TWI620711B - Method for manufacturing flexible graphite powder as lithium ion anode material - Google Patents

Abstract

The invention relates to a method for manufacturing a lithium ion anode material with flexible graphite powder, the steps comprising: (A) providing a dry flexible graphite after a pulverization process, and then grading to obtain a uniform flexible graphite powder; (B) the uniform flexibility The graphite powder is subjected to a ball milling process with a solvent to obtain a solution containing flexible graphite; (C) the solution containing the flexible graphite is coated on a metal foil, and a rolling process is performed to obtain a negative electrode material. Thereby, the negative electrode material can be processed into a negative electrode pole piece by external processing, and then combined with a battery lower cover, a separator paper, a positive electrode pole piece, a spring piece and a battery upper cover to form a lithium ion battery.

Description

Method for manufacturing flexible graphite powder as lithium ion anode material

The invention relates to a method for preparing a battery anode material, in particular to a method for preparing a lithium ion battery anode material containing flexible graphite powder.

The current 3C products, future electric vehicles, smart grids or cloud technologies all need to rely heavily on lithium-ion batteries. In addition, the energy generated by natural resources such as solar energy and wind power also needs to rely on lithium-ion batteries for storage. The installation, due to the size of the market, is already a very obvious trend.

With the rapid development of modern technology and quality of life, all kinds of 3C high-tech electronic products tend to be light, thin, short, small and multi-functional development, while batteries are safe, low-cost, high-quality and environmentally friendly. High-performance lithium-ion batteries have emerged. Among them, high-performance lithium-ion battery anode materials can be made using materials such as meta-carbon microspheres, natural graphite, and artificial graphite.

High-performance lithium-ion batteries are used in small computers and mobile phones for small size and light weight. Materials require higher energy density (high capacitance), and the charge and discharge rate should be completed within 0.5-1 hours. The capacitance of lithium ion battery anode materials using natural graphite and artificial graphite is difficult to break through the theoretical capacity of 372 mAh/g, and it is difficult to diffuse due to the mass transfer of lithium ions and electrolytes. To the internal structure, it limits the charge and discharge speed of the battery itself.

Flexible graphite powder is a kind of conductive material with low electrical resistance and high thermal conductivity. It is characterized by small density, large specific surface area and porosity. There are voids between layers to allow some compounds to enter. The single-layer graphite structure can be effectively stored higher than natural stone. The amount of lithium ion twice is currently used in industries such as printed circuit boards (M200832796), ultra-high capacitance (M508604) and electrode plates (M201543734), but the processing applications of flexible graphite powder often encounter brittleness. The shortcomings of difficult processing result in low preparation yield.

Therefore, it is extremely necessary in the industry to develop a method for manufacturing a negative electrode material of a lithium ion battery using a flexible graphite powder. The flexible graphite powder can improve the high energy density characteristics of the capacity and the charge and discharge rate, and the lithium graphite is used as a raw material to prepare lithium. The anode material of the ion battery can be combined with the efficiency and quality to prepare a high-quality, high-yield anode material for lithium ion batteries.

In view of the above disadvantages of the prior art, the main object of the present invention is to provide a method for manufacturing a negative electrode material of a lithium ion battery by using a flexible graphite powder, integrating a uniform flexible graphite powder, a solvent, a metal foil, a ball milling process, and a Process such as rolling press to obtain the desired negative electrode material.

In order to achieve the above object, according to one aspect of the present invention, a method for manufacturing a negative electrode material of a lithium ion battery using a flexible graphite powder is provided, the steps comprising: (A) providing a dry flexible graphite after a pulverization process, and then sieving The mesh is sieved to obtain a uniform flexible graphite powder; (B) the uniform flexible graphite The powder is subjected to a ball milling process with a solvent to obtain a solution containing flexible graphite; (C) the solution containing the flexible graphite is coated on a metal foil, and a rolling process is performed to obtain a negative electrode material.

In the above step (A), the dried flexible graphite is placed in an RT-N12 pulverizer, pulverized at a high rotation speed of about 26,000 rpm or more (but not limited thereto), and then the pulverized powder is placed. After the oven is dried and sieved through a sieve mesh having a mesh area of about 80-400 mesh (but not limited thereto), a flexible graphite powder having a very uniform particle size can be obtained.

In the step (B), the solvent may be N-methylpyrrolidone (NMP) (but not limited thereto), for example, 10% of PvDF/NMP may be used, and the ball milling process may be provided with a plurality of ceramic balls. The ball mill performs ball milling treatment, and a certain proportion of KS-4 and SuperP and the like may be added to the ball milling process to make the solution containing the flexible graphite contain a certain proportion of the auxiliary agent.

In the step (C) of the present invention, the metal foil may be a copper foil (but not limited thereto), and the solution containing the flexible graphite may be uniformly coated on the copper foil by a doctor blade, and the thickness thereof may be in the range of 20- 200μm (but not limited to this); and the copper foil sheet is encrypted by a rolling machine after the copper foil sheet is adjusted (with a spacing of 1mm or less, but not limited thereto), and can be cut into a diameter of 12mm (but not as The circular battery negative pole piece of the above), the battery negative electrode piece prepared above can be combined with the battery lower cover, the separation paper, the positive electrode pole piece, the spring piece and the battery upper cover to form a lithium ion battery.

The above summary and the following detailed description and drawings are intended to further illustrate the manner and means by which the creation achieves its intended purpose. efficacy. Other purposes and advantages of this creation will be explained in the following description and drawings.

S101-S103‧‧‧Steps

The first figure is a flow chart of a method for manufacturing a flexible graphite powder as a lithium ion negative electrode material according to the present invention.

The embodiments of the present invention are described by way of specific examples, and those skilled in the art can readily understand the advantages and effects of the present invention from the disclosure of the present disclosure.

Conventionally, when natural graphite is used as the negative electrode material, its capacitance is 320-350 mAh/g, and the capacitance rapidly drops to 200-250 mAh/g when 5 C-rate is rapidly charged and discharged; and flexible graphite is inserted into ions between graphite layers. The z-axis interlayer distance increases, which can increase the space for containing relevant ion content. The capacitance is higher than that of natural graphite. At the same time, the interlayer distance is increased and the surface area is increased. A large number of activation points and contact surfaces are formed, which can make the charge and discharge electrochemical. The reaction area is improved to achieve rapid charge and discharge. The flexible graphite powder can increase the capacity and charge and discharge rate. Generally, the flexible graphite has a capacity of at least 350 mAh/g at 5 C-rate, indicating that the material has high energy density characteristics.

In the invention, the flexible graphite powder is pulverized and classified by a high-speed pulverizer, and a graphite flake having a uniform particle size distribution can be obtained microscopically, the uniformity of the granularity of the flexible graphite can be improved, and the negative electrode pole piece can be uniformly coated on the copper foil. Since the negative electrode and the sheet (graphite pole piece) have high conductivity, the gap formed by the acid intercalation in the sheet structure allows more lithium ions to be stored in the material, so the lithium ion battery negative electrode produced by the invention The material has high capacity characteristics; the flexible graphite of the present invention is obtained by using scaly natural graphite powder as a raw material, acidified, etc., and then appropriately washed and dried to obtain expandable graphite powder. The expandable graphite powder is heated at a high temperature (700~1000 °C) for instant heating, that is, an expanded vermicular expanded graphite, the expansion ratio of which is 100-500 times, and the worm-like graphite is finally rolled (rolled The pressure is made into flexible graphite, and the flexible graphite is prepared by a pressure sintering process (about 10-100 kN/cm ² , 2000-3000 ° C).

Please refer to the first figure, which is a manufacturing method of a lithium ion anode material using flexible graphite powder. As shown in the figure, the present invention provides a method for preparing a carbide raw material, the steps comprising: (A) providing a dry flexible graphite after a pulverization process, and then grading to obtain a uniform flexible graphite powder S101, wherein The pulverization process is carried out by placing the dry flexible graphite into an RT-N12 pulverizer, pulverizing at a high rotation speed of 26,000 rpm or more, and then placing it in an oven to dry, wherein the solvent is NMP; (B) the uniform flexible graphite powder and the The solvent is subjected to a ball milling process to obtain a solution S102 containing flexible graphite, wherein the solvent is N-methylpyrrolidone (NMP), and the ball milling process is performed by ball milling using a plurality of ceramic ball mills; (C) The solution containing the flexible graphite is coated on a metal foil and subjected to a rolling process to obtain a negative electrode material S103, wherein the metal foil is a copper foil (sheet).

Example

A manufacturing process using flexible graphite as a negative electrode material and preparing a lithium ion battery is as follows: (1) After acidifying the natural graphite powder, the powdery graphite is treated by high temperature (700-1000 ° C), and the powder is shaped. Graphite forms worm-like graphite powder; (2) worm-like graphite powder is rolled (rolled) to form porous embryos with porous flexible graphite; (3) flexible graphite primordial is placed in a high-temperature furnace and sintered under pressure (about 10-100kN/cm ² , 2000-3000 ° C), can obtain flexible graphite; (4) put the flexible graphite into the RT-N12 pulverizer, at 26000 rpm for 10-30 seconds and then cool for 1-5 minutes, this After repeating the steps 5-10 times, the mixture was placed in an oven at 105 ° C for 2 hours, and then the powder was placed on a sieve of 80-400 mesh. The powder was sieved for 1 hour, and the powder of the lower layer was collected and sieved. After the pellet is less than 50μm, it is placed in the oven again for drying for at least 4 hours; (5) The graphite powder is weighed as a negative electrode material, and a certain proportion of KS-4 and SuperP and other auxiliary agents are added and placed in a plurality of ceramic balls. In a 50mL ball mill tank, adjust the speed of 350rpm and roll for 4 hours, and will contain 10% PVDF/NMP After entering, and depending on the viscosity of the solution, a few grams of NMP is added dropwise, and then placed in a ball mill for 1 hour; (6) a copper foil having a length and width of about 20 cm × 10 cm and a thickness of about 20 to 30 μm is taken, and the solution in the above-mentioned roller barrel is taken. Placed in a scraper mold, uniformly coated on a copper foil with a 20-200 um scraper, and then placed the wet film-containing copper foil in an oven to dry, adjust the temperature to 80 ° C and place it overnight (about 16-20 hours); 7) Encrypt the copper foil sheet with a roller press, adjust the pitch to 1mm or less, and cut the rolled copper foil into a circular negative pole piece with a diameter of 12mm by using a punching machine, and weigh the weight and several pieces of the circular negative pole piece. The weight of the round copper foil of the same shape can obtain the weight of the negative electrode material on the pole piece, and then the pole piece is placed in a 90 ° C oven for 3 hours, and then placed in the drying chamber for more than 12 hours; (8) ready to wash The cleaned battery module material (battery upper and lower cover CR2032, stainless steel pole piece and spring piece) and the cut 15mm release paper (Celgard 2325), the above materials are sequentially from bottom to top for the battery lower cover and negative electrode piece , separator paper, positive pole piece, spring piece and battery cover, each layer needs to drop 1M LiPF6 electrolyte (EC: EMC: DMC=1 1:1) 1-3 drops, and then put into the tablet mold to complete the assembly of the lithium ion battery; (9) take out the battery in the mold, bag and mark the number, the weight of the negative pole piece and the formula ratio, in the battery The weight and theoretical capacity of the negative electrode material are converted into the current of the C-Rate to be measured, and the battery capacity is recorded, which is converted into the capacitance density and the coulombic efficiency.

In the invention, the flexible graphite powder is made into a coin cell battery, and a half-cell capacity test is carried out. The capacity measuring machine model used is BAT-750B, and the current density test range is 0.1-5.0 C. -rate, the experimental results are listed in Table 1: It can be seen from Table 1 that the capacitance of flexible graphite obtained from 0.1 C-rate is about 390 mAh/g, and the capacitance decreases slightly with the increase of C-rate. Finally, the capacitance can be maintained at 368 mAh/g at 5.0 C-rate. It shows that the flexible graphite powder has high capacitance characteristics at high charge and discharge rates.

The invention utilizes the characteristics of flexible graphite as the anode material of the lithium battery, has the advantages of high electric capacity and high charge and discharge rate, and the measured reversible electric capacity is nearly 400 mAh/g, which is higher than that of the general natural graphite material (330-350 mAh/g). The capacitance increased by about 15-20%.

The above-described embodiments are merely illustrative of the features and functions of the present invention and are not intended to limit the scope of the technical content of the present invention. Any person skilled in the art can modify and change the above embodiments without departing from the spirit and scope of the creation. Therefore, the scope of protection of this creation should be as listed in the scope of the patent application described later.

Claims (9)

The invention relates to a method for manufacturing a negative electrode material of a lithium ion battery by using a flexible graphite powder, the steps comprising: (A) providing a dry flexible graphite after a pulverization process, and then grading to obtain a uniform flexible graphite powder, wherein the dry flexible graphite The pressure sintering process is performed at 2000-3000 ° C; (B) the uniform flexible graphite powder is subjected to a ball milling process with a solvent to obtain a solution containing flexible graphite; (C) the solution containing the flexible graphite is applied to On a metal foil, a rolling process is performed to obtain a negative electrode material, wherein the rolling process comprises a roller press to encrypt the negative electrode material at a pitch of 1 mm or less. The method for manufacturing a negative electrode material for a lithium ion battery according to the first aspect of the patent application, wherein the pulverizing process is to put the dry flexible graphite into a pulverizer, and pulverize at a high speed of 26,000 rpm or higher. Place in an oven to dry. The flexible graphite powder is a method for preparing a negative electrode material for a lithium ion battery according to the first aspect of the patent application, wherein the grading is sifted through a sieve, and the granules after sieving are less than 50 μm. The method for producing a lithium ion battery anode material according to the first aspect of the patent application, wherein the solvent is NMP. The method for manufacturing a lithium ion battery anode material according to the first aspect of the patent application scope, wherein the ball milling process system is subjected to ball milling treatment by using a plurality of ceramic ball ball mills. The method for manufacturing a negative electrode material for a lithium ion battery according to the first aspect of the patent application, wherein the metal foil is a copper foil. The flexible graphite powder is a method for producing a negative electrode material for a lithium ion battery according to the fifth aspect of the invention, wherein the solution containing the flexible graphite is coated on the copper foil to have a thickness ranging from 20 to 200 μm. The flexible graphite powder is a method for manufacturing a negative electrode material for a lithium ion battery according to the first aspect of the patent application, wherein the negative electrode material is converted into a negative electrode piece after being processed by an outer shape. The method for manufacturing a lithium ion battery anode material according to the seventh aspect of the patent application scope, wherein the anode pole piece and the battery lower cover, the separator paper, the positive electrode pole piece, the spring piece and the battery upper cover are combined into a lithium Ion battery.