WO2012036385A2

WO2012036385A2 - Anode active material, nonaqueous lithium secondary battery containing same, and preparation method thereof

Info

Publication number: WO2012036385A2
Application number: PCT/KR2011/006110
Authority: WO
Inventors: 김영준; 조용남; 박민식
Original assignee: 전자부품연구원
Priority date: 2010-09-16
Filing date: 2011-08-19
Publication date: 2012-03-22
Also published as: WO2012036385A3

Abstract

The present invention relates to an anode active material, a nonaqueous lithium secondary battery, and a preparation method thereof. The surface of a carbonaceous material is modified without using an electrolyte additive, and the reactivity and structural stability of the surface is improved, thereby obtaining long lifetime characteristics without deteriorating charge/discharge efficiency and rate characteristics when applied as an anode active material of a nonaqueous lithium secondary battery. According to the present invention, the anode active material comprises a carbonaceous material, and a coating layer formed on the surface of the carbonaceous material through hetero atom substitution, wherein the hetero atom can be phosphorus (P) or sulfur (S). A side reaction with an electrolyte on the surface of the carbonaceous material is inhibited and the structural stability of the surface is enhanced by forming a coating layer on the surface of the carbonaceous material with a hetero atom such as phosphorus (P) or sulfur (S), thereby improving the lifetime characteristics and rate characteristics of a lithium secondary battery.

Description

Anode Active Material, Non-aqueous Lithium Secondary Battery Having It and Manufacturing Method Thereof

The present invention relates to a non-aqueous lithium secondary battery and a method for manufacturing the same, and more particularly, to perform a side treatment of the carbon-based material applied as a negative electrode active material of the lithium secondary battery through heterogeneous element substitution to perform side reactions with the electrolyte on the surface. The present invention relates to a negative active material, a non-aqueous lithium secondary battery having the same, and a method of manufacturing the same, which suppresses and improves structural stability, thereby improving life and rate characteristics of a lithium secondary battery.

With the spread of portable small electric electronic devices, new secondary batteries such as nickel-metal hydride batteries and lithium secondary batteries have been actively developed.

Among them, a lithium secondary battery is a battery in which metal lithium is used as a negative electrode active material and a nonaqueous solvent is used as an electrolyte. Since lithium is a metal with a high tendency to ionize, development of a battery with high energy density is possible because of high voltage expression. Lithium secondary batteries using lithium metal as a negative electrode active material have been used for a long time as next generation batteries.

However, the lithium secondary battery, in which metal lithium is used as the negative electrode active material, grows and discharges from the negative electrode to dendrite as the charge and discharge are repeated, and penetrates the separator which is an insulator. There was a short disadvantage.

As a means for solving the problem of a lithium secondary battery whose cycle life is shortened due to deterioration of the negative electrode, it has been proposed to use a carbon-based material capable of inserting / desorbing lithium ions as a negative electrode active material as a negative electrode active material.

In a lithium secondary battery using a carbon-based material as a negative electrode, the reaction at the negative electrode during the charging and discharging removes lithium ions into the intercalation layer of carbon. During charging, electrons are transferred to the carbonaceous material of the negative electrode so that the carbon becomes negatively charged. In this case, lithium ions inserted into the positive electrode are detached and inserted into the carbonaceous material of the negative electrode. On the contrary, lithium ions inserted into the carbonaceous material of the negative electrode are removed and then inserted into the positive electrode. By using such a mechanism, deposition of metallic lithium at the negative electrode can be prevented, and a lithium secondary battery having good cycle life can be realized.

Lithium secondary batteries using this carbon-based material as a negative electrode active material have been put to practical use, which is called a lithium ion secondary battery, and has been widely used for power supply of portable electronic and communication devices. However, when the carbon-based material is used as the negative electrode active material, the charge and discharge potential of lithium is lower than the stable range of the existing non-aqueous electrolyte, so that decomposition reaction of the electrolyte occurs during charge and discharge, which is the current lithium secondary battery in which the carbon-based material is applied to the negative electrode. The low initial charge and discharge efficiency, the degradation of life characteristics and the rate characteristics are pointed as the root cause. For this reason, a method of stabilizing the surface of a carbon-based negative electrode active material using an electrolyte additive having a higher decomposition potential than conventional carbonate-based electrolytes such as various VC and FEC to secure long life characteristics of a non-aqueous lithium secondary battery using carbonaceous materials It is proposed.

However, these electrolyte additives improve the life characteristics, but could not solve the problem of lowering the rate characteristics and the charge and discharge efficiency.

Therefore, an object of the present invention is to modify the surface of the carbon-based material without using an electrolyte additive and improve the surface reactivity and structural stability, when applied as a negative electrode active material of a non-aqueous lithium secondary battery, long life without deterioration of charge and discharge efficiency and rate characteristics The present invention provides a negative electrode active material, a non-aqueous lithium secondary battery, and a method for manufacturing the same, which are surface-treated through heterogeneous element substitution capable of securing characteristics.

In order to achieve the above object, the present invention includes a carbon-based material, and a coating layer formed on the surface of the carbon-based material through heterogeneous substitution, the hetero-element is a negative electrode for a non-aqueous lithium secondary battery containing phosphorus (P) It provides an active material.

In the negative active material for a non-aqueous lithium secondary battery according to the present invention, the hetero element may include sulfur (S).

In the negative electrode active material for a non-aqueous lithium secondary battery according to the present invention, the carbonaceous material is at least in artificial graphite, natural graphite, graphitized carbon fiber, graphitized mesocarbon microbead, petroleum coke, resin, carbon fiber and pyrolytic carbon It may include one.

In the negative active material for a non-aqueous lithium secondary battery according to the present invention, the carbonaceous material is L _{a (110)} > 10 nm, L _{c (002)} > 10 nm. L _{a (110)} = 0.89λ / [B ₁₁₀ cos (θ ₁₁₀ )], L _{c (002)} = 0.89λ / [B ₀₀₂ cos (θ ₀₀₂ )], and λ is Cu Kα (λ = 0.15418 nm). It is a wavelength value and B is a full width at half-maximum (FWHM) value for the (110) or (002) peak according to the Bragg diffraction angle.

In the negative active material for a non-aqueous lithium secondary battery according to the present invention, the carbon-based material may have a d ₀₀₂ value of 0.344 nm or less with respect to the (002) peak.

In the negative active material for a non-aqueous lithium secondary battery according to the present invention, the carbon-based material may have a specific surface area of 10 m ² / g or less.

In the negative active material for a non-aqueous lithium secondary battery according to the present invention, the carbon-based material may have a degree of graphitization value of 0.4 to 1.0. The graphitization degree can be calculated as (3.44-d ₀₀₂ ) / (0.086).

In the negative active material for a non-aqueous lithium secondary battery according to the present invention, the coating layer may be 10% by weight or less compared to the carbonaceous material.

In the negative active material for a non-aqueous lithium secondary battery according to the present invention, the coating layer may be formed uniformly or partially on the surface of the carbonaceous material.

The present invention also provides a non-aqueous lithium secondary battery comprising a negative electrode having the negative electrode active material described above.

The present invention also includes a preparation step of preparing a carbon-based material and a heterogeneous material, and forming a coating layer through heterogeneous element substitution on the surface of the carbon-based material by using the heterogeneous material. The elemental material contains phosphorus (P).

In the method of manufacturing a negative active material for a non-aqueous lithium secondary battery according to the present invention, the hetero element material may include sulfur (S).

In the method for producing a negative active material for a non-aqueous lithium secondary battery according to the present invention, the hetero element material is NH₄PF₆, (NH₄)₂PO₄,NH₄PO₃, (NH₄)₂SO₃, (NH₄)₂SO₄, NH₄SO₄ And (NH₄)₂S₂O₈ At least one of the.

And in the method for producing a negative active material for a non-aqueous lithium secondary battery according to the present invention, the forming step, the step of dissolving the hetero-element material in a solvent to form a solution, the carbon-based material in the solution and uniformly mixed To form a mixture, a drying step of vacuum drying the mixture, and heat treatment of the dried material dried in the drying step by pyrolysis to form the coating layer based on the dissimilar elements on the surface of the carbonaceous material. It may include a step.

According to the present invention, by forming a coating layer on the surface of the carbon-based material used as a negative electrode active material of the non-aqueous lithium secondary battery through the substitution of heterogeneous elements such as phosphorous or sulfur, the surface of the surface of the carbon-based material by the coating layer formed In addition to reducing side reactions, structural stability can be achieved.

In addition, the negative electrode active material according to the present invention has an effect of improving the affinity with the electrolyte solution to improve the life characteristics and rate characteristics of the non-aqueous lithium secondary battery.

In addition, due to the simple surface treatment process there is an effect that can also improve the production efficiency of the negative electrode active material.

1 is a flowchart illustrating a method of manufacturing a negative active material for a non-aqueous lithium secondary battery, which is surface treated through dissimilar element substitution according to an embodiment of the present invention.

2 is a photograph showing a negative electrode active material according to an embodiment of the present invention and a comparative example.

3 is a view showing the results of EDS (Energy Dispersive Spectroscopy) analysis of the negative electrode active material according to Example 1 of the present invention.

4 is a view showing an EDS analysis result of a negative active material according to Example 2 of the present invention.

FIG. 5 is a graph showing XPS (X-ray Photoelectron Spectroscopy) analysis results of the anode active material according to Example 1 of the present invention.

6 is a graph showing the XPS analysis result of the negative electrode active material according to Example 2 of the present invention.

7 is a graph showing the results of X-ray diffraction (XRD) analysis of the negative electrode active material according to the Examples and Comparative Examples of the present invention.

8 is a graph showing the life characteristics of the non-aqueous lithium secondary battery according to the surface treatment temperature of the negative electrode active material according to the embodiment and the comparative example of the present invention.

9 is a graph showing the rate characteristics of the non-aqueous lithium secondary battery according to the Examples and Comparative Examples of the present invention.

In the following description, only parts necessary for understanding the operation according to the embodiment of the present invention will be described, it should be noted that the description of other parts will be omitted so as not to distract from the gist of the present invention.

Also, the terms or words used in the specification and claims described below should not be construed as being limited to the ordinary or dictionary meanings, and the inventors should use the concept of terms to explain their own invention in the best way. It should be interpreted as meanings and concepts corresponding to the technical idea of the present invention based on the principle that it can be properly defined. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only one preferred embodiment of the present invention, and do not represent all of the technical idea of the present invention, various modifications that can be substituted for them at the time of the present application It should be understood that there may be equivalents and variations.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention.

The negative active material for a non-aqueous lithium secondary battery according to the present invention includes a carbon-based material and a coating layer formed through heterogeneous element substitution on the surface of the carbon-based material. In this case, the heterologous element includes phosphorus (P) or sulfur (S).

The carbon-based material may be at least one selected from materials consisting of amorphous carbon such as artificial graphite, natural graphite, graphitized carbon fiber, graphitized mesocarbon microbead, petroleum coke, resin plastic, carbon fiber, and pyrolytic carbon.

In particular, in order to stably form the coating layer through heterogeneous element substitution on the carbon-based material, it is preferable to use the following carbon-based material in order to improve the life characteristics and rate characteristics of the non-aqueous lithium secondary battery to which the negative electrode active material is applied.

That is, it is preferable to use the thing of La ₍₁₁₀₎ > 10 nm and Lc ₍₀₀₂₎ > 10 nm as _a carbon type material. L _{a (110)} = 0.89λ / [B ₁₁₀ cos (θ ₁₁₀ )] and L _{c (002)} = 0.89λ / [B ₀₀₂ cos (θ ₀₀₂ )]. Where λ is the wavelength value of Cu Kα (λ = 0.15418 nm) and B is the full width at half for the (110) or (002) peak according to the Bragg diffraction angle -maximum) value. As the carbonaceous material, it is preferable to use a d ₀₀₂ value of 0.344 nm or less with respect to the (002) peak.

In addition, as the carbon-based material, those having a degree of graphitization value of 0.4 to 1.0 are preferably used. Graphitization degree = (3.44- _d002 ) / (0.086) can be calculated here.

In addition, it is preferable to use a carbonaceous material having a specific surface area of 10 m ² / g or less.

The coating layer may be formed by heat-treating the surface of the carbon-based material by a pyrolysis method using a heterogenous material of 10 wt% or less of the carbon-based material. That is, in the process of thermally dissociating the hetero element material, the components except the hetero element in the hetero element material are removed and the hetero element forms a coating layer on the surface of the carbon-based material. The coating layer may be uniformly formed on the entire surface of the carbonaceous material or may be formed only on a part of the surface of the carbonaceous material depending on the amount of the dissimilar element material to be heat treated. Heteroelement materials can exist in various compound forms, including heteroatoms, such as NH₄PF₆, (NH₄)₂PO₄,NH₄PO₃, (NH₄)₂SO₃, (NH₄)₂SO₄, NH₄SO₄, (NH₄)₂S₂O₈And the like, but are not limited thereto.

Thus, by forming a coating layer on the surface of the carbon-based material used as the negative electrode active material of the non-aqueous lithium secondary battery according to the present invention through the substitution of hetero elements such as phosphorus or sulfur, the surface of the surface by the coating layer formed on the surface of the carbon-based material In addition to reducing side reactions, structural stability can be achieved. In addition, the negative electrode active material according to the present invention can improve the affinity with the electrolyte solution to improve the life characteristics and rate characteristics of the non-aqueous lithium secondary battery. In addition, the production efficiency of the negative electrode active material may be improved due to a simple surface treatment process.

Such a method of manufacturing a negative active material for a non-aqueous lithium secondary battery, which is surface treated with a heterogeneous material according to the present invention will be described with reference to FIG. 1. 1 is a flowchart illustrating a method of manufacturing a negative active material for a non-aqueous lithium secondary battery, which is surface-treated through heterogeneous element substitution according to an embodiment of the present invention.

Referring to Figure 1, the method for producing a negative electrode active material according to the present invention is a step of preparing a carbon-based material and hetero-element material (S11), and forming a coating layer using the hetero-element material on the surface of the carbon-based material Steps S13 to S19 are included.

First, in step S11, a carbonaceous material and a heterogeneous material are prepared. In this case, as the carbonaceous material, an average particle size of 15 μm or less may be used. Heterogeneous element is NH₄PF₆, (NH₄)₂PO₄,NH₄PO₃, (NH₄)₂SO₃, (NH₄)₂SO₄, NH₄SO₄, (NH₄)₂S₂O₈ And the like can be used.

Next, in step S13, the dissimilar element material is dissolved in deionized water to form an aqueous solution. In this case, although an example of using deionized water is disclosed as the solvent, an organic solvent such as alcohol may be used.

Subsequently, the carbon-based material is mixed with the aqueous solution in step S15 to form a mixture. In this case, the mixing step according to step S15 may be performed for about 5 minutes so that the carbon-based material is uniformly mixed in the aqueous solution.

Next, the mixture is vacuum dried in step S17. For example, vacuum drying according to step S17 may be performed for about 1 to 5 hours at 80 to 150 degrees.

The dried product dried in step S17 is thermally treated in the step S19 to form a negative electrode active material according to the present invention, which is a carbon-based material surface-treated with a dissimilar element material. That is, in the process of thermally dissociating the hetero element material, the components except the hetero element in the hetero element material are removed and the hetero element forms a coating layer on the surface of the carbon-based material. At this time, the heat treatment step according to the step S19 may be performed in an inert atmosphere at 200 to 3000 degrees or more for 1 hour. For example, the heat treatment step may be carried out in an elevated temperature of 10 ℃ / min, Ar or N ₂ atmosphere.

On the other hand, the forming step (S13 ~ S19) according to the present invention discloses an example of forming a coating layer on the surface of the carbon-based material by forming a carbon-based material and a heterogeneous material in an aqueous solution, and then heat-treated through vacuum drying It is not limited. For example, a dissimilar element material may be dissolved in a solvent to form a solution, and then the solution may be sprayed on a carbon-based material, followed by heat treatment of the carbon-based material from which the solution is sprayed to form a coating layer on the surface of the carbon-based material. Alternatively, after mixing the carbon-based material and the powder of the hetero element material, the mixed powder may be heat-treated to form a coating layer on the surface of the carbon-based material. That is, the coating layer is formed on the surface of the carbon-based material by a dry method, and the heat treatment is disclosed in an inert atmosphere, but may be performed in a vacuum atmosphere or an oxidizing atmosphere.

In order to evaluate the life characteristics and rate characteristics of the non-aqueous lithium secondary battery to which the negative electrode active material according to the present invention is applied, a non-aqueous lithium secondary battery was manufactured as follows. In this case, a carbon-based material surface-treated with a hetero element material was used as the negative electrode active material. In the comparative example, a carbon-based material that was not surface treated with a heteroelement material was used as the negative electrode active material. And since the manufacturing of the non-aqueous lithium secondary battery according to the Examples and Comparative Examples except for the negative electrode active material proceeds in the same way, will be described with reference to the manufacturing method of the non-aqueous lithium secondary battery according to the embodiment.

A slurry was prepared using water as a solvent with 96 wt% of the negative active material, the binder SBR, and the thickener CMC as 2 wt%, respectively. The slurry was applied to a copper foil (Cu foil) having a thickness of 20 µm, dried, compacted in a press, dried for 16 hours at 120 ° C. in a vacuum, and an electrode was manufactured from a disc having a diameter of 12 mm. As the counter electrode, a lithium metal foil punched to a diameter of 14 mm was used, and a PE film was used as the separator. As the electrolyte solution, a mixed solution in which EC / DMC of 1M LiPF ₆ was mixed at 3: 7 was used. After the electrolyte solution was impregnated into the separator, the separator was sandwiched between the working electrode and the counter electrode, and a case of Sus (SUS) product was manufactured as a test cell for electrode evaluation, that is, a non-aqueous lithium secondary battery.

In this case, the carbon-based material may be at least one selected from materials including amorphous carbon such as artificial graphite, natural graphite, graphitized carbon fiber, graphitized mesocarbon microbead, petroleum coke, resin plastic, carbon fiber, and pyrolytic carbon.

Heterogeneous material is NH₄PF₆, (NH₄)₂PO₄,NH₄PO₃, (NH₄)₂SO₃, (NH₄)₂SO₄, NH₄SO₄, (NH₄)₂S₂O₈It includes, but is not limited to this.

The carbon-based material surface-treated with a heterogeneous material may be applied as a negative electrode active material of a non-aqueous lithium secondary battery using a carbonate electrolyte. In addition, the carbon-based negative active material surface-treated with a heterogeneous material may be applied to a lithium secondary battery to which a non-aqueous electrolyte driven in a voltage range of 0 V to 5 V or less is applied.

On the other hand, the production of the negative electrode plate is one or two or more kinds of powders of the negative electrode active material surface-treated with a dissimilar element material, which are usually used as conductive agents, binders, fillers, dispersants, ion conductive agents, pressure enhancers, etc. The additive component is added to form a slurry or paste with a suitable solvent (organic solvent). The slurry or paste thus obtained is coated and dried on an electrode support substrate using a doctor blade method or the like, and then pressed using a rolling roll or the like is used as the negative electrode plate.

In this case, as the conductive agent, graphite, carbon black, acetylene black, Ketjen Black, carbon fiber, metal powder, or the like may be used. PVdF, polyethylene, etc. can be used as a binder. The electrode support substrate (also referred to as 'current collector') can be made of foil, sheet or carbon fiber such as copper, nickel, stainless steel, aluminum, or the like.

A lithium secondary battery is manufactured by using the negative electrode thus prepared. The form of the lithium secondary battery may be any one of a coin, a button, a sheet, a cylinder, a square, and the like. The positive electrode, electrolyte, separator, etc. of the lithium secondary battery shall be used for the existing lithium secondary battery.

The positive electrode active material includes a positive electrode active material capable of reversibly intercalating and deintercalating lithium ions. Representative examples of the cathode active material include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , or LiNi1-x-yCo xMy _O 2 (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1 , M may be a lithium-transition metal oxide, such as metals such as Al, Sr, Mg, La, etc., and may use one or two or more of the above-described positive electrode active material. On the other hand, the above-mentioned positive electrode active material is only one example, but is not limited thereto.

The electrolyte solution may be a non-aqueous electrolyte solution in which lithium salt is dissolved in an organic solvent, an inorganic solid electrolyte, a composite material of an inorganic solid electrolyte, and the like, but is not limited thereto.

As the solvent of the non-aqueous electrolyte, carbonate, ester, ether or ketone can be used. The carbonate is dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC) , Propylene carbonate (PC), butylene carbonate (BC) and the like can be used. Esters include butyrolactone (BL), decanolide, valerolactone, mevalonolactone, caprolactone, n-methyl acetate, n-ethyl acetate, n- Propyl acetate and the like can be used. Dibutyl ether or the like may be used as the ether. As the ketone, polymethylvinyl ketone may be used. In addition, the non-aqueous electrolyte according to the present invention is not limited to the type of non-aqueous organic solvent.

Examples of the lithium salt of the non-aqueous electrolyte solution include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiAlO ₄ At least one selected from the group consisting of LiAlCl ₄ , LiN (CxF2x + 1SO2) (CyF2x + 1SO2), wherein x and y are natural water, and LiSO ₃ CF ₃ .

As the separator, a porous film made from polyolefin such as PP or PE, or a porous material such as nonwoven fabric may be used.

Examples and Comparative Examples

In the comparative example, natural graphite having an average particle size of 15 µm or less was used as the negative electrode active material as a carbon-based material which was not surface treated with a heteroelement material.

In Example 1, in order to introduce phosphorus (P) into the hetero element, natural graphite having an average particle size of 15 μm or less, which was surface treated using NH ₄ PF ₆ as the hetero element material, was used as the negative electrode active material.

In Example 2, in order to introduce sulfur (S) into the hetero element, natural graphite having an average particle size of 15 µm or less, which was surface-treated with (NH ₄ ) ₂ SO ₄ as the hetero element material, was used as the negative electrode active material.

The negative electrode active materials according to Example 1 and Example 2 were prepared as follows. In order to introduce phosphorus (P) and sulfur (S) on the surface of natural graphite among carbon materials, 3 wt% of NH ₄ PF ₆ and (NH ₄ ) ₂ SO ₄ were dissolved in DI water, respectively. The surface of the natural graphite was uniformly coated, and finally, a negative active material for a non-aqueous lithium secondary battery including phosphorus or sulfur on the surface was prepared by heat treatment at 800 ° C.

Comparing the morphology (morphology) of the negative electrode active material according to Example 1, Example 2 and Comparative Example prepared as described above, as shown in Figure 2, no change in the surface structure or the formation of impurities of the natural graphite base material.

As a result of EDS and XPS analysis of the negative electrode active materials according to Examples 1 and 2, it was confirmed that phosphorus and sulfur were uniformly present on the surface of natural graphite. 3 and 4 compare element mapping results of surfaces obtained by EDS analysis to natural graphite materials in which phosphorus and sulfur are introduced to the surfaces, respectively. As shown in FIG. 3, in the negative active material according to Example 1, 0.59 wt% of phosphorus was detected on the natural graphite surface. As shown in FIG. 4, 0.28 wt% of sulfur was detected on the surface of the natural graphite of the negative active material according to Example 2.

XPS analysis was performed for surface structure analysis of the anode active materials according to Examples 1 and 2, and the results are shown in FIGS. 5 and 6. Referring to FIG. 5, in Example 1, P 2p peaks (131 to 135eV) are formed on the surface. In addition, referring to Figure 6, Example 2 can be seen that the S 2p peak (161 ~ 168eV) is formed on the surface. This means that phosphorus and sulfur on the surface of natural graphite form a specific bond with carbon of natural graphite.

In addition, XRD analysis was performed for the analysis of the negative active material according to Comparative Example, Example 1 and Example 2, the results are shown in FIG. Referring to FIG. 7, formation of impurities or secondary phases after introduction of heterogeneous elements could not be confirmed. Based on the XRD results, the results of calculating L _{a (110)} and L _{c (002)} are shown in Table 1 below. The change of L _{a (110)} after the introduction of the heterogeneous element was insignificant, and the decrease of L _{c (002)} was confirmed.

Table 1

	L _{c (002)} [nm]	L _{a (aa 0)} [nm]
Comparative example	35.854	71.413
Example 1	31.512	71.402
Example 2	32.268	71.422

Table 2 shows the d ₀₀₂ values and FWHM (full-width at half maximum) values of Comparative Examples, Examples 1 and 2 through the obtained XRD data. After introduction of the heterogeneous element, the change of d ₀₀₂ value was insignificant and the FWHM was increased. This is judged to be because a part of P or S introduced into the surface is substituted on the surface. In addition, as a result of measuring the specific surface area of Comparative Example, Example 1 and Example 2, Comparative Example was 2.7845 m ² / g, Example 1 was 2.7461 m ² / g, and Example 2 was 2.7199 m ² / g.

TABLE 2

The life and rate characteristics of the non-aqueous lithium secondary battery including the negative electrode active materials according to Comparative Example, Example 1 and Example 2 were confirmed as follows.

First, in order to examine the effect on the life characteristics of the non-aqueous lithium secondary battery according to the type of heterogeneous material used, using a non-aqueous lithium secondary battery to which the negative electrode active material of Comparative Example, Example 1 and Example 2 was applied The same test was performed. That is, the non-aqueous lithium secondary battery to which the comparative examples and the negative electrode active materials of Examples 1 and 2 were applied was subjected to 3 cycle charging and discharging at a current of 0.2C (72 mA / g), followed by 0.5C (180 mA / g). Charging and discharging was performed for 50 cycles with the current of), and the results are shown in FIG. As can be seen in Figure 8, Example 1 and Example 2, the surface treatment of the hetero-element material is improved compared to the comparative example.

And to examine the effect of the surface treatment according to the type of heterogeneous material used on the rate characteristics of the non-aqueous lithium secondary battery, the non-aqueous lithium secondary battery to which the negative electrode active materials of Comparative Examples, Examples 1 and 2 are applied The following test was carried out using. That is, the non-aqueous lithium secondary battery to which the negative electrode active materials of Comparative Example, Example 1 and Example 2 were applied is subjected to 1 cycle charging and discharging at a current of 0.2C (72 mA / g). Charging was then fixed at a current of 0.5C (180 mA / g), 0.2C (72 mA / g), 0.5C (180 mA / g), 1C (360 mA / g), 2C (720 mA / g) , 3C (1080 mA / g), 5C (1800 mAh / g) to perform the discharge for 3 seconds each. Then, charging and discharging were performed for 2 cycles each at a current of 0.2C (72 mA / g), and the results are shown in FIG. 9. As can be seen in Figure 9, it was confirmed that the rate characteristic after surface treatment was also improved.

These results indicate that the coating layer formed on the surface of the natural graphite formed by surface treatment with a heterogeneous material effectively suppresses side reactions due to direct contact with the electrolyte and improves the structural stability of the surface of the natural graphite, thereby improving the surface stability of the heterogeneous material. It shows that it is effective in increasing the life characteristics and output characteristics of the non-aqueous lithium secondary battery to which the active material is applied.

On the other hand, the embodiments of the present invention disclosed in the specification and drawings are merely presented specific examples to aid understanding, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention can be implemented in addition to the embodiments disclosed herein.

Claims

Carbon-based materials;

And a coating layer formed on the surface of the carbon-based material through heterogeneous element substitution.

The hetero element is a negative active material for a non-aqueous lithium secondary battery, characterized in that it comprises phosphorus (P).
The method of claim 1,

The hetero-element is a negative active material for a non-aqueous lithium secondary battery, characterized in that containing sulfur (S).
The method according to claim 1 or 2,

The carbonaceous material is a negative electrode for a non-aqueous lithium secondary battery, characterized in that it comprises at least one of artificial graphite, natural graphite, graphitized carbon fiber, graphitized mesocarbon microbead, petroleum coke, resin plastic, carbon fiber and pyrolytic carbon Active material.
The method of claim 3,

The carbonaceous material is L a (110) > 10 nm, L c (002) > 10 nm,

L a (110) = 0.89λ / [B 110 cos (θ 110 )], L c (002) = 0.89λ / [B 002 cos (θ 002 )], and λ is Cu Kα (λ = 0.15418 nm). A non-aqueous lithium secondary, characterized in that the wavelength value, B is the full width at half-maximum (FWHM) value for the (110) or (002) peak according to the Bragg diffraction angle. Battery negative electrode active material.
The method of claim 4, wherein

The carbon-based material is a negative active material for a non-aqueous lithium secondary battery, characterized in that the d 002 value for the (002) peak is 0.344nm or less.
The method of claim 3,

The carbonaceous material has a specific surface area of 10 m 2 / g or less, the negative active material for a non-aqueous lithium secondary battery.
The method of claim 3,

The carbon-based material has a degree of graphitization value of 0.4 to 1.0, and the graphitization degree = (3.44-d 002 ) / (0.086), characterized in that the negative active material for a non-aqueous lithium secondary battery.
The method according to claim 1 or 2,

The coating layer is a negative active material for a non-aqueous lithium secondary battery, characterized in that less than 10% by weight compared to the carbon-based material.
The method of claim 8,

The coating layer is a negative active material for a non-aqueous lithium secondary battery, characterized in that formed on the surface of the carbon-based material uniformly or partially.
A negative electrode active material having a carbon-based material and a coating layer formed on the surface of the carbon-based material through heterogeneous element substitution, wherein the hetero element includes a negative electrode having the negative electrode active material including phosphorus (P) or sulfur (S). Non-aqueous lithium secondary battery, characterized in that.
Preparing a carbon-based material and a dissimilar element material;

And forming a coating layer through heterogeneous element substitution on the surface of the carbonaceous material using the heterogenous material.

The hetero element material is a method for producing a negative active material for a non-aqueous lithium secondary battery, characterized in that it comprises phosphorus (P).
The method of claim 11,

The hetero-element material is a method for producing a negative active material for a non-aqueous lithium secondary battery, characterized in that it further comprises sulfur (S).
The method of claim 12, wherein the heteroelement material is

NH4PF6, (NH4)2PO4, NH4PO3, (NH4)2SO3, (NH4)2SO4, NH4SO4 And (NH4)2S2O8 Method for producing a negative active material for a non-aqueous lithium secondary battery, characterized in that it comprises at least one.
The method of claim 13, wherein the forming step,

Dissolving the heteroatomic material in a solvent to form a solution;

Adding the carbonaceous material to the solution and uniformly mixing to form a mixture;

Drying the vacuum to dry the mixture;

Heat-treating the dried material dried in the drying step by pyrolysis to form the coating layer based on the heterogeneous element on the surface of the carbon-based material;

Method for producing a negative active material for a non-aqueous lithium secondary battery comprising a.