WO2018032977A1

WO2018032977A1 - Manufacturing method of negative-electrode material for lithium-ion battery

Info

Publication number: WO2018032977A1
Application number: PCT/CN2017/095832
Authority: WO
Inventors: 许志
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: CN107768607A; CN107768607B

Abstract

A manufacturing method of a negative-electrode material for a lithium-ion battery, the manufacturing method thereof comprising the following steps: growing silicon nanospheres on a graphene surface to form a graphene/silicon nanoshpere composite material; sugar-coating the graphene/silicon nanosphere composite material; and carbonizing the sugar-coated graphene/silicon nanosphere composite material to form a composite material of carbon/graphene/silicon nanospheres. The manufacturing method of the present invention is simple and has a high production yield rate. The silicon nanospheres are miniature and uniform, and combined with graphene, thus effectively reducing silicon volume expansion caused by delithiation during a charging-discharging process, lowering an internal stress of an electrode, and preventing damage caused by over-expansion of silicon spheres.

Description

Method for preparing anode material of lithium ion battery

Technical field

The invention relates to the technical field of solar cells, and in particular to a method for preparing a negative electrode material of a lithium ion battery.

Background technique

Lithium-ion batteries are characterized by high voltage, high specific energy, no memory effect, long cycle life and no environmental pollution. They are the most widely used rechargeable mobile power sources. Lithium-ion battery anode materials are the core of current lithium-ion battery research. The negative electrode materials of commercial lithium ion batteries are mostly graphite materials. Graphite has a crystalline layered structure, which is easy to intercalate and deintercalate lithium ions, forming an interlayer compound LiC6, which is a stable negative electrode material. However, the theoretical specific capacity of the graphite anode is only 372 mAh/g, which limits the further development of the lithium ion battery.

Silicon-based anode materials have a specific capacity of up to 4200 mAh/g, which seems to be an ideal high-capacity and safe anode material, but silicon-based materials have a 320% volume change during lithium-intercalation, which often leads to silicon. The active material is pulverized and falls off from the coated collector, losing charge and discharge characteristics. In addition, silicon is an intrinsic semiconductor material. If it is not doped or coated, its conductivity is much worse than that of carbon materials such as graphite. Therefore, an effective conductive network cannot be formed to achieve efficient and rapid charge and discharge.

At present, there are certain solutions to the problems existing in silicon-based materials. The mechanical properties of the material can be improved by treating silicon to nanometer size, or by surface modification, doping, recombination, etc., to improve the mechanical properties of the material to relieve the internal stress generated by volume expansion during the process of deintercalating lithium. Damage to materials. On the other hand, pure nano-silicon is easy to agglomerate, and the preparation method is complicated and energy-consuming. Furthermore, it is generally achieved by compounding a silicon particulate material with a carbon material. This method is generally first After the silicon particles and the carbon material are ball-milled, heat treatment is performed. A composite material of silicon and carbon material having a smaller particle diameter can be obtained by high-speed ball milling, and the carbon material can improve conductivity and suppress volume expansion of silicon during charge and discharge cycles. In the preparation of the composite material, since the silicon raw material used is silicon particles, a uniform and small-sized silicon particle material cannot be obtained by ball milling alone; the carbon material and silicon cannot be composited in the nanometer scale range, and the conductivity of the carbon material is The buffering effect cannot be fully exerted, affecting the electrochemical properties of the material. Therefore, the existing composite technology of nano-silicon and carbon material composites needs to be improved.

Summary of the invention

In view of the above problems, the present invention provides a preparation method of a lithium ion battery anode material which is simple in preparation method and high in production yield.

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, and the preparation method thereof comprises the following steps:

Growing nano silicon spheres on the surface of graphene to form graphene/nanosilicon composite material;

The graphene/nanosilicon composite material is subjected to sugar coating treatment;

The graphene/nanosilicon composite material after the sugar treatment is carbonized to form a carbon/graphene/nanosilicon sphere composite.

Further, the nano silicon ball is grown on the surface of the graphene to form a graphene/nanosilicon composite material, wherein the graphene is placed in the reaction chamber, the vacuum is evacuated, and the reaction chamber is heated. When the temperature reaches 500° C. to 1000° C., A carrier gas of 1-500 sccm is introduced, the pressure in the reaction chamber is maintained at 0.01 Torr to 10 Torr, and 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 attached to the surface of the graphene to form graphite. Alkene/nanosilicon composite.

Further, the reaction gas is at least one of SiH ₄ and SiH ₂ Cl ₂ .

Further, the carrier gas is at least one of N ₂ and Ar.

Further, the claimed sugar treatment is to impregnate the graphene/nanosilicon sphere composite into the syrup in a molten state, so that the surface of the graphene/nanosilicon sphere composite is completely covered by the syrup.

Further, the carbonization treatment is to take out the graphene/nano-silica composite material completely covered by the syrup and put it into a vacuum environment, and raise the temperature to 400-800 ° C at a heating rate of 5 ° C / min - 15 ° C / min, The carbonization treatment is maintained for 1-10 hours, so that the outer layer coated syrup forms a carbon coating layer to coat the graphene/nanosilicon sphere composite material to form a carbon/graphene/nanosilicon sphere composite material.

Further, the graphene is graphene having a hydroxyl group, a carboxyl group or an epoxy group on the surface.

Further, the nano silicon sphere is a crystalline silicon nano silicon sphere having a size of 1-60 nm.

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

The preparation method of the invention is simple, the production yield is high, the size of the nano silicon sphere is small and uniform, and the combination with the graphene can effectively reduce the volume expansion of the silicon itself caused by the deintercalation of lithium during the charging and discharging process, and reduce the internal stress of the electrode and avoid The silicon ball is over-expanded and damaged; the carbon nano-protective film is formed on the outermost layer by the sugar coating and carbonization treatment, and the nano-silicon sphere can be further protected, and the SEI film is formed on the outer surface of the carbon film to effectively avoid the SEI film in the silicon ball active material. Excessive deposition and flaking of the surface causes loss of silicon material.

DRAWINGS

The accompanying drawings, which are incorporated in the claims In the drawing:

1 is a flow chart of a method for preparing a negative electrode material for a lithium ion battery according to the present invention;

2 is a schematic view showing the structure of a carbon/graphene/nano-silica composite material of the present invention.

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.

Example 1

Referring to FIG. 1 , a method for preparing a negative electrode material for a lithium ion battery, the preparation method thereof comprises the following steps:

S01, growing nano silicon spheres on the surface of graphene to form a graphene/nanosilicon composite material;

S02, performing sugar coating on the graphene/nanosilicon composite material;

S03, carbonizing the graphene/nanosilicon composite material after the sugar treatment to form a carbon/graphene/nanosilicon sphere composite material.

As shown in FIG. 2, the carbon/graphene/nanosilicon sphere composite of the present invention comprises a nano-silicon sphere 2 grown on the surface of graphene 1 and a carbon coating layer 3 of the outermost layer, since the nano-silicon sphere 2 is small and uniform in size. It is distributed on the surface of graphene 1, and graphene 1 and carbon coating layer 3 play a double protection role on nano-silicon sphere 2, which can effectively alleviate the volume expansion of nano-silica sphere 2 during charge-discharge cycle and avoid cracking and pulverization. At the same time, the excellent electrical conductivity of the graphene 1 can effectively increase the electrical conductivity of the composite material, thereby further increasing the charge-discharge ratio capacity of the composite material.

The preparation method of the invention is simple, the production yield is high, the size of the nano silicon sphere is small and uniform, and the graphite The combination of olefins can effectively reduce the volume expansion of silicon itself caused by lithium deintercalation during charge and discharge, reduce the internal stress of the electrode, avoid excessive damage of the silicon ball and damage it; form a layer of carbon in the outermost layer through sugar coating and carbonization treatment. The protective film can further protect the nano silicon ball, and the SEI film is formed on the outer surface of the carbon film to effectively prevent the SEI film from excessively depositing and peeling off on the surface of the silicon ball active material, thereby causing loss of the silicon material.

Example 2

S01, a nano silicon ball is grown on the surface of the graphene, the graphene powder is placed in the HTCVD reaction chamber, the vacuum is applied, and the reaction chamber is heated. When the temperature reaches 850 ° C, 150 sccm of argon gas is introduced to make the reaction chamber pressure Maintaining at about 1.2 Torr, 13sccm of silane (SiH ₄ ) is introduced into the reaction chamber, and SiH ₄ is decomposed at a high temperature to form a nano-silica ball having a size of about 8 nm attached to the graphene surface to form a graphene/nanosilicon composite. material;

S02, the graphene/nanosilicon composite material is subjected to sugar coating treatment, and the graphene/nanosilicon sphere composite material is impregnated into the molten syrup, so that the surface of the graphene/nanosilicon sphere composite material is completely covered by the syrup;

S03, carbonizing the graphene/nano-silicon composite material after the sugar treatment, and taking the graphene/nano-silica composite material completely covered by the syrup into a vacuum environment, and heating up at a heating rate of 5 ° C/min. To 700 ° C, and maintained carbonization for 3 h, the outer layer coated syrup forms a carbon coating layer to coat the graphene / nano silicon ball composite material to form a carbon / graphene / nano silicon ball composite.

Example 3

S01, growing nano silicon spheres on the surface of graphene, placing graphene powder into the HTCVD reaction chamber, vacuuming and heating the reaction chamber, and introducing 200 sccm of argon gas to a pressure of the reaction chamber when the temperature reaches 850 °C. Maintaining at about 2 Torr, then introducing 30 sccm of dichlorosilane (SiH ₂ Cl ₂ ) into the reaction chamber, and SiH ₂ Cl ₂ is decomposed at a high temperature to form a nano-silica ball having a size of about 25 nm attached to the graphene surface;

S03, carbonizing the graphene/nanosilicon composite material after the sugar treatment, and taking the graphene/nano-silica composite material completely covered by the syrup into a vacuum environment, and heating up at a heating rate of 10 ° C/min. To 600 ° C, and maintained carbonization for 5 h, so that the outer layer of coated syrup forms a carbon coating layer, the graphene / nano silicon ball composite material is coated inside to form carbon / graphene / nano silicon ball composite .

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 principles of the present invention should be included in the protection of the present invention. Within the scope.

Claims

A method for preparing a negative electrode material for a lithium ion battery, characterized in that the preparation method comprises the following steps:

Growing nano silicon spheres on the surface of graphene to form graphene/nanosilicon composite material;

The graphene/nanosilicon composite material is subjected to sugar coating treatment;

The graphene/nanosilicon composite material after the sugar treatment is carbonized to form a carbon/graphene/nanosilicon sphere composite.
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 to form a graphene/nanosilicon composite material, wherein the graphene is placed in the reaction chamber and pumped. The reaction chamber is heated by a vacuum, and when the temperature reaches 500 ° C - 1000 ° C, a carrier gas of 1-500 sccm is introduced, the pressure in the reaction chamber is maintained at 0.01 Torr - 10 Torr, and a reaction gas of 1-500 sccm is introduced into the reaction chamber. The reaction gas decomposes at a high temperature to form a nano-silicon sphere attached to the surface of the graphene to form a graphene/nanosilicon composite.
The method according to claim 2, wherein the reaction gas is at least one of SiH 4 and SiH 2 Cl 2 .
The method of preparing a negative electrode material for a lithium ion battery according to claim 2, wherein the carrier gas is at least one of N 2 and Ar.
The method for preparing a negative electrode material for a lithium ion battery according to claim 2, wherein the coating sugar is treated by impregnating the graphene/nanosilicon ball composite into a molten syrup to make graphene/nanosilicon The surface of the ball composite is completely covered with syrup.
The method for preparing a negative electrode material for a lithium ion battery according to claim 2, wherein the carbonization treatment is performed by taking the graphene/nanosilicon ball composite material completely covered by the syrup into a vacuum environment, and 5 The heating rate of °C/min-15°C/min is raised to 400-800 °C, and The 1-10h carbonization treatment causes the outer layer coated syrup to form a carbon coating layer to coat the graphene/nanosilicon sphere composite material to form a carbon/graphene/nanosilicon sphere composite material.
The method for preparing a negative electrode material for a lithium ion battery according to claim 1, wherein the graphene is graphene having a hydroxyl group, a carboxyl group or an epoxy group on the surface.
The method for preparing a negative electrode material for a lithium ion battery according to claim 1, wherein the nano silicon ball is a crystalline silicon nano silicon ball having a size of 1-60 nm.