KR100625957B1 - Lithium ion battery - Google Patents

Abstract

The present invention relates to a lithium ion battery having improved safety, and according to the present invention, a predetermined amount of oxygen absorbent is further included in an electrode or an electrolyte to occlude oxygen that may occur during a charging reaction, thereby reducing the possibility of ignition due to oxygen generation. Removal can improve battery safety.

Description

Lithium ion battery

The present invention relates to a lithium ion battery, and more particularly to a lithium ion battery with improved safety.

Recently, as the use of rechargeable secondary batteries as power sources for computers, portable cassettes, radios, portable telephones, and the like, there is an increasing need for rechargeable secondary batteries having a long lifespan and a large capacity.

Conventionally, lead-acid batteries or nickel / cadmium batteries are mainly used as rechargeable secondary batteries. However, lithium secondary batteries have emerged as replacement batteries because of limited capacity improvement.

The history of lithium secondary batteries is more than 30 years, but only a few have begun to be put into practical use. The reason for this is that they have not been developed, and the satisfactory battery size, capacity, and long life cannot be obtained. Many problems still remain. In addition, in the case of a lithium ion battery among lithium secondary batteries, there is a problem in the safety of the battery, for example, the electrolyte may ignite during charging.

A lithium ion battery usually consists of a cathode comprising a lithium composite oxide as an active material, an anode containing a lithium metal, a lithium alloy or a carbonaceous material as an active material, and an electrolyte solution containing a non-aqueous organic solvent and a lithium salt.

As the cathode active material, lithium composite oxides such as lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, or those in which metal elements are added thereto are usually used. Lithium complex oxide represents a reaction mechanism in which lithium ions move to the cathode during charging to form metal oxides and release electrons. For example of lithium cobalt oxide in lithium composite oxide, the reaction of the cathode active material upon charging is shown below.

^{_{LiCoO 2 → CoO 2 + Li +}} + e -

However, if the amount of lithium ions moving to the cathode becomes excessive as overcharging occurs or charging / discharging is repeated, cobalt oxide is decomposed into metal cobalt and oxygen even if the ambient environment such as temperature or humidity changes only a little. There is a problem in that the safety of the battery is greatly impaired, such as reacting to ignite the electrolyte solution.

Several methods have been proposed to overcome this problem.

The representative methods are methods of increasing the binding force of oxygen or reducing the degree of decomposition into oxygen by changing the composition or structure of the lithium composite oxide used as the cathode active material.

However, these methods are practically limited because they usually involve a reduction in the capacity of the active material.

Another method is to change the separator to shut down the battery when it reaches a certain temperature. However, this method is also not very effective in terms of improving stability.

The present invention is directed to improving this problem.

The technical problem to be achieved by the present invention is to provide a lithium ion battery with improved safety.

Technical problem of the present invention is a lithium ion battery comprising a cathode electrode, an anode electrode and an electrolyte, the electrolyte may be made by a lithium ion battery characterized in that it comprises a non-aqueous organic solvent, a lithium salt and an oxygen sorbent. .

In addition, a technical problem of the present invention is a lithium ion battery comprising a cathode electrode, an anode electrode and an electrolyte, wherein the cathode electrode or the anode electrode comprises an electrode active material, a conductive agent, a binder and an oxygen absorber It can be made by a battery.

In this case, as the non-aqueous organic solvent, propylene carbonate (PC), ethylene carbonate (EC), ethylmethyl carbonate, methyl acetate, γ-butyrolactone, 1,3-dioxo Lan (1,3-dioxolane), dimethoxyethane, dimethylcarbonate, diethylcarbonate, tetrahydrofuran (THF), dimethylsulfoxide and polyethylene glycol dimethyl ether ( Preference is given to using at least one solvent selected from polyethyleneglycol dimethylether).

The lithium salt is not particularly limited as long as it is a lithium compound that is dissociated in an organic solvent to give lithium ions, and specific examples thereof include lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), and Lithium hexafluorophosphate (LiPF ₆ ), lithium trifluoromethansulfonate (LiCF ₃ SO ₃ ), lithium bistrifluoromethansulfonylamide (LiN (CF ₃ SO ₂ ) ₂ ), and the like And the content is at normal levels.

In addition, the active material, the conductive agent, the binder is not particularly limited as long as it is commonly used in the field of the present invention.

In addition, the oxygen absorbent is at least one selected from the group consisting of dipropylamine, phenol, pyrocatechol and pyrogallol, the content of which is 0.1 to 5% by weight relative to the total weight of the electrolyte, or 0.1 to the total weight of the electrode active material It is preferable that it is-2 weight%.

Oxygen scavenger according to the present invention is contained in the cathode electrode, the anode electrode or the electrolyte and serves to occlude oxygen that may be generated from the cathode electrode plate during charging.

delete

delete

That is, the compound used as the oxygen absorbing agent in the present invention contains radicals capable of causing a radical reaction in the molecule such as amines, hydroxyl groups and the like, and these radicals adsorb and remove oxygen atoms.

These oxygen absorbers should be added within the range of excellent affinity with the non-aqueous organic solvent or electrode active material, which is the main component of the electrolyte, and do not impair the intrinsic properties of the battery. On the other hand, if it exceeds the above range, it is not preferable because it lowers the capacity and life characteristics of the battery.

The lithium ion battery according to the present invention may be manufactured according to a method commonly used in the field of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1

A lithium composite oxide, a conductive agent (Super-P carbon) and a binder (KW 1300, manufactured by Kureha) were mixed in a weight ratio of 94: 3: 3, and then N-methylpyrrolidone was added thereto and sufficiently mixed to form a cathode slurry. The composition was formed.

The cathode slurry composition was applied to a 140 μm thick aluminum steel mesh and then dried to complete the cathode electrode plate.

Separately, graphite and a binder ((KW 1300, manufactured by Kureha) were mixed at a weight ratio of 92: 8, and then N-methylpyrrolidone was added thereto and sufficiently mixed to form an anode slurry composition.

The anode slurry composition was applied to a 120 μm thick copper steel mesh and then dried to complete the anode plate.

Subsequently, a separator film was interposed between the prepared cathode electrode plate and the anode electrode plate, followed by thermocompression bonding to complete the electrode assembly.

Finally, 151.9 g of LiPF ₆ and 6 g of pyrogallol were mixed with 1000 ml of a mixed organic solvent in which ethylene carbonate, dimethyl carbonate and diethyl carbonate were mixed at a weight ratio of 4: 4: 1, to prepare an electrolyte solution. Five lithium ion batteries were prepared by impregnating the prepared electrode assembly.

Five lithium ion batteries were charged at 0.5C and 4.2V, respectively.

Cell penetration experiments were performed in which charged cells were placed in a closed chamber and nails penetrated the cells.

The results are shown in Table 1 below.

Example 2

A lithium composite oxide, a conductive agent (Super-P carbon), a binder (KW 1300, manufactured by Kuraha) and dipropylamine (manufactured by Aldrich) were mixed in a weight ratio of 93: 3: 3: 1, and then N- Methylpyrrolidone was added and mixed well to form a cathode slurry composition.

The cathode slurry composition was applied to a 140 μm thick aluminum steel mesh and then dried to complete the cathode electrode plate.

The anode plate was prepared in the same manner as in Example 1.

Subsequently, a separator film was interposed between the prepared cathode electrode plate and the anode electrode plate, followed by thermocompression bonding to complete the electrode assembly.

Finally, 151.9 g of LiPF ₆ was mixed with 1000 ml of a mixed organic solvent in which ethylene carbonate, dimethyl carbonate, and diethyl carbonate were mixed at 4: 4: 1 to prepare an electrolyte solution, and then the electrode assembly was impregnated with lithium. Five ion cells were prepared.

Five lithium ion batteries were charged at 0.5C and 4.2V, respectively.

Cell penetration experiments were performed in which charged cells were placed in a closed chamber and nails penetrated the cells.

The results are shown in Table 1 below.

Comparative example

Five lithium ion batteries were manufactured in the same manner as in Example 1, except that no oxygen absorbent was added in the preparation of the electrolyte.

Five lithium ion batteries were charged at 0.5C and 4.2V, respectively.

Cell penetration experiments were performed in which charged cells were placed in a closed chamber and nails penetrated the cells.

The results are shown in Table 1 below.

Battery number Final reaching temperature after penetration (℃) Example 1 One 200 2 180 3 195 4 220 5 205 Example 12 One 250 2 230 3 225 4 240 5 245 Comparative Example 1 One Thermal runaway 2 Thermal runaway 3 Thermal runaway 4 Thermal runaway 5 Thermal runaway

As can be seen from the results of Table 1, in the batteries (Examples 1 and 2) to which the oxygen absorbent according to the present invention was added, a phenomenon such as thermal explosion did not occur even after the nail penetrated. However, in a battery prepared without adding an oxygen sorbent (Comparative Example 1), the temperature was not developed due to thermal explosion.

According to the present invention, a lithium ion battery having no possibility of ignition due to oxygen generation can be provided by occluding oxygen that may occur during charging reaction by adding a predetermined amount of oxygen absorbent during the production of the electrode plate of the battery or during the preparation of the electrolyte solution. That is, the lithium ion battery according to the present invention can be used safely without causing safety problems such as ignition of an electrolyte even under poor conditions in which charging and discharging are repeated or a sudden change in the surrounding environment such as temperature or humidity occurs.                     

Claims (6)

In a lithium ion battery comprising a cathode electrode, an anode electrode and an electrolyte solution, And the electrolyte comprises at least one oxygen absorber selected from the group consisting of an organic electrolyte and dipropylamine, phenol, pyrocatechol and pyrogallol. delete The lithium ion battery according to claim 1, wherein the content of the oxygen absorbent is 0.1 to 5% by weight based on the total weight of the electrolyte. In a lithium ion battery comprising a cathode electrode, an anode electrode and an electrolyte solution, And the cathode electrode or the anode electrode comprises at least one oxygen absorber selected from the group consisting of an electrode active material, a conductive agent, a binder and dipropylamine, phenol, pyrocatechol and pyrogallol. delete The lithium ion battery according to claim 4, wherein the content of the oxygen absorbent is 0.1 to 2% by weight based on the total weight of the electrode active material.