WO2018032974A1

WO2018032974A1 - Method of preparing material of negative electrode of lithium ion battery

Info

Publication number: WO2018032974A1
Application number: PCT/CN2017/095797
Authority: WO
Inventors: 孙绍庆
Original assignee: 福建新峰二维材料科技有限公司
Priority date: 2016-08-15
Filing date: 2017-08-03
Publication date: 2018-02-22
Also published as: CN107768659A

Abstract

The invention discloses a method of preparing a material of a negative electrode of a lithium ion battery, effectively mitigating a size effect of silicon. The method comprises the following steps: firstly, preparing a modified graphene microchip; secondly, growing, on a surface of the graphene microchip, a silicon nanosphere, so as to obtain a graphene microchip-silicon nanosphere composite material; and depositing, using an atomic layer deposition technique, and on the surface of the graphene microchip-silicon nanosphere, a metal oxide layer; performing an electrostatic spinning and calcination treatment to obtain a carbon nanofiber composite material; performing an acid treatment on the carbon nanofiber composite material, removing a metal oxide layer to form a gap structure; and finally, forming a carbon coating layer covering outside the carbon nanofiber composite material. The method disclosed in the invention is utilized to prepare, using a simple preparation process, an accurate and controllable gap structure, effectively providing a space for volume expansion of the silicon in a charging and discharging process, and further protecting, using the carbon coating layer formed at the outermost layer, the silicon nanosphere, ensuring integrity of the electrode structure, and increasing stability of the electrode structure.

Description

Method for preparing lithium ion battery anode material with effective buffering silicon volume effect

Technical field

The invention relates to the technical field of a preparation method of a lithium ion battery anode material, in particular to a preparation method of a lithium ion battery anode material which effectively buffers the silicon volume effect.

Background technique

Lithium-ion batteries (LIBs) are ubiquitously used in portable electronics and network storage due to their relatively high discharge voltage, energy density, and good power performance. At present, more research is pursuing the electrode material with high theoretical capacity to replace the graphite anode material that has been developed. Among them, the silicon-based anode material is the most attractive alternative because it has a very high theoretical capacity of 4200 mAh g-1 (forming a fully lithiated state of Li4.4Si) and a low discharge voltage (the average deintercalation lithium voltage of Si is 0.4V). However, the cycle life of the electrode is limited due to cracking and pulverization caused by a large volume change (up to 311%) during charge and discharge.

Although numerous nano-silicon-based materials including silicon micro/nanotubes, nano-silicon spheres/carbon composites, nanoporous silicon and nanowires have been proposed as silicon anode materials that can improve cycle stability, but to make each silicon nanoparticle The manufacture of silicon-based electrodes with free expansion space remains a huge challenge. Another key factor limiting the long cycle life of silicon-based electrodes is the formation of an unstable solid electrolyte interface (SEI) on the surface of the electrode. If the SEI layer is deformed or broken, a new SEI needs to be formed on the surface of the electrode during the next charging process, which will result in poor cell coulombic efficiency, while the deposited solid electrolyte interface (SEI) will also hinder the transport of lithium ions. Many studies have focused on improving the stability of electrodes such that lithium-ion batteries still have relatively high capacities in tens or even hundreds of cycles. However, it is still far from meeting the cycle life required for its practical application. Therefore, now Nano silicon-based material preparation techniques for use in the preparation of anode materials for lithium ion batteries have yet to be improved.

Summary of the invention

In view of the above problems, the present invention provides a method for preparing a lithium ion battery anode material which effectively buffers the silicon volume effect.

In order to solve the above technical problem, the technical solution adopted by the present invention is: a method for preparing a negative electrode material for a lithium ion battery that effectively buffers a silicon volume effect, the method comprising the steps of: preparing a modified graphene microchip; and using a graphene microchip Nano-silicon spheres are grown on the surface to obtain graphene microchip-nano-silica composites; a precise thickness of metal oxide layer is deposited on the surface of graphene microchip-nano-silica sphere by atomic layer deposition technique; metal oxide layer is deposited on the surface The graphene microchip-nanosilicon sphere composite material is uniformly dispersed into the electrospinning solution, and is subjected to electrospinning and calcination treatment to obtain a carbon nanofiber composite material; the carbon nanofiber composite material is subjected to acid treatment to completely remove the metal oxide The layer forms a void structure, that is, a void structure is left between the nano-silicon spheres or graphene and the carbon nanofibers; and a carbon coating layer is formed on the outer surface of the carbon nanofiber composite.

Further, the method for preparing the modified graphene microchip is to first place the expanded graphite in a container, add 100-1000 ml of an organic solvent, and then oscillate under the condition of an ultrasonic vibration power of 300-1200 W and a temperature of 20-150 ° C. 1-24h, a graphene microchip suspension is obtained; then, it is allowed to stand for 20-300 min, the upper layer suspension is taken, the precipitate is removed, and after filtration, it is dried at 60-80 ° C to obtain a graphene microchip; then the obtained graphene micro Add the tablets to 20-100ml concentrated sulfuric acid, keep the solution temperature below 4 °C, slowly add 0.5-20g potassium permanganate, keep the solution temperature below 10 °C and magnetically stir for 60-120min and during magnetic stirring, Slowly add 150ml of deionized water; stir After the end of the mixing, 1-5 ml of hydrogen peroxide was added, and stirring was continued for 10-30 min; finally, the surface-modified graphene microchip was obtained by filtration and drying.

Further, the organic solvent is at least one of NMP, DMF, toluene, chlorobenzene, and trichloroethylene.

Further, the nano silicon ball is grown on the surface of the graphene microchip by a chemical vapor deposition (CVD) method; first, the graphene microchip is placed in a reaction chamber, vacuum is applied, and the reaction chamber is heated, when the temperature reaches After the reaction temperature, a carrier gas of 1-500 sccm is introduced to maintain the pressure of the reaction chamber at 0.01 Torr - 10 Torr, and then a reaction gas of 1-500 sccm is introduced into the reaction chamber, and the reaction gas is decomposed at a high temperature to form a nano-silica ball. On the surface of the graphene microplate of the substrate material, after the reaction is completed, the reaction gas, the carrier gas, and the heating device are sequentially turned off to obtain a graphene microchip-nanosilicon ball composite material.

Further, the nano-silica spheres grown on the surface of the graphene microchip have a size of about 1-100 nm and a reaction temperature of 650 ° C - 1000 ° C.

Further, the reaction gas for growing the nano silicon sphere on the surface of the graphene microchip is at least one of silane (SiH ₄ ) and dichlorosilane (SiH ₂ Cl ₂ ); the carrier gas is nitrogen (N ₂ ), argon At least one of gases (Ar).

Further, the metal oxide layer is at least one of nickel oxide, aluminum oxide, tin oxide, titanium oxide, and the like, and the metal oxide layer has a thickness of about 10 to 60 nm.

Further, the carbon nanofiber composite material comprises a graphene microchip which is completely covered by the inside, a nano silicon sphere and a graphene microchip-nanosilicon sphere composite material whose edge is not completely coated.

Further, the forming a carbon coating layer on the outer surface of the carbon nanofiber composite material is at least one of atomic layer deposition technology (ALD), chemical vapor deposition (CVD), and sugar recombination technology. In the formula, an amorphous silicon carbon coating layer is formed on the surface of the carbon nanofiber composite material, and the graphene-nanosilicon sphere composite material with the carbon nanofiber edge not completely coated may be coated to increase the stability of the electrode structure.

From the above description of the structure of the present invention, the present invention has the following advantages over the prior art:

1. The invention provides a negative electrode material for a lithium ion battery as an effective buffering silicon volume effect, and the preparation process is simple. By depositing nano silicon balls on the surface of the modified graphene microchip, the nano silicon ball is uniform in size and good in dispersion and does not agglomerate. At the same time, a precise and controllable void structure is formed between the nano silicon ball or the graphene and the carbon nanofiber, which can effectively buffer the volume expansion of the silicon during charging and discharging, and further buffer the silicon by utilizing the high flexibility and high conductivity of the graphene. The volume effect and increase the efficiency of electron and ion transport.

2. The invention further forms a carbon coating layer on the outermost layer to further protect the nano silicon ball, and at the same time can cover the nano silicon ball which cannot be completely covered by the edge of the carbon nanofiber, and ensure that each nano silicon sphere particle is packaged. Cover protection, there is room for free expansion, to ensure the integrity of the electrode structure, increase the stability of the electrode structure.

3. The lithium-ion battery prepared by using the anode material of the invention has the first coulombic efficiency of 84%-90%, and can maintain a specific capacity of 2000 mAh/g after circulating for 1050 cycles at a current density of 700 mA/g, and the average attenuation per cycle. The rate is only about 0.006%, showing excellent long-term cycle stability and rate performance.

DRAWINGS

The accompanying drawings, which are incorporated in, The illustrative embodiments and the description thereof are intended to explain the present invention and are not intended to limit the invention. In the drawing:

1 is a flow chart of a method for preparing a negative electrode material for a lithium ion battery which effectively buffers a silicon volume effect according to the present invention;

2 is a schematic structural view of a negative electrode material of a lithium ion battery which effectively buffers the volumetric effect of silicon according to the present invention;

Fig. 3 is a comparison diagram of charge and discharge of an embodiment of the present invention and a comparative example.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in FIG. 1, a method for preparing a negative electrode material for a lithium ion battery that effectively buffers a silicon volume effect, the method comprising the steps of:

S01, preparing a modified graphene microchip;

S02, growing nano silicon spheres on the surface of the graphene microchip to obtain a graphene microchip-nanosilicon sphere composite material;

S03, depositing a metal oxide layer of precise thickness on the surface of the graphene microchip-nanosilicon sphere by atomic layer deposition technology;

S04, uniformly depositing a graphene microchip-nanosilicon sphere composite material with a metal oxide layer on the surface thereof into an electrospinning solution, performing electrospinning and calcination treatment to obtain a carbon nanofiber composite material;

S05, acid treatment of carbon nanofiber composite material to completely remove metal oxide layer formation a void structure, that is, leaving a void structure between the nano silicon sphere or the graphene and the carbon nanofiber;

S06, forming a carbon coating layer on the outer surface of the carbon nanofiber composite material.

As shown in FIG. 2, the structure of an anode material of a lithium ion battery having an effective buffering silicon volume effect prepared by the present invention comprises carbon nanofibers 21, graphene microchips 13 inside and outside the carbon nanofibers, and nano silicon. The ball 11, the void structure 12, and the outermost carbon coating 22. The anode material can ensure that each nano-silicon sphere particle has a free expansion space during charge and discharge, thereby preparing an ultra-stable lithium ion battery.

The preparation process of the invention is simple, and the nano silicon ball is uniformly distributed on the surface of the graphene microchip by depositing the nano silicon sphere on the surface of the modified graphene microchip, and the dispersibility is good and not agglomerated; and the graphene-nanosilicon sphere composite material is simultaneously used. The surface is deposited with a precisely controllable metal oxide layer, and the metal oxide layer is removed after the carbon nanofiber coating, so that a void structure is formed between the nano silicon sphere and the graphene and the carbon nanofiber, which can effectively buffer the silicon in the surface. The volume expansion during charge and discharge, the high flexibility and high conductivity of graphene can further buffer the volume expansion of silicon and increase the transmission efficiency of electrons and ions; finally, the amorphous carbon coating layer can be formed on the outermost layer. The nano-silicon spheres covered by some carbon nanofiber edges can not be completely covered, and can further buffer the volume expansion of the nano-silicon spheres, ensuring that each nano-silicon sphere particles are coated and protected, and have free expansion space to ensure electrode structure. Integrity.

The specific embodiment of the present invention can adopt the following embodiments:

Example 1

Firstly, the expanded graphite was placed in a container, 250 ml of NMP was added, stirred uniformly, and then shaken for 10 hours under ultrasonic vibration power of 800 W at a temperature of 75 ° C to obtain a graphene microchip suspension; then allowed to stand for 180 min, and the upper suspension was taken. , remove the precipitate, filter and dry at 70 ° C Graphene microchip; then the obtained graphene microchip was added to 80 ml of concentrated sulfuric acid, keeping the solution temperature below 4 ° C, slowly adding 1 g of potassium permanganate, keeping the solution temperature below 10 ° C and magnetically stirring for 90 min, while simultaneously stirring During the magnetic stirring process, 150 ml of deionized water was slowly added; after the stirring, 3 ml of hydrogen peroxide was added, and stirring was continued for another 20 minutes; finally, the surface-modified graphene microchip was obtained by filtration and drying;

Then, the obtained graphene microchip is placed in a chemical vapor deposition (CVD) reaction chamber, vacuum is applied, and the reaction chamber is heated. When the temperature reaches 800 ° C, 100 sccm of argon gas is introduced to maintain the pressure of the reaction chamber at 1 Torr. Left and right, then 60sccm of silane (SiH ₄ ) is introduced into the reaction chamber, and SiH ₄ decomposes at a high temperature to form a nano-silica ball having a size of about 50 nm attached to the surface of the graphene microchip of the substrate material to obtain a graphene microchip- Nano silicon ball composite material;

Then, a layer of nickel oxide (NiO) with a thickness of about 24 nm is deposited on the surface of the graphene-nanosilicon composite by atomic layer deposition (ALD); then it is uniformly dispersed into the electrospinning solution and electrospun Silk and calcination treatment method for preparing carbon nanofiber composite material comprising graphene-nanosilicon spheres; then the carbon nanofiber composite material is placed in an acid for acid treatment to remove nickel oxide and remain in the original position of nickel oxide Lower void structure. Finally, an amorphous carbon coating layer is formed on the outermost surface by atomic layer deposition (ALD) to obtain a lithium ion battery anode material.

The lithium ion battery prepared by the negative electrode material was cycled 1050 times at a current density of 700 mA/g, and still maintained a specific capacity of about 2002 mAh/g, and the first charge and discharge coulombic efficiency reached 86.3%.

Example 2

First, the expanded graphite was placed in a container, 150 ml of DMF was added, stirred uniformly, and then shaken for 8 hours under the condition of ultrasonic vibration power of 1000 W and temperature of 80 ° C to obtain a graphene microchip suspension; Then, it was allowed to stand for 180 min, the upper layer suspension was taken, the precipitate was removed, and after filtration, it was dried at 70 ° C to obtain a graphene microchip; then the obtained graphene microchip was added to 100 ml of concentrated sulfuric acid to keep the solution temperature below 4 ° C. Slowly add 0.5 potassium permanganate, keep the solution temperature below 10 ° C and magnetically stir for 120 min, while slowly adding 150 ml of deionized water during magnetic stirring; add 3 ml of hydrogen peroxide after stirring, and continue stirring for 30 min; Finally, filtering and drying to obtain surface-modified graphene microchips;

Then, the obtained graphene microchip is placed in a chemical vapor deposition (CVD) reaction chamber, vacuum is applied, and the reaction chamber is heated. When the temperature reaches 850 ° C, 150 sccm of argon gas is introduced to maintain the pressure of the reaction chamber at 1.3. Around Torr, 80sccm of silane (SiH ₄ ) was introduced into the reaction chamber, and SiH ₄ was decomposed at a high temperature to form a nano-silica ball having a size of about 50 nm attached to the surface of the graphene microchip of the substrate material to obtain a graphene microchip. - nano silicon ball composite material;

Then, an aluminum oxide layer with a thickness of about 26 nm is deposited on the surface of the graphene-nanosilicon composite by atomic layer deposition (ALD); then it is uniformly dispersed into the electrospinning solution and electrospun and calcined. The method of treatment prepares a carbon nanofiber composite comprising graphene-nanosilicon spheres; the carbon nanofiber composite is then placed in an acid for acid treatment to remove the alumina and leave a void structure at the original location of the alumina. Finally, an amorphous carbon coating layer is formed on the outermost surface by chemical vapor deposition (CVD) to obtain a lithium ion battery anode material.

The lithium ion battery prepared by the negative electrode material was cycled 1050 times at a current density of 700 mA/g, and still maintained a specific capacity of about 1982 mAh/g, and the first charge and discharge coulombic efficiency reached 88.9%.

As shown in Figure 3, the comparative example is a pure nano-silicon sphere. The negative electrode material circulates at a current density of 700 mA/g, with a very rapid capacity decay from the beginning.

The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and scope of the invention are intended to be included within the scope of the invention.

Claims

A method for preparing a negative electrode material for a lithium ion battery that effectively buffers a silicon volume effect, characterized in that the method comprises the following steps:

Preparing a modified graphene microchip;

A nano silicon sphere is grown on the surface of the graphene microchip to obtain a graphene microchip-nanosilicon sphere composite material;

Depositing a metal oxide layer on the surface of the graphene microchip-nanosilicon sphere by atomic layer deposition technique;

The graphene microchip-nanosilicon sphere composite material with a metal oxide layer deposited thereon is uniformly dispersed into an electrospinning solution, and subjected to electrospinning and calcination treatment to obtain a carbon nanofiber composite material;

Acid-treating the carbon nanofiber composite material to remove the metal oxide layer to form a void structure;

A carbon coating is formed on the outside of the carbon nanofiber composite.
The method for preparing a negative electrode material for a lithium ion battery according to claim 1, wherein the step of preparing the modified graphene microchip is to first place the expanded graphite in a container and add 100-1000 ml. The organic solvent is then shaken for 1-24 hours under the condition of ultrasonic vibration power of 300-1200 W and temperature of 20-150 ° C to obtain a graphene microchip suspension; then, it is allowed to stand for 20-300 min, and the upper layer suspension is taken to remove the precipitate. After filtration, drying at 60-80 ° C to obtain graphene microchips; then adding the obtained graphene microchips to 20-100 ml of concentrated sulfuric acid, keeping the solution temperature below 4 ° C, slowly adding 0.5-20 g of permanganic acid Potassium, keep the solution temperature below 10 °C and magnetically stir for 60-120min and slowly add 150ml of deionized water during magnetic stirring; add 1-5ml of hydrogen peroxide after stirring, continue stirring for 10-30min; Dry to obtain modified graphene microchips.
The method for preparing a negative electrode material for a lithium ion battery according to claim 2, wherein the organic solvent is NMP, DMF, toluene, chlorobenzene or trichloroethylene. At least one of them.
The method for preparing a negative electrode material for a lithium ion battery according to claim 1, wherein the nano silicon ball is grown on the surface of the graphene microchip by a chemical vapor deposition (CVD) method; The graphene microchip is placed in the reaction chamber, vacuum is applied and the reaction chamber is heated. When the temperature reaches the reaction temperature, 1-500 sccm of carrier gas is introduced to maintain the pressure of the reaction chamber at 0.01 Torr-10 Torr, and then the reaction is carried out. A reaction gas of 1-500 sccm is introduced into the chamber, and the reaction gas is decomposed at a high temperature to form a nano-silicon sphere attached to the surface of the graphene microchip of the substrate material. After the reaction is completed, the reaction gas, the carrier gas, and the heating device are sequentially closed. A graphene microchip-nanosilicon sphere composite was obtained.
The method for preparing a negative electrode material for a lithium ion battery according to claim 4, wherein the size of the nano silicon sphere grown on the surface of the graphene microchip is about 1-100 nm, and the reaction temperature is 650 ° C. -1000 ° C.
The method for preparing a negative electrode material for a lithium ion battery according to claim 4, wherein the reaction gas for growing the nano silicon ball on the surface of the graphene microchip is silane (SiH 4 ) or dichlorosilane ( At least one of SiH 2 Cl 2 ); the carrier gas is at least one of nitrogen (N 2 ) and argon (Ar).
The method for preparing a negative electrode material for a lithium ion battery according to claim 1, wherein the metal oxide layer is at least one of nickel oxide, aluminum oxide, tin oxide, titanium oxide, and the like. The metal oxide layer has a thickness of about 10 to 60 nm.
Preparation of lithium ion battery anode material effective buffering silicon volume effect according to claim The method is characterized in that: the carbon nanofiber composite material comprises a graphene microchip which is completely covered by the inside, a nano silicon sphere and a graphene microchip-nanosilicon sphere composite material whose edge is not completely coated.
The method for preparing a lithium ion battery anode material according to claim 1, wherein the carbon coating layer is formed on the outer surface of the carbon nanofiber composite material by atomic layer deposition (ALD), chemistry At least one of vapor deposition (CVD) and sugar recombination techniques forms an amorphous silicon carbon coating on the surface of the carbon nanofiber composite.