KR20030059729A - New non-aqueous electrolyte and lithium secondary battery using the same - Google Patents

Abstract

PURPOSE: A novel nonaqueous electrolyte solution and a lithium secondary battery using the solution are provided, wherein the battery shows an excellent stability and an improved lifetime. CONSTITUTION: The nonaqueous electrolyte solution comprises a lithium salt; an electrolyte compound; and 0.5-5 wt% of 1,3-divinyltetramethyldisiloxane. Preferably the lithium salt is at least one selected from the group consisting of LiClO4, LiCF3SO3, LiPF6, LIBF4 and LiN(CF3SO2)2. The lithium secondary battery comprises a positive electrode capable of absorbing and discharging a lithium ion; a negative electrode capable of absorbing and discharging a lithium ion; a porous separator; and the nonaqueous electrolyte solution. Preferably the active material of the positive electrode is at least one lithium transition metal oxide selected from the group consisting of LiCoO2, LiNiO2, LiMn2O4, LiMnO2 and LiNi1-xCoxOx (0<x<1); and the active material of the negative electrode is carbon, lithium metal or lithium alloy.

Description

New Non-Aqueous Electrolyte and Lithium Secondary Battery Using the Same

The present invention relates to a non-aqueous electrolyte containing a new additive and a lithium secondary battery using the same, and more particularly, to a non-aqueous electrolyte containing a new additive that can improve battery performance, such as battery life and stability, and a lithium secondary using the same It relates to a battery.

Lithium secondary batteries are mainly used in mobile phones and computers because of their high capacity and light weight. In order to improve the performance of the lithium secondary battery, various additives have been developed, and these additives have been variously developed according to the purpose of improving battery life, improving temperature characteristics, and preventing swelling.

The electrolyte solution for a lithium ion secondary battery is generally formed by a combination of a cyclic carbonate and a linear carbonate. The cyclic carbonates used therein are EC, PC, GBL, and the like, and linear carbonates include DEC, DMC, and EMC.

Currently, various compounds such as VC (vinylene carbonate) and VEC (vinylethylene carbonate) are known as representative additives to improve the lifetime.

However, the use of such compounds is not preferable because of the problems such as poor low-temperature performance or swelling of the battery.

SUMMARY OF THE INVENTION In view of the problems of the prior art, an object of the present invention is to provide a non-aqueous electrolyte additive which has a vinyl group at the terminal and has excellent stability of the passivation membrane through crosslinking to improve the life of the battery.

Another object of the present invention is to provide a lithium secondary battery comprising the nonaqueous electrolyte additive.

Figure 1 shows the life test results for Examples 1 to 3 and Comparative Example 1 according to the present invention.

In order to achieve the above object, the present invention provides a lithium secondary battery non-aqueous electrolyte containing a lithium salt and an electrolytic nucleus compound,

It provides a non-aqueous electrolyte containing 0.5 to 5% by weight of 1,3-divinyltetramethyldisiloxane.

In addition, the present invention is a lithium secondary battery,

a) a positive electrode capable of occluding and releasing lithium ions;

b) a negative electrode capable of occluding and releasing lithium ions;

c) a porous separator; And

d) iii) lithium salts;

Ii) electrolyte compounds; And

Viii) 1,3-divinyltetramethyldisiloxane

Non-aqueous electrolyte solution containing

It provides a lithium secondary battery comprising a.

Hereinafter, the present invention will be described in detail.

The present invention is to provide a non-aqueous electrolyte for a lithium secondary battery comprising an additive capable of improving the life of the battery and a lithium secondary battery comprising the same.

The lithium secondary battery of the present invention includes a positive electrode capable of occluding and releasing lithium ions, a negative electrode capable of occluding and releasing lithium ions, a porous separator, and an electrolyte solution.

In particular, the present invention uses a siloxane-based compound as an additive to the nonaqueous electrolyte, preferably 1,3-divinyltetramethyldisiloxane to improve the life.

The 1,3-divinyltetramethyldisiloxane has a functional group having a double bond at both ends and siloxane, ethylene oxide, etc. capable of conducting lithium ions at the center thereof, and conducts lithium well and is stable through crosslinking. This is excellent and forms a passive film. That is, 1,3-divinyltetramethyldisiloxane, which is used as an additive, contributes to the formation of a passivation film on the cathode surface, and this passivation film suppresses further decomposition of the electrolyte. Thereby, the lifetime of a battery can be improved, without impairing the overall performance of a battery.

The content of 1,3-divinyltetramethyldisiloxane is preferably used in 0.5 to 5% by weight. If the content of the 1,3-divinyltetramethyldisiloxane is less than 0.5% by weight, the effect of the additive is insignificant. If the content of the 1,3-divinyltetramethyldisiloxane is less than 5% by weight, the negative irreversibility of the negative electrode is large and the capacity of the battery is reduced.

In addition, the nonaqueous electrolyte of the present invention includes a cyclic carbonate and a linear carbonate as the electrolytic nucleus compound. Examples of the cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), gamma butyrolactone (GBL), and the like. For example, the linear carbonate is preferably selected from the group consisting of diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), and methyl propyl carbonate (MPC).

The non-aqueous electrolyte of the present invention includes a lithium salt, and specifically 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 . Do.

Moreover, in the lithium secondary battery of this invention, it is preferable to use carbon, lithium metal, or an alloy as an active material of a negative electrode. Other metals such as TiO ₂ and SnO ₂ , which can occlude and release lithium and have a potential for lithium of less than ₂ V, can also be used.

In the present invention, a lithium-containing transition metal oxide is used as the positive electrode active material, for example, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiMnO _2, and LiNi _1-X Co _X O ₂ (where 0 <X <1) It is preferable to select at least one from the group consisting of. In addition, an anode made of a metal oxide such as MnO ₂ or a combination thereof may be used.

In addition, the present invention uses a porous separator in the manufacture of a lithium secondary battery, for example, a polyolefin-based porous separator can be used.

The lithium ion secondary battery of the present invention is prepared by inserting a porous separator between the negative electrode and the positive electrode in a conventional manner, by adding a non-aqueous electrolyte containing a lithium salt and additives, such as LiPF ₆ described above.

It is preferable that the external shape of the lithium secondary battery according to the present invention is cylindrical or rectangular in shape of a can. In addition, the battery may include a pouch-type battery.

The present invention will be described in more detail with reference to the following examples. However, the examples are only for illustrating the present invention and not for limiting the present invention.

EXAMPLE

Examples 1 to 3

As an electrolyte solution, a 1M LiPF ₆ solution having a composition of EC: EMC = 1: 2 was used, and 1, 2, and 3 wt% (Examples 1, 2, and 3) of 1,3-divinyltetramethyl were respectively added to the electrolyte. Disiloxane was added and used. The negative electrode used was artificial graphite, and the positive electrode was LiCoO ₂ . Thereafter, a rectangular battery was manufactured by a conventional method to perform a life test.

Comparative Example 1

An electrolyte solution prepared in the same manner as in Example 1 but without addition of 1,3-divinyltetramethyldisiloxane was used.

(Life test)

The life test results of Examples 1 to 3 and Comparative Example 1 are shown in FIG. 1. 1, it can be seen that in Examples 1 to 3, the lifespan is superior to that of Comparative Example 1.

The effect of the added amount was the same in Example 1 (including 1% by weight) and Example 2 (including 2% by weight), and in the case of Example 3 (including 3% by weight) Examples 1 and 2 Although slightly dropped, the service life was superior to Comparative Example 1.

As described above, the present invention can provide a lithium secondary battery having excellent stability and improved battery life by using an additive in an electrolyte having a vinyl group at an end thereof and having excellent stability through crosslinking to form a passivation film.

Claims (8)

In the nonaqueous electrolyte solution for lithium secondary batteries containing a lithium salt and an electrolytic nucleus compound, A non-aqueous electrolyte comprising 0.5 to 5% by weight of 1,3-divinyltetramethyldisiloxane. In a lithium secondary battery, a) a positive electrode capable of occluding and releasing lithium ions; b) a negative electrode capable of occluding and releasing lithium ions; c) a porous separator; And d) iii) lithium salts; Ii) electrolyte compounds; And Viii) 1,3-divinyltetramethyldisiloxane Non-aqueous electrolyte solution containing Lithium secondary battery comprising a. The method of claim 2, The lithium secondary battery having a content of 1,3-divinyltetramethyldisiloxane of d) iii) is 0.5 to 5% by weight based on the electrolyte. The method of claim 2, The active material of the positive electrode of a) is a lithium transition metal oxide is LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiMnO ₂ and LiNi _1-X Co _X O ₂ (here, 0 <X <1) from the group consisting of 1 A lithium secondary battery, which is a lithium transition metal oxide selected from at least one species. The method of claim 2, The lithium secondary battery, wherein the active material of the negative electrode of b) is carbon, lithium metal or alloy. The method of claim 2, A pouch type lithium ion battery wherein the lithium salt of d) iii) 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 . The method of claim 2, The cyclic carbonate wherein the electrolyte compound of d) ii) is selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), and gamma butyrolactone (GBL); And a linear carbonate selected from the group consisting of diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), and methyl propyl carbonate (MPC). The method of claim 2, The lithium secondary battery is a cylindrical or angular or pouch type lithium secondary battery made of cans.