KR20070031807A - Additives for non-aqueous electrolytes and electrochemical device using the same - Google Patents

Abstract

The present invention (a) an electrolyte salt; (b) an electrolyte solvent; And (c) at least one substituent selected from the group consisting of cyano group (-CN), isocyanate group (-NCO), thiocyanate group (-SCN) and isothiocyanate group (-NCS) A battery electrolyte comprising a sulfonate-based compound, an electrode formed with the sulfonate-based compound or a chemical reaction product thereof on part or all of a surface thereof, and an electrochemical device including the electrolyte and / or an electrode.

In the present invention, by using a sulfonate-based compound containing a cyano group, an isocyanate group, a thiocyanate group and / or an isothiocyanate group as one component of the electrolyte solution, it is possible to improve the high temperature life characteristics of the electrochemical device.

Sultone compound, nonaqueous electrolyte, electrochemical device, lithium secondary battery, high temperature life

Description

ADDITIVES FOR NON-AQUEOUS ELECTROLYTES AND ELECTROCHEMICAL DEVICE USING THE SAME

1 is a graph comparing the reduction voltages of the respective electrolytes using the half cells including the electrolyte solutions of Example 2 and Comparative Examples 1 to 3. FIG.

FIG. 2 is a diagram showing differential scanning calorimetry (DSC) results obtained by charging and discharging half-cells of Examples 1 and 2 and Comparative Examples 1 to 3, respectively, and then collecting and analyzing a negative electrode.

3 is a graph showing high temperature (60 ° C) cycle characteristics of lithium secondary batteries manufactured in Examples 1 and 2 and Comparative Examples 1 to 3, respectively.

The present invention relates to a battery electrolyte comprising a nonaqueous electrolyte additive capable of improving cycle characteristics and high temperature characteristics of the battery, an electrode having improved thermal safety of the electrode, and an electrochemical device including the same, preferably a nonaqueous electrolyte secondary battery. .

Recently, interest in energy storage technology is increasing. With the application of cell phones, camcorders, notebook PCs, and even electric vehicles to energy, efforts to research and develop electrochemical devices are becoming more concrete. The electrochemical device is the field attracting the most attention in this respect, and among them, the development of a secondary battery capable of charging and discharging has been the focus of attention. Recently, research and development on the design of new electrodes and batteries have been conducted in order to improve capacity density and specific energy.

Among the secondary batteries currently applied, lithium secondary batteries developed in the early 1990s have a higher operating voltage and greater energy density than conventional batteries such as Ni-MH, Ni-Cd, and sulfuric acid-lead batteries that use an aqueous electrolyte solution. I am in the spotlight. However, such a lithium secondary battery has a problem in that performance deteriorates as charging and discharging are repeated. This problem, in particular, has a problem that becomes more serious as the operating / storage temperature of the battery increases. Therefore, development of a method for improving the high temperature life of the nonaqueous electrolyte lithium secondary battery is continuously required.

Korean Patent Nos. 0450199 and US 2002-0197537 disclose that the lifespan and temperature characteristics of a battery are improved by using a sulfonate-based compound of Formula 2 as an electrolyte additive.

[Formula 2]

(이때, R₁ 내지 R₂는 알킬기, 알케닐기 또는 아릴기임.)

(Wherein R ₁ to R ₂ are alkyl, alkenyl or aryl groups)

In addition, Japanese Patent Application Laid-Open No. 2000-13304 reported that the lifespan and storage characteristics of a battery can be improved by using the compound represented by the following formula (3).

[Formula 3]

(이때, R은 알킬기임.)

(Wherein R is an alkyl group)

As described above, sulfonate (SO ₃ ) -based compounds have been known to be used as an electrolyte additive to improve battery performance.

The present inventors continue to improve the performance of the battery using a sulfonate (SO ₃ ) -based compound, while sulfonate-based compounds substituted with specific substituents, such as cyano group, isocyanate group, thiocyanate group, isothio When using a sulfonate-based compound in which one or more cyanate groups are substituted, it was first discovered that the long-life characteristics and high temperature stability of a lithium secondary battery are remarkably improved over conventional sulfonate-based compounds in which the aforementioned substituent is not introduced.

Accordingly, the present invention provides a battery electrolyte containing a sulfonate-based compound having one or more substituents introduced therein as an electrolyte component, an electrode containing the compound on an electrode active material, an electrochemical device including the electrolyte and / or an electrode. It aims to provide.

The present invention (a) an electrolyte salt; (b) an electrolyte solvent; And (c) at least one electron withdrawing group selected from the group consisting of cyano group (-CN), isocyanate group (-NCO), thiocyanate group (-SCN) and isothiocyanate group (-NCS) A battery electrolyte comprising a sulfonate-based compound containing at least one (EWG) and an electrochemical device having the electrolyte, preferably a lithium secondary battery.

The present invention also relates to sulfonates comprising at least one substituent selected from the group consisting of cyano (CN) groups, isocyanate groups (-NCO), thiocyanate groups (-SCN) and isothiocyanate groups (-NCS). Provided is an electrode in which a series compound or a chemical reaction product thereof is formed on part or all of a surface thereof, and an electrochemical device including the electrode, preferably a lithium secondary battery.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present invention uses a sulfonate (SO ₃ ) -based compound as a constituent of an electrolyte solution, but a sulfonate in which one or more specific substituents such as cyano group, isocyanate group, thiocyanate group and / or isothiocyanate group are substituted. It is characterized by using a series compound.

Due to the features described above, the lithium secondary battery of the present invention can realize better long-life characteristics and higher temperature characteristics than when an unsubstituted conventional sulfonate-based compound having no substituent is introduced as an electrolyte component. The reason why the compound exhibits an excellent effect compared to other similar sulfonate-based compounds is not clear, but it can be estimated as follows.

1) In general, compounds having alkenyl groups are polymerized by reducing and oxidizing each electrochemically, thereby forming a kind of polymer membrane. In fact, conventional sulfonate-based compounds composed of sulfonate group (SO ₃ ) and alkenyl group (see KR 0450199 and US 2002-0197537, Formula 2) have been described in the above-described polymer membrane on the surface of the negative electrode and the positive electrode during initial charging of the battery. This polymer membrane forms a side reaction between the electrode active material and the electrolyte solvent by acting as a passive film that prevents further degradation of additives and other electrolytes; And preventing the collapse of the electrode due to co-intercalation of the electrolyte solvent into the electrode active material, and minimizing performance degradation of the battery by faithfully performing a role of a tunnel of conventional lithium ions.

Therefore, in the present invention, the sulfonate-based compound composed of the aforementioned sulfonate group (SO ₃ ) and alkenyl group is used, but is a cyano group (CN), an isocyanate group (-NCO), a thiocyanate group (-SCN) and iso Sulfonate-based compounds in which an electron withdrawing group (EWG) substituent such as a thiocyanate group (-NCS) is introduced are intended to be used.

As such, sulfonate-based compounds substituted with one or more EWG substituents have a lower self-reducing voltage compared to conventional sulfonate-based compounds with unsubstituted or electron donating (EDG) substituents (higher reduction voltages in half cells). Since it is easily decomposed under a lower starting voltage, it exhibits high reactivity with the cathode. Therefore, it is possible to easily form a robust and dense SEI film on the surface of the negative electrode by decomposing during initial charging, and more specifically, to improve overall performance of a battery to be obtained by introducing a sulfonate-based compound, and thus, irreversible capacity of the battery. By reducing the efficiency of the battery, it is possible to fully improve the overall performance of the battery, such as minimizing the battery capacity and improving the life characteristics.

It is assumed that this reducing property is mainly affected by the electronic effect. That is, when the introduced substituent has an electron donating ability, an electrical effect of increasing the electron density of the additive occurs. Therefore, as the electron donating substituent is introduced, the reduction voltage becomes higher (lower voltage in the half cell), so that the reduction reaction becomes difficult, whereas when the electron withdrawing substituent is introduced as in the present invention, the self-reducing voltage of the sulfonate-based compound is introduced. This decreases (reduced voltage increases in the half cell) so that the reduction reaction at the negative electrode can be easily performed.

Also, 2) cyano group (cyano, -C≡N), isocyanate group (isocyanate, -N = C = O) and thiocyanate group (thiocyanate, -SC≡N) introduced into the sulfonate compound of the present invention. And isothiocyanate (-N = C = S) and the like are electron withdrawing groups having a high dipole moment. The above substituents are strongly bonded to the transition metal or transition metal oxide, carbon material and the like exposed on the surface of the electrode active material, and particularly, at a high temperature of 45 ° C. or more, the functional group and the surface of the electrode active material are more strongly bonded to form a complex. A protection layer is formed. Therefore, the sulfonate-based compound in which the substituent of the above-described characteristics is introduced during the initial charging of the battery forms an inert film in the state of being adsorbed on the surface of the electrode. In addition, the formed inert film is strongly bonded to the surface of the electrode active material so that the stability of the inactive film is continuously maintained due to repeated charging and discharging, thereby maintaining battery performance. In particular, the high temperature performance cycle characteristic of 45 degreeC or more can be improved significantly.

One of the components constituting the battery electrolyte according to the present invention is one of cyano (CN), isocyanate group (-NCO), thiocyanate group (-SCN) and / or isothiocyanate group (-NCS) group Any sulfonate-based compound containing the above electron withdrawing group (EWG) can be used without particular limitation. In particular, it is preferable to include an alkenyl group in the compound in order to generate a polymerization reaction while being reduced and oxidized electrochemically.

The sulfonate-based compound may be represented by the compound of Formula 1.

In the above formula,

R ₁ is an alkenyl group having 2 to 10 carbon atoms,

R ₂ is an alkyl group having 1 to 10 carbon atoms including at least one substituent selected from cyano (CN) group, isocyanate group (-NCO), thiocyanate group (-SCN) and isothiocyanate group (-NCS), It is a functional group selected from the group which consists of an alkenyl group, an aryl group, and a phenyl group.

Since the compound of Formula 1 includes an electron withdrawing group (EWG) such as an alkenyl group, a cyano group, an isocyanate group, a thiocyanate group, an isothiocyanate group, and the like in the compound itself, Not only can it be easily decomposed to form a firm and dense SEI film on the surface of the cathode, but also a kind of anodic protective film can be simultaneously formed through chemical bonding between the aforementioned substituent and the surface of the cathode active material such as transition metal and transition metal oxide. have. That is, a kind of complex protective film is formed by forming a coordinating bond by donation of a lone pair of electrons present in a substituent. Therefore, due to the protective film formed on the positive electrode, the cathode characteristics related to the life characteristics, the cycle characteristics and the like, and the cathode characteristics associated with the high temperature storage characteristics can be maximized, respectively, thereby increasing the overall performance and safety of the battery. .

In addition to the substituents described above, sulfonate-based compounds in which substituents are introduced that can provide a mechanism of action similar to the above and impart an improved battery performance are also within the scope of the present invention.

The content of the sulfonate-based compound can be adjusted according to the goal of improving the overall performance of the battery, but preferably 0.1 to 10 parts by weight per 100 parts by weight of the electrolyte. When the content of the sulfonate-based compound is less than 0.1 parts by weight, the effect of improving long-life and high temperature properties is insignificant, and when the content of the sulfonate-based compound exceeds 10 parts by weight, performance may be reduced due to an increase in the amount of irreversible reactions.

The battery electrolyte to which the sulfonate-based compound is to be added together includes conventional electrolyte components known in the art, such as electrolyte salts and organic solvents.

Using the electrolyte salts is A ⁺ B ^- A salt of the structure, such as, A ⁺ is Li ^+, Na ^+, K ⁺ comprises an alkaline metal cation or an ion composed of a combination thereof, such as, and B ^- is PF ₆ ^-, BF _{^{4 -, Cl -, Br -}} , I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 2 SO 2) 3 ^- is a salt containing an anion ion or a combination thereof, such as. In particular, a lithium salt is preferable.

Organic solvents may be used conventional solvents known in the art, such as cyclic carbonates and / or linear carbonates, non-limiting examples of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl Carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC) , Gamma butyrolactone (GBL), fluoroethylene carbonate (FEC), methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, pentyl acetate, methyl propionate, ethyl propionate, ethyl propionate, propionic acid Butyl or mixtures thereof. Moreover, the halogen derivative of the said organic solvent can also be used.

The present invention also provides an electrode in which a sulfonate-based compound or a chemical reaction product thereof including one or more substituents selected from the group consisting of a cyano group, an isocyanate group, a thiocyanate group and an isothiocyanate group is formed on part or all of a surface thereof. to provide.

In this case, the electrode may be a cathode in which the aforementioned sulfonate-based compound is electrochemically reduced to form a solid electrolyte interface (SEI) coating on part or all of the surface thereof, and / or a cyano group included in the sulfonate-based compound, At least one substituent selected from an isocyanate group, a thiocyanate group, and an isothiocyanate group may be an anode in which a protective layer in the form of a complex is formed by chemically bonding to the surface of the electrode active material. If possible, it is preferable that a protective film is formed on both electrodes in order to improve the overall performance of the battery.

When the electrode is charged and discharged using the above-described electrolyte solution, EWG substituents of sulfonate-based compounds in the electrolyte solution, such as cyano group, isocyanate group, thiocyanate group, isothiocyanate group, etc., form a complex with the surface of the electrode active material. It may be made automatically through, or may be formed by coating the compound on the surface of the electrode active material, or in combination with the electrode material, or by coating on the other electrode surface prepared.

As such, when the sulfonate-based compound including the EWG substituent includes an electrode in which a strong complex is formed through a chemical reaction with a carbon material, a transition metal or a transition metal oxide on the surface of the electrode active material, the carbon material and transition in the electrode It stabilizes metal and transition metal oxides to prevent dissolution of some of the transition metals from electrode active materials during charging and discharging, as well as exothermic reactions caused by the electrolyte reacting directly with the electrode surface when a physical impact is applied from the outside. By effectively controlling the retardation and decay of the structure of the electrode active material, it is possible to prevent ignition and rupture due to the temperature rise inside the battery. In particular, the sulfonate-based compound containing the EWG group described above can provide a thermally stable electrode because it strongly protects the electrode surface at a high temperature of more than 45 ℃ than room temperature.

The method for manufacturing the electrode according to the present invention is not particularly limited, but is prepared by applying and drying a conventional method known in the art as an example, that is, an electrode slurry including a positive electrode active material or a negative electrode active material on a current collector. . In this case, a small amount of a conductive agent and / or a binder may be optionally added.

The positive electrode active material may be a conventional positive electrode active material that can be used for the positive electrode of the conventional electrochemical device, non-limiting examples thereof, such as LiM _x O _y (M = Co, Ni, Mn, Co _a Ni _b Mn _c ) Lithium transition metal composite oxides (for example, lithium manganese composite oxides such as LiMn ₂ O ₄ , lithium nickel oxides such as LiNiO ₂ , lithium cobalt oxides such as LiCoO ₂ , and some of manganese, nickel and cobalt oxides thereof Or a vanadium oxide containing lithium or the like, or a chalcogen compound (for example, manganese dioxide, titanium disulfide, molybdenum disulfide, or the like). Preferably LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li (Ni _a Co _b Mn _c ) O ₂ (0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1), LiNi _1-Y Co _Y O ₂ , LiCo _1-Y Mn _Y O ₂ , LiNi _1-Y Mn _Y O ₂ (where 0 ≦ Y <1), Li (Ni _a Co _b Mn _c ) O ₄ (0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), LiMn _2-z Ni _z O ₄ , LiMn _2-z Co _z O ₄ ( Here, 0 <Z <2), LiCoPO ₄ , LiFePO _4, or a mixture thereof is mentioned.

The negative electrode active material may be a conventional negative electrode active material that can be used for the negative electrode of the conventional electrochemical device, non-limiting examples of lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, Lithium adsorbents such as graphite or other carbons. Non-limiting examples of the positive electrode current collector is a foil made by aluminum, nickel or a combination thereof, and non-limiting examples of the negative electrode current collector by copper, gold, nickel or copper alloy or a combination thereof Foils produced.

Conventional binders may be used, and non-limiting examples thereof include polyvinylidene fluoride (PVDF) or styrene butadiene rubber (SBR).

The present invention provides an electrochemical device including an anode, a cathode, a separator, and an electrolyte, wherein the electrolyte is an electrolyte containing a sulfonate-based compound substituted with the aforementioned EWG substituent; The anode, the cathode or the positive electrode provides an electrochemical device, characterized in that the sulfonate-based compound containing the above-described EWG substituent or a chemical reaction product thereof is an electrode formed on part or all of the surface.

Electrochemical devices include all devices that undergo an electrochemical reaction, and specific examples thereof include all kinds of primary, secondary cells, fuel cells, solar cells, or capacitors. In particular, a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery among the secondary batteries is preferable.

The electrochemical device of the present invention may be prepared by inserting a porous separator between a positive electrode and a negative electrode in a conventional manner known in the art and adding the electrolyte solution.

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

The external shape of the electrochemical device manufactured by the above method is not limited, but cans are cylindrical, coin-shaped, square or pouch types.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the following examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

EXAMPLES 1-2. Manufacture of Electrolyte and Lithium Secondary Battery]

Example 1

1-1. Manufacture of electrolyte

A 1M LiPF ₆ solution having a composition of EC: EMC = 3: 7 was used as the electrolyte, and 2.0 parts by weight of the compound of Formula 4 was added to the electrolyte.

[Formula 4]

1-2. Half cell manufacture

Coin-type half cells were manufactured by a conventional method using artificial graphite as a positive electrode and lithium metal foil as a negative electrode, and the electrolyte solution prepared in Example 1-1 was injected.

1-3. Full cell manufacturing

A coin-type battery was manufactured by a conventional method using a LiCoO ₂ positive electrode and an artificial graphite negative electrode, and the electrolyte prepared in Example 1-1 was injected.

Example 2

An electrolyte and a battery were prepared in the same manner as in Example 1, except that 2.0 parts by weight of the compound of Formula 5 was added to the electrolyte instead of the compound of Formula 4.

[Formula 5]

Comparative Example 1 to 3. Lithium Secondary Battery Manufacturing

Comparative Example 1

An electrolyte and a battery were manufactured in the same manner as in Example 1, except that 2.0 parts by weight of the compound of Formula 6 was added to the electrolyte instead of the compound of Formula 4.

[Formula 6]

Comparative example  2

An electrolyte and a battery were manufactured in the same manner as in Example 1, except that 2.0 parts by weight of the compound of Formula 7 was added to the electrolyte instead of the compound of Formula 4.

[Formula 7]

Comparative Example 3

A battery was manufactured in the same manner as in Example 1, except that a conventional electrolyte solution was used instead of an additive.

Experimental Example 1.Reduction Voltage Comparison of Sulfonate Compounds

DQ / dV plot was obtained by discharging a coin half cell prepared by a conventional method to 5 mV at 0.1 C using the electrolyte solutions prepared in Examples 2 and Comparative Examples 1 to 3, respectively, and are shown in FIG. 1. It was.

As a result, the half cell of Example 2 using a cyano group-containing sulfonate-based compound as one component of the electrolyte solution, at a higher potential (lower potential on a full cell basis) than the half cell of Comparative Examples 1 to 3 It was confirmed that a reduction peak was observed. Therefore, it was confirmed that the reduction potential at the negative electrode of the sulfonate compound was changed by the introduction of the electron withdrawing group (EWG).

Experimental Example 2. Confirmation of Cathode SEI Film Formation

According to the present invention, the following experiment was conducted to confirm whether the formation of the SEI film on the negative electrode by the sulfonate compound in which the electron withdrawing group was introduced.

The batteries prepared in Examples 1 and 2 and Comparative Examples 1 to 3 were charged and discharged three times at 0.2 ° C. at 23 ° C. three times, and then, the batteries were disassembled in a discharged state to collect a negative electrode. Thereafter, DSC (differential scanning calorimetry) analysis was performed on the collected negative electrode, and the results are shown in FIG. 2. For reference, the exothermic reaction observed between 70 and 100 ° C. is known to be due to the thermal collapse of the SEI film on the surface of the cathode.

As shown in Figure 2, it can be seen that the exothermic reaction pattern due to the SEI collapse of the negative electrode according to the type of the electrolyte additive is different from each other. This can also be indirect evidence of SEI formation by electrolyte additives.

Experimental Example  3. High temperature cycle characteristic evaluation

In order to evaluate the performance of the lithium secondary battery manufactured according to the present invention, the following experiment was performed.

Lithium secondary batteries of Examples 1 and 2 using a cyano group-containing sulfonate-based compound as an electrolyte component were used. As a control thereof, a sulfonate-based compound containing no cyano group was used or conventionally used. The batteries of Comparative Examples 1 to 3 using the phosphorus electrolyte solution were used. Each battery was repeatedly charged and discharged at 4.2 V and 3 V sections at a current of 0.5 C at a temperature of 60 ° C.

As a result of the experiment, the battery of Comparative Example 3 using a conventional electrolyte solution showed a significant cycle reduction even before several cycles, including the battery of Comparative Example 1 and the cyano group using a conventional sulfonate-based compound containing no cyano group However, the battery of Comparative Example 2 using a conventional sulfonate-based compound in which no alkenyl group was present also showed a significant cycle life reduction (see FIG. 3). This proves that the formation of the inert film (SEI) is not properly performed when using the aforementioned sulfonate compound. On the other hand, the battery of Example 1 and Example 2 using a cyano group-containing sulfonate-based compound as one component of the electrolyte showed a gentle cycle decrease even after 60 cycles, and showed excellent cycle characteristics. It was confirmed that the high temperature long life characteristics were improved (see FIG. 3).

In the present invention, by using a sulfonate-based compound having a specific electron withdrawing substituent as an electrolyte solution component, the high temperature life characteristics of the lithium secondary battery can be significantly improved.

Claims (12)

(a) electrolyte salts; (b) an electrolyte solvent; And (c) at least one electron withdrawing group (EWG) selected from the group consisting of cyano group (-CN), isocyanate group (-NCO), thiocyanate group (-SCN) and isothiocyanate group (-NCS) Sulfonate-based compounds containing one or more A battery electrolyte comprising a. The electrolyte of claim 1, wherein the sulfonate compound is a compound having an alkenyl group. The electrolyte of claim 1, wherein the sulfonate-based compound is a compound represented by Formula 1 below: [Formula 1]

In the above formula, R ₁ is an alkenyl group having 2 to 10 carbon atoms, R ₂ is a functional group selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an alkenyl group, an aryl group and a phenyl group including at least one substituent selected from a cyano group, an isocyanate group, a thiocyanate group and an isothiocyanate group. The method of claim 1, wherein the sulfonate-based compound is a compound capable of electrochemically chemically reacting to form a passivation layer in the battery, the self-reduction potential is reduced by the introduction of an electron withdrawing group (EWG) The electrolyte solution characterized by. The electrolyte of claim 1, wherein the sulfonate-based compound is present in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the electrolyte. An electrode in which a sulfonate-based compound comprising at least one substituent selected from the group consisting of a cyano group, an isocyanate group, a thiocyanate group, and an isothiocyanate group, or a chemical reaction product thereof is formed on part or all of a surface thereof. The electrode of claim 6, wherein the sulfonate-based compound is a compound represented by Formula 1 below: [Formula 1]

In the above formula, R ₁ is an alkenyl group having 2 to 10 carbon atoms, R ₂ is a functional group selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an alkenyl group, an aryl group and a phenyl group including at least one substituent selected from a cyano group, an isocyanate group, a thiocyanate group and an isothiocyanate group. The electrode of claim 6, wherein the sulfonate-based compound is electrochemically reduced to form a solid electrolyte interface (SEI) coating on part or all of the surface thereof. The complex of claim 6, wherein the electrode is in a complex form by combining one or more substituents selected from cyano, isocyanate, thiocyanate and isothiocyanate groups in the sulfonate-based compound with the surface of the electrode active material. Electrode characterized in that the protective layer (protection layer) is formed. An electrochemical device comprising an anode, a cathode, a separator, and an electrolyte, wherein the electrolyte is an electrolyte according to any one of claims 1 to 5. An electrochemical device comprising an anode, a cathode, a separator, and an electrolyte, wherein the anode, the cathode, or the positive electrode is an electrode according to any one of claims 6 to 9. The electrochemical device of claim 10, wherein the electrochemical device is a lithium secondary battery.

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