Electrode for lithium secondary battery and lithium secondary battery comprising same

Abstract

An electrode for a lithium secondary battery according to embodiments of the present disclosure comprises an electrode plate including lithium metal and a coating layer disposed on at least one surface of the electrode plate and including a fluorinated polyimide-based resin and boron nitride.

Description

Electrode for lithium secondary battery and lithium secondary battery including same

[0001] The present disclosure provides an electrode for a lithium secondary battery and a lithium secondary battery including the same.

[0002]

[0003] Secondary batteries, which can be repeatedly charged and discharged, are widely used as power sources for portable electronic communication devices such as camcorders, mobile phones, and laptops, thanks to the advancements in the information and communication and display industries. Furthermore, battery packs containing secondary batteries are being developed and applied as power sources for eco-friendly vehicles such as hybrid vehicles.

[0004] Examples of secondary batteries include lithium secondary batteries, nickel-cadmium batteries, and nickel-hydrogen batteries. Among these, lithium secondary batteries are actively being researched and developed due to their high operating voltage and energy density per unit weight, as well as their advantages in charging speed and weight reduction.

[0005] Graphite and silicon are commonly used as anode materials for lithium secondary batteries. However, graphite and silicon have high reaction potentials and low capacities, limiting their ability to increase the energy density and capacity of lithium secondary batteries. Therefore, efforts are underway to improve energy density by using lithium metal, which has low potential and high capacity, as anode materials.

[0006] However, when lithium metal is used as the anode material, lithium can grow unevenly on the surface of the lithium metal during the charging process, forming lithium dendrites. This can cause the anode and cathode to come into contact, potentially leading to short circuits, overheating, and explosions. Furthermore, the electrode volume can repeatedly expand and contract during the deposition and desorption process, potentially compromising the stability of the lithium secondary battery.

[0007] In this case, a solid electrolyte is introduced into the lithium secondary battery to prevent uneven deposition of lithium metal.

[0008]

[0009] An object of the present disclosure is to provide an electrode for a lithium secondary battery having improved mechanical properties.

[0010] An object of the present disclosure is to provide a lithium secondary battery with improved stability.

[0011]

[0012] An electrode for a lithium secondary battery according to the present disclosure comprises an electrode plate including lithium metal and a coating layer disposed on at least one surface of the electrode plate and including a fluorinated polyimide-based resin and boron nitride.

[0013] In one embodiment, the fluorinated polyimide resin may include repeating units derived from an aromatic diamine and repeating units derived from an aromatic dianhydride. At least one of the aromatic diamine and the aromatic dianhydride may include a fluorine atom.

[0014] In one embodiment, the aromatic diamine may comprise two aminophenyl structures.

[0015] In one embodiment, the aromatic diamine may be a biphenyl diamine substituted with at least one fluoroalkyl group having 1 to 3 carbon atoms.

[0016] In one embodiment, the aromatic diamine may include at least one selected from the group consisting of 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB), 2,2'-bis(trifluoromethyl)-4,4'-benzidine (TFDB), and 4,4'-oxybis[3-(trifluoromethyl)aniline (6FODA).

[0017] According to one embodiment, the aromatic dianhydride may include a compound represented by the following chemical formula 1.

[0018] [Chemical Formula 1]

[0019]

[0020] (In chemical formula 1, L is a divalent organic group having 1 to 30 carbon atoms).

[0021] In one embodiment, the aromatic dianhydride is 4,4'-hexafluoroisopropylidene diphthalic anhydride (6FDA), biphenyltetracarboxylic dianhydride (BPDA), oxydiphthalic dianhydride (ODPA), sulfonyl diphthalic anhydride (SO2DPA), (isopropylidenediphenoxy) bis (phthalic anhydride) (6HDBA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride (TDA), 1,2,4,5-benzene tetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride (BTDA), bis (carboxyphenyl) dimethylsilane dianhydride (SiDA), bis (dicarboxyphenoxy) diphenyl sulfide It may include at least one selected from the group consisting of dianhydride (BDSDA), pyromellitic dianhydride (PMDA), and ethylene glycol bis(anhydrotrimellitate) (TMEG100).

[0022] According to one embodiment, the content of the fluorinated polyimide resin may be 50 wt% to 99.9 wt% of the total weight of the coating layer.

[0023] In one embodiment, the boron nitride may be a hexagonal boron nitride flake.

[0024] According to one embodiment, the average particle diameter (D50) of the boron nitride may be 10 nm to 100 nm.

[0025] According to one embodiment, the content of the boron nitride may be 0.1 wt% to 50 wt% of the total weight of the coating layer.

[0026] According to one embodiment, the thickness of the coating layer may be 1 μm to 10 μm.

[0027] A lithium secondary battery according to the present disclosure may include the electrode for a lithium secondary battery as a negative electrode and may further include a positive electrode opposite to the electrode for a lithium secondary battery.

[0028]

[0029] An electrode for a lithium secondary battery according to exemplary embodiments of the present disclosure can implement a lithium secondary battery in which lithium metal can be uniformly deposited during repeated charge and discharge.

[0030] In addition, the electrode for a lithium secondary battery according to exemplary embodiments of the present disclosure can suppress dendrite formation on a lithium metal surface during repeated charge and discharge.

[0031] A lithium secondary battery according to exemplary embodiments of the present disclosure can have improved life characteristics by including the electrode for the lithium secondary battery.

[0032]

[0033] FIG. 1 is a schematic cross-sectional view showing an electrode for a lithium secondary battery according to exemplary embodiments.

[0034] FIGS. 2 and 3 are schematic plan views and cross-sectional views, respectively, showing lithium secondary batteries according to exemplary embodiments.

[0035] Figures 4a and 4b are a photograph and an SEM image of the cathode surface of Example 5, respectively.

[0036] Figures 5a and 5b are a photograph and an SEM image of the cathode surface of Example 6, respectively.

[0037] Figures 6a and 6b are a photograph and an SEM image of the cathode surface of Example 7, respectively.

[0038] Figures 7a and 7b are a photograph and an SEM image of the cathode surface of Example 8, respectively.

[0039] Figures 8a and 8b are a photograph and an SEM image of the cathode surface of Comparative Example 1, respectively.

[0040] Figures 9a and 9b are a photograph and SEM image of the cathode surface of Comparative Example 2, respectively.

[0041] Figures 10a and 10b are a photograph and an SEM image of the cathode surface of Comparative Example 3, respectively.

[0042] Figure 11 is a photograph of the cathode surface of Comparative Example 4.

[0043] Figure 12 is an SEM image of the cross-section of the cathode of Example 5.

[0044] Figure 13 is an SEM image of the cathode cross-section of Comparative Example 1.

[0045] Figure 14 is a graph showing the capacity retention rate according to the number of cycles of the lithium secondary batteries of Example 5 and Comparative Examples 1 and 2.

[0046] According to embodiments provided by the present disclosure, an electrode for a lithium secondary battery is provided, comprising an electrode plate including lithium metal and a coating layer disposed on at least one surface of the electrode plate, the coating layer including a fluorinated polyimide-based resin and boron nitride. In addition, a lithium secondary battery including the electrode for a lithium secondary battery is provided.

[0047] The terms “upper”, “lower”, “top”, “lower”, “bottom”, “first”, “second”, etc. used in this specification indicate the relative positions of each component and do not imply an absolute superior-subordinate relationship.

[0048] Hereinafter, unless otherwise specifically defined, when a part such as a layer, film, thin film, region, or plate is said to be “on” or “over” another part, this may include not only the case where it is “directly on” the other part, but also the case where there is another part in between.

[0049] Hereinafter, the present disclosure will be described in detail with reference to the attached drawings. However, these are merely exemplary and the present disclosure is not limited to the specific embodiments described as examples.

[0050] FIG. 1 is a schematic cross-sectional view showing an electrode for a lithium secondary battery according to exemplary embodiments.

[0051] Referring to FIG. 1, an electrode for a lithium secondary battery (hereinafter, abbreviated as “electrode”) includes an electrode plate (125) and a coating layer (120).

[0052] The electrode plate (125) includes lithium metal. The term "lithium metal" may mean a lithium alloy in which lithium atoms are metallically bonded, or a lithium alloy in which lithium atoms and other metal atoms are metallically bonded.

[0053] The electrode plate (125) may have a lithium metal layer formed on a support by deposition or the like, or may include lithium foil or lithium alloy foil.

[0054] The electrode plate (125) can supply lithium when the lithium secondary battery is discharged, and can accumulate lithium when it is charged. In this case, lithium may be deposited on the surface of the electrode plate (125).

[0055] The electrode plate (125) may be made of lithium metal or may include a lithium alloy. For example, the electrode plate (125) may include an alloy of lithium and copper.

[0056] The thickness of the electrode plate (125) may be, for example, 10 ㎛ to 100 ㎛.

[0057] A coating layer (120) is disposed on at least one surface of an electrode plate (125). The coating layer (120) has high lithium mechanical strength and can physically suppress the growth of dendrites formed when lithium is unevenly accumulated on the surface of the electrode plate (125) when the lithium secondary battery is charged. In addition, the coating layer (120) can prevent a decrease in the coulombic efficiency of the lithium secondary battery when the electrode plate (125) including highly reactive lithium metal comes into direct contact with an electrolyte and causes a side reaction.

[0058] The coating layer (120) may be formed on at least a portion of one surface of the electrode plate (125). For example, as in FIG. 1, it may be formed on a portion of, but not the entire, surface of the electrode plate (125). Alternatively, the coating layer may be formed with the same area on the entire surface of the electrode plate.

[0059] The coating layer (120) includes a fluorinated polyimide-based resin. The fluorinated polyimide-based resin contains nitrogen and fluorine atoms, which can react with lithium ions moving during charging and discharging of a lithium secondary battery to form inorganic components such as LiF and Li3N on the electrode surface. Accordingly, lithium metal can be induced to be more uniformly deposited on the surface of the electrode plate (125), and the mechanical and electrochemical properties of the electrode for a lithium secondary battery can be improved.

[0060] In one embodiment, the fluorinated polyimide-based resin may include repeating units derived from an aromatic diamine and repeating units derived from an aromatic dianhydride. At least one of the aromatic diamine and the aromatic dianhydride may include a fluorine atom. For example, the aromatic diamine and / or the aromatic dianhydride may include 1 to 10 fluorine atoms. In some embodiments, the aromatic diamine and the aromatic dianhydride may each include 5 to 10 fluorine atoms.

[0061] The above aromatic diamine and / or the aromatic dianhydride may contain a fluorine atom, and the fluorine atom may be included as a substituent in the aromatic diamine and / or the aromatic dianhydride at least once. Alternatively, the aromatic diamine and / or the aromatic dianhydride may contain at least one fluorinated alkyl group having 1 to 10 carbon atoms as a substituent in the aromatic diamine and / or the aromatic dianhydride.

[0062] In one embodiment, the aromatic diamine may comprise two aminophenyl structures. For example, the aromatic diamine may comprise a structure in which an aminophenyl group is linked to or directly bonded to a divalent organic group such as an oxy group (-O-) or a carbonyl group (-C(=O)-).

[0063] In one embodiment, the aromatic diamine may be biphenyl diamine (benzidine) substituted with at least one fluoroalkyl group having 1 to 3 carbon atoms. For example, the aromatic diamine may be biphenyl diamine (benzidine) substituted with at least one trifluoromethyl group.

[0064] In one embodiment, the aromatic diamine may include 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB), 2,2'-bis(trifluoromethyl)-4,4'-benzidine (TFDB), 4,4'-oxybis[3-trifluoromethyl]aniline (6FODA), and the like. These may be used alone or in combination of two or more. For example, the aromatic diamine may be 2,2'-bis(trifluoromethyl)-4,4'-benzidine (TFDB).

[0065] According to one embodiment, the aromatic dianhydride may include a compound represented by the following chemical formula 1.

[0066] [Chemical Formula 1]

[0067]

[0068] In chemical formula 1, L may be a divalent organic group having 1 to 30 carbon atoms.

[0069] The above "organic group" may include a divalent hydrocarbon group such as a substituted or unsubstituted alkylene group having 1 to 30 carbon atoms, a substituted or unsubstituted alkenylene group having 2 to 30 carbon atoms, a substituted or unsubstituted alkynylene group having 2 to 30 carbon atoms, a substituted or unsubstituted cycloalkylene group having 3 to 30 carbon atoms, or a substituted or unsubstituted arylene group having 6 to 30 carbon atoms.

[0070] The above "substitution" may mean that any hydrogen of the hydrocarbon group is replaced with a halogen, a hydroxyl group, a carboxyl group, a cyano group, a nitro group, a 5-7 membered heterocycle, a halogenated alkyl group having 1 to 30 carbon atoms, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an alkynyl group having 2 to 30 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, etc. In addition, the above "substitution" may mean that any methylene group of the hydrocarbon group is replaced with an ether group, a thioether group, a primary to tertiary amine group, a carbonyl group, an alkenylene group, an alkynylene group, an ester group, a carbonate group, a sulfonate group, a sulfonyl group, etc.

[0071] In one embodiment, the aromatic dianhydride is 4,4'-hexafluoroisopropylidene diphthalic anhydride (6FDA), biphenyltetracarboxylic dianhydride (BPDA), oxydiphthalic dianhydride (ODPA), sulfonyl diphthalic anhydride (SO2DPA), (isopropylidenediphenoxy) bis (phthalic anhydride) (6HDBA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride (TDA), 1,2,4,5-benzene tetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride (BTDA), bis (carboxyphenyl) dimethylsilane dianhydride (SiDA), bis (dicarboxyphenoxy) diphenyl sulfide It may include dianhydride (BDSDA), pyromellitic dianhydride (PMDA), ethylene glycol bis(anhydrotrimellitate) (TMEG100), etc. These may be used alone or in combination of two or more.

[0072] A fluorinated polyimide resin can be manufactured by reacting an aromatic diamine and an aromatic dianhydride as shown in Scheme 1 below.

[0073] [Scheme 1]

[0074]

[0075] In the above scheme 1, the amine group of the aromatic diamine and the anhydride group of the aromatic dianhydride can react to form an amide group and a carboxyl group. For example, the anhydride group of the aromatic dianhydride and the amine group of the aromatic diamine can react (1) to form a polyamic acid. A polyamic acid can be prepared by polymerizing a monomer mixture containing an aromatic diamine and an aromatic dianhydride.

[0076] The above aromatic diamine and aromatic dianhydride can be mixed in a molar ratio of about 1.05:1 to 0.95:1, and reaction (1) can be performed at a temperature of 20°C to 25°C for about 15 to 20 hours.

[0077] Thereafter, the polyamic acid may be imidized (2) and converted into a fluorinated polyimide resin. The imidization may be a heat treatment, and for example, may be a heat treatment at a temperature of about 150°C to 300°C for 50 to 100 minutes. In some embodiments, the imidization may be performed under vacuum conditions.

[0078] In one embodiment, the content of the fluorinated polyimide-based resin may be from 50 wt% to 99.9 wt% of the total weight of the coating layer. In some embodiments, the content of the fluorinated polyimide-based resin may be from 60 wt% to 99 wt%, from 70 wt% to 95 wt%, or from 80 wt% to 92 wt% of the total weight of the coating layer.

[0079] Within the above range, the coating layer (120) and the electrode plate (125) can be more firmly attached, and the durability of the coating layer (120) can be improved so that boron nitride particles do not come off during battery charging and discharging.

[0080] The coating layer (120) includes boron nitride. Boron nitride is a ceramic, non-conductive, and has a high affinity for lithium metal. Accordingly, it can induce more uniform deposition of lithium moving to the electrode plate (125), while also increasing the mechanical strength of the coating layer (120).

[0081] In one embodiment, the boron nitride may be plate-shaped particles as flakes. For example, the boron nitride may be plate-shaped particles having an area (nm 2 ) divided by the thickness (nm) can be 20 nm to 100 nm.

[0082] In one embodiment, the thickness of the boron nitride may be 20 nm or less. For example, it may be 15 nm or less, 10 nm or less, 7 nm or less, or 5 nm or less. Within the above range, lithium moving to the electrode plate (125) may be more uniformly deposited while maintaining the mechanical strength of the coating layer (120). In one embodiment, the boron nitride may be hexagonal boron nitride. In the case of a hexagonal crystal structure, it may be formed of a hexagonal arrangement of boron atoms and nitrogen atoms and may have a flat 2D structure. Accordingly, the surface lithium wettability is excellent, which may induce more uniform lithium deposition. In addition, the hexagonal boron nitride may have better electrical insulation properties due to a large band gap of about 5.9 eV, and may be more physically and mechanically stable.

[0083] In one embodiment, the content of the boron nitride may be from 0.1 wt% to 50 wt% of the total weight of the coating layer. In some embodiments, the content of the boron nitride may be from 1 wt% to 40 wt%, from 5 wt% to 30 wt%, or from 8 wt% to 20 wt% of the total weight of the coating layer.

[0084] Within the above range, the mechanical strength of the coating layer (120) can be further increased, and lithium can be induced to be uniformly deposited on the surface of the electrode plate (125) without interfering with lithium accumulation.

[0085] The above coating layer may further include a fluorinated organic binder resin different from the fluorinated polyimide resin. For example, the fluorinated organic binder resin may include a polyvinylidene fluoride polymer or copolymer. For example, the fluorinated organic binder resin may include polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, etc. These may be used alone or in combination of two or more.

[0086] In one embodiment, the thickness of the coating layer may be from 1 μm to 10 μm. For example, the thickness of the coating layer may be from 3 μm to 7 μm.

[0087] According to exemplary embodiments, a composition for a coating layer including a fluorinated polyimide resin and boron nitride may be applied to at least one surface of an electrode plate (125) and dried to manufacture an electrode for a lithium secondary battery.

[0088] The composition for the above coating layer may have a solid content of about 5 wt% to 20 wt% of the total weight of the composition. The 'solid content' may include unreacted monomers or impurities in addition to the fluorinated polyimide resin and boron nitride, excluding the solvent.

[0089] Among 100 parts by weight of solid content included in the composition for the coating layer, the content of the fluorinated polyimide-based resin may be 50 parts by weight to 99.9 parts by weight, and the content of the boron nitride may be 0.1 parts by weight to 50 parts by weight.

[0090] According to exemplary embodiments, the content of boron nitride relative to the fluorinated polyimide resin in the solid content included in the composition for the coating layer may be 0.5 wt% to 40 wt%, 0.5 wt% to 10 wt%, or 0.5 wt% to 2 wt%. Within the above range, the degree of lithium deposition on the negative electrode may be more uniform, and the capacity retention rate of the lithium secondary battery may be improved.

[0091] After applying the composition for the coating layer on one surface of the electrode plate (125), the solvent can be removed by drying to form a coating layer. The drying can be performed at a temperature of about 50°C to 100°C and can be performed for a sufficient time until the solvent is removed.

[0092] A lithium secondary battery according to the present disclosure includes an electrode for a lithium secondary battery. In one embodiment, the lithium secondary battery includes the electrode for a lithium secondary battery as an anode, and may further include a cathode facing the electrode for a lithium secondary battery. In this case, the lithium secondary battery may be a lithium metal battery. The term "lithium metal battery" may refer to a type of lithium secondary battery having a high capacity and efficiency by using lithium metal itself as an anode material, unlike a lithium ion battery having an anode including a silicon and / or graphite anode material.

[0093] FIGS. 2 and 3 are schematic plan views and cross-sectional views, respectively, showing lithium secondary batteries according to exemplary embodiments.

[0094] Referring to FIGS. 2 and 3, a lithium secondary battery may include a positive electrode (100) and an electrode (130) for a lithium secondary battery as a negative electrode opposite to the positive electrode (100).

[0095] The positive electrode (100) may include a positive electrode current collector (105) and a positive electrode composite layer (110) disposed on at least one surface of the positive electrode current collector (105).

[0096] The positive electrode current collector may comprise stainless steel, nickel, aluminum, titanium, or an alloy thereof. The positive electrode current collector may also comprise aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver. The thickness of the positive electrode current collector is not limited thereto, but may be, for example, 10 μm to 50 μm.

[0097] The positive electrode active material layer may include a positive electrode active material. The positive electrode active material may include a compound capable of reversibly intercalating and deintercalating lithium ions.

[0098] According to exemplary embodiments, the positive electrode active material may include a lithium-nickel metal oxide. The lithium-nickel metal oxide may further include at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0099] In some embodiments, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or crystal structure represented by the following chemical formula 2.

[0100] [Chemical Formula 2]

[0101] Li x Ni a M b O 2+z

[0102] In Chemical Formula 2, 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b≤0.4, -0.5≤z≤0.1 may be satisfied. As described above, M may include Co, Mn, and / or Al.

[0103] The chemical structure represented by Chemical Formula 2 represents the bonding relationship included in the layered structure or crystal structure of the positive electrode active material and does not exclude other additional elements. For example, M includes Co and / or Mn, and Co and / or Mn can serve as the main active element of the positive electrode active material together with Ni. Chemical Formula 2 is provided to express the bonding relationship of the above main active elements and should be understood as a formula encompassing the introduction and substitution of additional elements.

[0104] In one embodiment, auxiliary elements may be further included in addition to the main active element to enhance the chemical stability of the positive electrode active material or the layered structure / crystal structure. The auxiliary elements may be incorporated into the layered structure / crystal structure to form bonds, and in this case, it should be understood that they are also included within the chemical structure range represented by Chemical Formula 2.

[0105] The auxiliary element may include, for example, at least one of Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, or Zr. The auxiliary element may also act as an auxiliary active element that contributes to the capacity / output activity of the positive electrode active material together with Co or Mn, for example, Al.

[0106] For example, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or crystal structure represented by the following chemical formula 2-1.

[0107] [Chemical Formula 2-1]

[0108] Li x Ni a M1 b1 M2 b2 O 2+z

[0109] In Chemical Formula 2-1, M1 may include Co, Mn, and / or Al. M2 may include the auxiliary elements described above. In Chemical Formula 2-1, 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b1+b2≤0.4, -0.5≤z≤0.1 may be satisfied.

[0110] The above-described positive electrode active material may further include a coating element or doping element. For example, elements substantially identical to or similar to the above-described auxiliary elements may be used as the coating element or doping element. For example, the above-described elements may be used singly or in combination of two or more.

[0111] The above coating element or doping element may be present on the surface of the lithium-nickel metal oxide particle, or may penetrate through the surface of the lithium-nickel metal composite oxide particle and be included in the bonding structure represented by the above chemical formula 2 or chemical formula 2-1.

[0112] The above positive electrode active material may include a nickel-cobalt-manganese (NCM) lithium oxide. In this case, an NCM lithium oxide with an increased nickel content may be used.

[0113] Ni can be provided as a transition metal associated with the output and capacity of a lithium secondary battery. Therefore, by employing a high-content (High-Ni) composition as described above in the positive electrode active material, a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0114] However, as the Ni content increases, the long-term storage stability and lifespan stability of the cathode or secondary battery may relatively deteriorate, and side reactions with the electrolyte may also increase. However, according to exemplary embodiments, the inclusion of Co can maintain electrical conductivity, while improving lifespan stability and capacity retention characteristics through Mn.

[0115] The content of Ni (e.g., the mole fraction of nickel among the total moles of nickel, cobalt, and manganese) in the NCM-based lithium oxide may be 0.6 or more, 0.7 or more, or 0.8 or more. In some embodiments, the content of Ni may be 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95.

[0116] In some embodiments, the positive electrode active material may include a lithium cobalt oxide-based active material, a lithium manganese oxide-based active material, a lithium nickel oxide-based active material, or a lithium iron phosphate (LFP)-based active material (e.g., LiFePO4).

[0117] In some embodiments, the positive electrode active material may include, for example, a Mn-rich active material, an LLO (Li rich layered oxide) / OLO (Over Lithiated Oxide) active material, or a Co-less active material having a chemical structure or crystal structure represented by Chemical Formula 3.

[0118] [Chemical Formula 3]

[0119] p[Li2MnO3]·(1-p)[Li q JO2]

[0120] In chemical formula 3, 0 <p<1이고, 0.9≤q≤1.2이며, J는 Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg 및 B 중 적어도 하나의 원소를 포함할 수 있다.

[0121] For example, a positive electrode slurry can be prepared by mixing the positive electrode active material in a solvent. The positive electrode slurry can be coated on a positive electrode current collector, and then dried and rolled to prepare a positive electrode mixture layer. The coating process can be performed by methods such as gravure coating, slot die coating, multilayer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, casting, etc., but is not limited thereto. The positive electrode mixture layer can further include a binder and optionally can further include a conductive agent, a thickener, etc.

[0122] Non-limiting examples of solvents used in the preparation of the above positive electrode slurry include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, and the like.

[0123] The above binder may include polyvinylidene fluoride (PVDF), vinylidene fluoride-co-hexafluoropropylene copolymer, polyacrylonitrile, polymethylmethacrylate, acrylonitrile butadiene rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), etc. In one embodiment, a PVDF series binder may be used as the positive electrode binder.

[0124] The conductive material may be added to enhance the conductivity and / or mobility of lithium ions or electrons of the positive electrode composite layer. For example, the conductive material may include, but is not limited to, carbon-based conductive materials such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fiber (VGCF), carbon fiber, and / or metal-based conductive materials including perovskite materials such as tin, tin oxide, titanium oxide, LaSrCoO3, and LaSrMnO3.

[0125] If necessary, the positive electrode slurry may further include a thickener and / or a dispersant. In one embodiment, the positive electrode slurry may include a thickener such as carboxymethyl cellulose (CMC).

[0126] In some embodiments, a separator (140) may be interposed between the positive electrode (100) and the electrode (130) for a lithium secondary battery. The separator (140) may include a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, an ethylene / methacrylate copolymer, or the like. The separator (140) may also include a nonwoven fabric formed of high-melting-point glass fibers, polyethylene terephthalate fibers, or the like.

[0127] According to exemplary embodiments, an electrode cell is defined by a cathode (100), an electrode for a lithium secondary battery (130), and a separator (140), and a plurality of the electrode cells may be stacked to form an electrode assembly (150) in the form of, for example, a jelly roll. For example, the electrode assembly (150) may be formed by winding, lamination, folding, or the like of the separator (140).

[0128] An electrode assembly (150) may be housed together with an electrolyte within a case (160) to define a lithium secondary battery. According to exemplary embodiments, a non-aqueous electrolyte may be used as the electrolyte.

[0129] The non-aqueous electrolyte may include a lithium salt as an electrolyte and an organic solvent. The lithium salt may be, for example, Li + X - is expressed as and the anion of the lithium salt (X - ) as F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - Examples include:

[0130] Examples of the organic solvent that can be used include propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, and tetrahydrofuran. These may be used alone or in combination of two or more.

[0131] In other embodiments, a solid electrolyte layer may be interposed between the positive electrode and the electrode for a lithium secondary battery. The solid electrolyte layer may include a sulfide-based electrolyte, an oxide-based electrolyte, or a polymer electrolyte.

[0132] In this case, the lithium secondary battery may not include a separator and an electrolyte. The solid electrolyte layer substantially functions as a separator and can prevent short circuits between the positive electrode and the electrode for a lithium secondary battery. In addition, the solid electrolyte layer allows lithium ions to move between the positive electrode and the electrode for a lithium secondary battery.

[0133] The above sulfide-based solid electrolyte may include an LPS-based solid electrolyte containing Li, P, and S, an LGPS-based solid electrolyte containing Li, P, Ge, and S, or an LSiPSCl-based solid electrolyte containing Li, Si, P, S, and Cl.

[0134] For example, Li2S-P2S5, Li as a sulfide-based solid electrolyte 10 GeP2S 12 , Li 10 SnP2S 12 , Li 9.54 Si 1.74 P1.44 S 11.7 Cl 0.3 , Li 10 (Si 0.5 Ge 0.5 )P2S 12 , Li 10 (Ge 0.5 Sn 0.5 )P2S 12 , Li 10 (Si 0.5 Sn 0.5 )P2S 12 , Li 10 GeP2S 11.7 O 0.3 , Li 9.6 P3S 12 , Li9P3S9O3, Li 10.35 Ge 1.35 P 1.65 S 12 , Li 10.35 Si 1.35 P 1.65 S 12 , Li 9.81 Sn 0.81 P 2.19 S 12 , Li 9.42 Si 1.02 P 2.1 S 9.96 O 2.04 , Li6PS5Cl, etc. can be used.

[0135] The above oxide-based solid electrolyte may include a metal oxide or an ion-conducting compound containing oxygen. For example, as the oxide-based solid electrolyte, Al2O3, ZnO2, Ce2O3, TiO2, ZrO2, HfO2, MnO2, MgO, WO 2, Metal oxides such as V2O5, LLTO compounds, LLZO compounds, Li6La2CaTa2O 12 , Li6La2ANb2O 12 (A is Ca or Sr), Li2Nd3TeSbO 12 , Li3BO 2.5 N 0.5 , Li9SiAlO8, LAGP compounds, LATP compounds, Li 1+x Ti 2-xAl x Si y (PO4) 3-y (0≤x≤1, 0≤y≤1), LiAl x Zr 2-x (PO4)3(0≤x≤1, 0≤y≤1), LiTi x Zr 2-x Examples include (PO4)3(0≤x≤1, 0≤y≤1), LISICON compounds, LIPON compounds, perovskite compounds, and NASICON compounds.

[0136] As illustrated in FIGS. 2 and 3, electrode tabs (positive electrode tabs and negative electrode tabs) may protrude from the positive electrode collector (105) and negative electrode collector (125) belonging to each electrode cell and extend to one side of the case (160). The electrode tabs may be fused together with the one side of the case (160) to form electrode leads (positive electrode leads (107) and negative electrode leads (127)) that extend or are exposed to the outside of the case (160).

[0137] The above lithium secondary battery can be manufactured in a cylindrical, square, pouch or coin shape using, for example, a can.

[0138] Hereinafter, embodiments of the present disclosure will be further described with reference to specific experimental examples. The examples and comparative examples included in the experimental examples are merely illustrative of the present invention and do not limit the scope of the appended claims. It will be apparent to those skilled in the art that various changes and modifications to the examples are possible within the scope and technical idea of ​​the present disclosure, and it is also natural that such changes and modifications fall within the scope of the appended claims.

[0139] The embodiments of the present disclosure described above include the following aspects, and can be implemented through at least one of the following aspects. A first aspect. An electrode plate including lithium metal; and

[0140] An electrode for a lithium secondary battery, comprising a coating layer disposed on at least one surface of the electrode plate and containing a fluorinated polyimide resin and boron nitride.

[0141] Second aspect. In the first aspect, the fluorinated polyimide resin comprises a repeating unit derived from an aromatic diamine and a repeating unit derived from an aromatic dianhydride,

[0142] An electrode for a lithium secondary battery, wherein at least one of the aromatic diamine and the aromatic dianhydride contains a fluorine atom.

[0143] Third aspect. An electrode for a lithium secondary battery, wherein the aromatic diamine comprises two aminophenyl structures in the second aspect.

[0144] Aspect 4. An electrode for a lithium secondary battery, wherein in any one of the second aspect and the third aspect, the aromatic diamine is a biphenyl diamine substituted with at least one fluoroalkyl group having 1 to 3 carbon atoms.

[0145] Aspect 5. An electrode for a lithium secondary battery, wherein in any one of aspects 2 to 4, the aromatic diamine comprises at least one selected from the group consisting of 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB), 2,2'-bis(trifluoromethyl)-4,4'-benzidine (TFDB), and 4,4'-oxybis[3-trifluoromethyl]aniline (6FODA).

[0146] Aspect 6. In any one of aspects 2 to 5, the aromatic dianhydride comprises a compound represented by the following chemical formula 1: An electrode for a lithium secondary battery:

[0147] [Chemical Formula 1]

[0148]

[0149] (In chemical formula 1, L is a divalent organic group having 1 to 30 carbon atoms).

[0150] Aspect 7. In any one of the second to sixth aspects, the aromatic dianhydride is 4,4'-hexafluoroisopropylidene diphthalic anhydride (6FDA), biphenyltetracarboxylic dianhydride (BPDA), oxydiphthalic dianhydride (ODPA), sulfonyl diphthalic anhydride (SO2DPA), (isopropylidenediphenoxy) bis (phthalic anhydride) (6HDBA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride (TDA), 1,2,4,5-benzene tetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride (BTDA), bis (carboxyphenyl) dimethylsilane dianhydride (SiDA), bis (dicarboxyphenoxy) An electrode for a lithium secondary battery, comprising at least one selected from the group consisting of diphenyl sulfide dianhydride (BDSDA), pyromellitic dianhydride (PMDA), and ethylene glycol bis(anhydrotrimellitate) (TMEG100).

[0151] Aspect 8. An electrode for a lithium secondary battery, wherein in any one of aspects 1 to 7, the content of the fluorinated polyimide resin is 50 wt% to 99.9 wt% of the total weight of the coating layer.

[0152] Aspect 9. An electrode for a lithium secondary battery, wherein in any one of aspects 1 to 8, the boron nitride comprises hexagonal boron nitride flakes.

[0153] Aspect 10. An electrode for a lithium secondary battery, wherein in any one of aspects 1 to 9, the average particle diameter (D50) of the boron nitride is 10 nm to 100 nm.

[0154] Aspect 11. An electrode for a lithium secondary battery, wherein the content of boron nitride in any one of aspects 1 to 10 is 0.1 wt% to 50 wt% of the total weight of the coating layer.

[0155] Aspect 12. An electrode for a lithium secondary battery, wherein the coating layer has a thickness of 1 μm to 10 μm in any one of aspects 1 to 11.

[0156] A 13th aspect. A lithium secondary battery comprising an electrode for a lithium secondary battery according to any one of the first to twelfth aspects as a negative electrode, and further comprising a positive electrode opposite to the electrode for the lithium secondary battery.

[0157]

[0158] Example 1

[0159] (1) Manufacturing of fluorinated polyimide resin

[0160] A solution was prepared by adding 3.36 g of 2,2'-bis(trifluoromethyl)benzidine (TFDB) to 31 g of diethylformamide (DEF). 4.44 g of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) was added to the solution, and the mixture was stirred at room temperature for 18 hours to prepare a polyamic acid (F-polyamic acid) dispersion. At this time, the molar ratio of TFDB and 6FDA was 1.05:1, and the content of solids (polyamic acid) in the solution was 20 wt%.

[0161] The above polyamic acid dispersion was heat-treated at a temperature of 200°C and under vacuum conditions for 1 hour to carry out imidization, and finally a fluorinated polyimide-based resin was manufactured.

[0162] (2) Manufacturing of electrodes for lithium secondary batteries

[0163] The above fluorinated polyimide resin was added to N-methylpyrrolidone (NMP) to a solid content of 10 wt%, and stirred to prepare a fluorinated polyimide resin dispersion. 99.9 parts by weight of the above fluorinated polyimide resin dispersion (9.99 parts by weight of fluorinated polyimide resin, 89.91 parts by weight of NMP) was added boron nitride (thickness: 3.0 nm, diameter: less than 100 nm, BET specific surface area: 400 m 2 / g or less, Nextirials) was added at 0.1 part by weight to prepare a composition for a coating layer.

[0164] The composition for the above coating layer was applied onto one side of a lithium metal plate (20 μm thick) and vacuum dried overnight in an oven at 80°C to manufacture an electrode for a lithium secondary battery. At this time, the thickness of the coating layer was 3 μm.

[0165]

[0166] (3) Manufacturing of lithium secondary batteries

[0167] LiNi as positive electrode active material 0.6 Co 0.2 Mn 0.2 A slurry of positive electrode active material was prepared by adding N-methylpyrrolidone as a solvent to a mixture containing O2, carbon black as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of 94:2:4. The positive electrode active material slurry was coated on one surface of an aluminum current collector (thickness 10 ㎛), and the resulting mixture was dried and rolled to prepare a positive electrode having a positive electrode active material layer of approximately 40 ㎛ in thickness.

[0168] A positive electrode and a negative electrode (electrode for a lithium secondary battery) were notched to a predetermined size and laminated, and a separator (polyethylene, 13 μm thick) was interposed between the positive electrode and the negative electrode. The positive electrode / separator / negative electrode assembly was placed in a coin-shaped case, and an electrolyte was injected to manufacture a coin cell.

[0169] The electrolyte was prepared by dissolving 1.0 LiPF6 in a mixed solvent of EC / EMC (3 / 7; volume ratio) and adding 5 wt% of fluoroethylene carbonate (FEC).

[0170]

[0171] Example 2

[0172] 99.7 parts by weight of a fluorinated polyimide resin dispersion (9.97 parts by weight of fluorinated polyimide resin, 89.73 parts by weight of NMP) was added boron nitride (thickness: 3.0 nm, diameter: less than 100 nm, BET specific surface area: 400 m 2 An electrode for a lithium secondary battery and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a composition for a coating layer was manufactured by adding 0.3 parts by weight of Nextirials ( / g or less).

[0173]

[0174] Example 3

[0175] 99.5 parts by weight of a fluorinated polyimide resin dispersion (9.95 parts by weight of fluorinated polyimide resin, 89.55 parts by weight of NMP) was added boron nitride (thickness: 3.0 nm, diameter: less than 100 nm, BET specific surface area: 400 m 2 An electrode for a lithium secondary battery and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a composition for a coating layer was manufactured by adding 0.5 parts by weight of Nextirials ( / g or less).

[0176]

[0177] Example 4

[0178] 99.3 parts by weight of a fluorinated polyimide resin dispersion (9.93 parts by weight of fluorinated polyimide resin, 89.37 parts by weight of NMP) was added boron nitride (thickness: 3.0 nm, diameter: less than 100 nm, BET specific surface area: 400 m 2An electrode for a lithium secondary battery and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a composition for a coating layer was manufactured by adding 0.7 parts by weight of Nextirials ( / g or less).

[0179]

[0180] Example 5

[0181] 99 parts by weight of a fluorinated polyimide resin dispersion (9.9 parts by weight of fluorinated polyimide resin, 89.1 parts by weight of NMP) was added boron nitride (thickness: 3.0 nm, diameter: less than 100 nm, BET specific surface area: 400 m 2 An electrode for a lithium secondary battery and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a composition for a coating layer was manufactured by adding 1 part by weight of Nextirials ( / g or less).

[0182]

[0183] Example 6

[0184] 98 parts by weight of a fluorinated polyimide resin dispersion (9.8 parts by weight of fluorinated polyimide resin, 88.2 parts by weight of NMP) was added boron nitride (thickness: 3.0 nm, diameter: less than 100 nm, BET specific surface area: 400 m 2 An electrode for a lithium secondary battery and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a composition for a coating layer was manufactured by adding 2 parts by weight of Nextirials ( / g or less).

[0185]

[0186] Example 7

[0187] 97 parts by weight of a fluorinated polyimide resin dispersion (9.7 parts by weight of fluorinated polyimide resin, 87.3 parts by weight of NMP) was added boron nitride (thickness: 3.0 nm, diameter: less than 100 nm, BET specific surface area: 400 m 2An electrode for a lithium secondary battery and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a composition for a coating layer was manufactured by adding 3 parts by weight of Nextirials ( / g or less).

[0188]

[0189] Example 8

[0190] 96 parts by weight of a fluorinated polyimide resin dispersion (9.6 parts by weight of fluorinated polyimide resin, 86.4 parts by weight of NMP) was added boron nitride (thickness: 3.0 nm, diameter: less than 100 nm, BET specific surface area: 400 m 2 An electrode for a lithium secondary battery and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a composition for a coating layer was manufactured by adding 4 parts by weight of Nextirials ( / g or less).

[0191]

[0192] Comparative Example 1

[0193] An electrode for a lithium secondary battery and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a fluorinated polyimide resin dispersion was applied to one side of a lithium metal plate (20 ㎛ thick) and vacuum-dried overnight in an oven at 80°C to manufacture a negative electrode for a lithium battery.

[0194]

[0195] Comparative Example 2

[0196] An electrode for a lithium secondary battery and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a composition for a coating layer was manufactured by adding 1 part by weight of silicon dioxide (diameter: 200 nm, Sigma-Aldrich) to 99 parts by weight of a fluorinated polyimide-based resin dispersion (9.9 parts by weight of fluorinated polyimide-based resin, 89.1 parts by weight of NMP).

[0197]

[0198] Comparative Example 3

[0199] An electrode for a lithium secondary battery and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a composition for a coating layer was manufactured by adding 5 parts by weight of silicon dioxide (diameter: 200 nm, Sigma-Aldrich) to 86 parts by weight of a fluorinated polyimide-based resin dispersion (5 parts by weight of fluorinated polyimide-based resin, 81 parts by weight of NMP).

[0200]

[0201] Comparative Example 4

[0202] Polydimethylsiloxane (PDMS) precursor (Base, Sylgard 184, Dow) and dimethylsiloxane oligomer (Curing agent, Dow) were mixed at a weight ratio of 10:1 and stirred. The mixture was then cast onto a lithium metal plate (20 μm thick) using a doctor blade and vacuum-dried overnight in an oven at 80°C to form a polydimethylsiloxane (PDMS) film. The coating layer thickness at this time was 3 μm.

[0203] An electrode for a lithium secondary battery and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a film was formed on a lithium metal plate using polydimethylsiloxane.

[0204]

[0205] Experimental Example 1: Lithium Electrodeposition Evaluation

[0206] A positive electrode (thickness 100 um) containing a copper current collector was placed on the electrode (thickness 8 um) for lithium secondary batteries of the examples and comparative examples. 4 mAh / cm 2 , 1 mA / cm 2 Lithium was deposited on a lithium secondary battery electrode, and the battery was disassembled to separate the negative electrode. Surface images of the separated negative electrodes were captured using a camera and a scanning electron microscope (SEM), and the surfaces of each negative electrode were compared.

[0207] The degree of electrodeposition is shown in Table 1 by comparing the cathode surfaces of the examples and comparative examples.

[0208] ◎: Electrodeposition was uniform, and lithium dendrites were observed on less than 5% of the total area.

[0209] ○: Electrodeposition was uniform, and lithium dendrites were observed on less than 30% of the total area.

[0210] △: Uneven deposition or lithium dendrites observed over 30% of the total area

[0211] Figures 4a and 4b are photographs and SEM images of the cathode surface of Example 5.

[0212] Figures 5a and 5b are a photograph and an SEM image of the cathode surface of Example 6, respectively.

[0213] Figures 6a and 6b are a photograph and an SEM image of the cathode surface of Example 7, respectively.

[0214] Figures 7a and 7b are a photograph and an SEM image of the cathode surface of Example 8, respectively.

[0215] Figures 8a and 8b are photographs and SEM images of the cathode surface of Comparative Example 1.

[0216] Figures 9a and 9b are photographs and SEM images of the cathode surface of Comparative Example 2.

[0217] Figures 10a and 10b are a photograph and an SEM image of the cathode surface of Comparative Example 3, respectively.

[0218] Figure 11 is a photograph of the cathode surface of Comparative Example 4.

[0219] In addition, Fig. 12 shows an SEM image of the cross-section of the cathode of Example 5, and Fig. 13 shows an SEM image of the cross-section of the cathode of Comparative Example 1.

[0220] Referring to FIGS. 4a to 10b, 12 and 13, the negative electrode of the embodiment showed that even when charge and discharge were repeated, lithium was uniformly deposited on the negative electrode surface, so that dendrites were not formed significantly, and the coating layer was not damaged, so that the negative electrode surface was smooth even when viewed with the naked eye.

[0221] Referring to Figure 11, lithium deposition did not occur because the PDMS coating layer did not allow lithium ions to pass through during lithium deposition.

[0222] On the other hand, the negative electrodes of the comparative examples had uneven lithium deposition on the negative electrode surface during repeated charge and discharge cycles, resulting in an unsmooth surface. Furthermore, some areas showed signs of damage to the coating layer or excessive lithium deposition, resulting in discoloration. While not intended to be bound by a specific theory, it is thought that in Comparative Examples 2 and 3, the lithium formed droplets in agglomeration and was locally deposited because the silicon dioxide did not directly react with lithium metal.

[0223] The negative electrode of the embodiment comprises boron nitride and a fluorinated polyimide-based resin. The coating layer comprising boron nitride and a fluorinated polyimide-based resin has high mechanical strength and acts as a physical barrier to enable more uniform growth of lithium on the surface of the lithium metal negative electrode. In addition, boron nitride has a higher lithium affinity than silicon dioxide, which further suppresses dendrite formation on the surface of the negative electrode.

[0224]

[0225] Experimental Example 2: Capacity Retention Rate Evaluation

[0226] The lithium secondary batteries of the examples and comparative examples were charged (CC-CV 0.1C 4.3V 0.1C CUT-OFF) and discharged (CC 0.1C 2.7V CUT-OFF) in a 25 ℃ chamber as the first cycle. Then, the charge (CC-CV 0.2C 4.3V 0.1C CUT-OFF) and discharge (CC 0.2C 2.7V CUT-OFF) were made as the second cycle. After that, a cycle test was performed by charging (CC-CV 0.5C 4.3V 0.1C CUT-OFF) and discharging (CC 0.5C 2.7V CUT-OFF). The discharge capacity value after each cycle with respect to the initial discharge capacity was calculated as the capacity retention rate (%), and the number of cycles at which the capacity retention rate was 70% with respect to the number of cycles is shown in Table 1 below.

[0227] Figure 1 is a graph of the capacity retention rate according to the number of cycles of the lithium secondary batteries of Example 5 and Comparative Examples 1 and 2.

[0228] Referring to Fig. 14, the lithium secondary battery of Example 5 had a high capacity retention rate of 70% or more up to about 70 cycles. The capacity retention rate of the lithium secondary battery of Comparative Example 1 dropped sharply from about 40 cycles, and the capacity retention rate of the lithium secondary battery of Comparative Example 2 dropped sharply from about 45 cycles.

[0229] Electrodeposition Evaluation Cycle Number Example 1◎100 Example 2◎85 Example 3◎81 Example 4◎75 Example 5○73 Example 6○55 Example 7○54 Example 8○52 Comparative Example 1△39 Comparative Example 2△42 Comparative Example 3△40 Comparative Example 4△-

[0230]

[0231] The cathodes of the examples included a high-mechanical-strength coating layer, which prevented uneven accumulation of lithium metal on the cathode surface even during repeated charge and discharge cycles. Consequently, the charge and discharge stability of the cathode was enhanced, leading to improved lifespan characteristics of the lithium secondary battery.

[0232] In Comparative Example 4, electrodeposition occurred very unevenly, and the secondary battery could not be operated.

[0233] The above description is merely an example of applying the principles of the present disclosure, and other configurations may be further included without departing from the scope of the present disclosure.

Claims

An electrode plate comprising lithium metal; and An electrode for a lithium secondary battery, comprising a coating layer disposed on at least one surface of the electrode plate and containing a fluorinated polyimide resin and boron nitride. In the first paragraph, the fluorinated polyimide resin includes a repeating unit derived from an aromatic diamine and a repeating unit derived from an aromatic dianhydride, An electrode for a lithium secondary battery, wherein at least one of the aromatic diamine and the aromatic dianhydride contains a fluorine atom. An electrode for a lithium secondary battery, wherein the aromatic diamine in the second paragraph comprises two aminophenyl structures. An electrode for a lithium secondary battery, wherein the aromatic diamine is a biphenyl diamine substituted with at least one fluoroalkyl group having 1 to 3 carbon atoms, in any one of claims 2 and 3. An electrode for a lithium secondary battery, wherein the aromatic diamine comprises at least one selected from the group consisting of 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB), 2,2'-bis(trifluoromethyl)-4,4'-benzidine (TFDB), and 4,4'-oxybis[3-trifluoromethyl]aniline (6FODA), in any one of claims 2 to 4. An electrode for a lithium secondary battery, wherein the aromatic dianhydride comprises a compound represented by the following chemical formula 1 in any one of claims 2 to 5: [Chemical Formula 1] (In chemical formula 1, L is a divalent organic group having 1 to 30 carbon atoms). In any one of claims 2 to 6, the aromatic dianhydride is 4,4'-hexafluoroisopropylidene diphthalic anhydride (6FDA), biphenyltetracarboxylic dianhydride (BPDA), oxydiphthalic dianhydride (ODPA), sulfonyl diphthalic anhydride (SO2DPA), (isopropylidenediphenoxy) bis (phthalic anhydride) (6HDBA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride (TDA), 1,2,4,5-benzene tetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride (BTDA), bis (carboxyphenyl) dimethylsilane dianhydride (SiDA), bis (dicarboxyphenoxy) An electrode for a lithium secondary battery, comprising at least one selected from the group consisting of diphenyl sulfide dianhydride (BDSDA), pyromellitic dianhydride (PMDA), and ethylene glycol bis(anhydrotrimellitate) (TMEG100). An electrode for a lithium secondary battery, wherein the content of the fluorinated polyimide resin in any one of claims 1 to 7 is 50 wt% to 99.9 wt% of the total weight of the coating layer. An electrode for a lithium secondary battery according to any one of claims 1 to 8, wherein the boron nitride comprises hexagonal boron nitride flakes. An electrode for a lithium secondary battery, wherein the average particle diameter (D50) of the boron nitride is 10 nm to 100 nm in any one of claims 1 to 9. An electrode for a lithium secondary battery, wherein the content of boron nitride is 0.1 wt% to 50 wt% of the total weight of the coating layer, in any one of claims 1 to 10. An electrode for a lithium secondary battery, wherein the coating layer has a thickness of 1 µm to 10 µm according to any one of claims 1 to 11. A lithium secondary battery comprising an electrode for a lithium secondary battery according to any one of claims 1 to 12 as a negative electrode, and further comprising a positive electrode facing the electrode for a lithium secondary battery.

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