A method for preparing Si-Ti alloy nanopowder and its application

Abstract

This invention belongs to the field of lithium-ion battery technology and provides a method for preparing Si-Ti alloy nanoparticle anode materials and their applications. Based on a DC arc plasma method, this invention first involves uniformly melting pure silicon and pure titanium blocks in a vacuum melting furnace to prepare Si-Ti alloy bulk materials. Then, using the Si-Ti alloy bulk material as the anode and a tungsten rod as the cathode, the device is placed in a DC arc plasma discharge chamber, and a vacuum of -0.1 MPa is applied. A certain amount of argon and hydrogen is introduced to ignite and evaporate the alloy block, obtaining Si-Ti nanoparticle materials with a particle size ranging from 20 to 120 nm. This method is time-saving and low-cost, enabling simple and efficient preparation of lithium-ion battery anode materials. Furthermore, the Si-Ti alloy nanoparticles prepared by this method have high purity and good dispersibility. The lithium-ion batteries prepared by this invention exhibit high specific capacity and good cycle stability.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and specifically to a method for preparing Si-Ti alloy nanopowder for lithium-ion batteries based on a DC arc plasma method, and its application. Background Technology

[0002] Lithium-ion batteries have advantages such as safety and environmental friendliness, and have broad application prospects in portable electronic devices, electric vehicles, energy storage, space technology, biomedicine, and national defense. Currently, the main commercial lithium-ion battery anode material is graphite (theoretical specific capacity 372 mAh / g). With the advancement of technology, electronic devices have placed higher demands on the energy density of battery materials. However, graphite anodes have reached their maximum capacity (commercial graphite reaches 350 mAh / g), while silicon can form a Li15Si4 alloy phase with lithium at room temperature, with a theoretical specific capacity as high as 3572 mAh / g, far exceeding that of commercial graphite. Moreover, silicon accounts for 26.4% of the Earth's crust, is low in cost, and is environmentally friendly. Therefore, silicon anode materials have always attracted the attention and development of researchers and are currently the most promising next-generation lithium-ion battery anode material.

[0003] However, elemental silicon expands by up to 300% in volume during charge and discharge, and its intrinsic conductivity is low. This massive volume expansion easily leads to material structure collapse, detachment from the current collector, and pulverization, causing irreversible capacity loss and limiting the commercialization of silicon anodes. Therefore, improving the conductivity and cycle stability of silicon-based anode materials is a key research focus. Summary of the Invention

[0004] This invention addresses the aforementioned research focus by providing a method for preparing Si-Ti alloy nanopowder for lithium-ion batteries. This method is based on a DC arc plasma method, using pure silicon and pure titanium blocks as raw materials to melt and produce Si-Ti alloy blocks. These alloy blocks are then used as anodes and tungsten rods as cathodes to evaporate the alloy blocks and prepare Si-Ti alloy nanopowder. By utilizing the excellent conductivity and volume support of the transition metal titanium, titanium is added to the silicon matrix, thereby improving the conductivity and cycle performance of the silicon-based anode material and effectively enhancing its initial coulombic efficiency, exhibiting superior electrochemical performance.

[0005] The value of this invention lies in providing a simple, efficient, and low-cost method for preparing silicon-based anode materials. The Si-Ti alloy nanopowder prepared by this method has high purity and good dispersibility. This method adopts a two-step synthesis method and has excellent prospects for industrialization.

[0006] The technical method used in this invention is as follows:

[0007] A method for preparing Si-Ti alloy nanopowder, using DC arc hydrogen plasma as a heat source, Si-Ti alloy bulk material as the anode and raw material, and evaporating the bulk raw material in a mixed atmosphere of active and inert gases to obtain Si-Ti alloy nanopowder, the steps are as follows:

[0008] Step 1: Preparation of alloy ingots

[0009] Take silicon and titanium blocks with a mass ratio of 10 to 1:1 and place them in a copper crucible of a vacuum melting furnace. Use a tungsten rod as the cathode and silicon and titanium blocks as the target and anode. Evacuate to -0.1 MPa, introduce 0.04 MPa argon gas, ignite the arc, and repeatedly melt into an alloy ingot under a current of 300 A.

[0010] Step 2: Preparation of nanopowders

[0011] (1) Using an automatic control DC arc plasma device, place the alloy ingot obtained in step 1 into a copper crucible as a target material, use the alloy ingot raw material as the anode and the tungsten rod as the cathode, and adjust the cathode tungsten rod to be directly above the target material.

[0012] (2) Evacuate to -0.1MPa, introduce a mixed atmosphere of argon and hydrogen with a pressure ratio of 4 to 1:1, and obtain Si-Ti alloy nanoparticles after arc evaporation of the alloy block.

[0013] (3) Under the action of hydrogen plasma heat source, the anode evaporates to form atomic clusters and condenses into nanoparticles, which are deposited on the water-cooled reaction chamber wall.

[0014] (4) After the nanoparticles are completely deposited, air is introduced for passivation. After passivation, the powder is collected to obtain Si-Ti alloy nanoparticles.

[0015] The silicon block and titanium block are respectively solar polycrystalline silicon scrap silicon blocks and commercially purchased titanium blocks.

[0016] The voltage for evaporation of the alloy block is 15–40V; the current for evaporation of the alloy block is 20–200A.

[0017] The distance between the cathode and the target is 3-5 mm.

[0018] A lithium-ion battery Si-Ti alloy nanopowder anode material was prepared using the above-mentioned physical method.

[0019] The prepared lithium-ion battery Si-Ti alloy nanoparticle anode material has a particle size of 20–120 nm.

[0020] An anode material comprising the aforementioned Si-Ti alloy nanopowder anode material.

[0021] A negative electrode material, which also includes a conductive agent, a binder, and a solvent.

[0022] An electrode sheet comprising the aforementioned negative electrode material.

[0023] A lithium-ion battery, wherein the above-mentioned electrode sheet is used as the negative electrode.

[0024] When the particle size of Si-Ti alloy nanopowder anode material is 20-80 nm, the battery prepared from it has an initial charge-discharge coulombic efficiency of 78.9%-83.6% at a current density of 1 A / g, an initial discharge specific capacity of 2936.7-3394.3 mAh / g, and a reversible cycle specific capacity of 955.2-1064.8 mAh / g after 100 cycles.

[0025] The beneficial effects of this invention are: the method is time-saving and low-cost, enabling simple and efficient preparation of lithium-ion battery anode materials; and the Si-Ti alloy nanopowder prepared by this method has high purity and good dispersibility. The lithium-ion batteries prepared by this invention have high specific capacity and good cycle stability. Attached Figure Description

[0026] Figure 1 The image shows the XRD pattern of the Si-Ti alloy nanopowder prepared in Example 1 of this invention.

[0027] Figure 2 This is a SEM image of the Si-Ti alloy nanopowder prepared in Example 1 of the present invention.

[0028] Figure 3 This is an HRTEM image of the Si-Ti alloy nanopowder prepared in Example 1 of the present invention.

[0029] Figure 4 This is a cycle performance diagram of the button cell prepared in Example 1 of the present invention. Detailed Implementation

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Reagents or instruments used that do not specify the manufacturer are all conventional products that can be purchased commercially.

[0031] Example 1

[0032] A method for preparing Si-Ti alloy nanopowder using DC arc plasma, the specific steps of which are as follows:

[0033] Weigh out pure silicon blocks and pure titanium blocks in a 1:1 mass ratio, place them in a copper crucible in a vacuum melting furnace, evacuate to -0.1 MPa, introduce 0.04 MPa argon gas as a protective gas, and melt them into alloy ingots in the vacuum melting furnace (control the main parameters of the vacuum melting furnace: voltage 20V, current 200A), and melt the two into an alloy under high current conditions.

[0034] After cooling is complete, air is introduced into the vacuum melting furnace to atmospheric pressure, and the alloy ingot is removed.

[0035] Transfer the alloy ingot into the copper crucible of the automatically controlled DC arc plasma equipment, install the tungsten rod, and close the hatch.

[0036] The vacuum is evacuated to -0.1 MPa, and a mixture of argon and hydrogen gas (argon:hydrogen = 1:1) is introduced. The cooling water system is turned on, the power supply is connected and the arc is ignited. The current and the distance between the two electrodes are adjusted to maintain the stability of the arc (current 100-200A, voltage 15-25V). The alloy ingot target material is fully evaporated, forming gaseous atoms and ions. After nucleation, growth and condensation, they aggregate into nanoparticles and deposit on the reaction chamber wall. After the nanoparticles are completely deposited, an appropriate amount of air is introduced for passivation. After passivation for a certain period of time, the powder is collected to obtain Si-Ti alloy nanoparticles.

[0037] The prepared Si-Ti alloy nanopowder was applied to the negative electrode material of lithium-ion batteries for battery assembly and electrochemical performance testing.

[0038] Weigh the lithium-ion battery anode material, binder, and conductive agent according to a specific mass ratio. Place the Si-Ti alloy nanopowder with a particle size of 20-80 nm prepared in Example 1, the conductive agent Ketjen black, and the binder PAA in a mortar and grind them evenly.

[0039] After the mixed powder above is ground evenly, N-methylpyrrolidone (NMP) solution is added drop by drop, and the mixture is ground evenly again to prepare a paste with a certain fluidity, which is then evenly coated onto the copper foil.

[0040] Then, the copper foil was placed in a vacuum drying oven and dried at 100°C for 8 hours.

[0041] After drying is complete, the vacuum drying oven is closed and the product is cooled to room temperature. It is then taken out, punched into electrode sheets with a diameter of 14 mm, and assembled into button cells in an argon-filled glove box. 1M LiPF6 / EC+DMC (1:1 volume ratio, ethylene carbonate (EC), dimethyl carbonate (DMC)) is used as the electrolyte, and pure lithium foil is used as the counter electrode.

[0042] After 24 hours of activation, the battery was subjected to constant current charge-discharge test and rate performance test at room temperature using the LAND battery testing system. The test voltage range was 0.01 to 3.00 V (vs. Li / Li+).

[0043] SEM image of the Si-Ti alloy nanopowder obtained in Example 1 is shown below. Figure 2 As shown, the particle size of Si-Ti alloy nanoparticles ranges from 20 to 80 nm and is uniform.

[0044] HRTEM image of the Si-Ti alloy nanopowder obtained in Example 1 is shown below. Figure 3 As shown, the internal lattice spacing is 0.31 nm, which is the (111) crystal plane of Si, and the external lattice spacing is 0.29 nm, which is the (202) crystal plane of TiSi2.

[0045] The cycle performance diagram obtained in Example 1 is shown below. Figure 4 As shown, the cycling performance measured under a current density of 1 A / g shows that 33.7% of the capacity remains after 100 cycles and 24% of the capacity remains after 200 cycles.

[0046] Example 2

[0047] A method for preparing Si-Ti alloy nanopowder using DC arc plasma is the same as in Example 1, except that:

[0048] The mass ratio of pure silicon block to pure titanium block is changed to 5:1, the ratio of argon gas to hydrogen gas is changed to 2:1, the current is changed to 70-100A, and the voltage is changed to 20-30V.

[0049] The other methods are the same.

[0050] Si-Ti alloy nanoparticles with a particle size of 20–100 nm were prepared. The Si-Ti alloy nanoparticles were used to prepare lithium-ion batteries in accordance with the method of Example 1. The prepared lithium-ion batteries were tested for cycle performance under a current density of 1 A / g. After 100 cycles, 28.3% of the capacity remained, and after 200 cycles, 23.3% of the capacity remained.

[0051] Example 3

[0052] A method for preparing Si-Ti alloy nanopowder using DC arc plasma is the same as in Example 1, except that:

[0053] The mass ratio of pure silicon block to pure titanium block is changed to 10:1, the ratio of argon gas to hydrogen gas is changed to 4:1, the current is changed to 20-70A, and the voltage is changed to 35-40V.

[0054] The other methods are the same.

[0055] Si-Ti alloy nanoparticles with a particle size of 20–120 nm were prepared. The Si-Ti alloy nanoparticles were used to prepare lithium-ion batteries in accordance with the method of Example 1. The prepared lithium-ion batteries were tested for cycle performance under a current density of 1 A / g. After 100 cycles, 25.7% of the capacity remained, and after 200 cycles, 21.5% of the capacity remained.

Claims

1. A method for preparing Si-Ti alloy nanopowder as an anode material for lithium ion batteries, using a direct current arc hydrogen plasma as a heat source, using a Si-Ti alloy bulk body as an anode and a raw material, evaporating the bulk body raw material in a mixed atmosphere of active gas and inert gas, and obtaining Si-Ti alloy nanopowder, characterized by, The steps are as follows: ​ Step 1: preparing alloy ingot Take silicon block and titanium block with a mass ratio of 10-1:1, and place them into a copper crucible of a vacuum melting furnace, use a tungsten rod as a cathode, the silicon block and the titanium block as target material and anode, vacuumize to-0.1 MPa, introduce 0.04 MPa argon gas, arc, and repeatedly melt into alloy ingot under a current of 300 A; Step 2: preparing nano-powder (1) use an automatic control direct current arc plasma equipment, place the alloy ingot prepared in step 1 into a copper crucible as target material, use the alloy ingot raw material as anode, and a tungsten rod as cathode, adjust the cathode tungsten rod to be directly above the target material; the distance between the cathode and the target material is 3-5 mm; (2) vacuumize to-0.1 MPa, introduce a mixed gas atmosphere with an argon-hydrogen gas pressure ratio of 4-1:1, arc evaporation of the alloy block to obtain Si-Ti alloy nanoparticles; wherein, the voltage of alloy block evaporation is 15-40 V; the current of alloy block evaporation is 20-200 A; (3) under the action of hydrogen plasma heat source, the anode is evaporated to form atomic clusters and condense into nanoparticles, which are deposited on the inner wall of the water-cooled reaction chamber; (4) after the nano-powder is completely deposited, introduce air for passivation, collect the powder after passivation to obtain Si-Ti alloy nano-powder, and the Si-Ti alloy nano-powder is a nano-eutectic alloy powder formed by elemental Si phase and eutectic phase TiSi2.

2. The method for preparing Si-Ti alloy nanopowder for lithium-ion battery anode materials according to claim 1, characterized in that, The particle size of the Si-Ti alloy nano-powder negative electrode material is 20-80 nm.

3. The method for preparing Si-Ti alloy nanopowder for lithium-ion battery anode materials according to claim 2, characterized in that, The lithium ion battery prepared by using the Si-Ti alloy nano-powder negative electrode material has a first charge-discharge coulomb efficiency of 78.9%-83.6% under a current density of 1 A / g, a first discharge specific capacity of 2936.7-3394.3 mAh / g, and a reversible cycle specific capacity of 955.2-1064.8 mAh / g after 100 cycles.

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