KR101413433B1 - Binder for Secondary Battery Providing Excellent Cycle property and Secondary Battery by Using Same - Google Patents

Abstract

The present invention provides a binder for a secondary battery excellent in cycle characteristics and a secondary battery using the same.
The secondary battery binder of the present invention includes any one component selected from rosin and rosin derivatives, thereby providing a secondary battery having improved cycle performance by improving the performance of the battery.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binder for a secondary battery having excellent cycle characteristics and a secondary battery using the binder.

The present invention relates to a binder for a secondary battery having excellent cycle characteristics and a secondary battery using the same, and more particularly, to a binder for an electrode of a secondary battery including a component selected from rosin and rosin derivatives, And a binder for a secondary battery capable of improving battery performance, and a secondary battery using the same.

Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy or clean energy is increasing. As a part of this, the most active field of research is electric power generation and storage.

At present, a typical example of an electrochemical device utilizing such electrochemical energy is a secondary battery, and the use area thereof is gradually increasing.

2. Description of the Related Art [0002] Recently, as technology development and demand for portable devices such as portable computers, portable telephones, and cameras have increased, the demand for secondary batteries as energy sources has been rapidly increasing. Higher energy densities and operating potentials Many studies have been made on a lithium secondary battery having a long self discharge rate, and it has been commercialized and widely used.

In addition, as the interest in environmental problems grows, researches on electric vehicles and hybrid electric vehicles that can replace fossil fuel-based vehicles such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution, . Although nickel-metal hydride secondary batteries are mainly used as power sources for such electric vehicles and hybrid electric vehicles, researches using lithium secondary batteries having high energy density and discharge voltage are being actively carried out, and they are in the commercialization stage.

Conventionally, a typical lithium secondary battery uses graphite as a negative electrode active material, charging and discharging proceed while repeating a process in which lithium ions in an anode are inserted into a negative electrode and desorbed. The theoretical capacity of the battery varies depending on the kind of the electrode active material, but the charging and discharging capacities decrease with the progress of the cycle.

This phenomenon is most likely caused by the separation of the electrode active material or between the electrode active material and the current collector due to the volume change of the electrode caused by the progress of charging and discharging of the battery, so that the active material fails to function. In addition, lithium ions inserted into the negative electrode may not be properly discharged during the insertion or desorption, and the active sites of the negative electrode may be reduced. As a result, the charge / discharge capacity and lifetime characteristics of the battery may decrease as the cycle progresses.

Particularly, in order to increase the discharge capacity, when a material such as silicon, tin, silicon-tin alloy having a large discharging capacity is mixed with natural graphite having a theoretical discharge capacity of 372 mAh / g is used, The volume expansion of the negative electrode material is remarkably increased. As a result, the negative electrode material is separated from the electrode material. As a result, the capacity of the battery is drastically lowered due to repeated cycles.

Therefore, it is possible to prevent separation between the electrode active material or between the electrode active material and the current collector during the production of the electrode with strong adhesive force, and to control the volume expansion of the electrode active material generated during repetitive charging and discharging with strong physical properties, There is a great demand in the art for a study on a binder and an electrode material capable of improving the performance of the electrode.

Polyvinylidene fluoride (PVdF), which is currently widely used as a binder for positive and negative electrodes, is a polymer resin dissolved in an organic solvent such as N-methyl-2-pyrrolidone (NMP). Although PVdF is not an adhesive originally, PVdF has good compatibility with graphite materials, and by adding about 8 to 10% of graphite, it is possible to produce a polar plate having a high adhesive force and is widely used as a binder of an electrode active material.

However, since PVdF covers the active material in such a state that the polymer fibers are filled, the cell performance inherent in the electrode active material deteriorates in terms of capacity and efficiency. In addition, PVdF tends to be broken and the cycle characteristics to be degraded when a material having a large specific surface area such as natural graphite or metal-based active material and having a high expansion / shrinkage ratio during charging / discharging is used as an electrode active material due to lack of flexibility. Further, the electrolyte tends to absorb and expand the carbonate-based electrolyte, and the output capacity is significantly lowered as the cycle progresses.

Another binder used in the lithium secondary battery is a rubber latex such as styrene-butadiene rubber (SBR) as an aqueous binder. This SBR is eco-friendly and reduces the content of binder used to improve the capacity and initial charge / discharge efficiency of the secondary battery. In this case, however, since the adhesion persistence is improved due to the elasticity of the rubber, There is a limitation in the use of the electrode because it can not be utilized for a high-capacity active material which requires a high-adhesive electrode having a large volume expansion upon charging / discharging.

Therefore, there is a high need for developing a binder which can improve the cycle characteristics of the battery and improve the performance of the battery.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a binder for an electrode of a secondary battery including any one component selected from rosin and rosin derivatives, And a secondary battery using the same.

According to an aspect of the present invention, there is provided an electrode binder for a secondary battery,

Rosin, and rosin derivatives. In some cases, the binder may further contain a fluorine-containing polymer. At this time, any one component selected from the rosin and rosin derivatives may contain 5 to 50% by weight based on the total weight of the binder, and the fluorine-containing polymer may include 50 to 95% by weight based on the total weight of the binder have.

In one preferred embodiment, the rosin may be at least one selected from rosin, rosin and tall oil rosin. The rosin derivative may be a hydrogenated rosin, a modified rosin obtained by reacting rosin with maleic anhydride, Formylated rosin, and polymerized rosin.

Further, the fluorine-containing polymer may be at least one selected from the group consisting of polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), a copolymer of polyvinylidene fluoride-tetrafluoroethylene (PVdF -TEE) or a combination thereof.

In some cases, the binder may further contain at least one material selected from the group consisting of a viscosity modifier and a filler.

To achieve the second object of the present invention, there is provided a secondary battery according to the present invention, comprising: a binder for an electrode of a secondary battery; And an electrode active material, and the binder for the electrode of the secondary battery may include any one selected from rosin and rosin derivatives. In some cases, the binder for the electrode of the secondary battery may further include a fluorine-containing polymer.

At this time, any one component selected from the rosin and rosin derivatives may contain 5 to 50% by weight based on the total weight of the binder, and the fluorine-containing polymer may include 50 to 95% by weight based on the total weight of the binder can do.

As one preferred example, the rosin may be at least one selected from rosin rosin, wood rosin and tall oil rosin. The rosin derivative may be a hydrogenated rosin, a modified rosin obtained by reacting rosin with maleic anhydride, A rosin, a rosin, a rosin, a rosin, a rosin, a rosin, and a rosin.

Further, the fluorine-containing polymer may be at least one selected from the group consisting of polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), a copolymer of polyvinylidene fluoride-tetrafluoroethylene (PVdF -TEE) or a combination thereof.

The negative electrode active material of the electrode active material may be at least one selected from the group consisting of metal oxides and lithium metal complex oxides.

The metal may be titanium, and the oxide may be at least one selected from the group consisting of TiO ₂ , Li ₄ Ti ₅ O ₁₂ and LiTi ₂ O ₄ .

And the electrode mixture of the secondary battery is applied to the electrode current collector.

The present invention may be a lithium secondary battery including the electrode for the secondary battery.

As described above, the electrode binder of the secondary battery according to the present invention contains any one component selected from rosin and rosin derivatives, so that it is possible to maintain a good binding force between the electrode active material and the current collector, Insertion and desorption of Li ^& lt ^{; + &} gt ^; ions are improved. Accordingly, the electrode binder of the secondary battery manufactured according to the present invention has excellent cycle characteristics, and the performance of the battery can be improved.

In addition, the combination of a negative electrode active material using titanium oxide or lithium titanium oxide and a binder produced according to the present invention actively promotes the migration of Li ⁺ ions, thereby improving the performance of the battery.

1A is a graph showing a cyclic voltammogram of a binder film according to Experimental Example 1;
1B is a cyclic voltammogram of the electrode according to Experimental Example 1;
2 is a Nyquist plot of an electrode according to Experimental Example 2;
FIG. 3A shows a result of evaluation of the capacity characteristic according to the C-rate according to Experimental Example 2 of the present invention; FIG.
FIG. 3B is a graph showing the capacity characteristics according to Experiment 2 of the present invention at another C-rate;
4A is an XPS spectrum of titanium 2p (energy level) according to the present invention;
4B is an XPS spectrum of oxygen 1s (energy level) according to the present invention.

Hereinafter, the present invention will be described in more detail with reference to examples and the like, but the following examples are intended to illustrate the present invention, and the scope of the present invention is not limited thereto.

Accordingly, the binder for the electrode of the secondary battery according to the present invention comprises any one component selected from rosin and rosin derivatives, and may further include a fluorine-containing polymer.

When the binder according to the present invention is applied to an electrode of a secondary battery, it is possible to maintain an excellent bonding force between the electrode active material that undergoes volume change during charging and discharging and between the electrode active material and the current collector.

In addition, since a commonly used binder is contained in the form of an electrically insulating polymer, the binder of the present invention deteriorates the performance of the battery by inhibiting the movement of lithium ions and electrons and the like, while the binder of the present invention is selected from rosin and rosin derivatives By using one component, the charge transfer resistance is reduced, and insertion and desorption of Li ⁺ ions are improved, so that there is an advantage that the performance of the battery can be improved.

In this configuration, any one component selected from the rosin and rosin derivatives includes 5 to 50% by weight based on the total weight of the binder, and the fluorine-containing polymer contains 50 to 95% by weight based on the total weight of the binder .

Specifically, when any one component selected from rosin and rosin derivatives is less than 5% by weight, in other words, when the content of the fluorine-containing polymer exceeds 95% by weight, a large amount of the electrically insulating fluorine- The performance of the battery can be deteriorated. On the other hand, if any one component selected from rosin and rosin derivatives exceeds 50% by weight, the adhesive force between the electrode active material and the current collector may be significantly lowered. More preferably, any one selected from rosin and rosin derivatives is contained in an amount of 20 to 40% by weight, and the fluorine-containing polymer is contained in an amount of 60 to 80% by weight.

The rosin may be at least one selected from among rosin, rosin, and tall oil rosin. The rosin derivative may be at least one selected from hydrogenated rosin, modified rosin obtained by reacting rosin with maleic anhydride, And a polymerized rosin. Preferably, rosin rosin can be used.

Further, the fluorine-containing polymer may be at least one selected from the group consisting of polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), a copolymer of polyvinylidene fluoride-tetrafluoroethylene (PVdF -TEE) or a combination thereof.

In the present invention, the binder preferably further comprises at least one material selected from the group consisting of a viscosity modifier and a filler. These viscosity modifiers and fillers are described in more detail below.

Examples of the solvent used in the production of the binder include organic solvents such as NMP (N-methylpyrrolidone), DMF (dimethylformamide), acetone and dimethylacetamide, and water. These solvents may be used alone or in combination of two or more Can be mixed and used. The amount of the solvent to be used is sufficient to dissolve and disperse the electrode active material, the binder and the conductive material in consideration of the coating thickness of the slurry and the production yield.

The binder of the secondary battery includes an electrode binder and an electrode active material capable of intercalating and deintercalating lithium, wherein the binder for the electrode of the secondary battery is a secondary battery comprising any one component selected from rosin and rosin derivatives, Thereby providing an electrode mixture for a battery. At this time, the binder for the electrode of the secondary battery may further include a fluorine-containing polymer.

The binder for the electrode of the secondary battery may be contained in the range of, for example, 0.5 to 20% by weight, and preferably 1 to 10% by weight, based on the weight of the electrode mixture.

In this configuration, any one component selected from the rosin and rosin derivatives includes 5 to 50% by weight based on the total weight of the binder, and the fluorine-containing polymer contains 50 to 95% by weight based on the total weight of the binder . Concretely, when any one component selected from rosin and rosin derivatives is less than 5% by weight, the movement of lithium ions and electrons can be inhibited and the performance of the battery can be deteriorated as described above. On the other hand, when any one component selected from rosin and rosin derivatives exceeds 50% by weight, the adhesive force between the electrode active material and the current collector may be significantly lowered. More preferably, 20 to 40% by weight of any one component selected from rosin and rosin derivatives is contained, and 60 to 80% by weight of the fluorine-containing polymer is included.

The rosin may be at least one selected from the group consisting of rosin, rosin and tall oil. The rosin derivative may be selected from hydrogenated rosin, modified rosin obtained by reacting rosin with maleic anhydride, And rosins obtained from rosins. Preferably, rosin rosin can be used.

Further, the fluorine-containing polymer may be at least one selected from the group consisting of polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), a copolymer of polyvinylidene fluoride-tetrafluoroethylene (PVdF -TEE) or a combination thereof.

It is preferable that the electrode mixture of the secondary battery further includes a conductive material. That is, it is possible to provide an electrode for a secondary battery in which the electrode active material and the conductive material are bonded to the current collector by the binder for an electrode described above.

Such an electrode can be prepared by preparing a slurry by adding a binder, an electrode active material and a conductive material to a predetermined solvent such as water or NMP, applying the slurry on a collector, followed by drying and rolling. The electrode active material and the conductive material will be described later in more detail.

The electrode for the secondary battery may be an anode or a cathode. The positive electrode is prepared, for example, by applying a mixture of a positive electrode active material, a conductive material, a binder and the like on the positive electrode current collector, and drying the mixture. The negative electrode is formed by applying a mixture of the negative electrode active material, Followed by drying.

The electrode active material in the electrode is a material capable of causing an electrochemical reaction, and the positive electrode active material and the negative electrode active material exist depending on the type of the electrode.

The type of the negative electrode active material is not particularly limited as long as it exhibits high hydrophilicity and polarity and does not adversely affect the operating characteristics of the battery. Preferably, the negative electrode active material is a metal oxide and a lithium metal composite oxide And so on. These may be used alone or in the form of a mixture of two or more.

Preferable examples of the metal include titanium, a metalloid, an optional mixture thereof, and more preferably titanium, but the present invention is not limited thereto.

Preferable examples of the oxide capable of storing and releasing the ions include TiO ₂ , Li ₄ Ti ₅ O _12, and LiTi ₂ O ₄ , but are not limited thereto.

The titanium oxide or lithium titanium oxide has a potential higher than 0 V and less than 2 V with respect to the lithium metal reference electrode and has a higher potential than graphite having almost the same potential as lithium. Therefore, when titanium oxide or lithium titanium oxide is instantaneously applied at a low temperature due to a relatively high potential, lithium ions are occluded and released into the titanium oxide or lithium titanium oxide, It is possible to realize an instantaneous output that can not be implemented. In addition, the lithium secondary battery can suppress the growth of lithium dendrite due to the potential difference.

On the other hand, the positive electrode active material is a lithium transition metal oxide, for example, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or the like containing _two or more transition metals and substituted with one or more transition metals Layered compounds; Lithium manganese oxide substituted with one or more transition metals; Formula _{LiNi 1-y M y O 2} ( where, M = Co, Mn, Al , Cu, Fe, Mg, B, Cr, and Zn or Ga,, 0.01 ≤y≤0.7 include one or more elements of the element) A lithium nickel-based oxide represented by the following formula: _{Li 1 + z Ni 1/3 Co 1/3} Mn 1/3 O 2, Li 1 + z Ni 0.4 Mn 0.4 Co 0.2 O 2 , such as _{Li 1 + z Ni b Mn c} Co 1- (b + c + d _{) M d O (2-e} ) Ae ( here, -0.5≤z≤0.5, 0.1≤b≤0.8, 0.1≤c≤0.8, 0≤d≤0.2 , 0≤e≤0.2, b + c + d < 1, M = Al, Mg, Cr, Ti, Si or Y and A = F, P or Cl); And the formula _{Li 1 + x M 1-y} M 'y PO 4-z X z ( wherein, M = a transition metal, preferably Fe, Mn, Co or Ni, M' = Al, Mg or Ti, X = F, S or N, and -0.5? X? +0.5, 0? Y? 0.5, and 0? Z? 0.1), but the present invention is not limited thereto.

The conductive material is a component for further improving the conductivity of the electrode active material and may be added in an amount of 0.01 to 30% by weight based on the total weight of the electrode mixture. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Carbon powders such as carbon nanotubes and fullerene; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The electrode assembly of the secondary battery may be applied to an electrode current collector. In the electrode, the current collector is a portion where electrons move in the electrochemical reaction of the active material. Depending on the type of the electrode, the positive electrode collector and the negative electrode collector exist.

The cathode current collector is generally made to have a thickness of 3 to 500 mu m. The positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, the positive electrode current collector may be formed on the surface of stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum or stainless steel Carbon, nickel, titanium, silver, or the like may be used.

The negative electrode current collector is generally made to have a thickness of 3 to 500 mu m. The positive electrode current collector is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery. For example, the positive electrode current collector is formed on the surface of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, Carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used.

These current collectors preferably have a thickness of 3 to 200 탆 and include fine irregularities on the surface to enhance the bonding force with the electrode active material and can be used as a film, a sheet, a foil, a net, a porous body, a foam, And the like.

The mixture (electrode mixture) of the electrode active material, the conductive material, the binder and the like may further contain at least one substance selected from the group consisting of a viscosity adjusting agent and a filler.

The viscosity adjusting agent may be added up to 30% by weight based on the total weight of the electrode mixture, so as to control the viscosity of the electrode mixture so that the mixing process of the electrode mixture and the coating process on the collector may be easy. Examples of such viscosity modifiers include carboxymethylcellulose, polyacrylic acid, and the like, but are not limited thereto.

The filler is an auxiliary component for suppressing the expansion of the electrode. The filler is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery, and examples thereof include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

The present invention also provides a lithium secondary battery comprising the secondary battery electrode.

The lithium secondary battery generally comprises a separator and a non-aqueous electrolyte containing a lithium salt in addition to the electrode.

The separator is an insulating thin film interposed between the anode and the cathode and having high ion permeability and mechanical strength. The pore diameter of the separator is generally 0.01 to 10 mu m and the thickness is generally 5 to 300 mu m. As such a separation membrane, for example, a sheet or a nonwoven fabric made of an olefin-based polymer such as polypropylene which is chemically resistant and hydrophobic, glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The lithium-containing non-aqueous electrolyte is composed of a non-aqueous electrolyte and a lithium salt.

Examples of the nonaqueous electrolytic solution include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, But are not limited to, lactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, Nitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives , Tetrahydrofuran derivatives, ether, methyl pyrophosphate, ethyl propionate and the like can be used.

The lithium salt is a material which is soluble in the non-aqueous liquid electrolyte and includes, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide have.

In some cases, organic solid electrolytes, inorganic solid electrolytes, etc. may be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, Polymers containing ionic dissociation groups, and the like can be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , A nitride, a halide, and a sulfate of Li such as Li ₃ PO ₄ -Li ₂ S-SiS ₃ can be used.

For the purpose of improving the charge-discharge characteristics and the flame retardancy, the non-aqueous liquid electrolyte may contain, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride and the like are added It is possible. In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further added to impart nonflammability. In order to improve the high-temperature storage characteristics, carbon dioxide gas may be further added. FEC (Fluoro-Ethylene Carbonate, PRS (Propene Sultone), FEC (Fluoro-Ethylene Carbonate), and the like.

The secondary battery according to the present invention can be preferably used as a power source for electric vehicles, hybrid electric vehicles and the like which require particularly excellent cycle characteristics and high rate characteristics.

{Example}

[Example 1]

The solvent NMP was added so that the weight ratio of PVdF as the first binder was 10 wt%, and the PVdF polymer was completely dissolved in the solvent while stirring was maintained at about 60 DEG C for 2 hours. A small amount of rosin was added to the same NMP solvent as the second binder component to completely dissolve the rosin, and the two solutions were mixed in a weight ratio of PVdF: Rosin Rosin = 6: 4 to prepare an electrode binder for a secondary battery.

[Example 2]

A binder was produced in the same manner as in Example 1, except that the binder for electrode of the secondary battery was produced in the same manner as in Example 1 except that the composition of the binder was a weight ratio of PVdF: Rosin Rosin = 8: 2.

[Comparative Example 1]

A binder was produced in the same manner as in Example 1, except that the binder for electrode of the secondary battery was produced without adding rosin.

[Experimental Example 1]

1-1. Binder film manufacturing

The binder prepared in each of Examples 1 to 2 and Comparative Example 1 was coated on aluminum foil to a thickness of 500 mu m using a doctor blade and then dried at 130 DEG C for 2 hours and then aluminum foil was removed To prepare a binder film.

1-2. Manufacture of slurry and cathode

Li ₄ Ti ₅ O ₁₂ was added as an oxide capable of intercalating and deintercalating lithium ions using the binder prepared in each of Examples 1 to 2 and Comparative Example 1 to prepare an anode active material. The slurry was prepared so that the weight ratio of the negative electrode active material: the binder: conductive material was 90: 5: 5, and then applied to a copper foil to prepare a negative electrode.

1-3. Cyclic Voltammogram (CV) Analysis

Cyclic Voltammogram analysis of the binder film prepared in 1-1 and the negative electrode prepared in 1-2 was carried out, and the results are shown in FIGS. 1A to 1B, respectively.

For reference, the three graph lines located on the upper layer in the graphs of FIGS. 1A and 1B show the CV in the oxidation reaction, and the three graph lines located in the lower layer show the CV in the reduction reaction. For reference, in all of the following graphs, Example 1 is represented by a green line, Example 2 is indicated by a blue line, and Comparative Example 1 is represented by a red line.

Referring to FIG. 1A, the current peak of the binder film prepared according to Comparative Example 1 is strong, whereas the current peaks of Examples 1 and 2 containing rosin rosin are weakened. The weaker current peak means less reactivity, meaning that the binder film is electrochemically stable.

Referring to FIG. 1B, it is observed that the current peak of Comparative Example 1 is smaller than that of Examples 1 and 2. This is because the performance of the battery using the binder manufactured according to Examples 1 and 2 is improved .

[Experimental Example 2]

Using the respective binders prepared in Examples 1 to 2 and Comparative Example 1, a lithium secondary battery was prepared as described below, and its battery characteristics were measured.

2-1. Slurry and electrode manufacturing

Li ₄ Ti ₅ O ₁₂ was added as an oxide capable of intercalating and deintercalating lithium ions to prepare an anode active material. The slurry was prepared so that the weight ratio of the negative electrode active material: the binder: conductive material was 90: 5: 5, and then applied to a copper foil to prepare a negative electrode.

2-2. Manufacture of lithium secondary battery

A coin-shaped half-cell (CR2016) was assembled in the argon-filled glove box using the anode, the lithium anode, the polyethylene separator, and the electrolyte solution. The electrolytic solution was LiPF ₆ (Panaxitec) dissolved in a molar ratio of 1: 1: 1 in a volume ratio of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate of 1: 1: 1.

The lithium secondary battery produced by the above method was discharged at a rate of 0.005 V at a rate of 0.1 C, charged at 1 V, charged and discharged twice, and then charged and discharged at a current density of 1 C for 58 cycles. Capacity characteristics of each C rate were evaluated and shown in FIG. 3A.

Example 1 using the binder prepared according to the present invention showed a discharge capacity and a cycle stability of 165 mAh / g for 60 cycles at a current density of 1 C, Example 2 showed a discharge capacity of 163 mAh / g Respectively. However, the electrode using the binder produced according to Comparative Example 1 exhibited a discharge capacity of 157 mAH / g, which is lower than that of Example 1 and Example 2.

In addition, the 55 cycle characteristics at 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, 5 C and 10 C rate current densities were evaluated and the results are shown in FIG. Example 1, Example 2, and Comparative Example 1 exhibited somewhat similar discharge capacities and cycle stability up to a current density of 0.1C to 1C, but Example 1 and Example 2 at a current density of 2C to 10C were comparable to Comparative Example 1 It can be confirmed that the discharge capacity is remarkably excellent.

As described above, when the electrode is manufactured using the binder prepared according to the examples 1 and 2, the reason for the excellent capacity is that the movement of lithium ions is free. Specifically, referring to FIG. 2, it can be seen that when the electrode is manufactured using the binder according to the first and second embodiments, the impregnation of the electrolyte solution is smooth and the lithium ion moves rapidly in the electrode. As a result, the insertion and desorption of Li ^& lt ^{; + &} gt ^; ions are improved to decrease the charge transfer resistance and increase the capacity.

Also, referring to FIGS. 4A and 4B, the reason why the energy level 2p _3/2 peak is gradually shifted is that Ti ³⁺ is oxidized to Ti ⁴⁺ by the phase transition of the LTO electrode. The more the electrons move from Ti ³⁺ to Ti ⁴⁺ , the faster the Li ions move and the better the performance of the battery.

The embodiments of the present invention described above and shown in the drawings should not be construed as limiting the technical idea of the present invention. The scope of protection of the present invention is limited only by the matters described in the claims, and those skilled in the art will be able to modify the technical idea of the present invention in various forms. Accordingly, such improvements and modifications will fall within the scope of the present invention as long as they are obvious to those skilled in the art.

Claims (15)

Any one component selected from rosin and rosin derivatives; And
Containing fluorine-containing polymer,
The rosin and the rosin derivative may contain 20 to 40% by weight based on the total weight of the binder, and the fluorine-containing polymer may include 60 to 80% by weight based on the total weight of the binder. Wherein the binder is a binder. delete delete The method according to claim 1,
The rosin is at least one selected from rosin, rosin and tall oil rosin,
Wherein the rosin derivative is at least one selected from hydrogenated rosin, modified rosin obtained by reacting rosin with maleic anhydride, formylated rosin, and polymerized rosin. The method according to claim 1,
The fluorine-containing polymer may be selected from the group consisting of polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), a copolymer of polyvinylidene fluoride-tetrafluoroethylene (PVdF-TEE ) Or a combination thereof. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; The method according to claim 1,
Wherein the binder further comprises at least one material selected from the group consisting of a viscosity modifier and a filler. A binder for an electrode of a secondary battery; And
Electrode active material,
Wherein the binder for the electrode of the secondary battery is any one selected from rosin and rosin derivatives; And
A fluorine-containing polymer,
The rosin and the rosin derivative is contained in an amount of 20 to 40% by weight based on the total weight of the binder, and the fluorine-containing polymer is contained in an amount of 60 to 80% by weight based on the total weight of the binder Wherein the electrode assembly of the secondary battery comprises: delete delete 8. The method of claim 7,
The rosin is at least one selected from rosin, rosin and tall oil rosin,
Wherein the rosin derivative is at least one selected from hydrogenated rosin, modified rosin obtained by reacting rosin with maleic anhydride, formylated rosin, and polymerized rosin. 8. The method of claim 7,
The fluorine-containing polymer may be selected from the group consisting of polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), a copolymer of polyvinylidene fluoride-tetrafluoroethylene (PVdF-TEE ) Or a combination thereof. 8. The method of claim 7,
Wherein the negative active material of the electrode active material is at least one selected from the group consisting of a metal oxide and a lithium metal composite oxide. 13. The method of claim 12,
Wherein the metal is titanium,
Wherein the oxide is at least one selected from the group consisting of TiO ₂ , Li ₄ Ti ₅ O ₁₂ and LiTi ₂ O ₄ . The electrode for a secondary battery according to claim 13, wherein the electrode mixture of the secondary battery is applied to the electrode current collector. A lithium secondary battery comprising the electrode for a secondary battery according to claim 14.

Images