Negative electrode current collector and negative electrode-free battery comprising same

Abstract

The present invention relates to a negative electrode current collector and a negative electrode-free battery comprising same, the negative electrode current collector comprising: a copper substrate; and a coating layer disposed on at least one surface of the copper substrate and including lithium-substituted polyacrylic acid.

Description

Negative current collector and negative electrode battery including the same

[0001] The present invention relates to a negative electrode current collector in which lithium dendrites are suppressed and a negative electrode battery comprising the same.

[0002] With the recent development of the information society leading to advancements in personal IT devices and computer networks, and the accompanying increase in the overall society's dependence on electrical energy, there is a demand for the development of battery technology to efficiently store and utilize electrical energy.

[0003] In particular, with the growing interest in solving environmental problems and realizing a sustainable circular society, research on energy storage devices such as lithium-ion batteries and electric double-layer capacitors is being conducted extensively. Among these, lithium-ion batteries are receiving attention as battery systems that theoretically have the highest energy density within battery technology.

[0004] A lithium secondary battery is structured such that an electrolyte is impregnated into an electrode assembly composed of a positive electrode, a negative electrode, and a separator. The positive electrode is manufactured by coating a positive electrode composite containing a positive electrode active material onto aluminum foil, and the negative electrode is manufactured by coating a negative electrode composite containing a negative electrode active material onto copper foil. Conventionally, lithium transition metal oxides such as lithium iron phosphate, lithium cobalt oxide, and lithium nickel-cobalt-manganese oxide have been used as the positive electrode active material, while carbon-based active materials and silicon-based active materials have been used as the negative electrode active material.

[0005] With the recent increase in demand for high-energy-density batteries, research is being conducted on negative electrode-free batteries (or anode-free batteries) that do not utilize carbon-based or silicon-based negative electrode active materials with large irreversible capacity. Instead, lithium ions supplied from the anode are electrodeposited onto the negative current collector during charging to act as the negative electrode active material. Since negative electrode-free batteries do not include a negative electrode composite layer, they can incorporate a larger anode composite layer, which is desirable from the perspective of high energy density. Furthermore, these negative electrode-free batteries are advantageous in terms of capacity because the absence of carbon-based or silicon-based negative electrode active materials prevents the occurrence of negative irreversible capacity, allowing the full utilization of the anode capacity.

[0006] However, copper current collectors generally used as negative electrode current collectors have uneven surfaces, resulting in a non-uniform current density distribution and an unstable interface between the negative electrode current collector and the electrolyte. Consequently, lithium transferred from the positive electrode is electrodeposited onto the negative electrode current collector during charging, leading to the formation of lithium dendrites and increased adverse reactions with the electrolyte. When lithium dendrites form, lithium ions are lost, reducing charge / discharge efficiency, and increased adverse reactions with the electrolyte degrade lifespan characteristics.

[0007] Therefore, there is a need for the development of technology to suppress the formation of lithium dendrites on the negative current collector for anode-free batteries.

[0008] The present invention aims to solve the above-mentioned problems by providing a negative electrode current collector and a negative electrode battery including the same, wherein a coating layer containing lithium-substituted polyacrylic acid is formed on a copper current collector to suppress the generation of lithium dendrites when applied to a negative electrode battery.

[0009] [1] The present invention provides a negative current collector comprising a copper substrate; and a coating layer disposed on at least one surface of the copper substrate and comprising lithium-substituted polyacrylic acid.

[0010] [2] The present invention provides a negative current collector in which the lithium-substituted polyacrylic acid of [1] comprises repeating units represented by the following chemical formula 1.

[0011] [Chemical Formula 1]

[0012]

[0013] [3] The present invention provides a negative current collector in which, in [1] or [2], the lithium-substituted polyacrylic acid is composed of repeating units represented by the following chemical formula 1 and repeating units represented by the following chemical formula 2.

[0014] [Chemical Formula 1]

[0015]

[0016] [Chemical Formula 2]

[0017]

[0018] [4] The present invention provides a negative current collector in which, in at least one of [1] to [3], the thickness of the copper substrate is 3 μm to 15 μm.

[0019] [5] The present invention provides a negative current collector in which, in at least one of [1] to [4], the copper substrate is an electrolytic copper foil or a rolled copper foil.

[0020] [6] The present invention provides a negative current collector in which, in at least one of [1] to [5], the thickness of the coating layer is 30 nm to 5 μm.

[0021]

[0067] The present invention provides a cathode current collector in which, in at least one of [1] to [6], the total thickness of the cathode current collector is 3.03 μm to 20 μm.

[0022] [8] The present invention provides a non-anode battery comprising a positive electrode; a negative electrode current collector according to any one of [1] to [7]; and an electrolyte.

[0023] [9] The present invention, in the above [8], wherein the anode is a positive active material Li2MnO3, yLi2MnO3·(1-y)LiM a O2(here, M a It includes Ni, Co, Mn, Al, Fe, V, Cr, Ti, Ta, Mg, Y, Zr, Ca, Sr, W, or combinations thereof, and 0 <y<1임), Li z Mn 1-e-f Ni e M b f O2(here, M b ... comprises Co, Al, Fe, V, Cr, Ti, Ta, Mg, Y, Zr, Ca, Sr, W, or a combination thereof, and 1 <z≤1.5, 0.1≤e≤0.5, 0≤f≤0.5임), Li2S 또는 이들의 조합을 포함하는 것인 무음극 전지를 제공한다.

[0024]

[0010] The present invention provides a non-anode battery comprising a separator between the positive electrode and the negative electrode current collector, in addition to the above [8] or [9].

[0025]

[0011] The present invention provides a non-anode battery having an initial Coulomb efficiency of 90% or more in at least one of [8] to

[0010] .

[0026] The negative current collector according to the present invention forms a lithium-substituted polyacrylic acid coating layer on the surface of a copper substrate, thereby increasing the flatness of the surface of the negative current collector and stabilizing the reactivity at the interface between the negative current collector and the electrolyte.

[0027] In addition, the lithium-substituted polyacrylic acid contains lithium-substituted carboxyl groups at a high density, and due to the presence of lithium ions substituted on the carboxyl groups, the structural diffusion of lithium ions within the coating layer increases, making the lithium ion flux uniform and suppressing the formation of lithium dendrites.

[0028] The negative current collector according to the present invention can be usefully applied to a negative electrode battery. When the negative current collector according to the present invention is applied to a negative electrode battery, the lithium ion flux appears relatively uniformly on the surface of the negative current collector during charging, so the occurrence of lithium dendrites due to the non-uniformity of the lithium ion flux is reduced, and accordingly, the initial lithium loss due to the occurrence of lithium dendrites is minimized, thereby improving the initial Coulomb efficiency.

[0029] Figure 1 is an SEM image showing the surface condition of a lithium-substituted polyacrylic acid-coated negative current collector prepared according to Example 1.

[0030] Figure 2 is an SEM image showing the surface condition of a lithium unsubstituted polyacrylic acid-coated negative current collector prepared according to Comparative Example 1.

[0031] Figure 3 is an SEM image showing the surface condition of the uncoated copper foil used in Comparative Example 2.

[0032] Figure 4 shows SEM images of the surface condition of the negative current collector of Example 1 after lithium ion electrodeposition, observed at different magnifications.

[0033] Figure 5 shows SEM images of the surface condition of the negative current collector of Comparative Example 1 after lithium ion electrodeposition, observed at different magnifications.

[0034] Figure 6 is an SEM image showing the surface condition of the negative electrode current collector (copper foil) of Comparative Example 2 after lithium ion electrodeposition.

[0035] FIG. 7 is a capacitance-voltage profile measured by charging each of the coin half cells prepared in Example 1 and Comparative Examples 1 and 2 at a constant current of 1 mAh for 1 hour, and then discharging them to 0.5 V at a constant current of 0.5 mA.

[0036] The terms used in this specification are for describing embodiments of the invention and are not intended to limit the invention.

[0037] In this specification, the singular form includes the plural form unless specifically stated otherwise.

[0038] As used herein, “comprises” and / or “comprising” do not exclude the presence or addition of one or more other components in addition to the mentioned components.

[0039]

[0040] The present invention will be described in detail below.

[0041]

[0042] <Cathode Current Collector>

[0043] A negative current collector according to the present invention comprises a copper substrate and a coating layer disposed on at least one surface of the copper substrate. The coating layer comprises lithium-substituted polyacrylic acid.

[0044] The copper substrate may be a copper thin film that can be used as a negative current collector in the relevant technical field, for example, an electrolytic copper foil or a rolled copper foil. Although not particularly limited, in the case of an electrolytic copper foil manufactured using an electroplating method, a thinner thickness can be achieved compared to a rolled copper foil, which has the advantage of reducing the weight of the battery and improving the energy density of the battery. In addition, in the case of an electrolytic copper foil, since the thickness can be controlled by adjusting the current application time or temperature, it is advantageous in terms of process flexibility and cost.

[0045] The copper substrate may have a thickness of 3 µm to 15 µm, preferably 5 µm to 12 µm, and more preferably 6 µm to 10 µm. When the copper substrate thickness satisfies the above range, excellent energy density can be achieved while securing mechanical strength. If the thickness of the copper substrate is too thin, mechanical strength is reduced, and if it is too thick, the total thickness of the battery increases, which may result in a decrease in energy density.

[0046]

[0047] The above coating layer comprises lithium-substituted polyacrylic acid. Preferably, the coating layer may be composed of lithium-substituted polyacrylic acid.

[0048] The above coating layer can be formed by applying a lithium-substituted polyacrylic acid solution to at least one surface of a copper substrate and then drying it.

[0049] The above lithium-substituted polyacrylic acid refers to a polymer in which lithium is substituted on the carboxyl group of polyacrylic acid, and, for example, may be a polymer containing repeating units represented by the following [Chemical Formula 1].

[0050] [Chemical Formula 1]

[0051]

[0052] Preferably, the lithium-substituted polyacrylic acid may consist of repeating units represented by the following [Formula 1] and repeating units represented by the following [Formula 2].

[0053] [Chemical Formula 1]

[0054]

[0055] [Chemical Formula 2]

[0056]

[0057] The above lithium-substituted polyacrylic acid can be prepared, for example, by reacting a lithium raw material, such as lithium hydroxide, with polyacrylic acid.

[0058] The lithium-substituted polyacrylic acid may have a weight-average molecular weight of 100,000 to 800,000, specifically 200,000 to 400,000, and an acid substitution rate of 5% to 40%, specifically 15% to 35%. When the weight-average molecular weight and acid substitution rate of the lithium-substituted polyacrylic acid satisfy the above ranges, a uniform lithium ion flux can be formed, and homogeneous lithium deposition without dendrites can be achieved.

[0059]

[0060] The above lithium-substituted polyacrylic acid contains lithium-substituted carboxyl groups at a high density, and due to the presence of lithium ions substituted in the carboxyl groups, the structural diffusion of lithium ions increases during charging and discharging. Here, structural diffusion refers to the solid-state diffusion of lithium ions, and as structural diffusion increases, the uniformity of the lithium ion flux is improved, which can suppress the formation of lithium dendrites.

[0061] In addition, when lithium-substituted polyacrylic acid is coated on a copper substrate, surface roughness is reduced, and consequently, interfacial stability with the electrolyte is improved, which reduces adverse reactions with the electrolyte and improves lifespan characteristics.

[0062] The thickness of the coating layer may be 30 nm to 5 µm, 100 nm to 4 µm, or 500 nm to 3 µm. When the coating layer thickness satisfies the above range, uniform lithium ion deposition without lithium dendrites can be achieved.

[0063]

[0064] The total thickness of the negative current collector including the copper substrate and the coating layer may be 3.03 μm to 20 μm, 5.5 μm to 15 μm, or 6.5 μm to 13 μm. When the thickness of the negative current collector satisfies the above range, electrical conductivity, lithium mobility, mechanical properties, and energy density can be appropriately maintained.

[0065]

[0066] Cathode-less battery

[0067] Next, a negative electrode battery according to the present invention will be described.

[0068] In the present invention, a non-anode battery refers to a battery that does not include a negative electrode active material, such as a carbon-based negative electrode active material, a silicon-based negative electrode active material, or lithium metal, during battery assembly. In a non-anode battery, lithium ions provided from the positive electrode are electrodeposited onto a negative electrode current collector during charging to form a lithium metal layer, and then, during discharging, lithium ions are released from the electrodeposited lithium metal layer and move to the positive electrode to perform charging and discharging.

[0069] The anode-free battery according to the present invention comprises a negative current collector according to the present invention as described above. Specifically, the anode-free battery comprises a positive electrode, a negative current collector according to the present invention, and an electrolyte. If necessary, the anode-free battery may further comprise a separator between the positive electrode and the negative current collector.

[0070] Since the above-mentioned cathode current collector is the same as described above, a detailed explanation is omitted.

[0071] The above anode is positioned opposite the above cathode current collector.

[0072] The above positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector.

[0073] The above positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, aluminum, stainless steel, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The above positive current collector may generally have a thickness of 3 μm to 500 μm.

[0074] The above positive active material layer is formed on the positive current collector and includes a positive active material.

[0075] The above-mentioned positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and may be a lithium-containing compound known to be applicable as a positive electrode active material in the relevant technical field.

[0076] For example, the positive electrode active material may be a lithium metal oxide, lithium sulfide, or a combination thereof comprising one or more metals such as cobalt, manganese, nickel, or aluminum and lithium. The lithium metal oxide is, for example, Li x1 Mn 1-a M 1 a O2(here, M 1 ... comprises Ni, Co, Al, Fe, V, Cr, Ti, Ta, Mg, Y, Zr, Ca, Sr, W or combinations thereof, where 0.9≤x1≤1.3, 0≤a≤0.6), lithium manganese-based oxides such as Li2MnO3, LiMn2O4, etc.; Li x2 Co 1-b M 2 b O2(here, M 2 ... comprises Al, Fe, V, Cr, Ti, Ta, Mg, Y, Zr, Ni, Mn, Ca, Sr, W or combinations thereof, and is a lithium cobalt-based oxide such as (0.9≤x2≤1.1, 0≤b≤0.5); Li x3 Ni 1-c M 3c O2(here, M 3 lithium nickel-based oxides such as (containing Co, Mn, Al, Fe, V, Cr, Ti, Ta, Mg, Y, Zr, Ca, Sr, W or combinations thereof, where 0.9≤x3≤1.2, 0≤c≤0.7); Li x4 Fe 1-d M 4 d PO4(here, M 4 Examples include lithium metal phosphates such as Co, Mn, Al, Fe, V, Cr, Ti, Ta, Mg, Y, Zr, Ca, Sr, W or combinations thereof (where 0.9≤x4≤1.1 and 0≤d≤0.8), and any one or more of these compounds may be included.

[0077] In the case of a negative electrode battery, since lithium ions provided by the positive electrode active material are electrodeposited on the negative electrode current collector to form a lithium metal layer, it is more preferable to use a lithium-rich compound with a high lithium ion content. The lithium-rich compound is, for example, Li2MnO3, yLi2MnO3·(1-y)LiM a O2(here, M a It includes Ni, Co, Mn, Al, Fe, V, Cr, Ti, Ta, Mg, Y, Zr, Ca, Sr, W, or combinations thereof, and 0 <y<1임), Li z Mn 1-e-f Ni e M b f O2(here, M b ... comprises Co, Al, Fe, V, Cr, Ti, Ta, Mg, Y, Zr, Ca, Sr, W, or a combination thereof, and 1 <z≤1.5, 0.1≤e≤0.5, 0≤f≤0.5임), Li2S 또는 이들의 조합일 수 있다.

[0078] The above positive active material may be included in an amount of 80% to 99% by weight based on the total weight of the positive active material layer.

[0079] The above positive active material layer may further include a binder and / or a conductive material in addition to the aforementioned positive active material.

[0080] The above binder is a component that assists in the bonding of the active material and the conductive material, and the bonding to the current collector, and may be, for example, polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, various copolymers, etc. The above binder may be included in an amount of 0.1% to 10% by weight based on the total weight of the positive active material layer.

[0081] The above conductive material is intended to improve the conductivity of the positive electrode active material layer, and it only needs to have conductivity without causing chemical changes in the battery, and its type is not particularly limited.

[0082] The conductive material may be, for example, carbon-based materials such as graphite, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon nanotubes, etc.; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; metal powders such as aluminum or nickel powder; conductive phishes such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. The conductive material may be included in an amount of 0.1% to 10% by weight based on the total weight of the positive electrode active material layer.

[0083] The above-mentioned anode may be manufactured by mixing an anode active material and, optionally, a conductive material and / or a binder in a solvent to prepare an anode slurry, applying the anode slurry onto an anode current collector, and then drying and rolling. The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone) and may be used in an amount that results in a desirable viscosity when the anode active material and, optionally, the binder and conductive material are included. For example, the concentration of the solid component including the anode active material and, optionally, the binder and conductive material may be 50% to 95% by weight, preferably 70% to 90% by weight.

[0084]

[0085] Next, the electrolyte may be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc., which can be used in the manufacture of a lithium secondary battery.

[0086] For example, the above electrolyte may include an organic solvent and a lithium salt.

[0087] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, gamma-butyrolactone, ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a C2 to C20 straight-chain, branched, or cyclic hydrocarbon group and may include a double aromatic ring or ether bond); and amides such as dimethylformamide. Dioxolanes such as 1,3-dioxolane; or sulfolanes, etc. may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.

[0088] The above lithium salt can be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries.

[0089] Specifically, the above lithium salts may include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO2, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2.

[0090] It is preferable to use the above lithium salt within a range of 0.1 to 7 M, specifically 0.8 to 3.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0091]

[0092] The above separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. It can be used without special limitations as long as it is a separator typically used in lithium secondary batteries, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte wettability. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and it may optionally be used in a single-layer or multi-layer structure.

[0093]

[0094] Meanwhile, the above-described non-anode battery may further include a lithium metal layer between the copper substrate and the coating layer. The lithium metal layer may be formed by lithium ions emitted from the positive electrode during charging being electrodeposited on the copper substrate. Meanwhile, during discharge, lithium ions may be detached from the lithium metal layer and move to the positive electrode. Depending on the battery efficiency, a portion of the lithium metal layer may remain between the copper substrate and the coating layer during discharge, or it may not remain.

[0095]

[0096] In the anode-free battery according to the present invention as described above, by applying a negative electrode current collector having a lithium-substituted polyacrylic acid coating layer formed on a copper substrate, the lithium ion flux appears relatively uniformly on the surface of the negative electrode current collector during charging. Therefore, in the case of the anode-free battery according to the present invention, the occurrence of lithium dendrites due to the non-uniformity of the lithium ion flux is low, and accordingly, the initial lithium loss due to the occurrence of lithium dendrites is minimized, thereby improving the initial Coulomb efficiency. Specifically, the anode-free battery according to the present invention may have an initial Coulomb efficiency of 90% or more, preferably 92% or more, and more preferably 94% or more.

[0097]

[0098] The cathode-free battery according to the present invention can be usefully used as a power source in various fields such as electronic devices like mobile phones, laptop computers, and digital cameras, energy storage systems (ESS), and electric vehicles.

[0099]

[0100] The present invention will be explained in more detail below through specific embodiments. However, the following embodiments are merely examples to aid in understanding the invention and do not limit the scope of the invention. It is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of this description, and it is natural that such variations and modifications fall within the scope of the appended claims.

[0101]

[0102] Example 1

[0103] A copper foil with a thickness of 8 μm was prepared. A lithium-substituted polyacrylic acid solution (solid content 11.2%) was applied onto the copper foil and dried to form a coating layer with a thickness of 4 μm, thereby manufacturing a negative electrode current collector A.

[0104] An electrode assembly was manufactured by sequentially stacking the negative current collector A, the polyethylene separator, and the lithium metal electrode (counter electrode) prepared above, and then housing it in a battery case, injecting an electrolyte, and sealing it to manufacture a coin half cell. As the electrolyte, an organic solvent was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75, to which LiPF6 was added at a concentration of 1.25 mol / L.

[0105]

[0106] Comparative Example 1

[0107] A negative current collector B was prepared in the same manner as in Example 1, except that a non-lithium-substituted polyacrylic acid solution was used to form the coating layer instead of a lithium-substituted polyacrylic acid solution.

[0108] In addition, a coin half cell was manufactured in the same manner as in Example 1, except that a negative current collector B was used instead of a negative current collector A.

[0109]

[0110] Comparative Example 2

[0111] A coin half cell was manufactured in the same manner as in Example 1, except that a copper foil without a coating layer was used as the negative current collector instead of negative current collector A.

[0112]

[0113] Experimental Example 1: Evaluation of surface condition of cathode current collector

[0114] The surfaces of the cathode current collectors used in Example 1, Comparative Example 1, and Comparative Example 2 were observed using a scanning electron microscope (SEM) and are shown in FIGS. 1 to 3.

[0115] Figure 1 is an SEM image showing the surface condition of a negative electrode current collector coated with lithium-substituted polyacrylic acid prepared according to Example 1, and Figure 2 is an SEM image showing the surface condition of a negative electrode current collector coated with lithium-unsubstituted polyacrylic acid prepared according to Comparative Example 1. Figure 3 is an SEM image showing the surface condition of an uncoated copper foil used in Comparative Example 2.

[0116] Through FIGS. 1 to 3, it can be seen that the surface of the negative current collector of Example 1 and Comparative Example 2, which has a coating layer formed, is formed smoothly, whereas the surface roughness of the copper foil of Comparative Example 2, which has no coating layer formed, is high.

[0117]

[0118] Experimental Example 2: Measurement of Lithium Dendrites

[0119] 1 mAh / cm² for each of the coin half cells prepared in Example 1 and Comparative Examples 1 and 2 above 2 After applying a current to electrodeposit lithium ions onto the negative current collector, the surface of the negative current collector was observed using a scanning electron microscope (SEM) and is shown in FIGS. 4 to 6.

[0120] Figure 4 shows SEM images of the surface condition of the negative electrode current collector of Example 1 after lithium ion electrodeposition, observed at different magnifications. Figure 5 shows SEM images of the surface condition of the negative electrode current collector of Comparative Example 1 after lithium ion electrodeposition, observed at different magnifications. Figure 6 shows SEM images of the surface condition of the negative electrode current collector (copper foil) of Comparative Example 2 after lithium ion electrodeposition.

[0121] Through FIGS. 4 to 6, it can be seen that lithium is uniformly electrodeposited and no dendrites occur in the negative current collector of Example 1, which has a lithium-substituted polyacrylic acid coating layer formed thereon, whereas partial formation of lithium dendrites is observed in the negative current collector of Comparative Example 1, which has a lithium-unsubstituted polyacrylic acid coating layer formed thereon. Additionally, it can be seen that severe lithium dendrites occurred in the copper foil of Comparative Example 2, which does not have a coating layer formed thereon.

[0122]

[0123] Experimental Example 3: Initial Efficiency Measurement

[0124] Each of the coin half cells prepared in Example 1 and Comparative Examples 1 and 2 above was charged with a constant current of 1 mAh for 1 hour, and then discharged to 0.5 V with a constant current of 0.5 mA while measuring the capacitance-voltage profile to measure the initial Coulomb efficiency. The measurement results are shown in Fig. 7 and Table 1 below.

[0125] Initial Coulomb Efficiency (%) Example 195 Comparative Example 185 Comparative Example 281

[0126] Through Figure 7 and Table 1, it can be seen that when using the negative current collector of Example 1, which has a lithium-substituted polyacrylic acid coating layer, the initial Coulomb efficiency is improved by more than 10% compared to when using the negative current collector of Comparative Example 1, which has a lithium-non-substituted polyacrylic acid coating layer, and Comparative Example 2, which has no coating layer.

Claims

1. Copper substrate; and A negative current collector comprising a coating layer comprising lithium-substituted polyacrylic acid disposed on at least one surface of the copper substrate.

2. In Paragraph 1, A negative current collector in which the above lithium-substituted polyacrylic acid comprises repeating units represented by the following chemical formula 1. [Chemical Formula 1] 3. In Paragraph 1, The above lithium-substituted polyacrylic acid is a negative current collector composed of repeating units represented by the following chemical formula 1 and repeating units represented by the following chemical formula 2. [Chemical Formula 1] [Chemical Formula 2] 4. In Paragraph 1, The copper substrate above is a negative current collector having a thickness of 3㎛ to 15㎛.

5. In Paragraph 1, The above copper substrate is a negative current collector, which is an electrolytic copper foil or a rolled copper foil.

6. In Paragraph 1, The above coating layer is a negative current collector having a thickness of 30 nm to 5 μm.

7. In Paragraph 1, The above-mentioned cathode current collector is a cathode current collector having a total thickness of 3.03㎛ to 20㎛.

8. Anode; and A negative current collector according to any one of claims 1 to 7; and A negative electrode battery containing an electrolyte.

9. In Paragraph 8, The above anode is Li2MnO3 as the anode active material, yLi2MnO3·(1-y)LiM a O2(here, M a It includes Ni, Co, Mn, Al, Fe, V, Cr, Ti, Ta, Mg, Y, Zr, Ca, Sr, W, or combinations thereof, and 0 <y<1임), Li z Mn 1-e-f Ni e M b f O2(here, M b ... comprises Co, Al, Fe, V, Cr, Ti, Ta, Mg, Y, Zr, Ca, Sr, W, or a combination thereof, and 1 <z≤1.5, 0.1≤e≤0.5, 0≤f≤0.5임), Li2S 또는 이들의 조합을 포함하는 것인 무음극 전지.

10. In Paragraph 8, A non-cathode battery further comprising a separator between the positive and negative current collectors.

11. In Paragraph 8, A cathode-free battery with an initial Coulomb efficiency of 90% or more.

Images