KR100354247B1 - Lithium secondary batteries - Google Patents

Abstract

The present invention relates to a lithium secondary battery with improved safety and reliability. Lithium secondary batteries may decompose an electrolyte during charging and discharging or due to an increase in temperature, thereby generating gas inside. The present invention can prevent the battery from swelling or bursting of the exterior material due to the internal pressure of the generated gas by mounting a material capable of adsorbing such gas into the battery in the form of a film or a gas permeable material.

Description

Lithium secondary batteries

The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery having improved safety and reliability of a rectangular lithium ion battery and a lithium polymer battery.

A lithium secondary battery is typically formed by impregnating an electrolyte comprising a lithium salt and a non-aqueous organic solvent in an electrode assembly having a cathode and an anode having an active material layer formed on a current collector, and a separator interposed between the cathode and the anode.

The lithium secondary battery is a lithium composite oxide such as lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide as a cathode active material, carbon or graphite is mainly used as the anode active material. Lithium complex oxides represent a reaction mechanism in which lithium ions move to the anode during charging to form metal oxides and release electrons. For example, the charge of the cathode active material during charging of lithium cobalt oxide in the lithium composite oxide is shown in the following scheme.

_{LiCoO 2 → Li x CoO 2 +} (1-x) Li + + (1-x) e -

However, as overcharging or recharging and recharging are repeated, lithium cobalt oxide may partially dissociate and generate oxygen gas.

In addition, as the non-aqueous organic solvent of the electrolyte, propylene carbonate, ethylene carbonate, γ-butyrolactone, 1,3-dioxolane, dimethoxyethane, dimethyl carbonate, diethyl carbonate, tetrahydrofuran, dimethyl sulfoxide and polyethylene glycol dimethyl Ether and the like are used, and this non-aqueous organic solvent is decomposed to generate gas when the lithium secondary battery is overcharged or charged at a temperature higher than normal charging conditions. When the pressure inside the lithium secondary battery increases due to such a gas, the battery swells and becomes difficult to use, and in severe cases, there is a risk of explosion.

As described above, the lithium secondary battery uses a safety vent capable of discharging the pressure when the internal pressure rises in order to solve the gas generation problem caused by overcharge and temperature rise.

However, unlike lithium-ion batteries that use nickel-plated cans as steel plates, lithium secondary batteries use nylon, nylon-co-acrylic acid (EAA), and PE films on aluminum foil. The multilayer film aluminum container (aluminum pouch) which coated this is used.

Therefore, when the internal pressure increases due to the generation of gas, the rectangular lithium ion battery or the lithium polymer battery has a weak force that can withstand the pressure, as compared to the cylindrical lithium ion battery using the nickel-plated can as an exterior material. Despite the installation of the safety valve, the container is easily inflated or burst at a relatively low pressure, so there is a risk of explosion.

Therefore, the technical problem to be achieved by the present invention is to provide a lithium secondary battery with improved reliability and safety by inserting a material that can adsorb the gas generated in the lithium secondary battery in order to solve the problems described above.

1 is a partially cutaway perspective view of a rechargeable lithium battery according to one embodiment of the present invention.

2 is a perspective view of a lithium secondary battery according to another embodiment of the present invention.

<Brief description of symbols for main parts of the drawings>

10, 20: electrode assembly 11: gas adsorption film

12: Separator 13: Cathode

14: anode 15, 25: anode tab

16, 26: cathode tab 17, 27: vessel

28: gas adsorption vessel 29: gas adsorption material

The present invention to achieve the above technical problem,

An electrode assembly having a cathode, a separator, and an anode sequentially stacked and having a cathode tab connected to the cathode and an anode tab connected to the anode;

A gas adsorption film laminated on at least one surface of the electrode assembly and formed of a gas adsorption material and a polymer binder; And

It is made of a flexible foil to provide a lithium secondary battery comprising a container for sealing the electrode assembly and the film.

In the present invention, the polymer binder is preferably any one selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride vinyl chloride, and mixtures thereof.

Another aspect of the present invention for achieving the above technical problem,

An electrode assembly having a cathode, a separator, and an anode sequentially stacked and having a cathode tab connected to the cathode and an anode tab connected to the anode;

A container made of a flexible foil to surround and seal the electrode assembly; And

It is interposed between the electrode assembly and the container, and provides a lithium secondary battery comprising a gas adsorption material and a gas adsorption vessel surrounding the gas adsorption material and the gas permeable material.

In both aspects of the invention, the gas adsorbent material is preferably activated carbon or carbon black.

As described above, the lithium secondary battery contains a possibility of gas generation therein due to decomposition of the lithium composite oxide used as the cathode active material, decomposition of the non-aqueous organic solvent included in the electrolyte, vaporization of the electrolyte, and the like.

Unlike lithium ion batteries, which use nickel-plated cans as steel plates, lithium secondary batteries have a strong ability to withstand the pressure generated by internal gases. In the case of a square lithium ion battery or a lithium polymer battery using a multi-layer aluminum pouch coated with polyethylene-co-acrylic acid (PEA) or PE film, the pressure-bearing force is relatively weak. By incorporating a substance capable of adsorbing gas into the battery, the battery is safe and reliable.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it is not limited to the following Example of this invention.

<Example 1>

1 is a partially cutaway perspective view of a rechargeable lithium battery according to one embodiment of the present invention.

As shown in the drawing, a cathode 13 having an active material layer composed of an active material and an additive in each current collector, an anode 14, and a separator 12 interposed between the anode and the cathode plate to insulate them, and the cathode 12 ) And an electrode assembly 10 having a cathode tab 15 interconnecting each other and an anode tab 16 interconnecting each of the anodes 14. The electrode assembly 10 is wrapped and sealed in a container 17 made of a flexible material, and the cathode tab 15 and the anode tab 16 are exposed to the outside of the container 17 to serve as battery terminals. Done.

On one surface of the electrode assembly 10, a gas adsorption film 11 including a gas adsorption material and a polymer binder is stacked. In the present exemplary embodiment, only the case where the film 11 is laminated on one surface of the electrode assembly is assumed, but the present invention is not limited thereto and may be laminated on at least one surface.

The film 11 is prepared by dispersing a polymer binder and a gas adsorbent in a low boiling point organic solvent such as acetone, casting a thin film to a support, and then evaporating the low boiling point solvent and then separating it from the support.

The polymer binder is preferably a water repellent binder such as polytetrafluoroethylene or polyvinylidene fluoride and a mixed binder thereof, and the gas adsorbent is preferably activated carbon or carbon black having a large specific surface area.

The container 17 is formed by coating nylon (Nylon), EAA (polyethylene-co-acrylic acid), PE film, or the like on an aluminum foil. The material of the container is not limited to the above-described embodiment, and any material may be used as long as it is a flexible material that has a predetermined tensile force and can be insulated from the electrode assembly.

In the lithium secondary battery according to the above embodiment, the film including the gas adsorption material is attached to the electrode assembly, so that the gas generated by the overcharge or the temperature rise may be adsorbed, thereby reducing the pressure inside the battery.

<Example 2>

2 is a perspective view of a lithium secondary battery according to another embodiment of the present invention.

The electrode assembly 20, the cathode tab 25, the anode tab 26, and the container 27 are the same as described in the first embodiment.

In this embodiment, a gas adsorption vessel 28 made of a gas-permeable material containing a gas adsorption material 29 therein is interposed between the electrode assembly 20 and the container 27. In the present embodiment, it is assumed that only one side of the container is interposed, but may be interposed anywhere if the space between the electrode assembly 20 and the container 27.

The gas-permeable material forming the gas adsorption vessel 28 may be used without particular limitation as long as it has a property of allowing gas to pass therethrough and a material capable of uniformly forming a container. For example, low density polyethylene is mentioned.

Therefore, the lithium secondary battery according to the embodiment can adsorb the gas generated therein, thereby preventing the battery from swelling or exploding due to an increase in pressure inside the container.

As described above, the lithium secondary battery according to the present invention contains a gas adsorption film and a gas adsorption vessel capable of gas adsorption, so that nylon (Nylon), EAA (polyethylene-co-acrylic acid), and PE film are coated on aluminum foil. The use of a coated container also prevents the container from exploding.

Although described with reference to the embodiment shown in the drawings of the present invention, this is merely exemplary, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (5)

An electrode assembly having a cathode, a separator, and an anode sequentially stacked and having a cathode tab connected to the cathode and an anode tab connected to the anode; A gas adsorption film laminated on at least one surface of the electrode assembly, the gas adsorption material consisting of activated carbon, carbon black, or a mixture thereof and a polymer binder; And Lithium secondary battery comprising a container for sealing the electrode assembly and the film made of a flexible foil. delete The lithium secondary battery according to claim 1, wherein the polymer binder is any one selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride vinyl chloride, and mixtures thereof. An electrode assembly having a cathode, a separator, and an anode sequentially stacked and having a cathode tab connected to the cathode and an anode tab connected to the anode; A container made of a flexible foil to surround and seal the electrode assembly; And A lithium secondary battery interposed between the electrode assembly and the container, the gas adsorption material comprising activated carbon, carbon black, or a mixture thereof, and a gas adsorption container surrounding the electrode adsorption material. delete