TWI749605B - Lithium ion battery silicon carbon electrode material and preparation method thereof - Google Patents

Abstract

A lithium ion battery silicon carbon electrode material and a preparation method thereof are provided. The lithium ion battery silicon carbon electrode material includes a graphite particle and a resin carbon layer. The resin carbon layer is smoothly coated on a surface of the graphite particle, and silicon or silicon compound and a conductive material are coated in the resin carbon layer.

Description

Silicon carbon electrode material of lithium ion battery and preparation method thereof

The invention relates to an electrode material and a preparation method thereof, and particularly relates to a lithium ion battery silicon-carbon electrode material and a preparation method thereof.

In the existing lithium battery industry, the negative electrode is dominated by graphite materials such as natural graphite or artificial graphite. Graphite has the essential characteristics of low electrochemical potential, and its layered structure also happens to be suitable for the migration and storage of lithium ions. In addition, the rate of volume change caused by graphite during charging and discharging is small, and therefore, it has become the mainstream material for the negative electrode of commercial lithium batteries. However, in recent years, due to the lightweight and long-term output of 3C vehicles and electric vehicles, the requirements for battery energy density have also increased rapidly. Graphite with a theoretical specific capacitance of only 372mAhg-1 has gradually been unable to meet the needs of future energy storage batteries. In contrast, lithium-silicon compounds with 9 to 11 times the graphite specific capacitance have become the mainstream technology development of high energy density anode materials.

However, due to the high storage capacity of silicon for lithium ions, the silicon lattice is forced to produce about 400% volume expansion when alloying with lithium ions. This high volume expansion rate will cause the silicon to separate from each other, causing the electrode to peel off from the current collector after powdering. In addition, the contact area between silicon and the electrode becomes smaller and the distance becomes longer, and the electric field cannot effectively act on the electrode. Therefore, lithium ions and electrons cannot be effectively used, resulting in a rapid decline in battery cycle times and greatly reducing battery life. On the other hand, intrinsic silicon itself has poor conductivity, resulting in high internal resistance and slow heat dissipation, which also greatly affects the performance of the battery. Based on the above, how to prevent the silicon electrode from falling off and increase the ability of the silicon electrode to conduct electrons to increase the cycle life of the silicon anode is the most important issue that must be overcome in the current commercialization of the silicon anode.

The invention provides a lithium ion battery silicon-carbon electrode material and a preparation method thereof, so as to improve the life of the lithium battery silicon-carbon negative electrode material.

The silicon carbon electrode material of the lithium ion battery of the present invention includes graphite particles and a resin carbon layer. The resin carbon layer smoothly covers the surface of the graphite particles, and the silicon or silicon compound and conductive material are coated in the resin carbon layer.

In an embodiment of the present invention, the average thickness of the resin carbon layer is 5 nm to 500 nm, the average thickness change rate is 12.34%, and the thickness change standard deviation is 5.16.

In an embodiment of the present invention, the particle size of the graphite particles is 5 μm to 30 μm.

In an embodiment of the present invention, the conductive material includes metal nano particles, conductive carbon black, acetylene black, graphene, carbon nanotubes, or flake graphite.

The preparation method of the silicon-carbon electrode material of the lithium ion battery of the present invention includes the following steps. First, the graphite particles, silicon or silicon compound and conductive material are mixed, and then the resin is added for stirring and mixing, and the resin reactant is added during or after the curing process. Afterwards, carbonization is performed so that the resin carbon layer is smoothly coated on the surface of the graphite particles, and the silicon or silicon compound and the conductive material are coated in the resin carbon layer.

In an embodiment of the present invention, relative to 100 wt% of graphite particles, the addition amount of silicon or silicon compound and conductive material is 5 wt% to 20 wt%.

In an embodiment of the present invention, relative to 100 wt% of graphite particles, the amount of resin added is 10 wt% to 50 wt%.

In an embodiment of the present invention, relative to 100 wt% of graphite particles, the addition amount of the resin reactant is 5 wt% to 15 wt%.

In an embodiment of the present invention, the resin includes phenolic resin, urea resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin, polyurethane, polyethylene, polypropylene, poly Styrene, ABS resin, polyvinyl chloride, acrylic resin, nylon POM, polycarbonate, cellulose resin or polyethylene terephthalate.

In an embodiment of the present invention, the conductive material includes metal nano particles, conductive carbon black, acetylene black, graphene, carbon nanotubes, or flake graphite.

In an embodiment of the present invention, the resin reactant includes sucrose, glucose, cellulose, astaxanthin, plant acid, or a combination thereof.

In an embodiment of the present invention, carbonization is performed under an inert gas at 600°C to 1000°C.

Based on the above, the present invention provides a lithium-ion battery silicon-carbon electrode material and a preparation method thereof. The resin carbon layer is smoothly coated on the surface of the graphite particles by adding a resin reactant. The silicon or silicon compound and the conductive material are included. Covered in the resin carbon layer without exposure. In this way, chemical modification methods are used to improve the shortcomings of hard carbon first-lap irreversibility and higher BET, while retaining the advantages of hard carbon steel structure, so as to effectively improve the life performance of lithium-ion battery silicon carbon anode materials.

In this article, the range represented by "a value to another value" is a general way to avoid listing all the values in the range one by one in the specification. Therefore, the record of a specific numerical range covers any numerical value in the numerical range and the smaller numerical range defined by any numerical value in the numerical range, as if the arbitrary numerical value and the smaller numerical value are clearly written in the specification The scope is the same.

The following examples are listed in conjunction with the accompanying drawings for detailed description, but the provided examples are not intended to limit the scope of the present invention. In addition, the drawings are for illustrative purposes only, and are not drawn in accordance with the original dimensions.

FIG. 1 is a schematic diagram of a silicon-carbon electrode material for a lithium ion battery according to an embodiment of the present invention.

Please refer to Figure 1, the lithium ion battery silicon carbon electrode material of the present invention includes graphite particles 10 and a resin carbon layer 20. The resin carbon layer 20 smoothly coats the surface of the graphite particles 10, silicon or silicon compound (in Figure 1, for example It is nanosilicon 30, but the present invention is not limited to this) and the conductive material 40 is coated in the resin carbon layer 20 without being exposed. In this embodiment, the particle size of the graphite particles is, for example, 5 μm to 30 μm, the average thickness of the resin carbon layer 20 is, for example, 5 nm to 500 nm, the average thickness change rate is 12.34%, and the thickness change standard deviation is 5.16. It can be seen that the resin carbon layer 20 is smoothly coated on the graphite particles 10 and has a uniform thickness. In more detail, the average thickness, average thickness change rate, and thickness change standard deviation of the resin carbon layer 20 are obtained by image processing through a scanning electron microscope (Scanning Electron Microscope, SEM). The definition of the average rate of change of thickness is as follows. The minimum value obtained by image processing is used as the basic value, and each value is subtracted from the basic value and the average is taken. The conductive material may include metal nano particles, conductive carbon black, acetylene black, graphene, carbon nanotubes or flake graphite. The metal nano particles are, for example, composed of aluminum, silver or copper, but the present invention is not based on this. Is limited.

The present invention also provides a method for preparing the silicon-carbon electrode material of a lithium ion battery, which is used to manufacture the silicon-carbon electrode material of a lithium ion battery in FIG. 1, and the preparation method includes the following steps. First, the graphite particles, silicon or silicon compound and the conductive material are uniformly mixed, then the resin is added for stirring and mixing, and the resin reactant is added during or after the curing process. In this embodiment, relative to 100 wt% of graphite particles, the addition amount of silicon or silicon compound and conductive material is, for example, 5 wt% to 20 wt%, and the addition amount of resin is, for example, 10 wt% to 50 wt%. The addition amount of the reactant is 5 wt% to 15 wt%. In more detail, the resin may include phenolic resin, urea resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin, polyurethane, polyethylene, polypropylene, polystyrene, ABS resin, polyvinyl chloride, acrylic resin, nylon POM, polycarbonate, cellulose resin or polyethylene terephthalate, conductive materials can include nano metal particles, conductive carbon black, acetylene black, Graphene, carbon nanotubes or flake graphite, the resin reactant may include sucrose, glucose, cellulose, astaxanthin, plant acid or a combination thereof. Afterwards, for example, carbonization is carried out under an inert gas at 600°C to 1000°C, so that the resin carbon layer 20 is smoothly coated on the surface of the graphite particles 10. However, the present invention is not limited to this) and the conductive material 40 is coated in the resin carbon layer 20 without being exposed.

In the prior art, the resin composite silicon carbon material that has not been processed by the preparation method of the present invention cannot form a smoothly coated resin carbon layer on the surface of the graphite particles, nor can it coat silicon or silicon compounds and conductive materials in the resin. The carbon layer is not exposed, but an uneven layer with rhomboid is formed on the surface of the graphite particles, and silicon or silicon compounds and conductive materials are easily exposed. In contrast, because the method for preparing a silicon-carbon electrode material for a lithium ion battery provided by the present invention adds a resin reactant for chemical modification, a smoothly coated resin carbon layer can be formed on the surface of the graphite particles, and Silicon or silicon compound and conductive material are coated in the resin carbon layer without being exposed. In more detail, through the preparation method of the lithium ion battery silicon carbon electrode material of the present invention, the BET of the prepared lithium ion battery silicon carbon electrode material can be ^{reduced from 17.78 m 2} /g to 2.99 m ² /g, and the first lap irreversibility rate It can be reduced from 20% to 10% to 14%, and the capacitance can reach 570mAh/g at the first turn. Therefore, it can effectively increase the life of the silicon-carbon electrode material of lithium-ion batteries.

In this example, the BET is measured by Micromeritics ASAP2020, and the sample is first dehumidified at 350°C for 1 hour, and then the specific surface area (m ² /g) of the powder is calculated using the nitrogen absorption and de-negative curve. The first lap irreversibility rate is measured using Arbin LBT20084 (the power measured under the following conditions, the first lap discharge power/first lap charge power is the first lap efficiency): First lap charge and discharge 0.1C charge to 0.01V 0.1C discharge to 2.0V Cycle charge and discharge 1C charge to 0.01V 1C discharge to 2.0V

Hereinafter, the silicon-carbon electrode material of the lithium ion battery and the preparation method thereof of the above-mentioned embodiment will be described in detail through experimental examples. However, the following experimental examples are not intended to limit the present invention. Experimental example

In order to prove that the preparation method of the silicon-carbon electrode material for lithium-ion batteries of the present invention can effectively increase the life of the silicon-carbon electrode material for lithium-ion batteries, this experimental example is specially made as follows.

Add 15g of silicon and flake graphite to 100g of graphite. After stirring, add 30g of epoxy resin (Epoxy) and 5g of glucose and further stir. After curing, carbonize with inert gas at 850°C to form the lithium ion of the present invention. Battery silicon carbon electrode material. After using this material to make button batteries in a conventional manner, the measurement results show that the BET can be ^{reduced from 17.78 m 2} /g to 2.99 m ² /g, and the first-lap irreversibility rate can be reduced from 20% to 10% to 14%. The capacitor can reach 570mAh/g for the first turn.

In summary, the present invention provides a silicon carbon electrode material for lithium ion batteries and a preparation method thereof. By adding a resin reactant, the resin carbon layer can be smoothly coated on the surface of the graphite particles. The material is covered in the resin carbon layer without being exposed. In this way, chemical modification is used to improve the shortcomings of hard carbon's first-lap irreversibility and higher BET. The BET can be ^{reduced from 17.78 m 2} /g to 2.99 m ² /g, and the first-lap irreversibility can be reduced from 20% to 10%. 14%, the first lap of the capacitor can reach 570mAh/g, while retaining the advantages of the hard carbon steel structure, in order to effectively improve the life performance of the lithium-ion battery silicon carbon anode material.

10: Graphite particles 20: Resin carbon layer 30: Nano silicon 40: conductive material

FIG. 1 is a schematic diagram of a silicon-carbon electrode material for a lithium ion battery according to an embodiment of the present invention.

10: Graphite particles

20: Resin carbon layer

30: Nano silicon

40: conductive material

Claims (10)

A silicon-carbon electrode material for a lithium ion battery, comprising: graphite particles; and a resin carbon layer, which is smoothly coated on the surface of the graphite particles, silicon or silicon compounds and conductive materials are coated in the resin carbon layer, wherein The average thickness of the resin carbon layer is 5 nm to 500 nm, the average thickness change rate is 11% to 17%, and the thickness change standard deviation is 4 to 6. According to the first item of the scope of patent application, the silicon-carbon electrode material for lithium ion batteries, wherein the graphite particles have a particle size of 5 μm to 30 μm. According to the first item of the scope of patent application, the silicon-carbon electrode material for lithium ion batteries, wherein the conductive material includes metal nano particles, conductive carbon black, acetylene black, graphene, carbon nanotubes or flake graphite. A preparation method of silicon carbon electrode material for lithium ion battery includes: mixing graphite particles, silicon or silicon compound and conductive material, adding resin for stirring and mixing, adding resin reactant during or after curing; and carbonization , So that the resin carbon layer is smoothly coated on the surface of the graphite particles, the silicon or the silicon compound and the conductive material are coated in the resin carbon layer, wherein relative to 100wt% of the graphite The particles, the silicon or the silicon compound and the conductive material are added in an amount of 5 wt% to 20 wt%. According to the method for preparing a silicon-carbon electrode material for a lithium ion battery as described in item 4 of the scope of the patent application, the resin is added in an amount of 10% to 50% by weight relative to 100% by weight of the graphite particles. According to the method for preparing a silicon-carbon electrode material for a lithium ion battery as described in item 4 of the scope of patent application, the addition amount of the resin reactant is 5 wt% to 15 wt% relative to 100 wt% of the graphite particles. The method for preparing silicon-carbon electrode material for lithium ion batteries as described in item 4 of the scope of patent application, wherein the resin includes phenolic resin, urea resin, melamine resin, unsaturated polyester resin, epoxy resin, and silicone resin , Polyurethane, polyethylene, polypropylene, polystyrene, ABS resin, polyvinyl chloride, acrylic resin, nylon POM, polycarbonate, cellulose resin or polyethylene terephthalate . As described in item 4 of the scope of patent application, the method for preparing silicon-carbon electrode material for lithium ion batteries, wherein the conductive material includes metal nano particles, conductive carbon black, acetylene black, graphene, carbon nanotubes or flake graphite . As described in item 4 of the scope of patent application, the method for preparing a silicon-carbon electrode material for a lithium ion battery, wherein the resin reactant includes sucrose, glucose, cellulose, astaxanthin, plant acid or a combination thereof. As described in item 4 of the scope of patent application, the method for preparing silicon-carbon electrode materials for lithium-ion batteries, wherein carbonization is carried out under an inert gas at a temperature of 600°C to 1000°C.

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