KR100328151B1 - Nonaqueous Battery Electrolyte - Google Patents

Abstract

The present invention relates to a battery non-aqueous electrolyte prepared by adding 1,3 propanediol cyclic sulfate (1,3-propanediol cyclic sulfate) to the battery non-aqueous electrolyte consisting of an organic solvent and a lithium salt. The battery nonaqueous electrolyte reduces gas generation in the battery without degrading the performance of the basic electrolyte, thereby increasing the high temperature stability.

[Formula 1]

Description

Non-aqueous Electrolyte for Battery {Nonaqueous Battery Electrolyte}

The present invention relates to a non-aqueous electrolyte solution for batteries, and more particularly, to a lithium electrolyte dissolved in an organic solvent as a basic electrolyte solution, and to adding 1,3 propanediol cyclic sulfate (1,3-propandiol cyclic sulfate) thereto. The non-aqueous electrolyte for lithium ion secondary batteries characterized by the above-mentioned.

Conventionally, miniaturized and slimmed lithium ion secondary batteries used in notebook computers, camcorders, mobile phones, etc. have a lithium metal mixed oxide as a positive electrode active material, a carbon material or metal lithium as a negative electrode, and dissolve an appropriate amount of lithium salt in an organic solvent. What was made was comprised as electrolyte solution.

More specifically, conventional organic solvents used as electrolyte in lithium secondary batteries include ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), 2 or more types are selected from ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), etc., and lithium salts, such as LiPF ₆ , are used as a solute.

The electrolyte used in the lithium secondary battery reacts with the carbon constituting the negative electrode during initial charging to form a thin film on the surface of the negative electrode. The type of the formed film varies greatly depending on the solvent or additives used in the electrolyte and greatly affects battery performance. It is known to be mad.

In the initial formation process, lithium ions from lithium metal oxides used as anodes are moved to and inserted into carbon electrodes used as cathodes. At this time, lithium ₂ reacts with the carbon cathodes due to the strong reactivity of Li ₂ CO ₃ , Li. ₂ O, LiOH, etc. are formed, and these form a film called Solid Electrolyte Inteface (SEI) on the surface of the cathode. After the SEI film is formed, it functions as an ion tunnel to pass only lithium ions. This ion tunnel effect prevents the organic solvents of the electrolyte from intercalating with the lithium ions in the carbon anode, thereby destructing the structure of the carbon anode. In addition, once this film is formed, the lithium ions do not react with the carbon cathode or other materials again, thereby reversibly maintaining the amount of lithium ions. In other words, the generated SEI film acts as a passivation layer so that the electrolyte can continue stable reaction without any further decomposition of the electrolyte during charging and discharging (J. Power Sources, 51 (1994) pp. 79 To 104)

However, when exposed to high temperatures at full charge (4.2V), the SEI film slowly collapses due to increased electrochemical and thermal energy, causing side reactions to continue on new cathode surfaces exposed to the surrounding electrolyte. At this time, the internal pressure of the battery is increased by gases such as H ₂ , CO, CO ₂ , CH ₄ , C ₂ H ₄ and C ₂ H ₆ , which occur continuously, resulting in a decrease in battery performance and It causes problems such as poor mounting.

An object of the present invention is to overcome the problems of the prior art as described above, to provide a non-aqueous electrolyte for the battery to which the appropriate compound is added to change the SEI film formation reaction on the negative electrode surface of the lithium secondary battery, the charge and discharge efficiency of the battery And it is to significantly improve the high temperature stability of the battery without reducing the life performance.

That is, the present invention provides a battery non-aqueous electrolyte comprising a 1,3 propanediol cyclic sulfate of the general formula (1) in a battery non-aqueous electrolyte consisting of an organic solvent and a lithium salt.

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

Battery non-aqueous electrolyte of the present invention is a lithium ion secondary battery using a crystalline graphite or lithium metal as a negative electrode and a lithium metal compound as a positive electrode between 1,3 propanediol to suppress decomposition of the organic solvent during high temperature storage in a fully charged state And a click sulphate.

The nonaqueous electrolyte organic solvent preferably used in the present invention is a cyclic carbonate compound (Cyclic carbonate) as ethylene carbonate, propylene carbonate, -Butyrolactone, and the like, and also as a linear carbonate compound, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl methyl carbonate, ethyl propyl carbonate and the like can be cited. In addition, propyl acetate, methyl Solvents of esters such as acetate, ethyl acetate, butyl acetate, methyl propionate and ethyl propionate are also possible. More preferably, it is advantageous to select and use two or more kinds in these organic solvents.

As the lithium salt added to the organic solvent in the present invention, it is preferable to use one or two or more selected from LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , and LiCF ₃ SO ₃ , wherein the salt concentration is preferably 0.7. To 2.0 molar concentration range. If the salt concentration is less than 0.7 mol, the conductivity of the electrolyte is lowered, the performance of the electrolyte is lowered, and if it exceeds 2.0 mol, there is a problem that the low temperature performance is lowered as the viscosity increases at low temperatures.

It is preferable that the 1,3 propanediol cyclic sulfate used characteristically in the present invention is added at 0.1% by weight or more and 10% by weight or less. When the content of the additive in the present invention is less than 0.1% by weight, it is difficult to expect the effect of inhibiting gas generation, which is the purpose of the present invention. Because it occurs.

In a preferred aspect of the present invention, an example of a preferred nonaqueous electrolyte solution for batteries is a basic electrolyte solution in which 1 mol of LiPF ₆ is dissolved in a solvent in which ethylene carbonate and dimethyl carbonate are mixed at a ratio of 5: 5. It is composed by adding 0.1 to 10% by weight of 1,3 propanediol cyclic sulfate of the formula (1).

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples.

Example 1

A solution obtained by dissolving LiPF ₆ as a solute in a molar amount of ethylene carbonate and dimethyl carbonate at a ratio of 5: 5 was used as a basic electrolyte solution, and 0.5 wt% of 1,3 propanediol cyclic sulfate was added thereto. An electrolyte solution was obtained, and a rectangular battery of 30 mm x 48 mm x 6 mm was prepared using the same. At this time, as the active material of the negative electrode is a crystalline graphite (trade name: MCF) the binder is a polyvinylidene fluoride resin (Ployvinylidene Fluoride, PVDF), respectively 92: as was used by mixing at a ratio of 8, the active material of the anode is LiCoO ₂ Was used by mixing PVDF as a binder and carbon as a conductor in a ratio of 92: 4: 4.

To evaluate the thickness increase rate and the discharge capacity of the battery when stored at high temperature (85 ℃, 4 days) in the fully charged state of the prepared battery and the results are shown in Table 1 and Table 2.

Example 2

Except that 1.0 wt% of 1,3 propanediol cyclic sulfate was used, the same procedure as in Example 1 was carried out, and the battery performance was evaluated. The results are shown in Tables 1 and 2.

Example 3

Except that the additive 1,3 propanediol cyclic sulfate was used in the same manner as in Example 1 except that the battery performance was evaluated and the results are shown in Table 1 and Table 2.

Example 4

Except that 5.0 wt% of 1,3 propanediol cyclic sulfate was used in the same manner as in Example 1, and then the battery performance was evaluated and the results are shown in Table 1 and Table 2.

Comparative example

Except for using only the basic electrolyte solution without the addition of 1,3 propanediol cyclic sulfate was carried out in the same manner as in Example 1 to evaluate the battery performance and the results are shown in Table 1 and Table 2.

Electrolyte composition 0 hours 4 hours 24 hours 48 hours 72 hours 96 hours Comparative example 7.9% 8.8% 11.6% 13.4% 17.4% 21.5% Example 1 5.9% 6.3% 9.2% 11.6% 15.0% 18.6% Example 2 5.2% 5.4% 8.3% 9.9% 13.7% 16.5% Example 3 4.7% 5.3% 7.6% 8.8% 12.3% 15.9% Example 4 3.9% 4.5% 7.0% 8.7% 13.0% 17.7%

Electrolyte composition Residual discharge capacity Comparative example 82.0% Example 1 83.1% Example 2 83.8% Example 3 85.4% Example 4 84.9%

According to the nonaqueous electrolyte solution for batteries according to the present invention, it is possible to greatly reduce the thickness expansion of the battery by reducing the gas generation rate during high temperature storage in a fully charged state, thereby reducing the incidence of mounting failure of the lithium secondary battery.

Claims (4)

A nonaqueous electrolyte solution for batteries comprising an organic solvent and a lithium salt, wherein the nonaqueous electrolyte solution for a battery comprises 1,3 propanediol cyclic sulfate of the general formula (1). [Formula 1] The nonaqueous electrolyte solution for batteries according to claim 1, wherein the content of the 1,3 propanediol cyclic sulfate is 0.1 to 10% by weight based on the total nonaqueous electrolyte. The method of claim 1, wherein the organic solvent is ethylene carbonate, propylene carbonate, Butyrolactone, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl acetate, ethyl acetate, propyl acetate, butylacetate, methyl propionate, ethyl propionate At least one selected from the group consisting of non-aqueous electrolyte solution for batteries. The method of claim 1, wherein the lithium salt is at least one selected from the group consisting of LiPF ₆ , LiClO ₄ , LiAsF ₅ , LiBF ₄ , LiCF ₃ SO ₃ , the concentration is 0.7 to 2.0 mol for batteries Nonaqueous electrolyte.