KR20220121609A - Method for manufacturing composite cathode active material for lithium ion battery - Google Patents

Abstract

The present invention relates to a method for manufacturing a composite cathode active material for a lithium-ion battery and a composite cathode active material for a lithium-ion battery manufactured thereby. The method for manufacturing a composite cathode active material for a lithium-ion battery according to the present invention comprises a step of performing a relatively low-temperature thermal treatment process, thereby giving excellent economic efficiency. Therefore, the composite cathode active material for a lithium-ion battery manufactured according to the present invention comprises an additional coating layer including unit sheet containing a carbon composite, which prevents an electrolyte from coming in direct contact with the cathode active material to inhibit reaction between the electrolyte and the cathode active material. Accordingly, SEI generation is inhibited to reduce surface resistance and maintain ion conductivity. In addition, the composite cathode active material for a lithium-ion battery according to the present invention comprises an additional coating layer including unit sheet containing a carbon composite and is structurally stable, so that insertion and desorption of a lithium-ion can be stably performed and capacity can be stably maintained even though charging or discharging is performed for a long time under a high-voltage environment.

Description

Method for manufacturing composite cathode active material for lithium ion battery

It relates to a method for manufacturing a composite positive electrode active material for a lithium ion battery, and a composite positive electrode active material for a lithium ion battery manufactured thereby.

With the development of mobile electronic devices such as cell phones, tablets, and laptops, secondary batteries that can reversibly store and utilize energy have recently been attracting attention. In particular, due to the advent of the electric vehicle or large-scale energy storage device market requiring high output and energy density, the demand for high-output and high-density secondary batteries is expected to increase.

Among them, the lithium ion battery has a high capacity and high energy density, unlike the conventional nickel hydride battery or nickel cadmium battery, so that research and development is being actively carried out in response to the increase in demand for high-performance secondary batteries.

Among the components included in the lithium ion battery, the cathode active material accounts for 40% of the unit price and acts as a factor that has the greatest influence on the electrochemical performance.

However, although the conventionally used positive electrode active material has a high theoretical capacity, in reality, the problem of structural instability caused by excessive desorption-insertion of lithium ions inside the positive electrode active material during the charge-discharge process, the reactivity and voltage range of the active material-electrolyte interface When the battery is driven in a high voltage range due to an increase in the internal resistance of the battery due to the decomposition of the electrolyte due to the increase, the capacity decreases rapidly, and only about 50% of the theoretical capacity is used.

Accordingly, there was a need for research to prevent contact between the electrolyte and the surface of the positive electrode active material and to improve structural stability.

Republic of Korea Patent Publication No. 10-2175842

The present invention is intended to solve the above problems, and the specific objects thereof are as follows.

The present invention prepares a first precursor by coating the surface of the positive electrode active material with a silane-based coating agent, and coating the surface of the first coated positive electrode active material with a unit sheet precursor containing a carbon composite to prepare a second precursor, and then heat treating it An object of the present invention is to provide a method for manufacturing a composite cathode active material comprising the steps.

In addition, prepared by the above manufacturing method, the cathode active material; a coating layer containing a silane-based coating agent on the surface of the cathode active material; and an additional coating layer including a unit sheet including a carbon composite on the surface of the coating layer;

The object of the present invention is not limited to the object mentioned above. The objects of the present invention will become more apparent from the following description, and will be realized by means and combinations thereof described in the claims.

A method for manufacturing a composite positive electrode active material for a lithium ion battery according to the present invention comprises the steps of preparing a first precursor by coating the surface of the positive electrode active material with a silane-based coating agent; Preparing a unit sheet precursor by peeling the unit sheet from the carbon-based layered structure in which a plurality of unit sheets including a carbon composite are stacked; preparing a second precursor by coating the surface of the first precursor with the unit sheet precursor; and heat-treating the second precursor.

The carbon composite may include at least one selected from the group consisting of fluorocarbons (CF _x ), graphene fluoride, fluorinated carbon nanotubes, and fluorocarbon composites.

In the step of preparing the unit sheet precursor, the carbon-based layered structure may be added to a polar solvent, followed by ultrasonication.

The ultrasonic treatment may be performed under conditions of 2 to 24 hours and 20 to 40 kHz.

The polar solvent may include at least one selected from the group consisting of N-methyl-2-pyrrolidone (N-Methyl-2-Pyrrolidone; NMP), methyl alcohol, ethyl alcohol, isopropyl alcohol, and THF. .

The preparing of the first precursor may include preparing a mixture by mixing the cathode active material and a silane-based coating agent; and mixing the mixture at a temperature of 75 to 85° C. for 20 to 28 hours at a stirring speed of 1000 to 1500 rpm.

In the preparing of the second precursor, the first precursor and the unit sheet precursor may be mixed and then stirred.

The stirring may be performed at a stirring speed of 500 to 800 RPM.

In the heat treatment of the second precursor, the heat treatment may be performed at a temperature of 350 to 450° C. for 10 to 14 hours.

A composite positive electrode active material for a lithium ion battery according to the present invention includes a positive electrode active material; a coating layer containing a silane-based coating agent on the surface of the cathode active material; and an additional coating layer including a unit sheet including a carbon composite on the surface of the coating layer.

The carbon composite may include at least one selected from the group consisting of fluorocarbon (CF _x ), graphene fluoride, carbon fluoride nanotube, and fluorocarbon composite.

The method for manufacturing a composite positive electrode active material for a lithium ion battery of the present invention performs a relatively low-temperature heat treatment process, and thus has an advantage of excellent economic efficiency.

In addition, in the composite cathode active material for lithium ion batteries manufactured by the above manufacturing process, an additional coating layer including a unit sheet including a carbon composite prevents direct contact between the electrolyte and the cathode active material, so there is an effect of suppressing the reaction between the electrolyte and the cathode active material. In addition, since the generation of SEI is suppressed, there is an effect of reducing the surface resistance and maintaining the ionic conductivity.

In addition, the composite positive electrode active material for a lithium ion battery according to the present invention includes an additional coating layer including a unit sheet including a carbon composite and is structurally stable, so that insertion-desorption of lithium ions can be stably performed, and in a high voltage environment It has the effect of stably maintaining the capacity even after charging and discharging for a long time.

The effects of the present invention are not limited to the above-mentioned effects. It should be understood that the effects of the present invention include all effects that can be inferred from the following description.

1 is a flowchart schematically illustrating a method for manufacturing a composite positive electrode active material for a lithium ion battery according to the present invention.
FIG. 2A is an SEM image of the composite positive active material according to Example 1, and FIG. 2B is an SEM image of the positive electrode active material according to Comparative Example 1. Referring to FIG.
3 is a graph showing the XRD analysis results of the composite positive electrode active material according to Example 1 and the positive electrode active material according to Comparative Example 1. FIG.
4 is a graph evaluating the capacity according to the number of cycles of the lithium secondary batteries according to Example 2 and Comparative Example 2. Referring to FIG.

The above objects, other objects, features and advantages of the present invention will be easily understood through the following preferred embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed subject matter may be thorough and complete, and that the spirit of the present invention may be sufficiently conveyed to those skilled in the art.

In describing each figure, like reference numerals have been used for like elements. In the accompanying drawings, the dimensions of the structures are enlarged than the actual size for clarity of the present invention. Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. The singular expression includes the plural expression unless the context clearly dictates otherwise.

In the present specification, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It is to be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof. Also, when a part of a layer, film, region, plate, etc. is said to be “on” another part, this includes not only cases where it is “directly on” another part, but also cases where another part is in between. Conversely, when a part, such as a layer, film, region, plate, etc., is "under" another part, this includes not only cases where it is "directly under" another part, but also cases where there is another part in between.

Unless otherwise specified, all numbers, values, and/or expressions expressing quantities of ingredients, reaction conditions, polymer compositions and formulations used herein include, among other things, the numbers, values and/or expressions such that these numbers essentially occur in obtaining such values, among others. Since they are approximations reflecting various uncertainties in the measurement, it should be understood as being modified by the term "about" in all cases. Also, where the disclosure discloses numerical ranges, such ranges are continuous and inclusive of all values from the minimum to the maximum inclusive of the range, unless otherwise indicated. Furthermore, when such ranges refer to integers, all integers inclusive from the minimum to the maximum inclusive are included, unless otherwise indicated.

In this specification, when a range is described for a variable, the variable will be understood to include all values within the stated range including the stated endpoints of the range. For example, a range of “5 to 10” includes the values of 5, 6, 7, 8, 9, and 10, as well as any subranges such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc. It will be understood to include any value between integers that are appropriate for the scope of the recited range, such as 5.5, 6.5, 7.5, 5.5 to 8.5 and 6.5 to 9, and the like. Also for example, a range of “10% to 30%” includes values such as 10%, 11%, 12%, 13%, and all integers up to and including 30%, as well as 10% to 15%, 12% to It will be understood to include any subrange, such as 18%, 20% to 30%, etc., as well as any value between reasonable integers within the scope of the recited range, such as 10.5%, 15.5%, 25.5%, and the like.

The positive electrode active material used in conventional lithium-ion batteries has a rapid capacity decrease when driven in a high voltage range due to structural instability problems in the charge-discharge process and an increase in internal resistance caused by the active material-electrolyte reaction. However, there was a problem that only about 50% of the theoretical capacity was used.

In order to solve this problem, studies of forming an oxide coating layer are being conducted, but this also requires a high-temperature heat treatment process, and the coating layer acts as a resistance to reduce ionic conductivity.

Accordingly, the present inventors have studied diligently to solve the above problem. As a result, when manufacturing a composite positive electrode active material for a lithium ion battery including a coating layer including a unit sheet including a carbon composite, a relatively low temperature heat treatment process is performed to perform a composite positive electrode. The effect of inhibiting the reaction between the electrolyte and the positive electrode active material while manufacturing the active material, the effect of reducing the surface resistance, the effect of maintaining the ionic conductivity, the effect of stably performing insertion/desorption of lithium ions, and the effect of long-term charging and desorption in a high voltage environment The present invention was completed by confirming that there is an effect of stably maintaining the capacity even after discharging.

1 is a flowchart schematically illustrating a method for manufacturing a composite positive electrode active material for a lithium ion battery according to the present invention. Referring to this, coating the surface of the positive electrode active material with a silane-based coating agent to prepare a first precursor (S10); Preparing a unit sheet precursor by peeling the unit sheet from the carbon-based layered structure in which a plurality of unit sheets including a carbon composite are stacked (S20); preparing a second precursor by coating the surface of the first coated cathode active material with the unit sheet precursor (S30); and heat-treating the second precursor (S40).

The step of preparing the first precursor (S10) is a step of preparing the first precursor by coating the surface of the positive electrode active material with a silane-based coating agent. By coating a silane-based coating agent on the surface of the positive electrode active material, the surface charge of the positive electrode active material is replaced with a positive charge, and through electrostatic attraction, a unit sheet precursor containing fluorocarbon having a negative surface charge is coated on the surface. .

Specifically, preparing the first precursor may include preparing a mixture by mixing the cathode active material and a silane-based coating agent; mixing the mixture at a temperature of 75-85° C. for 20-28 hours at a stirring speed of 1000-1500 rpm; may include

The positive electrode active material is a positive electrode active material that can be used in a lithium ion battery, and may be an oxide active material or a sulfide active material. For example, the oxide active material is a rock salt layer active material such as LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , Li _1+x Ni _1/3 Co _1/3 Mn _1/3 O ₂ , LiMn ₂ O ₄ , Li Spinel-type active material such as (Ni _0.5 Mn _1.5 )O ₄ , LiNiVO ₄ , LiCoVO ₄ inverse spinel-type active material, LiFePO ₄ , LiMnPO ₄ , LiCoPO ₄ , LiNiPO ₄ Olivine-type active material such as Li ₂ FeSiO ₄ , Li ₂ Silicon-containing active material such as MnSiO ₄ , LiNi _0.8 Co _(0.2-x) Al _x O ₂ (0<x<0.2), rock salt layer type active material in which a part of transition metal is substituted with a dissimilar metal, Li _1+x Mn _{2- xy} M _y O ₄ (M is at least one of Al, Mg, Co, Fe, Ni, and Zn, 0<x+y<2) may be a spinel-type active material in which a part of the transition metal is substituted with a different metal. In addition, the sulfide active material may be copper chevrel, iron sulfide, cobalt sulfide, nickel sulfide, etc., and is not limited to including a specific component, but preferably has a high theoretical capacity (274 mAh/g) and is stably driven for a long time. Lithium cobalt oxide (LiCoO ₂ ), which is a possible rock salt layer-type active material, may be included.

After adding a solvent to the positive electrode active material, ultrasonication may be performed in advance. This is to prevent aggregation of the positive electrode active material and to uniformly disperse it in the solvent. The solvent may include a solvent capable of well mixing both the positive electrode active material and a silane-based coating agent to be described later, for example, toluene and N-methyl-2-pyrrolidone (NMP). The ultrasonic treatment may be performed under conditions of 5 to 30 minutes and 20 to 40 kHz.

A mixture may be prepared by mixing the positive electrode active material and the silane-based coating agent added to the solvent.

The silane-based coating agent is a conventional silane-based coating agent for coating the cathode active material of a lithium ion battery, for example, 3-aminopropyl trimethoxysilane ((3-aminopropyl) trimethoxysilane), 3-aminopropyl triethoxysilane It may include at least one selected from the group consisting of ((3-aminopropyl)triethoxysilane) and aminopropylsilane, and is not limited to including only a specific component, but preferably, a positive surface charge is applied to the active material. It may include 3-aminopropyl trimethoxysilane ((3-aminopropyl)trimethoxysilane) having an amine group that can be imparted.

The mixture may be mixed at a temperature of 75-85° C. for 20-28 hours at a stirring rate of 1000-1500 pm. Out of the above range, if the mixing temperature is too low, the reaction of the silane coating agent is slow and it takes a lot of time to form a uniform coating. If the mixing temperature is too high, the solvent may excessively evaporate or damage the active material. There is a disadvantage that In addition, if the mixing time is too short, a uniform coating layer is not formed because the silane coating agent does not have enough time to react with the hydroxyl groups on the surface of the active material. If the mixing time is too long, the active material surface may be chemically modified. There is a disadvantage that In addition, if the stirring speed is too slow, there is a disadvantage that the positive electrode active material is precipitated, and if the stirring speed is too fast, the reaction between the silane coating agent and the active material is not performed smoothly, so that the coating layer may not be properly formed on the active material.

After the stirring, the method may further include washing and drying the first precursor. This is to remove the remaining silane coating solution after the reaction is finished. Specifically, the first precursor may be washed with the solvent contained in the mixture, and then vacuum dried at a temperature of 55 to 75° C. for 22 to 26 hours.

The step of preparing the unit sheet precursor (S20) is a step of finally producing a unit sheet structure including the unit sheet by peeling the unit sheet from the carbon-based layered structure in which a plurality of unit sheets including a carbon composite are stacked. When a composite positive electrode active material is prepared using a unit sheet precursor peeled from the layered structure into a unit sheet containing a carbon composite, the surface stability of the active material is increased, and a side reaction with the electrolyte in a high voltage environment is reduced, thereby increasing the lifespan characteristics. because there is

Specifically, a carbon-based layered structure in which a plurality of unit sheets including the carbon composite are stacked is added to a polar solvent, and then a unit sheet precursor can be obtained by ultrasonic treatment.

The carbon composite is a material capable of forming a unit sheet and finally forming a carbon-based layered structure, for example, fluorocarbon (CF _x ), graphene fluoride, fluorinated carbon nanotubes, 1 selected from the group consisting of fluorocarbon composites It may include more than one species, and the fluorocarbon composite may be, for example, synthetic fluoride graphite, natural fluoride graphite, low crystalline carbon fluoride, etc., and is not limited to including only a specific component, but preferably on the surface of the active material. It may contain carbon fluoride (CF _x ) that prevents direct contact with the electrolyte and inhibits side reactions by forming lithium fluoride.

The polar solvent is a solvent capable of dissolving all of the unit sheet including the carbon-based layered structure and the carbon composite peeled therefrom, for example, the polar solvent is N-methyl-2-pyrrolidone (N-Methyl- 2-Pyrrolidone; NMP), may include one or more selected from the group consisting of methyl alcohol, ethyl alcohol, isopropyl alcohol, and THF, and is not limited to including only a specific component, but preferably, a C-F bond It may contain N-methyl-2-pyrrolidone (NMP), which is a type of dipolar solvent that can change the chemical environment of the carbon complex constituting it.

The ultrasonic treatment for obtaining the unit sheet precursor may be performed under conditions of 2 to 24 hours and 20 to 40 kHz to peel the unit sheet including the carbon composite from the carbon-based layered structure. If the above conditions for peeling the unit sheet from the carbon-based layered structure are deviated, there is a disadvantage in that peeling is not made or fluorine is excessively separated from the unit sheet.

The step of preparing the second precursor ( S30 ) is a step of preparing a second precursor by coating the surface of the first precursor with the unit sheet precursor.

Specifically, after mixing the first precursor and the unit sheet precursor, the second precursor may be prepared by stirring. Through the above treatment, in order to solve the charge imbalance between the carbon composite contained in the unit sheet in the unit sheet precursor and the surface of the first precursor, the surface of the active material that is relatively heavy and positively charged in the solvent is light and negatively charged. The unit sheet precursors are bonded due to the electrostatic attraction due to the binding relationship, and as a result, the surface of the first precursor is coated with the unit sheet including the carbon composite in the unit sheet precursor to prepare the second precursor.

The stirring can be performed under a stirring speed condition of 500 to 800 RPM, and if the stirring speed is fast outside the above range, there is a disadvantage in that a non-uniform unit sheet coating is formed on the surface of the first precursor.

The step of heat-treating the second precursor (S40) includes heat-treating the second precursor and finally, a coating layer containing a silane-based coating agent on the surface of the cathode active material; and an additional coating layer including a unit sheet including a carbon composite on the surface of the coating layer. This is to form lithium fluoride that protects the surface of the active material and increases stability through the heat treatment.

The heat treatment for preparing the composite positive electrode active material for a lithium ion battery may be performed at a temperature of 350 to 450° C. for 10 to 14 hours. Out of the above range, if the heat treatment time is too short, the reaction between the first precursor and the unit sheet precursor does not occur sufficiently, so that the formation of the coating layer containing fluorocarbon is unevenly formed, and if the heat treatment time is too long, the surface of the first precursor The disadvantage is that it can be excessively oxidized or damaged. In addition, if the heat treatment temperature is too low, the reaction between the unit sheet precursor and the first precursor does not occur, so a coating layer is not formed. There are disadvantages that cause

That is, the method for manufacturing a composite positive electrode active material for a lithium ion battery according to the present invention performs a relatively low temperature heat treatment process, and thus has an advantage of excellent economic efficiency.

The composite positive electrode active material for a lithium ion battery according to the present invention is manufactured by the above manufacturing process, the positive electrode active material; a coating layer containing a silane-based coating agent on the surface of the cathode active material; and an additional coating layer including a unit sheet including a carbon composite on the surface of the coating layer.

That is, the composite positive electrode active material for a lithium ion battery according to the present invention is manufactured by the above manufacturing process, and an additional coating layer including a unit sheet including a carbon composite prevents direct contact between the electrolyte and the positive electrode active material, so that the reaction between the electrolyte and the positive electrode active material is As well as having an inhibitory effect, since the SEI generation is suppressed, there is an effect of reducing the surface resistance and maintaining the ionic conductivity. In addition, since the additional coating layer including the unit sheet is structurally stable, insertion-desorption of lithium ions can be stably performed, and the capacity is stably maintained even when charging and discharging for a long time in a high voltage environment.

The present invention will be described in more detail with reference to the following examples. The following examples are only examples to help the understanding of the present invention, and the scope of the present invention is not limited thereto.

Example 1: Preparation of composite positive electrode active material for lithium ion battery

(S10) The first precursor was prepared as follows. Specifically, lithium cobalt oxide (LiCoO ₂ ) was used as the positive electrode active material. To coat the positive electrode active material with 3-aminopropyl trimethoxysilane, which is used as a silane-based coating agent, 4 g of the positive electrode active material was added to a three-necked flask filled with 200 ml of toluene, a solvent, and ultrasonication was performed at 20 kHz for 30 minutes. do. And, when the ultrasonic treatment was finished, 2ml of aminopropyl trimethoxysilane ((3-aminopropyl)trimethoxysilane), a silane-based coating agent, was added to prepare a mixture. Then, the mixture was stirred at 1000 rpm at 80° C. for 24 hours using a mantle, and then heat-treated at 400° C. for 12 hours. Then, the heat-treated mixture was washed three times using a centrifuge, and toluene was used as the washing solvent. Then, the first precursor was prepared by vacuum drying at a temperature of 60° C. for 24 hours.

(S20) A carbon-based layered structure in which a plurality of unit sheets including fluorocarbon (CF _x ) are laminated is placed in 100 ml of N-methyl-2-pyrrolidone (NMP), a polar solvent, and ultrasonication is performed for 2 hours. In the process, a unit sheet precursor containing 0.5 g of a unit sheet containing fluorocarbon (CF _x ), which is a carbon composite, was obtained.

(S30) 0.3 g of the first precursor is put into 50 ml of ultrapure water, dispersed, and then put into a beaker together with 50 ml of the unit sheet precursor peeled off through ultrasonication under the condition of 20 kHz for 30 minutes and stirred for 1 hour to the second precursor got The second precursor was washed three times through a centrifuge, and the solvent was washed with water and then dried.

(S40) The dried second precursor was heat-treated at 400° C. for 12 hours using an electric furnace to finally prepare a composite cathode active material for a lithium ion battery.

Example 2: Lithium ion battery manufacturing using positive electrode including composite positive active material for lithium ion battery

As a positive electrode, the composite positive electrode active material for a lithium ion battery according to Example 1 was used. In addition, a lithium metal foil was used as the negative electrode. In addition, as the electrolyte, an electrolyte in which LiPF ₆ salt of 1M concentration was dissolved in a non-aqueous electrolyte in which ethylene carbonate (EC) and ethylmethyl carbonate (EMC) were mixed in a 1:1 volume ratio was used. In addition, using a porous polyethylene (PE) separator as a separator, a coin cell (2032 type) lithium ion battery was finally manufactured.

Comparative Example 1: Conventional positive electrode active material

Compared with Example 1, a conventional lithium cobalt oxide (LiCoO ₂ ) that does not contain a coating layer, not a composite positive electrode active material for a lithium ion battery, was used as a positive electrode active material.

Comparative Example 2: Lithium-ion battery manufacturing using a positive electrode including a conventional positive electrode active material

Compared with Example 2, a lithium ion battery was prepared in the same manner as in Example 2, except that the conventional positive electrode active material according to Comparative Example 1 was used instead of the composite positive electrode active material for a lithium ion battery.

Experimental Example 1: Scanning electron microscope (SEM) analysis of positive electrode active material

SEM analysis results of the composite positive electrode active material according to Example 1 and the positive electrode active material according to Comparative Example 1 are shown in FIGS. 2A and 2B .

Specifically, FIG. 2A is an SEM image of the composite positive active material according to Example 1, and FIG. 2B is an SEM image of the positive electrode active material according to Comparative Example 1. As shown in FIG.

Referring to FIGS. 2A and 2B , the composite cathode active material according to Example 1 showed a particle size distribution of 5 to 10 μm, and a layered structure was not seen on the surface. Accordingly, the particle size distribution of the cathode active material according to Comparative Example 1 was similar to that of Example 1, but unlike Example 1, it was confirmed that the layered structure was clearly exposed on the surface. Accordingly, it was confirmed that the composite positive electrode active material for a lithium ion battery according to the present invention has an additional coating layer including a unit sheet including a carbon composite on the surface thereof.

Experimental Example 2: X-ray diffraction (XRD) analysis of cathode active material

The results of XRD analysis of the composite positive active material according to Example 1 and the positive electrode active material according to Comparative Example 1 are shown in FIG. 3 .

3, since there was no difference in the XRD analysis results of the composite positive electrode active material according to Example 1 and the positive electrode active material according to Comparative Example 1, the composite positive electrode active material for a lithium ion battery according to the present invention includes a carbon composite on the surface It was confirmed that there was no significant change in the structure of the positive electrode active material even when an additional coating layer including the unit sheet was formed.

Experimental Example 3: Battery life performance evaluation

The performance evaluation results of the lithium ion batteries according to Example 2 and Comparative Example 2 are shown in FIG. 4 .

Specifically, FIG. 4 is a graph evaluating the capacity according to the number of cycles of the lithium secondary batteries according to Example 2 and Comparative Example 2. Referring to FIG.

On the other hand, for performance evaluation, the lithium ion battery was charged to 4.5 V and then discharged to 3 V, and charged and discharged at 0.1 C twice in total. Thereafter, 1 to 50 charge/discharge was performed at 0.5C.

In the case of Example 2, it was confirmed that the decrease in capacity had a more gentle slope than Comparative Example 2. Specifically, after charging and discharging up to 50 cycles, Example 2 showed a higher capacity of 50 mAh/g than Comparative Example 2.

That is, it can be seen that the lithium ion battery prepared with the composite positive electrode active material for lithium ion battery according to the present invention exhibits stable lifespan characteristics even in a high voltage environment.

Claims (11)

preparing a first precursor by coating the surface of the positive electrode active material with a silane-based coating agent;
Preparing a unit sheet precursor by peeling the unit sheet from the carbon-based layered structure in which a plurality of unit sheets including a carbon composite are stacked;
preparing a second precursor by coating the surface of the first precursor with the unit sheet precursor; and
A method for manufacturing a composite positive electrode active material for a lithium ion battery comprising the step of heat-treating the second precursor. According to claim 1,
The carbon composite is fluorocarbon (CF _x ), graphene fluoride, fluorinated carbon nanotubes, a composite cathode active material manufacturing method for a lithium ion battery comprising at least one selected from the group consisting of fluorocarbon composites. According to claim 1,
The step of preparing the unit sheet precursor
After the carbon-based layered structure is added to a polar solvent, the method for producing a composite positive electrode active material for a lithium ion battery is to perform ultrasonic treatment. 4. The method of claim 3,
The method for producing a composite cathode active material for a lithium ion battery is that the ultrasonic treatment is performed under conditions of 2 to 24 hours and 20 to 40 kHz. 4. The method of claim 3,
The polar solvent comprises at least one selected from the group consisting of N-methyl-2-pyrrolidone (N-Methyl-2-Pyrrolidone; NMP), methyl alcohol, ethyl alcohol, isopropyl alcohol, and THF. A method for manufacturing a composite cathode active material for a lithium ion battery. According to claim 1,
The step of preparing the first precursor,
preparing a mixture by mixing the cathode active material and a silane-based coating agent; and
Mixing the mixture at a temperature of 75-85° C. for 20-28 hours at a stirring speed of 1000-1500 rpm; According to claim 1,
The step of preparing the second precursor,
A method for manufacturing a composite positive electrode active material for a lithium ion battery by mixing the first precursor and the unit sheet precursor and then stirring. 8. The method of claim 7,
The agitation is a composite cathode active material manufacturing method that is performed under the stirring speed condition of 500 ~ 800 RPM. According to claim 1,
In the step of heat-treating the second precursor,
The heat treatment is a composite cathode active material manufacturing method that is performed at a temperature of 350 to 450 ℃ for 10 to 14 hours. positive electrode active material;
a coating layer containing a silane-based coating agent on the surface of the positive electrode active material; and
A composite positive electrode active material for a lithium ion battery comprising a; an additional coating layer including a unit sheet including a carbon composite on the surface of the coating layer. 11. The method of claim 10,
The carbon composite is a composite cathode active material for a lithium ion battery comprising at least one selected from the group consisting of fluorocarbon (CF _x ), graphene fluoride, carbon fluoride nanotube, and fluorocarbon composite.

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