CN116904822B - Lamellar stacked silicon-germanium alloy material and preparation method and application thereof - Google Patents
Lamellar stacked silicon-germanium alloy material and preparation method and application thereof Download PDFInfo
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- CN116904822B CN116904822B CN202311184696.3A CN202311184696A CN116904822B CN 116904822 B CN116904822 B CN 116904822B CN 202311184696 A CN202311184696 A CN 202311184696A CN 116904822 B CN116904822 B CN 116904822B
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- 239000000956 alloy Substances 0.000 title claims abstract description 99
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- 238000002360 preparation method Methods 0.000 title claims abstract description 32
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- 239000000203 mixture Substances 0.000 claims description 14
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Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C28/00—Alloys based on a metal not provided for in groups C22C5/00 - C22C27/00
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/36—Alloys obtained by cathodic reduction of all their ions
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a lamellar stacked silicon-germanium alloy material, a preparation method and application thereof, wherein the preparation method comprises the following steps: preparing electrolyte salt, wrapping silicon oxide and germanium by using foam nickel, manufacturing a working electrode, then inserting the working electrode into the molten electrolyte salt to electrolyze the silicon oxide and the germanium, and washing, soaking and drying the obtained product after the electrolysis is completed to obtain the lamellar stacked silicon-germanium alloy material. In the alloy material provided by the invention, the combination of silicon and germanium accelerates the kinetics of lithium transportation, is beneficial to free intercalation and rapid diffusion of lithium ions, and improves the electrochemical multiplying power characteristic of the material. The lamellar stacked silicon-germanium alloy material has lamellar stacked structure characteristics, has a large number of gaps, large interlayer spacing and weak interaction, can effectively relieve volume change in the lithium removal and intercalation processes, and further improves the electrochemical performance of the lamellar stacked silicon-germanium alloy material serving as a negative electrode material of a lithium ion battery. The two are overlapped together to greatly improve the electrochemical performance of the lamellar stacked silicon-germanium alloy.
Description
Technical Field
The invention belongs to the technical field of lithium ion battery cathode materials, and particularly relates to a lamellar stacked silicon-germanium alloy material, and a preparation method and application thereof.
Background
In recent years, due to rapid rise of portable electronic products and electric automobile markets, there has been a great demand for advanced Lithium Ion Batteries (LIBs), which has prompted many students to develop various novel LIBs materials. In order to better meet the market demand, the energy density and the power density of the lithium ion battery should be improved, and the specific capacity of the anode and the cathode is also one of the key factors for determining the energy density level of the battery. The specific capacity of the graphite cathode which is commercially used at present is about 372 mAh g -1 The current market demands cannot be met. Si and Ge materials in IVA elements are considered as ideal candidate materials for the LIBs of the next generation because of high theoretical specific capacity and low lithium intercalation potential. However, both of them belong to alloy reaction type materials, and the volume expansion is large in the electrode delithiation or lithium intercalation alloying process, which can lead to electrode particle breakage, and at the same time, the solid electrolyte interface film (SEI) is repeatedly grown, which can destroy the stability of the battery, and cannot be popularized and applied in a large scale.
Alloying Si and Ge into Si and GeThe SiGe alloy is prepared by combining the two materials, so that the advantages of the two materials can be fully utilized, the physical and chemical properties of the SiGe alloy are improved, and the lithium storage property of the SiGe alloy is enhanced. The main reasons are as follows: (i) The combination of Ge in Si can accelerate the kinetics of lithium transport and improve Li + Is a migration rate of (a); (ii) Si and Ge react with Li at different initial potentials, so that Si and Ge do not expand at the same time, and strain stress can be gradually released; (iii) When Li is intercalated into one of the components, the other component will act as a buffer to mitigate the volume change. However, the dramatic volume change (up to 400%) of the electrode in the reaction with lithium intercalation and deintercalation still does not avoid the Si-based or Ge-based material to expand in volume until the electrode breaks up and pulverizes, thereby reducing the cycle life of the electrode.
An effective way to overcome this problem is to design and synthesize complex micro-or nanostructured materials, such as nanotubes or hollow spheres, that can maintain their structural integrity over multiple cycles. However, the construction of such Si, ge or Si-Ge alloyed materials is generally accomplished by a typical multi-step hard template method, including forming a template having a desired specific shape, followed by removal of the internal template by a specific process, requiring complex equipment and cumbersome processes. Molten salt electrolysis is a process that is easily scalable and does not require expensive equipment and the use of toxic precursors. Furthermore, the microstructure of the product can be changed by regulating and controlling electrolysis conditions and precursors.
For the above reasons, the present application has been specifically proposed.
Disclosure of Invention
In view of the above, the embodiment of the invention provides a lamellar stacked silicon-germanium alloy material, and a preparation method and application thereof, so as to solve the technical problems in the prior art.
In a first aspect, an embodiment of the present invention provides a layered stacked sige alloy material, where the layered stacked sige alloy material is a layered stack of sige alloy and has a chemical composition of Si x Ge y Wherein: x is more than or equal to 1 and less than or equal to 2, and y=1.
As a preference for some embodiments of the lamellar stacked silicon germanium alloy material of the invention, the lamellar stacked silicon germanium alloy material has the chemical composition: x=1.5.
In a second aspect, the embodiment of the invention also provides a preparation method of the lamellar stacked silicon-germanium alloy material, which comprises the following steps:
s1, preparing electrolyte salt;
s2, wrapping silicon oxide and germanium by using foam nickel, and manufacturing a working electrode;
s3, heating electrolyte salt to a molten state, inserting a working electrode and an anode into the molten electrolyte salt, respectively connecting with a negative electrode and a positive electrode of a power supply, and electrolyzing the silicon oxide and the germanium by taking the molten electrolyte salt as electrolyte;
and S4, after the electrolysis is completed, taking out the working electrode, removing foam nickel, washing, soaking in hydrofluoric acid, washing, and drying to obtain the lamellar stacked silicon-germanium alloy material.
As some examples of the preparation method of the present invention, the electrolyte salt in step S1 is a hydrochloride salt or a mixed hydrochloride salt.
As some examples of the preparation method of the present invention, the electrolyte salt in the step S1 is CaCl 2 、NaCl、MgCl 2 And LiCl.
As a preference for some embodiments of the preparation method of the present invention, the electrolyte salt in step S1 is CaCl 2 -NaCl、CaCl 2 、CaCl 2 -MgCl 2 、CaCl 2 -NaCl-MgCl 2 、NaCl-MgCl 2 、CaCl 2 -LiCl or CaCl 2 -one of LiCl-NaCl.
As a preference for some embodiments of the preparation method of the present invention, the electrolyte salt in step S1 is CaCl 2 -NaCl, formulated as follows: caCl is added with 2 And NaCl according to the mole ratio of (0.5-2): 1 are mixed and dried for 10 to 15 hours at the temperature of 100 to 220 ℃ to obtain the electrolyte salt.
As some examples of the preparation method of the present invention, step S2 comprises wrapping silicon oxide and germanium with foam nickel, and making into working electrode by the following specific methods: weighing SiO and Ge powder according to the stoichiometric ratio of Si and Ge elements, fully mixing the raw materials, grinding uniformly, wrapping by foam nickel, and fixing on a conductive molybdenum wire to form a working electrode.
In step S3, the electrolyte salt is placed in a graphite crucible and heated to 500-900 ℃ to melt the electrolyte salt, a working electrode is inserted into the melted electrolyte salt, the graphite crucible is used as an anode, the working electrode is connected with a power negative electrode, the graphite crucible is connected with a power positive electrode, and the melted electrolyte salt is used as an electrolyte for electrolysis. It will be appreciated that the electrolyte salt is controlled to be in a molten state during electrolysis.
As some examples of the preparation method of the present invention, the specific process of step S3 electrolysis is: the electrolysis is carried out in a constant voltage mode, the electrolysis voltage is controlled to be 2.2V-2.8V in the electrolysis process, the electrolysis time is 5-10 h, and the electrolysis process is carried out in an inert atmosphere, wherein the inert atmosphere comprises a rare gas atmosphere or a nitrogen atmosphere.
In step S4, after the electrolysis is completed, the working electrode is taken out and naturally cooled under the protective atmosphere, molybdenum wires and foam nickel are removed, deionized water and hydrochloric acid are used for washing in sequence, and the solution is soaked in hydrofluoric acid for 25-35 min to etch and remove SiO which is not completely electrolyzed 2 Washing with deionized water, and drying to obtain the brown yellow lamellar stacked silicon-germanium alloy material.
As some examples of the preparation method of the present invention, in the step S4, the concentration of hydrochloric acid used for washing is 0.5M-1.5M, the concentration of hydrofluoric acid used for soaking is 0.1M-1.5M, and the protective atmosphere is a rare gas atmosphere or a nitrogen atmosphere.
In a third aspect, the embodiment of the invention also provides a lithium ion battery anode material, which comprises a silicon-germanium alloy material, a conductive agent and a binder, wherein the silicon-germanium alloy material is a lamellar stacked silicon-germanium alloy material prepared by any one of the preparation methods.
In a fourth aspect, the embodiment of the invention also provides a lithium ion battery, and the negative electrode of the lithium ion battery uses the negative electrode material of the lithium ion battery.
In a fifth aspect, the embodiment of the invention also provides an application of the lamellar stacked silicon-germanium alloy material obtained by any one of the preparation methods in a lithium ion battery.
One or more technical solutions provided in the embodiments of the present application at least have the following technical effects or advantages:
the foam nickel is used for wrapping the silicon oxide and the germanium and is used as a working electrode, the working electrode is used as a cathode to be connected with a power supply cathode to carry out melting electrolysis in a melting electrolyte salt, silicon and germanium can be alloyed in the electrolysis process, the morphology is changed specifically, the microstructure of the silicon-germanium alloy presents lamellar stacking characteristics, obvious gaps exist between lamellar layers, and the volume expansion of the silicon-germanium alloy in the lithium removing and inserting process can be effectively buffered. In the preparation process of the material, high-value equipment is not needed, toxic precursors are not needed, and the process is simple.
In the lamellar stacked silicon-germanium alloy material, the combination of silicon and germanium accelerates the kinetics of lithium transportation, is beneficial to free intercalation and rapid diffusion of lithium ions, and improves the electrochemical multiplying power characteristic. In addition, the lamellar stacked silicon-germanium alloy material has the characteristic of lamellar stacked structure, a large number of gaps are formed between lamellar structures, interlayer spacing is large, interaction is weak, and volume change of an electrode in the lithium removing or inserting process can be relieved, so that electrochemical performance of the electrode serving as a negative electrode material of a lithium ion battery is improved. The co-superposition of the two factors greatly improves the electrochemical performance of the lamellar stacked silicon-germanium alloy as the anode material of the lithium ion battery. Compared with other single raw materials, the lamellar stacked silicon-germanium alloy material has the advantages of being low in specific surface area and large in tap density, the first coulomb efficiency of the lithium ion battery is effectively improved, the combination of silicon and germanium accelerates the dynamics of lithium transportation, the rate capability is improved, and the rate capability and the cycle stability of the lithium ion battery are improved.
The constant current charge and discharge test results show that in the preferred embodiment of the invention, the lamellar stacked silicon-germanium alloy material is in a range of 0.2 to 0.2A g -1 The first coulomb efficiency under the current density can reach 82.59 percent, at 1A g -1 The discharge specific capacity after 100 circles of current density circulation is up to 1090.4mAh g -1 Capacity retention ratio of84.74% with current density from 0.5. 0.5A g -1 Gradually increase to 8A g -1 The electrode capacity is 1465.7mAh g -1 Gradually decrease to 535.4mAh g -1 While when the current density is from 8A g -1 Recovery to 0.5A g -1 The capacity of the electrode can be restored to 1336.8mAh g -1 。
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is evident that the drawings in the following description are only some embodiments of the present invention and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.
FIG. 1 shows a lamellar stacked Si obtained in example 1 of the present invention 1.5 Ge 1 XRD pattern of material (C) and original silica (a) and germanium (B) and standard cards.
FIG. 2 is a sheet-like stacked Si prepared in example 1 of the present invention 1.5 Ge 1 Scanning electron microscope image of the material.
FIG. 3 is a scanning electron microscope image of the original silica.
Fig. 4 is a scanning electron microscope image of the original germanium powder.
FIG. 5 shows a lamellar stacked Si obtained in example 1 of the present invention 1.5 Ge 1 Transmission electron microscopy of the material.
Fig. 6 shows XRD patterns of the layered stacked sige materials prepared in examples 1, 2 and 3 of the present invention, and standard cards of sige and sige.
FIG. 7 shows Si obtained in example 2 of the present invention 1 Ge 1 Scanning electron microscope image of the material.
FIG. 8 shows Si obtained in example 3 of the present invention 2 Ge 1 Scanning electron microscope image of the material.
FIG. 9 is a lamellar stacked Si 1.5 Ge 1 Material (A), si 1 Ge 1 Material (B), si 2 Ge 1 Material (C), commercialButton cell assembled from negative electrode material prepared from silicon oxide (D) and original germanium powder (E) is 0.2A g -1 A first-turn charge-discharge curve at current density.
FIG. 10 is a sheet-like stacked Si 1.5 Ge 1 Material (A), si 1 Ge 1 Material (B), si 2 Ge 1 Button cell assembled from negative electrode material prepared from material (C), commercial silicon oxide (D) and original germanium powder (E) was found to be 0.2. 0.2A g -1 Activated for 3 turns under current density at 0.5A g -1 A graph of the cycle stability for a cycle of 100 cycles at current density.
FIG. 11 is a sheet-like stacked Si 1.5 Ge 1 Material (A), si 1 Ge 1 Material (B) and Si 2 Ge 1 Button cell assembled by negative electrode material prepared by material (C) is 0.2A g -1 ～8A g -1 Graph of the rate performance tested at current density.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention.
The following description of the embodiments of the present invention will be made in detail and with reference to the embodiments of the present invention, but it should be apparent that the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, are intended to fall within the scope of the present invention.
For a better understanding of the present invention, and not to limit its scope, all numbers expressing quantities, percentages, and other values used in the present application are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated otherwise, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. Each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
Embodiments of the present application provide a lamellar stacked silicon-germanium alloy material in which silicon and germanium combine to form a solid solution compound and which has lamellar stacked structure characteristics with a large number of voids between lamellar structures.
Based on the same inventive concept, the embodiment of the application also provides a preparation method of the lamellar stacked silicon-germanium alloy material, which comprises the following steps:
s1, preparing electrolyte salt;
s2, wrapping silicon oxide and germanium powder by using foam nickel and taking the foam nickel as a working electrode;
s3, heating and melting electrolyte salt, inserting a working electrode into the melted electrolyte salt, connecting the working electrode with a power negative electrode, connecting an anode with a power positive electrode, and electrolyzing by taking the melted electrolyte salt as electrolyte;
and S4, after the electrolysis is completed, taking out the working electrode, removing foam nickel, washing, soaking in hydrofluoric acid, washing, and drying to obtain the lamellar stacked silicon-germanium alloy material.
Based on the same inventive concept, the embodiment of the application also provides a lithium ion battery anode material, which comprises a silicon-germanium alloy material, a conductive agent and a binder, wherein the silicon-germanium alloy material is the lamellar stacked silicon-germanium alloy material prepared by the preparation method.
It will be appreciated that the conductive agent and the binder used in the above embodiments are all conventional conductive agents and binders in the prior art, and for example, carbon black, conductive graphite, carbon fiber, carbon nanotube and graphene can be used as the conductive agent; the commercial conductive agents are SPUERLi, S-O, KS-6, KS-15, SFG-6, SFG-15, 350G, acetylene black (Ab), ketjen black (Kb), vapor Grown Carbon Fiber (VGCF), etc. The binder can be Sodium Alginate (SA), polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR) emulsion, carboxymethyl cellulose (CMC) and the like.
Based on the same inventive concept, the embodiment of the application also provides a lithium ion battery, and the negative electrode of the lithium ion battery utilizes the negative electrode material of the lithium ion battery.
Based on the same inventive concept, the embodiment of the application also provides an application of the lamellar stacked silicon-germanium alloy material prepared by the preparation method in a lithium ion battery.
The preparation method and application of the lamellar stacked silicon germanium alloy material of the present application are further described in the following specific examples. This section further illustrates the summary of the invention in connection with specific embodiments, but should not be construed as limiting the invention. The technical means employed in the examples are conventional means well known to those skilled in the art, unless specifically stated. Unless specifically stated otherwise, the reagents, methods and apparatus employed in the present invention are those conventional in the art.
The commercial silica (CAS No. 10097-28-6) of the following examples of the present invention had a particle size of about 1 μm and the germanium powder (CAS No. 04-0545) had a particle size of about 5. Mu.m. The parameters of the silicon oxide and germanium are provided merely to illustrate the operability of embodiments of the lamellar stacked silicon germanium alloy material produced. Lamellar stacked silicon-germanium alloy materials prepared by taking silicon oxide and germanium with different specifications as starting materials fall into the scope of the invention.
Example 1: the embodiment provides a preparation method of a lamellar stacked silicon-germanium alloy material, which comprises the following steps:
s1, 65.5g CaCl 2 And 34.5g of NaCl as electrolyte salt, which was poured into a mortar to be thoroughly mixed and ground, and after grinding, was transferred into a graphite crucible having a height of 80mm, an inner diameter of 65mm and a wall thickness of 5mm, and dried in a blast drying oven at 200℃for 12 hours to remove water;
s2, weighing 500mg of commercial silicon oxide and 549mg of germanium, wherein the total area is 16mm 2 The foam nickel of the electrode is used for wrapping silicon oxide and germanium, and molybdenum wires with the diameter of 0.1mm are used for fixing the molybdenum wires with the diameter of 1mm to serve as working electrodes;
s3, caCl is filled in 2 Placing the graphite crucible with NaCl electrolyte salt into a section of closed quartz tube, vertically placing the quartz tube in a pit furnace, heating to 850 ℃, and preserving heat at 850 ℃ for 10min until CaCl is obtained 2 After NaCl is completely melted, a working electrode is stretched into molten electrolyte salt, a graphite crucible is used as an anode, a working electrode is used as a cathode, the graphite crucible and the working electrode are respectively connected with a positive electrode and a negative electrode of a power supply, 2.5V constant voltage electrolysis is carried out for 10 hours under the atmosphere of nitrogen, and a current-time curve in the electrolysis process is recorded by a computer.
S4, after the electrolysis is completed, extracting a working electrode from molten electrolyte salt, naturally cooling the working electrode to room temperature in Ar gas, carefully removing foam nickel and molybdenum wires, cleaning with deionized water and 1M hydrochloric acid to remove residual molten salt, soaking the working electrode in 1M hydrofluoric acid for 30min, and etching residual SiO 2 Washing with deionized water for 3 times, suction filtering, collecting, and vacuum drying at 60deg.C for 12 hr to obtain Si 1.5 Ge 1 The silicon germanium alloy material is laminated.
Fig. 1 shows an X-ray diffraction pattern of the original silicon oxide, original germanium, and the lamellar stacked silicon-germanium alloy material prepared in example 1. In fig. 1, curve a is the X-ray diffraction pattern of the original silicon oxide, curve B is the X-ray diffraction pattern of the original germanium, and curve C is the X-ray diffraction pattern of the lamellar stacked silicon-germanium alloy material prepared in example 1. As can be seen from fig. 1, the silicon oxide has typical amorphous X-ray diffraction peaks, the diffraction peaks of the germanium powder substantially coincide with those of the standard card, and the Si crystal layer generated by electrolysis of the silicon oxide appears around the Ge crystal, thereby forming a SiGe alloy, without significant phase separation signals, with the diffraction peaks between Si and Ge. Fig. 2 is a scanning electron microscope image of the lamellar stacked silicon germanium alloy material prepared in example 1 of the present invention, fig. 3 is a scanning electron microscope image of original silicon oxide, fig. 4 is a scanning electron microscope image of original germanium powder, and fig. 5 is a transmission electron microscope image of the lamellar stacked silicon germanium alloy material prepared in example 1 of the present invention. As can be seen from fig. 2 to 5, the original silicon oxide is composed of smooth particles with different particle sizes, the original germanium powder is a bulk metal with rough surface, the morphology of the product is significantly changed after electrolysis, the microstructure of the product shows lamellar stacking characteristics, and obvious gaps exist between lamellar layers. The combination of silicon and germanium in the product can accelerate the kinetics of lithium transportation, improve the rate capability, has large interlayer spacing of lamellar structures with a large number of gaps, has weak interaction, is favorable for free intercalation and rapid diffusion of lithium ions, can provide enough space for volume expansion generated in the processes of delithiation and lithium intercalation, and is favorable for lamellar stacked silicon-germanium alloy materials to be used as silicon anode materials of lithium ion batteries by combining the above structural advantages.
Example 2: the embodiment provides a preparation method of a lamellar stacked silicon-germanium alloy material, which comprises the following steps:
s1, 65.5g CaCl 2 And 34.5g of NaCl as electrolyte salt, which was poured into a mortar to be thoroughly mixed and ground, and after grinding, was transferred into a graphite crucible having a height of 80mm, an inner diameter of 65mm and a wall thickness of 5mm, and dried in a blast drying oven at 200℃for 12 hours to remove water;
s2, weighing 400mg of commercial silicon oxide and 658.6mg of germanium, and using a total area of 16mm 2 The foam nickel of the electrode is used for wrapping silicon oxide and germanium, and molybdenum wires with the diameter of 0.1mm are used for fixing the molybdenum wires with the diameter of 1mm to serve as working electrodes;
s3, caCl is filled in 2 Placing the graphite crucible with NaCl electrolyte salt into a section of closed quartz tube, vertically placing the quartz tube in a pit furnace, heating to 850 ℃, and preserving heat at 850 ℃ for 10min until CaCl is obtained 2 After NaCl is completely melted, a working electrode is stretched into molten electrolyte salt, a graphite crucible is used as an anode, a working electrode is used as a cathode, the graphite crucible and the working electrode are respectively connected with a positive electrode and a negative electrode of a power supply, 2.5V constant voltage electrolysis is carried out for 10 hours under the atmosphere of nitrogen, and a current-time curve in the electrolysis process is recorded by a computer.
S4, after the electrolysis is completed, the working electrode is extracted from the molten electrolyte salt and naturally cooled to room temperature in Ar gas, then foam nickel and molybdenum wires are carefully removed, deionized water and 1M hydrochloric acid are used for cleaning and removing residual molten salt, then the solution is soaked in 1M hydrofluoric acid for 30min,etching residual SiO 2 Washing with deionized water for 3 times, suction filtering, collecting, and vacuum drying at 60deg.C for 12 hr to obtain Si 1 Ge 1 The silicon germanium alloy material is laminated.
Example 3: the embodiment provides a preparation method of a lamellar stacked silicon-germanium alloy material, which comprises the following steps:
s1, 65.5g CaCl 2 And 34.5g of NaCl as electrolyte salt, which was poured into a mortar to be thoroughly mixed and ground, and after grinding, was transferred into a graphite crucible having a height of 80mm, an inner diameter of 65mm and a wall thickness of 5mm, and dried in a blast drying oven at 200℃for 12 hours to remove water;
s2, weighing 500mg of commercial silicon oxide and 411.6mg of germanium, and using a total area of 16mm 2 The foam nickel of the electrode is used for wrapping silicon oxide and germanium, and molybdenum wires with the diameter of 0.1mm are used for fixing the molybdenum wires with the diameter of 1mm to serve as working electrodes;
s3, caCl is filled in 2 Placing the graphite crucible with NaCl electrolyte salt into a section of closed quartz tube, vertically placing the quartz tube in a pit furnace, heating to 850 ℃, and preserving heat at 850 ℃ for 10min until CaCl is obtained 2 After NaCl is completely melted, a working electrode is stretched into molten electrolyte salt, a graphite crucible is used as an anode, a working electrode is used as a cathode, the graphite crucible and the working electrode are respectively connected with a positive electrode and a negative electrode of a power supply, 2.5V constant voltage electrolysis is carried out for 10 hours under the atmosphere of nitrogen, and a current-time curve in the electrolysis process is recorded by a computer.
S4, after the electrolysis is completed, extracting a working electrode from molten electrolyte salt, naturally cooling the working electrode to room temperature in Ar gas, carefully removing foam nickel and molybdenum wires, cleaning with deionized water and 1M hydrochloric acid to remove residual molten salt, soaking the working electrode in 1M hydrofluoric acid for 30min, and etching residual SiO 2 Washing with deionized water for 3 times, suction filtering, collecting, and vacuum drying at 60deg.C for 12 hr to obtain Si 2 Ge 1 The silicon germanium alloy material is laminated.
XRD patterns of the lamellar stacked silicon germanium materials prepared in examples 1, 2 and 3 shown in FIG. 6 are all uniform alloy phases, andthere is no significant separation signal because the lattice mismatch of the silicon crystal layer formed by electrolytic oxidation of the silicon sub-oxide occurs during the growth of the germanium substrate, resulting in a lattice distortion, and therefore the resulting lamellar stacked silicon-germanium alloy (111) peak is located between silicon and germanium. FIG. 7 shows Si obtained in example 2 1 Ge 1 The outer layer nanoclusters inherit the size and shape of original SiO, a lamellar structure appears in the inner layer nanoclusters, the thickness and the size of the whole particles become large due to the combination of agglomerates and lamellar matters, the tendency of lamellar stacking is presented, but the inner layer is less, and the free intercalation and rapid diffusion of lithium ions and the volume expansion of the lithium deintercalation process are not facilitated. FIG. 8 shows Si obtained in example 3 2 Ge 1 Scanning electron microscopy of alloy materials, and when the stoichiometric ratio of Si to Ge element is 2:1, the stack of sheets is too tight and is also detrimental to alleviating volume expansion.
Example 4: the embodiment provides a lithium ion battery anode material, which comprises a silicon-germanium alloy material, a conductive agent and a binder, wherein the silicon-germanium alloy material is the lamellar stacked silicon-germanium alloy material prepared in the embodiment 1; specifically, the preparation method of the anode material comprises the following steps: the lamellar stacked silicon germanium alloy material obtained in example 1, si 1.5 Ge 1 The mass ratio of the active material to the conductive agent (SP) to the binder (sodium alginate) is 8:1: and 1, uniformly mixing and grinding, coating the mixture on a copper foil, and drying the mixture at 60 ℃ for 12 hours to obtain the lithium ion battery anode material.
The embodiment further provides a lithium ion battery through the equipment, specifically: the polypropylene film (Celgard 2400) is used as a diaphragm, the anode material of the lithium ion battery is used as an anode, a metal lithium foil is used as a cathode, and 1M lithium hexafluorophosphate (LiPF) 6 ) Ethylene Carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) (volume ratio 1:1: 1) 10% fluoroethylene carbonate (FEC) is added into the mixed solution as electrolyte, and the complete CR2032 button battery is assembled. Electrochemical performance testing was performed on the coin cell using constant current charge-discharge (GCD) technology. The voltage window is 0.01V-1.5V, and the current density is testedIs 0.2. 0.2A g -1 ～8A g -1 。
Example 5: the embodiment provides a lithium ion battery anode material, which comprises a silicon-germanium alloy material, a conductive agent and a binder, wherein the silicon-germanium alloy material is the lamellar stacked silicon-germanium alloy material prepared in the embodiment 2; specifically, the preparation method of the anode material comprises the following steps: the lamellar stacked silicon germanium alloy material obtained in example 2, si 1 Ge 1 The mass ratio of the active material to the conductive agent (SP) to the binder (sodium alginate) is 8:1: and 1, uniformly mixing and grinding, coating the mixture on a copper foil, and drying the mixture at 60 ℃ for 12 hours to obtain the lithium ion battery anode material.
The embodiment further provides a lithium ion battery through the equipment, specifically: the polypropylene film (Celgard 2400) is used as a diaphragm, the anode material of the lithium ion battery is used as an anode, a metal lithium foil is used as a cathode, and 1M lithium hexafluorophosphate (LiPF) 6 ) Ethylene Carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) (volume ratio 1:1: 1) 10% fluoroethylene carbonate (FEC) is added into the mixed solution as electrolyte, and the complete CR2032 button battery is assembled. Electrochemical performance testing was performed on the coin cell using constant current charge-discharge (GCD) technology. The voltage window is 0.01V-1.5V, and the test current density is 0.2. 0.2A g -1 ～8A g -1 。
Example 6: the embodiment provides a lithium ion battery anode material, which comprises a silicon-germanium alloy material, a conductive agent and a binder, wherein the silicon-germanium alloy material is the lamellar stacked silicon-germanium alloy material prepared in the embodiment 3; specifically, the preparation method of the anode material comprises the following steps: the lamellar stacked silicon germanium alloy material obtained in example 3, si 2 Ge 1 The mass ratio of the active material to the conductive agent (SP) to the binder (sodium alginate) is 8:1: and 1, uniformly mixing and grinding, coating the mixture on a copper foil, and drying the mixture at 60 ℃ for 12 hours to obtain the lithium ion battery anode material.
The embodiment further provides a lithium ion battery through the equipment, specifically: with polypropylene film (Celgard 240)0) The separator was made of the above lithium ion battery negative electrode material as a negative electrode, a metal lithium foil as a positive electrode, and 1M lithium hexafluorophosphate (LiPF 6 ) Ethylene Carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) (volume ratio 1:1: 1) 10% fluoroethylene carbonate (FEC) is added into the mixed solution as electrolyte, and the complete CR2032 button battery is assembled. Electrochemical performance testing was performed on the coin cell using constant current charge-discharge (GCD) technology. The voltage window is 0.01V-1.5V, and the test current density is 0.2. 0.2A g -1 ～8A g -1 。
Comparative example 1: the comparative example provides a lithium ion battery anode material comprising a silicon active material, a conductive agent and a binder, wherein the silicon active material is non-electrolyzed commercial silicon oxide; specifically, the preparation method of the anode material comprises the following steps: the mass ratio of the commercial silicon oxide (as an active substance) to the conductive agent (SP) to the binder (sodium alginate) is 8:1:1, uniformly mixing and grinding, coating the mixture on a copper foil, and drying the mixture for 12 hours at 60 ℃ to obtain the negative electrode material.
The comparative example further assembled a lithium ion battery, specifically: the membrane is made of polypropylene film (Celgard 2400), the cathode material is used as the cathode, the metal lithium foil is used as the anode, and 1M lithium hexafluorophosphate (LiPF) 6 ) Ethylene Carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) (volume ratio 1:1: 1) 10% fluoroethylene carbonate (FEC) is added into the mixed solution as electrolyte, and the complete CR2032 button battery is assembled. Electrochemical performance testing was performed on the coin cell using constant current charge-discharge (GCD) technology. The voltage window is 0.01V-1.5V, and the test current density is 0.2. 0.2A g -1 ～0.5A g -1 。
Comparative example 2: the comparative example provides a lithium ion battery anode material comprising a germanium active substance, a conductive agent and a binder, wherein the germanium active substance is germanium particles with the particle size of 5 mu m; specifically, the preparation method of the anode material comprises the following steps: germanium particles (serving as active substances), a conductive agent (SP) and a binder (sodium alginate) are mixed according to the mass ratio of 8:1:1, uniformly mixing and grinding, coating the mixture on a copper foil, and drying the mixture for 12 hours at 60 ℃ to obtain the negative electrode material.
The comparative example further assembled a lithium ion battery, specifically: the membrane is made of polypropylene film (Celgard 2400), the cathode material is used as the cathode, the metal lithium foil is used as the anode, and 1M lithium hexafluorophosphate (LiPF) 6 ) Ethylene Carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) (volume ratio 1:1: 1) 10% fluoroethylene carbonate (FEC) is added into the mixed solution as electrolyte, and the complete CR2032 button battery is assembled. Electrochemical performance testing was performed on the coin cell using constant current charge-discharge (GCD) technology. The voltage window is 0.01V-1.5V, and the test current density is 0.2. 0.2A g -1 ～0.5A g -1 。
FIG. 9A is a graph of Si in example 4 1.5 Ge 1 Button cell assembled by anode materials prepared by lamellar stacking silicon germanium alloy is 0.2A g -1 The first charge and discharge curve at current density, curve B, is the first charge and discharge curve obtained in example 5 using Si 1 Ge 1 Button cell assembled by anode materials prepared by lamellar stacking silicon germanium alloy is 0.2 Ag -1 The first charge and discharge curve at current density, C curve, is the first charge and discharge curve obtained in example 6 using Si 2 Ge 1 Button cell assembled by anode materials prepared by lamellar stacking silicon germanium alloy is 0.2 Ag -1 The first charge-discharge curve at current density, D curve, is that of the button cell assembled from the negative electrode material prepared from commercial silica in comparative example 1 at 0.2 ag -1 The first charge-discharge curve at current density, E curve, is that of the button cell assembled from the anode material prepared from germanium powder in comparative example 2 at 0.2 ag -1 A first-turn charge-discharge curve at current density. As can be seen from FIG. 9, si 1.5 Ge 1 、Si 1 Ge 1 、Si 2 Ge 1 The first coulombic efficiencies of button cells assembled from commercial silicon oxide and germanium powders were 82.59%, 71.78%, 76.90%, 46.71%, 65.68%, respectively. Si (Si) 1.5 Ge 1 、Si 1 Ge 1 And Si (Si) 2 Ge 1 The first effect of the button cell assembled by materials is greatly improved due to the combination of silicon and germanium, and the Si electrode can be effectively improvedAnd has smaller specific surface area, which can reduce side reaction generation. When silica is used as the negative electrode material, li is generated during the first lithiation process 2 O and Li 4 SiO 4 And irreversible products, resulting in very low first-order effects.
FIG. 10A is a graph of Si in example 4 1.5 Ge 1 Button cell assembled by anode materials prepared by lamellar stacking silicon germanium alloy is 0.2A g -1 Activated for 3 turns under current density at 0.5A g -1 The cycle stability curve for 100 cycles at current density of (C) and the curve B are the values obtained in example 5 using Si 1 Ge 1 Button cell assembled by anode materials prepared by lamellar stacking silicon germanium alloy is 0.2A g -1 Activated for 3 turns under current density at 0.5A g -1 The cycle stability curve for 100 cycles at current density of (C) is the curve obtained in example 6 with Si 2 Ge 1 Button cell assembled by anode materials prepared by lamellar stacking silicon germanium alloy is 0.2A g -1 Activated for 3 turns under current density at 0.5A g -1 The cycle stability curve for 100 cycles at current density of (D) for button cell assembled from the negative electrode material prepared with commercial silica in comparative example 1 was 0.2. 0.2A g -1 Activated for 3 turns under current density at 0.5A g -1 The cycle stability curve of 100 cycles at current density of (a) and the E curve of (b) were 0.2. 0.2A g for a coin cell assembled from the negative electrode material prepared from germanium powder in comparative example 2 -1 Activated for 3 turns under current density at 0.5A g -1 A cycling stability profile for 100 cycles at current density. As can be seen from FIG. 10, si 1.5 Ge 1 、Si 1 Ge 1 、Si 2 Ge 1 Specific capacities of the button cell assembled from commercial silicon oxide and germanium powder after 100 circles are 1457.1mAh g respectively -1 、713.7mAh g -1 、163.0mAh g -1 、544.6mAh g -1 And 829.9mAh g -1 。Si 1.5 Ge 1 The capacity retention rate of the button cell assembled by lamellar stacking of the silicon-germanium alloy materials can reach 86.7% after the button cell is cycled for 100 circles. Si (Si) 1.5 Ge 1 Excellent cyclic stability of lamellar stacked silicon-germanium alloy materialThe lamellar structure with uniform gaps can well relieve volume expansion caused in the lithiation process and maintain the stability of the electrode structure.
FIG. 11A is a graph of Si in example 4 1.5 Ge 1 Button cell assembled by anode materials prepared by lamellar stacking silicon germanium alloy is 0.2A g -1 ～8A g -1 The rate performance curve tested at current density, curve B, is that of example 5, si 1 Ge 1 Button cell assembled by anode materials prepared by stacking silicon germanium alloy in sheet form is 0.2A g -1 ～8A g -1 The rate performance curve tested at current density, C curve, is that of example 6, si 2 Ge 1 Button cell assembled by anode materials prepared by lamellar stacking silicon germanium alloy is 0.2A g -1 ～8A g -1 A rate performance curve tested at current density. As can be seen from FIG. 11, si 1.5 Ge 1 Button cells assembled from sheet stacked silicon germanium alloy materials have advantages over Si 1 Ge 1 And Si (Si) 2 Ge 1 Is set from 0.5 to A g with current density -1 Gradually increase to 8A g -1 The electrode capacity is 1465.7mAh g -1 Gradually decrease to 535.4mAh g -1 While when the current density is from 8A g -1 Recovery to 0.5A g -1 The capacity of the electrode can be restored to 1336.8mAh g -1 The lithium ion intercalation material has good reversibility, and is beneficial to free intercalation and rapid diffusion of lithium ions due to large interlayer spacing and weak interaction of the lamellar structure with a large number of gaps. To sum up, si 1.5 Ge 1 The lamellar stacked silicon-germanium alloy material has excellent electrochemical performance and good application prospect.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (11)
1. A lamellar stacked silicon-germanium alloy material, characterized in that the lamellar stacked siliconThe germanium alloy material is formed by stacking lamellar layers and has the chemical composition of Si x Ge y Wherein: x is more than or equal to 1 and less than or equal to 2, and y=1;
the lamellar stacked silicon-germanium alloy material is prepared by the following method:
s1, preparing electrolyte salt;
s2, wrapping silicon oxide and germanium by using foam nickel, and manufacturing a working electrode;
s3, heating electrolyte salt in a graphite crucible to a molten state, inserting a working electrode into the molten electrolyte salt, taking the graphite crucible as an anode, connecting the working electrode with a power negative electrode, connecting the graphite crucible with a power positive electrode, and electrolyzing the silicon oxide and the germanium by taking the molten electrolyte salt as an electrolyte;
and S4, after the electrolysis is completed, taking out the working electrode, removing foam nickel, washing, soaking in hydrofluoric acid, washing, and drying to obtain the lamellar stacked silicon-germanium alloy material.
2. The layered stacked sige alloy material of claim 1 wherein x is 1.5 in the chemical composition of the layered stacked sige alloy material.
3. A method for preparing a lamellar stacked silicon germanium alloy material according to claim 1 or 2, characterized in that it comprises the following steps:
s1, preparing electrolyte salt;
s2, wrapping silicon oxide and germanium by using foam nickel, and manufacturing a working electrode;
s3, heating electrolyte salt in a graphite crucible to a molten state, inserting a working electrode into the molten electrolyte salt, taking the graphite crucible as an anode, connecting the working electrode with a power negative electrode, connecting the graphite crucible with a power positive electrode, and electrolyzing the silicon oxide and the germanium by taking the molten electrolyte salt as an electrolyte;
and S4, after the electrolysis is completed, taking out the working electrode, removing foam nickel, washing, soaking in hydrofluoric acid, washing, and drying to obtain the lamellar stacked silicon-germanium alloy material.
4. The method for preparing a layered stacked silicon-germanium alloy material according to claim 3, wherein the electrolyte salt in step S1 is CaCl 2 、NaCl、MgCl 2 And LiCl.
5. The method of claim 4, wherein the electrolyte salt in step S1 is CaCl 2 -NaCl、CaCl 2 、CaCl 2 -MgCl 2 、CaCl 2 -NaCl-MgCl 2 、NaCl-MgCl 2 、CaCl 2 -LiCl or CaCl 2 -one of LiCl-NaCl.
6. The method of claim 5, wherein the electrolyte salt in step S1 is CaCl 2 -NaCl; the preparation method comprises the following steps: caCl is added with 2 And NaCl according to the mole ratio of (0.5-2): 1 are mixed and dried for 10 to 15 hours at the temperature of 100 to 220 ℃ to obtain the electrolyte salt.
7. The method for preparing a lamellar stacked silicon-germanium alloy material according to claim 3, wherein the step S2 comprises the steps of: weighing SiO and Ge powder according to the stoichiometric ratio of Si and Ge elements, fully mixing the raw materials, grinding uniformly, wrapping by foam nickel, and fixing on a conductive molybdenum wire to form a working electrode.
8. The method for producing a layered stacked silicon-germanium alloy material according to claim 3, wherein in step S3, the electrolyte salt is heated to 500 ℃ to 900 ℃ to be melted, electrolysis is performed in a constant voltage mode, the electrolysis voltage is controlled to be 2.2V to 2.8V during the electrolysis, the electrolysis time is 5h to 10h, and the electrolysis is performed in an inert atmosphere including a rare gas atmosphere or a nitrogen atmosphere.
9. The method of preparing a layered stacked silicon-germanium alloy material according to claim 3, wherein in step S4, after the electrolysis is completed, the working electrode is taken out, naturally cooled in a protective atmosphere, molybdenum wires and foam nickel are removed, and then washed with deionized water and hydrochloric acid in sequence, and then soaked in hydrofluoric acid for 25 to 35 minutes to etch and remove incompletely electrolyzed SiO 2 Washing with deionized water, and drying to obtain lamellar stacked silicon-germanium alloy material;
wherein the concentration of hydrochloric acid used for washing is 0.5-1.5M, the concentration of hydrofluoric acid used for soaking is 0.1-1.5M, and the protective atmosphere is rare gas atmosphere or nitrogen atmosphere.
10. The lithium ion battery anode material comprises a silicon-germanium alloy material, a conductive agent and a binder, and is characterized in that the silicon-germanium alloy material is a lamellar stacked silicon-germanium alloy material prepared by the preparation method according to any one of claims 3-9.
11. Use of a lamellar stacked silicon-germanium alloy material obtained by the preparation method according to any one of claims 3-9 in a lithium ion battery.
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| CN115172714A (en) * | 2022-07-28 | 2022-10-11 | 赣州市瑞富特科技有限公司 | Silicon nanowire/silicon nanoparticle binary cluster material and preparation method and application thereof |
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| CN109698319A (en) * | 2018-12-28 | 2019-04-30 | 蜂巢能源科技有限公司 | Cathode of solid state battery and preparation method thereof and solid state electrode |
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