KR100804980B1 - Additives for secondarty battery and lithium secondary battery using the same - Google Patents

Abstract

The present invention is a secondary battery electrolyte, the electrolyte is a) cyclic acid anhydride (cyclic acid hydride); And b) a secondary battery electrolyte comprising at least one sulfide selected from the group consisting of a sultone, a sulfone, and a sulfonate compound, and a lithium secondary battery having the same.

In the lithium secondary battery according to the present invention, by using cyclic acid anhydride and sulfide together as an electrolyte additive, the cycle characteristics and high temperature storage characteristics of the battery can be improved due to the improvement of the stability of the electrolyte.

Cyclic acid anhydride, sultone, sulfone, sulfonate, sulfide, electrolyte, lithium secondary battery

Description

ADDITIVES FOR SECONDARTY BATTERY AND LITHIUM SECONDARY BATTERY USING THE SAME}

1 is a lithium secondary battery of Example 1 prepared with succinic anhydride (SA) and propane sultone (PS) using an electrolyte additive, a battery of Comparative Example 1 without using an electrolyte additive, succinic anhydride And room temperature cycle characteristics of the lithium secondary batteries of Comparative Example 2 and Comparative Example 3 each containing propane sultone, respectively.

FIG. 2 shows a lithium secondary battery of Example 2 having a case in which a succinic anhydride (SA) and propane sultone (PS) are used as electrolyte additives and a case in which an aluminum film is laminated, without using an electrolyte additive. It is a result of the high temperature (90 degreeC) preservation experiment of the battery of the comparative example 4 which uses the battery of the comparative example 4 with a case which laminated | stacked the film, and propane sultone as an electrolyte additive, and provided with the case which laminated the aluminum film.

The present invention relates to an electrolyte having improved stability and a secondary battery, preferably a lithium secondary battery having improved cycle characteristics and high temperature storage characteristics, including the electrolyte.

In recent years, with the trend of miniaturization and weight reduction of electronic devices, miniaturization and weight reduction of batteries acting as power sources are also required. BACKGROUND ART Lithium-based secondary batteries have been put to practical use as small, light weight, high capacity rechargeable batteries, and are used in portable electronic and communication devices such as small video cameras, mobile phones, and notebook computers.

The lithium secondary battery is composed of a positive electrode, a negative electrode, and an electrolyte, and transfers energy while reciprocating both electrodes such that lithium ions from the positive electrode active material are inserted into a negative electrode active material, such as carbon particles, and are detached again when discharged. Since it is possible to charge and discharge.

In order to manufacture a conventional 4.2V class lithium secondary battery with a high capacity, high output and high voltage battery of 4.35V or more, a process of increasing the theoretical usable capacity of the cathode active material in the battery is required. In order to increase the available capacity of the positive electrode active material, the positive electrode active material may be doped using a transition metal or a non-transition metal such as aluminum or magnesium, or the charging end voltage of the battery may be increased. As the voltage of the lithium secondary battery is increased to 4.35V or more, the usable capacity in the battery increases by 15% or more, but as the reactivity between the positive electrode and the electrolyte increases, decomposition of the surface of the positive electrode and oxidation of the electrolyte occur. Therefore, there was a problem that the performance and safety of the battery is lowered.

In order to solve the above problems, an additive such as Cyclo Hexyl Benzene (CHB) or Biphenyl (BP) was used, but the additive is used for overcharging not only a high voltage battery of 4.35V or higher but also a 4.2V class battery. Alternatively, even at high temperatures, side reactions occur due to a decrease in stability of the electrolyte and an increase in reactivity between the positive electrode and the electrolyte, thereby causing oxidation of the electrolyte, gas generation inside the battery, and swelling of the battery, and thus, battery performance and safety. This was degraded. In particular, the battery is greatly inflated by hydrogen gas produced by polymerization with a conductive polymer at high temperature (90 ° C) storage, far exceeding 10%, which is normally required, and also by forming an insulator on the anode. There was a problem that the performance is reduced by preventing the movement of.

The inventors have found that the use of cyclic acid anhydrides and sulfides in combination with electrolyte additives improves the high temperature storage and cycle characteristics of secondary batteries, in particular lithium secondary batteries.

Accordingly, an object of the present invention is to provide an electrolyte solution containing cyclic acid anhydride and sulfide and a secondary battery including the electrolyte solution.

The present invention is a secondary battery electrolyte, the electrolyte is a) cyclic acid anhydride (cyclic acid anhydride); And b) a secondary battery electrolyte comprising one or more sulfides selected from the group consisting of sultone, sulfone and sulfonate compounds, and a lithium secondary battery having the same.

Hereinafter, the present invention will be described in detail.

The present invention is characterized by using cyclic acid anhydride and sulfides of sultones, sulfones and sulfonates in combination as an electrolyte additive for a secondary battery. In this case, examples of the secondary battery to which the present invention may be applied include a lithium secondary battery, more specifically, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

Due to the above characteristics, the secondary battery of the present invention, preferably lithium secondary battery can improve the performance and high temperature storage characteristics.

That is, in the case of using a conventional conventional electrolyte solution, side reaction occurs due to deterioration of stability of electrolyte solution and increase of reactivity between positive electrode and electrolyte solution when overcharge or high temperature storage of 4.2V class battery as well as 4.35V or higher high voltage battery. Swelling of the battery due to the increase, and there was a problem that the cycle characteristics and high temperature storage characteristics are deteriorated

In contrast, the present invention suppresses side reactions between the electrode and the electrolyte, decomposition additives and other electrolytes due to the inert film formed by sulfides and cyclic acid anhydrides used in combination with the electrolyte additives on the surface of the electrode. Since the gas generation and the swelling characteristics of the battery can be reduced, it is possible to implement the safety and performance of the battery. In particular, the cyclic acid anhydride and sulfide additives exhibit a superior synergistic effect than the use alone, which is an electrode, in particular a cathodic protection effect, compared to a film formed by using an inert film formed by the cyclic anhydride and sulfide additive alone, respectively. It is assumed to raise it.

According to the present invention, one of the additives added to the electrolyte of the secondary battery, preferably the lithium secondary battery, is an acid anhydride, and is preferably in a cyclic form represented by the following Chemical Formula 1.

(I)

(I)

In the above formula,

R is an alkyl group, alkenyl group or an allyl group having 1 to 20 carbon atoms, with or without heteroatoms; It is an alkoxy group, ester group, an ether group, a phenyl group, and a double hetero atom is O, S, N, or a halogen atom.

The cyclic acid anhydride represented by Formula 1 forms a passive film on the surface of the electrode, preferably the cathode while being reduced, and this inactive film serves to prevent further decomposition of the additive and other electrolytes. In general, linear acid anhydrides have a lower tendency to form inert membranes than cyclic acid anhydrides, or inert membranes formed do not play a sufficient role, whereas cyclic acid anhydrides are not only easy to form inert membranes but are also excellent in reduced inert membranes formed. Electrolytic solution decomposition prevention and electrode protection effect are shown.

Non-limiting examples of cyclic acid anhydrides include succinic anhydride, maleic anhydride, glutaric anhydride, itaconic anhydride and the like, with succinic anhydride being particularly preferred. The amount of the cyclic acid anhydride is preferably 0.01 to 10% by weight per 100% by weight of the electrolyte. If less than 0.01% by weight the effect is minimal. If it exceeds 10% by weight, the excess additives decompose and carbon dioxide and hydrogen gas may be generated, and this gas generation may result in deterioration of the performance and stability of the battery.

The other one of the additives added to the electrolyte of the secondary battery, preferably the lithium secondary battery according to the present invention is a sulfide, sultones, sulfones, sulfonate compounds or mixtures thereof. This is preferred.

Sultone compounds are saturated hydrocarbons or unsaturated hydrocarbon sultones represented by the following Formula 2, and non-limiting examples thereof include propane sultone (PS), propene sultone, ethyl sultone, butene sultone, and the like. Propane sultone is particularly preferred.

(Ⅱ)

(Ⅱ)

In the above formula,

R ₁ is an alkyl group or alkenyl group having 1 to 5 carbon atoms.

The sulfone compound is represented by the following Chemical Formula 3, and non-limiting examples thereof include dimethyl sulfone, dimethyl sulfone, divinyl sulfone, and the like.                     

(Ⅲ)

(Ⅲ)

In the above formula,

R ₂ and R ₂ ′ are selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group or alkenyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms or a phenyl group or phenoxy group unsubstituted or substituted with a halogen atom, and are independent of each other to be.

The sulfonate compound is represented by the following Chemical Formula 4, and non-limiting examples thereof include methyl methane sulfonate, ethyl methane sulfonate, and the like.

(Ⅳ)

(Ⅳ)

In the above formula,

R ₂ and R ₂ ′ are selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group or alkenyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms or a phenyl group or phenoxy group unsubstituted or substituted with a halogen atom, and are independent of each other to be.

The sulfides of Chemical Formulas 2 to 4 added to the electrolyte form a passive film on the electrode surface during initial charging of the battery. The inactive film not only suppresses side reactions between the electrode and the electrolyte, but also suppresses gas generation at high temperature. It plays a role.                     

The amount of the sultone, sulfone, and sulfonate compounds represented by Chemical Formulas 2 to 4 is preferably 0.01 to 10% by weight per 100% by weight of the electrolyte. If the amount of sulfide is less than 0.01% by weight, it is impossible to form a high-density inert film, so it is impossible to suppress the reaction between the electrode and the electrolyte at a high temperature. When the amount of the sulfide is more than 10% by weight, the viscosity of the electrolyte is increased and the thickness of the inert electrode is thick. As the film is formed, the internal resistance is increased and the capacity of the battery is lowered.

The present invention a) a positive electrode comprising a positive electrode active material capable of occluding and releasing lithium; b) a negative electrode comprising a negative electrode active material capable of occluding and releasing lithium; c) an electrolyte solution to which the electrolyte additive is added; And d) provides a lithium secondary battery comprising a separator. In this case, the lithium secondary battery includes a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.

The lithium secondary battery of the present invention may be prepared by inserting a porous separator between the positive electrode and the negative electrode according to a conventional method known in the art and adding an electrolyte solution to which the additive is added.

The positive electrode active material may be _a lithium transition metal composite oxide such as LiM _x O _y (M = Co, Ni, Mn, Co _a Ni _b Mn _c ) (for example, lithium manganese composite oxide such as LiMn ₂ O ₄ , LiNiO _2, etc.). Lithium cobalt oxides such as lithium nickel oxide, LiCoO ₂ , and manganese, nickel, and cobalt in which some of these oxides are substituted with other transition metals, or lithium-containing vanadium oxide, or a chalcogenide compound (for example, manganese dioxide) , Titanium disulfide, molybdenum disulfide, etc.) may be used. Since the present invention is useful not only for 4.2V class batteries, but also for high voltage batteries of 4.35V or higher class, the positive electrode active material is doped with a metal selected from Al, Mg, Zr, Fe, Zn, Ga, Sn, Si, Ge, or a mixture thereof. You can.

The negative electrode active material is preferably carbon, lithium metal or an alloy thereof. In addition, other lithium may be occluded and released, and metal oxides such as TiO ₂ , SnO _2, and the like having a potential of less than ₂ V may be used. The negative electrode can be prepared by conventional methods known in the art.

The electrolyte solution according to the present invention comprises a conventionally used electrolyte solvent, lithium salt, the above-mentioned additives, ie cyclic acid anhydride and sulfide.

The lithium salt may be at least one 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 electrolyte solvent is ethylene co (Ca) 1 selected from the group consisting of nates, propylene carbonate, butylene carbonate, vinylene carbonate, sulfolane, γ-butylo lactone, dimethyl carbonate, diethyl carbonate, 1,2-dimethoxy ethane, tetrahydrofuran and mixtures thereof More than one species can be used.

The separator may be a porous separator, for example, a polypropylene-based, polyethylene-based, or polyolefin-based porous separator may be used, but is not limited thereto.

Although the external shape of the lithium secondary battery manufactured by the above method is not limited, it is possible to have a cylindrical, coin-shaped, square or pouch type of cans.

The invention is explained in more detail based on the following examples and experimental examples. However, Examples and Experimental Examples are for illustrating the present invention and are not limited to these.

[Examples 1-2]. Lithium secondary battery manufacturing

Example 1

LiNi _0.5 Mn _1.5 O ₂ was used as the positive electrode active material, and the mixing ratio was 90% by weight of LiNi _0.5 Mn _1.5 O ₂ , 5% by weight of Super-P (conductor), and 5% by weight of PVDF (binder) as a solvent. (N-methyl-2-pyrrolidone) was added to prepare a positive electrode slurry, and then coated on an aluminum (Al) current collector to prepare a positive electrode. Metal lithium was used as a negative electrode, and a positive electrode was manufactured using a manufactured positive electrode. As an electrolyte, an EC / EMC solution was used in 1M LiPF ₆ , and 1% by weight of succinic anhydride (SA) and 3% by weight of propane sultone (PS) were added to the electrolyte.

Example 2

As the negative electrode material, artificial graphite was used, and the mixing ratio was 94% by weight of artificial graphite, 1% by weight of Super-P (conductive agent), and 5% by weight of PVDF (binder), and the negative electrode slurry was added to NMP as a solvent. After manufacturing, the negative electrode was prepared by coating on a copper (Cu) current collector. A bicell having a capacity of 60 mAh was manufactured using the prepared negative electrode, the positive electrode prepared in Example 1, and an aluminum laminated film case (Al laminated film case). As an electrolyte, an EC / EMC solution was used in 1M LiPF ₆ , and 2% by weight of succinic anhydride (SA) and 3% by weight of propane sultone (PS) were added to the electrolyte.

[Comparative Examples 1-5]. Lithium secondary battery manufacturing

Comparative Example 1

A lithium secondary battery was manufactured in the same manner as in Example 1, except that succinic anhydride and propane sultone were not used in the electrolyte.

Comparative Example 2

A lithium secondary battery was manufactured in the same manner as in Example 1, except that only 1 wt% of succinic anhydride was used as an electrolyte.

Comparative Example 3

A lithium secondary battery was manufactured in the same manner as in Example 1, except that only 3 wt% of propane sultone was used as the electrolyte.

Comparative Example 4

A lithium secondary battery was manufactured in the same manner as in Example 2, except that succinic anhydride and propane sultone were not used in the electrolyte.

Comparative Example 5

A lithium secondary battery was manufactured in the same manner as in Example 2, except that only 3 wt% of propane sultone was used as the electrolyte.                     

Experimental Example 1. Performance Evaluation of Lithium Secondary Battery

In order to evaluate the performance of the lithium secondary battery including cyclic acid anhydride and sulfide as an electrolyte additive according to the present invention, the following experiment was conducted.

The lithium secondary battery of Example 1, prepared by adding succinic anhydride (SA) and propane sultone (PS) to the electrolyte, was used, and a comparative example including the battery of Comparative Example 1, which did not use the electrolyte additive as a control, and succinic anhydride. The battery of Comparative Example 3 containing the battery of 2 and propane sultone was used.

Each battery was charged to 4.8 V with a charging current of 0.5 C to obtain a charging capacity, and 0.5 C discharge was performed to 3 V to obtain a discharge capacity. In this case, the irreversible capacity is defined as the difference between the charge capacity and the discharge capacity, that is, irreversible capacity = (charge capacity-discharge capacity), and the cumulative irreversible accumulation of the irreversible capacity generated each time when the charge and discharge are repeated several times. It is defined as capacity. Since the cumulative irreversible capacity is mainly generated by side reactions of the electrolyte, the cumulative irreversible capacity may be used as a measure of electrolyte stability. That is, the smaller the cumulative irreversible capacity, the more stable the electrolyte may be determined.

Figure 1 shows the cumulative irreversible capacity of each lithium secondary battery prepared in Example 1 and Comparative Examples 1 to 3. The battery of Comparative Example 2 prepared using succinic anhydride (SA) as the electrolyte additive was shown to have a reduced cumulative irreversible capacity compared to the battery of Comparative Example 1 without using the electrolyte additive, but did not include propane sultone (PS). The battery of Comparative Example 3 showed an increase in cumulative irreversible capacity. In contrast, the lithium secondary battery of Example 1 including both succinic anhydride and propane sultone showed a significantly reduced cumulative irreversible capacity than the batteries of Comparative Examples 1 and 2, and it was confirmed that the stability of the electrolyte was improved (FIG. 1). This confirmed that synergistic effect was obtained when succinic anhydride and propane sultone were used together as an electrolyte additive.

As a result, it was confirmed that the lithium secondary battery manufactured using cyclic anhydride and sulfide according to the present invention as an electrolyte additive was improved in performance based on the stability of the electrolyte due to the synergistic effect of each additive.

Experimental Example 2 Evaluation of High Temperature Storage Characteristics

In order to evaluate the high temperature storage characteristics of the lithium secondary battery including the cyclic acid anhydride and sulfide as the electrolyte additive according to the present invention, the experiment was performed as follows.

The bicell of Example 2 prepared by adding succinic anhydride (SA) and propane sultone (PS) to the electrolytic solution and using an aluminum film laminated case was used. The battery of Comparative Example 4, which did not use the electrolyte additive and the outer case in which the aluminum film was laminated, were used, and the battery of Comparative Example 5 containing propane sultone as the electrolyte additive was used.

The cell thickness increase was measured while preserving each cell at 4.8 V for 4 hours at a high temperature of 90 ° C. Since the increase in thickness is due to gas generation inside the battery, the smaller the increase in thickness, the smaller the amount of gas generated and the higher the stability of the electrolyte.

The battery of Comparative Example 4, which was prepared by adding the battery of Comparative Example 4 and propane sultone (PS) without using an electrolyte additive, showed a large battery thickness increase rate, but the succinic anhydride (SA) and propane sultone (PS) were used. The battery of Example 2, prepared by adding all to the electrolyte, showed a remarkably small increase in battery thickness (see FIG. 2). This is due to the improved stability of the electrolyte.

As a result, it was confirmed that the lithium secondary battery of the present invention has excellent high temperature storage characteristics and cycle characteristics due to the cyclic acid anhydride and sulfide additives added together in the electrolyte solution.

Lithium secondary battery according to the present invention is cyclic acid anhydride; And by using a sulfide consisting of sultone, sulfone or sulfonate together with the electrolyte additive, the cycle characteristics and high temperature storage characteristics of the battery can be improved due to the stability of the electrolyte.

Claims (12)

In the electrolyte solution for secondary batteries, the electrolyte solution a) cyclic acid anhydride; And b) a secondary battery electrolyte comprising one or more sulfides selected from the group consisting of sulfones and sulfonate compounds, The sulfone compound is a compound represented by the following general formula (III); The sulfonate compound is a secondary battery electrolyte characterized in that the compound represented by the general formula (IV):

(Ⅲ)

(Ⅳ) In the above formula, R2 and R2 'is selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group or alkenyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms or a phenyl group or phenoxy group unsubstituted or substituted with a halogen atom. , Independent of each other. The electrolyte solution according to claim 1, wherein the cyclic acid anhydride is a compound represented by the following general formula (I).

(I) Wherein R is an alkyl group, alkenyl group or an allyl group having 1 to 20 carbon atoms, with or without a hetero atom; an alkoxy group, an ester group, an ether group, a phenyl group, wherein a double hetero atom is O, S, N or Halogen atom.) The electrolyte of claim 1, wherein the cyclic acid anhydride is succinic anhydride. The electrolyte of claim 1, wherein the amount of the cyclic acid anhydride used is 0.01 to 10 wt% per 100 wt% of the electrolyte. delete delete delete The electrolyte of claim 1, wherein the sulfone compound is a dimethyl sulfone, diphenyl sulfone, or divinyl sulfone compound. delete The electrolyte of claim 1, wherein the sulfonate compound is methyl methane sulfonate, ethyl methane sulfonate. The electrolyte of claim 1, wherein the amount of one or more sulfides selected from the group consisting of sultone, sulfone and sulfonate compounds is 0.01 to 10 wt% per 100 wt% of the electrolyte. a) a positive electrode comprising a positive electrode active material capable of occluding and releasing lithium; b) a negative electrode comprising a negative electrode active material capable of occluding and releasing lithium; c) the electrolyte of any one of claims 1 to 4, 8, 10, and 11; And d) membrane Lithium secondary battery comprising a.

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