CN106684364B

CN106684364B - Nano porous material and preparation method thereof

Info

Publication number: CN106684364B
Application number: CN201710056842.2A
Authority: CN
Inventors: 朱嘉; 宗麟奇; 刘畅
Original assignee: Nanjing University
Current assignee: Moguang Xinneng Technology Suzhou Co ltd
Priority date: 2017-01-26
Filing date: 2017-01-26
Publication date: 2020-04-24
Anticipated expiration: 2037-01-26
Also published as: CN106684364A

Abstract

The invention relates to a nano porous material and a preparation method thereof. The porous bodyThe material contains M simple substance, wherein M is Si and/or Ge; the particle size of the porous material is 20-150 nm, the porosity is 0.2-0.8, and the specific surface area is 15-300 m²(ii) in terms of/g. The porous material has better performance as an electrode material.

Description

Nano porous material and preparation method thereof

Technical Field

The invention belongs to the field of nano materials, and particularly relates to a nano porous material and a preparation method thereof.

Background

The lithium ion battery has the advantages of high specific energy, small volume, light weight, long cycle life, small self-discharge and the like, and is widely applied to the fields of portable electronic equipment, electric automobiles, space technology, national defense industry and the like.

Among many new-generation high-specific-energy lithium ion battery cathode materials, silicon has the advantages of high theoretical capacity (about 13 times of graphite), abundant yield and the like, and is one of the most potential materials for replacing graphite cathode materials in the future. However, silicon undergoes a large volume expansion during charge and discharge, resulting in a rapid decay of battery capacity. One approach to solve the above problems is to form silicon material into nano-particles, such as silicon nano-particles, silicon nano-wires, etc.

Disclosure of Invention

It is an object of the present invention to provide a porous material, a further object of the present invention to provide a method for preparing a porous material, a further object of the present invention to provide a composition, a further object of the present invention to provide a method for preparing the above composition, and a further object of the present invention to provide a lithium ion battery.

The invention provides a porous material, which contains M simple substance, wherein M is Si and/or Ge;

the particle size of the porous material is 20-150 nm, the porosity is 0.2-0.8, and the specific surface area is 15-300 m²/g。

In one embodiment, the porous material of any one of the present invention has one or more of the following features,

preferably, the particle size of the porous material is 50 to 150nm, such as 50 to 130nm, such as 50 to 110nm, such as 60 to 100nm, and further such as 70 to 90 nm;

preferably, the porosity of the porous material is 0.3 to 0.8, such as 0.4 to 0.8, such as 0.5 to 0.8, such as 0.6 to 0.7;

preferably, the specific surface area of the porous material is 40-300 m²A g, further example is 100 to 300m²A g, further for example 150 to 300m²A further example is 200 to 300m²A further example is 230 to 300m²G, further for example 230 to 270m²A further example is 240 to 260m²/g；

Preferably, the apparent density of the porous material is 0.5-2.2 g/cm³For example, 0.5 to 2g/cm³For example, 0.5 to 1.5g/cm³For example, 0.6 to 1.1g/cm³For example, 0.6 to 0.8g/cm³；

Preferably, the pore size distribution curve of the porous material has a characteristic peak at 10-50 nm, such as a characteristic peak at 5-15 nm, such as a characteristic peak at 15-25 nm, such as a characteristic peak at 25-35 nm;

preferably, the porous material has only one characteristic peak on the pore size distribution curve;

preferably, in a 40-50 ten thousand-fold TEM picture of the porous material, a porous structure (such as a foam-like porous structure) can be observed;

preferably, the porous material contains more than 50 weight percent of the M simple substance;

preferably, the porous material contains more than 90 wt% of the M simple substance;

preferably, the porous material contains more than 99 weight percent of M simple substance;

preferably, M is Si.

In still another aspect, the present invention provides a method of preparing a porous material, comprising:

i) ball-milling a mixture of a raw material M simple substance and an oxidant to obtain an oxide of M;

m is Si and/or Ge;

ii) heat treating the oxide of M;

iii) acid washing the heat treated oxide of M;

preferably, the porous material is a porous material according to any one of the present invention.

In one embodiment, the process of any of the present invention, step i), has one or more of the following features:

preferably, the purity of the elemental feed M is greater than about 99.5%, preferably greater than 99.9%;

preferably, the shape of the simple substance M is spherical, spheroidal, blocky, rod-like or irregular;

preferably, the volume of the simple substance M is 1-10 mm³Preferably 3 to 7mm³；

Preferably, the molar ratio of the simple substance M to the oxidant is 1: 0.8-1.8, such as 1: 1.0-1.5, and further such as 1: 1.2-1.4.

preferably, the oxidizing agent comprises water;

preferably, the ball milling is carried out under a vacuum or a non-oxidizing atmosphere, which may be an inert gas atmosphere, such as an argon atmosphere;

preferably, the rotation speed of the ball milling is 500-2000 r/min, such as 800-1200 r/min;

preferably, the diameter of the grinding ball used for ball milling is 1-5 mm, such as 3-4 mm;

preferably, the material of the grinding ball used for ball milling is ZrO₂；

Preferably, the mass ratio of the ball-milled material balls is 1: 20;

preferably, the time of ball milling is 1 to 5 hours, for example 3 to 4 hours.

preferably, the oxide of M is MO_xX is 0.2 to 1.8 (for example, x is 0.5 to 1.7, for example, x is 1.0 to 1.6, and further for example, x is 1.2 to 1.4);

preferably, the oxide of M is an amorphous material;

preferably, the oxide of M has a particle size of 50 to 200nm, for example 50 to 150 nm.

Preferably, the oxide of M has no distinct crystal structure in a TEM photograph;

preferably, in an XRD curve of the oxide of M, a steamed bun peak exists in a range of a 2 theta angle of 10-40 degrees;

preferably, the oxide of M has an XRD profile as shown in profile b of fig. 2;

preferably, the oxide of M is in a Raman spectrum at a wavelength of 475-500 cm^-1Has a peak at the position of (a).

In one embodiment, the method of any of the present invention, step ii), has one or more of the following features:

preferably, the heat treatment is performed in a vacuum or non-oxidizing atmosphere, for example, an inert gas atmosphere, for example, a mixed gas atmosphere of argon and hydrogen, preferably, the content of hydrogen in the non-oxidizing atmosphere is 1 to 3 vol%;

preferably, the temperature of the heat treatment is 500-1500 ℃, for example 800-1200 ℃;

preferably, the heat treatment time is 1 to 5 hours, for example 3 to 5 hours.

In one embodiment, the method of any of the present invention, step iii), has one or more of the following features:

preferably, the acid used for acid cleaning comprises hydrofluoric acid, and the concentration of the hydrofluoric acid is preferably 0.1-1 mol/L, and is further preferably 0.3-0.8 mol/L;

preferably, the pickling time is more than 0.1 hour, preferably 0.3-0.7 hour;

preferably, the acid wash further comprises one or more of filtration, washing and drying.

In a further aspect, the invention provides a composition comprising an electrically conductive component and a porous material according to any of the invention;

preferably, the conductive component is carbon and/or a conductive polymer;

preferably, the carbon is selected from graphite, hard carbon, soft carbon, carbon black, activated carbon, C₆₀One or more of graphene, graphene oxide or carbon nanotubes;

preferably, the composition is the product of ball milling mixing the porous material of any of the present invention and the electrically conductive component.

In one embodiment, the composition of any of the present invention has one or more of the following features:

preferably, the specific surface area of the composition is 2-30 m²G, e.g. 5 to 30m²A further example is 10 to 30m²A further example is 15 to 30m²A further example is 20 to 30m²/g；

Preferably, in the composition, the mass ratio of the M element to the carbon element is 1: 0.01-10, such as 1: 0.1-0.2;

preferably, the composition is used as a lithium ion battery negative electrode material, and the specific discharge capacity after the lithium ion battery negative electrode material is cycled for 1000 weeks is 1000-1500 mAh/g, such as 1100-1400 mAh/g, and further such as 1200-1300 mAh/g under the current density of 1C.

In a further aspect, the present invention provides a process for the preparation of a composition according to any one of the present invention, comprising the steps of:

the porous material of any of the present invention is mixed with the conductive component and ball milled.

In one embodiment, a method of making a composition of any of the present invention has one or more of the following features:

preferably, the rotation speed of the ball milling is 300-800 r/min, such as 500 r/min;

preferably, the time of ball milling is 1 to 3 hours, such as 2 hours;

preferably, the grinding ball has a diameter of 3 to 8mm, for example 5 mm;

preferably, the material of the grinding ball is ZrO₂；

Preferably, the mass ratio of the raw material Si or the raw material Ge to the grinding balls is 1: 15-25, such as 1: 20.

In one embodiment, the use of a porous material according to any of the present invention, or a composition according to any of the present invention, as an electrode material;

preferably, the electrode material is a lithium ion battery negative electrode material.

In a further aspect, the present invention provides an electrode material comprising a porous material according to any one of the present invention, or a composition according to any one of the present invention;

In a further aspect, the invention provides a battery comprising a porous material according to any of the invention or a composition according to any of the invention;

preferably, the negative electrode material of the battery comprises the porous material of any one of the present invention or the composition of any one of the present invention;

preferably, the battery is a lithium ion battery.

In one embodiment, the particle size is the average particle size as measured by a laser particle size diffractometer, such as the average particle size as measured by a laser particle size diffractometer D [2,0 ].

The invention has the advantages of

One or more embodiments of the invention may have one or more of the following advantages:

1) the particle size of the porous material is small;

2) the porosity of the porous material is high;

3) the specific surface area of the porous material is large;

4) the pore volume of the porous material is large;

5) the porous material or the composition has higher specific capacity when being used as the lithium ion battery cathode material;

6) the porous material or the composition has good cycle performance when being used as a lithium ion battery cathode material;

7) the preparation method of the porous material has simple process;

8) the preparation method of the porous material has low cost.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:

FIG. 1 is a Raman spectrum of intermediates A4 and A';

FIG. 2 is an X-ray diffraction (XRD) profile of intermediate products A4 and A';

FIG. 3 is a Transmission Electron Microscope (TEM) photograph of intermediate A4;

FIG. 4 is a Transmission Electron Microscope (TEM) photograph of intermediate product B4;

FIG. 5 is a Transmission Electron Microscope (TEM) photograph of the porous material D4;

FIG. 6 shows nitrogen adsorption-desorption curves of porous materials D3-D5 and product D';

FIG. 7 is a graph showing the distribution of pore sizes of the porous materials D3-D5 and the product D';

FIG. 8 is a Transmission Electron Microscope (TEM) photograph of porous materials D4-D5;

fig. 9 is a cycle performance curve of the lithium ion battery of example 3.

Detailed Description

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

The instruments and materials used in the examples are shown in table 1 below:

TABLE 1

Examples 1 to 6

i) The raw material Si simple substance was mixed with water (deionized water) in a molar ratio shown in table 1, followed by ball milling. The raw material Si simple substance is Si block with the purity of about 99.9 percent and the volume of about 5mm³。

The ball milling atmosphere is argon, the rotating speed of the ball mill is 1000r/min, the diameter of a grinding ball used by the ball mill is 3mm, and the material is ZrO₂The material-ball ratio (the total mass of the raw material silicon simple substance and water: the mass of the grinding balls) is 1:20, and the ball milling time is 3 hours, so that an intermediate product A is obtained, and the number of the intermediate product A is A1-A6.

ii) heat-treating the intermediate products A1-A6 of step i) in a tube furnace. The heat treatment temperature was 1000 ℃ and the time was 4 hours. The heat treatment atmosphere was an argon-hydrogen mixture (hydrogen gas 2 vol%) at a flow rate of 100 sccm. Intermediate products B with numbers of B1-B6 were obtained.

iii) acid washing the intermediate products B1-B6 of step ii). The acid used for the acid cleaning was 0.5M aqueous hydrofluoric acid solution, and the acid cleaning time was 0.5 hours. And filtering, washing and drying the product after acid washing to obtain the porous materials of the examples 1-6, wherein the numbers of the porous materials are D1-D6.

Comparative example 1

i) Referring to example 1, the raw material Si was ball-milled in a ball mill alone without adding water. The raw material Si is Si block with purity of about 99.9% and volume of about 5mm³。

The ball milling atmosphere was argon. The rotation speed of the ball mill is 1000 r/min. The diameter of a grinding ball used by the ball mill is 3 mm. Ball milling time 3 hours, intermediate a'.

ii) heat-treating the intermediate product A' of step i) in a tube furnace. The heat treatment temperature was 1000 ℃ and the time was 4 hours. The heat treatment atmosphere was an argon-hydrogen mixture (hydrogen gas was 2 vol%) at a flow rate of 100sccm, to obtain an intermediate product B'.

iii) acid washing of the intermediate product B' of step ii). The acid used for pickling was hydrofluoric acid, which was 0.5M aqueous hydrofluoric acid. The acid washing time was 0.5 hour. After the acid wash the product was filtered, washed and dried to obtain the product of comparative example 1, code D'.

TABLE 1

Testing and characterization

(1) Fig. 1 shows raman spectra of intermediate products a4 and a'. Curves a4 and a 'of fig. 1 represent the raman spectral lines of intermediates a4 and a', respectively. Curve A4 shows the wavelength of 475-500 cm^-1The characteristic peak indicates that the intermediate product A4 is an oxide of Si, i.e., SiO_xA material. Curve A' shows the wavelength of 500-525 cm^-1The characteristic peak is shown, which indicates that the intermediate product A' is the simple substance Si.

(2) Figure 2 shows the X-ray diffraction (XRD) patterns of intermediate products a4 and a'. Curves a4 and a 'of fig. 2 are XRD diffraction curves of intermediate products a4 and a', respectively. The curve A4 has an amorphous specific steamed bun peak at the position of the 2 theta angle of 10-40 degrees, which indicates that A4 is an amorphous material. Curve A 'shows the diffraction peaks of elemental Si in the crystal planes of [111], [220], [311], [400] and [331], which indicates that the intermediate product A' is elemental silicon.

(3) Fig. 3 shows a Transmission Electron Microscope (TEM) photograph of intermediate a 4. As shown in the figure, the particle size of A4 is about 50-150 nm, and no crystal structure is observed in the figure. The inset in the upper right hand corner of fig. 3 is the electron diffraction pattern of intermediate a4, where a halo diffraction pattern can be observed, further demonstrating that intermediate a4 is an amorphous (amorphous) material.

(4) The oxygen contents of the intermediate products A1-A6 of examples 1-6 were analyzed by X-ray fluorescence spectroscopy (XRF) to calculate SiO_xThe value of x of (a); the average particle diameters (D2, 0) of the intermediate products A1-A6 and A' were also determined by a laser particle size analyzer]) The results are shown in Table 2 below.

TABLE 2

(5) Fig. 4 is a Transmission Electron Microscope (TEM) photograph of intermediate product B4 of example 4. As shown in FIG. 4, there are a plurality of lighter colored particles of about 50-150 nm in size, which are distributed with a plurality of darker colored regions. The insert in the upper right corner of the sheet of FIG. 4 is an electron diffraction pattern of dark regions, which are ring-shaped, and these dark regions are judged to be Si according to the electron diffraction pattern, so that the lighter particles in the pattern represent SiO₂. As illustrated, the intermediate product B4 contains Si and SiO₂Is represented by Si-SiO₂A material. Removal of Si-SiO by acid pickling of step iii)₂SiO in material₂After that, a porous material was obtained.

(6) FIG. 5 is a Transmission Electron Microscope (TEM) photograph of the porous material D4 of example 4, at a magnification of 40 to 50 ten thousand. As shown in fig. 5, a foam-like porous structure was observed, further demonstrating that the porous material D4 was porous.

(7) BET-Nitrogen adsorption tests were performed on the porous materials D1 to D6 of examples 1 to 6, and the apparent densities (g/cm)³) Actual porosity, specific surface area (m)²(iv)/g); the average particle size (nm) of the porous materials D1 to D6, and the product D' of comparative example 1, were also tested using a laser particle size tester.

Apparent density is sample mass/total sample volume;

actual porosity ═ pore volume/total sample volume;

in addition, the theoretical porosities of the porous materials D1-D6 were calculated, and the theoretical porosities were intermediate products B (Si-SiO)₂Material) SiO₂Volume to total volume ratio, i.e.

Theoretical porosity ═ Si — SiO₂SiO in material₂Volume of (A)/Si-SiO₂Total volume of material.

The results of the above tests are shown in table 3 below.

TABLE 3

As can be seen from Table 3, the apparent densities of the porous materials D1-D6 were 0.71-2.185 g/cm³(ii) a The theoretical porosity is 0.25-0.98; the actual porosity is 0.21-0.70; the average particle size is 24 to 156 nm. The average particle size of the product D' was 177 nm.

FIG. 6 shows nitrogen adsorption-desorption curves of the porous materials D3-D5 and the product D' of comparative example 1.

FIG. 7 shows pore size distribution plots of porous materials D3-D5 and product D', with pore size (nm) on the abscissa and dV/dlogD (cm) on the ordinate³In terms of/g). Curves D3, D4, D5 and D 'of fig. 7 correspond to pore size distribution curves of the porous materials D3-D5 and the product D', respectively. The aperture range corresponding to the peak value of the aperture distribution curve of D4 is 5-15 nm, the aperture range corresponding to the peak value of the aperture distribution curve of D3 is 15-25 nm, and the aperture range corresponding to the peak value of the aperture distribution curve of D5 is 25-35 nm. The pore size distribution curve of D' has substantially no peak.

Fig. 8 (a) and (b) are Transmission Electron Microscope (TEM) photographs of porous materials D4 and D5, respectively, and as shown in fig. 8 (a), D4 has a very clear porous structure. As shown in FIG. 8 (b), the minimum feature size of D5 is 5 to 10nm (the minimum feature size is the size of the smallest unit of silicon structure in the porous material).

Examples 7 to 12

The porous materials D1 to D6 of example 1 were mixed with graphene, respectively, and then ball-milled. The mass ratio of the porous material to the graphene is 10:1, the ball milling atmosphere is argon, the ball milling speed is 500r/min, the diameter of a grinding ball is 5mm, the material ball ratio is 1:20, and the ball milling time is 2 hours. Compositions of examples 7 to 12 were obtained, Nos. E1 to E6.

The BET method was used to measure the specific surface areas of compositions E1 to E6, as shown in Table 4 below.

TABLE 4

Comparative example 2

Metallic silicon of 98% purity was used as a raw material, which was first impacted into millimeter-sized particles (. about.10 mm), and then ball-milled for 5 hours at 500r/min using a ball mill. The product was taken up in 20mM AgNO₃And 5M HF solution, ethanol was used as a solvent, and the reaction was carried out at 50 ℃ for 2 hours. Finally, the sample was pickled with a high-concentration nitric acid for 1 hour to remove Ag on the surface, to obtain a porous silicon powder, numbered D ".

Adding the prepared porous silicon powder D 'into a graphene oxide solution (Si: GO is 1:1 in mass ratio), performing ultrasonic treatment for 1 hour, performing suction filtration to the surface of filter paper with a millimeter pore diameter, drying in a vacuum drying oven at 110 ℃, then cutting a sample into strips, annealing in a tube furnace in an argon-hydrogen mixed gas (hydrogen content is 2 vol%) atmosphere at 100 ℃ for 1 hour to obtain a composition of porous silicon and graphene, and numbering E'.

Example 3 (Battery test)

The composition E4 of example 10 and the composition E ″ of comparative example 2 were assembled as negative electrode active materials, respectivelyForming a 2032 type button lithium ion battery. The electrode material slurry is formed by mixing an active material, a conductive agent (acetylene black) and a binder (cmc) according to a mass ratio of 80:10: 10. The electrolyte LB303 contains 1mol/L LiPF₆A mixed solution of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC), wherein the mass ratio of EC to DMC to DEC is 1:1: 1.

And testing the cycle charge and discharge performance of the lithium ion battery by using a battery testing system. The charging and discharging current is 1C, the upper and lower critical voltages are 0.01-1.5V, and the cycle number is 1000. The measured cell performance data are shown in table 5 below.

FIG. 9 is a graph of the Discharge specific Capacity (Discharge Capacity) and the coulombic efficiency (coulombic efficiency) of the lithium ion battery as a function of the cycle number, wherein the curves E4-a and E4-b are respectively the Discharge specific Capacity and the coulombic efficiency of the lithium ion battery containing the composition E4 as a function of the cycle number. Curve E "is the plot of specific discharge capacity versus cycle number for the lithium ion battery containing composition E". As shown in the figure, the lithium ion battery containing the composition E4 shows higher specific discharge capacity and capacity retention rate. Table 5 shows the specific discharge capacity and cycling efficiency of a lithium ion battery containing the active material E4 as a function of cycle number.

TABLE 5

Number of cycles	50	200	400	600	800	1000
							Specific discharge capacity mAh/g	1440	1421	1362	1320	1282	1250
Capacity retention ratio%	80.4	79.4	76.1	73.7	71.6	69.8

As shown in fig. 9 and table 5, after the lithium ion battery with the active material E4 is cycled at 1C for 1000 weeks, the specific capacity is 1250mAh/g, the coulombic efficiency is greater than 99%, and the capacity retention rate is 69.8%. This shows that the composition E4 has higher specific capacity and better cycle performance as the negative electrode material of the lithium ion battery.

Considering that the mass ratio of the porous material to the graphene in composition E4 is 10:1, i.e., the porous material is the main component in composition E4. It is inferred that the combination of the porous material and various conductive substances (such as carbon and conductive polymers) has higher specific capacity and better cycle performance as the negative electrode of the lithium ion battery.

Considering that Si and Ge have similar properties, it is inferred that, by replacing the Si element in the above embodiments with Ge element, porous Ge with high specific surface area and high pore volume can be obtained, and the same or similar technical effects can be obtained.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention and not to limit it; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art will understand that: modifications to the specific embodiments of the invention or equivalent substitutions for parts of the technical features may be made; without departing from the spirit of the present invention, it is intended to cover all aspects of the invention as defined by the appended claims.

Claims

1. A method of making a porous material, comprising:

m is Si and/or Ge, and the oxide of M is MO_x，x＝0.5～1.6；

ii) heat treating the oxide of M;

iii) pickling the heat treated oxide of M with an acid comprising hydrofluoric acid;

the porous material contains a simple substance M, wherein M is Si and/or Ge;

the particle size of the porous material is 20-150 nm, the porosity is 0.2-0.8, and the specific surface area is 15-300 m²/g；

The oxidant comprises water.

2. The method of claim 1, step i) having one or more of the following features:

-the purity of the simple substance M of the raw material is greater than 99.5%;

the shape of the simple substance M is spherical, spheroidal, blocky, rod-like or irregular;

the volume of the raw material M simple substance is 1-10 mm³；

The molar ratio of the raw material M simple substance to the oxidant is 1: 0.8-1.8;

ball milling is carried out in a vacuum or non-oxidizing atmosphere.

3. The method of claim 1, step i) having one or more of the following features:

-ball milling is carried out under an inert gas atmosphere;

the rotating speed of the ball milling is 500-2000 r/min;

the diameter of a grinding ball used for ball milling is 1-5 mm;

the material of the grinding balls used for ball milling is ZrO₂；

-the mass ratio of ball-milled balls is 1: 20;

the time of ball milling is 1 to 5 hours.

4. The method of claim 1, wherein the ball milling is performed under an argon atmosphere.

5. The method of claim 1, step i) having one or more of the following features:

the molar ratio of the raw material M simple substance to the oxidant is 1: 1.0-1.5;

-the purity of the simple substance M of the raw material is greater than 99.9%;

the volume of the M simple substance as the raw material is 3-7 mm³；

The rotating speed of the ball milling is 800-1200 r/min;

the diameter of a grinding ball used for ball milling is 3-4 mm;

the time of ball milling is 3 to 4 hours.

6. The method of claim 1, step i) having one or more of the following features:

-the oxide of M is MO_x，x＝0.5～1.4；

-the oxide of M is an amorphous material;

-the particle size of the oxide of M is 50 to 200 nm;

-no crystal structure is evident in a TEM photograph of the oxide of M;

-in the XRD profile of the oxide of M, there is a steamed bun peak at a 2 theta angle in the range of 10-40 °;

-said oxide of M having a Raman spectrum at a wavelength of 475 to 500cm^-1Has a peak at the position of (a).

7. The method of claim 1, step i) having one or more of the following features:

-the oxide of M is MO_x，x＝1.2～1.4；

-the particle size of the oxide of M is 50 to 150 nm.

8. The method of claim 1, step ii) having one or more of the following features:

-the heat treatment is carried out in a vacuum or non-oxidizing atmosphere;

-the temperature of the heat treatment is 500 to 1500 ℃;

the heat treatment time is 1 to 5 hours.

9. The method of claim 8, step ii) having one or more of the following features:

-the non-oxidizing atmosphere is an inert gas atmosphere;

-the temperature of the heat treatment is 800 to 1200 ℃;

the heat treatment time is 3 to 5 hours.

10. The method of claim 8, wherein the non-oxidizing atmosphere is a mixed gas atmosphere of argon and hydrogen.

11. The method according to claim 10, wherein the content of hydrogen in the non-oxidizing atmosphere is 1 to 3 vol%.

12. The method of claim 1, step iii) having one or more of the following features:

the acid used for pickling is hydrofluoric acid, and the concentration of the hydrofluoric acid is 0.1-1 mol/L;

the time for pickling is 0.1 hour or more.

13. The method of claim 12, step iii) having one or more of the following features:

the acid used for pickling is hydrofluoric acid, and the concentration of the hydrofluoric acid is 0.3-0.8 mol/L;

the pickling time is 0.3 to 0.7 hour.

14. The method of claim 1, further comprising one or more of filtering, washing, and drying after the pickling.

15. A porous material obtained by the process of any one of claims 1 to 14.

16. A porous material according to claim 1, having one or more of the following characteristics,

-the particle size of the porous material is 50-150 nm;

-the porosity of the porous material is between 0.3 and 0.8;

the specific surface area of the porous material is 40-300 m²/g；

The apparent density of the porous material is 0.5 to 2.2g/cm³；

The pore size distribution curve of the porous material has a characteristic peak within the range of 10-50 nm;

-only one characteristic peak on the pore size distribution curve of the porous material;

-a 40-50 ten thousand TEM picture of the porous material, a porous structure can be observed;

-the porous material contains more than 50% by weight of simple substance M;

m is Si.

17. A porous material according to claim 1, having one or more of the following characteristics,

-the particle size of the porous material is 50 to 130 nm;

-the porosity of the porous material is between 0.4 and 0.8;

the specific surface area of the porous material is 100 to 300m²/g；

The apparent density of the porous material is 0.5 to 2g/cm³；

The pore size distribution curve of the porous material has a characteristic peak within the range of 5-15 nm;

in a 40-50 ten thousand-fold TEM picture of the porous material, a foam-like porous structure can be observed;

-the porous material contains 90% by weight or more of simple substance M.

18. A porous material according to claim 1, having one or more of the following characteristics,

-the particle size of the porous material is 50-110 nm;

-the porosity of the porous material is between 0.5 and 0.8;

the specific surface area of the porous material is 150-300 m²/g；

The apparent density of the porous material is 0.5 to 1.5g/cm³；

The pore size distribution curve of the porous material has a characteristic peak within the range of 15-25 nm;

-the porous material contains more than 99 wt% of the simple substance M.

19. A porous material according to claim 1, having one or more of the following characteristics,

-the particle size of the porous material is 60 to 100 nm;

-the porosity of the porous material is between 0.6 and 0.7;

the specific surface area of the porous material is 200 to 300m²/g；

The apparent density of the porous material is 0.6 to 1.1g/cm³；

The pore size distribution curve of the porous material has a characteristic peak in the range of 25-35 nm.

20. A porous material according to claim 1, having one or more of the following characteristics,

-the particle size of the porous material is 70-90 nm;

-the porosity of the porous material is between 0.6 and 0.7;

the specific surface area of the porous material is 230-300 m²/g；

The apparent density of the porous material is 0.6-0.8 g/cm³。

21. A porous material according to claim 1, which has the following characteristics,

the specific surface area of the porous material is 230 to 270m²/g。

22. A porous material according to claim 1, which has the following characteristics,

the specific surface area of the porous material is 240-260 m²/g。

23. A composition comprising an electrically conductive component and a porous material as claimed in any one of claims 15 to 22.

24. The composition of claim 23, characterized by any one of the following:

-the conductive component is carbon and/or a conductive polymer;

-said composition is the product of ball milling mixing of a porous material according to any one of claims 15 to 22 and an electrically conductive component.

25. The composition of claim 24, said carbon being selected from the group consisting of graphite, hard carbon, soft carbon, activated carbon, C₆₀One or more of graphene, graphene oxide or carbon nanotubes.

26. The composition of claim 24, said carbon being selected from the group consisting of graphite, carbon black, soft carbon, activated carbon, C₆₀One or more of graphene, graphene oxide or carbon nanotubes.

27. A composition according to claim 23, which has one or more of the following characteristics:

-the specific surface area of the composition is 2 to 30m²/g；

The conductive component is carbon and/or a conductive polymer, and the mass ratio of the M element to the carbon element in the composition is 1: 0.01-10;

the composition is used as a lithium ion battery negative electrode material, and the specific discharge capacity after 1000 cycles is 1000-1500 mAh/g under the current density of 1C.

28. A composition according to claim 23, which has one or more of the following characteristics:

-the specific surface area of the composition is 2 to 30m²/g；

The conductive component is carbon and/or a conductive polymer, and the mass ratio of the M element to the carbon element in the composition is 1: 0.1-0.2;

29. A composition according to claim 23, which has one or more of the following characteristics:

-the specific surface area of the composition is 5 to 30m²/g；

The composition is used as a lithium ion battery negative electrode material, and the specific discharge capacity after 1000 cycles is 1100-1400 mAh/g under the current density of 1C.

30. A composition according to claim 23, which has one or more of the following characteristics:

-the specific surface area of the composition is 10 to 30m²/g；

31. A composition according to claim 23, which has one or more of the following characteristics:

-the specific surface area of the composition is 15 to 30m²/g；

32. A composition according to claim 23, which has one or more of the following characteristics:

-the specific surface area of the composition is 20 to 30m²/g；

The composition is used as a lithium ion battery negative electrode material, and the specific discharge capacity after 1000 cycles is 1200-1300 mAh/g under the current density of 1C.

33. A method of preparing a composition according to any one of claims 23 to 32, comprising the steps of:

mixing the porous material of any one of claims 15 to 22 with the electrically conductive component and ball milling.

34. The method of claim 33, having one or more of the following features:

-ball milling is carried out in a vacuum or non-oxidizing atmosphere;

the rotating speed of the ball milling is 300-800 r/min;

the ball milling time is 1 to 3 hours;

-the grinding ball has a diameter of 3-8 mm;

the material of the grinding balls is ZrO₂；

The mass ratio of the raw material Si or the raw material Ge to the grinding ball is 1: 15-25.

35. The method of claim 34, the non-oxidizing atmosphere being an inert gas atmosphere.

36. Use of a porous material as claimed in any one of claims 15 to 22 or a composition as claimed in any one of claims 23 to 29 as an electrode material.

37. Use according to claim 36, wherein the electrode material is a lithium ion battery negative electrode material.

38. An electrode material comprising the porous material of any one of claims 15 to 22, or the composition of any one of claims 23 to 32.

39. The electrode material of claim 38, which is a lithium ion battery negative electrode material.

40. A battery comprising a porous material as claimed in any one of claims 15 to 22 or a composition as claimed in any one of claims 23 to 32.

41. A battery according to claim 40, the negative electrode material of the battery comprising a porous material according to any one of claims 15 to 22 or a composition according to any one of claims 23 to 32.

42. The battery of claim 40, which is a lithium ion battery.