WO2013159471A1

WO2013159471A1 - Porous thin film silicon-based negative electrode material of high-performance lithium ion cell and preparation method thereof

Info

Publication number: WO2013159471A1
Application number: PCT/CN2012/079976
Authority: WO
Inventors: 刘萍; 乔永民; 李辉; 吴敏昌; 丁晓阳; 李�杰; 郑俊军
Original assignee: 宁波杉杉新材料科技有限公司
Priority date: 2012-04-26
Filing date: 2012-08-10
Publication date: 2013-10-31
Also published as: JP2014521196A; JP5951014B2; CN102683656A; CN102683656B

Abstract

Disclosed are a porous thin film silicon-based negative electrode material of a high-performance lithium ion cell and a preparation method thereof. The present invention adopts a three-dimensional porous current collector material, such as a copper foil mesh, a copper wire mesh, foamed copper, or foamed nickel. A magnetron sputtering method is used to form a layer of a silicon thin film or a silicon-metal composite thin film on the copper foil mesh, copper wire mesh, foamed copper, or foamed nickel, and then a three-dimensional porous thin film silicon-based negative electrode material is formed through heat treatment. In the present invention, with the forming of the three-dimensional porous structure and the silicon-metal alloy, and a fine bonding force between the thin film negative electrode material and the three-dimensional porous current collector, the cell prepared using the porous thin film silicon-based negative electrode material has high discharge capacity and initial charge-discharge efficiency, and good cycle performance. The method of the present invention is easy to operate, and has wide application prospect in the field of lithium cell negative electrode.

Description

High-performance lithium ion battery porous film silicon-based anode material and preparation method thereof

Technical field

The invention relates to a lithium ion anode material with high specific capacity and cycle stability, and particularly relates to a porous film silicon-based anode material and a preparation method thereof, and belongs to the field of lithium ion batteries.

Background technique

Lithium-ion batteries are known as the ideal energy source, green energy source and leading power source in the 21st century, showing broad application prospects and potentially huge economic benefits. With advances in the electronics industry, electric vehicles, and aerospace technology, higher performance is required for the performance of lithium-ion batteries that provide energy. Therefore, to achieve breakthroughs in energy density and power density of lithium-ion batteries, the crucial "bottleneck" problem is how to design and develop new electrode materials.

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), and the volume expansion in the process of inserting and deintercalating lithium is basically 9%. Below, it exhibits high coulombic efficiency and excellent cycle stability. However, the lower theoretical lithium storage capacity of the graphite electrode itself (LiC ₆ , 372 mAh/g) makes it difficult to make breakthroughs. 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 Theoretical lithium storage capacity (Li ₂₂ Si ₅ , 4200mAh/g), low lithium insertion potential (less than 0.5V) Vs Li/Li+), low electrolyte reactivity, abundant natural reserves, and low price have attracted much attention. 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. In the process of highly inserting and deintercalating lithium, the silicon-based material has a very significant volume expansion (volume expansion rate >300%) similar to that of general alloy materials. The resulting mechanical stress causes the electrode material to gradually powder during the cycle. The material structure is destroyed 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 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 this kind of materials.

So far, measures to improve the performance of silicon anodes include: by designing the composition and microstructure of silicon-based anode materials to suppress their volume changes and improve conductivity; developing binders and electrolyte additives suitable for silicon anodes; exploring new current collectors and Electrode structure, etc. Among them, the breakthrough of electrochemical properties of silicon-based materials is still the key to commercialization of silicon anodes. The main strategy for improving silicon-based materials is to design the composition and microstructure of the material to accommodate the bulk 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, control capacity attenuation, and improve cycle stability; and thinning of the material can make lithium The ions diffuse rapidly, resulting in reversibility of the material and high current cycle stability. (3) The compounding is to use the synergistic effect between the components of the composite material to achieve the complementary advantages. It 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 a multi-phase composite anode material to improve the long-term cycle 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 of a silicon-nonmetal composite system and a silicon-metal composite system. The latter is also classified into a silicon/inert lithium intercalation metal composite system and a silicon/active lithium intercalation metal composite system according to whether the metal has lithium intercalation activity. From the existing research, the silicon/inert lithium intercalation composite has better cycle stability, and the capacity of the silicon/active lithium intercalation composite is higher.

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 recombining with the metal is to improve the conductivity of silicon on the one hand, and to disperse and buffer on the other hand. 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. It can alleviate the internal stress caused by the volume effect, thereby enhancing the structural stability of the material and improving 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.

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 far from the industrialization.

(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 The volume expansion effect of flushing Si 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. Other methods have limited effectiveness in improving stability and are highly polluting to the environment. Finding a matrix that is more capable of buffering volume changes and having higher conductivity; Designing and constructing a more porous film structure is undoubtedly one of the main strategies for developing silicon-based anode materials.

Summary of the invention

The object of the present invention is to adapt to the development trend of lithium ion batteries, and to solve the problem of serious volume effect of lithium ion battery high-capacity silicon-based anode material in electrochemical lithium-intercalation process, affecting the cycle performance of electrode materials, and low-level materials. The conductive property provides a novel high-capacity three-dimensional porous thin film silicon-based anode material preparation method with high reversibility and good cycle performance without introducing a conductive agent and a binder.

In order to achieve the above object, the present invention integrates an active/active, active/inactive composite system, a porous and thin film method to prepare a three-dimensional porous film silicon-based anode material. The technical solution adopted is: a method for preparing a three-dimensional porous film silicon-based anode material for a lithium ion battery, comprising the following steps: Step (1): cleaning a three-dimensional porous current collector material to remove impurities such as surface oil and surface oxide. The three-dimensional porous current collector material is an inert lithium intercalation metal; the inert lithium intercalation metal refers to a metal that cannot form an intermetallic compound or alloy with lithium; and the inert lithium intercalation metal is preferably a copper foil mesh, considering economic cost. Any one of copper wire mesh, copper foam, and foamed nickel; Step (2): RaRotate elemental silicon, or elemental silicon and metal ruthenium by magnetron sputtering method [Radio-frequency (RF) magnetron sputtering method] Co-sputtering on a copper foil mesh, a copper mesh, a copper foam or a foamed nickel current collector to obtain a three-dimensional porous thin film silicon-based electrode precursor, the metal M being an active lithium intercalation metal; the active lithium intercalation metal Means a metal that forms an intermetallic compound or alloy with lithium, such as magnesium, calcium, aluminum, bismuth, tin, lead, arsenic, antimony, bismuth, platinum, silver, gold, cadmium, indium, etc.; In view of environmental requirements and economic costs, the active lithium intercalation metal is preferably tin, magnesium and aluminum. Any one or a combination of two or more; and the step (3): subjecting the three-dimensional porous thin film silicon-based electrode precursor obtained in the step (2) to heat treatment under vacuum or an inert atmosphere to obtain a three-dimensional porous thin film silicon-based negative electrode material. As used herein, the term "silicon based" refers to a lithium ion battery anode material that uses silicon and a silicon metal alloy as active materials. The term "vacuum" means a degree of vacuum of at least lx 10- ² Pa.

In the step (1) of the above technical solution, the copper foil mesh, the copper mesh or the foamed copper has a porosity of not less than 95.0%, an average pore diameter of 50 to 200 μm, and a thickness of 50 μm to 400 μm.

In the step (2) of the above technical solution, the purity of the elemental silicon target used is at least 99.99%. The purity of the Sn target, the Mg target, and the A1 target used was at least 99.99%. The "purity" refers to the mass percentage. The mass ratio of the elemental silicon to the metal M is between 1:1 and 9:1. When two or more metals are used, the ratio of the mass sum of the elemental silicon to the two or more metals is 1:1. Until 9:1. The composition of the alloy film is controlled mainly by controlling the sputtering power of the silicon target and the metal target, and the ratio of silicon to metal directly affects the capacity and cycle stability of the porous film material.

In the step (2), the working conditions of the magnetron sputtering method are: (1) the background vacuum is 1.0×10-5 to 1. Ox 10- ³ Pa; (2) the working pressure during sputtering is 0.2 to 0.8 Pa; (3) The flow rate of argon Ar is 40 to 60 sccm; (4) The sputtering power of different targets is as follows: Si is 150 to 300 W, A1 is 30 to 60 W, Sn is 25 to 50 W, and Mg is 30 to 60 W; (5) The sample table revolution speed is 15 to 20 rpm; (6) The sputtering time is 2 to 8 hours. As used herein, the term "working gas pressure" refers to the pressure of an inert gas (e.g., argon) used in performing a magnetron sputtering operation.

In the step (2), the magnetron sputtering porous film has a thickness of 300 nm to 3 μm. In the step (3) of the above technical solution, the heat treatment refers to heating the three-dimensional porous thin film silicon-based electrode precursor obtained in the step (2) to 200 ° C to 800 ° C and making it at 200 ° C. After being kept at 800 ° C for 2 to 5 hours, it is alloyed; then, after cooling to 100 ° C to 200 ° C, it is further incubated for 1 to 3 hours to be annealed; The electric heating is stopped, allowed to cool to room temperature with the furnace, and the heat treatment process is always maintained in a vacuum or an inert atmosphere. The rate of temperature rise during the temperature increase is 3 to 15 ° C / min. The "warming to 200 ° C to 800 ° C" means heating from room temperature to 200 ° C to 800 ° 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 an inert atmosphere" means the process of the heat treatment, including the temperature rise, the two heat preservation, and the stage of cooling with the furnace are always kept vacuum or inert. Atmosphere. However, in order to save energy, especially when vacuum conditions are formed by using a vacuum device, since the operation of the vacuum device requires energy consumption, when it is cooled to below 85 ° C, the vacuum device can be allowed to be turned off.

As used herein, the alloying treatment means holding the alloy 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, by interdiffusion or partial interdiffusion to form a corresponding alloy, alloy The formation is beneficial to improve the electrochemical performance (specific capacity and cycle performance) of the three-dimensional porous thin film silicon-based anode material. The annealing treatment can promote the homogenization of the alloy composition, grain refinement, stress elimination, increase the bonding force between the material and the current collector, and improve the plasticity for processing. The heat treatment improves the microstructure of the three-dimensional porous film silicon-based electrode precursor, so that the elemental silicon or Si-M microparticles are uniformly and stably distributed in the three-dimensional network structure of the copper foil mesh, the copper mesh, the copper foam or the foamed nickel. In the middle, the bonding between the materials and the matrix is improved, and the mechanical properties of the material are also improved, thereby suppressing the volume change of the active material during charging and discharging, and improving the cycle stability of the silicon-based anode material.

Another aspect of the invention provides a high performance lithium ion battery three dimensional porous film silicon based negative electrode material prepared by the method described herein.

The beneficial effects of the present invention are as follows:

(1) With magnetron sputtering technology, it is not necessary to add conductive agent and adhesive. The preparation of electrode active material and electrode forming are completed at the same time, which simplifies the process and reduces the process cost.

(2) The active material of the porous film electrode of the present invention is mainly a partial alloy formed of Si and Si-M; the specific storage capacity of lithium can be adjusted by the content of high-capacity silicon as the main active material in the electrode active material.

(3) The active lithium intercalation metal M itself has good conductivity and lithium intercalation performance, and the 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 Internal stress caused by the effect, thereby enhancing the structural stability of the material and improving its cycle performance;

(4) The electrode active material is sputtered into the three-dimensional network porous structure of the current collector in the present invention, without introducing an adhesive, as compared with the electrode prepared by directly coating the electrode active material on the current collector foil. It has better electrical contact (that is, the porous structure of the current collector can enhance the bonding force between the current collector and the active material of the film), which is favorable for large current charge and discharge;

(5) The current collector having a three-dimensional network porous structure in the present invention provides a "conducting and yet High toughness" skeleton, which not only serves as an electrode support and current collector, but also can utilize its physical and chemical affinity to interdiffusion or partial interdiffusion with the active anode material during heat treatment, thereby improving the structure of the entire battery. Coordination of stability and performance; on the other hand, since the system itself has a three-dimensional network porous structure, the contact area between the material and the electrolyte can be greatly improved, and the polarization can be reduced; the volume of the alloy electrode during charging and discharging can be alleviated. Change, improve the charge and discharge cycle performance of the alloy electrode; can also improve the high rate charge and discharge performance of the alloy electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Fig. 2 is a view showing a three-dimensional porous film silicon-based negative electrode material of Example 1.

Fig. 3 is a view showing a three-dimensional porous film silicon-based negative electrode material of Example 2.

Fig. 4 is a view showing a three-dimensional porous film silicon-based negative electrode material of Example 5.

Fig. 5 is a view showing a three-dimensional porous film silicon-based negative electrode material of Example 6.

Fig. 6 is a graph showing the cycle performance of a three-dimensional porous film silicon-based negative electrode 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 having a porosity of 98.0% and an average pore diameter of ΙΟΟμπι and a thickness of 70 μm was sequentially ultrasonically cleaned with copper, 10% by mass of dilute hydrochloric acid, distilled water and absolute ethanol to remove surface oil and surface. Impurities such as oxides.磁 Using magnetron sputtering, with a purity of 99.99% Si as the target, the copper foil mesh current collector as the substrate, the background vacuum is 1.0x l0_ ³ Pa, the working pressure at the time of sputtering is 0.2Pa, Ar gas Ar The flow rate was 40 sccm, the sputtering power of the Si target was 150 W, the revolution speed of the sample stage was 15 rpm, the sputtering time was 2 hours, and the thickness of the film obtained by sputtering was 300 nm. The obtained three-dimensional porous film silicon-based electrode precursor is placed in a box furnace and heat-treated under vacuum or an inert atmosphere at a heat treatment temperature of 700 ° C, a heating rate of 12 ° C / min, and a holding time of 3.5 hours. It is alloyed; then it is cooled to 200 ° C and then insulated for 1.5 h, and then annealed; after the end of the heat, the electric heating is stopped, and the furnace is cooled to room temperature to obtain a three-dimensional porous film silicon-based anode material. Its electrode active material is mainly Si. To prevent oxidation, the heat treatment process always maintains a vacuum or an inert atmosphere.

The obtained three-dimensional porous film silicon-based composite negative electrode sheet and metallic lithium 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 2300 mAh/g, the first efficiency is 88%, and after 50 cycles, it can still maintain 95% capacity.

Example 2: A copper foam having a porosity of 98.0%, an average pore diameter of 150 μm, and a thickness of 400 μm was sequentially ultrasonically washed with copper, 10% by mass of dilute hydrochloric acid, distilled water and absolute ethanol to remove surface oil and surface oxidation. Impurities such as matter.磁 Using magnetron sputtering, with a purity of 99.999% Si as the target, a copper foam current collector as the substrate, a background vacuum of 1.0x lO_ ⁴ Pa, a working pressure of 0.8 Pa during sputtering, Ar gas The flow rate was 60 sccm, the sputtering power of the Si target was 300 W, the traveling speed of the sample stage was 20 rpm, the sputtering time was 8 hours, and the thickness of the film obtained by sputtering was 1.0 μm. The obtained three-dimensional porous film silicon-based electrode precursor is placed in a box furnace and heat-treated under vacuum or an inert atmosphere at a heat treatment temperature of 800 ° C, a heating rate of 15 ° C / min, and a holding time of 2 hours. It is alloyed; then it is kept at 200 ° C for another 2 hours. After annealing, the electric heating is stopped, and the furnace is cooled to room temperature to obtain a three-dimensional porous thin film silicon-based anode material, and the electrode active material is mainly Si. To prevent oxidation, the heat treatment process always maintains a vacuum or an inert atmosphere.

The obtained three-dimensional porous film silicon-based negative electrode sheet and metallic lithium 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 2600 mAh/g, the first efficiency is 92%, and after 50 cycles, it can still maintain 97% capacity.

Example 3: A copper foil mesh having a porosity of 98.0%, an average pore diameter of 50 μm, and a thickness of 50 μm was sequentially ultrasonically cleaned with copper, 10% (mass percent) diluted hydrochloric acid, distilled water and absolute ethanol to remove surface oil and surface. Impurities such as oxides.磁 Using magnetron sputtering, with a purity of 99.998% Si and a purity of 99.99% Sn as targets (and Si: Sn=l: l), copper foil mesh current collector as the substrate, the background vacuum is 2.0 Xl (T ⁴ Pa, working pressure at sputtering is 0.3 Pa, flow rate of Ar gas is 40 sccm, sputtering power of Si target is 200 W, sputtering power of Sn target is 25 W, revolution speed of sample stage is 18 rpm, sputtering The film thickness was 3.0 μm when the time was 8 hours. The obtained three-dimensional porous film silicon-based electrode precursor was placed in a box furnace and heat-treated under vacuum or an inert atmosphere at a heat treatment temperature of 200 ° C. It is 3 ° C / min, the holding time is 5 hours, it is alloyed; then it is kept at 100 ° C for 3 hours, then it is annealed; after the heat is kept, the electric heating is stopped, so that After cooling to room temperature with the furnace, a three-dimensional porous film silicon-based anode material is obtained, and the electrode active material is mainly a part of alloy formed by Si and Si-Sn. To prevent oxidation, the heat treatment process always maintains a vacuum or an inert atmosphere.

The obtained three-dimensional porous film silicon-based negative electrode sheet and metallic lithium 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 1300 mAh/g, the first efficiency is 91%, and after 50 cycles, it can still maintain 97% capacity.

Example 4: A copper mesh having a porosity of 96.0% and an average pore diameter of ΙΟΟμπι and a thickness of 150 μm was sequentially ultrasonically cleaned with copper, 10% (mass%) diluted hydrochloric acid, distilled water and absolute ethanol to remove impurities such as surface oil and surface oxide. .磁 Using magnetron sputtering, with a purity of 99.997% Si and a purity of 99.999% Sn (and Si: Sn=5: 1), copper mesh collector as the substrate, the background vacuum is 6.0 Xl (T ⁴ Pa, working pressure is 0.4 Pa during sputtering, flow rate of Ar gas is 50 sccm, sputtering power of Si target is 300 W, sputtering power of Sn target is 50 W, revolution speed of sample stage is 20 rpm, sputtering time is The thickness of the film obtained by sputtering was 2.3 μm in 6 hours. The obtained three-dimensional porous film silicon-based electrode precursor was placed in a box furnace and heat-treated under vacuum or an inert atmosphere at a heat treatment temperature of 230 ° C and a heating rate of 5 °C/min, holding time is 3.5 hours, make it alloying; then let it cool down to 100 °C for another 2 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 anode material is obtained, and the electrode active material is mainly a part of alloy formed by Si and Si-Sn. To prevent oxidation, the heat treatment process always maintains a vacuum or an inert atmosphere.

The obtained three-dimensional porous film silicon-based negative electrode sheet and metallic lithium 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 1600mAh/g, the first efficiency is 88%, and after 50 cycles, it can still maintain 94% capacity.

Example 5: A copper foil mesh having a porosity of 98.0%, an average pore diameter of 50 μm, and a thickness of ΙΟΟμπι was sequentially ultrasonically cleaned with copper, 10% (mass percent) diluted hydrochloric acid, distilled water and absolute ethanol to remove surface oil and surface. Impurities such as oxides.磁 Using magnetron sputtering, with a purity of 99.996% Si and a purity of 99.995% of Mg as targets (and Si: Mg=6: 1), copper foil mesh current collector as the substrate, the background vacuum is 2.0 Xl (T ⁴ Pa, working pressure at sputtering is 0.5Pa, flow rate of argon Ar is 50sccm, sputtering power of Si target is 200W, sputtering power of Mg target is 30W, revolution speed of sample stage is 15 rpm, sputtering time is The thickness of the film obtained by sputtering was 2.2 μm in 4 hours. The obtained three-dimensional porous film silicon-based electrode precursor was placed in a box furnace and heat-treated under vacuum or an inert atmosphere at a heat treatment temperature of 550 ° C and a heating rate of 9 °C/min, holding time is 4 hours, make it alloying; then let it cool down to 150 °C for another 2 hours, let it carry out Annealing treatment; After the end of the heat preservation, the electric heating is stopped, and the furnace is cooled to room temperature to obtain a three-dimensional porous film silicon-based anode material, and the electrode active material is mainly a part of alloy formed by Si and Si-Mg. To prevent oxidation, the heat treatment process always maintains a vacuum or an inert atmosphere.

The obtained three-dimensional porous film silicon-based negative electrode sheet and metallic lithium 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 90%, and after 50 cycles, it can still maintain 95% capacity.

Example 6: A foamed nickel having a porosity of 96.0%, an average pore diameter of 150 μm, and a thickness of 300 μm was sequentially ultrasonically washed with copper, 10% by mass of dilute hydrochloric acid, distilled water and absolute ethanol to remove surface oil and surface oxidation. Impurities such as matter.磁 Using magnetron sputtering, with a purity of 99.999% Si and a purity of 99.999% Mg (and Si: Mg=9: 1), a foamed nickel current collector as the matrix, the background vacuum is 1.0xl (T ⁴ Pa, working pressure is 0.6 Pa during sputtering, flow rate of Ar gas is 60 sccm, sputtering power of Si target is 300 W, sputtering power of Mg target is 60 W, revolution speed of sample stage is 18 rpm, sputtering time is 6 The thickness of the film obtained by sputtering was 2.0 μm. The obtained three-dimensional porous film silicon-based electrode precursor was placed in a box furnace and heat-treated under vacuum or an inert atmosphere at a heat treatment temperature of 620 ° C and a heating rate of 10 °. C/min, the holding time is 2.5 hours, and it is alloyed; then it is kept at 200 °C for another hour, then it is annealed; after the heat is kept, the electric heating is stopped, and it is cooled with the furnace. At room temperature, a three-dimensional porous thin film silicon-based negative electrode material is obtained, and the electrode active material is mainly a partial alloy formed of Si and Si-Mg. To prevent oxidation, the heat treatment process always maintains a vacuum or an inert atmosphere.

The obtained three-dimensional porous film silicon-based negative electrode sheet and metallic lithium 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 2100 mAh/g, the first efficiency is 88%, and after 50 cycles, it can still maintain 93% capacity.

Example A copper mesh having a porosity of 98.0% and an average pore diameter of ΙΟΟμπι and a thickness of 50 μm was sequentially ultrasonically cleaned with copper, 10% (mass%) diluted hydrochloric acid, distilled water and absolute ethanol to remove impurities such as surface oil and surface oxide. .磁 Using magnetron sputtering, with a purity of 99.995% Si and a purity of 99.995% A1 as targets (and Si: Al=8: 1), copper mesh collector as the matrix, the background vacuum is 6.0 Xl (T ⁴ Pa, working pressure is 0.2Pa during sputtering, flow rate of Ar gas is 40sccm, sputtering power of Si target is 200W, sputtering power of A1 target is 30W, revolution speed of sample table is 15rpm, sputtering time is After 4 hours, the thickness of the film obtained by sputtering was 1.8 μm. The obtained three-dimensional porous film silicon-based electrode precursor was placed in a box furnace and heat-treated under vacuum 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 thin film silicon-based negative electrode material is obtained, and the electrode active material is mainly a partial alloy formed of Si and Si-Al. To prevent oxidation, the heat treatment process always maintains a vacuum or an inert atmosphere.

The obtained three-dimensional porous film silicon-based negative electrode sheet and metallic lithium 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 92%, and after 50 cycles, it can still maintain 97% capacity.

Example 8: A foamed copper having a porosity of 96.0%, an average pore diameter of 200 μm, and a thickness of 200 μm was sequentially ultrasonically washed with copper, 10% by mass of dilute hydrochloric acid, distilled water and absolute ethanol to remove surface oil and surface oxidation. Impurities such as matter.磁 Using magnetron sputtering, with a purity of 99.999% Si and a purity of 99.999% A1 as targets (and Si: Al=4: 1), a copper foam current collector as the matrix, the background vacuum is 1.0xl (T ⁵ Pa, working pressure is 0.8Pa during sputtering, flow rate of Ar gas is 60sccm, sputtering power of Si target is 300W, sputtering power of A1 target is 60W, revolution speed of sample table is 20rpm, sputtering time is 6 The film thickness obtained by sputtering is 2.6 μm. The obtained three-dimensional porous film silicon-based electrode precursor is placed in a box furnace and heat-treated under vacuum 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, and it is alloyed; then it is kept at 200 °C for 2 hours, then it is retreated. After the heat treatment, the electric heating is stopped, and the furnace is cooled to room temperature to obtain a three-dimensional porous film silicon-based anode material, and the electrode active material is mainly a part of alloy formed by Si and Si-Al. To prevent oxidation, the heat treatment process always maintains a vacuum or an inert atmosphere.

The obtained three-dimensional porous film silicon-based negative electrode sheet and metallic lithium 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 1700 mAh/g, the first efficiency is 91%, and after 50 cycles, it can still maintain 95% capacity.

Example 9: A foamed nickel having a porosity of 95.0%, an average pore diameter of 150 μm, and a thickness of 400 μm was sequentially ultrasonically washed with copper, 10% by mass of dilute hydrochloric acid, distilled water and absolute ethanol to remove surface oil and surface oxidation. Impurities such as matter.磁 Using magnetron sputtering, with a purity of 99.996% Si, a purity of 99.995% Sn, and a purity of 99.996% of Mg as targets (and Si: (Sn+Mg)=7: 1 ), foamed nickel set The fluid is a matrix, the background vacuum is 3.0xl (T ⁴ Pa, the working pressure is 0.3Pa during sputtering, the flow rate of Ar gas is 50sccm, the sputtering power of Si target is 200W, and the sputtering power of Sn target is 25W, Mg The target sputtering power was 30 W, the sample stage revolution speed was 15 rpm, the sputtering time was 5 hours, and the film thickness obtained by sputtering was 2.7 μm. The obtained three-dimensional porous film silicon-based electrode precursor was placed in a box furnace under vacuum. Or heat treatment under an inert atmosphere, the heat treatment temperature is 230 ° C, the heating rate is 5 ° C / min, the holding time is 5 hours, and it is alloyed; then it is kept at 100 ° C for another 3 hours. After annealing, the electric heating is stopped, and the furnace is cooled to room temperature to obtain a three-dimensional porous thin film silicon-based anode material, and the electrode active material is mainly a part of alloy formed by Si, Si-Sn and Si-Mg. To prevent oxidation, the heat treatment process always maintains a vacuum or an inert atmosphere.

The obtained three-dimensional porous film silicon-based negative electrode sheet and metallic lithium 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 98% capacity.

Example 10: A copper foil mesh having a porosity of 97.0% and an average pore diameter of ΙΟΟμπι and a thickness of 90 μm was sequentially ultrasonically cleaned with copper, 10% (mass%) diluted hydrochloric acid, distilled water and absolute ethanol to remove impurities such as surface oil and surface oxide. .磁 Using magnetron sputtering, with a purity of 99.998% Si, a purity of 99.996% A1 and a purity of 99.995% of Mg as targets (and Si: (Al+Mg)=9: 1), copper foil mesh The current collector is a substrate, the background vacuum is 5.0×1 (T ⁴ Pa, the working pressure is 0.5 Pa when sputtering, the flow rate of Ar gas is 40 sccm, the sputtering power of Si target is 200 W, and the sputtering power of A1 target is 30 W, The sputtering power of the Mg target was 30 W, the traveling speed of the sample stage was 18 rpm, the sputtering time was 7 hours, and the thickness of the film obtained by sputtering was 2.9 μm. The obtained three-dimensional porous film silicon-based electrode precursor was placed in a box furnace. Heat treatment under vacuum or inert atmosphere, heat treatment temperature is 600 °C, heating rate is 6 °C / min, holding time is 3.5 hours, it is alloyed; then it is kept at 200 °C for 2 hours. After annealing, the electric heating is stopped, and the furnace is cooled to room temperature to obtain a three-dimensional porous thin film silicon-based anode material, and the electrode active material is mainly a part formed of Si, Si-Al and Si-Mg. Alloys. To prevent oxidation, the heat treatment process always maintains a vacuum or an inert atmosphere.

The obtained three-dimensional porous film silicon-based negative electrode sheet and metallic lithium 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 90%, and after 50 cycles, it can still maintain 97% capacity.

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

Claims

Claim

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

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

Step (2): 单 co-sputtering elemental silicon, or elemental silicon and metal M on a copper foil mesh, a copper mesh, a copper foam or a foamed nickel current collector by magnetron sputtering to obtain a three-dimensional porous thin film silicon base An electrode precursor, the metal M being a metal capable of forming an intermetallic compound or alloy with lithium, that is, an active lithium intercalation metal;

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

2 . The method for preparing a three-dimensional porous film silicon-based anode material for a high-performance lithium ion battery according to claim 1 , wherein in the step (1), the copper foil mesh, the copper mesh or the copper foam The porosity is not less than 95.0%, the average pore diameter is 50 to 200 μm, and the thickness is 50 μm to 400 μm.

The method according to claim 1, wherein in the step (2), the purity of the elemental silicon target used is at least 99.99%.

The method for preparing a three-dimensional porous thin film silicon-based negative electrode material for a high performance lithium ion battery according to claim 1, wherein in the step (2), the active lithium intercalated metal target has a purity of at least 99.99. %.

The method for preparing a three-dimensional porous thin film silicon-based negative electrode material for a high-performance lithium ion battery according to any one of claims 1 to 4, wherein in the step (2), the elemental silicon and the The mass ratio of metal ruthenium is between 1:1 and 9:1.

The method for preparing a three-dimensional porous thin film silicon-based negative electrode material for a high performance lithium ion battery according to claim 1, wherein in the step (2), the working condition of the magnetron sputtering method is:

(1) The background vacuum is 1.0x 10-5 to 1.0 l0" ³ Pa; (2) The working pressure during sputtering is 0.2 to 0.8 Pa;

(3) The flow rate of argon Ar is 40 to 60 sccm;

(4) The sputtering power of different targets is as follows: Si is 150 to 300 W, A1 is 30 to 60 W, Sn is 25 to 50 W, and Mg is 30 to 60 W;

(5) The sample table revolution speed is 15 to 20 rpm;

(6) The sputtering time is 2 to 8 hours.

The method for preparing a three-dimensional porous film silicon-based anode material for a high performance lithium ion battery according to claim 6, wherein in the step (2), the thickness of the magnetron sputtering porous film is 300 匪To 3μπι.

The method for preparing a three-dimensional porous film silicon-based negative electrode material for a high-performance lithium ion battery according to claim 1, wherein in the step (3), the heat treatment means that the heat is heated by electric heating. The three-dimensional porous thin film silicon-based electrode precursor obtained in the step (2) is heated to 200 ° C to 800 ° C, and is kept at 200 ° C to 800 ° C for 2 to 5 hours to be alloyed. After the temperature is lowered to 100 ° C to 200 ° C for another 1 to 3 hours, it is annealed; after the heat is kept, the electric heating is stopped, the furnace is cooled to room temperature, and the heat treatment process is always kept vacuum. Or an inert atmosphere.

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

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