KR100751634B1 - Anode material for secondary battery and secondary batteries using the same - Google Patents

Abstract

The present invention relates to a negative electrode material for a secondary battery and a secondary battery using the same. In the negative electrode material for secondary batteries according to the present invention, the negative electrode material for secondary batteries according to the present invention is produced by coating a high crystalline core carbon material with a coated carbon material and firing the surface energy of the coated carbon material. It is characterized by being 1.25 times or less of energy. In this case, the highly crystalline core carbon material is preferably natural graphite. The negative electrode material for a secondary battery according to the present invention is manufactured by coating a coated carbon material on a high crystalline core carbon material, and then undergoing a predetermined firing process, by adjusting the surface energy ratio of the core carbon material by appropriately controlling the surface energy ratio of the core carbon material. In addition, there is an advantage in that a secondary battery having excellent electrical characteristics may be provided by solving a problem of a decrease in charge and discharge efficiency and a decrease in charge and discharge capacity of a battery manufactured using natural graphite due to a conventional electrolyte solution decomposition reaction.

Cathode material, coated carbon material, core carbon material, secondary battery, electrolyte solution, surface energy

Description

Anode material for secondary battery and secondary batteries using the same}

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to.

1 is a process flowchart illustrating a process of manufacturing an electrode using a negative electrode material for a secondary battery according to the present invention.

The present invention relates to a negative electrode material for a secondary battery and a secondary battery using the same. More specifically, the high crystalline core carbon material is coated with a coated carbon material, and the surface energy ratio thereof has a constant value, thereby decomposing an electrolyte solution of the battery. The present invention relates to a negative electrode material for a secondary battery and a secondary battery using the same, which can solve the problem of deterioration of battery characteristics due to the present invention.

Recently, with the rapid dissemination of electronic devices that use batteries such as mobile phones, portable notebook computers, and electric vehicles, the demand for small, lightweight, and relatively high capacity secondary batteries is increasing, and this trend is further accelerated.

Natural graphite, which is used as a negative electrode active material of a secondary battery, is excellent in initial discharge capacity but has a problem in that charge / discharge efficiency and charge / discharge capacity are suddenly lowered as the charge / discharge cycle is repeated. This problem is known to be due to the electrolyte decomposition reaction that occurs at the edge (edge) of the high crystalline natural graphite.

On the other hand, some techniques for coating pitches on natural graphite have been introduced, but the pitch coated on natural graphite improves certain physical properties, and research results on the use of such materials as electrode materials are presented. In particular, there is no disclosure about the relationship between the surface energy of natural graphite and the pitch coated thereon.

The present invention is to cover the pitch of natural graphite, but to find a physical factor that can be related to the improvement of the electrical properties, and by performing a constant adjustment to these factors, a new type of 2 that can solve the problems of the conventional electrical properties It was created in an effort to develop a negative electrode material for vehicle batteries.

The technical problem to be achieved by the present invention is to solve the problem of lowering the charge and discharge efficiency and the charge and discharge capacity of the battery due to the electrolyte decomposition reaction generated at the interface with the electrolyte when using natural graphite as a negative electrode active material, An object of the present invention to provide a secondary battery negative electrode material and a secondary battery using the same that can achieve the technical problem.

The negative electrode material for a secondary battery according to the present invention, which is provided to attain one technical problem to be achieved by the present invention, is prepared by coating a high crystalline core carbon material with a coated carbon material and firing the surface energy of the coated carbon material. It is characterized by being 1.25 times or less of the surface energy of the core carbon material. In this case, the highly crystalline core carbon material is preferably natural graphite.

The secondary battery according to the present invention provided to achieve another technical problem to be achieved by the present invention is characterized by using a negative electrode material for a secondary battery satisfying the conditions according to the above as a negative electrode of the battery.

The secondary battery preferably has a discharge capacity of the negative electrode material of 330 mAh / g or more and a charge / discharge efficiency of 90% or more.

Hereinafter, specific examples will be described in order to help the understanding of the present invention, and in the following case, with reference to the drawings will be described in more detail. However, embodiments according to the present invention can be modified in many different forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

In the present invention, when the surface energy of the coating material (coated carbon material) is smaller than a predetermined reference value (less than 1.25 times) compared to the surface energy of the coating material (core carbon material), the property of spreading over the surface of the coating material is strong. In view of the fact that the coating is excellent, the inventors have focused on the fact that the battery characteristics can be improved by improving the coating properties from the viewpoint of the surface energy between materials. If the surface energy of the material to be coated (coated carbon material) is greater than a certain reference value compared to the surface energy of the material to be coated (core carbon material), the coating property of the material to be coated is not good and the properties of the material to be coated remain. Done. That is, when the surface energy of the coated carbon material is 1.25 times or more compared to the core carbon material, the coated carbon material is not uniformly coated on the surface of the core carbon material, and the characteristics of the natural graphite used as the core carbon material are maintained. Thus, the protection against the electrolyte decomposition reaction is not sufficiently achieved, and the problem of poor battery characteristics pointed out in the related art can be reproduced as it is. In order to solve the above-mentioned problems, the present invention is to cover the natural graphite surface by coating the surface of the natural graphite with a less crystalline carbide, the initial discharge capacity can be reduced by a small amount, but the charge and discharge efficiency is improved The focus is on things.

< Example  1 to 4> and < Comparative example  1 to 3

As the negative electrode material, the ratio of the surface energy of the coated carbon material to the surface energy of the core carbon material is spherical natural as the core carbon material as set in Examples 1 to 4 and Comparative Examples 1 to 3 as shown in Table 1 below. Graphite carbon material was used, and a pitch corresponding to the material covering the same was used. In contrast, in the case of Comparative Example 1, the coated carbon material was not used.

division Surface energy of core carbon material (A) Surface energy of coated carbon material (B) Surface energy ratio (B / A) Example One 57 41 0.72 2 57 55 0.96 3 57 64 1.12 4 57 71 1.25 Comparative example One 57 - - 2 57 75 1.32 3 57 84 1.47

Surface energy measurement

Surface energy of the carbon material shown in Table 1 was measured as follows.

The surface energy of natural graphite used as core carbon material is 100 g of natural graphite in a 500 ml reactor, a small amount of N-methylpyrrolidone (NMP) and polyvinylidene fluoride (PVDF) as a binder, The slurry obtained by kneading using a mixer was applied on a copper foil and measured as surface energy of an electrode prepared by compression drying. To this end, surface energy was measured using the Sessile Drop method using a contact angle measuring system (KRUSS).

The surface energy of the pitch used as the coating carbon material was put into a 500 ml reactor with a pitch of 100 g and a small amount of N-methylpyrrolidone (NMP) and polyvinylidene fluoride (PVDF) as a binder. The slurry obtained by kneading was applied on a copper foil, and measured as surface energy of the electrode prepared by compression drying. To this end, surface energy was measured using the Sessile Drop method using a contact angle measuring system (KRUSS).

Cathode material  Used electrode manufacturing

1 is a process flowchart illustrating a process of manufacturing an electrode using the negative electrode material for a secondary battery according to the present invention. Hereinafter, a test electrode for evaluating battery characteristics of the negative electrode material for a secondary battery according to the present invention was performed by performing steps S1 to S5.

Mixing step of the material (S1)

The pitch melted with tetrahydrofuran (THF) in spherical natural graphite carbon material, which is the core carbon material according to Table 1, is mixed uniformly by wet stirring at normal pressure for 2 hours at a ratio of 9: 1 to 10: 1 by weight. And then dried.

Firing step (S2)

The dried resultant was first calcined stepwise at 1,100 ° C. for 1 hour, and at 1,500 ° C. for 1 hour.

Differential removal step (S3)

After the firing process of the second step, by classification, the fine powder was removed.

Kneading step (S4)

100 g of a mixture of graphite carbon material and pitch, the finely divided anode material, was placed in a 500 ml vial, and a small amount of N-methylpyrrolidone (NMP) and polyvinylidene fluoride (PVDF) were added as a binder. After mixing, the mixture was kneaded using a blender.

Electrode manufacturing step (S5)

Finally, it was pressed and dried on a copper foil to prepare a test electrode. The charging and discharging efficiency of each test electrode thus prepared was evaluated by using a coin cell.

Battery characteristics (discharge capacity and Charging and discharging  Efficiency)

The charge-discharge test of the pitch coated spherical graphite carbon material regulates the electric potential in the range of 0 to 1.5V, charges until it becomes 0.01V at a charge current of 0.5 mA / cm 2, and maintains a voltage of 0.01V, Charging was continued until the charging current became 0.02 mA / cm 2. And the discharge current discharged to 1.5V at 0.5 mA / cm <2>. In Table 2, charge and discharge efficiency indicates the ratio of the discharged capacitance to the charged capacitance. Based on the data shown in Table 1 and Table 2, when the surface energy of the coated carbon material is less than 1.25 times compared to the surface energy of the core carbon material, the initial charge and discharge efficiency is 90% or more, and the 25th discharge capacity is 330. When the surface energy of the coated carbon material is 1.25 times or more compared to the surface energy of the core carbon material, the initial charge and discharge efficiency is less than 90%, and the 25th discharge capacity is 330 mAh / g. It can be seen that the value is less than. The discharge capacity of the negative electrode material is 330 mAh / g or more, and when the charge and discharge efficiency is 90% or more, the battery is evaluated as being preferable.

division 1st discharge capacity (mAh / g) First charge and discharge efficiency (%) 25th discharge capacity (mAh / g) Example One 348.2 94.2 345.2 2 351.4 93.6 341.1 3 352.9 93.1 338.9 4 353.8 92.2 336.3 Comparative example One 362.7 87.2 294.2 2 357.7 89.1 319.2 3 358.9 88.7 315.3

As can be seen through Table 2, in Comparative Examples 1 to 3, the charge and discharge efficiency of the first time was not reached 90%, so that the charge and discharge efficiency was low, and the discharge capacity of the 25th time was 330, which is a reference value. It can be seen that it is less than ㎃h / g. In particular, in the case where the coated carbon material is not used as in Comparative Example 1, it can be seen that the discharge capacity decreases rapidly as the number of charge and discharge cycles is repeated. On the other hand, in the case of Examples 1 to 4, the discharge capacity of the secondary battery was measured to be 330 mAh / g or more in both the first and the 25th times, and the first charge and discharge efficiency exceeded 90%. It can confirm that it has, and can confirm clearly the preferable effect which concerns on this invention.

Optimal embodiments of the present invention described above have been disclosed. Although specific terms have been used herein, they are used only for the purpose of describing the present invention in detail to those skilled in the art, and are not used to limit the scope of the present invention as defined in the meaning or claims.

The negative electrode material for a secondary battery according to the present invention is manufactured by coating a coated carbon material on a high crystalline core carbon material, and then undergoing a predetermined firing process, by adjusting the surface energy ratio of the core carbon material by appropriately controlling the surface energy ratio of the core carbon material. In addition, there is an advantage in that a secondary battery having excellent electrical characteristics may be provided by solving a problem of a decrease in charge and discharge efficiency and a decrease in charge and discharge capacity of a battery manufactured using natural graphite due to a conventional electrolyte decomposition reaction.

Claims (4)

In the negative electrode material for a secondary battery, The negative electrode material for the secondary battery is manufactured by coating natural graphite, which is a high crystalline core carbon material, with a coated carbon material and firing it, wherein the surface energy of the coated carbon material is 1.25 times or less than the surface energy of the core carbon material. Battery anode material. A secondary battery manufactured by using the negative electrode material for a secondary battery according to claim 1 as a negative electrode of the battery. delete delete

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