CN105047892A - Porous silicon material, and preparation method and application thereof - Google Patents

Abstract

The invention discloses a porous silicon material, its preparation method and application. The porous silicon material is mainly prepared from iron-silicon alloy for metallurgy through mechanical ball milling and acid etching. Its size is micron/submicron level, has a diamond structure, belongs to the Fd-3m(227) space group, and has A reactive phase that can react with lithium (Li), and a large number of hierarchical pore structures of different sizes are distributed on the surface and inside. The porous silicon material can be used as the negative electrode active material of lithium-ion batteries, and when it is applied to lithium-ion batteries, it exhibits the characteristics of high (first) coulombic efficiency, high capacity and excellent cycle stability, and its preparation process is simple. It can be implemented with conventional equipment, the raw materials used are cheap and easy to obtain, the process is easy to control, the reproducibility is good, the yield is high, the product quality is stable, and it is suitable for large-scale production.

Description

Porous silicon material, its preparation method and application

technical field

The present invention particularly relates to a porous silicon material and its preparation method and application, such as its use as a high coulombic efficiency porous silicon negative electrode active material and/or its application in batteries, especially lithium-ion batteries, belonging to the field of material science.

Background technique

Environmental pollution and climate change are major problems in the 21st century. In order to solve this problem, governments of various countries have invested a lot of energy in developing new energy industries, such as: solar energy, wind energy, tidal energy and so on. Lithium-ion battery, as a reliable means of energy storage, has been a research hotspot since its inception. At present, the commercial lithium-ion battery anode materials use carbon materials, which have the advantages of high cycle efficiency, long cycle life, and low electrode potential. With the gradual clarification of the huge application market in the fields of new energy vehicles, wind energy and solar energy storage, and smart grid energy storage and conversion, power lithium-ion batteries have received unprecedented attention. Graphite anode materials have many shortcomings in power lithium-ion batteries, which cannot meet the needs of high-power lithium batteries.

As an important factor to improve battery energy and cycle life, lithium-ion battery anode materials should be favored by researchers. Compared with other negative electrode materials, the lithium storage capacity of silicon-based negative electrode materials is as high as 3579mAh/g, and it has the advantages of lower lithium extraction potential (<0.5Vvs.Li/Li ⁺ ), so it has been widely recognized by researchers once proposed. Pay attention and become a research hotspot, and it is expected to become the anode material of the next generation of lithium-ion batteries. However, researchers have found that silicon-based negative electrode materials will undergo serious volume changes (volume expansion of more than 300%) during the process of lithium intercalation and deintercalation. Due to volume changes, electrode pulverization and peeling will lead to sharp decline in performance and poor cycle performance. At the same time, the first coulombic efficiency of silicon-based negative electrode materials is also low, and the intrinsic conductivity of silicon is low, so the formed SEM is unstable and easy to fall off. These disadvantages limit its practical application in Li-ion batteries. In addition, the preparation process for preparing high-performance silicon-based negative electrode materials is relatively complicated and the preparation cost is also high.

Therefore, it is urgent to develop a negative electrode material with high first Coulombic efficiency, high theoretical capacity, low cost and good cycle stability in this field.

Contents of the invention

In view of the deficiencies of the prior art, an object of the present invention is to provide a porous silicon material, which has the characteristics of (for the first time) high Coulombic efficiency, high theoretical specific capacity, and good battery cycle stability.

In order to realize the aforementioned object of the invention, the technical solutions adopted in the present invention include:

Some embodiments of the present invention provide a porous silicon material, which is mainly prepared from a metallurgical iron-silicon alloy through mechanical ball milling and acid etching.

Further, the porous silicon material has a diamond structure, belongs to the Fd-3m(227) space group, and has a reaction phase capable of reacting with lithium (Li).

Further, the size of the porous silicon material is micron/submicron level, and a large number of pores are distributed on the surface and inside of the porous silicon material.

Further, the shape of the porous silicon material is irregular granular.

Further, the particle size of the porous silicon material is 0.1 μm˜10 μm, preferably 0.5 μm˜5 μm.

Further, the specific surface area of the porous silicon material is in the range of 0.5-50m ² /g, more preferably 5-25m ² /g.

Further, a large number of hierarchically structured pores are distributed on the surface and inside of the particles of the porous silicon material.

Another object of the present invention is to provide a method for preparing the porous silicon material.

In some embodiments, the preparation method of the porous silicon material includes:

The porous silicon material is obtained by performing mechanical ball milling on the metallurgical iron-silicon alloy and then performing acid etching.

Another object of the present invention is to provide the use of the porous silicon material in the preparation of chemical energy storage devices.

Wherein, the chemical energy storage device includes but not limited to a battery.

Another object of the present invention is to provide a battery negative electrode material, which includes the porous silicon material as the negative electrode active material.

Further, the negative electrode material may further include a conductive agent and/or a binder and the like.

Another object of the present invention is to provide a battery, which includes positive electrode material, negative electrode material, electrolyte and separator, wherein the negative electrode material includes the porous silicon material or the electrode negative electrode material.

Another object of the present invention is to provide a device comprising the porous silicon material, the battery negative electrode material or the battery.

Compared with the prior art, the advantages of the present invention at least include:

(1) The present invention has successfully prepared a porous silicon material that can be used as the negative electrode active material of a battery. When it is directly applied (without post-treatment such as carbon coating), it shows a high Coulombic efficiency for the first time (>88%), High theoretical specific capacity (>1500mAh/g), good battery cycle stability and other characteristics, far superior to similar materials in the prior art;

(2) The preparation process of the porous silicon material provided by the present invention is simple and can be implemented with only conventional equipment, and the raw materials used are all cheap and easy to obtain, the process is easy to control, the reproducibility is good, the yield is high, the product quality is stable, and it is suitable for large-scale Production.

The technical solution of the present invention will be explained in more detail below. However, it should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described in the following (such as embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, we will not repeat them here.

Description of drawings

Fig. 1 is the XRD figure of the porous silicon material prepared in the embodiment 1 of the present invention;

Fig. 2 is the pore size distribution diagram of the pores in the porous silicon material prepared in Example 1 of the present invention;

Fig. 3 is the SEM figure of the porous silicon material prepared in the embodiment 1 of the present invention;

Fig. 4 is the TEM figure of the porous silicon material prepared in the embodiment 1 of the present invention;

Figure 5 is a graph showing the cycle performance of the electrode based on the porous silicon material in Example 1 of the present invention;

Fig. 6 is a graph of the rate performance of the electrode based on the porous silicon material in Example 1 of the present invention;

Figure 7 is a graph showing the cycle performance of the electrode based on the porous silicon material in Example 2 of the present invention;

Fig. 8 is a graph showing the cycle performance of the electrode based on the porous silicon material in Example 3 of the present invention;

Fig. 9 is a graph showing the cycle performance of the electrode based on the porous silicon material in Example 4 of the present invention;

Fig. 10 is a graph showing the cycle performance of the electrode based on the porous silicon material in Example 5 of the present invention;

Fig. 11 is a graph showing cycle performance of an electrode based on a porous silicon material in a comparative example.

Detailed ways

As mentioned above, in view of many deficiencies in the prior art, the inventor of this case has been able to propose the technical solution of the present invention after long-term and in-depth research and extensive practice, as detailed below.

Porous silicon negative electrode active material

The first aspect of the present invention provides a porous silicon material (hereinafter also referred to as a porous silicon negative electrode active material), which is mainly prepared from a metallurgical iron-silicon alloy as a raw material.

Further, the porous silicon material is mainly prepared from metallurgical iron-silicon alloy as raw material through mechanical ball milling and acid etching.

Further, the size of the porous silicon material is micron/submicron level, and a large number of pores with different sizes are distributed on the surface and inside of the particle.

Further, the porous silicon material has a reactive phase capable of reacting with lithium (Li).

Further, the porous silicon material has a diamond structure.

Further, the porous silicon material belongs to the Fd-3m(227) space group.

Further, the shape of the porous silicon material is irregular granular.

Further, the particle size range of the porous silicon material is 0.1-10 μm, more preferably 0.5-5 μm.

Further, the specific surface area of the porous silicon material is 0.5-50m ² /g, more preferably 5-25m ² /g.

More preferably, a large number of pores of hierarchical structure are distributed on the surface and inside of the particles of the porous silicon material.

Specifically, in the channels of the hierarchical structure, micropores account for 10%-40%, mesopores account for 20%-30%, and macropores account for 30%-70%.

Among them, the definitions of micropores, mesopores, and macropores are the same as those defined by the International Union of Pure and Applied Chemistry (IUPAC), that is, the diameter of micropores is less than 2nm, the diameter of macropores is greater than 50nm, and the diameter of mesopores (or mesopores) is between Between 2 and 50nm.

In the present invention, the iron-silicon alloy material obtains strain, defects and microstructure through the mechanical ball milling process, and at the same time, a porous structure, especially a multi-level structure channel, is formed by acid etching, which can effectively improve the cycle performance of the porous silicon negative electrode material and effectively relieve the silicon Huge volume expansion problem during alloying.

Preparation method of porous silicon negative electrode active material

The preparation method of the porous silicon negative electrode active material includes: ultrasonic chemical method, wet chemical method, mechanochemical reaction (such as mechanical alloying method and mechanical ball milling method) and the like.

In a preferred embodiment, a method for preparing a porous silicon negative electrode active material includes: using a metallurgical iron-silicon alloy as a raw material, preparing the target product through mechanical ball milling and acid etching.

In a more specific embodiment, the preparation method may include the following steps:

(i) metallurgical iron-silicon materials that provide silicon sources;

(ii) ball milling the iron-silicon alloy;

(iii) performing metal-assisted acid etching of the iron-silicon alloy in an acid etching reagent to prepare a porous silicon material.

In a preferred example, the mass percentage of silicon in the metallurgical iron-silicon alloy is 1-99%, and the mass percentage of metal impurities is 1-99%; based on the total weight of the metallurgical iron-silicon alloy.

In another preferred example, the mass percentage of silicon in the metallurgical iron-silicon alloy is 20-99 wt%, and the mass percentage of metal impurities is 1-80 wt%, based on the total weight of the metallurgical iron-silicon alloy.

In another preferred example, the mass percentage of silicon in the metallurgical iron-silicon alloy is 50-90 wt%, and the mass percentage of metal impurities is 10-50 wt%, based on the total weight of the metallurgical iron-silicon alloy.

In another preferred example, the mass percentage of silicon in the metallurgical iron-silicon alloy is 70-80 wt%, and the mass percentage of metal impurities is 20-30 wt%, based on the total weight of the metallurgical iron-silicon alloy.

In another preferred example, in the metallurgical iron-silicon alloy, the mass percentage of silicon is about 70-80 wt%, based on the total weight of the alloy.

In another preferred example, the preparation method includes: dry ball milling and/or wet ball milling, and acid etching.

Furthermore, wet ball milling is particularly preferred in the preparation method, wherein the addition of the solvent makes the iron-silicon alloy particles easily adhere to the grinding balls, so that the energy of the grinding balls can be fully transferred to the iron-silicon alloy particles, Moreover, the solvent can also reduce the surface energy of the iron-silicon alloy particles, limit the agglomeration of the iron-silicon alloy particles, and promote the refinement of the iron-silicon alloy particles.

In another preferred embodiment, the ball milling atmosphere is selected from the group consisting of air, argon, nitrogen, ammonia, and argon-hydrogen mixed gas.

In another preferred example, the rotational speed of the mechanical ball mill is 200r/min to 500r/min, especially preferably selected from the following group: 200r/min, 250r/min, 300r/min, 350r/min, 400r/min, 450r /min, 500r/min.

In another preferred example, the mechanical ball milling time is 1h-64h, especially preferably selected from the following group: 1h, 2h, 4h, 8h, 12h, 24h, 36h, 48h, 64h.

In another preferred example, the ball-to-material ratio (grinding ball: raw material, mass ratio) is 1:1-20:1, especially preferably selected from the following group: 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 8:1, 12:1, 16:1, 20:1.

In another preferred example, the solvent may be selected from the group consisting of deionized water, absolute ethanol, ethylene glycol, acetone or combinations thereof.

In another preferred example, the solvent-to-material ratio is 1:5 to 5:1, especially preferably selected from the following group: 1:5, 1:4, 1:3, 1:2, 1:1, 2 :1, 3:1, 4:1, 5:1.

In the preparation process of the porous silicon material of the present invention, by performing mechanical ball milling on the iron-silicon alloy particles, the iron-silicon alloy can obtain high energy from the outside during the ball milling process, thereby introducing strain, defects and microstructures into the material, and then lead to changes in the properties of the material.

Further speaking, the aforementioned changes in material properties mainly refer to changes in particle surface structure, crystal structure, physicochemical properties, and mechanochemical properties of the iron-silicon alloy particles, and are not limited thereto.

Furthermore, the above-mentioned changes in the surface structure of the particles mainly refer to the violent collision and grinding of the iron-silicon alloy particles due to the action of mechanical force during the ball milling process, the particle size is continuously reduced, and new surface defects are continuously formed. Formation, the specific surface area increases, the chemical bonds on the surface of the particles are broken, and the surface structure becomes amorphous.

Furthermore, the above-mentioned crystal structure change mainly means that the iron-silicon alloy particles are refined under the action of strong mechanical force, resulting in defects such as dislocations and twins in the crystal lattice, and changes in the grain boundary structure.

Furthermore, the aforementioned changes in physical and chemical properties mainly mean that under the action of strong mechanical force, the specific surface area and crystal structure of the particles of the iron-silicon alloy particles change greatly, and the corresponding physical and chemical properties also change significantly. The surface energy and electrical conductivity are significantly improved.

Furthermore, the aforementioned mechanochemical property changes mainly refer to changes in the chemical composition of the iron-silicon alloy particles under the action of strong mechanical force, solid solution reaction, oxidation-reduction reaction and crystal form transformation, etc. .

In another preferred embodiment, the acid etching reagent is selected from the group consisting of dilute hydrochloric acid, dilute nitric acid, dilute sulfuric acid, hydrofluoric acid or combinations thereof.

In another preferred example, the acid treatment method is selected from the group consisting of standing, stirring, ultrasonic treatment or a combination thereof.

In another preferred example, the acid treatment time is 1h-48h, especially preferably selected from the following group: 1h, 2h, 5h, 8h, 12h, 18h, 36h, 48h.

Also, in a more specific implementation case, a method for preparing a porous silicon material using an iron-silicon alloy as a raw material specifically includes the following steps:

(i) Weigh a certain amount of industrial iron-silicon alloy and put it into a ball mill tank, add a solvent, and finally weigh a certain amount of grinding balls, and set the mass ratio of the grinding balls to the iron-silicon alloy to 8:1;

(ii) ball milling the above-mentioned sample for 24 hours at a speed of 300r/min under an air atmosphere;

(iii) Pickling the fine-grain silicon alloy obtained by ball milling with 2M hydrochloric acid solution for 12 hours; then cleaning the oxide layer existing on the surface with 10% hydrofluoric acid for 6 hours;

(iv) Suction filtering and cleaning the etched material to prepare a porous silicon material.

Wherein, the iron-silicon alloy can be purchased through commercial channels.

Wherein, the material of the ball mill jar and the balls can be preferably selected from the following group: stainless steel, agate, zirconia and the like.

Wherein, the porous silicon material described in step (iv) can be washed by suction filtration with water or ethanol several times.

In the preparation process of the present invention, the properties of the material are changed by mechanical ball milling of the iron-silicon alloy particles, and then acid-etched to form a porous silicon material with a special shape and structure. When applied as the negative electrode active material of lithium-ion batteries, it exhibits the characteristics of high (first) Coulombic efficiency, high capacity and excellent cycle stability. Especially beyond the expectation of the inventors of this case, the first coulombic efficiency of the porous silicon material of the present invention is very high (close to 90%) even without carbon coating, and the battery cycle efficiency remains stable. Significantly better than similar materials reported in the literature.

Batteries Containing Negative Active Materials

The porous silicon negative electrode active material of the present invention can be applied to chemical energy storage devices, such as the field of batteries.

In one embodiment, an article comprises or is made of said porous silicon material.

In another preferred example, the product includes a lithium ion battery or a negative electrode material for a battery.

In one embodiment, a battery negative active material includes or is made of the porous silicon material.

In one embodiment, a negative electrode material includes the porous silicon material as the negative electrode active material.

In another preferred example, the negative electrode material further includes a conductive agent and/or a binder.

In another preferred example, in the negative electrode material, the content of the porous silicon material is 60-80wt%.

In another preferred example, the content of the conductive agent is 10-20wt%.

In another preferred example, the content of the binder is 10-20 wt%, based on the total weight of the negative electrode material.

In another preferred example, in the negative electrode material, the mass ratio of the porous silicon material, the conductive agent, and the binder is (70±10):(10±2):(20±2).

In one embodiment, a battery includes a positive electrode material, a negative electrode material, an electrolyte and a separator, and the negative electrode material includes the porous silicon material as the negative electrode active material.

In one embodiment, the negative electrode material is mainly composed of the porous silicon material, a conductive agent and a binder.

More preferably, in the negative electrode material, the content of the porous silicon material is 60-90wt%, the content of the conductive agent is 10-20%, and the content of the binder is 10-20wt%.

Wherein, the binder includes a polymer derivative having a carboxyl group, but is not limited thereto.

In another preferred example, the battery further has a casing.

The material of the casing is not particularly limited, and may be metal materials, non-metallic inorganic materials, organic materials or other composite materials.

In another preferred example, the battery is preferably an anhydrous battery.

Further, the separator may be any existing battery separator in the art, such as polytetrafluoroethylene separator, ceramic porous membrane, glass fiber separator, etc., and is not limited thereto.

In one embodiment, the electrolyte solution includes one or more than two kinds of electrolyte salts and/or one or more than two kinds of solvents.

In another preferred example, the electrolyte salt includes positive ions, for example, lithium salt can be used. Preferred lithium salts include, but are not limited to, lithium hexafluorophosphate, lithium perchlorate, lithium chloride, lithium bromide, and the like.

In another preferred embodiment, the battery is a lithium battery, and the electrolyte salt is selected from lithium salts, but not limited thereto.

In another preferred example, the electrolyte salt meets the following requirements: during charging, the positive ions of the electrolyte salt can pass through the electrolyte, from the positive electrode material to the negative electrode material, and during the discharge process, the electrolyte salt Positive ions can pass through the electrolyte, from the negative electrode material to the positive electrode material.

In another preferred example, the solvent is preferably an organic solvent, such as but not limited to ethyl methyl carbonate (MethylEthylCarbonate), dimethyl carbonate (DimethylCarbonate), diethyl carbonate (DiethylCarbonate), ethylene carbonate Ethylene Carbonate, Propylene Carbonate, 1,2-Dimethoxyethane, 1,3 Dioxolane, Anisole, Acetate, Propionate, Butyrate, Diethyl Ether, Acetonitrile, propionitrile.

In another preferred example, the organic solvent includes at least one cyclic carbonate derivative substituted by one or more halogen atoms, such as 4-fluoro-1,3-dioxol-2-one, But not limited thereto, it can improve the cycle performance of the electrode.

The electrolyte solvent may be used alone, or may contain two or more kinds of solvents, and the electrolyte salt may be used alone, or may contain two or more kinds of lithium salts.

Moreover, the inventors of the present case have found through a large number of experiments that when the porous silicon material of the present invention is directly used as the negative electrode active material and the aforementioned various electrolytes, especially various lithium-ion battery electrolytes, all show the first Coulombic efficiency (approximately 90%), high charge-discharge specific capacity and stable battery cycle efficiency, etc., indicating that the porous silicon material of the present invention has quite good universality.

The anode material is not particularly limited, and can be selected with reference to existing technologies in the art, or existing anode materials in the art can be used.

In a preferred example, the positive electrode material includes one or more active metal oxides as the positive electrode active material, and the active metal oxide also includes an inactive metal element selected from the following group: manganese ( Mn), iron (Fe), cobalt (Co), vanadium (V), nickel (Ni), chromium (Cr), or combinations thereof, without limitation.

Preferably, the positive electrode material further includes components selected from the group consisting of metal oxides, metal sulfides, transition metal oxides, transition metal sulfides, or combinations thereof, but not limited thereto.

In another preferred example, the aforementioned active metal is lithium.

In another preferred example, when the battery is a lithium battery, the positive electrode material further includes a component selected from the following group:

LiMnO ₂ ,

LiMn ₂ O ₄ ,

LiCoO ₂ ,

Li ₂ CrO ₇ ,

LiNiO ₂ ,

LiFeO ₂ ,

LiNi _x Co _1-X O ₂ (0<x<1),

LiFePO ₄ ,

LiMn _z Ni _1-Z O ₂ (0<z<1, such as LiMn0.5Ni0.5O2),

LiMn _0.33 Co _0.33 Ni _0.33 O ₂ ,

LiMc _0.5 Mn _1.5 O ₄ , Mc is a divalent metal;

LiNi _x Co _y Me _z O ₂ , Me represents one or several elements of Al, Mg, Ti, B, Ga, Si, x>0;y<1,z<1,

transition metal oxides,

transition metal sulfides,

or a combination thereof.

Wherein, the transition metal oxide may be preferably selected from, but not limited to, MnO ₂ , V ₂ O ₅ and the like.

Wherein, the transition metal sulfide may be preferably selected from but not limited to FeS ₂ , MoS ₂ , TiS ₂ and the like.

Among them, lithium-ion transition metal oxides have been used more, and more preferably, they can be selected from LiMn ₂ O ₄ , LiCoO ₂ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ , LiFePO ₄ and LiNi _0.33 Mn _0.33 Co _0.33 O One or more of ₂ , but not limited thereto.

The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. For the experimental methods without specific conditions indicated in the following examples, the conventional conditions or the conditions suggested by the manufacturer are usually followed. Also, unless otherwise stated, the following percentages and parts are by weight.

Preparation of Example 1 Porous Silicon Negative Active Material (i.e. "porous silicon material"):

1) Weigh 2g of metallurgical iron-silicon alloy, 2g of absolute ethanol and 16g of agate balls, and add them to a 100ml agate ball mill jar respectively.

2) Put the ball mill jar into the ball mill, set the ball mill parameters, the speed is 300r/min, the working time is 24 hours, and every 20 minutes of work is 10 minutes of rest.

3) Suction filtration, washing and drying of the ball-milled small particles of iron-silicon alloy.

4) Measure 100ml of 2M hydrochloric acid solution into a 200ml beaker, slowly add small grains of iron-silicon alloy, and keep stirring until the addition is complete. Put the beaker into an ultrasonic instrument for ultrasonic dispersion for 30min. Remove the beaker and place it on a magnetic stirrer for 24 h of continuous stirring. Filter and dry.

5) Add the sample treated with hydrochloric acid into 10% hydrofluoric acid solution, and keep stirring for 24 hours. Suction filtration, washing and drying to prepare porous silicon material.

The crystal phase, pore size distribution and morphology of the porous silicon negative electrode active material prepared in this example were analyzed. Its XRD spectrum is shown in FIG. 1 , and it can be seen from the spectrum that the prepared porous silicon is a pure-phase silicon material. Figure 2 is a pore size distribution diagram of the porous silicon material, and the pore size distribution is uniform, indicating that the pores of the material present a hierarchical structure. Figure 3 and Figure 4 are SEM photos and TEM photos of the porous silicon material respectively. It can be seen from Figure 3 and Figure 4 that the prepared porous silicon material presents a unique pore structure with a particle size of 1-2 μm.

Electrochemical Performance Analysis of Porous Silicon Negative Active Material Lithium Batteries:

The porous silicon material, the conductive agent and the binder are uniformly mixed according to the ratio of 70:10:20, and coated on the carrier fluid. The conductive agent is carbon black (SuperP), and the binder is sodium carboxymethyl cellulose (CMC).

Cell assembly was performed in an argon-filled glove box. The counter electrode is a lithium electrode, and the electrolyte is fluoroethylene carbonate (FEC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) of 1M lithium hexafluorophosphate (LiPF ₆ ) (volume ratio 1:1:1) solution, the charging and discharging voltage range is 0.01V-1.5V. The aforementioned LiPF ₆ , FEC, DMC, and EMC can also be replaced by other solutes and solvents listed above.

Test conditions: the load capacity of the tested pole piece is 1.5mg/cm ² , respectively at 50mA/g, 100mA/g, 200mA/g, 500mA/g, 1000mA/g, 2000mA/g, 5000mA/g, 10000mA/g Tested under equal current conditions. As shown in Table 1 below, when tested under 500mA/g charge and discharge conditions (the first two cycles were activated at a current density of 50mA/g), after many cycles, the porous silicon material still maintained good cycle stability, and the charge ratio The capacity retention rate was 81.5% (under the condition of 500mA/g). Figure 5 and Figure 6 are the cycle performance diagram and the rate performance diagram of the porous silicon negative electrode material, respectively. In the rate performance diagram of Figure 6, at a current density of 5000mA/g, the reversible capacity of the material is still as high as 550mAh/g, showing that the hierarchically structured pores have good electron and ion transport properties.

Table 1 Example 1 Porous silicon material is used as the cycle performance test result of negative electrode active material

Preparation of Example 2 Porous Silicon Negative Active Material:

1) Weigh 2g of metallurgical iron-silicon alloy, 1g of absolute ethanol and 8g of agate balls in an argon atmosphere, and add them to a 100ml agate ball mill jar.

2) Put the ball mill pot into the ball mill, set the ball mill parameters, the speed is 400r/min, the working time is 12h, and every 10min of work is 10min of rest.

3) Suction filtration, washing and drying of the ball-milled small particles of iron-silicon alloy.

4) Measure 100ml of 10% hydrofluoric acid solution into a 200ml plastic beaker, slowly add small grains of iron-silicon alloy, and keep stirring until the addition is complete. Put the beaker into an ultrasonic instrument for ultrasonic dispersion for 30min. Remove the beaker and place it on a magnetic stirrer for 12 h of continuous stirring. Suction filtration, washing and drying to prepare porous silicon material.

The porous silicon material obtained in this example was tested in a manner similar to that of Example 1, and the cycle performance test results are shown in FIG. 7 .

Preparation of Example 3 Porous Silicon Negative Active Material:

1) Weighing 2g of metallurgical iron-silicon alloy, 0.4g of absolute ethanol and 2g of zirconia balls were weighed in an argon atmosphere, and added to 100ml of zirconia ball mill jars respectively.

2) Put the ball mill pot into the ball mill, set the ball mill parameters, the speed is 200r/min, the working time is 64h, and every 20min of work is 10min of rest.

3) Suction filtration, washing and drying of the ball-milled small particles of iron-silicon alloy.

4) Measure 100ml of 10% hydrofluoric acid solution into a 200ml plastic beaker, slowly add small grains of iron-silicon alloy, and keep stirring until the addition is complete. Put the beaker into an ultrasonic instrument for ultrasonic dispersion for 30 min. Remove the beaker and place it on a magnetic stirrer for 1 h of continuous stirring. Suction filtration, washing and drying to prepare porous silicon material.

The porous silicon material obtained in this example was tested in a manner similar to that of Example 1, and the cycle performance test results are shown in FIG. 8 .

Preparation of embodiment 4 porous silicon negative electrode active material:

1) Weighing 2g of metallurgical iron-silicon alloy, 10g of absolute ethanol and 40g of steel balls in an argon atmosphere, respectively, and adding them to a 200ml steel ball mill jar.

2) Put the ball mill jar into the ball mill, set the ball mill parameters, the rotation speed is 500r/min, the working time is 1h, and rest for 10min every 10min.

3) Suction filtration, washing and drying of the ball-milled small particles of iron-silicon alloy.

4) Measure 100ml of 10% hydrofluoric acid solution into a 200ml plastic beaker, slowly add small grains of iron-silicon alloy, and keep stirring until the addition is complete. Put the beaker into an ultrasonic instrument for ultrasonic dispersion for 30min. Remove the beaker and place it on a magnetic stirrer for 48 hours of continuous stirring. Suction filtration, washing and drying to prepare porous silicon material.

The porous silicon material obtained in this example is tested in a manner similar to Example 1, wherein the electrolyte is changed to ethylene carbonate (EthyleneCarbonate), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) of 1M lithium hexafluorophosphate (LiPF6). ) (volume ratio 1:1:1) solution. The cycle performance test results are shown in Figure 9.

Preparation of Example 5 Porous Silicon Negative Active Material:

1) Weigh 2g of metallurgical iron-silicon alloy and 8g of agate balls under air condition, and add them into 100ml agate ball mill jar respectively.

2) Put the ball mill jar into the ball mill, set the ball mill parameters, the speed is 300r/min, the working time is 24 hours, and every 20 minutes of work is 10 minutes of rest.

3) Washing and drying the small grains of the ball-milled iron-silicon alloy.

4) Measure 100ml of 5% hydrofluoric acid solution into a 200ml plastic beaker, slowly add small grains of iron-silicon alloy, and keep stirring until the addition is complete. Put the beaker into an ultrasonic instrument for ultrasonic dispersion for 30min. Remove the beaker and place it on a magnetic stirrer for 5 h of continuous stirring. Suction filtration, washing and drying to prepare porous silicon material.

The porous silicon material obtained in this example was tested in a manner similar to that of Example 1, and the cycle performance test results are shown in FIG. 10 .

In addition, the inventors of this case also referred to Examples 1-3, and replaced the other process conditions listed above, such as other various ball milling speeds, ball milling time, ball-to-material ratio, solvent-to-material ratio, and other types of acid etching. Reagents, other types of acid treatment time, etc. were used to produce porous silicon materials, and the morphology and performance of the obtained product were tested with reference to the method of Example 1, and it was found that (for the first time) Coulombic efficiency, capacity and cycle stability Property etc. are all approximate with embodiment 1 product.

The preparation of comparative example porous silicon negative electrode active material:

1) Weigh 2g of metallurgical iron-silicon alloy, crush it by physical cutting, and sieve to obtain small particles of iron-silicon alloy with relatively uniform particle size distribution, wash and dry.

2) Measure 100ml of 2M hydrochloric acid solution into a 200ml beaker, slowly add small grains of iron-silicon alloy, and keep stirring until the addition is complete. Put the beaker into an ultrasonic instrument for ultrasonic dispersion for 30min. Remove the beaker and place it on a magnetic stirrer for 24 h of continuous stirring. Filter and dry.

3) Add the sample treated with hydrochloric acid into 10% hydrofluoric acid solution, and keep stirring for 24 hours. Suction filtration, washing and drying to prepare porous silicon material.

The porous silicon material obtained in this comparative example is tested in a manner similar to that of Example 1, and the cycle performance test results are shown in Figure 11 and Table 2. It can be seen that the charge-discharge performance of the porous silicon material prepared without ball milling It is obviously worse than the electrochemical performance of the negative electrode material prepared by the ball milling process of the present invention, which proves that the present invention has changed the performance of the material by performing mechanical ball milling on the iron-silicon alloy particles in the early stage, and then through acid etching to form The porous silicon material with special morphology and structure exhibits excellent electrochemical performance beyond the expectations of those skilled in the art.

Table 2 The cycle performance test results of the porous silicon material of the control example as the negative electrode active material

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, there may be various modifications and changes in the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims (10)

1. A porous silicon material, characterized in that it has a diamond structure, belongs to the Fd-3m (227) space group, and has a reactive phase capable of reacting with lithium; Preferably, the size of the porous silicon material is micron or submicron level, more preferably, the particle size of the porous silicon material is 0.1 μm to 10 μm, especially preferably 0.5 μm to 5 μm; Preferably, a plurality of pores are evenly distributed on the surface and inside of the particles of the porous silicon material; Further preferably, pores of a hierarchical structure are distributed on the surface and inside of the particles of the porous silicon material; More preferably, in the channels of the hierarchical structure, micropores account for 10%-40%, mesopores account for 20%-30%, and macropores account for 30%-70%; Especially preferably, the specific surface area of the porous silicon material is 0.5-50 m ² /g, more preferably 5-25 m ² /g. 2. A method for preparing a porous silicon material, characterized in that it comprises: performing mechanical ball milling on a metallurgical iron-silicon alloy, followed by acid etching to obtain the porous silicon material. 3. the preparation method of porous silicon material according to claim 2, is characterized in that: The silicon content in the metallurgical iron-silicon alloy is 1wt%-99wt%, and the content of metal impurities is 1wt%-99wt%; Preferably, the silicon content in the metallurgical iron-silicon alloy is 20wt%-99wt%, and the metal impurity content is 1wt%-80wt%; Preferably, the silicon content in the metallurgical iron-silicon alloy is 50wt%-90wt%, and the content of metal impurities is 10wt%-50wt%; Preferably, the silicon content in the metallurgical iron-silicon alloy is 70wt%-80wt%, and the content of metal impurities is 20wt%-30wt%. 4. the preparation method of porous silicon material according to claim 2, is characterized in that: The mechanical ball milling includes wet ball milling and/or dry ball milling; And/or, the ball milling atmosphere of the mechanical ball milling includes air, argon, nitrogen, ammonia or a mixed atmosphere of argon and hydrogen; And/or, the ball milling speed of the mechanical ball mill is 200r/min～500r/min, more preferably selected from the following group: 200r/min, 250r/min, 300r/min, 350r/min, 400r/min, 450r/min, 500r/min; And/or, the ball milling time of the mechanical ball milling is 1h～64h, more preferably selected from the following group: 1h, 2h, 4h, 8h, 12h, 24h, 36h, 48h, 64h; And/or, the ball-to-material ratio used in the mechanical ball mill is 1:1-20:1, more preferably from the following group: 1:1, 2:1, 3:1, 4:1, 5:1, 6 :1, 8:1, 12:1, 16:1, 20:1; And/or, the grinding balls used in the mechanical ball mill include any one or a combination of two or more of steel balls, agate balls, corundum balls, tungsten carbide balls and zirconia balls. 5. according to the preparation method of claim 2 or 4 described porous silicon materials, it is characterized in that: The mechanical ball milling adopts wet ball milling, wherein the solvent includes any one or a combination of two or more of deionized water, absolute ethanol, ethylene glycol and acetone; And/or, the mechanical ball milling adopts wet ball milling, wherein the ratio of solvent to material is 1:5 to 5:1, more preferably selected from the following group: 1:5, 1:4, 1:3, 1:2, 1 :1, 2:1, 3:1, 4:1, 5:1. 6. The preparation method of the porous silicon material according to claim 2, characterized in that it comprises: performing metal-assisted acid etching on the iron-silicon alloy after mechanical ball milling in an acid etching reagent to prepare the porous silicon material; Preferably, the acid etching reagent includes any one or a combination of two or more of dilute hydrochloric acid, dilute nitric acid, dilute sulfuric acid, and hydrofluoric acid; And/or, the acid etching treatment method includes any one or a combination of two or more of standing, stirring, and ultrasonic treatment; And/or, the time of the acid etching treatment is 1h-48h, more preferably selected from the following group: 1h, 2h, 5h, 8h, 12h, 18h, 36h, 48h. 7. A porous silicon material prepared by the method of any one of claims 2-6. 8. A battery negative electrode material, characterized in that: It comprises the porous silicon material as claimed in claim 1 or 7 as negative electrode active material; Preferably, the negative electrode material comprises 60wt% to 80wt% of the porous silicon material; Preferably, the negative electrode material also includes a conductive agent and/or a binder; Further preferably, the negative electrode material includes 10wt% to 20wt% conductive agent; Further preferably, the negative electrode material comprises 10wt% to 20wt% binder; More preferably, the negative electrode material comprises the porous silicon material, a conductive agent and a binder in a mass ratio of (70±10):(10±2):(20±2). 9. A battery comprising positive electrode material, negative electrode material, electrolyte and separator, characterized in that said negative electrode material comprises the porous silicon material according to claim 1 or 7 or the battery negative electrode material according to claim 8. 10. A device, characterized by comprising the porous silicon material according to claim 1 or 7, the battery negative electrode material according to claim 8, or the battery according to claim 9.