KR100280997B1 - Anode active material for lithium ion battery and manufacturing method thereof - Google Patents

Abstract

In order to provide a negative electrode active material for lithium ion batteries having a large discharge capacity and high charge and discharge efficiency, transition metals such as Ni, Co, Fe, Mo, Cr, alkali metals such as Na and K, alkaline earth metals such as Mg and Ca , A solution containing B, Al, Ga, Ge, Si, Sn, P, or a compound thereof in water or an organic solvent to prepare a solution, and then the solution is made of natural graphite, artificial graphite, cokes, Soft carbon or hard carbon is deposited or stirred, followed by drying, followed by drying of transition metals such as Ni, Co, Fe, Mo, Cr, alkali metals such as Na and K, Mg and Ca Alkaline earth metals such as B, Al, Ga, Ge, Si, Sn, P or compounds thereof are deposited on the surface of the carbon material. Subsequently, by heat-treating this, a crystalline graphite core, transition metals such as Ni, Co, Fe, Mo, Cr, alkali metals such as Na and K, alkaline earth metals such as Mg and Ca, B, Al, Ga, Provided is a negative electrode active material for a lithium ion battery including a carbon shell of a crystalline graphite structure or an amorphous structure having different physical properties from a turbostratic structure or a core portion to which Ge, Si, Sn, or P is added. .

Description

Anode active material for lithium ion battery and manufacturing method thereof

Industrial use field

The present invention relates to a negative electrode active material for a lithium ion battery and a method for manufacturing the same, and more particularly, to a negative electrode active material for a lithium ion battery having a large discharge capacity and excellent charge and discharge efficiency and a method for manufacturing the same.

Prior art

Lithium metal was first used as a negative electrode active material of a lithium secondary battery, but the capacity of the lithium secondary battery was rapidly decreased, and the separator was destroyed as lithium precipitates to form a dendrite phase, thereby reducing the battery life. To solve this problem, a lithium alloy was used instead of lithium metal, but it did not significantly improve the problem of using lithium metal.

Thereafter, a carbon material capable of intercalating and deintercalating lithium ions was used as a negative electrode active material. In the case of using a relatively simple process of coke among the carbon materials, there is a disadvantage that the electrochemical performance of the battery greatly varies depending on the type of electrolyte. In the case of using natural graphite which is relatively inexpensive, there is a problem in that the charge and discharge efficiency is low and the electrode workability is lowered. The carbonaceous negative electrode active material is generally manufactured in spherical or fibrous form and is used. In addition to the disadvantage of high manufacturing cost, there is a problem in that the discharge capacity and the charge / discharge efficiency are not sufficient.

In order to solve the above problems, an object of the present invention is to provide a negative electrode active material for a lithium ion battery having a large discharge capacity and high charge and discharge efficiency, and a method of manufacturing the same.

In order to achieve the above object of the present invention, the present invention is in the group consisting of crystalline graphite core and transition metal, alkali metal, alkaline earth metal, group 3B element, group 4B element, group 5B element and mixtures thereof A negative electrode active material for a lithium ion battery including a carbon shell to which an element selected is added, wherein the carbon shell is a turbostratic carbon layer or a crystalline graphite layer or an amorphous carbon layer having a physical property different from that of the core. The negative electrode active material for phosphorus lithium ion batteries is provided.

In addition, the present invention provides a method for producing the negative electrode active material, water containing a material selected from the group consisting of transition metals, alkali metals, alkaline earth metals, Group 3B elements, Group 4B elements, Group 5B elements and mixtures thereof Or a process of preparing a solution by dissolving in an organic solvent, the solution comprising natural graphite, artificial graphite, cokes, soft carbon, hard carbon, and mixtures thereof Depositing or stirring a carbon material selected from the group; and drying the carbon material deposited or stirred with the solution to form a transition metal, an alkali metal, an alkaline earth metal, a Group 3B element, a Group 4B element, or a Group 5B element on the surface of the carbon material. And a process for depositing an element selected from the group consisting of mixtures thereof, and transition metals, alkali metals, alkaline earth metals, group 3B elements, group 4B elements, and group 5B elements. And it provides a method for producing a negative electrode active material for a lithium ion battery comprising a step of heat-treating a carbon material in which an element selected from the group consisting of a mixture thereof is deposited on the surface.

In addition, the present invention is a method for producing the negative electrode active material, a material containing an element selected from the group consisting of transition metals, alkali metals, alkaline earth metals, Group 3B elements, Group 4B elements, Group 5B elements and mixtures thereof A process for preparing a solution by dissolving in water or an organic solvent, the solution comprising natural graphite, artificial graphite, cokes, soft carbon, hard carbon, and mixtures thereof Mixing the carbon material selected from the group, and spray-drying the mixture to form a transition metal, alkali metal, alkaline earth metal, group 3B element, group 4B element, group 5B element, and mixtures thereof on the surface of the carbon material. A process for depositing an element selected from the group consisting of transition metals, alkali metals, alkaline earth metals, group 3B elements, group 4B elements, group 5B elements, and mixtures thereof It provides a method for producing a negative electrode active material for a lithium ion battery comprising a step of heat-treating the carbon material in which the selected element is deposited on the surface.

Hereinafter, the present invention will be described in more detail.

Solution of a substance containing transition metals such as Ni, Co, Fe, Mo, Cr, alkali metals such as Na and K, alkaline earth metals such as Mg and Ca, B, Al, Ga, Ge, Si, Sn, P and the like To prepare. In this case, water or an organic solvent may be used as the solvent. Boron acid, boron oxide, etc. may be used as a material including B. Nickel nitrate, nickel sulfate, nickel acetate, and the like may be used as a material containing Ni, and silicates may be used as a material containing Si. Can be used. The amount of the material containing the transition metal, alkali metal, alkaline earth metal, etc. is preferably 0.1-20% by weight of the carbon material, and as an organic solvent, ethanol, isopropyl alcohol, toluene, benzene, hexane, tetrahydrofuran, etc. Can be used.

In this solution, natural graphite, artificial graphite, cokes, soft carbon, hard carbon, or mixtures thereof are deposited or stirred and then dried to dry the elements on the surface of the carbon material. Precipitating or mixing the carbon material in the mixed solution and spray-dried to precipitate or adsorb the elements on the surface of the carbon material. In this case, the particle size of the elements precipitated or adsorbed on the surface is preferably 5 μm or less, more preferably 2 μm or less.

Subsequently, when the material is added to the heat treatment process under an inert atmosphere, the carbon material surface may have different physical properties from those of the turbotastic structure, the amorphous structure, or the core part due to the interaction between the elements deposited on these surfaces and the carbon material. A carbon layer of crystalline graphite structure is formed. Here, the turbostatic structure refers to a structure that exhibits extremely low crystallinity and small crystal size, similar to the amorphous structure, and exhibits a somewhat disordered orientation. The carbon layer of the crystalline graphite structure having physical properties different from that of the core portion refers to the carbon layer of the crystalline graphite structure having a crystallinity different from that of the core portion or having a different crystal structure.

When using natural graphite or artificial graphite as the carbon material, the heat treatment temperature is preferably 700-3000 ° C., and when using coke, digraphitizable carbon or non-graphitizable carbon, the heat treatment temperature is 2000-3000 ° C. Can further facilitate the formation of the crystalline graphite core.

In the final prepared active material, the crystalline graphite core is 50-99% by weight, and the carbon shell of the crystalline graphite structure or amorphous structure exhibiting physical properties different from that of the turbostatic structure or the core portion is preferably 1-50% by weight. Do. If the carbon shell is less than 1% by weight, the discharge capacity and the charge and discharge efficiency may be lowered. If the carbon shell is more than 50% by weight, the voltage flatness may be poor.

In addition, in the negative electrode active material according to the present invention, the value of I (110) / I (002), which is a diffraction intensity ratio between the (002) plane and the (110) plane, was less than 0.04 in X-ray diffraction analysis.

In addition, the Raman spectroscopy strength ratio I (1360) / I (1580) of the crystalline graphite core of the negative electrode active material according to the present invention is 0.3 or less, and the Raman spectroscopy strength ratio of the carbon shell I (1360). / I (1580) showed at least 0.2.

Those skilled in the art will be able to easily manufacture a lithium ion battery according to a known battery manufacturing method using the negative electrode active material of the present invention.

The following presents a preferred embodiment to aid the understanding of the present invention. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited to the following examples.

Example 1

Boric acid was dissolved in distilled water and natural graphite was mixed. Distilled water was dried to deposit 5 micrometers or less of boronic acid fine particles on the surface of natural graphite particles. The powder thus obtained was heat-treated at 2600 ° C. under inert atmosphere to prepare an active material.

Polyvinylidene fluoride was mixed with N-methyl pyrrolidone as the active material and the binder to prepare a slurry, and then cast on a copper foil and dried to prepare an electrode plate. A battery was produced using lithium metal as a counter electrode and propylene carbonate containing 1 mol of LiPF ₆ as an electrolyte.

Example 2

Except for using artificial graphite instead of natural graphite in Example 1 was carried out in the same manner as in Example 1.

Example 3

Example 2 was carried out in the same manner as in Example 2, except that nickel nitrate was used instead of boronic acid.

Example 4

In Example 2, a silicate was used instead of boronic acid, and the heat treatment process was performed in the same manner as in Example 2 except that the temperature of the heat treatment process was 1700 ° C instead of 2600 ° C.

Example 5

Except for using coke instead of natural graphite in Example 1 was carried out in the same manner as in Example 1.

Example 6

Example 5 was carried out in the same manner as in Example 5, except that nickel nitrate was used instead of boronic acid.

Example 7

Example 5 was carried out in the same manner as in Example 5, except that silicate was used instead of boronic acid.

Comparative Example 1

Except for using the natural graphite powder as the active material it was carried out in the same manner as in Example 1.

Comparative Example 2

It carried out similarly to Example 1 except having used the artificial graphite powder as an active material.

Comparative Example 3

The same procedure as in Example 1 was conducted except that the coke powder was used as the active material.

Table 1 shows the electrochemical characteristics of the battery according to Examples 1-7 and Comparative Examples 1-3.

Discharge capacity (h / g) Example 1 352 Example 2 320 Example 3 335 Example 4 313 Example 5 338 Example 6 316 Example 7 290 Comparative Example 1 347 Comparative Example 2 303 Comparative Example 3 280

As shown in the results of Table 1, it can be seen that Example 1-7 shows a larger discharge capacity than Comparative Examples 1-3. The active material of Example 1-7 has a high charge and discharge efficiency, since the core portion is crystalline graphite and the shell portion is a carbon layer of a crystalline graphite structure or an amorphous structure having different physical properties from the turbostrast structure and the core portion.

As described above, the present invention provides a negative electrode active material for a lithium ion battery having a large discharge capacity and high charge and discharge efficiency. In addition, since the active material has a surface of a turbostratic structure, a crystalline graphite structure having a different physical property from that of the core portion, or an amorphous carbon structure, propylene carbonate may be used as an electrolyte, and other electrolytic solutions may have excellent electrochemical properties. It provides an active material.

Claims (12)

Crystalline graphite cores; And A negative electrode active material for a lithium ion battery comprising a carbon shell to which an element selected from the group consisting of transition metals, alkali metals, alkaline earth metals, group 3B elements, group 4B elements, group 5B elements, and mixtures thereof is added. The carbon shell is a turbostratic carbon layer or a crystalline graphite layer or amorphous carbon layer having a different physical property from the core. The method of claim 1, wherein the transition metal is selected from the group consisting of Ni, Co, Fe, Mo and Cr, the alkali metal is Na or K, the alkaline earth metal is Mg or Ca, the Group 3B element is An element selected from the group consisting of B, Al and Ga, the Group 4B element is an element selected from the group consisting of Si, Ge and Sn, the Group 5B element is P, characterized in that the lithium ion battery negative electrode active material. The negative active material of claim 1, wherein the active material comprises 50-99 wt% crystalline graphite core and 1-50 wt% carbon shell. The negative active material of claim 1, wherein the active material has an I-110 (I) / I (002) of 0.04 or less, which is an X-ray diffraction intensity ratio between the (002) plane and the (110) plane. 2. The Raman spectroscopy strength ratio I (1360) / I (1580) of the crystalline graphite core is 0.3 or less, and the Raman spectroscopy strength ratio of the carbon shell is I (1360) / I. 1580 is a lithium ion battery negative electrode active material of 0.2 or more. Preparing a solution by dissolving a material comprising an element selected from the group consisting of transition metals, alkali metals, alkaline earth metals, group 3B elements, group 4B elements, group 5B elements, and mixtures thereof in water or an organic solvent; Depositing or stirring the carbon material selected from the group consisting of natural graphite, artificial graphite, cokes, soft carbon, hard carbon, and mixtures thereof; ; Drying the carbon material deposited or stirred with the solution to precipitate an element selected from the group consisting of transition metals, alkali metals, alkaline earth metals, group 3B elements, group 4B elements, group 5B elements, and mixtures thereof on the surface of the carbon material; Making process; And An anode active material for a lithium ion battery comprising a step of heat-treating a carbon material in which an element selected from the group consisting of transition metals, alkali metals, alkaline earth metals, group 3B elements, group 4B elements, group 5B elements, and mixtures thereof is deposited on the surface thereof. Manufacturing method. Preparing a solution by dissolving a material comprising an element selected from the group consisting of transition metals, alkali metals, alkaline earth metals, group 3B elements, group 4B elements, group 5B elements, and mixtures thereof in water or an organic solvent; Mixing a carbon material selected from the group consisting of natural graphite, artificial graphite, cokes, soft carbon, hard carbon, and mixtures thereof; Spray drying the mixture to precipitate an element selected from the group consisting of transition metals, alkali metals, alkaline earth metals, group 3B elements, group 4B elements, group 5B elements and mixtures thereof on the surface of the carbon material; And An anode active material for a lithium ion battery comprising a step of heat-treating a carbon material in which an element selected from the group consisting of transition metals, alkali metals, alkaline earth metals, group 3B elements, group 4B elements, group 5B elements, and mixtures thereof is deposited on the surface thereof. Manufacturing method. The method of claim 6 or 7, wherein the transition metal is selected from the group consisting of Ni, Co, Fe, Mo and Cr, the alkali metal is Na or K, the alkaline earth metal is Mg or Ca, Group 3B element is an element selected from the group consisting of B, Al and Ga, the Group 4B element is an element selected from the group consisting of Si, Ge and Sn, the Group 5B element is a lithium ion, characterized in that P Method for producing a negative electrode active material for a battery. The amount of the element selected from the group consisting of the transition metal, the alkali metal, the alkaline earth metal, the Group 3B element, the Group 4B element, the Group 5B element, and mixtures thereof is 0.1% of the carbon material. The negative electrode active material manufacturing method for lithium ion batteries which is -20 weight%. The method of claim 6 or 7, wherein the element selected from the group consisting of the transition metal, alkali metal, alkaline earth metal, Group 3B element, Group 4B element, Group 5B element and mixtures thereof deposited on the surface of the carbon material. A particle size is 5 micrometers or less manufacturing method of the negative electrode active material for lithium ion batteries. The method of claim 6, wherein the temperature of the heat treatment process is 700-3000 ° C. when the carbon material is natural graphite or artificial graphite. The method of claim 6, wherein the temperature of the heat treatment process is 2000-3000 ° C. when the carbon material is selected from the group consisting of coke, digraphitizable carbon, and nongraphitizable carbon.