Metal selenide nano-silicon-carbon composite material and its preparation method, application and battery

Abstract

The present invention discloses a metal selenide nano-silicon-carbon composite material and its preparation method, application and battery. The preparation method comprises: (1) calcining a mixture of transition metal M and silicon powder under inert gas protection to obtain a metal precursor; (2) calcining a mixture of the metal precursor and SeCl4 under inert gas protection, and then washing to obtain a metal selenide nano-silicon composite material; (3) granulating and carbonizing a mixture of the metal selenide nano-silicon composite material and a carbon source to obtain the metal selenide nano-silicon-carbon composite material. The preparation method of the present invention can simultaneously prepare nano-sized metal selenides and silicon materials, and the prepared metal selenide nano-silicon-carbon composite material has excellent high-rate specific capacity and cycle life.

Description

Technical Field

[0001] The present invention specifically relates to a metal selenide nano-silicon-carbon composite material and a preparation method, application and battery thereof. Background Art

[0002] As an important energy storage component, secondary lithium / sodium ion batteries can realize the mutual conversion of electrical energy and its chemical energy, and play an indispensable role in smart grids, new energy vehicles, consumer electronics, etc. Traditional carbon-based negative electrodes such as graphite and hard carbon have limited specific capacity and are difficult to meet the long-life application requirements of lithium / sodium ion batteries. Therefore, it is necessary to seek negative electrode materials with high energy density and long life.

[0003] The theoretical specific capacity of silicon is much higher than that of carbon-based materials such as artificial graphite, which are widely used at present. It is also abundant in nature, and the cost of raw materials and preparation is relatively low. As a new type of negative electrode, it can be used in lithium / sodium-ion battery negative electrodes to greatly improve the battery energy density. However, silicon undergoes a huge volume expansion during the charging and discharging process, which can easily lead to problems such as pulverization of electrode materials, destruction of electrode structure, and repeated formation of SEI film, thereby reducing the battery's cycle stability and first coulomb efficiency. In addition, silicon itself has low electronic conductivity and ionic conductivity, which is not conducive to rate characteristics and cycle performance.

[0004] Researchers have invented a series of high-performance silicon negative electrode material preparation methods based on the silicon material nanotechnology route, including sand milling, silane deposition, and thermal evaporation. It has been proven that nano-sized silicon helps to improve the cycle life of electrode materials. However, these methods rely on sand mills and deposition equipment, with low preparation volume, complex processes, and difficulty in large-scale mass production. In order to meet the application needs of the secondary battery long-life industry, it is necessary to develop new silicon negative electrode preparation technologies to achieve high-performance silicon negative electrode performance improvement and preparation cost optimization from the perspective of material component design and preparation methods. Summary of the invention

[0005] The technical problem solved by the present invention is to overcome the problems existing in the prior art such as the complicated nano-process of silicon negative electrode materials, high equipment requirements, and poor intrinsic conductivity of the materials, and provide a metal selenide nano-silicon-carbon composite material and its preparation method, application, and battery. The preparation method of the present invention can simultaneously prepare nano-sized metal selenide and silicon materials, and the prepared metal selenide nano-silicon-carbon composite material has excellent high-rate specific capacity and cycle life.

[0006] The present invention solves the above technical problems through the following technical solutions:

[0007] The present invention provides a method for preparing a metal selenide nano-silicon-carbon composite material, which comprises the following steps:

[0008] (1) calcining a mixture of transition metal M and silicon powder under inert gas protection to obtain a metal precursor;

[0009] (2) calcining the mixture of the metal precursor and SeCl4 under the protection of an inert gas, and then washing it to obtain a metal selenide nano-silicon composite material;

[0010] (3) Granulating and carbonizing the mixture of the metal selenide nano-silicon composite material and the carbon source to obtain the metal selenide nano-silicon carbon composite material.

[0011] In step (1), the transition metal M is preferably one or more of Fe, Co, Mn and Cr, more preferably Fe.

[0012] In step (1), the silicon powder can be conventional in the art, generally commercially available or self-prepared, the main component of the silicon powder is silicon, and the purity is greater than 95%. The particle size of the silicon powder can be 0.5-5 μm, preferably 0.5-2 μm.

[0013] In step (1), the molar ratio of the transition metal M to the silicon powder may be 1:(0.5-3), such as 1:0.6, 1:1, 1:1.5 or 1:2, preferably 1:(0.6-1.5).

[0014] In step (1) and / or step (2), the inert gas may be a conventional industrial inert gas, such as nitrogen or argon.

[0015] In step (1) and / or step (2), the calcination is generally carried out in a tubular furnace.

[0016] In step (1), the rate of heating to the calcination temperature is preferably 2-10°C / min, such as 5°C / min.

[0017] In step (1), the calcination temperature is preferably 500-1000°C, such as 600°C, 700°C or 900°C.

[0018] In step (1), the calcination time is preferably 2 to 10 hours, more preferably 2 to 8 hours, such as 3 hours, 4 hours or 6 hours.

[0019] In step (1), the chemical formula of the metal precursor is generally MSi X , 0.5≤x≤3, for example, x is 0.6, 1 or 2. When M is Fe, the chemical formula of the metal precursor may be FeSi, Fe5Si3, FeSi2, Fe2Si5, or Fe3Si2.

[0020] In step (2), during the calcination process, the metal precursor reacts with SeCl4 to generate nano-silicon, metal selenide and soluble chloride. When the metal precursor is FeSi, the chemical reaction formula is: 3FeSi+SeCl4→FeSe+2FeCl2+3Si.

[0021] In step (2), the molar ratio of the metal precursor to the SeCl4 may be (1.0-3.5):1, preferably (2.5-3.5):1, for example 3:1.

[0022] In step (2), the calcination temperature is preferably 400-850°C, such as 500°C, 550°C or 600°C.

[0023] In step (2), the calcination time is preferably 0.5-8 h, such as 1 h, 2 h, 3 h or 4 h.

[0024] In step (2), the washing can be performed by one or more of deionized water, ethanol and dilute acid, preferably deionized water, ethanol and dilute acid are used in sequence. The dilute acid can be dilute hydrochloric acid, for example, 0.5M dilute hydrochloric acid. According to the conventional art, the washing generally needs to be dried, for example, by oven drying.

[0025] In step (2), the particle size D of the metal selenide nano-silicon composite material is 50 It can be 10-300nm.

[0026] In step (3), the carbon source may be one or more of asphalt, petroleum coke and phenolic resin.

[0027] In step (3), the mass ratio of the metal selenide nano-silicon composite material to the carbon source may be (5-20):1, preferably (8-15):1, for example 10:1.

[0028] In step (3), the preparation method of the mixture can be conventional in the art, for example, the metal selenide nano-silicon composite material and the carbon source are ball-milled to obtain the mixture.

[0029] In step (3), the granulation is preferably spray granulation. The operation and conditions of the spray granulation may be conventional in the art. Before the spray granulation, it is generally necessary to first prepare a mixture of the metal selenide nano-silicon composite material and a carbon source into a slurry, and then pump the slurry into a spray granulator for granulation. The solvent in the slurry may be conventional in the art, such as ethanol. The solid content in the slurry may be 40%-60%, for example 50%, and the solid content refers to the percentage of the total mass of the solid matter in the slurry to the mass of the slurry. Before the granulation, the slurry generally needs to be mixed evenly. The process parameters of the spray granulation may be an air inlet temperature of 170-210°C (for example 190°C) and an air outlet temperature of 110-140°C (for example 120°C).

[0030] In step (3), according to the conventional art, the carbonization is generally carried out under the protection of an inert gas. The carbonization temperature may be 400-800° C., such as 600° C. The carbonization time may be 0.5-4 h, such as 1 h or 2 h.

[0031] The present invention also provides a metal selenide nano-silicon-carbon composite material prepared by the above-mentioned preparation method.

[0032] In the present invention, the metal selenide nano-silicon-carbon composite material is generally a core-shell structure, the core is composed of nano-silicon and metal selenide, and the shell is a carbon layer. The particle size D of the metal selenide nano-silicon-carbon composite material is 50 It can be 1 to 20 microns.

[0033] The present invention also provides an application of the metal selenide nano-silicon-carbon composite material as described above in a lithium ion battery or a sodium ion battery.

[0034] The present invention also provides a secondary ion battery, which comprises a positive electrode, a negative electrode, an electrolyte and a separator, wherein the negative electrode comprises the metal selenide nano-silicon-carbon composite material as described above. The secondary ion battery is preferably a lithium ion battery or a sodium ion battery.

[0035] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0036] The reagents and raw materials used in the present invention are commercially available.

[0037] The positive and progressive effects of the present invention are:

[0038] The preparation method of the present invention does not rely on high-cost raw materials and equipment such as silane and sand mills. A composite material of nano-silicon material and metal selenide is simultaneously prepared by a solid-phase synthesis method. Advantages of metal selenide such as higher ion / electronic conductivity, lower lithium insertion expansion effect, and high specific capacity are utilized to significantly improve the specific capacity, rate performance, and cycle life of nano-silicon. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a SEM image of the metal selenide nano-silicon-carbon composite material prepared in Example 1;

[0040] Figure 2 This is a SEM image of the metal selenide nano-silicon composite material prepared in step (2) of Example 2. DETAILED DESCRIPTION

[0041] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0042] Example 1

[0043] (1) Metallic iron powder and silicon powder (Aladdin, purity of 99.9%, particle size of 1 μm) were mixed uniformly in a molar ratio of 1:1 and placed in a crucible, added to a tube furnace, heated to 600°C at a heating rate of 5°C / min in a nitrogen atmosphere, kept at this temperature for 3 hours, and then naturally cooled to room temperature to obtain a precursor FeSi;

[0044] (2) Precursors FeSi and SeCl4 were mixed in a molar ratio of 3:1, heated to 500°C at a heating rate of 2°C / min in a tube furnace in a nitrogen atmosphere, kept warm for 2 hours, and then naturally cooled to room temperature; the reaction product was then washed with deionized water, ethanol, and 0.5M dilute hydrochloric acid, and dried to obtain a metal selenide nano-silicon composite material;

[0045] (3) The metal selenide nano-silicon composite material and asphalt in a mass ratio of 10:1 were mixed by a mechanical ball mill at a speed of 1000 rpm for 10 min, and then the mixed sample was prepared into a slurry with a solid content of 50% in ethanol and pumped into a spray granulator. Spray granulation was carried out under the conditions of an air inlet temperature of 190°C and an air outlet temperature of 120°C; after granulation, it was transferred to a tubular furnace and heated at 600°C for 1 h in a nitrogen atmosphere. After heating, it was naturally cooled to room temperature to obtain a metal selenide nano-silicon-carbon composite material.

[0046] Example 2

[0047] Compared with Example 1, except that the metal iron powder is replaced by metal manganese powder, the other parameters and conditions are the same as those of Example 1.

[0048] Example 3

[0049] Compared with Example 1, except that the metal iron powder is replaced by metal cobalt powder, the other parameters and conditions are the same as those of Example 1.

[0050] Example 4

[0051] Compared with Example 1, except that the metal iron powder is replaced by metal chromium powder, the other parameters and conditions are the same as those of Example 1.

[0052] Example 5

[0053] Compared with Example 1, except that the molar ratio of metallic iron powder to silicon powder is adjusted to 1:2, other parameters and conditions are the same as those of Example 1.

[0054] Example 6

[0055] Compared with Example 1, except that the heating temperature in step (2) is changed to 600° C., the other parameters and conditions are the same as those in Example 1.

[0056] Example 7

[0057] Compared with Example 1, except that the heating time in step (2) is changed to 4 hours, the other parameters and conditions are the same as those in Example 1.

[0058] Comparative Example 1

[0059] Commercial crude silicon is sand-milled to the limit in an ethanol medium to obtain nano-silicon with a particle size of about 200 nm, and then asphalt accounting for 10% of the mass of the nano-silicon is added and the mixture is ball-milled at 1000 rpm for 10 min in a mechanical ball mill. The mixture is heated at 600°C for 1 h in a nitrogen atmosphere. After cooling, the sample is prepared into a slurry with a solid content of 50% in ethanol and pumped into a spray granulator. Spray granulation is carried out under the conditions of an air inlet temperature of 190°C and an air outlet temperature of 120°C to obtain a nano-silicon-carbon material.

[0060] Effect Example

[0061] (1) Morphology and particle size characterization

[0062] Figure 1 This is a SEM image of the metal selenide nano-silicon-carbon composite material prepared in Example 1, showing that the material is spherical after spray granulation; Figure 2 This is a SEM image of the metal selenide nano-silicon composite material prepared in step (2) of Example 2. It can be seen that the material morphology is agglomerated nanoparticles with a size of less than 200 nanometers.

[0063] The particle sizes of the metal selenide nano-silicon composite material prepared in step (2) of Examples 1-7 and the nano-silicon prepared in Comparative Example 1 were statistically analyzed using a laser particle size distribution analyzer MS3000, as shown in Table 1.

[0064] (2) Lithium-ion battery electrochemical performance test

[0065] The metal selenide nano-silicon-carbon composite materials prepared in Examples 1 to 7 and the nano-silicon-carbon materials prepared in Comparative Example 1 were subjected to half-cell tests. The test method is: the above materials are uniformly mixed with a binder CMC (sodium carboxymethyl cellulose) and conductive carbon black in a mass ratio of 80:10:10, adjusted into a slurry, coated on a copper foil with a coating thickness of 100 microns, and dried at 80°C in vacuum for 12 hours to prepare a lithium battery negative electrode sheet. The simulated battery assembly was carried out in an argon-filled glove box, using a 1 mol / L LiPF6 electrolyte (the solvent is EC, DMC and FEC, EC:DMC=1:1 (volume ratio), FEC accounts for 5% of the total volume of the solvent), a polypropylene microporous membrane as a diaphragm, and a metal lithium sheet as a counter electrode. The electrochemical performance test was carried out on a LandCT2001A battery tester at a temperature of 20°C and a charge and discharge voltage range of 0.01 to 1.5V (1C=1000mAh g -1 ), the test results are shown in Table 1.

[0066] Table 1

[0067]

[0068]

[0069] According to the above experimental results, the metal selenide nano silicon-carbon composite material prepared by the present invention has excellent high-rate specific capacity and cycle life. However, in the preparation process of Comparative Example 1, since it is difficult to further reduce the size during the sanding process, the stress during the lithium ion deintercalation process is difficult to release by deformation, which is more likely to cause pulverization and capacity decay, and due to the poor electron / ion transmission performance of pure silicon, the high-rate specific capacity and cycle performance of high-current charge and discharge are significantly worse than those of the embodiment.

[0070] Although the specific embodiments of the present invention are described above, it should be understood by those skilled in the art that this is only for illustration and the protection scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A method for preparing a metal selenide nano-silicon-carbon composite material, characterized in that: The following steps are involved: (1) calcining a mixture of transition metal M and silicon powder under inert gas protection to obtain a metal precursor; (2) calcining the mixture of the metal precursor and SeCl4 under the protection of an inert gas, and then washing it to obtain a metal selenide nano-silicon composite material; (3) Granulating and carbonizing the mixture of the metal selenide nano-silicon composite material and the carbon source to obtain the metal selenide nano-silicon carbon composite material.

2. The method for preparing the metal selenide nano-silicon-carbon composite material according to claim 1, characterized in that: The transition metal M is one or more of Fe, Co, Mn and Cr, preferably Fe; And / or, the particle size of the silicon powder is 0.5-5 μm, preferably 0.5-2 μm; And / or, the molar ratio of the transition metal M to the silicon powder is 1:(0.5-3), such as 1:0.6, 1:1, 1:1.5 or 1:2, preferably 1:(0.6-1.5).

3. The method for preparing the metal selenide nano-silicon-carbon composite material according to claim 1 or 2, characterized in that: In step (1), the calcination temperature is 500-1000° C., for example, 600° C., 700° C. or 900° C.; And / or, in step (1), the calcination time is 2 to 10 hours.

4. The method for preparing the metal selenide nano-silicon-carbon composite material according to claim 1 or 2, characterized in that: The chemical formula of the metal precursor is MSi X , 0.5≤x≤3; And / or, in step (2), the molar ratio of the metal precursor to the SeCl4 is (1.0-3.5):1, preferably (2.5-3.5):1, for example 3:

1.

5. The method for preparing the metal selenide nano-silicon-carbon composite material according to claim 1 or 2, characterized in that: In step (2), the calcination temperature is 400-850°C, for example, 500°C, 550°C or 600°C; And / or, in step (2), the calcination time is 0.5-8h, such as 1h, 2h, 3h or 4h.

6. The method for preparing the metal selenide nano-silicon-carbon composite material according to claim 1 or 2, characterized in that: In step (2), the particle size D of the metal selenide nano-silicon composite material is 50 10-300nm; And / or, in step (3), the carbon source is one or more of asphalt, petroleum coke and phenolic resin; And / or, in step (3), the mass ratio of the metal selenide nano-silicon composite material to the carbon source is (5-20):1, preferably (8-15):1, for example 10:

1.

7. The method for preparing the metal selenide nano-silicon-carbon composite material according to claim 1 or 2, characterized in that: In step (3), the granulation is spray granulation; preferably, before the spray granulation, the mixture of the metal selenide nano-silicon composite material and the carbon source is first made into a slurry, and then the slurry is pumped into a spray granulator for granulation; preferably, the process parameters of the spray granulation are an air inlet temperature of 170-210°C and an air outlet temperature of 110-140°C; And / or, the carbonization temperature is 400-800°C; And / or, the carbonization time is 0.5-4h.

8. A metal selenide nano-silicon-carbon composite material obtained by the method for preparing a metal selenide nano-silicon-carbon composite material as claimed in any one of claims 1 to 7.

9. Use of the metal selenide nano-silicon-carbon composite material as claimed in claim 8 in a lithium ion battery or a sodium ion battery.

10. A secondary ion battery, characterized in that: It comprises a positive electrode, a negative electrode, an electrolyte and a separator, wherein the negative electrode comprises the metal selenide nano-silicon-carbon composite material as claimed in claim 8.

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