WO2017190587A1

WO2017190587A1 - Method for preparing lithium ion battery silicon anode through combination of diffusion welding and dealloying with laser surface remelting technique

Info

Publication number: WO2017190587A1
Application number: PCT/CN2017/080803
Authority: WO
Inventors: 黄婷; 孙丁月; 肖荣诗; 杨武雄
Original assignee: 北京工业大学
Priority date: 2016-05-02
Filing date: 2017-04-17
Publication date: 2017-11-09
Also published as: CN105870405B; CN105870405A

Abstract

A method for preparing a lithium ion battery silicon anode through combination of diffusion welding and dealloying with laser surface remelting technique, comprising: preparing an aluminum-silicon alloy precursor by a laser surface remelting technique; welding the aluminum-silicon alloy precursor to a current collector through a diffusion welding process; and using a corrosive agent to remove element aluminum from the precursor to finally obtain a silicon anode metallurgically bonded to the current collector. The silicon material prepared according to the method is metallurgically bonded to the current collector, thus shedding of the silicon material from the current collector can be avoided effectively during charging and discharging; in addition, the operation is simple and efficiency is high.

Description

Method for preparing lithium ion battery silicon negative electrode by laser surface remelting technology composite diffusion welding and dealloying

Technical field

The invention relates to the field of preparation of a negative electrode of a lithium ion battery, in particular to a method for preparing a silicon negative electrode of a lithium ion battery by composite diffusion welding and de-alloying using a laser surface remelting technique.

Background technique

Lithium-ion batteries have been widely used in modern communications, portable electronic products, and hybrid vehicles due to their high specific energy, long life in charge and discharge, no pollution, and safety. The lithium ion battery is mainly composed of four parts, a positive electrode, a negative electrode, a separator and an electrolyte. The negative electrode is an important factor in determining the performance and price of a lithium ion battery. At present, the commercial anode material of lithium ion battery is mainly graphite carbon, the theoretical capacity is 372 mA·h/g, and the actual capacity is close to the theoretical value, which cannot meet the current demand.

The theoretical lithium storage capacity of silicon is 4200 mA·h/g, which is about ten times that of graphite. The voltage platform is moderate, and it is expected to replace graphite as a new anode material for lithium ion batteries. At present, silicon materials prepared by template method (magnesium thermal reduction method, CVD method) and non-template method (chemical etching method, electrochemical etching method) are micro-nano powders, and it is necessary to add a conductive agent and a binder to the surface of the current collector. . However, during the charging and discharging process of silicon, 300% volume change occurs, causing great damage to the structure of the electrode, thereby causing the silicon material to fall off with the current collector, losing electrical contact, and rapidly degrading the cycle performance.

By directly depositing silicon particles on the substrate by deposition sputtering, the structure and function can be directly integrated, but the combination of them and the current collector is mechanically combined. After several cycles, the active material and the current collector fall off. Loss of electrical contact, so the cycle performance drops rapidly. Cao Feifei et al. used magnetron sputtering to deposit silicon particles on the surface of copper. The current charge and discharge capacity was 1890m·Ah/g and 3800m·Ah/g at a current density of 300mA/g. (Cu-Si Nanocable Arrays as High-Rate Anode Materials for Lithium-Ion Batteries.. Feifei Cao et al. Adv. Mater. 2011, 23, 4415–4420) However, the silicon material prepared by the above method is still mechanically combined with the current collector. The damage of the electrode structure due to the volume change of silicon cannot be avoided.

The invention adopts a laser surface remelting composite diffusion welding and a de-alloying method, firstly preparing an aluminum-silicon precursor alloy coating on an aluminum alloy substrate by using a laser surface remelting technique, and then welding the precursor alloy with copper, and finally De-alloying, a silicon negative electrode metallurgically bonded to a copper current collector was prepared.

Summary of the invention

In order to solve the above problems, the present invention provides a method for preparing a silicon negative electrode of a lithium ion battery by composite diffusion welding and de-alloying using a laser surface remelting technique.

1. The invention adopts the following technical scheme: preparing a molten silicon layer of aluminum-silicon alloy by laser surface remelting technology, and separating the molten layer from the substrate to obtain an aluminum-silicon alloy precursor, and then using the diffusion welding to form the aluminum-silicon alloy precursor After welding with the current collector, the aluminum-silicon alloy precursor is subjected to chemical de-alloying treatment with an etchant to remove the elemental aluminum, and finally a silicon negative electrode combined with the current collector metallurgy is obtained.

2. Further, when the precursor is prepared by laser surface remelting technology, the remelting material is an aluminum silicon alloy, and the chemical composition percentage thereof is: Al: 50-95%, Si: 5-50%.

3. Further, the laser remelting treatment has a power density of 2 × 10 ⁴ to 2.5 × 10 ⁵ W/cm ² and a scanning speed of 2 to 30 mm/s.

4. Further, the current collector material is copper.

5. Further, the diffusion welding temperature is 450 to 550 ° C, the pressure is 0.5 to 2 Mpa, and the welding time is 0.5 to 1.5 hours.

6. Further, the etchant used for chemical de-alloying is sodium hydroxide, potassium hydroxide, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid or hydrofluoric acid.

7. Further, the concentration of sodium hydroxide, potassium hydroxide, hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid for chemical alloying is 1 to 5 mol/L, and the etching time is 2 to 12 hours.

When the silicon content is less than 5%, the active material silicon is too small, and when the silicon content is more than 50%, coarse primary silicon is formed, and the micro-nano silicon structure cannot be formed.

The invention adopts the method of laser surface remelting technology for compound diffusion welding and dealloying to prepare silicon negative electrode of lithium ion battery, and the advantages thereof are as follows:

1) The aluminum-silicon alloy precursor prepared by laser surface remelting technology has finer structure and obviously improves the uniformity of micro-nano silicon structure after chemical de-alloying.

2) The combination of silicon and copper current collector metallurgy can effectively prevent porous silicon from escaping from the current collector during charge and discharge, and can be directly used for the negative electrode of lithium ion battery.

DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a SEM image of a lower cross section of a silicon negative electrode of the present invention.

2 is a SEM image of a high-power lower cross section of a silicon negative electrode of the present invention.

detailed description

The present invention will be further described in detail below with reference to specific embodiments, and two embodiments are provided, but the invention is not limited to the following embodiments.

Example 1

1. Raw materials:

(1) Aluminum-silicon bulk alloy, Al: Si = 95: 5 wt.%.

(2) Corrosion solution: 3 mol/L HCL solution.

2. Preparation method

1. Preparation of aluminum-silicon alloy precursor:

The laser remelting process was carried out on the IPG fiber laser YLS-6000 and its supporting KUKA robot. The laser power was 4.5 kW, the scanning speed was 8 mm/s, and the spot diameter was 5 mm. The surface of the aluminum-silicon alloy was laser remelted. , protective gas: argon, protective gas flow: 18L / min. The fused layer is then separated from the substrate to obtain an aluminum silicon alloy precursor.

Second, diffusion welding:

The aluminum-silicon alloy precursor is closely adhered to the copper current collector, and the aluminum silicon cladding layer is closely adhered to the copper current collector, and heated in a vacuum atmosphere for 1 hour to raise the temperature from room temperature to 530 ° C. Applying a pressure of 0.5 KPa, the micro-plastic deformation of the joint interface is brought into close contact, and after 1 hour of heat preservation, the atoms mutually diffuse to form a strong metallurgical bond.

Third, chemical dealloy treatment:

The sample obtained by diffusion welding was immersed in a 3 mol/L HCL solution for 2 hours, then washed 3 times with deionized water, and then placed in a mass percentage of 2% HF ethanol solution for 2 hours to dissolve the silicon surface. SiO _{2 was} washed several times with deionized water and absolute ethanol to obtain a silicon negative electrode, which was finally stored in alcohol for use.

Silicon anode performance index: the first charge and discharge efficiency is 73.53%, the first charge and discharge capacity is 2500mA·h/g, 3400mA·h/g. The capacity after 500 cycles was 500 mA·h/g.

Example 2

1. Raw materials:

(1) Aluminum-silicon bulk alloy, Al: Si = 88: 12 wt.%.

(2) Corrosion solution: 3 mol/L HCL solution.

2. Preparation method

First, the preparation of aluminum-silicon alloy:

The laser remelting process was carried out on the IPG fiber laser YLS-6000 and its supporting KUKA robot. The laser power was 5.5 kW, the scanning speed was 10 mm/s, and the spot diameter was 5 mm. The surface of the aluminum-silicon alloy was laser remelted. , protective gas: argon, protective gas flow: 18L / min. The molten layer is then separated from the substrate to obtain an aluminum silicon alloy precursor.

Second, diffusion welding:

The aluminum-silicon alloy precursor is closely adhered to the copper current collector, heated in a vacuum for 1 hour, and raised from room temperature to a temperature of 520 ° C, and a pressure of 0.5 KPa is applied thereto to make the joint interface micro-plastic deformation to achieve close contact. After 1 hour of heat retention, the atoms diffuse together to form a strong metallurgical bond.

Third, chemical dealloy treatment:

The sample obtained after diffusion welding was immersed in a 3 mol/L HCL solution for 8 hours, then washed 3 times with deionized water, and then placed in a mass percentage of 2% HF ethanol solution for 2 hours, and the dissolved silicon surface may exist. The SiO _{2 was} washed several times with deionized water and absolute ethanol to obtain a silicon negative electrode.

Silicon anode performance index: The first charge and discharge capacity is 2400 mA·h/g, 3300 mA·h/g, the first charge and discharge cycle efficiency is 72.73%, and the capacity after 20 cycles is 460 mA·h/g.

Example 3

1. Raw materials:

(1) Aluminum-silicon bulk alloy (-325 mesh, 99%), Al: Si = 50: 50 wt.%.

(2) Corrosion solution: 3 mol/L HCL solution.

2. Preparation method

First, the preparation of aluminum-silicon alloy:

The laser remelting process was carried out on the IPG fiber laser YLS-6000 and its supporting KUKA robot. The surface of the aluminum-silicon alloy was laser remelted to obtain the aluminum-silicon alloy precursor. Laser power: 5.5 kW, scanning speed: 6 mm/s, spot diameter: 5 mm, shielding gas: argon, protective gas flow: 15 L/min. The fused layer is then separated from the substrate to obtain an aluminum silicon alloy precursor.

Second, the diffusion welding process:

Third, chemical dealloy treatment:

The sample obtained by diffusion welding was immersed in a 3 mol/L HCL solution for 10 hours, the reaction was stopped, and then washed 3 times with deionized water, followed by stirring in a 2% by mass HF ethanol solution for 2 hours to dissolve the silicon surface. The SiO ₂ which may be present is washed several times with deionized water and absolute ethanol to obtain a silicon negative electrode.

Silicon anode performance index: the first charge and discharge efficiency is 74.27%, the first charge and discharge capacity is 2540mA·h/g, 3420mA·h/g, and the capacity after 10 cycles is 750mA·h/g.

Example 4

1. Raw materials:

(1) Aluminum-silicon bulk alloy, Al: Si = 88: 12 wt.%.

(2) Corrosion solution: 3 mol/L HCL solution.

2. Preparation method

First, the preparation of aluminum-silicon alloy:

The laser remelting process was carried out on the IPG fiber laser YLS-6000 and its supporting KUKA robot. The laser power was 5.5 kW, the scanning speed was 7 mm/s, and the spot diameter was 5 mm. The laser remelting treatment was performed on the surface of the aluminum-silicon alloy. , protective gas: argon, protective gas flow: 18L / min. The molten layer is then separated from the substrate to obtain an aluminum silicon alloy precursor.

Second, diffusion welding:

The aluminum-silicon alloy precursor is closely adhered to the copper current collector, heated in a vacuum for 1 hour, and raised from room temperature to a temperature of 550 ° C, and a pressure of 1 KPa is applied thereto to make the joint interface micro-plastic deformation reach close contact, and then After 1 hour of heat retention, the atoms diffuse together to form a strong metallurgical bond.

Third, chemical dealloy treatment:

The sample obtained after the diffusion welding was immersed in a 3 mol/L HCL solution for 12 hours, then washed three times with deionized water, and then placed in a mass percentage of 2% HF ethanol solution for 2 hours, and the dissolved silicon surface may exist. The SiO _{2 was} washed several times with deionized water and absolute ethanol to obtain a silicon negative electrode.

Silicon anode performance index: The first charge and discharge capacity is 3900mA·h/g, 2800mA·h/g, the first charge and discharge cycle efficiency is 71.79%, and the capacity after 2000 cycles is 2000mA·h/g.

1 and 2 are cross-sectional SEM images of a silicon negative electrode of Example 4 of the present invention.

Claims

A method for preparing silicon anode of lithium ion battery by laser surface remelting composite diffusion welding and dealloying, characterized in that: laser surface remelting technology is used to prepare aluminum silicon alloy molten layer, and the molten layer is separated from the substrate The aluminum-silicon alloy precursor is obtained, and then the aluminum-silicon alloy precursor is welded to the current collector by diffusion welding. Finally, the aluminum-silicon alloy precursor is subjected to chemical de-alloying treatment with an etchant to remove the elemental aluminum, and finally obtains the current metallurgy with the current collector. Combined silicon negative electrode.
The method for preparing a silicon negative electrode for a lithium ion battery by laser surface remelting by composite diffusion welding and de-alloying according to claim 1, wherein when the precursor is prepared by laser surface remelting, the remelting material is an aluminum silicon alloy. The chemical composition percentage is: Al: 50 to 95%, Si: 5 to 50%.
The method for preparing a silicon negative electrode for a lithium ion battery by laser surface remelting composite de-alloying according to claim 1, wherein the laser remelting treatment has a power density of 2×10 4 to 2.5×10 5 W/cm 2 . The scanning speed is 2 to 30 mm/s.
The method of claim 1, wherein the current collector material is copper.
The method for preparing a silicon negative electrode for a lithium ion battery by using a laser surface remelting technique for composite diffusion welding and de-alloying according to claim 1, wherein the diffusion welding temperature is 450 to 550 ° C, the pressure is 0.5 to 2 Mpa, and the welding time is 0.5 to 1.5. hour.
The method for preparing a silicon anode of a lithium ion battery by using a laser surface remelting technique for composite diffusion welding and de-alloying according to claim 1, wherein the etchant used for chemical de-alloying is sodium hydroxide, potassium hydroxide, hydrochloric acid, sulfuric acid, Nitric acid, phosphoric acid or hydrofluoric acid.
The method for preparing a silicon negative electrode for a lithium ion battery by laser surface remelting composite diffusion welding and de-alloying according to claim 1, characterized in that: chemical de-alloying uses sodium hydroxide, potassium hydroxide, hydrochloric acid, sulfuric acid, nitric acid, The concentration of hydrofluoric acid is 1 to 5 mol/L, and the etching time is 2 to 12 hours.