Positive electrode current collector for lithium secondary battery, method for manufacturing same, and lithium secondary battery comprising same

Abstract

A positive electrode current collector for a lithium secondary battery according to an embodiment of the present invention may include a stacked structure that may include an aluminum layer, an aluminum-copper alloy layer formed on the aluminum layer, and a copper layer formed on the aluminum-copper alloy layer, and a surface of the stacked structure may be doped with at least one metal element. Therefore, the conductivity of the positive current collector can be improved, and the battery resistance can be reduced.

Description

Technical Field

[0001] The present invention relates to a positive electrode current collector for a lithium secondary battery, a method for manufacturing the positive electrode current collector for a lithium secondary battery, and a lithium secondary battery comprising the positive electrode current collector for a lithium secondary battery. Background Art

[0002] Secondary batteries are batteries that can be repeatedly charged and discharged, and with the development of information communication and display industries, secondary batteries are widely used as a power source for portable electronic communication devices such as camcorders, mobile phones, notebook computers, etc. In addition, battery packs including secondary batteries are being developed in recent years and used as a power source for environmentally friendly vehicles such as hybrid vehicles.

[0003] Examples of secondary batteries include lithium secondary batteries, nickel-cadmium batteries, and nickel-metal hydride batteries. Among them, lithium secondary batteries have high operating voltage and energy density per unit weight, and are advantageous in terms of charging speed and light weight, and therefore are being actively developed and used.

[0004] For example, a lithium secondary battery may include: an electrode assembly including a positive electrode, a negative electrode and a separator (separation membrane); and an electrolyte impregnated with the electrode assembly. The lithium secondary battery may also include an outer packaging material such as a soft pack type outer packaging material that accommodates the electrode assembly and the electrolyte.

[0005] In the lithium secondary battery, the positive electrode active material can be coated on the positive electrode current collector and then dried and rolled to form a positive electrode. The positive electrode active material is filled in the lithium secondary battery at a high density, so that it can have high capacity and high power characteristics. In addition, by reducing the thickness of the positive electrode current collector, the amount of the positive electrode active material can be increased without increasing the volume of the lithium secondary battery.

[0006] However, if the density of the positive active material is increased, the positive current collector may be deformed such as wrinkles or the positive current collector may be broken due to the expansion and contraction caused by the charge and discharge of the positive active material layer. In addition, when the thickness of the positive current collector is reduced, the resistance of the positive current collector may increase.

[0007] For example, Korean Patent No. 10-2283842 discloses an electrode current collector for a lithium secondary battery including a novel conductive material. Summary of the invention

[0008] 1. Technical issues to be resolved

[0009] A technical problem of the present invention is to provide a positive electrode current collector for a lithium secondary battery with reduced resistance.

[0010] A technical problem of the present invention is to provide a method for manufacturing the positive electrode current collector for a lithium secondary battery.

[0011] A technical problem of the present invention is to provide a lithium secondary battery comprising the positive electrode current collector for a lithium secondary battery.

[0012] (II) Technical solution

[0013] A positive electrode current collector for a lithium secondary battery according to an exemplary embodiment may include a stacked structure including an aluminum layer, an aluminum-copper alloy layer formed on the aluminum layer, and a copper layer formed on the aluminum-copper alloy layer, and a surface of the stacked structure may be doped with at least one metal element.

[0014] In some embodiments, the aluminum-copper alloy layer may include Al 2 Cu, AlCu and AlCu 2 At least one of .

[0015] In some embodiments, the aluminum-copper alloy layer may include Al 2 Cu layer, AlCu-containing layer and AlCu-containing layer 2 At least two or more layers.

[0016] In some embodiments, the copper layer may include: an undoped layer, which is disposed on the aluminum-copper alloy layer and is not doped with the metal element; and a metal-doped layer, which is disposed on the undoped layer and is doped with the metal element.

[0017] In some embodiments, the metal doping layer may include copper doped with the metal element.

[0018] In some embodiments, the metal element may include at least one of nickel, magnesium and zinc.

[0019] In some embodiments, the metal elements may include nickel, magnesium and zinc.

[0020] In some embodiments, the content of zinc in the metal elements may be greater than or equal to the sum of the content of nickel and the content of magnesium.

[0021] In some embodiments, the content of the metal element may be 0.1 wt % to 3 wt % relative to the total weight of the stacked structure.

[0022] A lithium secondary battery according to an exemplary embodiment includes a positive electrode including the positive electrode collector for a lithium secondary battery and a positive electrode active material layer formed on at least one side of the positive electrode collector; and a negative electrode disposed opposite to the positive electrode.

[0023] In the method for manufacturing a positive electrode current collector for a lithium secondary battery according to an exemplary embodiment, an aluminum foil and a copper foil may be hot-rolled to form a first preliminary current collector including an aluminum-copper alloy layer. The first preliminary current collector may be heat-treated to dope a metal element on a surface of the first preliminary current collector.

[0024] In some embodiments, the aluminum-copper alloy layer may be formed between the aluminum foil and the copper foil.

[0025] In some embodiments, the step of heat-treating the first preliminary current collector may include cold-rolling the first preliminary current collector and annealing the cold-rolled first preliminary current collector.

[0026] In some embodiments, metal elements may be doped on the surface of the first preliminary current collector through the annealing process.

[0027] In some embodiments, after the cold rolling process and before the annealing process, a step of coating a doping solution containing the metal element on the surface of the cold-rolled first preliminary current collector may be further included.

[0028] In some embodiments, the cold rolling process and the annealing process may be repeated.

[0029] In some embodiments, the cold rolling process and the annealing process may include: performing a first cold rolling on the first preliminary current collector to form a second preliminary current collector, performing a first annealing process on the second preliminary current collector to form a third preliminary current collector, performing a second cold rolling on the third preliminary current collector to form a fourth preliminary current collector, and performing a second annealing process on the fourth preliminary current collector.

[0030] In some embodiments, the temperature of the first annealing process may be higher than the temperature of the second annealing process.

[0031] (III) Beneficial effects

[0032] According to an exemplary embodiment, the positive electrode current collector for a lithium secondary battery may include a stacked structure, the stacked structure including an aluminum layer, an aluminum-copper alloy layer and a copper layer arranged in sequence. Metal elements such as nickel, magnesium and zinc may be doped on the surface of the stacked structure. Therefore, the energy density and conductivity of the lithium secondary battery can be improved, and the resistance can be reduced.

[0033] In addition, the doping content of the metal element may be 0.1 wt % to 3 wt % relative to the total weight of the stacked structure. Therefore, the resistance of the secondary battery may be reduced while the capacity characteristics may be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figures 1 to 5 is a schematic cross-sectional view showing a positive electrode collector for a lithium secondary battery according to an exemplary embodiment.

[0035] Figure 6 and Figure 7 is a schematic flowchart for explaining a method for manufacturing a positive electrode current collector for a lithium secondary battery according to an exemplary embodiment.

[0036] Figure 8 is a schematic cross-sectional view showing a positive electrode for a lithium secondary battery according to an exemplary embodiment.

[0037] Fig. 9 and Fig.10 are schematic plan views and cross-sectional views illustrating a lithium secondary battery according to an exemplary embodiment. DETAILED DESCRIPTION

[0038] The exemplary embodiment of the present invention provides a positive electrode current collector for a lithium secondary battery including aluminum, copper and a dopant metal and a method for manufacturing the same. In addition, a lithium secondary battery including the positive electrode current collector for a lithium secondary battery is provided.

[0039] The embodiments of the present invention are described in more detail below with reference to the accompanying drawings. However, the drawings in this specification are used to illustrate preferred embodiments of the present invention and serve to further understand the technical concept of the present invention together with the contents of the above invention, so the present invention should not be interpreted as being limited to the contents recorded in the drawings.

[0040] Figures 1 to 5 is a schematic cross-sectional view showing a positive electrode collector for a lithium secondary battery according to an exemplary embodiment.

[0041] Reference Figure 1 , the positive electrode current collector 105 may include a stacked structure including an aluminum (Al) layer 110, an aluminum-copper alloy layer 120 formed on the aluminum layer 110, and a copper (Cu) layer formed on the aluminum-copper alloy layer 120. The surface of the stacked structure may be doped with at least one metal element.

[0042] Therefore, even if the thickness of the positive electrode collector 105 is reduced, high conductivity can be maintained, thereby improving the energy density of the positive electrode 100. In addition, by providing copper with a high theoretical capacity in the outer shell layer, deformation and fracture of the positive electrode collector 105 can be suppressed even if a high-density positive electrode active material layer is formed on the positive electrode collector 105.

[0043] According to an exemplary embodiment, a surface of the copper layer may be doped with a metal element.

[0044] For example, the copper layer may include an undoped layer 130 disposed on the aluminum-copper alloy layer 120 and a metal doping layer 140 disposed on the undoped layer 130 and doped with the metal element.

[0045] The undoped layer 130 may be a layer not doped with the metal element. For example, the undoped layer 130 may be a copper metal layer not including the doping metal.

[0046] In some embodiments, the metal element may be doped on the surface and the surface layer of the copper layer and then diffused into the interior of the copper layer. Therefore, a metal doping layer 140 containing doped copper may be formed in the surface region of the copper layer.

[0047] Therefore, the electrical conductivity of the positive electrode current collector 105 can be improved, and a sharp composition change of the doped copper formed on the surface layer of the copper layer can be alleviated.

[0048] In some embodiments, the metal element may include at least one of nickel, magnesium and zinc.

[0049] Therefore, the electrical conductivity of the positive electrode collector 105 may be improved by the high electrical conductivity of the nickel, the magnesium, and the zinc.

[0050] In some embodiments, the doping content of the metal element (eg, nickel, magnesium and / or zinc) may be 0.1 wt % to 3 wt % or 0.3 wt % to 1.5 wt % relative to the total weight of the stacked structure.

[0051] Within the above range, due to the doping of the metal element, the electrical conductivity of the stacked structure can be improved. In addition, by preventing the excessive diffusion of the doping element into the copper layer, the excessive expansion of the metal doping layer of the positive electrode current collector can be prevented.

[0052] In some embodiments, the metal elements may include nickel, magnesium and zinc elements at the same time. For example, nickel, magnesium and zinc may be surface-doped into the copper layer.

[0053] In one embodiment, the doping content of zinc may be higher than the sum of the doping content of nickel and the doping content of magnesium, thereby increasing the conductivity of the positive electrode current collector and thus reducing the resistance of the lithium secondary battery.

[0054] For example, the doping content of the nickel or the magnesium may be 0.1 wt % to 3 wt % or 0.1 wt % to 0.5 wt % relative to the total weight of the stacked structure.

[0055] For example, the doping content of zinc may be 0.1 wt % to 3 wt % or 0.3 wt % to 1.0 wt % relative to the total weight of the stacked structure.

[0056] Reference Figure 2 The positive electrode current collector 105 may include a stacked structure including an aluminum layer 110 , aluminum-copper alloy layers 120 formed on both surfaces of the aluminum layer 110 , and a copper layer formed on each of the aluminum-copper alloy layers 120 .

[0057] Both sides of the stacked structure may be doped with metal elements. For example, the copper layer may include an undoped layer 130 and a metal doped layer 140 doped with the metal element.

[0058] Therefore, even if a high-density active material layer is formed on the positive electrode current collector 105 , it is possible not to cause breakage.

[0059] In some embodiments, the positions of the copper layer and the aluminum layer 110 may be interchanged.

[0060] Reference Figure 3 The positive electrode current collector 105 may include a copper layer, aluminum-copper alloy layers 120 formed on both sides of the copper layer, and an aluminum layer 110 formed on each of the aluminum-copper alloy layers 120 .

[0061] Therefore, the electrical conductivity of the positive electrode current collector 105 can be improved, and price competitiveness can be ensured.

[0062] When the copper layer is located at the center of the stacked structure, the metal element may be doped on the surface of the aluminum layer 110. For example, the aluminum layer 110 may include an undoped layer 130 disposed on the aluminum-copper alloy layer 120 and a metal doped layer 140 disposed on the undoped layer 130. The metal doped layer 140 may include aluminum doped with the metal element.

[0063] According to an exemplary embodiment, the aluminum-copper alloy layer 120 may include Al 2 Cu, AlCu and AlCu 2 For example, the aluminum-copper alloy of the aluminum-copper alloy layer 120 may include Al 2 Cu, AlCu and AlCu2 At least one of the alloys represented.

[0064] In some embodiments, the aluminum-alloy layer 120 may have a single composition. For example, the aluminum-alloy layer 120 may be formed as a single layer containing AlCu.

[0065] In some embodiments, the composition of the aluminum-copper alloy of the aluminum-copper alloy layer 120 may be sequentially changed. For example, the aluminum concentration and the copper concentration in the aluminum-copper alloy layer 120 may change from the aluminum layer 110 to the copper layer. The term "concentration" used in this specification may refer to, for example, a molar ratio or an atomic ratio (atomic %) of aluminum and copper.

[0066] In some embodiments, the copper concentration of the aluminum-copper alloy layer 120 may increase as approaching the copper layer. In some embodiments, the aluminum concentration of the aluminum-copper alloy layer 120 may decrease as approaching the copper layer.

[0067] Reference Figure 4 The aluminum-copper alloy layer 120 may contain Al 2 Cu and AlCu as aluminum-copper alloys.

[0068] According to an exemplary embodiment, the aluminum-copper alloy layer 120 may include Al 2 The Cu layer 122 and the AlCu containing layer 124 are stacked.

[0069] In some embodiments, the aluminum-copper alloy layer 120 can be sequentially provided from the aluminum layer 110 to the aluminum layer 111. 2 Cu layer 122, AlCu layer 124. For example, the positive electrode current collector 105 may include an aluminum layer 110, an AlCu layer 124 formed on both sides of the aluminum layer 110, and a Cu layer 122. 2 The Cu layer 122 is formed on the Al-containing 2 An AlCu containing layer 124 on the Cu layer 122 and a copper layer formed on the AlCu containing layer 124 .

[0070] Therefore, deformation and breakage of the positive electrode current collector 105 can be prevented, and the energy density of the positive electrode can be improved.

[0071] Reference Figure 5 The aluminum-copper alloy layer 120 may include Al 2 Cu, AlCu and AlCu 2 As aluminum-copper alloy.

[0072] According to an exemplary embodiment, the aluminum-copper alloy layer 120 may include Al 2 Cu layer 122, AlCu containing layer 124 and AlCu containing layer 2The stacked structure of layer 126 .

[0073] In some embodiments, the Al-containing 2 Cu layer 122, AlCu layer 124, AlCu 2 For example, the positive electrode current collector 105 may include an aluminum layer 110, an Al-containing 2 The Cu layer 122 is formed on the Al-containing 2 The AlCu-containing layer 124 on the Cu layer 122 and the AlCu-containing layer 124 formed on the AlCu-containing layer 124 2 layer 126 and formed on the AlCu 2 Copper layer on layer 126.

[0074] Including Al 2 Cu layer 122, AlCu containing layer 124 and AlCu containing layer 2 The aluminum-copper alloy layer 120 of layer 126 may implement a gradual alloy composition change to the composition changes of the aluminum layer 110 and the copper layer.

[0075] Therefore, the aluminum-copper alloy layer 120 may buffer the composition change between the aluminum layer 110 and the copper layer, and may prevent the aluminum layer 110 and the copper layer from being separated from each other.

[0076] In some embodiments, the thickness of the aluminum layer 110 may be 3 μm to 15 μm or 4 μm to 10 μm. Within the above range, the thickness of the positive electrode collector 105 may be thinner, and the volume energy density of the secondary battery may be increased.

[0077] In some embodiments, the thickness of the aluminum-copper alloy layer 120 may be 0.1 μm to 3 μm or 0.5 μm to 1.5 μm. Within the above range, the aluminum-copper alloy layer 120 can sufficiently buffer the composition changes of the aluminum layer 110 and the copper layer.

[0078] In some embodiments, the thickness of the copper layer may be 1 μm to 10 μm or 3 μm to 7 μm. Within the above range, the price competitiveness of the positive electrode collector 105 can be ensured while forming a high-density active material layer, and the deformation or fracture of the positive electrode collector 105 can be suppressed due to the high theoretical capacity of the copper layer.

[0079] Figure 6 and Figure 7 is a schematic flowchart for explaining a method for manufacturing a positive electrode current collector for a lithium secondary battery according to an exemplary embodiment. Figure 7 yes Figure 6 Specific flow chart of the S20 process.

[0080] Reference Figure 6 and Figure 7 , aluminum foil can be prepared (eg, S10 process).

[0081] According to an exemplary embodiment, an aluminum ingot is cast from an aluminum alloy, and the aluminum ingot is homogenized and hot-rolled, so that an aluminum foil may be prepared.

[0082] In some embodiments, an aluminum ingot may be cast from an aluminum alloy.

[0083] The aluminum alloy can be placed in a furnace and heated to above the melting point of aluminum to be melted. For example, the aluminum alloy can be heated to above 700°C or above 800°C to melt the aluminum inside the aluminum alloy. The molten aluminum is placed in a mold, and the mold can be cooled to below the melting point of aluminum. Therefore, an aluminum ingot of high-purity aluminum can be cast from the aluminum alloy.

[0084] In some embodiments, the aluminum ingot may be homogenized by heat treating the ingot.

[0085] For example, the aluminum ingot may be homogenized by heat-treating the aluminum ingot at 350° C. to 600° C. or 400° C. to 550° C. Within the above range, segregation within aluminum grains may be effectively removed, and aluminum grains may be refined.

[0086] In some embodiments, the homogenized aluminum ingot may be hot rolled to prepare aluminum foil.

[0087] For example, the homogenized aluminum ingot may be hot-rolled by heat-treating it at 350° C. to 500° C. or 400° C. to 450° C. Within the above range, aluminum grains are recrystallized without segregation inside the aluminum grains, thereby forming an aluminum foil.

[0088] According to an exemplary embodiment, a copper foil may be bonded to the aluminum foil prepared through the above process, hot-rolled, and homogenized to form a first preliminary current collector including an aluminum-copper alloy layer (eg, S20 process).

[0089] In some embodiments, a copper foil may be placed on the aluminum foil and rolled to form a first preliminary alloy layer (eg, S22 process).

[0090] For example, a copper foil may be placed on the aluminum foil and bonded to the aluminum foil and the copper foil by a roll-to-roll process. The roll-to-roll process may be performed at, for example, 250° C. to 450° C. or 300° C. to 400° C. Within the above range, the aluminum foil and the copper foil may be recrystallized and bonded without cracks caused by high or low temperatures.

[0091] In some embodiments, the first preliminary alloy layer may be hot rolled to form a second preliminary alloy layer (eg, S24 process).

[0092] By hot rolling the first preliminary alloy layer, aluminum and copper can be recrystallized at the contact portion between the aluminum foil and the copper foil. 2 Cu, AlCu and / or AlCu 2 Represents aluminum-copper alloy.

[0093] For example, hot rolling may be started by heat treating the bonded aluminum foil and copper foil at 500 to 700° C. or 550 to 650° C. Within the above range, the aluminum foil and copper foil do not melt and recrystallize, thereby forming an aluminum-copper alloy.

[0094] For example, the hot rolling may be terminated at 300° C. to 450° C. or 300° C. to 400° C. Within the above range, recrystallization may be completed without generating a riding mark, thereby forming an aluminum-copper alloy.

[0095] In some embodiments, the second preliminary alloy layer may be homogenized to form a first preliminary current collector including an aluminum-copper alloy layer (eg, S26 process).

[0096] For example, the homogenization may be initiated by heat-treating the first preliminary current collector including the aluminum-copper preliminary alloy layer at 300° C. to 500° C. or 400° C. to 450° C. Within the above range, the aluminum-copper alloy may be recrystallized without segregation.

[0097] For example, the first preliminary current collector including the aluminum-copper preliminary alloy layer may be heat-treated at 250° C. to 450° C. or 300° C. to 400° C. to terminate homogenization. Within the above range, recrystallization is completed without generating ridges, and thus the first preliminary current collector including the aluminum-copper alloy layer may be formed.

[0098] According to an exemplary embodiment, the first preliminary current collector may be subjected to a heat treatment to dope a metal element on the surface of the first preliminary current collector, thereby manufacturing the positive electrode current collector 105 (eg, S30 process and S40 process).

[0099] According to some embodiments, heat-treating the first preliminary current collector may include performing a cold rolling process on the first preliminary current collector and performing an annealing process on the cold-rolled first preliminary current collector.

[0100] In some embodiments, after the cold rolling process and before the annealing process, a doping solution containing the metal element may be coated on the surface of the cold-rolled first preliminary current collector.

[0101] In some embodiments, the doping solution coated on the surface of the first preliminary current collector may be doped on the first preliminary current collector by an annealing process. The metal may be, for example, nickel (Ni), magnesium (Mg) and / or zinc (Zn).

[0102] For example, during the annealing process, the metal element (e.g., nickel, magnesium, and / or zinc) may diffuse horizontally or vertically on the surface of the first preliminary current collector, so that the surface and surface layer of the copper layer may be doped with the metal element.

[0103] For example, the total weight of the metal element relative to the total weight of the first preliminary current collector may be 0.1 wt % to 3 wt % or 0.5 wt % to 1.5 wt %. Within the above range, the metal element may form a layer and be doped on the copper layer, and the reduction in capacity characteristics of the secondary battery caused by excessive reduction in the content of undoped copper may be prevented.

[0104] In some embodiments, the cold rolling process and the annealing process may be repeated.

[0105] In some embodiments, the first preliminary current collector may be subjected to a first cold rolling to form a second preliminary current collector having a reduced thickness.

[0106] For example, the ratio of the thickness of the second preliminary current collector to the thickness of the first preliminary current collector may be 0.4 to 0.6 or 0.45 to 0.55. Thus, the second preliminary current collector may be formed while preventing cracks caused by excessive rolling.

[0107] For example, the first cold rolling may be performed at 10° C. to 120° C. or 25° C. to 100° C. Within the above range, the mechanical strength and hardness of the second preliminary current collector may be improved.

[0108] In some embodiments, the second preliminary current collector may be subjected to a first annealing process to form a third preliminary current collector.

[0109] For example, the temperature of the first annealing process may be higher than the temperature of the second annealing process described below. For example, the first annealing process may be performed on the second preliminary current collector at 300° C. to 450° C. or 350° C. to 400° C. Within the above range, the internal stress of the second preliminary current collector may be removed and softened.

[0110] For example, the first annealing of the second preliminary current collector may be performed for 1 hour to 3 hours or 1 hour to 2 hours. Within the above range, copper and aluminum-copper alloys may also be softened by annealing.

[0111] In some embodiments, the third preliminary current collector may be subjected to a second cold rolling to form a fourth preliminary current collector having a reduced thickness.

[0112] For example, a ratio of the thickness of the fourth preliminary current collector to the thickness of the first preliminary current collector may be 0.02 to 0.1 or 0.04 to 0.06. Thus, a fourth preliminary current collector having improved mechanical strength and reduced thickness may be formed.

[0113] For example, the second cold rolling may be performed at 10° C. to 120° C. or at 25° C. to 100° C. Within the above range, the mechanical strength and hardness of the fourth preliminary current collector may be improved.

[0114] In some embodiments, the fourth preliminary current collector may be subjected to a second annealing to form the positive electrode current collector 105 .

[0115] For example, the temperature of the second annealing process may be lower than the temperature of the first annealing process described above. For example, the fourth preliminary current collector may be subjected to the second annealing at, for example, 200° C. to 450° C. or at 200° C. to 400° C. Within the above range, the internal stress of the fourth preliminary current collector may be removed and softened, thereby achieving miniaturization of metal crystals.

[0116] For example, the second annealing of the fourth preliminary current collector may be performed for 3 to 24 hours or 5 to 20 hours. Within the above range, aluminum, aluminum-copper alloy, and copper may be sufficiently annealed and softened, and impurities (eg, rolling oil) may be volatilized and removed.

[0117] In some embodiments, the first annealing process and the second annealing process may include doping of metal elements.

[0118] In some embodiments, the fourth preliminary current collector may be cooled to room temperature (25° C.) at 40° C. / hour to 60° C. / hour or 45° C. / hour to 55° C. / hour. Therefore, the ductility and strength of the positive electrode current collector 105 may be improved.

[0119] Figure 8 is a schematic cross-sectional view showing a positive electrode for a lithium secondary battery according to an exemplary embodiment.

[0120] Reference Figure 8The positive electrode 100 may include a positive electrode collector 105 and a positive electrode active material layer 150 , wherein the positive electrode active material layer 150 is provided by coating a positive electrode active material on the positive electrode collector 105 .

[0121] The positive electrode 100 may be manufactured by coating a positive electrode slurry on the positive electrode collector 105, rolling and drying the coating. The positive electrode slurry may be prepared by mixing and stirring the positive electrode active material with a binder, a conductive material and / or a dispersing material in a solvent.

[0122] According to an exemplary embodiment, the positive electrode current collector 105 may include the aluminum layer 110, the aluminum-copper alloy layer 120, and the copper layer. In some embodiments, the aluminum-copper alloy layer 120 may include Al 2 Cu layer, AlCu layer and / or AlCu 2 Therefore, even if the amount of the positive electrode active material contained in the positive electrode active material layer 150 increases, the positive electrode current collector 105 does not deform or break.

[0123] According to an exemplary embodiment, the positive electrode active material may include a compound that can reversibly intercalate and deintercalate lithium ions. The positive electrode active material may include lithium-transition metal composite oxide particles. For example, the lithium-transition metal composite oxide particles include nickel (Ni) and may further include at least one of cobalt (Co) or manganese (Mn).

[0124] For example, the lithium-transition metal composite oxide particles may be represented by the following Chemical Formula 1.

[0125] [Chemical formula 1]

[0126] Li x Ni 1-y M y O 2+z

[0127] In Chemical Formula 1, 0.9≤x≤1.1, y may be 0≤y≤0.7, and z may be -0.1≤z≤0.1. M may represent one or more elements selected from Na, Mg, Ca, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, or Zr.

[0128] The positive electrode binder may include an organic binder such as polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or a water-based binder such as styrene-butadiene rubber (SBR), and may be used together with a thickener such as carboxymethyl cellulose (CMC).

[0129] For example, a PVDF-based binder may be used as a positive electrode binder. In this case, the amount of the binder used to form the positive electrode active material layer may be reduced and the amount of the positive electrode active material may be relatively increased, thereby improving the power and capacity of the secondary battery.

[0130] The conductive material may be included to promote electron migration between active material particles. For example, the conductive material may include carbon-based conductive materials such as graphite, carbon black, graphene, carbon nanotubes, and / or tin, tin oxide, titanium oxide, LaSrCoO 3 、LaSrMnO 3 Metal-based conductive materials such as perovskite substances.

[0131] Fig. 9 and Fig.10 1 and 2 are respectively a schematic plan view and a cross-sectional view showing a lithium secondary battery according to an exemplary embodiment. Fig.10 It is along Fig. 9 A cross-sectional view taken along the thickness direction along the line II'.

[0132] Reference Fig. 9 and Fig.10 The lithium secondary battery may include a positive electrode 100 including the positive electrode current collector 105 and a negative electrode 160 opposite to the positive electrode.

[0133] According to an exemplary embodiment, the negative electrode 160 may include a negative electrode collector 165 and a negative electrode active material layer 170 formed by coating a negative electrode active material on the negative electrode collector 165 .

[0134] The negative electrode active material can be any negative electrode active material known in the art that can intercalate and deintercalate lithium ions without particular limitation. For example, the negative electrode active material can be a carbon-based material such as crystalline carbon, amorphous carbon, carbon composite, carbon fiber, etc.; a lithium alloy; silicon or tin, etc. As an example of the amorphous carbon, hard carbon, coke, mesocarbon microbead (MCMB) calcined at 1600 °C or lower, mesophase pitch-based carbon fiber (MPCF), etc. can be cited.

[0135] As an example of the crystalline carbon, graphite-based carbon such as natural graphite, graphitized coke, graphitized MCMB, graphitized MPCF, etc. can be cited. As the elements contained in the lithium alloy, aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium, etc. can be cited.

[0136] The silicon-based active material can include SiO x (0 < x < 2) or SiO containing a lithium compound x (0 < x < 2). SiO containing a Li compound x can be SiO containing lithium silicate x . Lithium silicate can be present in at least a part of the SiO x (0 < x < 2) particles. For example, it can be present inside and / or on the surface of the SiO x (0 < x < 2) particles. In one embodiment, the lithium silicate can include Li 2 SiO 3 , Li 2 Si 2 O 5 , Li 4 SiO 4 , Li 4 Si 3 O 8 etc.

[0137] The silicon-based active material can also contain a silicon-carbon composite compound such as silicon carbide (SiC), etc.

[0138] The negative electrode current collector 165 can include, for example, gold, stainless steel, nickel, aluminum, titanium, copper, or their alloys. In one embodiment, the negative electrode current collector 165 can include copper or a copper alloy.

[0139] For example, the negative electrode active material can be mixed and stirred with the above-mentioned binder, conductive material, thickener, etc. in a solvent to prepare a slurry form. After the slurry is coated on at least one surface of the negative electrode current collector 165, rolling and drying are performed to manufacture the negative electrode 160 including the negative electrode active material layer 170.

[0140] The binder and the conductive material may be substantially the same or similar to the above-mentioned materials. In some embodiments, for compatibility with the carbon-based active material, the binder used to form the negative electrode may include a water-based binder such as styrene-butadiene rubber (SBR), and may be used together with a thickener such as carboxymethyl cellulose (CMC).

[0141] The separator 180 may be inserted between the positive electrode 100 and the negative electrode 160. The separator 180 may include a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, an ethylene / methacrylate copolymer, etc. The separator 180 may also include a non-woven fabric formed of a high melting point glass fiber, a polyethylene terephthalate fiber, etc.

[0142] In some embodiments, the area (e.g., the area in contact with the separator 180) and / or volume of the negative electrode 160 may be greater than that of the positive electrode 100. Therefore, lithium ions generated from the positive electrode 100, for example, can smoothly migrate to the negative electrode 160 without being precipitated in the middle. Therefore, the effect of simultaneously improving power and stability can be more easily achieved through the above-mentioned composite hydroxide particles or in combination with the positive electrode active material.

[0143] According to an exemplary embodiment, a battery cell is defined by the positive electrode 100 , the negative electrode 160 , and the separator 180 , and a plurality of battery cells may be stacked to provide an electrode assembly 190 .

[0144] The electrode assembly 190 may be housed in the case 200 together with an electrolyte to define a lithium secondary battery. According to an exemplary embodiment, the electrolyte may use a non-aqueous electrolyte.

[0145] The non-aqueous electrolyte solution contains a lithium salt as an electrolyte and an organic solvent. + X - Represents, and as the anion of the lithium salt (X - ) can be exemplified by F - , Cl - Br - ,I - 、NO 3 - 、N(CN) 2 - , BF 4 - , ClO 4 - PF 6 - ,(CF 3 ) 2 PF 4- , (CF 3 ) 3 PF 3 - , (CF 3 ) 4 PF 2 - , (CF 3 ) 5 PF - , (CF 3 ) 6 P - , CF 3 SO 3 - , CF 3 CF 2 SO 3 - , (CF 3 SO 2 ) 2 N - , (FSO 2 ) 2 N - , CF 3 CF 2 (CF 3 ) 2 CO - , (CF 3 SO 2 ) 2 CH - , (SF 5 ) 3 C - , (CF 3 SO 2 ) 3 C - , CF 3 (CF 2 ) 7 SO 3 - , CF 3 CO 2 - , CH 3 CO 2 - , SCN - and (CF 3 CF 2 SO 2 ) 2 N - etc.

[0146] The organic solvent may be, for example, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, cyclopentane, γ-butyrolactone, propylene sulfite, tetrahydrofuran, etc. These may be used alone or in combination of two or more.

[0147] like Fig. 9 As shown, the tabs (positive tabs and negative tabs) may protrude from the positive current collector 105 and the negative current collector 165 belonging to each electrode unit and extend to one side of the housing 200. The tabs may be fused with the one side of the housing 200 and form electrode leads (positive lead 107 and negative lead 167) extending to the outside of the housing 200 or exposed to the outside of the housing 200.

[0148] The lithium secondary battery may be manufactured in, for example, a cylindrical shape using a can, a prismatic shape, a pouch type, a coin shape, or the like.

[0149] Below, specific experimental examples are proposed to help understand the present invention, but this is only used to illustrate the present invention and is not used to limit the claims. Various changes and modifications can be made to the embodiments within the scope of the present invention and the technical concept. This is clear to those skilled in the art, and it is natural that such changes and modifications fall within the scope of the claims.

[0150] Examples and Comparative Examples

[0151] Example 1

[0152] 1) Manufacturing of positive electrode current collector

[0153] A positive electrode current collector (9 μm thick) was manufactured by forming an aluminum layer with a thickness of 4 μm, forming an aluminum-copper alloy layer with a thickness of 1 μm on both sides of the aluminum layer, and forming a copper layer with a thickness of 1.5 μm on the aluminum-copper alloy layer.

[0154] Specifically, copper foil is bonded on both sides of the aluminum foil by a roll-to-roll process. The metal foil bonded with the aluminum foil and the copper foil is hot rolled at 600°C to form an aluminum-copper preliminary alloy layer by recrystallization of aluminum and copper. The aluminum-copper preliminary alloy layer is formed by homogenizing the aluminum-copper alloy layer at 450°C. After that, a first cold rolling, a first annealing process (simultaneously doped with a metal element once), a second cold rolling, and a second annealing process (simultaneously doped with the metal element twice) are performed to manufacture a positive electrode current collector including an aluminum-copper alloy layer. The first annealing process is performed at 400°C, and the metal element is doped once to the surface of the copper layer and diffused while the first annealing process is performed. The second annealing process is performed at 350°C, and the metal element is doped twice to the surface of the copper layer doped with the metal element once and diffused while the second annealing process is performed. A protrusion for forming a positive electrode tab is provided on one side of the positive electrode current collector.

[0155] The aluminum-copper alloy layer is formed in sequence from the aluminum in the center to the 2 Cu layer, AlCu layer and AlCu 2 layer.

[0156] The metal element is nickel, and the doping is performed such that the weight of the nickel element is 0.5 wt % relative to the total weight of the positive electrode current collector.

[0157] 2) Manufacturing of positive electrode

[0158] LiNi as the positive electrode active material 0.6 Co 0.2 Mn 0.2 O 2 , carbon black as a positive electrode conductive material, and polyvinylidene fluoride (PVDF) as a positive electrode binder are mixed in a weight ratio of 95:3:2 to prepare a positive electrode slurry, and then the positive electrode slurry is coated on the area of ​​the positive electrode collector except the protrusion (positive electrode ear), and dried and rolled to form a positive electrode active material layer.

[0159] 3) Manufacturing of negative electrode

[0160] A negative electrode slurry was prepared by dispersing a negative electrode active material in which artificial graphite and natural graphite were mixed at a weight ratio of 7:3, styrene-butadiene rubber, and carboxymethyl cellulose at a weight ratio of 97:1:2 in distilled water.

[0161] The negative electrode slurry is applied on a copper foil having a protrusion (negative electrode tab) on one side, except for the protrusion, and dried and rolled to manufacture a negative electrode.

[0162] 4) Manufacturing of lithium secondary batteries

[0163] A polyethylene separator (thickness of 20 μm) was inserted between the positive electrode and the negative electrode to form a unit electrode assembly. The unit electrode assemblies were stacked to have a capacity of 80 Ah, thereby forming an electrode assembly. A positive electrode lead and a negative electrode lead were welded to the positive electrode tab and the negative electrode tab, respectively, for connection.

[0164] Prepare 1M LiPF 6 Solution (30:70 v / v EC / EMC mixed solvent), and then added so that 1 wt% of fluoroethylene carbonate (FEC), 0.3 wt% of ethylene carbonate (VC), and 0.5 wt% of lithium difluorophosphate (LiPO 2 F 2 ) was 1 wt %, 1,3-propane sultone (1,3-Propane sultone, PS) was 0.5 wt %, and 1,3-propylene sultone (Prop-1-ene-1,3-sultone, PRS) was 0.5 wt %, thereby preparing an electrolyte solution.

[0165] The electrode assembly is housed in a soft pack (casing) such that partial regions of the positive electrode lead and the negative electrode lead are exposed to the outside, and three surfaces other than the electrolyte injection portion surface are sealed.

[0166] The electrolyte solution is injected into the soft package, and the electrolyte solution injection portion is sealed, thereby manufacturing a lithium secondary battery.

[0167] Example 2

[0168] A lithium secondary battery was manufactured by the same method as in Example 1, except that the doped metal element was magnesium, and the doping was performed so that the weight of the magnesium element was 0.5 wt % relative to the total weight of the positive electrode current collector.

[0169] Example 3

[0170] A lithium secondary battery was manufactured by the same method as in Example 1, except that the doped metal element was zinc, and the doping was performed so that the weight of the zinc element relative to the total weight of the positive electrode current collector was 0.5 wt %.

[0171] Example 4

[0172] A lithium secondary battery is manufactured by the same method as in Example 1, except that the doped metal elements are nickel and magnesium, and the doping is performed so that the weight of the nickel element relative to the total weight of the positive electrode collector is 0.2 wt %, and the weight of the magnesium element relative to the total weight of the positive electrode collector is 0.3 wt %.

[0173] Example 5

[0174] A lithium secondary battery is manufactured by the same method as in Example 1, except that the doped metal elements are nickel and magnesium, and the doping is performed so that the weight of the nickel element relative to the total weight of the positive electrode collector is 0.3 wt %, and the weight of the magnesium element relative to the total weight of the positive electrode collector is 0.2 wt %.

[0175] Example 6

[0176] A lithium secondary battery is manufactured by the same method as in Example 1, except that the doped metal elements are nickel, magnesium and zinc, and the doping is performed so that the weight of the nickel element relative to the total weight of the positive electrode collector is 0.1 wt%, the weight of the magnesium element relative to the total weight of the positive electrode collector is 0.1 wt% and the weight of the zinc element relative to the total weight of the positive electrode collector is 0.3 wt%.

[0177] Example 7

[0178] A lithium secondary battery is manufactured by the same method as in Example 1, except that the doped metal elements are nickel, magnesium and zinc, and the doping is performed so that the weight of the nickel element relative to the total weight of the positive electrode collector is 0.1 wt%, the weight of the magnesium element relative to the total weight of the positive electrode collector is 0.1 wt% and the weight of the zinc element relative to the total weight of the positive electrode collector is 0.5 wt%.

[0179] Example 8

[0180] A lithium secondary battery is manufactured by the same method as in Example 1, except that the doped metal elements are nickel, magnesium and zinc, and the doping is performed so that the weight of the nickel element relative to the total weight of the positive electrode collector is 0.1 wt %, the weight of the magnesium element relative to the total weight of the positive electrode collector is 0.1 wt %, and the weight of the zinc element relative to the total weight of the positive electrode collector is 1.0 wt %.

[0181] Example 9

[0182] A lithium secondary battery was manufactured by the same method as in Example 1, except that an aluminum layer with a thickness of 4 μm was formed, an aluminum-copper alloy layer with a thickness of 1.5 μm was formed on both sides of the aluminum layer, and a copper layer with a thickness of 4 μm was formed on the aluminum-copper alloy layer, thereby manufacturing a positive electrode current collector (with a thickness of 15 μm).

[0183] Comparative Example 1

[0184] A lithium secondary battery was manufactured by the same method as in Example 1, except that no metal element was doped when manufacturing the positive electrode current collector.

[0185] Comparative Example 2

[0186] A lithium secondary battery was manufactured by the same method as in Example 1, except that a 15 μm aluminum foil was used as the positive electrode current collector. In addition, no metal element was doped during the manufacture of the positive electrode current collector.

[0187] Comparative Example 3

[0188] A lithium secondary battery was manufactured by the same method as in Example 1, except that an aluminum layer with a thickness of 4 μm was formed, an aluminum-copper alloy layer with a thickness of 1.5 μm was formed on both sides of the aluminum layer, and a copper layer with a thickness of 4 μm was formed on the aluminum-copper alloy layer, thereby manufacturing a positive electrode current collector (with a thickness of 15 μm).

[0189] Furthermore, no metal element is doped when manufacturing the positive electrode current collector.

[0190] Experimental example

[0191] (1) Measurement of fracture compaction density

[0192] When manufacturing the positive electrodes of the lithium secondary batteries according to the examples and comparative examples, the positive electrode current collector was coated with 20 mg / cm 2 Then, the positive electrode slurry was coated at a loading of 3.7 g / cm 3 The positive electrode slurry was initially rolled at a density of 0.05 g / cm2 at intervals of 100 m if there was no breakage. 3 The compacted density of the material is then used to measure the critical fracture density for initial fracture.

[0193] (2) Measurement of resistance of positive electrode current collector

[0194] Using an electrode resistance meter (HIOKI), a constant current was applied to the battery electrode surface, and the volume resistivity of the composite layer and the interface resistance between the composite layer and the current collector were calculated from the potential distribution to measure the average resistance of the positive electrode current collector.

[0195] (3) Measurement of battery resistance of secondary batteries

[0196] The battery resistance was measured by applying a current of 1 C for 10 seconds at a point where the state of charge (SOC) of the secondary batteries according to the embodiment and the comparative example was set to 50% and calculating a change in voltage.

[0197] The evaluation results are shown in Table 1 below.

[0198] [Table 1]

[0199]

[0200] Referring to Table 1, in the example using the positive electrode collector doped with a metal element on the copper layer, the fracture compaction density and the adhesive strength are improved, and the resistance of the positive electrode collector and the secondary battery is reduced.

[0201] In Example 2 using magnesium element as the metal element, the adhesive strength was slightly increased.

[0202] In Example 3 using zinc element as the metal element, the resistance of the positive electrode current collector and the resistance of the secondary battery slightly increased.

[0203] In Examples 6 to 8 in which nickel element, magnesium element, and zinc element were mixed as metal elements, the fracture compaction density was slightly increased.

[0204] In Comparative Example 1 in which a metal element is not doped on the copper layer, compared with Example 1 having the same thickness, the fracture compaction density and the adhesive strength are reduced, and the resistance of the positive electrode collector and the resistance of the secondary battery are increased.

[0205] Compared with Example 9 having the same thickness, Comparative Example 2 in which no metal element is doped on the copper layer and only aluminum foil is used, the fracture compaction density and the adhesive strength are significantly reduced, and the resistance of the positive electrode collector and the resistance of the secondary battery are significantly increased.

[0206] In Comparative Example 3 in which the copper layer was not doped with a metal element, compared with Example 9 having the same thickness, the fracture compaction density and the adhesive strength were reduced, and the resistance of the positive electrode collector and the resistance of the secondary battery were increased.

Claims

1. A positive electrode current collector for a lithium secondary battery, comprising a stacked structure, the stacked structure comprising an aluminum layer, an aluminum-copper alloy layer formed on the aluminum layer, and a copper layer formed on the aluminum-copper alloy layer, wherein a surface of the stacked structure is doped with at least one metal element.

2. The positive electrode current collector for a lithium secondary battery according to claim 1, in, The aluminum-copper alloy layer includes Al 2 Cu, AlCu and AlCu 2 At least one of .

3. The positive electrode current collector for a lithium secondary battery according to claim 2, in, The aluminum-copper alloy layer includes Al 2 Cu layer, AlCu-containing layer and AlCu-containing layer 2 At least two or more stacked structures in a layer.

4. The positive electrode current collector for a lithium secondary battery according to claim 1, in, The copper layer includes: an undoped layer, which is disposed on the aluminum-copper alloy layer and is not doped with the metal element; and a metal-doped layer, which is disposed on the undoped layer and is doped with the metal element.

5. The positive electrode current collector for a lithium secondary battery according to claim 4, in, The metal doping layer includes copper doped with the metal element.

6. The positive electrode current collector for a lithium secondary battery according to claim 1, in, The metal element includes at least one of nickel, magnesium and zinc.

7. The positive electrode current collector for a lithium secondary battery according to claim 6, in, The metal elements include nickel, magnesium and zinc.

8. The positive electrode current collector for a lithium secondary battery according to claim 7, in, The content of zinc in the metal elements is greater than or equal to the sum of the content of nickel and the content of magnesium.

9. The positive electrode current collector for a lithium secondary battery according to claim 1, in, The doping content of the metal element is 0.1 wt % to 3 wt % relative to the total weight of the stacked structure.

10. A lithium secondary battery, include: A positive electrode, comprising the positive electrode current collector according to claim 1 and a positive electrode active material layer formed on at least one side of the positive electrode current collector; as well as A negative electrode is arranged opposite to the positive electrode.

11. A method for producing a positive electrode current collector for a lithium secondary battery, wherein The following steps are involved: hot rolling an aluminum foil and a copper foil to form a first preliminary current collector including an aluminum-copper alloy layer; as well as The first preliminary current collector is heat-treated to dope a metal element on a surface of the first preliminary current collector.

12. The method for producing a positive electrode current collector for a lithium secondary battery according to claim 11, in, The aluminum-copper alloy layer is formed between the aluminum foil and the copper foil.

13. The method for producing a positive electrode current collector for a lithium secondary battery according to claim 11, in, The step of heat-treating the first preliminary current collector includes performing a cold rolling process on the first preliminary current collector and performing an annealing process on the cold-rolled first preliminary current collector.

14. The method for producing a positive electrode current collector for a lithium secondary battery according to claim 13, in, Metal elements are doped on the surface of the first preliminary current collector through the annealing process.

15. The method for producing a positive electrode current collector for a lithium secondary battery according to claim 14, in, After the cold rolling process and before the annealing process, the method further includes coating a doping solution containing the metal element on the surface of the cold-rolled first preliminary current collector.

16. The method for producing a positive electrode current collector for a lithium secondary battery according to claim 13, in, The cold rolling process and the annealing process are repeatedly performed.

17. The method for producing a positive electrode current collector for a lithium secondary battery according to claim 16, in, The cold rolling process and the annealing process include: The first preliminary current collector is subjected to a first cold rolling to form a second preliminary current collector, performing a first annealing process on the second preliminary current collector to form a third preliminary current collector, The third preliminary current collector is subjected to a second cold rolling to form a fourth preliminary current collector, A second annealing process is performed on the fourth preliminary current collector.

18. The method for producing a positive electrode current collector for a lithium secondary battery according to claim 17, in, The temperature of the first annealing process is higher than the temperature of the second annealing process.

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