CN105024055A - Lithium-ion battery porous nanometer silicon-carbon composite negative electrode material and preparation method thereof - Google Patents

Abstract

The invention provides a lithium-ion battery porous nano-silicon-carbon composite negative electrode material and a preparation method thereof. Specifically, the method comprises the steps of: (1) providing a silicon-active metal alloy block; (2) using the alloy The block is reacted with a liquid phase pore-forming agent to remove the active metal in the alloy block to obtain a porous silicon nanomaterial; (3) cleaning the porous silicon nanoparticle with hydrofluoric acid to remove silicon oxide to obtain a hydrogenated Porous silicon nanomaterials cleaned with hydrofluoric acid; (4) calcining the porous silicon nanomaterials cleaned with hydrofluoric acid in the presence of a carbon source in an inert gas to obtain porous silicon-carbon composite electrode materials. The porous silicon material prepared by the method has a nano-porous structure, and the silicon nano-particles are small and uniform in size, can be used as a negative electrode material of a lithium ion battery, and shows high discharge specific capacity and charge-discharge cycle stability.

Description

A kind of lithium-ion battery porous nano-silicon-carbon composite negative electrode material and preparation method thereof

technical field

The invention relates to the field of lithium-ion battery negative electrode materials, in particular, the invention relates to a porous nano-silicon material with high specific capacity and good cycle performance that can be used as a lithium-ion battery negative electrode material, and a preparation method thereof.

Background technique

At present, graphite and modified graphite are widely used in commercial lithium-ion battery materials, but their theoretical capacity is only 372mAh/g, and their volume specific capacity is 883mAh/cm ³ , which cannot meet the needs of the current development of high-energy power batteries. In recent years, the development of new lithium-ion electrode materials has attracted widespread attention from scientists all over the world, especially the development of negative electrode materials with high energy density, good cycle life and simple preparation process has become one of the hot spots in the research of lithium-ion battery electrodes. Anode materials such as silicon, germanium, and tin are expected to replace carbon-based materials as anode materials for lithium-ion batteries due to their higher theoretical capacities (ca.4200, ca.1600, and ca.990mAh/g, respectively). However, looking at the problems of silicon, germanium, tin and other negative electrode materials, they are mainly reflected in the following aspects: (1) silicon, germanium, tin and other negative electrode materials have large volume changes during the electrochemical cycle, and the theoretical ratio The silicon anode material with the highest capacity has a volume expansion of up to 300%, which causes the rapid attenuation and degradation of the electrochemical cycle performance of the lithium-ion battery itself, seriously affecting the service life of the lithium-ion battery; Due to the instability of the structure, the intercalation and extraction of Li ⁺ will lead to the cracking, pulverization, and shedding of the active electrode material, which will form a new electrode surface layer and consume lithium, resulting in a large irreversible capacity loss. Therefore, the service life of lithium-ion batteries based on conventional micron-scale silicon-based negative electrode materials has become a bottleneck restricting its technological development, and has also hindered the commercialization of silicon-based negative electrode materials; (3) due to the poor conductivity of silicon itself, It affects the progress of the high-rate charge and discharge process of the lithium-ion battery.

Compared with germanium and tin, the theoretical capacity of silicon is higher, reaching 4212mAh/g. At the same time, due to the relatively low production cost of negative silicon, it has become the top priority in the research of lithium-ion battery negative electrodes. Therefore, how to effectively suppress the damage of the internal structure of the lithium-ion battery caused by the volume change of the silicon-based negative electrode during battery charging and discharging and how to effectively improve the conductivity of the silicon-based negative electrode material, so as to improve the electrochemical cycle performance of the silicon-based lithium-ion battery problems that need to be solved in this field.

To sum up, there is still a lack of silicon nanomaterials in the art that have good electrical conductivity and can be used as negative electrode materials for lithium-ion batteries to prepare batteries with high discharge specific capacity and charge-discharge cycle stability.

Contents of the invention

The invention provides a silicon nanometer material with good electrical conductivity, which can be used as negative electrode material of lithium ion battery to prepare battery with high discharge specific capacity and charge and discharge cycle stability.

A first aspect of the present invention provides a method for preparing a porous silicon-carbon composite material, the method comprising the steps of:

(1) providing a silicon-active metal alloy block;

(2) reacting the alloy block with a liquid phase pore-forming agent to remove the active metal in the alloy block to obtain a porous silicon nanomaterial;

(3) cleaning the porous silicon nanomaterial with hydrofluoric acid to remove silicon oxide, and obtaining a porous silicon nanomaterial cleaned with hydrofluoric acid;

(4) Calcining the porous silicon nanomaterial cleaned with hydrofluoric acid in the presence of a carbon source in an inert gas to obtain a porous silicon-carbon composite material.

In another preferred example, in the alloy block, the mass percentage of silicon is 1-99%, preferably 10-80%.

In another preferred example, the mass ratio of the hydrofluoric acid solution is 1%-30%.

In another preferred example, in the step (4), the temperature range of the calcination is 300-1900°C, preferably 400-1700°C, more preferably 600-1500°C.

In another preferred example, in the step (4), during the calcination process, the heating rate is 1-10° C./min.

In another preferred example, in the step (4), the reaction time is 0.1-24 hours, preferably 0.2-12 hours, more preferably 0.2-5 hours.

In another preferred example, the porous silicon nanomaterials cleaned with hydrofluoric acid are porous silicon nanoparticles with uniform composition and appearance; preferably, the porous silicon nanomaterials cleaned with hydrofluoric acid The silicon oxide content in the material is ≤2%, preferably ≤1%, more preferably ≤0.5%.

In another preferred example, in the step (4), it also includes: post-processing the porous silicon-carbon composite electrode material; preferably, the post-processing includes: washing, filtering, drying dry, or a combination thereof.

In another preferred embodiment, the "removal" refers to the removal of at least 95%, preferably at least 98%, and more preferably at least 99% of the active metals in the alloy bulk.

In another preferred embodiment, the active metal is selected from the group consisting of aluminum, iron, magnesium, zinc, calcium, lead, or combinations thereof.

In another preferred example, the alloy bulk is an aluminum-silicon alloy bulk.

In another preferred example, the size of the aluminum-silicon alloy block is 0.1mm-60mm.

In another preferred embodiment, the liquid-phase pore-forming agent is a solution capable of reacting with active metals but not reacting with elemental silicon; preferably, the liquid-phase pore-forming agent is an inorganic acid; more preferably, The liquid-phase pore-forming agent is a strong inorganic acid.

In another preferred embodiment, the liquid phase pore former is selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, or combinations thereof.

In another preferred example, the liquid-phase pore-forming agent is an inorganic acid solution with a solution concentration of 0.5%-35% by mass.

In another preferred embodiment, the carbon source is a carbon-containing gas, preferably selected from the group consisting of methane, ethane, propane, ethylene, propylene, acetylene, propyne, or combinations thereof.

In another preferred example, the carbon source is one or a combination of at least two of methane, ethane, propane, ethylene, propylene, acetylene, and propyne.

In another preferred embodiment, the inert gas is selected from the group consisting of nitrogen, helium, argon, neon, or combinations thereof.

In another preferred example, the inert gas is one or a combination of at least two of nitrogen, helium, argon, and neon; preferably one or at least two of nitrogen, helium, and argon combination of species.

The second aspect of the present invention provides a porous silicon-carbon composite electrode material, which is prepared by the method described in the first aspect of the present invention.

In another preferred example, the electrode material is a lithium ion battery electrode material.

In another preferred example, in the material, the mass ratio of the carbon element is 2-30wt% of the total weight of the material, preferably 3-20wt%.

In another preferred example, in the material, the impurity content (ie content of elements other than silicon and carbon) is ≤1%, preferably ≤0.5%, more preferably ≤0.1%.

In another preferred embodiment, the impurity is selected from the group consisting of Al, Ti, K, V, Mn, Ni, or combinations thereof.

In another preferred embodiment, the material further contains a conductive metal; preferably, the conductive metal is selected from the group consisting of Cu, Ag, Zn, Fe, Al, or a combination thereof.

In another preferred example, the electrode material has one or more characteristics selected from the following group:

The electrode material is nanoparticles, and the particle size of the nanoparticles is 5nm-300nm;

The specific surface area of the electrode material is 10-500cm ² /g;

In another preferred example, the discharge specific capacity of the negative electrode material is >900mAh/g, preferably >1000mAh/g, >1100mAh/g, and most preferably, the discharge specific capacity of the negative electrode material is 1200-1600mAh/g.

In another preferred embodiment, the Coulombic efficiency (after the second charge-discharge cycle) of the negative electrode material is ≥92%, preferably ≥95%, more preferably ≥97%.

The third aspect of the present invention provides a negative electrode of a battery, the negative electrode of the battery is prepared with the material as described in the second aspect of the present invention, or the negative electrode of the battery contains the material as described in the second aspect of the present invention Material.

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

In another preferred example, the conductive agent is selected from the following group: acetylene black, SUPER P-Li, carbon fiber, coke, graphite, mesocarbon microspheres, hard carbon, or a combination thereof; preferably selected from carbon nano tubes, carbon nanowires, carbon nanospheres, graphene, or combinations thereof.

In another preferred example, the adhesive is selected from the group consisting of polyvinylidene fluoride (PVDF), lithium polyacrylate (Li-PAA), styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC ), or a combination thereof.

In another preferred example, in the negative electrode material, the content of the silicon-carbon composite electrode material is 60-90wt%;

The content of the conductive agent is 5-15wt%;

The content of the binder is 5-25wt%, based on the total weight of the negative electrode material.

In another preferred example, in the negative electrode material, the mass ratio of the silicon-carbon composite electrode material, conductive agent, and binder is (80±10):(10±2):(10± 2).

The fourth aspect of the present invention provides a product, the product is prepared with the material as described in the second aspect of the present invention, or the product contains the material as described in the second aspect of the present invention, or The product has the battery negative electrode as described in the third aspect of the present invention.

In another preferred example, the battery is a lithium ion battery.

In another preferred example, the product is a battery, and the battery includes a positive electrode material, a negative electrode material, an electrolyte and a separator, and the negative electrode material includes the material as described in the second aspect of the present invention.

In another preferred example, the battery is a lithium battery.

In another preferred example, the battery further has a casing; and the casing is selected from the group consisting of metal materials, composite materials, or combinations thereof.

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

In another preferred example, the separator is selected from the group consisting of ceramic porous membranes, porous membranes made of synthetic resin, and glass fiber membranes.

In another 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;

Preferably, the positive electrode active material further includes components selected from the group consisting of metal oxides, metal sulfides, transition metal oxides, transition metal sulfides, or combinations thereof of inactive metals.

In another preferred example, the active metal is lithium.

In another preferred example, when the battery is a lithium battery, the positive electrode active 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; LiMn _0.5 Ni _0.5 O ₂ ),

LiMn _0.33 Co _0.33 Ni _0.33 O ₂ ,

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

LiNi _x Co _y Me _z O ₂ , where 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.

In another preferred example, the transition metal oxide is a lithium ion transition metal oxide.

In another preferred embodiment, the electrolyte solution includes one or more electrolyte salts; and the electrolyte solution includes one or more organic solvents.

In another preferred example, when the battery is a lithium battery, the electrolyte salt is a lithium salt.

In another preferred example, the organic solvent includes at least one cyclic carbonate derivative substituted by one or more halogen atoms; preferably, the organic solvent includes 4-fluoro-1, 3-dioxolan-2-one.

In another preferred example, during the charging process, the positive ions of the electrolyte salt can pass through the electrolyte, from the positive electrode material to the negative electrode material.

In another preferred example, during the discharge process, the positive ions of the electrolyte salt can pass through the electrolyte, from the negative electrode material to the positive electrode material.

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 a scanning electron microscope picture of the porous silicon-carbon composite negative electrode material of Example 1.

FIG. 2 is a physical diagram of the porous silicon-carbon composite negative electrode material in Example 1. FIG.

3 is an X-ray diffraction pattern of the porous silicon-carbon composite negative electrode material of Example 1.

FIG. 4 is a charge-discharge curve diagram of the porous silicon-carbon composite negative electrode material in Example 1. FIG.

5 is the charge-discharge curve and Coulombic efficiency diagram of the porous silicon-carbon composite negative electrode material of Example 2 (▲ is the Coulombic efficiency curve).

Detailed ways

The present inventor has prepared a porous silicon-carbon composite electrode material after long-term and in-depth research. The battery prepared by using the material has higher theoretical specific capacity and better cycle stability of the battery, and is particularly suitable as a negative electrode active material of a lithium battery. Based on the above findings, the inventors have accomplished the present invention.

the term

As used herein, the terms "carbon coating" or "carbon composite" are used interchangeably to refer to the process of calcining a pore-formed porous silicon material in the presence of a carbon source to form a silicon-carbon composite material.

Porous Nano-Silicon-Carbon Composite Material and Its Preparation

The invention provides a method for preparing a porous silicon-carbon composite material. The method uses an aluminum-active metal alloy block as a raw material, reacts with a liquid-phase pore-forming agent to form porous silicon particles; After surface or excess silicon oxide, carbon coating is performed to obtain a porous silicon-carbon composite material. The material obtained by the method of the invention is used as the negative electrode of the lithium ion battery, and has high discharge specific capacity and charge and discharge stability.

Specifically, the method includes the steps of:

(1) providing a silicon-active metal alloy block;

(2) reacting the alloy block with a liquid phase pore-forming agent to remove the active metal in the alloy block to obtain a porous silicon nanomaterial;

(3) cleaning the porous silicon nanomaterial with hydrofluoric acid to remove silicon oxide, and obtaining a porous silicon nanomaterial cleaned with hydrofluoric acid;

(4) Calcining the porous silicon nanomaterial cleaned with hydrofluoric acid in the presence of a carbon source in an inert gas to obtain a porous silicon-carbon composite material.

In another preferred example, in the alloy block, the mass percentage of silicon is 1-99%, preferably 10-80%.

The concentration of the hydrofluoric acid solution is not particularly limited, preferably, the hydrofluoric acid solution is a dilute solution, more preferably, the mass ratio of the hydrofluoric acid solution is 1%-30%.

In another preferred example, in the carbon coating step (ie step (4)), the temperature range of the calcination is 300-1900°C, preferably 400-1700°C, more preferably 600°C ~1500°C.

During the carbon coating process, the calcination temperature needs to be raised slowly; in another preferred example, in the step (4), during the calcination process, the temperature increase rate is 1-10°C /min rate of heating.

In another preferred example, in the step (4), the reaction time is 0.1-24 hours, preferably 0.2-12 hours, more preferably 0.2-5 hours.

In another preferred example, the porous silicon nanomaterials cleaned with hydrofluoric acid are porous silicon nanoparticles with uniform composition and morphology.

In the carbon coating step (ie, step (4)), it is preferred to further include: post-processing the porous silicon-carbon composite electrode material; preferably, the post-processing includes: washing, Filter, dry, or a combination thereof.

The active metal is not particularly limited, and any metal that can react with a solution that does not react with silicon (ie, a liquid phase pore former) can be selected. In a preferred embodiment of the present invention, the active metal is selected from the group consisting of aluminum, iron, magnesium, zinc, calcium, lead, or combinations thereof.

In another preferred example, the alloy bulk is an aluminum-silicon alloy bulk. The size of the aluminum-silicon alloy block is not particularly limited. Preferably, the diameter of the silicon-aluminum alloy block is 0.1 mm to 60 mm.

The liquid-phase pore-forming agent can be any solution that can react with active metals but not react with elemental silicon; preferably, the liquid-phase pore-forming agent is an inorganic acid; more preferably, the The liquid phase pore former is a strong inorganic acid.

In another preferred embodiment, the liquid phase pore former is selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, or combinations thereof.

In another preferred example, the liquid-phase pore-forming agent is an inorganic acid solution with a solution concentration of 0.5%-35% by mass.

The carbon source may be carbon-containing gas, such as gaseous hydrocarbons. Preferably, the carbon source is selected from the group consisting of methane, ethane, propane, ethylene, propylene, acetylene, propyne, or combinations thereof. In another preferred example, the carbon source is one or a combination of at least two of methane, ethane, propane, ethylene, propylene, acetylene, and propyne.

The inert gas may be any gas that does not react with carbon source or silicon, such as (but not limited to) a gas selected from the group consisting of nitrogen, helium, argon, neon, or combinations thereof.

In another preferred example, the inert gas is one or a combination of at least two of nitrogen, helium, argon, and neon; preferably one or at least two of nitrogen, helium, and argon combination of species.

This porous silicon-carbon composite electrode material can well alleviate the problem of volume expansion during the lithium intercalation process of silicon negative electrode materials, and improve the cycle of negative electrode materials for silicon-based lithium-ion batteries while maintaining a high battery capacity. Stability can meet the requirements of high-performance lithium-ion battery anode materials.

battery anode material

The silicon-carbon composite electrode material of the invention can be used as negative electrode active material for preparing battery negative electrode material.

In another preferred example, the battery negative electrode material further includes a conductive agent and/or a binder. Wherein, the adhesive is preferably at least one selected from polyvinylidene fluoride (PVDF), lithium polyacrylate (Li-PAA), styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC). .

In another preferred example, the conductive agent is selected from the following group: acetylene black, SUPER P-Li, carbon fiber, coke, graphite, mesocarbon microspheres, hard carbon, or a combination thereof; preferably selected from carbon nano tubes, carbon nanowires, carbon nanospheres, graphene, or combinations thereof.

In another preferred example, in the negative electrode material, the content of the silicon/carbon composite negative electrode active material is 60-90wt%;

The content of the conductive agent is 5-15wt%;

The content of the binder is 5-25wt%, based on the total weight of the negative electrode material.

In another preferred example, in the negative electrode material, the mass ratio of the negative electrode active material, conductive agent, and binder is (80±10):(10±2):(10±2).

The negative electrode material of the present invention reaches a stable Coulombic efficiency and discharge specific capacity after multiple charge-discharge cycles, especially, after more than 2 charge-discharge cycles, Coulombic efficiency and discharge specific capacity reach the highest value (greater than the first time charge-discharge cycle). In a preferred example, after the battery is charged and discharged 2-10 times, the charge-discharge specific capacity and Coulombic efficiency reach the highest.

Batteries Containing Porous Silicon-Carbon Composite Negative Active Materials

The porous silicon-carbon composite negative electrode active material prepared by the invention can be applied to the battery field. Wherein, a preferred battery includes a positive electrode material, a negative electrode material, an electrolyte, and a separator, and the negative electrode material includes the porous silicon-carbon composite electrode material according to the present invention as the negative electrode active material. Preferably applied to lithium batteries.

The negative electrode material is composed of the above-mentioned porous silicon/carbon composite negative electrode active material, a conductive agent and a binder. The content of the porous silicon-carbon composite electrode material is 60-90wt%, the content of the conductive agent is 5-15%, and the content of the binder is 5-25wt%. In another preferred example, the ratio of porous silicon-carbon composite electrode material, conductive agent, and binder is 80:10:10.

In another preferred example, the battery further has a casing. The shell is not particularly limited, and may be made of metal materials or other composite materials.

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

The separator of the battery can be any existing battery separator in the art, such as a polytetrafluoroethylene separator, a ceramic porous membrane, a glass fiber separator, and the like.

During the charging process, the positive ions of the electrolyte salt can pass through the electrolyte, from the positive electrode material to the negative electrode material; during the discharge process, the positive ions of the electrolyte salt pass through the electrolyte, from the negative electrode material to the positive electrode material.

The electrolyte solution includes a solvent and an electrolyte salt dissolved in the solvent. Described solvent is preferably an organic solvent, including (but not limited to): Methyl Ethyl Carbonate (Methyl Ethyl Carbonate), Dimethyl Carbonate (Dimethyl Carbonate), Diethyl Carbonate (Diethyl Carbonate), Ethylene Carbonate (Ethylene Carbonate), Propylene Carbonate (Propylene Carbonate), 1,2-Dimethoxyethane, 1,3-Dioxolane, Anisole, Acetate, Propionate, Butyrate, Diethyl Ether , Acetonitrile, propionitrile. Another preferred organic solvent includes cyclic carbonate derivatives with halogen atoms, which can improve the cycle performance of the electrode. Carbonate derivatives include 4-fluoro-1,3-dioxolan-2-one and the like.

Said electrolyte salt includes positive ions, such as lithium salt can be used. Preferred lithium salts include lithium hexafluorophosphate, lithium perchlorate, lithium chloride, lithium bromide, and the like.

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

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.

For example, when the battery is a lithium battery, its positive electrode material can include one or more lithium metal oxides, such as manganese (Mn), iron (Fe), cobalt (Co), vanadium (V), nickel (Ni), chromium (Cr) and other metal oxides. The positive electrode active material may also include one or more metal oxides and metal sulfides. Such as (including but not limited to): 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<x<1; LiMn _0.5 Ni _0.5 O ₂ ), LiMn _0.33 Co _0.33 Ni _0.33 O ₂ , LiMc _0.5 Mn _1.5 O ₄ , where Mc is a divalent metal; LiNi _x Co _y Me _z O ₂ , where Me represents one or several elements of Al, Mg, Ti, B, Ga, Si, x>0; y, z<1. In addition, the positive electrode active material may also include transition metal oxides, such as MnO ₂ , V ₂ O ₅ ; transition metal sulfides, such as FeS ₂ , MoS ₂ , TiS ₂ . Among them, lithium ion transition metal oxides have been used more, including: 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 ₂ .

The main advantages of the present invention include:

(1) The present invention successfully prepares porous silicon/carbon composite negative electrode active materials. Compared with other existing materials, this material has a higher theoretical specific capacity.

(2) The porous silicon/carbon composite anode material structure of the present invention alleviates the mechanical stress caused by volume expansion and contraction of silicon during charging and discharging, and eliminates the volume effect;

(3) The novel production process of the porous silicon/carbon composite negative electrode material for lithium ion batteries of the present invention has the advantages of low production cost, simple process, and easy large-scale production;

(4) The porous silicon/carbon composite negative electrode active material prepared by the present invention can be successfully applied to lithium batteries, exhibiting higher capacity and better cycle stability.

Below in conjunction with specific embodiment, further illustrate the present invention. 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. Percentages and parts are by weight unless otherwise indicated.

General method charge and discharge performance test

The test conditions for the first charge and discharge performance test and cycle performance test in the following examples are:

The specific capacity is calculated on the basis of 4000mAh/g, the charging rate is 0.1C (that is, it takes 10 hours to charge and discharge according to the theoretical capacity) or 0.05C (that is, it takes 20 hours to charge and discharge according to the theoretical capacity), and the charge and discharge voltage The range is 0.01V ~ 1.5V.

The instrument used in the embodiment is respectively:

XRD: Bruker AXS from Germany; Model: D8Advance;

SEM: Hitachi, Japan; Model: S～4800;

Example 1

Add 25g of aluminum-silicon alloy blocks (containing about 20% silicon) with a diameter of 0.1mm to 60mm into 300ml of 5% dilute hydrochloric acid solution for reaction, and stir evenly with magnetic force. After the mixed solution is fully reacted, the mixed solution is filtered and rinsed with deionized water and ethanol to remove AlCl to obtain porous silicon nanoparticles; then the porous silicon nanoparticles are added to ₅ % mass ratio of hydrogen After cleaning with hydrofluoric acid solution, the surface of porous silicon nanoparticles or excess silicon oxide has been removed, filtered, fully rinsed with deionized water and ethanol, and porous nano-silicon with single composition and uniform appearance is collected, as shown in Figure 1.

Then calcined in argon (80%)/(20%) acetylene gas atmosphere at 400°C (heating up to 400°C at a rate of 5°C/min) for 20 minutes to obtain a porous silicon-carbon composite electrode material, as shown in Figure 2.

The XRD structure analysis was carried out on the porous nano-silicon prepared in Example 1, and the test results are shown in FIG. 3 . It can be seen from Fig. 3 that the prepared porous silicon nanoparticles are crystalline silicon with good crystallinity, and the main peaks are at 28.44° (111 plane), 47.30° (220 plane), 56.12° (311 plane), 69.13° (400 plane). plane), 76.38 ° (331 plane), there is no appearance of other impurity peaks. It is proved that the prepared porous silicon nanoparticles are high-purity polysilicon.

Mix the porous silicon-carbon composite electrode material, conductive carbon (Super-P) and lithium polyacrylate (Li-PAA) in a solvent in a mass ratio of 80:10:10, stir evenly to obtain a negative electrode slurry, and use a lithium sheet As the negative electrode, the charge/discharge test was carried out at a rate of 0.1C. It was measured that the first discharge specific capacity of the composite electrode material at room temperature was 1479.4mAh/g, the charge specific capacity was 1137.3mAh/g, and the first Coulombic efficiency could be as high as 76.9%. The secondary discharge specific capacity is 1707.8mAh/g, the charge specific capacity is 1558.9mAh/g, and the Coulombic efficiency can be as high as 91.3%. The third discharge specific capacity is 1675.5mAh/g, the charge specific capacity is 1575.4mAh/g, and the Coulombic efficiency can be as high as 94.0%, showing an upward trend, showing good cycle stability, as shown in Figure 4.

Example 2

Add 35g of aluminum-silicon alloy blocks (containing about 30% silicon) with a diameter of 0.1mm to 60mm into 400ml of 5% dilute hydrochloric acid solution for reaction, and stir evenly with magnetic force. After the mixed solution is fully reacted, the mixed solution is filtered and fully rinsed with deionized water and ethanol to obtain porous silicon nanoparticles; then the porous silicon nanoparticles are added to a 5% mass ratio hydrofluoric acid solution for cleaning , after the surface of the porous silicon nanoparticles or excess silicon oxide has been removed, filter, rinse thoroughly with deionized water and ethanol, and collect porous silicon nanoparticles with a single composition and uniform appearance. Then, it was calcined for 10 minutes in an argon (80%)/(20%) acetylene gas atmosphere at 690°C (increasing the temperature to 690°C at a rate of 10°C/min) for 10 minutes to obtain a porous silicon/carbon composite electrode material. Mix porous silicon-carbon composite electrode material, conductive carbon (Super-P) and sodium carboxymethyl cellulose (CMC) in a solvent according to a mass ratio of 70:20:10, and stir evenly to obtain negative electrode slurry. The sheet is the negative electrode, and the charge/discharge test is carried out at a rate of 0.05C. It is measured that the first discharge specific capacity of the composite electrode material at room temperature is 1466.1mAh/g, the charge specific capacity is 898.1mAh/g, and the first Coulombic efficiency can be as high as 61.3%. The second discharge specific capacity is 1175.1mAh/g, the charge specific capacity is 1034.8mAh/g, and the Coulombic efficiency can be as high as 88.1%. The third discharge specific capacity is 1114.8mAh/g, the charge specific capacity is 1038.9mAh/g, and the Coulombic efficiency can be as high as 93.2%, showing an upward trend and showing good stability. Table 1 shows the electrochemical properties of the prepared silicon-carbon anode material, and FIG. 5 shows the charge-discharge curve and Coulombic efficiency diagram of the porous silicon-carbon composite anode material in Example 2.

Table 1 embodiment 2 makes the electrochemical performance of the silicon carbon negative electrode material that lithium-ion battery is used

Cycles Charging specific capacity (mAh/g) Discharge specific capacity (mAh/g) Coulombic efficiency 1 898.1 1466.1 61.3%

2 1034.8 1175.1 88.1% 3 1038.9 1114.8 93.2% 4 1041.9 1100.0 94.7% 5 1032.8 1082.0 95.4% 6 1039.8 1082.0 96.1% 7 1039.3 1081.6 96.1% 8 1021.4 1056.3 96.7% 9 1015.2 1045.0 97.2% 10 1001.5 1029.1 97.3% 11 1013.1 1038.9 97.5% 12 1017.1 1046.1 97.2% 13 998.8 1024.8 97.5% 14 1005.0 1034.1 97.2% 15 993.6 1024.4 97.0%

Example 3

Add 30g of aluminum-silicon alloy blocks (containing about 50% silicon) with a diameter of 0.1mm to 60mm into 300ml of 10% dilute hydrochloric acid solution to fully react, and stir evenly with magnetic force. After the mixed solution is fully reacted, the mixed solution is filtered and fully rinsed with deionized water and ethanol to obtain porous silicon nanoparticles; then the porous silicon nanoparticles are added to a 10% mass ratio hydrofluoric acid solution for cleaning , after the surface of the porous silicon nanoparticles or excess silicon oxide has been removed, filter, rinse thoroughly with deionized water and ethanol, and collect porous silicon nanoparticles with a single composition and uniform appearance. Then, it was calcined for 30 minutes in an argon (80%)/(20%) ethylene gas atmosphere at 800°C (increasing the temperature to 800°C at a rate of 5°C/min) to obtain a porous silicon/carbon composite electrode material. Using a lithium sheet as the negative electrode, the charge/discharge test was carried out at a rate of 0.05C. It was measured that the first discharge specific capacity of the composite electrode material at room temperature was 1428.3mAh/g, the charge specific capacity was 1305.4mAh/g, and the first coulombic efficiency was as high as 91.4 %, the specific capacity of the second discharge is 1722.0mAh/g, the specific capacity of the third discharge is 1539.0mAh/g, and the Coulombic efficiency of the second and third discharges can be as high as 95-97%. After 50 charge-discharge cycles, the Coulombic efficiency can still be as high as 97%, and after the second charge-discharge cycle, the discharge specific capacity is plateau, which means that after several charge-discharge cycles, the intercalation/detachment of the electrode material Lithium capacity gradually reaches a steady state. The negative electrode material made of the material of the invention has good cycle stability after multiple charge and discharge cycles.

All documents mentioned in this application are incorporated by reference in this application as if each were individually incorporated by reference. In addition, it should be understood that after reading the above teaching content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Claims (10)

1. a preparation method for porous silicon-carbon composite, is characterized in that, comprises step:

(1) one silicon-active metal alloy block is provided;

(2) carry out reacting to remove the active metal in described alloy block with described alloy block and liquid phase pore creating material, obtain porous silicon nano material;

(3) porous silicon nano material described in hydrofluoric acid clean is used to remove silica, to obtain the porous silicon nano material through hydrofluoric acid clean process;

(4) in inert gas, under carbon source exists, the described porous silicon nano material through hydrofluoric acid clean process is calcined, obtains porous silicon-carbon composite.

2. the method for claim 1, is characterized in that, described active metal is selected from lower group: aluminium, iron, magnesium, zinc, calcium, lead, or its combination.

3. the method for claim 1, is characterized in that, described liquid phase pore creating material is the solution that can react with active metal and not react with elemental silicon; Preferably, described liquid phase pore creating material is inorganic acid; More preferably, described liquid phase pore creating material is inorganic acid.

4. the method for claim 1, is characterized in that, described carbon source is carbonaceous gas, is preferably selected from lower group: methane, ethane, propane, ethene, propylene, acetylene, propine, or its combination.

5. the method for claim 1, is characterized in that, described inert gas is selected from lower group: nitrogen, helium, argon gas, neon, or its combination.

6. porous silicon-carbon composite electrode material, is characterized in that, described electrode material prepares by the method as described in as arbitrary in claim 1-5.

7. material as claimed in claim 6, it is characterized in that, described electrode material has the one or more features being selected from lower group:

Described electrode material is nano particle, and preferably, the particle diameter of described nano particle is 5nm-300nm;

The specific area of described electrode material is 10-500cm ²/ g;

The specific discharge capacity of described negative material is >900mAh/g, be preferably >1000mAh/g, >1100mAh/g, best, the specific discharge capacity of described negative material is 1200-1600mAh/g;

The coulombic efficiency (after second time charge and discharge cycles) of described negative material is >=92%, and being preferably >=95%, is more preferably >=97%.

8. a battery cathode, is characterized in that, prepared by described battery cathode material as claimed in claim 6, or described battery cathode is containing, for example material according to claim 6.

9. goods, is characterized in that, prepared by described goods material as claimed in claim 6, or described goods are containing, for example material according to claim 6, or described goods have battery cathode as claimed in claim 8.

10. goods as claimed in claim 9, it is characterized in that, described goods are batteries, and described battery positive pole, negative pole, electrolyte and barrier film, and described negative material comprises material as claimed in claim 6, or described negative pole is battery cathode according to claim 8.