WO2013159470A1

WO2013159470A1 - Three-dimensional porous silicon-based composite negative electrode material of lithium ion cell and preparation method thereof

Info

Publication number: WO2013159470A1
Application number: PCT/CN2012/079901
Authority: WO
Inventors: 刘萍; 乔永民; 李辉; 吴敏昌; 丁晓阳; 谢秋生; 郑俊军
Original assignee: 上海杉杉科技有限公司
Priority date: 2012-04-26
Filing date: 2012-08-09
Publication date: 2013-10-31
Also published as: CN102683655A; KR101621133B1; KR20140031953A; CN102683655B

Abstract

Disclosed are a porous silicon-based composite negative electrode material of a lithium ion cell and a preparation method thereof. The present invention adopts a three-dimensional grid structure, so that electrode active materials are evenly dispersed therein and on the surface, and the three-dimensional grid structure has a current collector material having a high-temperature resisting feature and fine conductivity, such as a copper foil mesh, a copper wire mesh, foamed copper, or foamed nickel. Moreover, a dipping method is used to combine slurry containing monatomic silicon or a mixture of monatomic silicon and metal M with the copper foil mesh, copper wire mesh, foamed copper, or foamed nickel, so as to form a three-dimensional porous silicon-based composite negative electrode material through heat treatment (alloying and annealing treatment). In the present invention, through the forming of the three-dimensional porous structure and the silicon metal alloy, and the fine bonding force between the negative electrode material and the three-dimensional porous current collector material, the cell prepared using the porous silicon-based composite negative electrode material has high discharge capacity and initial charge-discharge efficiency, and good cycle performance.

Description

Three-dimensional porous silicon-based composite anode material for lithium ion battery and preparation method thereof

The invention relates to the technical field of lithium ion battery electrode materials, in particular to a lithium ion battery porous silicon composite anode material and a preparation method thereof.

Background technique

In the research field of lithium ion batteries, the research focus is on the anode material. The ideal anode material should have the following conditions: 1 with good charge and discharge reversibility and cycle life; 2 small irreversible capacity for the first time; 3 good compatibility with electrolyte solvent; 4 higher specific capacity; 5 safe, no Pollution; 6 rich in resources, low prices, etc. The existing anode materials are difficult to meet the above requirements at the same time. At present, the commercial anode materials for lithium ion batteries are mainly carbon materials.

(including graphite, hard carbon and soft carbon, etc.), the volume expansion in the process of inserting and deintercalating lithium is basically below 9%, showing high coulombic efficiency and excellent cycle stability. However, the lower theoretical lithium storage capacity (LiC ₆ , 372 mAh/g) of the graphite electrode itself makes it difficult to make breakthrough progress. Therefore, research and development of new anode materials with high specific capacity, high charge and discharge efficiency, high cycle performance, high rate charge and discharge performance, high safety, and low cost have become extremely urgent, and have become the research field of lithium ion batteries. Hot topics, and is of great significance for the development of lithium-ion batteries.

In the research of new non-carbon anode materials, it is found that Si, Al, Mg, Sn and other metals which can be alloyed with Li and their alloys have a reversible lithium storage capacity much higher than that of graphite anodes, and silicon has the highest The theoretical lithium storage capacity (Li ₂₂ Si ₅ , 4200mAh/g), low lithium insertion potential (less than 0.5V vs Li/Li + ), low reactivity of the electrolyte, abundant natural reserves, low price, etc. . Elemental silicon, silicon oxides, silicon metal compounds, and silicon/carbon composites are the most studied silicon-based materials. However, silicon is a semiconductor material that has limited conductivity and is incompatible with conventional electrolytes. Silicon-based materials are highly embedded In the process of delithiation, similar to general alloy materials, there is a very significant volume expansion.

(The volume expansion ratio is >300%), and the resulting mechanical stress causes the electrode material to be gradually pulverized during the cycle, the material structure is broken, and the electrical contact between the active materials is lost, resulting in a decrease in cycle performance. In addition, the silicon-based material has a large irreversible capacity for the first time, which may be caused by the decomposition of electrolyte solution and the presence of impurities such as oxides. The above reasons limit the commercial application of silicon-based materials. Therefore, while obtaining high capacity, how to improve the cycle stability of silicon-based materials, reduce its first irreversible capacity, and make it commercialized and practical, has become the research focus and difficulty of such materials.

To date, measures to improve the performance of silicon anodes include: by designing the composition and microstructure of silicon-based anode materials to suppress volume changes and improve conductivity; developing binders and electrolyte additives for silicon anodes; exploring new current collectors and Electrode structure, etc. Among them, the breakthrough of electrochemical performance of silicon substrate itself is still the key to commercialization of silicon anode. The main strategy for improving the silicon substrate is to design the composition and microstructure of the material to accommodate the volumetric effect of the silicon and maintain the conductive network of the electrode. The main ways are nanocrystallization, thin film formation, composite, and porous.

(1) Reducing the particle size of the active body (such as nanometer size) is one way to improve the stability of the alloy. Nanomaterials have the characteristics of large specific surface area, short ion diffusion path, strong peristaltic property and high plasticity, which can alleviate the volume effect of alloy materials and improve their electrochemical performance. However, ultrafine powders, especially nanomaterials, cause more oxide impurities and more surface film formation and more electrolyte deposition and penetration, which leads to an increase in the first irreversible capacity, significantly reducing the efficiency of the first cycle. And the nanomaterials will undergo intense agglomeration during the cycle, and the agglomerated materials no longer exhibit the characteristics of the nanoparticles, thereby limiting the further improvement of the cycle performance.

(2) Thinning of materials is also one of the effective methods to effectively improve the cycle stability of materials. This is because the film material has a large specific surface area thickness ratio, and thinning the material can effectively slow down the volume expansion effect due to alloying, and control the capacity attenuation. High cycle stability; and thinning of the material allows rapid diffusion of lithium ions, resulting in reversibility of the material and high current cycle stability.

(3), compounding is to use the synergistic effect between the components of the composite material to achieve the purpose of complementing each other. The invention mainly introduces an active or inactive buffer matrix with good conductivity and small volume effect while reducing the volume effect of the silicon active phase, and prepares the multiphase composite anode material, and improves the long-term circulation stability of the material by volume compensation and electrical conductivity. Sex. According to the type of the dispersed matrix introduced, it can be roughly classified into two types: a silicon-nonmetal composite system and a silicon-metal composite system.

In recent years, Si-metal composite materials have received attention from battery researchers. Metal elements capable of forming a stable compound with silicon include Li, Fe, Ti, Mn, Cu, Co, Ni, Al, Zn, Sn, Mg, and the like. The alloying or partial alloying of a metal element which forms a stable compound with silicon can fully utilize the advantages of good electrical conductivity, ductility and high mechanical strength of the metal. The addition of metal can not only improve the charge transfer of Si and lithium. The reaction increases the conductivity of the silicon electrode and suppresses or buffers the volume change of the silicon in the case of charge and discharge. That is, the purpose of compounding with metal is to improve the conductivity of silicon on the one hand, and to disperse and buffer on the other hand. So far, the reported silicon metal composites are Si-Ni-C, Si-Mn, Al-Si-Mn, FeSi-C, Si-Co-Co ₃ 0 ₄ , Si-Zn-C, Si-Al-Mn. , Si—Al—Sn, Si—Mn—C, Si—Cu—C, Si—Sn—C, Ti—Si, and Ti—Si—Al. According to whether the metal has lithium intercalation activity, the silicon-metal composite system can be divided into two types: silicon/inert lithium intercalation composite system and silicon/active lithium intercalation metal composite system. From the existing research, the silicon/inert lithium intercalation composite has good cycle stability, and the capacity of the silicon/active lithium intercalation composite is high.

The active lithium intercalation metal material (M=Sn, Mg, A1, etc.) itself has lithium intercalation property, and the lithium intercalation effect of Si and M at different potentials as the active center causes the volume expansion of the material to occur at different potentials. Relieves internal stresses due to volumetric effects, thereby Enhance the structural stability of the material and improve its cycle performance. Among them, when tin forms Li ₄ . ₄ Sn alloy, its theoretical mass specific capacity is 994 mAh/g, and the volume specific capacity can be as high as 7200 mAh/cm 3 ; A1 theoretical specific capacity is 2235 mAh/g; Mg theoretical specific capacity is 2205 mAh/g, Compared with carbon materials, it has a high specific capacity, which is of great significance for the development of electrical miniaturization. According to the literature search of the prior art, Kim H. et al., "The insertion mechanism of lithium into Mg ₂ Si anode material for Li-, published in Journal of The Electrochemical Society, 1999, Vol. 146, No. 12, pp. 4401-4405. ion batteries "(lithium ion battery Mg ₂ Si negative electrode material for lithium intercalation mechanisms) paper with a vapor deposition method of the M _g2 Si nano alloy, its first lithium intercalation capacity up to 1370mAh / g, but the cycling properties of the electrode material is Poor, the capacity is less than 200mAh/g after 10 cycles.

The inactive lithium intercalation metal material has no lithium intercalation property, although it can improve the cycle performance of the material, but the inert matrix has a limited buffering effect on the volume change of the active material; and a certain volume (mass) material in the battery assembly The contribution to capacity does not limit the volumetric energy density (mass energy density) of the assembled battery, which limits the application of this material in future high energy density batteries.

It can be seen that the achievements in the research of silicon-based composite materials are still far from the industrialization. Finding a matrix that is more capable of buffering volume changes and having higher conductivity; Designing and constructing a superior composite structure is undoubtedly the mainstream of future development of silicon-based composite materials.

(4) Design a porous structure and reserve an expansion space. Porous materials have the following advantages due to their unique structure: 1 porous structure has a high specific surface area, large openings allow the transport of liquid electrolyte; 2 porous structure allows the electrolyte to fully contact the active material, reducing lithium ions Diffusion path; 3 porous structure can improve the conductivity of lithium ions, thereby increasing the electrochemical reaction rate; 4 porous structure can provide reactive sites, improve the efficiency of electrochemical reactions; 5 no need to add binder and conductive agent; 6 effective absorption and slow Chong Si The volume expansion effect improves the cycle performance of the material.

In summary, the use of nano-materials has a poor effect on improving the cycle properties of alloy materials; single active doping or inert doping can partially inhibit the volume expansion of silicon-based materials, but still cannot completely solve the problem of silicon dispersion and agglomeration. . At the same time, considering the large-scale production and manufacturing costs, the preparation of composite anodes combined with porosity should be the main strategy for the development of silicon-based anode materials.

SUMMARY OF THE INVENTION The specific capacity, the first charge and discharge efficiency, the cycle performance are not ideal, and can not be commercialized for use in a lithium ion battery; providing a three-dimensional porous silicon-based composite anode material that is low in cost and can be commercially applied to a lithium ion battery and Its preparation method. The three-dimensional network porous silicon metal composite anode material for lithium ion battery prepared by the integrated active/active, active/inactive composite system and the porous method of the invention can improve the conductivity of the silicon anode material while alleviating the volume expansion problem. Thereby improving its electrochemical performance (specific capacity, rate performance, especially cycle performance). In order to achieve the above object, the technical solution adopted by the present invention is: a method for preparing a three-dimensional porous silicon-based composite anode material for a lithium ion battery, comprising the following steps: Step (1): cleaning a three-dimensional porous current collector material; The fluid material is an inert lithium intercalation metal; the inert lithium intercalation metal refers to a metal that does not form an intermetallic compound or alloy with lithium. The inert lithium intercalation metal is preferably any one of a copper foil mesh, a copper mesh, a copper foam, and a foamed nickel, in view of economic cost;

Step (2): adding a mixture of elemental silicon or elemental silicon and metal M, and a binder to a solvent, the solvent is an aqueous solvent or an oil solvent, and sufficiently stirring to obtain a slurry; the three-dimensional porous current collector material After being immersed in the slurry, after fully impregnating and scraping off the surface excess slurry, a three-dimensional porous current collector material system impregnated with the slurry is formed; and then the three-dimensional porous current collector material system impregnated with the slurry is placed at Vacuum drying at 80~90°C Drying 0.5~lh, and then rolling under pressure of 2~6MPa, to obtain a three-dimensional porous silicon-based composite electrode precursor; wherein, the metal M is an active lithium intercalation metal;

And the step (3): the three-dimensional porous silicon-based composite electrode precursor obtained in the step (2) is heat-treated in a vacuum or an inert atmosphere to obtain a three-dimensional porous silicon-based composite negative electrode material.

In the above technical solution, the cleaning step of the step (1) is: a three-dimensional porous current collector material, such as copper foil mesh or copper mesh or copper foam or nickel foam, followed by copper, 10% diluted hydrochloric acid, distilled water and none. Ultrasonic cleaning of water ethanol. The reagents used were of analytical grade and the solution was prepared in two distilled waters. The purpose of cleaning is to remove impurities such as surface oil and surface oxides.

In the step (1), the three-dimensional porous current collecting material has an average pore diameter of 100-200 μm and a thickness of 400 μπ! ~ 1000μπι.

In the step (2), the mixture of the elemental silicon, the elemental silicon and the metal ruthenium is present in a powder form, and the particle size is on the order of micrometers, submicrometers or nanometers. The metal ruthenium is an active lithium intercalation metal. The active lithium intercalation metal refers to a metal capable of forming an intermetallic compound or alloy with lithium, such as magnesium, calcium, aluminum, bismuth, tin, lead, arsenic, antimony, bismuth, platinum, silver, gold, cadmium, cadmium, indium. Wait. The mixture of elemental silicon and metal ruthenium refers to a mixture of any one or two or more of elemental silicon and active lithium intercalation metal, wherein the active lithium intercalation metal has a purity of at least 99.5%.

The active lithium intercalation metal is preferably any one or a combination of two or more of tin, magnesium and aluminum in view of environmental protection requirements and economic costs; the silicon, tin, magnesium and aluminum have a purity of at least 99.5%.

In the step (2), the aqueous solvent is preferably water or an aqueous solution of ethanol; and the oily solvent is preferably ruthenium-mercaptopyrrolidone, dinonyl amide or dimethyl sulfoxide.

In the mixture of elemental silicon and metal ruthenium, the ratio of elemental silicon to metal ruthenium directly affects the capacity and cycle stability of the composite. In order to achieve a good synergistic effect between the components, that is, to exert the high-capacity characteristics of silicon and the good electrical conductivity of tin, magnesium and aluminum, the quality of elemental silicon and metal ruthenium in the mixture of elemental silicon and metal ruthenium The ratio is 1:1~9:1. When two or more metals are used for the metal ruthenium, the ratio of the mass sum of the elemental silicon to the two or more metals is 1:1 to 9:1. The binder is carboxymethyl cellulose, polyamide-imide And one of polyacrylic acid.

The mixture ratio of the elemental silicon or elemental silicon to the metal M and the binder is 36: 1-45:1. The solvent is added in an amount to ensure a solid content of the slurry of 30% to 40% so that a three-dimensional porous current collector material such as a copper foil mesh or a copper mesh or a copper foam or a foamed nickel current collector is sufficiently impregnated in the slurry. The solids content of the slurry refers to the mass of solid matter in the slurry as a percentage of the total mass of the slurry.

In the step (3), the heat treatment refers to heating the three-dimensional porous silicon-based composite electrode precursor obtained in the step (2) to 200 ° C - 850 ° C and making it at 200 ° C - 850 ° C. Under the condition of 2-6 hours of heat preservation, it is alloyed; then it is cooled to 100 °C -200 °C for another 1-3 hours, and then annealed; after the end of the heat, the electric heating is stopped. Allow it to cool to room temperature with the furnace.

The "heating up to 200 °C - 850 °C" means heating from room temperature to 200 °C - 850 °C. In order to prevent oxidation, the heat treatment is carried out in a vacuum or an inert atmosphere. The "heat treatment in a vacuum or inert atmosphere" means the process of the heat treatment, including the temperature rise, the two heat preservation stages, and the vacuum or inert atmosphere is always maintained in the stage of cooling with the furnace. However, in order to save energy, especially when vacuum conditions are formed by using a vacuum device, energy is consumed due to the operation of the vacuum device, and when cooled to below 85 °C, the vacuum device can be allowed to be turned off.

The alloying treatment refers to holding at a temperature lower than the melting point of the substrate, Si and metal M and the eutectic temperature of the relevant alloy for a period of time, and by forming interdiffusion or partial interdiffusion to form a corresponding alloy, the formation of the alloy is favorable for improvement. Electrochemical performance (specific capacity and cycle performance) of a three-dimensional porous silicon-based composite electrode material. The annealing treatment can promote the homogenization of the alloy composition, the grain refinement, the stress elimination, the binding force between the material and the current collector, and the improvement of the plasticity for processing. The heat treatment improves the microstructure of the three-dimensional porous silicon-based composite electrode precursor, so that the elemental silicon or Si-M microparticles are uniformly and stably distributed in the three-dimensional network of the copper foil mesh or the copper mesh or the foamed copper or the foamed nickel. In the structure, the bonding between the materials and the substrate is improved, and the mechanical properties of the material are also improved, thereby suppressing The volume change of the active material during charge and discharge improves the cycle stability of the silicon-based composite anode material.

As used herein, "vacuum" means a degree of vacuum of at least 1 x 1 (T ² Pa.

As used herein, "room temperature" refers to a temperature range of 18 to 25 °C.

As used herein, "purity" refers to the percentage by mass.

During the heat treatment, the temperature rises too fast, and it is easy to cause cracking or the like due to excessive shrinkage. Therefore, the temperature increase rate is preferably 3-15 ° C / min during the heating process.

Another aspect of the present invention provides a three-dimensional porous silicon-based composite negative electrode material for a lithium ion battery, characterized in that the three-dimensional porous silicon-based composite negative electrode material of the lithium ion battery is prepared by the above preparation method.

The beneficial effects of the present invention are as follows:

(1) The invention eliminates the need to separately add a conductive agent, which simplifies the process operation and further reduces the process cost.

(2) The active lithium intercalation metal M itself has good electrical conductivity and lithium intercalation performance. The present invention utilizes the lithium intercalation effect of Si and metal M at different potentials, so that the volume expansion of the material occurs at different potentials, which can alleviate the volume The internal stress caused by the effect enhances the structural stability of the material and improves its cycle performance.

(3) The three-dimensional porous silicon-based composite anode material of the lithium ion battery of the invention is used as a porous composite electrode, and the electrode active material is mainly a part of alloy formed by Si and Si-M; the specific capacity of lithium storage can be mainly active in the electrode active material. The content of the high-capacity elemental silicon of the substance is adjusted.

(4) The inert lithium intercalation metal current collector material of the present invention, such as copper foil mesh or copper mesh or copper foam or nickel foam, has a three-dimensional network structure, can uniformly disperse the electrode active material therein, and has a certain high temperature resistance. Good characteristics and electrical conductivity. The three-dimensional porous current collector material not only serves as an electrode support and a current collector, but also can be used in the heat treatment process. It is possible to use the physical and chemical affinity of itself to interdiffusion or partial interdiffusion with the active negative electrode material to form a silicon/inert lithium intercalation metal alloy (such as forming Si-Cu or Si-Ni alloy), thereby improving the structure of the entire composite battery. The synergy between stability and performance; on the other hand, because the system itself has a three-dimensional network structure, the contact area between the material and the electrolyte can be greatly improved, and the polarization can be reduced; the volume change of the alloy electrode during charging and discharging can be alleviated, Improve the charge and discharge cycle performance of the alloy electrode; also improve the high rate charge and discharge performance of the alloy electrode.

(5) In the present invention, the three-dimensional porous structure, the formation of the silicon metal alloy, and the good bonding force between the negative electrode material and the three-dimensional porous current collector material enable the battery prepared by the porous silicon-based composite negative electrode material to have a higher discharge specific capacity. , first charge and discharge efficiency and good cycle performance. The method of the invention has the advantages of simple operation, low cost and easy scale production, and has broad application prospects in the field of lithium ion battery negative electrodes. DRAWINGS

Figure 1 is a flow chart of the method of the present invention.

Figure 2 is a topographical view of the foamed copper of Example 1.

3 is a three-dimensional porous silicon-based composite anode material prepared in Example 1.

4 is a cycle performance curve of a three-dimensional porous silicon-based composite anode material prepared in Example 1.

detailed description

The embodiments of the present invention are described in detail below. The present embodiment is implemented on the premise of the technical solution of the present invention, and the detailed implementation manner and the specific operation process are given. However, the protection scope of the present invention is not limited to the following implementation. example.

Example 1

A copper foil mesh or copper mesh or copper foam or foamed nickel having an average pore diameter of 150 μm and a thickness of 700 μm is sequentially ultrasonically washed with copper, 10% diluted hydrochloric acid, distilled water and absolute ethanol to remove In addition to surface oil and surface oxides and other impurities. Elemental Si powder (purity: 99.5%, ϋ ₅₀ = 1.5 μm) and carboxymethyl cellulose (CMC) were added to water at a mass ratio of 36:1, and the slurry was sufficiently stirred to obtain a solid content of 35%. Immersing a copper foil mesh or a copper mesh or a copper foam or a foamed nickel current collector in the slurry, fully impregnating and scraping off the excess slurry on the surface to form a copper foil mesh or copper mesh impregnated with the slurry or a foamed copper or foamed nickel current collector system, followed by vacuum drying the copper foil mesh or copper mesh or copper foam or foamed nickel current collector system impregnated with the slurry at 80 ° C for 1 h, then at a pressure of 4 MPa Pressing to obtain a three-dimensional porous silicon-based composite electrode precursor of a desired thickness. The obtained three-dimensional porous silicon-based composite electrode precursor is placed in a box furnace and heat-treated in a vacuum (vacuum degree: 2 x lO_ ³ Pa) or an inert atmosphere at a heat treatment temperature of 820 ° C and a heating rate of 12 ° C. /min, the holding time is 4 hours, and it is alloyed; then it is cooled to 200 °C and then kept for 2h, and then annealed; after the end of the heat, the electric heating is stopped, and the furnace is cooled to room temperature. A three-dimensional porous silicon-based composite anode material is obtained, and the electrode active material is mainly Si. To prevent oxidation, a vacuum or inert atmosphere is maintained throughout the heat treatment.

The three-dimensional porous silicon-based composite negative electrode sheet prepared from the foamed copper substrate and the lithium metal were subjected to electrochemical performance test, and the test current density was 0.6 mA/cm ² , and the charge and discharge voltage was 0-2.0 V. The discharge capacity of the negative pole piece can reach 2200 mAh/g, the first efficiency is 86%, and after 50 cycles, it can still maintain 93% capacity.

Example 2:

A copper foil mesh or copper mesh or foamed copper or foamed nickel having an average pore diameter of ΙΟΟμπι, thickness ΙΟΟΟμπι is sequentially ultrasonically cleaned with copper, 10% diluted hydrochloric acid, distilled water and absolute ethanol to remove impurities such as surface oil and surface oxide. . The elemental Si powder (purity: 99.9%, D ₅₀ =100 nm) and polyamide-imide (PAI) were added to N-mercaptopyrrolidone in a mass ratio of 45:1, and the slurry was sufficiently stirred to obtain a solid content of 30. %). Immersing a copper foil mesh or a copper mesh or a copper foam or a foamed nickel current collector in the slurry, fully impregnating and scraping off the surface After excess slurry, a copper foil mesh or copper mesh or copper foam or foamed nickel current collector system impregnated with the slurry is formed, followed by a copper foil mesh or copper mesh or copper foam or foamed nickel current collector impregnated with the slurry. The system was vacuum dried at 90 ° C for 0.5 h, and then rolled under a pressure of 6 MPa to obtain a three-dimensional porous silicon-based composite electrode precursor having a desired thickness. The obtained three-dimensional porous silicon-based composite electrode precursor is placed in a box furnace and heat-treated under a vacuum (vacuum degree of 2 x 10 ^-3 Pa) or an inert atmosphere at a heat treatment temperature of 850 ° C and a heating rate of 15 °. C/min, holding time is 2 hours, make it alloying; then let it cool down to 200 °C for 1.5 hours, then make it annealed; after the end of the heat, stop electric heating, let it cool with the furnace At room temperature, a three-dimensional porous silicon-based composite anode material is obtained, and the electrode active material is mainly Si. To prevent oxidation, a vacuum or inert atmosphere is maintained throughout the heat treatment.

The three-dimensional porous silicon-based composite negative electrode sheet prepared from the foamed nickel substrate and the lithium metal were subjected to electrochemical performance test, and the test current density was 0.6 mA/cm ² , and the charge and discharge voltage was 0-2.0 V. The discharge capacity of the negative pole piece can reach 2500 mAh/g, the first efficiency is 90%, and after 50 cycles, it can still maintain 95% capacity.

Example 3:

A copper foil mesh or copper mesh or copper foam or foamed nickel having an average pore diameter of 1 ΟΟμπι and a thickness of 400 μm is sequentially ultrasonically cleaned with copper, 10% diluted hydrochloric acid, distilled water and absolute ethanol to remove surface oil and surface oxide. Impurities. Si-Sn mixed powder (Si purity 99.8%, ϋ ₅₀ = 1.5 μm; Sn purity 99.6%, D ₅₀ = 100 nm; and Si: Sn = 1: 1) and polyacrylic acid [poly (acrylic acid)] The slurry was added to an aqueous ethanol solution at a mass ratio of 36:1, and sufficiently stirred to obtain a slurry (solid content: 32%). Immersing a copper foil mesh or a copper mesh or a copper foam or a foamed nickel current collector in the slurry, fully impregnating and scraping off the excess slurry on the surface to form a copper foil mesh or copper mesh impregnated with the slurry or a copper foam or foamed nickel current collector system, followed by vacuum drying the copper foil mesh or copper mesh or foamed copper or foamed nickel current collector system impregnated with the slurry at 80 ° C for 1 h, then rolling at 2 MPa pressure, Get the required thickness of the 3D Porous silicon-based composite electrode precursor. The obtained three-dimensional porous silicon-based composite electrode precursor is placed in a box furnace, and heat-treated under vacuum (vacuum degree: lx lO- ³ Pa) or an inert atmosphere, the heat treatment temperature is 200 ° C, and the heating rate is 3 ° C. /min, keep the alloying time for 6 hours, then heat it to 100 °C for another 3 hours, then anneal it; after the heat is over, stop the electric heating and let it cool with the furnace. At room temperature, a three-dimensional porous silicon-based composite anode material is obtained, and the electrode active material is mainly a part of alloy formed by Si and Si-Sn. To prevent oxidation, a vacuum or inert atmosphere is maintained throughout the heat treatment.

The three-dimensional porous silicon-based composite negative electrode sheet prepared from the copper foil mesh substrate and the metallic lithium were subjected to electrochemical performance test, and the current density was 0.6 mA/cm ² , and the charge and discharge voltage was 0-2.0 V. The discharge capacity of the negative pole piece can reach 1200 mAh/g, the first efficiency is 89%, and after 50 cycles, it can still maintain 97% capacity.

Example 4:

A copper foil mesh or copper mesh or copper foam or foamed nickel having an average pore diameter of 150 μm and a thickness of 700 μm is sequentially ultrasonically cleaned with copper, 10% diluted hydrochloric acid, distilled water and absolute ethanol to remove impurities such as surface oil and surface oxide. . Si-Sn mixed powder (Si purity 99.7%, ϋ ₅₀ = 1.8 μπι; Sn purity 99.9%, D ₅₀ = 500 nm; and Si: Sn = 5: 1) and carboxymethyl cellulose (CMC) 40: 1 mass ratio was added to water, and the slurry was thoroughly stirred to obtain a solid content of 34%. Immersing a copper foil mesh or a copper mesh or a copper foam or a foamed nickel current collector in the slurry, fully impregnating and scraping off the excess slurry on the surface to form a copper foil mesh or copper mesh impregnated with the slurry or a copper foam or foamed nickel current collector system, followed by vacuum drying the copper foil or copper mesh or copper foam or foamed nickel current collector system impregnated with slurry at 85 V for 1 h, then rolling at 4 MPa A three-dimensional porous silicon-based composite electrode precursor having a desired thickness is obtained. The obtained three-dimensional porous silicon-based composite electrode precursor is placed in a box furnace, and heat-treated under vacuum (vacuum degree: lx lO- ³ Pa) or an inert atmosphere, the heat treatment temperature is 230 ° C, and the heating rate is 5 ° C. /min, holding time is 4 hours, make it into After alloying treatment; then, after cooling to 100 ° C for another 2 hours, it is annealed; after the heat is kept, the electric heating is stopped, and the furnace is cooled to room temperature to obtain a three-dimensional porous silicon-based composite anode material. The electrode active material is mainly a partial alloy formed of Si and Si-Sn. To prevent oxidation, a vacuum or inert atmosphere is maintained throughout the heat treatment.

The three-dimensional porous silicon-based composite negative electrode sheet prepared from the copper mesh substrate and the lithium metal were subjected to electrochemical performance test, and the test current density was 0.6 mA/cm ² , and the charge and discharge voltage was 0-2.0 V. The discharge capacity of the negative pole piece can reach 1500 mAh/g, the first efficiency is 86%, and after 50 cycles, it can still maintain 95% capacity.

Example 5

A copper foil mesh or copper mesh or copper foam or foamed nickel having an average pore diameter of 150 μm and a thickness of 400 μm is sequentially ultrasonically cleaned with copper, 10% diluted hydrochloric acid, distilled water and absolute ethanol to remove impurities such as surface oil and surface oxide. . Si-Mg mixed powder (Si purity 99.6%, ϋ ₅₀ = 1.5 μπι; Mg purity 99.5%, ϋ ₅₀ = 3 μπι; and Si: Mg = 6: 1) and polyamide-imide (PAI) The slurry was added to the dimercaptoamide at a mass ratio of 38:1, and the slurry was sufficiently stirred (solid content: 36%). Immersing a copper foil mesh or a copper mesh or a copper foam or a foamed nickel current collector in the slurry, fully impregnating and scraping off the excess slurry on the surface to form a copper foil mesh or copper mesh impregnated with the slurry or a copper foam or foamed nickel current collector system, followed by vacuum drying the copper foil mesh or copper mesh or copper foam or foamed nickel current collector system impregnated with the slurry at 80 ° C for 1 h, then at 2 MPa pressure Pressing to obtain a three-dimensional porous silicon-based composite electrode precursor of a desired thickness. The three dimensional porous silicon precursor resulting composite electrode was placed in the box furnace, heat treatment is performed under a vacuum (degree of vacuum of 1 X 10_ ³ Pa) or an inert atmosphere, the heat treatment temperature of 550 ° C, heating rate of 9 ° C /min, keep the alloying time for 5 hours, then heat it to 150 °C for 2 hours, then anneal it; after the heat is kept, stop the electric heating and let it cool with the furnace. At room temperature, a three-dimensional porous silicon-based composite anode material is obtained, and the electrode active material is mainly Part of the alloy formed by Si and Si-Mg. To prevent oxidation, a vacuum or inert atmosphere is maintained throughout the heat treatment.

The three-dimensional porous silicon-based composite negative electrode sheet prepared from the copper foil mesh substrate and the metallic lithium were subjected to electrochemical performance test, and the current density was 0.6 mA/cm ² , and the charge and discharge voltage was 0-2.0 V. The discharge capacity of the negative pole piece can reach 1800mAh/g, the first efficiency is 88%, and after 50 cycles, it can still maintain 96% capacity.

Example 6:

A copper foil mesh or copper mesh or copper foam or foamed nickel having an average pore diameter of 200 μm and a thickness of μμπι is sequentially ultrasonically cleaned with copper, 10% diluted hydrochloric acid, distilled water and absolute ethanol to remove impurities such as surface oil and surface oxide. . Si-Mg mixed powder (Si purity 99.9%, ϋ ₅₀ = 1.8 μπι; Mg purity 99.9%, ϋ ₅₀ = 5 μπι; and Si: Mg = 9: 1) and polyacrylic acid [poly (acrylic acid)] The slurry was added to the water at a mass ratio of 42:1, and the slurry was sufficiently stirred to have a solid content of 38%. Immersing a copper foil mesh or a copper mesh or a copper foam or a foamed nickel current collector in the slurry, fully impregnating and scraping off the excess slurry on the surface to form a copper foil mesh or copper mesh impregnated with the slurry or a copper foam or foamed nickel current collector system, followed by vacuum drying the copper foil or copper mesh or copper foam or foamed nickel current collector system impregnated with the slurry at 90 ° C for 0.5 h, then at a pressure of 6 MPa Rolling was performed to obtain a three-dimensional porous silicon-based composite electrode precursor of a desired thickness. The three dimensional porous silicon precursor resulting composite electrode was placed in the box furnace, heat treatment is performed under a vacuum (degree of vacuum of 2 x lO_ ³ Pa) or an inert atmosphere, the heat treatment temperature of 620 ° C, heating rate in 10 ° C /min, keep the alloying time for 3 hours, then heat it to 200 °C for another hour, then make it annealed. After the heat is over, stop the electric heating and let it cool down with the furnace. At room temperature, a three-dimensional porous silicon-based composite anode material is obtained, and the electrode active material is mainly a part of alloy formed by Si and Si-Mg. To prevent oxidation, a vacuum or inert atmosphere is maintained throughout the heat treatment. The three-dimensional porous silicon-based composite negative electrode sheet prepared from the foamed copper substrate and the lithium metal were subjected to electrochemical performance test, and the test current density was 0.6 mA/cm ² , and the charge and discharge voltage was 0-2.0 V. The discharge capacity of the negative pole piece can reach 2000mAh/g, the first efficiency is 86%, and after 50 cycles, it can still maintain 94% capacity.

Example 7

A copper foil mesh or copper mesh or copper foam or foamed nickel having an average pore diameter of 1 ΟΟμπι and a thickness of 400 μm is sequentially ultrasonically cleaned with copper, 10% diluted hydrochloric acid, distilled water and absolute ethanol to remove surface oil and surface oxide. Impurities. The Si-Al mixed powder (Si purity 99.5%, ϋ ₅₀ = 1.5 μm; A1 purity 99.5%, D ₅₀ = 100 nm; and Si: Al = 8: 1) and carboxymethyl cellulose (CMC) 39: 1 mass ratio was added to water, and the slurry was obtained by thorough stirring (solid content: 35%). Immersing a copper foil mesh or a copper mesh or a copper foam or a foamed nickel current collector in the slurry, fully impregnating and scraping off the excess slurry on the surface to form a copper foil mesh or copper mesh impregnated with the slurry or a copper foam or foamed nickel current collector system, followed by vacuum drying the copper foil mesh or copper mesh or copper foam or foamed nickel current collector system impregnated with the slurry at 80 ° C for 1 h, then rolling at 2 MPa pressure A three-dimensional porous silicon-based composite electrode precursor having a desired thickness is obtained. The obtained three-dimensional porous silicon-based composite electrode precursor is placed in a box furnace, and heat-treated at a vacuum degree of 1 X l (T ³ Pa ) or an inert atmosphere at a heat treatment temperature of 550 ° C and a heating rate of 6 °C/min, holding time is 4 hours, make it alloying; then let it cool down to 150 °C for another 3 hours, then make it annealed; after the end of the heat, stop electric heating, make it with the furnace After cooling to room temperature, a three-dimensional porous silicon-based composite negative electrode material is obtained, and the electrode active material is mainly a partial alloy formed of Si and Si-Al. To prevent oxidation, a vacuum or an inert atmosphere is always maintained during the heat treatment.

The three-dimensional porous silicon-based composite negative electrode sheet prepared from the copper mesh substrate and the lithium metal were subjected to electrochemical performance test, and the test current density was 0.6 mA/cm ² , and the charge and discharge voltage was 0-2.0 V. The discharge specific capacity of the negative pole piece can reach 1900mAh/g, for the first time. The efficiency is 90%, and after 50 cycles, it can still maintain 96% capacity.

Example 8

A copper foil mesh or copper mesh or copper foam or foamed nickel having an average pore diameter of 200 μm and a thickness of μμπι is sequentially ultrasonically cleaned with copper, 10% diluted hydrochloric acid, distilled water and absolute ethanol to remove impurities such as surface oil and surface oxide. . Si-Al mixed powder (Si purity 99.9%, ϋ ₅₀ = 1.8 μπι; A1 purity 99.9%, D ₅₀ = 500 nm; and Si: Al = 4: 1) and polyamide-imide (PAI) The slurry was added to the dimethyl sulfoxide at a mass ratio of 43:1, and the slurry was sufficiently stirred to have a solid content of 40%. Immersing a copper foil mesh or a copper mesh or a copper foam or a foamed nickel current collector in the slurry, fully impregnating and scraping off the excess slurry on the surface to form a copper foil mesh or copper mesh impregnated with the slurry or a foamed copper or foamed nickel current collector system, followed by vacuum drying the copper foil mesh or copper mesh or foamed copper or foamed nickel current collector system impregnated with the slurry at 90 ° C for 0.5 h, then at a pressure of 6 MPa Pressing to obtain a three-dimensional porous silicon-based composite electrode precursor of a desired thickness. The obtained three-dimensional porous silicon-based composite electrode precursor is placed in a box furnace, and heat-treated at a vacuum (vacuum degree of lx lO_ ³ Pa) or an inert atmosphere at a heat treatment temperature of 650 ° C and a heating rate of 8 ° C / min. , the holding time is 2 hours, it is alloyed; then it is kept at 200 ° C for 2 hours, then it is annealed; after the end of the heat, the electric heating is stopped, and it is cooled to room temperature with the furnace. A three-dimensional porous silicon-based composite anode material is obtained, and the electrode active material is mainly a part of alloy formed by Si and Si-Al. In order to prevent oxidation, the three-dimensional porous silicon-based composite negative electrode piece and the metallic lithium composed of the copper-clad matrix were subjected to electrochemical performance test by vacuum or inert gas during the heat treatment, and the test current density was 0.6 mA/cm ² . The charge and discharge voltage is 0-2.0V. The discharge capacity of the negative pole piece can reach 1600mAh/g, the first efficiency is 89%, and after 50 cycles, it can still maintain 95% capacity.

Example 9 A copper foil mesh or copper mesh or foamed copper or foamed nickel having an average pore diameter of 150 μm and a thickness of 800 μm is sequentially ultrasonically cleaned with copper, 10% diluted hydrochloric acid, distilled water and absolute ethanol to remove impurities such as surface oil and surface oxide. . Si-Sn-Mg mixed powder (Si purity 99.9%, D ₅₀ = 100 nm; Sn purity 99.8%, D ₅₀ = 100 nm; Mg purity 99.6%, D ₅₀ = 500 nm; and Si: (Sn+Mg) ) = 7: 1 ) and carboxymethyl cellulose (CMC) was added to water at a mass ratio of 40:1, and the slurry was sufficiently stirred to obtain a solid content of 33%. Immersing a copper foil mesh or a copper mesh or a copper foam or a foamed nickel current collector in the slurry, fully impregnating and scraping off the excess slurry on the surface to form a copper foil mesh or copper mesh impregnated with the slurry or a foamed copper or foamed nickel current collector system, followed by vacuum drying the copper foil mesh or copper mesh or copper foam or foamed nickel current collector system impregnated with the slurry at 80 ° C for 1 h, then rolling at 4.5 MPa pressure Pressing to obtain a three-dimensional porous silicon-based composite electrode precursor of a desired thickness. The obtained three-dimensional porous silicon-based composite electrode precursor is placed in a box furnace, and heat-treated at a vacuum degree (l ³ Pa (T ³ Pa ) or an inert atmosphere, the heat treatment temperature is 230 ° C, and the heating rate is 5 ° C / Min, the holding time is 5 hours, and it is alloyed; then it is further heated for 3 hours after being cooled to 100 ° C, and then annealed; after the heat is kept, the electric heating is stopped, and the furnace is cooled to room temperature. A three-dimensional porous silicon-based composite anode material is obtained, and the electrode active material is mainly a part of alloy formed by Si, Si-Sn and Si-Mg. To prevent oxidation, a vacuum or an inert atmosphere is always maintained during the heat treatment.

The three-dimensional porous silicon-based composite negative electrode sheet prepared from the foamed nickel substrate and the lithium metal were subjected to electrochemical performance test, and the test current density was 0.6 mA/cm ² , and the charge and discharge voltage was 0-2.0 V. The discharge capacity of the negative pole piece can reach 1900 mAh/g, the first efficiency is 91%, and after 50 cycles, it can still maintain 97% capacity.

Example 10

A copper foil mesh or copper mesh or copper foam or foamed nickel having an average pore diameter of ΙΟΟμπι and a thickness of 500 μm is sequentially ultrasonically washed with copper, 10% diluted hydrochloric acid, distilled water and absolute ethanol to remove In addition to surface oil and surface oxides and other impurities. Si-Al-Mg mixed powder (Si purity 99.8%, Ο ₅₀ = 1.5 μπι; A1 purity 99.8%, D ₅₀ = 500 nm; Mg purity 99.7%, ϋ ₅₀ = 1.0 μπι; and Si: (Al +Mg)=9: 1) and polyamide-imide (PAI) were added to N-mercaptopyrrolidone in a mass ratio of 45:1, and stirred sufficiently to obtain a slurry (solid content: 39%). Immersing a copper foil mesh or a copper mesh or a copper foam or a foamed nickel current collector in the slurry, fully impregnating and scraping off the excess slurry on the surface to form a copper foil mesh or copper mesh impregnated with the slurry or a foamed copper or foamed nickel current collector system, followed by vacuum drying the copper foil mesh or copper mesh or foamed copper or foamed nickel current collector system impregnated with the slurry at 90 ° C for 0.5 h, then at a pressure of 2.5 MPa Rolling was performed to obtain a three-dimensional porous silicon-based composite electrode precursor of a desired thickness. The obtained three-dimensional porous silicon-based composite electrode precursor is placed in a box furnace and heat-treated under vacuum (vacuum degree of 2 10" ³ Pa) or an inert atmosphere at a heat treatment temperature of 600 ° C and a heating rate of 6 ° C / Min, holding time is 4 hours, make it alloying; then let it cool down to 200 °C for another 2 hours, then make it annealed; after the end of the heat, stop electric heating, let it cool down to room temperature with the furnace , a three-dimensional porous silicon-based composite anode material is obtained, and the electrode active material is mainly a part of alloy formed by Si, Si-Al and Si-Mg. To prevent oxidation, a vacuum or an inert atmosphere is always maintained during the heat treatment.

The three-dimensional porous silicon-based composite negative electrode sheet prepared from the copper foil mesh substrate and the metallic lithium were subjected to electrochemical performance test, and the current density was 0.6 mA/cm ² , and the charge and discharge voltage was 0-2.0 V. The discharge capacity of the negative pole piece can reach 2100 mAh/g, the first efficiency is 90%, and after 50 cycles, it can still maintain 96% capacity.

The above is only the preferred embodiment of the present invention, and it is not intended to limit the present invention, and equivalent structural changes are still within the scope of protection of the technical solutions of the present invention.

Claims

O 2013/159470 . , , , , PCT/CN2012/079901 Claims

A method for preparing a three-dimensional porous silicon-based composite anode material for a lithium ion battery, comprising the steps of:

Step (1): cleaning the three-dimensional porous current collector material; the three-dimensional porous current collector material is made of an inert lithium intercalation metal;

Step (2): adding a mixture of elemental silicon or elemental silicon and metal ruthenium to a solvent, the solvent is an aqueous solvent or an oily solvent, and sufficiently stirring to obtain a slurry; the three-dimensional porous current collector material Immersing in the slurry to form a three-dimensional porous current collector material system impregnated with the slurry; and then vacuum drying the three-dimensional porous current collector material system impregnated with the slurry at 80 to 90 ° C for 0.5 to 1 h, And then rolling under a pressure of 2~6MPa to obtain a three-dimensional porous silicon-based composite electrode precursor; wherein the metal M is an active lithium intercalation metal;

The method for preparing a three-dimensional porous silicon-based composite anode material for a lithium ion battery according to claim 1, wherein in the step (1), the three-dimensional porous current collector material has an average pore diameter of 100-200 μm, Thickness 400μπ! ~ 1000μπι.

The method for preparing a three-dimensional porous silicon-based composite anode material for a lithium ion battery according to claim 1, wherein in the step (2), the active lithium intercalation metal is selected from the group consisting of magnesium, calcium, aluminum, and strontium. Any one or a combination of two or more of tin, lead, arsenic, antimony, bismuth, platinum, silver, gold, rhodium, cadmium and indium.

The method for preparing a three-dimensional porous silicon-based composite anode material for a lithium ion battery according to claim 1, wherein in the step (2), the mixture of the elemental silicon, the elemental silicon and the metal ruthenium is in a powder form. The form exists and the particle size is micron, submicron or nano.

The method for preparing a three-dimensional porous silicon-based composite anode material for a lithium ion battery according to any one of claims 1 to 4, wherein in the step (2), the mixture of the elemental silicon and the metal ruthenium is The mass ratio of elemental silicon to metal ruthenium is 1:1 to 9:1. O 2013/159470 . , , , , PCT/CN2012/079901 Claims

The method for preparing a three-dimensional porous silicon-based composite anode material for a lithium ion battery according to claim 5, wherein in the step (2), the binder is carboxymethyl cellulose, polyamide- One of an imide and a polyacrylic acid.

The method for preparing a three-dimensional porous silicon-based composite negative electrode material for a lithium ion battery according to claim 6, wherein in the step (2), the solid content of the slurry is 30% to 40%.

The method for preparing a three-dimensional porous silicon-based composite anode material for a lithium ion battery according to claim 7, wherein in the step (3), the heat treatment refers to the three-dimensional obtained by the step (2). The porous silicon-based composite electrode precursor is heated to 200 ° C - 850 and allowed to stand at 200 ° C - 850 ° C for 2-6 hours for alloying treatment; then it is cooled to 100 ° C - After heat preservation at 200 ° C for 1-3 hours, it is annealed; after the end of the heat preservation, the electric heating is stopped, and it is cooled to room temperature with the furnace.

The method for preparing a three-dimensional porous silicon-based composite anode material for a lithium ion battery according to claim 8, wherein in the step (3), the temperature rising rate during the heating process is 3-15 ° C / Min.

A three-dimensional porous silicon-based composite negative electrode material for a lithium ion battery, which is produced by the production method according to any one of claims 1-9.