TW201307605A - Vapor-phase deposition method for modifying powder surface, manufacturing method of electrode and electrode - Google Patents

Abstract

A vapor-phase deposition method for modifying powder surfaces is applied to coat nano conductive layer on powder surfaces. Therefore, the conductive property and the stability of powder can be improved. The modified powder can be used to manufacture the electrode of Li-battery so as to improve the charging/discharging rate.

Description

Vapor deposition method for powder upgrading, electrode manufacturing method and electrode thereof

The invention relates to a powder upgrading method, an electrode manufacturing method and an electrode thereof, in particular to a method for performing powder reforming by vapor deposition, an electrode manufacturing method and an electrode thereof.

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 and lithium nickel cobalt batteries still have safety problems compared with lithium iron phosphate batteries, so lithium batteries will gradually become more complete in the future. The development of lithium iron phosphate batteries without safety issues.

The lithium iron phosphate battery cathode material has a "strong covalent chain" between molecules, and the structure is stable without safety problems, and has no safety problem of combustion and explosion; it is quite advantageous compared with the safety of lithium-cobalt batteries. Lithium iron phosphate battery purely in terms of material cost, lithium iron phosphate battery is the lowest of all lithium-ion batteries (15~28 USD/kg, lithium cobalt 26~50 USD/kg), and the future will increase with the technology to improve the yield. After gradually becoming popular, the price is expected to gradually decline. Due to the impact of environmental awareness, the hybrid electric vehicle has received much attention from the market and has a good market growth potential in the future. Because of the advantages of internal combustion engine (engine) and electric motor, the hybrid electric vehicle can make up for its shortcomings and effectively reduce fuel consumption and pollution. At present, the hybrid electric vehicles are mainly nickel-hydrogen batteries. In the future, 2/3 will use lithium-ion batteries, and lithium iron phosphate with no explosion and high current will be the star of tomorrow. Assume that the battery used in a hybrid electric vehicle requires about NT$200,000. It is estimated that the fuel-electric hybrid battery market will reach NT$120 billion in 2007 and will grow to RMB420 billion in 2010.

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 that it is considered to be a safer battery technology; the cell structure can remain 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; in other words, the low volume energy density of the electrode will limit the application of the battery in the hand-held product, and cannot be applied to the motor device with high discharge rate. The conductivity of the lithium iron phosphate electrode is dependent on process technology to improve.

Moreover, a conventional technique uses a liquid phase method to reform a lithium iron phosphate electrode powder, and a liquid phase modification requires a long-chain compound, which has a complicated process and a waste liquid problem, and therefore needs to be improved.

One of the objects of the present invention is to provide a powder reforming method for powder modification to achieve the purpose of low cost and effective improvement of powder characteristics.

Embodiments of the present invention provide a powder reforming method for powder upgrading, comprising the steps of: placing a powder in a reactor and uniformly dispersing the powder in the reactor; and introducing at least one conductor a gas phase precursor enters the reactor; and adjusting parameters of the reactor to convert the gas phase precursor of the conductor into a solid phase conductor layer and depositing the solid phase conductor layer on the surface of the powder.

Embodiments of the present invention provide a method for fabricating an electrode, comprising the steps of: placing an electrode powder in a reactor, and uniformly dispersing the electrode powder in the reactor; and introducing a gas phase precursor of at least one conductor Entering the reactor; adjusting the parameters of the reactor to convert the gas phase precursor of the conductor into a solid phase conductor layer, and depositing the solid phase conductor layer on the surface of the electrode powder to form a modified electrode a powder; and the modified electrode powder is formed into an electrode.

The embodiment of the present invention further provides an electrode formed by the electrode powder, wherein the surface of the electrode powder has a solid phase conductor layer, and the solid phase conductor layer provides a first path and a second a path by which electrons can be transmitted along the first path and ions can be transported along the second path.

The invention has the following beneficial effects: the invention mainly uses a gas phase method to deposit a conductive layer on the surface of the powder, which is favorable for uniform heat transfer and mass transfer, and can shorten the reaction time, so the overall process is simple and the cost is low; The modification method of the invention can be applied to the electrode powder to form a good electron conduction path and an ion conduction path on the surface of the electronic powder and the interface between the powders, thereby greatly increasing the high charge and discharge rate of the battery electrode.

For a better understanding of the features and technical aspects of the present invention, reference should be made to the accompanying drawings.

The invention provides a powder reforming method for powder modification, which uses a gas phase to convert into a solid phase to coat a conductive layer on a powder to achieve the purpose of modifying the powder, and the invention further comprises an electrode The powder is modified by the above method, so that the produced battery electrode has a better electron transfer effect, thereby improving the characteristics of the battery itself.

Please refer to FIG. 1A to FIG. 3; the powder reforming method for powder upgrading proposed by the present invention comprises at least the following steps: Step 1: providing a reactor 20 (as shown in FIG. 3) and placing the powder 10 thereon. In the reactor 20, the powder 10 is uniformly dispersed in the reactor 20; and in order to achieve uniform distribution of the powder 10, in this step, a step of introducing an inert gas into the reactor 20 is further included, and the step is controlled. The flow rate of the inert gas is to uniformly disperse the powder 10 in the reactor 20. Specifically, the present invention is a description of the surface modification of a commercial grade lithium iron phosphate powder used in a lithium battery, but is not intended to limit the present invention; for example, a lithium battery positive electrode material powder: lithium cobalt oxide powder, manganese Lithium acid powder, lithium nickel cobalt oxide powder, lithium nickel cobalt manganese oxide powder, or other materials such as carbon powder, ceramic powder, semiconductor material powder, metal powder, alloy powder, and polymer powder The same can be applied to the present invention. In addition, the reactor 20 further includes a cold trap system 23 connected to the outlet end 202 of the reactor 20 to recover the exhaust gas and a portion of the extracted powder.

In the present embodiment, the lithium iron phosphate powder is placed in the reactor 20, and nitrogen gas (i.e., inert gas) is introduced from the inlet end 201 of the reactor 20 through the gas valve 21C, by the gas flow unit 21 ( For example, the proton flow meter accurately controls the flow rate and adjusts the flow rate to achieve fluidization of the powder 10, thereby uniformly dispersing the powder 10 in the reactor 20. It should be noted that the flow rate of the inert gas must be controlled in accordance with the diameter of the reactor 20. If the flow rate is too small, the powder 10 will not be uniformly dispersed. Conversely, an excessive flow rate will cause the powder 10 to be flushed out from the outlet end 202. In a specific embodiment, the diameter of the reactor 20 is 5 cm, and the flow rate of the inert gas is preferably controlled to 200 to 1000 cc/min, but not limited thereto.

Step 2: introducing a gas phase precursor of at least one conductor into the reactor 20; step 3 is to adjust the parameters of the reactor 20 to convert the gas phase precursor of the conductor into the solid phase conductor layer 11, 11' (eg 1A and 1B), the solid phase conductor layers 11, 11' are deposited on the surface of the powder 10. In one embodiment, a gaseous precursor of carbon is selected and passed to reactor 20, such as a gas phase compound containing one carbon to four carbons, such as alkynes, alkenes, alcohols, alkanes, and Various carbon-containing gas phase precursors; then in step three, the heating device 22 (including the heater 221 and the temperature control device 222) is used to bring the reactor 20 to a predetermined reaction temperature, and the reaction time is controlled to make the solid phase The conductor layers 11, 11' are deposited to form a predetermined thickness on the surface of the powder 10.

In a specific embodiment, a gas phase precursor of acetylene is introduced into the gas phase through the gas valve 21A and the hydrogen gas is supplied through the gas valve 21B. The reaction temperature is set between 500 and 900 ° C, and the reaction time is set at Between 30 and 120 minutes, the nanocarbon layer (i.e., the solid phase conductor layer 11 shown in Fig. 1A) can be uniformly deposited on the surface of the lithium iron phosphate powder, and the carbon layer thickness is between 5 and 30 nm. According to SEM analysis, the original lithium iron phosphate powder has a size between 5 and 10 microns (as shown in Annexes (a) and (b)), and the lithium iron phosphate powder modified by the present technology has no appearance. Significant difference; please refer to XRD analysis (Fig. 4), the original lithium iron phosphate powder has high crystallinity, and after upgrading by the vapor deposition method of the present invention, the powder still has a relatively high crystallinity display (as shown in the figure). 5 (b)), that is, it has not changed its original crystallinity after upgrading. In addition, as shown in the figure, the presence of the carbon layer was not found in the modification time of 120 minutes, mainly due to the low content of the nanocarbon layer (less than 5%).

In addition, please refer to the TEM analysis (as shown in Annex II (a), (b)) after 30 minutes of vapor deposition, the surface of the lithium iron phosphate powder has a nanocarbon layer of about 5 nm thickness, and 120 minutes through 120 minutes. After the fluidized modification, the surface of the lithium iron phosphate powder has a nano carbon layer having a thickness of about 30 nm. From the above observation, the vapor deposition method of the present invention can laminate the nano carbon layer (ie, the solid phase conductor layer 11). On the surface of the powder 10.

In the invention, the modified lithium iron phosphate powder (ie, the electrode powder) is sintered or calcined to form an electrode, and the battery is assembled into a battery and compared with a conventional lithium battery for charging and discharging. Referring to Figure 5(a), the charge-discharge behavior of the button-type lithium-ion half-cell assembled with the original lithium iron phosphate powder has a reversible power of 120 mAh/g at a low charge-discharge rate (0.1 C). Capacity, but it cannot be applied to charge and discharge at high charge and discharge rates (such as 10 C). On the other hand, as shown in FIG. 5(b), the charge and discharge behavior of the battery prepared by the electrode powder after the reaction time of 120 minutes is remarkably improved, and the reversible capacity at the time of low charge and discharge can be maintained, and 10 Charge and discharge are performed under C, for example, maintaining a reversible capacity of 50 mAh/g.

As shown in Figure 6, after 30 minutes of reaction time modification, the battery can still maintain 66% of the capacitance at 3 C charge and discharge rate compared to 0.1 C; the modification of the reaction time via 120 minutes After that, the battery can maintain 50% of the capacity at 10 C charge and discharge rate compared to 0.1 C; conversely, the conventional battery cannot store power at the 3 C charge and discharge rate.

In another embodiment, a gas phase precursor of acetylene is also used as the carbon, but before the acetylene is introduced, a catalyst layer is formed on the surface of the powder 10, such as coating the metal cobalt on the surface of the powder 10. The reaction temperature is between 500 and 900 ° C, and the reaction time is set between 30 and 120 minutes, so that the carbon nanotubes can be uniformly deposited (that is, the solid phase conductor layer 11' shown in FIG. 1B has a carbon nanotube On the surface of the lithium iron phosphate powder, the thickness of the carbon layer is between 5 and 30 nm.

By SEM analysis (as shown in Annexes III (a), (b)), the original lithium iron phosphate powder has a size between 5 and 10 microns, and after upgrading by the vapor deposition method of the present invention, a large amount can be found. The crimped carbon nanotubes are evenly grafted onto the surface of the powder. The carbon nanotubes have a diameter of about 20 to 50 nanometers and a length of about several micrometers. In other words, the present invention can graft the carbon nanotubes onto the surface of the electrode powder. .

As shown in Fig. 8, after grafting through the carbon nanotubes, the battery performance has been significantly improved, especially in the case of high charge and discharge, the battery still has good charge and discharge performance, for example, the battery can still be charged and discharged at a rate of 3 C. The battery capacity is maintained at about 75%; on the contrary, the conventional battery cannot store power at the 3C charge and discharge rate.

Therefore, the present invention proposes a method of coating a conductive layer (such as a carbon layer, a carbon tube, etc.) on the surface of a micron or submicron powder by a vapor deposition technique, and when applied to an electrode powder, not only the powder is lifted. The conductive property of the body can guide the ion diffusion and reduce the ion diffusion resistance. As shown in FIG. 2, the conductive layer on the surface of the electrode powder can provide a first path P1 and a second path P2, so that electrons can be along the The first path P1 is transmitted, and the ions can be transported along the second path P2. Specifically, since the surface of the lithium iron phosphate powder is uniformly coated by the nano carbon layer or the carbon tube system, the surface of the powder can be The interface between the powders constitutes a good electron conduction path (ie, the first path P1); since the nanocarbon layer is an amorphous carbon layer, the diffusion resistance to lithium ions is low, and if the surface of the lithium iron phosphate grows nanometer Carbon tube, lithium ion is also easy to diffuse on the surface of the powder, and electrons can be transported one-dimensionally through the carbon nanotubes, which can greatly reduce the ion diffusion resistance and improve the effect of electron conduction, so that the original powder can be improved. The ability to transport electrons and ions, and The aggregation inhibiting effect acting between the powder.

On the other hand, the present invention does not limit the material of the solid phase conductor layer 11, for example, a metal organic compound is used as a gas phase precursor, and a gas phase precursor such as tin, zinc, copper or the like is introduced into the reactor 20, and the reaction temperature is controlled. The solid phase conductor layer 11 of the above metal can be formed on the surface of the powder 10, and the effect of improving the electrical conductivity of the powder can be achieved.

In summary, the present invention has at least the following advantages:

1. The invention utilizes a fluid method to uniformly distribute the powder, and the powder is modified by the reaction of the gas phase precursor, and the high charge and discharge rate of the battery electrode of the lithium iron phosphate can be greatly improved in application, compared with the liquid. The phase powder upgrading method has simple process, can improve battery performance, and can reduce the manufacturing cost thereof.

2. The modified lithium iron phosphate powder prepared by the invention has a uniform nano carbon layer on the surface, which greatly increases the gram capacity of the product, and does not need to add a large amount of conductive additive when manufacturing the electrode; in other words, the conductive can be reduced. The amount of added material is used to reduce costs and does not require complicated machines or processes, so it meets the requirements of commercial scale.

3. The present invention can also deposit a nano-coating on different carriers to fabricate an article coated with a conductive layer, such as a catalyst, a nanomaterial, a ceramic powder, a semiconductor package, etc.; therefore, the present invention It has the characteristics of effectively improving the conductivity of various powders, avoiding powder aggregation and deterioration, and making the powder easier to store.

4. The invention can save energy consumption and processing time, has high mass transfer rate, and the powder to be modified can be in contact with the precursor gas molecules in the gas phase, and the gas-solid reaction is carried out at an appropriate temperature to achieve The purpose of uniform coating of the nano conductive layer.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and the equivalents of the present invention are intended to be included within the scope of the present invention.

10. . . Powder

11, 11'. . . Solid conductor layer

20. . . reactor

201. . . Entrance end

202. . . Exit end

twenty one. . . Gas flow unit

21A, 21B, 21C. . . Air valve

twenty two. . . heating equipment

221. . . Heater

222. . . Temperature control device

twenty three. . . Condensing device

P1. . . First path

P2. . . Second path

Fig. 1A is a schematic view showing the modification of the powder by the method of the present invention.

Figure 1B is a schematic view showing another aspect of the method of the present invention after upgrading the powder.

Fig. 2 is a schematic view showing the paths of electrons and ions of the modified powder forming electrode of the present invention.

Fig. 3 is a schematic view showing a machine for carrying out the vapor deposition method of the present invention.

Figure 4 is a graph showing the XRD analysis of the powder before and after the modification.

Fig. 5A is a graph showing charge and discharge characteristics of a battery using an electrode before modification.

Fig. 5B is a graph showing the charge and discharge characteristics of a battery using an electrode modified with a carbon layer.

Fig. 6 is a graph showing comparison of charge and discharge characteristics of a battery using an electrode after modification and modification with a carbon layer.

Fig. 7 is a graph showing the charge and discharge characteristics of a battery using an electrode modified with a carbon nanotube.

Fig. 8 is a graph showing comparison of charge and discharge characteristics of a battery using an electrode modified with a carbon nanotube before modification.

10. . . Powder

P1. . . First path

P2. . . Second path

Claims (13)

A powder reforming method for powder upgrading comprises the steps of: placing a powder in a reactor and uniformly dispersing the powder in the reactor; introducing a gas phase precursor of at least one conductor into the reactor The reactor; and adjusting the parameters of the reactor to convert the gas phase precursor of the conductor into a solid phase conductor layer and depositing the solid phase conductor layer on the surface of the powder. The method for vapor-depositing a powder modified according to claim 1, wherein in the step of placing the powder in a reactor, the step of introducing an inert gas into the reactor is further controlled. The flow rate of the inert gas is to uniformly disperse the powder in the reactor. The method for vapor-depositing a powder modified according to claim 1, wherein in the step of introducing a gas phase precursor of at least one conductor into the reactor, a gas phase precursor of carbon is introduced. The reactor. The method for vapor-depositing a powder modified according to claim 3, wherein the gas phase precursor of the carbon is a gas phase compound containing one carbon to four carbons; and the gas phase of the conductor is made In the step of converting the precursor into a solid phase conductor layer, the solid phase conductor layer is a heterogeneous carbon layer. The method for vapor-depositing a powder modified according to claim 3, wherein before the step of introducing a gaseous precursor of carbon into the reactor, the method further comprises: forming a surface of the powder a step of contacting the catalyst layer; wherein the gas phase precursor of the carbon is a gas phase compound containing one carbon to four carbons, and the solid phase is in the step of converting the gas phase precursor of the conductor into a solid phase conductor layer The conductor layer has a carbon nanotube. The method for vapor reforming the powder modified according to claim 4 or 5, wherein the step of adjusting the parameters of the reactor further comprises the step of: providing a heating device to bring the reactor to a The reaction temperature is predetermined; and the reaction time is controlled such that the solid phase conductor layer is deposited to form a predetermined thickness on the surface of the powder. An electrode manufacturing method comprising the steps of: placing an electrode powder in a reactor, and uniformly dispersing the electrode powder in the reactor; and introducing a gas phase precursor of at least one conductor into the reactor; Adjusting the parameters of the reactor, converting the gas phase precursor of the conductor into a solid phase conductor layer, and depositing the solid phase conductor layer on the surface of the electrode powder to form a modified electrode powder; The modified electrode powder is fabricated into an electrode. The method for fabricating an electrode according to claim 7, wherein the step of placing the electrode powder in a reactor further comprises the step of introducing an inert gas into the reactor, and controlling the flow rate of the inert gas. The electrode powder is uniformly dispersed in the reactor. The method of fabricating an electrode according to claim 7, wherein in the step of introducing a vapor phase precursor of at least one conductor into the reactor, a gas phase precursor of carbon is introduced into the reactor. The method for fabricating an electrode according to claim 9, wherein the gas phase precursor of the carbon is a gas phase compound containing one carbon to four carbons; and the gas phase precursor of the conductor is converted into a solid phase. In the step of conducting the conductor layer, the solid phase conductor layer is a heterogeneous carbon layer. The electrode manufacturing method according to claim 9, wherein the step of forming a catalyst layer on the surface of the electrode powder before the step of introducing a gas phase precursor of carbon into the reactor Wherein the gas phase precursor of the carbon is a gas phase compound containing one carbon to four carbons, and in the step of converting the gas phase precursor of the conductor into a solid phase conductor layer, the solid phase conductor layer has a naphthalene Carbon tube. The electrode preparation method according to claim 10 or 11, wherein the step of adjusting the parameters of the reactor further comprises the steps of: providing a heating device to bring the reactor to a predetermined reaction temperature; and controlling The reaction time is such that the solid phase conductor layer is deposited to form a predetermined thickness on the surface of the powder. An electrode formed by an electrode powder, wherein the surface of the electrode powder has a solid phase conductor layer, the solid phase conductor layer providing a first path and a second path, so that the electron can be Transmitted along the first path, and ions can be transported along the second path.