Negative electrode current collector and method for producing the same

Abstract

The negative electrode current collector according to the present invention includes a copper thin film having peaks and valleys formed thereon, and metal particles disposed in at least some of the valleys, the metal particles having a higher standard reduction potential than lithium ions and capable of forming a solid solution with lithium (Li).

Description

[Technical Field]

[0001] The present invention relates to a negative electrode current collector and a method for producing the same. [Background technology]

[0002] As technological development and demand for electric vehicles and energy storage systems (ESS) increases, the demand for batteries as energy sources is rapidly increasing, and research into batteries that can meet various requirements is being conducted. In particular, research into lithium secondary batteries, which have high energy density and excellent life and cycle characteristics as power sources for such devices, is being actively conducted.

[0003] In general, a lithium secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, an electrolyte, etc. The negative electrode may have a structure in which a negative electrode active material layer is laminated on one or both sides of a negative electrode current collector, and the negative electrode current collector is typically made of a copper thin film.

[0004] On the other hand, lithium metal batteries use lithium metal as the negative electrode active material, and utilize an electrochemical reaction in which the lithium metal at the negative electrode loses electrons and moves to the positive electrode through the electrolyte when the battery is discharged, and lithium ions move to the negative electrode through the electrolyte and are stored in the negative electrode active material when the battery is charged. Lithium metal batteries have the advantage of theoretically having a significantly higher energy capacity than commercial lithium-ion batteries, which use graphite or other materials as the negative electrode active material.

[0005] However, when a lithium metal battery using a copper thin film as a negative electrode current collector is charged and discharged, the flux of lithium ions concentrates around defects (terraces, kinks, and / or steps) in the copper thin film, causing uneven lithium nucleation and dendrite growth. For example, when a copper thin film is used as a negative electrode current collector in a lithium metal battery, lithium dendrites grow randomly on the surface of the copper thin film during charge and discharge, and the lithium dendrites penetrate the separator, causing a short circuit between the positive and negative electrodes.

[0006] Therefore, there is a need to develop a technology to suppress the random growth of lithium dendrites on the negative electrode current collector in lithium metal batteries. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention is intended to solve the above problems, and provides a negative electrode current collector capable of suppressing random growth of lithium dendrites on the negative electrode current collector, and a method for producing the same. [Means for solving the problem]

[0008] According to one embodiment of the present invention, there is provided a negative electrode current collector including: a copper thin film having peaks and valleys formed thereon; and metal particles disposed in at least some of the valleys, the metal particles having a standard reduction potential higher than that of lithium ions and capable of forming a solid solution with lithium (Li).

[0009] The metal particles may be silver (Ag).

[0010] The size of the metal particles may be 0.1 nm to 1000 nm.

[0011] The metal particles may be hydrophilic particles.

[0012] At least some of the recesses according to the present invention may include hydrophilic groups.

[0013] At least some of the protrusions according to the present invention may include hydrophobic groups, in which case at least some of the protrusions may include at least one of silane, polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE).

[0014] The copper thin film according to the present invention may be an electrolytic copper foil or a rolled copper foil.

[0015] The negative electrode current collector according to the present invention has a thickness of 4 μm to 20 μm or a center line surface roughness (R a ) may be 0.1 μm to 0.5 μm.

[0016] According to another embodiment of the present invention, there is provided a method for manufacturing a negative electrode current collector, the method including the steps of: manufacturing a copper thin film having protrusions and recesses formed therein; and disposing, in at least some of the recesses, metal particles having a standard reduction potential higher than that of lithium ions and capable of forming a solid solution with lithium (Li).

[0017] The step of disposing metal particles capable of forming a solid solution with lithium (Li) in at least some of the recesses may include the steps of hydrophobizing at least some of the protrusions and coating the copper thin film with hydrophilic metal particles. In this case, the step of hydrophobizing at least some of the protrusions may include coating the surface of the copper thin film with at least one of silane, polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE).

[0018] In the method for producing a negative electrode current collector of the present invention, the copper thin film may be produced by an electrolytic plating process.

[0019] According to yet another embodiment of the present invention, there is provided a lithium secondary battery including a negative electrode including the above-described negative electrode current collector, a positive electrode, and a separator disposed between the negative electrode and the positive electrode. [Effects of the Invention]

[0020] The present invention provides an anode current collector in which metal particles with a higher standard reduction potential than lithium ions are disposed in valleys formed in a copper thin film. The metal particles act as seeds that cause uniform lithium distribution on the anode current collector during charging and discharging of a battery. Specifically, the metal particles are used to prevent lithium electrodeposited on the anode current collector from becoming Li 0 The metal particles act as heterogeneous nucleation sites by forming a solid solution with the lithium before forming a pure Li phase. As a result, the metal particles can lower the interface energy of the negative electrode current collector and regulate the nucleation that initiates lithium dendrite growth during battery charge and discharge to an appropriate level, thereby preventing the dendritic growth of lithium electrodeposited on the negative electrode current collector and ensuring uniform lithium deposition. In addition, by suppressing the random growth of lithium dendrites on the surface of the copper thin film, the problem of lithium dendrites penetrating the separator and causing a short circuit between the positive and negative electrodes can be prevented.

[0021] The method for manufacturing a negative electrode current collector according to the present invention does not involve artificial photolithography or dry chemical etching processes, thereby simplifying the process steps and reducing manufacturing costs.

[0022] In addition, the method for manufacturing a negative electrode current collector according to the present invention is highly applicable since both electrolytic copper foil and rolled copper foil can be used as the copper thin film contained in the negative electrode current collector. [Brief explanation of the drawings]

[0023] The drawings attached to the specification illustrate preferred embodiments of the present invention and, together with the above-described content of the invention, serve to further understand the technical concept of the present invention, and therefore the present invention should not be interpreted as being limited solely to the matters depicted in such drawings.

[0024] [Figure 1] FIG. 2 is a cross-sectional view of a negative electrode current collector according to the present invention. [Figure 2] This is a phase equilibrium diagram of lithium and copper. [Figure 3] This is a phase equilibrium diagram of lithium and silver. DETAILED DESCRIPTION OF THE INVENTION

[0025] The advantages and features of the present invention, as well as methods for achieving them, will become more apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and can be realized in various different forms. The present embodiments are provided merely to complete the disclosure of the present invention and to enable those skilled in the art to fully understand the scope of the invention. The present invention is defined only by the scope of the claims. The same reference numerals refer to the same elements throughout the specification.

[0026] Unless otherwise defined, all terms (including technical and scientific terms) used herein will be used in the sense commonly understood by those skilled in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries will not be interpreted ideally or excessively unless clearly defined otherwise.

[0027] The terms used in this specification are for the purpose of describing the embodiments and are not intended to limit the present invention. In this specification, the singular includes the plural unless otherwise stated in the phrase. As used in this specification, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other elements in addition to the elements mentioned.

[0028] In this specification, when a part is said to include a certain component, it does not mean that it may further include other components, unless otherwise specified.

[0029] In this specification, the expression "A and / or B" means A, B, or A and B.

[0030] In this specification, "%" means % by weight unless expressly indicated otherwise.

[0031] <Negative electrode current collector> The negative electrode current collector according to the present invention includes a copper thin film having peaks and valleys formed thereon, and metal particles disposed in at least some of the valleys, the metal particles having a higher standard reduction potential than lithium ions and capable of forming a solid solution with lithium (Li).

[0032] The negative electrode current collector of the present invention will be described in more detail below with reference to FIG.

[0033] Fig. 1 is a cross-sectional view of a negative electrode current collector 100 according to the present invention. The negative electrode current collector 100 according to the present invention does not cause chemical changes in the battery and is conductive. As shown in Fig. 1, the negative electrode current collector 100 includes a copper thin film 110 and metal particles 120.

[0034] The copper thin film 110 may be an electrolytic copper foil or a rolled copper foil. Specifically, the copper thin film 110 may be an electrolytic copper foil manufactured by an electrolytic plating process. The copper thin film 110 includes peaks 112 and valleys 114. Specifically, the copper thin film 110 may include defects, and the peaks 112 and valleys 114 may be formed on the surface of the copper thin film 110.

[0035] The protrusions 112 refer to regions on the surface of the copper thin film 110 that protrude relatively more than the recesses 114. At least some of the protrusions 112 may contain a hydrophobic group. Specifically, at least some of the protrusions 112 may contain an oil-based binder, more specifically, at least one of silane, polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE). The protrusions 112 containing the hydrophobic materials listed above have hydrophobic properties.

[0036] The recesses 114 refer to valley regions on the surface of the copper thin film 110 that are relatively recessed compared to the protrusions 112. Since the copper thin film 110 of the present invention is an electrolytic copper foil and has hydrophilicity, when the protrusions 112 are coated with a hydrophobic material, the recesses 114 have relatively hydrophilicity.

[0037] On the other hand, the metal particles 120 may be disposed in at least some of the recesses 114. Specifically, the metal particles 120 may be in physical contact with the copper located in the recesses 114, or may form an alloy with the copper located in the recesses 114.

[0038] The metal particles 120 act as seeds that cause uniform lithium distribution on the negative electrode current collector 100 during charging and discharging of the battery. Specifically, the metal particles 120 act as seeds that allow lithium electrodeposited on the negative electrode current collector 100 to be uniformly distributed as Li 0It acts as a heterogeneous nucleation site by forming a solid solution with the lithium before forming a pure Li phase.

[0039] The metal particles 120 may have a higher standard reduction potential than that of lithium ions in order to form a solid solution with the lithium electrodeposited on the negative electrode current collector 100. Specifically, the metal particles 120 may be silver (Ag).

[0040] FIG. 2 is a phase equilibrium diagram of lithium and copper (Cu), and FIG. 3 is a phase equilibrium diagram of lithium and silver (Ag). As shown in FIG. 2, copper contained in the copper thin film 110 forms a solid solution with lithium only under conditions of a relatively low lithium content. Therefore, when a copper thin film not including the metal particles 120 of the present invention is used as a negative electrode current collector, random dendrite growth due to lithium electrodeposited on the negative electrode current collector cannot be suppressed. In contrast, as shown in FIG. 3, silver particles used as the metal particles 120 can form a solid solution with lithium even under conditions of a relatively high lithium content (e.g., 40 to 50 atomic %). This prevents the dendritic growth of lithium electrodeposited on the negative electrode current collector, suppressing random lithium dendrite growth and resulting in uniform lithium deposition on the negative electrode current collector.

[0041] The size of the metal particles 120 may be 0.1 nm to 1000 nm, specifically 0.1 nm to 500 nm, and more specifically 0.5 nm to 100 nm. In this case, the size of the metal particles 120 can be measured by an image analysis method using a Hitachi FE-SEM device. When the size of the metal particles 120 satisfies the above numerical range, the metal particles 120 can exist in a dispersed state in a solution before being placed on the copper thin film 110, and can be easily placed in the recesses 114 having a size of several μm when placed on the copper thin film 110 without the need for a separate adhesive component.

[0042] Meanwhile, the thickness of the negative electrode current collector 100 may be 4 μm to 20 μm, specifically 5 μm to 15 μm, and more specifically 6 μm to 12 μm. When the thickness of the negative electrode current collector satisfies the above numerical range, the mechanical properties of the negative electrode current collector are ensured, while the manufacturing cost of a battery manufactured from the negative electrode current collector can be reduced and the energy density can be increased.

[0043] The center line surface roughness (R a The center line surface roughness (R a When the thickness (μm) of the copper thin film 110 satisfies the above numerical range, the protrusions 112 and the recesses 114 are formed on the surface of the copper thin film 110 manufactured by the electrolytic plating method, and the metal particles 120 can be easily arranged in the recesses 114.

[0044] <Method of manufacturing negative electrode current collector> Next, a method for producing the negative electrode current collector according to the present invention will be described.

[0045] A method for manufacturing a negative electrode current collector according to the present invention includes the steps of manufacturing a copper thin film having protrusions and recesses formed thereon, and disposing metal particles capable of forming a solid solution with lithium (Li) in at least some of the recesses. In this case, the negative electrode current collector manufactured by the method may be the negative electrode current collector according to the present invention described above.

[0046] Hereinafter, each step of the method for manufacturing the negative electrode current collector according to the present invention will be described in more detail.

[0047] (1) Producing a copper thin film having protrusions and recesses The method for manufacturing a negative electrode current collector according to the present invention begins with a step of manufacturing a copper thin film having protrusions and recesses formed thereon.

[0048] Specifically, copper thin films can be manufactured by an electrolytic plating process. Electrolytic plating processes are advantageous in terms of process flexibility and cost, since the thickness of the plated foil can be easily adjusted by adjusting the magnitude of the applied current, the current application time, the temperature, etc. Furthermore, electrolytic plating processes can produce thin copper thin films, thereby increasing the energy density of batteries.

[0049] For example, a method for manufacturing a copper thin film using electroplating is as follows. First, a reaction vessel is prepared, which includes a rotating anode drum and a positive electrode plate disposed opposite the rotating anode drum. An electrolyte containing copper ions and water is then filled into the reaction vessel. Next, while applying electricity to the rotating anode drum and the positive electrode plate, the rotating anode drum is rotated to electrodeposit copper onto the surface of the rotating anode drum. Finally, the electrodeposited copper is continuously extracted from the reaction vessel, thereby finally manufacturing the copper thin film. The copper thin film manufactured in this manner contains defects, resulting in the formation of protrusions and recesses on the surface of the copper thin film.

[0050] (2) disposing metal particles in at least some of the recesses; Next, metal particles that have a standard reduction potential higher than that of lithium ions and can form a solid solution with lithium (Li) are placed in at least some of the recesses.

[0051] Specifically, the step of placing metal particles capable of forming a solid solution with lithium (Li) in at least a portion of the recess may include a step of hydrophobizing at least a portion of the protrusion, and a step of coating the copper thin film with metal particles having hydrophilic properties.

[0052] The step of hydrophobizing at least some of the protrusions may be a step of disposing a hydrophobic substance on the protrusions. For example, the hydrophobic substance can be disposed on the protrusions by applying a liquid containing a hydrophobic substance to the surface of the copper thin film using a roller and then drying the liquid. In this case, the liquid containing the hydrophobic substance does not penetrate into recesses having a size of several micrometers, so the hydrophobic substance is not disposed in the recesses. The hydrophobic substance may include an oil-based binder, and specifically, may include at least one of silane, polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE).

[0053] The step of coating the copper thin film with hydrophilic metal particles may be a step of applying a solution containing metal particles to the surface of the copper thin film, at least some of the protrusions of which have been hydrophobically treated, by spraying and / or dipping, wherein the metal particles are disposed in at least some of the recesses while avoiding the hydrophobic protrusions.

[0054] Thereafter, the copper thin film is dried at 40°C to 50°C, thereby removing the solvent in the colloidal solution coated / applied on the surface of the copper thin film.

[0055] The method for manufacturing a negative electrode current collector according to the present invention does not involve artificial photolithography or dry chemical etching processes, thereby simplifying the process steps and reducing manufacturing costs.

[0056] <Lithium secondary battery> The lithium secondary battery of the present invention may include a negative electrode, a positive electrode, a separator, and an electrolyte, wherein the negative electrode includes the negative electrode current collector of the present invention described above.

[0057] The negative electrode according to the present invention may not include a negative electrode active material layer disposed on a negative electrode current collector. In this case, a lithium secondary battery including the negative electrode may be an anodeless battery. For example, in the lithium secondary battery according to the present invention, lithium metal is formed on the surface of the negative electrode current collector during charging, and the lithium metal serves as a negative electrode active material.

[0058] The lithium secondary battery of the present invention prevents the dendritic development of lithium electrodeposited on the negative electrode current collector and inhibits the random growth of lithium dendrites on the surface of the negative electrode current collector, thereby allowing for uniform lithium deposition on the negative electrode current collector and preventing the problem of lithium dendrites penetrating the separator and causing a short circuit between the positive electrode and the negative electrode.

[0059] On the other hand, the positive electrode includes a positive electrode current collector and may also include a positive electrode active material layer formed on the positive electrode current collector.

[0060] The positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, the current collector may be stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like.

[0061] The positive electrode current collector can have a thickness of 3 μm to 500 μm, and can have fine irregularities on its surface to enhance the adhesive strength of the positive electrode active material layer. It can be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0062] The positive electrode active material layer may contain a positive electrode active material, and may further contain a conductive material, a binder, and the like, as necessary.

[0063] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium metal oxide containing one or more metals such as cobalt, manganese, nickel, aluminum, etc. and lithium. More specifically, the lithium metal oxide is a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), a lithium-nickel-cobalt-based oxide (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), a lithium-manganese-cobalt-based oxide (e.g., LiCo 1-Y2 Mn Y2 [[ID=1,6]]O2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), a lithium-nickel-manganese-cobalt-based oxide (e.g., Li(Ni p Co q Mn r )O2 (where 0 < p < 1, 0 < q < 1, 0 < r < 1, p + q + r = 1) or Li(Ni p1 Co q1 Mn r1 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r1 < 2, p1 + q1 + r1 = 2), etc.), a lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r2 [[ID=%8]]M s2 )O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r2, and s2 are the atomic fractions of the respective independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, and p2 + q2 + r2 + s2 = 1), etc.), a lithium iron phosphate (e.g., Li 1+a Fe1-x M x (PO 4-b )X b (wherein M is one or more selected from Al, Mg, and Ti, and X is one or more selected from F, S, and N, and -0.5≦a≦0.5, 0≦x≦0.5, 0≦b≦0.1), and the compound may contain one or more compounds thereof.

[0064] Among them, the lithium metal oxides include LiCoO2, LiMnO2, LiNiO2, and lithium nickel manganese cobalt oxides (e.g., Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), lithium nickel manganese cobalt aluminum oxide (e.g., Li(Ni 0.86 Co 0.05 Mn 0.07 Al 0.02 )O2), lithium iron phosphate (e.g., LiFePO4), and the like, and any one or a mixture of two or more thereof may be used.

[0065] The positive electrode active material may be contained in an amount of 60 to 99 wt %, preferably 70 to 99 wt %, and more preferably 80 to 98 wt %, based on the total weight of the positive electrode active material layer.

[0066] The positive electrode conductive material is a component for further improving the conductivity of the positive electrode active material, and such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive. For example, carbon powders such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; graphite powders such as natural graphite, artificial graphite, and graphite, which have a highly developed crystal structure; conductive fibers such as carbon fiber and metal fiber; carbon fluoride powder; conductive powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

[0067] Generally, the positive electrode conductive material may be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the positive electrode active material layer.

[0068] The positive electrode binder is a component that assists in binding the active material, conductive material, etc. to the current collector.

[0069] Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, various copolymers, and the like.

[0070] Typically, the positive electrode binder may be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the positive electrode active material layer.

[0071] On the other hand, the separator may be disposed between the negative electrode and the positive electrode. Any separator commonly used in lithium secondary batteries can be used without any particular limitation, and it is particularly preferred that the separator has low resistance to the movement of electrolyte ions and has excellent ability to retain moisture in the electrolyte solution.

[0072] For example, the separation membrane may be a porous polymer film containing a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof. Alternatively, the separation membrane may be a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber.

[0073] The lithium secondary battery according to one embodiment of the present invention may include an electrolyte. In this case, the electrolyte may be a non-aqueous electrolyte. The non-aqueous electrolyte may include an organic solvent and a lithium salt commonly used in the art, and is not particularly limited.

[0074] The organic solvent can be any organic solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent that may be used include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether and tetrahydrofuran; ketone-based solvents such as cyclohexanone; aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; and carbonate-based solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC).

[0075] Among these, carbonate-based solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate, propylene carbonate, etc.) having high ionic conductivity and high dielectric constant, which improve the charge / discharge performance of batteries, and low-viscosity linear carbonate-based compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, etc.) are more preferred.

[0076] The lithium salt can be any compound that can provide lithium ions used in lithium secondary batteries without any particular limitations. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The lithium salt is preferably contained in the electrolyte at a concentration of approximately 0.6 mol% to 2 mol%.

[0077] Meanwhile, the non-aqueous electrolyte according to the present invention may further contain an additive, although this is not essential, to further improve the physical properties of the secondary battery.

[0078] Examples of such additives include at least one selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, nitrile compounds, sultone compounds, sulfate compounds, phosphate compounds, borate compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

[0079] The cyclic carbonate compound may be, for example, vinylene carbonate (VC), vinyl ethylene carbonate (VEC), or the like.

[0080] The halogen-substituted carbonate compound may be, for example, fluoroethylene carbonate (FEC).

[0081] The nitrile compound may be, for example, succinonitrile, adiponitrile, hexanetricyanide, 1,4-dicyano-2-butene, or the like.

[0082] The sultone compound may be, for example, 1,3-propane sultone, 1,3-propene sultone, or the like.

[0083] The sulfate-based compound may be, for example, ethylene sulfate (Esa), trimethylene sulfate (TMS), methyl trimethylene sulfate (MTMS), or the like.

[0084] The phosphate-based compound may be, for example, one or more compounds selected from the group consisting of lithium difluoro(bisoxalate)phosphate, lithium difluorophosphate, tetramethyltrimethylsilylphosphate, trimethylsilylphosphite, tris(2,2,2-trifluoroethyl)phosphate, and tris(trifluoroethyl)phosphite.

[0085] The borate-based compound may be, for example, tetraphenylborate, lithium oxalyldifluoroborate (LiODFB), or the like.

[0086] The benzene-based compound may be, for example, fluorobenzene, the amine-based compound may be, for example, triethanolamine or ethylenediamine, and the silane-based compound may be, for example, tetravinylsilane.

[0087] The lithium salt-based compound is a compound different from the lithium salt contained in the non-aqueous electrolyte, and may be one or more compounds selected from the group consisting of LiPO2F2, LiODFB, LiBOB (lithium bis(oxalatoborate) (LiB(C2O4)2)) and LiBF4.

[0088] On the other hand, the additives may be used alone or in combination of two or more.

[0089] The total amount of the additives may be 1 wt % to 20 wt %, preferably 1 wt % to 15 wt %, based on the total weight of the electrolyte solution. When the additives are contained within the above range, a coating can be stably formed on the electrode, which can suppress ignition during overcharge, and it is possible to prevent side reactions from occurring during the initial activation step of the secondary battery and the additives from remaining or being precipitated.

[0090] The lithium secondary battery of the present invention can be fabricated by placing an electrode assembly formed by disposing a separator between a positive electrode and a negative electrode in a battery case, injecting an electrolyte, and then sealing the battery case. Alternatively, the lithium secondary battery can be fabricated by stacking the electrode assemblies, impregnating the stack with an electrolyte, and then placing the resulting assembly in a battery case and sealing it.

[0091] The battery case may be one commonly used in the relevant field, and is not limited in shape depending on the intended use of the battery, and may be, for example, cylindrical, square, pouch, coin, etc., but is not limited thereto.

[0092] The lithium secondary battery according to an embodiment of the present invention can be used not only as a battery cell used as a power source for a small device, but also as a unit battery for a medium- to large-sized battery module including a plurality of battery cells. Preferred examples of the medium- to large-sized device include an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and an energy storage system (ESS).

[0093] The present invention will be described in more detail below with reference to specific examples. However, the following examples are merely illustrative to aid in understanding the present invention and are not intended to limit the scope of the present invention. It is obvious to those skilled in the art that various changes and modifications can be made within the scope and technical concept of the present description, and it is obvious that such changes and modifications are included in the scope of the appended claims.

[0094] Examples and Comparative Examples Example (1) Manufacturing of negative electrode current collector A reaction vessel including a negative electrode rotating drum and a positive electrode plate facing the negative electrode rotating drum was prepared, and the reaction vessel was filled with an electrolyte solution containing copper sulfate and water. Next, while applying electricity to the negative electrode rotating drum and the positive electrode plate, the negative electrode rotating drum was rotated to electrodeposit copper onto the surface of the negative electrode rotating drum. The electrodeposited copper was then continuously extracted from the reaction vessel to obtain an 8 μm-thick electrolytic copper foil.

[0095] Next, the surface of the electrolytic copper foil was coated with silane, and then colloidal silver was sprayed onto the electrolytic copper foil to arrange silver particles on the surface of the electrolytic copper foil.Then, the solvent remaining on the electrolytic copper foil was dried with hot air to prepare a negative electrode current collector.

[0096] (2) Manufacture of lithium secondary batteries As the negative electrode, the negative electrode current collector on which no other negative electrode active material layer was disposed was used.

[0097] A cathode slurry was prepared by adding LiCoO2, polyvinylidene fluoride (PVDF), carbon nanotubes (CNTs), and carbon black in a weight ratio of 97.59:1.18:0.24:0.09 to an N-methylpyrrolidone (NMP) solvent and stirring the mixture. The cathode slurry was applied to one surface of a 10 μm-thick aluminum thin film at a rate of 18.60 mg / cm. 2 The dried positive electrode slurry was roll pressed and dried in a vacuum oven at 130°C for 6 hours, and then punched out to produce a positive electrode.

[0098] The negative electrode, positive electrode, and porous polyethylene separator (thickness: 12 μm) prepared as above were stacked to prepare an electrode assembly.

[0099] An electrolyte was prepared by dissolving LiPF6 in a solvent (mass ratio of EC:PC:EP:PP = 20:10:25:45) to a concentration of 1.2 M.

[0100] The electrode assembly was housed in a battery case, the electrolyte was poured into the battery case, and the battery case was then sealed to manufacture a lithium secondary battery (anode-less battery).

[0101] Comparative Example 1 A negative electrode current collector was manufactured in the same manner as in Example 1, except that the process of spraying colloidal silver onto the electrolytic copper foil was not performed.

[0102] A lithium secondary battery was manufactured in the same manner as in the Examples, except that the negative electrode current collector manufactured by the above method (i.e., a negative electrode current collector not containing silver particles) was used.

[0103] Comparative Example 2 A negative electrode current collector was manufactured in the same manner as in Example 1, except that the process of coating the surface of the electrolytic copper foil with silane was not performed.

[0104] A lithium secondary battery was manufactured in the same manner as in the Examples, except that the negative electrode current collector manufactured by the above method (i.e., the negative electrode current collector not including the hydrophobic coating layer) was used.

[0105] Experimental Example 1 The lithium secondary batteries prepared in each of the examples and comparative examples 1 and 2 were charged and discharged at a temperature of 45°C, and the number of charge-discharge cycles until a short circuit between the positive electrode and the negative electrode occurred was measured. Specifically, one cycle is defined as a full charge and then a full discharge of the lithium secondary battery, and the total number of cycles until the separator in the lithium secondary battery opened and a short circuit between the positive electrode and the negative electrode occurred was measured and is shown in Table 1 below.

[0106] [Table 1]

[0107] As shown in Table 1, in the example in which silver particles were contained in the recesses of the negative electrode current collector, the total number of cycles until a short circuit between the positive and negative electrodes occurred was significantly higher than in Comparative Example 1 in which silver particles were not contained and Comparative Example 2 in which silver particles were coated without a hydrophobic coating. [Explanation of symbols]

[0108] 100 Negative electrode current collector 110 Copper thin film 112 Protrusion 114 recess 120 Metal particles

Claims

1. a copper thin film having protrusions and recesses formed thereon; The negative electrode current collector includes metal particles that are disposed in at least some of the recesses, have a standard reduction potential higher than that of lithium ions, and are capable of forming a solid solution with lithium (Li).

2. The negative electrode current collector according to claim 1 , wherein the metal particles are silver (Ag).

3. 2. The negative electrode current collector according to claim 1, wherein the metal particles have a size of 0.1 nm to 1000 nm.

4. The negative electrode current collector according to claim 1 , wherein the metal particles are hydrophilic particles.

5. The negative electrode current collector according to claim 1 , wherein at least some of the recesses contain hydrophilic groups.

6. The negative electrode current collector according to claim 1 , wherein at least some of the protrusions include a hydrophobic group.

7. The negative electrode current collector according to claim 1 , wherein at least some of the protrusions include at least one of silane, polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE).

8. The negative electrode current collector according to claim 1 , wherein the copper thin film is an electrolytic copper foil or a rolled copper foil.

9. 2. The negative electrode current collector according to claim 1, wherein the negative electrode current collector has a thickness of 4 μm to 20 μm.

10. Center line surface roughness (R ａ 2. The negative electrode current collector according to claim 1, wherein the average particle size is 0.1 μm to 0.5 μm.

11. fabricating a copper thin film having protrusions and recesses; and disposing metal particles having a standard reduction potential higher than that of lithium ions and capable of forming a solid solution with lithium (Li) in at least some of the recesses.

12. The step of disposing metal particles capable of forming a solid solution with lithium (Li) in at least a portion of the recesses includes: applying a hydrophobic treatment to at least a portion of the protrusion; The method for producing a negative electrode current collector according to claim 11 , further comprising: coating the copper thin film with hydrophilic metal particles.

13. 13. The method of claim 12, wherein the step of hydrophobizing at least a portion of the protrusions comprises coating a surface of the copper thin film with at least one of silane, polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE).

14. The method for producing a negative electrode current collector according to claim 11 , wherein the copper thin film is produced by an electrolytic plating process.

15. a negative electrode comprising the negative electrode current collector according to claim 1; A positive electrode and a separator disposed between the negative electrode and the positive electrode.

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