;
[0073] S3: Maintain the temperature box pressure for 5 minutes, and after the temperature reaches room temperature, transfer to an argon glove box to collect the amorphous silicon.
[0074] Example 7
[0075] The method for preparing amorphous silicon in this embodiment comprises the following steps:
[0076] S1. In an argon glove box, inject 25 μL of monosilane and 0.5 mL of n-hexane into the reactor at a volume ratio of 1:20, then take out and put into a heating device;
[0077] S2: The reactor reaches a supercritical state, i.e. the temperature is raised to 400°C and the pressure is 35MPa;
[0078] S3: Maintain the temperature box pressure for 10 minutes, and after the temperature reaches room temperature, transfer to an argon glove box to collect amorphous silicon.
[0079] Example 8
[0080] The method for preparing amorphous silicon in this embodiment comprises the following steps:
[0081] S1. In an argon glove box, inject 25 μL of trisilane and 5 mL of n-pentane into the reactor at a volume ratio of 1:200, then take them out and put them into a heating device;
[0082] S2: The reactor reaches a supercritical state, i.e. the temperature is raised to 350°C and the pressure is 28MPa;
[0083] S3: Maintain the temperature box pressure for 10 minutes, and after the temperature reaches room temperature, transfer to an argon glove box to collect amorphous silicon.
[0084] Comparative Example 1
[0085] The difference between this comparative example and Example 1 is that the silicon negative electrode material is prepared by heating.
[0086] The method for preparing a silicon negative electrode by conventional heating method comprises the following steps:
[0087] 25 μL of trisilane gas was sintered and thermally decomposed in an argon atmosphere, and the temperature was raised to 600° C. at 5° C. / min, kept at that temperature for 3 h, and then cooled to obtain a silicon negative electrode material.
[0088] The materials prepared in Examples 1 to 8 and Comparative Example 1 were used as negative electrode materials, and lithium sheets were used as positive electrode materials. Button-type half-cells were assembled to conduct electrochemical performance tests. The results are shown in Table 1. The silicon negative electrode material prepared in Example 1 and the material prepared in Comparative Example 1 were subjected to XRD testing. The test results are shown in Table 1. Figure 1 It can be seen that the material prepared in Example 1 is amorphous silicon, while the material prepared in Comparative Example 1 is crystalline silicon.
[0089] The silicon negative electrode material prepared in Example 1 and the material prepared in Comparative Example 1 were used to assemble button-type half-cells, and the cycle performance was tested at room temperature. The test results are shown in Figure 2 .from Figure 2 It can be seen that the cycle performance of the silicon negative electrode material prepared in Example 1 is significantly better than that in Comparative Example 1.
[0090] Table 1
[0091]
[0092] It can be seen from Table 1 that the use of the supercritical silicon negative electrode prepared by the present invention as a lithium battery negative electrode material has good comprehensive electrochemical properties, and its first charge and discharge efficiency is more than 90%, and the 50-week cycle capacity retention rate is more than 82%. The first charge and discharge efficiency of the negative electrode material of Comparative Example 1 is 82.6%, and the 50-week cycle capacity retention rate is 45.9%. Compared with the embodiment, the first irreversible capacity loss of the comparative example is larger, and the cycle performance is poor.
[0093] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
[0094] The parts not elaborated in detail in the description of the present invention belong to the known technology in the art. The above embodiments are provided only for the purpose of describing the present invention, and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. Various equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be included in the scope of the present invention.
Claims
1. A method for preparing amorphous silicon, characterized in that: The steps include: S1: adding a certain volume ratio of silane gas and straight-chain saturated hydrocarbon solvent into the reactor; S2: heating and pressurizing the reactor to reach a supercritical state; S3: After maintaining the supercritical state for a certain period of time, amorphous silicon can be obtained by collection.
2. The preparation method according to claim 1, characterized in that: Step S1 and step S3 are performed in an inert gas atmosphere.
3. The preparation method according to claim 1, characterized in that: The silane gas is And / or, the straight-chain saturated hydrocarbon solvent is at least one of n-pentane, n-hexane, n-heptane and n-octane.
4. The preparation method according to claim 1, characterized in that: The supercritical state is maintained for 5 minutes to 30 minutes.
5. The preparation method according to claim 1, characterized in that: The volume ratio of the silane gas to the straight-chain saturated hydrocarbon solvent is 1:(10-500).
6. The preparation method according to claim 5, characterized in that: The volume ratio of the silane gas to the straight-chain saturated hydrocarbon solvent is 1:(20-200).
7. The preparation method according to claim 1, characterized in that: The temperature of the supercritical state is 200° C. to 600° C., and the pressure is 5 MPa to 50 MPa.
8. The preparation method according to claim 1, characterized in that: The temperature of the supercritical state is 300° C. to 500° C., and the pressure is 20 MPa to 40 MPa.
9. Use of the amorphous silicon according to claim 1 as a negative electrode material for lithium-ion batteries.
10. A lithium ion battery, characterized in that: The lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator, wherein the negative electrode sheet comprises amorphous silicon obtained by the method for preparing amorphous silicon according to any one of claims 1 to 8.