KR100868135B1 - Anode active material for secondary battery and method for preparing thereof and secondary battery containing the same for anode - Google Patents

Abstract

The present invention relates to a negative electrode active material for a secondary battery, a method for manufacturing the same, and a secondary battery including the same as a negative electrode. The negative electrode active material for a secondary battery of the present invention is characterized by comprising a core carbon material, a low crystalline carbon, and a fluorine-based compound. According to the present invention, by stabilizing the surface of the negative electrode active material to reduce the effect of the organic electrolyte solution decomposition reaction, which is the main cause of irreversible capacity, and to reduce the influence on the acid generated by oxidation of the electrolyte during charging / discharging to improve the efficiency and cycle characteristics There are advantages to it.

Negative electrode active material, fluorine compound, negative electrode material, secondary battery, charge / discharge efficiency

Description

Anode active material for secondary battery and method for preparing sugar and secondary battery containing the same for anode}

The present invention relates to a negative electrode active material for a secondary battery, a method for manufacturing the same, and a secondary battery including the same as a negative electrode. More specifically, in the preparation of a negative electrode active material, a low crystalline carbon and a fluorine-based compound are used together on the surface of a core carbon material. 2) It can improve the efficiency and cycle characteristics by stabilizing the surface of the negative electrode active material, thereby reducing the influence of the organic electrolyte decomposition reaction, which is the main cause of irreversible capacity, and reducing the influence on the acid produced by oxidation of the electrolyte during charging and discharging. The present invention relates to a negative active material for a secondary battery, a method of manufacturing the same, and a secondary battery including the same as a negative electrode.

As portable electronic devices such as video cameras, cordless phones, mobile phones, and notebook computers are rapidly spreading in daily life, the demand for secondary batteries used as a power source has increased greatly. Among them, lithium secondary batteries have high capacity and high energy density. Due to the high battery characteristics, active research and development has been carried out at home and abroad, and is currently the most widely used secondary battery.

A lithium secondary battery basically consists of a positive electrode, a negative electrode, and an electrolyte. Therefore, research and development of a lithium secondary battery can be largely divided into studies on a cathode, an anode material, and an electrolyte.

Among these, natural graphite, which is used as a negative electrode material for lithium secondary batteries, exhibits excellent initial capacity but poor efficiency and cycle capacity. This phenomenon is known to be due to the electrolyte decomposition reaction in the highly crystalline natural graphite edge portion.

In order to overcome this problem, the low-crystalline carbon is surface-treated (coated) on natural graphite and heat-treated at 1,000 ° C or higher to coat low-crystalline carbide on the surface of natural graphite, thereby reducing the initial capacity by a small amount, but increasing efficiency and cycle capacity. An anode active material having improved characteristics can be obtained. In particular, when artificial graphite of low crystalline carbon, which is used as a cladding material, by high temperature heat treatment to reduce the initial capacity reduction, it is possible to reduce the initial capacity and to suppress the electrolyte decomposition reaction.

In addition, Korean Patent Application No. 2004-0050876 includes one or more metals and graphite selected from the group consisting of Si, Sn, and Al, and can suppress volume expansion of the electrode plate by absorbing the volume expansion of the metal in the cathode active material itself. Disclosed is graphite.

To date, graphite and metals containing metals and metal oxides such as Ni, Al, Ag, Cu, Si and Sn have been mentioned in patents and papers. It was.

Accordingly, efforts to solve the above-mentioned problems of the prior art have been continued in the related art, and the present invention has been devised under such a technical background.

The technical problem to be achieved by the present invention is to stabilize the surface of the negative electrode active material to reduce the effect of the organic electrolyte decomposition reaction, the main cause of irreversible capacity, and to reduce the influence on the acid produced by oxidation of the electrolyte during charge / discharge efficiency and cycle It is an object of the present invention to provide a secondary battery negative electrode active material, a method for manufacturing the same, and a secondary battery including the same as a negative electrode to improve the characteristics, and to achieve such a technical problem.

The negative electrode active material for a secondary battery for achieving the technical problem to be achieved by the present invention, the core carbon material; Low crystalline carbon; The fluorine compound is, CsF, KF, LiF, NaF, RbF, TiF, AgF, AgF _2, BaF _2, CaF _2, CuF _2, CdF _2, FeF _2, HgF _2, and made, jidoe including; and fluorine-based compound Hg ₂ F ₂ , MnF ₂ , MgF ₂ , NiF ₂ , PbF ₂ , SnF ₂ , SrF ₂ , XeF ₂ , ZnF ₂ , AlF ₃ , BF ₃ , BiF ₃ , CeF ₃ , CrF ₃ , DyF ₃ , EuF ₃ , _{GaF 3, GdF 3, FeF 3} , HoF 3, InF 3, LaF 3, LuF 3, MnF 3, NdF 3, VOF 3, PrF 3, SbF 3, ScF 3, SmF 3, TbF 3, TiF 3, TmF 3 _{, YF 3, YbF 3, TiF} 3, CeF 4, GeF 4, HfF 4, SiF 4, SnF 4, TiF 4, VF 4, ZrF 4, NbF 5, SbF 5, TaF 5, BiF 5, MoF 6, ReF ₆ , SF ₆ and WF _{6 It} is characterized in that a single or a mixture of two or more selected from the group consisting of. A method of manufacturing a negative electrode active material for a secondary battery for achieving the technical problem to be achieved by the present invention, preparing a core carbon material, low crystalline carbon and fluorine-based compound; Coating the surface of the prepared core carbon material with a mixture of low crystalline carbon and a fluorine compound; Drying the core carbon material whose surface is coated with a mixture of low crystalline carbon and fluorine-based compounds; And a step of firing the dried core carbon material; doedoe progress, including the fluorine-based compound is, CsF, KF, LiF, NaF, RbF, TiF, AgF, AgF _2, BaF _2, CaF _2, CuF _2, CdF ₂ , FeF ₂ , HgF ₂ , Hg ₂ F ₂ , MnF ₂ , MgF ₂ , NiF ₂ , PbF ₂ , SnF ₂ , SrF ₂ , XeF ₂ , ZnF ₂ , AlF ₃ , BF ₃ , BiF ₃ , CeF ₃ , CrF _{3, DyF 3, EuF 3,} GaF 3, GdF 3, FeF 3, HoF 3, InF 3, LaF 3, LuF 3, MnF 3, NdF 3, VOF 3, PrF 3, SbF 3, ScF 3, SmF 3, TbF ₃ , TiF ₃ , TmF ₃ , YF ₃ , YbF ₃ , TiF ₃ , CeF ₄ , GeF ₄ , HfF ₄ , SiF ₄ , SnF ₄ , TiF ₄ , VF ₄ , ZrF ₄ , NbF ₅ , SbF ₅ , TaF ₅ , BiF ₅ , MoF ₆ , ReF ₆ , SF ₆ and WF ₆ is characterized in that a single substance or a mixture of two or more selected from the group consisting of.

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The secondary battery for achieving the technical problem to be achieved by the present invention, characterized in that the negative electrode material prepared by applying a slurry for electrode plate production comprising the negative electrode active material prepared by the above method to the electrode current collector, characterized in that it comprises a negative electrode material .

Hereinafter, preferred embodiments of the present invention will be described in detail. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described herein are only exemplary embodiments of the present invention, and do not represent all of the technical ideas of the present invention, and various equivalents and modifications that may substitute them at the time of the present application may be used. It should be understood that there may be.

The present invention has a technical feature that can improve the efficiency and cycle characteristics at the same time by coating the surface of the core carbon material with the fluorine-based compound in the preparation of the negative electrode active material coating the low crystalline carbon on the core carbon material have.

The fluorine-containing compound is meant any compound that contains fluorine, for example, CsF, KF, LiF, NaF, RbF, TiF, AgF, AgF _2, BaF _2, CaF _2, CuF _2, CdF _2, FeF _2, HgF ₂ , Hg ₂ F ₂ , MnF ₂ , MgF ₂ , NiF ₂ , PbF ₂ , SnF ₂ , SrF ₂ , XeF ₂ , ZnF ₂ , AlF ₃ , BF ₃ , BiF ₃ , CeF ₃ , CrF ₃ , DyF ₃ , EuF _{3, GaF 3, GdF 3,} FeF 3, HoF 3, InF 3, LaF 3, LuF 3, MnF 3, NdF 3, VOF 3, PrF 3, SbF 3, ScF 3, SmF 3, TbF 3, TiF 3, _{TmF 3, YF 3, YbF 3} , TiF 3, CeF 4, GeF 4, HfF 4, SiF 4, SnF 4, TiF 4, VF 4, ZrF 4, NbF 5, SbF 5, TaF 5, BiF 5, MoF 6 , ReF ₆ , SF ₆ or WF ₆ can be used alone or in combination of two or more.

The fluorine compound is preferably included in an amount of 1 to 30 parts by weight, more preferably 1 to 15 parts by weight, based on 100 parts by weight of the core carbon material. In the content limit of the fluorine-based compound, if the lower limit is less than the amount is extremely small and does not reduce the influence on the acid produced by the side reaction of the electrolyte solution is not preferable, if the upper limit exceeds the capacity due to its own weight However, reduced energy density is undesirable.

When the size of the fluorine-based compound is small, the area covering the carbon material is increased to further reduce the influence on the acid generated by the side reaction of the electrolyte. Accordingly, the fluorine-based compound may be pulverized to a desired size prior to mixing with the low crystalline carbon, and the size of the fluorine compound may be adjusted in various ways as desired.

The low crystalline carbon coated on the core carbon material together with the fluorine-based compound may be pitch, tar, phenol resin, furan resin, or furfuryl alcohol.

The low crystalline carbon is preferably included in 0.1 to 30 parts by weight based on 100 parts by weight of the core carbon material. In the lower limit of the content of the low crystalline carbon, if the lower limit is less than the amount is extremely small, it is not preferable because it does not reduce the electrolyte solution decomposition reaction, which lowers the efficiency or cycle capacity of the core carbon material, and when the upper limit is exceeded The weight itself is undesirable because of reduced capacity or energy density.

In addition, the core carbon material coated with the low crystalline carbon and the fluorine-based compound may of course use a conventional material used in the art. For example, the core carbon material may use natural graphite, artificial graphite, or a mixture thereof, and in particular, it is preferable to use natural graphite.

As described above, the core carbon material having the low crystalline carbon and the fluorine-based compound coated on the surface may be dried and fired according to a conventional method to prepare a final negative electrode active material.

In addition, the present invention is a secondary battery comprising a separator and an electrolyte interposed between the positive electrode, the negative electrode, both electrodes, the electrode plate comprising a slurry for producing a negative electrode active material containing a negative electrode active material prepared by the above-described manufacturing method as the negative electrode It characterized in that it comprises a negative electrode material prepared by coating as a negative electrode.

A small amount of a conductive agent or a binder may be selectively added to the slurry for preparing a negative electrode plate containing the negative electrode active material, as necessary. The use amount of the conductive agent or binder can be appropriately adjusted and used to the extent commonly used in the art, the range does not affect the present invention.

The conductive agent may be used as long as it is an electron conductive material that does not cause chemical change in the battery configured. For example, carbon black such as acetylene black, ketjen black, farnes black, thermal black, and the like, natural graphite, artificial graphite, or conductive fibrous fibers, and the like, and in particular, carbon black, graphite powder, or carbon fiber is preferably used. Do.

As the binder, a thermoplastic resin, a thermosetting resin, or a mixture thereof may be used, and in particular, polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE) may be used, and more preferably polyfluorinated Vinylidene is used.

As described above, the slurry for preparing a cathode plate including the negative electrode active material and optionally at least one of a conductive agent and a binder is then applied to an electrode current collector, and then dried by removing a solvent or a dispersion medium to bind the active material to the current collector. At the same time, the active material is bound to each other.

The electrode current collector is not particularly limited as long as it is made of a conductive material, and it is particularly preferable to use a foil made of copper, gold, nickel, a copper alloy, or a combination thereof.

The secondary battery of the present invention can be prepared by inserting a porous separator between the positive electrode and the negative electrode in a conventional manner known in the art.

The electrolyte is a non-aqueous electrolyte containing a lithium salt and an electrolyte compound, wherein the lithium salt is selected from the group consisting of LiClO ₄ , LiCF ₃ SO ₃ , LiPF ₆ , LiBF ₄ , LiAsF ₆ and LiN (CF ₃ SO ₂ ) ₂ . Preference is given to compounds of species or more. In addition, the electrolyte compounds include ethylene carbonate (EC), propylene carbonate (PC), gamma butyrolactone (GBL), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC) and methyl propyl carbonate (MPC). It is preferable that it is 1 or more types chosen from the group which consists of.

In manufacturing the battery of the present invention, it is preferable to use a porous separator as a separator, and non-limiting examples include a polypropylene-based, polyethylene-based or polyolefin-based porous separator.

The secondary battery of the present invention is not limited in appearance, but may be cylindrical, square, pouch or coin type using a can.

Hereinafter, in order to help the understanding of the present invention will be described in more detail through preferred examples and comparative examples.

Example 1

Pitch and LiF dissolved in tetrahydrofuran in 100 parts by weight of spherical natural graphite were mixed in 10 parts by weight and 2 parts by weight, respectively, mixed by wet stirring at normal pressure for 2 hours or more, and then dried to prepare a mixture. The mixture was calcined for 1 hour at 1,100 ° C. and 1,500 ° C. for 1 hour, and then classified to remove fine powder to prepare a negative electrode active material.

100 g of the negative electrode active material prepared above was put into a 500 ml reactor, and a small amount of N-methylpyrrolidone (NMP) and polyvinylidene fluoride (PVDF) were added as a binder, followed by kneading using a mixer. Slurry was prepared. Then, the above prepared slurry for producing a plate was pressed and dried on a foil foil, and used as an electrode. At this time, the electrode density was 1.5 g / cm 3 and the electrode thickness was 70 μm.

Example 2

The same procedure as in Example 1 was conducted except that SiF ₄ was used instead of LiF used in Example 1.

Example 3

It was carried out in the same manner as in Example 1 except that SnF ₄ was used instead of LiF used in Example 1.

Comparative Example 1

100 parts by weight of spherical natural graphite was mixed with 10 parts by weight of the pitch dissolved in tetrahydrofuran, followed by wet stirring at normal pressure for 2 hours or more, followed by drying to prepare a mixture. The mixture was calcined first and second at 1,100 ° C. and 1,500 ° C. for 1 hour, and classified to remove fine powder to prepare a negative electrode active material.

100 g of the prepared negative electrode active material was placed in a 500 ml reactor, and a small amount of N-methylpyrrolidone (NMP) and polyvinylidene fluoride (PVDF) were added as a binder, followed by kneading using a mixer to prepare an electrode. Slurry was prepared. Then, the prepared slurry for electrode production was pressed and dried on a foil foil, and used as an electrode. At this time, the electrode density was 1.5 g / cm 3 and the electrode thickness was 70 μm.

In order to evaluate the charge / discharge efficiency using the electrodes prepared in Examples 1 to 3 and Comparative Example 1 to prepare a coin cell (Coin cell) to evaluate the charge / discharge characteristics through the following test, the results It is shown in Table 1 below.

First, the charge / discharge test regulates the potential in the range of 0 to 1.5 V to charge until the charging current is 0.5 V / cm 2 until it becomes 0.01 V, maintains the voltage of 0.01 V, and the charging current becomes 0.02 mA / cm 2. Charging continued until. The discharge current was discharged up to 1.5 V at 0.5 mA / cm 2. In Table 1, the charge / discharge efficiency shows the ratio of the discharged capacity to the charged capacity.

division Example 1 Example 2 Example 3 Comparative Example 1 1 ^st cycle discharge capacity (mAh / g) 350.3 352.1 352.8 353.8 1 ^st cycle efficiency (%) 94.1 93.7 93.4 92.1 50 ^st cycle capacity retention rate (%) 92.8 93.5 92.1 86.3

As shown in Table 1, in the case of Examples 1 to 3 using the negative electrode active material prepared by coating the low crystalline carbon and the fluorine-based compound together on the core carbon material surface according to the present invention, only the low crystalline carbon was applied to the core carbon material. Although the first cycle discharge capacity and the efficiency were similar to those of the coated Comparative Example 1, the capacity retention rate during the 50th cycle was confirmed to be superior to that of Comparative Example 1.

As described above, although the present invention has been described by means of a limited embodiment, the present invention is not limited thereto and will be described below by the person skilled in the art and the technical spirit of the present invention. Of course, various modifications and variations are possible within the scope of the claims.

According to the present invention, the low crystalline carbon and the fluorine-based compound are used together in the preparation of the negative electrode active material to coat the surface of the core carbon material to stabilize the surface of the negative electrode active material to reduce the effects of the organic electrolyte solution decomposition reaction, which is the main cause of irreversible capacity, The efficiency and cycle characteristics can be improved by reducing the influence on the acid produced by oxidation of the electrolyte during discharge.

Claims (13)

Core carbon material; Low crystalline carbon; And Fluorine-based compound, including; The fluorine compound is, CsF, KF, LiF, NaF , RbF, TiF, AgF, AgF 2, BaF 2, CaF 2, CuF 2, CdF 2, FeF 2, HgF 2, Hg 2 F 2, MnF 2, MgF 2 , NiF ₂ , PbF ₂ , SnF ₂ , SrF ₂ , XeF ₂ , ZnF ₂ , AlF ₃ , BF ₃ , BiF ₃ , CeF ₃ , CrF ₃ , DyF ₃ , EuF ₃ , GaF ₃ , GdF ₃ , FeF ₃ , HoF _{3, InF 3, LaF 3,} LuF 3, MnF 3, NdF 3, VOF 3, PrF 3, SbF 3, ScF 3, SmF 3, TbF 3, TiF 3, TmF 3, YF 3, YbF 3, TiF 3, _{CeF 4, GeF 4, HfF 4} , SiF 4, SnF 4, TiF 4, VF 4, ZrF 4, NbF 5, SbF 5, TaF 5, BiF 5, MoF 6, ReF 6, the group consisting of SF ₆ and WF ₆ A negative electrode active material for a secondary battery, characterized in that a single substance or a mixture of two or more selected from. The method of claim 1, The fluorine-based compound is a negative electrode active material for a secondary battery, characterized in that contained in 1 to 30 parts by weight based on 100 parts by weight of the core carbon material. The method of claim 1, The core carbon material is a negative electrode active material for a secondary battery, characterized in that a single substance or a mixture of two or more selected from the group consisting of natural graphite and artificial graphite. The method of claim 1, The low crystalline carbon is a negative electrode active material for a secondary battery, characterized in that a single material or a mixture of two or more selected from the group consisting of pitch, tar (tar), phenolic resin, furan resin and fulfuryl alcohol. The method of claim 1, The low crystalline carbon, the negative electrode active material for a secondary battery, characterized in that contained in 0.1 to 30 parts by weight with respect to 100 parts by weight of the core carbon material. The core carbon material, a low crystalline carbon and CsF, KF, LiF, NaF, RbF, TiF, AgF, AgF _2, BaF _2, CaF _2, CuF _2, CdF _2, FeF _2, HgF _2, Hg ₂ F _2, MnF ₂ , MgF ₂ , NiF ₂ , PbF ₂ , SnF ₂ , SrF ₂ , XeF ₂ , ZnF ₂ , AlF ₃ , BF ₃ , BiF ₃ , CeF ₃ , CrF ₃ , DyF ₃ , EuF ₃ , GaF ₃ , GdF ₃ , _{FeF 3, HoF 3, InF 3} , LaF 3, LuF 3, MnF 3, NdF 3, VOF 3, PrF 3, SbF 3, ScF 3, SmF 3, TbF 3, TiF 3, TmF 3, YF 3, YbF 3 _{, TiF 3, CeF 4, GeF} 4, HfF 4, SiF 4, SnF 4, TiF 4, VF 4, ZrF 4, NbF 5, SbF 5, TaF 5, BiF 5, MoF 6, ReF 6, SF 6 and WF Preparing a fluorine-based compound which is a single substance or a mixture of two or more selected from the group consisting of ₆ ; Coating the surface of the core carbon material with a mixture of the low crystalline carbon and the fluorine-based compound; Drying the core carbon material whose surface is coated with a mixture of the low crystalline carbon and fluorine-based compounds; And And firing the dried core carbon material. The method of claim 6, The fluorine-based compound is a method for producing a negative electrode active material for a secondary battery, characterized in that contained in 1 to 30 parts by weight based on 100 parts by weight of the core carbon material. The method of claim 6, The core carbon material is a single material or a mixture of two or more selected from the group consisting of natural graphite and artificial graphite, the method for producing a negative electrode active material for secondary batteries. The method of claim 6, The low crystalline carbon is a single material or a mixture of two or more selected from the group consisting of pitch, tar, phenol resin, furan resin, and furfuryl alcohol. The method of claim 6, The low crystalline carbon is 0.1 to 30 parts by weight based on 100 parts by weight of the core material carbon material manufacturing method of a negative electrode active material for a secondary battery. A secondary battery comprising a negative electrode material prepared by applying a slurry for electrode plate production comprising a negative electrode active material prepared by the method according to any one of claims 6 to 10 to the electrode current collector as a negative electrode. delete delete