KR20140118517A - An additive for nonaqueous electrolyte of lithium secondary battery - Google Patents

Abstract

The present invention relates to a non-aqueous electrolyte for a battery, and the non-aqueous electrolyte is formed by adding a compound of chemical formula 1 to a non-aqueous electrolyte for a battery, which comprises an organic solvent and a lithium salt. The present invention provides a non-aqueous electrolyte for a lithium secondary battery, which improves cycle characteristics and low-temperature output performances simultaneously. In chemical formula 1, n is 0-3 and R is CH_3 or CH(CH_3)_2.

Description

[0001] The present invention relates to a non-aqueous electrolyte additive for lithium secondary batteries,

The present invention relates to a non-aqueous electrolyte additive for lithium secondary batteries, and more particularly to a novel non-aqueous electrolyte containing additives capable of lowering battery resistance at low temperatures, improving output characteristics, and improving cycle characteristics, and lithium The present invention relates to a secondary battery.

BACKGROUND ART [0002] A lithium secondary battery is a power source that is indispensably used in portable IT equipment, and the technology has been remarkably developed in recent years. Due to the development of performance, the use area is expanded to a large-capacity battery such as an energy storage device and an electric automobile, and a large capacity, cycle safety and reliability of performance under severe conditions are required as the performance thereof. .

The lithium secondary battery is mainly composed of a positive electrode made of a lithium composite oxide, a negative electrode made of a carbon material or a lithium metal, and a nonaqueous electrolyte. As the nonaqueous electrolytic solution, carbonates such as ethylene carbonate (EC) and propylene carbonate (PC) are used.

Since the lithium secondary battery using LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ or the like as an anode partially decomposes oxidatively locally at the time of charging in a nonaqueous electrolytic solution, the decomposed matter inhibits a desirable electrochemical reaction of the battery, .

As a cathode, for example, a lithium secondary battery using a highly crystallized carbon material such as natural graphite or artificial graphite is subjected to reduction and decomposition at the surface of a negative electrode when the negative electrode electrolyte is filled, Some reduction decomposition occurs during repetition, resulting in deterioration of battery performance.

Particularly, decomposition of the electrolyte on the positive electrode or the negative electrode causes gas to be generated, causing the battery to swell and gas to be caught between the electrodes, which hinders the movement of the lithium ion, thereby deteriorating battery performance.

More specifically, the non-aqueous electrolyte for a lithium secondary battery is prepared by dissolving LiPF ₆ as an electrolyte in a solvent of a cyclic or chain type carbonate and various esters. Examples of the cyclic carbonate-based electrolyte include ethylene carbonate and propylene carbonate. Although ethylene carbonate has a high dielectric constant and is widely used, it has a disadvantage in that it has a low boiling point because it exists in a solid state at room temperature because of its high boiling point. In the case of propylene carbonate, the freezing point is low, There is a disadvantage that the electrode becomes unstable due to the reactivity with the cathode. Therefore, in order to improve the low-temperature characteristics of the non-aqueous electrolyte, a chain carbonate electrolyte having a low-temperature characteristic is mixed and used. Vinyl carbonate is mainly used as an additive, and this additive has a characteristic of improving a high-temperature cycle characteristic, but has a disadvantage in that a low-temperature output performance is deteriorated by a film formed by a decomposition reaction.

Electrodes and electrolytes used in lithium secondary batteries are unstable at high voltage, and various additives are used to supplement them. The main role of the additive is to form a solid electrolyte interface (SEI) to inhibit further reaction between the electrode and the electrolyte, thereby preventing deterioration of the battery performance.

As a conventional technique relating to an additive for a nonaqueous electrolyte for a secondary battery,

In Publication No. 10-2010-0098057, ESA (ethylene sulfate) and PS (propane sultone) are used as additives to improve the performance and used as an electrolyte for HEV secondary batteries.

In Publication No. 10-2001-0095509, 1,3-propanediol cyclic sulfate was added to improve the performance of a lithium secondary battery.

However, satisfactory charging and discharging efficiency could not be obtained with the above-described compounds, and there was a limit in charging and discharging with high efficiency even at a low temperature.

Disclosed is a novel non-aqueous electrolyte additive for lithium secondary batteries for improving cycle characteristics and low-temperature power of IT devices or automotive lithium secondary batteries.

More particularly, the present invention provides a non-aqueous electrolyte additive which improves the performance of a lithium secondary battery by complementing the shortcomings of conventional ESA as a sulfone-based compound as an ESA (ethylene sulfate) derivative.

The present invention provides a nonaqueous electrolyte additive for a lithium secondary battery represented by the following general formula (1).

[Chemical Formula 1]

n = 0 ~ 3, R = CH 3, CH (CH 3) 2

INDUSTRIAL APPLICABILITY The present invention improves the output of a lithium secondary battery and improves the performance of an energy storage device and a middle- or large-sized lithium secondary battery for an automobile as an additive for improving low-temperature and high-temperature characteristics.

The present invention provides a nonaqueous electrolyte solution for a lithium secondary battery, which comprises a lithium salt, a nonaqueous organic solvent and a compound represented by the following formula (1).

[Chemical Formula 1]

n = 0 ~ 3, R = CH 3, CH (CH 3) 2

Particularly, by using an additive having a relatively higher reduction potential than vinyl carbonate as a conventional additive, a decomposition reaction occurs earlier than vinyl carbonate to form an SEI film. Next, a film formed by vinyl carbonate is produced by a vinyl carbonate unit So that it takes less resistance than the coated film.

The present invention relates to a non-aqueous electrolyte for a lithium secondary battery containing the above additive; A positive electrode comprising a lithium intercalation compound; And a negative electrode comprising a carbon, a carbon composite, a lithium metal, or a lithium alloy.

The lithium secondary battery may be a lithium ion battery or a lithium polymer battery.

The lithium salt is selected from the group consisting of LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₄ , LiAlCl ₄ , ≪ / RTI >

Preferably, the concentration of the lithium electrolyte is from 0.5 to 1.5 M.

The non-aqueous organic solvent may be used for mixing the cyclic carbonate and the chain carbonate.

Preferably, the non-aqueous organic solvent is selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate At least one selected from the group consisting of ethylene carbonate (EC) vinylene carbonate (VC), vinylethylene carbonate (VEC), propylene carbonate (PC), and butylene carbonate (BC).

The compound of Formula 1 may be included in the non-aqueous organic solvent in a weight ratio of 0.1 to 5.

Hereinafter, the present invention will be described in more detail by way of examples, but these examples are for illustrative purposes only and should not be construed as limiting the present invention.

Comparative Example

A positive electrode containing lithium manganese oxide (LiMn ₂ O ₄ ) and a negative electrode containing carbon (graphite carbon) were laminated together with a separator to produce a laminate type lithium ion battery. 2% by weight of vinyl carbonate (VC), 1% by weight of ethylene sulfate (C ₂ H ₄ O ₄ S) as an additive, 2% by weight of propane 1 wt% of the sultone was added and 1.0M LiPF ₆ was added.

Example

A positive electrode containing lithium manganese oxide (LiMn ₂ O ₄ ) and a negative electrode containing carbon (graphite carbon) were laminated together with a separator to produce a laminate type lithium ion battery. 2% by weight of vinyl carbonate (VC), 3 kinds of ethylene sulfate-derived compounds (C ₄ H ₈ O ₄ S, C (methyl ethyl ketone)) as an additive were added to a solvent in which ethylene carbonate and methyl ethyl carbonate were mixed in a volume ratio of 3: ₅ H ₁₀ O ₄ S, and C ₆ H ₁₂ O ₄ S), 1 wt% of propane sultone, and 1.0M LiPF ₆ was added.

Battery performance evaluation

With respect to the batteries manufactured in the above Comparative Examples and Examples,

Charging and discharging powers were measured and compared at constant currents of 50, 55, 60, 65 and 70 w for 5 s at room temperature (23 ° C) and low temperature (-30 ° C)

Table 1 shows the charging output test (Charge power (W) at 23 ℃) at room temperature, Table 2 shows the discharging output test (Charge power (W) power (W) at -30 ℃), and Table 4 compares discharge output test (Charge power (W) at -30 ℃) at low temperature.

Compound

State of charge (%) ESA LA-10 LA-11 LA-12 30 28.5 39.0 38.5 37.8 50 26.7 31.0 30.5 30.0 95 5.20 7.8 7.7 7.5

Compound

State of charge (%) ESA LA-10 LA-11 LA-12 30 29.3 31.8 31.2 31.0 50 35.2 40.0 39.5 37.8 95 51.5 57.8 57.0 56.5

Compound

State of charge (%) ESA LA-10 LA-11 LA-12 20 1.64 1.93 2.00 1.90 40 1.51 1.78 1.80 1.77 60 1.36 1.57 1.59 1.56 80 1.30 1.40 1.43 1.43 100 1.17 1.22 1.20 1.95

Compound

State of charge (%) ESA LA-10 LA-11 LA-12 20 1.58 1.70 1.71 1.74 40 1.69 1.86 1.90 1.87 60 1.87 2.07 2.09 2.07 80 2.68 2.98 2.95 3.03 100 2.92 3.45 3.50 3.48

The above tests were conducted on three newly synthesized compounds (C ₄ H ₈ O ₄ S, C ₅ H ₁₀ O ₄ S, and C ₆ H ₁₂ O ₄ S) based on the ESA being used as an additive in current HEV batteries .

 The nonaqueous electrolyte according to the present invention exhibits excellent characteristics at normal temperature and low temperature charge / discharge output, and thus shows an improved effect compared to the additive materials used in existing lithium secondary batteries at room temperature and low temperature output.

Claims (5)

Lithium salt, a non-aqueous organic solvent, and a compound represented by the following formula (1).
[Chemical Formula 1]

n = 0 ~ 3, R = CH 3, CH (CH 3) 2 The nonaqueous organic solvent according to claim 1, wherein the non-aqueous organic solvent is a mixture of cyclic carbonate and chain carbonate (in the range of 5% to 50% by volume of the linear carbonate of cyclic carbonate) Non-aqueous electrolyte for secondary battery. The nonaqueous electrolyte solution for a lithium secondary battery according to claim 1, wherein the compound of Formula 1 is contained in an amount of 0.1 to 5 parts by weight based on the nonaqueous organic solvent. According to claim 1, wherein the lithium salt is _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiClO 4, LiCF 3 SO 3, Li (CF 3 SO 2) 2 N, LiC 4 F 9 SO 3, LiAlO 4, LiAlCl ₄ , LiCl, and LiI. The nonaqueous electrolyte solution for a lithium secondary battery according to claim ₁ , The method of claim 2, wherein the carbonate is selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate Wherein the electrolyte is at least one selected from the group consisting of ethylene carbonate (EC) vinylene carbonate (VC), vinylethylene carbonate (VEC), propylene carbonate (PC) and butylene carbonate (BC).