TWI455393B - Method and device of preparing electrode powder - Google Patents

Description

Electrode powder manufacturing method and device thereof

The invention relates to an electrode powder, in particular to a method for manufacturing an olivine structure and a device thereof, and the process technology for rapidly synthesizing electrode powder by high frequency can greatly reduce the sintering time of the electrode powder.

In order to cope with the increasingly advanced 3C electronic products and the need for electric vehicles to solve environmental and energy problems, the development of high-performance portable energy has become an important goal of the world's major industries. Among various types of batteries, lithium secondary batteries (including lithium ions and lithium polymers) have become the main products of secondary batteries and occupy a large market. Lithium-ion secondary batteries have high energy density (because of high voltage, about 3.5~4.5V), high capacitance density (120~180mAh/g), stable discharge voltage, long cycle life, and low self-discharge rate (<10 %), the use of a wide temperature range (-20 ~ 50 ° C), and no memory effect and other advantages are most favored. Since the discharge capacity and cycle life of lithium ion batteries are important indicators for judging the merits of the battery, research on cathode and anode materials for lithium ion secondary batteries has attracted attention.

Lithium-ion batteries are mainly used in portable consumer electronic products, mainly mobile phones, notebook computers, digital cameras, etc. Lithium-ion batteries can be distinguished into lithium cobalt, lithium manganese, and lithium depending on the cathode material. Nickel-cobalt, lithium iron phosphate battery, etc., of which lithium-cobalt battery is the mainstream, accounting for more than 90% (generally referred to as lithium-ion battery refers to lithium-cobalt battery), but lithium-cobalt battery has safety problems and out of stock problems Recently, various battery manufacturers have begun to look for new alternative cathode materials, such as lithium manganese batteries, but lithium manganese, lithium nickel cobalt batteries compared to lithium iron phosphate (Lithium Iron Phosphate, also known as lithium iron phosphorus, referred to as LFP) batteries still have safety issues, so lithium batteries will gradually develop toward lithium iron phosphate batteries that have no safety problems in the future.

The olive-type crystal structure of lithium iron phosphate makes its crystal lattice deformation smaller than other battery structures and improves the discharge process; its cycle period is therefore extremely long, and it can also resist oxidation and acid corrosion, so that the battery can have More electrolyte choices and their performance are also optimized. Lithium iron phosphate has a longer shelf life when the battery is not in use. Another advantage of lithium iron phosphate is considered to be the "safest" battery technology; the cell structure remains stable at temperatures as high as 300 to 500 degrees Celsius, and can withstand up to 700 degrees Celsius. Under the same temperature conditions, lithium batteries using materials such as cobalt, nickel, manganese, etc. will begin to disintegrate and even have the possibility of explosion. However, the material still has disadvantages such as low volume energy density and poor conductivity of the material; low volume energy density will limit the application of the battery in hand-held products, and cannot be applied to motor applications with high discharge rate, while conductivity depends on Process technology to improve.

At present, the patents of the most upstream compounds of lithium iron phosphate are mastered by three professional materials companies, Li _1-x MFePO _{4 of} Al23, LiMPO _{4 of} Phostech and LiFePO ₄ ‧ MO of Aleees, and have also developed very mature mass production. Technology, the largest of which has reached 250 tons per month. The most common mass production process of lithium iron phosphate is solid phase synthesis, emulsification drying, sol-gel method and solution co-precipitation method, but all require long-time sintering, generally about 10 to 20 hours. Not only is it time consuming and power is lost.

In view of this, the present invention replaces the conventional resistive heating technique by using a high-frequency induction heat-accelerating electrode powder growth technique. The invention provides a method for manufacturing an electrode powder and a device thereof, which can rapidly grow a highly crystalline electrode powder under the control of a suitable oxygen barrier gas to be applied to the preparation of a next generation electrode material.

The embodiment of the invention provides a method for manufacturing an electrode powder, which comprises the following steps. First, the precursor of the electrode powder is placed in a reaction vessel, and the reaction vessel is evacuated and filled with a gas for blocking oxygen, wherein the reaction vessel is placed inside the solenoid of the high-frequency coil. Then, the high-frequency coil is passed through the high-frequency alternating current so that the precursor of the electrode powder is induced to increase in temperature by passing through the high-frequency alternating current. Next, the precursor of the control electrode powder is heated to the reaction temperature for a predetermined reaction time.

Embodiments of the present invention provide an apparatus for manufacturing an electrode powder, which includes a high frequency coil, a reaction container, and a high frequency generator. The high frequency coil has a solenoid and is used to pass high frequency alternating current. The reaction vessel is placed inside the solenoid of the high-frequency coil to accommodate the precursor of the electrode powder. The high frequency generator is coupled to the high frequency coil for generating high frequency alternating current, and the high frequency alternating current is used to raise the precursor of the electrode powder to the reaction temperature. Wherein, when the reaction vessel accommodates the precursor of the electrode powder, the reaction vessel is evacuated and filled with a gas for blocking oxygen, and the gas for blocking oxygen is nitrogen or an inert gas.

In summary, the present invention has the following beneficial effects: the present invention utilizes high-frequency induction heating to rapidly crystallize the precursor of the electrode powder, and In combination with the addition of the carbon precursor, the uniform carbon layer is formed to form a conductive layer on the surface of the electrode powder to improve the high charge and discharge rate. The process of the invention is simple, and the reaction time and the production cost can be greatly reduced. Compared with the conventional method, the invention does not require complicated liquid phase or solid phase upgrading technology, and has no waste disposal problem, and can achieve the effects of simplifying the process and improving work efficiency.

The detailed description of the present invention and the accompanying drawings are to be understood by the claims The scope is subject to any restrictions.

In this embodiment, a highly crystalline electrode powder is prepared by using a high-frequency technique, and the high-frequency technique has the following features: (1) The heating speed is fast. High frequency (or RF) heating, the heat is generated by the material itself, so the heating is rapid, the temperature of the heated material is uniform inside and outside, no surface overheating and surface damage occur, and the end stage equalization project is not needed. It takes 20~40 hours to reduce the traditional drying time to 10~20 minutes. (2) Selective heating. If two different materials are placed together in a high-frequency heating device, the power of the high-frequency will be automatically adjusted according to the mass loss factor. Therefore, we can choose PP material or glass fiber as the conveyor belt material, because their loss coefficient is small, no heat is generated. The same principle, when drying paper or fiber, high-frequency energy will concentrate on the wet. Part (because the water content is higher, the loss coefficient is larger) and the dry part absorbs less energy, so that the moisture content of the product can be automatically adjusted to be uniform. (3) Reduce standby time and precise temperature control. The high-frequency heating machine can be started and stopped immediately, without waiting time, and the final moisture content of the product can be precisely controlled by adjusting the conveying speed and power. (4) Significant space saving. Because the heating time is greatly reduced compared with the traditional method, it can also save a lot of space for installation. In today's land, it can save a lot of investment in the land plant. (5) Improve the operating environment. Conventional heating methods often produce a lot of waste heat and damage, while high-frequency heating does not produce waste heat, the operating environment is elegant, and the product defect rate is almost reduced to zero. (6) Save energy. High-frequency heating is the heat generated by the object to be heated, and the energy is directly converted into heat. It does not need to be conducted, so the efficiency is extremely high, which can save a lot of energy.

The present invention proposes to use a high-frequency inductive heating process to prepare a highly crystalline electrode powder. 1A and FIG. 1B, FIG. 1A is a schematic diagram of a high-frequency coil for high-frequency induction heating according to an embodiment of the present invention, and FIG. 1B is a schematic diagram of a reaction container of an apparatus for manufacturing an electrode powder according to an embodiment of the present invention. . As shown in FIGS. 1A and 1B, this is a high-frequency coil 11 and a reactor steel body 12 for high-cycle induction heating. The high-frequency coil 11 has end points 11a, 11b and a solenoid 11c.

Please refer to FIG. 2. FIG. 2 is a schematic diagram of an apparatus for manufacturing an electrode powder according to an embodiment of the present invention. The electrode powder manufacturing apparatus 1 includes a vacuum steel body 10, a high-frequency coil 11, a reaction container 12, and a high frequency generator 13.

The high frequency coil 11 and the reaction vessel 12 are placed in the vacuum steel body 10. The vacuum steel body 10 has at least one gas valve 10a, 10b, which in the present embodiment has gas valves 10a, 10b. The reaction vessel 12 is placed inside the solenoid 11c of the high-frequency coil 11 for accommodating the precursor of the electrode powder. The high-frequency generator 13 connects the both end points 11a and 11b of the high-frequency coil 11.

The air valve 10a of the vacuum steel body 10 is for extracting air in the vacuum steel body 10. The gas valve 10b is used to inject a gas that blocks oxygen, such as nitrogen or an inert gas such as helium, neon, or argon. The reaction vessel 12 is for accommodating the precursor of the electrode powder, so that the air of the reaction vessel 12 can be evacuated when the vacuum steel body 10 is evacuated and the oxygen-blocking gas is poured, and the reaction vessel 12 can be filled. It is enough to enter the gas that blocks oxygen. In the present embodiment, the reaction vessel 12 may be unsealed, and at this time, the vacuum steel body 10 accommodating the reaction vessel 12 is discharged or filled with gas only through the gas valve (10a, 10b), but the present invention is not limited thereto. On the other hand, when the reaction vessel 12 also has a gas valve (not shown), the discharge or discharge of the air in the reaction vessel 12 can be directly controlled by the gas valve of the reaction vessel 12. Those skilled in the art should readily infer the manner in which the gas in the reaction vessel 12 is discharged or filled, and will not be described again.

The high frequency coil 11 is used to pass high frequency alternating current. The high frequency generator 13 is for generating high frequency alternating current, and the high frequency alternating current is used to raise the temperature of the precursor of the electrode powder to the reaction temperature. The high-frequency generator 13 is electrically connected to the end points 11a and 11b of the high-frequency coil 11 so that the induced magnetic field (Induced Magnetic Field) formed by the solenoid 11c of the high-frequency coil 11 causes the electrode powder The precursor of the body (precursor having a polar molecule) is oscillated and heated, and further nucleation and growth are performed. By uniformly coating a precursor of the appropriate electrode powder with a layer of carbon conductive material, the conductivity of the electrode powder is increased, and the high discharge rate of the battery is greatly increased. Further, the reaction container 12 may be provided with two or more heat generators (not shown) which respectively form two induced currents (Induced Current) through the induced magnetic field to generate a high-frequency electric field, and further enable the reaction vessel 12 The precursor of the electrode powder in the inside uniformly receives the high-frequency electric field and the induced magnetic field of the solenoid 11c to form a nucleus or a crystal.

The high-frequency coil 11 for high-cycle inductive heating has a frequency range of 100 kHz to 300 MHz, and the reaction steel body can accommodate the precursor of the electrode powder. In this embodiment, the precursor of the electrode powder comprises lithium carbonate, iron phosphate and conductive carbon material. The ratio of lithium, iron and phosphate in the formula is 1:1:1, and the carbon addition is about 1-5. Wt%, the ingredients are mixed via a high speed grinder, and the precursor of the electrode powder is placed in the reaction steel body. When the reaction vessel 12 accommodates the precursor of the electrode powder, the reaction vessel 12 is evacuated and filled with a gas for blocking oxygen.

2 and FIG. 3, FIG. 3 is a flow chart showing a method of manufacturing an electrode powder according to an embodiment of the present invention. This manufacturing method includes the following steps. First, in step S310, the precursor of the electrode powder is placed in a reaction vessel, and the reaction vessel is vacuum-extracted and filled with a gas for blocking oxygen, wherein the reaction vessel is placed in a high-frequency coil. Inside the solenoid. Then, in step S320, the high-frequency coil is passed through the high-frequency alternating current so that the precursor of the electrode powder is induced to increase in temperature by transmitting the high-frequency alternating current. Next, in step S330, the precursor of the electrode powder is controlled to be heated to the reaction temperature for a predetermined reaction time.

In step S310, since the lithium iron phosphate powder is sintered, heat treatment is required in an anaerobic environment, so that the reaction steel body is first subjected to vacuum pumping, and the vacuum degree is about 10 ^-1 to 10 ^-2 Torr ( Between between torr). Then pass high-purity nitrogen to form an anaerobic environment.

In step S330, the temperature rise curve in the reaction vessel is set to rise from room temperature to 700 degrees Celsius, and high cycle heating is performed, and the process time is about 1 to 2 hours. When the high temperature program is finished, a highly crystalline electrode powder can be obtained. As shown in FIG. 4, the lithium iron phosphate electrode powder produced in the present example was observed by a high-magnification electron microscope, and its particle diameter was uniform, and the size was about 0.3 μm to 2 μm. This average particle size and particle size distribution are similar to those of commercial electrode powders.

Referring to FIG. 5, FIG. 5 is a X-ray diffraction spectrum of lithium iron phosphate powder produced by the method for manufacturing an electrode powder according to an embodiment of the present invention, and curve A in FIG. 5 shows a commercial lithium iron phosphate (LFP) powder. Curve B shows the powder prepared in this example. Commercial lithium iron phosphate (LFP) powder has high crystallinity. Compared with the powder prepared in this example, there is no significant difference between the two. This result shows that high frequency induction heating also has a synthetic high crystalline electrode. The ability of the powder can be known from the present embodiment, and only a high cycle process of 1 to 5 hours is required, and the purpose of synthesizing the powder can also be achieved.

Please refer to FIG. 6. FIG. 6 is a diagram showing a charge-discharge diagram of a button type battery assembled by a lithium iron phosphate powder produced by the method for manufacturing an electrode powder according to an embodiment of the present invention, showing heating and synthesis at different discharge rates. The lithium iron phosphate (LFP) electrode powder has a charging capacity of 170 mAhg ^-1 at 0.1 C and a discharge capacity of about 160 mAhg ^-1 . The results show that the performance of the lithium iron phosphate powder can be significantly improved if the appropriate high-cycle synthesis parameters can be adjusted (the theoretical capacity of lithium iron phosphate is 170 mAhg ^-1 ). In addition, it can be observed from the figure that the self-made lithium iron phosphate powder can be rapidly charged and discharged at 5 C.

Please refer to FIG. 7. FIG. 7 is a schematic diagram showing the stability test of a lithium iron phosphate powder assembled button type battery produced by the method for manufacturing an electrode powder according to an embodiment of the present invention at different charge and discharge rates. This material not only has high charge and discharge capacity, but also can be stably operated at different charge and discharge rates, and has good stability.

[Possible efficacy of the embodiment]

According to the embodiment of the present invention, the above-described method for manufacturing an electrode powder extremely has the following advantages. The invention utilizes high-frequency induction heating to prepare the high-crystalline powder of the electrode powder, and the reaction time can be greatly reduced. Compared with the conventional resistance heating method, the process of the invention is simple, and the manufacturing cost thereof can also be reduced.

According to the actual test of the present invention, the high-frequency inductively heated lithium iron phosphate powder of the present invention has a nano carbon layer on the surface, and it is not necessary to add a large amount of conductive additive when the electrode is coated; in other words, the conductive addition can be reduced. The amount of material used, and does not require complex machines or processes, it meets the requirements of commercial scale.

The invention can also prepare high-crystalline electrode powders, such as catalysts, nano materials, ceramic powders and other kinds of lithium ion electrode materials, etc., in a short time by using precursors of different electrode powders; The invention has the ability to rapidly synthesize powder and is easy to replace the traditional sintering process. .

The above description is only an embodiment of the present invention, and is not intended to limit the scope of the invention.

1‧‧‧Electrode powder manufacturing device

11‧‧‧High frequency coil

11a, 11b‧‧‧ endpoint

11c‧‧‧ Solenoid

12‧‧‧Reaction container

13‧‧‧High Frequency Generator

10‧‧‧vacuum steel body

10a, 10b‧‧‧ gas valve

1A is a schematic illustration of a high frequency coil for high cycle inductive heating in accordance with an embodiment of the present invention.

Fig. 1B is a schematic view showing a reaction container of an apparatus for producing an electrode powder according to an embodiment of the present invention.

Fig. 2 is a schematic view showing an apparatus for manufacturing an electrode powder according to an embodiment of the present invention.

Fig. 3 is a flow chart showing a method of manufacturing an electrode powder according to an embodiment of the present invention.

Fig. 4 is a microscopic view showing an electrode powder of an embodiment of the present invention.

Fig. 5 is a view showing an X-ray diffraction spectrum of lithium iron phosphate powder produced by the method for producing an electrode powder according to an embodiment of the present invention.

Fig. 6 is a charge and discharge diagram of a button type battery assembled by lithium iron phosphate powder produced by the method for producing an electrode powder according to an embodiment of the present invention, at different discharge rates.

Fig. 7 is a view showing the stability test of a lithium iron phosphate powder assembled button type battery produced by the method for producing an electrode powder according to an embodiment of the present invention at different charge and discharge rates.

1. . . Electrode powder manufacturing device

11. . . High frequency coil

12. . . Reaction vessel

13. . . High frequency generator

10. . . Vacuum steel body

10a, 10b. . . Air valve

Claims (11)

A method for manufacturing an electrode powder, comprising: placing a precursor of the electrode powder in a reaction vessel, vacuuming the reaction vessel, and pouring a gas for blocking oxygen to form a gas An oxygen environment, wherein the reaction vessel is placed inside a solenoid of a high-frequency coil; the high-frequency coil is passed into a high-frequency alternating current so that the precursor of the electrode powder transmits the high-frequency alternating current Inducing the temperature rise; and controlling the precursor of the electrode powder to raise the temperature to a reaction temperature for a predetermined reaction time. The method for producing an electrode powder according to claim 1, wherein the precursor of the electrode powder comprises a lithium ion battery powder, a ceramic material, a semiconductor material or a nano material. The method for producing an electrode powder according to claim 1, wherein the gas for blocking oxygen is nitrogen or an inert gas. The method for producing an electrode powder according to claim 1, wherein the reaction temperature is between 400 degrees Celsius and 1100 degrees Celsius, and the predetermined reaction time is less than 360 minutes. The method for producing an electrode powder according to claim 1, wherein the high-frequency alternating current has a frequency of between 100 kHz and 300 MHz. The method for producing an electrode powder according to claim 1, wherein in the step of vacuum evacuating the reaction vessel, the vacuum of the vacuum pumping is between 10 ^-1 and 10 ^-2 Torr (torr) between. An apparatus for manufacturing an electrode powder, comprising: a high-frequency coil having a solenoid for passing a high-frequency alternating current; a reaction vessel disposed inside the solenoid for accommodating a precursor of the electrode powder; and a high-frequency generator connected to the high-frequency coil for generating the high-frequency alternating current for the high-frequency alternating current The precursor of the electrode powder is heated to a reaction temperature; wherein, when the reaction vessel accommodates the precursor of the electrode powder, the reaction vessel is evacuated and filled with oxygen to block oxygen. The gas is used to form an anaerobic environment, and the gas for blocking oxygen is nitrogen or an inert gas. The apparatus for manufacturing an electrode powder according to claim 7, wherein the precursor of the electrode powder comprises a lithium ion battery powder, a ceramic material, a semiconductor material or a nano material. The apparatus for manufacturing an electrode powder according to claim 7, wherein the reaction temperature is between 400 degrees Celsius and 1100 degrees Celsius, and the predetermined reaction time is less than 360 minutes. The apparatus for manufacturing an electrode powder according to claim 7, wherein the high-frequency alternating current has a frequency of between 100 kHz and 300 MHz. The apparatus for producing an electrode powder according to claim 7, wherein the vacuum of the vacuum evacuation is between 10 ^-1 and 10 ^-2 torr when the reaction vessel is evacuated.