KR20040025091A - Electorlyte plate for lithium secondary batteries and lithium secondary batteries comprising the same - Google Patents

Abstract

PURPOSE: Provided is an electrode plate for a lithium secondary battery having excellent stability and life property. A lithium secondary battery comprising the electrode plate is also provided. CONSTITUTION: The electrode plate for a lithium secondary battery comprises active materials, a binder and an amine-based polymer. In particular, the amine-based polymer is a polyethyleneimine represented by the following formula 1, wherein each of x and y is a mole ratio of each monomer, x is 0.1 to 99.9, y is 99.9 to 0.1, and x+y=100.

Description

ELECTROLYTE PLATE FOR LITHIUM SECONDARY BATTERIES AND LITHIUM SECONDARY BATTERIES COMPRISING THE SAME

[Industrial use]

The present invention relates to a lithium secondary battery electrode plate and a lithium secondary battery comprising the same, and more particularly, to a lithium secondary battery electrode plate having excellent stability and lifespan characteristics and a lithium secondary battery including the electrolyte.

[Prior art]

Recently, with the trend toward miniaturization and light weight of portable electronic devices, the need for high performance and high capacity of batteries used as power sources for these devices is increasing. Lithium secondary batteries, which are currently commercialized and used, are the elements of the digital age, which are rapidly being applied to portable phones, notebook computers, camcorders, and so on, which are referred to as 3C. In particular, with the rapid development of portable electronic devices, there is an increasing demand for light and high capacity secondary batteries.

Lithium secondary batteries are prepared by reversibly inserting and detaching lithium ions as a positive electrode and a negative electrode, and filling an organic or polymer electrolyte between the positive electrode and the negative electrode, and lithium ions are inserted / desorbed at the positive electrode and the negative electrode. When produced, electrical energy is generated by oxidation and reduction reactions.

The binder used for the positive electrode and the negative electrode binds the active material and the conductive agent to the current collector. In order to manufacture a high capacity battery, it is necessary to increase the amount of active material present in the electrode plate and to reduce the amount of the conductive agent or the binder. However, since a certain amount or more of a binder must be used to attach the active material and the conductive agent to the current collector, there is a limit to simply reducing the amount.

The binder should impart sufficient physical strength to the electrode plate with only a small amount of addition, so that a high energy density electrode can be produced, have no reactivity with the electrolyte, and maintain a stable form in the battery operating temperature range. In addition, it should be well soluble in the organic solvent used in the preparation of the slurry for producing the electrode plate, and should not be dissolved in the electrolyte. Until now, there are very few materials satisfying all of these properties, so the choice of materials for use as a binder is very small. Therefore, only materials satisfying the above properties can be used rather than selecting a material having excellent binding ability of the active material, which is the main purpose of the binder. Attempts have been made to improve the properties of the binder by mixing two or more binder materials that meet the above properties. For example, US Pat. No. 6,294,290 describes an example in which polyvinylidene fluoride and a rubber polymer are mixed and used as a binder.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a lithium secondary battery electrode plate having excellent stability and lifespan characteristics.

An object of the present invention is also to provide a lithium secondary battery comprising the electrode plate.

1 is a graph showing the life characteristics of the lithium secondary battery prepared in Example 1 and Comparative Example 1.

In order to achieve the above object, the present invention is an active material; Provided is an electrode plate for a lithium secondary battery including a binder and an amine polymer.

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

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

The electrode plate for lithium secondary batteries of the present invention is characterized by containing an amine polymer. This amine-based polymer is physically combined with the binder to increase the binding strength of the binder. As the amine polymer, polyethyleneimine represented by the following Chemical Formula 1 may be preferably used.

[Formula 1]

In Chemical Formula 1,

x and y are molar ratios of each monomer, where x is 0.1 to 99.9, y is 99.9 to 0.1, and the sum of x and y is 100.

Polyethyleneimine of Formula 1 is prepared by a thermocycling process of esterified monoethanolamine and sodium hydroxide.

Polyethyleneimine is a polyamine having a net structure due to crosslinking of polyethyleneimine, having primary, secondary and tertiary amino nitrogen groups and having high cation density and high polarity as shown in the following Chemical Formula 2, and is a water-soluble polymer. Very reactive

[Formula 2]

Polyethyleneimine of the formula (2) has a good hydrophilic amino group and a hydrophilic ethylene group having excellent adhesion that can be easily combined with other materials. Therefore, when the polyethylenimine of the formula (2) is added during the manufacture of the electrode plate, the polyethyleneimine of the formula (2) is physically bonded to the binder to increase the binding force of the binder to the electrode plate, thereby reducing the interfacial resistance of the electrode plate.

Therefore, the lithium secondary battery including the amine polymer of the present invention, in particular, the electrode plate containing the polyethylenimine of the formula (1) has a small change in interfacial resistance and excellent stability and life characteristics.

As the active material used in the present invention, it means both a positive electrode active material or a negative electrode active material usually used in a lithium secondary battery. That is, a material capable of an electrochemically reversible redox reaction, a compound capable of forming a lithium-containing compound reversibly with lithium ions, a lithium intercalation compound capable of reversible insertion / desorption of lithium ions, and the like. have.

Examples of a compound capable of reversibly forming a lithium-containing compound with lithium ions include silicon (Si), titanium nitrate, tin dioxide (SnO ₂ ), and the like. The lithium intercalation compound refers to a carbonaceous material, and a lithium intercalation compound.

As the carbonaceous material, both amorphous carbon, crystalline carbon, or a mixture thereof may be used. Examples of the amorphous carbon include soft carbon (low temperature calcined carbon) or hard carbon (hard carbon calcined carbon), and crystalline carbon includes plate-like, spherical or fibrous natural graphite or artificial graphite.

All of the existing lithium metal oxides or lithium-containing chalcogenide compounds may be used as the thiolated intercalation compound. Preferred examples of such lyerated intercalation compounds are the following formulas (1) to (13):

Li _x Mn _1-y M _y A ₂ (1)

Li _x Mn _1-y M _y O _2-z A _z (2)

Li _x Mn ₂ O _4-z A _z (3)

Li _x Mn _2-y M _y A ₄ (4)

Li _x Co _1-y M _y A ₂ (5)

Li _x CoO _2-z A _z (6)

Li _x Ni _1-y M _y A ₂ (7)

Li _x NiO _2-z A _z (8)

Li _x Ni _1-y Co _y O _2-z A _z (9)

Li _x Ni _1-yz Co _y M _z A _α (10)

Li _x Ni _1-yz Co _y M _z O _2-α A _α (11)

Li _x Ni _1-yz Mn _y M _z A _α (12)

Li _x Ni _1-yz Mn _y M _z O _2-α A _α (13)

Wherein 0.95 ≦ x ≦ 1.1, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.5, 0 ≦ α ≦ 2, and M is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V or rare earth elements At least one element selected from the group consisting of, A is an element selected from the group consisting of O, F, S and P.

As the conductive agent and the binder used in the present invention, all conductive agents and binders can be used in the production of electrodes of a lithium secondary battery.

The conductive agent is not particularly limited, but a conductive material such as a graphite material, a carbon material, or a conductive polymer may be preferably used. The graphite-based material is KS 6 (manufactured by Timcal) and the carbon-based material includes super P (MMM company), ketchen black, denka black, acetylene black, carbon black, and the like. . Examples of the conductive polymer include polyaniline, polythiophene, polyacetylene, polypyrrole, and the like. These conductive conductive agents may be used alone or in combination of two or more thereof.

The binder is polyethylene oxide, polyvinyl pyrrolidone, alkylated polyethylene oxide, crosslinked polyethylene oxide, polyvinyl ether, poly (methyl methacrylate), polyvinylidene fluoride, polyhexafluoropropylene and poly Copolymers of vinylidene fluoride (trade name: Kynar), poly (ethyl acrylate), polytetrafluoroethylene, polyvinylchloride, polyacrylonitrile, polyvinylpyridine, polystyrene, derivatives thereof, blends, copolymers, etc. This can be used.

The content of the amine polymer of the present invention is preferably 5 to 50 parts by weight based on 100 parts by weight of the binder. If the content of the amine polymer is less than 5 parts by weight with respect to 100 parts by weight of the binder, there is a problem in that the binding strength is very bad and the viscosity of the slurry is lowered. If the content of the amine polymer is more than 50 parts by weight, the dispersion of the slurry is not good and the viscosity is high. As the content of the positive or negative electrode mixture becomes higher, it becomes an obstacle to increase the capacity per the combined weight of the battery.

The amine polymer is added when the binder solution is prepared. The slurry for preparing the electrode plate is prepared by dissolving a binder in an organic solvent to prepare a binder solution and then adding an amine polymer. It manufactures by disperse | distributing a conductive agent and an active material here. The amine polymer may be added to the slurry anywhere in the above step, but is preferably added to the binder solution.

When manufacturing the electrode plate according to the present invention can increase the binding capacity of the binder can reduce the amount of the binder used up to 2.5%. The amount of the active material can be increased by that amount, thereby increasing the capacity per mixture.

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

As described above, the lithium secondary battery including the lithium secondary battery electrode plate containing the amine polymer of the present invention has excellent stability and lifespan characteristics.

Hereinafter, preferred examples and comparative examples of the present invention are described. The following examples and comparative examples are described for the purpose of more clearly expressing the present invention, but the contents of the present invention are not limited to the following examples and comparative examples.

<Example 1>

A positive electrode active material slurry was prepared by dissolving 94 g of LiCoO ₂ , 3 g of Super-P, and 3 g of polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone. The positive electrode active material slurry was coated on an AL-foil having a width of 4.9 cm and a thickness of 147 μm, dried, rolled, and cut into plastic dimensions to prepare a positive electrode.

89.8 g of mesocarbofiber (MCF: manufactured by Petoca Co., Ltd.), 0.2 g of oxalic acid, 1 g of polyethyleneimine, and 9 g of PVDF were dissolved in N-methyl-2-pyrrolidone to prepare a negative electrode active material slurry. The negative electrode active material slurry was coated on an AL-foil having a width of 5.1 cm and a thickness of 178 μm, dried, rolled, and cut into plastic dimensions to prepare a negative electrode.

A separator was placed between the positive electrode and the negative electrode and wound to make an electrode assembly. The electrode assembly was placed in a battery case, and then a mixture composed of an electrolyte consisting of a precursor / initiator / liquid electrolyte was injected under reduced pressure.

Subsequently, the resultant was cured at 80 ° C. for 2 hours to prepare a lithium secondary battery. As the electrolyte solution, 1.3 M 30: 55: 5: 10 volume ratio LiPF ₆ : EC: EMC: PC: FB was used. Polyethylene glycol dimethacrylate was used as a precursor, and GER, which is a multifunctional acrylate, was used as an initiator.

Comparative Example 1

Example 1, except that 89.8 g of mesocarbofiber (MCF: manufactured by Petoca), 0.2 g of oxalic acid, 0.2 g of oxalic acid, and 10 g of PVDF were dissolved in N-methyl-2-pyrrolidone to prepare a negative electrode active material slurry. The same procedure was followed.

Life characteristic evaluation

1 is a graph showing the life characteristics of the lithium secondary battery prepared in Example 1 and Comparative Example 1. As shown in Figure 1 it can be seen that the life characteristics of the lithium secondary battery prepared by the addition of polyethyleneimine in the production of the plate.

The lithium secondary battery including the electrode plate for lithium secondary batteries containing the amine polymer of the present invention is excellent in stability and lifespan characteristics.

Claims (5)

Active material; A plate for lithium secondary battery comprising a binder and an amine polymer. The electrode plate of claim 1, wherein the amine polymer is polyethyleneimine of Formula 1 below: [Formula 1] In Chemical Formula 1, x and y are molar ratios of each monomer, where x is 0.1 to 99.9, y is 99.9 to 0.1, and the sum of x and y is 100. The positive electrode for a lithium secondary battery according to claim 1, wherein the content of the amine polymer in the positive or negative electrode for a lithium secondary battery is 5 to 50 parts by weight based on 100 parts by weight of the binder. The electrode plate for lithium secondary batteries in which the electrically conductive agent was further added to the electrode plate of any one of Claims 1-3. A lithium secondary battery comprising the electrode plate of claim 4.