Lithium secondary battery for vehicles and method for its production

Abstract

Lithium secondary battery for vehicles, comprising: a negative electrode containing lithium; a negative electrode coating layer provided over the negative electrode and comprising a disulfide polymer; an electrolyte layer provided over the negative electrode coating layer; and a positive electrode provided above the electrolyte layer, wherein the disulfide polymer is represented by the following formula 1: where R is -OH, where the polymer loading level of the negative electrode coating layer is 0.025 mg / cm 2 up to 0.25 mg / cm 2 amounts, wherein the electrolyte layer comprises a carbonate-based electrolyte.

Description

BACKGROUND(a) Technical area

[0001] The present invention relates to a lithium secondary battery for vehicles and a method for producing the same. (b) State of the art

[0002] Lithium secondary batteries are attracting considerable attention as next-generation power sources for vehicles. There is a need to develop lithium secondary batteries with long cycle life and high charge / discharge capacity for use as power sources for vehicles.

[0003] KR 10 2014 0 023 548 A, KR 10 2016 0 103 998 A, KR 10 2015 0 145 046 A, and KR 10 2015 0 166 976 A disclose related technologies relating to secondary batteries. J. Song et al. (SONG, Jongchan [et al.]: Polysulfide rejection layer from alpha-lipoic acid for high-performance lithium–sulfur battery. In: Journal of Materials Chemistry A, Vol. 3, 2015, No. 1, pp. 323-330. ISSN 2050-7496) describe a polysulfide barrier layer made of alpha-lipoic acid for high-performance lithium-sulfur batteries. US 6,277,514 B1 discloses a protective layer for separators for electrochemical cells. US 2010 / 0 035 161 A1 describes an electrode with a film on an electrode active material.

[0004] The information disclosed in this background section is intended only to facilitate understanding of the background of the invention and may therefore contain information that does not constitute prior art already known to a person of ordinary skill in the art in this country. SUMMARY OF REVELATION

[0005] One aspect of the present invention provides a lithium secondary battery for vehicles that can have a long cycle life and high efficiency by improving the reversibility of lithium.

[0006] Another aspect of the present invention provides a method for manufacturing a lithium secondary battery for vehicles which can have a long cycle life and high efficiency by improving the reversibility of lithium.

[0007] The present invention provides a lithium secondary battery for vehicles comprising a negative electrode containing lithium, a negative electrode coating layer provided over the negative electrode and containing a disulfide polymer, an electrolyte layer provided over the negative electrode coating layer, and a positive electrode provided over the electrolyte layer.

[0008] The disulfide polymer is represented by the following formula 1: where R is -OH. The polymer loading rate of the negative electrode coating layer is 0.025 to 0.25 mg / cm 2 . The electrolyte layer comprises a carbonate-based electrolyte.

[0009] The disulfide polymer can have a molecular weight of 1,000 to 10,000,000.

[0010] The mass loading degree of the negative electrode coating layer can be 1 to 1,000 µg·cm -2 be.

[0011] The thickness of the negative electrode coating layer may be less than the thickness of the negative electrode.

[0012] The negative electrode coating layer may further comprise an inorganic substance.

[0013] The inorganic substance may contain at least one of Al 2 O 3 , SiO 2 , TiO 2 or mixtures thereof.

[0014] The present invention further provides a method of manufacturing a lithium metal-air battery for vehicles, comprising providing a negative electrode comprising lithium, providing a negative electrode coating layer comprising a disulfide polymer over the negative electrode, providing an electrolyte layer over the negative electrode coating layer, and providing a positive electrode over the electrolyte layer.

[0015] In providing the negative electrode coating layer, the disulfide polymer is represented by the following formula 1: where R is -OH. The polymer loading rate of the negative electrode coating layer is 0.025 to 0.25 mg / cm 2 . The electrolyte layer comprises a carbonate-based electrolyte.

[0016] Providing a negative electrode coating layer may comprise preparing a cyclic disulfide monomer represented by the following formula 2:wherein R is -OH; and polymerizing the cyclic disulfide monomer to form the disulfide polymer represented by formula 1.

[0017] The formation of the disulfide polymer can be carried out by applying heat or light.

[0018] The formation of the disulfide polymer can be carried out at 100 to 140°C for 2 to 4 hours.

[0019] When providing a negative electrode coating layer, the disulfide polymer may have a molecular weight of 1,000 to 10,000,000. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other features of the present invention will now be described in detail with reference to certain embodiments thereof illustrated in the accompanying drawings, which are given below for illustrative purposes only and thus do not limit the present invention, and in which: Fig. 1 is a schematic sectional view illustrating a lithium secondary battery for vehicles according to an embodiment of the present invention; Fig. 2 is a flowchart schematically illustrating a method for manufacturing a lithium secondary battery for vehicles according to an embodiment of the present invention; Fig. 3A shows SEM analysis results of the surface of a negative electrode coating layer; Fig. 3B shows SEM analysis results of the side surfaces of a negative electrode and the negative electrode coating layer; Fig. 4A shows SEM analysis results of the surface of a negative electrode coating layer of Example 1 after 5 charge / discharge cycle tests; Fig. 4B shows SEM analysis results of the surface of the negative electrode coating layer of Example 1 after 5 charge / discharge cycle tests; Fig. 5 is a graph showing the change behavior of voltage capacity based on a charge / discharge test at 0.34 mA cm -2 with respect to Examples 1 and 2 and Comparative Example 1; and Fig. 6 is a graph showing a voltage versus time measured under conditions of 0.1 mA cm -2 and 10 hours / half cycle with respect to Example 3, Comparative Example 2 and Comparative Example 3. DETAILED DESCRIPTION

[0021] The aspects, features, and advantages will become clear from embodiments with reference to the accompanying drawings. However, the present invention is not limited to the embodiments and may be embodied in various forms. The embodiments are merely proposed to provide those skilled in the art with a thorough and complete understanding of the inventive context and to sufficiently inform those skilled in the art of the technical spirit of the present invention.

[0022] Like reference numerals refer to like elements throughout the description of the figures. In the drawings, the sizes of the structures have been exaggerated for clarity. It should be understood that while the terms "first," "second," etc., may be used herein to describe various elements, these elements are not intended to be limited by these terms and are used merely to distinguish one element from another. For example, within the scope defined by the present invention, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. The singular forms are intended to include the plural forms unless the context clearly indicates otherwise.

[0023] It is further understood that the terms "comprise," "includes," "comprises," or "has," when used in this specification, specify the presence of stated features, numbers, steps, acts, elements, components, and / or combinations thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, acts, elements, components, and / or combinations thereof. In addition, it is understood that when an element, such as a layer, film, region, or substrate, is referred to as being "on" another element, it may be directly on top of the other element, or an intervening element may be present. It is further understood that when an element, such as a layer, film, region, or substrate, is referred to as being "under" another element, it may be directly beneath the other element, or an intervening element may be present.

[0024] One example for secondary batteries proposes the suppression of dendrite growth with high-stiffness inorganic particles. Another example proposes the induction of uniform lithium plating. Another example proposes the inhibition of electrolyte degradation. The above technologies have the limitation that they do not propose a suitable solution associated with the reversibility of the negative electrode, i.e., the lithium electrode.

[0025] The lithium secondary battery for vehicles according to an embodiment of the present invention will be described below.

[0026] Fig. 1 is a schematic sectional view showing a lithium secondary battery for vehicles according to an embodiment of the present invention.

[0027] Referring to Fig. 1, the lithium secondary battery 10 for vehicles according to an embodiment of the present invention can be used as a power source for vehicles. The vehicle can be a means of transporting an object, a person, or the like. The vehicle can be, for example, a land vehicle, a marine vessel, or an aircraft. Examples of a land vehicle can be cars including passenger cars, vans, trucks, semi-trailer trucks and sports cars, bicycles, motorcycles, trains, and the like. Examples of a marine vessel can be ships and submarines. Examples of an aircraft can be airplanes, hang gliders, hot air balloons, helicopters, and small aircraft such as drones.

[0028] The lithium secondary battery 10 for vehicles according to an embodiment of the present invention undergoes an electrochemical reaction by charging / discharging. During charging, the oxidation / reduction reaction of metal or the oxidation / reduction reaction of oxygen occurs at a positive electrode 400. At this time, electrons are also generated, which can be moved to a negative electrode 100 via, for example, an external circuit. At the negative electrode 100, oxygen molecules, lithium ions, and electrons react with each other to generate electrical energy and heat energy. During discharging, lithium ions are released from the negative electrode 100 and moved through an electrolyte layer 300c to the positive electrode 400. The electrons are moved to the positive electrode 400 via, for example, the external circuit.

[0029] The lithium secondary battery 10 for vehicles according to an embodiment of the present invention is not particularly limited as long as the negative electrode 100 comprises lithium, for example, solid-state batteries, lithium-ion batteries, metal-air batteries, and the like.

[0030] The lithium secondary battery 10 for vehicles according to an embodiment of the present invention includes a negative electrode 100, a negative electrode coating layer 200, an electrolyte layer 300, and a positive electrode 400.

[0031] The negative electrode 100 comprises lithium. The thickness of the negative electrode 100 may be greater than the thickness of the negative electrode coating layer 200.

[0032] In embodiments, the negative electrode coating layer 200 is provided on the negative electrode 100. The negative electrode coating layer 200 comprises a disulfide polymer. Generally, during charging / discharging of the lithium secondary battery for vehicles, the electrolyte between the negative electrode and the electrolyte layer is decomposed, and lithium dendrites and the like are accumulated, forming a porous layer. At this time, if the porous layer is spaced apart from the lithium metal connected to a current collector, the reversibility of the lithium is deteriorated due to insufficient electrical contact. The lithium secondary battery for vehicles according to an embodiment of the present invention includes a negative electrode coating layer containing a disulfide polymer to prevent or inhibit the porous layer from being spaced apart from the negative electrode.Accordingly, the electron conduction channel is maintained, allowing high lithium reversibility to be maintained even during continuous charging / discharging. In one embodiment, the negative electrode coating layer is formed directly on the negative electrode, and in another embodiment, another layer may be interposed between the negative electrode coating layer and the negative electrode.

[0033] The negative electrode coating layer 200 comprises a disulfide polymer and thus exhibits high adhesiveness and elasticity. The molecular weight of the disulfide polymer can be 1,000 to 10,000,000. If the molecular weight of the disulfide polymer is smaller than the above-defined range, the adhesiveness of the negative electrode coating layer 200 deteriorates and the physical shape of the coating layer cannot be well maintained. Therefore, the reversibility of lithium may deteriorate. If the molecular weight of the disulfide polymer is larger than the range, the lithium ion conductivity in the negative electrode coating layer 200 may rapidly deteriorate.

[0034] The disulfide polymer is represented by the following formula 1:wherein R is -OH; n is a suitable natural number calculated in the range of a molecular weight of the disulfide polymer; and “*” represents the bond to an adjacent functional group or compound.

[0035] The thickness of the negative electrode coating layer 200 may be smaller than the thickness of the negative electrode 100. If the thickness of the negative electrode coating layer 200 is greater than or equal to the thickness of the negative electrode 100, the movement of lithium ions may be difficult due to increased resistance of the coating layer. For example, the thickness of the negative electrode coating layer 200 may be 0.1 μm to 10 μm.

[0036] The polymer loading rate of the negative electrode coating layer 200 is 0.025 mg / cm 2 up to 0.25 mg / cm 2. If the polymer loading degree is smaller than the above-defined range, the adhesiveness of the negative electrode coating layer 200 may deteriorate, and thus the reversibility of lithium may deteriorate, and if the polymer loading degree is larger than the range, it may be difficult for lithium ions to pass through the negative electrode coating layer 200.

[0037] The negative electrode coating layer 200 may further comprise an inorganic substance. The inorganic substance may improve the rigidity of the negative electrode coating layer 200. The inorganic substance comprises, for example, at least one of Al 2 O 3 , SiO 2 or TiO 2 In embodiments, the mass loading level of the surface of the negative electrode coating layer may be 1 µg·cm -2 up to 1,000 µg·cm -2 be.

[0038] The electrolyte layer 300 is provided over the negative electrode coating layer 200. The electrolyte layer 300 may comprise a liquid electrolyte or a solid electrolyte. The electrolyte layer comprises a carbonate-based electrolyte. The term "~-based" as used herein may mean that a compound contains a compound corresponding to a "~" or a derivative of "~". The term "derivative" means a compound modified by introducing a functional group, oxidation, reduction, or substitution, or the like, of an atom from a specific compound as a precursor while maintaining the structure and properties of the precursor.

[0039] The electrolyte layer 300 comprises, for example, LiPF 6 . The electrolyte layer 300 comprises, for example, LiPF 6 which is contained in ethylene carbonate (EC) and diethyl carbonate (DEC).

[0040] The positive electrode 400 is provided above the electrolyte layer 300. The positive electrode 400 is not particularly limited as long as it can constitute the lithium secondary battery 10.

[0041] Generally, when charging / discharging a lithium secondary battery for vehicles, the electrolyte between the negative electrode and the electrolyte layer decomposes, and lithium dendrites and the like accumulate into a porous layer. At this time, if the porous layer is spaced apart from the negative electrode, the reversibility of lithium between the negative electrode and the electrolyte layer deteriorates. The lithium secondary battery for vehicles according to one embodiment of the present invention includes a negative electrode coating layer containing a disulfide polymer to prevent or inhibit the porous layer from being spaced apart from the negative electrode. Accordingly, the reversibility of lithium can be improved. Furthermore, the cycle life of the lithium secondary battery can be increased, and the charge / discharge capacity can be increased.

[0042] The following describes a method for manufacturing the lithium secondary battery for vehicles according to an embodiment of the present invention. The following detailed description focuses on the difference from the lithium secondary battery for vehicles according to an embodiment of the present invention described above, and the same features as the lithium secondary battery for vehicles according to an embodiment of the present invention will be omitted.

[0043] Fig. 2 is a flowchart schematically illustrating a method for manufacturing a lithium secondary battery for vehicles according to an embodiment of the present invention.

[0044] Referring to Fig. 1 and Fig. 2, the method for manufacturing a lithium metal-air battery for vehicles of the present invention includes providing a negative electrode 100 containing lithium (S100), providing a negative electrode coating layer 200 containing a disulfide polymer over the negative electrode 100 (S200), providing an electrolyte layer 300 over the negative electrode coating layer 200 (S300), and providing a positive electrode 400 over the electrolyte layer 300 (S400).

[0045] The negative electrode 100 is provided (S100). The negative electrode 100 comprises lithium.

[0046] The negative electrode coating layer 200 is provided over the negative electrode 100 (S200). The negative electrode coating layer 200 comprises a disulfide polymer. The molecular weight of the disulfide polymer may be 1,000 to 10,000,000. If the molecular weight of the disulfide polymer is less than the above-defined range, the adhesiveness of the negative electrode coating layer 200 deteriorates, the physical shape of the coating layer cannot be well maintained, and the reversibility of lithium may deteriorate. If the molecular weight of the disulfide polymer is greater than the above-defined range, the lithium ion conductivity at the negative electrode coating layer 200 may rapidly deteriorate.

[0047] In the step of providing the negative electrode coating layer 200 (S200), the disulfide polymer is represented by the following formula 1:wherein R is -OH; and n is defined as above.

[0048] The step of providing the negative electrode coating layer 200 (S200) may comprise providing an acyclic disulfide monomer represented by the following formula 2: wherein R is -OH; and polymerizing the cyclic disulfide monomer to form the disulfide polymer represented by formula 1.

[0049] The formation of the disulfide polymer can be achieved by applying heat or light. For example, the formation of the disulfide polymer is carried out at 100°C to 140°C for 2 to 4 hours. If the temperature and time are within the above-defined range, polymerization cannot be sufficiently carried out. If the temperature and time are not within the above-defined range, the disulfide polymer will not dissolve in a coating solution due to elongated chains of the disulfide polymer.

[0050] The step of providing the negative electrode coating layer 200 (S200) may include preparing a coating solution and dropping the coating solution to form a negative electrode coating layer 200.

[0051] The step of preparing a coating solution can be performed by adding a disulfide polymer to a solution. The solution can be, for example, dimethyl ether (DME). The disulfide polymer can be added in an amount of 0.1 to 10.0 wt% based on the total weight of the coating solution. By varying the concentration of the polymer in the solution, the thickness or density of the negative electrode coating layer can be controlled.

[0052] The polymer loading rate of the negative electrode coating layer 200 is 0.025 mg / cm 2 up to 0.25 mg / cm 2. The adhesiveness of the negative electrode coating layer 200 deteriorates and the physical shape of the coating layer cannot be well maintained, so that the reversibility of lithium may deteriorate, and when the molecular weight of the disulfide polymer is larger than the range, the lithium ion conductivity at the negative electrode coating layer 200 may deteriorate rapidly.

[0053] The coating solution is dropped and dried to form the negative electrode coating layer 200m, the drying can be carried out at room temperature.

[0054] The electrolyte layer 300 is provided over the negative electrode coating layer 200 (S300). The electrolyte layer 300 may include a liquid electrolyte or a solid electrolyte.

[0055] The positive electrode 400 is provided above the electrolyte layer 300 (S400). The electrolyte layer comprises a carbonate-based electrolyte.

[0056] The positive electrode 400 is not particularly limited as long as it can constitute the lithium secondary battery 10, but a positive electrode coating layer containing a disulfide polymer may be further provided between the positive electrode 400 and the electrolyte layer 300c. The disulfide polymer may be the same as or different from the polymer contained in the negative electrode coating layer.

[0057] In embodiments, the negative electrode 100 and the positive electrode 400 may be separated from each other by a separator. The separator comprises, for example, polypropylene.

[0058] Generally, during the charging / discharging of a lithium secondary battery for vehicles, a porous layer is formed between the negative electrode and the electrolyte layer. At this time, if the porous layer is spaced apart from the negative electrode, the reversibility of lithium between the negative electrode and the electrolyte layer deteriorates. The method for manufacturing a lithium secondary battery for vehicles according to an embodiment of the present invention includes providing a negative electrode coating layer containing a disulfide polymer so that peeling of the porous layer from the negative electrode can be prevented. Accordingly, the reversibility of lithium can be improved. Furthermore, the cycle life of the lithium secondary battery can be increased, and the charging / discharging capacity can be improved.

[0059] The present invention will now be further explained with reference to specific examples. However, these examples are intended only to illustrate the present invention and should not be construed as limiting the scope of the present invention. ExampleSynthesis of disulfide polymer

[0060] Alpha-lipoic acid (ALA), represented by the following formula 3, was polymerized at 120°C for 3 hours. Upon polymerization of the ALA monomer to form a poly-ALA, a yellow gel with high viscosity was obtained. Preparation of coating solution

[0061] Poly-ALA is not dissolved in polycarbonate (PC), but dissolves well in DME. Accordingly, poly-ALA was added to a dimethyl ether (DME) solution to form a transparent yellow solution. Example 1

[0062] A negative electrode with a thickness of 20 µm was formed using lithium. 0.1 wt% of poly-ALA, based on the total weight of the coating solution, was added to form a coating solution. The coating solution was applied to the surface of the negative electrode by a drop-coating method and dried under vacuum at room temperature to form a negative electrode coating layer. At this time, the polymer loading rate of the negative electrode coating layer was 0.025 mg / cm 2 . A lithium metal coated with a coating layer was used as the negative electrode to fabricate a button cell for testing. A positive electrode was fabricated using LiCoO 2 , PVdF and carbon (91.5:4.1:4.4, wt%) and coated on an aluminum foil with a thickness of 15 µm. A polypropylene separator (thickness 20 µm) and the positive

[0063] Electrode were stacked on the negative lithium electrode, and a liquid electrolyte [1M LiPF 6 in EC / DEC (EC and DEC are mixed in a volume ratio of 1:1)] was injected to form a button cell.

[0064] The results of SEM analysis of the surface of the negative electrode coating layer are shown in Fig. 3A, and the results of SEM analysis of the side surfaces of the negative electrode and the negative electrode coating layer are shown in Fig. 3B. As can be seen from the Fig. 3A and Fig. 3B, the surface of the negative electrode coating layer is uniform and smooth, and a negative electrode coating layer is formed on the surface of the negative electrode. Example 2

[0065] The same procedure as in Example 1 was performed, except that the coating solution was formed by adding 1 wt% of poly-ALA based on the total weight of the coating solution. At this time, the loading rate of the negative electrode coating layer was 0.25 mg cm -2 . Example 3

[0066] A negative electrode coating layer was prepared using lithium with a thickness of 450 µm in the same manner as in Example 1. The prepared lithium-coated negative electrode was stacked to face another lithium-coated negative electrode with a polypropylene separator interposed therebetween, and a liquid electrolyte [1M LiPF 6 in EC / DEC (EC and DEC are mixed in a volume ratio of 1:1)] was injected to produce a symmetric lithium cell. Comparison example 1

[0067] The same procedure as in Example 1 was carried out except that the negative electrode coating layer was not formed. Comparison example 2

[0068] The same procedure as in Example 3 was performed except that an electrolyte layer was formed using 1M LiTFSI in dioxolane (DOL) / dimethoxyethane (DME). Comparison example 3

[0069] The same procedure as in Example 3 was carried out except that the negative electrode coating layer was not formed. Measurement of physical properties1. SEM analysis

[0070] 5 charge / discharge cycle tests were conducted, SEM analysis was performed on the surface of the negative electrode coating layer of Example 1, the results of SEM analysis are shown in Fig. 4A, the SEM analysis was performed on the surface of the negative electrode coating layer of Comparative Example 1, and the results of the SEM analysis are shown in Fig. 4B.

[0071] As can be seen from the Fig. 4A and Fig. As can be seen from Figure 4B, in Comparative Example 1, a dendrite structure and a porous membrane (porous layer) are formed, and the adhesion between the porous membrane and the negative electrode deteriorates. On the other hand, in Comparative Example 2, the porous membrane is maintained by the negative electrode coating layer, and the surface of the negative electrode also retains its gloss. 2. Charge / discharge test

[0072] The charge / discharge test was carried out under the condition of 0.34 mA·cm -2 on the structures of Examples 1 and 2 and Comparative Example 1, and the results are shown in Fig. 5. As can be seen from Fig. As can be seen from Figure 5, a high charge / discharge capacity was achieved compared to Examples 1 and 3 and Comparative Example 1. 3. Assessment of the suitability of the electrolyte

[0073] The voltages of Example 3, Comparative Example 1 and Comparative Example 2 were measured under conditions of 0.1 mA·cm -2 and 10 hours / half cycle, and the results are in Fig. 6. Comparative Example 2 showed a higher overpotential than Comparative Example 1 and a gradual decrease in the overpotential with increasing cycle number. This means that cell operation is not possible in Comparative Example 2. This is considered to be due to the fact that the negative electrode coating layer is dissolved in DME, which increases the resistance in the cell.

[0074] In Example 3, the overpotential was 0.5 V or less, the negative electrode coating layer was not dissolved, and cycles were stably operated.

[0075] As is apparent from the above, the lithium secondary battery for vehicles according to an embodiment of the present invention can improve the reversibility of lithium, prolong the cycle life, and increase the charge / discharge capacity.

[0076] According to the method for manufacturing the lithium secondary battery for vehicles according to an embodiment of the present invention, a lithium secondary battery that can improve the reversibility of lithium, prolong the cycle life, and increase the charge / discharge capacity can be provided.

Claims

[1] Lithium secondary battery for vehicles, comprising: a negative electrode containing lithium; a negative electrode coating layer provided over the negative electrode and comprising a disulfide polymer; an electrolyte layer provided over the negative electrode coating layer; and a positive electrode provided above the electrolyte layer, wherein the disulfide polymer is represented by the following formula 1: where R is -OH, where the polymer loading level of the negative electrode coating layer is 0.025 mg / cm 2 up to 0.25 mg / cm 2 amounts, wherein the electrolyte layer comprises a carbonate-based electrolyte. [2] The lithium secondary battery for vehicles according to claim 1, wherein the disulfide polymer has a molecular weight of 1,000 to 10,000,000. [3] A lithium secondary battery for vehicles according to claim 1, wherein the mass loading rate of the negative electrode coating layer is 1 µg·cm -2 up to 1000 µg·cm -2 amounts. [4] The lithium secondary battery for vehicles according to claim 1, wherein the negative electrode coating layer has a thickness smaller than that of the negative electrode. [6] The lithium secondary battery for vehicles according to claim 1, wherein the negative electrode coating layer further comprises an inorganic substance. [7] A lithium secondary battery for vehicles according to claim 6, wherein the inorganic substance contains at least one of Al 2 O 3 , SiO 2 , TiO 2 or mixtures thereof. [8] A method of manufacturing a lithium metal-air battery for vehicles, comprising: Providing a negative electrode comprising lithium; Providing a negative electrode coating layer comprising a disulfide polymer over the negative electrode; Providing an electrolyte layer over the negative electrode coating layer; and Providing a positive electrode over the electrolyte layer, wherein in providing the negative electrode coating layer, the disulfide polymer is represented by the following formula 1: where R is -OH, where the polymer loading level of the negative Electrode coating layer 0.025 mg / cm 2 up to 0.25 mg / cm 2 wherein the electrolyte layer comprises a carbonate-based electrolyte. [9] The method of claim 8, wherein providing a negative electrode coating layer comprises: Preparing a cyclic disulfide monomer represented by the following formula 2: where R is -OH; and Polymerizing the cyclic disulfide monomer to form the disulfide polymer represented by Formula 1. [10] The method of claim 9, wherein the formation of the disulfide polymer is carried out by applying heat or light. [11] The process of claim 9, wherein the formation of the disulfide polymer is carried out at 100°C to 140°C for 1 hour to 4 hours. [12] The method according to claim 9, wherein the disulfide polymer in providing a negative electrode coating layer has a molecular weight of 1,000 to 10,000,000.

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